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CORNELL 

UNIVERSITY 

LIBRARY 


FROM 

The  'Pstnte  of   S.F.'^age 


Cornell  University  Library 
QD  253.R38   1922 


3    1924  021    409   507 


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Library 


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tine  Cornell  University  Library. 

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http://www.archive.org/details/cu31924021409507 


AN  INTRODUCTION  TO  THE  STUDY 

OF  THE 

COMPOUNDS  OF  CARBON 

OR 

ORGANIC  CHEMISTRY 

BY 

IRA    REMSEN 


REVISED  AND  ENLARGED 
WITH  THE   COLLABORATION  OF  THE  AUTHOR 

BY 

W.    R.   ORNDORFF,    Ph.D. 

PROFESSOR   OF   ORGANIC   CHEMISTRY,    CORNELL    UNIVERSITY 


D.    C.    HEATH    &   CO.,    PUBLISHERS 

BOSTON  NEW  YORK  CHICAGO 


Copyright,  1885,  1901,  1903,  1909,  and  1922 
By  IRA   REMSEN 

2  I  2 


PREFACE 

Quoting  from  the  preface  to  the  first  edition :  "  This  book 
is  intended  for  those  who  are  beginning  the  subject.  For  this 
reason,  special  care  has  been  taken  to  select  for  treatment  such 
compounds  as  best  serve  to  make  clear  the  fundamental  prin- 
ciples. General  relations  as  illustrated  by  special  cases  are  dis- 
cussed rather  more  fully  than  is  customary  in  books  of  the  same 
size;  and,  on  the  other  hand,  the  number  of  compounds  taken 
up  is  smaller  than  usual.  The  author  has  endeavored  to  avoid 
dogmatism,  and  to  lead  the  student,  through  a  careful  study  of 
the  facts,  to  s^e  for  himself  the  reasons  for  adopting  the  preva- 
lent views  in  regard  to  the  structure  of  the  compounds  of  carbon. 
Whenever  a  new  formula  is  presented,  the  reasons  for  using  it 
are  given  so  that  it  may  afterward  be  used  intelligently.  It  is 
believed  that  the  book  is  adapted  to  the  needs  of  all  students  of 
chemistry,  whether  they  intend  to  foUow  the  pure  science,  or 
to  deal  with  it  in  its  applications  to  the  arts,  medicine,  etc.  It 
is  difficult  to  see  how,  without  some  such  general  introductory 
study,  the  technical  chemist  and  the  student  of  medicine  can 
comprehend  what  is  usually  put  before  them  under  the  heads 
of  'Applied  Organic  Chemistry'  and  'Medical  Chemistry.'" 

These  words  apply  to  the  present  edition.  For  some  time  I 
have  been  aware  that  the  book  needed  a  thorough  overhauling, 
but  one  thing  and  another  prevented  me  from  undertaking  the 
work.  Finally,  I  decided  to  ask  Dr.  W.  R.  Orndorff  of  Cornell 
University  to  join  me.  He  consented,  and  the  many  additions 
and  corrections  that  have  been  made  are  largely  due  to  him. 
I  have  great  confidence  in  his  accuracy  and  thoroughness,  and 
I  am  sure  that  these  qualities  wiU  be  evident  to  those  who  may 
examine  and  use  this  new  edition. 

Organic  chemistry  has  come  very  much  to  the  front  in  the 
last  few  years,  and  I  suppose  it  is  true  that  for  one  who  studied 


IV  CHEMISTRY 

the  subject  at  the  time  the  book  was  written  a  hundred  study  it 
now.  Most  of  these  are  in  the  early  stages  of  their  study,  and 
I  have  had  them  principally  in  mind.  At  the  same  time  a  good 
deal  of  new  material  has  been  introduced  which  will,  I  believe, 
be  helpful  to  those  who  have  passed  beyond  the  first  stage. 

I  make  no  apology  and  offer  no  explanation.  I  do  not  see 
how  any  one  can  acquire  a  working  knowledge  of  the  subject 
without  learning  about  compounds  and  a  good  many  of  them. 
The  acquisition  of  this  knowledge  is  much  facilitated  by  a  study 
of  the  structure  of  the  compounds.  Organic  chemistry  is  to  a 
large  extent  structural  chemistry.  Without  this  aid  the  sub- 
ject would  be  confusion  worse  confounded.  Structural  formulas 
play  somewhat  the  same  part  as  mathematics  in  some  related 
subjects.  We  do  not,  however,  need  to  be  told  that  they  are 
not  the  end.  Properly  used  they  reveal  the  inner  nature  of  the 
things  they  represent,  and  they  are  therefore  of  great  value. 

One  change  has  been  made  that  will  be  noted  at  once.  The 
descriptions  of  laboratory  experiments  have  been  omitted. 
I  am  informed  that  in  most  laboratories  special  manuals  de- 
signed for  that  purpose  have  come  into  use,  and  it  is  clear  there- 
fore that  it  is  not  necessary  to  include  this  matter  in  the  book. 
Professor  Orndorff  long  ago  prepared  such  a  laboratory  manual 
and  a  new  edition  will  appear  at  about  the  same  time  as  this 
book. 

Cross  references  abound  throughout  the  text  and  appear  in 
parenthesis  in  heavy-faced  tj^e. 

Ira  Remsen. 


CONTENTS 

CHAPTER  I 
INTRODUCTION 

PAGE 

Sources  of  organic  compounds.  —  Purification  of  organic  compounds. 

—  Determination  of  tlie  boiling  point.  —  Determination  of  the 
melting  point.  —  Analysis.  —  Formula.  —  Structural  formula.  — 
General  principle  of  classification  of  the  compounds  of  carbon      .         i 

CHAPTER  II 
METHANE  AND  ETHANE.  —  HOMOLOGOUS  SERIES 

Methane.  —  Ethane     .  ig 

CHAPTER  III 

HALOGEN  DERIVATIVES  OF  METHANE  AND  ETHANE 

Substitution.  —  Chloromethane,  Bromometha^e,  lodomethane.  — 
Diiodomethane.  —  Chloroform,  Bromoform,  Iodoform,  Carbon 
tetrachloride.  —  Chloroethane,  Bromoethane,  lodoethane.  —  Isom- 
erism          25 

CHAPTER  IV 

OXYGEN  DERIVATIVES  OF  METHANE  AND  ETHANE 

Alcohols.  —  Methyl  alcohol.  —  Ethyl  alcohol.  —  Fermentation.  — 
Denatured  alcohol.  —  Alcohol  for  scientific  work.  — ■  Alcoholic  bev- 
erages. —  Ethers.  —  Dimethyl  ether.  —  Ethyl  ether.  —  Mixed 
ethers.  —  Aldehydes.  —  Formic  aldehyde.  —  Acetic  aldehyde.  — 
Paraldehyde.  —  Metaldehyde.  —  Chloral.  —  Acids.  —  Formic  acid. 

—  Acetic  acid.  —  Acetyl  chloride.  —  Acetic  anhydride.  —  Ethereal 
salts  or  Esters.  —  Methylsulphuric  acid.  —  Dimethyl  sulphate.  — 
Ethyl  nitrate.  —  Ethyl  nitrite.  —  Ethylsulphuric  acid.  —  Diethyl 
sulphate.  —  Ethyl  formate.  —  Ethyl  acetate.  —  Acetone  35 


VI  CONTENTS 

CHAPTER  V 
SULPHUR  DERIVATIVES  OF  METHAIfE  AND  ETHANE 

PAGE 

Mercaptans.  —  Ethyl  mercaptans.  —  Thio  ethers.  —  Sulphonic  acids       76 

CHAPTER  VI 

NITROGEN  DERIVATIVES  OF  METHANE  AND  ETHANE 

Cyanogen.  —  Hydrocyanic  acid.  —  Cyanides.  —  Sodium  cyanide.  — 
Sodium  ferrocyanide.  —  Potassium  ferrocyanide.  —  Cyanogen 
chloride.  —  Cyanic  acid.  —  Cyanuric  acid.  —  Thiocyanic  acid.  — 
Potassium  thiocyanate.  —  Ammonium  thiocyanate.  —  Ferric  thio- 
cyanate.  —  Cyanides  or  Nitriles.  —  Methyl  cyanide.  —  Ethyl 
cyanide.  —  Isocyanides  or  Carbylamines.  —  Ethyl  isocyanide. — 
Isocyanates.  —  Thiocyanates.  —  Isothiocyanates  or  Mustard 
oils.  —  Substituted  ammonias.  —  Methylamine.  —  Dimethylamine. 

—  Substituted  hydrazines.  —  Nitro  compounds.  —  Nitroform.  — 
Nitrochloroform.  —  Nitroso  and  Isonitroso  compounds.  —  Ful- 
minic  acid        .  .  ....  .  76 

CHAPTER  VII 

DERIVATIVES  OF  ]VIETHANE  AND  ETHAl^TE  CONTAINING 
PHOSPHORUS,  ARSENIC,  ETC. 

Phosphorus  compounds.  —  Arsenic  compounds.  —  Zinc  ethyl.  — 
Sodium  ethyl.  —  Grignard  reaction.  —  Retrospect  .         .110 

CHAPTER  VIII 

THE  HYDROCARBONS  OF  THE  MARSH  GAS  SERIES,  OR 
PARAFFINS 

Petroleum.  —  Synthesis  of  the  paraffins.  —  Isomerism  among  the 
paraffins. — Hexanes  .  .  115 

CHAPTER   IX 

OXYGEN  DERIVATIVES  OF  THE  HIGHER  MEMBERS  OF 
THE  PARAFFIN  SERIES 

Alcohols.  —  Normal  propyl  alcohol.  —  Secondary  propyl  alcohol.  — 
Secondary  alcohols.  —  Butyl  alcohols.  —  Pentyl  or  amyl  alcohol. 

—  Aldehydes.  —  Acids.  —  Fatty  acids.  —  Propionic  acid.  — 
Butyric    acid.  —  Valeric    acids.  —  Palmitic    acid.  —  Stearic    acid. 


CONTENTS  Vll 

PAGE 

—  Soaps.  —  Polyacid  alcohols  and  Polybasic  acids.  —  Diacid 
alcohols.  —  Ethylene  alcohols.  —  Ethylene  chlorohydrin.  —  Oxalic 
acid.  —  Dibasic  acids.  —  Malonic  acid.  —  Succinic  acid.  —  Isosuc- 
cinic  acid.  —  Triacid  alcohols.  —  Glycerol.  —  Glycerol  and  Fatty 
acids.  —  Ethereal  salts.  —  Fats.  —  Butter.  —  Tribasic  acid.  —  Tri- 
carballylic  acid.  —  Tetracid  alcohols.  —  Pentacid  alcohols.  —  Hex- 
acid  alcohols.  —  Mannitol.  —  Mannitol  hexanitrate.  —  Mannitol 
hexacetate.  —  Dulcitol.  —  Sorbitol.  —  Hep tacid  alcohols        .        .129 

CHAPTER  X 

MIXED   COMPOUNDS  —  DERIVATIVES  OF  THE  PARAFFINS 

Hydroxy  acids.  —  Carbonic  acid.  —  Carbonyl  chloride.  —  Ethyl 
chlorocarbonate.  —  GlycoUc  acid.  —  Lactic  acids.  —  Levolactic 
acid.  —  Hydraciylic  acid.  —  Hydroxysulphonic  acids.  —  Isothionic 
acid.  —  Lactones.  —  Hydroxy  acids.  —  Glyceric  acid.  —  Other 
hydroxy   monobasic   acids.  —  Mannonic   acids.  —  Gluconic  acids. 

—  Tartronic  acid.  —  Hydroxysuccinic  acids.  —  Malic  acid.  —  In- 
active malic  acid.  —  Dextro  malic  acid.  —  Mesoxalic  acid.  —  Di- 
hydroxysuccinic  acid.  —  Tartaric  acid.  —  Racemic  acid.  —  Levo- 
tartaric  acid.  —  Mesotartaric  acid.  —  Citric  acid.  —  Trihydroxy- 
glutaric  acids.  —  Tetrahydroxyadipic  acids.  —  Aldehyde  acids  and 
Ketone  acids.  —  Glyoxylic  acid.  —  Pyiivic  acid.  —  Acetoacetic 
acid.  —  Ethyl  acetoacetate.  —  Levulic  acid  ....     176 

CHAPTER  XI 

CARBOHYDRATES 

Monosaccharoses,  monoses.  —  Trioses.  —  Tetroses.  —  Pentoses.  — 
Xyloses.  —  Hexoses.  —  Grape  sugar,  corn  sugar.  —  Glucose.  — 
Mannose.  —  Galactoses.  —  Fructose.  —  Synthesis  of  the  sugars 
occurring  in  nature.. —  Polysaccharoses.  —  Cane  sugar,  beet  sugar, 
sucrose,  saccharose.  —  Sugar  of  milk,  lactose.  —  Maltose,  malt  sugar. 

—  Colloidal  polysaccharides.  —  Starch.  —  Dextrins.  —  Inulin.  — 
Glycogen.  —  Cellulose.  —  Cellulose  nitrates.  —  Cellulose  acetate    .     212 

CHAPTER  XII 

MIXED  COMPOUiroS  CONTAINING  NITROGEN 

Amino  acids.  —  Aminoformic  acid.  —  Glycocoll,  glycine,  aminoace- 
tic  acid.  —  Ethyl  diazoacetate.  —  Diazomethane.  —  Sarcosine.  — 
Betaine.  —  Aminopropionic  acids.  —  Leucine.  —  Isolucine.  —  Se- 


VIU  CONTENTS 

PAGE 

rine.  —  Cystine.  —  Aminosulphonic  acids.  —  Taurine. — Amino  di- 
basic acids.  —  Acid  amides.  —  Hofmann's  reaction.  —  Asparagine. 

—  Succinimide.  —  Cyanamide.  —  Calcium  cyanamide.  —  Guani- 
dine.  —  Creatine.  —  Creatinine.  —  Urea,  carbamide.  —  Semicarba- 
zide.  —  Substituted  ureas.  —  Ureids.  —  Parabanic  acid.  —  Oxaluric 
acid.  —  Uric  acid.  —  Polypeptides .     247 

CHAPTER  Xni 

UNSATURATED  CARBON  COMPOUNDS 

Distinction  between  saturated  and  unsaturated  compounds.  —  Un- 
saturated normal  hydrocarbons.  —  Ethylene,  ethene,  olefiant  gas. 

—  Propylene.  —  Alcohols.  —  Vinyl  alcohol.  —  Allyl  alcohol.  — 
Allyl  compounds.  —  AUyl  mustard  oil.  —  Acrolein,  acrylic  alde- 
hyde, propenal.  —  Acids.  —  Acrylic  acid  series.  —  Crotonic  acids. 

—  Isocrotonic  acids.  —  Oleic  acid.  —  Hardening  of  liquid  fats.  — 
Polybasic  acids  of  the  ethylene  group.  —  Fumaric  and  maleic  acids. 

—  Aconitic  acid.  —  Acetylene  and  its  derivatives.  —  Acetylene, 
ethine.  —  Allylene.  —  Allene.  —  Dimethylacetylene.  —  Propargyl 
alcohol.  —  Propiolic  acid.  —  Tetrolic  acid.  —  Sorbic  acid.  —  Linolic 
acid.  —  Hexatriene.  —  Dipropargyl  ....     273 

CHAPTER  XIV 
CARBOCYCLIC  COMPOUNDS 

Cyclopentane.  —  Cyclohexane  ....    304 

CHAPTER  XV 

THE  BENZENE  SERIES  OF  HYDROCARBONS,  C;^i„.6. 
AROMATIC  COMPOUNDS 

Hydrocarbons  of  the  benzene  series.  —  Benzene  cyclohexatriene.  — 
Toluene.  —  Xylenes.  —  Ethylbenzene.  —  Pseudocumene.  —  Hemi- 
meUithene.  —  Cumene.  —  Hydroaromatic  hydrocarbons.  —  Cyclo- 
hexane. —  Action  of  halogens  on  benzene.  —  Addition  products.  — 
Halogen  substitution  products  of  benzene.  —  Monochlorobenzene. 

—  Bromobenzene.  —  lodobenzene.  —  Dibromobenzene.  —  Halogen 
derivatives  of  toluene.  —  Benzyl  chloride.  —  Benzal  chloride.  — 
Halogen  derivatives  of  the  higher  members  of  the  benzene  series. 

—  Nitro  compounds  of  benzene  and  toluene.  —  Chloronitro- 
benzenes.  —  Dinitrobenzene.  —  Chlorodinitrobenzene.  —  Phenyl- 
nitromethane.  —  Nitrotoluenes.  —  Dinitrotoluene.  —  Symmetrical 


CONTENTS  IX 


trinitrotoluene.  —  Trinitrotertiarybutyl-»j-xylene.  —  Amino  com- 
pounds of  benzene,  etc.  —  Aniline.  —  Derivatives  of  aniline.  — 
^-Nitroaniline.  —  Atoxyl.  —  o-Phenylenediamine.  —  m-Phenylene- 
diamine.  —  />-Phenylenediamine.  —  Dimethylaniline.  —  Diethyl- 
aniline.  —  Diphenylamine.  —  Nitrosodiphenylamine.  —  Acetanilide. 

—  PhenylglycocoU.  —  Hydroxyethylaniline.  —  Phenyl    isocyanate. 

—  Thiocarbanilide.  —  Toluidines.  —  Diazo  compounds  of  the 
benzene  hydrocarbons.  —  Reactions  of  the  diazonium  salts.  — 
Diazo  and  isodiazo  compounds  of  benzene.  —  Diazobenzene 
potassium     oxide.  —  Diazoamino     compounds.  —  Nitrosobenzene. 

—  Azoxybenzene.  —  Azobenzene.  —  Hydrazobenzene.  —  Aromatic 
hydrazines.  —  Phenylhydrazine.  —  Methylphenylhydrazine.  — 
Azo  dyes.  —  Aromatic  sulphonic  acids.  —  Monacid  phenols.  — 
Diacid  phenols.  —  Triacid  phenols.  —  Aromatic  alcohols,  alde- 
hydes,   and    ketones.  —  Aromatic    ketones.  —  Monobasic    acids. 

—  Substitution  products  of  benzoic  acid.  —  Meta-nitrobenzoic  acid. 

—  Para-nitrobenzoic  acid.  —  Anthranilic  acid.  —  Isatin.  —  Meta- 
and  para-aminobenzoic  acids.  —  Hippuric  acid.  —  Sulphobenzoic 
acid.  —  Toluic  acids.  —  a-Toluic  acid.  —  Oxindol.  —  Mesitylenic 
acid.  —  Hydrocinnamic    acid.  —  Ortho-aminohydrocinnamic    acid. 

—  Hydrocarbostyril.  —  Dibasic  acids.  —  Phthalic  acid.  —  Phthalyl 
chloride.  —  Isophthalic  acid.  —  Terephthalic  acid.  —  Hydro- 
phthalic  acids.  —  Hexabasic  acid.  —  Mellitic  acid.  —  Phenol  acids, 
hydroxy  acids  of  the  benzene  series.  —  Mono-hydroxybenzoic 
acids.  —  Salicylic  acid.  —  Acetylsalicylic  acid.  —  Phenyl  salicylate. 

—  Thiosalicylic  acid.  —  Meta-hydroxybenzoic  acid.  —  Para- 
hydroxybenzoic  acid.  —  Anisic  acid.  —  Dihydroxybenzoic  acids.  — 
Protocatechuic   acid.  —  Adrenaline.  —  Piperonal.  —  Vanillic   acid. 

—  Trihydroxybenzoic  acids.  —  Gallic  acid.  —  Tannic  acid.  —  Dep- 
sides.  — ^-Benzoquinone.  —  o-Benzoquinone.  —  Furan,  Thiophene, 
Pyrrol.  —  Pyridine  bases.  —  Lutidines.  —  Terpenes  and  camphors. 

—  Hemiterpenes.  —  Cyclic  terpenes.  —  Monocylic  terpenes.  — 
Monocylic  alcohols  and  ketones.  —  Bicyclic  terpenes.  —  o-Pinene. 

—  Terpin  hydrate.  —  Camphene.  —  Bicyclic  alcohols  and  ke- 
tones. —  Borneol.  —  Isoborneol.  —  (i-Camphor.  —  Geraniol.  — 
Geranial.  —  Polyterpenes.  —  Caoutchouc         .         .        .  306 

CHAPTER  XVI 

DIPHENYLMETHANE,  TRTPHENYLMETHANE,  TETRAPHENYI^ 
METHANE,  AND  THEIR  DERIVATIVES 

.  Diphenyhnethane.   —  Triphenylmethyl.  —  Tetramethyldiaminotri- 
phenylmethane.  —  ^-Trinitrotriphenylmethane.  —  Triphenylmeth- 


X  CONTENTS 

PAOID 

ane  dyes.  —  Acid  fuchsine.  —  Derivatives  of  pararosaniline  and 
rosaniline.  —  Methyl  violet.  —  Crystal  violet.  —  Aniline  blue.  — 
Phenolphthalein.  —  Fluorescein.  —  Eosin.  —  Tetraethylrhodamine. 

—  Sulphonphthaleins.  —  Phenosulphonphthalein     .  462 

CHAPTER  XVII 
PHENYLETHYLENE  AND  DERIVATIVES 

Styrene.  —  Cinnamyl  alcohol.  —  Cinnamic  acid.  —  Coumarin     .  479 

CHAPTER  XVIII 

PHENYLACETYLEPTE  AND  DERIVATIVES 

Phenylacetylene.  —  Orthonitrophenylpropiolic  acid.  —  Indigo  and  re- 
lated compounds.  —  Indigo  blue.  —  Synthetic  indigo.  —  Dioxindol. 

—  Indoxyl.  —  Indol.  —  Methylindol. — Tryptophan       .        .  482 

CHAPTER  XIX 

HYDROCARBONS  CONTAINING  TWO  BENZENE  RESIDUES 
IN  DIRECT  COMBINATION 

Diphenyl.  —  Benzidine.  —  Benzidine       dyes.  —  Carbazole.  —  Naph- 
thalene. —  Substitution  products  of  naphthalene.  —  Homologues 
of       naphthalene.  —  a-Chloronaphthalene.  —  a-Kitronaphthalene. 

—  /3-Nitronapthalene.  —  Naphthalenesulphonic  acids.  —  Naphthols. 

—  a-Naphthol.  —  ar-Tetrahydro-o-naphthol.  —  /3-Naphthol.  — 
/3-Naphthylmethylether.  —  oc-Tetrahydro-iS-naphthoI.  —  Naphthol- 
sulphonic  acids.  —  Nitronaphthols.  —  Aminonaphthols.  —  o-Naph- 
thylamine.  —  Naphthyla,minesulphonic  acids.  —  Azo  dyes  of  the 
naphthalene  series.  —  Congo  red.  —  Orange  11.  —  Ponceau.  —  Fast 
red.  —  Quinones  of  the  naphthalene  series.  —  Naphthazarin.  — 
Quinoline  and  isoquinoline  and  their  derivatives.  —  Quinoline.  — 
Homologues  and  derivatives  of  quinoline 490 

CHAPTER  XX 

ANTHRACENE  AND  PHENANTHKENE  AND  SOME  OF  THEIR 
DERIVATIVES 

Anthracene.  —  Anthraquinone.  — Alizarin.  —  Purpurin.  —  Acridine.  ■ 

—  Chrysaniline.  —  Phenanthrene.  —  Phenanthroquinone         .         .     514 


CONTENTS  XI 

PAGE 

CHAPTER  XXI 

GLUCOSIDES 

The  Methylglucosides.  -  Aesculin.  —  Amygdalin.  —  Arbutin.  — 
Coniferin.  —  Helicin.  —  Phloridzin.  —  Salicin.  —  Saponins.  — 
Cinigrin    ...  .        .  528 

CHAPTER  XXII 

PLANT  ALKALOIDS 

Alkaloids  derived  from  pyridine.  —  Piperine.  —  Nicotine.  —  Atropine. 
—  Cocaine.  —  Alkaloids  derived  from  quinoline.  —  Cinchona  alka- 
loids. —  Quinine.  —  Cinchonine.  —  Strychnos  alkaloids.  —  Strych- 
nine. —  Bmcine.  —  Alkaloids  derived  from  isoquinoline.  —  Mor- 
phine. —  Narcotine.  —  The  Proteins.  —  The  simple  proteins.  — 
Conjugated  proteins.  —  Derived  proteins  532 

Index 545 


ORGANIC    CHEMISTRY 


CHEMISTRY  OF  THE 
COMPOUNDS  OF  CARBON 


CHAPTER  I 
INTRODUCTION 

In  studying  the  compounds  of  carbon,  one  cannot  fail  to  be 
struck  by  their  large  number,  and  by  the  ease  with  which  they 
undergo  change  when  subjected  to  various  influences.  Mainly 
on  account  of  the  large  number  (200,000),  though  partly  on  ac- 
count of  peculiarities  in  their  chemical  conduct,  it  is  customary 
to  treat  of  these  compounds  by  themselves.  At  first.  Chem- 
istry was  divided  into  Inorganic  and  Organic  Chemistry,  as  it 
was  believed  that  there  were  fundamental  differences  between 
the  compounds  included  under  the  two  heads.  Those  com- 
pounds which  form  the  mineral  portion  of  the  earth's  crust  were 
treated  under  the  first  head,  while  those  which  were  found  ready 
formed  in  the  organs  of  plants  or  animals  were  the  subject  of 
organic  chemistry.  It  was  believed  that,  as  the  organic  com- 
pounds are  elaborated  under  the  influence  of  the  life  process, 
there  must  be  something  about  them  which  distinguishes  them 
from  the  inorganic  compounds  in  whose  formation  the  life  pro- 
cess has  no  part.  Graduafly,  however,  this  idea  has  been  aban- 
doned ;  for,  one  by  one,  many  of  the  compounds  which  are  found 
in  plants  and  animals  have  been  made  in  the  chemical  labora- 
tory, and  without  the  aid  of  the  life  process.  The  first  instance 
of  the  artificial  preparation  of  an  organic  compound  was  that 
of  urea,  a  constituent  of  the  urine.  This  substance  was 
obtained  by  Wohler  in  1828  by  the  action  of  a  solution  of 


2  IXTRODUCTION 

ammonia  on  lead  cyanate  (then  considered  to  be  an  inorganic 
compound,  as  it  was  made  in  the  laboratory).  Up  to  the  time  of 
Wohler's  discovery,  the  formation  of  urea,  hke  that  of  other 
organic  compounds,  was  thought  to  be  necessarily  connected 
with  the  life  process ;  but  it  was  thus  shown  that  urea  could 
be  formed  without  the  intervention  of  life.  Afterward,  it  was 
shown  that  potassium  cyanide  can  be  made  by  passing  nitrogen 
over  a  heated  mixture  of  carbon  and  potassium  carbonate ;  and, 
as  potassium  cyanate  can  be  made  from  the  cyanide  by  oxida- 
tion, and  is  easily  converted  into  lead  cyanate,  it  follows  that 
urea  can  be  made  from  the  elements.  Finally,  in  1853,  Berthe- 
lot  succeeded  in  effecting  the  synthesis  of  the  fats.  Since  that 
time,  every  year  has  witnessed  the  artificial  preparation,  by 
purely  chemical  means,  of  compounds  of  carbon  which  are  found 
in  the  organs  of  plants  and  animals. 

It  hence  appears  that  the  formation  of  the  compounds  of  car- 
bon is  not  dependent  upon  the  life  process ;  that  they  are  simply 
chemical  compounds  go\emed  by  the  same  laws  that  govern 
other  chemical  compounds ;  and  the  name.  Organic  Chemistry, 
signifying,  as  it  does,  that  the  compounds  included  under  it 
are  necessarily  related  to  the  organism,  is  misleading.  Organic 
chemistry  is  nothing  but  the  Chemistry  of  the  Compounds  of  Car- 
bon. It  is  not  a  science  independent  of  inorganic  chemistry, 
but  is  just  as  much  a  part  of  chemistry  as  the  chemistry  of  the 
compounds  of  sodium,  or  of  the  compounds  of  sihcon,  etc. 

The  name  Chemistry  of  the  Compounds  of  Carbon  has  been 
objected  to  as  being  too  broad.  Strictly  speaking,  this  title 
includes  the  carbonates,  and  it  is  customary  to  treat  of  these 
widely  distributed  substances  under  the  head  of  Inorganic 
Chemistry.  Most  books  on  Inorganic  Chemistry  also  deal  with 
some  of  the  simpler  compounds  of  carbon,  such  as  the  oxides, 
cyanogen,  marsh  gas,  etc.,  because  they  are  of  such  common 
occurrence  and  so  important  that  it  is  essential  that  the  student 
should  have  a  knowledge  of  them  as  soon  as  possible. 

Sources  of  Organic  Compounds.  —  Many  organic  compounds 
are  obtained  from  plants  and  animals.  Thus,  sugar  from  the 
sugar  cane,  the  sugar  beet,  or  the  maple  tree;  starch  from 


SOURCES  OF  ORGANIC   COMPOUNDS  3 

Indian  corn  or  the  potato ;  sugar  of  milk,  casein,  and  fat  from 
milk ;  albumin  from  the  egg ;  urea,  uric  acid,  and  hippuric  acid 
from  the  urine ;  tartaric  acid  from  grapes ;  citric  acid  from 
lemons  and  grape  fruit;  malic  acid  from  apples;  gallic  acid 
and  tannin  from  nut  galls ;  caffein  from  coffee  or  tea ;  theo- 
bromine from  cocoa ;  and  cellulose  from  wood  or  cotton.  The 
alkaloids  are  obtained  from  plants,  quinine  from  cinchona  bark ; 
strychnine  from  nux  vomica;  morphine  from  the  poppy;  and 
nicotine  from  tobacco.  Various  coniferous  trees,  such  as  the 
pine,  yield  turpentine  and,  when  this  is  distilled,  it  gives  the 
volatile  oil  of  turpentine  and  a  residue  called  rosin.  The  essen- 
tial oils  also  furnish  a  large  number  of  important  substances. 
Thus,  the  oil  of  cloves  contains  eugenol ;  the  oil  of  anise  seed, 
anethol ;  the  oil  of  sassafras,  safrol ;  and  the  oil  of  eucalyptus, 
eucalyptol.  Gum  camphor,  used  in  such  large  quantities  in 
making  celluloid,  is  obtained  from  the  camphor  tree  {Laurus 
camphora),  which  is  now  being  successfully  grown  in  Florida. 
Rubber  or  caoutchouc,  of  such  great  importance  nowadays,  is  ob- 
tained from  the  rubber  tree  {Hevea  hraziliensis),  indigenous  to 
Brazil,  and  from  the  same  tree,  cultivated  on  large  plantations  in 
Ceylon  and  other  tropical  countries.  The  fats  are  obtained  from 
both  animal  and  vegetable  sources.  The  solid  fats,  called  tallows, 
from  beef  and  mutton  fat ;  lard  from  hog  fat ;  cotton  seed  oil  from 
cotton  seed ;  olive  oil  from  olives ;  and  linseed  oil  from  flax  seed. 

Many  organic  compounds  are  obtained  by  fermentation. 
Thus  the  fermentation  of  sugar  solutions  by  yeast  gives  alco- 
hols. When  alcoholic  solutions,  such  as  cider  or  wine,  are  ex- 
posed to  the  air,  they  ferment  and  become  vinegar,  owing  to 
the  conversion  of  the  alcohol  into  acetic  acid,  by  the  action  of 
the  bacterium  aceti.  Milk  exposed  to  the  air  becomes  sour 
because  of  the  transformation  of  the  sugar  of  milk  into  lactic 
acid  by  the  lactic  acid  ferment.  Another  form  of  lactic  acid 
occurs  in  flesh  and  hence  is  called  sarcolactic  acid. 

A  great  many  organic  compounds  are  now  obtained  from  the 
by-products  of  some  chemical  industry,  and  the  utilization  of 
these  by-products  (formerly  thrown  away  or  burned  as  fuel) 
has  become  an  important  source  of  wealth.     Wood  is  distilled 


4  IXTRODUCTION 

for  the  purpose  of  making  charcoal  (for  use  in  the  manufacture 
of  gunpowder  and  as  a  fuel)  and  formerly  the  volatile  products 
were  lost.  They  are  now  condensed  and  from  the  distillate 
wood  alcohol,  acetone,  and  acetic  acid  are  obtained.  Bitummous 
coal  is  distilled  in  closed  retorts  for  the  purpose  of  making  coal 
gas  for  illuminating  purposes.  One  of  the  by-products  is  coal 
tar.  From  this  more  organic  substances  are  now  made  than 
are  obtained  from  all  other  sources  combined.  Dyes,  perfumes, 
flavoring  essences,  antiseptics,  medicinal  remedies  and  the 
modern  high  explosives,  such  as  picric  acid  and  TNT,  are  some 
of  the  organic  compounds  obtained  from  this  source  and  hence 
called  coal  tar  products.  In  the  coking  of  coal  to  make  coke, 
for  use  in  the  manufacture  of  iron  and  steel,  the  volatile  products, 
formerly  burned,  are  now  recovered  and  converted  into  valuable 
organic  compounds.  Indeed,  many  of  the  coal  tar  products 
are  not  now  made  from  coal  tar,  but  from  the  by-products  of 
the  coking  ovens.  Petroleum  consists  almost  entirely  of  com- 
pounds of  carbon  and  hydrogen,  and  from  it  by  distillation  are 
obtained  gasolene,  kerosene,  vaseline,  paraffin  wax,  and  the 
lubricating  oils.  Bones  are  distilled  for  the  purpose  of  making 
boneblack  or  ivory  black  used  as  a  pigment.  The  volatile 
products  when  condensed  are  known  as  bone  oil,  from  which 
are  obtained  a  large  number  of  organic  compounds  containing 
carbon,  hydrogen,  and  nitrogen  and  having  basic  properties 
like  ammonia.  Certain  of  these  basic  compounds,  found  in 
bone  oil  and  also  in  coal  tar,  ha\'e  been  obtained  from  some  of 
the  alkaloids,  and  some  of  the  alkaloids  ha\'e  already  been  made 
from  these  constituents  of  bone  oil.  From  the  compounds 
obtained  from  the  above  sources  most  of  the  organic  compounds 
are  now  made  in  the  laboratory  or  in  the  factory. 

Purification  of  organic  compounds.  —  Before  the  natural 
compounds  of  carbon  can  be  studied  chemically,  they  must 
be  freed  from  foreign  substances ;  and  before  the  constituents 
of  the  complex  mixtures,  petroleum,  coal  tar,  and  bone  oil 
can  be  studied,  they  must  be  separated  and  purified.  The 
processes  of  separation  and  purification  are,  in  many  cases, 
extremely  diflEicult.     If  the  substance  is  a  solid,  different  methods 


PURIFICATION  OF  ORGANIC   COMPOUNDS  5 

may  be  used,  according  to  the  nature  of  the  substance.  Crys- 
tallization is  more  frequently  made  use  of  than  any  other  pro- 
cess. This  is  well  illustrated,  on  the  large  scale,  in  the  refining 
of  sugar,  which  consists,  essentially,  in  dissolving  the  raw  sugar 
in  water,  filtering  through  bone  black,  which  absorbs  coloring 
matter,  and  then  evaporating  down  to  crystallization.  When 
two  or  more  substances  are  found  together,  they  may,  in  many 
cases,  be  separated  by  what  is  called  fractional  crystallization. 
This  consists  in  evaporating  the  solution  until,  on  cooling,  a 
comparatively  small  part  of  the  substance  is  deposited.  This 
deposit  is  filtered  off,  and  the  solution  further  evaporated,  when 
a  second  deposit  is  obtained,  and  so  on  to  the  end.  The  suc- 
cessive deposits  thus  obtained  are  then  recrystallized,  each 
separately,  until,  finally,  some  of  the  deposits  are  found  to 
be  homogeneous. 

The  chief  solvents  used  are  water,  alcohol,  ether,  petroleum 
ether,  benzene,  and  carbon  bisulphide,  alcohol  being  the  one 
most  generally  apphcable. 

In  the  case  of  liquids,  the  process  of  distillation  is  used.  The 
forms  of  apparatus  and  mode  of  procedure  are  described  in 
various  laboratory  manuals,'  and  the  subject  of  distillation  is 
treated  fully  in  a  recent  book  to  which  reference  is  here  made.^ 

For  the  separation  of  liquids  of  different  boiling  points,  the 
process  of  fractional  or  partial  distillation  is  much  used.  When  a 
mixture  of  two  or  more  hquids  of  different  boiUng  points  is  boiled, 
it  will  be  noticed  generally  that  the  boihng  point  gradually  rises 
from  that  of  the  lowest  boiling  substance  to  that  of  the  highest. 
Thus,  ordinary  alcohol  boils  at  78°,  and  water  at  100°.  If  the 
two  are  mixed  and  the  mixture  distilled,  it  will  be  found  that 
it  begins  to  boil  at  78°,  but  that  very  little  passes  over  at  this 
temperature.  Gradually,  as  the  distillation  proceeds,  the 
temperature  indicated  by  the  thermometer  becomes  higher 
and  higher,  until  at  last  100°  is  reached,  when  all  distils 
over.     Now  the  distillates  obtained  at  the  different  tempera- 

M  Laboratory  Manual  of  Organic  Chemistry,  by  W.  R.  OrndorfE  (D.  C. 
Heath  &  Co.). 

'^Distillation:  Principles  and  Processes,  by  Sidney  Young -(Macmillan). 


6  INTRODUCTION 

tures  differ  from  each  other  in  composition.  Those  obtained 
at  the  lower  temperatures  are  richer  in  alcohol  than  those  ob- 
tained at  the  higher  temperatures,  but  none  of  them  contains 
pure  alcohol  or  pure  water.  In  order  to  separate  the  two,  there- 
fore, we  must  proceed  as  follows :  A  number  of  clean,  dr)-  flasks 
are  prepared  for  collecting  the  distillates.  The  boiling  is  begun, 
and  the  point  at  which  the  first  drop  of  the  distillate  appears 
in  the  receiver  is  noted.  That  which  passes  over  while  the 
mercury  rises  through  a  certain  number  of  degrees  (3,  5,  or  10, 
according  to  the  character  of  the  mixture)  is  collected  in  the 
first  flask.  The  recei\-er  is  then  changed,  without  interruption 
of  the  boiling,  and  that  which  passes  over  while  the  mercury 
rises  through  another  interval  equal  to  the  first  is  collected  in 
the  second  flask.  The  receiver  is  again  changed,  and  a  third 
distillate  collected ;  and  so  on,  until  the  liquid  has  all  been  dis- 
tilled over.  It  has  thus  been  separated  into  a  number  of  frac- 
tions, each  of  which  has  passed  over  at  a  different  temperature. 
In  the  case  of  alcohol  and  water,  for  example,  we  might  ha\'e 
collected  distillates  from  78°  to  83°,  from  83°  to  88°,  from  88° 
to  93°,  from  93°  to  98°,  from  98°  to  100°.  Now  a  clean  dis- 
tilling flask  is  taken,  and  into  this  the  first  fraction  is  poured. 
This  is  distilled  until  the  thermometer  marks  the  upper  limit 
of  the  original  first  fraction  (83°),  the  new  distillate  being  col- 
lected ui  the  flask  which  contained  the  first  fraction.  When 
this  upper  limit  is  reached,  the  boiling  is  stopped.  Some  of 
the  liquid  is  left  in  the  distilling  flask.  That  is  to  say,  assum- 
ing that  in  the  first  distillation  the  first  fraction  was  collected 
between  78°  and  83°,  on  boiUng  this  fraction  the  second  time 
it  will  not  all  come  over  between  these  points ;  when  83°  is 
reached  some  wiU  be  left  in  the  flask.  The  second  fraction  is 
now  poured  into  the  distilling  flask  through  a  funnel  tube,  and 
the  boiling  is  again  started.  Of  the  second  fraction,  a  portion 
will  pass  over  below  the  point  at  which  it  began  to  boil  (83°) 
when  first  distilled.  Collect  in  the  proper  flask,  and  continue 
the  boiling  until  the  thermometer  marks  the  highest  point  of 
the  fraction  last  introduced,  changing  the  receiver  whenever 
the  indications  of  the  thermometer  require  it.     Now  stop  the 


DETERMINATION  OF  THE   BOILING   POINT  7 

boiling,  and  pour  in  fraction  No.  3,  and  so  on  until  all  the  frac- 
tions have  been  subjected  to  a  second  distillation.  On  examin- 
ing the  new  fractions,  it  will  be  found  that  the  liquid  tends  to 
accumulate  in  the  neighborhood  of  certain  points  corresponding 
to  the  boiling  points  of  the  constituents  of  the  mixture.  The 
distilling  flask  is  now  cleaned,  and  the  whole  process  repeated. 
A  further  separation  is  thus  efiected.  By  continuing  the  dis- 
tillation in  this  way,  pure  substances  can,  in  many  cases,  even- 
tually be  obtained.  In  many  cases  perfect  separation  cannot 
be  eSected  by  means  of  fractional  distillation ;  as,  for  example, 
in  the  case  of  alcohol  and  water.  But  still  it  is  valuable,  even 
in  such  cases,  as  it  makes  it  possible  to  purify  the  substances, 
at  least  partially. 

Various  devices  have  been  introduced  for  the  purpose  of 
rendering  the  process  of  fractional  distillation  more  rapid  and 
more  efficacious.  One  of  these  that  has  been  extensively  used 
with  good  results  is  the  Hempel  distilling  tube.  This  is  "  a  wide 
vertical  tube,  filled  with  glass  beads  of  special  construction,  and 
constricted  below  to  prevent  the  beads  falling  out.  A  short, 
narrower,  vertical  tube  with  side  delivery  tube  is  fitted  by  means 
of  an  ordinary  cork  into  the  wide  tube."  *  The  wide  vertical 
tube  is  fitted  into  the  stopper  of  the  distilling  flask. 

The  best  examples  of  distillation  carried  on  on  the  large 
scale  are  those  of  alcohol  and  petroleum.  Probably  the  best 
example  of  fractional  distillation  is  that  of  the  light  oil  obtained 
from  coal  tar.  This  process  is  carried  on  in  the  so-called 
"  column  stills,"  of  which  there  are  several  varieties.  Some  of 
them  are  very  efficient. ^ 

Determination  of  the  boiling  point. — In  dealing  with  liquids, 
it  often  is  extremely  difficult  to  tell  whether  they  are  pure  or 
not.  The  first  and  most  important  physical  property  utilized 
for  this  purpose  is  the  boiling  temperature,  commonly  called 
the  boiling  point.  This  is  determined  by  means  of  the  apparatus 
used  for  distilling,  such  as  is  described  above.  The  temperature 
noted  on  the  thermometer  when  the  liquid  is  boiling  is  the  boil- 
ing point.    When  great  accuracy  is  required,  the  point  observed 

'  See  Distillation:  Principles  and  Processes,  by  Sidney  Young  (MacmillaiV 


8  INTRODUCTION 

directly  must  be  corrected,  in  consequence  of  the  expansion  of 
the  glass  and  the  cooling  of  that  part  of  the  column  of  mercury 
which  is  not  in  the  vapor.  Full  directions  for  making  these 
corrections  can  be  found  in  larger  books.  A  pure  chemical 
compound  always  has  a  constant  boiling  point  under  the  same 
barometric  pressure.  On  the  other  hand,  a  constant  boiling 
point  does  not  necessarily  indicate  a  pure  compound.' 

Determination  of  the  melting  point.-  —  Just  as  the  boil- 
ing pomt  is  a  ^-ery  characteristic  property  of  liquids,  so  the 
melting  point  is  an  equally  characteristic  property  of  many 
soHd  substances.  If  a  substance  begins  to  melt  at  a  certain 
temperature,  and  does  not  melt  completely  at  that  temperature, 
it  is,  in  all  probability,  impure.  By  means  of  the  melting  point 
minute  quantities  of  impurities,  which  might  readily  escape 
detection  by  other  means,  are  often  found.  In  dealing  with 
the  compounds  of  carbon,  determinations  of  melting  points 
are  very  frequently  made.  A  pure  chemical  compound  has 
a  constant  melting  point.  The  determination  is  made  as  fol- 
lows :  SmaU  tubes  are  prepared  by  heating  a  piece  of  ordinary 
soft  glass  tubing  of  4°"°  to  s™°  diameter,  and  drawing  it  out. 
If  the  parts  are  drawn  apart  about  12™  to  15™,  two  small 
tubes  may  be  made  from  the  narrowed  portion  by  melting 
together  in  the  middle,  and  then  fiUng  off  each  piece  where  it 
begins  to  grow  wider  near  the  large  tube.  These  small  tubes 
must  have  thin  walls,  and  be  of  such  internal  diameter  that  an 
ordinary  pin  can  be  introduced  into  them.  A  small  quantity 
of  the  substance  to  be  tested  is  placed  in  one  of  the  tubes,  enough 
to  make  a  minute  column  of  about  5™"  in  height.  The  tube 
containing  the  substance  is  fastened  to  a  thermometer  by  means 
of  a  small  rubber  band  or  by  fine  platinum  wire.  The  band  is 
placed  near  the  upper  part  of  the  tube,  and  the  lower  part  of 
the  tube,  containing  the  substance,  is  placed  against  the  bulb 
of  the  thermometer.     The  thermometer  bulb  is  now  immersed 

'  See  Distillation :  Principles  and  Processes,  by  Sidney  Young  (Macmillan) . 

'  For  details  in  determining  melting  points  and  boiling  points,  see 
A  Method  for  the  Identification  0}  Pure  Organic  Compounds,  by  J.  P. 
MuUiken. 


ANALYSIS  9 

in  a  tube  containing  pure  sulphuric  acid.  The  sulphuric  acid 
is  gently  heated  by  a  small  flame  until  the  substance  melts. 

A  convenient  form  of  apparatus  for  determining  melting 
points  is  the  Thiele  tube  modified  by  Dennis.' 

It  does  not  necessarily  follow  that,  if  a  substance  has  a  sharp 
melting  point,  it  is  pure.  It  may  be  a  eutectic  mixture  which 
has  a  constant  melting  point.  In  order  to  avoid  this  error, 
the  substance  should  be  crystallized  from  a  number  of  different 
solvents,  using  solvents  as  unlike  each  other  as  possible.  If 
the  melting  point  remains  constant  from  all  these  solvents,  it 
is  practically  certain  that  the  substance  is  pure,  for  it  is  extremely 
unlikely  that  the  two  components  of  a  eutectic  mixture  would 
have  the  same  solubility  in  all  the  solvents.  It  is  much  more 
Ukely  that  one  mixture  would  crystallize  from  one  solvent  and 
another  from  another  solvent,  that  is,  that  the  melting  point 
would  change  with  the  solvent.  If  a  substance  has  a  constant 
boiling  point  and  also  a  sharp  and  definite  melting  point,  there 
is  no  doubt  that  it  is  pure. 

Analysis.  —  Having  purified  the  compounds,  the  next  step 
is  to  determine  their  composition.  A  comparatively  small 
number  of  the  compounds  ordinarily  met  with  consist  of  car- 
bon and  hydrogen  only ;  the  largest  number  consist  of  these 
two  elements  together  with  oxygen ;  many  contain  carbon, 
hydrogen,  oxygen,  and  nitrogen.  But,  in  the  derivatives  of  the 
fundamental  compounds,  all  other  elements  may  occur.  Thus 
the  hydrogen  may  be  partly  or  wholly  replaced  by  chlorine, 
bromine,  or  iodine,  as  in  the  so-called  substitution  products ; 
and  any  metal  may  occur  in  the  salts  of  the  acids  of  carbon. 
The  estimation  of  carbon  and  hydrogen  is  the  principal 
problem  in  the  analysis  of  the  compounds  of  carbon.  This  is 
effected  by  what  is  known  as  the  combustion  process.  A  known 
weight  of  the  substance  is  completely  burned  in  oxygen,  the 
carbon  being  thus  converted  into  carbon  dioxide,  and  the  hydro- 
gen into  water.  These  two  products  are  collected,  the  water 
in  a  tube  containing  sulphuric  acid,  the  carbon  dioxide  in  a 

'  See  L.  M.  Dennis,  Journal  of  Industrial  and  Engineering  Chemistry, 
Vol.  12,  p.  366. 


ro  INTRODUCTION 

solution  of  potassium  hydroxide,  and  weighed.  From  the 
weights  of  the  products  the  weights  of  carbon  and  hydrogen 
and  the  percentages  are  calculated.  The  percentages  are 
added  together  and  the  sum  subtracted  from  loo.  The  differ- 
ence is  the  percentage  of  oxygen,  provided  the  substance  con- 
tains only  these  elements. 

A  detailed  description  of  the  apparatus  and  of  the  method 
of  procedure  need  not  be  given  here,  as  they  can  be  found  in 
any  book  on  anahtical  chemistry.  A  brief  description,  however, 
may  not  be  out  of  place.  The  combustion  is  effected  in  a  hard- 
glass  tube  which  is  heated  by  means  of  a  gas  or  electric  furnace 
constructed  for  the  purpose.  Ordinarily,  the  substance  is  placed 
in  a  narrow  porcelain  or  platinum  vessel,  called  a  boat,  which 
is  introduced  into  the  combustion  tube  filled  with  granulated 
copper  oxide.  The  tube  is  then  connected  with  (i)  a  U-tube 
containing  sulphuric  acid ;  (2)  a  set  of  bulbs  containing  a  solu- 
tion of  potassium  h}'droxide,  and  constructed  so  as  to  secure 
thorough  contact  of  the  passing  gases  with  the  solution;  and 
(3)  a  smaU  U-tube  containing  sulphuric  acid.  During  the  com- 
bustion, a  current  of  pure  dry  oxygen  is  passed  through  the  tube ; 
and,  finally,  the  oxygen  is  displaced  by  air.  The  method  at 
present  used  was  devised  by  Liebig.  It  has  contributed  very 
greatly  to  our  knowledge  of  the  compounds  of  carbon. 

Two  methods  are  in  common  use  for  the  estimation  of  nitro- 
gen in  carbon  compounds.  The  first  is  known  as  the  absolute 
method.  This  consists  in  oxidizing  the  substance  by  copper 
oxide;  decomposing,  by  means  of  a  roll  of  heated  metallic 
copper,  any  oxides  of  nitrogen  which  may  have  been  formed, 
and  collecting  the  nitrogen.  The  volume  of  the  nitrogen  thus 
obtained  is  measured,  and  its  weight  calculated.  The  chief 
difficulty  in  this  method  consists  in  removing  all  the  air  contained 
in  the  apparatus  before  the  combustion  is  made.  The  simplest 
way  is  to  displace  the  air  by  passing  pure  carbon  dioxide  through 
the  apparatus  until  the  gas  that  passes  out  is  completely  absorbed 
by  caustic  potash.  The  combustion  is  then  made  by  heating 
the  tube  containing  the  substance  and  copper  oxide  and  a  layer 
of  copper  foil  or  wire  gauze;    and,  finally,  carbon  dioxide  is 


FORMULA  II 

again  passed  through  at  the  end  of  the  operation.  The  only- 
three  gases  that  can  be  present,  assuming  that  the  substance 
contained  nothing  but  carbon,  hydrogen,  oxygen,  and  nitro- 
gen, are  carbon  dioxide,  water  vapor,  and  free  nitrogen.  The 
water  vapor  is,  of  course,  condensed,  and  the  carbon  dioxide  is 
absorbed  by  passing  the  gases  through  a  solution  of  potassium 
hydroxid,e,  leaving  the  nitrogen  thus  alone. 

The  method  now  most  extensively  used  is  that  devised  by 
Kjeldahl.  This  consists  in  oxidizing  the  substance  by  heating 
it  with  concentrated  sulphuric  acid,  potassium  sulphate,  and  a 
little  copper  sulphate.  By  this  means  all  the  nitrogen  contained 
in  the  substance  under  examination  is  converted  into  ammonia, 
which,  of  course,  unites  with  the  sulphuric  acid.  The  ammonia 
is  set  free  by  the  addition  of  sodium  hydroxide,  and  is  estimated 
by  absorption  in  standard  acid. 

In  regard  to  the  estimation  of  other  constituents  of  carbon 
compounds,  it  need  only  be  said  that  in  most  cases  it  is  neces- 
sary to  get  rid  of  the  carbon  and  hydrogen  by  some  oxidizing 
process  before  the  estimation  can  be  made.  Thus,  in  estimat- 
ing sulphur,  it  is  customary  to  fuse  the  substance  with  potas- 
sium nitrate  and  hydroxide,  when  the  carbon,  hydrogen,  and 
sulphur  are  oxidized,  and  the  sulphur,  in  the  form  of  potassium 
sulphate,  can  be  estimated  in  the  usual  way. 

Formula.  —  The  deduction  of  the  formula  of  a  compound 
from  the  results  of  the  analysis  involves  two  steps.  The  first 
is  a  matter  of  simple  calculation.  It  is  assumed  that  students 
who  use  this  book  are  already  familiar  with  the  method  of 
calculating  the  formula  from  the  analytical  results;  but  an 
example  will,  nevertheless,  be  given.  Suppose  that  the  analysis 
has  shown  that  the  substance  contains  52.18  per  cent  carbon, 
13.04  per  cent  hydrogen,  and  34.78  per  cent  oxygen.  To 
get  the  atomic  proportions,  divide  the  figures  representing 
the  percentages  of  the  elements  by  the  corresponding  atomic 
weights.     We  have  thus :  — 


Percentage 

At.  Wt. 

Relative  No.  or  Atoms 

c 

52.18       - 

12       = 

4-35      -          2 

H 

13.04       - 

I       = 

13.04     -         6 

0 

34.78       - 

^         16       = 

2.17     -        I 

12  INTRODUCTION 

That  is  to  say,  accepting  the  atomic  weights  1 2  for  carbon  and 
16  for  oxygen,  the  simplest  figures  representing  the  nmnber  of 
atoms  of  the  three  elements  in  the  compound  are  2  for  carbon, 
6  for  hydrogen,  and  i  for  oxygen.  According  to  this,  the 
simplest  formula  that  can  be  assigned  to  a  substance  gi\'ing 
the  above  results  on  analysis  is  C2H6O.  But  the  formula 
C4Hi202  is  equally  in  accordance  with  the  anal>'tical  results, 
and  we  can  only  decide  between  the  two  by  determining  the 
molecular  weight. 

Every  chemical  formula  is  intended  to  represent  the  relative 
weight  of  the  molecule  of  a  compound  and  the  composition  of 
the  molecule.  Our  conception  of  the  relative  weights  of  mole- 
cules is  based  almost  exclusively  on  .\vogadro's  law,  accord- 
ing to  which  equal  ^•olumes  of  all  gases  under  the  same  condi- 
tions of  temperature  and  pressure  contain  the  same  number  of 
molecules.  Hence,  b}-  comparing  the  weights  of  equal  volumes 
of  compounds  in  the  form  of  gas  or  vapor,  figures  are  obtained 
that  bear  to  one  another  the  same  relations  as  the  weights  of 
the  molecules. 

The  molecular  weight  of  a  gas  is  the  weight  of  any  volume 
of  that  gas  as  compared  with  the  weight  of  the  same  volume  of 
some  standard  gas,  both  being  measured  under  the  same  con- 
ditions of  temperature  and  pressure.  The  standard  generally 
used  is  oxygen,  and  its  molecular  weight  has  been  shown  to  be 
twice  as  great  as  its  atomic  weight,  that  is  to  say,  32.  The 
volume  occupied  by  32  grams  of  oxygen  at  0°  and  760™™  is  22.4 
liters.  It  follows,  therefore,  from  Avogadro's  law,  that  the  weight 
of  22.4  liters  of  any  gas  or  vapor  measured  at  0°  and  /(Jo™™  imll  be 
the  molecular  weight  of  that  gas  or  vapor. 

It  need  hardly  be  said  that  it  is  not  necessary  to  weigh  22.4 
liters  of  the  gas.  Any  volume  may  be  weighed  and  the  nec- 
essary corrections  made  for  temperature,  pressure,  and  \'olume. 
As  this  subject  is  fully  dealt  with  in  courses  in  Inorganic  Chemis- 
try which  alwa3's  precede  the  courses  in  Organic  Chemistry, 
it  need  not  be  further  discussed  here. 

To  illustrate  by  means  of  a  compound  whose  atomic  relations 
have  been  found  by  analysis  to  be  represented  by  the  formulas 


STRUCTURAL   FORMULA  13 

CzHeO,  C4H12O2,  CsHisOs,  or  some  higher  multiple  of  C2H6O. 
Suppose  that,  when  this  compound  is  converted  into  vapor,  the 
weight  of  22.4  liters  at  0°  and  760°™  is  found  to  be  46.2  grams. 
Then  the  molecular  weight  of  the  compound  is  46,  or  the  formula 
is  C2H6O,  and  not  C4H12O2,  nor  any  higher  multiple  of  C2H6O. 

The  molecular  weight  of  an  acid  can  be  determined  by  ana- 
lyzing its  salts.  To  illustrate  this  take  acetic  acid.  This  is  a 
monobasic  acid,  that  is  to  say,  it  gives  but  one  silver  salt  and 
hence  contains  but  one  hydrogen  atom  replaceable  by  a  metal. 
Now  analysis  of  acetic  acid  shows  that  it  has  the  composition 
represented  by  the  formulas  CH2O,  C2H4O2,  CsHeOs,  etc.  The 
analysis  of  the  silver  salt  shows  that  it  contains  64.67  per  cent 
silver,  hence  it  must  be  represented  by  the  formula  C2H302Ag 
and  not  CHOAg,  and  the  molecular  formula  of  acetic  acid  is 
therefore  C2H4O2,  and  not  CH2O. 

Two  other  methods  of  determining  molecular  weights,  the 
freezing  point  and  boiling  point  methods,  are  now  much  used. 
By  means  of  these  methods  the  molecular  weights  of  substances 
which  cannot  be  vaporized  without  undergoing  decomposition 
(such  as  sugar)  can  also  be  determined.  They  are  so  simple 
and  convenient  that  they  have  almost  entirely  supplanted  the 
other  methods.^ 

Structural  formula.  —  The  formulas  C2H6O,  C2H4O2,  CHCI3, 
etc.,  tell  us  the  composition  of  the  three  compounds  represented, 
and  also  the  weights  of  their  molecules.  In  studying  the 
chemical  conduct  of  these  compounds,  their  decompositions, 
and  the  modes  of  preparing  them,  we  become  acquainted  with 
many  facts  which  it  is  desirable  to  represent  by  means  of  the 
formulas.  Thus,  for  example,  only  one  of  the  four  atoms  of 
hydrogen  represented  in  the  formula  of  acetic  acid,  C2H4O2, 
can  be  replaced  by  metals.  It  plainly  differs  from  the  three 
remaining  hydrogen  atoms,  and  it  is  natural  to  conclude  that 
it  is  held  in  the  molecule  in  some  way  different  from  the  other 
three.  We  may,  therefore,  write  the  formula  H.C2H3O2,  which 
is  intended  to  call  attention  to  this  difference.     By  further 

'  For  details  of  these  methods  see  Practical  Physical  Chemistry  by 
A.  Findlay,  3d  edition,  1917. 


14  INTRODUCTION 

Study  of  acetic  acid,  we  find  that  the  particular  hydrogen, 
which  gives  to  it  its  acid  properties,  and  which,  in  the  above 
formula,  is  written  by  itself,  is  directly  connected  with  oxygen. 
It  can  be  removed  with  oxygen  by  simple  reactions,  and  the 
place  of  both  taken  by  one  atom  of  some  other  element,  as, 
for  example,  chlorine.  Thus,  when  acetic  acid  is  treated  with 
phosphorus  trichloride  it  is  converted  into  acetyl  chloride :  — 

3  H.C2H3O2  +  PCI3,  =  3  C2H3OCI  +  P(0H)3. 

Acetyl  chloride 

The  result  of  the  action  is  the  direct  substitution  of  one  atom 
of  chlorine  for  one  atom  of  hydrogen  and  one  atom  of  oxygen  in 
acetic  acid,  a  fact  which  points  to  an  intimate  connection  be- 
tween the  hydrogen  and-  oxygen  in  the  acid.  Further,  when 
acetyl  chloride  is  treated  with  water,  acetic  acid  is  regenerated, 
hydrogen  and  oxygen  from  the  water  taking  the  place  of  the 
chlorine,  as  represented  in  this  equation :  — 

C2H3OCI  +  HOH  =  C2H3O.OH  +  HCl. 

From  facts  of  this  kind  the  conclusion  is  drawn  that  in  acetic 
acid  hydrogen  and  oxygen  are  connected,  or,  as  it  is  said,  linked 
together;  and  this  conclusion  is  represented  in  chemical  language 
by  the  formula  C2H3O.OH,  which  may  serve  as  a  simple  illus- 
tration of  what  are  called  structural  or  constitutional  formulas. 
It  does  not,  however,  tell  the  whole  story  and  may  therefore 
be  called  a  partial  structural  formula.  In  all  compounds  the 
attempt  is  made,  by  means  of  a  thorough  study  of  the  conduct 
of  the  compounds,  to  trace  out  the  connections  existing  between 
the  constituent  atoms.  When  this  can  be  done  for  all  the  atoms 
contained  in  a  molecule,  the  structure  or  constitution  of  the 
molecule  of  the  compound  is  said  to  be  determined.  The 
structural  formulas  which  have  been  determined  by  proper 
methods  have  proved  of  much  value  in  dealing  with  chemical 
reactions,  as  they  enable  the  chemist  who  understands  the  lan- 
guage in  which  they  are  written  to  see  relations  which  might 
easily  escape  his  attention  without  their  aid.  In  order  to  under- 
stand them,  however,  the  student  must  have  a  knowledge  of 


GENERAL   PRINCIPLE  OF   CLASSIFICATION  IS 

the  reactions  upon  which  they  are  based ;  and  he  is  warned  not 
to  accept  any  chemical  formula  unless  he  can  see  the  reasons 
for  accepting  it.  He  should  ask  the  question,  Upon  what  facts 
is  it  based?  whenever  a  formula  is  presented  for  the  first  time. 
If  he  does  this  conscientiously,  he  will  soon  be  able  to  use  the 
language  intelligently,  and  understand  the  relations  that  exist 
between  the  large  number  of  compounds  of  carbon.  If  he  does 
not,  his  mind  will  soon  be  in  a  hopeless  muddle,  and  what  he 
learns  will  be  of  Kttle  value.  For  the  beginner,  this  advice  is 
of  vital  importance :  Sticdy  with  great  care  the  reactions  of  com- 
pounds; study  the  methods  of  making  them,  and  the  decomposi- 
tions which  they  undergo.  The  formulas  are  hut  the  condensed 
expressions  of  the  conclusions  which  are  drawn  from  the  reactions 

General  principle  of  classification  of  the  compounds  of 
carbon.  —  The  fundamental  substances  dealt  with  under  the  head 
of  Inorganic  Chemistry  are,  of  course,  the  elements.  The  proper- 
ties of  the  elements  enable  us  to  separate  them,  for  study,  into  a 
number  of  groups ;  as,  for  example,  the  chlorine  group,  including 
bromine,  iodine,  and  fluorine ;  the  oxygen  group,  in  which  are 
included  sulphur,  selenium,  and  tellurium.  To  recall  the  method 
generally  adopted,  let  us  take  the  chlorine  group.  In  studying 
the  members  of  this  group,  there  is  found  great  similarity  in 
their  properties.  Their  hydrogen  compounds  next  present 
themselves,  and  here  also  great  similarity  is  met  with.  Then, 
in  turn,  the  oxygen,  and  the  oxygen  and  hydrogen  compounds 
are  taken  up,  and  again  the  resemblances  in  properties  be- 
tween the  corresponding  compounds  of  chlorine,  bromine,  and 
iodine  are  observed.  We  thus  have  groups  of  elements,  and 
of  the  compounds  of  these  elements,  as,  — 


CI 

CIH 

CIO3H 

Br 

BrH 

BrOaH 

I 

IH 

IO3H,  etc. 

Of  course,  the  chlorine  group  is  quite  distinct  from  the  oxygen 
group  and  from  all  other  groups ;  and  each  member  of  the 
chlorine  group  is,  at  least  so  far  as  we  know,  quite  independent 
of  the  other  members.     We  cannot  make  a  bromine  compound 


I 6  INTRODUCTION 

from  a  chlorine  compound,  nor  a  chlorine  compound  from  a 
bromine  compound,  without  directly  substituting  the  one  ele- 
ment for  the  other. 

Now,  when  we  come  to  study  the  compounds  of  carbon,  we 
shall  find  that  the  same  general  principle  of  classification  is  made 
use  of;  only,  in  consequence  of  the  peculiarities  of  the  com- 
pounds, the  system  can  be  carried  out  much  more  thoroughly ; 
the  members  of  the  same  group  can  be  transformed  one  into 
the  other,  and  it  is  also  possible  to  pass  from  one  group  to  another 
by  means  of  comparatively  simple  reactions. 

The  simplest  compounds  of  carbon  are  those  which  contain 
only  hydrogen  and  carbon,  or  the  hydrocarbons .  All  the  other 
compounds  may  be  regarded  as  derivatives  of  the  hydrocarbons. 
To  begin  with,  there  are  several  groups  or  series  of  hydrocarbons, 
which  correspond  somewhat  to  the  different  groups  of  elements. 
The  members  of  one  and  the  same  series  of  hydrocarbons  re- 
semble one  another  more  closely  than  the  members  of  one  and 
the  same  series  of  elements.  Although  we  have  indications 
of  the  existence  of  more  than  ten  series  of  these  hydrocarbons, 
only  three  or  four  of  the  series  are  at  all  well  known,  and  of 
these  but  two  include  more  than  two  or  three  members  that 
need  to  be  treated  of  in  this  book. 

Starting  with  any  series  of  hydrocarbons,  several  classes  of 
derivatives  can  be  obtained  by  treating  the  fundamental  com- 
pounds with  different  reagents.  The  chief  classes  of  these 
derivatives  are:  (i)  those  containing  halogens;  (2)  those  con- 
taining oxygen,  among  which  are  the  acids,  alcohols,  ethers, 
etc. ;  (3)  those  containing  sulphur ;  and  (4)  those  containing 
nitrogen.  Corresponding  to  every  hydrocarbon,  then,  we  may 
expect  to  find  representatives  of  these  different  classes  of  deriv- 
atives. But  the  relations  existing  between  any  hydrocarbon 
and  its  derivatives  are  the  same  as  those  existing  between  any 
other  hydrocarbon  and  its  derivatives.  Hence,  if  we  know 
what  derivatives  one  hydrocarbon  can  yield,  we  know  what 
derivatives  we  may  expect  to  find  in  the  case  of  every  other 
hydrocarbon.  The  student  who,  for  the  first  time,  undertakes 
the  study  of  the  chemistry  of  the  compounds  of  carbon  is  apt  to 


GENERAL   PRINCIPLE   OF  CLASSIFICATION  1 7 

feel  overwhelmed  by  the  enormous  number  of  them  described 
in  the  book  or  by  the  lecturer.  This  large  number  is  really  not 
a  serious  matter.  No  one  is  expected  to  become  acquainted 
with  every  compound.  A  great  many  of  these  need  only  be 
referred  to  for  the  purpose  of  indicating  the  extent  to  which 
the  series  to  which  they  belong  has  been  developed.  In  general, 
the  members  of  any  series  so  closely  resemble  one  another,  that, 
if  we  understand  the  simpler  members,  we  have  a  fair  knowledge 
of  the  more  complicated  members. 

It  is  proposed,  in  this  book,  to  treat  only  of  the  more  im- 
portant compounds  and  the  more  important  reactions,  the 
object  being  rather  to  give  a  clear,  general  view  of  the  subject 
than  detailed  information  regarding  particular  compounds. 
Should  the  student  desire  more  specific  information  concerning 
the  properties  of  any  of  the  compounds  mentioned,  he  can 
easily  find  it  in  some  larger  book.  It  will,  however,  hardly 
be  profitable  for  him,  at  the  outset,  to  burden  his  mind  with 
details.  He  may  thereby  sacrifice  the  general  view,  which  it 
is  so  important  he  should  gain  as  quickly  as  possible. 

The  plan  that  will  be  followed  is  briefly  this  :  Of  the  first  series 
of  hydrocarbons  the  first  two  members  will  be  treated.  Then 
the  derivatives  of  these  two  will  be  taken  up.  These  deriva- 
tives will  serve  admirably  as  representatives  of  the  correspond- 
ing derivatives  of  other  hydrocarbons  of  the  same  series,  and  of 
other  series.  Their  characteristics  and  their  relations  to  the 
hydrocarbons  will  be  dwelt  upon,  as  well  as  their  relations  to 
each  other.  Thus,  by  a  comparatively  close  study  of  two 
hydrocarbons  and  their  derivatives,  a  knowledge  of  the  prin- 
cipal classes  of  the  compounds  of  carbon  may  be  acquired. 
After  these  typical  derivatives  have  been  discussed,  the  entire 
series  of  hydrocarbons  will  be  taken  up  briefly,  only  such  facts 
being  dealt  with  at  all  fully  as  are  not  illustrated  by  the  first  two 
members. 

After  the  first  series  has  been  studied  in  this  way,  and  a  clear 
idea  of  the  relations  between  the  various  classes  obtained,  a 
second  series  will  be  taken  up  and  treated  in  a  similar  way, 
and  so  on.     But  only  a  few  of  the  series  require  much  attention 


1 8  INTRODUCTION 

at  the  beginning.  The  first  series  that  will  be  used  for  the  pur- 
pose of  illustrating  the  general  principles  is  one  of  the  two 
most  important  series,  and  the  only  two  that  need  be  taken  up, 
at  all  fully  at  present.  These  are  known  as  the  paraffin  series 
and  the  benzene  series. 


CHAPTER   II 

METHANE  AND   ETHANE  —  HOMOLOGOUS   SERIES 

Ir  we  were  to  study  all  the  hydrocarbons  known,  and  were 
then  to  arrange  them  in  groups  according  to  their  properties, 
we  should  find  that  a  large  number  of  them  resemble  marsh  gas 
in  their  general  conduct.  Some  of  the  points  of  resemblance 
are  these :  They  are  very  stable,  resisting  the  action  of  most 
reagents ;  and  nothing  can  be  added  to  them  directly,  —  if 
any  change  takes  place  in  them,  hydrogen  is  first  given  up.  On 
arranging  these  substances  according  to  the  number  of  carbon 
atoms  contained  in  them,  we  have  a  remarkable  series,  the  first 
six  members  of  which,  together  with  their  formulas,  are  in- 
cluded in  the  subjoined  table  :  — 

Methane  (or  Marsh  Gas)     ....  CH4 

Ethane CzHs 

Propane CsHg 

Butane C4Hio 

Pentane CeHij 

Hexane CbHm 

On  examining  the  formulas  given,  it  will  be  seen  that  the  dif- 
ference in  composition  between  any  two  consecutive  members 
is  represented  by  CHj.  Thus,  adding  CH2  to  marsh  gas,  CH4, 
we  get  ethane,  CjHe ;  adding  CH2  to  C2H6,  we  get  CsHg,  and  so 
on,  at  each  successive  step.  Any  series  of  this  kind,  in  which 
the  successive  members  increase  in  complexity  by  CHj,  is  called 
an  homologous  series. 

Just  as  the  members  of  an  homologous  series  of  hydrocarbons 
differ  from  one  another  by  CH2,  or  some  multiple  of  it,  so  also 
the  members  of  any  class  of  derivatives  of  these  hydrocarbons 
differ  from  one  another  in  the  same  way,  and  form  homologous 
series.    Thus,  running  parallel  to  the  hydrocarbons  mentioned 

19 


20  METHANE   AND   ETHANE 

above,  there  are  two  homologous  series  of  oxygen  derivatives, 
as  indicated  below :  — 

CH4  -  CH4O  -  CH2O2 
C2H6  -  C2H6O  -  C2H4O2 
CsHg  —  CsHgO  —  C3H6O2 
C4H10  —  C4HJ0O  —  C4H8O2 
C5H12  —  C6H12O  —  C5H10O2 
CeHn  —  CeHiiO  —  C6H12O2 

The  relation  observed  between  the  members  of  the  homologous 
series  mentioned  is  by  no  means  a  peculiarity  of  the  marsh 
gas  series  of  hydrocarbons  and  of  their  derivatives,  but  is  ob- 
served in  the  case  of  all  other  series  of  hydrocarbons  and  their 
derivatives. 

Strictly  speaking,  there  is  perhaps  no  analogy  for  this  re- 
markable fact  among  the  elements  and  their  compounds,  yet 
facts  which  suggest  analogy  are  known.  Take,  for  example, 
the  chlorine  series.     We  have 

Chlorine,  with  the  atomic  weight,  35.4. 
Bromine,     "  "  "        80. 

Iodine,         "  "  "       127. 

As  is  well  known,  the  difference  between  the  atomic  weights  of 
chlorine  and  bromine  is  approximately  equal  to  the  difference 
between  those  of  bromine  and  iodine.  In  other  words,  there 
is  a  regular  increase  in  the  atomic  weights  of  these  similar 
elements,  just  as  there  is  a  regular  increase  in  the  molecular 
weights  of  the  members  of  an  homologous  series.  The 
explanation  of  homology  in  the  sense  in  which  the  word  is 
used  in  connection  with  the  compounds  of  carbon  is,  as  will 
be  shown,  very  simple.  A  somewhat  similar  explanation  of 
the  relations  between  elements  belonging  to  the  same  group 
has  been  put  forward,  but  this  necessitates  a  consideration 
of  the  structure  of  atoms,  and  it  would  lead  too  far  to  take 
that  subject  up  here. 

The  view  at  present  held  in  regard  to  the  nature  of  homology 
is  founded,  primarily,  upon  the  idea  that  carbon  is  quadrivalent. 


HOMOLOGY  21 

If  carbon  is  quadrivalent,  it  of  course  follows  that  the  com- 
pound, marsh  gas,  CH4,  is  saturated;  that  is,  the  molecule 
cannot  take  up  anything  without  losing  hydrogen.  In  order, 
therefore,  that  we  may  get  a  compound  containing  two  atoms 
of  carbon  in  the  molecule,  some  of  the  hydrogen  must  first  be 
given  up.  With  our  present  views,  we  cannot  conceive  of 
combination  taking  place  directly  between  the  molecules  CH4 
and  CH4,  but  we  can  conceive  of  combination  taking  place 
between  the  residues  CH3  and  CH3,  to  form  a  molecule  C2H6, 
which  in  turn  is  saturated.  Representing  graphically  what  is 
believed  to  take  place,  we  have,  first,  marsh  gas,  which  we  may 
represent  thus, 

H 

H — C — ^H.     If  this  loses  one  atom  of  hydrogen,  we  have  the 

H 

H 

I 
unsaturated  residue  H — C — ,  which  is  capable  of  uniting  with 

H 

another  residue  of   the  same  kind  to  form  the  more  complex 
H     H 

molecule  H— C— C— H,  or  CjHe.    The  residue  CH3  is  called 

I       I 
H     H 

methyl.  It  appears  therefore  that  the  compound  C2H6,  ethane, 
is  methylmethane  or  dimethyl,  and  the  difference  CH2  in  com- 
position between  methane  and  ethane  is  thus  accounted  for. 
The  evidence  in  favor  of  this  view  will  be  presented  when  the 
reactions  by  means  of  which  the  hydrocarbons  are  made  are 
discussed.  The  explanation  offered,  and  now  accepted,  involves 
the  idea  that  carbon  atoms  unite  with  one  another.  And,  as  the 
explanation  for  the  relation  between  the  first  and  second  member 
is,  in  principle,  the  same  as  for  the  relation  between  the  second 
and  third,  the  third  and  fourth,  etc.,  it  appears  that  this  power 


22  METHANE  AND   ETHANE 

of  carbon  atoms  to  unite  with  one  another  is  very  extensive. 
It  is  to  the  power  that  carbon  possesses  of  forming  homologous 
series,  or  to  the  power  of  the  atoms  of  carbon  to  unite  with  one 
another,  that  we  owe  the  large  number  of  compounds  of  this 
element. 

Methane,  marsh  gas,  fire  damp,  CH4.  —  This  hydrocarbon 
is  found  rising  from  pools  of  stagnant  water  in  marshy  districts. 
If  a  bottle  is  filled  with  water  and  inverted  with  a  funnel  in 
its  neck  in  such  a  pool,  some  of  the  gas  can  be  collected  by  hold- 
ing the  funnel  over  the  bubbles  rising  from  the  bottom.  It 
is  also  found  mixed  with  air,  in  coal  mines,  and  sometimes 
issues  from  the  earth,  together  with  other  gases,  from  petroleum 
weUs.     It  is  a  constituent  of  natural  gas. 

It  can  be  prepared 

(i)  By  treating  aluminium  carbide,  C3AI4,  with  water :  — 
CsAU  +  12  H2O  =  3  CH4  +  4  A1(0H)3. 

(2)  In  pure  condition  by  treating  magnesium  methyl  iodide 
HaCMgl,  with  water  (112)  :  — 

Mg<  J  ^'  +  HOH  =  CH4  +  Mg<^^. 

(3)  By  passing  hydrogen  over  a  heated  mixture  of  nickel  and 
carbon. 

(4)  By  reduction  of  carbon  monoxide  or  dioxide  with  calcium 
hydride,  or  by  heating  finely  divided  carbon  with  calcium 
hydride. 

(s)   By  direct  combination  of  carbon  and  hydrogen  at  1200°. 

It  is  formed  in  the  dry  distillation  of  wood  and  coal,  and  is 
hence  contained  in  coal  gas.  It  is  also  formed,  as  its  occurrence 
in  marshes  indicates,  by  the  decomposition  of  organic  matter 
under  water.  It  is  most  readily  made  in  the  laboratory  by 
heating  a  mixture  of  sodium  acetate  and  soda-lime :  — 

NaCjHsOz  -1-  NaOH  =  CH4  4-  NazCOs. 

It  will  be  shown  hereafter  that  many  organic  acids  break 
down  in  a  similar  way,  yielding  a  hydrocarbon  and  a  car- 
bonate. 


ETHANE,   DIMETHYL  23 

Properties.  Marsh  gas  is  colorless  and  has  a  pleasant  alli- 
aceous odor.  It  is  slightly  soluble  in  water,  but  not  so  much 
so  as  to  prevent  its  collection  over  water.  It  burns.  Its  mix- 
ture with  air  often  explodes  when  a  flame  is  applied.  This 
mixture  is  the  cause  of  some  of  the  explosions  in  coal  mines. 
In  mines  it  is  known  as  fire  damp.  The  explosion  is  due  to  the 
rapid  combustion  of  the  marsh  gas.  The  products  are  carbon 
dioxide  and  water :  — 

CH4  +  2  O2  =  CO2  +  2  H2O. 

Carbon  dioxide  is  known  to  the  miner  as  choke  damp  or  after 
damp. 

The  most  common  cause  of  explosions  in  coal  mines  is  coal 
dust.  The  explosion  is,  in  fact,  an  extremely  rapid  combustion 
of  the  carbon,  giving  carbon  monoxide  and  dioxide. 

Reagents,  in  general,  do  not  act  readily  upon  marsh  gas. 
Chlorine  in  sunlight  gradually  takes  the  place  of  the  hydrogen, 
forming  substitution  products  which  will  be  treated  of  under 
the  head  of  the  halogen  derivatives  of  methane.  The  simplest 
of  them  has  the  composition  represented  by  the  formula  CH3CI, 
and  is  known  as  chloromethane  or  methyl  chloride  (26). 

Ethane,  dimethyl,  C2H6.  —  Ethane  rises  from  the  earth  from 
some  of  the  gas  wells  in  the  regions  in  which  petroleum  occurs. 
It  is  also  found  dissolved  in  crude  petroleum. 

It  can  be  made  from  methane  by  introducing  a  halogen  and 
making  a  compound  like  chloromethane,  CHgCl.  As  the  cor- 
responding iodine  derivative  is  less  volatile,  it  is  used.  This 
iodomethane,  CH3I,  is  treated  with  zinc  or  sodium  in  some 
neutral  medium,  as,  for  example,  anhydrous  ether.  The  reac- 
tion which  takes  place  is  represented  thus :  — 

CH3I  +  CH3I  -H  2  Na  =  H3C— CH3  +  2  Nal. 

Hence  the  name  dimethyl. 

This  method  of  building  up  more  complex  from  simpler  hydro- 
carbons has  been  used  extensively;  and  it  is  well  adapted  to 
show  the  relations  between  the  substances  formed  and  the  sim- 
pler ones  from  which  they  are  made. 


24  METHANE   AND    ETHANE 

An  operation  of  the  kind  involved  in  the  above  mentioned 
preparation  of  ethane  is  called  a  synthesis.  The  essential 
feature  of  the  synthesis  is  the  formation  of  a  more  complex 
substance  from  simpler  ones.  Our  knowledge  of  the  structure 
of  the  compounds  of  carbon  is  largely  dependent  upon  the  use 
of  various  methods  of  synthesis.  For  example,  in  the  case 
under  consideration,  the  synthesis  gives  us  at  once  a  clear  view 
of  the  relations  between  ethane  and  methane,  and  also  suggests 
that  homology  may  be  due  to  similar  relations  between  the 
successive  members  of  the  series,  —  a  view  which  is  fully  con- 
firmed by  the  synthetical  preparation  of  the  higher  members. 
A  similar  method  of  synthesis  has  been  used  in  the  preparation 
of  sodium  tetrathionate  from  sodium  thiosulphate.  The  action 
is  represented  thus :  — 

Na2S203  NaSaOa 

+ 12  =        I       +2  Nal. 
Na2S203  NaS203 

Two  mols.  sodium  Sodium  tetra- 

tbiosulphate  thionate 

Properties.  Ethane  is  a  colorless,  tasteless  gas  with  an  agree- 
able ethereal  odor.  It  resembles  methane  very  closely  in  its 
chemical  and  physical  properties.  It  is  made  on  the  large  scale 
by  the  reduction  of  ethylene. 


CHAPTER   III 
HALOGEN  DERIVATIVES   OF  METHANE  AND   ETHANE 

Substitution. — When  methane  and  chlorine  are  brought  to- 
gether in  sunlight,  hydrochloric  acid  gas  is  given  off,  and  one 
or  more  compounds  are  obtained,  according  to  the  length  of 
time  the  action  continues. 

The  simplest  product  thus  obtained  has  the  composition 
CH3CI.    The  reaction  is  represented  by  the  equation  :  — 

CH4  +  CI2  =  CH3CI  +  HCl. 

The  result  is  the  substitution  of  one  atom  of  chlorine  for  one 
atom  of  hydrogen.  This  is  known  as  substitution.  The  action 
may  proceed  further  and  result  in  the  formation  of  a  second 
product  thus :  — 

CH3CI  +  CI2  =  CH2CI2  +  HCl. 

While  these  reactions  illustrate  the  phenomenon  of  sub- 
stitution in  its  simplest  form,  the  substitution  products  of 
methane  and  ethane  are  more  readily  made  by  other  methods. 

We  shall  find  that  most  hydrocarbons  react  with  the  halogens 
and  some  with  other  reagents,  such  as  nitric  acid,  sulphuric 
acid,  and  that  thus  a  large  number  of  derivatives  can  be  made, 
differing  from  the  hydrocarbons  in  that  they  contain  one  or 
more  halogen  atoms  or  complex  groups  in  the  place  of  the  same 
number  of  hydrogen  atoms.  It  must  be  borne  in  mind  that 
the  mere  fact  that  chlorine,  in  acting  upon  marsh  gas,  is  sub- 
stituted for  an  equivalent  quantity  of  hydrogen,  does  not 
prove  that  the  chlorine  in  the  product  occupies  the  same  place 
that  the  replaced  hydrogen  did.  Nevertheless,  a  careful  study 
of  all  the  facts  regarding  the  products  thus  formed  has  led  to 
the  belief  that  the  substituting  atom  or  residue  does  occupy 
the  same  place,  or  bear  the  same  relation  to  the  carbon  atom 
that  the  hydrogen  did. 

25 


26  DERIVATIVES   OF  METHANE  AND   ETHANE 

The  name  substitution  products  properly  includes  all  products 
made  from  the  hydrocarbons,  or  from  other  carbon  compounds, 
by  the  substitution  process.  The  principal  ones  are  those 
formed  by  the  action  of  the  halogens,  or  the  halogen  substitution 
products;  those  formed  by  the  action  of  nitric  acid,  or  the 
nitro  substitution  products;  and  those  formed  by  the  action  of 
sulphuric  acid,  or  the  sulphonic  acids. 

Chloromethane,  methyl  chloride,  CH3CI.  —  Chloromethane 
can  be  made  by  chlorinating  methane  (25)  or  by  the  action 
of  hydrochloric  acid  on  methyl  alcohol :  — 

H3COH  +  HCl  =  H3CCI  +  H2O. 

For  this  reason  it  is  called  methyl  chloride.  It  will  be  shown 
that  methyl  alcohol  is  methyl  hydroxide,  and  that  it  acts  to- 
wards acids  like  a  metallic  hydroxide. 

It  is  a  colorless  gas  having  an  ethereal  odor.  It  burns  with 
a  white  flame  bordered  with  green.  Boiling  point  —23.73°; 
soluble  in  water  and  alcohol.  Used  in  local  anaesthesia  and  as  a 
me  thy  la  ting  agent. 

Bromomethane,  methyl  bromide,  CHsBr.  —  This  is  made  from 
methyl  alcohol  by  the  action  of  hydrobromic  acid  or  by  treating 
the  alcohol  with  phosphorus  and  bromine :  — 

3  H3COH  +  PBra  =  3  CHaBr  +  P(0H)3. 

It  does  not  burn.  It  is  a  gas  readily  condensed  to  a  liquid. 
Boiling  point  4.5°. 

lodomethane,  methyl  iodide,  CH3I,  is  made  by  the  action  of 
hydriodic  acid  on  methyl  alcohol  or  by  treating  methyl  alco- 
hol with  phosphorus  and  iodine. 

It  is  a  colorless  liquid,  boiling  at  45°. 

Dichloromethane,  methylene  chloride,  CH2CI2.  —  Methylene 
chloride  is  made  from  chloroform  in  alcoholic  solution  by  the 
action  of  zinc  and  hydrochloric  acid :  — 

CHCI3  +  H2  =  CH2CI2  +  HCl. 

It  can  also  be  made  by  the  action  of  chlorine  on  methylene 
iodide :  — 

H0CI2  -I-  CI2  =  H2CCI2  +  I2. 


CHLOROFORM  27 

It  is  a  by-product  of  the  manufacture  of  chloroform  from  carbon 
tetrachloride.  It  boils  at  41.6°  and  is  used  as  a  solvent  in 
place  of  chloroform.     Specific  gravity,  1.432. 

Dibromomethane,  methylene  bromide,  CH2Br2.  —  Methylene 
bromide  is  made  by  the  action  of  bromine  on  methylene  iodide. 
It  boils  at  96.s°-97.s°  It  can  also  be  made  from  bromoform 
by  reverse  substitution. 

Diiodomethane,  methylene  iodide,  CH2l2.  —  Methylene 
iodide  boils  at  181°  with  partial  decomposition.  It  is  the  heaviest 
of  all  known  organic  liquids.  Specific  gravity,  3.33  at  18° 
It  is  made  from  iodoform,  triiodomethane,  CHI3,  by  reducing 
it  with  hydriodic  acid  and  phosphorus  :  — 

CHI3  +  HI  =  CH2I2  +  I2. 

The  phosphorus  combines  with  the  iodine  set  free  in  the 
reaction.  This  is  a  case  of  reverse  substitution,  hydrogen  being 
substituted  for  iodine. 

Chloroform,  CHCI3.  —  Chloroform  was  first  used  as  an 
anaesthetic  in  surgical  operations  by  Dr.  Simpson  of  Edinburgh 
in  1848.  It  decomposes  into  phosgene  and  hydrochloric  acid 
in  the  presence  of  light  and  air :  — 

HCCI3  +  0   =  OCCI2  +  HCl. 

Chloroform  Phosgene 

This  decomposition  is  said  to  be  prevented  by  the  presence  of 
a  small  amount  of  alcohol,  so  that  the  chloroform  of  commerce 
always  contains  from  0.6  to  i  per  cent  of  alcohol.  It  is  not  much 
used  as  an  anaesthetic  at  the  present  time  in  this  country ;  ether 
or  a  mixture  of  nitrous  oxide  gas,  oxygen  and  ether  has  taken 
its  place,  as  they  are  much  safer  than  chloroform.  Chloroform 
is  made  in  the  laboratory  from  alcohol  or  acetone,  water,  and 
bleaching  powder.  The  reactions  will  be  explained  under 
chloral  and  acetone.  It  has  an  ethereal  odor  and  a  sweet 
taste.  It  is  a  heavy  liquid,  specific  gravity  1.5,  and  is  some- 
what soluble  in  water  (7  grams  in  a  liter).  It  boils  at  61.2° 
and  solidifies  at  —63.2°.  Chloroform  is  an  excellent  solvent  for 
many  organic  compounds,  and  it  is  largely  used  for  this  purpose 


28  DERIVATI\'ES   OF   METHANE  AND   ETHANE 

and  for  cleaning  fabrics.  It  does  not  burn.  It  is  a  powerful 
antiseptic,  preventing  fermentation  and  putrefaction.  Chloro- 
form is  now  made  on  the  large  scale  from  carbon  tetrachloride 
by  reverse  substitution,  iron  and  water  being  used  to  furnish 
the  nascent  hydrogen :  — 

CCI4  +  H2  =  HCCI3  +  HCl. 

Carbon  Chloroform 

tetrachloride 

The  nascent  hydrogen  also  acts  on  some  of  the  chloroform  to 
give  methylene  chloride,  which  is  a  by-product  of  this  method :  — 

HCCI3  +  H2  =  H2CCI2  +  HCl. 

Bromoform,  CHBra.  —  Bromoform  is  made  from  alcohol  or 
acetone  by  the  action  of  bromine  and  an  alkali.  Boiling 
point  146°.  It  is  used  as  a  remedy  in  whooping  cough.  The 
bromoform  of  the  U.  S.  Pharmacopeia  contains  4  per  cent  by 
weight  of  absolute  alcohol. 

Iodoform,  CHI3.  —  Iodoform  is  used  extensively  in  surgery 
as  it  prevents  infection,  and  aids  in  the  healing  of  wounds. 
It  is,  however,  not  used  as  much  as  formerly.  It  is  made  from 
alcohol  or  acetone  by  the  action  of  iodine  in  the  presence  of  an 
alkali.  It  is  volatile  with  steam  and  evaporates  even  at  ordi- 
nary temperatures.  It  crystallizes  in  yellow,  hexagonal  plates 
that  melt  at  119°.  It  has  a  penetrating,  sweetish  odor  which 
is  noticed  in  hospitals  where  it  is  used.  It  is  an  unstable 
substance  and  decomposes  readily,  yielding  iodine  as  one  of 
its  products.  It  is  to  this  fact  that  it  owes  its  antiseptic 
property. 

Carbon  tetrachloride,  CCI4.  —  Carbon  tetrachloride  cannot 
be  made  by  the  action  of  chlorine  on  carbon,  although  fluorine 
acts  readily  on  carbon  to  form  carbon  tetrafiuoride.  It  can 
be  made  by  the  action  of  chlorine  on  chloroform  in  the  presence 
of  iodine :  — 

HCCI3  +  ICl  =  CCI4  +  HI. 

Chloroform        Iodine        Carbon 

chloride      tetrachloride 

HI  +  CI2  =  HCl  -I-  ICl. 


EQUIVALENCE   OF   HYDROGEN   ATOMS  29 

The  iodine  serves  as  a  chlorine  carrier.  It  first  combines  with 
the  chlorine  to  form  iodine  chloride.  This  then  reacts  with 
the  chloroform,  giving  carbon  tetrachloride  and  hydriodic  acid. 
The  hydriodic  acid  is  immediately  acted  upon  by  the  chlorine 
to  form  hydrochloric  acid  and  regenerate  iodine  chloride.  Thus 
it  will  be  seen  that  the  iodine  acts  as  a  chlorine  carrier  and,  as 
it  is  used  over  and  over  again,  only  a  very  small  amount  of  it 
need  be  present.  These  chlorine  carriers  are  much  used  in 
chlorinating  organic  compounds  and  are  sometimes  indispensa- 
ble. Thus  chlorine  acts  very  slowly  on  chloroform,  but  in  the 
presence  of  iodine  the  reaction  takes  place  readily. 

Carbon  tetrachloride  is  made  on  the  large  scale  by  the  action 
of  chlorine  on  carbon  bisulphide  in  the  presence  of  a  chlorine 
carrier :  — 

CS2  +  3  CI2  =  CCI4  +  S2CI2. 

Carbon  Carbon 

bisulphide  tetrachloride 

The  action  consists  in  the  substitution  of  chlorine  for  sulphur. 
The  carbon  bisulphide  is  made  by  the  action  of  sulphur  vapor  on 
red-hot  carbon.  Carbon  tetrachloride  is  a  colorless  liquid, 
having  an  odor  similar  to  that  of  chloroform  and  boiling  at 
76.74°.  It  is  an  excellent  solvent,  especially  for  fats,  rubber, 
etc.,  and,  as  it  is  non-inflammable,  it  is  much  used  for  the 
extraction  of  fats  and  the  removal  of  grease  spots.  It  is  also 
used  as  a  fire-extinguisher  under  the  name  of  Pyrene.  As  stated 
above,  chloroform  is  now  made  from  it  on  the  large  scale  by 
reverse  substitution. 

Equivalence  of  the  hydrogen  atoms  in  methane. — ^The  inter- 
esting question  suggests  itself  whether  the  hydrogen  atoms  in 
methane  all  bear  the  same  relation  to  the  carbon  atom.  Assum- 
ing that  the  carbon  atom  is  quadrivalent,  and  that  each  of  the 
four  hydrogen  atoms  is  in  combination  with  it,  as  indicated  in 

H(i) 

I 
the  formula  (4)  H — C — H  (2),  do  the  atoms  numbered  i,  2, 

I 
H(3) 


30  DERIVATIVES   OF   METHANE   AND   ETHANE 

3,  and  4  bear  the  same  relation  to  the  carbon  or  not?  If  they 
do  not,  then,  on  replacing  H  (i)  by  chlorine,  the  product  should 
be  different  from  that  obtained  by  replacing  H  (2),  H  (3),  or 
H  (4) ;  or,  it  should  be  possible  to  make  more  than  one  variety 
of  chloromethane  and  of  similar  products.  This  subject  is  an 
extremely  difficult  one  to  deal  with.  It  can  only  be  said  that, 
although  chloromethane  has  been  made  in  several  ways,  the 
product  obtained  is  always  the  same  one ;  and  the  same  is  true 
of  all  other  monosubstitution  products  of  methane.  So  far  as 
emdence  of  this  kind  goes,  we  have  no  reason  for  believing  that  there 
are  any  differences  between  the  hydrogen  atoms  of  methane. 

This  conclusion  is  of  fundamental  importance  in  dealing  with 
the  higher  members  of  the  methane  series,  and,  indeed,  in  deal- 
ing with  all  carbon  compounds. 

The  formula  on  page  29  represents  the  carbon  atom  and 
the  four  hydrogen  atoms  in  a  plane.  As  will  be  pointed  out 
later,  however,  there  is  experimental  evidence  showing  that 
the  hydrogen  atoms  are  in  fact  arranged 
symmetrically  in  space  around  the  carbon 
atom.  This  important  conception  is  rep- 
resented by  the  adjoining  figure. 

The  carbon  atom  is  represented  as  situ- 
ated at  the  centre  of  a  regular  tetrahedron 
and  the  four  hydrogen  atoms  at  the  solid 
angles  of  the  tetrahedron,  a,  b,  c,  and  d.     Thus  each  hydrogen 
atom  bears  the  same  relation  to  the  carbon  atom. 

Chloroethane,  ethyl  chloride,  C2H6CI. 
Bromoethane,  ethyl  bromide,  C2H6Br. 
lodoethane,  ethyl  iodide,         C2H6I. 

These  substances  are  all  liquids  having  pleasant  ethereal 
odors.  The  first  boils  at  12.5°,  the  second  at  38.37°,  and  the 
third  at  72°  They  are  most  readily  made  from  alcohol,  by 
treating  it  with  the  corresponding  halogen  acids.  The  bromide 
and  iodide  can  also  be  made  by  treating  the  alcohol  with  red 
phosphorus  arid  the  halogen.  The  action  is  similar  to  that 
involved  in  making  hydrobromic  acid  by  treatirig  water  with 


ISOMERISM  31 

red  phosphorus  and  bromine.  It  will  be  shown  that  alcohol  is 
a  hydroxide  in  which  hydroxy!,  OH,  is  in  combination  with 
the  group  C2H6,  called  ethyl,  as  represented  in  the  formula 
CsHbOH.  When  bromine  is  brought  in  contact  with  red 
phosphorus,  the  tribromide,  PBrs,  is  formed,  and  this  acts  upon 
the  alcohol  thus :  — 

CsHbOH   Br  ] 

C2H6OH  +  Br  P  =  3  CaHsBr  +  P(0H)3. 

CzHeOH      Br  J 

When  water  is  used  instead  of  alcohol,  the  bromine  appears  in 
combination  with  hydrogen  as  hydrobromic  acid :  — 

3  HOH  +  PBra  =  3  HBr  +  P(0H)3. 

Ethyl  chloride  and  ethylidene  chloride,  C2H4CI2,  are  by-products 
of  the  manufacture  of  chloral.  Ethyl  bromide  is  made  on  the 
large  scale  and  is  used  in  making  diethylaniline  and  other  ethyl 
derivatives. 

Among  the  many  halogen  substitution  products  of  ethane 
containing  more  than  one  halogen  atom,  two  are  of  special 
interest.  These  are  the  two  dichloroethanes ,  both  of  which  are 
represented  by  the  formula  C2H4CI2.  The  existence  of  these 
substances,  having  the  same  composition  but  different  properties, 
affords  a  good  example  of  isomerism. 

Isomerism.  —  One  of  the  most  striking  and  interesting  facts 
with  which  we  become  familiar  in  studying  carbon  compounds 
is  the  frequent  occurrence  of  two,  and  often  more,  compounds 
containing  the  same  elements  in  the  same  proportions  by  weight. 
Substances  which  bear  this  relation  to  one  another  are  said  to 
be  isomeric. 

Isomerism  is  of  two  kinds :  (i)  Compounds  may  have  the 
same  percentage  composition  and  the  same  molecular  weight. 
Such  compounds  are  said  to  be  metameric.  The  dichloroethanes, 
C2H4CI2,  for  example,  are  metameric.  (2)  Compounds  that  have 
the  same  percentage  composition  but  different  molecular  weights 
are  said  to  be  polymeric.  Benzene,  CeHe,  and  styrene,  CsHs, 
are  polymers  of  acetylene,  C2H2. 


32  DERIVATIVES  OF  METHANE  AND   ETHANE 

The  cause  of  isomerism  is  undoubtedly  to  be  found  in  the 
different  ways  in  which  the  atoms  of  isomeric  compounds  are 
linked  together.  Our  structural  formulas,  which  show  the 
relations  between  the  parts  of  compounds  that  have  been 
traced  out  by  a  study  of  the  chemical  conduct  of  these  com- 
pounds, give  us  an  insight  into  the  cause  of  isomerism.  To 
illustrate,  take  the  two  dichloroethanes.  One  of  these  is  made 
by  treating  ethane,  the  other  by  treating  eth^'lene,  C2H4,  with 
chlorine.     In  the  first  case  the  action  is  substitution. 

C.He  +  2  CI2  =  C2H4CI2  +  2  HCl. 

Ethane  Ethylidene 

chloride 

In  the  second,  the  chlorine  is  added  directly  to  ethylene,  thus :  — 

CH2        CI      H2CCI 

II        +        =        I 
CH2       CI      H2CCI. 

Ethylene  chloride 

The  product  from  ethylene  is  called  ethylene  chloride,  boiling 
point  83.5°;  that  from  ethane,  ethylidene  chloride,  boiling  point 
59.2°.     It  will  be  shown  that  ethylene  is  represented  by  the  for- 

CH2 

mula    1 1      ;  that  is,  it  is  unsaturated.     In  it  only  two  hydrogen 
CH2 

atoms  are  in  combination  with  each  of  the  carbon  atoms.  Now, 
if  chlorine  is  brought  in  contact  with  this  substance,  we  should 
naturally  expect  each  of  the  carbon  atoms  to  take  up  one  atom 
of  chlorine,  and  thus  to  become  saturated,  as  represented  in  the 
above  equation. 

Chlorine  is  taken  up,  and  it  is  believed  that  the  ethylene 
chloride  obtained  has  the  structure  represented  by  the  above 
formula,  the  distinctive  feature  of  which  is  that  each  of  the 
chlorine  atoms  is  in  combination  with  a  different  carbon  atom. 

We  can,  however,  conceive  of  another  possibility;  viz.,  both 
the  chlorine  atoms  may  be  in  combination  with  the  same  carbon 

HCCI2 
atom,  as  represented  in  the  formula      |         ,  and  we  should  be 

CH3 


HEXACHLOROETHANE  33 

inclined  to  the  view  that  this  represents  the  structure  of  ethyli- 
dene  chloride,  as  there  are  but  two  dichloroethanes  known  and 
possible  according  to  theory.  Fortunately  there  is  experimental 
evidence  to  support  this  view.     It  will  be  shown  that  aldehyde 

0=CH 

has  the  formula  |    .     When  aldehyde  is  treated  with  phos- 

CH3 

phorus  pentachloride,  two  chlorine  atoms  take  the  place  of  the 
oxygen : — 

H3C— C=0  +  PCl6  =  H3C— C=Cl2  +  OPCI3 

Aldehyde  Ethylidene  chloride 

A  product  that  must  be  represented  by  the  above  formula  is 
formed,  and  this  is  identical  with  ethylidene  chloride  made  from 
ethane.  Thus  it  will  be  seen  that  the  difference  between  the  two 
isomeric  compounds,  ethylene  chloride  and  ethylidene  chloride, 
is  due  to  the  fact  that  in  the  former  the  two  chlorine  atoms  are 
in  combination  with  different  carbon  atoms,  while  in  the  latter 
both  chlorine  atoms  are  in  combination  with  the  same  carbon 
atom. 

Hexachloroethane,  C2CI6,  a  solid,  is  a  by-product  of  the 
manufacture  of  chloroform  :  — 

2  CCI4  +  Fe  =  CI3C— CCI3    +  FeCl2. 

Its  odor  suggests  that  of  camphor. 

This  formation  of  hexachloroethane  is  analogous  to  the 
synthesis  of  ethane  from  methyl  iodide  and  sodium  (23). 

General  characteristics  of  the  halogen  derivatives  0}  methane 
and  ethane.  The  one  characteristic  to  which  it  is  desirable 
that  special  attention  should  be  called  is  the  condition  of  the 
halogens  in  these  compounds.  In  general,  chlorine  in  combina- 
tion in  inorganic  compounds  can  be  detected  by  means  of  a 
solution  of  silver  nitrate,  for  when  dissolved  in  water  these 
compounds  are  ionized.  The  halogen  substitution  products  of 
the  hydrocarbons  are  not  ionized  by  water,  and  the  chlorine 
in  them  cannot  be  detected  by  means  of  silver  nitrate  in  the 
ordinary  way.     On   the   other  hand,   when   chloromethane  is 


34  DERIVATI\-ES   OF  METILA.NE   AND   ETHANE 

heated  with  silver  nitrate  in  a  sealed  tube,  the  chlorine  is  re- 
placed :  — 

H3C— CI  +  AgNOs  =  AgCl  +  H3C— NO3. 

Methyl  chloride  Methyl  nitrate 

Sodium  and  zinc  have  the  power  of  extracting  the  chlorine, 
bromine,  etc.,  from  halogen  derivatives,  and  this  fact  is  taken 
advantage  of  in  the  synthesis  of  many  hydrocarbons  (23). 

All  halogen  derivatives  are  reduced  to  the  hydrocarbon 
from  which  they  are  derived  by  the  action  of  nascent  hydro- 
gen:— 

H3CCI  -h  H2  =  CH4  -H  HCl. 


CHAPTER   IV 

OXYGEN  DERIVATIVES  OF  METHANE  AND  ETHANE 

There  are  several  classes  of  oxygen  derivatives  of  the  hydro- 
carbons. Among  them  are  the  important  compounds  known 
as  alcohols,  ethers,  aldehydes,  and  acids.  Each  of  these  classes 
will  be  taken  up  in  turn. 

I.  Alcohols 

Among  the  most  important  oxygen  derivatives  are  the  alco- 
hols, of  which  methyl  alcohol  and  ethyl  alcohol  are  the  best- 
known  examples.  As  far  as  composition  is  concerned,  these 
compounds  bear  simple  relations  to  the  two  hydrocarbons, 
methane  and  ethane.  These  relations  are  indicated  by  the 
formulas :  — 

Hydrocarbons  Alcohols 

CH4  CH4O 

CaHe  C2H6O 

The  molecule  of  the  alcohol  differs  from  that  of  the  corresponding 
hydrocarbon  by  one  atom  of  oxygen.  In  order  to  understand 
the  chemical  nature  of  alcohols,  it  will  be  best  to  study  with 
some  care  the  reactions  of  one ;  and  we  may  take  for  this  purpose 
the  simplest  one  of  the  series,  methyl  alcohol. 

Methyl  alcohol,  carbinol,  methanol,  CH4O.  — This  alcohol  is 
also  known  as  wood  alcohol  or  wood  spirit.  It  is  found  in 
nature  in  combination  with  salicylic  acid  in  the  oil  of  winter- 
green.  It  is  formed,  together  with  many  other  substances, 
in  the  dry  distillation  of  wood.  When  wood  is  distilled  for  the 
purpose  of  making  charcoal  an  aqueous  distillate  is  obtained 
containing  methyl  alcohol,  acetic  acid,  and  acetone.  This  is 
the  source  of  methyl  alcohol  and  the  chief  source  of  acetic  acid 

35 


36  DERIVATIVES   OF   METHANE   AND   ETHANE 

and  acetone.  The  acetic  acid  is  neutralized  by  means  of 
milk  of  lime  and  the  methyl  alcohol  and  acetone  are  distilled 
off  from  the  aqueous  solution  and  separated  by  fractional 
distillation.  It  is  difficult  to  eliminate  all  the  acetone  by 
fractional  distillation  alone,  so  that  the  methyl  alcohol  of  com- 
merce generally  contains  some  acetone,  though  in  recent  years 
the  apparatus  used  for  fractional  distillation  has  been  so 
improved  that  meth>-l  alcohol  practically  free  from  acetone 
is  thus  obtained. 

Methyl  alcohol  is  a  liquid  that  boils  at  64.7°,  melts  at  —97.8°, 
and  has  the  specific  gra\'ity  0.81  at  0°.  It  closely  resembles 
ordinary  alcohol  in  all  its  properties.  It  burns  with  a  non- 
luminous  flame.  When  taken  into  the  system  it  intoxicates. 
It  is  poisonous.  Blindness  and  death  may  be  caused  by  its 
internal  use.  It  is  an  excellent  solvent  for  fats,  oils,  resins,  and 
other  organic  substances,  and  is  extensively  used  for  this  purpose, 
and  for  methylating  and  the  preparation  of  formaldehyde  and 
in  denaturing  alcohol. 

1.  Action  of  hydrochloric,  hydrobromic,  and  other  acids  on 
methyl  alcohol.  The  action  of  a  few  acids  is  represented  by  the 
following  equations :  — 

CH4O  +  HBr      =  CHaBr         +  H2O ; 

Methyl  bromide 

CH4O  -I-  HCl      =  CH3CI        +  H2O ; 

Methyl  chloride 

CH4O  +  HNO3  =  CH3NO5    +  H2O; 

Methyl  nitrate 

CH4O  +  H2SO4  =  CH3HSO4  +  H2O. 

Monomethyl 
sulphate 

The  action  is  plainly  suggestive  of  that  of  alkaline  hydrox- 
ides or  bases.  In  each  case  the  acid  is  either  wholly  or  partly 
neutralized  and  water  is  formed,  just  as  the  acid  would  be 
neutralized  by  potassium  hydroxide. 

2.  Action- oj  phosphorus  trichloride.  When  phosphorus  tri- 
chloride acts  on  methyl  alcohol,  the  products  are  chloromethane 
and  phosphorous  acid :  — 

3  CH4O  -I-  PCI3  =  3  CH3CI  +  PO3H3. 


METHYL  ALCOHOL,   CARBINOL,   METHANOL  37 

Here  one  atom  of  chlorine  is  substituted  for  an  atom  of  hydrogen 
an'd  an  atom  of  oxygen,  the  reaction  being  like  that  which 
takes  place  between  water  and  phosphorus  trichloride :  — 

3  H2O  +  PCI3  =  3  HCIH-  PO3H3. 

This  fact  would  lead  us  to  suspect  that  there  is  a  close  resem- 
blance between  the  alcohol  and  water. 

3.  Action  of  potassium  and  sodium.  When  potassium  is 
brought  in  contact  with  pure  methyl  alcohol,  hydrogen  is  given 
off,  and  a  compound  containing  potassium  is  formed  :  — 

CH4O  +  K  =  H3COK  +  H. 

Further  treatment  of  this  compound  with  potassium  causes  no 
further  evolution  of  hydrogen,  so  that  plainly  one  of  the  four 
hydrogen  atoms  contained  in  methyl  alcohol  differs  from  the 
other  three. 

The  resemblance  between  methyl  alcohol  and  the  alkaline 
hydroxides ;  the  substitution  of  chlorine  for  hydrogen  and 
oxygen ;  the  resemblance  between  the  alcohol  and  water ;  and, 
finally,  the  substitution  of  potassium  for  one,  and  only  one, 
hydrogen  atom,  lead  to  the  conclusion  that  the  alcohol  contains 
hydrogen  and  oxygen  in  combination,  and  that  the  characteristic 
reactions  are  due  to  the  presence  of  the  group  called  hydroxyl^ 
OH.  The  analogy  between  the  alcohol,  an  alkaline  hydroxide, 
and  water  is  shown  by  these  formulas :  alcohol,  H3COH ; 
hydroxide,  KOH;  water,  HOH.  Thus  water  appears  as  the 
type  of  both  the  hydroxide  and  the  alcohol,  and  they  may  be 
regarded  as  derived  from  water  by  substituting  the  methyl  group, 
CH3,  for  one  hydrogen  atom  in  the  case  of  the  alcohol,  and 
substituting  an  atom  of  the  metal  potassium  for  one  hydrogen 
atom  in  the  case  of  the  hydroxide.  Thus  methyl  alcohol  is 
methyl  hydroxide.  Or,  on  the  other  hand,  methyl  alcohol 
may  be  regarded  as  marsh  gas  in  which  one  of  the  hydrogen 
atoms  is  replaced  by  hydroxyl.  The  two  views  are  in  fact 
identical. 

To  test  the  correctness  of  this  view,  we  may  make  methyl 
alcohol  in  some  way  that  will  show  us  of  what  parts  it  is  made 


38  DERIVATIVES   OF  METHANE   AND   ETHANE 

up.     Thus,  we  may  start  with  marsh  gas,  and  introduce  a 
halogen,  as  bromine :  — 

CH4  +  Br2  =  CHaBr  +  HBr. 

Bromomethane 

Now,  when  bromomethane  and  silver  hydroxide  are  brought 
together,  reaction  takes  place  as  represented  in  the  equation:  — 

CHsBr  +  AgOH  =  CH3OH  +  AgBr, 

and  methyl  alcohol  is  formed.     This  furnishes  strong  evidence 
in  favor  of  the  view  expressed  in  the  formula  CH3OH. 

The  reactions  above  presented  show  that  the  part  of  methyl 
alcohol  that  corresponds  to  the  metal  in  the  hydroxide  is  the 
group  CH3.  This  it  is  which  enters  into  the  acids  in  place  of 
their  hydrogen,  and  this  remains  unchanged  when  potassium 
acts  upon  the  alcohol.  It  has  received  the  name  methyl.  Hence 
we  have  the  names  methyl  alcohol,  methyl  bromide,  methyl 

.  ether,  etc.  A  group  which,  like  methyl,  appears  in  a  number 
of  compounds  is  called  a  radical,  or  residue.     These  names  are 

'  intended  simply  to  designate  that  part  of  a  carbon  compound 
which  remains  unchanged  when  the  compound  is  subjected  to 
various  transforming  influences. 

The  two  most  characteristic  reactions  of  methyl  alcohol 
are :  (i)  its  power  to  form  salt-like  compounds  when  treated 
with  strong  acids ;  and  (2)  its  power  to  form  an  acid  containing 
the  same  number  of  carbon  atoms  when  oxidized. 

The  neutral  compounds  formed  with  strong  acids  correspond  to 
the  salts  of  the  metals,  only  they  contain  the  radical,  methyl,  CH3, 
in  place  of  the  metals.  They  are  called  ethereal  salts  or  esters. 
The  acid  formed  by  oxidation  of  methyl  alcohol, has  the  com- 
position expressed  by  the  formula  CH2O2,  and  is  known  as 
formic  acid.  It  contains  one  atom  of  oxygen  more  and  two 
atoms  of  hydrogen  less  than  the  alcohol  from  which  it  is  formed. 
It  will  be  shown  that  this  acid  is  the  first  member  of  an  important 
series  of  acids,  known  as  the  fatty  acids,  each  of  which  bears  the 
same  relation  to  a  hydrocarbon  containing  the  same  number  of 
carbon  atoms  that  formic  acid  bears  to  marsh  gas. 


FERMENTATION  39 

Ethyl   alcohol,    methyl    carbinol,    ethanol,    CH3.CH2.OH.  — 

Ethyl  alcohol  occurs  in  a  number  of  plants  in  the  free 
condition  and  in  the  form  of  ethyl  esters  of  organic  acids.  It 
also  occurs  in  small  quantity  in  rain  and  snow  and  in  the  atmos- 
phere. Fresh  bread  made  with  yeast  contains  a  small  quantity 
of  alcohol. 

This  is  the  best-known  substance  belonging  to  the  class  of 
alcohols.  It  is  known  also  by  the  names  spirit  0}  wine,  ordinary 
alcohol,  and  grain  alcohol. 

The  one  method  of  manufacture  upon  which  we  are  dependent 
for  alcohol  is  the  fermentation  of  sugar  solutions. 

Fermentation.  —  Whenever  a  plant  juice  containing  sugar 
is  left  exposed  to  the  air,  it  gradually  undergoes  a  change  by 
which  it  loses  its  sweet  taste.  Usually  the  change  consists 
in  a  breaking  down  of  the  sugar  into  carbon  dioxide  and  alcohol. 
The  equation :  — 

CsHizOe  =  2  CsHeO  +  2  CO2 

Sugar  Alcohol 

expresses  what  takes  place  in  the  process  which  is  known  as 
alcoholic  fermentation.  Ninety-five  per  cent  of  the  sugar  can 
be  converted  into  alcohol  and  carbon  dioxide.  It  has  been 
shown  that  fermentation  is  caused  by  the  presence  of  microorgan- 
isms, either  animal  or  vegetable.  These  organisms,  which  are 
known  as  ferments,  are  of  different  kinds,  and  cause  different 
kinds  of  fermentation  with  dififerent  products.  Among  them 
the  following  may  be  specially  mentioned  :  — 

1.  Alcoholic  or  vinous  fermentation.  This  is  caused  by  a 
vegetable  ferment,  saccharomyces  or  yeast.  The  ferment  con- 
sists of  small,  round  cells  arranged  in  chains.  The  products 
of  its  action  are  alcohol  and  carbon  dioxide. 

2.  Lactic  acid  fermentation.  This  is  due  to  a  vegetable 
ferment,  bacterium  lactis,  which  is  contained  in  sour  milk.  It 
has  the  power  of  transforming  sugar  into  lactic  acid. 

3.  Acetic  acid  fermentation.  This  is  due  to  a  peculiar  vege- 
table ferment,  bacterium  aceti,  which  oxidizes  alcohol  in  the  pres- 
ence of  air  to  acetic  acid.     The  chemical  changes  brought  about 


40  DERIVATIVES   OF   iMETHANE   AND   ETHANE 

by  these  organisms  are  due  to  the  action  of  enzymes,'  which  are 
produced  by  the  organisms.  The  enzyme  that  decomposes 
sugar  into  alcohol  and  carbon  dioxide  is  called  zymase. 

The  germs  of  various  ferments  are  in  the  air ;  and,  whenever 
they  find  favorable  conditions,  they  develop  and  produce  their 
characteristic  effects.  They  will  not  develop  in  a  solution 
of  pure  sugar.  The  sugar  from  which  alcohol  is  obtained  is 
not  ordinary  cane  sugar,  but  grape  sugar,  or  glucose,  and  fructose. 
In  order  that  the  ferment  may  grow,  there  must  be  present  in 
the  solution,  besides  the  sugar,  substances  which  contain  nitrogen 
and  inorganic  salts,  especially  phosphates  and  potassium  salts. 
These,  as  well  as  the  sugar,  are  contained  in  the  juices  pressed 
out  from  fruits,  and  hence  these  juices  readily  undergo  fermen- 
tation. 

In  the  manufacture  of  alcohol  a  solution  containing  sugar  is 
first  prepared  from  sugar  beets  or  molasses  or  from  some  kind 
of  grain  or  potatoes.  In  case  the  solution  contains  grape  sugar 
or  fruit  sugar,  this  undergoes  fermentation  directly  when  the 
yeast  is  added.  If  the  substance  in  solution  is  cane  sugar, 
this  is  first  changed  by  the  enzyme,  invertase,  present  in  the 
yeast  into  grape  sugar  and  fruit  sugar,  and  the  fermentation 
then  takes  place  as  in  the  first  case.  When  grain  (Indian  corn 
in  this  country)  or  potatoes  are  used,  the  starch  is  first  converted 
into  sugar  by  the  enzyme,  diastase,  of  the  malt. 

To  obtain  alcohol  from  fermented  liquids,  these  must  be  dis- 
tilled. The  alcohol  thus  obtained  contains  water  and  a  mixture 
of  other  alcohols  called  fusel  oil.  The  latter  can  be  removed 
partly  by  fractional  distillation,  and  the  last  portions  can  be 
got  rid  of  by  filtering  through  charcoal.  The  water  cannot  be 
removed  completely  by  fractional  distillation,  though  a  product 
containing  95-96  per  cent  of  alcohol  can  be  obtained  in  this  way. 
This  mixture  has  a  constant  boiling  point  (78.15°). 

Absolute  alcohol  is  ordinary  alcohol  from  which  the  water  has 
been  removed  by  means  of  some  dehydrating  agent,  as  quick- 
lime, barium  oxide,  or  benzene.  By  continued  treatment  with 
freshly  burned  lime  the  quantity  of  water  can  be  reduced  to 
'  The  Nature  of  Enzyme  Action:  W.  M.  Bayliss,  4th  ed. 


DENATURED   ALCOHOL  41 

less  than  one-half  per  cent,  and  this  small  quantity  can  be  re- 
moved by  treatment  with  metallic  sodium  or  calcium. 

On  the  large  scale  the  dehydrating  agent  used  is  benzene. 
The  ternary  mixture  (water,  alcohol,  and  benzene)  boils  at 
64.85°  and  comes  over  first.  If  there  is  more  than  sufficient 
benzene  to  carry  over  all  the  water,  and  if  the  alcohol  is  present 
in  excess,  the  ternary  mixture  will  be  followed  by  the  binary 
mixture  (alcohol  and  benzene,  b.  p.  68.25°)  ^nd  the  last  sub- 
stance to  come  over  will  be  absolute  alcohol  (b.  p.  78.3°)  free 
from  water  and  benzene.' 

Ethyl  alcohol  has  a  spirituous,  pleasant  odor.  It  is  claimed, 
however,  that  absolutely  pure  anhydrous  alcohol  has  no  odor. 
It  remains  liquid  at  low  temperatures,  but  it  has  been  converted 
into  a  solid  which  melts  at  — 117.3°.  It  boils  at  78.37°  at  760"™ 
Like  methyl  alcohol  it  burns  with  a  non-luminous  flame,  which 
does  not  leave  a  deposit  of  soot  on  substances  placed  in  it. 
It  is  very  hygroscopic.  When  mixed  with  air,  its  vapor  explodes 
when  a  flame  is  applied.  Its  effects  upon  the  human  system 
are  well  known.  It  intoxicates  when  taken  in  dilute  form, 
while  in  concentrated  form  it  is  poisonous.  When  taken  in- 
ternally in  large  doses,  it  lowers  the  temperature  of  the 
body  from  0.5°  to  2°,  although  the  sensation  of  warmth  is 
experienced. 

Denatured  alcohol.  —  Alcohol  to  which  something  has  been 
added  to  make  it  unfit  for  use  as  a  beverage  can  be  withdrawn 
from  bond  for  use  in  the  industries  without  payment  of  the 
internal  revenue  tax  on  alcohol.  Such  alcohol  is  caUed  denatured  ■ 
alcohol.  Various  substances  are  employed  as  denaturing  agents. 
Among  those  authorized  by  the  United  States  government  are 
methyl  alcohol,  benzine,  and  pyridine  bases.  Completely 
denatured  alcohol  contains  methyl  alcohol  and  benzine  or  methyl 
alcohol  and  pyridine  bases.  This  is  used  as  a  source  of  heat, 
in  gas  engines  in  place  of  gasolene,  and  as  a  solvent  in  the  puri- 
fication and  preparation  of  a  large  number  of  pharmaceutical 
products,  dyestuffs,  etc.,  and  in  the  preparation  of  collodion, 
celluloid,  and  smokeless  powders. 

'  See  Distillation :  Processes  and  Principles,  by  Sidney  Young. 


42  DERIVATIVES   OF   METHANE   AXD   ETHANE 

Alcohol  for  scientific  work.  —  Educational  institutions  have 
the  privilege  of  withdrawing  ethyl  alcohol  from  bond  for  use  in 
scientific  work  and  in  teaching,  without  the  payment  of  the  tax. 

Alcoholic  beverages.  —  Most  of  the  alcohol  manufactured  at 
the  present  time  is  used  (except  in  the  United  States)  in  the 
form  of  beverages. 

The  milder  forms  of  beer  contain  from  2  to  3  per  cent ;  light 
wines,  such  as  claret,  about  8  per  cent ;  while  whisky,  brandy, 
rum,  and  other  distilled  liquors  sometimes  contain  as  much  as 
60  to  75  per  cent.  These  distilled  liquors  are  ordinary  alcohol 
with  water  and  small  quantities  of  substances  obtained  from  the 
fruit  or  grain  used  in  their  preparation,  or  obtained  by  standing 
in  barrels  made  of  oak  wood.  The  flavors  of  the  beverages  are 
due  to  these  substances. 

Chemical  conduct  of  ethyl  alcohol.  Ethyl  alcohol  conducts 
itself  chemically  like  methyl  alcohol.  The  products  formed 
contain  the  radical,  ethyl,  C2H6,  instead  of  methyl. 

Reactions  of  ethyl  alcohol.  With  acids  it  forms  ethereal  salts 
or  esters :  — 

CjHsOH  +  HCl        =  CjHsCl  +  H2O. 

Ethyl  chloride 

C2H6OH  +  HNO3        =  C2H6NO3         +  H2O. 

Ethyl  nitrate 

CjHsOH  +  ^>S04    =  *^'^'>S04  +  H2O. 

Monoethyl  sulphate 

With  phosphorus  trichloride  the  hydroxyl  group  is  replaced  by 
chlorine :  — 

3  C2H5OH  +  PCI3  =  3  CaHsCl  +  PO3H3. 

A  similar  reaction  takes  place  with  phosphorus  tribromide 
and  with  phosphorus  and  iodine,  giving  ethyl  bromide  and  ethyl 
iodide. 

The  ethyl  chloride  formed  in  the  reactions  above  represented 
is  identical  with  the  chloroethane  formed  by  the  action  of  chlorine 
on  ethane  :  — ■ 

C2H6  +  CI2  =  C2H5CI  +  HCl. 

Chloroethane 


ETHERS  ,  43 

Potassium  and  sodium  react  readily  with  the  alcohol  in  the 
cold,  forming  ethylates  :  — 

C2H5OH  +  Na  =  CjHeONa  +  H. 

Sodium  ethylate 

As  in  the  case  of  methyl  alcohol  only  one  atom  of  hydrogen  is 
replaced  by  the  metal  —  the  one  combined  with  the  oxygen. 

Finally,  alcohol  can  be  made  synthetically  from  ethane  by 
first  making  chloroethane  and  then  heating  with  water :  — 

CjHsCl  +  HOH  =  CjHeOH  +  HCl. 

Chloroethane  Ethyl  alcohol 

All  these  reactions  indicate  that  ethyl  alcohol  is  made  up  of 
the  radical  ethyl,  C2H6,  joined  to  hydroxyl,  OH,  or  that  it  is 
ethane  in  which  one  hydrogen  atom  is  replaced  by  a  hydroxyl 

CH3 

group.     Its  structural  formula  is  therefore  |       .     It  will  be  seen 

H2COH 
that  it  is  methyl  alcohol  in  which  a  methyl  group,  CH3,  is 
substituted  for  a  hydrogen  atom  of  the  original  methyl  group. 
It  is  hence  called  methyl  carbinol. 

When  oxidized,  ethyl  alcohol  gives  acetic  acid,  C2H4O2.  This 
is  the  reason  why  cider  or  wine  changes  to  vinegar  when  exposed 
to  the  air.  Methyl  and  ethyl  and  other  radicals  of  the  marsh 
gas  series  are  called  alkyl  groups. 

2.    Ethers 

When  an  alcohol  is  treated  with  potassium  or  sodium,  com- 
pounds are  formed  having  the  formulas  CHsONa,  CH3OK, 
C2H5OK,  C2H60Na.  If  sodium  methylate,  CHgONa,  is  treated 
with  a  monohalogen  derivative  of  a  hydrocarbon,  as,  for  example, 
iodomethane,  CH3I,  reaction  takes  place  thus :  — 

CH30Na  +  CH3I  =  C2H6O  +  Nal. 

This  reaction  shows  that  the  product  must  be  represented 
by  the  formula  H3C— O— CH3,  or  (CH3)20  It  is  dimethyl 
oxide  and  is  isomeric  with  ethyl  alcohol.  Comparing  it  with 
methyl  alcohol,  it  will  be  seen  that  it  is  obtained  from  the  alcohol 


44  DERIVATIVES   OF   METHANE   AND   ETHANE 

by  replacing  the  hydrogen  of  the  hydroxyl  by  rneth}'!,  CH3. 
Just  as  the  alcohol  is  analogous  to  the  hydroxide,  KOH,  so  the 
dimethjd  oxide  is  analogous  to  the  oxide,Jti^0.  It  is  the  first 
representative  of  a  class  of  compounds  'known  as  ethers,  which 
are  analogous  to  the  oxides  of  the  univalent  metals. 

Dimethyl  ether,  C2H6O,  (CH3)20,  is  a  gas  readily  condensed 
to  a  liquid,  boiling  at  -23.6°,  freezing  point  -138.5°.  It 
acts  as  an  anaesthetic.  One  volume  sulphuric  acid  absorbs 
600  volumes  dimethyl  ether.  This  ether  is  made  by  the 
action  of  sulphuric  acid  on  methyl  alcohol.  It  is  more 
soluble  in  water  than  ethyl  ether.  It  is  obtained  on  the 
large  scale  as  a  by-product  of  the  manufacture  of  dimethyl- 
aniline  (346). 

Ethyl  ether,  C4H10O,  (C2H6)20. — This  is  the  substance 
commonly  known  as  ether,  or  sulphuric  ether.  The  latter  name 
is  given  to  it  because  sulphuric  acid  is  used  in  its  manufacture. 
It  is  the  most  important  representative  of  the  class,  and  has  been 
known  since  the  first  half  of  the  sixteenth  century.  Ether 
can  be  made  from  alcohol  by  making  the  sodium  derivative  of 
alcohol,  C2H60Na,  and  heating  this  with  iodoethane- thus  :  — 

CjHsONa  +  C2H5I  =  (C2H5)20  +  Nal; 

or  by  converting  the  alcohol  into  ethyl  iodide  and  heating  this 
with  silver  oxide  :  — 

2  C2H5I  -f-  Ag20   =   (C2H5)20  +  2  A'gl. 

Ether  is  made  on  the  large  scale  by  heating  sulphuric  acid 
and  alcohol  in  certain  proportions,  and  then  distilling  the 
mixture  with  more  alcohol  as  described  below.  Two  distinct 
reactions  are  involved  in  this  process.  First,  when  alcohol 
and  sulphuric  acid  are  brought  together,  half  the  hydrogen 
of  the  acid  is  replaced  by  ethyl,  thus  :  — 

C2H5OH  +  H>S04  =  '^^^>SOi  +  H2O. 

The  product  formed  is  called  ethylsulphuric  acid  (monoeihyl 
sulphate) . 


ETHYL   ETHER  45 

When  ethylsulphuric  acid  is  lieated  to  about  130°  with 
alcohol,  ether  is  formed,  and  sulphuric  acid  is  regenerated :  — 

C2H5OH  +  "^^Hs^go,  =  ^=J?s>0  +  H2SO4. 

The  ether  thus  formed  distils  over ;  and,  if  alcohol  is  admitted 
to  the  mixture,  ethylsulphuric  acid  will  again  be  formed,  and 
with  excess  of  alcohol  it  will  yield  ether.  The  process  is  a  con- 
tinuous one,  a  small  amount  of  sulphuric  acid  converting  a  large 
amount  of  alcohol  into  ether. 

Ether  is  a  colorless  liquid  of  characteristic  odor  and  taste. 
It  boils  at  34.49°.  It  melts  at  —117.6°.  Specific  gravity, 
0.71994  at  15°. 

When  its  vapor  is  mixed  with  air,  the  mixture  explodes 
violently  when  a  flame  is  applied.  Ether  is  somewhat  soluble 
in  water,  and  water  is  also  somewhat,  though  less,  soluble  in 
ether ;  so  that  when  the  two  are  shaken  together  the  volume  of 
the  ether  becomes  smaller,  even  though  every  precaution  is 
taken  to  avoid  evaporation.  Ether  mixes  with  alcohol  in  all 
proportions.  It  is  a  good  solvent  for  resins,  fats,  alkaloids, 
and  many  other  classes  of  carbon  compounds. 

It  is  frequently  used  to  extract  substances  from  aqueous 
solutions.  It  is  used  technically  in  the  manufacture  of  collodion 
and  in  the  purification  of  gun  cotton. 

It  is  an  excellent  anaesthetic,  and  is  used  extensively  for  this 
purpose.  It  was  first  used  as  an  anassthetic  by  Dr.  Morton,  a 
dentist  of  Boston,  Mass.,  in  1846.  When  ether  is  brought  upon 
the  skin  in  the  form  of  spray,  the  cold  produced  by  the  rapid 
evaporation  is  so  great  as  to  cause  insensibility  to  pain. 

Manufacture  of  ether.  A  mixture  of  5  parts  of  alcohol  (90 
to  95  per  cent)  and  9  parts  of  concentrated  sulphuric  acid  is 
heated  in  a  still  to  127.5".  Ether,  water,  and  some  alcohol 
distil  over.  Alcohol  is  run  into  the  hot  mixture  in  the  still, 
so  that  the  volume  remains  constant  and  the  temperature  is 
kept  at  127.5°.  Ether  and  water  distil  over.  The  crude  ether 
contains  some  sulphur  dioxide.  It  is  washed  with  a  solution 
of  soda  to  remove  this,  and  freed  from  alcohol  and  water  by 


46  DERIVATIVES   OF   METHANE   AND   ETHANE 

distillation.  This  is  the  ether  of  commerce,  used  for  most 
technical  purposes.  To  remove  all  the  water  and  alcohol  the 
ether  is  distilled  over  sodium  which  combines  with  the  water 
and  the  alcohol. 

Chemical  conduct  of  ether.  Heated  to  150°  in  a  sealed  tube 
with  water  containing  a  small  amount  of  hydrochloric  acid 
ether  is  converted  into  alcohol :  — 

(C2H5)20  +  H2O  =  2  C2H5OH. 

Treated  with  hydriodic  acid,  alcohol  and  iodoethane  or  iodo- 
ethane  and  water  are  formed :  — 

(C2H6)20  +  HI  =  CaHsOH  +  CaHjI. 

(C2H5)20    +    2  HI    =    2    C2H6I    +  H2O. 

Mixed  ethers.  —  Just  as  ethyl  alcohol  yields  ethyl  ether, 
and  methyl  alcohol  yields  methyl  ether,  (CH3)20,  by  modifying 

C  H 

the  method,  a  mixed  ether,  methyl  ethyl  ether,    1,    ^>0,   can 

CH3 

be  obtained.     This  is  formed  by  treating  sodium  methylate 

with   iodoethane,  or  by  treating  sodium   ethylate  with  iodo- 

methane :  — 

CHsONa  +  C2H5I  =  S,'2'>0  +  Nal; 

(^±13 

CjHsONa  +  CH3I  =  S,'2'>0  +  Nal. 

It  is  formed  also  by  distilling  methyl  alcohol  with  ethylsulphuric 
acid,  or  ethyl  alcohol  with  methylsulphuric  acid  :  — 

^  H>0  +''^  H>SO^  =  CH;>0  +  H^SO.; 

™>o  +  c^>sa  =  ^^>o  +  H2S0.. 

Methyl  ethyl  ether  is  very  similar  to  ordinary  ether  in  its 
properties  and  reactions. 

Note  tor  Student.  Write  out  the  reactions  of  methyl  ethyl  ether 
with  water  and  with  hydriodic  acid.  In  the  first  reaction  with  hydriodic 
acid  the  methyl  group  combines  with  the  iodine. 


Hydrocarbons 

Alcohols 

CH4 

CH4O 

C2H6 

CaHeO 

FORMIC  ALDEHYDE,   FORMALDEHYDE  47 

3.   Aldehydes 

It  has  been  stated  above  that  when  methyl  and  ethyl  alcohols 
are  oxidized,  they  are  converted  into  acids  having  the  formulas 
CH2O2  and  C2H4O2,  respectively.  By  regulating  the  oxidation, 
products  can  be  obtained  intermediate  between  the  alcohols 
and  acids,  and  differing  from  the  alcohols  by  two  atoms  of 
hydrogen.  These  products  are  called  aldehydes,  from  alcohol 
dehydrogenatum,  from  the  fact  that  they  must  be  regarded 
as  alcohols  from  which  hydrogen  has  been  abstracted.  The 
relations  in  composition  between  the  hydrocarbons,  alcohols, 
aldehydes,  and  acids  are  shown  by  these  formulas :  — 

Aldehydes  Acids 

CH2O  CH2O2 

C2H4O  C2H4O2 

Formic  aldehyde,  formaldehyde,  methanal,  CH2O.  -^  This 
aldehyde  is  made  by  passing  the  vapor  of  methyl  alcohol  to- 
gether with  air  over  heated  copper  or  silver  wire  gauze  and 
collecting  the  gas  in  water :  — 

CH4O  +  O  =  H2CO  +  H2O. 

Methyl  alcohol  Fonnaldehyde 

At  ordinary  temperatures  it  is  a  gas,  which  condenses  when 
cooled  to  a  liquid  boiling  at  —21°.  It  is  manufactured  on  the 
large  scale,  and  comes  into  the  market  in  solution  in  water  under 
the  name  of  formalin  and  in  the  form  of  its  solid  polymer. 
Formalin  contains  from  35  to  40  per  cent  of  formaldehyde. 

It  is  used  in  the  manufacture  of  dyes  (indigo,  fuchsin,  etc.), 
and  pharmaceutical  preparations  (urotropine,  formamint,  etc.). 
On  account  of  its  germicidal  powers  it  is  very  largely  used  as  a 
disinfectant  and  as  a  preservative.  It  is  also  used  in  tanning, 
especially  in  the  manufacture  of  sole  leather,  in  waterproofing 
paper  and  textiles,  and  in  the  dyeing  of  fabrics ;  further,  in 
photography  for  hardening  the  films,  and  recently  in  the 
manufacture  of  synthetic  resins  and  plastics  (Bakelite  and 
Condensite  from  phenol  and  formaldehyde).  These  synthetic 
resins  are  used  in  the  manufacture  of  phonograph  records  and 


48  DERIVATIVES   OF   METHANE   AND   ETHANE 

for  many  other  purposes.     Formaldehyde  is  also  used  in  makm| 


mirrors. 


Although  known  since  1869,  formaldehyde  did  not  obtam  tech 
nical  importance  until  1 893  when  it  was  first  produced  on  the  largi 
scale.  Since  that  time  it  has  become  one  of  the  most  importan 
organic  compounds,  and  new  uses  for  it  are  constantly  bemj 
found.  When  its  solution  in  water  is  evaporated,  a  solid  sub 
stance  having  the  same  composition  as  formic  aldehyde  is  ob 
tained.  This  is  a  polymeric  variety,  and  is  represented  by  th( 
formula  (CH20)j:.  It  is  called  paraformaldehyde.  When  heatec 
it  gives  formaldehyde. 

In  order  to  gain  a  clearer  insight  into  the  nature  of  the  aide 
hydes,  it  will  be  best  to  study  acetic  aldehyde,  the  member  o 
the  group  that  has  been  longest  known. 

Acetic  aldehyde,  ethanal,  C2H4O.  — This  aldehyde  is  formec 
whenever  alcohol  is  brought  in  contact  with  an  oxidizing  mix 
ture,  as,  for  example,  potassium  bichromate  and  dilute  sul 
phuric  acid :  — 

C2H6O  +  O  =  C2H4O  +  H2O. 

Acetic  aldehyde  can  be  made  by  the  action  of  water  on  ethyli 
dene  chloride :  — 

TT  TT 

CH3— c/      +  H2O  =  CHs— c/    +  2HCI.  ■ 

^Cl2  X) 

Etbylidene  chloride  Aldehyde 

Aldehyde  has  been  made  commercially  from  acetylene  : — 
C2H2  +  H2O  =  C2H4O. 

Acetylene  Aldehyde 

Large  quantities  of  aldehyde  are  now  obtained  by  fractiona 
distillation  of  the  first  runnings  from  the  rectification  of  crud 
wood  alcohol.     (See  also  165.) 

Aldehyde  is  a  colorless  liquid,  boiling  at  20.8°.  It  mixes  wit! 
water  and  alcohol  in  all  proportions.  Its  odor  is  marked  ani 
characteristic. 

From  the  chemical  point  of  view,  the  most  characteristi 
property  of  aldehyde  is  its  power  to  unite  directly  with  othe 


METALDEHYDE  49 

substances.  It  unites  with  o:!i;ygen  to  form  acetic  acid ;  with 
hydrogen  to  form  alcohol ;  with  ammonia  to  form  aldehyde 
ammonia,  C2H4O.NH3 ;  with  hydrocyanic  acid  to  form  aldehyde 
hydrocyanide,  C2H4O.HCN;  with  the  acid  sulphites  of  the 
alkali  metals,  forming  compounds  represented  by  the  formulas 
C2H4O.HKSO3  and  C2H40.HNaS03 ;  and  with  other  substances. 
Indeed,  if  left  to  itself,  it  readily  changes  into  polymeric  modi- 
fications, uniting  with  itself  to  form  more  complex  compounds, 
paraldehyde  and  metaldehyde. 

Paraldehyde,  C6H12O3.  —  This  is  formed  by  adding  a  drop 
of  concentrated  sulphuric  acid  to  aldehyde,  which  causes  the 
liquid  to  become  hot.  On  cooling  to  0°,  paraldehyde  solidifies 
in  crystalline  form.  When  pure  it  melts  at  12.59°,  dissolves 
in  eight  times  its  own  volume  of  water,  and  boils  at  123-124°. 
When  distilled  with  sulphuric  acid,  hydrochloric  acid,  etc.,  it 
is  converted  into  aldehyde.  The  weight  of  22.4  liters  of  its 
vapor  has  been  found  to  be  132.4,  which  means  that  its  molecu- 
lar weight  is  132.4,  and  consequently  its  formula  is  (C2H40)3. 
It  is  a  polymeric  modification  of  aldehyde.  It  is  used  in  medi- 
cine as  an  hypnotic  and  in  the  preparation  of  organic  substances. 
Paraldehyde  is  the  form  in  which  aldehyde  is  bought  and 
sold. 

Metaldehyde.  —  Metaldehyde  is  formed  together  with  par- 
aldehyde, at  a  low  temperature  (below  0°)  by  the  action  of  hydro- 
chloric acid  gas.  It  crystallizes  in  needles,  which  are  insoluble 
in  water,  and  but  slightly  soluble  in  alcohol,  chloroform,  and  ether 
in  the  cold,  though  more  readily  at  a  slightly  elevated  tempera- 
ture. When  heated  to  200°  in  a  sealed  tube,  it  is  completely 
converted  into  aldehyde.  Determinations  by  the  freezing  point 
method  show  that  the  molecular  weight  of  metaldehyde  in 
phenol  corresponds  to  the  formula  (C2H40)4.  Distilled  with 
dilute  sulphuric  acid,  metaldehyde  is  converted  into  aldehyde. 

Aldehyde  is  a  strong  reducing  agent.  When  added  to  an 
ammoniacal  solution  of  silver  nitrate,  metallic  silver  is  deposited 
on  the  walls  of  the  vessel  in  the  form  of  a  brilliant  mirror.  It 
is  used  commercially  for  making  mirrors. 

Chemical  transformations  of  aldehyde.     As  aldehyde  is  pro- 


50  DERIVATI\'ES   OF   METHANE   AND    ETHANE 

duced  from  alcohol  by  oxidation,   so  alcohol  can  be  formed 
from  aldehyde  by  reduction :  — 

CaHeO  +  O    =  C2H4O  +  H2O ; 
C2H4O  +  H2  =  C2H6O. 

By  oxidation  aldehyde  is  converted  into  an  acid  of  the  formula 
C2H4O2,  which  is  acetic  acid :  — 

C2H4O  +  O    =  C2H4O2. 

Treated  with  phosphorus  pentachloride,  aldehyde  yields 
ethylidene  chloride,  C2H4CI2  (34).  This  reaction  is  of  special 
interest  and  importance,  as  it  helps  us  to  understand  the  relation 
between  aldehyde  and  alcohol.  Alcohol,  as  has  been  shown, 
is  ethyl  hydroxide,  C2H5.OH.  When  oxidized  it  loses  two 
atoms  of  hydrogen.  Is  the  hydrogen  of  the  hydroxyl  one  of 
the  two  which  are  given  off?  If  so,  what  readjustment  of  the 
oxygen  takes  place?  Such  are  the  questions  that  suggest 
themselves. 

To  understand  the  action  of  phosphorus  pentachloride  on 
aldehyde,  it  will  be  necessary  to  examine  briefly  the  action  of 
this  reagent  upon  compounds  containing  oxygen.  When  it  is 
brought  in  contact  with  water,  the  change  is  represented  by 
the  equation :  — 

HOH  +  PCls  =  POCI3  +  2  HCl. 

The  phosphorus  pentachloride  gives  up  two  atoms  of  chlorine 
and  takes  up  oxygen  in  its  place. 

Now,  when  phosphorus  pentachloride  is  brought  together 
with  an  alcohol,  a  substituted  water,  a  similar  reaction  takes 
place :  — 

C2H6.OH  +  PCI5  =  C2H6CI  +  POCI3  +  HCl. 

Ethyl  chloride 

Hydrochloric  acid  is  given  off,  and  ethyl  chloride  is  formed, 
which  is  regarded  as  alcohol  in  which  one  chlorine  atom  takes 
the  place  of  the  hydroxyl.  This  is  the  kind  of  action  that  takes 
place  whenever  a  chloride  of  phosphorus  acts  upon  a  compound 
containing  hydroxyl ;  and  hence  the  reaction  is  made  use  of  for 
determining  whether  hydroxyl  is  present  in  a  compound. 


METALDEHYDE  $1 

When  aldehyde  is  treated  with  phosphorus  pentachloride,  the 
action  is  entirely  different  from  that  just  described.  Instead 
of  one  chlorine  atom  taking  the  place  of  a  hydrogen  and  an 
oxygen  atom,  two  chlorine  atoms  take  the  place  of  the  oxygen 
atom:  —         ^^^^  _^  ^^^^  ^  C2H4CI2  +  POCI3. 

Ethylidene  chloride 

If  the  explanation  above  offered  of  the  action  of  phosphorus 
pentachloride  on  water  and  on  alcohol  is  correct,  it  follows  that 
aldehyde  is  not  a  hydroxyl  compound.  We  can  readily  under- 
stand why  two  chlorine  atoms  should  take  the  place  of  the  oxygen 
atom,  if  the  latter  is  in  combination  only  with  carbon  as  in  the 
group  >C0.  There  is  an  essential  difference  between  this 
kind  of  combination  and  that  which  we  have  in  hydroxyl  as 
=  C — 0 — H.  In  the  latter  condition  the  oxygen  serves  to  con- 
nect carbon  with  hydrogen ;  in  the  former  it  is  in  combination 
only  with  the  carbon,  and,  presumably,  the  energy  which  holds 
it  can  also  hold  two  atoms  of  chlorine  or  of  any  other  univalent 
element  with  which  it  can  unite.  So  that,  if  oxygen  is  present 
in  a  compound  combined  only  with  carbon,  we  should  expect 
two  chlorine  atoms  to  take  its  place  when  the  compound  is 
treated  with  phosphorus  pentachloride.  Let  R2CO  represent 
any  such  compound ;  then  we  should  have :  — 

R2CO  -1-  PCle  =  R2CCI2  +  POCI3; 

while,  when  oxygen  is  present  in  the  hydroxyl  condition,  we 
should  have :  — 

R3C— 0— H  +  PCIb  =  R3CCI  -I-  POCI3  +  HCl. 

Just  as  the  latter  reaction  is  used  to  detect  the  presence  of 
hydroxyl  oxygen,  so  the  former  is  used  to  detect  oxygen  in  the 
other  condition,  which  is  commonly  known  as  the  carbonyl 
dondition. 

In  terms  of  the  valence  hypothesis,  it  is  said  that  in  the 
hydroxyl  compounds  oxygen  is  in  combination  with  carbon  with 
one  of  its  affinities,  and  with  hydrogen  with  the  other,  while 
in  the  carbonyl  compounds  it  is  in  combination  with  carbon  with 
both  its  affinities  as  represented  thus,  >  C^O. 


52 


DERI\'ATIVES  OF  METHANE  AND   ETHANE 


According  to  the  above  reasoning  aldehyde  is  a  carbonyl 
compound,  or  it  contains  the  bivalent  group  >C=0.  The 
simplest  aldehyde  must  therefore  be  represented  by  the  formula 
HzC^O.  Its  homologue,  acetic  aldehyde,  is  CHs-HC^O. 
The  characteristic  properties  of  aldehyde  are  due  to  the  pres- 
ence of  this  group,  — HC^O,  which  is  called  the  aldehyde 
group.  That  aldehyde  does  not  contain  a  hydroxyl  group 
is  also  shown  by  the  fact  that  it  does  not  form  esters  with  acids 

as   alcohol  does.     That  the  formula  CHs.C^^      is  in  accord 

with  the  chemical  conduct  of  aldehyde  is  shown  by  the  reactions 
represented  below :  — 


CH3— C<      +  O 


CH; 


'-< 


OH 
O 


Acetic  acid 

CH3— C<     +  H2 
^0 

=  CH3— C^H 

Xh 

Ethyl  alcohol 

CH3— C<      +  NH3 
Xq 

=  CH3— C^OH 

\NH2 

Aldehyde  ammonia 

CH3— CC      +  HCN 
^0 

=  CH3— C^OH 

\CN 

Aldehyde  hydrocyanide 

CH3— C4      +  NaHS03 
^0 

=  CH3— Cf-OH 

XoSOaNa 

Aldehyde  sodium  bisulphite 

0 

3(CH3CHO)  =  ^^^^5 

/XcHCHs 

X/^0 
CHCH3 

Paraldehyde 

CHLORAL,   TRICHLORALDEHYDE  53 

Chloral,  trichloraldehyde,  CCI3CHO.  —  When  chlorine  acts 
upon  aldehyde,  in  the  presence  of  water  and  calcium  carbonate, 
substitution  takes  place,  and  trichloraldehyde  is  formed.  When 
alcohol  is  treated  with  chlorine,  a  double  action  takes  place. 
The  alcohol  is  first  changed  to  aldehyde  thus  :  — 

CH3.CH2OH  +  CI2  =  CH3.CHO  +  2  HCl. 

Then  the  chlorine  acts  upon  the  aldehyde,  and  is  substituted 
for  the  three  hydrogens  of  the  methyl,  forming  trichloralde- 

^  ^  ■  ~      CH3.CHO  +  6  CI  =  CCI3.CHO  +  3  HCl. 

In  reality  the  aldehyde  first  formed  combines  with  the  alcohol, 
forming  an  intermediate  product  which  is  acted  upon  by  the 
chlorine ;  and  the  chlorine  product  thus  formed  is  decomposed 
with  concentrated  sulphuric  acid,  forming  chloral.  The  essential 
features  of  the  reaction,  however,  are  stated  in  the  above 
equations.  Trichloraldehyde  is  the  substance  commonly  known 
as  chloral.  It  has  all  the  general  properties  of  aldehyde, 
and  the  conclusion  is  therefore  justified  that  it  contains  the 

O 

II 
aldehyde  group  — CH. 

Chloral  is  a  colorless  liquid,  which  boils  at  98°,  and  has  the 

specific  gravity  1.54  at  0°. 

Note  poe  Student.  —  Give  the  formulas  of  compounds  formed  when 
chloral  is  brought  together  with  ammonia,  hydrocyanic  acid,  and  the 
acid  sulphites  of  the  alkali  metals.  What  is  the  formula  of  the  acid 
formed  by  its  oxidation?  The  answer  is  given  in  the  statement  that 
the  general  chemical  conduct  of  chloral  is  the  same  as  that  of  aldehyde. 

When  chloral  and  water  are  brought  together,  they  unite 
with  evolution  of  heat  to  form  a  crystalline  compound,  chloral 
hydrate,  CCI3CHO  +  H2O,  which  is  easily  soluble  in  water,  and 
crystallizes  from  the  solution  in  beautiful,  colorless,  monoclinic 
prisms.  It  melts  at  47.4°  and  boils  at  97.5°,  dissociating  into 
chloral  and  water.  Taken  internally  in  doses  of  from  0.6  to 
2^,  it  causes  sleep.  In  larger  doses  it  acts  as  an  ansesthetic. 
It  is  a  habit-forming  drug. 


54  DERIVATIVES   OF   METHANE   AND   ETHANE 

Chloral  hydrate  is  an  example  of  a  compound  in  which  one 

ecu 

I /OH 
carbon  holds  two  hydroxyls  in  combination,  HC<' 

\0H 

When  heated  with  an  alkali,  chloral  and  chloral  hydrate  break 

down,  yielding  chloroform  and  a  formate  :  — 

CCI3.CHO  +  KOH  =  CHCI3  +  KCHO2. 

Chloral  Chloroform         Potassium 

formate 

Note  for  Student.  —  How  is  chloroform  made  from  alcohol?  How 
is  the  method  explained?  Answer  the  same  questions  for  iodoform. 
The  bleaching  powder  used  in  preparing  chloroform  furnishes  chlorine. 
Is  a  base  present  ? 

4.  Acids 
When  methyl  and  ethyl  alcohols  are  oxidized,  they  are  con- 
verted first  into  aldehydes,  and  then  the  aldehydes  take  up 
oxygen  and  are  converted  into  acids.  The  relations  in  compo- 
sition between  the  hydrocarbons,  alcohols,  aldehydes,  and  acids 
are  shown  in  the  subjoined  table :  — 

Hydrocarbons  Alcohols  Aldehydes  Acids 

CH4  CH4O  CH2O  CH2O2 

C2H6  C2H6O  C2H4O  C2H4O2 

The  two  acids  whose  formulas  are  here  given  are  the  well- 
known  substances,  formic  and  acetic  acids. 

Fonnic  acid,  methane  acid,  CH2O2.  —  This  acid  occurs  free 
in  nature  in  red  ants  {formica  rufa),  in  stinging  nettles,  in  fir 
cones,  in  some  fruits,  in  honey,  and  in  perspiration,  urine,  and 
extract  of  meat.  It  is  said  that  the  pain  and  swelling  caused 
by  the  stinging  of  bees,  hornets,  and  wasps  is  due  to  the  injec- 
tion of  a  small  amount  of  formic  acid. 

It  can  be  obtained  by  distilling  red  ants.  It  is  best  prepared 
in  the  laboratory  by  heating  oxalic  acid  with  glycerol.  Oxalic 
acid  has  the  composition  represented  by  the  formula  C2H2O4. 
When  heated  in  glycerol  to  ioo°  — 110°  it  breaks  down  into 
carbon  dioxide  and  formic  acid  (159) :  — 

C2H2O4  =  CO2  +  CH2O2. 
The  formic  acid  distils  over  at  this  temperature  into  the  receiver. 


FORMIC   ACID,   METHANE   ACID  55 

The  formation  of  formic  acid  by  oxidation  of  methyl  alcohol, 
and  by  treatment  of  chloral  with  an  alkali,  has  already  been 
mentioned.    The  following  methods  are  of  special  interest :  — 

(i)   By  the  action  of  carbon  monoxide  on  sodium  hydroxide : — 

CO  +  NaOH  =  H.COjNa. 

This  method  is  used  for  the  preparation  of  sodium  formate  on 
the  large  scale.  When  producer  gas  (containing  about  30  per 
cent  carbon  monoxide)  is  heated  to  120°  — 130°  under  a  pres- 
sure of  6  to  8  atmospheres  with  solid  sodium  hydroxide,  sodium 
formate  is  formed. 

(2)  By  the  action  of  metallic  potassium  upon  moist  carbon 
dioxide :  — 

2  CO2  +  2  K  +  H2O  =  HCO2K  +  HCO3K. 

(3)  By  treatment  of  a  concentrated  solution  of  ammonium 
carbonate  with  sodium  amalgam :  — 

C03(NH4)2  +  2  H  =  HCOzCNHi)  +  H2O  +  NH3. 

According  to  these  two  methods  formic  acid  appears  as  a 
reduction  product  of  carbonic  acid  formed  by  the  abstraction 
of  one  atom  of  oxygen :  — 

H2CO3  =  H2CO2  +  O. 

It  will  be  shown  that  all  organic  acids  may  be  regarded  as 
derivatives  of  either  formic  acid  or  carbonic  acid. 

(4)  When  hydrocyanic  acid  is  heated  with  a  dilute  mineral 
acid  or  with  a  solution  of  an  alkali,  it  gives  ammonia  and 
formic  acid :  — 

HCN  +  2  H2O  =  H2CO2  +  NH3. 

Of  course,  if  a  mineral  acid  is  present,  the  ammonium  salt  of 
this  acid  is  formed ;  and,  if  an  alkali  is  present,  the  formate  of 
the  alkali  metal  results.  A  reaction  similar  to  this  is  used  very  ex- 
tensively in  the  preparation  of  the  organic  acids,  as  will  be  shown. 
Anhydrous  formic  acid  can  be  made  by  dehydrating  either 
the  copper  or  lead  salt,  and  passing  dry  hydrogen  sulphide 


S6  DERIVATIA'ES   OF  METHANE   AND   ETHANE 

over  the  salt  heated  to  130°,  or  by  heating  a  mixture  of  dry 
sodium  formate  and  sodium  acid  sulphate  :  — 

HCOzNa  +  NaHSOi  =  NazSOi  +  H2CO2. 

It  is  a  colorless  liquid  boiling  at  100.8°  at  760"°™.  It  has  an 
irritating,  acrid  odor.  Dropped  on  the  skin,  it  causes  extreme 
pain  and  produces  blisters.  Its  specific  gravity  at  0°  is  1.24. 
When  cooled  down  it  solidifies  to  a  mass  of  crystals  which  melt 
at  8.3°  It  is  a  much  stronger  acid  than  acetic  acid.  It  is  a 
powerful  antiseptic,  and  is  hence  used  to  preserve  fruit  juices. 
As  it  is  now  made  very  cheaply,  it  is  displacing  acetic  acid  and 
other  acids  in  the  manufacture  of  leather,  in  dyeing  textiles, 
and  for  other  purposes. 

Concentrated  sulphuric  acid  decomposes  it  into  carbon  mon- 
oxide and  water :  — 

H2CO2  =  CO  +  H2O. 

It  is  easily  oxidized  to  carbonic  acid.  Hence  it  acts  as  a  re- 
ducing agent.  Heated  with  the  oxides  of  mercury  or  silver, 
they  are  reduced  to  the  metallic  condition  :  — 

HgO  +  H2CO2  =  Hg  +  H2O  +  CO2. 

Like  other  acids,  formic  acid  yields  a  large  number  of  salts  with 
bases,  and  ethereal  salts  or  esters  with  the  alcohols.  The 
salts  are  all  soluble  in  water,  and  some  of  them,  as  the  lead, 
copper,  and  barium  salts,  crystallize  very  well.  Some  of  the 
esters  will  be  mentioned  when  these  substances  are  taken  up 
as  a  class. 

Acetic  acid,  ethane  acid,  C2H4O2.  —  Acetic  acid  in  the  form 
of  wine  vinegar  was  known  to  the  ancients.  It  is  found  in  the 
free  condition  and  in  the  form  of  salts  in  plant  juices  and  in 
the  perspiration,  milk,  muscles,  and  excrement  of  animals. 
Esters  of  acetic  acid  also  occur  in  nature  as,  for  example,  tri- 
acetin  in  croton  oil. 

Acetic  acid  is  made 

(i)  By  the  oxidation  of  alcohol ;  and 

(2)  By  the  distillation  of  wood. 


ACETIC   ACID,   ETHANE   ACID  57 

When  pure  alcohol  is  exposed  to  the  air  it  undergoes  no 
change.  If,  however,  some  platinum  black  is  placed  in  it,  oxida- 
tion takes  place  and  acetic  acid  is  formed.  So  also  if  fermented 
liquors  that  contain  nitrogenous  substances  are  exposed  to  the 
air,  oxidation  takes  place,  and  the  liquor  becomes  sour  in  con- 
sequence of  the  formation  of  acetic  acid.  A  great  deal  of  acetic 
acid  is  made  by  exposing  cider  or  wine  to  the  action  of  the  air. 
The  product  is  known  as  cider  or  wine  vinegar.  The  formation 
of  vinegar  has  been  shown  to  be  due  to  the  action  of  a  micro- 
scopic organism  {Bacterium  aceti)  present  in  "  mo ther-of- vine- 
gar." This  serves  in  some  way  to  convey  the  oxygen  from  the 
air  to  the  alcohol.  The  "  quick- vinegar  process,"  much  used 
in  the  manufacture  of  vinegar,  consists  in  allowing  weak 
alcohol  to  pass  slowly  through  vats  filled  with  wood  shavings 
which  have  become  covered  with  Bacterium  aceti.  The  pres- 
ence of  the  organism  is  secured  by  first  pouring  strong  vinegar 
into  the  vats,  and  allowing  it  to  stand  for  one  or  two  days  in 
contact  with  the  shavings.  Air  is  admitted  near  the  bottom 
of  the  vats. 

When  wood  is  distilled,  the  aqueous  distillate  contains  wood 
alcohol,  acetone,  and  acetic  acid.  By  keeping  the  temperature 
down  comparatively  low,  the  amount  of  acetic  acid  obtained  is 
increased.  The  distillate  is  neutralized  with  lime,  the  wood 
alcohol  and  acetone  distilled  oil,  and  the  solution  of  crude  cal- 
cium acetate  thus  obtained  evaporated  to  dryness.  It  is  then 
treated  with  concentrated  sulphuric  acid,  and  the  acetic  acid 
distilled  off  under  diminished  pressure. 

The  crude  acid  containing  80  per  cent  acetic  acid  is  frac- 
tionated in  column  stills  and  an  acid  containing  98.99  per  cent 
acetic  acid  obtained.  The  chemically  pure  acetic  acid  is  made 
from  this  by  adding  potassium  permanganate,  to  oxidize  im- 
purities, and  distilling. 

Acetic  acid  was  also  manufactured  on  the  large  scale  during 
the  World  War  by  the  oxidation  of  acetic  aldehyde  made  from 
acetylene,  and  also  by  the  oxidation  of  ethyl  alcohol. 

It  is  used  in  medicine  in  the  form  of  its  salts,  in  the  manu- 
facture of  synthetic  remedies,  such  as  antipyrine,  aspirin,  anti- 


S8  DERIVATIVES  OF  METHANE  AND   ETHANE 

febrin,  phenacetin,  tannigen,  acetic  ether,  etc. ;  in  the  prepara- 
tion of  artificial  perfumes  and  extracts,  such  as  ionone,  coumarin, 
vanillin,  etc. ;  in  the  preparation  of  synthetic  dyes,  as  indigo, 
and  of  intermediates,  as  paranitroaniline ;  of  solvents,  as  acetin ; 
and  in  the  preparation  of  mordants  used  in  dyeing ;  in  the  form 
of  its  calcium  salt  in  the  manufacture  of  acetone ;  and  for  a  great 
variety  of  other  purposes.  Vinegar,  according  to  the  pure  food 
law,  must  contain  4  grams  acetic  acid  in  loo""-.  Acetic  acid  is 
a  preservative  and  in  the  form  of  vinegar  it  is  largely  used  for 
this  purpose  in  making  pickles,  chow  chow,  tomato  catsup,  etc. 

There  are  three  other  methods  which  may  be  used  for  making 
acetic  acid.     They  are :  — 

(i)  By  heating  sodium  methylate  with  carbon  monoxide :  — 

CHsONa  +  CO  =  CHs.COsNa. 

(2)  By  heating  carbon  dioxide  with  sodium  methyl :  — 

CO2  +  CHsNa  =  CHs.COzNa. 

(3)  By  heating  methyl  cyanide,  CH3CN,  with  a  dilute  mmeral 
acid  or  a  solution  of  an  alkali :  — 

CH3CN  +  2  H2O  =  CH3.CO2H  +  NH3. 

This  reaction  is  analogous  to  that  involved  in  the  formation 
of  formic  acid  from  hydrocyanic  acid.  These  reactions  show 
the  presence  of  a  methyl  group  in  acetic  acid. 

Pure  acetic  acid  is  a  colorless  liquid  that  boils  at  118.7°. 
It  has  a  very  penetrating,  pleasant,  acid  odor,  and  a  sharp  acid 
taste.  The  pure  substance  acts  upon  the  skin  like  formic  acid, 
causing  pain  and  raising  blisters.  It  solidifies  when  cooled  down, 
and  the  crystals  melt  at  16.54°.  The  pure  acid,  which  is  solid 
at  temperatures  below  16°,  is  known  as  glacial  acetic  acid.  Its 
specific  gravity  is  1.08  at  0°.  It  mixes  with  water  in  all  pro- 
portions. Glacial  acetic  acid  is  an  excellent  solvent  for  many 
organic  substances,  and  is  therefore  frequently  used  in  scientific 
research. 

Derivatives  of  acetic  acid.  Acetic  acid  yields  a  large  num- 
ber of  derivatives.    They  may  be  presented  briefly  under  two 


ACETIC   ACID,   ETHANE   ACID  59 

heads :  (i)  Those  which  are  formed  in  consequence  of  the  acid 
properties  and  which  necessitate  a  loss  of  the  acid  properties, 
as  the  salts,  ethereal  salts,  chloride,  and  anhydride ;  and 
(2)  those  in  which  the  acid  properties  remain  unchanged,  as  the 
chloroacetic  acids. 

Salts  of  acetic  acid.  The  acetates  of  the  alkalies  were  the 
first  compounds  of  carbon  ever  prepared.  The  potassium  and 
sodium  salts  are  used  in  medicine  and  in  the  chemical  laboratory. 
Both  crystallize,  the  sodium  salt  particularly  well. 

Calcium  acetate,  Ca(C2H302)2  +  2  H2O.  This  salt,  in  the 
impure  form,  known  as  "  gray  acetate  of  lime,"  is  the  product 
obtained  when  the  aqueous  distillate  from  wood  is  treated  with 
lime  and  the  solution  (after  distilling  off  the  wood  alcohol  and 
acetone)  is  evaporated  to  dryness.  It  is  the  material  from  which 
acetic  acid  and  acetone  are  made  on  the  large  scale.  Thousands 
of  tons  of  it  are  made  annually,  mostly  in  the  United  States. 

Lead  acetate,  (C2H302)2Pb  +  3  H2O.  This  salt,  which  is  com- 
monly known  as  sugar  of  lead,  is  made  on  the  large  scale  by 
dissolving  lead  oxide  in  acetic  acid.  It  crystallizes  well,  and 
is  soluble  in  1.5  parts  of  water  at  ordinary  temperatures.  Com- 
mercial sugar  of  lead  frequently  contains  an  excess  of  lead 
oxide  in  the  form  of  basic  salts.  A  solution  of  such  a  mixture 
becomes  turbid  when  allowed  to  stand  in  the  air,  or  gives  a 
precipitate  when  dissolved  in  ordinary  spring  water,  in  conse- 
quence of  the  formation  of  lead  carbonate. 

Lead  acetate  is  used  as  a  reagent  in  the  laboratory,  as  it  is 
one  of  the  few  soluble  salts  of  lead.  Like  all  soluble  salts  of 
lead  it  is  poisonous.  Technically  it  is  used  in  the  manufacture 
of  chrome  yellow,  white  lead,  and  other  lead  compounds. 

Cupric  acetate,  (C2ll302)2Cu  -|-  H2O.  This  salt  is  made  by 
dissolving  basic  copper  carbonate  in  acetic  acid.  It  crystallizes 
in  blue-green,  transparent  prisms.  A  basic  acetate,  formed  by 
the  action  of  acetic  acid  and  air  on  copper,  is  known  as  verdigris. 

Cupric  acetoarsenite,  3  Cu(As02)2  -t-  (C2H302)2Cu.  This 
double  salt  is  made  on  the  large  scale  by  precipitating  a  hot  solu- 
tion of  sodium  arsenite  with  a  solution  of  copper  sulphate  and 
then  adding  dilute  acetic  acid.     It  has  a  fine  bright  green  color, 


6o  DERn'ATIVES   OF   METHANE   AND   ETHAXE 

and  is  used  as  a  pigment  and  as  an  insecticide.  It  is  the  chief 
constituent  of  Emerald  green,  Paris  green,  or  Schweinfurt  green. 

Iron  forms  two  distinct  salts  with  acetic  acid,  the  ferrous 
salt,  (C2H302)2Fe  +  4  H2O,  and  the  feme  salt,  (C2H302)3Fe 
+  2H2O.  The  latter  is  formed  when  sodium  acetate  is  added 
to  a  neutral  solution  of  a  ferric  salt.  At  first  the  solution 
becomes  deep-red  in  color,  owing  to  the  formation  of  ferric 
acetate ;  but,  on  boiling,  aU  the  iron  is  precipitated  as  ferric 
hydroxide  and  acetic  acid  is  set  free.  Hence  this  salt  is  used 
for  the  purpose  of  separating  iron  from  manganese,  zinc,  cobalt, 
and  nickel  in  analytical  operations.  Aluminium  and  chromium 
acetates  are  decomposed  in  the  same  way  as  ferric  acetate. 

The  ethereal  salts  will  be  mentioned  briefly  when  this  class 
of  compounds  is  taken  up.  The  principal  one  is  ethyl  acetate 
or  acetic  ether,  which  is  formed  from  acetic  acid  and  ordinary 
alcohol.  When  a  mixture  of  these  two  substances  is  heated 
with  a  small  quantity  of  sulphuric  acid,  the  ester  is  formed  and 
can  be  recognized  by  its  pleasant  odor.  This  reaction  is  used 
for  the  detection  of  acetic  acid. 

Acetyl  chloride,  CH3COCI.  —  Just  as  alcohol,  when  treated 
with  phosphorus  trichloride,  yields  ethyl  chloride,  so  acetic  acid, 
when  treated  with  the  same  reagent,  yields  acetyl  chloride. 
The  two  reactions  are  perfectly  analogous.  They  consist  in 
the  substitution  of  chlorine  for  hydroxyl :  — 

3  CH3.COOH  +  PCI3  =  3  CH3.COCI  +  PO3H3. 

Acetyl  chloride 

Instead  of  phosphorus  trichloride  it  is  better  to  use  thionyl 
chloride :  — 

CH3COOH  +  OSCI2  =  CH3COCI  +  SO2  +  HCl. 

On  the  large  scale  sulphur>'l  chloride  is  used  :  — 

2  CHsCOONa  +  O2SCI2  =  2  CH3COCI  +  Na2S04. 

Acetj'l  chloride  is  a  colorless  liquid  which  boils  at  51°.  Water 
acts  upon  it  very  readily,  acetic  and  hydrochloric  acids  being 
formed :  — 

CH3COCI  +  H2O  =  CH3CO.OH  +  HCl. 


ACETIC   ANHYDRIDE,   ACETYL   OXIDE  6l 

In  this  case  the  chlorine  is  replaced  by  hydroxyl.  As  the 
substance  is  volatile,  it  fumes  in  contact  with  the  moisture 
of  the  air  in  consequence  of  the  formation  of  hydrochloric 
acid.  It  must  hence  be  kept  in  tightly  stoppered  bottles. 
In  handling  it,  care  must  be  taken  not  to  bring  it  near  the 
nose,  as  the  vapor  is  suffocating,  and  it  attacks  the  mucous 
membrane  of  the  eyes  and  nose,  producing  coughing  and  other 
bad  results. 

Acetyl  chloride  is  a  valuable  reagent  much  used  in  the  in- 
vestigation of  compounds  of  carbon.  Its  value  depends  upon 
its  action  towards  alcohols.  When  it  is  brought  together  with 
an  alcohol,  as,  for  example,  methyl  alcohol,  hydrochloric  acid 
is  evolved,  and  the  acetyl  group  takes  the  place  of  the  hydro- 
gen of  the  alcoholic  hydroxyl :  — 

CH3.OH  +  CIOC.CH3  =  CH3.O.OCCH3  +  HCl. 

The  product  is  an  ethereal  salt,  methyl  acetate.  This  kind  of 
action  takes  place  whenever  an  alcohol  is  treated  with  acetyl 
chloride.  Hence,  if  on  treating  a  substance  with  acetyl  chlo- 
ride, an  acetate  is  formed,  showing  that  hydrogen  is  replaced 
by  acetyl,  the  conclusion  is  justified  that  the  substance  contains 
alcoholic  hydroxyl. 

Acetyl  chloride  is  also  used  in  making  acetophenone  and 
acetyl  derivatives. 

Acetic  anhydride,  acetyl  oxide,  C4H6O3.  —  This  is  made  by 
abstracting  water  from  the  acid.  Like  most  other  organic  acids, 
acetic  acid  contains  hydroxyl,  as  has  been  shown  above.  It  may 
hence  be  represented  thus :  CH3COOH.  The  group  CH3CO  is 
known  as  acetyl.  Now  when  water  is  abstracted  from  the 
acid,  the  change  represented  in  this  equation  takes  place :  — 

CH3CO.OH  ^  CH3CO 
CH3CO.OH      CH3CO         ^     ' 

Hence,  according  to  this,  acetic  anhydride  appears  as  the  oxide 
of  acetyl,  while  the  acid  itself  is  the  hydroxide.  Acetic  an- 
hydride is  made  in  this  way  on  the  large  scale,  sulphur  chloride 
being  used  as  the  dehydrating  agent. 


62  DERnATIVES   OF   METHANE   AND   ETHANE 

It  is  prepared  in  the  laboratory  by  heating  sodium  acetate 
with  acetyl  chloride :  — 

CHsCO.ONa  +  CIOCCH3  =  (CH3CO)20  +  NaCl. 

Acetic  anhydride  is  a  colorless  liquid  which  boils  at  136.4°. 
Boiled  with  water  it  gives  acetic  acid. 

Acetic  anhydride  is  also  used  as  a  reagent  for  detecting 
alcoholic  hydroxyl.  With  methyl  alcohol,  for  example,  it  acts 
as  shown  in  the  following  equation :  — 

CH3OH  +  pjj'p°>0  =  CH3OOCCH3  +  CH3COOH. 

CXI3CU  Methyl  acetate  Acetic  acid 

With  all  substances  that  contain  alcoholic  hydroxyl  the  same 
kind  of  action  takes  place. 

Acetic  anhydride  is  used  principally  in  the  manufacture  of 
acetyl  cellulose.  It  is  also  used  in  making  synthetic  remedies, 
perfumes,  dyes,  etc. 

Halogen  substitution  products  of  acetic  acid.  These  bear  the 
same  relation  to  acetic  acid  that  the  substitution  products  of 
marsh  gas  bear  to  marsh  gas.  They  are  formed  by  the  simple 
substitution  of  a  halogen  for  hydrogen.  Only  three  of  the 
four  hydrogen  atoms  of  acetic  acid  are  capable  of  direct  replace- 
ment by  halogen — the  three  in  the  methyl  group.  The  fourth 
is  the  one  to  which  the  acid  properties  are  due.  Hence  the 
substitution  products  are  acids.  The  best-known  of  these  are 
the  chloroacetic  acids,  which  are  made  by  treating  the  acid  with 
chlorine  in  the  presence  of  a  chlorine  carrier,  as  sulphur.  They 
are  monochloroacetic,  dichloro acetic,  and  trichloroacetic  acids. 
Their  formation  is  represented  by  the  following  equations :  — 

CH3CO.OH  -I-  CI2  =  H2CCICO.OH  -1-  HCl; 
H2CCICO.OH  -I-  CI2  =  HCCI2CO.OH-I-  HCl; 
HCCI2CO.OH  +  CI2  =  CCI3CO.OH  +  HCl. 

Monochloroacetic  acid  is  also  made  from  acetylene  on  the 
large  scale  (299). 

When  treated  with  nascent  hydrogen  they  are  converted 
into  acetic  acid.  They  yield  salts,  ethereal  salts,  anhydrides, 
,  etc.,  just  the  same  as  acetic  acid  itself. 


ACETIC   ANHYDRIDE,   ACETYL   OXIDE  63 

Monochloroacetic  acid  is  a  crystalline  solid  melting  at  63°  and 
boiling  at  186°.  It  is  used  in  the  manufacture  of  synthetic 
indigo. 

Dichloroacetic  acid  is  also  made  by  boiling  chloral  hydrate  with 
a  solution  of  potassium  cyanide :  — 

CI3C.CHO  +  H2O  +  KCN  =  HCN  +  KCl  +  CI2CH.COOH. 

It  is  a  liquid  boiling  at  191°. 

Trichloroacetic  acid  is  a  solid  melting  at  57°  and  boiling  at  195°. 
It  is  formed  very  readily  by  oxidizing  chloral  with  nitric  acid :  — 

CI3C.CHO  +  0  =  CI3C.COOH. 

When  boiled  with  water  it  gives  carbon  dioxide  and  chloro- 
form :  — 

CI3C.COOH  =  CI3CH  +  CO2. 

Note  for  Sttjdent.  Compare  this  reaction  with  the  one  used  to 
prepare  marsh  gas  from  sodium  acetate  (22). 

The  chloroacetic  acids  are  very  much  stronger  acids  than  acetic 
acid.     This  is  due  to  the  introduction  of  the  negative  chlorine 
atoms.     Trichloroacetic  acid  is  comparable  in  strength  with  the. 
mineral  acids. 

Theory  in  regard  to  the  relations  between  the  acids,  alcohols, 
aldehydes,  and  hydrocarbons.  The  reactions  and  methods  of 
formation  of  acetic  acid  enable  us  to  form  a  clear  conception 
of  the  relation  of  its  constituents.  In  the  first  place  the  pres- 
ence of  hydroxyl  is  shown  by  the  reaction  with  phosphorus 
trichloride.  We  hence  have  C2H3O.OH  as  the  formula  repre- 
senting this  fact.  But  several  questions  still  remain  to  be 
answered.  There  is  another  oxygen  atom  to  be  accounted 
for;  and  the  relations  between  the  hydroxyl  and  this  oxygen 
must  be  determined  if  possible.  The  fact  that  this  second 
oxygen  is  not  replaced  by  chlorine  when  acetyl  chloride  is  treated 
with  phosphorus  trichloride  indicates  that  it  is  not  present  as 
hydroxyl,  and  all  methods  of  testing  for  hydroxyl  fail  to  show 
its  presence  in  acetyl  chloride.  Hence  we  may  conclude  that 
the  second  oxygen  atom  is  present  as  carbonyl,  CO.    This  leads 


64  DERIVATIVES   OF   METHAXE   AND   ETHAXE 

o 

us  to  the  formula  H — C— O — H  for    the   simplest    acid,   or 

formic   acid.     Accordingly,   formic   acid   appears   as   carbonic 

OTT 
acid,  0=C<^-^,  in  which  one   hydroxyl   has   been  replaced 
OH 

by  hydrogen.     It  has  already  been  shown  that  this  reduction 

can  be  accomplished  without  difficulty  and  that  carbonic  acid 

is  the  oxidation  product  of  formic  acid.     Now,  as  acetic  acid 

is  the  homologue  of  formic  acid,  there  is  good  reason  to  believe 

that  it  differs  from  the  latter  in  that  it  contains  methyl  in  place 

of  the  hydrogen,  which  is  in  direct  combination  with  carbon, 

and  this  view  is  confirmed  by  the  fact  that  acetic  acid  can  be 

made  from  sodium  methyl,  CHsNa,  from  sodium  methylate, 

NaOCHs,   and    from    methyl    cyanide,    CH3.CN.      The    acid 

O 

II 
must   hence  be  represented  by  the  formula   CH3 .  C — OH  or 

CH 
0C<_    '.    The  common  constituent  of  the  two  acids   is  the 
OH 

O 

II 
group  — C — 0 — H  or  — CO. OH,  which  is  known  as  carboxyl. 

Acetic  acid  is  closely  related  not  only  to  formic  but  to  car- 

OH 

bonic  acid.     It  mav  be  regarded  as  carbonic  acid,  0C<  „„,  in 

OH 

which  one  hydroxyl  is  replaced  by  the  radical  methyl.  In  a 
similar  way  we  shall  see  that  all  organic  acids  are  to  be  re- 
garded as  derived  either  from  formic  acid  or  from  carbonic 
acid.  Representing  now  the  simplest  hydrocarbon,  alcohol, 
aldehyde,  and  acid,  by  the  structural  formulas  deduced  from 
the  facts,  we  have  : 

fOTT 

[0 

C  H 
H 


H 

C^ 

^|H 

OH 

c 

H 
H 

IH 

H 

Marsh  gas 
(Methane) 

Met! 
(1^ 

yl  alcohol 
[ethanol) 

Formic 
aldehyd) 
(Methanal) 


aldehyde  ,JTi,"'''  ^°•J^ 

Methanah  (Methane  aad) 


RELATIONS   BETWEEN  ACIDS,   ALCOHOLS,   ETC.         65 

Methyl  alcohol  cannot  be  made  from  marsh  gas  by  oxi- 
dation, but  by  making  chlorome thane,  CH3CI,  then  substi- 
tuting hydroxy],  OH,  for  chlorine  we  get  methyl  alcohol.  Here 
we  have  replaced  one  hydrogen  of  marsh  gas  by  hydroxyl,  OH. 
Starting  with  methyl  alcohol,  we  might  expect  the  next  change 
caused  by  oxidation  to  consist  in  the  introduction  of  another 

fOH 

.     But  it  has  been 

xl 


oxygen  atom,  giving  a  compound  C  \ 


IH 

found  that,  except  under  certain  conditions  (54),  one  carbon  atom 
cannot  hold  two  hydroxyls  in  combination,  and  that,  if  such 
a  compound  is  formed,  it  loses  the  elements  of  water,  thus, 

fOH 

OH 

=  C{H  +  H2O.      The   result  would  be  formaldehyde. 

IH  ^^ 

This  kind  of  change  is  illustrated  in  the  formation  of  carbon 
dioxide  from  the  salts  of  carbonic  acid  when  they  are  treated 

OH 

with  acids.     Instead  of  getting  the  acid  OC  <  _„,  which  we 

should  naturally  expect,  we  get  this  minus  water :  — 
OC<qJJ=C02  +  H20. 

Now,  when  the  aldehyde  is  oxidized,  another  oxygen  atom  is 
introduced,  and  the  substance  thus  produced  is  formic  acid,  for 
the  hydroxyl  hydrogen  can  be  replaced  by  metals,  and  has  in 
general  the  characteristics  of  acid  hydrogen.  Carbon  in  com- 
bination with  oxygen  as  carbonyl,  and  at  the  same  time  with 
hydroxyl,  gives  the  compound  containing  it  acid  properties. 

I"" 
If,  finally,  formic  acid  C  {  OH  is  oxidized,  it  is  probable  that 

[H 
the  same  change  takes  place  as  when  the  alcohol  is  oxidized. 


represented  by  the  formula  C 


66  DERI\'ATIVES   OF  METHANE   AND   ETHANE 

That  is  to  say,  the  hydrogen  is  oxidized  to  hydroxy!,  when  a 
compound  containing  two  hydroxA-ls  in  combination  with  one 
carbon  atom  would  be  the  result.  This  is  carbonic  acid.  But 
this  breaks  down  into  water  and  carbon  dioxide,  which  are  the 
products  of  oxidation  of  formic  acid. 

All  the  many  representatives  of  the  great  classes  of  carbon 
compounds  known  as  the  hydrocarbons,  alcohols,  aldehydes, 
and  acids  are  derived  from  the  four  fundamental  substances, 
methane,  methyl  alcohol,  formic  aldehyde,  and  formic  acid. 
Replace  one  of  the  hydrogen  atoms  of  methane  by  a  radical, 
like  methyl,  CH3,  and  we  get  a  new  hydrocarbon,  which  may  be 

H 

XT 

If  a  radical  is  substituted 

XI 

R 

for  one  of  the  hydrogen  atoms  of  the  methyl  group  of  methyl 

fOH 

alcohol,  a  new  alcohol  is  formed,  C  ^  „  •    So  also  a  similar  re- 

xl 

R 

placement  of  a  hydrogen  atom  in  formic  aldehyde  by  a  radical 

gives  a  new  aldehyde,  C  j  H ;    and,  finally,  the  organic  acids 

fO  j^ 

may  be   represented   by   the   formulas  C  \  OH,  or  OC  <  -.^t 

U  ' 

which  show  their  relations  to  formic  and  carbonic  acids. 
Thus  ethane,  ethyl  alcohol,  acetic  aldehyde,  and  acetic  acid,  in 
which  the  radical  is  methyl,  CH3,  are  represented  by  these 
formulas :  — 

[0  fO 

C I  H  C I  OH 


H 

fOH 

H 

^    H 

H 

C^H 

CH3 

CH, 

Ethane 

Ethanol 

[  CH3       [  CH3 

Ethanal  Ethane  acid 

Hereafter  the  structural  formulas  of  the  alcohols,  aldehydes, 


ETHEREAL   SALTS   OR  ESTERS  67 

and  acids  will  be  represented  by  writing  the  hydroxyl  group  OH, 
the  aldehyde  group  CHO,  and  the  carboxyl  group  CO.OH  or 
CO2H,  separately  from  the  rest  of  the  formula. 

5.   Ethereal  Salts  or  Esters  —  Esteripication 

It  has  already  been  shown  that  alcohols  react  with  mineral 
acids  to  give  esters,  analogous  to  the  salts  of  the  univalent 
metals,  in  which  the  acid  hydrogen  is  replaced  by  the  radical 
methyl  or  ethyl.  In  the  same  way  esters  of  the  organic  acids 
are  formed :  — 

H3C.COOH  +  HOC2H6  =  H3C.COOC2H6  +  H2O. 

Acetic  acid  Ethyl  alcoliol  Ethyl  acetate 

Owing  to  the  fact  that  the  alcohols  are  weak  bases  and  that 
the  organic  acids  are  weak  acids  and  that  neither  are  ionized 
to  any  extent;  this  reaction  proceeds  slowly,  requiring  several 
hours  to  reach  equilibrium  at  the  boiling  point,  whereas  the 
neutralization  of  acetic  acid  by  sodium  hydroxide  solution  is 
instantaneous :  — 

H3C.COOH  +  HONa  =  HsC.COONa  +  HOH. 

Sodium  acetate 

The  reaction  between  any  acid  and  an  alcohol  is  also  a  re- 
versible one,  as  the  water  formed  hydrolyzes  the  ester  to  acid 
and  alcohol :  — 

H3C.COOH  +  HOCzHsI^HaC.COOCzHB  +  HOH; 

consequently  a  state  of  equilibrium  is  reached  after  a  time  and 
the  reaction  never  proceeds  to  completion,  as  in  the  case  of 
the  neutralization  of  an  acid  by  an  alkali.  For  example,  if 
equivalent  quantities  of  acetic  acid  and  ethyl  alcohol  are  used, 
only  about  66  per  cent  of  the  acid  can  be  converted  into  the 
ester.  In  order  to  increase  the  velocity  of  the  reaction  and  to 
obtain  a  larger  yield  of  the  ester,  a  catalytic  agent  is  used, 
either  a  small  amount  of  dry  hydrochloric  acid  or  concentrated 
sulphuric  acid.  It  is  customary  to  heat  the  organic  acid  with 
methyl  or  ethyl  alcohol,  containing  about  3  per  cent  of  dry 


68  DERI\'ATIVES   OF   METHANE   AND   ETHANE 

hydrochloric  acid  gas,  to  the  boiling  point  for  about  three 
hours. 

The  sulphuric  acid,  when  used  as  a  catalyst,  imites  with  the 

alcohol :  — 

C2H5OH  +  HHSO4  =  C2H6HSO4  +  HOH 

to  form  ethylsulphuric  acid,  which  then  reacts  with  the  organic 
acid  to  give  the  ester,  regenerating  the  sulphuric  acid,  which 
again  reacts  with  more  alcohol :  — 

C2H5HSO4  +  HOOC.CH3  =  C2H5OOC.CH3  +  H2SO4. 

This  process  with  sulphuric  acid  is  analogous  to  the  formation 
of  ether  and  hence  the  esters  are  frequently  called  ethereal 
salts  or  compound  ethers.  A  go  to  95  per  cent  yield  of  the  ester 
can  generally  be  obtained  by  the  catalytic  method  of  esterifi- 
cation.  The  esters  are  separated  from  the  excess  of  alcohol  and 
acids  by  pouring  the  mixture  into  water  in  which  the  esters  are 
generally  insoluble. 

Two  other  methods  of  preparing  the  esters  have  already 
been  given.  These  involve  the  action  of  the  chloride  of  the 
acid  or  of  the  acid  anhydride  on  the  alcohols  (61,  62). 

Another  method  is  to  heat  a  salt  of  the  acid  (usually  the  silver 
salt)  with  methyl  or  ethyl  iodide  :  — 

C2H5I  +  AgOOC.CHa  =  Agl  +  C2H6OOC.CH3; 

or  the  sodium  salt  is  treated  with  dimethyl  or  diethyl  sulphate :  — 

HaC.COONa  +  (CH3)2S04   =  H3C.COOCH3  +  Na.CH3.SO4. 

In  these  reactions  the  metal  is  directly  replaced  by  the  radical 
and  thus  the  relation  between  the  metallic  salts  and  the  ethereal 
salts  is  clearly  established. 

These  methods  of  preparing  ethereal  salts  are  of  general  ap- 
plication and  are  used  when  an  ester  cannot  readily  be  obtained 
by  the  catalytic  method. 

Among  the  more  important  methyl  and  ethyl  esters,  the  fol- 
lowing may  be  mentioned  :  — 

Methylsulphuric  acid,      ^    >  SO2,  formed  by  heating  methyl 


ETHYLS  ULPHURIC  ACID  69 

alcohol  and  sulphuric  acid  on  the  water  bath.  The  acid  itself, 
as  well  as  its  salts,  is  very  easily  soluble  in  water.  Anhydrous 
methylsulphuric  acid  is  made  by  the  action  of  sulphur  trioxide 
on  anhydrous  methyl  alcohol :  — 

H3COH  +  SO3  =  H3CO.SO2OH. 

Dimethyl  sulphate,  (CH30)2S02.  — When  anhydrous  methyl- 
sulphuric  acid  is  distilled  in  a  vacuum,  dimethyl  sulphate  passes 
over  and  sulphuric  acid  is  left  behind :  — 

2   H3CO.SO2OH  =    (CH30)2S02  +  H2SO4. 

It  is  an  oily  liquid,  boiling  at  i88.3"-i88.6°,  insoluble  in  water, 
and  is  very  poisonous.  It  is  largely  used  instead  of  the  more 
expensive  methyl  iodide  jox  the  purpose  of  introducing  methyl 
groups  into  organic  compounds  (68).  Dimethyl  sulphate  is 
also  made  by  absorbing  dimethyl  ether  (a  by-product  of  the 
manufacture  of  dimethylaniline)  in  fuming  sulphuric  acid :  — 

(CH3)20  +  SO3  =  (CHsOaSOz. 

Ethyl  nitrate,  C2H6ONO2,  is  made  by  treating  alcohol  with 
nitric  acid,  adding  urea  to  decompose  any  nitrous  acid  formed. 
Unless  precautions  are  taken  in  mixing  these  reagents,  oxidation 
of  the  alcohol  will  take  place,  and  a  violent  explosion  may 
result. 

Ethyl  nitrite,  C2H6O.NO,  boiling  at  17",  results  from  the  action 
of  the  anhydride  of  nitrous  acid  on  alcohol :  — 

2  CjHsOH  +  N2O3  =  2  C2H6ONO  -I-  H2O. 

An  alcoholic  solution  of  ethyl  nitrite  is  known  as  "  sweet  spirit 
of  nitre." 

Ethylsulphuric  acid,  C2H6O.SO2OH,  is  made  in  the  same  way 
as  the  methyl  compound.  Ethylsulphuric  acid  is  formed  when 
ethylene  is  absorbed  in  concentrated  sulphuric  acid :  — 

C2H4  +  H2SO4  =  C2H6O.SO2OH. 

Ethylene  Ethylsulphuric  acid 


70  DERIVATIVES   OF  METKLIXE   AND   ETH.\XE 

The  potassium  salt  is  used  in  preparing  ethyl  compounds.  Thus, 
ethyl  bromide  results  from  the  distillation  of  potassium  bromide 
and  potassium  ethylsulphate  :  — 

KO.SO2.OC2H6  +  KBr  =  K2SO4  +  CjHsBr. 

The  acid  and  its  salts  are  easily  soluble  in  water.  When 
boiled  with  water,  it  is  hydrolyzed,  yielding  alcohol  and  sulphu- 
ric acid:  — 

^'^'^>S02   +  H2O    =   H2SO1  +   C2H6OH. 

Diethyl  sulphate,  (C2H60)2S02,  is  made  by  distilling  anhy- 
drous ethylsulphuric  acid  or,  better,  its  dry  sodium  salt  in  a 
vacuum :  — 

2  C2H60.S020Na  =  (C2H60)2S02  +  Na2S04. 

It  is  a  colorless  liquid,  insoluble  in  water,  which  solidifies  at 
—  24.5°,  and  is  poisonous.  It  is  used  for  the  purpose  of  intro- 
ducing ethyl  groups  into  organic  compounds. 

Phosphoric  acid  yields  triethyl  phosphate,  (C2H5)3P04,  di- 
ethylphosphoric  acid,  (C2H6)2HP04,  and  ethylphosphoric  acid, 
C2H5H2PO4. 

There  are  also  similar  derivatives  of  arsenic,  boric,  silicic,  and 
other  mineral  acids. 

Of  the  ethereal  salts  which  the  two  alcohols  form  with  formic 
and  acetic  acids,  ethyl  formate  and  ethyl  acetate  are  the  best- 
known.  The  methods  of  preparing  them  have  already  been 
given.  They  are  both  liquids  having  pleasant  odors.  This  is 
indeed  a  characteristic  of  many  of  the  volatile  ethereal  salts 
of  the  organic  acids,  and  many  of  the  odors  of  fruits  and  flowers 
are  due  to  the  presence  of  one  or  another  of  these  compounds. 
Many  of  them  are  used  in  perfumery  and  for  flavoring  pur- 
poses instead  of  the  natural  substances. 

Ethyl  formate,  H.COOC2H5,  boiling  point  55",  is  used  in 
making  artificial  rum  or  arrack  and  in  the  synthesis  of  organic 
compounds. 


ETHYL  ACETATE,  ACETIC  ETHER         71 

Ethyl  acetate,  acetic  ether,  CH3.COOC2H5,  boiling  at  75°, 
is  made  on  the  large  scale  and  extensively  used  as  a  solvent 
for  nitrocellulose  and  cellulose  acetate  in  the  manufacture  of 
photographic  films,  leather  substitutes,  and  a  number  of  other 
products. 

Saponification  of  ethereal  salts.  Salts  of  most  metals  are 
instantaneously  decomposed  when  treated  with  a  solution  of  an 
alkaline  hydroxide,  as  caustic  soda  or  caustic  potash,  the  result 
being  a  salt  of  the  alkali  metal  and  the  hydroxide  of  the  replaced 
metal,  as  seen  in  the  case  of  copper  sulphate  and  sodium 
hydroxide :  — 

CuSOi  +  2  NaOH  =  Cu(0H)2  +  NazSOi. 

So  also  the  ethereal  salts  are  similarly  decomposed  when  treated 
with  solutions  of  the  alkalies,  though  not  as  readily  as  salts.  It 
is  usually  necessary  to  boil  the  ethereal  salt  with  a  solution  of  the 
alkali  when  decomposition  takes  place,  the  radical,  like  the  metal, 
appearing  in  the  form  of  the  hydroxide  or  alcohol,  and  the  alkali 
metal  taking  its  place.  Thus,  when  ethyl  sulphate  is  heated 
with  a  solution  of  caustic  potash,  this  reaction  takes  place :  — 

(C2H6)2S04  +  2  KOH  =  K2SO4  +  2  C2H6.OH; 

and  when  ethyl  acetate  is  heated  with  caustic  soda,  we  have 
this  reaction :  — 

CH3.COOC2H6  +  NaOH  =  CHs.COONa  +  CzHsOH. 

All  ethereal  salts  are  decomposed  by  boiling  with  the  caustic 
alkalies.  As  this  decomposition  is  best  known  on  the  large  scale 
in  the  preparation  of  soaps,  it  is  commonly  called  saponification. 
As  will  be  shown,  the  fats  are  ethereal  salts,  and  soap-making 
consists  in  hydrolyzing  fats  by  means  of  the  caustic  alkalies. 
Hence,  generally,  to  saponify  an  ethereal  salt  means  to  hydrolyze 
it  by  means  of  an  alkali  into  the  corresponding  alcohol  and 
the  alkali  salt  of  the  acid  contained  in  it. 

The  ethereal  salts  are  also  hydrolyzed  by  heating  them  with 
dilute  mineral  acids :  — 

CH3COOC2H6  +  H2O  =  CH3COOH  +  C2H6OH. 


72  DERIVATIVES   OF   METHANE  AND   ETHANE 

6.   Ketones  or  Acetones 

When  calcium  or  barium  acetate  is  distilled,  a  liquid  passes 
over  which  has  the  composition  CaHeO,  and  a  carbonate  remains 
behind.  The  reaction  has  been  carefully  studied,  and  has  been 
shown  to  take  place  in  accordance  with  the  following  equa- 
tion :  — 

^J?"^°°>Ca  =  H3CCOCH,  +  CaCO,. 
L-XI3.CUU 

The  formula  H3CCOCH3  represents  the  compound  acetone.  It 
is  the  best-known  representative  of  a  class  of  compounds  called 
ketones. 

Acetone,  dimethylketone,  propanone,  H3CCOCH3.  —  This 
substance  has  long  been  known  as  a  product  of  the  distillation 
of  acetates.  It  is  present  in  considerable  quantities  in  the 
products  of  the  distillation  of  wood,  and  is  separated  from  the 
mixture  after  the  removal  of  the  acetic  acid.  It  also  occurs  in 
the  blood  and  in  urine  in  small  quantity.  In  certain  patho- 
logical conditions  it  occurs  in  relatively  large  quantities  in  the 
urine,  as  in  acetonuria  and  in  diabetes  mellitus. 

It  can  be  purified  by  shaking  a  mixture  containing  it  with  a 
concentrated  solution  of  monosodium  sulphite.  It  unites  with 
the  salt,  forming  a  crystalline  compound  analogous  to  that 
formed  with  aldehyde.  The  compound  is  separated  and  puri- 
fied. When  distilled  with  a  solution  of  sodium  carbonate, 
pure  acetone  passes  over. 

Acetone  is  a  colorless  liquid  having  a  pleasant,  ethereal 
odor.  It  boils  at  56.53°.  It  is  a  good  solvent  for  many  carbon 
compounds.  It  is  used  in  the  manufacture  of  chloroform, 
sulphonal,  ionone,  iodoform,  and  in  gelatinizing  nitrocellulose 
in  the  manufacture  of  smokeless  powders  and  celluloid.  It  is 
also  used  as  a  solvent  for  acetylene  (Prestolite),  and  it  is  the 
material  from  which  isoprene,  used  in  the  synthesis  of  rubber, 
is  made.  In  the  laboratory  it  is  much  used  as  a  solvent  for 
purifying  and  recrystallizing  organic  compounds. 

Acetone  more  closely  resembles  the  aldehydes  than  any  other 
compounds  thus  far  dealt  with.     It  is  not  an  acid  nor  an  alcohol 


ACETONE,   DIMETHYLKETONE,   PROPANOKE  73 

as  it  does  not  form  salts  with  bases  or  esters  with  acids.  It 
is  not  an  ethereal  salt,  for  on  boiling  with  an  alkali  it  does  not 
yield  an  alcohol  and  the  salt  of  an  acid.  On  the  other  hand,  it 
unites  with  the  acid  sulphites  like  the  aldehydes.  Further, 
when  treated  with  phosphorus  pentachloride  its  oxygen  is  re- 
placed by  two  chlorine  atoms  thus  :  — 

(CH3)2CO  +  PCle  =  (CH3)2CCl2  +  POCU; 

and,  when  treated  with  nascent  hydrogen,  it  is  converted  into 
a  substance  having  alcoholic  properties.  These  facts  lead  to 
the  conclusion  that  the  substance  contains  carbonyl,  CO,  as  the 
aldehydes  do.  This  is  shown  in  the  formula  C2H6CO.  The 
formation  from  calcium  acetate  leads  further  to  the  belief  that 
the  group  C2H6  consists  of  two  methyls,  as  the  simplest  inter- 
pretation of  the  reaction  given  above.  According  to  this, 
acetone  is  a  compound  of  two  methyl  groups  and  carbonyl,  or 
it  is  carbon  monoxide  whose  two  free  affinities  have  been  satis- 
fied by  two  methyl  groups. 

This  view  can  be  tested  experimentally.  If  it  is  correct, 
it  will  be  seen  that  acetone  is  closely  related  to  acetyl  chloride. 
It  is  acetyl  chloride  in  which  the  chlorine  has  been  replaced 
by  methyl :  — 

CH3.CO.CI  CH3.CO.CH3. 

Acetyl  chloride  Acetone 

Now,  when  acetyl  chloride  is  treated  with  zinc  methyl,  Zn  (€113)2, 
it  yields  acetone  :  — 

2  CH3.COCI  +  Zn(CH3)2  =  2  CH3.CO.CH3  -I-  ZnCl2. 

It  will  be  seen  from  this  that  acetone  is  aldehyde,  CH3.CHO, 
in  which  the  aldehyde  hydrogen  has  been  replaced  by  methyl, 
CHs.CO.CHj. 

Like  the  aldehydes,  acetone  has  the  power  of  taking  up  other 
substances,  such  as  the  acid  sulphites,  ammonia,  hydrocyanic 
acid,  hydrogen,  etc.  This  power  is  connected  with  the  relation 
of  the  oxygen  to  the  carbon^  which  is  the  same  in  both  com- 
pounds. 


74  DERIVATIVES  OF  METHANE  AND   ETHANE 

By  reduction  with  nascent  hydrogen,  acetone  yields  an 
alcohol  of  the  formula  C3HsO,knowna,s secondary  propyl  alcohol, 
which  when  oxidized  yields  acetone :  — 

Acetone  Secondary  propyl 

alcohol 

Secondary  Acetone 

propyl  alcohol 

This  gives  another  method  for  the  preparation  of  ketones, 
viz.  oxidation  of  the  secondary  alcohols. 

The  relation  between  this  alcohol  and  acetone  is  the  same 
as  that  between  ethyl  alcohol  and  acetic  aldehyde.  But  while 
the  aldehyde  by  further  oxidation  yields  acetic  acid  by  simply 
taking  up  one  atom  of  oxygen,  acetone  is  decomposed  by 
oxidizing  agents,  and  yields  acetic  and  formic  acids :  — 

H3C.COCH3  +  30  =  H.COOH  +  H3C.COOH. 

Acetone  Formic  acid  Acetic  acid 

Towards  oxidizing  agents,  then,  ketones  (for  it  will  be  shown 
that  other  ketones  conduct  themselves  in  the  same  way)  act 
entirely  differently  from  the  aldehydes.  The  alcohol  above 
mentioned  as  related  to  acetone  is  the  simplest  representative 
of  the  secondary  alcohols,  which  differ  in  some  important  re- 
spects from  methyl  and  ethyl  alcohols. 

Considerable  quantities  of  acetone  are  now  made  by  the 
fermentation  of  maize  (Indian  corn)  by  the  Weizmann  pro- 
cess.i     (See  Butanol,  133.) 

Several  mixed  ketones,  such  as  methyl  ethyl  ketone 
CH3 — CO — CH2CH3  (butanone),  are  also  well  known.  This 
substance  occurs  in  crude  wood  alcohol  and  in  crude  acetone. 
In  its  chemical  conduct  it  resembles  acetone  very  closely.  On 
reduction  it  gives  secondary  butyl  alcohol  and  it  can  be  made  by 

^See  Distillation:  Principles  and  Processes.  By  Sidney  Young  (1922), 
for  technical  methods  of  making  and  distilling  acetone. 


ACETONE,  DIMETHYLKETONE,  PROPANONE     75 

the  oxidation  of  secondary  butyl  alcohol.  It  can  also  be  made 
by  the  action  of  zinc  ethyl  on  acetyl  chloride.  It  is  separated 
from  crude  acetone  by  fractional  distillation  in  column  stills, 
and  is  used  in  the  manufacture  of  the  soporific  trional  (79). 
Its  presence  in  crude  acetone  is  due  to  the  fact  that  the  crude 
calcium  acetate  used  in  the  manufacture  of  acetone  contains 
calcium  propionate :  — 

PIT  POO 

^^^QQ>Ca  =  CaC03  +  CU,COC,U,. 

The  most  important  representatives  of  the  six  classes  of  oxygen 
derivatives  of  the  hydrocarbons  have  thus  far  been  presented, 
and,  by  the  aid  of  a  study  of  their  chemical  conduct  and  of  the 
methods  used  in  their  preparation,  definite  views  in  regard  to 
the  relations  between  them  have  been  formed.  In  ordinary 
language  these  relations  may  be  briefly  expressed  thus :  The 
alcohols  are  the  hydroxyl  derivatives  of  the  hydrocarbons  or 
the  hydroxides  of  certain  groups  called  radicals;  the  ethers 
are  the  oxides  of  these  same  radicals ;  the  aldehydes  are  com- 
pounds consisting  of  carbonyl,  hydrogen,  and  a  radical;  the 
acids  are  compounds  of  carbonyl,  hydroxyl,  and  a  radical,  or, 
better,  they  are  carbonic  acid  in  which  hydrogen  and  oxygen, 
or  hydroxyl,  have  been  replaced  by  a  radical;  the  ethereal 
salts  are  compounds  like  ordinary  metallic  salts,  only  they 
contain  a  radical  in  place  of  the  metal ;  and,  finally,  the  ketones 
are  aldehydes  in  which  the  distinctively  aldehyde  hydrogen 
has  been  replaced  by  a  radical,  or  they  are  compounds  con- 
sisting of  carbonyl  and  two  radicals. 

These  ideas  are  expressed  in  formulas  thus,  R  being  any  uni- 
valent radical  like  methyl,  CH3,  or  ethyl,  C2H5 :  — 


Alcohol     . 
Ether 

.    R— 0— H. 
.    R— 0— R. 

Ethereal  salt 

.     R— C— 01 

II 

Aldehyde 
Acid    .    . 

.    R— C— H. 

II 
0 

.    R— C— OH. 

Ketone    .    . 

0 

.     R— C— R. 

II 
0 

o 


CHAPTER  V 
SULPHUR  DERIVATIVES   OF  METHANE   AND   ETHANE 

I.   Mercaptans 

The  simplest  derivatives  of  methane  and  ethane  containing 
sulphur  are  the  mercaptans  or  thioalcohols.  They  can  be  made 
by  a  method  similar  to  one  described  under  the  head  of  Alcohols. 
When  a  monohalogen  derivative  of  a  hydrocarbon,  as  bromo- 
methane,  CHsBr,  is  heated  with  the  hydroxide  of  a  metal,  an 
alcohol  is  formed :  — 

CHsBr  +  AgOH  =  CH3OH  +  AgBr. 

So,  also,  when  a  similar  halogen  derivative  is  heated  with  a 
hydrosulpkide  instead  of  a  hydroxide,  a  compound  is  obtained 
that  may  be  regarded  as  an  alcohol  in  which  the  ojxygen  has 
been  replaced  by  sulphur :  — 

CHsBr  +  KSH  =  CH3SH  +  KBr. 

The  compound  is  called  methylmercaptan  or  methanethiol. 

Ethyl  mercaptan,  ethanethiol,  C2H5.SH.  —  This  substance  can 
be  prepared  by  heating  iodoethane,  C2H6I,  with  an  alcoholic 
solution  of  potassium  hydrosulphide,  KSH ;  also  by  distilling  a 
mixture  of  the  concentrated .  solutions  of  potassium  ethylsul- 
phate  and  potassium  hydrosulphide  :  — 

^'^'>S04+KSH  =  K2SO4  +  C2H5SH. 

It  is  a  liquid  of  an  extremely  disagreeable  odor;  it  boils  at  37° ; 
is  difficultly  soluble  in  water,  and  is  inflammable.  As  it  is  the 
monoethyl  derivative  of  hydrogen  sulphide,  it  has  the  character 
of  a  weak  acid,  though  having  a  neutral  reaction.     It  dissolves 

76 


MERCAPTANS  77 

in  a  strong  solution  of  potassium  hydroxide  to  form  a  mercaptide, 
analogous  to  the  alcoholate :  — 

CjHbSH  +  HOK  =  C2H5SK  +  H2O. 

It  also  reacts,  in  alcoholic  solution,  with  mercuric  oxide :  — 

2  C2H5SH  +  HgO  =  (C2H5S)2Hg  +  H2O. 

Mercury  mercaptide 

For  this  reason  the  name  mercaptan  was  given  to  it  from 
corpus  mercurium  captans.  It  is  made  on  the  large  scale  for  the 
preparation  of  the  soporifics,  sulphonal  and  trional  (78,  79). 
It  forms  many  other  well-characterized  metallic  derivatives  like 
this  mercury  compound. 

When  mercaptan  is  treated  with  nitric  acid,  it  is  oxidized, 
the  product  having  the  formula  C2H6.SO3H :  — 

0 

II 
CjHsSH  +  30  =  C2H5— S— OH. 

II 

Ethylsulphonic  acid  1 

This  substance  is  hence  a  derivative  of  sulphuric  acid. 

It  will  thus  be  seen  that,  though  in  composition  mercaptan 
is  analogous  to  alcohol,  towards  oxidizing  agents  it  conducts 
itself  quite  differently.  In  the  case  of  alcohol  two  atoms  of 
hydrogen  are  replaced  by  one  of  oxygen :  — 

CH3.CH2OH   +02    =    CH3.COOH   +  H2O. 

Alcohol  Acetic  acid 

In  the  case  of  mercaptan  three  atoms  of  oxygen  are  added 
directly  to  the  molecule.  It  will  be  shown  that  this  new  acid, 
which  is  called  ethylsulphonic  acid,  bears  to  sulphuric  acid  a 
relation  similar  to  that  which  acetic  acid  bears  to  carbonic 
acid;  and  that  it  bears  to  sulphurous  acid  a  relation  similar 
to  that  which  acetic  acid  bears  to  formic  acid. 

When  treated  with  phosphorus  pentachloride  it  yields  a  chlo- 
ride, C2HB.SO2CI :  — 


78  DERIVATIVES  OF   METHANE  AND   ETHANi: 

C2H5.SO2OH  +  PCI5  =  C2H6.SO2CI  +  POCI3  +  HCl. 

Ethykulphuryl- 
cMoride 

When  this  is  treated  with  nascent  hydrogen  (zinc  and  hydro- 
chloric acid),  it  is  reduced  to  mercaptan :  — 

C2H6.SO2CI  +  6  H  =  C2H6.SH  +  HCl  +  2  H2O. 

2.   Tmo  Ethers 

These  are  compounds  similar  to  the  ethers.  They  contain 
sulphur  in  the  place  of  the  oxygen  of  the  ethers.  Such  are 
methyl  sulphide,  (CH3)2S,  and  ethyl  sulphide,  (C2H6)2S.  These 
are  made  by  treating  bromo-  or  iodomethane  or  ethane  with 
potassium  sulphide :  — 

2  C2H5I  +  K2S  =  (C2H5)2S  +  2  KI; 

or  by  treating  the  sodium  salt  of  methyl  or  ethyl  mercaptan 
with  methyl  or  ethyl  iodide :  — 

C2H6.SNa  +  C2H5I  =  (C2H5)2S  +  Nal. 

They  are  liquids  with  very  disagreeable  odors.  They  are 
present  in  Ohio  petroleum.  When  oxidized  with  concentrated 
nitric  acid  they  are  converted  into  sidphones,  two  atoms   of 

C2H6V  C2H6V 

oxygen  being  added,  thus  ^>S  +62=  /SO2. 

C2H6/  C2H6/ 

Acetone  reacts  with  ethyl  mercaptan  in  the  presence  of  hydro- 
chloric acid  and  gives  a  thio  ether :  — 

CH3\  HSC2H5  HaC.        /SC2H5 

>C0  +  =  H2O  +  >C< 

CH3/  HSC2H5  H3C/     \SC2H6 

When  this  ether  is  oxidized  with  potassium  permanganate,  it 
gives  the  sulphone :  — 


HsCx       /SO2C2H5 
H3C/     \sO2C2H6 
This  is  sulpbonal,  much  used  as  a  soporific  or  hypnotic. 


SULPHONIC  ACIDS  79 

Trional,  HgCv       /SO2C2H6 

C2H5/     \SO2C2H6, 

which  gets  its  name  because  it  contains  three  ethyl  groups, 
is  made  in  a  similar  manner  from  methyl  ethyl  ketone.  It  is 
said  to  be  a  better  hypnotic  than  sulphonal. 

A  derivative  of  diethyl  sulphide  that  played  a  very  important 
part  in  the  World  War  is  mustard  gas.    This  is  a  dichlorine  sub- 

CIH2C Ii2Cn. 

stitution  product  having  the  formula  /S.     It  is 

CIH2C— H2C/ 
made  by  the  action  of  ethylene  on  sulphur  chloride :  — 

CII2  y\2xX2 CII2CI 

SCI2  +  2  II  =   S< 

CH2         \CH2— CH2CI 

Ethylene  Mustard  gas 

Over  20  tons  a  day  were  made  in  the  United  States  by  this 
method  during  the  war. 

3.   SuLPHONic  Acids 

It  was  stated  above  that  when  mercaptan  is  oxidized  it  is 
converted  into  an  acid  of  the  formula  C2H6.SOSH,  or  ethyl- 
sulphonic  acid.  This  is  the  representative  of  a  large  class  of 
substances  which  are  commonly  made  by  treating  the  aromatic 
compounds  with  sulphuric  acid.  These  sulphonic  acids  can  best 
be  studied  in  connection  with  the  aromatic  series  of  hydro- 
carbons. Under  Benzene  it  will  be  shown  that  when  this 
hydrocarbon  is  treated  with  sulphuric  acid,  a  reaction  takes 
place  that  may  be  represented  thus :  — 


HO.  CeH, 


CeHe  +       \S02  =  >S02  +  H2O. 

HO^  HO/ 

Benzene  Benzenesulphonic  acid 

The  sulphonic  acid  thus  obtained  can  also  be  made  by  oxi- 
dizing the  corresponding  phenylmercaptan  or  hydrosulphide, 
CeHs.SH.    Accordingly,  the  sulphonic  acid  appears  to  be  sul- 


8o      SULPHUR   DERIVATI\'ES   OF   METHANE   AND    ETHANE 

phuric  acid  in  which  a  hydroxyl  has  been  replaced  by  the  phenyl 
radical,  CeHs.  We  may  conclude,  therefore  that  ethylsulphonic 
acid  formed  by  oxidizing  ethylmercaptan  bears  a  similar  relation 

to  sulphuric  acid,  and  corresponds  to  the  formula  /  SO2. 

HCK 

So,  also,  methylsulphonic  acid  obtained  by  oxidation  of  methyl- 

CH3X 

mercaptan  should  be  represented  by  the  formula  /SO2  or 

HO/ 

CH3.SO2OH.  Its  relation  to  sulphuric  acid  is  the  same  as  that 
of  acetic  acid  to  carbonic  acid.  The  sulphonic  acids  are  strong 
monobasic  acids,  hygroscopic,  and  readily  soluble  in  water. 
They  are  very  stable  substances  and  are  not  saponified  by  heat- 
ing with  solutions  of  the  caustic  alkalies,  but  form  stable  salts. 

^° 
They  contain  the  group  — S=0    known  as  the  sulphoxyl  group. 

\0H 

Another  method  by  which  the  sulphonic  acids  can  be  pre- 
pared consists  in  treating  a  sulphite  with  a  halogen  substitu- 
tion product.  Thus  ethylsulphonic  acid  can  be  prepared  from 
potassium  sulphite  and  iodoethane :  — 

K^      C2H5\ 
CaHsI  +    >S02  =     >S02  -I-  KI. 
KCK       KCK 

Potassium  ethylsulphonate 

According  to  this  reaction  the  sulphonic  acids  appear  to  be 
identical  with  the  acid  esters  of  sulphurous  acid,  but  they 
are  not  hydrolyzed  like  ethereal  salts.  The  sulphonic  acids 
as  a  class  are,  for  example,  much  more  stable  than  the  ethereal 
salts  as  a  class.  They  are  closely  related  to  sulphurous  acid, 
and  are  derived  from  it  by  the  substitution  of  a  radical  for 
hydrogen,  just  as  acetic  acid  may  be  regarded  as  derived  from 
formic  acid  by  the  substitution  of  a  radical  for  hydrogen.  These 
relations  are  represented  by  the  following  formulas :  — 


SULPHONIC   ACIDS 


8l 


OH 
OH 


OH 

Carbonic  acid,      0C<_.^  Sulphuric  acid,               02S< 

H  TT 

Formic  acid,         0C<^„  Sulphurous  acid,            02S<^.-. 

Uxl  OH 

PH  OT-T 

Acetic  acid,          0C<       '  Methylsulphonic  acid,  02S<    ^ 

Uxl  Oil 

Any  carboxylic     __     R  ,           ,  ,      .        .,        ^  ^^     R 

.,                    OL<_-._  Any  sulphomc  acid,      02S<_--. 

acid,                           OH  -^       ^                                 OH 

The  difiference  between  a  sulphonic  acid  and  an  ethereal  salt 

of  sulphuric  acid  should  be  specially  noted.     Compare  for  this 


purpose  ethylsulphuric  acid, 


C2H5O 
HO 


>S02,  and  ethylsulphonic 


C  H 
acid,    „_  >S02.     Both  are  monobasic  acids,  and  both  contain 
HU 

ethyl,  but  there  is  a  difference  of  one  atom  of  oxygen  in  their 
composition.  The  reactions  of  the  substances  are  such  as  to 
lead  to  the  conclusion  that  in  ethylsulphonic  acid  the  ethyl 
group  is  directly  connected  with  the  sulphur ;  and  that  in 
ethylsulphuric  acid  the  connection  is  established  by  means  of 
oxygen.  This  is  shown  by  the  fact  that  ethylsulphuric  acid 
is  readily  hydrolyzed  even  by  water  alone.  It  is  an  ester, 
whereas  ethylsulphonic  acid,  which  is  not  an  ester,  cannot  be 
saponified  even  by  boiling  with  the  strongest  alkalies.  The 
sulphonic  acids  are  decomposed,  however,  by  fusing  with  al- 
kalies (see  Benzenesulphonic  acid  (367)). 

The  strongest  argument  in  favor  of  this  view  of  the  structure 
of  the  sulphonic  acids  is  perhaps  that  which  is  founded  on  the 
formation  of  the  sulphonic  acids  by  oxidation  of  the  hydro- 
sulphides  or  mercaptans.  It  can  hardly  be  doubted  that  in 
ethyl  mercaptan  the  sulphur  is  in  direct  combination  with 
the  ethyl;    or,  to  go  still   farther,  that  it  is  in  combination 

H 
with  carbon,  as  represented  in  the  formula,  H3C — C — S — ^H. 

H 
Now,    by    oxidation    of    mercaptan,    three   atoms  of   oxygen 
are  added,  and  the  simplest  view  of   the  reaction  is  that  the 


82      SULPHUR   DERIXATIVES   OF   METHANE   AXD    ETHANE 

sulphur  is  left  undisturbed  in  its  relations  to  ethyl,  but  that 
it  has  taken  up  the  oxygen,  as  represented  in  the  formula 
C2H6— SO2.OH.  As  has  been  shown,  the  oxygen  can  be  re- 
moved again  by  nascent  hydrogen,  by  reducing  the  sulphuryl- 
chloride,  and  the  result  is  mercaptan.  The  study  of  the  sulphonic 
acids  in  their  relations  to  sulphuric  and  sulphurous  acids  has 
been  of  considerable  assistance  in  enabling  chemists  to  form 
conceptions  in  regard  to  theconstitution  of  these  two  acids.  The 
view  which  is  forced  upon  us  by  a  consideration  of  the  reactions 
described  above  is  that  sulphurous  acid  differs  from  sulphuric 

acid  in  containing  a  hydrogen  atom  in  place  of  hydroxyl,  as 

r\xj  XT 

represented    in  the  formulas  02S<_.„   and   02S<_„;    and 

Uxl  (J-H 

further,  that  in  sulphurous  acid  one  hydrogen  is  in  combination 

with  sulphur  and  the  other  with  oxygen.     According  to  this 

the  relation  is  the  same  as  that  between  carbonic  and  formic 

acids. 

Potassium  ethylsulphonate  is  i|omeric  with  potassium  ethyl 

sulphite  formed  by  the  action  of  sulphur  dioxide  on  potassium 

ethylate :  — 

C2H6OK  +  SO2  =  ^'^Q>SO. 

This  salt  is  very  unstable  and  is  hydrolyzed  by  water :  — 
^'^Q>SO  +  HOH  =  CzHoOH  +  KHSO3. 


CHAPTER  VI 
NITROGEN   DERIVATIVES   OF   METHANE   AND   ETHANE 

The  simplest  compounds  of  carbon  containing  nitrogen  are 
hydrocyanic  acid  and  cyanogen.  Hydrocyanic  acid  may  be 
regarded  as  marsh  gas  in  which  three  hydrogen  atoms  have  been 
replaced  by  one  nitrogen,  and  cyanogen  as  a  similar  derivative 

,    ^,  CH4  H3C — CH3 

of  ethane:-     ^^^  NC-CN  " 

Cyanogen,  (CN)2.  —  Most  organic  compounds  that  contain 
nitrogen  give  sodium  cyanide  when  heated  with  sodium.  So, 
also,  potassium  cyanide  is  formed  when  charcoal  containing 
nitrogen  is  heated  with  potassium  carbonate.  Cyanogen  itself 
is  readily  made  by  heating  mercuric  cyanide,  Hg(CN)2.  The 
decomposition  that  takes  place  is,  in  the  main,  like  the  simple 
decomposition  of  mercuric  oxide  in  preparing  oxygen :  — 

Hg(CN)2  =  Hg+(CN)2; 
HgO  =  Hg  +  0. 

But,  in  heating  mercuric  cyanide,  a  black  solid  substance,  para- 
cyanogen,  is  also  formed,  and  remains  behind  in  the  retort.  It 
has  the  same  composition  as  cyanogen,  and  although  its 
molecular  weight  is  not  known,  it  is  a  polymeric  form  of 
cyanogen,  as  heat  transforms  it  into  cyanogen. 

A  better  method  for  the  preparation  of  cyanogen  is  to  heat 
concentrated  solutions  of  potassium  cyanide  and  copper  sul- 
phate :  — 

4  KCN  +  2  CUSO4  =  2  K2SO4  +  Cu2(CN)2  +  C2N2. 

This  reaction  is  analogous  to  that  which  takes  place  when 
potassium  iodide  reacts  with  copper  sulphate,  setting  iodine 

83 


84     NITROGEN   DERIVATI\'ES   OF   METHANE   AND    ETHANE 

free.  Cyanogen  thus  resembles  the  halogens.  When  passed 
into  a  solution  of  potassium  hydroxide  it  reacts  very  much  as 
chlorine  does,  forming  potassium  cyanide  and  cyanate :  — 

2  KOH  +  C2N2  =  KCN  +  KOCN  +  H2O 
2  KOH  +  CI2      =  KCl  +  KOCl  +  H2O. 

Cyanogen  also  resembles  the  halogens  in  forming  an  acid  with 
hydrogen,  HCN,  analogous  to  the  halogen  acids,  the  salts  of  which 
resemble  those  containing  the  halogens.  Thus  silver  cyanide, 
precipitated  from  a  solution  of  potassium  cyanide  by  silver  ni- 
trate, is  soluble  in  ammonia  and  hence  resembles  silver  chloride. 

Cyanogen,  also  called  dicyanogen,  is  present  in  coal  gas  and 
in  the  blast  furnace  gases.  It  boils  at  —20.7°  and  melts  at 
—34.4°.  Water  at  20°  absorbs  4.5  times,  alcohol  23  times,  and 
cocoanut  charcoal  1075  times  its  volume  of  the  gas. 

Cyanogen  (Gr.  kuanos,  blue)  owes  its  name  to  the  fact  that 
several  of  its  compounds  have  a  blue  color.  It  is  a  colorless 
gas,  which  is  readily  soluble  in  water  and  alcohol,  and  is 
extremely  poisonous.  It  burns  with  a  purple-bordered  flame, 
giving  carbon  dioxide  and  nitrogen. 

In  aqueous  solution,  cyanogen  soon  undergoes  change,  and 
a  brown  amorphous  body,  azulmic  acid,  is  deposited.  The 
solution  then  contains  hydrocyanic  acid,  ammonium  oxalate, 
ammonium  carbonate,  and  urea. 

Hydrocyanic  acid,  prussic  acid,  HCN.  —  This  acid  is  found 
in  many  tropical  plants;  and  many  plants,  especially  the 
phanerogams,  contain  cyanogen  compounds  which  easily  split 
ofi  hydrocyanic  acid,  as  for  example,  amygdalin.  It  is  also 
found  in  coal  gas,  and  this  is  the  present  source  of  many  of 
the  cyanogen  compounds.  It  is  prepared  by  decomposing 
metallic  cyanides  with  hydrochloric  acid,  as  represented  in 
the  equation :  — 

KCN  -f-  HCl  =  KCl  +  HCN. 

It  can  also  be  made  by  heating  chloroform  with  alcoholic  am- 
monia and  caustic  potash :  — 

CHCI3  +  NH3  +  4  KOH  =  KCN  -h  3  KCl  -(-  4  H2O. 


SODIUM   CYANIDE  85 

It  is  a  volatile  liquid,  boiling  at  25°,  and  melting  between  —10° 
and  —  12°.  It  has  a  very  characteristic  odor,  suggesting  bitter 
almonds.  It  dissolves  in  water  in  all  proportions,  and  it  is 
this  solution  that  is  known  as  prussic  acid.  It  is  one  of  the 
weakest  acids.  Its  salts  are  decomposed  by  carbon  dioxide. 
Pure  hydrocyanic  acid  is  stable,  but  its  aqueous  solution 
decomposes  and  gives  ammonium  formate,  oxalate,  and  brown 
amorphous  products.  A  small  quantity  of  a  mineral  acid 
prevents  this  decomposition.  By  boiling  with  alkalies  or  acids 
it  is  converted  into  formic  acid  and  ammonia.  A  dilute 
aqueous  solution  of  hydrocyanic  add  is  used  in  medicine.  A 
concentrated  aqueous  solution  of  the  gas  and  the  gas  itself  is 
used  to  kill  insects,  parasites,  and  vermin.  It  is  extremely 
poisonous.  It  is  frequently  used  in  synthetic  work,  e.g.  in  the 
preparation  of  the  hydroxy  acids  from  aldehydes  and  ketones. 

Hydrocyanic  acid  can  be  detected  by  the  fact  that  when  its 
solution  is  treated  with  a  ferrous  and  a  ferric  salt,  made 
alkaline,  and  heated,  a  precipitate  of  Prussian  blue  is  formed 
when  the  mixture  is  acidified ;  or,  by  adding  yellow  ammonium 
sulphide  to  its  solution,  evaporating  to  dryness,  dissolving  in 
water,  and  then  adding  a  drop  of  a  solution  of  ferric  chloride. 
If  hydrocyanic  acid  is  present,  the  solution  turns  a  deep  blood- 
red  in  consequence  of  the  formation  of  ferric  thiocyanate. 

Cyanides.  —  Hydrocyanic,  like  hydrochloric  acid,  forms  a 
series  of  salts,  which  are  called  cyanides.  The  cyanides  of 
the  alkali  metals,  of  the  alkaline  earth  metals,  and  mercuric 
cyanide  are  soluble  in  water.  The  cyanides  of  the  heavy  metals 
have  a  marked  tendency  to  form  double  cyanides,  and  those 
double  cyanides  which  contain  an  alkali  metal  are  soluble  in 
water.  Hence,  the  precipitates  first  formed  by  potassium 
cyanide  in  solutions  containing  the  heavy  metals,  are  dissolved 
by  excess  of  the  cyanide. 

Sodium  cyanide,  NaCN,  is  the  most  important  of  all  the  cyan- 
ides on  account  of  its  use  in  extracting  gold  from  low-grade  ores,  in 
the  manufacture  of  synthetic  indigo,  and  in  gold  and  silver  plating. 
It  has  entirely  displaced  the  more  expensive  potassium  salt.  It 
is  made  on  the  large  scale  by  heating  sodium  in  an  atmosphere 


86  DERIVATIVES   OF  METHANE   AND   ETHANE 

of  dry  ammonia  gas  so  as  to  convert  it  into  sodium  amide  at 
the  lowest  possible  temperature  :  — 

NHs  +  Na  =  NaNHj  +  H. 

Carbon  is  then  added  and  the  temperature  gradually  raised 
to  3oo°-6oo°,  when  the  sodium  amide  is  converted  into  sodium 
cyanamide  (see  Cyanamide  260) :  — 

2  NaNHj  +  C  =  NasNCN  +  2  Hj. 

On  raising  the  temperature  to  70o°-8oo°  the  sodium  cyanamide 
unites  with  more  carbon  to  form  sodium  cyanide :  — 

NajNCN  +  C  =  2  NaCN. 

This  method  gives  a  very  pure  cyanide. 

A  low-grade  sodium  cyanide  (35-45  per  cent)  is  made  by  fusing 
commercial  calcium  cyanamide  (260)  with  sodium  chloride. 

Sodium  cyanide  is  extraordinarily  poisonous  and  great  care 
should  be  taken  in  working  with  it.  It  crystallizes  out  of  hot 
75  per  cent  alcohol  with  two  molecules  of  water  of  crystallization. 
It  dissolves  very  readily  in  water  and  the  solution  has  an  alka- 
line reaction  due  to  partial  hydrolysis  :  — 

NaCN  +  HOH  :$:  NaOH  -|-  HCN. 

When  this  solution  is  boiled  sodium  forinate  and  ammonia  are 
formed :  — 

NaCN  +  2  HOH  =  H.COONa  -|-  NH3. 

This  method  is  used  for  the  preparation  of  sodium  formate  and 
from  it  formic  acid.  The  carbon  dioxide  of  the  air  decomposes 
sodium  cyanide,  setting  hydrocyanic  acid  free,  and  hence  the 
salt  has  the  odor  of  hydrocyanic  acid.  In  the  presence  of  air 
sodium  cyanide  has  the  power  to  dissolve  gold,  and  large  quanti- 
ties are  now  used  for  the  purpose  of  extracting  gold  from  low- 
grade  ores :  — 

2  Au  -h  4  NaCN  -I-  HOH  -f-  O  =  2  NaAu(CN)2  -|-  2  NaOH. 

Sodium  cyanide  is  used  in  quantitative  analysis  and  also  in 
the  preparation  of  organic  compounds,  for  example  in  the 
preparation  of  veronal  (267)  and  of  synthetic  indigo. 


POTASSIUM   FERROCYANIDE  87 

Ferrous  and  ferric  cyanides,  Fe"(CN)2  and  Fe"'(CN)3,  are 
unknown.  When  a  solution  of  potassium  cyanide  is  added 
to  a  solution  of  a  ferrous  or  ferric  salt,  yellow  precipitates  are 
formed  which  dissolve  in  excess  of  potassium  cyanide  to  form 
double  cyanides,  potassium  ferrocyanide,  4  KCN.Fe"(CN)2, 
and  potassium  ferricyanide,  3  KCN.Fe"'(CN)3.  These  com- 
pounds are  salts  of  hydroferrocyanic  acid,  H4Fe"(CN)6,  and 
hydroferricyanic  acid,  H3Fe'"(CN)6,  and  these  acids  are  pre- 
cipitated when  strong  solutions  of  the  salts  are  treated  with 
concentrated  hydrochloric  acid.  The  aqueous  solutions  of  the 
salts  of  these  two  acids  do  not  contain  any  iron  ions,  or  cyanogen 
ions,  but  the  complex  ions,  ferrocyanogen,  Fe"(CN)6,  and 
ferricyanogen,  Fe"'(CN)6-  Thus,  they  are  not  poisonous  and 
give  no  precipitate  of  iron  hydroxide  with  alkalies,  nor  do  they 
react  with  silver  nitrate  to  give  insoluble  silver  cyanide  as  the 
simple  cyanides  do. 

Potassium  ferrocyanide  and  sodium  ferrocyanide  are  now 
manufactured  from  the  hydrocyanic  acid  present  in  coal  gas 
or  in  the  gases  from  the  coking  ovens.  In  the  Bueb  process, 
iron  sulphate  and  ammonia  are  used  to  combine  with  the 
hydrocyanic  acid,  the  resulting  compound  being  insoluble  am- 
monium ferrous  ferrocyanide :  — 

2  FeS04  -I-  2  H2S  -I-  4  NH3  =  2  FeS  -t-  2  (NH4)2S04 

and 

3  FeS  -h  6  NH3  +  12  HCN  =  (NH4)6Fe"(Fe"(CN)6)2  +  3H2S. 

The  insoluble  ammonium  ferrous  ferrocyanide  is  heated  with 
lime  to  recover  the  ammonia  and  to  give  calcium  ferrocyanide. 

In  the  Feld  process  iron  sulphate  and  lime  are  used  to  remove 
the  hydrocyanic  acid  from  the  gases,  the  final  product  being 
calcium  ferrocyanide  :  — 

FeS04  +  Ca(0H)2  =  Fe(0H)2  -|-  CaS04 

and 

Fe(0H)2  +  2  Ca(0H)2  +  6  HCN  =  Ca2Fe"(CN)6  -f  6  H2O. 

The  calcium  ferrocyanide  is  then  converted  into  the  potas- 
sium or  sodium  salt  by  heating  the  solution  with  potassium  or 


88  DERIVATIVES  OF  METHANE  AND   ETHANE 

sodium  carbonate,  filtering  off  the  calcium  carbonate,  and 
evaporating  the  solution  to  crystallization. 

Sodium  ferrocyanide,  Na4Fe"  (CN)6  +  I2H2O,  crystallizes 
in  yellow  monoclinic  prisms.  It  has  displaced  the  potassium 
salt  for  most  purposes. 

Potassium  ferrocyanide,  K4Fe"  (CN)6  +  3  H2O,  yellow  prus- 
siate  of  potash,  crystallizes  in  large  lemon-yellow,  monoclinic 
plates,  readily  soluble  in  water  but  insoluble  in  alcohol. 

When  the  ferrocyanide  is  treated  with  dilute  sulphuric  acid 
it  yields  hydrocyanic  acid  thus :  — 

2  [4  KCN.Fe(CN)2]  +  3  H2SO4 

=  6  HCN  +  2  [KCN.Fe(CN)2]  +  3  K2SO4. 

This  reaction  is  the  one  actually  made  use  of  for  the  prepara- 
tion of  hydrocyanic  acid,  which  is  separated  from  the  water  by 
fractional  distillation. 

When  concentrated  sulphuric  acid  is  used,  the  hydrocyanic 
acid  first  formed  is  hydrolyzed  to  formic  acid,  which  is  decom- 
posed by  the  sulphuric  acid  into  carbon  monoxide  and  water. 
This  method  is  used  in  the  laboratory  for  the  preparation  of 
carbon  monoxide. 

Potassium  ferricyanide,  K3Fe'"(CN)6. —  This  salt,  known 
as  red  prussiate  of  potash,  is  prepared  by  treating  the  ferro- 
cyanide with  chlorine  or  potassium  permanganate  :  — 

K4Fe"(CN)6  -I-  CI  =  K3Fe"'(CN)6  -|-  KCl. 

Potassium  ferricyanide  is  easily  soluble  in  water,  and  crys- 
tallizes from  its  concentrated  solutions  in  large,  dark-red, 
orthorhombic  prisms.  It  is  used  in  making  blue-print 
paper  and  as  a  reagent  in  the  laboratory. 

In  alkaline  solutions  it  is  an  excellent  oxidizing  agent.  Re- 
ducing agents,  such  as  hydrogen  sulphide,  sodium  thiosulphate 
(hyposulphite),  etc.,  convert  it  into  the  yellow  salt. 

Prussian  blue,  Turnbull's  blue,  or  Williamson's  blue  is  precipi- 
tated when  a  solution  of  potassium  or  sodium  ferrocyanide  is 


CYANIC   ACID  89 

treated  with  an  excess  of  ferric  chloride.  It  is  ferric  ferrocyanide, 
Fe4'"(Fe"(CN)6)3.  It  is  used  as  a  blue  pigment.  Soluble 
Prussian  blue  is  formed  when  a  solution  of  ferric  chloride  is 
treated  with  an  excess  of  potassium  or  sodium  ferrocyanide. 
It  is  potassium  ferric  ferrocyanide,  KFe"'(Fe"(CN)6). 

Sodium  ferricyanide,  Na3Fe"'(CN)6  +  H2O,  crystallizing  in 
ruby  red  prisms,  readily  soluble  in  water,  has  practically  dis- 
placed the  more  expensive  potassium  salt. 

For  a  full  account  of  the  many  compounds  of  the  metals  and 
cyanogen,  the  student  is  referred  to  larger  works.  '^ 

Cyanogen  chloride.  —  When  chlorine  is  allowed  to  act  upon 
cyanides  or  dilute  hydrocyanic  acid,  a  volatile  liquid  is  formed 
which  has  the  composition  represented  by  the  formula  NCCl. 
It  boils  at  12.5°,  and  its  vapor  acts  upon  the  eyes,  causing  tears. 
It  is  the  chloride  of  cyanic  acid.  It  is  known  as  liquid  cyanogen 
chloride  to  distinguish  it  from  its  polymer,  solid  cyanogen  chloride. 
The  latter,  known  as  cyanuric  chloride,  has  the  formula  (CN)3Cl3, 
(m.  p.  145°)  and  is  formed  by  treating  anhydrous  hydrocyanic 
acid  with  chlorine  in  direct  sunlight.  The  liquid  variety  is 
partially  transformed  into  the  solid  when  kept  in  sealed  tubes. 

Similar  compounds  of  cyanogen  with  bromine  and  iodine  are 
also  known. 

Cyanic  acid,  NCOH.  —  When  a  cyanide  of  an  alkali  is  fused 
with  an  oxidizing  agent  as  red  lead  it  takes  up  oxygen  and  is 
converted  into  a  cyanate :  — 

NCK  +  0  =  NCOK. 

Cyanic  acid  is  readily  hydrolyzed  by  water,  yielding  ammo- 
nium hydrogen  carbonate :  — 

NCOH  +  2  H2O  =  NH4HCO3. 
Hence  a  cyanate  effervesces  with  dilute  hydrochloric  acid  like 
a  carbonate. 

The  potassium  salt  is  readily  soluble  in  water,  but  is  hydro- 
lyzed when  heated  with  water,  yielding  ammonia  and  mono- 
potassium  carbonate :  — 

NCOK  +  2  H2O  =  KHCO3  +  NH3. 
1  Thorpe's  Dictionary  of  Applied  Chemistry,  article  on  Cyanides. 


go  DERIVATIVES   OF  METHANE  AND   ETHANE 

The  most  interesting  salt  of  cyanic  acid  is  ammonium  cyanate, 
NCO.NH4.  It  can  be  made  by  adding  ammonium  sulphate  to 
a  solution  of  the  potassium  salt.  It  is  readily  soluble  in  water ; 
but,  if  allowed  to  stand  in  solution,  or  if  its  solution  is  heated 
to  boiling,  it  is  completely  transformed  into  urea,  which  is  isomeric 
with  it.  The  interest  connected  with  this  transformation  was 
referred  to  in  the  introductory  chapter.  It  will  be  treated  of 
more  fully  under  urea. 

Cyanuric  acid,  C3N3HJO3  +  2  H2O.  —  This  acid  is  a  poly- 
mer of  cyanic  acid.  It  is  made  by  heating  cyanuric  chloride 
with  water,  and  also  by  heating  urea.  It  is  a  tribasic  acid. 
When  distilled  it  gives  cyanic  acid. 

Thiocyanic  acid,  NCSH.  —  Just  as  the  cyanides  of  the 
alkalies  take  up  oxygen  and  are  converted  into  cyanates,  so  also 
they  take  up  sulphur  and  are  converted  into  thiocyanates :  — 

NCK  +  S  =  NCSK. 

Potassium 
thiocyanate 

Potassium  thiocyanate  is  usually  made  by  fusing  potassium 
ferrocyanide  with  sulphur  and  potash :  — 

K4Fe(CN)6  +  K2CO3  +  8  S  =  6  KSCN  +  FeSa  +  CO2  +  O. 

It  crystallizes  in  long,  striated  prisms  extremely  soluble  in 
water.  It  is  deliquescent.  When  100  parts  of  water  at  10.8° 
are  mixed  with  150  parts  of  the  salt,  the  temperature  sinks  to 
—  23.7°  By  evaporation  of  the  solution,  the  salt  can  be  re- 
covered, as  it  is  not  hydrolyzed  by  water. 

Ammonium  thiocyanate,  NCS.NH4. —  This  salt  is  most  easily 
prepared  by  treating  carbon  bisulphide  with  concentrated 
alcoholic  ammonia :  — 

CS2  +  4  NH3  =  NCS.NH4  +  (NH4)2S. 

The  salt  crystallizes  in  plates.  It  melts  at  i3o°-i4o°,  and 
at  this  temperature  is  partly  transformed  into  the  isomeric 
substance  thiourea  (267).  (Analogy  to  transformation  of 
ammonium  cyanate  into  urea.) 


ETHYL   CYANIDE,   PROPANE  NITRILE  91 

Ferric  thiocyanate,  Fe(SCN)3,  is  the  red  compound  formed 
when  ferric  chloride  and  potassium  or  ammonium  thiocyanate 
react.    The  reaction  is  used  as  a  test  for  ferric  iron. 


Having  thus  dealt  with  the  more  important  simpler  cyanogen 
compounds,  some  of  the  nitrogen  derivatives  of  the  hydro- 
carbons will  now  be  taken  up.  These  may  be  divided  into 
three  classes :  — 

(i)    Those  which  are  related  to  the  cyanides; 

(2)  Those  which  are  related  to  ammonia; 

(3)  Those  which  are  related  to  nitric  acid. 

Cyanides  or  Nitriles 

Methyl  cyanide,  ethane  nitrile,  CH3.CN.  -^  This  is  present  in 
the  first  runnings  obtained  in  the  rectification  of  crude  benzene, 
CeHs.  It  is  formed  by  distilling  potassium  methyl  sulphate 
with  potassium  cyanide :  — 

^'>S04  +  KCN  =  K2SO4  +  CH3CN. 

It  is  best  made  from  potassium  cyanide  and  dimethyl  sulphate :  — 

KCN  +  (CH3)2S04  =  CH3CN  +  KCH3SO4. 

It  is  a  liquid,  boiling  at  81.6°;  miscible  in  all  proportions  with 
water;   it  burns  with  a  luminous  flame. 

According  to  the  method  of  preparation,  it  must  be  regarded 
as  an  ethereal  salt  of  hydrocyanic  acid,  containing  methyl  in 
the  place  of  the  potassium  of  the  potassium  salt. 

Ethyl  cyanide,  propane  nitrile,  C2H5.CN.  —  This  is  made  in 
the  same  way  as  the  methyl  compound.  Also  by  heating  chloro- 
ethane  with  potassium  cyanide :  — 

C^HsCl  +  KCN  =  C2H6.CN  +  KCl. 

It  is  a  liquid  boiling  at  97.08° ;  soluble  in  water;  it  is  just  as 
poisonous  as  hydrocyanic  acid. 


92  DERIVATIVES  OF  METHANE  AND   ETHANE 

The  two  most  characteristic  reactions  of  these  cyanides  are 
(i)  that  which  is  effected  by  solutions  of  caustic  alkalies  or 
mineral  acids,  and  (2)  that  effected  by  nascent  hydrogen. 

When  methyl  cyanide  is  heated  with  a  solution  of  caustic 
potash,  it  yields  potassium  acetate  and  ammonia :  — 

CH3.CN  +  H2O  +  KOH  =  CH3.CO2K  +  NH3. 

With  dilute  mineral  acids  acetic  acid  and  ammonia  are 
formed : 

CH3CN  +  2  H2O  =  CH3COOH  +  NH3. 

Acetic  acid 

This  reaction  is  strictly  analogous  to  that  which  takes  place 
with  hydrocyanic  acid,  yielding  formic  acid  (55).  In  the 
same  way  ethyl  cyanide  yields  propionic  acid,  C2H5.CO2H. 
Thus,  by  making  a  cyanide,  we  have  it  in  our  power  to  make 
an  acid  containing  the  same  number  of  carbon  atoms. 

This  reaction,  therefore,  makes  it  possible  to  pass  from  an 
alcohol  to  an  acid  containing  one  atom  of  carbon  more  than 
the  alcohol  contains.  It  has  been  of  great  service  in  the  study 
of  the  compounds  of  carbon. 

Note  por  Student.  —  Show  how,  by  starting  with  methyl  alcohol,  acetic 
acid  may  be  made  by  passing  through  the  cyanide.  How  is  acetic  acid 
converted  into  methyl  alcohol? 

There  are  two  ways  in  which  the  cyanogen  group  can  be 
linked  to  methyl  in  methyl  cyanide;  viz.,  either  by  the  carbon 
atom,  as  represented  in  the  formula,  H3C — C=N,  or  by  the 
nitrogen  atom,  as  represented  thus,  H3C— N=C.  The  ease 
with  which  the  nitrogen  is  separated  from  the  compound,  leav- 
ing the  two  carbon  atoms  united,  as  shown  in  the  reaction  with 
caustic  potash,  naturally  leads  to  the  conclusion  that  the  former 
view  is  the  correct  one.  If  this  is  correct,  it  would  appear  to 
follow  that  in  potassium  cyanide  the  potassium  is  in  combi- 
nation with  carbon,  as  represented  in  the  formula  K — C=N, 
and  further  that  in  hydrocyanic  acid  the  hydrogen  is  in  combi- 
nation with  carbon,  as  shown  thus,  H — C=N,  since  it  gives 
formic  acid  and  ammonia  when  hydrolyzed. 


ETHYL   CYANIDE,   PROPANE  NITRILE  93 

In  consequence  of  the  close  relation  existing  between  the 
cyanides  and  the  acids,  the  former  are  often  called  the  niiriles 
of  the  acids.  Thus  methyl  cyanide,  which  is  converted  into 
acetic  acid  by  boiling  with  dilute  mineral  acids,  is  called  the 
nitrile  of  acetic  acid,  or  aceionitrile,  ethane  nitrile.  In  the 
same  way  hydrocyanic  acid  itself  may  be  regarded  as  the  nitrile 
of  formic  acid,  or  formonitrile,  methane  nitrile. 

When  methyl  cyanide  is  treated  with  nascent  hydrogen, 
it  is  converted  into  a  substance  which  closely  resembles  am- 
monia, known  as  ethylamine.     It  will   be  shown  to  bear  to 

[C2H5 
ammonia  the  relation  indicated  by  the  formula  N  <  H      ;      i.e., 

IH 
it  is  ammonia  in  which  one  hydrogen  has  been  replaced  by  ethyl. 
The  reaction  may  be  represented  by  the  equation :  — 


H3C— C=N+4H  =  H3C— CH2— NH2 


C2H6 

orN]  H 
IH 


This  transformation  strengthens  the  conclusion  already  reached, 
that  the  two  carbon  atoms  in  methyl  cyanide  are  directly  united. 
If  this  were  not  the  case,  it  is  difiEicult  to  see  how  a  compound 
containing  ethyl  in  which  the  two  carbon  atoms  are  unques- 
tionably united,  could  be  formed  so  easily  from  it. 

Just  as  methyl  cyanide  yields  ethylamine  when  treated  with 
nascent   hydrogen,  so  hydrocyanic  acid   yields  methylamine, 

[CH3 
N    H     :  — 
H 


H— C=N  -1-  4  H  =  H3C— NH2 


The  amines,  or  substituted  ammonias,  will  be  treated  of 
more  fully  hereafter. 


94  DERIVATIVES   OF   METHANE  AND   ETHANE 

ISOCYANIDES    OR    CaRBYLAMINES 

If,  in  making  an  ethereal  salt  of  hydrocyanic  acid  from  a  salt, 
the  silver  salt  is  used,  a  compound  is  obtained  having  the  same 
composition  as  the  cyanide,  but  differing  very  markedly  from  it. 
The  substance  thus  obtained  is  called  an  isocyanide  or  carbyl- 
amine. 

Ethyl  isocyanide  or  ethyl  carbylamine,  C2H6NC.  —  This 
compound  is  obtained  when  silver  cyanide  and  iodoethane  are 
heated  together :  — 

C2H6I  +  AgNC  =  C2H5NC  +  Agl. 

It  is  also  formed  when  chloroform  and  ethylamine  are  heated 
with  potassium  hydroxide  in  alcoholic  solution :  — 

I  C2H6 
CHCI3  +  N  ^  H       +3  KOH  =  C2H6NC  +  3  KCl  +  3  H2O. 
IH 

It  is  a  liquid  boiling  at  79°.  It  is  characterized  by  an  extremely 
disagreeable  odor.  The  methyl  compound  obtained  by  the 
same  method  boUs  at  59.6°,  but  otherwise  has  properties  almost 
identical  with  those  of  ethyl  isocyanide. 

The  reactions  of  these  substances  are  quite  different  from 
those  of  the  cyanides.  They  are  decomposed  only  with  great 
difficulty  by  the  caustic  alkalies ;  but,  when  heated  with  dilute 
hydrochloric  acid,  they  undergo  an  interesting  change,  which 
is  represented  by  the  following  equation  in  the  case  of  the  methyl 
compound : 

CH3.NC  +  2  H2O  =  CH3NH2  +  H.CO2H. 

Methylamine  Formic  acid 

This  reaction  indicates  that  in  the  isocyanides  the  isocyanogen 
group  is  united  to  the  radical  by  means  of  nitrogen,  as  repre- 
sented by  the  formula  H3C — N=C.  This  is  probably  the 
reason  why  when  they  undergo  hydrolysis,  the  nitrogen  re- 
mains in  combination  with  the  radical,  while  the  carbon  of 
the  isocyanogen  group  passes  out  of  the  compound.  The  con- 
duct of  ethyl  isocyanide  is  represented  by  the  equation :  — 


ETHYL   ISOCYANIDE   OR   ETHYL   CARBYLAMINE        95 

C2HB.NC  +  2  H2O  =  C2H6NH2  +  H.CO2H. 

Ethylamine  Formic  acid 

The  isocyanides  are  reduced  by  nascent  hydrogen  to  secon- 
dary amines.    Thus  methyl  isocyanide  gives  dimethylamine :  — 

H3C— N=C  +  2  H2  =  H3C— N— CH3, 

H 

while  ethyl  isocyanide  gives  ethylmethylamine :  — 

C2H6— NC  +  2  H2  =  C2H6— N— CH3. 

I 
H 

These  reactions  show  that  the  radicals,  methyl  and  ethyl, 
are  in  combination  with  the  nitrogen  in  the  isocyanides. 

Some  chemists  assume  the  presence  of  bivalent  carbon  in  the 
isocyanides  as  in  carbon  monoxide. 

The  isocyanides  give  the  isocyanates  (96)  on  oxidation :  — 

H3C— N=C  +  O  =  H3C— N=c:=o. 

The  reactions  of  the  cyanides  and  of  the  isocyanides,  and 
the  conclusions  drawn  from  them,  admirably  illustrate  the 
methods  used  in  determining  the  structure  of  compounds  of 
carbon;  and  they  are  especially  valuable,  as  the  connection 
between  the  facts  and  the  conclusions,  as  expressed  in  the 
formulas,  can  be  traced  so  clearly. 

The  fact  that  the  silver  salt  of  hydrocyanic  acid  yields  iso- 
cyanides, while  the  potassium  and  other  salts  yield  cyanides, 
with  the  halogen  derivatives  of  the  hydrocarbons,  suggests 
that  in  silver  cyanide  the  metal  may  be  in  combination  with 
nitrogen  and  not  with  carbon,  while  in  the  potassium  salt 
it  may  be  in  combination  with  carbon.  Another  possible 
view  is  that  the  cyanides  in  general  have  the  constitution 
MN :  C,  in  which  M  represents  a  univalent  metal.  When 
ethyl  iodide  acts  upon  potassium  cyanide,  the  principal  reaction 
is  direct  addition :  — 


96  DERIVATIVES   OF  METHANE  AND   ETHANE 

KN :  C  +  CaHsI  =  KN :  C  <  ^'^^ 

If  the  product  should  break  down  with  elimination  of  potas- 
sium iodide,  the  result  would  be  a  cyanide,  N^C.C2H5.  In  the 
case  of  silver  cyanide  the  first  action  may  be  this :  - 

C2H6\ 

AgN:C  +  C2H6l=     Ag^N:C. 
1/ 

The  addition  product  thus  formed  would  then  break  down  into 
silver  iodide  and  the  isocyanide  C2H5N :  C. 

A  fact  to  be  borne  in  mind  in  connection  with  the  rela- 
tions between  the  cyanides  and  the  isocyanides  is  that  it 
has  been  shown  that  some  of  the  isocyanides  are  transformed 
into  cyanides  by  heat. 

Taking  into  consideration  the  facts  presented  by  hydrocyanic 
acid,  the  cyanides  and  isocyanides,  it  seems  not  improbable  that 
the  acid  is  capable  of  assuming  both  forms  represented  by  the 
formulas  HN :  C  and  N :  CH,  and  that  the  salts  are  derived  from 
one  or  the  other  of  these  forms  or  both.  Phenomena  of  this  kind 
are  not  uncommon.  Thus  diazomethane  reacts  with  hydrocyanic 
acid  and  gives  both  methyl  cyanide  and  methyl  isocyanide :  — 

H2CN2  +  HCN  =  H3C— CN  +  N2 ; 
H2CN2  -I-  HNC  =  H3C— NC  -I-  N2. 

A  compound  that  reacts  as  though  it  had  two  different  formulas 
is  called  a  tautomeric  compound.  The  phenomenon  is  called 
tautomerism. 

ISOCYANATES 

Two  series  of  compounds  bearing  to  cyanic  acid  the  same 
relation  that  the  cyanides  and  isocyanides  bear  to  hydrocyanic 
acid  may  be  expected. 

The  cyanates  of  the  formula  R — 0 — CN  have  not  yet  been 
obtained. 

In  the  isocyanates  (first  called  cyanates)  the  radical  is 
believed  to  be  united  to  the   nitrogen,   as   represented    thus, 


THIOCYANATES  97 

R — N^CO.  The  isocyanates  are  made  by  distilling  potas- 
sium cyanate  with  the  potassium  salt  of  methyl  or  ethyl- 
sulphuric  acid.  They  can  be  made  also  by  heating  iodo- 
methane  or  iodoethane  with  silver  cyanate.  They  are  very 
volatile  substances,  with  penetrating  and  suffocating  odors. 

The  isocyanates  readily  yield  substituted  ammonias  on 
hydrolysis,  just  as  the  isocyanides  do  :  — 

C2H6— N=CO  -I-  H2O  =  C2H6.NH2  +  CO2; 
CH3— N=CO  +  H2O  =  CH3.NH2  +  CO2. 

Thiocyanates 

The  ethereal  salts  of  thiocyanic  acid  are  easily  made  by  dis- 
tilling potassium  thiocyanate  and  the  potassium  salt  of  methyl- 
or  ethylsulphuric  acid  under  reduced  pressure  :  — 

^'>S04  +  KSCN  =  CH3SCN  +  K2SO4, 

and  also  by  the  action  of  cyanogen  chloride  on  sodium  methyl 
sulphide  or  sodium  ethyl  sulphide :  — 

HaCSNa  -I-  CICN  =  H3CSCN  +  NaCl, 

which  shows  at  once  the  structure  of  the  compounds.  The  ethyl 
compound,  which  is  very  similar  to  the  methyl  compound,  is 
a  liquid  boiling  at  142°. 

When  boiled  with  fuming  nitric  acid,  it  is  oxidized  to  ethyl- 
sulphonic  acid.  Now,  it  has  been  shown  that  in  ethylsulphonic 
acid  the  ethyl  is  in  combination  with  the  sulphur.  It  hence 
follows  that,  in  the  thiocyanates  obtained  from  potassium 
thiocyanate,  the  radical  is  also  in  combination  with  sulphur, 
as  indicated  in  the  formula,  C2H6 — S — CN.  This  view  is 
supported  by  the  fact  that  ethyl  thiocyanate  readily  yields 
ethyl  mercaptan  when  treated  with  nascent  hydrogen  :  — 

C2H5SCN  +  H2  =  C2H5SH  -I-  HCN. 

The  hydrocyanic  acid  first  formed  is  reduced  to  methyl- 
amine.  The  thiocyanates  are  converted  into  isothiocyanates 
or  mustard  oils  by  distillation. 


gS  DERIVATIVES   OF   METHANE   AND   ETHANE 

ISOTHIOCYANATES   OR   MUSTARD   OiLS 

These  are  compounds  isomeric  with  the  thiocyanates.  The 
best-known  member  of  the  class  is  ordinary  mustard  oil,  allyl 
isothiocyanate  (283),  to  the  presence  of  which  in  mustard  seed, 
the  pecuHar  pungent  odor  and  taste  of  mustard  are  due.  Hence 
they  are  generally  called  mustard  oils.  The  mustard  oils  are 
made  by  means  of  a  series  of  somewhat  complicated  reactions, 
which  it  is  rather  difficult  to  interpret  without  a  comparison 
with  some  similar  reactions  that  take  place  between  simpler 
substances. 

When  dry  ammonia  and  dry  carbon  dioxide  act  upon  each 
other,   so-called  anhydrous  ammonium  carbonate  is  formed. 

This  is  really  the  ammonium  salt  of  carbamic  acid,  OC  <_.„''. 

Uxl 

Its  formation  is  represented  thus :  — 

OCO  +  HNH2  =  OC<22  +NH3  =  oc<^^'. 

JNxla  JNrl2 

Carbamic  Ammonium 

acid  carbamate 

Now,  remembering  that  carbon  bisulphide  is  similar  to  carbon 
dioxide,  and  that  ethylamine  is  similar  to  ammonia,  we  can 
readily  understand  what  takes  place  when  these  two  sub- 
stances are  brought  together :  — 

SCS  +  HNHCA-  SC<^ja^^^^_.  SC<,'^«    . 

Ethyldithiocarbamic  acid  Ethylammonium  salt 

The  product  formed  is  the  ethylammonium  salt  of  the  acid 

SC<„„  ,  which  is  called  ethyldithiocarbamic  acid.    When 

a  solution  of  this  ethylammonium  salt  is  treated  with  silver 
nitrate,  the  corresponding  silver  salt  is  precipitated :  — 

^^<^HSk+^^^°-  SC<^aT^''^+  CANH3NO3. 

Etbylammoaium  nitrate 


ETHYL   MySTARD   OIL  gg 

Finally,  when  this  silver  salt  is  boiled  with  water,  it  breaks  down, 
yielding  ethyl  mustard  oil,  silver  sulphide,  and  hydrogen  sul- 
phide :  — 

2  SC<?'^^'^'  =  2  SCNC2H6  +  H2S  +  AgaS. 

^     S  Ethyl  mustard  oil 

Ethyl  mustard  oil  is  an  oily  liquid  that  does  not  mix  with 
water.  It  has  a  very  penetrating  odor,  and  acts  upon  the 
mucous  membrane  of  the  eyes  and  nose  in  the  same  way  as 
ordinary  mustard  oil.     Its  boiUng  point  is  134° 

Some  of  th?  arguments  have  been  stated  which  lead  to  the 
view  that  in  the  thiocyanates  the  radical  is  in  combination 
with  sulphur.  The  reactions  of  the  mustard  oils  lead  just  as 
clearly  to  the  conclusion  that  in  them  the  radical  is  in  com- 
bination with  nitrogen.  In  the  first  place,  they  are  made  from 
the  amines.  Again,  when  heated  with  dilute  mineral  acids, 
ethyl  mustard  oil  is  hydrolyzed,  yielding  ethylamine,  carbon 
dioxide,  and  hydrogen  sulphide :  — 

SC=NC2H5  -I-  2  H2O  =  C2H5NH2  +  H2S  +  CO2. 

And  further,  nascent  hydrogen  converts  it  into  ethylamine  and 
thioformic  aldehyde  (i.e.,  formic  aldehyde  in  which  the  oxygen 
has  been  replaced  by  sulphur) :  — 

SC=NC2H5  -f-  4  H  =  C2H6.NH2  +  H2CS. 

The  thioformic  aldehyde  is  at  once  polymerized  to  trithio- 
formic  aldehyde  (H2CS)3.  Thus,  the  thiocyanates  yield  mer- 
captans  with  nascent  hydrogen,  while  the  isothiocyanates 
yield  substituted  ammonias.  These  facts  point  to  the  relations 
expressed  in  the  formulas,  R — S — CN  for  the  thiocyanates, 
and  R — N==CS  for  the  isothiocyanates  or  mustard  oils. 


In  reviewing  now  the  compounds  of  the  hydrocarbons  which 
are  related  to  cyanogen,  it  appears  that  there  are  two  isomeric 
series  of  these,  the  names  and  general  formulas  of  which  are 
given  below :  — 


lOO  DERIVATIVES  OF   MEJHANE  AND   ETHANE 

Cyanides,  R — C^N    ....   Isocyanides  or    1  ^^ ^^ 

Carbylamines,  [ 

Cyanates,  R— 0— CN      .     .     .  Isocyanates,  R— N=CO. 

Thiocyanates,  R— S— CN     .     .   Isothiocya-  1 

nates  or  Mus-  >  R— N=CS. 
tard  oils,  ) 

Of  these  all  are  known  except  the  cyanates. 

Substituted  Ammonias 

When  methyl  iodide  is  treated  with  anamonia,  methyl- 
ammonium  iodide  is  formed :  — 

H3CI  +  NH3  =  H3CNH3I. 

This  reaction  is  analogous  to  that  which  takes  place  when 
ammonia  and  hydriodic  acid  combine  to  form  ammonium  iodide. 
When  methylammonium  iodide  is  distilled  with  a  solution  of 
potassium  hydroxide,  methylamine  is  obtained :  — 

H3CNH3I  +  KOH  =  H3C— NH2  +  KI  +  H2O, 

just  as  ammonia  results  when  ammonium  iodide  is  treated  with 
potassium  hydroxide. 

Methylamine  reacts  with  methyl  iodide  just  as  ammonia 
does,  giving  dimethylammonium  iodide :  — 

H3CNH2  +  H3CI    =    (H3C)2NH2l. 

With  potassium  hydroxide  this  yields  dimethylamine :  — 
(H3C)2NH2l  +  KOH  =  KI  +  H2O  +  (HsOzNH. 

Dimethylamine  also  reacts  with  methyl  iodide,  giving  tri- 
methylammonium  iodide :  — 

(H3C)2NH  +  H3CI  =  (H3C)3NHI, 

which  with  potassium  hydroxide  gives  trimethylamine :  — 

(H3C)3NHI  +  KOH  =  (H3C)3N  +  KI  +  H2O. 

Finally,    the    trimethylamine    combines   with   methyl   iodide, 
giving  tetramethylammonium  iodide :  — 

(H3C)3N  +  H3CI  =  (H3C)4NI. 


METHYLAMINE  lOI 

The  three  substances  methylamine,  dimethylamine,  and 
trimethylamine  are  regarded  as  substituted  ammonias  in  which 
one,  two,  and  three  hydrogen  atoms  of  ammonia  are  replaced 
by  methyl.  The  last  substance  is  ammonium  iodide  in  which 
all  four  hydrogen  atoms  are  replaced  by  methyl.  The  names  of 
the  substances  indicate  this  relationship. 

All  the  above  reactions  go  on  simultaneously  when  ammonia 
reacts  with  methyl  iodide,  the  ammonia  partly  setting  free  the 
substituted  ammonias  from  the  iodides,  and  they  react  at  once 
with  the  methyl  iodide  present.  It  is  hence  impossible  to  pre- 
pare pure  substances  by  this  method.  A  mbcture  of  the  amines 
is  always  obtained.  It  is,  however,  an  excellent  method  for 
the  preparation  of  tetramethylammonium  iodide. 

Methylamine,  H3CNH2.  —  This  compound  can  be  prepared 
by  treating  iodomethane  with  ammonia. 

It  is  best  made  from  dimethyl  sulphate  and  ammonia :  — 

(CH30)2S02  +  2  NH3  =  H3CNH2  +  H3CO  — SO2— ONH4 

Methylamine  Ammonium 

methyl  sulphate 

or  by  heating  formaldehyde  (40  per  cent  solution)  with  am- 
monium chloride :  — 

3  H.CHO  +  2  NH3  =  2  H3C— NH2  +  CO2  -I-  H2O. 

It  was  first  made  by  heating  methyl  isocyanate,  CH3N=:C0, 
with  a  solution  of  caustic  potash :  — 

CH3N=C0  -I-  H2O  =  CH3NH2  -I-  CO2. 

It  has  been  stated  that  it  is  formed  by  treating  hydrocyanic 
acid  with  nascent  hydrogen :  — 

HCN  -I-  4  H  =  CH3NH2. 

It  occurs  in  nature  in  herring  brine,  in  Mercurialis  perennis, 
and  is  one  of  the  products  of  the  distillation  of  nitrogenous 
animal  matter  as  well  as  of  wood. 

Methylamine  is  a  gas  that  is  easily  condensed  to  a  liquid. 
Its  boiling  point  is  —6°.  It  smells  like  ammonia  and  fish. 
It  burns  with  a  yellow  flame.     It  is  more  strongly  basic  and  more 


I02  DERIVATIVES   OF  METHANE   AND   ETHANE 

soluble  in  water  than  ammonia,  i  volume  of  water  at  12.5° 
taking  up  11 50  volumes  of  the  gas.  This  solution  acts  almost 
exactly  like  a  solution  of  ammonia  in  water.  Like  ammonia  it 
precipitates  many  metallic  hydroxides  from  solutions  of  their 
soluble  salts,  but,  unlike  ammonia,  it  does  not  dissolve  pre- 
cipitated hydroxides  of  nickel,  cobalt,  and  cadmium  when  added 
in  excess.     It  dissolves  aluminium  hydroxide. 

Methylamine  forms  salts  with  acids  in  the  same  way  that 
ammonia  does ;  that  is,  by  direct  addition.  The  action  towards 
nitric  and  sulphuric  acids  takes  place  in  accordance  with  the 
following  equations :  — 

NH2CH3  +  HNO3  =  (NH3CH3)N03; 

2  NH2CH3  +  H2SO4    =    (NH3CH3)2S04. 

These  salts  are  called  methylammonium  nitrate  and  methyl- 
ammonium  sulphate  respectively. 

Dimethylamine,  NH(CH3)2.  —  This  is  formed  by  heating 
iodomethane  with  alcoholic  ammonia  :  — 

2  CH3I  +  2NH3  =  NH(CH3)2.HI  +  NH4I 

and  by  the  action  of  nascent  hydrogen  on  methyl  isocyanide 
(95). 

It  is  also  formed,  together  with  methylamine,  as  a  product  of 
the  distillation  of  wood. 

It  is  best  made  from  nitrosodimethylaniline  (346)  by  heating  it 
with  a  solution  of  sodium  hydroxide :  — 

CeH4<JJ^^^^)^+  NaOH  =  HN(CH3)2  +  C,^<^f. 

Nitrosodimethylaniline  Dimethylamine  Sodium  salt  of 

nitrosophenol 

It  is  a  gas  which  condenses  to  a  liquid  at  7.2°.  Its  prop- 
erties are  much  like  those  of  methylamine. 

Trimethylamine,  N(CH3)3.  —  Trimethylamine  is  formed  as 
one  of  the  products  of  the  treatment  of  iodomethane  with 
ammonia.  It  occurs  rather  widely  distributed  in  nature, 
as  in  the  blossoms  of  the  English  hawthorn,  the  wild  cherry,  and 
the  pear.  It  is  contained  in  large  quantity  in  herring  brine,  and 
is  a  common  product  of  the  decomposition  by  heat  of  organic 


TRIMETHYLAMINE  103 

substances  that  contain  nitrogen,  like  betaine  of  the  sugar  beet. 
It  can  be  obtained  from  the  so-called  "  vinasse."  This  is  the 
liquid  left  after  fermenting  beet  sugar  molasses  and  distilling 
off  the  alcohol  formed.  When  it  is  evaporated  to  dryness,  and 
the  residue  subjected  to  dry  distillation,  trimethylamine  is 
given  off.  This  is  collected  as  the  hydrochloric  acid  salt, 
N(CH3)3HC1.  When  heated  with  hydrochloric  acid,  it  yields 
ammonium  chloride  and  chloromethane  :  — 

N(CH3)3HC1  +  3  HCl  =  3  CH3CI  +  NH4CI. 

The  chloromethane  is  utilized  for  the  purpose  of  producing  low 
temperatures  and  as  a  methylating  agent. 

Trimethylamine  is  made  by  heating  formalin  with  ammo- 
niurd  chloride  in  an  autoclave  to  iio'^ :  — 

9  HCHO  +  2  NH3  =  2  N(CH3)3  +  3  CO2  +  3  H2O. 

Trimethylamine  is  a  liquid  boiling  at  3.5°.  It  has  a  strong 
ammoniacal  and  fishy  odor.  It  is  very  soluble  in  water  and 
alcohol,  and  is  a  strong  base. 

The  ethylamines  are  very  much  like  the  methyl  compounds, 
and  hence  need  not  be  specially  described. 

When  triethylamine  is  heated  with  iodoethane,  the  two 
unite,  forming  the  compound  tetraethylammonium  iodide, 
N(C2H5)4l,  which  is  to  be  regarded  as  ammonium  iodide  in 
which  all  four  hydrogen  atoms  have  been  replaced  by  ethyl 
groups.  If  silver  oxide  is  added  to  the  aqueous  solution  of  the 
iodide,  silver  iodide  is  formed,  and  by  evaporation  of  the  filtrate 
crystals  of  tetraethylammonium  hydroxide,  N(C2H6)40H,  are 
obtained.  This  is  plainly  the  hjrpothetical  ammonium  hydrox- 
ide in  which  the  four  ammonium  hydrogens  have  been  replaced 
by  four  ethyl  groups.  Its  solutions  act  like  caustic  potash.  It 
is  very  caustic,  attacks  glass,  attracts  carbon  dioxide  from  the 
air,  saponifies  (71)  ethereal  salts,  and  gives  the  same  precipi- 
tates as  caustic  potash.  It  is  as  strong  a  base  as  potassium 
hydroxide. 

Tetramethylammonium  hydroxide,  (CH3)4NOH,  is  made  in 
the  same  way  as  the  tetraethyl  compound,  and  is  a  stronger 


I04  DERIVATIVES  OF  METHANE  AND   ETHANE 

base  than  tetraethylammonium  hydroxide.  When  heated  it 
gives,  trimethylamine  and  methyl  alcohol :  — 

(CH3)4NOH  =  (CH3)3N  +  CH3OH. 

Another  method  for  the  formation  of  substituted  ammonias 
in  which  but  one  radical  is  present,  as  ethylamine,  NH2.C2H6, 
or  in  general  NH2.R,  consists  in  treating  nitro  compounds  (107) 
with  nascent  hydrogen  compounds.  Nitro  compounds  are 
substitution  products  containing  the  group  NO2  in  the  place 
of  hydrogen.  Thus,  for  example,  when  nitromethane,  CH3.NO2 
is  treated  with  hydrogen,  this  reaction  takes  place :  — 

CH3.NO2  +  6  H  =  CH3.NH2  +  2  H2O. 

In  connection  with  the  aromatic  compounds,  it  will  be  shown 
that  this  reaction  is  a  most  important  one,  from  an  industrial 
as  well  as  a  scientific  point  of  view.  It  may  be  said  in  anticipa- 
tion that  the  manufacture  of  aniline,  and  consequently  of  all  the 
many  valuable  dyestuffs  and  other  compounds  derived  from  and 
related  to  aniline,  is  based  upon  this  reaction. 

Just  as  we  may  look  upon  methylamine  and  the  related  com- 
pounds as  ammonia  in  which  one  hydrogen  atom  is  replaced  by 
methyl,  so  also  we  may  regard  them,  and  with  equal  right,  as 
marsh  gas,  in  which  hydrogen  has  been  replaced  by  the  group 
or  residue  NH2.  Owing  to  the  frequency  of  the  occurrence  of 
this  univalent  group  in  carbon  compounds,  and  for  the  sake  of 
simplifying  the  nomenclature,  it  has  been  called  the  amino 
group,  and  the  compounds  containing  it  amino  compounds. 
Thus  the  compound^NH2£2H5rmay  be  called  either  ethyl- 
amine or  aminoethane. 

Similarly,  those  substituted  ammonias  which  contain  .two 
hydrocarbon  residues,  as  diethylamine,  NH(C2H6)2,  are  called 
Imino  compounds,  and  the  bivalent  group,  NH,  the  imino  group. 
Substituted  ammonias  containing  one  hydrocarbon  residue,  as 
ethylamine,  H2NC2H5,  are  called  primary  amines.  Those  con- 
taining two  residues,  as  diethylamine,  NH(C2H5)2,  are  known  as 
secondary  amines;  and  those  containing  three  residues,  as  tri- 
ethylamine,  N(CH3)3,  are  called  tertiary  amines. 


ACTION   OF  NITROUS   ACID  105 

Among  the  most  important  of  the  reactions  of  amino  com- 
pounds or  primary  amines  is  that  with  nitrous  acid.  In  order 
to  understand  what  takes  place  when  these  compounds  are 
treated  with  nitrous  acid,  it  is  necessary  to  keep  in  mind  the 
fact  that  they  are  substituted  ammonias  and  hence  that  their 
reactions  will  be  similar  to  those  which  take  place  with  ammonia 
itself.  Thus  with  nitrous  acid  ammonia  unites  directly  to  form 
ammonium  nitrite :  — 

NH3  +  HNO2  =  NH4.NO2. 

So  also  ethylamine  forms  ethylammonium  nitrite :  — 

NH2.C2H5  +  HNO2  =  NH3(C2H6).N02. 

Ammonium  nitrite  breaks  down  readily  into  free  nitrogen  and 

water :  —  NH4.NO2  =  N2  +  H2O  +  I-I2O. 

So  also  ethylammonium  nitrite  breaks  down  into  free  nitrogen, 
water,  and  alcohol:  — 

NH3(C2H6)N02  =  N2  +  H2O  +  C2H6.OH. 

The  two  reactions  are  strictly  analogous.  As  in  the  second 
case  we  start  with  a  substituted  ammonia,  we  get  as  a  product  a 
substituted  water  or  alcohol. 

This  reaction  has  been  used  extensively  in  the  preparation 
of  compounds  containing  hydroxyl.  For  ordinary  alcohol  it 
is  not  a  convenient  method  of  preparation ;  but  it  will  be  shown 
that  there  are  alcohols  for  the  preparation  of  which  it  is  by  far 
the  best  method.  The  essential  character  of  the  transformation 
effected  by  it  will  be  best  understood  by  comparing  the  formulas 
of  the  amino  compound  and  the  alcohol.  We  have  ethylamine, 
C2H6.NH2,  and  from  it  we  get  alcohol,  C2H6.OH.  Thus  it  will 
be  seen  that  the  transformation  consists  in  replacing  the  amino 
group  by  hydroxyl. 

With  secondary  amines  nitrous  acid  gives  nitroso  com- 
pounds :  — 

(C2H6)2 :  NH  +  HONO  =  H2O  +  (C2H5)2 :  N.N :  O. 

N  itrosodiethylam  ine 


Io6  DERIVATIVES   OF  METHANE  AND   ETHANE 

With  tertiary  amines  nitrous  acid  does  not  act,  or  acts  as  an 
oxidizing  agent.  Thus  the  reactions  with  nitrous  acid  enable 
us  to  distinguish  between  a  primary,  secondary,  and  tertiary 
amine.  Attention  should  also  be  called  to  the  fact  that  only 
the  primary  amines  give  isocyanides  (94)  and  mustard  oils  (98), 
and  hence  these  reactions  are  also  used  to  distinguish  the 
primary  amines  from  the  secondary  and  tertiary  amines. 


Substituted  Hydrazines 

There  is  an  important  class  of  compounds  that  bear  the 
same  relation  to  hydrazine,  HjN — NH2,  that  the  substituted 
ammonias  bear  to  ammonia.  The  reactions  by  which  they 
are  prepared  are  similar  to  those  used  in  making  the  sub- 
stituted ammonias.  Thus  methylhydrazine  results  from  the 
action  of  methyl  iodide  on  hydrazine,  and  dimethyl  hydrazine, 
(CH3)2N — NH2,  is  formed  by  reducing  nitrosodimethylamine 
(105) : - 

(CH3)2N— NO  +  2  H2  =  (CH3)2N.NH2  +  H2O. 

The  best-known  hydrazines  are  those  derived  from  the  hydro- 
carbons of  the  benzene  series,  as,  for  example,  phenylhydrazine, 
C6H5.NH.NH2  (360). 

Phenylhydrazine  reacts  with  aldehydes  and  ketones,  giving 
phenylhydrazones :  — 

H3C.CHO-hH2N.NHC6H5  =  CHaCHtN.NHCeHe-l-HsO; 

Aldehyde  phenyl  hydrazone 

„'^>C0  +  HzN.NHCeHs  =  ):„'>C:N.NHC6Hs  +  H2O. 
lisL  C±i3 

Acetone  phenylhydrazone 

Like  the  oximes  (109)  the  hydrazones  are  hydrolyzed  by  acids :  — 
H3C.CH:  N.NHCeHs  -t-  H20  =  H3C.CHO  -|-  C6H6NH.NH2. 

The  reactions  with  phenylhydrazine  and  hydroxylamine  (108) 
are  characteristic  of  the  aldehydes  and  the  ketones. 


NITRO  COMPOUNDS  107 

NiTRO  Compounds 

Reference  has  already  been  made  to  a  class  of  compounds, 
containing  the  group  NO2,  and  known  as  nitro  compounds. 
They  are  most  readily  made  by  treating  the  aromatic  hydrocar- 
bons with  nitric  acid.  This  method,  however,  is  not  applicable 
to  the  hydrocarbons  methane  and  ethane  and  their  homologues, 
as  these  are  not  readily  acted  upon  by  nitric  acid.  It  should  be 
noted,  however,  that  in  the  presence  of  aluminium  nitrate  reac- 
tion takes  place  between  the  paraffins  and  nitric  acid,  and 
nitro  compounds  are  thus  readily  made.  The  hydrocarbon 
benzene,  CeHe,  is  very  easily  acted  upon  by  nitric  acid,  when  the 
reaction  represented  by  the  following  equation  takes  place :  — 

CeHe  +  HONO2  =  CeHsNO^  +  H2O. 

Nitrobenzene 

The  action  is  like  that  which  takes  place  between  sulphu- 
ric   acid    and    benzene,    which    gives    benzenesulphonic    acid 

C  H 
„_>S02  (79).     In  each  case  a  hydroxyl  of  the  acid  is  re- 

placed  by  a  residue  of  the  hydrocarbon  and  water  is  formed. 
The  product  in  the  case  of  the  dibasic  acid,  sulphuric  acid,  is 
itself  an  acid,  while  the  product  in  the  case  of  the  monobasic 
nitric  acid  is  not  an  acid. 

The  nitro  derivatives  of  methane  and  ethane  have  been  made 
by  a  reaction  which  we  should  expect  to  yield  ethereal  salts 
of  nitrous  acid;  namely,  by  treating  iodomethane  or  -ethane 
with  silver  nitrite :  — 

CH3I  -I-  AgN02  =  CH3NO2  +  Agl. 

The  compound  CH3NO2,  which  is  known  as  nitromethane, 
does  not  conduct  itself  like  the  ethereal  salts  of  nitrous  acid. 
Methyl  nitrite,  CH3O.NO  (69),  can  be  saponified;  nitro- 
methane cannot. 

Note  for  Student.  —  Compare  the  reaction  just  referred  to  with  that 
which  takes  place  between  silver  cyanide  and  iodomethane;  and  that 
which  takes  place  between  iodoethane  and  potassium  sulphite.  What 
analogy  is  there  to  the  former  and  to  the  latter? 


Io8  DERIVATIVES   OF  METHANE  AND   ETHANE 

It  has  already  been  stated  that  the  nitro  derivatives  are 
converted  by  nascent  hydrogen  into  the  corresponding  amino 
derivatives  (104). 

Note  for  Student.  —  Write  the  equations  representing  the  reactions 
by  which  methyl  alcohol  can  be  converted  into  methylamine  by  means  of 
the  nitro  compound.     How  is  methylamine  converted  into  methyl  alcohol? 

Nitroform,  CH(N02)3,  as  the  formula  indicates,  is  trinitro- 
methane.  It  is  converted  into  tetranitromethane,  C(N02)4, 
when  treated  with  a  mixture  of  concentrated  sulphuric  and 
fuming  nitric  acids. 

Nitrochloroform,  C(N02)Cl3,  called  also  chloropicrin  and 
nitrotrichloromethane,  is  formed  by  distilling  methyl  or  ethyl 
alcohol  with  common  salt,  saltpetre,  and  sulphuric  acid.  It  is 
made  from  picric  acid  (378)  by  distilling  with  bleaching  powder, 
and  hence  the  name.  It  was  used  as  a  "  poison  gas  "  in  the 
World  War. 

NiTROSO   AND   ISONITEOSO    COMPOUNDS 

When  a  compound  containing  the  group  CH  is  treated  with 
nitrous  acid,  a  reaction  takes  place,  which  is  represented  thus :  — 

RsCH  +  HO.NO  =  R3C.NO  +  H2O. 

The  product  R3C.NO,  which  is  derived  from  the  original  sub- 
stance by  the  substitution  of  the  group  NO  for  a  hydrogen 
atom,  is  called  a  nitroso  compound.  By  oxidation  the  nitroso 
compounds  are  converted  into  nitro  compounds,  and  by  reduc- 
tion they  yield  the  same  products  as  the  corresponding  nitro 
compounds,  the  primary  amines. 

The  isonitroso  compounds  are  isomeric  with  the  nitroso 
compounds.  They  are  formed  when  ketones  or  aldehydes  are 
treated  with  hydroxylamine,  NH2.OH.  The  reaction  is  rep- 
resented thus :  — 

CH3  CH3 

I  I 

CO  +  H2N.0H  =  C=N— OH  +  H2O. 

I  I 

CH3  CH3 


FULMINIC   ACID  109 

The  hydrogen  of  the  hydroxyl  has  acid  properties.  The 
isonitroso  compounds  are  readily  hydrolyzed  by  hydrochloric 
acid,  yielding  an  aldehyde  or  ketone  and  hydroxylamine  hy- 
drochloride. They  are  generally  called  oximes.  Those  from 
aldehydes  are  called  aldoximes ;  those  from  ketones,  ketoximes. 

As  hydroxylamine  reacts  in  this  way  with  all  aldehydes  and 
with  all  ketones,  it  is  a  valuable  reagent  for  compounds  be- 
longing to  these  classes. 

By  reduction  the  oximes  are  converted  into  primary  amines :  — 

(H3C)2C:NOH  -f  2  H2  =  (CH3)2CHNH2  +  H2O, 
HsCCHiNOH  -h  2  H2  =  CH3CH2NH2  +  H2O. 

Aldoximes  lose  water  and  give  cyanides  when  heated  with  acetic 
anhydride :  — 

CH3 

I  CH3 

CH      =  I  +  H2O. 

II  C=N 
NOH 

By  means  of  these  two  reactions  acetic  aldehyde  can  be  con- 
verted into  ethylamine  or  into  methyl  cyanide  by  first  con- 
verting it  into  the  oxime. 

Fulminic  acid,  CNOH,  appears  to  be  an  isonitroso  compound, 
and  for  that  reason  finds  appropriate  mention  in  this  place. 
The  principal  compound  of  fulminic  acid  is  the  mercuric  salt, 
C2N202Hg,  commonly  known  as  fulminating  mercury.  It  is  pre- 
pared by  dissolving  mercury  in  an  excess  of  strong  nitric  acid, 
and  adding  the  solution  to  alcohol.  It  is  extremely  explosive. 
It  is  used  in  the  manufacture  of  percussion  caps  and  of  car- 
tridges for  the  explosion  of  dynamite  and  guncotton. 

When  fulminating  mercury  is  treated  with  concentrated  hy- 
drochloric acid,  it  yields  hydroxylamine  hydrochloride  and 
formic  acid.  Fulminic  acid  is  probably  the  oxime  of  car- 
bon monoxide,  and  should  be  represented  by  the  formula 
C=N — OH.  As  will  be  seen,  fulminic  acid  is  isomeric  with 
cyanic  and  cyanuric  acids  (89,  90). 


CHAPTER  VII 

DERIVATIVES    OF    METHANE    AND    ETHANE     CONTAINING 
PHOSPHORUS,   ARSENIC,   ETC. 

Phosphorus  compounds.  —  Corresponding  to  the  amines 
or  substituted  ammonias  are  the  substituted  phosphines,  which, 
as  the  name  implies,  are  related  to  phosphine,  PH3.  Methyl- 
phosphine,  PH2CH3,  dimethylpkosphine,  PH(CH3)2,  and  tri- 
methylphosphine,  P(CH3)3,  may  be  taken  as  examples. 

These  substances,  like  the  corresponding  amines,  form  salts 
with  acids,  though  not  as  readily.  The  hydroxide,  tetraethyl- 
phosphonium  hydroxide,  P(C2H6)40H,  is  a  very  strong  base, 
though  not  as  strong  as  the  corresponding  nitrogen  derivative. 

The  phosphines  have  one  marked  property  which  distin- 
guishes them  from  the  amines,  and  that  is  their  power  to  take 
up  oxygen  and  form  acids.  Thus,  ethylphosphine,  PH2.C2H6, 
when  treated  with  nitric  acid,  is  converted  into  ethylphos phonic 
acid,  PO(C2H6)(OH)2,  a  dibasic  acid,  bearing  to  phosphoric  acid 
the  same  relation  that  a  sulphonic  acid  bears  to  sulphuric  acid. 

Note  tor  Student.  —  What  is  the  relation?  What  other  class  of  acids 
bears  the  same  relation  to  carbonic  acid  ? 

Diethylphosphine,  PH(C2H5)2,  yields  diethylphosphinic  acid, 
PO(C2H6)20H,  and  trie  thy  Iphosphine  gives  triethylphosphine 
oxide,  (C2H6)3PO,  when  oxidized. 

These  compounds  are  not  commonly  met  with,  and  do  not 
play  a  very  important  part  in  the  study  of  the  compounds  of 
carbon. 

Arsenic  compounds.  —  The  most  characteristic  carbon  com- 
pound containing  arsenic  is  cacodyl,  a  name  given  to  it  on 
account  of  its  extremely  disagreeable  odor  (Gr.  kakodes, 
stinking).  The  oxide  is  prepared  by  distilling  a  mixture  of 
potassium  acetate  and  arsenic   trioxide.    The   reactions  that 


SODIUM  ETHYL  ill 

take  place  are  complicated,  and  several  products  are  formed. 
Chief  among  them  is  cacodyl  oxide :  — 

H3CCO2K      KOOCCH3    OAs\ 

+  +       >o 

H3CCO2K      KOOCCH3    OAs/ 

(H3C)2AS\ 

=  2K2COa  +  2CO2  +  >0. 

(H3C)2AS/ 

When  treated  with  hydrochloric  acid,  the  oxide  is  converted 
into  the  chloride  (CH3)2AsCl;  and,  when  the  chloride  is  treated 
with  zinc,  cacodyl  itself  is  produced.  Its  analysis  and  the 
determination  of  its  molecular  weight  lead  to  the  formula 
AS2C4H12,  which  should  be  represented  thus :  — 

(CH3)2AS. 

I        Cacodyl  is    therefore    analogous   to   tetramethyl- 
(CH3)2As. 

hydrazine. 
Note  foe  Student.  —  In  what  does  the  analogy  consist  ? 

It  is  extremely  poisonous  and  takes  fire  in  the  air. 

Zinc  ethyl,  Zn(C2H6)2,  is  made  by  treating  iodoethane, 
C2H5I,  with  zinc  alone  or  with  zinc  sodium.  The  reaction 
takes  place  in  two  stages.     First,  by  addition,  a  compound  of 

the  formula  Zn<  is  formed.     When  this  is  distilled,  zinc 

^2x15 

ethyl  and  zinc  iodide  are  formed :  — 

2  Zn<  -        =  Zn(C2H5)2  +  Znl2. 
^2x15 

It  is  a  liquid  boiling  at  118°.     It  takes  fire  in  the  air,  and  burns 
with  a  white  flame. 

Sodium  ethyl,  C2H6Na,  containing  some  zinc  ethyl,  is  obtained 
by  treating  the  latter  with  sodium.  Both  these  compounds 
have  been  used  to  a  considerable  extent  in  the  synthesis  of 


112  DERIVATIVES   OF  METHANE  AND   ETHANE 

carbon  compounds,  particularly  the  more  complex  hydro- 
carbons, and  they  will  be  frequently  referred  to  in  the  following 
pages. 

Note  for  Student.  —  What  is  formed  when  sodium  methyl  and  car- 
bon dioxide  are  allowed  to  act  upon  each  other  ? 

Many  of  the  derivatives,  like  the  above,  are  volatile  liquids. 
Such,  for  example,  are  mercury  ethyl,  Hg(C2H5)2,  aluminium 
ethyl,  A1(C2H5)3,  tin  tetraethyl,  Sn(C2H5)4,and  silicon  tetraethyl, 
Si(C2H5)4.  The  study  of  these  compounds  has  been  of  assist- 
ance in  enabling  chemists  to  determine  the  atomic  weights  of 
some  of  the  elements  which  do  not  form  volatile  inorganic 
compounds. 

Grignard  reaction.  —  When  magnesium  powder  is  added 
to  a  solution  of  an  organic  halide,  such  as  methyl  iodide,  ethyl 
bromide,  etc.,  in  anhydrous  ether,  magnesium  enters  into  com- 
bination with  the  halide,  forming  a  compound  that  reacts  easily 
with  a  variety  of  substances.  The  reaction  is  known  by  the  name 
of  the  discoverer,  Grignard.  A  simple  example  is  that  indicated 
below :  — 

CHsI-hMg    =  CHsMgl; 
CHsMgl  -I-  H2O  =  CH4  -I-  IMgOH. 

These  reactions,  as  will  be  seen,  afford  an  easy  method  of 
passing  from  methyl  iodide  to  methane. 

Reteospect 

In  the  introductory  chapter  (17)  these  words  were  used  in 
describing  the  plan  to  be  followed:  "  Of  the  first  series  of  hy- 
drocarbons two  members  will  be  treated.  Then  the  deriva- 
tives of  these  two  will  be  taken  up.  These  derivatives  will 
serve  admirably  as  representatives  of  the  corresponding  deriva- 
tives of  other  hydrocarbons  of  the  same  series  and  of  other 
series.  Their  characteristics  and  their  relations  to  the  hydro- 
carbons will  be  dwelt  upon,  as  well  as  their  relations  to  one 
another.  Thus  by  a  comparatively  close  study  of  two  hydro- 
carbons and  their  derivatives,  we  may  acquire  a  knowledge  of 


RETROSPECT  1 13 

the  principal  classes  of  the  compounds  of  carbon.  After  these 
typical  derivatives  have  been  discussed,  the  entire  series  of 
hydrocarbons  will  be  taken  up  briefly,  only  such  facts  being 
dealt  with  at  all  fully  as  are  not  illustrated  by  the  first  two 
members." 

In  accordance  with  the  plan  thus  sketched  we  have  thus  far 
studied  the  principal  derivatives  of  the  two  hydrocarbons, 
methane  and  ethane,  so  far  as  these  derivatives  represent  dis- 
tinct classes  of  compounds.  These  derivatives  were  classified 
first  into :  (i)  those  containing  halogens ;  (2)  those  containing 
oxygen ;  (3)  those  containing  sulphur ;  and  (4)  those  contain- 
ing nitrogen.  On  examining  each  of  these  classes  more  closely, 
we  found  that  the  halogen  derivatives,  such  as  chloromethane, 
bromoethane,  etc.,  bear  very  simple  relations  to  one  another. 
We  found  that  under  the  head  of  oxygen  derivatives,  the  most 
important  and  most  distinctly  characteristic  derivatives  of 
hydrocarbons  are  met  with ;  as,  the  alcohols,  ethers,  aldehydes, 
acids,  ethereal  salts,  and  ketones.  The  sulphur  derivatives, 
some  of  which  closely  resemble  the  oxygen  derivatives,  include 
the  sulphur  alcohols  or  mercaptans ,  thioethers,  and  sulphonic 
acids. 

On  beginning  the  treatment  of  the  nitrogen  derivatives  it 
was  found  to  be  desirable  first  to  take  up  certain  derivatives 
containing  the  cyanogen  group,  among  which  are  cyanogen, 
hydrocyanic  acid,  cyanic  acid,  and  thiocyanic  acid.  Many 
interesting  carbon  compounds  are  closely  related  to  these  funda- 
mental compounds.  Such,  for  example,  are  the  cyanides  and 
isocyanides,  the  isocyanates,  the  thiocyanates,  and  isothio- 
cyanates  or  mustard  oils.  Following  the  compounds  related 
to  cyanogen,  the. interesting  compounds  related  to  ammonia, 
the  substituted  ammonias  or  amines,  were  taken  up.  Then  came 
the  nitro  derivatives;  and,  finally,  the  compounds  of  the  hydro- 
carbon radicals  with  metals. 

It  is  of  the  greatest  importance  that  the  student  should 
master  the  preceding  portion  of  this  book.  If  he  studies  care- 
fully the  reactions  that  have  been  presented,  which  are  state- 
ments in  chemical  language  that  tell  us  the  conduct  of  the 


114  DERIVATIVES   OF   METHANE   AND   ETHANE 

various  classes  of  derivatives,  and  if  he  performs  the  experi- 
ments in  the  laboratory  manual,  he  will  have  a  general  knowl- 
edge of  the  kinds  of  relations  that  are  met  with  in  connection 
with  the  compounds  of  carbon  throughout  the  whole  field. 
As  stated  in  the  Introduction :  "  If  we  know  what  derivatives 
one  hydrocarbon  can  yield,  we  know  what  derivatives  we  may 
expect  to  find  in  the  case  of  every  other  hydrocarbon." 

The  more  the  student  practices  the  use  of  the  equations  thus 
far  given,  the  better  he  will  be  prepared  to  follow  the  remain- 
ing portions  of  the  book.  Indeed,  it  may  be  said  that,  if  he 
thoroughly  understands  what  has  gone  before,  what  follows  will 
appear  simple.  Whereas,  if  he  has  failed  at  any  point  to  catch 
the  meaning,  if  he  has  failed  to  see  the  connection,  he  had  better 
go  back  and  review  faithfully  or  he  will  soon  find  his  mind 
hopelessly  muddled,  and  relations  which  are  as  clear  as  day 
will  be  concealed  from  him. 

An  excellent  practice  is  to  trace  connections  between  the 
different  classes  of  compounds,  and  show  how  to  pass  from  one 
to  the  other.  Thus,  for  example :  (i)  Show  by  what  reactions 
it  is  possible  to  pass  from  marsh  gas  to  acetic  acid ;  and  from 
acetic  acid  to  marsh  gas.  (2)  How  can  we  pass  from  ordinary 
alcohol  to  ethylidene  chloride,  CH3.CHCI2,  and  from  ethylidene 
chloride  back  to  alcohol?  (3)  What  reactions  enable  us  to 
make  methylamine  from  its  elements  ?  (4)  How  can  acetone 
be  made  from  methylamine,  and  methylamine  from  acetone? 
(5)  What  reactions  are  necessary  in  order  to  make  ordinary 
ether  from  ethylamine  and  ethylamine  from  ether?  etc.,  etc. 
It  is  well  in  this  sort  of  practice  to  select  what  appear  to  be  the 
least  closely  related  compounds,  and  to  show  how  it  is  possible 
to  pass  from  one  to  the  other.  Be  sure  to  select  representatives 
of  all  the  classes  hitherto  mentioned,  and  to  bring  in  all  the 
important  reactions. 


CHAPTER  Vin 

THE    HYDROCARBONS    OF    THE    MARSH   GAS    SERIES,    OR 
PARAFFINS 

The  existence  of  the  homologous  series  of  hydrocarbons 
beginning  with  methane  and  ethane  was  mentioned  before  its 
first  two  members  were  discussed.  The  extent  of  the  series, 
and  the  names  and  formulas  of  the  more  important  members  of 
the  series,  together  with  their  melting  points  and  boiling  points, 
are  shown  in  the  table  on  the  following  page. 

The  explanation  of  the  remarkable  relation  in  composition 
existing  between  these  members,  a  relation  to  which  the  name 
homology  is  given,  has  already  been  given  (21).  The  number 
of  hydrogen  atoms  contained  in  a  member  of  this  series  bears 
a  constant  relation  to  the  number  of  carbon  atoms,  as  expressed 
in  the  general  formula  C„H2„+2.  On  examining  the  column 
headed  "  Boiling  point  "  it  will  be  seen  that,  as  we  pass  upward 
in  the  series,  the  boiling  point  becomes  higher  and  higher. 
The  first  four  members  are  gases  at  ordinary  temperatures, 
while  nonadecane,  C19H40,  boils  at  330°.  The  elevation  iii  the 
boiling  point  is  to  some  extent  regular,  as  will  be  observed. 
The  difference  between  butane,  C4H10,  and  pentane,  C6H12,  is 
36.4  — (—0.3)  =36.7°;  that  between  pentane  and  the  next 
member  is  69  —  36.4  =  32.6° ;  between  hexane  and  heptane 
it  is  98.4—  69  =  29.4°;  between  heptane  and  octane,  125.5 
—  98.4  =  27.1°;  and  finally,  between  octane  and  nonane  the 
difference  is  150.5  —  125.5  =  25°.  Thus  it  will  be  seen  that 
the  elevation  in  boiling  point  caused  by  the  addition  of  CH2 
decreases  as  we  pass  upward  in  the  series. 

The  chief  natural  source  of  the  paraffins  is  Pennsylvania 
petroleum ;  but  although  this  substance,  which  occurs  in 
such  enormous   quantities   in  nature,  consists  largely  of   the 


Il6       HYDROCARBONS   OF   THE   MARSH   GAS   SERIES 


MARSH    GAS  HYDROCARBONS 

Paraffins.  — •  Hydrocarbons,   C„H2„+2 


Formula 

Name 

Melting  Point 

Boiling  Point 

CH4 

Methane 

-184° 

-164°  (760) 

CjHe 

Ethane 

-172. 1 

-84.1  (749) 

C3H8 

Propane 

-187.8 

-44-5  (757) 

C4Hxo 

Butane 

-135 

-   0.3  (760) 

C5H12 

Pentane 

-147.5 

36.4  (760) 

CeHu 

Hexane 

-    94 

69     (760) 

C7H16 

Heptane 

-    97.1 

98.4 

CsHis 

Octane 

-    56.6 

125.5 

C9H20 

Xonane 

-    51 

150-5  (759) 

C10H22 

Decane 

-    3^ 

173 

C11H24 

Undecane 

-    25.6 

194.5 

C12H26 

Dodecane 

—    12 

215 

CuH28 

Tridecane 

-      6.2 

234 

C14H30 

Tetradecane 

5-5 

252 

C15H32 

Pentadecane 

10 

270 

C16H34 

Hexadecane 

18.3 

287.S 

C17H36 

Heptadecane 

2^.5 

303 

CiaH38 

Octadecane 

28 

317 

C19H40 

Nonadecane 

32 

330 

C20H42 

Eicosane 

37 

205  1 

C21H44 

Heneicosane 

40 

21S' 

C22H46 

Docosane 

44.4 

317.4 

C23H48 

Tricosane 

47-7 

320.7 

C24H50 

Tetracosane 

S°-7 

324.1 

C26H54 

Hexacosane 

58 

. 

C27H56 

Heptacosane 

60 

270^ 

C3lH64 

Hentriacontane 

68 

302  1 

C32H66 

Dotriacontane 

70 

310' 

C35H72 

Pentatriacontane 

75 

331^ 

C60H122 

Hexacontane 

102 

members  of  the  paraffin  series,  it  is  extremely  difficult  to  isolate 
them  from  the  mixture.  Prolonged  fractional  distillation  is 
not  sufficient.  If,  however,  some  of  the  purest  products  that 
can  thus  be  obtained  are  treated  with  concentrated  sulphuric 
acid,  and  afterwards  with  concentrated  nitric  and  sulphuric 
acids,  and  then  washed  with  water  and  alkali,  dried  and  re- 
distilled, they  can  be  obtained  in  approximately  pure  condition. 

1  These  boiling  points  are  taken  at  15mm  pressure. 


PETROLEUM   OR  ROCK   OIL  II 7 

Petroleum '  or  rock  oil  is  an  oily  liquid,  occurring  in  nature, 
varying  in  color  from  a  light  yellow  to  a  dark  red  or  even  black 
and  in  many  cases  having  a  greenish  fluorescence.  Some  speci- 
mens of  petroleum  are  light  mobile  fluids,  while  others  are 
heavier  and  more  viscous  and  some  are  semisolid.  They  are 
all  lighter  than  water,  ranging  in  specific  gravity  from  0.85  to 
0.94.  Heavy  Mexican  crude  has  nearly  the  same  specific  gravity 
as  water.  The  world's  production  of  petroleum  in  1920  was 
694,854,000  barrels  (of  42  gallons),  of  which  the  United  States 
produced  63.8  per  cent  (443,402,000  barrels  valued  at  $1,360,000,- 
000),  Russia,  3.6  per  cent  (25,429,600  barrels),  and  Mexico,  23.5 
per  cent  (163,540,000  barrels).  The  value  of  the  products  manu- 
factured from  petroleum  in  the  United  States  in  1914  was 
$396,361,405.  California  produces  more  petroleum  at  the  pres- 
ent time  than  any  other  state  in  the  Union,  105,668,000  barrels 
in  1920.     Texas  produced  96,000,000  barrels. 

Petroleum  is  an  exceedingly  complicated  mixture  of  hydro- 
carbons usually  containing  compounds  of  nitrogen  and  sulphur, 
though  the  amounts  of  these  are  generally  small.  Pennsyl- 
vania petroleum  consists  very  largely  of  the  saturated  paraffin 
hydrocarbons,  CnH2n+2,  and  the  members  from  CH4  to  C35H72 
have  been  isolated  from  it.  Olefines,  CJl^n  (275),  have  been 
found  in  Canadian  petroleum,  but  they  are  usually  present  in 
small  amount  in  most  petroleums.  Russian,  Japanese,  Cali- 
fornia, and  Texas  coastal  petroleums  consist  very  largely  of 
naphthenes,  which  are  saturated  hydrocarbons,  C7iH2re,  isomeric 
with  the  olefines,  but  having  a  closed  chain  structure. 
Hydrocarbons  of  the  benzene  series,  CnH2n-6,  also  occur  in  all 
petroleums,  but  in  small  amounts.  Pyridine  and  guinoline 
derivatives  have  been  found  in  California  petroleum,  and  in 
some  cases  they  constitute  10  to  20  per  cent  of  the  crude  product. 
Sulphides  from  methyl  sulphide  to  hexyl  sulphide  have  been 
isolated  from  Ohio  petroleum,  and  cyclic  sulphur  compounds, 
CnH2nS,  occur  in  Canadian  petroleum. 

It  is  generally  believed  that  petroleum  has  originated  from  the 

'  See  The  American  Petroleum  Industry,  by  R.  F.  Bacon  and  W.  A. 
Hamor.     1916. 


Il8        HYDROCARBONS  OF  THE  MARSH  GAS  SERIES 

decomposition  of  animal  and  vegetable  remains  (fats)  beneath 
the  earth's  surface  by  the  action  of  heat  and  pressure.^ 

Refining  of  petroJeum.  —  The  American  petroleums  are  divided  by 
the  refiners  into  "  Paraffin  base,"  "  Asphalt  base,"  and  "  Mixed 
base  "  crudes,  as  the  methods  of  refining  these  petroleums  are  different. 
Though  this  is  the  accepted  classification,  it  seems  best  to  include  a 
fourth  class,  "  Xaphthenic  base."  Many  Te.xas  petroleums  contain 
neither  asphalt  nor  paraffin,  but,  as  already  stated,  consist  largely  of 
naphthenes.  The  petroleums  from  Pennsylvania,  New  York,  West 
\'irginia,  Ohio,  Kentucky,  northern  Louisiana,  and  Canada  contain 
paraffin  wax ;  those  from  California  and  some  from  Texas,  asphalt ; 
while  those  from  Illinois,  Kansas,  Oklahoma,  northern  Texas,  and 
Mexico  contain  both  paraffin  wax  and  asphalt.  The  refining  of  petro- 
leum consists  in  separating  it  into  commercial  products,  such  as  gaso- 
lenes, naphthas,  lamp  oils  (kerosenes),  gas  oils,  fuel  oils,  spindle  oils, 
cylinder  oils,  paraffin  wax,  petrolatum  (vaseline),  dust-laying  oils, 
road  binders,  and  coke.'  The  petroleum  is  first  subjected  to  distillation. 
If  the  refiner  desires  to  produce  the  maximum  amount  of  gasolene  and  lamp 
oU  (kerosene)  he  uses  what  is  called  "  Cracking  Distillation,"  which  means 
the  breaking  down  of  the  higher-boiling,  heavier  fractions  by  destructive 
distillation  into  lighter  and  more  volatile  ones.  To  supplement  the  crack- 
ing that  occurs  normally  in  the  distillation  of  crude  petroleums,  extensive 
use  is  now  made  of  distillation  in  pressure  stills  in  which  the  distillation  is 
carried  on  under  pressure.  If,  on  the  other  hand,  he  wishes  to  produce  the 
maximum  yield  of  the  heavy  lubricating  oils  and  petroleum  asphalts  he 
uses  fractional  distillation,  injecting  dry  steam  into  the  petroleum  while 
it  is  being  heated  in  order  to  minimize  the  decomposition  of  the  petro- 
leum by  heat  and  separate  it  into  the  fractions  which  compose  it. 

Cracking  distillation  of  mid-con  I  in  en  I  petroleum.^  —  When  the  tempera- 
ture of  the  petroleum  in  the  still  reaches  1 75  to  200°  F.  some  gases,  largely 
butane  and  pentane,  are  given  off  and  soon  the  lightest  naphtha  begins  to 
distil  over.  The  temperature  in  the  still  becomes  gradually  higher  until 
it  reaches  about  325°  F.,  when  about  6  to  8  per  cent  of  crude  naphtha 
(200°  F.  boiling  point)  has  distilled  over.  This  is  set  aside  and  the  distil- 
lation continued  until  the  temperature  in  the  still  has  reached  about 
475°  F.  This  distillate  is  called  crude  heavy  naphtha.  It  represents  13 
to  15  per  cent  of  the  petroleum  and  has  an  average  boiling  point  of  about 

'  For  theories  on  the  origin  of  petroleum  see  The  American  Petroleum 
Industry,  Vol.  I,  p.  13. 

2  For  definitions  of  these  terms  and  others  used  in  the  petroleum  industry 
see  The  American  Petroleum  Industry,  Vol.  II,  p.  845. 

^  Based  on  a  description  by  the  late  F.  C.  Robinson,  chief  chemist,  Atlan- 
tic Refining  Co.  Philadelphia,  Pa. 


REFINING   OF   PETROLEUM  1 19 

300°  F.  The  distillation  is  then  continued  until  the  temperature  in 
the  still  has  reached  about  625°  F.  for  natural  lamp  oil,  which  repre- 
sents about  16  to  18  per  cent  of  the  petroleum  and  has  an  average  boil- 
ing point  of  about  450°  F.  When  the  still  has  reached  this  temperature 
"  cracking,''  or  destructive  distillation,  sets  in.  The  fires  are  slackened 
in  order  to  distil  very  slowly,  and  this  slow  distillation  is  continued  until 
the  temperature  in  the  still  reaches  675  to  700°  F.,  producing  a  distillate 
with  an  average  boiling  point  of  about  550°  F.,  but  containing  some 
gasolene,  some  lamp  oil,  and  much  heavier  oil  called  gas  and  fuel  oil 
stock.  The  yield  of  this  oil  is  about  30  per  cent.  In  this  distillation 
heavy  molecules  are  broken  down  into  lighter  ones  by  subjecting  them 
to  temperatures  at  which  they  are  unstable.  There  remains  in  the 
still  a  heavy  black  tar,  representing  about  42  per  cent  of  the  petroleum. 
This  is  the  source  of  paraffin  wax  and  the  paraf&n  lubricating  oils.  This 
tar  is  distilled  very  rapidly  in  order  to  avoid  cracking  as  much  as 
possible  and  to  produce  the  maximum  yield  of  paraffin  distillate  (about 
22  per  cent).  In  addition  to  this  there  is  also  produced  about  15  per 
cent  of  cracked  distillate.  At  the  end  of  the  distillation  the  stream 
becomes  so  heavy  that  it  will  sink  in  water  and  is  then  known  as  wax 
tailings,  which  amounts  to  about  one  per  cent  of  the  petroleum.  When 
the  distillation  stops,  there  remains  in  the  still  nothing  but  coke,  amount- 
ing to  about  4  per  cent  of  the  petroleum. 

The  crude  naphtha  is  distilled  usually  by  injecting  live  steam  into 
it,  for  the  purpose  of  separating  it  into  the  various  gasolenes  and  naph- 
thas that  compose  it  and  also  to  separate  it  from  the  small  amount  of 
lamp  oil  that  it  contains.  The  crude  heavy  naphtha  is  distilled  with 
steam  with  the  aid  of  external  heat.  It  contains  little  or  no  gasolene, 
but  about  50  per  cent  of  lamp  oil.  The  cracked  distillate  is  also  dis- 
tilled with  steam  to  remove  about  4  per  cent  of  crude  naphtha.  In 
practice  the  naphtha  and  lamp  oil  distillates  are  agitated  with  about 
one  per  cent  by  volume  of  sulphuric  acid  for  half  an  hour.  The  com- 
pounds that  give  color  and  odor  to  the  distillate  combine  with  the  acid, 
producing  a  heavy  black  viscous  mass  called  acid  sludge  which  settles  to 
the  bottom  of  the  vessel.  The  sludge  is  drawn  off  and  the  oil  washed 
with  water  and  alkali  to  remove  all  traces  of  acid  and  is  then  ready  for 
the  market. 

The  paraflSn  distillate  is  cooled  to  20  to  30°  F.,  causing  the  paraffin 
wax  (amounting  to  about  10  per  cent  of  the  distillate)  to  solidify.  This 
is  removed  from  the  liquid  oil  by  means  of  a  filter  press  and  decolorized 
by  filtering  it  while  hot  through  fuller's  earth.  Light  lubricating  oils 
are  made  from  the  filtrate  from  the  cold  filter  presses. 

In  the  case  of  the  refining  of  the  light  colored,  non-asphaltic  crude 
oils  from  which  the  valuable  cylinder  oils  are  made,  live  steam  is  injected 
into  the  oil  when  the  temperature  is  well  above  the  boiling  point  of  water 


I20       HYDROCARBONS  OF  THE  MARSH   GAS   SERIES 

in  order  to  avoid  destructive  distillation  and  to  produce  the  maximum 
yield  of  heavy  lubricating  oUs.  The  effect  of  this  current  of  steam 
through  the  oil  is  to  distil  the  oil  at  a  temperature  below  its  boiling  point, 
and  to  allow  a  heavy  oil  to  be  distilled  below  the  temperature  of  de- 
structive distillation.  The  crude  naphtha  is  first  distilled  off  as  de- 
scribed above,  but  the  temperature  only  reaches  280°  F.,  while  without 
steam  the  temperature  was  about  375°  F.  The  heating  is  continued, 
more  and  more  steam  being  injected,  until  the  crude  heavy  naphtha 
has  distilled  off.  At  this  point  the  temperature  has  reached  about 
330°  F.  while  without  steam  it  was  475°  F.  The  distillation  is  continued 
until  the  natural  lamp  oil  has  distilled  off.  At  this  point  the  tempera- 
ture in  the  still  is  only  500°  F.  while  without  steam  it  was  630°  F.  The 
distillation  is  now  carried  on  as  rapidly  as  possible,  more  and  more 
steam  being  admitted  to  avoid  cracking,  until  the  lubricating  oil  dis- 
tillate has  passed  over.  The  temperature  in  the  still  is  now  about 
620°  F.  The  distillation  is  now  stopped,  leaving  the  cylinder  oil  stock 
in  the  still.  The  various  fractions  are  then  put  through  the  same  pro- 
cesses as  the  corresponding  fractions  from  the  cracking  distillation.  It 
should  be  stated  that  large  quantities  of  gasolene  are  now  obtained 
also  from  (i)  the  gases  from  petroleum  wells,  (2)  from  natural  gas,  and 
(3)  from  the  cracking  of  petroleum  in  pressure  stills. 

Synthesis  of  the  paraffins.  —  Although  the  parafBins  occur 
in  nature,  and  can  be  obtained  in  pure  condition  from  natural 
sources,  we  are  dependent  upon  synthetical  operations  per- 
formed in  the  laboratory  for  our  knowledge  of  the  series  and 
the  relations  existing  between  them. 

It  has  already  been  shown  how  ethane  can  be  prepared  from 
methane  by  treating  methyl  iodide  with  sodium,  as  repre- 
sented in  this  equation  :  — 

CH3I  +  CH3I  -f  2  Na  =  C2H,  +  2  Nal. 

This  method  has  been  extensively  used  in  building  up  higher 
members  of  the  series.  Thus  from  ethyl  alcohol  we  can  make 
ethyl  iodide,  and  by  treating  this  with  sodium  get  butane, 
C4H10 :  — 

C2H5I  +  C2H5I  -I-  2  Na  =  C4H10  +  2  Nal. 

We  can  get  the  intermediate  member,  propane,  CsHg,  by 
mixing  methyl  iodide  and  ethyl  iodide  and  treating  the  mixture 
with  sodium :  — 

CH3I  -1-  CzHsI  -h  2  Na  =  CH3.C2H5  +  2  Nal. 


ISOMERISM   AMONG   THE   PARAFFINS  1 21 

A  large  number  of  the  members  of  the  parafHn  series  have  been 
made  by  this  method. 

Another  method  consists  in  treating  the  zinc  compounds  of 
the  radicals,  like  zinc  ethyl,  Zn(C2H6)2,  with  the  iodides  of  rad- 
icals. Thus  zinc  methyl  and  methyl  iodide  give  ethane ;  zinc 
ethyl  and  ethyl  iodide  give  butane,  etc. :  — 

Zn(CH3)2   +  2  CH3I    =  2  C2H6   +  Znl2 ; 
Zn(C2H6)2  +  2  C2H6I  =  2  C4Hi„  +  Znl2. 

ParaflBins  can  also  be  made  by  replacing  the  halogen  in  a  substi- 
tution product  by  hydrogen.  This  can  be  effected  by  nascent 
hydrogen :  — 

C4H9I  -h  2  H  =  C4H10  +  HI. 

Butyl  iodide  Butane 

As  these  halogen  substitution  products  can  easily  be  made 
from  the  alcohols,  it  follows  that  the  hydrocarbons  can  be  made 
from  the  corresponding  alcohols. 

The  Grignard  reaction  can  also  be  used  for  the  purpose  of 
passing  from  a  monohalogen  substitution  product  of  a  paraffin 
to  the  paraffin  itself  (112). 

Isomerism  among  the  paraffins.  —  It  has  already  been  stated 
that  the  evidence  is  strongly  in  favor  of  the  view  that  each 
of  the  four  hydrogen  atoms  of  marsh  gas  bears  the  same  relation 
to  the  carbon,  and  therefore  that,  as  regards  the  nature  of  the 
product,  it  makes  no  difference  which  hydrogen  atom  is  replaced 
by  a  given  atom  or  radical.  According  to  this,  as  ethane  is 
the  methyl  derivative  of  marsh  gas,  it  makes  no  difference  which 
of  the  hydrogen  atoms  of  marsh  gas  is  replaced  by  the  methyl, 
the  product  must  always  be  the  same,  or  there  is  only  one  ethane 
possible  according  to  the  theory,  and  only  one  ethane  has  ever  been 

H    H 

I      I 
made.    This   is   represented   by  the  formula,  H — C — C — H, 

H    H 

or  H3C — CH3.  In  ethane,  as  well  as  in  methane,  all  the  hy- 
drogen atoms  bear  the  same  relation  to  the  molecule,  and  it 


122        HYDROCARBONS  OF  THE  jNIARSH  GAS   SERIES 

should  make  no  difference  which  one  is  replaced  by  methyl. 
But  propane  is  regarded  as  derived  from  ethane  by  the  sub- 
stitution of  methyl  for  hydrogen ;  and,  as  it  makes  no  differ- 
ence which  hydrogen  is  replaced,  there  is  hut  one  propane  possible. 
Only  one  has  ever  been  made,  and  this  must  be  represented 

thus:  — 

H     H    H 

III 
H— C— C— C— H,  or  CH3.CH2.CH3. 

I       I       I 
H    H    H 

Now,  continuing  the  substitution  of  methyl  for  hydrogen, 
the  theory  indicates  the  possibility  of  the  existence  of  two 
compounds  of  the  formula  C4H10.  One  of  these  should  be 
obtained  by  substituting  methyl  for  one  of  the  three  hydrogens 
of  either  methyl  group  of  propane.  It  is  represented  by  the 
formula :  — 

H    H    H    H 

I       I        I       I 
H— C— C— C— C— H,  or  H3C.CH2.CH2.CH3. 

I       I       I       I 
H    H    H    H 

The  other  should  be  obtained  by  substituting  methyl  for  one 
of  the  two  hydrogens  of  the  group  CH2  contained  in  propane. 
This  would  give  a  hydrocarbon  of  the  formula :  — 

H    H    H 

I       I       I 
H— C— C— C— H,  or  CH3— CH— CH3. 

Ill  I 

H    C    H  CH3 

/l\ 
H  H  H 

The  theory  then  indicates  the  existence  of  two  butanes.  How 
about  the  facts?  Two,  and  only  two,  butanes  have  been  dis- 
covered. The  first  has  been  made  synthetically  by  treating 
ethyl  iodide  with  zinc :  — 

2  CH3.CH2I  +  Zn  =  CH3.CH2.CH2.CH3  +  Znl2. 


ISOMERISM   AMONG   THE   PARAFFINS  1 23 

The  method  of  synthesis  clearly  shows  which  of  the  two  pos- 
sible isomers  the  product  is.  It  is  known  as  normal  butane. 
It  is  a  gas  that  can  be  condensed  to  a  liquid  boiling  at  —  1°. 

The  second,  or  isobutane  (2-methylpropane),  is  made  from 
an  alcohol  which  will  be  shown  to  have  the  structure  represented 

CH3 

I 
by  the  formula  CH3 — C — OH    (see    Tertiary    butyl    alcohol, 

I 
CH3 

134),  by  replacing  the  hydroxyl  by  hydrogen.  It  is  a  gas 
which  when  liquefied  boils  at  —11.5°. 

Cymogene,  a  petroleum  distillation  product,  sp.  gr.  0.59  — 
0.636  and  boiling  at  0°,  is  nearly  pure  butane.  Isobutane  also 
occurs  in  American  petroleum. 

Applying  the  same  method  of  reasoning  to  the  next  members 
of  the  series,  how  many  isomeric  varieties  of  pentane,  C6H12, 
does  the  theory  suggest?  The  question  resolves  itself  into  a 
determination  of  the  number  of  kinds  of  hydrogen  atoms  con- 
tained in  the  two  butanes,  or  the  number  of  relations  to  the 
molecule  represented  among  the  hydrogen  atoms  of  the  butanes. 
This  determination  can  be  made  best  by  examining  the  struc- 
tural formulas.    Take  first  normal  butane  :  — 

H    H    H    H 

I       I      1       I 
H— C— C— C— C— H. 

I      I      I       I 
H    H   H    H 

In  this  there  are  plainly  two  different  relations  represented; 
viz.,  that  of  each  of  the  six  hydrogens  in  the  two  methyl  groups, 
and  that  of  each  of  the  four  hydrogens  of  the  two  CHj  groups. 
The  two  possible  methyl  derivatives  of  a  hydrocarbon  of  this 
formula  are  therefore  to  be  represented  thus :  — 

H3C.CH2.CH2.CH2.CH3,  (i) 

and  H3C.CH2.CH<^JJl  (2) 


124       HYDROCARBONS  OF  THE  MARSH  GAS   SERIES 

CHa 

I 
Now,  taking  isobutane,  HC — CH3,  it  will  be  seen  that  it  con- 

CH3 

sists  of  three  methyl  groups,  giving  nine  hydrogen  atoms  of  the 
same  kind,  and  one  CH  group,  the  hydrogen  of  which  bears  a 
different  relation  to  the  molecule  from  that  which  the  other 
nine  do.  There  are  therefore  two  possible  methyl  derivatives 
of  isobutane  which  must  be  represented  thus :  — 

CH3  CH3 

I  I 

HC— CH2.CH3  (3),       and        H3C— C— CH3.  (4) 

I  I 

CH3  CH3 

Apparently  four  pentanes  are  possible.  But  on  comparing 
formulas  (2)  and  (3),  it  will  be  seen  that,  though  written  a 
little  differently,  they  really  represent  the  same  compound. 
Thus  the  number  of  pentanes,  the  existence  of  which  is  indi- 
cated by  the  theory,  is  three,  and  these  are  represented  by 
formulas  (i),  (2),  and  (4).  They  are  all  known.  The  first  is 
called  normal  pentane,  boiling  point  36.3°;  the  second,  iso- 
pentane,  2-methylbutane  or  dimethylethylmethane,  boiling 
point  27.9°;  and  the  third,  2-2-dimethylpropane  or  tetra- 
methylmethane,  boiling  point,  9.5°. 

n-Pentane  is  made  thus  :  — 

C2H5I  +  C3H7I  +  2  Na  =  CsHiz  +  2  Nal, 

Ethyl  iodide    n-Propyl  iodide  n-Pentane 

which  shows  its  structure  to  be  CH3CH2CH2CH2CH3.  Di- 
methylethylmethane is  made  from  isoamyl  alcohol,  which  will 
be  shown  to  have  the  formula, 

^JJ'>CH.CH2.CH20H, 
t--rl3 

by  replacing  the  hydroxyl  by  hydrogen.  Hence  its  structure  is 
that  represented  above  by  formula  (2)  or  (3). 


HEXANES  125 

Tetramethylmethane  is  made  by  starting  with  acetone. 
Acetone  has  been  shown  to  consist  of  carbonyl  in  combina- 
tion with  two  methyl  groups,  as  represented  in  the  formula 
CH3 — CO — CH3.  It  has  also  been  shown  that,  by  treating  ace- 
tone with  phosphorus  pentachloride,  the  oxygen  is  replaced  by 
chlorine,  giving  a  compound  of  the  formula  CH3 — CCI2 — CH3. 
Now,  by  treating  this  chloride  with  zinc  methyl,  the  chlorine  is 
replaced  by  methyl  thus  :  — 

CH3 

I 
CH3— CCI2— CHs  +  Zn(CH3)2  =  CH3— C— CH3  -f-  ZnClj. 

I 
CH3 

The  product  is  tetramethylmethane,  and  this  synthesis 
shows  clearly  what  the  structure  of  the  hydrocarbon  is.  Nor- 
mal and  isopentane  have  been  isolated  from  Pennsylvania 
petroleum.  Tetramethylmethane  is  present  in  the  gas  from 
Caucasian  and  Rumanian  petroleum. 

The  commercial  pentane,  boiling  at  25^-40°,  used  in  the  pen- 
tane  lamp  for  determining  the  candle  power  of  illuminating 
gas,  consists  largely  of  normal  pentane  and  isopentane  with 
small  quantities  of  lower  and  higher  homologues.  It  is  also 
used  in  pentane  thermometers  for  determining  low  tempera- 
tures. 

Hexanes.  —  The  student  will  now  be  prepared  to  apply  the 
theory  to  the  determination  of  the  number  of  hexanes  possible. 
He  will  find  that  there  are  five.  The  theory  is,  in  this  case,  as 
in  the  preceding,  in  perfect  accordance  with  the  facts.  There 
are  five,  and  only  five,  hexanes  known :  — 

1.  Normal  hexane,  CH3.CH2.CH2.CH2.CH2.CH3,  (b.  p.  68°) 
has  been  isolated  from  Pennsylvania  petroleum.  It  is  the  prin- 
cipal constituent  of  volatile  petroleum  ether  boiling  at  68°-95°. 

2.  Dimethylpropylmethane,      CH3.CH2.CH2.CH<^„',      is 

C±l3 

found  in  American  and  Rumanian  petroleums  (boiling  point 
62°). 


126       HYDROCARBONS  OF  THE  MARSH   GAS  SERIES 

3.  Methyldiethylmethane,  CH3.CH<^'^,  is  present  in 
Rumanian  petroleum  (b.  p.  64°). 

4.  Dimethylisopropylmethane 
in  Caucasian  naphtha  (b.  p.  58°). 


4.   Dimethylisopropylmethane,  „  ^>HC — CH<„-_  .occurs 


CH3 

I 
5.  Trimethylethylmethane,  H3C — C — CH2.CH3,  is  found  in 

CH3 

American  and  Caucasian  naphtha  (b.  p.  49.6°). 

Passing  upward,  nine  heptanes  are  possible  according  to  the 
theory,  while  but  seven  have  thus  far  been  discovered ;  and, 
while  theory  indicates  the  possibility  of  the  discovery  of  eighteen 
hydrocarbons  of  the  formula  CgHig,  only  nine  are  known.  The 
theoretical  number  of  isomeric  varieties  of  the  higher  members 
of  the  series  is  very  great,  but  our  knowledge  in  regard  to  them 
is  limited,  and  it  is  impossible  to  say  whether  the  theory  will 
ever  be  confirmed  by  facts.  There  are  802  possible  isomers 
of  the  formula  Ci3H28-  It  may  be  that  there  is  some  law  limit- 
ing the  number  of  complicated  hydrocarbons.  It  is,  however, 
idle  to  speculate  upon  the  subject.  It  is  well  for  us  to  keep  in 
mind  that  a  thorough  knowledge  of  a  few  of  the  simplest  mem- 
bers of  the  series  is  all  that  is  necessary  for  the  present. 

Normal  heptane  occurs  in  the  turpentine  from  Pinus  sabiniana, 
a  native  of  California. 

On  examining  the  formulas  used  to  express  the  structure  of 
the  hydrocarbons,  it  will  be  found  that  they  can  be  divided  into 
three  classes :  — 

(i)  Those  in  which  there  is  no  carbon  atom  in  combination 
with  more  than  two  others ;  as :  — 

Propane     ....  CH3.CH2.CH3; 

Normal  butane  .     .  CH3.CH2.CH2.CH3; 

Normal  pentane      .  CH3.CH2.CH2.CH2.CH3 ; 

Normal  hexane  .     .  CH3.CH2.CH2.CH2.CH2.CH3. 


NOMENCLATURE  1 2  7 

(2)  Those  in  which  there  is  at  least  one  carbon  atom  in  com- 
bination with  three  others ;  as,  — 

Isobutane,  2-methylpropane      .     CH3.CH<„„  ; 

CH3 

Isopentane,  2-methylbutane      .     CH3.CH2.CH<  _„  ; 

Cxla 

Isohexane,  2-methylpentane      .     CH3.CH2.CH2.CH<    ^; 

Dimethyl-isopropylmethane,  „  p  ptt 

2-3-dimethylbutane       .     .     !;'^>CH— CH<^^'. 

XI3L-  CHa 

(3)  Those  in  which  there  is  at  least  one  carbon  atom  in 
combination  with  four  others ;  as  :  — 

CH3 

Tetramethylmethane,  2-2-dimethyl-  | 

propane CH3 — C — CH3; 

CH3 

CH3 

Trimethylethylmethane,  2-2-dimethyl-  | 

butane CjHs — C — CH3. 

I 
CH3 

The  members  of  the  first  class  are  called  normal  paraffins; 
those  of  the  second  class,  isoparafflns ;  and  those  of  the  third 
class,  neoparafflns. 

Only  the  members  of  the  same  class  are  strictly  comparable 
with  one  another.  Thus  it  has  been  found  that  the  boiling 
points  of  the  normal  hydrocarbons  bear  simple  relations  to 
one  another,  and  that  the  same  is  true  of  the  isoparafhns ; 
but,  on  comparing  the  boiling  points  and  other  physical  prop- 
erties of  normal  paraffins  with  those  of  the  iso  or  neoparaffins, 
no  such  simple  relations  are  observed. 

Regarding  the  names  of  the  paraffins,  the  simplest  nomen- 
clature in  use  is  that  according  to  which  the  hydrocarbons  are 
all   regarded   as   derivatives   of    methane.     Thus  propane   is 


128        HYDROCARBONS  OF  THE  M,\RSH   GAS   SERIES 


ethylmethane,  C 


C2H5 
H 
H 
H 


;  isobutane,  trime thylme thane,  C 


neopentane,  tetramethylmethane,  C 


fCH3 
CH3 
CH3' 
CH3 


fCHs 
CH3 
CH3 
H 


etc. 


Geneva  nomenclature.  —  The  nomenclature  for  the  hydrocar- 
bons recommended  by  the  International  Congress  of  Chem- 
ists at  Geneva  retains  the  names  used  at  present  for  the 
normal  hydrocarbons.  For  example,  pentane  is  the  compound 
CH3(CH2)3CH3.  In  the  case  of  the  iso  and  the  neohydrocar- 
bons,  the  longest  normal  chain  gives  the  name,  the  other  groups 
present  being  regarded  as  substituents.  The  position  of  the 
groups  is  indicated  by  numbering  the  carbon  atoms  in  the 
normal  chain.  Thus  isobutane  is  2-methylpropane,  isopen- 
tane  is  2-methylbutane,  and  tetramethylmethane  is  2-2-di- 
methylpropane  (127). 


CHAPTER   rX 

OXYGEN    DERIVATIVES    OF    THE    fflGHER    MEMBERS    OF 
THE   PARAFFIN   SERIES 

The  derivatives  of  the  higher  members  of  the  paraffin  series 
will  now  be  taken  up.  Not  much  need  be  said  in  regard  to  the 
halogen  derivatives.  A  few  of  them  will  be  mentioned  in  con- 
nection with  the  corresponding  alcohols.  The  chief  substances 
that  will  require  attention  are  the  alcohols  and  acids. 

Alcohols 

Normal  propyl  alcohol,  propanoI-1,  C3H7OH. — When  sugar 
undergoes  alcoholic  fermentation  with  yeast,  some  propyl 
alcohol  is  always  formed,  and  is  contained  in  "fusel  oil"  (4  to  7 
per  cent).  From  this  it  can  be  separated  by  fractional  distilla- 
tion. 

It  is  a  colorless  liquid  with  an  alcoholic  odor.    It  boils  at  97.19°. 

Note  for  Student.  —  Compare  with  the  boiling  points  of  methyl  and 
ethyl  alcohol. 

It  conducts  itself  like  the  first  two  members  of  the  series. 
By  oxidation  it  is  converted  into  propionic  aldehyde,  CsHeO, 
and  propionic  acid,  C3H6O2,  which  bear  to  it  the  same  relations 
that  acetic  aldehyde  and  acetic  acid  bear  to  ethyl  alcohol. 
It  is  therefore  a  primary  alcohol  (132). 

Secondary  propyl  or  isopropyl  alcohol,  propanol-2,  C3H7OH.  — 
The  reasons  for  regarding  the  alcohols  as  hydroxyl  derivatives 
of  the  hydrocarbons  have  been  given.  As  the  six  hydrogen 
atoms  of  ethane  are  all  of  the  same  kind,  but  one  ethyl  alcohol 
is  possible,  and  only  one  is  known.  But  just  as  there  are  two 
butanes  or  methyl  derivatives  of  propane,  so  there  are  two 
hydroxyl  derivatives  of  propane,  or  two  propyl  alcohols.     The 

129 


I30  DERIVATIVES  OF  THE  PARAFFINS 

first  is  the  one  obtained  from  "  fusel  oil,"  the  other  is  the  one 
called  secondary  propyl  alcohol.  This  has  already  been  referred 
to  under  Acetone  (74),  where  it  was  stated  that  acetone  is 
converted  into  secondary  propyl  alcohol  by  nascent  hydrogen. 
In  fact  this  is  one  of  the  methods  for  the  preparation  of  the 
alcohol. 

Isopropyl  alcohol  is  now  made  on  the  large  scale  from  propy- 
lene obtained  in  the  "  cracking "  (118)  of  petroleum.  The 
propylene  is  absorbed  in  sulphuric  acid,  giving  isopropyl  acid 
sulphate :  — 

H3C  H3C 

I  I 
HC+HO.SO2.OH    =     HC— OSO2OH 

II  I 
H2C                                H3C 

When  this  is  diluted  with  water  and  distilled  it  gives  isopropyl 
alcohol :  — 

H3C  H3C 

I  I 

HC— O.SO2.OH  +  H2O  =  HC— OH  +  02S(OH)2. 

I  I 

H3C  H3C 

Like  ethyl  alcohol  it  forms  a  constant  boiling  mixture 
with  water.  This  boils  at  80.37"  ^t  760°"°.  It  contains 
87.9  per  cent  isopropyl  alcohol  and  12. i  per  cent  water.  It 
is  used  as  a  solvent  and  for  the  preparation  of  isopropyl 
compounds,  e.g.  isopropyl  acetate.  It  is  sold  under  the  name 
Petrohol. 

It  is,  like  ordinary  propyl  alcohol,  a  colorless  liquid.  When 
pure  it  boils  at  82°.  While  all  its  reactions  show  that  it  is  a 
hydroxide,  it  conducts  itself  towards  oxidizing  agents  quite 
differently  from  the  alcohols  thus  far  studied.  It  is  con- 
verted first  into  acetone,  CsHsO,  which  is  isomeric  with  propionic 
aldehyde  obtained  from  ordinary  propyl  alcohol ;  by  further 
oxidation,  this,  however,  does  not  yield  an  acid  of  the  formula 
C3H6O2,  as  we  might  expect,  but  breaks  down,  yielding  two 


SECONDARY  ALCOHOLS  131 

simpler  acids;  viz.,  formic  acid,  CH2O2,  and  acetic  acid, 
C2H4O2  (74). 

Secondary  alcohols.  —  Secondary  propyl  alcohol  is  the 
simplest  representative  of  a  class  of  alcohols  known  as  sec- 
ondary alcohols.  They  are  made  by  treating  the  ketones  with 
nascent  hydrogen,  and  are  easily  distinguished  from  the  primary 
alcohols  by  their  conduct  towards  oxidizing  agents.  They 
yield  ketones  containing  the  same  number  of  carbon  atoms, 
and  then  these  break  down,  yielding  acids  containing  a  smaller 
number  of  carbon  atoms. 

Is  there  anything  in  the  structure  of  these  secondary  alcohols 
to  suggest  an  explanation  of  their  conduct  ?  Secondary  propyl 
alcohol  is  made  from  acetone  by  treating  this  with  nascent  hy- 
drogen.    Acetone  contains  two  methyl  groups  and  carbonyl,  as 

0 

II 
represented    by    the    formula    CH3 — C — -CHs.    The   simplest 

change  that  can  take  place  in  this  compound  under  the  influence 

of  hydrogen  is  that  represented  in  the  following  equation :  — 

O  H 

II  I 

CH3— C— CH3  +  H2  =  CH3— C— CH3. 

I 

OH 

The  very  close  connection  existing  between  acetone  and  second- 
ary propyl  alcohol,  and  the  fact  that  there  are  two  methyl 
groups  in  acetone,  make  it  appear  probable  that  there  are  also 
two  methyl  groups  in  secondary  propyl  alcohol,  as  represented 
in  the  above  formula. 

On  the  other  hand,  the  easy  transformation  of  primary 
propyl  alcohol  into  propionic  acid,  H3CCH2COOH,  which 
will  be  shown  to  contain  ethyl,  shows  that  in  the  alcohol 
ethyl  is  also  present.  Therefore,  we  may  conclude  that  the 
difference  between  primary  and  secondary  propyl  alcohol  is 
that  the  former  is  an  ethyl  derivative  and  the  latter  a  dimethyl 
derivative  of  methyl  alcohol  or  carbinol  as  represented  by 
the  formulas :  — 


132 


DERIVATIVES  OF  THE  PARAFFINS 


H 

CH2.CH3 

CH, 

c 

H 
H 

C' 

H 
H 

C' 

CH3. 
H 

OH 

OH 

OH 

Methyl  alcohol 
or  carbinol 

Ethyl  carbinol  or 

primary  propyl 

alcohol 

Dimethyl  carbinol 
or  secondary 
propyl  alcohol 

Primary  propyl  alcohol  is  methyl  alcohol  or  carbinol  in  which 
one  hydrogen  of  the  methyl  group  is  replaced  by  a  radical,  while 
secondary  propyl  alcohol  is  methyl  alcohol  or  carbinol  in  which 
two  hydrogens  are  replaced  by  radicals.  An  examination  of  all 
secondary  alcohols  known  shows  that  the  above  statement  can 
be  made  in  regard  to  all  of  them.  They  must  be  regarded  as 
derived  from  methyl  alcohol  by  the  substitution  of  two  radicals 
for  two  hydrogen  atoms  and  are  therefore  called  secondary  alco- 
hols. The  alcohols  of  the  first  class,  like  ethyl  and  ordinary 
propyl  alcohol,  are  derived  from  methyl  alcohol  by  the  sub- 
stitution of- owe  radical  for  one  hydrogen,  and  are  hence  called 
primary  alcohols. 

Another  way  of  stating  the  difference  between  primary  and 
secondary  alcohols  is  this :  Primary  alcohols  contain  the 
univalent  group  CH2OH ;  secondary  alcohols  contain  the 
bivalent  group  CHOH.  These  statements  necessarily  follow 
from  the  first  ones. 

A  primary  alcohol,  when  oxidized,  yields  an  aldehyde  and 
then  an  acid  containing  the  same  number  of  carbon  atoms  as 
the  alcohol. 

A  secondary  alcohol,  when  oxidized,  yields  a  ketone  contain- 
ing the  same  number  of  carbon  atoms  and  then  this  yields 
acids  containing  a  smaller  number  of  carbon  atoms. 

Recalling  what  was  said  regarding  the  nature  of  the  changes 
involved  in  passing  from  a  primary  alcohol  to  the  corresponding 
aldehyde  and  acid,  it  will  be  seen  that  the  formation  of  an  acid 
containing  the  same  number  of  carbon  atoms  is  impossible 
in  the  case  of  a  secondary  alcohol.  In  the  case  of  a  primary 
alcohol,  we  have :  — 


BUTYL  ALCOHOLS 


'^33 


R  [R 

H  H 

H  OH 

OH  I  OH 

Alcohol  Aldehyde 

In  the  case  of  the  secondary  alcohol,  we  have : 

f  R 
R 
OH 
OH 


R 

R 

H 

C 

OH. 

0 

0 

Add 


R 
R 
H 
OH 

Secondary  alcohol 


R 
R. 
O 


Ketone 


Further  introduction  gf  oxygen  cannot  take  place  without  a 
breaking  down  of  the  compound.  It  will  be  seen  that  the 
formulas  used  to  express  the  structure  of  the  compounds  are 
in  close  accordance  with  the  facts. 

Butyl  alcohols,  C4H9.OH. — Theoretically,  there  are  two 
possible  hydroxyl  derivatives  of  each  of  the  two  butanes,  mak- 
ing four  butyl  alcohols  in  all.  They  are  all  known.  Two  are 
primary  alcohols. 

1.  Normal  butyl  alcohol,  butanol-1,  CH3.CH2.CH2.CH2OH, 
boiling  point  117.7°,  gives  »-butyric  acid  on  oxidation. 

Normal  butyl  alcohol  is  now  made  on  the  large  scale  by  the 
fermentation  of  Indian  corn,  employing  an  anaerobic  organism 
(Weizmann  process).  The  distillate  from  the  fermented  mash 
contains  butanol  (56  per  cent),  acetone  (32  per  cent),  and  ethyl 
alcohol  (12  per  cent).  These  are  separated  by  subsequent 
rectification.  The  butyl  alcohol  is  sold  under  the  trade  name 
Butanol.  It  is  used  chiefly  in  the  lacquer  industry  and  as  a 
solvent  for  all  kinds  of  resins  and,  after  conversion  into  butyl 
acetate,  in  the  manufacture  of  leather  substitutes. 

2.  Isobutyl  alcohol,  2-methylpropanol-l,  r;„^>CH.CH20H, 

b.  p.  108°,  gives  isobutyric  acid  on  oxidation. 

Isobutyl  alcohol  is  obtained  on  the  large  scale  by  fractional 
distillation  of  fusel  oil,  which  contains  from  15  to  25  per  cent 
of  this  alcohol. 


134  DERIVATIVES  OF  THE  PARAFFINS 

OTT 

3.  Secondary  butyl  alcohol,  butanol-2,  CH3.CH2.CIK  „„  , 

(b.p.  99-9°),  is  made  by  treating  ethylmethyl  ketone  with  nas- 
cent hydrogen :  — 

OH 
CH3.CH2— CO— CH3  +  H2  =  CH3.CH2.CH<^jj^, 

and  gives  methylethyl  ketone  on  oxidation. 

Note  for  Student.  —  Compare   this   with  the   reaction  for  making 
secondary  propyl  alcohol. 

This  alcohol  is  also  made  from  butylene  in  the  same  way  that 
isopropyl  alcohol  is  made  from  propylene  (130). 

H2C.CH3  H2C.CH3 

I  •     I 

HC     +     HO— SO2— OH      =      HC— 0— SO2— OH 

II  I 
H2C                                                H3C 

H2C.CH3  H2C.CH3 

HC— 0— SO2OH    +    H2O    =      HCOH   +  S02(OH)2 

H3C  H3C 

Butylene,  like  propylene,  is  contained  in  the  mixture  of  gases 
formed  in  the  "  cracking  "  of  petroleum. 

4.  Tertiary  butyl   alcohol,  trimethyl   carbinol,  2-methylpro- 

CH3 

I 
panol-2,      CH3— C— OH,  (m.  p.  25°,  b.  p.  82.55°).    The  fourth 

CH3 

butyl  alcohol  has  properties  that  distinguish  it  from  the  primary 
aid  secondary  alcohols.  When  oxidized  it  yields  neither  an 
aldehyde  nor  a  ketone  containing  the  same  number  of  carbon 
atoms,  but  breaks  down  at  once,  yielding  compounds  contain- 
ing a  smaller  number  of  carbon  atoms.  Assuming  that  every 
primary  alcohol  contains  the  group  CH2OH,  and  that  every 
secondary  alcohol  contains  the  group  CHOH,  it  follows  that 


BUTYL   ALCOHOLS 


135 


the  two  primary  butyl  alcohols  and  secondary  butyl  alcohol 
must  have  the  formulas  above  assigned  to  them ;  and  it  follows 
further  that  the  fourth  butyl  alcohol  must  have  the  above 
formula,  as  this  represents  the  only  other  arrangement  of 
the  groups  possible,  according  to  the  theory.  This  formula 
represents  a  condition  that  does  not  exist  in  either  the  primary 
or  secondary  alcohols.  It  is  methyl  alcohol  in  which  all 
three  hydrogen  atoms  of  the  methyl  group  are  replaced  by 
methyl  groups.  Such  an  alcohol  is  hence  known  as  a  tertiary 
alcohol,  and  the  one  under  consideration  is  called  tertiary  butyl 
alcohol.  It  is  the  simplest  representative  of  the  class  of  tertiary 
alcohols.     It  contains  the  trivalent  group  C(OH). 

Tertiary  butyl  alcohol  is  made  by  treating  acetone  with 
methyl  magnesium  iodide,  CHaMgl  (Grignard  reagent),  and 
then  treating  this  product  with  water :  — 


(CH3)2CO  +  CHaMgl  =  C 


CH3 

CH3 

CH3 

lOMgl 


+  H2O 


=  C 


CH3 

CH3 

CH3 

lOMgl 

CH3 
CH3 


CH3  +  ^g<OH 


OH 


By  using  other  ketones  and  magnesium  compounds,  other 
tertiary  alcohols  can  be  obtained. 

With  hydriodic  acid  tertiary  butyl  alcohol  gives  tertiary 
butyl  iodide,  and  this  gives  isobutane  when  reduced  with  nas- 
cent hydrogen.  Isobutyl  alcohol,  when  treated  in  a  similar 
manner,  also  gives  isobutane.  The  other  two  butyl  alcohols 
give  normal  butane. 

Note  for  Student.  —  Write  the  equations. 

Characteristics  of  the  three  classes  of  alcohols.  To  recapitu- 
late, the  hydroxyl  derivatives  of  the  hydrocarbons  can  be 
divided  into  three  classes,  according  to  their  conduct  towards 
oxidizing  agents. 


136  DERIVATI\ES   OF  THE   PARAFFINS 

To  what  was  said  regarding  the  conduct  of  primary  and 
secondary  alcohols  on  oxidation  we  may  now  add :  Tertiary 
alcohols  do  not  yield  aldehydes,  acids,  or  ketones  containing 
the  same  number  of  carbon  atoms,  but  break  down,  yielding 
compounds  containing  a  smaller  number  of  carbon  atoms. 

The  formulas  representing  the  three  classes  of  alcohols  are :  — 


R 

R 

R 

■^ 
-•  ' 

H 

H 

c 

R 
H 

c. 

R 
R 

OH 

OH 

OH 

Pr 

unary 

Secondajy 

Tertiary 

Pentyl  alcohols,  amyl  alcohols,  CsHu.OH.  —  Eight  of  these 
are  possible,  and  aU  are  known.  Only  two  of  the  amyl  alcohols 
need  be  taken  up  here. 

Inactive  isoamyl  alcohol,  isobutyl  carbinol,  3-inethylbutanol-l, 

CH 

_„'>CH.CH2.CH20H.  —  This  alcohol,  together  with  at  least 

CH3 

one  other  of  the  same  composition,  forms  the  chief  part  of 
"fusel  oil."  B}-  fractional  distillation  of  this,  a  mixture  of 
two  amyl  alcohols  called  fermentation  amyl  alcohol  is  obtained, 
as  a  colorless  liquid,  having  a  penetrating  odor,  and  boiling  at 
128°  to  132°.  This  can  be  separated  into  two  isomeric  alcohols, 
one  of  which  is  inactive  isoamyl  alcohol  (87  per  cent),  (b.p.  131°), 
and  the  other  active  amyl  alcohol  (13  per  cent) ,  (b.p.  1 28°) .  The 
names  refer  to  the  behavior  of  the  substances  towards  polar- 
ized light,  the  former  having  no  action  upon  it,  the  latter 
turning  the  plane  of  polarization  to  the  left. 

The  method  of  separating  the  two  alcohols  is  as  follows: 
Fermentation  amyl  alcohol  (b.  p.  i28°-i32°)  is  converted  into 
the  two  amyl  acid  sulphates  by  means  of  concentrated  sulphuric 
acid,  and  the  barium  salts  of  these  are  separated  by  fractional 
crystallization.  The  barium  salt  of  the  active  amyl  acid  sul- 
phate is  more  than  twice  as  soluble  as  that  of  the  inactive  salt. 
The  pure  barium  salts  are  then  decomposed  separately  by 
dilute  sulphuric  acid  and  the  alcohols  recovered  by  boiling  with 
water  and  distilling.     In  this  way  the  pure  inactive  isoamyl 


ACTIVE   AMYL   ALCOHOL  13  7 

alcohol  and  the  pure  levorotatory  amyl  alcohol    have    been 
obtained. 

When  treated  with  oxidizing  agents  inactive  isoamyl  alcohol 
yields  an  acid  containing  the  same  number  of  carbon  atoms, 
and  is,  therefore,  a  primary  alcohol.  The  acid  has  been  made 
by  simple  reactions  which  show  that  it  must  be  represented  by 

the  formula  ^„'>CH.CH2.C02H.      (See  Valeric    Acid,    147.) 

Therefore,  the  alcohol  has  the  structure  represented  by  the 

above  formula. 

Active   amyl   alcohol,    secondary   butyl   carbinol,   2-methyl- 

CH  OH 
butanol-1,   CH3.CH2.CH<_,„^       .—  This,  as  stated  above,  is 

LH3 

obtained,    together   with   the  inactive  isoamyl  alcohol,  from 

fusel  oil.     It  is  a  primary  alcohol  as  it  gives  active  valeric  acid 

on  oxidation  (147). 

There  are  two  active  amyl  alcohols  known,  one  of  which  is 

dextrorotatory  and   the   other   levorotatory.     Both    turn    the 

plane   of  polarized   light   the  same   number  of   degrees,   one 

to  the  right  and  the  other  to  the  left.     A  mixture  of  the  two, 

in  equimolecular  proportions,  is,  therefore,  optically  inactive. 

All  three  of  these  alcohols  have  been  proved  to  have  the  same 

structure  represented  by  the  above  formula,  as  they  all  give 

valeric  acids,  H3C — CHj — CH<  _  _  _    ,  on  oxidation.    We  have 

CUOH 

here  to  deal  with  a  new  kind  of  isomerism.     Compounds  may 

conduct  themselves  chemically  in  the  same  way  and  yet  differ  in 

some  of  their  physical  properties,  as  in  their  action   toward 

polarized  light. 

An  ingenious  hypothesis  has  been  put  forward  to  explain 
that  particular  kind  of  isomerism  which  shows  itself  in  the  action 
of  organic  compounds  in  the  liquid  or  gaseous  state  or  in  solu- 
tion, upon  polarized  light.  Our  ordinary  structural  formulas 
have  nothing  whatever  to  do  with  the  relations  of  the  atoms 
and  groups  in  space.  They  indicate  chemical  relations  that 
are  discovered  by  a  study  of  chemical  reactions. 

Let  us  suppose  that  in  a  carbon  compound  the  carbon  atom 


138 


DERIVATIVES  OF  THE  PARAFFINS 


is  situated  at  the  centre  of  a  tetrahedron,  and  that  the  four 
atoms  or  groups  which  it  holds  in  combination  are  at  the  angles 
of  the  tetrahedron,  as  represented  in  figures  below.  If  these 
groups  are  all  different  in  hind,  and  only  in  this  case,  it  is  pos- 
sible to  arrange  them  in  two  ways  in  space  with  reference  to 
the  central  carbon  atom.  The  two  arrangements  are  shown  in 
the  figures. 


The  diflFerence  between  the  two  arrangements  in  space  is  that 
which  is  observed  between  either  one  and  its  reflection  in  a 
mirror,  or  between  a  right  hand  and  a  left  hand.' 

A  carbon  atom  in  combination  with  four  different  kinds  of 
atoms  or  groups  is  called  an  asymmetric  carbon  atom.  When- 
ever, therefore,  a  compound  contains  an  asymmetric  carbon  atom, 
there  are  two  possible  arrangements  of  its  parts  in  space,  which 
correspond  to  the  right-handed  and  the  left-handed  tetrahedron. 
It  can  be  shown  that  if  the  arrangement  of  the  groups  in  one  of 
these  figures  rotates  the  plane  of  polarized  light  to  the  right 
(clockwise),  the  other  will  rotate  it  the  same  number  of  de- 
grees to  the  left  (counter-clockwise). 

In  active  amyl  alcohol  there  is  an  asymmetric  carbon  atom 
as  shown  in  the  formula 

CH3  (2) 
I 
(i)H— C-C2Hb(3) 

CH2OH  (4) 

the  central  carbon  atom  appearing  in  combination  with 
(i)  hydrogen,  (2)  methyl,  (3)  ethyl,  and  (4)  the  primary  alcohol 


1  This  can  be  made  clearer  by  means  of  models  which  can  easily  be 
constructed  of  stout  wire  and  corks. 


ACTIVE   AMYL   ALCOHOL  I39 

group.  Hence,  according  to  the  hypothesis  just  stated,  there 
are  two  possible  arrangements  in  space  of  the  constituents  of 
this  compound,  one  corresponding  to  the  right-handed  tetra- 
hedron and  the  other  to  the  left-handed  tetrahedron.  Both 
are  secondary  butyl  carbinols,  i.e.  they  are  structurally  identical. 
The  inactive  variety  is  formed  by  a  combination  of  the  two 
active  compounds. 
On  oxidation  active  amyl  alcohol  gives  active  valeric  acid, 

H3C 

I 

H C -02115, 

COOH 

as  the  asymmetric  carbon  atom  is  still  present  in  this  compound. 
If  the  active  amyl  alcohol  is  treated  with  hydriodic  acid,  it 
gives  active  amyl  iodide, 

H3C  H3C 

I  I 

H — C — C2H5  H — C — C2H5, 

I  I 

H2C0H  H2C1 

as  this  compound  also  contains  an  asymmetric  carbon  atom. 

When  this  is  treated  with  nascent  hydrogen  it  gives  iso- 
pentane, 

H3C 

H — C — C2H5 

I 
H3C 

and  isopentane  is  optically  inactive.  It  does  not  contain  an 
asymmetric  carbon  atom,  as  two  of  the  groups  are  now  the  same. 
Both  (f-amyl  alcohol  and  /-amyl  alcohol  give  isopentane,  and 
hence  it  will  be  seen  that  this  kind  of  isomerism  is  due  to  the 
asymmetric  carbon  atom,  for  it  disappears  when  the  asymmetric 
carbon  atom  disappears. 

If,  however,  the  active  amyl  iodide  is  treated  with  ethyl  iodide 
and  sodium,  a  heptane  results. 


I40  DERIVATIVES  OF  THE  PARAFFINS 

H3C 

I 
H — C — CjHs, 

H2C — Calls 

and  this  is  optically  active,  as  it  still  contains  an  asymmetric 
carbon  atom. 

The  branch  of  chemistry  that  has  to  deal  with  this  kind 
of  isomerism  is  called  stereochemistry.  The  phenomena  of  stereo- 
chemistry have  been  the  subject  of  extensive  investigations  and 
the  facts  established  furnish  a  strong  foundation  for  the  theory 
expounded  above.* 

Commercial  isoamyl  acetate,  C5H11O.CO.CH3,  (boiling  point 
i38.5°-i39°),  is  made  from  fermentation  amyl  alcohol  (b.  p. 
i28°-i32°),  acetic  acid,  and  a  small  quantity  of  sulphuric  acid. 
It  is  burned  in  the  Hefner  lamp  to  determine  the  candle  power 
of  illuminating  gas.  Its  chief  use,  however,  is  as  a  solvent  in 
the  preparation  of  lacquers  (Zapon)  and  of  leather  substitutes 
{Fabrikoid)  and  in  the  manufacture  of  fruit  essences. 

Isoamyl  nitrite,  C5HuO.NO,  a  yellow  fluid  with  a  fruity  odor, 
(boiling  point  97°-98°),  is  made  from  fermentation  amyl  alco- 
hol by  the  action  of  nitrous  acid.  It  is  used  in  the  preparation 
of  diazonium  and  isonitroso  compounds,  and  in  medicine,  par- 
ticularly in  cases  of  angina  pectoris. 

A  list  of  some  of  the  more  important  members  of  the  series 
is  given  below.  In  naming  the  alcohols,  it  is  best  to  refer 
them  to  methyl  alcohol,  just  as  the  hydrocarbons  are  referred 
to  marsh  gas.  Calling  methyl  alcohol  carbinol,  we  get  such 
names  as  methylcarbinol,  diethylcarbinol,  etc.,  which  convey  at 
once  an  accurate  idea  concerning  their  structure.  A  few  illus- 
trations will  suffice.    Take  the  alcohols  above :  — 

fCH3 
I  jj 
Ethyl  alcohol  is  methylcarbinol,  ^  \  n     ' 

[oh 

'  See  Stereochemistry,  by  A.  W.  Stewart,  second  edition  (1919). 


ACTIVE  AMYL   ALCOHOL 


141 


Primary  propyl  alcohol  is  ethylcarbinol,    C 


Secondary  propyl  alcohol  is  dimethyl- 
carbinol, 


Tertiary  butyl  alcohol  is  trimetkyl- 
carbinol, 


Inactive  isoamyl  alcohol  is  isobutyl- 
carhinol. 


CH2CH3 

H 

H  ' 

OH 

CH3 
CH3 
H     ' 
OH 

CH3 
CH3 
CH3' 
OH 

\  CH2.CH< 
H 
H 
OH,  etc.,  etc., 


CH3 

CH3 


Geneva  nomenclature.  —  The  "  official  "  names  of  the  alcohols 
end  in  "  -ol,"  the  normal  primary  alcohols  being  designated 
as  methanol,  ethanol,  propanol,  butanol,  pentanol,  etc.,  while 
isobutyl  alcohol  is  called  2-methylpropanol-i ;  isoamylalcohol, 
3-methylbutanol-i ;  and  active  amyl  alcohol,  2-methylbutanol-i. 
In  the  case  of  the  secondary  alcohols  the  position  of  the  hydroxyl 
group  is  given,  thus,  propanol- 2  is  secondary  propyl  alcohol  and 
butanol-2  is  secondary  butyl  alcohol.  In  the  case  of  the 
tertiary  alcohols  the  positions  of  the  hydrocarbon  residue  and 
the  hydroxyl  group  are^  both  designated,  thus,  trimethyl 
carbinol  is  2-methylpropanol-2. 

Cetyl  alcohol,  C16H33.OH,  in  the  form  of  the  palmitic  ester, 
is  the  chief  constituent  of  spermaceti. 

Ceryl  alcohol,  C26H53.OH,  as  the  cerotic  ester  is  found  in 
Chinese  wax. 

Myricyl  alcohol,  CsoHe.i-OH,  occurs  in  beeswax  and  in  car- 
nauba  wax  as  the  palmitic  ester. 

The  alcohols  are  obtained  from  these  esters  by  saponification 
with  alcoholic  caustic  potash.  Of  most  of  the  higher  members 
only  the  normal  primary  alcohol  is  known. 


142  DERIVATIVES  OF  THE  PARAFFINS 

The  following  table  will  give  some  idea  of  the  extent  to 
which  the  series  of  alcohols  derived  from  the  paraffins  has  been 
investigated.  There  are  fourteen  hexyl  alcohols  and  fourteen 
heptyl  alcohols  known. 

alcohols  of  the  methyl  alcohol  series 
Series  C„H2„+i.0H 

Methyl  alcohol,  b.  p.  64.7° CH3.OH 

Ethyl  "  78.32 C2H6.OH 

n-Propyl  "  97.19 C3H7.OH 

n-Butyl  "  117.7  C4H9.OH 

n-Pentyl  "  137.8  CsHu.OH 

n-Hexyl  "  156.8  CeHis.OH 

n-Heptyl  "  175.8  CjHu.OH 

n-Octyl  "  195.5  CgHw.OH 

n-Nonyl  "  213.5  C9H19.OH 

Cetyl  "  m.p.      48  C16H33.OH 

Ceryl  "  m.p.      79  CjeHss.OH 

Myricyl       "  m.p.      88  C30H61.OH 

2.    Aldehydes 

It  follows  from  what  has  been  said  concerning  the  properties 
of  primary  alcohols,  that  there  should  be  an  aldehyde  corre- 
sponding to  every  primary  alcohol.  Many  of  these  have  been 
prepared.  They  resemble  ordinary  acetic  aldehyde  so  closely 
that  it  is  unnecessary  to  take  them  up  individually.  If  the 
structure  of  the  alcohol  from  which  an  aldehyde  is  formed  by 
oxidation  is  known,  the  structure  of 'the  aldehyde  is  also  known. 

Besides  the  one  method  for  the  preparation  of  aldehydes 
that  has  been  mentioned,  viz.,  the  oxidation  of  primary  alcohols, 
there  is  one  other  that  should  be  specially  noted.  It  consists 
in  distilling  calcium  formate  with  the  calcium  salt  of  a  higher 
fatty  acid.  Thus,  when  a  mixture  of  calcium  acetate  and 
calcium  formate  is  distilled,  acetic  aldehyde  is  formed  as  repre- 
sented by  the  equation :  — 

^^f  °°>Ca  =  CH3.CHO  +  CaCOj. 

HLUU  Aldehyde 


FATTY   ACIDS  143 

This  method  has  been  used  to  a  considerable  extent  in  making 
the  higher  members  of  the  series. 

3.    Acids 

Formic  and  acetic  acids  are  the  first  two  members  of  an 

homologous  series  of  similar  acids,  called  the  fatty  acids  because 

several  of  them  occur  in  large  quantities  as  glycerol  esters  in 

the  natural   fats.     The  names   and   formulas  of  some  of  the 

principal  members  are  given  in  the  following  table.    The  reasons 

for  representing  the  acids  as  compounds  containing  the  carboxyl 

group,  CO2H,  have  already  been  given.  ^  ^ 

J-tn/Wvv'U     £N--  FATTY  ACIDS       ^iSjL-  UUd    ^-^-  c 

Series  C„H2„+i.C02H,  or  C„H2„02  ^     / 

Formic  acid         b.  p.  100.8° ITICO2H 

Acetic       "(;c>luU,"8.7        CH3.C62H 

Propionic  ''  ,    "^  141  C2H6.CO2H 

n-Butyric      "    ^'""'162.4        C3H7.CO2H 

n- Valeric      "  185.4 C4H9.CO2H 

n-Caproic  or        i 

„       .        -J        r  205  C5Hii.CU2rl 

Hexoic  acids      J 

CEnanthylic  or  1 

n-Heptoic  acids    J  "3  CeHis.COaH 

Caprylicor        ^HMw-f  l/^^-^  nxx    nr^xj 

Octoic  acids      h-P-\6.S        C,H..C02H 


h^' 


U  ll. 


Pelargonicor     |"        ^^^  C8H17.CO2H 

Nonic  acids       J 

Capric  acid  31.4  C9H19.CO2H 

Laurie  "  44  CUH23.CO2H 

Myristic  acid  54  C13H27.CO2H 

^  Palmitic      "  62.6  C16H31.CO2H 

Margaric     "  60"  C16H33.CO2H 

-  Stearic        "  69.3  C17H36.CO2H 

Arachidic    "  77  C19H39.CO2H 

Behenic       "  84  C21H43.CO2H 

Hyenic        "  77-78 C24H49.CO2H 

Cerotic        "  78.5  C26H53.CO2H 

Melissic      "  91  y  C29H69.C02H 


144  DERIVATIVES  OF  THE  PARAFFINS 

Propionic  acid,  propane  acid,  C3H602(C2H5.C02H). — Pro- 
pionic acid  is  formed  in  small  quantity  (i)  by  the  distillation  of 
wood;  (2)  by  the  fermentation  of  calcium  lactate  or  malate 
with  certain  microorganisms;  (3)  by  heating  ethyl  cyanide 
(propionitrile)  with  a  solution  of  caustic  potash :  — 

C2H5.CN  +  KOH  +  H2O  =  C2H5.CO2K  +  NH3; 

and  (4)  b}'  oxidizing  normal  propyl  alcohol  with  chromic  acid. 

This  last  method  is  used  on  the  large  scale. 

Other  methods  for  preparing  it  are  the  following :  — 

(i)    By  reducing  lactic  acid  or  acrylic  acid  with  hydriodic 

acid.     (This  will  be  explained  under  Lactic  acid  and  Acrylic 

acid.) 

(2)    By  the  action  of  carbon  dioxide  upon  sodium  ethyl :  — 

CO2  +  NaC2H6  =  CzHs.COzNa. 

It  is  a  colorless  liquid  with  a  penetrating  odor  somewhat 
resembling  that  of  acetic  acid.     It  boUs  at  141°. 

Note  for  Student.  —  Compare  with  boiling  points  of  formic  and  acetic 
acids. 

It  yields  a  large  number  of  derivatives  corresponding  to  those 
obtained  from  acetic  acid. 

Note  for  Student.  —  What  is  propionyl  chloride?  and  how  can  it  be 
prepared?     It  is  analogous  to  acetyl  chloride. 

The  monosubstitution  products  of  propionic  acid  present 
an  interesting  and  instructive  case  of  isomerism.  There  are 
two  chloropropionic  acids,  two  bromopropionic  acids,  etc.  Those 
products  which  are  obtained  by  direct  treatment  of  propionic 
acid  with  substituting  agents  are  called  a-products,  and  the 
isomeric  substances  /3-products.  Thus  we  have  a-chloropro- 
pionic  (b.  p.  186°),  and  a-bromopropionic  acid  (b.  p.  204°),  made 
by  treating  propionic  acid  with  chlorine  or  bromine  ;  fi-chloro- 
propionic  acid  (m.p.  4.i.5°,h.p.  204°),  a.nd ^-bromopropionic  acid 
(m.  p.  62.5°),  made  by  treating  acrylic  acid  (286)  with  hydro- 
chloric or  hydrobromic  acid.  The  usual  method  of  representa- 
tion indicates  the  possibility  of  the  existence  of  two  isomeric 


PROPIONIC  ACID,   PROPANE  ACID  145 

chloropropionic  acids,  and  of  similar  monosubstitution  products 
of  propionic  acid.    The  acid  is  represented  thus  :  — 

CH3.CH2.CO2H. 

Now,  if  chlorine  should  enter  into  the  compound,  as  repre- 
sented by  the  formula  CH2CI.CH2.CO2H,  (i)  we  should  have 
one  of  the  chloropropionic  acids ;  while,  if  it  should  enter  as 
indicated  in  the  formula  CH3.CHCI.CO2H,  (2)  we  should  have 
the  isomeric  product.  There  are  two  chloropropionic  acids 
actually  known,  and  the  theory  gives  two  formulas.  How  can 
we  tell  which  of  the  formulas  represents  a-chloropropionic 
acid,  and  which  the  |8-acid?  Only  by  carefully  studying  the 
reactions  and  methods  of  formation  of  both  compounds.  The 
best  evidence  is  furnished  by  a  study  of  the  lactic  acids,  which 
will  be  shown  to  be  monohydroxypropionic  acids,  o-chlor- 
propionic  acid  can  be  transformed  into  one  of  the  lactic  acids, 
a-hydroxypropionic  acid,  by  heating  with  water :  — 

CH3CHCICOOH  +  H2O  =  CH3.CHOH.COOH  +  HCl. 

The  structure  of  this  acid  is  represented  by  the  formula 
CH3.CH(0H)  CO2H,  and  by  replacing  the  hydroxyl  of  this  lactic 
acid  by  chlorine,  a-chloropropionic  acid  is  formed.  It  therefore 
follows  that  formula  (2)  above  given  is  that  of  a-chloropropionic 
acid,  and  formula  (i)  that  of  0-chloropropionic  acid.  Further, 
any  monosubstitution  product  of  propionic  acid  that  can  be 
made  directly  from  a-chloropropionic  acid,  or  converted  directly 
into  this  acid,  is  an  a-product,  and  has  the  general  formula :  — 

CH3.CHX.CO2H ; 

and,  similarly,  the  (3-products  have  the  general  formula :  — 

CH2X.CH2.CO2H, 

in  which  X  represents  any  univalent  atom  or  group. 

It  will  be  noted  that  the  a-substitution  products  contain  an 
as3Tnmetric  carbon  atom,  while  the  j3-products  do  not.  Opti- 
cally active  a-chloro-  and  a-bromopropionic  acids  have  been 
isolated. 


146  DERIVATIVES  OF  THE   PARAFFINS 

Butyric  acid,  C4H8O2  (C3H7.CO2H).  —  Normal  butyric  acid, 
butane  acid,  CH3.CH2.CH2.CO2H.  When  butter  which  contains 
2-3  percent  of  w-butyric  acid  is  boiled  with  a  solution  of  caustic 
potash  the  potassium  salts  of  butyric  acid  and  of  some  of  the 
higher  members  of  the  series  are  found  in  the  solution  at  the  end 
of  the  operation.  Butter,  like  other  fats,  belongs  to  the  class 
of  compounds  known  as  ethereal  salts ;  and  these,  as  we  have 
seen,  when  boiled  with  solutions  of  the  alkalies,  are  saponified, 
yielding  an  alcohol  and  alkali  salts  of  the  acids  (saponification). 
In  the  case  of  butter  and  of  nearly  all  other  fats,  the  alcohol 
formed  is  glycerol.  Butyric  acid  occurs  in  other  fats  besides 
butter,  and  free  in  perspiration  and  in  the  feces.  It  also  occurs 
in  many  plants  in  the  form  of  esters. 

It  is  most  readily  made  by  the  butyric  acid  fermentation  of 
sugar  in  the  presence  of  chalk. 

Other  methods  for  the  preparation  of  butyric  acid  are :  — 

(i)    By  oxidation  of  normal  butyl  alcohol ;  and 

(2)  By  heating  normal  propyl  cyanide,  CH3.CH2.CH2CN, 
with  a  solution  of  caustic  potash. 

The  acid  is  a  liquid  having  an  acid,  rancid  odor,  like  that  of 
rancid  butter.  It  boils  at  162.4°.  Like  the  lower  members 
of  the  series  it  mixes  with  water  in  all  proportions  at  ordinary 
temperatures. 

Ethyl  huty rate,  C3H7.CO2C2H6  (b.  p.  120°),  has  a  pleasant  odor 

resembling  that  of  pineapples.     It  is  used  under  the  name  of 

essence  of  pineapples.     Its  alcoholic  solution  forms  the  artificial 

banana  oil. 

CH3 
Isobutyric    acid,    methylpropane    acid,  >CH.C02H. — 

CH3 

From  the  two  propyl  alcohols  the  two  chlorides,  propyl  chloride, 

CH3 
CH3.CH2.CH2CI,   and   isopropyl    chloride,    „-^  >CHC1,     can 

HI3 

be  made,  and  from  these  the  corresponding  cyanides,  — • 

Propyl  cyanide CH3.CH2.CH2CN, 

CH3 
and      Isopropyl  cyanide    ....     „     >  CHCN. 

dl3 

When  boiled  with  a  solution  of  caustic  potash,  the  former  is 


ACTIVE   VALERIC   ACIDS  147 

converted  into  normal  butyric  acid,  as  stated  above ;   while  the 

latter  yields  isobutyric  acid,     ^>CH.C02H.    This  acid  can 

also  be  prepared  by  oxidizing  isobutyl  alcohol, 

):^'>CH.CH20H. 
CH3 

It  is  found  in  nature  in  the  carob  bean  (St.  John's  bread). 

Isobutyric  acid  is  a  liquid  that  boils  at  155.5'^.  Its  odor  is 
less  unpleasant  than  that  of  the  normal  acid. 

Valeric  acids,  C5H10O2  (C4H9.CO2H).  —  Four  carboxyl  de- 
rivatives of  the  butanes  are  possible.  Four  acids  of  the  formula 
C5H10O2  are  known. 

CH 

Isovaleric  acid,  >CH.CH2.C02H. — This   acid  is  made 

CH3 

by  oxidizing  isoamyl  alcohol.     It  can  also  be  made  (and  this 

reaction  reveals  the  structure  of  the  acid)  by  starting  with  iso- 

CH3 
butyl  alcohol  _      >CH.CH20H,  converting  this  first  into  the 

chloride  and  then  into  the  cyanide,  and,  finally,  transforming 

CH3 
the  cyanide,   „„  >CH.CH2CN,  into   the  acid.     It  occurs  in 

valerian  root,  whence  its  name.  It  is  a  liquid  of  unpleasant 
odor,  boiling  at  174°. 

Isoamyl  isovalerate,  C4H9.CO2C5H11,  has  the  odor  of  apples, 
and  is  used  under  the  name  of  essence  of  apples. 

CH 

Active  valeric  acids,  >CH.CH2.CH3. — These  acids  are 

HO2C 

prepared  by  oxidation  of  the  active  amyl  alcohols.  Although 
the  alcohol  turns  the  plane  of  polarization  to  the  left,  the 
acid  turns  it  to  the  right.  The  alcohol  is  levorotatory,  and 
the  acid  dextrorotatory.  The  levo  acid  has  also  been  isolated. 
The  dl-a.cid  (optically  inactive)  has  been  made  syntheti- 
cally. All  have  the  same  boiling  point,  177°.  These  acids 
contain  an  asymmetric  carbon  atom.  (See  Active  amyl 
alcohol,  137.) 

The  dl-SLcid  is  obtained  by  heating  methylethylmalonic  acid 
(161)  to  its  melting  point :  — 


148  DERIVATIVES   OF  THE   PARAFFINS 

HaC.       /COOH  HsC.        /COOH 

>C<  =  >C<  +     CO2. 

HsC/      \COOH  C2H5/      ^H 

Compounds  containing  an  asymmetric  carbon  atom,  when 
prepared  synthetically,  are  almost  always  equimolecular  mix- 
tures of  the  two  optically  active  forms  and  are  hence  optically 
inactive  by  external  compensation. 

The  higher  acids  of  the  series  are  found  in  various  fats.  They 
are  difficultly  soluble  in  water.  The  highest  members  are 
solids  insoluble  in  water.  The  two  best-known,  because  occur- 
ring in  largest  quantit}',  are  palmitic  and  stearic  acids.  These 
occur  in  the  form  of  esters  of  ghxerol,  in  all  the  common  fats 
which  will  be  treated  of  under  Glycerol  (164). 

Palmitic  acid,  H3C(CH2)i4C02H  occurs,  together  with  stea- 
ric, oleic,  and  other  fatty  acids,  as  esters  of  glycerol  in  vege- 
table and  animal  fats.  For  example,  it  is  found  in  butter, 
human  fat,  olive  oil,  cocoanut  oil,  bayberry  tallow,  and  in 
large  quantity  in  pahn  oil,  whence  its  name.  It  also  occurs 
in  the  form  of  esters  of  the  monacid  alcohols  as  waxes,  e.g. 
spermaceti  (cetyl  palmitate).  It  is  best  made  from  palm  oil 
or  bayberry  tallow  by  boiling  with  caustic  soda  and  decompos- 
ing the  sodium  palmitate  formed  by  means  of  dilute  sulphuric 
acid ;  the  precipitated  palmitic  acid  is  then  repeatedly  crys- 
tallized from  hot  alcohol  until  it  has  the  correct  melting 
point,  62.6°. 

Stearic  acid,  H3C(CH2)i6C02H  (m.  p.  69.3°),  in  the  form  of 
esters  of  glycerol,  is  found  in  many  fats,  especially  tallows,  as 
mutton  suet  and  beef  suet.  It  is  best  prepared  from  the  com- 
mercial stearic  acid  of  which  "  stearin  "  candles  are  made.  This 
consists  essentially  of  a  mixture  of  stearic  and  palmitic  acids. 
By  dissolving  this  mixture  in  hot  alcohol  and  adding  a  hot 
alcoholic  solution  of  magnesium  acetate,  a  precipitate  of  almost 
pure  magnesium  stearate  is  obtained.  This  is  washed  with 
alcohol,  dried,  decomposed  with  hydrochloric  acid,  and  the 
stearic  acid  recrystallized  from  alcohol  until  it  has  the  correct 
melting  point. 


SOAPS  149 

Compared  with  the  strong  mineral  acids,  like  hydrochloric 
acid,  the  fatty  acids  are  all  very  weak  acids. 

Soaps.'  —  In  speaking  of  the  decomposition  of  ethereal  salts 
by  boiling  with  solutions  of  the  alkalies,  it  was  stated  that  this 
process  is  called  saponification  because  it  is  best  exemplified 
in  the  manufacture  of  soaps  from  fats.  The  fats  are  themselves 
rather  complicated  ethereal  salts.  When  they  are  boiled  with  a 
solution  of  an  alkali,  as  caustic  soda,  glycerol  is  liberated,  and  the 
alkali  salts  of  the  acids  are  formed.     These  salts  are  called  soaps. 

Soaps  soluble  in  water  are  the  potassium  or  sodium  salts  of 
palmitic,  stearic,  and  oleic  acids,  the  hard  soaps  being  the 
sodium  salts,  principally  of  the  solid  fatty  acids,  while  the  soft 
soaps  are  potassium  salts,  chiefly  oleates.  The  soaps  are 
"salted  out"  of  their  aqueous  solutions  by  the  addition  of 
common  salt,  as  they  are  insoluble  in  the  brine  formed.  The 
potassium  soaps  are  converted  into  the  sodium  soaps  by  this 
"  salting  out  "  process.  These  soaps  form  a  clear  solution  when 
dissolved  in  a  little  water,  but  in  a  larger  quantity  of  water 
they  are  partially  hydrolyzed,  yielding  free  alkali  and  the  free 
fatty  acid  or  an  acid  salt.  The  cleansing  action  of  soap  is 
usually  attributed  to  the  presence  of  the  small  amount  of  free 
alkali  formed :  — 


\ 


CirHaBCOONa  +  HOH  ::^  CijHasCOOH  +  NaOH, 

This  hydrolysis  is  analogous  to  that  which  takes  place  with 
inorganic  salts  of  a  weak  acid  with  a  strong  base,  and  increases 
on  dilution.  It  is,  however,  probable  that  the  cleansing  action 
of  soap  is  largely  due  to  its  power  to  emulsify  oils  and  fats. 

The  calcium,  barium,  and  magnesium  soaps  are  insoluble  in 
water,  and  hence  a  precipitate  of  the  calcium  soap  is  formed  when 
"  hard  "  water  is  used  with  soap.  The  lead  soaps  are  formed  by 
boiling  fats  with  lead  oxide  and  water,  and  were  formerly  used 
in  medicine  under  the  name  of  "  lead  plaster."  Lead  and  man- 
ganese soaps  (made  from  linseed  oil) ,  dissolved  in  linseed  oil  and 
thinned  with  turpentine  or  benzine,  form  the  liquid  "  driers  "  of 
the  painters,  used  to  hasten  the  drying  of  raw  linseed  oil. 
^  See  article  on  Soap  in  Thorpe's  Dictionary  of  Applied  Chemistry, 


I50  DERIVATIVES   OF  THE   PARAFFINS 

Floating  soaps  are  sodium  soaps,  usually  made  from  cocoanut 
oil,  in  which  the  specific  gravity  of  the  soap  is  lowered  by  filling 
the  soap  with  minute  air  bubbles. 

The  so-called  "  liquid  soaps,"  so  much  used  in  lavatories, 
are  solutions  of  potassium  cocoanut-oil  soaps  and  glycerol  in 
water.  They  usually  contain  from  15  to  20  per  cent  anhydrous 
soap  and  from  5  to  10  per  cent  glycerol.  Some  contain  glucose 
in  the  place  of  glycerol.  Many  of  them  contain  a  small  amount 
of  free  oleic  acid. 

Calcium  soaps,  usually  called  lime  soaps,  made  by  the  action 
of  slaked  lime  on  fats,  are  used  in  large  quantities  in  the  manu- 
facture of  lubricating  greases. 

Zinc  stearate  is  used  in  toilet  powders. 

POLYACID   ALCOHOLS    AND    POLYBASIC   ACIDS 

I.  DiAciD  Alcohols 

The  alcohols  thus  far  treated  of  are  the  simplest  kind. 
They  correspond  to  the  simplest  metallic  hydroxides,  as  potas- 
sium hydroxide,  KOH.  Just  as  these  simplest  metallic  hydrox- 
ides are  called  monacid  bases,  so  the  simplest  alcohols  are  called 
monacid  alcohols.  But,  as  is  well  known,  there  are  metallic 
hydroxides,  like  calcium  hydroxide,  Ca(0H)2,  barium  hydrox- 
ide, Ba(0H)2,  etc.,  that  contain  two  hydroxyls,  and  are  hence 
known  as  diacid  bases;  and  so,  too,  there  are  diacid  alcohols 
that  bear  to  the  monacid  alcohols  the  same  relation  that  the 
diacid  bases  bear  to  the  monacid  bases.  Only  one  alcohol  of 
this  kind,  derived  from  the  paraffin  hydrocarbons,  is  important 
enough  to  call  for  treatment  here. 

Ethylene  alcohol  or  glycol,  ethanediol,  C2H602,C2H4(OH)2. — 
Glycol  is  made  by  starting  with  ethylene,  a  hydrocarbon  of  the 
formula  C2H4.  When  this  is  brought  together  with  bromine, 
the  two  unite  directly,  forming  ethylene  bromide,  C2H4Br2 :  — 

CH2      Br       HsCBr 

II       +   I      =        I 
CH2       Br       HzCBr. 


DIACID   ALCOHOLS  151 

By  replacing  the  two  bromine  atoms  by  hydroxyls,  ethylene 
alcohol  or  glycol  is  formed. 

The  reactions  involved  are  represented  by  the  following 
equations :  — 

_  „  ^Br  ^  KOC2H3O      „  „  ^OCjHsO  ^     ^„ 
^^^^<Br  +  KOC2H3C  =  ^^^<OC2H30  +  '  ^^' 

Potassium  acetate  Diacetylglycol 

^^H^<OC;hS  +  ^^<OT  =  ^^"^<Sh  +  Ba(C.H30.). 

Glycol  can  also  be  made  by  heating  ethylene  bromide  with  a 
solution  of  potassium  carbonate :  — 

C2H4<:r'+:^';>co  +  h^o  =  C2H4<^„  +  2  KBr  +  CO2; 

Br     KO  OH 

and  by  heating  ethylene  bromide  with  silver  oxide  and  water :  — 

T>  OIT 

C2H4<gJ  +  AgjO  +  H2O  =  C2H4<Qjj  +  2  AgBr. 

These  methods  of  formation  show  clearly  that  ethylene  alcohol 
is  the  dihydroxyl  derivative  of  ethane. 

Ethylene  alcohol  is  now  made  on  the  large  scale  by  hydrolyz- 
ing  ethylene  chlorohydrin  with  water :  — 

H2CCI  H2COH 

I         +  HOH  =       I         +  HCl. 
H2COH  H2COH 

The   ethylene  chloiohydrin  is  made  by  passing  ethylene  into 
aqueous  h3rpochlorous  acid :  — 

H2C  H2CCI 

ll+HO— Cl=       I        • 
H2C  H2COH 

Glycol  is  a  colorless,  inodorous,  somewhat  sirupy  liquid, 
that  boils  at  197".  It  has  a  sweetish  taste,  and  was  hence 
called  glycol   (Gr.  glykys,  sweet).     The    other  diacid  alcohols 


152  DERIVATIVES  OF  THE  PARAFFINS 

of  this  series  are  also  called  glycols.  It  is  miscible  in  all 
proportions  with  water  and  alcohol,  but  is  not  very  soluble  in 
ether.     It  is  not  poisonous. 

The  derivatives  of  ethylene  alcohol  are  not  so  numerous  as 
those  of  the  better  known  members  of  the  methyl  alcohol 
series,  but  those  which  are  known  are  of  the  same  general  char- 
acter. The  reactions  of  the  alcohol  are  the  same  as  those  of  the 
monacid  alcohols,  but  it  presents  more  possibilities.  In  most 
cases  in  which  a  monacid  alcohol  yields  one  derivative,  ethylene 
alcohol  yields  two.     Thus,  with  sodium,  the  two  compounds, 

sodium  glycol,  C2H4<„p.  ,  and  disodium  glycol,  C2H4<         , 

have  been  obtained ;  from  these,  by  treating  with  ethyl  iodide, 

OP  TT 

the  two  ethers,  ethyl  glycol  ether,  C2H4<_--      ,    and    diethyl 

OC  H 

glycol  ether,  C2H4<„„  „^  are    made.     By    treatment    with 

OH 

hydrochloric  acid,  the  chloride,  C2H4<  _.  ,  known  as  ethylene 

chlorohydrin,  is  formed  from  glycol;    and  by  treatment  with 
phosphorus  pentachloride,  ethylene  chloride,  C2H4CI2,  results. 
H2CCI 
Ethylene  chlorohydrin,       |         is  a  liquid  boiling  at  132°  and 
H2COH, 
miscible   with    water.      It    is    the    monochlorine    substitution 
product  of  ethyl  alcohol  and  yields  ethyl  alcohol  on  reduction 
and  monochloroacetic  acid  on  oxidation.     When  distilled  with 
a  solution  of  caustic  potash  it  gives  ethylene  oxide :  — 

H2C— OH  H2C\ 

1  +  KOH  =  KCl  +  H2O  +         I  >0. 

H2C— CI  H2C/ 

This  is  a  liquid  of  ethereal  odor  boiling  at  12.5°,  miscible  with 
water  and  gradually  combining  with  it  to  form  glycol.     It  is 

H3C 
isomeric  with  acetic  aldehyde,  which  is  ethylidene  oxide      | 

HCO 
Ethylene  chlorohydrin  and  ethylene  oxide  are  characterized 
by  great  chemical  reactivity,  and  they  are  hence  used  in  the 


ETHYLENE  CHLOROHYDRIN  153 

preparation  of  a  large  number  of  organic  substances.  Ethylene 
chlorohydrin  combines  with  aniline  to  give  hydroxyethyl- 
aniline,  and  this  is  used  in  the  manufacture  of  indigo  on  the 
large  scale  in  Germany. 

With   sodium   sulphide,   ethylene   chlorohydrin  gives   thio- 

diglycol,  S<„„  „„  _,„,  which  is  converted  into  mustard  gas 

0x12^X120x1 

(79)  by  the  action  of  strong  hydrochloric  acid.  This  is  the 
method  by  which  mustard  gas  was  first  made  during  the  World 
War. 

The  conduct  of  glycol  towards  acids  is  like  that  of  a  diacid 
base.  It  forms  neutral  and  alcoholic  esters,  of  which  the  acetates 
may  serve  as  examples.    Thus  we  have  the 

Monoacetate,  C2H4<  , 

Uxl 

and  the  Diacetate,       C2H4<^_„^; 

(JC2Xl3(J 

the  former  still  containing  alcoholic  hydroxyl  and  corresponding 
to  a  basic  salt ;  the  latter  being  a  neutral  compound. 
When  acetyl  chloride  acts  upon  the  alcohol  at  ordinary  tem- 

perature,  the  product  has  the  formula  C2H4<_.  ^    ^    :  — 
OH  +  CIOCCH3    ^  OCOCH3 

U2H4<Qjj  ^  CH3COCI  '-2"4<Q   ^  jj(-,j  ^  CH3COOH. 

There  are  two  ways  in  which  the  structure  of  a  compound  of 
the  formula   C2H4(OH)2   can  be  represented.    These   are,  — 

CH2OH 

(i)     I  ,  in  which  each  hydroxyl  is  represented  in  combina- 

CH2OH 

CH(0H)2 
tion  with  a  different  carbon  atom ;  and  (2)  |  ,  in  which 

CH3 

both  hydroxyls  are  represented  in  combination  with  the  same  car- 
bon atom.  The  question  suggests  itself,  to  which  of  these  formulas 
does  ethylene  alcohol  correspond?    To  answer  this  question, 


IS4  DERIVATIVES   OF  THE   PARAFFINS 

recall  what  was  said  regarding  the  two  dichloroethanes  (32), 
known  as  ethylene  chloride  and  ethylidene  chloride.  The  former 
of  these  corresponds  to  the  formula  CH2CI.CH2CI,  while 
the  latter,  which  is  formed  from  aldehyde  by  replacing  the 
carbonyl  oxygen  by  two  chlorine  atoms  (50),  is  represented  by 
the  formula  CHCU.CHj.  When  the  chlorine  atoms  of  ethylene 
chloride  are  replaced  by  hydroxyls,  ethylene  alcohol  is  produced. 
Hence,  the  alcohol  has  the  formula  HOH2C — CH2OH,  or 
each  of  the  hydroxyls  is  in  combination  with  a  dififerent  carbon 
atom.     When  oxidized,  ethylene  alcohol  gives,  first,  glycolic 

CH2OH  COOH 

acid,    I  ,  and  then  oxahc  acid,    |  .    This  furnishes 

COOH  COOH 

independent  evidence  that  the  alcohol  contains  two  primary 
alcohol  groups,  and  it  must  therefore  be  represented  by  the 

CH2OH 
formula  | 

CH2OH 
All  attempts  to  make  the  isomeric  diacid  alcohol  correspond- 
ing to  ethylidene  chloride,  and  having  both  hydroxyls  in  com- 
bination with  the  same  carbon  atom,  as  represented  in  the 

CH(0H)2 
formula  |  ,  have  failed.     Instead  of  getting  ethylidene 

CH3 
alcohol,  aldehyde  is  obtained.     Aldehyde  is  ethylidene  alcohol 
minus  water :  — 

CH3— CH(0H)2  =  CH3— CHO  +  H2O. 

It  is  believed  that  one  carbon  atom  cannot,  under  ordinary 
conditions,  hold  in  combination  more  than  one  hydroxyl 
group.     If  this  is  true,  then  ethylidene  alcohol  cannot  be  pre- 

OH 

pared  any  more  than  the  hypothetical  carbonic  acid,  0C<  _,„> 

Uxl 

can   be.     So,    too,    the    simplest   diacid    alcohol   conceivable, 

viz.,    methylene  alcohol,  CH2(OH)2,  cannot  exist,  but  would 

break  down,  if  formed  at  all,  into  water  and  formic  aldehyde  :  — 

CH2(OH)2  =  H2O  -I-  H.CHO. 


DIBASIC  ACIDS  1 55 

(See,  however,  Chloral  hydrate  (54)  and  discussion  regarding 
the  oxidation  of  alcohol  to  aldehyde  (65).) 

Ethyl  alcohol,  as  was  pointed  out,  may  be  regarded  either  as 
ethane  in  which  one  hydrogen  is  replaced  by  hydroxyl,  or  as 
water  in  which  one  hydrogen  is  replaced  by  ethyl.  Ethyl,  like 
all  the  radicals  contained  in  the  monacid  alcohols,  is  univalent. 
It  is  ethane  less  one  atom  of  hydrogen,  just  as  methyl  is  methane 
less  one  atom  of  hydrogen.  Each  has  the  power  of  uniting  with 
one  atom  of  hydrogen,  or  another  univalent  element,  or  of  tak- 
ing the  place  of  one  atom  of  hydrogen. 

If  two  atoms  of  hydrogen  are  taken  from  methane  and  ethane, 
the  residues  or  radicals  CHj  and  C2H4  are  left.  These  can  unite 
with  two  atoms  of  hydrogen,  or  take  the  place  of  two  atoms  of 
hydrogen,  and  they  are  hence  called  bivalent  radicals. 

Just  as  ethylene  alcohol  is  regarded  as  ethane  in  which  two 
hydrogen  atoms  are  replaced  by  two  hydroxyls,  so  it  may  be 
regarded  as  water  in  which  the  bivalent  radical  ethylene  re- 
places two  hydrogens  belonging  to  two  different  molecules  of 
water :  — 

H— O— H    H— O— H  H— 0— C2H4— O— H 

Two  molecules  water  Ethylene  alcohol 

2.   Dibasic  Acids 

Just  as  there  are  diacid  alcohols  derived  from  the  paraffins, 
so  there  are  dibasic  acids  which  are  regarded  as  derivatives 
of  the  paraffins.  It  has  been  shown  that  the  simplest  acids, 
the  monobasic  fatty  acids,  are  closely  related  to  formic  and 
carbonic  acids ;  that  they  are  to  be  regarded  as  derived  from  the 
latter  by  replacement  of  a  hydroxyl  by  a  radical,  or  as  derived 
from  the  paraffins  by  the  introduction  of  the  carboxyl  group, 
CO2H.  The  conditions  existing  in  this  group  are  essential  to 
the  acid  properties.  If  two  carboxyls  are  introduced  into  marsh 
gas,  a  substance  of  the  formula  CH2(C02H)2  is  formed,  and 
this  is  a  dibasic  acid.  It  contains  two  acid  hydrogens,  and 
is  capable  of  forming  two  series  of  salts,  the  acid  and  neutral 
salts,  like  other  dibasic  acids.     It  may  be  regarded  also  as 


156  DERIVATIVES  OF  THE  PARAFFINS 

derived  from  two  molecules  of  carbonic  acid  by  the  replacement 
of  two  hydroxyls  by  the  bivalent  radical  CH2 :  — 

OT-T 
OC<OH  OC<OH 

Two  molecules  carbonic  acid  Dibasic  acid 

The  general  methods  of  preparation  available  for  the  build- 
ing up  of  the  series  of  dibasic  acids  are  modifications  of  those 
used  in  making  the  monobasic  acids.    They  are  :  — 

1.  Oxidation  of  diacid  primary  alcohols.  Just  as  a  mon- 
acid  primary  alcohol,  R.CH2OH,  yields  by  oxidation  a  mono- 
basic acid,  so  a  diacid  primary  alcohol,  R"(CH20H)2,  yields 
a  dibasic  acid,  R"(C02H)2. 

2.  Hydrolysis  oj  the  dicyanides,  R"(CN)2,  with  solutions  of 
the  caustic  alkalies. 

3.  Oxidation  of  the  primary  alcohol  acids.  These  are  com- 
pounds which  are  at  the  same  time  alcohol  and  acid ;  as,  for 
example,  hydroxyacetjc  acid,  which  is  acetic  acid  in  which  one 
of  the  hydrogen  atoms  of  the  hydrocarbon  residue,  methyl, 
has  been  replaced  by  hydroxyl,  as  represented  in  the  formula 
CH2OH 

I  .     When  this  is  oxidized  the  alcoholic  group,  CH2OH, 

CO2H 

is  converted  into  carboxyl,  and  oxalic  acid,  a  dibasic  acid,  is 
formed. 

4.  From  the  cyanogen  derivatives  of  the  monobasic  acids,  such 

CN 

as  cyanacetic  acid,  CH2<  „„  „,  b^i  the  hydrolysis  of  the  cyanogen 

group  into  carboxyl. 

DIBASIC  ACIDS,  CJIsn-jOi 


„   «        V     Ionization 
"■  "^^      ^=  Constant 

Oxalic      acid     . 

.       .       .       .    189.5°!    lO.O                (C02H)2 

Malonic      " 

.       .       .       .     135.6            0.163          CH2(C02H)2 

Succinic     " 

.       .       .       .    182.8            0.006s        (CH2)2(C02H)2 

'  Anhydrous  acid. 

OXALIC  ACID,   ETHANE  DIACID 


157 


DIBASIC  ACIDS  {Continued) 


M.  P. 

«.     Ionization 
Constant 

97-5 

0.0047         (CH2)3(C02H)2 

183 

0.0037         (CH2)4(C02H)2 

105 

0.0032         (CH2)6(C02H)2 

140 

0.0026         (CH2)6(C02H)2 

106.5 

(CH2)7(C02H)2 

134-5 

(CH2)8(C02H)2 

112 

(CH2)u(C02H)2 

132 

(CH2)l6(C02H), 

Glutaric  acid 

Adipic  " 
Pimelic 

Suberic  " 

Azelaic  " 

Sebacic  " 

Brassylic  " 

Roccellic  " 


The  members  of  this  series  differ  from  one  another  by  CH2 
or  a  multiple  of  this,  but  while  in  the  paraffin  series  this  difference 
is  due  to  the  substitution  of  methyl  for  hydrogen,  this  may  or 
may  not  be  the  case  in  this  series.  This  will  appear  as  the  in- 
dividual members  are  taken  up,  though  it  is  obvious  that  the 
second  member,  malonic  acid,  is  not  a  methyl  derivative  of 
oxalic  acid.  In  the  case  of  the  higher  members  of  the  series 
there  are  two  possibilities. 

Oxalic  acid,  ethane  diacid,  C2H2O4,  (C02H)2 .  —  In  one  sense, 
according  to  the  accepted  definition,  oxalic  acid  is  not  a  member 
of  the  series  with  which  we  are  dealing,  as  it  is  not  derived  from 
a  hydrocarbon  by  replacement  of  two  hydrogen  atoms  by  two 
carboxyl  groups ;  nor  is  it  derived  from  two  molecules  of  carbonic 
acid  by  replacement  of  two  hydroxyls  by  a  bivalent  radical. 
Still  it  is  in  other  respects  so  closely  allied  to  the  members  of 
the  series,  and  has  so  many  reactions  in  common  with  the  other 
members,  that  it  must  necessarily  be  taken  up  here. 

Oxalic  acid  occurs  very  widely  distributed  in  nature ;  as  in 
certain  plants  of  the  oxalis  varieties,  in  the  form  of  the  acid 
potassium  salt ;  as  the  calcium  salt  in  many  plants  and  in 
urinary  calculi ;  and  as  the  ammonium  salt  in  guano. 

It  is  formed  by  the  action  of  nitric  acid  upon  many  organic 
substances,  particularly  the  different  varieties  of  sugar  and  the 
carbohydrates,  such  as  starch,  cellulose,  etc. 

On  the  large  scale,  oxalic  acid  is  made  by  heating  wood, 
shavings  or  sawdust  with  caustic  potash  and  caustic  soda  to  240° 


IS8  DERIVATIVES  OF  THE  PARAFFINS 

to  250°.  The  mass  is  extracted  with  water,  and  the  solution 
evaporated  to  the  specific  gravity  1.35,  when  sodium  oxalate 
crystallizes  out  on  cooling.  The  crystallized  sodium  oxalate  is 
dissolved  in  boiling  water,  boiled  with  milk  of  lime,  the  precip- 
itate of  calcium  oxalate  extracted  several  times  with  boiling 
water,  and  decomposed  with  dilute  sulphuric  acid.  After  filter- 
ing, the  solution  of  oxalic  acid  is  then  evaporated  to  specific 
gravity  i.ii5,  and  allowed  to  stand  until  the  gypsum  has  set- 
tled, filtered,,  and  evaporated  to  crystallization.  It  is  purified 
by  recrystallizing  several  times  from  water. 
Other  methods  are  the  following :  — • 

1.  The  spontaneous  transformation  of  an  aqueous  solution 
of  cyanogen :  — 

CN  CO2H 

I       +4H20  =  |  +2NH3; 

CN  CO2H 

CN  C02(NH4) 

or,  really,  |       -|-  4  H2O  =  | 

CN  C02(NH4) 

2.  Heating  carbon  dioxide  with  sodium  :  — 

2  CO2  -j-  2  Na  =  C204Na2. 

3.  Heating  sodium  formate  to  360° :  — 

2  H.COjNa  =  C204Na2  +  2  H. 

This  method  is  now  used  on  the  large  scale  for  the  manufacture 
of  sodium  oxalate  and  from  it  oxalic  acid. 

Oxalic  acid  is  a  very  much  stronger  acid  than  its  homologues, 
as  is  shown  by  its  ionization  constant.     (See  table  (156).) 

Oxalic  acid  crystallizes  from  water  in  monoclinic  prisms  con- 
taining two  molecules  of  water  (C2H2O4  -|-  2  H2O)  which  melt 
at  101.5°.  It  loses  this  water  at  100°,  and  then  melts  at  189.5°. 
It  sublimes  at  157°,  but,  if  heated  higher,  it  breaks  down  into 
carbon  monoxide,  carbon  dioxide,  formic  acid,  and  water :  — 

2  C2H2O4  =  2  CO2  4-  CO  -I-  HCO2H  -1-  H2O. 
Sulphuric  acid  decomposes  it  into  carbon  monoxide,  carbon 


MALONIC  ACID,   PROPANE  DIACID  1 59 

dioxide,  and  water.  Heated  with  glycerol  to  110°,  carbon 
dioxide  and  formic  acid  are  formed  (see  Formic  acid,  54) :  — 

C2H2O4  =  CO2  +  HCO2H. 

It  is  an  excellent  reducing  agent,  and  is  used  to  standardize 
solutions  of  potassium  permanganate. 

It  is  used  in  bleaching  leather,  in  laundries  to  remove  ink 
and  rust  spots,  in  bleaching  straw  goods,  in  cleaning  powders, 
as  a  solvent  for  Prussian  blue  in  making  blue  ink,  in  the 
preparation  of  dyes,  as  a  reagent  in  analytical  chemistry, 
and  in  photography.  It  is  also  used  in  dyeing  and  in  calico 
printing. 

Oxalic  acid  is  poisonous. 

Salts  of  oxalic  acid.  Like  all  dibasic  acids,  oxalic  acid  forms 
acid  and  neutral  salts  with  metals.  All  the  salts  are  insoluble 
except  those  of  the  alkali  metals  and  the  ammonium  salts. 
Among  those  most  common  are  the  CLcid  potassium  salt,  C2O4HK, 
which  is  found  in  the  sorrels  or  plants  of  the  oxalis  variety ;  the 
ammonium  salt,  C204(NH4)2;  and  calcium  oxalate,  C204Ca, 
which,  being  insoluble  in  water  and  acetic  acid,  is  used  as  a 
means  of  detecting  calcium  in  the  presence  of  magnesium,  and 
of  estimating  calcium  and  oxalic  acid. 

Malonic  acid,  propane  diacid,  CH2(C02H)2.  —  This  acid  was 
first  made  by  oxidation  of  malic  acid  (193),  and  was  hence  called 
malonic  acid.  It  can  best  be  made  by  starting  with  acetic  acid. 
The  necessary  steps  are  :  (1)  making  chloroacetic  acid;  (2)  trans- 
forming chloroacetic  acid  into  cyanacetic  acid;  (3)  heating 
cyanacetic  acid  with  a  solution  of  an  alkali. 

Note  for  Student.  —  Write  the  equations  representing  the  three  steps 
mentioned. 

It  is  a  solid  that  crystallizes  in  laminae.  It  breaks  down  at 
a  temperature  above  135.6°,  which  is  its  melting  point,  into 
carbon  dioxide  and  acetic  acid :  — 

CH2  <  ^^  =  CH3CO2H  +  CO2 


l6o  DERIVATIVES   OF  THE   PARAFFINS 

All  organic  acids  with  two  carboxyl  groups  attached  to  the  same 
carbon  atom  lose  a  molecule  of  carbon  dioxide  when  heated  above 
their  melting  points. 

POOP  TT 

DJe^AW  wo/ojioie,  H2C <„_„„%',  is   made    from    monochloroacetic 

acid  by  first  heating  with  potassium  cyanide  :  — 

and  then  converting  the  cyanacetic  acid  thus  formed  into  the  ester  by 
the  action  of  alcoholic  hydrochloric  acid :  — 

H2C  <  ^QQj^  +  2  HCl  +■  2  H2O  =  HjC  <  ^Q°^  +  NH^Cl  +  KCl ; 
«^C<^°°g  +  ^  HOC.H.  =  H.C<^0°^;g;  +  2  H.O. 

It  boils  at  198°.     The  two  methylene  hydrogen  atoms  are  replaceable 

by  sodium,  giving  a  monosodium,        >C(COOC2H6)2,  and  a  disodium 

salt,  Na2C(COOCaH6)2.  When  these  are  heated  with  ethyl  iodide,  esters 
of  the  homologues  of  malonic  acid  are  obtained :  — 

C2HJ  +  ^>C(COOC2H6)2  =  Nal  +  '''^'>  CCCOOCzHj), 

2  C2H6I  +  Na2C(COOC2H6)2  =  2  Nal  +  (C2H6)2C(COOC2H6)2. 

When  these  esters  are  hydrolyzed    the  homologues  of  malonic  acid 

result:     (C2H6)CH(COOH)2    and    (C2Hs)2C(COOH)2.      These,    when 

heated   to  their  melting  points,  lose  carbon  dioxide,  just   as   malonic 

acid  does,   and  give  homologues  of  acetic  acid.     By  means  of  this 

"  malonic   ester   synthesis,"    as   it  is  called,  a  large   number  of   the 

homologues    of    malonic    and    acetic    acids    have    been    made.     It   is 

possible  to  introduce  two  different  alkyl  groups  into  the  ester.     Thus 

if  the  monoethyl  derivative  obtained  above  is  treated  with  sodium, 

P  TT 
it    gives  >C(COOC2H6)2,     which     with     methyl     iodide     gives 

P  TT 

^    '>C(COOC2H6)2,  and   this  when  hydrolyzed  gives  methylethyl- 

malonic  acid, 

CaHj  COOH 

CH,        ^COOH 


SUCCINIC  ACID,   ETHYLENESUCCINIC  ACID  l6l 

When  heated  above  its  melting  point  this  loses  carbon  dioxide   and 

gives  methylethylacetic  acid, 

H 

I 
H3C  —  C  —  C2I16, 

I 

COOH 

or  (^/-valeric  acid,  which  can  be  resolved  into  its  optically  active  com- 
ponents.    (See  Valeric  acid  147  and  Lactic  acid  182.) 

Carbon  Suboxide,  C3O2,  is  formed  in  small  quantity  when  dry  malonic 
acid  is  distilled  in  a  vacuum  with  phosphorus  pentoxide :  — 

H2C(COOH)2  =  C3O2  +  2  H2O. 

It  is  a  gas  with  a  pungent  odor.  It  condenses  to  a  liquid  boiling  at  7°- 
With  water  it  forms  malonic  acid.  At  ordinary  temperatures  it  poly- 
merizes to  a  reddish  black,  amorphous  mass.  It  may  have  the  con- 
stitution represented  by  the  formula,  O^C^C^C=0. 

Succinic  acids,  C4H6O4,  C2H4(C02H)2.  —  Regarding  these 
acids  as  derived  from  ethane  by  the  substitution  of  two  car- 
boxyls  for  two  hydrogens,  it  is  clear  that  two  are  possible,  one 
corresponding  to  ethylene  chloride  and  another  to  ethylidene 
chloride.  Two  are  actually  known.  One  is  the  well-known 
succinic  acid;  the  other  is  called  isosuccinic  acid. 

Succinic  acid,  ethylenesuccinic  acid,  butane  diacid, 
CH2.CO2H 

I  .  —  This  acid  occurs  in  amber  (hence  its  name,  from 

CH2.CO2H 

Lat.  succinum,  amber) ;  in  some  varieties  of  lignite ;  in  many 
plants ;  and  in  the  animal  organism. 

It  is  formed  under  many  conditions,  especially  by  oxida- 
tion of  fats  with  nitric  acid,  by  fermentation  of  calcium  malate 
with  certain  microorganisms,  and,  in  small  quantity,  in  the 
alcoholic  fermentation  of  sugar.  Among  the  methods  for  its 
preparation  are :  — 

I.  Hydrolysis  of  ethylene  cyanide  (made  from  ethylene 
bromide)  with  a  solution  of  a  caustic  alkali :  — 

■  CH2CN  CH2.CO2K 

1  -I-  2  KOH  -I-  2  H2O  =   I  -t-  2  NH3. 

CH2CN  CH2.CO2K 


l62  DERIVATIVES  OF  THE  PARAFFINS 

2.  Similarly,  by  the  hydrolysis  of  /3-cyanpropionic  acid 
(made  from  |8-iodopropionic  acid  (190))  with  a  solution  of  an 
alkali. 

Note  for  Student.  — What  is  /3-cyanpropionic  acid? 

3.  Reduction  of  tartaric  and  malic  acids  by  means  of  hy- 
driodic  acid.  These  well-known  acids  will  be  shown  to  be 
hydroxyl  derivatives  of  succinic  acid,  and  the  reaction  here 
mentioned  will  be  explained.  The  methods  actually  used  in 
the  preparation  of  succinic  acid  are :  (i)  the  distillation  of  amber, 
and  (2)  the  fermentation  of  ammonium  tartrate  with  certain 
bacteria. 

The  acid  crystallizes  in  monoclinic  prisms,  that  melt  at  182.8°. 
It  boils  at  235°,  at  the  same  time  giving  off  water,  and  yielding 
the  anhydride:  — 

Succinic  anhydride  is  a  solid  substance  that  crystallizes  well 

from  a  mixture  of  chloroform  and  toluene.     It  melts  at  120°, 

and  boUs  at  261°.     It  is  best  made  by  the  action  of  thionyl 

chloride  on  the  acid  :  — 

CO 
C2H4(COOH)2  +  SOCI2  =  C2H4<^Q>0  +  SO2  +  2  HCl. 

It  is  converted  into  succinic  acid  by  boiling  with  water.  When 
boiled  with  alcohols  it  yields  the  corresponding  ester  acids. 
For  example,  with  ordinary  alcohol  monoethyl  succinate  is 
formed :  — 

C2H.<^0>o  +  C2H.OH  =  C2H.<^00^^^; 

Among  the  salts  basic  ferric  succinate,  C4H404.Fe(OH),  is  of 
special  interest,  as  it  is  entirely  insoluble  in  water,  and  can 
therefore  be  used  for  the  purpose  of  separating  iron  and  alu- 
minium from  manganese,  zinc,  nickel,  and  cobalt  quantita- 
tively :  — 

2  FeCla  +  3  C2H4(COONH4)2  -1-  2  H2O 

=  2  HO.Fe.C4H404  +  C2H4(COOH)2  +  6  NH4CI. 


TRIACID   ALCOHOLS  163 

CH(C02H)2 
Isosuccinic  acid,  ethylidenesuccinic  acid,  |  .    This 

CH3 

acid  is  made  by  hydrolyzing  a-cyanpropionic  acid  (made  from 
a-bromopropionic  acid)  with  a  solution  of  an  alkali. 

Note  for  Student.  —  What  is  a-cyanpropionic  acid  and  how  is  it  made? 

Isosuccinic  acid  forms  crystals  that  melt  with  decomposition 
between  i2o°-i3s°.  Heated  above  its  melting  point  it  breaks 
down  into  propionic  acid  and  carbon  dioxide :  — 

CH(C02H)2        CH2CO2H 
I  =     I  +CO2. 

CH3  CH3 

Isosuccinic  acid  Propionic  acid 

Isosuccinic  acid  is  a  methyl  derivative  of  malonic  acid.    Ordi- 
nary succinic  acid  is  not. 

Note  for  Student.  —  Note  carefully  the  difference  between  the 
two  succinic  acids,  as  shown  by  their  conduct  when  heated.  What  is 
the  difference  ? 

Acids  of  the  formula  C6H8O4,  C3H6(C02H)2.  —  Four  acids 
of  the  formula  C6H8O4  are  known,  only  one  of  which,  however, 
need  be  mentioned  here. 

Glutaric  acid,  pentane  diacid,  CH2(CH2COOH)2,  made  by 
the  hydrolysis  of  trimethylene  cyanide :  — 

XT    ^      .CH2.CN  „     „  „     „  CH2.CO2H  - 

^^^<CH2.CN+  4H2O  =  H2C<^jj^^Q^jj+  2  NH3. 
It  melts  at  97.5°  and  is  soluble  in  water,  alcohol,  and  in  ether. 

Teiacid  Alcohols 

The  existence  of  monacid  alcohols  corresponding  to  the  mon- 
acid  bases,  like  potassium  hydroxide,  and  of  diacid  alcohols 
corresponding  to  the  diacid  bases,  like  calcium  hydroxide,  sug- 
gests the  possible  existence  of  triacid  alcohols  corresponding  to 
triacid  bases,  like  ferric  hydroxide.    There  is  only  one  alcohol 


1 64  DERIVATIVES   OF  THE   PARAFFINS 

of  this  kind  derived  from  the  paraffin  hydrocarbons  that  is  at 
all  well  known.  This  is  the  common  substance  glycerin  or 
glycerol. 

Glycerol,  glycerin,  propane  triol  1,2,3,  CaHgOs. — As  has 
been  stated  repeatedly,  glycerol  (commonly  called  glycerin) 
occurs  very  widely  distributed  as  the  alcoholic  constituent  of 
the  fats.  The  acids  with  which  it  is  in  combination  are  mostly 
members  of  the  fatty  acid  series,  though  one,  oleic  acid,  which  is 
found  frequently,  is  a  member  of  the  acrylic  acid  series  (286). 
Besides  oleic  acid  the  two  acids  most  frequently  met  with  in 
fats  are  palmitic  and  stearic  acids.  When  a  fat  is  saponified 
with  caustic  potash,  it  yields  free  glycerol  and  the  potassium 
salts  of  the  acids.  The  reactions  involved  in  the  synthesis  of 
palmitin  and  stearin  and  in  the  saponification   of    these  fats 

-/,     ,  /      .Formation       ,  ,        ^n- 
C3Hb(OH)3  +3  H0.6C.Ci5H3i  =  C3H6(O.OC.Ci6H3i)3  +  3  H2O. 

Glycerol  Palmitic  acid  Glyceryl  tripalmitate, 

or  Palmitin 

C3H6(OH)3  +  3  HO.OC.CitHjs  =  C3H6(O.OC.Ci7H35)3  +  3  H2O. 
Glycerol  Stearic  acid  Glyceryl  tristearate, 

or  Stearin 

Saponification 
C3H6(O.OC.CuH3i)3  +  3  KOH  =  C3H6(OH)3  +  3  C16H31.CO2K.. 

Palmitin  Glycerol  Potassium  palmitate ' 

C3H6(O.OC.C,vH35)3  +  3  KOH  =  C3H6(OH)3  +  3  C17H36.CO2K. 

Stearin  Glycerol  Potassium  stearate 

Manufacture  of  Glycerol  and  Fatty  Acids 

Besides  this  method  of  saponifying  the  fats  by  alkalies  used 
in  soap-making,  glycerol  is  made  on  the  large  scale  as  a  by- 
product of  the  manufacture  of  candles.  Several  methods  are 
used  to  hydrolyze  the  fats  into  free  fatty  acids  and  glycerol,  of 
which  the  following  are  the  most  important :  — 

(i)  By  heating  with  water  under  pressure  in  an  autoclave, 
a  small  quantity  of  lime,  magnesia,  or  zinc  oxide  being  added 
to  aid  the  hydrolysis. 


MANUFACTURE   OF  GLYCEROL   AND   FATTY  ACIDS      165 

(2)  By  heating  with  concentrated  sulphuric  acid  to  120°. 
This  method  not  only  hydrolyzes  the  fats  into  glycerol  and 

fatty  acids,  but  also  converts  the  liquid  oleic  acid  into  a  solid 
fatty  acid.     (See  Oleic  acid.) 

(3)  By  heating  with  water  and  Twitchell's  reagent.  This  re- 
agent is  made  by  heating  commercial  oleic  acid  and  an  aro- 
matic hydrocarbon,  like  naphthalene,  with  concentrated  sulphuric 
acid  and  washing  out  the  excess  of  sulphuric  acid  with  water. 

(4)  By  means  of  a  fat-splitting  enzyme,  lipase,  found  in  castor 
oil  seed  (Ricinus  communis). 

The  aqueous  solution  of  glycerol  obtained  in  these  processes 
is  concentrated  to  remove  water,  and  the  glycerol  is  purified  by 
distillation  in  a  vacuum.  The  purest  glycerol  on  the  market  is 
that  used  in  making  nitroglycerin.  This  is  usually  distilled 
a  second  time,  in  order  to  remove  as  much  water  as  possible 
and  to  eliminate  impurities  that  might  cause  explosions  when 
the  glycerol  is  used  in  the  manufacture  of  nitroglycerin. 

Formation  and  synthesis.  —  Glycerol  is  formed  in  small  quan- 
tity (about  3  per  cent  of  the  sugar  used)  in  the  fermentation 
of  sugar  with  yeast.  This  amount  may  be  increased  to  38 
per  cent  by  bringing  about  the  fermentation  of  the  sugar  solu- 
tion in  the  presence  of  large  amounts  of  sodium  sulphite. 
Under  these  conditions  the  amount  of  alcohol  formed  is  dimin- 
ished while  the  amount  of  glycerol  is  increased.  An  equivalent 
quantity  of  acetic  aldehyde  (which  combines  with  the  sodium 
bisulphite  produced  by  the  action  of  carbon  dioxide  on  the 
sodium  sulphite)  is  produced  together  with  glycerol :  — 

CeHisOe  =    C3H6(OH)3   +  CH3CHO  +  CO2. 

Glucose  Glycerol  Acetaldehyde 

It  will  be  seen  from  this  that  glycerol  and  acetic  aldehyde 
are  intermediate  products  in  the  fermentation  of  sugar  by 
yeast  to  alcohol  and  carbon  dioxide.  During  the  World  War 
over  a  million  kilograms  of  glycerol  per  month  were  made  in 
Germany  from  beet  sugar  molasses  by  this  method. 

Glycerol  has  been  made  synthetically  from  propylene  chloride, 
CaHeCU,  made  from  propylene  (279)  and  chlorine.    The  neces- 


1 66  DERIVATIVES   OF  THE   PARAFFINS 

sary  steps  are:  (i)  treatment  with  iodine  chloride,  giving 
CsHsCls ;  (2)  treatment  of  the  trichloropropane  with  water, 
thus  replacing  the  three  chlorine  atoms  by  hydroxyl  groups :  — 

CH2  CH2CI  CH2CI  CH2OH 

II  I  I  I 

CH       — >■      CHCl     — >-     CHCl     — >■    CHOH. 

I  I  I  I 

CH3  CH3  CH2CI  CH2OH 

That  each  chlorine  atom  in  trichloropropane  is  connected 
with  a  different  carbon  atom  follows  from  its  synthesis  from 
allyl  chloride  and  chlorine :  — 

CH2  H2CCI 

II  CI  I 

CH      +  I      =         HCCl. 

I  CI  I 

H2C— CI  H2CCI 

Allyl  chloride  Trichloropropane 

(3)  Another  method  that  leads  to  the  synthesis  of  glycerol 
consists  in  oxidizing  allyl  alcohol  (283).  This  reaction  is  rep- 
resented thus :  — 

CH2  H2COH 

C        +  HOH  +  O  =   HCOH. 

I  I 

H2COH  H2COH 

Ally!  alcohol  Glycerol 

Properties.  —  Glycerol  is  a  syrupy  colorless  liquid,  with  a 
sweetish  taste.  (Compare  with  glycol.)  It  mixes  with  alcohol 
and  water  in  all  proportions,  but  is  insoluble  in  ether.  At  low 
temperatures- it  slowly  solidifies,  forming  deliquescent  crystals 
which  melt  at  20".  Pure  glycerol  boils  at  290°  almost  without 
decomposition.  If  salts  are  present,  it  undergoes  decomposition 
at  the  boiling  temperature.  It  is  purified  by  distillation  under 
diminished  pressure.  It  is  volatile  with  water  vapor.  It  does 
not  evaporate  at  ordinary  temperatures.  It  attracts  moisture 
from  the  air,  and  retains  its  oily  feel.  It  makes  the  skin 
soft  without  objectionable  results. 


MANUFACTURE   OF   GLYCEROL  AND    FATTY  ACIDS      1 67 

Glycerol  finds  extensive  use  in  medicine,  in  the  preparation 
of  cosmetics,  in  the  textile  industry,  in  the  manufacture  of  to- 
bacco (to  prevent  drying),  as  a  sweetening  agent  in  the  prep- 
aration of  drinks,  in  the  preparation  of  self-inking  pads  (to 
prevent  the  drying  up  of  the  ink),  in  the  preparation  of  the 
ink  rolls  used  in  printing,  in  automobile  radiators,  gas  meters, 
etc.,  to  prevent  freezing  in  cold  weather.  Its  chief  use  is  in  the 
manufacture  of  nitroglycerin. 

The  world's  production  of  glycerol  is  about  85,000  tons 
annually,  most  of  which  is  made  and  used  in  this  country. 
When  glycerol  is  heated  with  a  dehydrating  agent,  such  as 
sodium  bisulphate,  it  gives  acrolein  (285),  and  this  fact  is  made 
use  of  as  a  test  for  glycerol  or  the  fats.  Another  test  for  glycerol 
is  to  heat  a  borax  bead  moistened  with  the  fluid  in  the  flame 
of  a  bunsen  burner.  If  glycerol  is  present,  boric  acid  is  set 
free  and  colors  the  flame  green.  The  acid  properties  of  glycerol 
are  also  shown  by  the  fact  that  alkalies  give  no  precipitate  of 
copper  hydroxide  when  added  to  a  solution  of  copper  sulphate 
containing  glycerol.  This  is  due  to  the  formation  of  a  soluble 
copper  salt  of  glycerol.    (See  Fehling's  solution.) 

The  reactions  of  glycerol  all  clearly  lead  to  the  conclusion 
that  it  is  a  triacid  alcohol. 

(i)  The  three  hydroxyl  groups  can  be  replaced  successively 
by  chlorine,  giving  the  compounds, — 

Monochlorohydrin,     CICH2CHOHCH2OH ; 
Dichlorohydrin,         CICH2CHOHCH2CI ; 
Trichlorohydrin,        CICH2CHCICH2CI. 

The  last  compound  is  really  trichloropropane. 

The  monochloro  and  the  dichlorohydrins  are  made  by  dis- 
solving anhydrous  glycerol  in  glacial  acetic  acid,  saturating 
with  hydrochloric  acid  gas,  heating,  and  then  distilling  off  the 
acetic  acid.  The  monochlorohydrin  is  separated  from  the 
dichlorohydrin  by  fractional  distillation  in  a  vacuum.  The 
trichlorohydrin  is  made  by  heating  the  dichlorohydrin  with 
phosphorus  pentachloride. 

Monochlorohydrin  is  chiefly  used  for  the  purpose  of  making 


1 68  DERIVATIVES  OF  THE  PARAFFINS 

the  dinitrate,  C1CH2CH(0N02)CH2(0N02).  This  is  a  yellow 
liquid,  (b.  p.  i90°-i93°),  which  does  not  solidify  at  -25"  to 
-30°.  It  is  therefore  added  to  nitroglycerin  to  prevent  it  from 
solidifying  at  low  temperatures.  Monochlorohydrin  is  also 
used  in  organic  syntheses. 

Dichlorohydrin  is  used  as  a  solvent  for  shellac,  resins  (copal), 
nitrocellulose  (celluloid),  etc.,  and  in  organic  syntheses. 

(2)  Glycerol  forms  three  classes  of  ethereal  salts  containing 
one,  two,  and  three  acid  residues  respectively.  For  example, 
with  acetic  anhydride  these  reactions  take  place :  — 

f  OH  r  0C2H3O 

1.  C3H6    OH  +  (C2H30)20      =  C3H6    OH  +  C2H4O1,. 

I  OH  I  OH 

Monoacetin 

f  OH  f  OC2H3O 

2.  C3H6    OH  +  2  (C2H30)20  =  C3H6    OC2H3O  +  2  C2H4O2. 

I  OH  I  OH 

Diacetin 

fOH  rOC2H30 

3.  C3H6^  OH  +  3  (C2H30)20  =  C3H6  OC2H3O  +  3  C2H4O2. 

I  OH  IOC2H3O 

Triacetin 

The  last  reaction  (formation  of  triacetin)  is  used  for  the  quan- 
titative determination  of  glycerol  in  the  commercial  product. 

Commercial  "  ace  tin  "  is  a  mixture  of  mono  and  diacetin  and 
contains  very  little  triacetin.  It  is  made  by  boiling  glycerol 
and  glacial  acetic  acid  together  for  48  hours  and  distilling  off 
the  excess  of  acetic  acid.  It  is  used  as  a  solvent  for  basic  dyes, 
especially  indulins,  and  for  tannin  in  dyeing  cotton. 

In  regard  to  the  relation  of  the  hydroxyl  groups  to  the 
carbon  atoms  of  the  radical  C3H6,  the  syntheses  of  glycerol 
show  that  each  hydroxyl  is  in  combination  with  a  different 

CH2OH 
carbon  atom  as  represented  in  the  formula  CHOH,  and,  for  the 

CHjOH 

following  additional  reasons ; 


MANUFACTURE  OF  GLYCEROL  AND  FATTY  ACIDS   1 69 

In  the  first  place,  it  has  been  shown  that  compounds  con- 
taining two  hydroxyls  in  combination  with  the  same  carbon 
atom  are  unstable.  They  readily  lose  water.  It  would  follow 
from  this  that  the  simplest  triacid  alcohol  must  contain  at 
least  three  atoms  of  carbon,  just  as  the  simplest  diacid  alcohol 
must  contain  at  least  two  atoms  of  carbon.  We  have  seen 
above  that  glycerol,  the  simplest  triacid  alcohol  known,  does 
contain  three  atoms  of  carbon. 

Further,  if  the  above  formula  of  glycerol  is  correct,  it  con- 
tains two  primary  alcohol  groups,  CH2OH,  and  one  secondary 
alcohol  group,  CHOH.  Now,  it  has  been  shown  that  the  group 
CH2OH  is  converted  into  carboxyl ;  and  the  group  CHOH  into 
carbonyl  CO  by  oxidizing  agents.  Therefore,  we  should  expect 
by  oxidizing  glycerol  to  get  acids  having  the  formulas, — 

CO2H  CO2H  CO2H 

CHOH  CHOH  CO 

CH2OH  CO2H  CO2H 

Glyceric  acid  Tartronic  acid  M  esoxalic  acid 

Products  having  these  formulas  actually  are  obtained  by  oxida- 
tion of  glycerol,  the  first  being  glyceric  acid  (189)  the  second 
tartronic  acid  (192),  and  the  third  inesoxalic  acid  (196). 

Just  as  ethyl  alcohol,  C2H5OH,  is  regarded  as  water,  HOH, 
in  which  one  hydrogen  is  replaced  by  the  univalent  radical  C2H5, 

H>0 
and  glycol,  C2H4     _,  is  regarded  as  two  molecules  of  water  in 

H  >*-' 

which  two  hydrogen  atoms  are  replaced  by  the  bivalent  radical 
C2H4,  so  also  glycerol  may  be  regarded  as  three  molecules  of 
water  in  which  three  hydrogen  atoms  are  replaced  by  the  tri- 
valent  radical  C3H6,  thus :  — 


HOH 

roH 

HOH 

C3H6    OH. 

HOH 

I  OH 

molecules  water 

Glycerol 

170  DERIVATIVES  OF  THE  PARAFFINS 

Ethereal  salts  or  esters  of  glycerol.  —  Among  the  important 
esters  of  glycerol  are  the  nitrates.     Several  of  these  are  known ; 

fONOj  fONOa 

viz.,  the  mononitrates,  CzHii  OH    ,  dinitrates,  C3H6 1  ONO2, 

I  OH  I  OH 

and  the  trinitrate,  C3H5(ON02)3,  the  latter  being  the  chief 
constituent  of  nitroglycerin.  Nitroglycerin  is  prepared  by 
adding  glycerol  slowly  to  a  mixture  of  concentrated  sulphuric 
and  nitric  acids,  the  temperature  being  kept  below  10°.  It 
is  a  pale  yellow  oil  insoluble  in  water.  At  low  temperatures 
it  crystallizes  in  long  needles.  It  explodes  very  violently  by 
concussion.  It  can  be  burned  in  an  open  vessel,  but  if  heated 
quickly  it  explodes.  The  products  of  the  chemical  change  that 
takes  place  are  carbon  dioxide,  steam,  free  nitrogen  and  oxygen 
which  occupy  10,000  times  the  volume  of  the  nitroglycerin  :  — 

4  C3H6(ON02)3  =  12  CO2  +  10  H2O  (vapor)  +  6  N2  +  O2. 

This  fact  accounts  for  the  enormous  explosive  power  of  the 
substance. 

On  account  of  the  danger  and  difiSculty  of  handling  it  in  the 
liquid  state,  nitroglycerin  as  such  is  used  only  for  special  pur- 
poses, such  as  blasting  oil  wells.  Approximately  7,000,000 
pounds  are  used  in  this  manner  each  year  in  the  United  States. 

Dynamite,  introduced  by  Nobel  in  1867,  was  originally  75 
parts  of  nitroglycerin  absorbed  in  25  parts  of  kieselguhr.  This 
made  a  plastic  mass,  safe  and  convenient  to  handle.  Kiesel- 
guhr, however,  is  inert,  and  produces  no  gas  on  explosion  of  the 
dynamite.  A  distinct  improvement  was  made  by  the  substitu- 
tion for  kieselguhr  of  a  mixture  of  wood  flour  and  a  nitrate,  such 
as  sodium  or  potassium  nitrate.  The  dynamites  manufactured 
in  America  at  present  are  mixtures  of  this  type  and  contain  from 
10  per  cent  to  70  per  cent  nitroglycerin.  No  kieselguhr  dyna- 
mite has  been  manufactured  in  the  United  States  since  about 
1890. 

In  1870,  Nobel  discovered  that  a  small  percentage  of  collodion 
cotton  would  cause  nitroglycerin  to  form  a  stiff  jelly.     A  mix- 


FATS  171 

ture  of  91  per  cent  nitroglycerin  and  9  per  cent  of  this  nitro- 
cellulose is  called  blasting  gelatin.  It  is  a  stiff,  plastic  jelly, 
giving  only  gases  on  explosion,  and  is  the  strongest  explosive 
known. 

Gelignites  and  gelatin  dynamites  are  prepared  by  making  a 
thinner  jelly  —  containing  lower  ratios  of  nitrocellulose  —  and 
incorporating  therein  a  mixture  of  wood  flour  and  sodium  or 
potassium  nitrate. 

All  of  these  blasting  explosives  are  detonated  by  means  of 
mercury  fulminate. 

The  annual  production  in  the  United  States  of  commercial 
blasting  explosives  containing  nitroglycerin  is  approximately 
300,000,000  pounds. 

In  the  manufacture  of  some  types  of  smokeless  powder,  nitro- 
glycerin is  used  to  gelatinize  nitrocellulose.  Cordite  and  hal- 
listite  are  the  most  important  of  such  types.  They  contain 
from  30-60  per  cent  nitroglycerin,  and  from  35-65  per  cent 
nitrocellulose. 

When  treated  with  alkali,  nitroglycerin  is  saponified,  yielding 
glycerol  and  a  nitrate.  This  shows  that  it  is  an  ester  of  nitric 
acid,  and  not  a  nitro  compound. 

Fats.  —  The  natural  fats  consist  almost  entirely  of  the  fatty 
acid  esters  of  glycerol.  It  has  usually  been  assumed  that  the 
fats  are  simply  mixtures  of  varying  amounts  of  the  neutral 
esters,  tripalmitin,  tristearin,  and  triolein,  and  that  the  fat  is 
solid,  semi-solid,  or  liquid,  according  to  the  amount  of  olein 
(which  is  liquid)  present.  Recent  investigations  show  that 
mixed  esters,  compounds  containing  different  fatty  acids 
combined  with  the  same  glycerol  molecule,  occur  much  more 
frequently  than  had  been  supposed.  Thus  oleopalmito- 
butyrate :  — 

H2C— 0-COCi7H33  l^bi"  '"   '  /   C  r 

HC— O-COCisHai 

H2C— O-COCsHv 

has  been  isolated  from  cow's  butter,  and  other  mixed  esters  of 


172  DERIVATIVES   OF  THE   PARAFFINS 

glycerol  have  been  isolated  from  beef  tallow,  lard,  cocoa  butter 
and  olive  oil.  Human  fat  consists  mainly  of  tripalmitin  and 
a  dioleostearin.  Glycerol  is  the  only  polyacid  alcohol  found 
in  fats. 

Fats  are  very  widely  distributed  in  nature,  both  in  plants 
and  animals.  They  are  of  the  highest  importance  from  the 
economic  and  physiological  point  of  view,  forming  one  of  the 
three  great  classes  of  foodstuffs. 

They  are  the  source  of  the  manufacture  of  soaps,  candles, 
and  glycerol.' 

In  the  digestion  of  fats  in  the  intestines,  they  are  completely 
hydrolyzed  in  the  alkaline  digestive  fluids  into  glycerol  and  soap 
by  means  of  an  enzyme,  lipase,  present  in  these  fluids.  The 
glycerol  and  some  of  the  fatty  acids  are  then  recombined  in 
the  epithelial  cells  of  the  intestines,  probably  by  means'  of  the 
lipase,  into  the  fats  characteristic  of  the  animal. 

Butter  consists  of  mixed  esters  of  glycerol  with  the  following 
acids :  myristic,  palmitic,  oleic,  and  stearic  acids,  which  are  not 
volatile,  and  butyric,  caproic,  caprylic,  and  capric  acids,  which 
are  volatile  with  steam.  Trihutyrin  is  not  present  in  butter. 
All  the  acids  mentioned  except  oleic  acid  are  members  of  the 
fatty  acid  series.  Some  of  these  acids  are  soluble  and  some 
are  insoluble  in  water.  The  percentage  of  insoluble  fatty  acids 
contained  in  butter  has  been  found  to  be  about  88  per  cent. 
As  the  proportion  of  insoluble  fatty  acids  contained  in  butter 
substitutes,  which  must  be  labelled  oleomargarin  in  the  United 
States,  is  greater  than  that  contained  in  butter,  it  is  not  a 
diffi-cult  matter  to  distinguish  between  the  two  by  determining 
the  amount  of  these  acids  contained  in  them. 

Legally  in  the  United  States  butter  must  contain  82.5  per 
cent  butter  fat  of  a  specific  gravity  of  not  less  than  0.905  at 
40°  compared  with  water  at  40°  taken  as  unity.  The  butter 
fat  must  also  contain  enough  volatile  fatty  acids  in  a  5  gram 
sample  to  neutralize  not  less  than  24  cc.  of  o.i-N  sodium 
hydroxide  solution  (Reichert-Meissl  Number). 

'  See  Chemical  Technology  and  Analysis  of  Oils,  Fats  and  Waxes,  by 
J.  Lewkowitsch,  6th  ed.,  1921. 


TETRACID   AND   PENTACID   ALCOHOLS  I 73 

Tribasic  Acid 

Tricarballylic  acid,  C3H6(C02H)3.  —  This  acid  can  be  made 
from  trichlorohydrin,  CsHsCls  (167),  by  replacing  the  chlorine 
by  cyanogen,  and  heating  the  tricyanhydrin  thus  obtained  with 
a  solution  of  an  alkali.  It  can  be  made  also  by  treating  aconitic 
acid  (295)  with  nascent  hydrogen.  It  crystallizes  from  water 
in  orthorhombic  prisms  that  melt  at  i62'^-i64° 

Tetracid  Alcohols 

Erythritol,  eiythrite,  butane  tetrol  1,2,3,4,  CH20H(CHOH)2CH20H.— 

This  substance  occurs  free  in  one  of  the  algae  (Protococcus  vulgaris) 
and  as  the  ester  of  orsellinic  acid  in  several  lichens.  It  crystallizes  from 
water  in  tetragonal  prisms.  It  has  a  sweet  taste.  The  fact  that  the 
simplest  tetracid  alcohol  contains  four  atoms  of  carbon,  two  of  which 
are  asymmetric,  should  be  specially  noted.  Erythritol  gives  secondary 
butyl  iodide  with  hydriodic  acid. 

The  erythritol  occurring  in  nature  is  optically  inactive.  Dextro  and 
levoerythritol,  and  the  inactive  mixture  of  the  two  are  also  known. 
When  oxidized  it  gives  erythronic  acid,  CH20H(CHOH)2C02H,  and 
then  mesotartaric  acid,  (CHOH)2(C02H)2  (202). 

Tetrabasic  acids  derived  from  the  hydrocarbons  of  the  paraffin  series  have 
been  made,  but  they  are  not  important. 

Pentacid  Alcohols 

Pentane  pentol  1,2,3,4,5,  CH20H(CHOH)aCH20H.  —  One  pentacid 
alcohol,  adonitol,  occurs  in  nature  in  Adonis  vernalis.  It  is  also 
formed  by  the  reduction  of  the  pentose,  ribose  (218),  with  sodium 
amalgam.  It  is  soluble  in  water  and  in  ethyl  alcohol,  but  is  insoluble 
in  ether.  Its  melting  point  is  102°  The  other  pentacid  alcohols, 
xylitol  and  arabitol,  are  stereoisomers  of  adonitol  and  are  obtained  by 
the  reduction  of  the  pentoses,  xylose  and  arabinose  (217).  Dextro, 
levo,  and  optically  inactive  (dl)  modifications  of  arabitol  are  known. 
From  the  above  formula  it  will  be  seen  that  it  contains  three  asymmetric 
carbon  atoms,  one  of  which  is  pseudosymmetrical.' 

Rhamnitol,  hexane  pentol  1,2,3,4,5,  obtained  by  reducing  the  pentose, 
rhamnose  (218),  is  a  pentacid  alcohol  containing  six  carbon  atoms. 
It  has  the  formula  CH20H(CHOH)4.CHj,  and  is  optically  active. 
Rhodeitol  and  fucitol  are  stereoisomers  of  rhamnitol. 

'  See  Stereochemistry,  by  A.  W.  Stewart,  for  explanation  of  pseudo- 
symmetry. 


174  DERI\^VTIVES   OF  THE  PARAFFINS 

These  alcohols  are  closely  related  to  the  sugars  called  pentoses.  The 
pentoses  are  formed  from  them  by  mild  oxidation,  and  they  are  formed 
from  the  pentoses  by  reduction. 


Pentabasic  acids  have  been  made,  but  they  are  of  no  special  im- 
portance.   

Hexactd  Alcohols 

Hexane  hexol  1,2,3,4,5,6,  CH20H(CHOH)4CH20H.  —  There 
are  several  hexacid  alcohols  known.  Most  of  them  are  derived 
from  hexane,  and  have  the  composition  represented  by  the 
formula  C6H8(OH)6.  It  will  be  noticed  that  these  hexacid 
alcohols  contain  six  carbon  atoms,  four  of  which  are  asymmetric. 
They  are  closely  related  to  the  sugars,  mannose,  fructose, 
galactose,  and  glucose. 

Mannitol,  mannite,  CeHsCOHje.  —  Mannite  is  very  widely 
distributed  in  the  vegetable  kingdom.  It  occurs  most  abund- 
antly in  manna,!  which  is  the  partly  dried  sap  of  the  manna 
ash  (Fraxinus  ornus),  a  tree  cultivated  in  Sicily.  It  is  obtained 
from  incisions  in  the  bark  of  the  tree.  Mannitol  makes  up  30 
to  60  per  cent  of  manna.  It  is  found  also  in  certain  mush- 
rooms, in  celery,  in  olives,  in  the  leaves  of  syringa  (mock 
orange),  and  in  many  other  plants.  It  forms  20  per  cent  of 
dried  Agaricus  integer. 

Mannitol  is  formed  in  the  lactic  acid  fermentation  of  sugar. 
It  is  formed  also  by  the  action  of  nascent  hydrogen  on  fructose 
or  mannose.  It  crystallizes  in  needles,  or  rhombic  prisms, 
easily  soluble  in  water  and  in  alcohol.     It  has  a  sweet  taste. 

Nitric  acid  converts  mannitol  into  mannosaccharic  acid, 
H00C(CH0H)4C00H,  (205).  When  boiled  with  concentrated 
hydriodic  acid,  it  is  converted  into  a  mixture  of  2-iodo-  and 
3-iodohexane,  CeHial. 

Mannitol  hexanitrate,  (nitromannite) ,  C6H8(O.N02)6,  is 
formed  by  treating  mannitol  with  a  mixture  of  concentrated 
sulphuric  and  nitric  acids.  It  is  a  solid  substance  and  is  very 
explosive.     (Analogy  with  nitroglycerin.) 

•  The  manna  of  the  Scriptures  was  probably  obtained  from  the  branches 
of  Tammarix  ^allica,     Jt  contains  no  mannite,  but  a  fermentable  sugar. 


HEXACID   ALCOHOLS  175 

Mannitol  hexacetate,  C6H8(O.C2H30)6,  is  formed  by  treat- 
ing mannitol  with  acetic  anhydride.  Its  formation,  as  well  as 
that  of  the  hexanitrate,  shows  that  mannitol  is  a  hexacid  alco- 
hol. The  number  of  acetyl  groups  that  enter  into  a  compound 
when  it  is  treated  with  acetic  anhydride  shows  how  many  hydroxyl 
groups  are  in  the  compound. 

There  are  three  varieties  of  mannitol  —  dextromannitol,  levo- 
mannitol,  and  a  mixture  of  the  two  known  as  inactive  mannitol, 
or  a-acritol. 

Dulcitol,  C6H8(OH)6. — This  alcohol  occurs  in  a  kind  of 
manna  obtained  from  Madagascar,  the  source  of  which,  how- 
ever, is  unknown.  It  is  formed  by  treating  sugar  of  milk  or 
galactose  with  nascent  hydrogen. 

Nitric  acid  oxidizes  dulcitol,  forming  mucic  acid  (206), 
H00C(CH0H)4C00H,  stereoisomeric  with  mannosaccharic 
acid.  Like  mannitol,  when  boiled  with  hydriodic  acid,  it 
yields  a  mixture  of  2-iodo-  and  3-iodohexane,  CeHisI. 

Sorbitol,  C6H8(OH)6 -H  H2O.  —  Ordinary  sorbitol  occurs  in 
the  ripening  berries  of  the  mountain  ash  {Sorbus  aucuparia), 
and  other  fruits,  as  plums,  cherries,  apples,  etc.  It  is  formed 
by  reduction  of  glucose  and  also,  together  with  mannitol,  by 
the  reduction  of  fructose.  This  variety  is  known  as  (^'-sorbitol 
because  it  is  formed  from  glucose,  which  is  dextrorotatory. 
I'-Sorbitol  is  also  known,  having  been  obtained  by  the  reduction 
of  levoglucose.  Sorbose  bacteria  convert  (^'-sorbitol  into 
«Z'-sorbose  (234). 

Mannitol,  sorbitol,  and  dulcitol  are  stereoisomers.  Talitol 
and  iditol  are  stereoisomers  of  mannitol,  dulcitol,  and  sorbitol. 

There  are  hexabasic  acids  known  belonging  to  this  series,  but 
they  are  not  important. 

Heptacid  Alcohols,  etc 

Perseitol,  C7H8(OH7),  occurs  in  the  fruit,  seeds,  and  leaves  of  Laurus 
persea,  and  has  been  made  synthetically  from  dextromannose  by  treating 
it  with  hydrocyanic  acid,  hydrolyzing  the  nitrile  obtained,  and  reducing  the 
lactone  of  the  acid  thus  formed.  It  is  also  called  dextromannoheptitol.  By 
similar  reactions  an  octacid  alcohol  and  an  alcohol  with  nine  hydroxyls 
have  also  been  made  from  glucose. 


CHAPTER  X 

MIXED    COMPOUIIDS  —  DERIVATIVES    OF    THE    PARAFFINS 

Under  this  head  are  included  compounds  that  belong  at  the 
same  time  to  two  or  more  of  the  chief  classes  already  studied. 
Thus,  there  are  substances  that  are  at  the  same  time  alcohols 
and  acids.  There  are  others  that  are  at  the  same  time  alco- 
hols and  aldehydes,  alcohols  and  ketones,  acids  and  ketones, 
etc.  Among  them  are  many  of  the  most  important  natural  com- 
pounds of  carbon.  The  first  class  that  presents  itself  is  that 
of  the  alcohol  acids  or  acid  alcohols;  that  is,  substances  that 
combine  within  themselves  the  properties  of  both  alcohol  and 
acid.     They  are  the  oxy  acids  or  hydroxy  acids. 

Hydroxy  Acids,  C„H2„03 

These  acids  may  be  regarded  either  as  monobasic  acids  into 
which  one  alcoholic  hydroxyl  has  been  introduced,  or  as  mon- 
acid  alcohols  into  which  one  carboxyl  has  been  introduced.  As 
their  acid  properties  are  more  prominent  than  the  alcoholic 
properties,  they  are  commonly  referred  to  the  acids.  Running 
parallel,  then,  to  the  series  of  fatty  acids,  we  may  look  for  a  series 
of  hydroxy  acids,  each  of  which  differs  from  the  corresponding 
fatty  acid  by  one  atom  of  oxygen,  or  by  containing  one  hydroxyl 
in  the  place  of  one  hydrogen,  thus :  — 

Fatty  Acms  Hydroxy  Acms 

H.CO2H         Formic    Acid      HO.CO2H  Carbonic  Acid. 

CH3.CO2H     Acetic         "        CH2<^^„       Glycolic       " 

C2H6.CO2H    Propionic    "       C2H4<^"„       Lactic 

Hj2xl 

etc.  etc. 

176 


CARBONIC   ACID  177 

The  first  member  of  the  series,  which  by  analogy  would  be 
called  hydroxyformic  acid,  is  plainly  the  ordinary  hypotheti- 
cal carbonic  acid.  Although  its  relation  to  formic  acid  is 
the  same  as  that  of  the  next  member  of  the  series  to  acetic 
acid,  it  has  no  properties  in  common  with  the  alcohols ;  but, 
owing  to  its  structure,  it  is  a  dibasic  acid,  while  the  other  mem- 
bers of  the  series  are  not.  Nevertheless,  it  may  be  referred  to 
here  for  the  sake  of  a  few  of  its  derivatives,  which  are  somewhat 
allied  to  those  of  the  hydroxy  acids. 

OH 

Carbonic  acid,  H2CO3,  OC  <       .  —  It  is  believed  that  this 

OH 

compound  exists  in  solutions  of  carbon  dioxide  in  water.  When 
this  solution  is  treated  with  zinc  dust  hydrogen  is  evolved  and 
zinc  carbonate  is  formed.  It  is  a  feeble  dibasic  acid,  and  breaks 
down  into  water  and  carbon  dioxide  whenever  it  is  set  free  from 
its  salts.  We  have  seen  that  this  instability  is  characteristic 
of  compounds  containing  two  hydroxyls  in  combination  with 
the  same  carbon  atom. 

Among  the  derivatives  of  carbonic  acid  that  should  be  men- 
tioned here  are  the  ethereal  salts.    These  may  be  made  :  — 

1.  By  heating  silver  carbonate  with  alkyl  iodides;  as,  for 
example :  — 

2.  By  heating  the  alcohols  or  sodium  alcoholates  with  car- 
bonyl  chloride,  OCCI2 :  — 

OCCI2  +  2  C2H5OH  =  OC(OC2H5)2  +  2  HCl. 

Carbonyl  chloride,  phosgene,  OCCI2,  is  the  chloride  of  car- 
bonic acid.  It  was  first  obtained  by  the  direct  union  of  car- 
bon monoxide  and  chlorine  in  the  sunlight,  hence  the  name 
phosgene  (Gr.  phos,  light;  Gr.  gennas,  I  produce).  It  results 
also  from  the  oxidation  of  chloroform  (27)  and  from  the  action 
of  fuming  sulphuric  acid  (80  per  cent  SO3)  on  carbon  tetra- 
chloride :  — 

CI2CCI2  -I-  SO3  -1-  H2SO4  =  OCCI2  -I-  2  CISO2OH. 


178  DERIVATIVES   OF  THE  PARAFFINS 

It  is  most  conveniently  prepared  in  the  laboratory  by  the  last 
method.  Technically  it  is  made  by  conducting  carbon  monoxide 
and  chlorine  over  some  catalytic  agent  (bone  black).  It  is  a 
colorless  gas  with  a  suffocating  odor.  It  is  readUy  condensed 
to  a  liquid  below  8°.  It  is  very  soluble  in  benzene  and 
toluene.  It  is  poisonous.  As  an  acid  chloride  it  is  hydrolyzed 
by  water  into  carbon  dioxide  and  hydrochloric  acid.  It  hence 
reacts  with  acids  abstracting  water  and  forming  acid  an- 
hydrides.    It  converts  aldehyde  into  ethylidene  chloride :  — 

H3C.CHO  +  OCCI2  =  OCO  +  H3C.CHCI2. 

With  ammonia  it  gives  urea  (262).     Large  quantities  are  used 

in  making  dyes,  intermediates,  and  in  synthetic  work.     It  was 

used  as  a  "  poison  gas  "  during  the  World  War. 

Cl 
Ethyl  chlorocarbonate,  OC<  ,  boils  at  93°  and  acts  as 

OC2H5 

an  acid  chloride  and  as  an  ester,  e.g.  it  is  hydrolyzed  by  water 

to  hydrochloric  acid  and  ethyl  hydrogen  carbonate,  which  is 

unstable   and   breaks  down  into  carbon  dioxide  and  alcohol. 

It  is  largely  used  in  synthetic  work  and  for  the  purpose  of 

introducing  the  carboxyl  group  into  compounds. 

It  may  be  regarded  as  the  ethyl  ester  of  monochloroformic 

acid,    Cl.COOH;    and,   properly   speaking,   should   be   called 

ethyl  chloroformate. 

Carbon  bisulphide  acts  like  carbon  dioxide  towards  alkalies  and  alco- 
hols, and  yields  a  number  of  ether  acids  and  ethereal  salts  containing 
sulphur.    Thus,  when  carbon  bisulphide  is  added  to  a  solution  of  caustic 

or*  TT 
potash  in  alcohol,  a  potassium  salt  of  the  formula  SC<„^    '  is  formed. 

This  is  called  potassium  xanthate.  Free  xanthic  acid  is  very  unstable, 
breaking  down  into  alcohol  and  carbon  bisulphide.  The  formation  of  the 
salt  is  represented  thus :  — 

OP  W 
CS2  +  KOH  -I-  CjHsOH  =  SC<g^'    '  +  H2O. 

A  similar  salt  made  from  ordinary  amyl  alcohol  has  been  used  for  the  pur- 
pose of  destroying  phylloxera,  the  insect  that  is  so  destructive  to  grape- 
vines, particularly  in  the  wine  districts  of  France. 


METHODS   OF  PREPARING  HYDROXY  ACIDS  179 

General  methods  for  the  preparation  of  hydroxy  acids :  — 

1.  Heating  a  halogen  derivative  of  an  acid  with  water  or 
silver  hydroxide :  — 

Bromoacetic  acid  Hydroxyacetic  acid 

2.  By  treating  an  amino  derivative  of  an  acid  with  nitrous 
acid  (106) :  — 

CH,<2qJjj  +  HNO2  =  CH2<^Q^jj  +  N2  +  H2O. 

Aminoacetic  acid 

3.  From  aldehydes  or  ketones  by  first  converting  them  into 
the  cyanhydrins  by  the  action  of  hydrocyanic  acid,  and  hydro- 
lyzing  the  latter :  — 

H3C.HCOH.CN  +  2  H2O  =  H3C.HCOH.COOH  +  NH3; 

(H3C)2C<°JJ  +  2  H2O  =  (H3C)2C<°QQjj  +  NH3. 

As  the  aldehydes  and  ketones  are  readily  made  from  the  primary 
and  secondary  alcohols  by  oxidation,  this  is  an  indirect  method 
of  introducing  carboxyl  into  the  alcohols  in  place  of  hydrogen. 
This  method  always  gives  an  a-hydroxy  acid.  *. 

4.  By  hydrolysis  of  glycol  cyanhydrin,  made  from  ethylene 
chlorohydrin  (152) :  — 

H2C— CN  H2C— COOH 

I  +  2  H2O  =       I  +  NH3. 

H2C— OH  H2C— OH 

This  method  gives  a  ;8-hydroxy  acid. 

5.  By  the  reduction  of  aldehyde  or  ketone  acids :  — 

CH3  CH3 

H— C  =  0  H2C.OH 

CO        +  H2  =  HCOH     ;  .  +  H2  = 

0  =  C— OH  0  =  C.OH 

COOH  COOH 

Pyruvic  acid  Lactic  acid  Glyoxylic  acid  Glycolic  acid 


l8o  DERIVATIVES   OF  THE   PARAFFINS 

Glycolic   acid,   hydroxyacetic  acid,    oxyacetic   acid,    ethanol 

OH 

acid,  C2H4O3,  CH2<  .  —  Glycolic  acid  is  found  in  nature 

CO2H 

in  unripe  grapes,  and  in  the  leaves  of  the  wild  grape  {Ampelopsis 

hederacea) . 

It  can  be  made  from  glycocoll,  which  is  aminoacetic  acid  (see 

reaction  2,  above),  from  bromo  or  chloroacetic  acid  and  water 

(see  reaction  i,  above),  and  by  the  oxidation  of  glycol :  — 

CH2OH  CO2H 

I  +  O2  =    I  +  H2O. 

CH2OH  CH2OH 

Glycol  Glycolic  acid 

This  results  in  transforming  one  of  the  primary  alcohol  groups, 
CH2OH,  contained  in  glycol,  into  carboxyl. 

Note  for  Student.  —  What  would  be  formed  by  conversion  of  both 
the  primary  alcohol  groups  of  glycol  into  carboxyl? 

It  can  also  be  made  by  careful  oxidation  of  ethyl  alcohol 
with  nitric  acid.  For  this  purpose  a  mixture  of  alcohol  and 
nitric  acid  is  allowed  to  stand  until  no  further  action  takes 
place.  Glycolic  acid  crystallizes  from  the  solution  on  evapora- 
tion. 

Glycolic  acid  forms  crystals  that  are  easily  soluble  in  water, 
alcohol,  and  ether.  It  melts  at  80°.  It  is  a  very  much  stronger 
acid  than  acetic  acid. 

As  an  acid,  glycolic  acid  forms  a  series  of  salts  with  metals, 
and  ethereal  salts  with  alcohol  radicals.  The  latter,  of  which 
ethyl  glycolate  may  be  taken  as  an  example,  can  be  made  by 
means  of  one  of  the  reactions  usually  employed  for  making 
ethereal  salts;  for  example,  by  treating  silver  glycolate  with 
ethyl  iodide :  — 

^«^<?02Ag  +  C^H^I  =  CH2<°«^^j^^  +  AgI. 

In  this  reaction,  as  well  as  in  the  formation  of  salts  of  glycolic 
acid,  the  alcoholic  hydroxyl  remains  unchanged. 


LACTIC   ACIDS  l8l 

As   an   alcohol,   glycolic   acid  forms  ethers  of  which  ethyl- 

glycolic  acid,  CH2<„„  „  ,  may  serve  as  an  example.     It  wUl 
L,U2il 

be  seen  that  this  is  isomeric  with  ethyl  glycolate.  But  while  the 
latter  has  alcoholic  properties,  the  former  has  acid  properties. 
Ethyl  glycolate  is  a  liquid  that  boils  at  i6o°.  Ethylglycolic 
acid  is  a  liquid  that  boils  at  206°  to  207°.  Finally,  as  an  alco- 
hol, glycolic  acid  forms  ethereal  salts,  of  which  acetyl- 
glycolic  acid  may  serve  as  an  example.  This  is  glycolic  acid 
in  which  the  hydrogen  of  the  hydroxyl  is  replaced  by  acetyl, 

O  C  TT  O 
CH2<„„  Tj  '    •     As  will  be  seen,  this  bears  the  same  relation 
LO2H 

to  glycolic  acid  and  acetic  acid  that  ethyl  acetate,  C2H5.O.C2H3O, 

bears  to  alcohol  and  acetic  acid. 

Glycolic  acid  and  some  of  the  other  acids  of  the  series  lose 
water  when  heated,  and  yield  anhydrides.    Thus  glycolic  anhy- 

H2COH 
dride,       I  ,   is  formed  when  glycolic  acid    is 

OC— OCH2.COOH 
heated  to  100°.    This  substance  is  plainly  an  ester,  an  alcohol, 
and  an  acid. 

Allien  glycolic  acid  is  distilled  in  a  vacuum  it  yields  glycolide, 
which  is  derived  from  the  acid  as  represented  in  this  equation :  — 

H2C.OH         HO— C=:0      H2C— O— CO 

I  +  1=1  1+2  H2O. 

0=:C.OH         HO— CH2  OC— O— CH2 

It  is  a  double  ester  resulting  from  the  interaction  of  the  alco- 
holic hydroxyl  of  each  molecule  of  the  glycolic  acid  with  the 
carboxyl  of  the  other. 

Glycolide  is  insoluble  in  cold  water.  When  boiled  for  a 
long  time  with  water,  it  is  converted  into  glycolic  acid.  It 
melts  at  87°. 

Lactic    acids,    hydroxypropionic    acids,    oxypropionic    acids, 

OH 
CsHeOs,  C2H4<__,  „.  —  In  treating  of  propionic  acid,  it  was 
CO2XI 

pointed   out  that  two  series  of   mono   substitution  products 


l82  DERIVATIVES  OF  THE  PARAFFINS 

of  the  acid  are  known,  which  are  designated  as  the  a-  and  /3- 
series.  Accordingly  we  should  expect  to  find  two  hydroxy- 
propionic  acids,  the  a-  and  the  /3-acid,  and  both  are  known. 
The  a-hydroxypropionic  acids  or  lactic  acids  contain  an  asym- 
metric carbon  atom :  — 

H 

1 
HaC— C— COOH 

OH 

and  the  dextro,  levo,  and  inactive  (dl)  forms  predicted  by  the 
theory  (see  active  Amyl  alcohols,  137)  are  all  known. 

fi-Hydroxypropionic,  hydracrylic  acid,  HOH2C.CHi.COOH,  does 
not  contain  an  asymmetric  carbon  atom  and  is  only  known  in 
one  form,  which,  of  course,  is  optically  inactive. 

I.  Lactic  acid,  inactive  ethylidenelactic  acid,  a-hydroxy- 
propionic  acid,  propanol-2-acid,  H3C.CHOH.COOH.  —  This 
acid  is  formed  in  the  lactic  acid  fermentation  of  milk  sugar, 
cane  sugar,  or  glucose  and  is  hence  called  fermentation  lactic 
acid.  It  can  also  be  obtained  from  the  carbohydrates  by 
the  action  of  alkalies.  From  50  to  60  per  cent  of  glucose 
or  fructose  can  be  converted  in  this  way  into  inactive  lactic 
acid :  — 

CeHizOe  =  2  C3H6O3. 

Glucose  Lactic  add 

With  certain  lactic  acid  bacteria  over  98  per  cent  of  glucose 
can  be  converted  into  inactive  dZ-lactic  acid.  This  micro- 
organism is  extremely  sensitive  to  the  free  acid,  and  hence  the 
fermentation  is  brought  about  in  the  presence  of  calcium  or 
zinc  carbonate  to  neutralize  the  free  acid  as  fast  as  it  is  formed. 
The  lactic  acid  is  afterwards  set  free  from  these  salts  by  means 
of  sulphuric  acid. 

As  in  the  case  of  the  fermentation  of  glucose  to  alcohol  (39, 40) 
the  formation  of  lactic  acid  from  sugar  is  caused  by  an  enzyme 
produced  by  the  microorganism.  This  lactic  acid  fermentation 
plays  a  very  important  part  in  many  practical  processes,  as  in 
butter-making,  when  the  cream  is  allowed  to  become  sour 


LACTIC  ACID  183 

before  churning,  or  a  "  starter"  (lactic  acid  ferment)  is  added  to 
it ;  in  the  ripening  of  cheese ;  in  the  fermentation  of  cabbage 
in  making  sauerkraut;  and  in  the  change  of  cucumbers  into 
dUI  pickles.  Silage,  used  largely  as  a  cattle  food,  contains 
large  quantities  of  lactic  acid.  Lactic  acid  is  also  present  in 
small  quantity  in  wines  and  in  opium.  That  lactic  acid  is 
a-hydroxypropionic  acid  follows  from  its  formation  from 
a-chloro-  and  a-bromopropionic  acids  by  heating  with  solutions 
of  the  alkalies,  from  pyruvic  acid  by  reduction  (see  method 
5,  179),  and  from  aldehyde  (see  method  3, 179).  The  inactive 
dlr-lactic  acid  always  results  from  these  chemical  methods  of 
preparation.  Lactic  acid  was  first  isolated  from  sour  milk  and 
hence  its  name  (lac,  milk). 

Commercial  lactic  acid  is  a  thick,  hygroscopic  syrup,  sp.  gr. 
1.21-1.22,  that  contains  about  80  per  cent  acid.  It  mixes  with 
water  and  alcohol  in  all  proportions  and  can  be  extracted  from 
its  aqueous  solutions  by  means  of  ether.  When  purified  by 
distillation  in  a  vacuum,  lactic  acid  forms  crystals  that  melt  at 
18°.  The  zinc  salt  of  the  inactive  dl-acid  crystallizes  with  3 
molecules  of  water  of  crystallization,  while  the  zinc  salts  of  both 
the  dextro  and  the  levo  acid  contain  only  2  molecules  of  water 
of  crystallization.  The  zinc  salts  of  the  two  active  acids  are 
also  much  more  soluble  in  water  than  that  of  the  inactive  dl- 
acid.  Hence  when  equal  amounts  of  these  salts  are  dissolved 
in  water,  the  zinc  salt  of  the  inactive  dl-acid  with  3  molecules 
of  water  crystallizes  out  of  the  solution.  Heated  with  hydriodic 
acid  all  the  lactic  acids  are  reduced  to  propionic  acid :  — 

H3C.CHOH.COOH  +  2  HI  =  CH3.CH2.COOH  +  H2O  +  I2. 

This  shows  that  the  isomerism  is  due  to  the  asymmetric  carbon 
atom  as  it  disappears  with  the  asymmetric  carbon  atom.  With 
hydrobromic  acid  lactic  acid  gives  a-bromopropionic  acid :  — 

H3C.CHOH.COOH  +  HBr  =  HOH  +  H3C.CHBr.COOH 

and  the  d-,  1-,  and  (iZ-varieties  of  this  acid  are  all  known,  as 
it  still  contains  the  asymmetric  carbon  atom. 


l84  DERIVATIVES  OF  THE  PARAFFINS 

The  lactic  acid  obtained  by  the  fermentation  of  the  carbo- 
hydrates is  ahnost  always  the  inactive  d^variety.  Systematic 
investigation  has  shown  that  it  depends  essentially  on  the  nature 
of  the  microorganism  and  the  conditions  as  to  whether  the  in- 
active (dl)  or  active  acid  is  obtained.  Seldom  is  the  dextro 
or  levo  form  obtained  alone ;  generally  the  inactive  acid  is 
formed  with  a  sUght  excess  of  the  d-  or  the  /-  acid. 

Lactic  acid  has  been  identified  as  an  intermediate  product 
in  the  alcohoUc  fermentation  of  glucose  :  — • 

CeHizOe    ;«"     2C3H6O3. 

Glucose  Lactic  add 

It  has  been  suggested  that  it  then  gives  ethyl  alcohol  by  the 
loss  of  carbon  dioxide  :  — 

H3C— C^OH        =  H3CCH2OH  +  CO2. 
\COOH 

The  objection  to  this  suggestion,  however,  is  that  lactic  acid  is 
not  converted  into  alcohol  and  carbon  dioxide  by  fermentation 
with  yeast. 

Lactic  acid  is  used  as  a  mordant  in  dyeing,  especially  in  the 
form  of  its  antimony  compound;  in  the  leather  industry  to 
remove  lime  and  the  calcium  salts  of  the  fatty  acids  from  the 
skins  after  they  have  been  dehaired  in  the  lime- vat ;  and  in 
the  form  of  its  compound  with  titanic  acid  in  the  manufacture 
of  leather.  It  is  also  used  in  the  manufacture  of  alcohol  (to 
prevent  the  growth  of  other  organisms  than  yeast).  Several 
salts  of  lactic  acid  are  used  in  medicine. 

When  heated  with  dilute  sulphuric  acid,  lactic  acid  gives 
acetic  aldehyde  and  formic  acid  :  — 

H3C.CHOH.COOH  =  H3C.CHO  +  H.COOH. 

This  reaction,  which  is  characteristic  of  the  a-hydroxy  acids, 
is  used  as  a  test  for  lactic  acid.  When  oxidized  all  the  lactic 
acids  give  pyruvic  acid,  CH3.CO.COOH  (207),  and  this  proves 
the  presence  of  the  secondary  alcohol  group  in  lactic  acid.     It 


LEVOLACTIC   ACID  185 

will  be  noted  that  pyruvic  acid  does  not  contain  an  asymmetric 
carbon  atom.  When  lactic  acid  is  distilled  in  a  vacuum,  lactide, 
a  double  ester  analogous  to  glycolide,  results :  — 

H3CCHOH         HOOC  H3CCH— 0— CO 

I            +              I             =1  1  +2  H2O. 

COOH  HOCHCH3         OC— 0 CHCH3 

2  Mols.  of  lactic  acid  Lactide 

This  forms  colorless  plates  melting  at  1 20°.  It  is  insoluble  in 
water,  but  is  converted  into  lactic  acid  by  boUing  with  water. 

2.  Sarcolactic  acid,  dextrolactic  acid,  H3C.CHOH.COOH, 
occurs  in  the  liquid  expressed  from  meat,  whence  its  name. 
It  is  therefore  most  readily  obtained  from  the  extract  of  meat. 
It  crystallizes  in  prisms,  melting  at  2S°-26°  and  is  extraordina- 
rily hygroscopic.  It  resembles  the  inactive  dl-a.cid  very  closely 
in  its  properties  and  in  its  conduct  towards  reagents,  but  while 
the  fermentation  lactic  acid  is  optically  inactive,  this  lactic 
acid  is  dextr orolzXory .     Its  salts  and  esters  are  levoroidXory . 

3.  Levolactic  acid,  CH3.CHOH.COOH.  — This  second  opti- 
cally active  modification  of  lactic  acid  was  first  obtained  by  fer- 
menting cane  sugar  with  the  levolactic  acid  bacillus.  It  turns  the 
plane  of  polarized  light  to  the  left,  the  same  number  of  degrees 
that  sarcolactic  acid  turns  it  to  the  right,  while  its  salts  and 
esters  are  dextrorotdXory .  Its  other  physical  properties,  such 
as  melting  point,  solubility,  crystal  system,  etc.,  are  the  same 
as  those  of  sarcolactic  acid,  in  accordance  with  the  stereo- 
chemical theory. 

Both  optically  active  forms  have  been  obtained  from  the 
inactive  liWactic  acid  by  the  use  of  the  proper  microorganisms, 
one  organism  destroying  one  form  and  another  organism  the 
opposite  variety.  Another  method  that  has  been  used  for 
this  purpose  is  fractional  crystallization  of  the  strychnine  salt 
of  the  inactive  ii?-acid.  Strychnine  is  a  levorotatory  base, 
hence  there  are  two  salts  ((f-acid-/-base  and  ^acid-^base) . 
These  two  salts  are  not  mirror  images  and  have  different  solu- 
bilities. The  strychnine  salt  of  the  levo  acid  (Z-acid-Z-base)  is 
less   soluble    and  crystallizes  out  first.     By  precipitating  the 


1 86  DERIVATI\^ES  OF  THE  PARAFFINS 

strychnine  with  ammonia  the  ammonium  salts  of  the  active  acids 
are  obtained  from  the  strychnine  salts. 

The  lactic  acids  are  very  much  stronger  acids  than  propionic 
acid  and  much  stronger  than  hydracrylic  acid. 

4.  Hydracrylic  acid,  j3-hydroxypropionic  acid,  propanol-3-acid, 
CH2OHCH2CO2H.  —  Hydracrylic  acid  is  made  by  boiUng  /3-iodo- 
propionic  acid  with  water  or  silver  oxide  and  water :  — 

CH2I  CH2.OH 

I  +  HOH  =1  +  HI. 

CH2.CO2H  CH2.CO2H 

CH2 

It  is  made  also  by  starting  with  ethylene,  |1     .     When  this 

CH2 
is  treated  with  hypochlorous  acid,  HOCl,  it  is  converted  into 

CH2CI 
ethylene  chlorhydrin,  ]  (152).     By  substituting  cyanogen 

CH2OH 

CH2CN 
for   chlorine   and   boiling  the  cyanhydrin,    |  ,  thus  ob- 

CH2OH 
tained  with  an  alkali,  hydracrylic  acid  is  obtained. 

These  reactions  clearly  show  that  hydracrylic  acid  is  an 
ethylene  compound,  and  as  it  is  made  from  /S-iodopropionic 
acid  by  replacing  the  iodine  with  hydroxyl,  it  follows  further 
that  the  /3-substitution  products  of  propionic  acid  are  ethylene 
compounds,  and  that  the  a-products  are  ethylidene  compounds 
(145).  When  oxidized,  hydracrylic  acid  gives  malonic  acid, 
CH2(COOH)2.  This  proves  the  presence  of  the  primary  alcohol 
group.     With  hydriodic  acid  it  gives  /3-iodopropionic  acid. 

Hydracrylic  acid  is  a  syrup.  Its  salts  differ  markedly  from 
those  of  the  inactive  and  active  lactic  acids.  When  heated,  it 
loses  water  and  is  transformed  into  acrylic  acid,  CH2 :  CH.CO2H 
(286) ;  and  acrylic  acid  when  heated  with  a  solution  of  sodium 
hydroxide  gives  sodium  hydracrylate :  — 

CH2:  CHCOOH  +  NaOH  =  CHjOHCHjCOONa. 

The  difference  in  conduct  between  ethylidenelactic  acid  and 
hydracrylic  acid,  when  heated,  is  interesting  and  suggestive. 


LACTONES  187 

When  ethylidenelactic  acid  is  heated  it  gives  lactide.  Both  the 
alcohoUc  and  acid  hydroxyls  take  part  in  the  reaction.  Whereas, 
when  ethylenelactic  acid  is  heated,  only  the  alcoholic  properties 
are  destroyed,  the  carboxyl  remaining  intact. 

Hydroxysulphonic  acids.  —  It  has  been  pointed  out  that 
the  sulphonic  acids  and  the  carboxylic  acids  are  analogous; 
that,  for  example,  methylsulphonic  acid,  CH3.SO3H,  is  analogous 
to  methylcarboxylic  or  acetic  acid,  CH3.CO2H.  Now,  just  as 
the  hydroxy  acids  already  treated  of  are  derived  from  the 
carboxylic  acids  by  the  introduction  of  hydroxyl,  so  there  are 
hydroxy  acids  derived  in  a  similar  way  frorh  the  sulphonic 
acids.    Only  one  such  acid  is  well  known.     It  is  — 

H2COH 

Isethionic  acid,  ethane-2-ol-l-sulphoiiic  acid,       |  ,  also 

H2CSO2OH 
called  fi-hydroxyethylsulphonic  acid.     It  is  analogous  to  hydra- 
crylic  acid.     It  is  prepared  by  passing  sulphur  trioxide  into 
well-cooled  alcohol  or  ether  and  boiling  the  product  with  water ; 
and  also  by  treating  taurine  (264)  with  nitrous  acid :  — 

CH2.NH2  CH2OH 

I  +  HNO2  =1  +  H2O  +  N2. 

CH2.SO3H  CH2.SO3H 

When     oxidized     isethionic     acid     gives     sulphoacetic    acid, 

COOTT 
H2C<__  „  .    This  proves  its  structure.     It  is  isomeric  with 

ethylsulphuric  acid,  C2H6HSO4,  and  is  distinguished  from  this 
by  the  fact  that  the  sulphonic  acid  group  is  not  removed  by 
boiling  with  water. 

Note  for  Student.  —  What  is  formed  when  ethylsulphuric  acid  is 
boiled  with  water? 

Lactones 

The  monohydroxy  monobasic  acids  of  the  paraflSn  series  are 
designated  as  a-,  j3-,  y-,  S-,  etc.,  hydroxy  acids,  according  to  the 
position  of  the  hydroxyl  with  reference  to  the  carboxyl.  When 
the  hydroxyl  is  united  with  the  carbon  atom  with  which  the  car- 
boxyl is  united,  the  product  is  called  an  a-hydroxy  acid.     When 


l88  DERIVATI\'ES   OF  THE  PARAFFINS 

the  hydroxyl  is  united  with  the  next  carbon  atom  in  the  chain, 
the  product  is  called  a  /3-hydroxy  acid,  etc.  The  following 
examples  will  make  this  clear :  — 

Acids  of  the  formulas 
CH2(OH).C02H;  CH3.CH(OH).C02H; 

CH3.CH2.CH(OH).C02H  are  a-hydroxy  acids. 

Acids  of  the  formulas 

CH2(OH).CH2.C02H;  CH3.CH(OH).CH2.C02H; 
CH3.CHo.CH(OH).CH2.C02H  are  /3-hydroxy  acids. 

Acids  of  the  formulas 

CH2(OH).CH2.CH2.C02H  and  CH3CHOHCH2CH2CO2H, 

are  y-hydroxy  acids. 

Similarly,  an  acid  of  the  formula 
CH2(OH).CH2.CH2.CH2.C02H  is  called  a  S-hydroxy  acid. 

The  y-  and  S-acids  differ  from  the  others  in  this  respect  that 
they  lose  the  elements  of  water  when  set  free  from  their  salts. 
Thus,  when  a  salt  of  y-hydroxybutyric  acid  in  solution  is 
treated  with  a  mineral  acid,  a  neutral  compound  is  precipitated 
and  not  the  acid  corresponding  to  the  salt.  The  compound 
thus  formed  is  called  a  lactone.  The  reaction  between  sodium 
y-hydroxybutyrate  and  hydrochloric  acid  is  represented  by  the 
following  equation :  — 

CH2(OH).CH2.CH2.C02Na  +  HCl 

=  CH2.CH2.CH2.CO  +  NaCl  +  H2O. 

I o 1 

The  change  from  the  free  acid  to  the  lactone  may  be  repre- 
sented thus :  — 

CH2.CH2(OH)       CH2.CH2V 

I  =1  >0  +  H2O. 

CHo.CO.OH  CH2.CO  ^ 

The  reaction  is  similar  to  that  which  takes  place  when  suc- 
cinic acid  is  heated :  — 


GLYCERIC  ACID  1 89 

CH2.CO.OH       CH2.C0\ 


>0  +  H2O. 
CH2.CO.OH      CH2.CO-' 

The  product  in  this  case  is  an  anhydride.  The  lactones  may 
be  defined  as  anhydrides  of  hydroxy  acids  or  better  as  inner 
esters.  They  are  neutral,  but  they  form  salts  of  the  corre- 
sponding hydroxy  acids  when  they  are  boiled  for  some  time 
with  bases  in  solution  (saponification  of  the  inner  ester). 

The  ease  with  which  five-  or  iix-membered  rings  are  formed  is 
a  characteristic  property  of  carbon  compounds.'  It  is  due  to 
the  tetrahedral  arrangement  of  the  atoms  around  the  carbon 
atoms. 

Hydroxy  Acids,  C„H2„04 

The  acids  just  treated  of  are  mono  hydroxy  monobasic  acids. 
Similarly,  there  are  dikydroxy  monobasic  acids,  which  are  de- 
rived from  the  monohydroxy  acids  by  the  introduction  of  a 
second  hydroxyl.  Thus,  if  into  lactic  acid,  CH3CHOHCO2H, 
a  hydroxyl  should  be  introduced  into  the  methyl,  the  product 
would  have  the  formula  CH2OHCHOHCO2H.  This  is  the 
best  known  dihydroxy  monobasic  acid  of  the  paraffin  series. 

CH2OH 

I 
Glyceric    acid,    propane-diol-2,3-acid,    C3H8O4,   CHOH  . — 

I 
CO2H 

This  acid  has  been  referred  to  as  the  first  product  of  the  oxida- 
tion of  glycerol.  It  is  prepared  by  allowing  glycerol  and  fum- 
ing nitric  acid  to  stand  together  at  ordinary  temperature  for 
some  time,  and  then  evaporating  on  the  water  bath.  It  can 
also  be  made  by  treating  (3-chlorolactic  acid  (made  by  the 
oxidation  of  monochlorohydrin)  with  water.  It  is  optically 
inactive. 

Both  optically  active  varieties  of  glyceric  acid  have  been 
obtained  from  the  inactive  variety  by  the  methods  used  to 

1  See  Stereochemistry,  by  A.  W.  Stewart,  for  the  explanation  of  this 
remarkable  property  of  the  carbon  atoms. 


I  go 


DERIVATIVES  OF  THE   PARAFFFNS 


resolve  inactive  lactic  acid  into  d-  and  Mactic  acids.     It  will 
be  seen  that  the  acid  contains  an  asymmetric  carbon  atom. 

Glyceric  acid  is  a  thick  syrup  that  mixes  with  water  and 
alcohol,  but  is  insoluble  in  ether.     When  treated  with  concen- 
trated  hydriodic  acid  and  phosphorus,   it  is   converted  into 
P-iodopropionic  acid.    This  conversion  involves  two  reactions :  — 
CH2OH  CH2I 


(i) 


CHOH  +  HI     =  CHOH  +  HjO, 
CO2H 

CH2I 


CO2H 

^-lodolactic  acid 

CH2I 


(2) 


CHOH  +  2  HI  =  CH2  +  H2O  +  2  I. 


CO2H  CO2H 

^-lodopropionic  acid  (3-iodopropane  acid)  melts  at  82°,  is 
readily  soluble  in  hot  water,  but  difficultly  soluble  in  cold  water. 
It  is  frequently  used  in  organic  syntheses. 

Other  Hydroxy  Monobasic  Acids 

Just  as  a  dihydroxy  monobasic  acid  is  formed  by  oxidation  of 
the  triacid  alcohol,  glycerol,  so  by  oxidation  of  the  tetracid 
alcohols,  erythritols,  trihydroxy  monobasic  acids  are  formed. 
These  are  the  erythronic  and  threonic  acids.  Their  relation  to 
the  erythritols  is  like  that  of  the  glyceric  acids  to  glycerol :  — 

CH2OH  CH2OH  CH2OH  CH2OH 


CHOH 
CH2OH 

Glycere 


CHOH 
CO2H 

Glyceric  acids 


CHOH 
CHOH 
CH2OH 

Erythritols 


CHOH 
CHOH 
CO2H 

Erythronic  acids 
Threonic  acids 


d-  and  /-Erythronic  acids  and  the  inactive  dl-iorra  and  d-  and 
/-  and  (fZ-threonic  acids  are  known.  The  formula  contains  two 
asymmetric  carbon  atoms,  and  four  stereoisomers  are  possible. 


GLUCONIC  ACIDS 


191 


Similarly,  corresponding  to  the  pentacid  alcohols,  adonitol,  arabitol, 
and  xylitol,  stereoisomeric  tetrahydroxy  monobasic  acids  having  the 
same  structural  formula,  H2COH.(HCOH)3.COOH,  are  known.  As 
these  acids  contain  three  asymmetric  carbon  atoms,  eight  optically 
active  stereoisomers  (four  d-  and  four  /-  forms)  and  four  optically 
inactive  dl-ioims  are  theoretically  possible.  They  are  known  as 
arabonic,  ribonic,  xylonic,  and  lyxonic  acids  from  the  fact  that  they 
are  made  by  the  oxidation  of  the  sugars  (pentoses),  arabinose,  ribose, 
xylose,  and  lyxose.  Dextro-,  levo-,  and  inactive  (dl)  forms  of  all  these 
acids  are  known. 

Pentahydroxy  monobasic  acids  are  also  known  and  are  of  special 
importance  on  account  of  their  connection  with  the  most  important 
sugars,  the  hexoses.  They  are  made  from  the  aldopentoses  by  the 
cyanhydrin  reaction  and  from  the  aldohexoses  by  oxidation. 

Mannonic  acids,  C6Hi207[C6H6(OH)5C02H]. —Three  acids 
are  included  in  this  group.  They  are  the  dextro,  the  levo,  and 
the  inactive  (dl)  varieties,  or  d-mannonic,  l-mannonic,  dl-man- 
nonic  acids.  They  are  related  to  the  three  mannitols  and  the 
three  mannoses.  As  will  be  shown  farther  on,  the  mannoses 
are  pentahydroxy  aldehydes,  and  the  relations  here  referred  to 
are  represented  by  the  following  formulas :  — 

CH2OH  CH2OH  CH2OH 


CHOH 


CHOH 


CHOH 


CHOH 


CHOH 


CHOH 


CHOH 


CHOH 


CHOH 


CHOH 


CHOH 


CHOH 


CH2OH 

Maanitols 


CHO 

Mannoses 


CO2H 

Mannonic  acids 


The  difference  between  the  three  mannonic  acids  is  of  the 
same  kind  as  that  between  the  three  lactic  acids.  The  dextro 
and  levo  varieties  are  optical  antipodes,  while  the  inactive 
form  is  a  combination  of  the  dextro  and  levo  varieties. 

Gluconic  acids,  C6Hi207[C5H6(OH)5C02H].  —  The  three  glu- 
conic acids  are  related  to  the  three  glucoses  in  the  same  way 
that  the  mannonic  acids  are  related  to  the  mannoses.     Dextro- 


192  DERIVATIVES   OF   THE   PARAFFINS 

gluconic  acid  is  formed  by  the  oxidation  of  (f-glucose  and  of  cane 
sugar.  When  heated  with  quinoline  to  140°,  it  is  partly  con- 
verted into  i-mannonic  acid.  Similarly  d-mannonic  acid  is 
partly  converted  into  (i-gluconic  acid  by  the  same  process. 
Three  gulonic  acids,  three  galactonic  acids,  and  idonic  and 
talonic  acids  of  the  same  composition  and  structure  as  the 
mannonic  and  the  gluconic  acids  are  also  known. 
The  existence  of  so  many  acids  of  the  formula 

CH2OH.CHOH.  CHOH.CHOH.CHOH.  CO2H 

is  due  to  the  fact  that  it  contains  four  asymmetric  carbon 
atoms  and  the  groups  at  the  end  of  the  chain  are  different.  The 
total  number  of  isomers  possible,  according  to  the  stereochemi- 
cal theory  is  twenty-four  —  eight  dextro  and  eight  levo,  besides 
eight  racemic  (dl)  forms. 

Hydroxy  Acids,  C„H2n_205 

The  acids  included  under  this  head  are  monohydroxy  dibasic 
acids.  They  bear  the  same  relation  to  the  dibasic  acids  of  the 
oxalic  acid  series  that  the  simplest  hydroxy  acids  bear  to  the 
members  of  the  formic  acid  series.  The  principal  members  of 
this  series,  and  the  only  ones  that  will  be  treated  of,  are  tartronic 
acid  and  the  malic  acids. 

Tartronic  acid,  propanol  diacid, 

C3H405-hiH20,  CH(OH)<^^'^- 

—  This  acid  was  first  obtained  from  tartaric  acid  and  hence 
the  name.     It  can  be  made :  — 

(i)  By  boiling  bromomalonic  acid  with  silver  oxide  and 
water :  — 

(2)  By  heating  bromocyanacetic  acid  with  a  solution  of 
caustic  potash :  — 

CHBr<^^^H  +  f  KOH  =  ^^^OHXcoS  +  ^«^  +  ^^^ 


MALIC   ACID  193 

The  bromocyanacetic  acid  is  made  by  heating  dibromo- 
acetic  acid  with  an  alcohohc  solution  of  potassium  cyanide. 

Tartronic  acid  crystallizes  in  prisms  with  a  half  molecule  of 
water  of  crystallization.  It  is  easily  soluble  in  water,  alcohol, 
and  ether.  The  anhydrous  acid  melts  at  185-187°  with  evolu- 
tion of  carbon  dioxide  and  water,  and  forms  glycolide  (181) :  — 

Glycolic  acid 

PITT  CH2— 0— CO 

(2)         2  CH2<J:^„„  =1  1+2  H^O. 

LOOM       co_0— CH2 

Glycolide 

Note  for  Student.  —  Compare  reaction  (i)  with  that  which  takes 
place  when  isosuccinic  acid  is  heated. 

Tartronic  acid  is  also  formed  by  the  oxidation  of  glycerol 
and  by  the  reduction  of  mesoxalic  acid.  On  oxidation  it  gives 
mesoxalic  acid,  0C(C00H)2,  a  proof  of  the  presence  of  the 
secondary  alcohol  group. 

Hydroxysuccinic  acids,  HOOC.CHOH.CH2.COOH.  — There 
is  only  one  monohydroxy  succinic  acid  possible  structurally, 
but,  as  will  be  seen  from  the  above  formula,  it  contains  an 
asymmetric  carbon  atom  and  dextro-,  levo-,  and  inactive  {dl) 
forms  are  possible  and  all  are  known.  They  are  called  malic 
acids  {malum,  apple). 

CH(OH).C02H 
Z-Malic  acid,  C4H6O6,  |  .  —  This  acid  is  very 

CH2.CO2H 

widely  distributed  in  the  vegetable  kingdom,  as  in  the  unripe 
berries  of  the  mountain  ash,  in  apples,  cherries,  etc. 

It  is  present  in  the  sap  of  the  sugar  maple  as  the  neutral  cal- 
cium salt,  and  this  separates,  when  the  sap  is  evaporated  to  a 
syrup,  as  a  granular,  sandy  precipitate.  Hence  it  is  called 
"  sugar  sand."  The  same  insoluble  neutral  calcium  salt  is 
formed  when  the  juice  of  the  berries  of  the  mountain  ash  is 
boiled  with  milk  of  lime.     In  order  to  prepare  malic  acid  from 


194  DERIVATIVES  OF  THE  PARAFFINS 

this  salt,  it  is  first  treated  with  exactly  the  right  amount  of 
oxalic  acid  to  convert  it  into  the  soluble  calcium  acid  malate, 
and  this,  after  filtering  off  the  calcium  oxalate,  is  crystallized 
from  the  solution  and  purified  by  recrystallization.  The  pure 
calcium  acid  malate  is  then  decomposed  in  aqueous  solution 
with  the  exact  amount  of  oxalic  acid  necessary  to  precipitate 
all  the  calcium,  the  solution  filtered  and  evaporated  on  the 
water  bath.  • 

It  can  also  be  made  by  treating  aspartic  acid,  which  is  amino- 
succinic  acid,  HOOC.HzC.CHCNHOCOaH,  with  nitrous  acid, 
and  by  treating  /-tartaric  acid  with  hydriodic  acid. 

Malic  acid  crystallizes  in  needles.  It  melts  at  ioo°.  It  is 
very  easily  soluble  in  water  and  in  alcohol,  but  only  slightly 
soluble  in  ether.  The  dilute  aqueous  solutions  are  feuorotatory. 
A  34  per  cent  solution  is  optically  inactive  at  20°.  More  con- 
centrated solutions  are  dex/rorotatory. 

When  heated,  it  loses  water  and  5delds  fumaric  acid  and 
maleic  anhydride  (290).  Fumaric  and  maleic  acids  are 
stereoisomeric,  and  both  are  represented  by  the  formula 
C2H2(C02H)2.  The  reaction  mentioned  is  represented  by  the 
following  equation :  — 

C2H3(OH)<^°^^    =    C2H2<^qJ^  +  H2O. 

Malic  acid  Fumaric  and 

maleic  acid 

Note  for  Student.  —  Compare  this  reaction  with  that  which  takes 
place  when  hydracrylic  acid  is  heated. 

When  boiled  with  hydriodic  acid,  all  the  malic  acids  are 
reduced  to  succinic  acid. 

Note  for  Student.  —  Compare  this  reaction  with  the  conduct  of 
lactic  and  glyceric  acids  when  treated  with  hydriodic  acid. 

Treated  with  hydrobromic  acid,  malic  acid  is  converted  into 
monobromosuccinic  acid. 

When  oxidized  all  the  malic  acids  give  oxaloacetic  acid 
HOOC.OC.H2CCOOH,  a  proof  of  the  presence  of  the  second- 
ary alcohol  group. 


INACTIVE   MALIC   ACID  IQS 

The  reactions  just  described  show  clearly  that  malic  add  is 
monohydroxysuccinic  acid.  Nevertheless,  if  hydroxysuccinic 
acid  is  made  by  treating  bromosuccinic  acid  with  silver  oxide 
and  water,  the  product  is  not  identical  with  ordinary  malic 
acid,  though  the  two  resemble  each  other  very  closely.  The 
acid  thus  obtained  is 

CO  H 

Inactive  malic  acid,  C2H3(OH)<    ^    .  —  Inactive     malic 

acid  can  be  made  not  only  by  this  method,  but  by  several  others, 
which  show  that  the  relation  between  it  and  succinic  acid 
is  that  expressed  in  the  formula  given.  Like  ordinary  malic 
acid,  it  is  unquestionably  a  monohydroxysuccinic  acid. 

Other  reactions  for  the  preparation  of  inactive  malic  acid 
are:  — 

(i)  By  heating  dichloropropionic  acid  (made  from  acrylic 
acid  (286)  and  chlorine)  with  potassium  cyanide  and  boiling 
the  product  with  a  solution  of  caustic  potash :  — 

CH2CN 
CH2CI.CHCI.CO2H  +  KCN  =1  +  KCl 

CHCI.CO2H 

CH2CN  CH2.CO2K 

I  +  2  KOH  +  H2O  =   I  +  KCl  +  NH3. 

CHCI.CO2H  CH(0H).C02H 

(2)  By  heating  maleic  or  fumaric  acid  with  water  in  a  sealed 
tube : — 

C2H2<^Q^^  +  H2O  =  C2H3(OH)<^°^^;  and 

(3)  By  reducing  racemic  acid  (200)  with  hydriodic  acid. 

By  mixing  equal  quantities  of  the  acid  ammonium  salts  of  the 
d-malic  acid  and  the  Z-malic  acid,  dissolved  in  water,  the  acid 
ammonium  salt  of  the  inactive  malic  acid  crystallizes  out  of  the 
solution. 

The  properties  of  inactive  malic  acid  are  very  much  like 
those  of  the  active  malic  acids.  As  regards  their  chemical 
conduct  they  are  identical.    The  principal  difference  between 


196  DERIVATIVES   OF  THE   PARAFFINS 

them  is  observed  in  their  conduct  towards  polarized  light. 
They  present  another  case  of  stereoisomerism  of  the  same  kind 
as  that  referred  to  in  connection  with  the  stereoisomeric  amyl 
alcohols  (137)  and  the  lactic  acids  (182). 

Dertromalic  acid.  —  Inactive  malic  acid  bears  the  same 
relation  to  two  active  acids  that  inactive  lactic  acid  bears  to  the 
two  active  varieties  of  that  acid.  When  the  cinchonine  salt  of 
inactive  malic  acid  is  subjected  to  fractional  crystallization,  it 
gives  cinchonine  Z-malate  and  cinchonine  rf-malate. 

One  of  these  is  a  salt  of  l-malic  acid,  while  the  other  is  a  salt 
of  the  stereoisomeric  d-malic  acid.  The  latter  is  also  obtained 
by  reducing  d-tartaric  acid  (198)  with  hydriodic  acid. 

Hydroxy  Acids,  C„H2n-206 

These  are  dihydroxy  dibasic  acids.  The  chief  members  of 
the  group  are  mesoxalic  acid  and  the  different  modifications  of 
tartaric  acid. 

Mesoxalic    acid,    C3H4O6,  C(0H)2<__.^„.  — This   acid   is 

obtained  from  alloxan,  a  derivative  of  uric  acid  (267).  It  has 
been  made  also  by  boiling  dibromomalonic  acid  with  baryta 
water  and  by  oxidizing  glycerol  (169). 

Note  for  Student.  —  Explain  these  reactions. 

The  acid  forms  deliquescent  needles.  When  its  aqueous 
solution  is  boiled,  it  loses  carbon  dioxide  and  water,  and  glyoxylic 
acid,  a  half  aldehyde  of  oxalic  acid,  is  formed :  — 

C(0H)2<ph^„    =1  +  CO2  +  H2O. 

LU2H  (3Q^JJ 

Glyoxylic  acid 

When  reduced,  it  gives  tartronic  acid.  Mesoxalic  acid  affords 
an  example  of  a  rare  condition ;  viz. ,  the  existence  of  a  compound 
in  which  two  hydroxyls  are  in  combination  with  the  same  car- 
bon atom.  This  same  condition  exists  in  chloral  hydrate 
(64).     The  acid  readUy  loses  water  and  passes  over  into  the 


DIHYDROXYSUCCINIC   ACIDS 


197 


form  0C(C00H)2.  With  hydroxylamine  it  gives  an  oxime, 
H0N=C(C00H)2,  and  with  phenylhydrazine  a  phenylhydra- 
zone,  thus  showing  the  presence  of  the  ketone  group. 

Dihydroxysuccinic  acids,  HOOOiCHOH.CHOH.COOH. — 
There  are  four  acids  known,  all  of  which  have  this  structural 
formula  and  which  are  stereoisomers.    They  are :  — 

(i)  Dextro-  or  (/-tartaric  acid,  (m.  p.  170°) ; 

(2)  Levo-  or  /-tartaric  acid,  (m.  p.  170°) ; 

(3)  Racemic  acid,  (m.  p.  204°),  which  is  made  up  of  equal 
parts  of  the  d-  and  the  /-tartaric  acids,  and  which  is  hence 
optically  inactive ;  and 

(4)  Mesotartaric  acid,  (m.  p.  140°),  which  is  also  optically 
inactive. 

An  examination  of  the  above  formula  will  show  that  it  con- 
tains two  asymmetric  carbon  atoms  and  that  each  of  these 
asymmetric  carbon  atoms  is  united  to  the  same  groups,  (H), 
(OH),  (COOH),  and  (CHOH.COOH).  There  are  then  three 
possible  arrangements  in  space  of  the  groups  connected  with 
these  two  asymmetric  carbon  atoms  :  — 


HO 


-COOH 


OH 


It  is  customary  to  project  these  space  formulas  on  the  plane 
of  the  paper  and  to  omit  the  asymmetric  carbon  atoms,  thus :  — 


HO- 


COOH 
— H 


H- 


COOH 

Levotartaric  acid 
I 


H- 


COOH 
—OH 


-OH     HO- 


— H 
COOH 


Dextrotartaric  acid 

n 


H- 


COOH 
—OH 


H- 


-OH 


COOH 

Mesotartaric  acid 
UI 


igS  DERIVATI^■ES   OF  THE  PARAFFINS 

I  and  II  contain  no  plane  of  s5mimetry  and  bear  the  image- 
object  relation  to  each  other.  They  therefore  represent  the 
two  optically  active  tartaric  acids,  and  the  combination  of  the 
two  represents  the  inactive  racemic  acid.  Ill  has  one  plane 
of  symmetry,  as  the  upper  half  and  the  lower  half  of  the  molecule 
bear  the  image-object  relation  to  each  other.  This  form  of 
tartaric  acid  should  be  optically  inactive,  for  if  the  upper  half 
of  the  molecule  rotates  the  plane  of  polarized  light  to  the  right, 
the  lower  half  will  rotate  it  the  same  number  of  degrees  to  the 
left.    This  represents  mesotartaric  acid. 

d-Tartaric  acid. — This  acid  occurs  very  widely  distrib- 
uted in  the  vegetable  kingdom,  especially  in  fruits,  sometimes 
in  the  free  state,  but  generally  in  the  form  of  the  acid  potassium 
salt,  as  in  grapes.  It  also  occurs  in  the  berries  of  the  mountain 
ash,  in  sumach  berries,  in  tamarinds,  mulberries,  pineapples, 
etc.,  and  in  potatoes  and  cucumbers.  It  is  prepared  from  argol 
or  crude  "  tartar,"  which  is  an  impure  acid  potassium  tartrate. 
When  the  juice  of  the  grape  is  fermented  in  making  wine,  this 
salt,  which  is  insoluble  in  alcohol,  is  deposited  together  with  the 
yeast,  coloring  matter,  etc.  It  is  heated  with  excess  of  hydro- 
chloric acid,  the  solution  filtered  and  boiled  with  milk  of  lime. 
The  insoluble  calcium  salt  is  heated  with  water  to  remove  sol- 
uble salts  and  decomposed  with  sulphuric  or  oxalic  acid,  and  the 
tartaric  acid  purified  by  crystallization  frojn  water.  The  acid 
crystallizes  from  water  in  transparent,  monoclinic  prisms.  It 
is  readily  soluble  in  water  and  alcohol,  but  is  insoluble  in  ether. 
It  melts  at  1 70°.  Its  solution  turns  the  plane  of  polarized  light  to  the 
right.  It  is  used  in  medicine,  in  dyeing,  and  in  the  manufacture 
of  cream  of  tartar  baking  powders.  Treated  with  hydriodic 
acid,  it  gives  first  (/-malic  acid,  and  then  succinic  acid :  — 

CHOH.COOH        CH2.COOH 
^^)  CHOH.COOH  +  2  HI  =  CHOH.COOH  "^  ^^^  +  ^^- 

Tartaric  acid  *i-Malic  add 

CH2.COOH  CH2.COOH 

^^^      CHOH.COOH  +  2  HI  =  CH2.COOH  +  ^'*^  +  ^2- 

d-Malic  acid  Succinic  acid 


TARTARIC   ACID  199 

From  these  reactions  it  will  be  seen  that  tartaric  acid  is  di- 
hydroxysuccinic  acid,  and  malic  acid  is  monohydroxysuccinic 
acid. 

Tartaric  acid  forms  two  series  of  salts.  The  neutral  alkali 
salts  are  readily  soluble,  the  neutral  salts  of  the  other  metals 
are  difficultly  soluble  or  insoluble  in  water. 

Acid  potassium  tartrate,  KOOC.CHOH.CHOH.COOH,  is  diffi- 
cultly soluble  in  water  and  is  used  as  a  test  for  tartaric  acid. 
It  is  the  chief  constituent  of  argol  or  crude  "  tartar.''  In  the 
pure  form,  as  used  in  medicine  and  in  baking  powders,  it  is 
known  as  "  cream  of  tartar.''  Cream  of  tartar  baking  powders 
are  mixtures  of  cream  of  tartar  and  sodium  bicarbonate  with 
some  starch  or  flour.  With  water,  in  the  dough,  the  following 
reaction  takes  place  :  — 

CHOH.COOK  CHOH.COOK 

I  +  NaHCOs  =1  +  CO2  +  H2O, 

CHOH.COOK  CHOH.COONa 

Cream  of  tartar  Rochelle  salt 

and  the  carbon  dioxide  liberated  raises  the  dough. 

Sodium  potassium  tartrate,  KOOC.CHOH.CHOH.COONa,  + 
4  H2O.  —  This  salt  is  characterized  by  its  remarkable  power  of 
crystallization.  It  is  known  as  Rochelle  salt  or  Seignette  salt 
and  is  much  used  as  a  laxative. 

Seidlitz  powders  consist  of  (i)  a  mixture  of  Rochelle  salt  and 
sodium  bicarbonate  in  the  blue  paper  and  (2)  tartaric  acid  in 
the  white  paper.  These  are  dissolved  in  water  separately  and 
the  solutions  brought  together,  when  a  rapid  evolution  of  carbon 
dioxide  takes  place,  making  the  dose  less  unpleasant  to  take. 
Isomorphous  with  Rochelle  salt  is 

Sodium  ammonium  tartrate,  NaOOC.CHOH.CHOH.COONH4 
+  4  H2O,  obtained  in  the  separation  of  racemic  acid  into  the 
d-  and  Z-tartaric  acids  (201). 

CHOH.COOv 

Calcium  tartrate,  |  /Ca  +  4  H2O,  occurs  in  grapes 

choh.coq/ 

and  in  senna  leaves.     It  is  almost  insoluble  in  water  and  is 
precipitated  in  crystalline  form  when  a  solution  of  calcium  chlo- 


200  DERIVATIVES  OF  THE  PARAFFINS 

ride  is  added  to  that  of  a  neutral  tartrate.     This  reaction  is 
used  for  the  detection  of  tartaric  add. 

CHOH.COOK 
Potassium  antimonyl  tartrate,    \  +  ^  H2O. — 

CHOH.COO.SbO 
This  salt  is  known  as  tartar  emetic.  It  is  prepared  by  dissolving 
four  parts  of  antimony  oxide  and  five  parts  of  cream  of  tartar 
in  50  parts  of  water  and  allowing  the  solution  to  stand.  It 
crystallizes  in  rhombic  octahedra.  It  loses  its  water  of  crys- 
tallization partly  in  the  air  and  is  anhydrous  at  100°.  When  the 
anhydrous  salt  is  heated  to  i6o°-i65°,  it  loses  a  molecule  of  water 
and  is  converted  into  potassium  antimony  tartrate,  KSbC4H206, 
which  gives  tartar  emetic  when  dissolved  in  water.  Tartar 
emetic  is  extensively  used  as  a  mordant  in  dyeing  and  in 
medicine. 

In  the  presence  of  Rochelle  salt,  sodium  hydroxide  does  not 
precipitate  copper  hydroxide  from  a  solution  of  copper  sulphate. 
This  is  due  to  the  formation  of  a  complex  soluble  salt  in  which 
the  copper  replaces  the  two  hydrogen  atoms  of  the  two  hydroxyl 
groups : — 

/O— CH.COOK 
Cu<         I 

\0— CH.COONa 

It  is  probable  that  a  similar  salt  is  present  in  Fehling's  solution 
(223). 

Racemic  acid,  d-C4H606  +  i-C4H606+2H20.  —  This  acid  oc- 
curs together  with  d- tartaric  acid  in  grapes  and  is  obtained  in  the 
purification  of  the  crude  tartar  by  recrystallization.  The  acid 
potassium  racemate  being  more  soluble  than  the  acid  potassium 
tartrate  remains  in  the  mother  liquors.  (^-Tartaric  acid  when 
heated  with  water  in  a  sealed  tube  to  i6o°-i65°  is  converted 
into  racemic  acid  and  mesotartaric  acid.  By  heating  100  grams 
of  d- tartaric  acid  with  700  grams  of  water  containing  350  grams 
of  sodium  hydroxide  for  two  hours,  50  grams  of  racemic  acid 
and  30  grams  of  mesotartaric  acid  are  obtained.  When  equal 
quantities  of  (i-tar-taric  and  Z-tartaric  acids,  in  concentrated 
aqueous  solutions,  are  brought  together,  elevation  of  the  tem- 


RACEMIC  ACID  201 

perature  takes  place,  and  racemic  acid  crystallizes  out  of  the 
solution. 

Racemic  acid  differs  from  the  d-  and  the  /-tartaric  acids 
in  being  optically  inactive.  It  crystallizes  in  triclinic  prisms 
which  contain  2  molecules  of  water  of  crystallization,  whereas, 
the  two  active  acids  crystallize  in  monoclinic  prisms  without 
water  of  crystallization.  Racemic  acid  loses  its  water  of  crys- 
tallization at  110°  and  then  melts  at  204°,  with  decomposition. 
In  water,  it  is  much  less  soluble  than  tartaric  acid.  Calcium 
racemate,  2  CaC4H40f)+8  H2O,  is  much  less  soluble  in  water 
than  calcium  tartrate,  and  hence  a  solution  of  racemic  acid 
gives  a  precipitate  with  a  solution  of  calcium  sulphate,  while  a 
solution  of  tartaric  acid  does  not. 

Racemic  acid  is  formed  together  with  mesotartaric  acid  when 
the  silver  salt  of  dihromo succinic  acid  is  boiled  with  water :  — 

HCBrCOOAg  HCOHCOOH 

I  +  2  H2O  =       I  +2  AgBr. 

HCBrCOOAg  HCOHCOOH 

Silver  salt  of  Racemic  acid  and 

dibromosuccinic  acid  mesotartaric  acid 

Racemic  acid  is  also  formed  when  fumaric  acid  (294)  is 
oxidized  with  a  dilute  solution  of  potassium  permanganate :  — 

HCCOOH  HCOHCOOH 

II  +H20  +  0=      I 

HCCOOH  HCOHCOOH 

Fumaric  acid  Racemic  acid 

There  are  three  methods  by  which  racemic  acid  can  be  sepa- 
rated into  the  optically  active  tartaric  acids,  all  of  which  we  owe 
to  Pasteur. 

I.  When  sodium  ammonium  racemate  is  allowed  to  crystal- 
lize out  of  its  solution,  below  27",  it  splits  up  into  sodium  ammo- 
nium rf-tartrate  and  sodium  ammonium  Z-tartrate.  Since  these 
two  salts  crystallize  in  forms  on  which  right-handed  and  left- 
handed  hemihedral  faces  are  present,  so  that  the  two  crystals 
bear  the  image-object  relation,  it  is  possible  to  separate  them 
from  each  other  mechanically.  The  acids  obtained  from  the 
two  sets  of  crystals  are  (^-tartaric  and  Z-tartaric  acids. 


202  DERIVATIVES   OF  THE   PARAFFINS 

2.  The  second  method  consists  in  combining  racemic  acid  with 
an  optically  active  base,  e.g.  Z-cinchonine.  Two  salts  are  formed 
(i)  dZ-acid-Z-base  and  (2)  Z-acid-Z-base.  As  these  two  salts  do 
not  bear  the  image-object  relation  to  each  other,  they  have 
different  solubilities  and  can  be  separated  by  fractional  crys- 
tallization. 

3.  The  third  method  depends  on  the  action  of  microorgan- 
isms. For  example,  penicillium  glaucum,  when  grown  in  a 
solution  of  ammonium  racemate,  uses  up  the  (f-tartaric  acid  more 
rapidly  than  the  Z-tartaric  acid,  so  that  the  solution  becomes 
levorotatory. 

Levotartaric  acid,  HOOC.CHOH.CHOH.COOH,  has  been 
obtained  from  racemic  acid  by  the  methods  given  above.  It 
has  the  same  melting  point,  the  same  solubilities,  and  in  general 
the  same  physical  and  chemical  properties  as  the  dextroacid. 
It  turns  the  plane  of  polarized  light  the  same  number  of  degrees 
to  the  lejt  that  the  dextroacid  turns  it  to  the  right.  It  has 
also  been  made  by  the  oxidation  of  ?-erythritol  (173)  and 
Z-threose  (216). 

Mesotartaric  acid,  HOOC.CHOH.CHOH.COOH  -|-  H2O.  — 
Like  racemic  acid  this  acid  is  optically  inactive,  but  unlike  race- 
mic acid  it  cannot  be  separated  into  optically  active  compo- 
nents. It  is  said  to  be  optically  inactive  by  internal  compen- 
sation, while  racemic  acid  is  optically  inactive  by  external 
compensation.  (See  space  formulas,  197.)  It  is  obtained  to- 
gether with  racemic  acid  by  heating  tartaric  acid  with  water 
in  a  sealed  tube  to  i6o°-i65°  or  with  a  solution  of  caustic  soda. 
It  results  also  by  the  oxidation  of  natural  erythritol  (which  is 
the  internally  compensated  form  of  erythritol)  and  of  phenol. 
It  is  formed  when  maleic  acid  (294)  is  oxidized  with  a  dilute 
solution  of  potassium  permanganate :  — 

H— C— COOH  HCOH— COOH 

II  +H20  +  0=       I 

H— C— COOH  HCOH— COOH 

Maleic  acid  Mesotartaric  acid 

Mesotartaric  acid  crystallizes  in  rectangular  plates,  having  the 
composition  C4H6O6  +  H2O,  and  it  also  resembles  racemic  acid 


CITRIC  ACID,  HYDROXYTRICARBALLYLIC   ACID      203 

very  closely  in  its  chemical  and  physical  properties.  The  de- 
hydrated acid  melts  at  140°,  and  it  differs  also  from  the  active 
tartaric  acids  and  from  racemic  acid  in  solubility  and  other 
physical  properties.  It  differs  most  markedly  from  its  stereo- 
isomers in  that  its  acid  potassium  salt  is  readily  soluble  in  water. 
It  is  not  precipitated  from  its  solution  by  a  solution  of  calcium 
sulphate  (distinction  from  racemic  acid). 

Hydroxy  Acids,  C„H2n-407 

These  are  monohydroxytribasic  adds.  Citric  acid  is  the  only 
one  of  importance. 

Citric  acid,  hydroxytricarballylic  acid, 

fCOsH 
CeHgO,  +  H2O,  CsHiCOH)^  CO2H.  — 

ICO2H 

Citric  acid,  like  malic  and  tartaric  acids,  is  widely  distributed 
in  nature  in  many  varieties  of  fruit,  especially  in  lemons  and 
in  grapefruit,  in  which  it  occurs  in  the  free  condition.  It  is 
found  in  currants,  whortleberries,  raspberries,  gooseberries,  etc., 
and  in  milk. 

It  is  prepared  from  lemon  juice,  and  also  by  the  fermenta- 
tion of  glucose  by  citromyces  pfeferianus  and  a  few  other  mould 
fungi.  After  boiling  and  filtering  the  solution  it  is  boiled  with 
milk  of  lime.  The  calcium  salt  thus  obtained  in  the  form  of  a 
precipitate  is  collected,  and  decomposed  with  the  calculated 
quantity  of  sulphuric  acid.  One  hundred  parts  of  lemons  yield 
5^  parts  of  the  acid. 

Citric  acid  crystallizes  with  a  molecule  of  water  of  crystalli- 
zation in  rhombic  prisms  which  are  very  easily  soluble  in  water 
and  alcohol.  The  crystallized  acid  melts  at  about  100°,  the 
anhydrous  at  153°.  Heated  to  175°,  it  loses  water  and  yields 
aconitic  acid  (295) :  — 

C3H4(OH)(C02H)3    =   C3H3(C02H)3   +  H2O. 
Aconitic  acid 

Aconitic  acid  takes  up  hydrogen,  and  is  transformed  into 
tricarballylic   acid   (173).     Thus  a   clear  connection  between 


204  DERIVATIVES  OF  THE  PAR.\FFINS 

tricarballylic  acid  and  citric  acid  is  traced;  the  latter  is 
hydroxytricarballylic  acid.  Citric  acid  can  be  made  from 
dichlorohydrin  by  first  converting  this  into  dichloroacetone  by 
oxidation :  — 

CH2CI  H2CCI 

CHOH  — >-  CO. 

CH2CI  H2CCI 

The  dichloroacetone  is  combined  with  hydrocyanic  acid  to  form 
the  cyanhydrin,  and  this  is  hydrolyzed  to  the  corresponding 

H.CCl  HoCCl 

'1  I 

acid :  —  HO— C— CN  — >- HO— C— COOH.     The  potassium 

I  I 

H2CCI  H2CCI 

salt  of  this  acid  is  then  heated  with  a  concentrated  solution 
of  potassium  cyanide,  and  the  product  hydrolyzed  to  citric 

H2CCN  H2C.COOH 

acid :—  HOC— COOK  — >■  HOC.COOH.     (Write  out  aU  the 

I  I 

H2CCN  H2C.COOH 

equations.) 

This  synthesis  shows  that  the  hydroxyl  in  citric  acid  is  in 
combination  with  the  central  carbon  atom. 

When  rapidly  heated  to  a  temperature  above  175°,  citric  acid 
first  gives  aconitic  acid.  This  loses  water  and  carbon  dioxide 
and  gives  itaconic  anhydride  (295).  This  anhydride  is  then 
partly  converted  into  citraconic  anhydride  (295)  by  the  action 
of  heat. 

Citric  acid  is  used  in  calico  printing,  in  medicine,  in  the  manu- 
facture of  lemonade  and  other  drinks  and  as  a  corrective  against 
scurvy.  It  is  also  used  in  analytical  chemistry  and,  in  the  form 
of  ferric  ammonium  citrate,  in  the  manufacture  of  blue  print 
paper. 

Citrates.  —  A  few  of  the  salts  of  citric  acid  are :  — 


TETRAHYDROXYADIPIC   ACIDS  205 

Monopotassium  citrate,  KH2.C6H6O7  +  2  H2O ; 

Dipotassium  citrate,  K2H.C6H5O7; 

Tripotassium  citrate,  K3.C6H5O7  +  H2O.  All  these  potas- 
sium salts  are  easily  soluble  in  water. 

Calcium  citrate,  Ca3(C6H607)2  +  4  H2O.  —  This  salt  is  formed 
by  boiling  a  solution  of  a  citrate  of  an  alkali  metal  and  calcium 
chloride.  It  is  more  easily  soluble  in  cold  than  in  hot  water ; 
hence  boiling  causes  a  precipitate  in  dilute  solutions. 

Magnesium  citrate,  Mg3(C6H607)2  +  14  H2O.  —  This  is  made 
by  dissolving  magnesia  in  a  solution  of  citric  acid.  It  is  used 
as  a  laxative. 

Trihydroxyglutaric  acids,  HOOC.(CHOH)8.COOH.  — These  stereo- 
isomeric  acids  are  important  as  oxidation  products  of  the  pentoses, 
CHO.(CHOH)8CH20H.  They  are  also  formed  by  the  oxidation  of 
the  pentacid  alcohols,  adonitol,  arabitol,  and  xylitol,  and  of  the 
monobasic  acids  arabonic,  ribonic,  xylonic,  and  lyxonic  acids  (191). 
Ribotrihydroxyglutaric  acid  obtained  by  the  oxidation  of  ribose  and 
ribonic  acid  and  xylotrihydroxyglutaric  acid  by  the  oxidation  of  xylose 
and  xylonic  acid  are  optically  inactive  by  intramolecular  compensation. 
d-  and  i-Trihydroxyglutaric  acids  and  the  racemic  modification  {dl-iorm) 
are  also  known.  Thus  all  five  of  the  acids  predicted  by  the  theory  are 
known.  All  these  stereoisomers  are  reduced  to  glutaric  acid  by  heating 
with  hydriodic  acid  ;  — 

C3H3(OH)8(COOH)2  +  6  HI  =  C3He(COOH)2  +  3  H2O  +  6  1. 

Trihydroxyglutaric  acids  Glutaric  acid 

This  proves  the  presence  of  the  normal  carbon  chain  in  all  these 
acids,  and  that  the  isomerism  is  due  to  the  asymmetric  carbon 
atoms. 

Tetrahydroxyadipic  acids,  HOOC.(CHOH)4.COOH.  —These 
stereoisomeric  acids  result  from  the  oxidation  of  the  hexoses, 
CHO.(CHOH)4.CH20H,  or  of  the  hexacid  alcohols  mannitol, 
dulcitol,  and  sorbitol.  They  are  also  formed  by  the  oxida- 
tion of  the  hexonic  acids,  HOOC.(CHOH)4.CH20H  (191). 
Saccharic  acid,  first  obtained  by  the  oxidation  of  cane  sugar 
(saccharose)  with  nitric  acid,  is  known  in  a  dextro-,  levo-,  and 
racemic  {dl-)  form.  It  results  from  the  oxidation  of  sorbitol, 
glucose,  gulose,  gluconic  and  gulonic  acids.     M  anno  saccharic 


2o6  DERI\'ATI\ES   OF  THE   PARAFFINS 

acid,  also  known  in  the  d-,  1-,  and  dl-iorms,  is  obtained  by  oxi- 
dation of  the  mannitols,  mannoses,  and  the  mannonic  acids. 
Idosaccharic  acid,  another  stereoisomer,  results  from  the  oxida- 
tion of  idonic  acid.  Miicic  acid,  first  obtained  by  the  oxidation 
of  milk  sugar  with  nitric  acid,  is  formed  by  the  oxidation  of 
dulcitol,  the  galactoses,  and  the  galactonic  acids.  It  is  optically 
inactive  by  intramolecular  compensation.  When  heated  with 
pyridine  to  140°,  mucic  acid  is  partially  converted  into  aUomucic 
acid,  which  is  also  optically  inactive  by  intramolecular  compen- 
sation. Talomncic  acid,  the  oxidation  product  of  the  taloses 
and  talonic  acids,  is  optically  active,  and  d-,  1-,  and  dl-iorms  of 
it  are  known.  Theoretically  there  should  be  8  active  (4  d-  and 
4  Z-),  2  inactive,  and  4  racemic  {dl-)  forms  of  these  acids.  They 
are  all  reduced  to  adipic  acid  by  heating  with  hydriodic  acid :  — 

C4H4(OH)4(COOH)2  -t-  8  HI  =  C4Hs(COOH)2  -|-  4  H2O  -|-  8  I. 

Saccharic  and  mucic  acids  Adipic  acid 

They  are  hence  tetrahydroxyadipic  acids.  The  fact  that  they 
all  yield  adipic  acid  proves  that  the  isomerism  is  due  to  the  asym- 
metric carbon  atoms,  and  that  they  all  contain  a  normal  carbon 
chain. 

Aldehyde  Acids  and  Ketone  Acids 

Glyoxylic  acid,  ethanal  acid,  CHO.COOH  -t-  H2O,  occurs 
frequently  in  plants,  especially  in  unripe  fruits.  It  is  readily 
prepared  from  dichloroacetic  acid  by  superheating  in  a  sealed 
tube  with  water.  (Write  out  the  equation. )  It  crystallizes  with  a 
molecule  of  water  in  rhombic  prisms,  dissolves  readily  in  water 
and  alcohol,  and  is  volatile  with  steam.  The  acid  and  most 
of  its  salts  crystallize  with  a  molecule  of  water,  which  would 
indicate  that,  like  chloral  hydrate  and  mesoxalic  acid  (196), 
this  acid  contains  two  hydroxyl  groups  joined  to  the  same 
carbon  atom,  HC(0H)2.C00H,  i.e.  that  it  is  dihydroxyacetic 
acid.  In  its  reactions,  however,  the  acid  behaves  as  if  it 
contained  the  aldehyde  group,  e.g.  it  gives  an  oxime  with 
hydroxylaraine  and  a  phenylhydrazone  with  phenylhydrazine. 


ACETOACETIC   ACID  207 

It  combines  with  sodium  bisulphite  and  with  ammonia,  and 
reduces  an  ammoniacal  solution  of  silver  nitrate.  On  reduction 
it  gives  glycolic  acid,  and  on  oxidation  oxalic  acid.  (Write  out 
all  the  equations.) . 

Pyruvic  or  pyroracemic  acid,  propanone  acid,  CHs.CO.COOH, 
is  an  example  of  an  a-ketone-acid.  As  its  name  indicates,  it  is 
obtained  by  distilling  racemic  (or  tartaric)  acid  with  potassium 
bisulphate.  In  this  decomposition  glyceric  acid  is  first  formed 
from  the  tartaric  acid  by  the  elimination  of  carbon  dioxide, 
which  gives  pyruvic  acid  by  the  loss  of  water :  — 

HOOC.CHOH.CHOH.COOH  — >-  CH2OH.CHOH.COOH 
— >-  H3C.CO.COOH  +  H2O. 

Pyruvic  acid  results  from  the  oxidation  of  the  lactic  acids,  and  it 
can  also  be  made  from  acetyl  chloride,  by  converting  this  into 
acetyl  cyanide  and  hydrolyzing.  Its  constitution  follows  from 
these  methods  of  preparation.  It  is  a  liquid,  solidifying,  when 
pure,  at  i3°-i4°  and  boiling  at  i65°-i7o°  (with  slight  decomposi- 
tion), and  soluble  in  water,  alcohol,  and  ether.  It  has  the  odor 
of  acetic  acid.  Owing  to  the  acidifying  influence  of  the  carbonyl 
group,  it  is  a  strong  acid,  much  stronger  than  propionic  acid. 
When  reduced,  it  gives  dl-\a.ctic  acid.  Towards  hydroxylamine, 
phenylhydrazine,  and  hydrocyanic  acid  it  reacts  as  a  ketone. 
(Write  out  the  equations.)  It  is  made  technically  and  is  used 
in  the  preparation  of  atophg.n  and  related  compounds. 

Acetoacetic  acid,  butanone-3-acid,  CH3.CO.CH2.COOH,  is 
the  best  known  y8-ketone  acid.  It  is  obtained  by  very  careful 
hydrolysis  of  its  ethyl  ester  at  a  low  temperature.  It  is 
extremely  unstable,  decomposing  into  carbon  dioxide  and  ace- 
tone when  set  free  from  its  salts.  This  instability  sharply 
distinguishes  the  /3-ketone  acids  from  the  a-  and  y-ketone 
acids  which  are  stable.  It  is  present  in  the  urine  of  persons 
affected  with  diabetes  mellitus.  The  ethyl  ester  is  prepared 
by  the  action  of  sodium  on  ethyl  acetate  containing  a  small 
amount  of  ethyl  alcohol.  The  sodium  first  acts  on  the  ethyl 
alcohol,  forming  sodium  ethylate.  This  then  reacts  with  the 
ethyl  acetate,  forming  a  salt  of  orthoacetic  acid  :  — 


2o8  DERIVATI\ES   OF  THE  PARAFFINS 

O  /ONa 

HsC.cf  +  Na— 0— C2H5  =  HsC.C^OCjHs, 

^O-C^Hs  ^OCaHs 

which  at  once  reacts  with  another  molecule  of  ethyl  acetate :  — 

/ONa        H\  /ONa 

HjCCf-OCzHs  +  H-^C.COOC2H6  =  H3C.C4         +  2  C2H5OH, 
\0C2H5     h/  ^CH.COOC.Hs 

regenerating  the  alcohol,  and  forming  the  sodium  salt  of  the  ester. 
The  ester  is  obtained  by  treating  this  sodium  salt  with  acetic 
acid,  the  product  first  formed  passing  over  into  the  more  stable 
ketone  form :  — 

OH 

I  — >-    H3C.CO.CH2.COOC2H6. 

H3C.C=CH.COOC2H6 

Ethyl  acetoacetate  is  a  colorless  liquid  boiling  at  181°,  having 
a  pleasant  fruity  odor.  It  is  only  slightly  soluble  in  water,  but 
readily  soluble  in  alcohol  and  ether.     It  is  volatile  with  steam. 

It  undergoes  hydrolysis  in  three  ways  :  — 

1.  Normal  hydrolysis,  giving  the  acid  and  alcohol.  (See 
above.) 

2.  Ketone  hydrolysis,  brought  about  by  heating  the  ester 
with  dilute  sulphuric  acid  or  with  dilute  aqueous  alkali :  — 

ch3.cox:h2.;coo;C2H5  ^  cH3.co.CH3  +  CO2  +  C2H6OH. 

3.  Acid  hydrolysis,  which  takes  place  with  concentrated  alco- 
holic potash  or  soda :  — 

^^'+ OHl^H  +  H°i  OH  =  '  CH3COOH  +  C2H5OH. 

When  treated  with  sodium  or  sodium  ethylate,  the  ester  gives 
the  sodium  salt :  — 


/ONa  ■ 
H3C.C4 

x:h.cooc2H5. 


ETHYL  ACETOACETATE  209 

This  forms  an  addition  product  with  an  alkyl  iodide :  — 
ONaH 
H3CC  —  C.COOC2H6, 
I       R 

which  by  the  elimination  of  sodium  iodide  gives  an  alkyl  de- 
rivative of  acetoacetic  ester :  — 

H 

(i)  H3C— OC— C.COOC2H6. 

R 

This  compound  undergoes  the  ketone  hydrolysis  and  the  acid 
hydrolysis  in  the  same  way  that  ethyl  acetoacetate  does, 
yielding  homologues  of  acetone : — • 

HsC.COXlHR.iCOOiCjHB  ^  H3C.CO.CH2R  +  CO2  +  C2H6OH, 

and  homologues  of  acetic  acid :  — 

H3C.C0.1CHR.COOIC2H6_  +  CjHjOH. 

+  OHi    H  +  H  1  OH  "  H3C.COOH+  H2CR.COOH 

The  compound  (i)  also  reacts  with  sodium  or  sodium  ethylate 
to  give  a  sodium  salt :  — 

ft 

ONa 

1 
HsC.C^CR.COOCaHs, 

and  with  an  alkyl  iodide  this  forms  an  addition  product :  — 

ONaR 

I        I 
H3C.C  — C.COOC2H6, 

I        I 
I       R' 


2IO  DERIVATIVES  OF  THE  PARAFFINS 

which  by  the  elimination   of    sodium  iodide  gives  a  dialkyl 
derivative  of  acetoacetic  ester :  — 

HsC.CO.CRR'.COOCzHs. 

This  compound  also  undergoes  the  ketone  hydrolysis :  — 


H3C.CO.CRR' 
+  H 


•^°°|^'g=^=H3C.CO.CHRR'+C02+C2H60H, 


giving  higher  homologues  of  acetone ;  and  the  acid  hydrolysis :  — 

HsC.CO.ICRR'.COOiCaH,  _  +  C2H5OH, 

+  OH  1    H  +  H  :  OH  ~   H3C.COOH  +  CHRR'.COOH 

giving  higher  homologues  of  acetic  acid. 

This  acetoacetic  ester  synthesis,  as  it  is  called,  has  been  of 
great  value  in  building  up  the  homologues  of  acetone  and  acetic 
acid  and  in  the  synthesis  of  numerous  other  compounds.  Ethyl 
acetoacetate  is  one  of  the  most  valuable  synthetic  reagents  of 
organic  chemistry.  It  is  made  on  the  large  scale  and  is  used  in 
the  manufacture  of  antipyrine,  salipyrine,  pyramidon,  and  per- 
fumes (ionone).  It  is  also  used  in  the  preparation  of  dimethyl- 
glyoxime  and  of  dyes  (dianil  yellow). 

Ethyl  acetoacetate  has  been  isolated  in  two  forms.  By  cooling 
to  a  low  temperature,  the  ketone  form,  CH3.CO.CH2COOC2H6, 
separates  in  crystals  melting  at  —39°.  The  enol  form, 
H3C.C(OH)=CH.COOC2H6,  is  obtained  from  the  sodium 
compound  suspended  in  petroleum  ether  by  treating  it,  at  a 
very  low  temperature,  with  an  equivalent  quantity  of  anhydrous 
hydrochloric  acid,  filtering  ofi  the 'sodium  chloride  formed  and 
evaporating  the  petroleum  ether  at  a  low  temperature.  This 
form  of  the  ester  does  not  solidify  until  cooled  in  liquid  air. 
The  two  forms  differ  in  solubility  and  also  in  their  chemical 
reactions  and  physical  properties.  The  enol  form  reacts  with 
a  solution  of  ferric  chloride,  giving  a  violet  coloration,  while  the 
ketone  form  gives  no  color.  The  enol  form  dissolves  at  once  in 
caustic  alkalies,  forming  a  salt,  while  the  ketone  form  does  not 
(except  as  it  is  slowly  transformed  into  the  enol  form).  With 
bromine  the  enol  form  combines  instantaneously,  while  the 


LEVULIC  ACID,   PENTANONE-4  ACID  211 

ketone  form  does  not,  and  this  difference  is  made  use  of  to  deter- 
mine the  amount  of  the  enol  form  present  in  the  ester.  In  the 
liquid  state  the  ester  contains  about  90  per  cent  of  the  ketone 
form,  the  two  forms  being  in  equilibrium.  Ethyl  acetoacetate 
is  a  typical  tautomeric  compound  (96)  and  may  react  either 
in  the  ketone  or  the  enol  form.  The  sodium  salt  is  a  derivative 
of  the  enol  form  as  shown  above. 

The  reactions  of  ethyl  acetoacetate  are  in  accord  with  the 
view  that  it  is  a  tautomeric  substance.  For  example,  it  reacts 
with  sodium  bisulphite,  with  hydrocyanic  acid,  and  with  hy- 
droxylamine  just  as  the  ketones  do.  (Write  out  the  equations.) 
With  ammonia,  however,  it  gives  /3-aminocrotonic  acid, 
CH3C(NH2)^CHCOOH,  and,  when  treated  with  phosphorus 
pentachloride,  /3-chlorocrotonic  acid,  CH3CC1=:CHC00H. 
These  reactions  are  best  explained  by  assuming  the  enol  formula 
for  ethyl  acetoacetate,  CH3C(OH)=CHCOOC2H5  (ethyl 
j3-hydroxycrotonate) . 

Levulic  acid,  pentanone-4  acid,  CH3.CO.CH2.CH2.COOH, 
is  a  y-ketone  acid.  When  hexoses  (especially  levulose)  are 
boiled  with  concentrated  hydrochloric  acid,  this  acid,  together 
with  formic  acid  and  humus  substances,  is  formed,  and  this  is 
the  best  method  of  preparation.  Its  formation  from  the  hexoses 
is  characteristic  and  is  used  to  determine  the  presence  of  these 
sugars.  Levulic  acid  is  a  crystalline  substance  melting  at  37.2°, 
soluble  in  water,  and  so  stable  that  it  can  be  distilled  (under 
reduced  pressure).  It  boils,  with  only  slight  decomposition,  at 
about  250°.  It  reacts  with  hydroxylamine  to  form  an  oxime, 
with  phenylhydrazine  to  give  a  phenylhydrazone,  and  forms  an 
addition  product  with  hydrocyanic  acid,  showing  the  presence 
of  the  ketone  group.  On  reduction  with  sodium  amalgam  it 
gives  the  sodium  salt  of  y-hydroxyvaleric  acid :  — 

CH3.CO.(CH2)2.C02Na  +  H2  =  CH3.CHOH.(CH2)2.C02Na. 


CHAPTER  XI 
CARBOHYDRATES 

Among  the  mixed  compounds  are  the  important  substances 
known  as  carbohydrates.  This  name  was  originally  given  to 
them  because  they  consist  of  carbon  in  combination  with  hy- 
drogen and  oxygen  in  the  proportion  to  form  water,  as  shown 
in  the  formulas,  for  glucose,  C6H12O6,  starch,  CeHioOs,  etc. 
The  name  is,  however,  inaccurate,  as  some  substances  belong- 
ing to  this  group  are  now  known  that  do  not  contain  hydrogen 
and  oxygen  in  the  proportion  to  form  water.  Such  a  substance, 
for  example,  is  rhamnose,  C6H12O6.  Further,  there  are  many 
carbon  compounds,  as,  for  example,  formic  aldehyde,  CH2O, 
acetic  acid,  C2H4O2,  and  lactic  acid,  CsHeOs,  that  contain  hy- 
drogen and  oxygen  in  the  proportion  characteristic  of  most  of 
the  carbohydrates,  but  do  not  belong  to  this  group.  The 
name  carbohydrate  has,  however,  been  used  so  long  that  it 
would  be  difficult  to  supplant  it. 

The  carbohydrates  may  be  conveniently  classified  under 
three  heads.     These  are  :  — 

I .   Monosaccharoses,  monoses,  or  simple  sugars.  —  Examples  of 
these  are  glucose,  fructose,  arabinose,  and  mannose. 
-    2.    Polysaccharoses,  polyoses,  or  complex  sugars.  —  Examples 
are  cane  sugar,  sugar  of  milk,  maltose,  isomaltose,  and  raffinose. 

3.  Colloidal  polysaccharoses  or  polyoses.  —  Examples  are  cel- 
lulose, starch,  and  glycogen.  ys^  o^-,  0  ^  cy  \M  y  d  U-? 

The  polysaccharoses  give  the  simple  sugars  on  hydrolysis 
with  dilute  acids. 

I  The  monoses  are  the  simplest  carbohydrates.  Those  which 
are  best  known  have  the  composition  C6H12O6,  and  are  related 
to  the  hexacid  alcohols,  sorbitol,  mannitol,  and  dulcitol, 
C6H8(OH)6.  There  are,  however,  simpler  ones,  such  as  ara- 
binose,  CsHioOs,   erythrose,   C4H8O4,   and  glycerose,   CsHeOs; 


GLYCERIC   ALDEHYDE  213 

and  some  that  are  more  complex,  as  heptose,  C7H14O7,  octose, 
CsHieOg,  and  nonose,  CsHigOg.  The  monoses,  therefore,  fall 
into  classes  which  are  called  trioses,  teiroses,  pentoses,  hexoses, 
etc.,  according  to  the  numbe'r  of  oxygen  atoms  contained  in  them. 
By  methods  that  will  be  explained  below,  it  has  been  shown 
.  that  the  monoses  or  simple  sugars  are  aldehyde  alcohols  {aldoses) 

'  — CHOH 

or  ketone  alcohols  (ketoses)  containing  the  group,      | 

—CO 
The  termination  -ose  is  reserved  for  the  sugars. 

I.     MONOSACCHAROSES,    MONOSES 

A.  Trioses,  CsHeOs     ~ 

The  simplest  aldotriose  is  glyceric  aldehyde, 

CH2OH.CHOH.CHO; 

the  simplest  ketotriose  is  dihydroxyacetone, 

CH2OH.CO.CH2OH. 

When  glycerol  is  oxidized  with  bromine  water  in  the  presence 
of  soda  or  with  hydrogen  peroxide,  a  mixture  of  these  two  sub- 
stances, known  as  glycerose,  is  obtained.  When  this  mixture 
is  treated  with  dilute  alkalies,  it  gives  a-acrose  (di-fructose), 
CfiHiaOe  (232). 

dZ-Glyceric  aldehyde,  propane-diol-2,  3-al, 

CH2OH.CHOH.CHO, 

is  made  by  oxidizing  acrolein  diethylacetal  with  a  dilute  solu- 
tion of  potassium  permanganate  and  hydrolyzing  the  acetal 
formed :  — 


H2C 

H2COH 

H— C                  -1-  H2O  +  0  = 

=   HCOH. 

H— C=(OC2H6)2 

Acrolein  diethylacetal 

HC(OC2Hb)2 
Diethylacetal  of  glyceric  aldehyde 

214  CARBOHYDRATES 


H2COH 

H2COH 

HCOH             +  H2O   = 

HCOH  +  2  CjHsOH. 

HC(OC2H6)2 

HCO 

Glyceric  aldehyde 

It  crystallizes  in  needles,  tastes  sweet,  is  soluble  in  water,  but 
only  slightly  soluble  in  organic  solvents,  is  not  hygroscopic, 
and  not  volatile  with  steam.  It  melts  at  138°  and  reduces 
Fehling's  solution  in  the  cold.  Bromine  water  oxidizes  it  to 
^Z-glyceric  acid.  With  phenylhydrazine  in  solution  in  acetic 
acid  it  gives  the  same  phenylglycerosazone  (m.  p.  i3i°-i32°) 
that  dihydroxyacetone  does :  — 

H2COH  H2COH 

HCOH  +  HzN.NH.CeHs  =   HCOH  +  H2O. 

HCO  HC^N.NH.CeHs 

Phenylhydrazone  of  glyceric 
aldehyde 

H2COH  H2COH 

HCOH      +  C6H5NH.NH2  =       CO        4-  CeHsNHj  +  NH3. 

Aniline 

HC=N.NH.C6H5  HC^N.NH.CeHs 

H2COH  H2COH 

CO        +  HsN.NH.CeHs  =  C=:N.NH.C6H6  +  H2O. 

HC^N.NH.CeHs  HC^N.NH.CeHs 

Phenylglycerosazone 

The  glyceric  aldehyde  first  reacts  with  phenylhydrazine  to 
form  the  phenylhydrazone,  just  as  any  aldehyde  does.  (See 
Phenylhydrazine.)  With  an  excess  of  phenylhydrazine  the 
secondary  alcohol  group  is  changed  to  a  ketone  group  by  the 
loss  of  two  hydrogen  atoms.  This  reduces  a  molecule  of  phenyl- 
hydrazine  to  aniline  and  ammonia.  The  compound  containing 
the  ketone  group  then  reacts  with  another  molecule  of  phenyl- 
hydrazine  to  give   the  phenylglycerosazone  as  shown  above. 


DIHYDROXY  ACETONE  215 

Glyceric  aldehyde  is  slowly  converted  into  alcohol  and  carbon 
dioxide  by  yeast  or  a  solution  of  zymase.  The  crystallized 
glyceric  aldehyde  is  bimolecular.  In  aqueous  solution  it  slowly 
changes  to  the  monomolecular  form,  more  quickly  when  heated. 
Glyceric  aldehyde  is  optically  inactive,  as  it  is  a  mixture  of  the 
d-  and  the  Z-forms.  (Does  it  contain  an  asymmetric  carbon 
atom?) 

Dihydroxyacetone,propane-diol-l,3-one,CH20H.CO.CH20H, 
is  made  by  oxidizing  glycerol  by  means  of  the  sorbose  bacteria. 
When  its  aqueous  solution  is  evaporated  in  a  vacuum,  colorless 
prisms  are  obtained,  which  melt  at  about  80°.  This  form  is 
bimolecular;  in  aqueous  solution  it  changes  to  the  mono- 
molecular  form.  It  reduces  Fehling's  solution  in  the  cold  and 
gives  the  same  phenylglycerosazone  with  phenylhydrazine  that 
glyceric  aldehyde  does :  — 

H2COH  H2COH 

CO     +  HjN.NH.CeHs  =        C=N.NH.C6H6  +  H2O. 

H2COH  H2COH 

Phenylhydrazone  of 
dihy  droxy  ac  e  tone 

H2COH  H2COH 

C=N.NH.C6H6  =        C=:N.NH.C6H6. 

H2COH  +  C6H5NH.NH2  HCO  +  C8H5NH2  +  NH3 

Aniline 

H2COH  H2COH 

C=N.NH.C6H6  =  C=N.NH.C6H5  +  H2O. 

HCO  +  HaN.NH.CeHs  HC^N.NH.CeHj 

Phenylglycerosazone 

In  these  reactions  the  dihydroxyacetone  first  forms  the  phenyl- 
hydrazone, just  as  any  ketone  does;  and  with  excess  of  phenyl- 
hydrazine  this  loses  two  hydrogen  atoms  from  one  of  the  primary 
alcohol  groups,  converting  it  into  an  aldehyde  group,  which  at 
once  reacts  with  another  molecule  of  phenylhydrazine  to  give 


2l6  CARBOHYDRATES 

phenylglycerosazone,  as  shown  above.  Dihydroxyacetone  has  a 
sweet  taste  and  ferments  with  yeast  or  zymase.  It  forms  a  weO- 
crystallized  compound  with  sodium  bisulphite  and  an  oxime 
(m.  p.  83°-84°)  with  hydroxylamine.  Both  dihydroxyacetone 
and  glyceric  aldehyde  give  glycerol  on  reduction. 

B.    Tetroses,  C4H.iOi 

Your steieoisomericaldotelroses,  CHaOH.CHOH.CHOH.CHOjbutane- 
triol-2,  3,  4-als,  are  theoretically  possible  as  the  formula  contains  two 
asymmetric  carbon  atoms,  and  the  groups  attached  to  the  two  asym- 
metric carbon  atoms  are  not  the  same,  d-  and  /-Erythrose  and  the 
inactive  (dl-)  form  of  erythrose  have  been  obtained  by  the  degrada- 
tion of  the  d-,  1-,  and  dZ-arabonic  acids  by  oxidizing  them  with  hydrogen 
peroxide  in  the  presence  of  ferric  salts :  — 


H2COH 

H2COH 

H2COH 

H2C0H 

(HCOH)s 

(HCOH)2 

->  (HC0H)2 

->  (HCOH)  J 

+  CO2. 

CHO 

HCOH 
OCOH 

CO 
OCOH 

HCO 

Arabinoses 

Arabonic  acids 

a-Ketone  adds 

Aldotetxoses 

/-Threose  has  been  obtained  in  a  similar  manner  from  /-xylonic  acid. 
The  formula  for  the  simplest  ketotetrose, 

CH2OH.CHOH.  CO.CH2OH, 

butane-triol-i,  3, 4-one-2,  contains  only  one  asymmetric  carbon  atom,  and 
therefore  only  d-,  /-,  and  dl-lorms  are  to  be  expected.  d-Erythrulose 
results  from  the  oxidation  of  erythritol  by  the  sorbose  bacteria.  It 
is  not  attacked  by  bromine  water,  while  the  erythroses  and  threose 
are  oxidized  by  this  reagent  to  erythronic  and  threonic  acids.  Further 
oxidation  of  these  acids  gives  the  tartaric  acids.  rf/-Erythrulose  results 
from  the  oxidation  of  the  natural  erythritol  with  hydrogen  peroxide 
in  the  presence  of  iron  salts  or  with  bromine.  All  the  tetroses  are  known 
only  in  the  form  of  syrups,  and  they  do  not  undergo  fermentation  with 
yeast. 

C.   Pentoses,   CsHioOs 

Eight  optically  active  stereoisomeric  aldopentoses,  CHjOH. 
(CH0H)3CH0,  pentane-tetrol-2,  3,  4,  5-als,  are  theoretically 
possible,  and  all  are  known  with  the  exception  of  /-lyxose.  None 
of  the  pentoses  occur  free  in  nature. 


XYLOSES 


217 


I  -Arabinose,'  in  the  form  of.  polysaccharoses  known  as 
"  arabans,"  ^  is  very  widely  distributed  in  the  plant  world. 
It  was  first  obtained  by  the  hydrolysis  of  gum  arable,  and  hence 
its  name.  It  can  also  be  made  by  the  hydrolysis,  with  mineral 
acids,  of  cherry  gum  or  of  sugar  beet  chips,  after  extracting  the 
beet  sugar.  It  crystallizes  in  prisms,  melts  about  160°,  is  very 
soluble  in  water,  and  has  a  sweet  taste.  Although  this  variety 
of  arabinose  is  dextrorotatory  it  is  called  T-arabinose,  because  of 
its  close  relationship  in  configuration  to  Z-glucose  and  Z-mannose. 

d'-Arabinose  was  first  made  artificially  by  the  degradation 
of  (i-glucose  (220)  by  oxidizing  (i-gluconic  acid  with  hydrogen 
peroxide  in  the  presence  of  ferric  salts :  — 

CH2OH  CH2OH  CH2OH  CH2OH 


(CH0H)4  — 

■^(CH0H)4- 

-5-(CHOH)3- 

-^(CHOH)3  +  C02. 

CHO 

COOH 

co 

COOH 

CHO 

d-Glucose 

(i-GIuconic 

a-Ketone 

d'-Aiabinose 

acid 

acid 

It  has  also  been  obtained  by  the  hydrolysis  of  the  glucosides, 
barbaloin  and  isobarbaloin,  contained  in  Barbados  aloes. 

d/-Arabinose  was  first  obtained  by  combining  the  d-  and  /-vari- 
eties. In  the  disease  known  as  pentosuria  this  sugar  is  present 
in  the  urine.  On  reduction,  the  arabinoses  give  the  arabitols, 
and  on  oxidation,  first,  the  arabonic  acids  and  then  the  tri- 
hydroxyglutaric  acids  (205). 

Xyloses.  —  Z'-Xylose  in  the  form  of  "  xylans  "  is  widely 
distributed  in  plants.  It  is  best  made  from  wood  gum  (xylan), 
and  hence  the  name,  or  from  corn  cobs,  by  hydrolysis  with 
mineral  acids.  It  is  sometimes  called  wood  sugar.  It  tastes 
very  sweet,  is  dextrorotatory,  yields  xylitol  on  reduction  and 

'  The  sign  I'  signifies  that  the  substance  is  dextrorotatory,  but  is  derived 
from,  or  closely  related  to,  substances  that  are  levorotatory.  Similarly  the 
sign  d'  signifies  that  the  substance  is  levorotatory,  but  derived  from,  or 
related  to,  substances  that  are  dextrorotatory. 

^  These  are  starch-like  carbohydrates  which  undergo  hydrolysis  to  the 
corresponding  sugars.     Thus  arabans  give  arabinose,  xylans,  xylose,  etc. 


2l8  CARBOHYDRATES 

/'-xylonic  and  xylotrihydroxyglutaric  acids  on  oxidation. 
■d'-Xylose  has  been  made  by  the  degradation  of  d-gulonic  acid 
by  oxidizing  it  with  hydrogen  peroxide  in  the  presence  of  ferric 
salts.  (See  Arabinose.)  The  rfZ-variety  results  when  a  mixture 
of  equal  parts  of  the  active  components  is  crystallized  from 
alcohol. 

Riboses.  —  r-Ribose  is  obtained  from  /-arabonic  acid  by  heating 
it  with  pyridine,  when  it  undergoes  molecular  rearrangement  into 
/'-ribonic  acid.  On  reducing  the  lactone  of  this  acid  /'-ribose  is  formed. 
It  has  a  sweet  taste,  is  dextrorotatory,  and  melts  at  87°  On  reduction 
it  gives  adonitol,  and  on  oxidation  Z'-ribonic  and  ribotrihydroxyglutaric 
acids.  (i'-Ribose  has  been  obtained  from  certain  nucleic  acids  by 
hydrolysis.     It  is  levorotatory  and  melts  at  86°-87° 

Lyxose.  —  d'-Lyxose  is  made  from  i-xylonic  acid,  which  undergoes 
molecular  rearrangement  on  heating  with  pyridine  into  (i'-lyxonic 
acid.  When  the  lactone  of  this  acid  is  reduced  it  gives  d'-lyxose.  It 
has  also  been  made  by  the  degradation  of  (i-galactonic  acid.  (See 
(i'-Arabinose.)  The  name  is  derived  from  xylose  by  reversing  the  order 
of  the  letters  xyl-.  It  is  levorotatory  and  gives  d'-arabitol  on  reduction 
and  i'-lyxonic  and  trihydroxyglutaric  acids  on  oxidation. 

Rhamnose  occurs  in  the  plant  kingdom  in  a  very  large  number  of 
glucosides  (quercitrin,  xanthorhamnin,  etc.),  from  which  it  is  prepared  by 
hydrolysis.  It  crystallizes  well  from  water  (CjHijOs+HjO),  tastes  sweet, 
melts  at  93°-94°,  and  is  optically  active.  On  reduction  it  gives  rhamnitol, 
and  on  oxidation  with  bromine  water  rhamnonic  acid.  It  is  a  methyl- 
pentose,  CH3.(CHOH)4CHO,  since  it  gives  methylfurfuraldehyde  on  dis- 
tillation with  hydrochloric  acid,  whereas  the  above  mentioned  pentoses 
give  furfuraldehyde.  This  reaction  is  characteristic  of  the  pentoses  and 
pentosans,  and  is  used  for  their  quantitative  determination:  — 


HO        H 

I  I 

CH— CHOH  I  , 

I  =  p>0        +       3H2O; 


CH=CH 

I     > 

CH=C— CHO 


CH— COH 

I      /\ 
HO    H     CHO 

Pentose  Furfuraldehyde 

HO    H    CHg  ^TT 

CH— C— OH  .    CH=C 

CH— C— OH  I  /°       +    3H2O. 

I      /\  CH=C.CHO 

HO    H    CHO 

Rhamnose  Methylfurfuraldehyde 


GLUCOSE  219 

Isorhamnose,  rhodeose.  isorhodeose,  fucose,  and  quinovose  are  stereoisomers 
of  rhamnose.     None  of  the  pentoses  are  fermentable  with  yeast. 

Ketopentoses  have  not  yet  been  isolated  in  the  pure  condition. 

D.   Hexoses,  C6H12O6 

The  hexoses  are  the  most  important  monoses  and  the 
ones  which  have  been  longest  known.  Three  aldohexoses, 
CH20H.(CHOH)4.CHO,  (f-glucose,  <i-mannose,  and  (^-galactose, 
and  one  ketohexose,  CH20H.(CHOH)3.CO.CH20H,  d'-fructose, 
occur  in  nature. 

Sixteen  optically  active,  stereoisomeric,  aldohexoses, 
CH20H(CHOH)4CHO,  hexane-pentol-2,  3,  4,  5,  6-als,  are  theo- 
retically possible,  of  which  thirteen  are  now  known. 

d-Glucose  is  the  most  important  monose.  On  account  of 
its  abundant  occurrence  in  grapes  it  is  ordinarily  called  grape 
sugar.  As  its  solution  is  dextrorotatory,  it  was  formerly 
called  dextrose  to  distinguish  it  from  the  levorotatory  fructose 
(levulose).  As  d-,  1-,  and  dl-iorma  of  glucose  are  now  known, 
this  name  has  been  discarded.  In  the  free  condition  d-glucose 
occurs  widely  distributed  in  the  plant  world,  frequently  to- 
gether with  d'-huctose,  sometimes  together  with  cane  sugar, 
especially  in  sweeLfruits.  ^fj"\r      '  -  r-  '  . 

A  mixture  of  (f-glucose  and  (i'-fructose  (invert  sugar)  forrns 
the  principal  constituent  of  honey.  (i-Glucose  occurs  regularly 
in  small  quantity  in  blood,  lymph,  and  in  human  urine  (less 
than  o.  I  per  cent) .  In  the  disease  diabetes  mellitus  the  amount 
of  (f-glucose  in  the  urine  may  rise  to  12  per  cent,  corresponding 
to  500  to  1000  grams  per  day.  (i-Glucose  also  occurs  in  the 
free  state  in  the  white  and  yolk  of  the  egg.  In  the  combined 
state  it  occurs  in  many  glticosides  (527).  These  give  glucose  as 
one  of  the  products  on  hydrolysis  with  dilute  mineral  acids  or 
with  certain  enzymes.  It  is  a  constituent  of  the  polyoses  or 
complex  sugars,  C12H22O11,  from  which  it  results  on  hydrolysis. 
Thus,  cane  sugar  is  hydrolyzed  by  dilute  mineral  acids  or  by  the 
enzyme,  invertase,  to  (i-glucose  and  (f' -fructose  :  — 

C12H22OU  +  H2O  =  C6H12O6  +  C6Hi206; 

Cane  sugar  d-Glucose  d '-Fructose 


220  CARBOHYDRATES 

milk  sugar,  or  lactose,  into  d-glucose  and  d-galactose  by  acids 
or  lactase :  — 

C12H22O11  +  H2O  =  CeHiaOe  +  CeHijOe ; 

Milk  sugar  (i-Glucose  (i-Galactose 

and  malt  sugar,  or  maltose,  into  two  molecules  of  <f-glucose  by 
acids  or  maltase :  — 

C12H22O11  +  H20=  2  C6H12O6. 

Maltose  d-Glucose 

In  plants  J-glucose  is  very  abundant  in  the  form  of  the  poly- 
saccharoses,  starch  and  cellulose,  while  in  animals  it  occurs  as 
the  polyose,  glycogen.  These  are  hydrolyzed  by  dilute  mineral 
acids  giving  d-glucose  as  the  final  product :  — 

(CeHioOs)™  +  WH2O  =  ^(CsHnOe). 
Starch  (f-Glucose 

<?-Glucose  is  best  prepared  in  the  laboratory  by  the  hydrolysis 
of  pure  cane  sugar  with  hydrochloric  acid.  It  is  separated  from 
the  d'-fructose,  formed  at  the  same  time,  by  crystallization  from 
alcohol.  On  the  large  scale  ci-glucose  is  made  by  the  hydrolysis 
of  starch  with  hydrochloric  acid.  In  this  country  corn  starch 
is  used ;  in  Europe  potato  starch. 

The  commercial  name  "glucose"  must  be  distinguished  from 
rf-glucose  used  by  the  chemist  for  the  chemical  individual, 
C6Hi20is.  The  commercial  glucose  is  a  syrup,  which  it  would 
be  much  better  to  call  corn  syrup.  It  is  made  by  the 
partial  hydrolysis  of  the  starch  of  Indian  corn  with  dilute 
hydrochloric  acid,  in  closed  vessels  under  a  steam  pressure 
of  35  lb.  The  hydrolysis  of  the  starch  is  only  carried  to  a 
point  where  there  is  about  12  per  cent  of  reducing  sugars  present. 
When  the  conversion  of  the  starch  has  reached  this  point  the 
liquid  is  neutralized  with  a  dilute  solution  of  sodium  car- 
bonate, filtered,  decolorized  with  bone-char,  and  evaporated  in 
vacuum  pans  to  a  thick  syrup.  Enormous  quantities  of  this 
commercial  glucose  are  used  in  the  manufacture  of  con- 
fectionery. It  has  the  property  of  preventing  the  cane 
sugar,  with  which  it  is  usually  mixed,  from   crystallizing  or 


GRAPE  SUGAR,  CORN  SUGAR  221 

"  graining."  It  is  also  used  as  a  table  syrup,  either  alone  or 
mixed  with  cane  sugar  syrup  (molasses) ,  and  in  the  rnanuf acture 
of  jellies,  jams,  and  preserves.  It  is  used  in  very  large  quanti- 
ties to  fill  sole  leather  and  tanning  extracts,  as  a  constituent 
of  various  sizes  for  ropes  and  textiles,  and  in  chewing  gum  and 
chewing  tobacco. 

Grape  sugar,  corn  sugar,  is  the  name  given  to  the  crude 
(f-glucose  made  on  the  large  scale  and  used  in  the  manufacture 
of  vinegar,  lactic  acid,  etc.,  and  as  a  reducing  agent,  e.g.  in  dye- 
ing with  indigo  and  in  silvering  mirrors.  It  contains  70-86 
per  cent  (i-glucose  and  some  of  the  carbohydrates  intermediate 
between  starch  and  li-glucose  (dextrins,  maltose,  and  isomaltose). 
It  is  not  much  used  in  food  products  on  account  of  its  bitter, 
unpleasant  taste.  The  process  of  manufacture  is  the  same  as 
that  for  the  preparation  of  glucose  given  above,  except  that 
more  hydrochloric  acid  is  used  and  the  hydrolysis  of  the  starch 
is  carried  further.  When  a  sample  of  the  liquid  no  longer 
gives  a  precipitate  with  alcohol,  it  is  assumed  that  no  dextrin 
is  present,  as  dextrin  is  insoluble  in  alcohol.  After  neutralizing 
with  sodium  carbonate,  filtering,  and  decolorizing  with  bone-char, 
the  solution  is  concentrated  in  vacuum  pans  to  the  proper  point 
and  poured  while  hot  into  moulds.  Grape  sugar  is  a  wax-like, 
solid  mass  of  crystals  of  J-glucose  hydrate  (C6H12O6  -|-  H2O), 
white  when  fresh,  but  soon  turning  yellow  and  becoming  ex- 
tremely hard.  Anhydrous  grape  sugar  (dextrose),  said  to  be  99 
per  cent  pure  (i-glucose,  is  also  made  commercially  and  is  the 
purest  form  of  the  sugar  on  the  market. 

(i-Glucose  exists  in  two  stereoisomeric  modifications  which 
are  designated  as  a-  and  |3-(i-glucose.  The  a-form  is  always 
obtained  when  (i-glucose  crystallizes  from  its  aqueous  solutions 
in  the  cold  (as  the  hydrate,  C6H12O6  -|-  H2O)  or,  in  the  anhy- 
drous form,  from  a  boiling  saturated  solution  in  alcohol.  The 
anhydrous  form  of  the  a-<i-glucose  is  also  obtained  by  crystalliz- 
ing the  concentrated  aqueous  solution  at  30°  to  35°.  It  crystal- 
lizes in  needles  or  prisms,  melting  at  146°,  and  is  soluble  in  three 
parts  of  water  at  0°.  (3-(f-Glucose  is  obtained  when  a  concen- 
trated aqueous  solution  of  (f-glucose  is  dried  at  110°,  the  mass 


22  2  CARBOHYDRATES 

then  dissolved  in  an  equal  volume  of  water,  and  the  solution 
quickly  brought  to  crystallization  by  the  addition  of  absolute 
alcohol  with  vigorous  stirring.  It  forms  microscopic  crystals 
that  melt  at  148°  to  150°  and  dissolve  in  0.65  part  of  water  at 
15°.  Both  modifications  show  mutarotation,  i.e.  the  rotation  of 
the  freshly  prepared  solution  changes  on  standing  or  quickly  on 
the  addition  of  alkali  until  it  becomes  constant.  The  a-form 
shows  an  initial  specific  rotation  of  +111.2°,  the  /3-form  of 
17.5°.  On  standing  or  on  the  addition  of  alkali,  both  forms 
show  the  same  value,  +52.3°.  In  a  solution  of  J-glucose, 
which  gives  this  constant  value,  there  is  an  equilibrium  be- 
tween the  a  and  |8-forms,  corresponding  to  36.8  per  cent  a  and 
63.2  per  cent|3. 

The  strength  of  a  solution  of  d-glucose  is  usually  determined 
in  the  polarimeter  from  its  specific  rotation.  (^-Glucose  is 
about  half  as  sweet  as  cane  sugar  and  ferments  with  yeast  or 
zymase,  giving  alcohol  and  carbon  dioxide  as  the  main  products. 
The  natural  <f-glucose  is  dextrorotatory.  A  Z-glucose  and  a 
(i^glucose  have  been  made  synthetically  from  the  corresponding 
I'-  and  (i^arabinoses :  — 

CH2OH  CH2OH  CH2OH  CH2OH 

I  I  I  I 

(CH0H)3  — >■  (CH0H)4  — >-  (CH0H)4  — >■  (CH0H)4. 


CHO 

CN 

COOH 

CHO 

Arabinoses 

Arabinose- 
cyanhydrins 

Hexonic 
acids 

Hexoses 

/-Glucose  does  not  ferment  with  yeast,  but  otherwise  it  re- 
sembles (i-glucose  very  closely  except  that  it  is  levorotatory, 
—  51.4°  after  the  solution  has  stood  for  some  time.  When 
oxidized,  the  glucoses  give  the  gluconic  acids, 

CH2OH.  (CH0H)4.  COOH, 

and  then  the  saccharic  acids,  H00C.(CH0H)4.C00H  (206). 
As  these  acids  have  been  proved  to  contain  a  normal  carbon 
chain,  it  follows  that  the  glucoses  must  be  normal  compounds 
and  contain  a  primary  alcohol  group  and  an  aldehyde  group 
at  the  ends  of   the   chain.     On   reduction  the  glucoses  yield 


GLUCOSE  223 

the  sorbitols,  CH20H.(CHOH)4.CH20H  (175) —another  proof 
of  the  presence  of  the  aldehyde  group  in  them.  Heated  with 
acetic  anhydride  and  zinc  chloride,  the  glucoses  give  penta- 
acetates, 

CH2OCOCH3.  (CHOCOCH3)4.  CHO, 

showing  the  presence  of  five  alcohol  groups.  d-Glucose  gives 
an  oxime,  CH20H.(CHOH)4CH=NOH,  with  hydroxylamine, 
reduces  an  ammoniacal  solution  of  silver  nitrate  (forming  a 
silver  mirror),  and  reduces  Fehling's  solution  on  heating — re- 
actions which  are  characteristic  of  aldehydes.  The  reaction 
with  Fehling's  solution  is  frequently  made  use  of  to  detect  the 
presence  of  <f-glucose  and  to  determine  its  amount.  Fehling's 
solution  is  best  made  by  dissolving  69.3  grams  of  crystallized 
copper  sulphate  in  one  liter  of  water,  and  then  preparing  a 
solution  of  346  grams  Rochelle  salt  and  200  grams  of  anhydrous 
soda  in  a  liter  of  water.  In  using,  equal  volumes  of  the  two 
solutions  are  mixed,  and  the  mixture  diluted  with  an  equal 
volume  of  water.  With  this  solution  (f-glucose  can  be  shown  to 
be  present  in  solutions  containing  0.00005  per  cent  of  the  sugar. 
With  phenylhydrazine  (i-glucose  reacts,  like  all  aldehydes, 
giving  a  phenylhydrazone :  — 

CH2OH  CH2OH 

I  I 

(CH0H)4  +  H2N.NHC6H6  =  (CH0H)4  +  H2O. 

I  I 

CHO  HC=N.NHC6H5 

(i-Glucose  (t-Glucosephenylhydrazone 

Heated  with  an  excess  of  phenylhydrazine,  the  phenylhydra- 
zone loses  two  hydrogen  atoms,  just  as  the  phenylhydrazone  of 
glyceric  aldehyde  (215)  does :  — 

CH2OH  CH2OH 

(CH0H)4   +  CeHsNH.NHa      =      (CH0H)3 
HC=N.NHC6H6  CO  -|-  NH3  -|-  CeHsNHo, 

Aniline 

HC=N.NHC6H5 


2  24  CARBOHYDRATES 

and  the  compound  formed,  which  contains  a  ketone  group, 
reacts  with  another  molecule  of  phenylhydrazine  to  form 
(f-phenylglucosazone :  — 

CH2OH  CH2OH 

(CH0H)3  (CH0H)3 

CO        +    H2N.NHC6H6  =         C=N.NHC6H5  +  H2O. 

HC=N.NHC6H5  HC=N.NHC6H6 

d-Phenylglucosaaone 

This  c?-phenylglucosazone  is  almost  insoluble  in  water  and 
this  reaction  can  hence  be  used  to  show  the  presence  of 
(i-glucose  in  solutions.  It  crystallizes  from  dilute  alcohol  in 
yellow  needles,  that  melt,  when  rapidly  heated,  at  about  205°. 
Both  li-mannose  and  ^'-fructose  give  i-phenylglucosazone  when 
heated  with  an  excess  of  phenylhydrazine,  and  hence  in  testing 
solutions  for  rf-glucose  care  must  be  taken  to  be  sure  that  neither 
of  these  sugars  is  present. 

(i-Glucose,  like  all  aldehydes,  combines  with  hydrocyanic 
acid  to  form  a  cyanhydrin,  CH20H.(CHOH)4.CHOH.CN. 
When  this  is  hydrolyzed  it  gives  a  hexahydroxy-»-heptane  acid, 
CH2OH.  (CH0H)6.  COOH.  On  reduction  with  hydriodic  acid  and 
phosphorus  this  gives  nornaal  heptane  acid,  CH3.(CH2)6.COOH. 
This  is  a  proof  both  of  the  aldehyde  group  in  tf-glucose  and  of  the 
normal  structure,  for  M-heptane  acid  could  not  have  resulted 
from  a  ketose  or  from  an  aldose  containing  an  iso  chain.  (See 
Fructose.) 

It  has  been  shown  that  in  aqueous  solutions  of  (f-glucose 
there  are  present  in  addition  to  the  a-  and  j3-forms  (222)  small 
amounts  of  the  aldehyde  or  the  hydrate.  This  will  account 
for  the  aldehyde  reactions  of  ci-glucose  solutions  and  explain 
the  transformation  of  the  two  forms  of  the  (/-glucose  into  each 
other :  — 


H-;C— OH 

X   CHOH 
\^    CHOH  — s 
^CH        ^— 

CHOH+H2O  CHOH 

CH2OH  CH2OH  CH2OH 

a-i-Glucose  d-Glucose  |3-d-Glucose 

hydrate 

Glucose  hydrate,  C6H12O6  +  H2O,  like  chloral  hydrate,  con- 
tains two  hydroxyl  groups  attached  to  the  end  carbon 
atom.  When  this  loses  water  it  can  give  either  a-glucose  or 
/3-glucose  or  both,  compounds  analogous  to  the  7-lactones 
(187).  When  these  compounds  are  formed,  the  end  carbon 
atom  now  becomes  asymmetric,  and  hence  two  stereoisomers  are 
formed.  When  a-glucose  goes  over  into  /3-glucose  or  the  /3-form 
into  the  a-form,  glucose  hydrate  is  the  intermediate  product  as 
shown  above. 

d-Mannose  occurs  free  in  orange  peel  and  in  the  combined  state  in 
some  glucosldes,  but  especially  in  the  form  of  complex  polysaccharoses, 
mannosans,  it  is  very  widely  distributed  in  nature.  It  was  first 
made  by  carefully  oxidizing  mannitol  (hence  the  name),  when  it  is 
obtained  together  with  i'-fructose.  (Compare  with  glycerose.)  It  is 
best  made  from  the  ivory  nut,  so  largely  used  in  making  buttons. 
The  turnings  and  shavings,  obtained  as  a  waste  product  in  the  manu- 
facture of  buttons,  are  hydrolyzed  with  dilute  mineral  acid  and  the 
mannose  precipitated  from  the  solution  with  phenylhydrazine,  as 
mannosephenylhydrazone,  which,  unlike  glucosephenylhydrazone,  is 
only  slightly  soluble  in  water.  (i-Mannose  crystallizes  in  the  rhombic 
system,  melts  at  132°  arid  tastes  sweet.  It  is  readily  fermented  with 
yeast.  It  is  partially  converted  into  its  isomers  i-glucose  and  d,'- 
fructose  by  the  action  of  small  quantities  of  alkalies,  and  these  sugars 
are  partially  converted  into  mannose  by  the  same  reagent.  Especially 
characteristic  of  d-mannose  is  its  difficultly  soluble  phenylhydrazone, 
CH20H.(CHOH)4.CH  =  N.NHCeHj.  When  heated  with  an  excess 
of  phenylhydrazine  (/-mannose  gives  the  same  phenylglucosazone  that 
d-glucose  or  li'-fructose  does.     d-Mannose  is  dextrorotatory.     A  /-man- 


226 


CARBOHYDRATES 


nose  and  a  i/-mannose  have  been  prepared  synthetically  from  I'-  and 
d/-arabinose :  — 


CH2OH 
(CHOH), 

CHO 

?'-Arabinose 


CHzOH 

(CHOH), 

CHOH 


CN 

Cyanhydrins 


CHoOH 

« 

(CHOH), 
COOH 

/-Mannonic  and 
/-Gluconic  Acids 


CH2OH 

(CHOH), 

CHO 

^Mannose  and 
/-Glucose 


When  hydrocyanic  acid  combines  with  i'-arabinose  two  stereoisomeric 
cyanhydrins  are  formed  as  the  carbon  atom  to  which  the  cyanogen  group 
attaches  itself  becomes  asymmetric.  On  hydrolysis  these  two  cyan- 
hydrins give  /-mannonic  and  /-gluconic  acids,  which  are  not  optical 
antipodes,  and  hence  may  be  separated  from  each  other  by  crystalliza- 
tion of  their  lactones.  When  these  lactones  are  reduced,  /-mannose 
and  /-glucose  (223)  are  formed. 

Z-Mannose  resembles  its  optical  antipode  very  closely,  except  that 
it  is  not  fermented  by  yeast.  On  oxidation  the  mannoses  give  mannonic 
acids  and  then  the  mannosaccharic  acids.  On  reduction  they  give 
the  mannitols  (174). 

Galactoses,  —  (^-Galactose  is  found  frequently  in  plants  and  animals 
in  the  form  of  polysaccharoses,  galactans,  and  glucosides.  It  is 
a  constituent  of  milk  sugar  (lactose)  and  of  raffinose.  It  is  usually 
prepared  by  the  hydrolysis  of  milk  sugar  with  dilute  sulphuric  acid. 
Like  (/-glucose  it  exists  in  two  stereoisomeric  modifications,  a- 
and  P-.  The  a-form  crystallizes  from  water  with  one  molecule  of 
water  of  crystallization,  from  alcohol  in  the  anhydrous  form. 
d-Galactose  is  dextrorotatory.  The  solution  shows  mutarotation.  (See 
Glucose.)  On  oxidation  li-galactonic  and  mucic  acids  are  formed. 
On  reduction  dulcitol  results.  (/-Galactose  ferments  with  some  yeasts, 
but  more  diflScultly  than  (i-glucose.  It  gives  an  oxime  with  hydroxyl- 
amine,  which  is  difficultly  soluble  in  cold  water,  and  a  phenylhydrazone 
with  phenylhydrazine,  which  is  also  but  slightly  soluble  in  cold  water. 
/-Galactose  is  obtained  by  fermenting  (//-galactose  with  beer  yeast,  as 
it  does  not  undergo  fermentation.  It  is  oxidized  first  to  /-galactonic 
acid  and  then  to  mucic  acid.  On  reduction  it  gives  dulcitol.  With 
phenylhydrazine  it  forms  a  phenylhydrazone  rather  difficultly  soluble 
in  water.  (//-Galactose  is  made  by  the  oxidation  of  dulcitol  with  hydro- 
gen peroxide.  It  can  be  separated  into  its  optical  components  by 
means  of  (f-amylphenylhydrazine.  On  fermentation  with  beer  yeast 
/-galactose  is  left  in  the  solution. 

The  guloses  are  made  from  the  glucoses,  whence  the  name  by 
reversing  the  order  of  the  letters  "  lu."     (/-Gulose  is  obtained  from 


FRUCTOSE 


227 


(i-glucose  by  oxidizing  it  to  (i-saccharic  acid  and  then  reducing  its 
lactone,  forming  the  aldehyde  acid,  glucuronic  acid.  This  on  further 
reduction  gives  d-gulonic  acid,  the  lactone  of  which  reduces  to 
(f-gulose :  — 

CHO     COOH    COOH    CHO     CH2OH   CH2OH 
(CHOH)i  (CHOH)4  (CH0H)4  (CHOH),  (CH0H)4  (CH0H)4. 


CH20H 

CH2OH 

COOH 

COOH 

COOH 

CHO 

d-Glucose 

(f-Gluconic 

rf-Saccharic 

Glucuronic 

rf-Gulonic 

J-Gulose 

acid 

acid 

acid 

acid 

It  will  be  seen  from  this  synthesis  that  the  space  arrangement  of 
the  groups  around  the  four  asymmetric  carbon  atoms  must  be  the  same 
in  i-gulose  as  in  (i-glucose.  The  only  difference  is  in  the  positions  of 
the  primary  alcohol  group  and  the  aldehyde  group.  li-Gulose  hence 
gives  (i-sorbitol  on  reduction  and  (/-saccharic  acid  on  oxidation  just  as 
(i-glucose  does. 

It  is  known  only  in  the  form  of  a  colorless  syrup,  which  does  not 
ferment  with  yeast.     The  /-gulose  is  made  from  ^-xylose : 


/'-Xylose  ->    T-Xylose-  C 
cyanhydrins 


■  ^Gulonic 

acid 

-Idonic 

acid 


(Reduction  ^     ;.Gulose 
lactones)     ->■     T-Idose. 


It  is  not  fermentable  with  yeast,  has  a  sweet  taste  and  is  levorotatory. 
The  other  aldohexoses  have  been  made  in  a  similar  manner  from  the 
pentoses,  d-talose  from  i-lyxose,  d'-  and  Z'-idose  from  the  xyloses,  and 
allose  and  altrose  from  li'-ribose. 

d'-Fructose  (levulose)  is  the  most  important  ketose  known. 
In  the  free  condition  it  is  very  widely  distributed  in  plants. 
Together  with  (f-glucose  it  occurs  abundantly  in  sweet  fruits 
and  in  honey.  It  is  a  constituent  of  cane  sugar  and  of  rafiSnose 
and  occurs  also  in  certain  starch-like  compounds,  e.g.  in  inulin 
of  the  dahlia  root.  It  is  formed  in  the  hydrolysis  of  cane  sugar, 
but  is  best  prepared  from  inulin,  as  it  is  the  only  sugar  formed 
in  the  hydrolysis  of  this  carbohydrate.  (i'-Fructose  reduces 
Fehling's  solution  more  rapidly  than  any  of  the  other  natural 
sugars,  (i'- Fructose  crystallizes  from  absolute  alcohol  in  rhombic 
prisms,  melting  at  95°-io5°,  from  concentrated  aqueous  solu- 
tions in  needles  with  ^H20.  It  is  said  to  be  one  and  a  half 
times  as  sweet  as  cane  sugar.     It  is  used  in  place   of   cane 


2  28  CARBOHYDRATES 

sugar  by  diabetics.  It  ferments  with  yeast  as  readily  as 
cf-glucose  and  is  levorotatory.  It  is  formed  together  with 
(/-mannose  by  cautious  oxidation  of  mannitol  with  nitric  acid, 
whUe  oxidation  of  mannitol  with  the  sorbose  bacteria  gives 
(f'-fructose  alone.  (f'-Fructose  is  also  formed  by  molecular 
rearrangement  of  li-glucose  and  of  <i-mannose  by  alkali.  Con- 
siderable quantities  of  if'-fructose  result  from  the  action  of 
strong  sulphuric  acid  on  d-g\\xcose.  When  oxidized  with  dilute 
nitric  acid  rf'-fructose  gives  glycolic  acid,  oxalic  acid,  and 
mesotartaric  acid,  but  no  saccharic  acid  (distinction  from 
J-glucose) :  — 

CH2OH  COOH 

(CH0H)3  CH2OH      CHOH 


CO                +  2  O2 

=  COOH 

Glycolic 

+  CHOH  - 

CH20H 

acid 

COOH 

(/'-Fructose 

Mesotartaric 
add 

The  oxalic  acid  results  from  the  oxidation  of  some  of  the  gly- 
colic acid.  When  oxidized  by  mercuric  oxide  in  the  presence 
of  a  solution  of  barium  hydroxide  d'-fructose  gives  glycolic  acid 
and  i-erythronic  acid :  — 

CH2OH  CH2OH 

(CH0H)3  CH2OH       CHOH 


CO           +O2 

=  COOH 

GlycoUc 

-f-  CHOH  . 

CH20H 

add 

COOH 

d '-Fructose 

(^Erythronic 
acid 

The  formation  of  these  products  on  oxidation  shows  that 
rf '-fructose  is  a  ketose  having  the  above  structure.  On  reduction 
also  (f' -fructose  differs  from  (i-glucose,  as  it  gives  equal  amounts 
of  (i-mannitol  and  t^sorbitol,  whereas  (i-glucose  gives  i-sorbitol 
only:  — 


FRUCTOSE 

CHjOH 

CH2OH 

CH2OH 

(CHOH)e 

(CH0H)3 

(CH0H)3 

CO         + 

2H2   = 

H— C—OH 

+ 

HO— C— H      . 

CH20H 

i'-Fructose 

CH2OH 

ti-MannitoI 

CH2OH 

(i-SorbitoI 

229 


It  will  be  seen  from  the  above  formulas  that,  when  the  ketone 
group  is  reduced  to  the  secondary  alcohol  group,  the  carbon 
atom  italicized  becomes  asymmetric,  and  hence  two  stereo- 
isomers are  formed.  This  is  another  proof  of  the  presence  of 
the  ketone  group  in  rf'-fructose. 

(f'-Fructose  combines  with  hydrocyanic  acid  to  give  a  cyan- 
hydrin,  I :  — 


CH20H 

CH2OH 

CH3 

(CH0H)3 

(CH0H)3 

(CH2)3 

HOC.CN 

HOCCOOH, 

HCCOOH. 

CH2OH 

CH2OH 

CH3 

I 

II 

ni 

When  this  is  hydrolyzed  it  gives  a  hexahydroxyheptoic  acid,  II, 
isomeric  with  that  obtained  from  glucose  (225).  When  this 
acid  is  reduced  with  hydriodic  acid  and  phosphorus  it  gives 
methyl-w-butylacetic  acid.  III,  isomeric  with  the  w-heptane 
acid  obtained  from  glucose.  It  follows  from  this  that 
^'-fructose  must  be  a  ketose  having  the  above  structure. 

With  hydroxylamine  (f'-fructose   gives  an  oxime,  isomeric 
with  that  obtained  from  li-glucose,, 

CH20H(CHOH)3C=NOH.CH20H. 

It    also    reacts    with    phenylhydrazine    to    give    a   phenyl- 
hydrazone, 

CH20H.(CH0H)3.C.CH20H 

II 
N.NHCfiHs, 

Fructose  phenylhydrazone 

isomeric  with   that   obtained   from  J-glucose.     When  heated 


230    -  CARBOHYDRATES 

with  an  excess  of  phenylhydrazine,  this  phenylhydrazone  loses 
two  atoms  of  hydrogen  from  the  primary  alcohol  group,  convert- 
ing it  into  an  aldehyde  group  :  — 

CH2OH.  (CHOH)  3.  C.  CH2OH 


N.NHCeHe 

Fructose  phenylhydrazone 


+  CeHs.NHNHa 


CH2OH.  (CHOH)  3.  C.  CHO 

1 1  +  NH3  +  C6H5NH2. 

N.NHCeHs  Aniline 

This  compound  then  reacts  with  another  molecule  of  phenyl- 
hydrazine  to  give  (f-phenylglucosazone :  — 

CH2OH  CH2OH 

(CHOH)  3  (CHOH)  3 

C=N.NHC6H6  +  H2N.NHC6H5  =  C=N.NHC6H6  -|-  HjO. 
HCO  HC^N.NHCeHs 

(i-Phenylglucosazone 

The  c^-phenylglucosazone  thus  obtained  is  identical  with  that 
formed  by  the  action  of  an  excess  of  phenylhydrazine  on  (i-glucose 
or  on  (f-mannose.  It  follows  from  this  that  the  arrangement  of 
the  groups  in  space  around  the  three  asymmetric  carbon  atoms 
must  be  the  same  in  fructose,  glucose  and  mannose.' 

When  this  rf-phenylglucosazone  is  treated  with  fuming  hydro- 
chloric acid,  the  phenylhydrazine  residues  are  split  off,  and  a 
compound  containing  a  ketone  and  an  aldehyde  group  and 
hence  called  glucosone  is  formed :  — 

CH2OH  CH2OH 

(CH0H)3  (CH0H)3 

C=N.NHC6H5-|-2  H2O     =     CO         H-gCeHsNH.NHaHCl. 

Phenylhydrazine 
HC=N.NHC6H6-|-2  HCl  HCO  hydrocUoride 

d-Phenylglucosazone  tf-GIucosone 

'■  For  the  methods  used  in  the  determination  of  the  configuration  of  the 
sugars  by  Emil  Fischer  and  others  see  Stereochemistry,  by  A.  W.  Stewart, 
page  so. 


FRUCTOSE  231 

On  reduction  with  zinc  and  acetic  acid  this  d-glucosone  gives 
(i '-fructose :  — 

CH2OH  CH2OH 

(CH0H)3  (CH0H)3 

CO  +  2  H  =    CO 

HCO  CH2OH. 

rf-Glucosone  rf'-Fnictose 

By  means  of  these  reactions,  it  will  be  seen  that  it  is  possible 
to  convert  (i-glucose  and  (i-mannose  into  d'-huctose.  As 
d'-imctose  gives  both  sorbitol  and  mannitol  on  reduction,  and 
sorbitol  on  oxidation  gives  (f-glucose,  and  mannitol  li-mannose,  it 
is  also  possible  to  obtain  both  rf-glucose  and  c?-mannose  from 
d'-hnctose.  For  this  reason  this  fructose  is  called  d'-iractose, 
although  it  is  ZeDo-rotatory.  With  methylphenylhydrazine 
(i '-fructose  gives  a  methylphenylglucosazone  more  readily  than 
(f-glucose  does. 

d/-Fructose  is  of  great  historical  interest,  as  it  was  the  first 
sugar  prepared  synthetically,  and  from  it  the  sugars  occurring 
in  nature  have  been  obtained.     It  has  been  made  :  — 

(i)  By  the  condensation  of  formaldehyde  with  bases  (formose). 
In  this  synthesis  it  is  probable  that  the  aldehyde  of  glycolic 
acid  is  first  formed  by  the  condensation  of  two  molecules  of 
formaldehyde :  — 

Hx  CH2OH 

H2C=:0-f        >C=:0=     I 

W  CHO 

Formaldehyde  Glycolic  aldehyde 

and  that  this  undergoes  further  condensation  to  the  hexose. 
(See  below.) 

This  condensation  is  called  the  aldol  condensation,  as  the 
product  formed  is  an  aldehyde  alcohol.  Aldol  itself  is  obtained 
by  the  condensation  of  two  molecules  of  acetic  aldehyde  with 
bases :  — 


232  CARBOHYDRATES 

HsC.Cr^O      H.CH2.C=0      HaC.CHOH.CHs.C^O 

+  •  = 

H  H  H 

2  mols.  o{  acetic  aldehyde  Aldol 

From  the  above  formula  it  will  be  seen  that  it  is  /3-hydroxy- 
butyric  aldehyde,  and  that  it  is  not  a  sugar,  as  it  does  not  contain 
the  group, — CHOH — CO — .  This  aldol  condensation  is  very 
important,  and  it  has  been  suggested  that  the  sugars  occurring 
in  nature  are  built  up  in  plants  by  its  means  from  formaldehyde, 
formed  by  the  action  of  the  green  coloring  matter  of  plants 
(chlorophyll)  and  water,  in  the  presence  of  sunlight,  on  the 
carbon  dioxide  of  the  air :  — 

0=C=0  +  H2O  =  H2=C=0  +  O2. 

It  is  well  known  that  green  plants  take  up  carbon  dioxide  from 
the  air  and  set  free  an  equal  amount  of  oxygen. 

(2)  The  second  method  of  preparing  (/^fructose  artificially 
starts  with  acrolein,  CH2.=CH.CH0.  This  takes  up  bro- 
mine, forming  acrolein  dibromide,  CH2Br.CHBr.CHO,  which 
with  barium  hydroxide  gives  glyceric  aldehyde, 

CH2OH.CHOH.CHO. 

It  has  already  been  shown  that  alkalies  transform  aldoses  into 
ketoses,  and  it  is  believed  that  the  barium  hydroxide  converts 
a  part  of  the  glyceric  aldehyde  into  dihydroxyacetone.  These 
two  substances  then  undergo  the  aldol  condensation  and  form 
(iZ-f  ructose :  — 


CH2OH 

CH20H 

CH2OH 

(CHOH), 

CHOH    + 

CO 

CO 

CHO 

HCHOH 

. 

Glyceric  aldehyde 

Dihydroxyacetone 

CH2OH. 

(//-Fructose 

The    sugar    thus   obtained   from    acrolein   was    first    called 
a-acrose  by  Emil  Fischer  before  he  had  proved  it  to  be  identical 

with  ^/-fructose. 


FRUCTOSE  233 

(3)  The  third  method  of  synthesis,  also  due  to  Emil  Fischer, 
depends  on  the  aldol  condensation  of  a  mixture  of  glyceric  alde- 
hyde and  dihydroxyacetone,  glycerose,  obtained  by  the  oxida- 
tion of  glycerol. 

(4)  The  fourth  method  depends  on  the  aldol  condensation  of 
glycolic  aldehyde,  CH2OH.CHO,  which  is  regarded  by  some 
chemists  as  the  simplest  sugar,  as  it  gives  all  the  reactions 
characteristic  of  the  aldoses  and  has  a  sweet  taste.  It  under- 
goes the  aldol  condensation  with  dilute  alkalies,  even  at  0°, 
and  gives  (^Z-erythrose  and  a-acrose :  — 

CH2OH.CHO  +  HCH0H.CH0=CH20H.CH0H.CH0H.CH0. 

2  mols.  of  glycolic  aldehyde  dZ-Erythrose 

If  the  erythrose  then  undergoes  molecular  rearrangement  under 
the  influence  of  the  alkali  into  erythrulose,  and  this  undergoes 
the  aldol  condensation  with  the  glycolic  aldehyde,  a-acrose 
results :  — 

CH2OHCHO  -t-  CH2OHCHOHCOCH2OH  = 

Glycolic  aldehyde  Erythrulose 

CH20H(CHOH)3COCH20H 

a-Acrose 

/'-Fructose  is  obtained  by  fermenting  the  ^/-fructose  with 
yeast,  as  only  the  c?'-fructose  undergoes  fermentation. 

Synthesis  of  the  sugars  (hexoses)  occurring  in  nature.  —  The 
(//-fructose  on  reduction  gives  c?Z-mannitol,  which  on  oxidation 
is  converted  into  (iZ-mannonic  acid.  This  can  be  separated  into 
its  optically  active  isomers,  and  the  (i-mannonic  acid  lactone 
gives  (i-mannose  on  reduction.  J-Mannonic  acid  when  heated 
with  quinoline  is  partially  converted  into  rf-gluconic  acid,  and 
this  gives  i-glucose  when  its  lactone  is  reduced.  From  both 
(i-mannose  and  (i-glucose,  (i-phenylglucosazone  is  obtained,  and 
from  this  by  the  method  given  above  (/'-fructose  is  made. 

/'-Fructose  (see  above)  gives  /'-sorbitol  on  reduction.  When 
this  is  oxidized  with  the  sorbose  bacteria,  /'-sorbose,  stereo- 
isomeric  with  (/'-fructose,  results.  This  undergoes  molecular 
rearrangement  with  alkalies,  giving  (/-galactose.  The  following 
scheme  gives  these  results  in  outline  :  — 


234  CARBOHYDRATES      , 

(//-Fructose 


dZ-Mannitol  /'-Fructose 

I  ,     I 

(//-Mannonic  acid  /  -Sorbitol 

I  I 

-d  -Mannonic  acid  /'-Sorbose 


(/-Gluconic  acid      d-Mannose  d-Galactose 

d-Glucose 


(f-Phenvlglucosazone 

(/-Glucosone 

I 
d '-Fructose 

Thus  all  the  hexoses  occurring  in  nature  have  been  made  synthet- 
ically, and  this  is  justly  regarded  as  one  of  the  greatest  achieve- 
ments of  modern  chemistry. 

POLYSACCHAROSES,    POLYOSES    OR    COMPLEX    SUGARS 

These  sugars  either  occur  in  nature,  e.g.,  cane  sugar  and  sugar 
of  milk,  or  are  made  from  the  more  complgx  natural  carbo- 
hydrates, as  maltose  (malt  sugar)  from  starch  by  the  action  of 
diastase.  Their  most  characteristic  property  is  that  they 
undergo  hydrolysis  when  heated  with  dilute  mineral  acids  or 
under  the  influence  of  certain  enzymes  into  the  monosaccharoses 
or  monoses.  Thus  cane  sugar  gives  (/-glucose  and  (/'-fructose ; 
milk  sugar  gives  (/-glucose  and  (/-galactose ;  and  malt  sugar 
gives  two  molecules  of  (/-glucose.  These  sugars  are  hence  called 
disaccharoses  or  hexodioses. 

Raffinose '  is  an  example  of  a  trisaccharose  or  hexotriose,  as  it 
gives  three  monoses  (hexoses)  on  hydrolysis  with  dilute  mineral 
acids :  — 

'  RafiSnose  resembles  sucrose  very  closely  in  its  properties,  but  is  tasteless. 


CANE   SUGAR  235 

C18H32O16  +  2  H2O  =  C6H12O6  +  C6H12O6  +  CeHisOe. 
Raffinose  (^Glucose  tf-Galactose  d'-Fructose 

Crystalline  tetra-,  penta-,  and  hexasaccharoses  are  also 
known.  All  these  complex  sugars  have  the  general  formula, 
(CeHioOs)!  +  H2O,  e.g.,  disaccharoses  (C6Hio05)2  +  H2O,  tri- 
saccharoses  (C6Hio05)3  +  H2O,  tetrasaccharoses  (C6Hio05)4  + 
H2O,  etc. 

Owing  to  the  ease  with  which  they  are  hydrolyzed  to  monoses, 
the  complex  sugars  are  regarded  as  anhydrides  of  the  hexoses. 
The  hexodioses  are  the  most  important  of  these  sugars.  They 
are  neutral,  colorless  compounds  having  a  sweet  taste,  readily 
soluble  in  water  and  crystallize  better  than  the  monosaccharoses. 

Cane  sugar,  beet  sugar,  sucrose,  saccharose,  CisHjaOn,  is 
the  most  important  of  all  the  sugars  and  the  one  which  has  been 
longest  known.  When  the  term  sugar  alone  is  used  it  always 
refers  to  this  compound.  The  production  and  refining  of  this 
sugar  has  become  one  of  the  great  modern  industries.  Its 
importance  as  a  food  is  shown  by  the  fact  that  the  world's 
production  in  19 20-1 921  is  estimated  to  be  over  17,000,000  long 
tons,  of  which  slightly  over  one  quarter  is  beet  sugar,  the  rest 
cane  sugar.  Cane  sugar  occurs  extensively  distributed  in 
plants  and  plays  a  very  important  part  in  the  metabolism  of 
plants.  It  is  found,  always  in  the  free  condition,  in  sorghum, 
in  certain  palms,  in  the  sugar  maple,  in  coffee,  walnuts,  and  other 
nuts,  in  the  blossoms  of  plants  and  in  honey.  It  occurs  espe- 
cially abundantly  in  sugar  cane  (about  14.5  per  cent)  and  in  the 
sugar  beet  (16-20  per  cent)  and  these  two  plants  supply  practi- 
cally all  the  world's  sugar,  though  a  small  quantity  is  made 
from  the  sugar  maple  (maple  sugar). 

When  sugar  cane  is  used,  it  is  crushed  and  mixed  with  water 
to  extract  all  the  sugar.  The  juice  is  then  filtered,  treated  with 
lime  and  heated  to  the  boiling  point  to  remove  acids  (which 
would  hydrolyze  the  cane  sugar),  proteids,  coloring  matters, 
and  other  impurities.  After  filtering,  the  purified  juice  is 
sometimes  bleached  with  sulphur  dioxide  and  the  faintly  alkaline 
juice  is  concentrated  in  vacuum  evaporators  to  a  syrup.  This 
is  then  further  concentrated  in   vacuum  pans   till  the  sugar 


236  CARBOHYDRATES 

begins  to  crystallize.  The  crystals  of  sugar  are  separated  from 
the  mother  liquor  by  means  of  centrifugals,  which  are  rapidly 
revolving  fine  sieves.  These  retain  the  crystals,  but  expel 
the  mother  liquor  by  centrifugal  force.  After  washing  in  the 
centrifugals  with  a  small  quantity  of  water  to  remove  the 
adhering  molasses,  the  crystals  are  dried. 

When  sugar  beets  are  used,  the  juice  is  extracted  by  the  dif- 
fusion process.  The  beets  are  sliced  and  loosely  packed  in  the 
cells  of  the  diffusion  apparatus  through  which  hot  water  cir- 
culates in  such  a  manner  that  fresh  water  comes  into  contact 
with  the  nearly  exhausted  beets.  This  dilute  sugar  solution 
then  passes  into  the  next  cell  containing  partially  exhausted 
beets,  and  so  on,  until  finally  the  fresh  beets  are  extracted  with 
the  strongest  sugar  solution.  The  cell  walls  of  the  beets  allow 
the  sugar  to  diffuse  through,  but  hold  back  colloidal  substances. 
The  juice  is  first  treated  with  lime  and  then  with  carbon  dioxide 
to  remove  most  of  the  lime,  filtered,  decolorized  with  sulphur 
dioxide,  and  then  concentrated  as  described  above. 

Considerable  sugar  is  left  in  the  molasses,  and  this  is  recovered 
in  part  by  precipitating  the  sugar  as  tribasic  calcium  saccharate, 
Ci2H220ii.3CaO,  which  is  then  decomposed  by  carbon  dioxide 
and  the  filtrate  concentrated  for  the  crystallization  of  the 
sugar. 

Cane  sugar  factories  produce  a  large  quantity  of  molasses, 
which  is  utilized  as  a  table  syrup,  in  making  alcohol,  and  in 
baking. 

Beet  sugar  molasses  is  unfit  for  human  food  on  account  of 
its  impurities  and  disagreeable  taste.  It  is  used  in  making 
alcohol  and  as  cattle  food. 

The  raw  sugar  obtained  as  described  above  contains  about 
96  per  cent  sucrose.  It  is  colored  and  contains  impurities  and 
must  be  further  refined  before  it  is  used  as  a  food.  This  is  done 
in  sugar  refineries.  The  raw  sugar  is  treated  with  a  small  quan- 
tity of  water  or  with  dUute  sugar  solution.  This  removes  most 
of  the  impurities  and  leaves  the  crystals.  These  are  separated 
from  the  syrup  by  means  of  centrifugals,  dissolved  in  water,  and 
the  solution  treated  with  lime.    The  excess  of  lime  and  the  cal- 


CANE  SUGAR  237 

cium  salts  are  then  precipitated  with  mono  calcium  phosphate  or 
phosphoric  acid  as  calcium  phosphate  and  the  solution  filtered. 
It  is  then  decolorized  with  sulphur  dioxide  or  bone  black  and 
concentrated  in  vacuum  pans  to  crystallization.  The  white 
sugar  of  commerce  is  extraordinarily  pure.  It  contains  at 
least  99.9  per  cent  sucrose. 

Sucrose  crystallizes  in  the  monoclinic  system.  It  is  very 
soluble  in  water,  but  difficultly  soluble  in  alcohol.  It  melts 
at  about  160°  and  then  solidifies  to  an  amorphous  glass-like 
mass.  When  more  strongly  heated  it  turns  brown,  undergoes 
decomposition,  and  forms  a  mixture  of  substances  called 
caramel  much  used  in  making  confectionery.  Heated  still 
higher  it  carbonizes,  forming  sugar  charcoal,  and  gives  off 
gases.  Sucrose  does  not  reduce  Fehling's  solution,  is  -not 
changed  by  the  action  of  dilute  alkalies,  and  does  not  react  with 
phenylhydrazine.  The  aqueous  solution  is  dextrorotatory 
(W?  =  +66.5°),  and  it  does  not  show  mutarotation  (223).  When 
hydrolyzed  with  dilute  mineral  acids  or  with  the  enzyme, 
invertase,  sucrose  gives  a  mixture  of  equal  parts  of  rf-glucose 
and  d'-fructose.  As  d'-fructose  is  very  much  more  strongly 
levorotatory  (  —  93°)  than  d-glucose  is  dextrorotatory  (+  52.3°) 
the  mixture  is  levorotatory.  For  this  reason  it  is  called  invert 
sugar  and  the  term  "  inversion  "  is  used  for  the  hydrolysis  of 
the  disaccharoses  into  monosaccharoses.  Cane  sugar  does  not 
undergo  fermentation  directly,  but  only  after  hydrolysis  into 
glucose  and  fructose.  Most  of  the  varieties  of  yeast  produce 
the  enzyme,  invertase,  which  hydrolyzes  the  cane  sugar,  and 
the  glucose  and  fructose  then  ferment.  Cane  sugar  is  twice  as 
sweet  as  (i-glucose,  but  it  is  not  as  sweet  as  (i'-fructose. 

Cane  sugar  gives  an  octaacetate,  Ci2Hi403(OCOCH3)8,  with 
acetic  anhydride.    This  melts  at  67^  and  has  a  bitter  taste. 

It  also  forms  an  octamethyl  derivative,  Ci2Hi403(OCH3)8. 
The  following  formula  has  been  suggested  for  sucrose :  — 

CH2OH 

CH20H.CHOH.CH(CHOH)2.CH— 0— C— CH(CHOH)2.CH20H. 

I 0 1 


d-Glucose  residue  tf'-Fructose  residue 


238  CARBOHYDRATES 

It  is  in  accord  with  the  fact  that  sucrose  contains  eight  hy- 
drox}'l  groups,  does  not  reduce  Fehling's  solution  nor  react 
with  phen}'lhydrazine  (no  longer  contains  a  carbonyl  group), 
and  undergoes  hydroh'sis  so  readily  and  quantitatively  into 
(f-glucose  and  (i'-fructose. 

Sucrose  has  not  yet  been  made  synthetically. 

To  determine  cane  sugar  quantitatively,  in  raw  sugars  for 
example,  use  is  made  of  its  property  of  rotating  the  plane  of 
polarized  light.  The  rotation  is  determined  in  a  polariscope 
(sactharimeter)  ha\-ing  a  scale  which  enables  the  percentage  of 
sugar  to  be  read  directly.  The  inversion  of  cane  sugar  is 
brought  about  by  an  extremely  small  amount  of  acid;  thus  when 
a  mixture  of  80  parts  of  sugar  and  20  parts  of  water  containing 
only  0.005  Pfir  cent  hydrochloric  acid  is  digested  in  boiling  water 
for  one  hour,  it  is  almost  completely  hydroh'zed.  The  inversion 
is  a  catalytic  phenomenon  and  is  due  to  the  hydrogen  ions  of  the 
acid.  Since  it  has  been  found  that  the  in\ersion  constant  and 
the  hydrogen  ion  concentration  are  proportional,  the  velocity 
of  inversion  of  cane  sugar  is  used  to  determine  the  strength  of 
acids.  The  rate  of  hydrolysis  of  sucrose  is  1000  times  more 
rapid  than  that  of  lactose  or  maltose. 

Sugar  of  milk,  lactose,  C12H22O11+H2O,  is  found  in  the  milk 
of  all  mammals,  and  it  is  the  only  sugar  present  in  this  secretion. 
It  does  not  occur  in  plants.  It  is  prepared  by  the  evaporation  of 
the  whey,  which  is  the  fluid  left  when  the  casein  and  the  fat  of 
skimmed  milk  are  precipitated  by  rennet  in  making  cheese.  It 
is  purified  by  recrystallization  from  water.  It  dissolves  in  6 
parts  of  cold  water  and  25  parts  of  hot  water.  It  crystallizes 
from  water  at  ordinary  temperatures  with  a  molecule  of  water 
of  crystallization,  but,  if  crystallized  from  water  above  95°,  the 
crystals  contain  no  water.  It  is  about  one  fourth  as  sweet  as 
cane  sugar.  Like  (f-glucose  it  exists  in  an  a-  and  a  /3-form  and 
shows  mutarotation,  due  to  the  formation  of  a  mixture  of  these 
two  forms  in  equilibrium  ([a]f  =  +55.3°).  On  long  boiling 
with  dilute  mineral  acids  lactose  is  hydrolyzed  to  rf-glucose  and 
(i-galactose.  This  same  effect  is  produced  by  the  enzyme, 
lactase,  which  is  present  in  certain  varieties  of  yeast  (tortdcB)  and 


MALTOSE,   MALT   SUGAR  239 

in  the  intestines  of  the  calf.  It  is  not  hydrolyzed  by  invertase, 
nor  will  lactase  hydrolyze  cane  sugar.  Lactose  is  not  fermented 
by  beer  yeast,  as  this  yeast  contains  no  lactase.  It  is-  fermented 
by  certain  microorganisms  (torulcs),  which  produce  lactase. 
Milk  sugar  is  converted  very  readily  into  lactic  acid  by  a  number 
of  bacteria.  It  reduces  Fehling's  solution,  forms  a  silver  mirror 
with  an  ammoniacal  solution  of  silver  nitrate,  and  gives  a 
phenyllactosazone  with  phenylhydrazine,  which  is  soluble  in 
boiling  water.  It  gives  an  octaacetate  with  acetic  anhydride. 
When  oxidized  with  bromine  water  it  gives  a  monobasic  acid, 
lactohionic  acid,  containing  twelve  carbon  atoms,  and  hence  it 
must  contain  an  aldehyde  group.  When  lactobionic  acid  is 
hydrolyzed  by  mineral  acids  it  gives  gluconic  acid  and  galac- 
tose, thus  proving  that  the  aldehyde  group  in  lactose  must  be 
in  the  glucose  residue.  The  following  formula  has  been  sug- 
gested for  lactose :  — 

CH20H.CHOH.CH.(CHOH)2.CH— 0— CH2.(CHOH)4.CHO. 

-0- 


Galactose  residue  Glucose  residue 

Lactose  is  used  in  the  manufacture  of  pharmaceutical  prepara- 
tions and  as  a  food. 

Maltose,  malt  sugar,  C12H22O11+H2O,  is  formed  from  starch 
by  the  action  of  malt  diastase.  Other  enzymes,  such  as  the 
ptyalin  of  the  saliva  and  the  amylopsin  of  the  pancreatic  juice, 
also  convert  starch  into  maltose.  Maltose  also  results  from  the 
hydrolysis  of  glycogen  by  enzymes.  It  crystallizes  in  needles 
containing  one  molecule  of  water  and  is  readily  soluble  in  water. 
Its  solution  shows  upward  mutarotation,  i.e.,  the  rotation  in- 
creases, as  the  equilibrium  value  ([a]^  =  -|-  137°)  is  greater 
than  the  initial  value.  It  reduces  Fehling's  solution  and  is 
easily  decomposed  by  alkalies.  It  is  completely  fermented  by 
beer  yeast.  This  is  due  to  the  presence  in  the  yeast  of  the 
enzyme,  maltase,  which  hydrolyzes  the  maltose  to  two  mole- 
cules of  (/-glucose,  which  then  ferment.  Dilute  mineral  acids 
also  hydrolyze  maltose  to  (/-glucose,  but  not  as  readily  as  cane 
sugar.     The  other  enzymes,  invertase,  diastase,  lactase,  etc., 


240  CARBOHYDRATES 

are  without  action  on  maltose.  It  reacts  with  phenylhydrazine 
to  form  a  phenylmaltosazone  and  on  oxidation  with  bromine 
water  gives  maltobionic  acid,  a  monobasic  acid,  containing  12 
carbon  atoms.  This  acid  when  hydrolyzed  with  mineral  acids 
gives  d-glucose  and  rf-gluconic  acid,  and  hence  maltose  must 
contain  an  aldehyde  group.  Maltose  gives  an  octaacetate  with 
acetic  anhydride,  and  hence  contains  8  hydro.xyl  groups.  It  is 
probably  stereoisomeric  with  lactose  (238)  and  has  the  same 
structural  formula. 

Maltose  is  the  intermediate  product  in  the  manufacture  of 
ethyl  alcohol  from  corn,  potatoes,  and  other  materials  con- 
sisting largely  of  starch.  The  starch  is  converted  into  maltose 
by  the  action  of  the  diastase  of  malt,  and  the  maltose  is  hydro- 
lyzed by  the  maltase  of  the  yeast  to  glucose,  which  then  under- 
goes fermentation  by  the  zymase  of  the  yeast  to  alcohol  and 
carbon  dioxide. 

Isomaltose  is  the  name  given  by  Emil  Fischer  to  a  disac- 
charose  obtained  by  him  by  the  action  of  strong  hydrochloric 
acid  on  J-glucose.  It  does  not  ferment  with  yeast.  It  is  prob- 
ably identical  with  the  disaccharose  called  revertose  obtained 
by  the  synthetical  action  of  maltase  on  J-glucose.  It  is  not 
hydrolyzed  by  maltase  or  invertase,  but  gives  d-glucose  with 
emulsin. 

Colloidal  '  Polysaccharoses 

The  carbohydrates  belonging  to  this  group,  of  which  starch 
and  cellulose  are  the  most  important  members,  are  amorphous, 
tasteless,  and,  for  the  most  part,  insoluble  substances,  which 
are  hydrolyzed  to  monoses  by  the  action  of  dilute  mineral  acids. 
They  belong  to  the  class  of  compounds  known  as  colloids. 
The  composition  of  those  regarded  as  anhydrides  of  the  hexoses 
is  expressed  by  the  formula  (C6H10O5);.  or  (CeHioOs)!  +  H2O 
(235).  The  molecular  weight  is  unknown,  but  is  undoubtedly 
very  large. 

*  By  "  colloidal "  polysacdiaroses  is  understood  polysaccharoses  which 
are  insoluble  in  water  (cellulose)  or  which  form  pseudo  solutions  in  this 
solvent  (starch,  inulin,  etc.).  See  Applied  Colloid  Chemistry,  by  W.  D. 
Bancroft. 


STARCH  241 

Starch  (CeHioOs)!  or  (CeHi'oOs)!  +  H2O,  is  found  in  the  form 
of  granules  having  an  organized  structure  in  many  different 
organs  of  green  plants,  particularly  as  a  reserve  maierial. 
Hence  it  is  found  especially  abundantly  in  tubers,  roots,  nuts, 
and  cereals,  e.g.,  in  all  kinds  of  grain  (wheat,  Indian  corn, 
etc.),  in  the  potato,  in  chestnuts,  and  in  acorns.  The  form  and 
size  of  the  starch  granules  are  characteristic  of  the  different 
plants,  and  it  is  frequently  possible  to  identify  the  origin  of  a 
starch  by  a  microscopic  examination.  In  this  country  starch 
is  generally  made  from  Indian  corn  (maize)  and  in  Europe  from 
potatoes.  Indian  corn  contains  55  per  cent  starch.  About 
forty  million  bushels  of  shelled  corn  are  used  annually  in  making 
starch  and  products  derived  from  starch  (glucose,  dextrins, 
malt  syrup,  etc.).  The  separation  of  the  starch  from  the  corn 
is  largely  mechanical.  The  corn  is  first  soaked  in  warm  water 
containing  some  sulphur  dioxide  and  when  soft  enough  is  passed 
through  a  mill  in  order  to  break  it  up.  The  germ  at  the  apex 
of  the  kernel  which  contains  most  of  the  oil  is  removed 
by  passing  the  mass  mixed  with  water  through  the  germ 
separators.  The  semifluid  mass  is  then  ground  and  passed 
over  sieves  of  bolting  cloth,  which  allow  the  starch  and  gluten 
in  suspension  in  water  to  pass  through  but  retain  the  bran. 
The  starch  liquor  is  allowed  to  settle  in  troughs  to  free  it  from 
the  lighter  gluten.  The  starch  is  then  washed  several  times 
with  water  by  decantation,  drained  on  wooden  frames  having 
cloth  bottoms,  and  dried  in  kilns. 

In  polarized  light  starch  grains  are  doubly  refracting.  Air- 
dried  starch  contains  10  to  20  per  cent  water.  It  can  be 
obtained  free  from  water  by  gradually  drying  at  increasing 
temperatures  up  to  109°-!  10°.  Starch  is  practically  insoluble 
in  cold  water.  When  heated  with  water  the  starch  grains 
swell,  burst  and  form  starch  paste.  If  starch  is  treated  with 
cold,  dilute  mineral  acid  for  some  days  it  is  converted  into 
soluble  starch.  This  dissolves  in  hot  water,  forming  a  solution 
that  is  strongly  dextrorotatory.  Soluble  starch  is  also  formed 
by  treatment  with  oxidizing  agents  or  with  alkalies.  It  is 
really  a  partially  hydrolyzed  starch  and  not  a  modification  of 


242  CARBOHYDRATES 

starch,  as  the  name  suggests.  Starch  is  especially  characterized 
by  the  blue  color  that  it  gives  with  iodine  dissolved  in  a  solu- 
tion of  potassium  iodide.  This  reaction  is  used  to  identify 
starch  granules  in  plants.  Starch  paste  and  soluble  starch 
also  give  this  reaction.  It  is  apparently  not  due  to  the  forma- 
tion of  a  chemical  compound  of  starch  and  iodine  nor  to  the 
formation  of  a  solid  solution  of  iodine  in  starch,  but  is  merely 
an  adsorption  phenomenon.  The  iodine  is  adsorbed  by  the 
starch.  Starch  forms  nitrates  with  a  mixture  of  nitric  and  sul- 
phuric acids  (nitrostarch  used  as  an  explosive)  and  acetyl 
derivatives  with  acetic  anhydride. 

The  most  important  transformation  of  starch  is  its  hydrolysis 
by  boiling  with  dilute  mineral  acids.  (^-Glucose  is  the  only  mono- 
saccharose  formed  in  this  hydrolysis,  and  under  the  proper  con- 
ditions the  starch  can  be  nearly  quantitatively  converted  into 
glucose.  The  hydrolysis  of  starch  by  the  diastase  of  malt  gives 
maltose,  and  under  the  proper  conditions  this  transformation 
can  be  made  nearly  quantitative.  Starch  can  be  determined 
quantitatively  by  converting  it  into  glucose  by  the  action  of 
dilute  acids  and  determining  the  amount  of  sugar  formed. 
Starch  as  it  is  obtained  technically  is  not  an  individual  com- 
pound, but  is  a  mixture  of  several  substances.  The  cell  walls 
of  the  starch  grains  consist  of  amylo pectin,  while  the  contents  of 
the  cell  form  the  amylase.  Starch  paste  is  essentially  a  solution 
of  amylose  thickened  by  undissolved  mucilaginous  amylopectin. 
Amylose,  which  forms  the  larger  part  of  starch,  is  itself  a  com- 
plex mixture  of  closely  related  substances  that  differ  in  solu- 
bility in  water.  The  so-called  soluble  starch  is  the  lowest 
member  of  this  series.  In  all  its  forms  amylose  is  soluble  in 
alkaline  fluids  without  forming  a  paste.  Even  with  warm  water 
it  never  forms  a  paste.  The  amylose  in  solution  gives  a  pure 
blue  color  with  a  solution  of  iodine,  but  the  pure  solid  amylose 
does  not.  That  starch  and  the  dried  starch  paste  give  a  blue 
color  with  iodine,  is  due  to  the  fact  that  amylose  is  present  in 
these  substances,  in  the  form  of  a  solid  solution.  Amylose  is 
only  attacked  by  diastase  when  it  is  in  solution,  and  on  hydrol- 
ysis with  diastase  gives  maltose  alone  without  perceptible  forma- 


INULIN  243 

tion  of  dextrins.  The  amylopectin  which  forms  the  smaller 
part  of  the  starch  substance  is  also  apparently  not  homogeneous. 
It  swells  with  warm  water  and  forms  a  mucilaginous  paste  and 
when  superheated  with  water  it  gives  a  sticky  solution.  With 
a  solution  of  iodine  it  gives  a  blue-violet  color  which  is  less  in- 
tense than  the  blue  color  -vyith  amylose.  The  dextrins  formed 
together  with  maltose  by  the  action  of  diastase  on  starch  are 
apparently  derived  from  the  amylopectin. 

Starch  is  of  very  great  importance  as  a  large  constituent  of 
our  food  (bread,  potatoes,  cereals,  etc.).  In  the  stomach  and 
intestines  starch  is  hydrolyzed  to  maltose  and  glucose  by  the 
enzymes  present  in  the  digestive  juices.  It  is  much  used  as 
an  adhesive  paste  and  in  laundries  for  stiffening  clothes.  In 
this  process  the  starch  is  converted  into  dextrin  by  the  hot  iron. 
Starch  is  also  the  material  from  which  commercial  glucose 
(starch  sugar)  and  the  dextrins  are  made. 

Dextrins  are  made  from  starch  either  by  heating  this  to 
i8o°-2oo°  or  by  first  moistening  the  starch  with  hydrochloric 
or  nitric  acid  and  then  gently  heating  it.  It  forms  a  white  or 
yellow  powder  and  is  used  as  an  adhesive,  especially  for  envelopes 
and  postage  stamps.  The  dextrins  form  colloidal  solutions  in 
water,  but  are  insoluble  in  absolute  alcohol.  As  the  name 
indicates  they  are  dextrorotatory  ([a]j  up  to  about  -|-  200°). 
They  are  completely  converted  into  maltose  by  malt  extract 
and  into  (Z-glucose  by  the  action  of  dilute  acids.  Apparently 
there  are  several  dextrins,  some  of  which  give  a  reddish-violet 
color  with  a  solution  of  iodine  (erythrodextrin)  while  others 
give  no  color  (acchroodextrin) .  Some  reduce  Fehling's  solution, 
others  do  not.  Dextrin,  also  known  as  British  gum,  is  used 
as  a  substitute  for  natural  gums. 

Inulin,  (CeHioOs),  -|-  H2O,  is  a  reserve  material  resembling 
starch,  found  in  dahlia  bulbs,  chicory  roots,  etc.  It  forms  a 
white  hygroscopic  powder,  consisting  of  doubly  refracting 
sphero-crystals,  which  is  very  soluble  in  warm  water  (forming 
a  colloidal  solution).  It  is  levorotatory  ([a]j  from  —33°  to 
—40°)  and  gives  no  color  with  a  solution  of  iodine.  Dilute  acids 
hydrolyze  it  more  readily  than  starch,  giving  only  (f' -fructose, 


244  CARBOHYDRATES 

It  is  also  hydrolyzed  to  (i'-fructose  by  the  enzyme,  inulase, 
but  is  not  acted  upon  by  diastase  or  the  pancreatic  juice. 

Glycogen  (liver  starch),  (CeHioOs)!  +  H2O,  is  a  reserve  ma- 
terial found  in  aU  developing  cells  of  the  animal  organism,  and  is 
especially  abundant  in  the  liver.  It  also  occurs,  in  small 
quantity,  in  the  muscular  tissue  of  animals,  in  yeast,  and  in 
mushrooms.  It  is  usually  prepared  from  fresh  liver.  When 
pure  it  forms  a  white,  tasteless,  and  inodorous  amorphous  powder, 
which  dissolves  in  water,  forming  an  opalescent  colloidal  solution. 
This  solution  is  dextrorotatory  ([a]j  =  +  i96°-i97°)  and  gives 
a  yellowish-brown  to  red-brown  color  with  a  solution  of  iodine. 
It  is  converted  almost  completely  into  (i-glucose  by  the  action 
of  dilute  acids,  though  it  is  not  attacked  even  by  strong  alkaline 
solutions.  It  is  also  hydrolyzed  by  the  ptyalin  of  the  saliva, 
yielding  maltose,  and  gives  maltose  and  J-glucose  with  liver 
extract. 

CeUulose,  (CeHioOs),,  or  (CeHioOe).  +  H2O.  —  Cellulose  is 
the  chief  constituent  of  the  cell  walls  of  plants.  It  also  occurs 
in  the  animal  kingdom.  Thus  the  tunica  of  the  Ascidia  is 
chiefly  cellulose.  It  is  usually  prepared  from  cotton,  which  is 
85  per  cent  cellulose,  by  extracting  it  with  water,  alcohol,  ether, 
dilute  alkalies,  and  acids,  as  cellulose  is  insoluble  in  all  these 
solvents.  This  cotton  cellulose  is  the  onl)-  variety  that  has 
been  carefully  investigated,  and  the  properties  ascribed  to 
cellulose  are  those  observed  in  a  study  of  this  product.  Absorb- 
ent cotton  and  filter  paper  are  usually  regarded  as  the  purest 
form  of  cellulose,  although  they  contain  small  amounts  of 
impurities  and,  on  account  of  the  energetic  treatment  to  which 
they  have  been  subjected  in  order  to  purify  them,  cannot  be 
regared  as  entirely  unchanged  cellulose.  Cellulose  is  strongly 
double  refracting  and  behaves  as  a  typical  colloid,  exhibiting 
the  phenomena  of  swelling  and  adsorption.  Air-dried  cellulose 
contains  6  to  8  per  cent  of  water,  which  may  be  removed 
by  drying  in  a  vacuum.  It  dissolves  in  Schweitzer's  reagent, 
which  is  a  solution  of  copper  oxide  in  ammonia,  and  also  in  a 
strong  solution  of  zinc  chloride.  Pure  cellulose  gives  a  yeUow 
or  brown  color  with  a  solution  of  iodine  and  this  becomes  blue 


CELLULOSE  245 

in  the  presence  of  concentrated  sulphuric  acid.  It  also  gives  a 
blue  color  with  iodine  dissolved  in  a  solution  of  potassium  iodide 
and  containing  zinc  chloride,  and  this  reaction  is  used  as  a  test  for 
cellulose.  Cellulose  dissolves  in  strong  sulphuric  acid  (showing 
the  presence  of  hydroxyl  groups).  If  the  solution  is  allowed 
t3  stand  until  it  gives  no  precipitate  when  diluted  with  water, 
and  the  very  dilute  solution  is  heated  in  an  autoclave  to  120°, 
the  cellulose  is  completely  hydrolyzed  to  ti-glucose.  When 
heated  with  acetic  anhydride,  acetic  acid,  and  some  sulphuric 
acid(acetolysis),  cellulose  gives  an  octaacetate  of  the  disaccha- 
rose  C12H22O11,  called  cellubiose,  from  which  the  sugar  itself 
is  obtained  by  saponification  with  alkali.  This  cellubiose  bears 
to  cellulose  very  much  the  same  relation  that  maltose  bears  to 
starch.  Like  maltose  it  gives  only  (i-glucose  when  hydrolyzed 
with  dilute  mineral  acids.  Cellulose,  like  starch,  is  therefore 
an  anhydride  of  (^-glucose.  It  is  apparently  very  much  more 
complex  than  starch,  and  probably  has  a  much  greater  mo- 
lecular weight.  With  acetic  anhydride  it  gives  a  triacetate, 
(CeHyCOCOCHs) 302)1,  showing  that  it  contains  three  alcoholic 
hydroxyl  groups.  A  cold  concentrated  solution  of  sodium  hy- 
droxide (30  per  cent)  converts  cellulose  into  cellulose  hydrate. 
The  alkali  causes  a  shrinking  of  the  fiber  and  combines  with  it 
to  form  an  alcoholate.  The  alkali  is  afterwards  removed 
by  washing  with  water.  This  "  mercerized  "  cotton,  as  it  is 
called  after  Mercer  who  introduced  the  method  into  the  textile 
industry,  has  a  much  greater  attraction  for  dyestuffs  and  gives 
deeper  shades  than  can  be  obtained  with  the  unmercerized 
cotton.  It  also  gives  a  silk-like  finish  to  the  cotton.  Cold 
concentrated  sulphuric  acid  produces  a  somewhat  greater 
change  in  the  cellulose  (hydrolysis).  Upon  this  change  depends 
the  manufacture  of  parchment  paper.  Unsized  paper  is  dipped 
into  80  per  cent  sulphuric  acid  for  15  to  20  seconds  and  then 
freed  from  the  acid  by  washing  with  water.  The  pores  of  the 
paper  become  filled  with  a  gelatinous  decomposition  product  of 
the  cellulose,  which  makes  it  tougher  and  less  porous.  Parch- 
ment paper  is  colored  blue-black  by  a  solution  containing 
iodine  and  potassium  iodide  (amyloid).     Cellulose  is  the  chief 


246  CARBOHYDRATES 

constituent  of  the  vegetable  textile  fabrics  (cotton,  linen,  hemp 
and  jute)  and  also  of  paper. 

Cellulose  nitrates,  nitrocellulose.  —  Cellulose  is  converted 
into  nitrates  (nitrocellulose)  by  the  action  of  a  mixture  of  nitric 
and  sulphuric  acids.  The  lower  nitrates  (10  per  cent  to  12  per 
cent  nitrogen,  soluble  in  ether-alcohol)  are  called  collodion 
cotton,  soluble  cotton,  etc.,  while  the  higher  nitrates  (about 
13  per  cent  nitrogen)  are  known  as  gun  cotton.  Celluloid  is 
a  solid  solution  of  collodion  cotton  and  camphor,  which  is  used 
for  manufacturing  man)'  articles  formerly  made  from  horn  or 
ivory.  Its  chief  use,  however,  is  for  photographic  films,  espe- 
cially motion  picture  films.  Gwi  cotton  is  used  as  a  high  ex- 
plosive for  filling  torpedoes  and  bombs  and  also,  when  properly 
gelatinized,  in  the  manufacture  of  s?nokeless  powders. 

Cellulose  acetate,  soluble  in  chloroform  and  also  in  a  mixture 
of  acetic  ether  and  alcohol,  forms  a  plastic  mass  with  camphor 
resembling  celluloid  and  is  used  in  making  motion  picture  films 
which  are  non-inflammable.  It  is  a  mixture  of  the  di-  and  tri- 
acetates.  It  is  also  used  in  making  artificial  silk.  Artificial  silk 
is  made  by  forcing  solutions  of  cellulose  or  its  esters  through 
fine  openings  into  a  bath  which  coagulates  the  thread.  This  is 
then  dried  and  wound  on  spools.  Collodion  cotton  in  solution 
in  ether-alcohol  was  first  used,  the  threads  being  "denitrated" 
in  a  bath  of  sodium  hydrosulphide  (Chardonnet  silk).  Another 
method  makes  use  of  a  solution  of  cellulose  in  copper-oxide- 
ammonia.  The  blue  solution  is  spun  into  a  bath  of  dilute  sul- 
phuric acid  which  coagulates  the  threads  and  removes  the  copper 
(Glanzstoff) .  The  latest  method,  which  has  superseded  the  other 
two,  starts  with  a  solution  of  viscose  made  by  the  action  of  sodium 
hydroxide  and  carbon  bisulphide  on  cellulose.  This  solution  con- 
tains the  sodium  salt  of  a  cellulose  xanthic  acid  (C6H9O4.O.CS.SH, 
simplest  formula).  It  is  coagulated  by  being  spun  into  a  bath 
containing  sodium  bisulphate.  0\-er  eight  million  pounds  of 
viscose  silk  were  made  in  the  United  States  in  1919.' 

'  For  further  information  concerning  the  Cellulose  Industries  and  the 
Manufacture  of  Paper  see  Industrial  Chemistry,  edited  by  Allen  Rogers, 
3d  ed.,  1920,  and  Technology  of  Cellulose  Esters,  by  E.  C.  Worden,  1921. 


CHAPTER  XII 

MIXED   COMPOUNDS   CONTAINING   NITROGEN 

In  connection  with  the  preparation  of  dibasic  acids  from 
monobasic  acids,  reference  was  made  to  cyanacetic  and  the  two 
cyanpropionic  acids.  These  are  simple  cyanogen  substitution 
products  analogous  to  chloroacetic  and  the  two  chloropropionic 
acids.  They  are  made  by  treating  the  chlorine  products  with 
potassium  cyanide.  They  have  been  useful  chiefly  in  the 
preparation  of  dibasic  acids,  as  described  in  connection  with 
malonic  and  the  two  succinic  acids.  It  will  therefore  not  be 
necessary  to  treat  of  them  individually  here. 

Note  tor  Student.  —  How  can  malonic  acid  be  made  from  acetic 
acid;  and  isosuccinic  acid  from  propionic  acid?     Give  the  equations. 

The  chief  substances  to  be  taken  up  under  the  head  of 
mixed  compounds  containing  nitrogen  are  the  amino  acids  and 
the  acid  amides.  As  will  be  seen,  both  these  classes  of  sub- 
stances are  of  special  interest,  as  they  represent  forms  of  com- 
bination which  are  favorite  ones  in  nature,  especially  in  the 
animal  kingdom,  some  of  the  most  important  substances  found 
in  the  animal  body,  such  as  urea,  uric  acid,  glycocoU,  proteins, 
etc.,  belonging  to  one  or  both  the  classes. 

Amino  Acids 

The  relation  of  an  amino  acid  to  the  simple  acid  is,  as  the 
name  implies,  the  same  as  that  of  an  amino  derivative  of  a  hydro- 
carbon to  the  hydrocarbon.  That  is  to  say,  it  is  to  be  regarded 
as  the  acid  in  which  the  amino  group,  NH2,  has  been  substituted 
for  a  hydrogen  atom  of  the  hydrocarbon  residue.  Thus,  amino- 
acetic  acid  is  represented  by  the  formula  H2NCH2COOH ;  while 
aminomethane,  or  methylamine,  is  represented  thus,  CH3.NH2. 
The    reasons    for    regarding    methylamine    as    a    substituted 

247 


248  MIXED   COMPOUNDS  CONTAINING  NITROGEN 

ammonia  have  been  stated.  The  formula  is  based  upon  the 
reactions  of  the  substance  and  the  methods  used  in  its  prepara- 
tion. The  same  arguments  lead  ir^  the  same  way  to  the  view 
that  the  amino  acids  are  substituted  ammonias,  and,  at  the 
same  time,  acids.  The  simplest  method  for  their  preparation 
consists  in  treating  halogen  derivatives  of  the  acids  with 
ammonia.  Thus  aminoacetic  acid  can  be  made  by  treating 
bromoacetic  acid  with  ammonia :  — 

C«^<m.H  +  ^  NH3  =  CH.<^H^jj  +  NH.Br. 

Note  for  Student.  —  Compare  this  reaction  with  that  rtiade  use  of  for 
making  methylamine. 

Aminoformic  acid,  carbamic  acid,  H2N.COOH.  —  This  acid 
is  not  known  in  the  free  condition.  Its  ammonium  salt, 
H2N.CO2NH4,  is  formed  when  dry  carbon  dioxide  and  dry 
ammonia  are  brought  together,  and  it  is  therefore  contained  in 
commercial  ammonium  carbonate :  — 

NH,  /NH2  NHj 

CO2  +  NH3  =  OC<p,„   ;     0C<  +  NH3  =    I 

^"  \0H  CO2NH4 

The  other  carbamates  are  prepared  from  the  ammonium 
salt.  They  are  hydrolyzed  when  heated  in  aqueous  solution, 
yielding  carbonates  and  ammonia.  Thus,  when  potassium 
carbamate  is  warmed  in  water  solution,  hydrolysis  takes  place, 
as  represented  in  the  equation :  — 

NH2.CO2K  +  H2O  =  NH3  +  HKCO3. 

The  ethereal  salts  of  carbamic  acid,  called  methanes,  are 
readily  made  by  treating  the  ethereal  salts  of  chlorocarbonic  acid 
(178)  with  ammonia :  — 

CI  NH2 

I  I 

CO2C2H5  +  2  NH3  =  CO2C2H5  +  NH4CI. 


GLYCOCOLL,   GLYCINE,   AMINOACETIC  ACID  249 

Aminoformic  acid  cannot  be  taken  as  a  fair  representative 

of  the  amino  acids,  any  more  than  carbonic  acid  can  be  taken 

as  a  fair  representative  of  the  hydroxy  acids. 

Glycocoll,  glycine,!         .       ^,  ..-,  f „„  ^NHj  \ 

•  J    K aminoethane  acid)     CH2<„„  „    . — 
aminoacetic  acid,  J  \  CO2H/ 

In  the  bile  there  are  two  comphcated  acids,  which  are  known 

as  glycocholic  and  taurocholic  acids.     When  glycochohc  acid 

is  boiled  with  hydrochloric  acid,  it  breaks  down,  yielding  cholic 

acid  and  glycocoll.      In  the  urine  of  horses  is  found  an  acid 

known  as  hippuric  acid.     When  this  is  boiled  with  hydrochloric 

acid,  it  breaks  down  into  benzoic  acid  and  glycocoll. 

When  uric  acid  is  treated  with  hydriodic  acid,  glycocoll  is 
one  of  the  products.  Further,  glycocoll  is  formed  when  gelatin 
or  glue  is  boiled  with  baryta  water  or  dilute  sulphuric  acid.  Its 
formation  from  bromoacetic  acid  and  ammonia,  mentioned  above, 
gives  the  clearest  indication  in  regard  to  its  relation  to  acetic  acid. 

Aminoacetic  acid  is  soluble  in  water,  insoluble  in  absolute 
alcohol  or  ether.  It  has  a  sweetish  taste,  and  is  sometimes  called 
gelatin  sugar. 

Aminoacetic  acid  has  both  acid  and  basic  properties.  It 
unites  with  strong  acids,  forming  salts ;  and  it  combines  with 
bases,  giving  metallic  salts  —  the  aminoacetates.  The  amino- 
acetfites  also  unite  with  salts,  forming  double  compounds. 

Examples  of  the  compounds  with  acids  are  the 

Hydrochloride ■CH2<„„  „      , 

CO2I1 

and  the  Nitrate CH2<!?^'^^°'; 

of  the  salts  with  metals, 

Zinc  aminoacetate       .     .     .    Zn(C2H4N02)2  +  H2O, 
and      Copper  mninoacetate       .     .     Cu(C2H4N02)2  +  H2O; 

of  the  compounds  with  salts,  the  double  salt  of 

Copper  ntirate  and  |  Cu(NO,)2.Cu(C2H.N02)2  +  2  H2O. 

Copper  aminoacetate  i  >  ^^ 


250  MIXED   COMPOUNDS   CONTAINING  NITROGEN 

Treated  with  nitrous  acid,  glycocoU  is  converted  into  hydroxy^ 
acetic  acid.     With  soda-lime  it  gives  methylamine. 

Note  for  Student.  —  Write  the  equations  representing  the  reactions 
that  take  place  when  glycocoU  is  treated  with  nitrous  acid  and  when  it  is 
heated  with  soda  lime. 

It  seems  probable  that  aminoacetic  acid  and  other  amino 
acids  are  really  inner  ammonium  salts,  formed  by  the  union  of 
the  acid  constituent,  carboxyl,  with  the  basic  constituent,  NHj. 
In  accordance  with  this  view  the  formula  should  be  written 
thus :  — 

CH,<™'>0. 

Ethyl  diazoacetate,  diazoacetic  ester,  is  formed  when  ethyl 
aminoacetate  reacts  with  nitrous  acid :  — 

^\ 
H2NCH2COOC2H6  +  HNO2  =  II  >CHCOOC2H5  +  2  H2O. 

W 

Diazoacetic  ester 

It  is  a  yellow  oil  having  a  characteristic  odor  and  boiling  at  141°. 
It  is  remarkably  active  chemically,  e.g.,  with  water  it  gives  ethyl 
glycolate :  — 

C2H6OOC.CHN2  +  H2O  =  C2H6OOC.CH2OH  +  N2. 

This  reaction  is  accelerated  by  the  presence  of  hydrogen  ions 
and  is  one  of  the  best  methods  for  the  detection  and  estimation 
of  these  ions.  Concentrated  hydrochloric  acid  reacts  similarly 
to  give  ethyl  monochloroacetate  and  iodine  gives  ethyl  diiodo- 
acetate.     (Write  the  equations.) 

On  reduction  hydrazinoacetic  acid  is  formed,  and  this  decom- 
poses in  the  presence  of  acids  at  ordinary  temperatures,  giving 
a  salt  of  hydrazine  and  glyoxylic  acid :  — 

HN\ 

I  >CHCOOH  -1-  H2SO4  +  H2O  =  N2H4H2SO4  +  OHC.COOH. 

HydraziDoacetic  acid  HydraziDe  sulphate         Glyoxylic  add 


BETAINE,   TRIMETHYLGLYCTNE  25 1 

It  was  this  decomposition  which  led  to  the  discovery  of  hydra- 
zine, and  from  this  hydronitric  or  hydrazoic  acid,  HN3. 

Diazomethane,  H2C^  ||,  is  prepared  by  decomposing  nitroso- 

methylurethane,  H3CN(NO)C02C2H5,  with  a  solution  of  an 
alkali :  — 

HsC.NCNO)  /N 

I  =H2C<  II  +CO2  +  C2H5OH. 

OCOC2H6  ^N 

It  is  a  yellow  gas,  exceedingly  poisonous,  and  characterized  by 
its  remarkable  chemical  activity.  It  converts  acids  into  methyl 
esters ;  alcohols  (and  phenols)  into  methyl  ethers ;  primary 
amines  into  secondary  amines  (aniline,  C6H6NH2,  into  mono- 
methylaniline,  CeHsNHCHa),  and  aldehydes  into  ketones  : 

H3C.CHO  +  CH2N2  =  CH3COCH3  +  N2. 

Aldehyde  Acetone 

Sarcosine,  methylglycocoU, 

.NH.CH3  ,NH2.CH3 

CH2<;  ,  or  CH2^       \o     .  —  When  bromoacetic  acid 

\cO2H  ^CO 

is  treated  with  methylamine,  a  reaction  takes  place  similar  to 
that  which  takes  place  with  ammonia,  the  product  being  methyl- 
glycocoU or  sarcosine :  — 

CH2< Jq^jj  +  2  CH3.NH2  =  CB.2<^q'^    '  +  NH3(CH3)Br. 

Sarcosine 

Sarcosine  is  a  product  of  the  hydrolysis  of  creatine,  which 
is  found  in  flesh,  and  of  caffeine,  which  is  a  constituent  of  coffee 
and  tea.  It  is  obtained  from  creatine  and  caffeine  by  boiling 
them  with  baryta  water.  Its  properties  are  much  like  those 
of  glycocoU.     It  is  an  inner  ammonium  salt. 

N(CH3)3 

Betaine,    trimethylglycine,    H2C<^  yO,    has     been     made 

CO 
synthetically    from     trimethylamine     and     monochloroacetic 
acid :  — 


252  MIXED   COMPOUNDS   CONTAINING  NITROGEN 

(CH3)3N+C1CH2C0        (CH3)3NCH2CO         (H3C)3N.CH2CO 

HO  CI  HO  +^^^      BeUine 

It  crystallizes  from  water  with  a  molecule  of  water  of  crystal- 
lization. From  its  formula  it  will  be  seen  that  it  is  an  inner 
ammonium  salt.  It  is  found  in  the  sugar  beet  (whence  its 
name)  and  accumulates  in  the  beet  sugar  molasses.  When 
heated  it  gives  trimethylamine,  and  it  is  the  betaine  of  beet  sugar 
molasses  that  is  the  source  of  the  trimethylamine  formed  from 
the  vinasse  (103).  Compounds  having  a  similar  structure  to 
betaine  are  called  betaines. 

NH 
Aminopropionic  acids,  C2H4<  .  —  These  acids  bear  to 

COOH 

propionic  acid  relations  similar  to  that  which  aminoacetic  acid 

bears  to  acetic  acid.     There  are  two,  corresponding  to  a-  and 

/3-chloropropionic  acids,  from  which  they  are  made. 

Their  properties  are  much  like  those  of  glycocoU. 

d-a-Aminopropionic  acid,  which  is  also  called  d-alanine,  is 
a  constant  product  of  the  hydrolysis  of  proteins  (538). 

Among  the  amino  derivatives  of  the  higher  members  of  the 
fatty  acid  series,  two  are  of  special  importance.  These  are 
lexicine  and  isoleucine. 

Leucine,  Z-a-aminoisobutylacetic  acid, 

^„'>CH.CH2.CH(NH2).COOH, 
t-rl3 

is  a  frequent  product  of  the  hydrolysis  of  vegetable  and  animal 
proteins. 

The  inactive  variety  has  been  made  from  isovaleric  aldehyde 
ammonia  and  hydrocyanic  acid  by  the  hydrolysis  of  the  nitrile 
thus  formed :  — 

CH3  H  CH3  H 

II  II 

CHCH2— C— OH  +  HCN  =  CHCH2— C— CN  — >-  COOH. 

II  II 

CH3  NH2  CH3         NH2  +  H2O 

Isovaleric  aldehyde  ammonia 


CYSTINE  253 

When  this  inactive  acid  is  resolved  into  its  optically  active 
components,  the  levo  variety  is  found  to  be  identical  with  the 
leucine  obtained  from  natural  sources. 

When  sugar  is  fermented  with  pure  yeast  in  the  presence  of 
leucine,  isobutyl  carbinol  (inactive  isoamyl  alcohol)  is  formed :  — 

(CH3)2CH.CH2.C^COOH  +  H2O 
\NH2 

Leucine 

=  (CH3)2.CH.CH2.CH20H  +  CO2  +  NH3. 

Isobutyl  carbinol 

Isoleucine,  fi-a-amino-/3-metliyl-/3-ethyl  propionic  acid, 

;;    '>CH.CH(NH2).COOH,    like   leucine,   is   a   frequent 

CHg 

product  of  hydrolysis  of  vegetable  and  animal  proteins.  It  is 
dextrorotatory  and  contains  two  asymmetric  carbon  atoms. 

Isoleucine  gives  secondary  butyl  carbinol  (active  amyl  alcohol) 
when  fermented  with  sugar  by  pure  yeast.  (Write  the  equation.) 
Inactive  amyl  alcohol  and  active  amyl  alcohol  (137)  are  the 
main  constituents  of  fusel  oil  and  result  from  the  protein  ma- 
terial contained  in  the  potatoes  or  corn  used  in  making  alcohol. 

Serine,  which  is  obtained  from  silk  glue  by  boiling  with  dilute 
acids,  has  been  shown  to  be  a-amino-/3-hydroxypropionic  acid, 
CH2(OH).CH(NH2).COOH,  by  treating  it  with  nitrous  acid 
when  it  gives  glyceric  acid  (189).  Optically  active  modifications 
are  also  known.     It  is  formed  in  the  hydrolysis  of  all  albumins. 

Cystine,  C6H12N2O4S2,  a  substance  sometimes  found  as  a 
crystalline  sediment  in  the  urine  of  human  beings  and  dogs, 
is  a  derivative  of  a-aminopropionic  acid.  It  is  frequently 
formed  in  the  hydrolysis  of  proteins.  Tin  and  hydrochloric 
acid  reduce  it  to  cystein,  C3H7NO2S.  The  two  substances 
bear  to  each  other  the  relation  represented  by  these  formulas :  — 

CH2.SH  CH2.S S.  H2C 

I  1  I 

HjN.CH  NH2.CH  HC.H2N 

COOH  COOH         HOOC 

Cystein'  Cystine 


254     mixed  compounds  containing  nitrogen 

Aminosulphonic  Acids 

Just  as  there  are  amino  derivatives  of  the  carboxylic  acids, 
so,  too,  there  are  amino  derivatives  of  the  sulphonic  acids. 
The  most  important  of  these  is 

CH2— SO3H 
Taurine,  /S-aminoethylsulphonic  acid,     |  — Taurine 

CH2— NH2. 
is  found  in  combination  with  cholic  acid  as  taurochoHc  acid, 
in  ox  bile,  and  the  bile  of  many  animals,  as  well  as  in  the  kidneys, 
lungs,  etc.  It  has  been  made  synthetically  from  isethionic 
acid  (187)  by  first  treating  the  acid  with  phosphorus  penta- 
chloride :  —    ■ 

C2H4<gQ  Qjj  +  2  PCI5  =  C2H4<gQ  ^j  +  2  POCI3  +  2  HCl; 

Isethionic  acid  Chloroethylsulphonyl  chloride 

The  chloroethylsulphonyl  chloride  is  then  treated  with  water :  — 
CI  CI 

Chloroethylsiilphonic  acid 

and  the  chloroethylsulphonic  acid  with  ammonia :  — 

Taurine 

Taurine  crystallizes  in  large  monoclinic  prisms.  It  is  a  very 
stable  substance,  and  can  be  boiled  with  concentrated  acids  with- 
out decomposition.     With  nitrous  acid  it  yields  isethionic  acid. 

It  unites  with  strong  bases  forming  salts,  but  not  with  acids. 
This  is  in  accordance  with  the  view  that  taurine  is  an  inner 

CH2— NHsK 
ammonium  salt  as  represented  by  the  formula     |  No. 

CH2— SO2  / 

Amino  Dibasic  Acids 

Aspartic  acid,  aminosuccinic  acid,  aminobutane  diacid, 

HO2C.H2C— CH(NH2).C02H. 


ACID   AMIDES  255 

Aspartic  acid  occurs  in  pumpkin  seeds,  and  is  frequently 
met  with  as  a  product  of  boiling  various  proteins  with  dUute 
acids.  Thus,  for  example,  it  is  formed  when  casein  and  albumin 
are  treated  in  this  way.  It  is  formed  also  when  asparagine 
(259)  is  boiled  with  acids  or  alkalies. 

Aspartic  acid  crystallizes  in  rhombic  prisms,  which  are  diffi- 
cultly soluble  in  water.  The  boiling  solution  of  the  natural 
product  is  levorotatory.  A  cold  solution  is  dextrorotatory. 
It  contains  an  asymmetric  carbon  atom,  and  the  three  varieties 
{d-,  1-,  and  dl-)  suggested  by  the  theory  are  known.  When 
treated  with  nitrous  acid,  each  is  converted  into  the  corre- 
sponding malic  acid. 

Acid  Amides 

When  the  ammonium  salt  of  acetic  acid  is  heated,  it  gives  off 
water,  and  a  compound  distills  over  which  is  known  as  acet- 
amide,  ethane  amide.  The  reaction  is  represented  by  the  follow- 
ing equation :  — 

CH3.COONH4  =  CH3.CONH2  +  H2O. 

An  investigation  of  the  ammonium  salts  of  other  carboxylic 
acids  shows  that  the  reaction  is  a  general  one,  and  a  class 
of  compounds,  known  as  the  acid  amides,  can  thus  be  ob- 
tained. Besi8es  this  method  there  are  two  others  of  general 
application  for  the  preparation  of  the  acid  amides.  One 
consists  in  treating  an  ethereal  salt  of  an  acid  with  ammonia. 
Thus,  when  ethyl  acetate  is  treated  with  ammonia,  this 
reaction  takes  place :  — 

CH3.CO2C2H5  -I-  NHs  =  CH3.CONH2  -1-  CzHbOH. 

The  other  reaction  consists  in  treating  the  acid  chlorides  with 
ammonia.    Thus,  to  get  acetamide,  we  may  treat  acetyl  chloride 
♦  (60)  with  ammonia :  — 

CH3.COCI  +  2  NH3  =  CH3.CONH2  -I-  NH4CI. 

This  last  reaction  is  perhaps  most  frequently  used.  It  shows 
the  relation  that  exists  between  acetic  acid  and  acetamide. 


2S6        MIXED   COMPOUNDS   COXTAINING  NITROGEN 

For  acetyl  chloride  is  made  from  acetic  acid  by  treatment  with 
phosphorus  trichloride,  and  is,  therefore,  to  be  regarded  as 
acetic  acid  in  which  the  hydroxyl  is  replaced  by  chlorine. 
Now,  by  treatment  with  ammonia  the  same  reaction  takes 
place  as  that  which  we  have  had  to  deal  with  in  the  prepara- 
tion of  amino  acids;  the  chlorine  is  replaced  by  the  amino 
group.  Therefore,  acetamide  is  acetic  acid  in  which  the 
hydroxyl  is  replaced  by  the  amino  group,  as  shown  in  the 
formulas :  — 

O  0 

II  II 

CH3C— OH  CH3— C— NH2. 

Acetic  acid  Acetamide 

As  the  hydroxyl  of  the  acid  is  replaced,  the  amide  is  not  an 
acid.  On  the  other  hand,  the  basic  properties  of  the  amino 
group  are  weakened  by  the  presence  of  the  acid  residue  as 
a  part  of  its  composition.  Acetamide  combines  with  hydro- 
chloric acid  gas,  and  the  hydrogen  atoms  of  the  amino  group 
can  be  replaced  by  metals,  owing  to  the  acidifying  influence 
of  the  CO-group.  It  is  therefore  a  weak  base  and  at  the  same 
time  a  weak  acid. 

The  amides  are  converted  into  ammonia  and  a  salt  of  the  acid 
when  boiled  with  solutions  of  strong  bases  :  — 

CH3CONH2  +  KOH  =  CH3CO2K  +  NH3. 

They  are  converted  into  cyanides  by  distilling  with  phos- 
phorus pentoxide,  P2O5 :  — 

CH3.CONH2  =  CH3CN  -I-  H2O. 

As  the  substance  obtained  in  this  way  is  identical  with  methyl 
cyanide,  which  is  formed  by  heating  the  potassium  salt  of 
methylsulphuric  acid  with  potassium  c>anide,  the  reaction 
furnishes  additional  evidence  in  favor  of  the  conclusion  that 
in  the  cyanides  the  carbon  and  not  the  nitrogen  of  the  cyanogen 
group  is  in  combination  with  the  hydrocarbon  residue,  as  rep- 
resented in  the  formula  CH3 — C^N. 


HOFMANN'S   REACTION  257 

As  the  amide  can  be  made  from  the  ammonium  salt,  and 
the  cyanide  or  nitrile  from  the  amide,  so,  by  starting  with  the 
cyanide,  the  amide  and  the  ammonium  salt  can  be  made.  The 
reaction  by  which  the  cyanides  are  converted  into  acids  is 
based  upon  these  relations  :  — 

R.COONH4  — >-  R.CONH2  — ^  R.CN, 

R.CN  — >-  R.CONH2  — >-  R.COONH4. 

By  treating  acid  amides  with  acid  chlorides,  more  com- 
plicated compounds  can  be  obtained.  Of  these  diacetamide, 
NH(C2H30)2,  and  triacetamide,  N(C2H30)3,  may  serve  as 
examples. 

The  preparation  of  an  acid  amide  by  treating  an  ester  with 
ammonia  is  well  illustrated  by  the  preparation  of  oxamide,  in 
which  ethyl  oxalate  is  first  prepared  and  this  then  converted 
into  the  amide  by  treating  it  with  aqueous  ammonia :  — 

COOH      C2H5OH      COOC2H5 

I  +  =1  +2  H2O. 

COOH      C2H5OH      COOC2HB 

Oxalic  acid  Alcohol  Ethyl  oxalate 

COOC2H5      NH3      CONH2 

I  -f  =1  +2  C2H6OH. 

COOC2H5      NH3      CONH2 

Ethyl  oxalate  Oxamide 

When  oxamide  is  heated  with  a  dehydrating  agent,  such  as 
phosphorus  pentoxide,  it  is  converted  into  cyanogen :  — 

CONH2       CN 

I  =1+2  H2O. 

CONH2      CN 

Hofmann's  reaction.  —  When  an  acid  amide  is  treated  with 
bromine  in  an  excess  of  sodium  hydroxide,  the  first  product 
formed  is  acetobromamide,  CH3C0NHBr :  — 

CH3CONH2  +  Br2  =  CHsCONHBr  +  HBr. 

Acetobromamide 

The  sodium  hydroxide  reacts  with  the  bromamide  (which  has 
acid  properties  owing  to  the  presence  of  the  carbonyl  group  and 


2S8        MIXED   COMPOUNDS   CONTAINING  NITROGEN 

the  bromine  atom)  to  form  a  salt,  CHsCONa.NBr,  which  is  un- 
stable. This  sodium  bromamide  undergoes  molecular  rearrange- 
ment (compare  with  the  Beckmann  rearrangement,  401) :  — 

CHsCONa  BrCONa 

II        — ^        II        — >-    CH3— N=C=0; 
BrN  CH3N 

Sodixun  bromamide      Intermediate  product  Methyl  isocyanate 

and  the  intermediate  product  by  the  loss  of  sodium  bromide 
forms  methyl  isocyanate.  This,  in  the  presence  of  the  alkali, 
gives  the  primary  amine  and  carbon  dioxide  :  — 

CH3NCO  +  H2O  =  CH3NH2  +  CO2. 

Methylamine 

It  is  thus  possible  by  starting  with  any  acid  to  pass  to  the  pri- 
mary amine  containing  the  same  hydrocarbon  radical  as  the 
acid.  In  the  case  of  acetic  acid  the  three  stages  are  represented 
below :  — 

CH3COOH  — >■  CH3CONH2  — >■  CH3NH2. 

Acetic  acid  Acetamide  Metiiylamine 

This  reaction  has  become  of  practical  importance  in  connection 
with  the  preparation  of  anthranilic  acid  (407). 

Amic  acids.  —  When  the  amide  of  a  dibasic  acid  (as  oxamide) 
is  boiled  with  aqueous  ammonia  hydrolysis  takes  place :  — 

OC— NH,  OC— ONH4 

I  +  H2O  =      I 

OC— NH2  OC— NH2 

Ammonium  oxamate 

and  the  ammonium  salt  of  oxamic  acid,  HOOC.CONH2,  results. 
Oxamic  acid,  like  carbamic  acid  (248),  is  both  an  acid  and  an 
amide.  It  forms  salts  and  other  derivatives  characteristic  of 
acids,  and,  like  the  amides  of  the  acids,  is  hydrolyzed  by 
alkalies  or  acids  to  oxalic  acid  and  ammonia. 

There  is  one  acid  of  this  kind  that  is  a  well-known  natural 
substance.  It  has  already  been  referred  to  in  connection  with 
aspartic  acid,  which  is  closely  related  to  it.     It  is 


SUCCINIMIDE  259 

Asparagine,      aminosuccinamic      acid,      C4H8N2O3  +  H2O, 

CH2.CONH2 

I  .  —  Asparagine  is  found  in  many  plants,  as  in 

CH(NH2).C00H 

asparagus,  beets,  peas,  beans,  vetches,  and  in  wheat.  It  can 
be  made  by  treating  monoethyl  aminosuccinate  with  ammonia. 

Note  for  Student.  —  What  reaction  takes  place  ?  Write  the  equa- 
tion.    How  is  monoethyl  aminosuccinate  made  ? 

Asparagine  forms  large  rhombic  crystals,  difficultly  soluble  in 
cold  water,  more  easily  in  hot  water.  When  boiled  with  acids 
or  alkalies,  it  is  converted  into  aspartic  acid  and  ammonia. 

Note  for  Student.  —  Note  that  only  the  amino  group  of  the  amide 
is  driven  out  of  the  compound  by  this  treatment.  The  other  amino 
group  which  is  contained  in  the  hydrocarbon  portion  of  the  compound 
is  not  affected. 

Nitrous  acid  converts  the  asparagines  into  the  malic  acids. 

Asparagine  contains  an  asymmetric  carbon  atom,  and  two 
optically  active  stereoisomeric  varieties  are  known.  The  levo- 
rotatory  variety  is  found  in  the  seeds  of  many  plants,  in  aspara- 
gus, in  beets,  in  peas,  beans,  and  in  vetch  sprouts.  The  dextro 
variety  is  also  found  in  vetch  sprouts.  It  is  distinguished  from 
ordinary  asparagine  by  its  sweet  taste. 

CO 

Succinimide,  C2H4<       >NH.  —  This    compound    deserves 

attention  in  this  connection,  as  it  represents  a  not  uncommon 
class  known  as  the  acid  imides.  They  are  formed  from  poly- 
basic  acids,  most  simply  from  dibasic  acids.  They  may  be 
regarded  as  the  anhydrides  in  which  the  imino  group  has  been 
substituted  for  an  oxygen  atom.  They  are  formed  from  the 
amides  by  loss  of  ammonia.     Thus  :  — 

CH2.CONH2      CH2.C0\ 
I  =   I  >NH  +  NH3; 

CH2.CONH2      CH2.CO/ 

Succinamide  Succinimide 

and  from  the  anhydrides  by  the  action  of  ammonia :  — 


26o         MIXED   COMPOUNDS   CONTAINING   NITROGEN 

CH2COV  CHjCOx 

I  >0  +  H2NH  =  I  >NH  +  H2O. 

CHjCCK  CH2CO/ 

The  hydrogen  atom  of  the  imido  group  is  replaceable  by  some 
metals,  or  the  imide  has  the  properties  of  a  weak  acid. 

Cyanamide,  N=C  — NH2.  —  In  treating  of  cyanic  acid,  the 
existence  of  two  chlorides  of  cyanogen  was  mentioned :  one, 
a  liquid  having  the  formula  NCCl ;  the  other,  a  solid  of  the 
formula  N3C3CI3.  When  the  former  is  treated  with  ammonia, 
it  is  converted  into  an  amide,  NC.NH2,  which  bears  to 
cyanic  acid,  NC.OH,  the  relation  of  an  amide.  Like  the  other 
simple  compounds  of  cyanogen,  cyanamide  readily  undergoes 
change.  Heated  to  150°  or  when  allowed  to  stand,  it  is  con- 
verted into  dicyandiamide,  C2N4H4 ;  whUe,  when  heated  to 
above  150°,  a  violent  reaction  takes  place,  and  in'cyantri- 
amide,  CsNeHe,  is  formed.  The  latter  compound  is  also  called 
melamine  and  cyanuramide,  and  from  certain  methods  of  forma- 
tion it  is  concluded  that  it  is  the  amide  of  cyanuric  acid.  It  is 
a  strong  monacid  base.  The  formation  of  these  compounds  is 
particularly  interesting,  as  illustrating  the  tendency  on  the  part 
of  the  simple  cyanogen  compounds  to  undergo  polymerization. 

Calcium  cyanamide,  N=C — -NCa. — This  compound  has 
come  into  prominence  as  a  fertilizer.  In  the  soil  it  furnishes 
the  nitrogen  necessary  for  the  growth  of  plants :  — 

NSC— NCa  +  2  H2O  =  Ca(0H)2  +  N^CNHj, 
and 

NSCNH2  +  H2O  =  0C<^^'  +  2  H2O  =  oc<°^2'- 

In  XI2  UJN  ri4 

Urea 

It  is  made  by  passing  nitrogen  over  calcium  carbide  heated 
to  75o°-iooo°  in  an  electric  furnace,  when  the  reaction  repre- 
sented in  this  equation  takes  place :  — 

CaCj  +  N2  =  CN2Ca  -1-  C. 

The  nitrogen  used  is  obtained  by  fractional  distillation  of  liquid 
air.  The  absorption  of  nitrogen  is  increased  by  the  presence 
of  10  per  cent  calcium  chloride. 


GUANIDINE  261 

Calcium  cyanamide  when  treated  with  superheated  steam 
gives  ofiE  all  its  nitrogen  in  the  form  of  ammonia :  — 

CaCN2  +  3  H2O  =  CaCOs  +  2  NH3. 

This  is  one  of  the  methods  of  "  fixing  "  the  nitrogen  of  the 
air.  The  ammonia  obtained  by  this  method  is  very  pure  and 
may  be  used  in  making  ammonium  salts  or  it  may  be  converted 
by  catalytic  oxidation  into  nitric  acid,  thus  converting  the 
nitrogen  of  the  air  into  the  valuable  nitric  acid  now  obtained 
from  Chili  saltpeter. 

When  calcium  cyanamide  in  water  is  treated  in  the  cold  with 
carbon  dioxide,  calcium  carbonate  is  precipitated  and  a  solution 
of  pure  cyanamide  is  obtained  :  — • 

CaCNz  +  H2O  +  CO2  =  CaCOs  +  N^C— NHj. 

Cyanamide 

By  heating  this  solution,  in  the  presence  of  a  catalyst,  such 
as  manganese  superoxide,  the  cyanamide  takes  up  water,  form- 
ing urea :  — 

N^c— NH2  +  H2O  =  oc<:; 


.NH2 


~NH2" 

Urea 

This  is  a  technical  method  for  the  manufacture  of  urea  on  the 
large  scale.  It  is  a  synthesis  of  urea  from  coal,  nitrogen  of 
the  air  and  water,  that  is,  from  the  elements. 

About  180,000  tons  of  calcium  cyanamide  are  produced 
annually. 

Guanidine,  CN3H5.  —  This  substance,  which  is  closely  related 
to  cyanamide,  was  first  obtained  by  the  oxidation  of  guanine 
(271).  It  can  also  be  made  by  treating  cyanogen  iodide  with 
ammonia :  — 

NCI  +  2NH,  =  HN:c4|;jjj, 

the  product  being  the  hydriodic  acid  salt  of  guanidine.  It  is 
best  made  by  heating  the  alcoholic  solution  of  cyanamide  with 
ammonium  chloride :  — 

NC.NH2  +  NH3  =  HN:C<^^'- 

NH2 


262        MIXED   COMPOUNDS   CONTAINING  NITROGEN 

It  is  a  very  strong  alkaline  base.     Boiled  with  dilute  sulphuric 
acid  or  baryta  water,  it  \delds  urea  and  ammonia :  — 

CN3H5  +  H2O  =  CON2H4  +  NH3. 

Guaaidlne  Urea 

Creatine,  C4H9N3O2.  —  This  substance  is  found  in  the  muscles 
of  all  animals.  It  is  usually  made  from  "  extract  of  meat." 
It  has  been  made  synthetically  by  bringing  cyanamide  and 
sarcosine  together.  The  reaction  is  analogous  to  that  made 
use  of  for  the  preparation  of  guanidine  :  — 


HN.CH3 

/NH2 
:C<       /CH2. 

\CH3 

r^c- 

-NH2 

+ 

1 

=  HN: 

COOH. 

H2C.CO2H 

Cyanamide 

Sarcosine 

Creatine 

Creatinine,  C4H7N3O,  in  small  quantity  is  a  constant  con- 
stituent of  human  urine.  Creatine  is  converted  into  creati- 
nine by  the  loss  of  water  when  its  solution  is  heated  with  dilute 
hydrochloric  acid.  In  contact  with  alkalies  creatinine  gradually 
takes  up  the  elements  of  water  and  forms  creatine.  It  is  a 
base,  forming  with  acids  well-crystallized  salts.  Its  relation  to 
creatine  is  represented  thus  :  — 

.NH2  .NH 1 

^^•^\n<CH2.C00H        ^^  =  *^\j^    CH2.CO. 

CH3  CH3 

Creatine  Creatimne 

Urea,  carbamide,  and  derivatives.  —  Closely  related  to  the 
nitrogen  compounds  just  referred  to  is  urea,  or  the  amide 
of  carbonic  acid.  Its  importance  and  certain  reactions  dis- 
tinguish it  from  the  other  acid  amides,  and  it  is  therefore 
treated  by  itself. 

Urea  is  found  in  the  urine  and  blood  of  all  mammals,  and  par- 
ticularly in  the  urine  of  carnivorous  animals.  It  is  the  final 
decomposition  product  of  the  proteins  in  the  animal  body. 
Human  urine  contains  from  2  to  3  per  cent ;  the  quantity 
given  off  by  an  adult  man  in  24  hours  being  about  3c  grams. 
Urea  can  be  made  by  the  following  methods :  — 


UREA,   OR   CARBAMIDE  263 

(i)    By  treating  carbonyl  chloride  with  ammonia :  — 
OCCI2  +  4  NH3  =  OCN2H4  +  2  NH4CI. 

(What  is  the  analogous  reaction  for  the  preparation  of  acetamide  ?) 

(2)  By  heating  ammonium  carbamate :  — 

oc<JJHl  =  0CN2H4  +  H20. 
0NH4 

(3)  By  treating  ethyl  carbonate  with  ammonia :  — 

OP  TT 

0C<^^'„'  +  2  NH3   =  OCN2H4  +  2  C2H6O. 

L)L,2n5 

(4)  By  the  addition  of  water  to  cyanamide :  — 

CN.NH2  +  H2O  =  OCN2H4. 

(5)  By  evaporation  of  ammonium  cyanate  in  aqueous  solu- 
tion :  — 

N^C(0NH4)  =  OCN2H4. 

This  reaction  is  of  special  interest,  for  the  reason  that  it  was  the 
first  example  of  the  formation,  by  artificial  methods  from  in- 
organic substances,  of  an  organic  compound  found  in  the  ani- 
mal body  (1). 

Urea  is  readily  obtained  from  urine.  It  crystallizes  from 
alcohol  in  large,  rhombic  prisms,  which  melt  at  132°.  It  is 
easily  soluble  in  water  and  alcohol.  Heated  with  water  in  a 
sealed  tube  to  180°,  or  boiled  with  dilute  acids  or  alkalies,  it 
breaks  down  into  carbon  dioxide  and  ammonia :  — 

CON2H4  +  H2O  =  CO2  -I-  2  NH3. 

The  same  decomposition  of  urea  takes  place  when  urine  is  al- 
lowed to  stand.  Hence  the  odor  of  ammonia  is  always  noticed 
in  the  neighborhood  of  stables  and  urinals  that  are  not  kept 
thoroughly  clean.  This  decomposition  is  due  to  the  action  of  a 
microorganism  known  as  micrococcus  urecB.  This  change  is  a  good 
example  of  the  way  in  which  nature  converts  useless  materia! 
into  useful  ones.     Urea  is  a  waste-product  of  the  life-process. 


a64        MIXED   COMPOUNDS   CONTAINING   NITROGEN 

After  it  has  left  the  body  it  ceases  to  be  of  value,  whereas 
carbon  dioxide  and  ammonia  are  essential  to  the  life  of  plants. 

The  enzyme,  urease,  present  in  the  extract  of  soy  bean, 
hydrolyzes  urea  into  ammonium  carbonate,  and  this  affords  one 
of  the  best  methods  of  estimating  urea. 

Sodium  hypochlorite  or  hypobromite  decomposes  urea  into 
carbon  dioxide,  nitrogen,  and  water :  — 

CO(N2H4)  +  3  NaOCl  =  CO2  +  3  NaCl  +  N2  +  2  H2O. 

The  carbon  dioxide  is  absorbed  by  the  solution  which  contains 
sodium  hydroxide,  and  the  nitrogen  can  then  be  measured. 
From  the  volume  of  nitrogen  obtained  the  amount  of  urea  can 
be  calculated.  This  is  the  basis  of  one  of  the  methods  used  for 
estimating  urea. 

Nitrous  acid  acts  in  a  similar  way  :  — 

CON2H4  +  2  HNO2  =  CO2  +  2  N2  +  3  H2O. 

When  heated,  urea  loses  ammonia,  and  yields,  first,  bitirct 
and,  finally,  cyannric  acid  (90)  :  — 


/NH2 

oc< 

>NH  +  NH3, 

oc< 

\NH2 

Urea 

Biuret 

3  CO(NH2)2  =  C3H3O3N3  +  3  NH3. 

Cyanuric  acid 

Biuret  in  alkaline  solution  gives  a  beautiful  violet  to  red  color 
with  a  drop  or  two  of  2  per  cent  solution  of  copper  sulphate. 
This  biuret  reaction  is  characteristic  of  the  proteins  and  some 
of  the  more  complicated  polj^eptides  (271). 

Urea  unites  with  acids,  bases,  and  salts.     The  hydrogen  of 
the  amino  groups  can  be  replaced  by  acid  or  alcohol  radicals, 

giving  compounds  of  which  acetyl  urea,  OC<T..rTT     ^    ^    >  ^^nd 

NH2 

ethylurea,   0C<.^^   ^    ^  are  examples. 


SUBSTITUTED   UREAS  265 

Among  the  compounds  with  acids,  the  following  may  be 
mentioned :  urea  hydrochloride,  CH4N2O.HCI ;  urea  nitrate, 
CH4N2O.HNO3;  and  urea  phosphate,  CH4N2O.H3PO4.  With 
mercuric  oxide,  2  HgO.CH4N20 ;  with  silver,  CH2N20.Ag2, 
etc.  With  salts  it  forms  such  compounds  as  2  CO(NH2)2. 
Hg(N03)2.3  HgO,  etc. 

Urea  is  used  as  a  stabilizer  in  smokeless  powders  and  cel- 
luloid, and  in  the  preparation  of  medical  remedies  (veronal, 
etc.). 

Semicarbazide,  H2NCONH.NH2 .  —  Hydrazine  hydrate  unites 
with  potassium  cyanate  to  form  semicarbazide :  — 

H2N— NH2  +  HNCO  =  0C<^^^^'. 

JNxl2 

Semicarbazide 

This  is  an  amino  derivative  of  urea.  Like  hydroxylamine  and 
phenylhydrazine  it  reacts  with  aldehydes  and  ketones  :  — 

OC<™'.OCH.H.  =  OC<-f=--.. 

Semicarbazide  Aldehyde  semicarbazone 

As  the  semicarbazones  are  well  crystallized  compounds  with 
sharp  melting  points,  semicarbazide  is  frequently  used  as  a 
reagent  for  aldehydes  and  ketones. 

Substituted  ureas.  —  These  are  derivatives  of  urea  which 
contain  hydrocarbon  residues  in  place  of  one  or  all  the  hydrogen 
atoms.  They  can  be  made  from  the  cyanates  of  substituted 
ammonias.  The  fundamental  reaction  is  the  spontaneous 
transformation  of  ammonium  cyanate  into  urea  :  — 

NC.ONH4  =  OC(NH2)2. 

In  the  same  way,  cyanates  of  substituted  ammonias  are 
transformed  into  substituted  ureas :  — 

NC.ONH3C2HB  =  oc<f;„  '  '; 

JNxl2 

NC.ONH2(C2H6)2  =  0C<^^'^'^',  etc. 


266        MIXED   COMPOUNDS   CONTAINING   NITROGEN 

The  urea  derivatives  which  contain  acid  radicals  are  made 
by  treating  urea  with  the  acid  chlorides :  — 

0C<^^  +  CHsOCl  =  OC<^iJ-^^^'^  +  HCI. 
jNri2  JNxl2 

Acetyl  urea 

Note  for  Student.  —  In  what  sense  is  acetyl  urea  analogous  to 
acetamide? 

Ureids  are  compounds  derived  from  urea  by  the  substitution 
of  acid  residues  for  one  or  more  of  the  hydrogen  atoms.  Thus, 
acetyl  urea  is  a  simple  ureid.  The  relation  between  the  ureid 
and  the  amide  is  shown  in  the  equations :  — 

CH3.COOH  +  HH2N  =  CH3.CONH2  +  H2O ; 

Acid  Amide 

Acid  Urea  Ureid 

The  ureids  of  dibasic  acids  resemble  in  the  same  way  the 
imides  of  these  acids.  One  urea  residue  takes  the  place  of  the 
two  acid  hydroxyls.  Thus,  in  the  case  of  oxalic  acid  the  relation 
is  shown  by  the  formulas  below :  — 

COOH  +  HHNv  CO.HNy 

I  >C0  =  I  >C0  +  2  H2O. 

COOH  +  HHN/  CO.HN/ 

Oxalic  acid  Urea  Ureid  of  oxalic  acid 

There  are  several  compounds  of  this  kind  that  are  of  im- 
portance :  — 

Parabanic  acid,]  CO.HNv 

Oxalyl  urea,       \  \  >C0.  —  This    is    formed    by  boil- 

«_.i. :j  rn  ttm/ 


Oxalureid,  J  CO.HN^ 
ing  uric  acid  with  strong  nitric  acid  and  with  other  oxidizing 
agents,  and  by  treating  a  mixture  of  oxalic  acid  and  urea  with 
phosphorus  oxychloride.  It  acts  like  an  acid,  the  hydrogen  of 
the  imido  group  being  replaceable  by  metals,  as  in  succinimide. 
It  readily  passes  over  into  salts  of  oxaluric  acid  when  heated 
with  a  solution  of  an  alkali :  — 


URIC  ACID  267 

CO.HNv  COOH 

I  >C0  +  H2O  =  I 

CO.NH/  CO.HN.CONH2. 

Oxaluric  acid 

Oxaluric  acid  bears  to  parabanic  acid  the  same  relation  that 
oxamic  acid  bears  to  oxamide.  It  occurs  in  the  form  of  the 
ammonium  salt  in  small  quantity  in  human  urine.  With 
phosphorus  oxychloride  it  gives  parabanic  acid  by  the  loss  of 
water. 

Barbituric  acid,  malonyl  urea,  C4H4N2O3  +  2  H2O, 

CO.NH 
CH2<  >CO 

'    CO.NH 

is  obtained  from  uric  acid  by  the  action  of  dilute  nitric  acid. 

It  has  been  made  artificially  by  treating  a  mixture  of  malonic 

acid  and  urea  with  phosphorus  oxychloride.    Heated  with  a 

solution  of  an  alkali,  it  breaks  down  into  malonic  acid  and  urea. 

CO  NH 
Diethylbarbituric  acid,  C(C2H6)2<^_'„„>CO,  made  by  the 

action  of  the  diethyl  ester  of  diethylmalonic  acid  upon  urea, 
is  an  excellent  soporific.  It  is  known  as  veronal.  The  mono- 
sodium  salt,  which  is  soluble  in  water,  is  known  as  medinal,  and 
is  also  a  soporific. 

Thiourea,  SC(NH2)2. — This  substance  is  formed  by  fusing 
ammonium  thiocyanate,  the  reaction  being  analogous  to  that 
by  which  urea  is  formed  from  ammonium  cyanate :  — 

NCSNH4  =  SC(NH2)2. 

It  forms  rhombic  prisms  melting  at  172°.  It  combines  with 
one  equivalent  of  acids,  forming  salts. 

A  number  of  derivatives  of  thiourea  have  been  made.  The}' 
resemble  those  obtained  from  urea. 

Uric  acid,  C6H4N4O3.  —  Uric  acid  occurs  in  human  urine  in 
small  quantity,  in  the  urine  of  carnivorous  animals,  and  in  the 
excrement  of  birds  and  of  reptiles.  In  these  animals  this 
substance  takes  the  place  of  urea,  and  most  of  the  nitrogen 
excretion  is  in  this  form.    The  excrement  of  reptiles  consists 


268        MIXED   COMPOUNDS   COXTAINING   NITROGEN 

almost  wholly  of  ammonium  urate.  In  arthritis  and  gout, 
uric  acid  is  deposited  in  the  joints,  in  the  form  of  insoluble  acid 
salts.  It  also  occurs  frequently  in  this  form  in  urinary  sediment 
and  sometimes  in  the  bladder  as  calculi. 

Uric  acid  forms  colorless,  crystalline  scales,  and  is  almost 
insoluble  in  water.     It  acts  like  a  weak  dibasic  acid. 

When  an  aqueous  solution  of  uric  acid  in  alkali  is  shaken 
with  methyl  iodide,  tetramethyluric  acid,  C5(CH3)4N403,  is 
formed.  \\Tien  this  is  hydrolyzed  with  concentrated  hydro- 
chloric acid,  all  the  nitrogen  is  gi\en  off  in  the  form  of  methyl- 
amine;  no  ammonia  is  formed.  This  proves  that  in  tetra- 
methyluric acid  the  four  nitrogen  atoms  are  all  combined  with 
methyl,  and  hence  that  in  uric  acid  the  four  hydrogen  atoms  are 
present  in  the  form  of  imino  groups,  C6(NH)403. 

Other  transformations  show  that  the  constitution  of  the  acid 
must  be  represented  by  the  formula 

NH— CO 

I  i 

CO     C— NH. 

I       II        >co. 

NH— C— NH/ 

According   to   this,   uric  acid   contains    two    urea   residues 

CO 

I 
combined  in  different  ways  with  the  group  C.     It  is  to  be  re- 

C 

garded  as  a  diureid  of  a  hypothetical  trihydroxyacrylic  acid, 
(HO)2C=C(OH).C02H.  That  this  view  is  correct  has  been 
shown  by  the  following  synthesis  of  uric  acid :  — 

Barbituric  acid  with  nitrous  acid  gives  the  isonitroso  com- 
pound :  — 

HN— CO  H— N— C=0 

OC     CIHH-OINOH    =    0=C     C=N— OH-hHaO. 

I       I  I       I 

HN— CO  H— N— C=0 

Barbituric  acid  Isonitruso barbituric  acid 


URIC   ACID 
By  reduction  this  forms  aminobarbituric  acid, 


269 


-C=0 


H— N- 

I  I 

0=C        Cr- 

I  I^H 

H— N C=0 


-NH2. 


This  combines  with  potassium  cyanate,  forming  a  potassium 
salt  of  pseudouric  acid  (analogous  to  the  formation  of  semi- 
carbazide).  This  acid  loses  a  molecule  of  water  and  gives  uric 
acid  as  shown  below. 


H— N- 


0=C 


H— N- 


C=0 

.NH 
C     ^CO 

I   HHNH 
-C=0 


-C=0 


Pseudouric  acid 


H— N 

I           I 
0=C        C N— H 

\c=0  +  H2O. 

H— N C N— H 

Uric  acid 


It  will  be  seen  that  uric  acid  contains  residues  not  only  of 
urea,  but  of  parabanic  acid,  of  barbituric  acid,  and  of  a  ureid 
of  mesoxalic  acid  (alloxan).  All  these  ureids  have  been  made 
from  uric  acid  by  the  action  of  nitric  acid. 

Uric  acid  and  related  compounds  are  derived  from  a  compound 
of  the  formula, 

(i)    N  =  CH(6) 

I  I 
(2)HC  (s)C  -  NHv 

II  II       (7)   >CH(8), 
(3)    N  -  C  -  N    ^ 

(4)     (9) 


to  which  the  name  purine  has  been  given. 

Purine  has  been  made  from  uric  acid  by  first  treating  it  with 
phosphorus  oxychloride,  which  gives  trichloropurine  :  — 


270        MIXED   COMPOUNDS   CONTAINING  NITROGEN 
N=C.OH  N=C— CI 

HO— C     C— NH  CI— C      C— N— H 


^C.OH 

N— C— N^  N— C— N- 

Tautomeric  form  of  uric  add  2. 6, 8-Trichloropurine 


\c— ci 

■ — r — >j^ 


On  reduction  this  gives  purine. 

As  shown  above,  uric  acid  acts  as  a  tautomeric  compound. 
It  may  be  represented  by  either  one  of  the  two  formulas, 

NH— CO  N=C.OH 

II  II 

CO     C— NHv  or        HO.C     C— NHs 
I        II         >co  nil         >C.OH. 

NH— C— NH/  N— C— N   ^ 

According  to  the  latter  formula  it  is  2,  6,  8-trihydroxypurine. 

Xanthine,  2,  6-dihydroxypurine,  C6H4N4O2,  is  found  in  all 
the  tissues  of  the  body  and  in  the  urine,  in  some  rare  urinary 
calculi,  and  in  several  animal  liquids.  It  is  formed  by  the 
action  of  nitrous  acid  on  guanine  :  — 

C5H5N5O  +  HNO2  =  C5H4N4O2  +  H2O  +  N2. 

In  this  case  the  nitrous  acid  causes  a  substitution  of  a  hydroxyl 
group  for  an  amino  group. 
Theobromine, 


o  .7  T^-      ^1.1       4.I.-       ,  C5H2(CH3)2N402,  is  a  substance  found 
3,7-Dimethylxanthine,  j 

in   chocolate  prepared   from  the  seed  of  the  cacao  tree.     It 

has  been  made  by  treating  the  lead  salt  of  xanthine  with  methyl 

iodide. 

Theophylline,  1,  3-dimethylxanthine,  is  found  in  tea. 

Caffeine,  theine,  1,  3,  7-trimethylxanthine, 

C6H(CH3)3N402  +  H2O, 

is  the  active  constituent  of  coffee  and  tea.  It  has  been  made 
from  theobromine  and  from  theophylline  by  the  introduction  of 
a  third  methyl  group. 


POLYPEPTIDES  271 

Thus,  as  will  be  seen,  a  close  connection  is  established  be- 
tween the  active  constituents  of  coffee,  tea,  and  chocolate  on 
the  one  hand,  and  xanthine  and  guanine  on  the  other. 

Guanine,  2-amino-6-hydroxypurine,  C5H3(NH2)N40,  is  found 
principally  in  guano,  from  which  it  is  prepared.  Oxidizing 
agents  convert  it  into  guanidine,  CNsHs.  Nitrous  acid  converts 
it  into  xanthine.  It  is  a  remarkable  fact  that  amino  com- 
pounds are  readily  transformed  into  hydroxy  compounds  in  the 
animal  organism  by  means  of  enzymes;  e.g.,  guanase,  found  in 
the  liver,  spleen,  lungs,  etc.,  hydrolyzes  guanine,  forming  xan- 
thine and  ammonia. 

Polypeptides  are  compounds,  closely  related  to  the  proteins 
(538),  which  have  been  made  from  the  amino  acids.  The  sim- 
plest example  is  glycylglycine,  (HjN.CHz.CO.NH.CHa.COOH, 
a  derivative  of  glycine,  H2N.CH2.COOH,  in  which  one  of  the 
amino  hydrogens  is  replaced  by  the  glycyl  group,  NH2.CH2.CO. 
It  is  called  a  dipeptide,  as  it  contains  two  residues  of  an  amino 
acid.  The  simplest  method  of  making  it  is  to  treat  glycine 
with  chloroacetyl  chloride  (made  from  chloroacetic  acid) :  — 

C1.CH2.C0|C1-|-H|NH.CH2.C02H  =  C1CH2.C0.NH.CH2.C02H 

Chloroacetyl  chloride  Glycine  Chloroacetylglycine  -i-  JJCl   ' 

The  chloroacetylglycine  formed  is  then  treated  with  ammonia :  — 

CICH2.CO.NH.CH2.COOH  +  2  NH3 

=  H2N.CH2.CO.NH.CH2.COOH  -f  NH4CI. 

Glycylglycine 

Glycylglycine  reacts  in  the  same  way  with  chloroacetyl  chloride, 
giving  chloroacetylglycylglycine, 

CICH2.CO.NH.CH2.CO.NH.CH2.COOH, 

which  reacts  with  ammonia  to  give  the  tripeptide, 

H2N.CH2.CO.NH.CH2.CO.NH.CH2.COOH. 

Diglycylglycine 

In  a  similar  manner  polypeptides  containing  4,  5,  6,  and  as 
many  as  18,  residues  of  amino  acids  have  been  prepared  by  Emil 


272       MIXED   COMPOUNDS   CONTAINING  NITROGEN 

Fischer.  This  last  polypeptide  contains  15  glycine,  and  3 
leucine  residues  and  has  a  molecular  weight  of  12 13.  It  is 
one  of  the  most  complex  substances  of  known  structure  that 
has  ever  been  made  synthetically. 

The  higher  poh-peptides  resemble  the  peptones  (541)  very 
closely  in  their  properties,  indicating  a  similarity  in  their  chem- 
ical structure.  For  example,  most  of  them  are  soluble  in 
water,  insoluble  in  alcohol,  and  they  have  a  bitter  taste  like  the 
peptones.  They  are  precipitated  by  phosphotungstic  acid,  give 
the  biuret  test  (264),  and  are  completely  hydrolyzed  to  amino 
acids  by  boiling  with  hydrochloric  acid,  reactions  which  are 
characteristic  of  the  proteins  and  the  peptones.  Some  of  the 
polypeptides  have  been  found  among  the  hydrolytic  cleavage 
products  of  the  proteins,  and  some  of  the  synthetic  polypeptides 
are  hydrolyzed  to  amino  acids  by  the  enzyme,  tr3rpsin,  of  the 
pancreatic  juice  just  as  the  peptones  are.  Pepsin,  the  enzyme 
found  in  the  gastric  juice,  which  hydrolyzes  the  proteins  to 
peptones,  does  not  hydrolyze  the  polypeptides.  There  is  no 
doubt  that  peptones  are  complicated  mixtures  of  polypeptides. 


CHAPTER  XIII 

UNSATURATED  CARBON  COMPOUNDS 

Distinction  between  Saturated  and  Unsaturated  Com- 
pounds. —  Most  of  the  compounds  thus  far  studied  are  called 
saturated  compounds.  This  is  an  appropriate  name  so  far  as 
the  hydrocarbons  themselves  and  some  of  the  classes  of  their 
derivatives  are  concerned.  The  expression  saturated  is  intended 
to  signify  that  the  compounds  have  no  power  to  unite  directly 
with  other  compounds  or  elements.  Thus,  marsh  gas  cannot 
be  made  to  unite  directly  with  anything.  Bromine,  for  ex- 
ample, must  first  displace  hydrogen  before  it  can  enter"  into 
combination :  — ■ 

CH4  -t-  Br2  =  CHsBr  +  HBr. 

Therefore  marsh  gas  is  saturated. 

On  the  other  hand,  a  compound  that  can  take  up  elements 
or  other  compounds  directly  is  called  unsaturated.  Thus, 
phosphorus  trichloride  is  unsaturated,  for  it  has  the  power 
to  take  up  two  chlorine  atoms  :  — 

PCI3  +  CI2  =  PCls. 

Ammonia  is  unsaturated,  for  it  can  take  up  a  molecule  of  a 
monobasic  acid :  — 

NH3-I-HCI  =  NH4CI. 

The  condition  of  unsaturation  is  met  with  among  carbon 
compounds  in  several  forms  :  — 

First.  The  aldehydes  act  like  unsaturated  compounds,  as 
shown  in  their  power  to  take  up  hydrogen,  ammonia,  hydro- 
cyanic acid,  sodium  bisulphite,  etc. 

Second.    The  ketones  also  act  like  unsaturated  compounds, 

273 


274  UNSATURATED   CARBON   COMPOUNDS 

though  their  power  in  this  respect  is  less  marked  than  that  of  the 
aldehydes. 

Third.  The  substituted  ammonias  are  unsaturated,  in  the 
same  sense  that  ammonia  itself  is  unsaturated. 

Fourth.  The  cyanides  take  up  hydrogen  directly,  and  are 
therefore  unsaturated  also. 

In  the  cyanides  carbon  and  nitrogen  are  linked  together 
in  a  different  way  from  that  in  the  substituted  ammonias, 
and  when  hydrogen  is  added  to  the  cyanogen  group,  — C:N, 
the  condition  is  changed  to  that  which  is  characteristic  of  the 
substituted  ammonias :  — 

hc;n  +  4  H  =  H3C— NH2. 

In  the  aldehydes  and  ketones,  carbon  is  in  combination  with 
oxygen  in  the  carbonyl  condition.  When  they  unite  with 
hydrogen  and  some  compounds,  such  as  hydrocyanic  acid,  the 
relation  between  the  carbon  and  oxygen  is  changed  to  the 
hydroxyl  condition.  The  changes  are-  represented  by  formulas 
such  as  the  following :  — 

M  /OH 

CH3C<^jj  +  H2  =  CHsC^jj   . 

(CH3)2C=0  +  HCN  =  (CH3)2C<^„- 

OH 

Fifth.  There  is  a  fifth  kind  of  unsaturation,  dependent  upon 
differences  in  the  relations  between  carbon  atoms,  and  it  is  this 
kind  which  is  ordinarily  meant  when  unsaturated  carbon  com- 
pounds are  spoken  of. 

The  kind  of  relation  between  the  carbon  atoms  in  all  the 
saturated  hydrocarbons  is  the  same  as  that  which  exists  between 
the  two  carbon  atoms  of  ethane,  and  this  is  represented  by  the 
formula  H3C — CH3.  This  formula  signifies  simply  that  the 
two  carbon  atoms  are  held  together  by  the  bonds  which  in  marsh 
gas  enabled  each  methyl  group  to  hold  one  hydrogen  atom. 
Abstracting  one  hydrogen  atom  from  each  of  two  molecules  of 
marsh  gas,  union  is  effected  between  the  carbon  atoms.     What 


UNSATURATED   NORMAL  HYDROCARBONS 


275 


would  result  if  two  hydrogen  atoms  were  abstracted,  and  union 
between  the  carbons  then  effected  ?  Theoretically  we  should 
get  a  compound  made  up  of  two  groups  CH2,  thus  H2C :  CH?, 
and  presumably  the  relation  between  the  carbon  atoms  in  this 
compound  would  be  different  from  the  relation  between  the 
carbon  atoms  in  ethane.  Without  pushing  these  speculations 
farther,  it  may  be  said  that  there  is  a  well-known  hydrocarbon 
of  the  formula  C2H4  that  differs  markedly  from  ethane.  It 
shows  the  property  of  unsaturation  very  clearly.  This  is 
olefiant  gas  or  ethylene.  It  is  the  first  of  an  homologous  series 
of  hydrocarbons,  only  a  few  of  which  are  well  known.  These 
hydrocarbons  yield  derivatives  like  those  obtained  from  the 
paraffins ;  though  of  these  few  are  known  as  compared  with 
the  number  of  the  paraffin  derivatives. 

Unsaturated  Normal  Hydrocarbons  C„H2n 
Olefines,  Alkylenes 


Formula 

Name 

Melting  Point 

Boiling  Point 

C2H4 

Ethylene,    Ethene 

-169° 

-102.5° 

CaHe 

Propylene,  Propene 

-47.8 

QH, 

Butylene,    Butene 

i-i-S 

CfiHio 

Amylene,     Pentene 

39.40 

CeHu 

Hexylene,    Hexene 

-    98.5 

67.7 

CvHj, 

Heptylene,  Heptene 

98-99 

CsH.e 

Octylene,     Octene 

124 

C«Hi8 

Nonylene,    Nonene 

147-148 

C10H20 

Decylene,    Docene 

172 

C11H22 

Undecylene 

195.4 

C12H24 

Dodecylene 

-    3I-S 

213-21S 

C13H26 

Tridecylene 

232.7 

C14H28 

Tetradecylene 

—    12 

127  (15,  mm) 

C15H30 

Pentadecylene 

247 

C16H32 

Hexadecylene 

4 

274 

CisHse 

Octadecylene 

18 

179  (15,  mm) 

C26H52 

Carotene 

58 

— 

CaoHffl) 

Melene 

62 

370-380 

The  members  are  homologous  with  ethylene.  They  bear  to 
the  paraffins  a  very  simple  relation,  each  one  containing  two 
atoms  of  hydrogen  less  than  the  paraffin  with  the  same  number 
of  carbon  atoms. 


276  UNSATURATED   CARBON   COMPOUNDS 

Ethylene,  ethene,  olefiant  gas,  C2H4,  CH2=CH2.  —  This  gas 
is  formed  from  many  organic  substances  when  they  are  sub- 
jected to  dry  distillation.  The  two  principal  reactions  which 
yield  it  are  :  — 

(i)  The  action  of  an  alcoholic  solution  of  potassium  hydrox- 
ide on  ethyl  chloride,  bromide,  or  iodide  :  — 

CzHjBr  +  KOH  =  C2H4  +  KBr  +  H2O. 

This  is  the  most  important  reaction  for  the  preparation  of  the 
unsaturated  compounds  of  the  ethylene  series.  It  is  applicable 
not  only  to  the  hydrocarbons  but  to  their  derivatives.  By 
means  of  it  it  is  possible  to  pass  from  any  saturated  compound 
to  the  corresponding  unsaturated  compound  of  the  ethylene 
series.  Thus  we  can  pass  from  ethane,  C2H6,  to  ethylene, 
C2H4,  by  first  introducing  bromine,  and  then  abstracting  h3'dro- 
bromic  acid  from  the  monobromine  substitution  product.  By 
treating  the  monobromine  substitution  products  of  other  sat- 
urated compounds  in  the  same  way,  the  corresponding  unsatu- 
rated compounds  can  be  made. 

(2)  The  action  of  sulphuric  acid  and  other  dehydrating  agents 
upon  alcohol :  — 

C2H6.OH  =  C2H4  +  H2O. 

In  the  case  of  sulphuric  acid,  ethyl  acid  sulphate  is  first  formed. 
This  when  heated  gives  ethylene  and  sulphuric  acid :  — 

C2H5HSO4  =  C2H4  +  H2SO4. 

Ethylene  is  made  on  the  large  scale  by  passing  the  vapor  of 
ethyl  alcohol  over  clay  balls  heated  to  300°  to  400° : 

C2H5OH  =  H2O  +  C2H4. 

Ethylene  is  made  most  conveniently  in  the  laboratory  from 
ethylene  bromide  by  removing  the  two  bromine  atoms  by  means 
of  the  zinc  copper  couple :  — 

C2H4Br2  -f-  Zn  =  ZnBrj  -|-  C2H4. 

Ethylene  is  a  colorless  gas  with  a  characteristic  sweetish  odor. 
It  can  be  condensed  to  a  liquid.     It  burns  with  a  luminous 


ETHYLENE,   ETHENE,    OLEFIANT   GAS  277 

flame.  With  oxygen  it  forms  a  mixture  that  explodes  when 
ignited.  Its  most  characteristic  property  is  its  power  to  unite 
directly  with  other  substances,  particularly  with  the  halogens  and 
with  halogen  acids.  Thus,  it  unites  with  chlorine  and  bromine, 
and  with  hydriodic  and  hydrobromic  acids :  — 

C2H4  +  CI2  =  C2H4CI2 ; 
C2H4  +  Br2  =  C2H4Br2 ; 
C2H4  +  HBr  =  C2H6Br; 
C2H4  +  HI     =  C2H5I. 

The  products  formed  with  chlorine  and  bromine  are  called 
ethylene  chloride  and  ethylene  bromide.  They  have  been  referred 
to  under  the  head  of  halogen  derivatives  of  the  paraffins. 
They  are  isomeric  with  ethylidene  chloride  and  ethylidene  bromide, 
which  are  formed  by  direct  substitution  of  chlorine  or  bromine 
for  two  hydrogens  of  ethane  or  from  aldehyde  (33). 

Ethylene  combines  with  hypochlorous  acid  in  aqueous  solu- 
tion to  form  ethylene  chlorhydrin :  — 

H2=C— OH 
C2H4  +  HOCl  =  I 

H2— C=C1 

Ethylene  chlorhydrin 

This  is  frequently  used  in  synthetical  work  (see  glycol  and 
ethylene  oxide). 

Ethylene  combines  with  sulphur  chloride  to  form  mustard 
gas  (79). 

Ethylene  combines  with  hydrogen  in  the  presence  of  finely 
divided  nickel  at  250°  to  give  ethane  :  — 

CH2  CH3 

II  +H2=| 

CH2  CH3 


It  combines  with  sulphuric  acid  to  give  ethyl  acid  sulphate : 

3      H 

Ethyl  acid  sulphate 


CH2      H— Ov      /.O  CH3 

CH2      H— 0/     ^O      H2C— O— SO2.OH 


+     K 


278  UNSATURATED   CARBON   COMPOUNDS 

Propylene  also  combines  with  sulphuric  acid  to  give  iso- 
propyl  acid  sulphate :  — 

H3CCH  H(X  HsCy 

II      +         >S02  =  >CH.0S020H, 

CH2      HCK  H3C/ 

which  decomposes  on  boiling  with  water,  forming  isopropyl 
alcohol  and  sulphuric  acid  (130). 

A  question  that  may  fairly  be  asked  concerning  the  structure 
of  ethylene  is  this :  Does  it  consist  of  two  groups,  CH2,  or  of 
a  methyl  group,  CH3,  and  CH?  Is  it  to  be  represented  by  the 
formula  CH2.CH2  or  CH3.CH?  Perhaps  the  clearest  answer 
to  this  question  is  found  in  the  fact  that  the  chloride  formed 
by  addition  of  chlorine  to  ethylene,  and  that  formed  by  replac- 
ing the  oxygen  in  aldehyde  by  chlorine,  are  not  identical.  All 
the  evidence  is  in  favor  of  the  view  that  aldehyde  is  correctly 

represented  by  the  formula  CHs.C'^    .     As  has  been  pointed 

out,  the  chloride  obtained  from  it  by  the  action  of  phos- 
phorus pentachloride  must  be  represented  thus,  CH3.CHCI2. 
Hence,  further,  it  appears  highly  probable  that  the  isomeric 
chloride  obtained  from  ethylene  must  be  represented  thus, 
CH2CI.CH2CI.  Now,  as  this  substance  is  formed  by  direct 
addition  of  chlorine  to  ethylene,  ethylene  must  have  the  formula 
CH2  CH3 

1 1      ,  and  not   j 
CH2  CH 

The  fact  that  it  has  been  impossible  to  prepare  methylene, 
CHj,  the  hydrocarbon  corresponding  to  carbon  monoxide,  may 
be  regarded  as  a  proof  that  ethylene  has  the  structure  represented 
by  the  above  formula.  All  attempts  to  prepare  methylene  by 
the  abstraction  of  the  halogens  from  methylene  chloride  or  iodide 
have  given  ethylene,  C2H4,  just  as  attempts  to  prepare  methyl, 
CH3,  have  given  ethane,  CjHe.  Another  proof  that  ethylene 
is  dimethylene  is  found  in  the  fact  that  only  one  propylene  has 
ever  been  made,  while  three  butylenes  are  known  (see  below). 
It  will  be  recalled  that  but  two  butanes  are  possible  and  known. 


OZONIDES  279 

Nothing  is  known  in  regard  to  the  relation  between  the  two 
carbon  atoms  of  ethylene,  except  that  it  is  probably  different 
from  that  which  exists  between  the  carbon  atoms  of  ethane. 
It  is  usually  represented  by  the  sign  (:=),  or  two  dots  (:); 

CH2 
thus,  1 1      or  CHa:CH2.    The  question  as  to  the  relation  between 
CH2 

the  carbon  atoms  in  ethylene  must  be  left  open.  If  either  of 
the  above  signs  is  used,  it  should  serve  mainly  as  an  indication 
of  the  kind  of  unsaturation  in  ethyleine,  the  compound  in  whose 
formula  it  is  written  having  the  power  to  take  up  two  atoms  of 
bromine,  a  molecule  of  hydrobromic  acid,  etc. 

AU  the  hydrocarbons  of  this  series  with  the  exception  of 
ethylene  polymerize  readily.  This  is  also  -true  of  some  of  the 
halogen  derivatives  of  ethylene.  It  is  a  characteristic  of  un- 
saturated compounds. 

When  ethylene  is  passed  into  a  dilute  solution  of  potassium 
permanganate  it  forms  glycol :  — 

CH2  H2COH 

II       -I-H2O-I-O   =        I 
CH2  H2COH 


Glycol 


With  ozone  it  gives  the  ozonide : 


CH2           0 

II    +  /\  = 

CH2       0—0 

H2C— Ov 

H2C— 0/ 

Ethylene  ozonide 

The  formation  of  ozonides  is  characteristic  of  compounds  con- 
taining the  ethylene  condition.  For  each  ethylene  double  bond 
one  molecule  of  ozone  is  added.  AUyl  alcohol  and  oleic  acid 
both  form  ozonides.    The  ozonides  are  decomposed  by  water :  — 

H2C— Ov 

-I-  H2O  =  2  H2CO  +  H2O2, 


I      >o 

H2C— 0/ 


Ethylene  ozonide  Formaldehyde 


28o  UNSATUR.\TED    CARBOX   COMPOUNDS 

and  the  products  formed  show  the  structure  of  the  unsaturated 
compound,  e.g.  the  formula  for  oleic  acid  has  been  confirmed 
by  the  products  formed  by  decomposing  oleic  acid  ozonide  with 
water. 

The  homologues  of  ethylene  bear  the  same  relation  to  it  that 
the  homologues  of  ethane  bear  to  this  hydrocarbon.     Propylene 

CH.CHs 

is  methylethylene,  1 1  ,  just  as  propane  is  methylethane, 

CH2 

CH2.CH3  CH.CH3 

I  .      Butylene      is      dimethylethylene,     |l  ,     or 
CH3                                                                             CH.CH3 

C(CH3)2  CH.C2H5 

II  ,  or  ethylethylene,  1 1  .  That  is  to  say,  in  the 
CH2                                         CH2 

hydrocarbons  of  the  ethylene  series  the  ethylene  condition 
between  the  carbon  atoms  occurs  only  once. 

The  "  official  "  names  of  the  olefine  hj'drocarbons  end  in 
-ene,  e.g.  ethene,  propene,  butene, .  etc.  The  three  butylenes 
are  called  i-butene  (CH3.CH2.CH^CH2) ;  2-butene  (CH3. 
CH=CH.CH3);  and  2-methylpropene  ((CH3)2=C=CH2). 
They  are  isomeric  with  tetramethylene  (cyclobutane)  (304), 
just  as  propylene  is  isomeric  with  cyclopropane. 

Alcohols,  C„H2nO 

These  alcohols  bear  to  the  ethylene  hydrocarbons  the  same 
relation  that  the  alcohols  of  the  methyl  alcohol  series  bear  to 
the  parafBns.  Only  one  is  well  known.  This  is  the  second 
member,  corresponding  to  propylene. 

Vinyl  alcohol,  ethenol,  H2C=CH0H,  is  present  in  crude 
ether.  It  goes  over  into  acetic  aldehyde,  CH3CHO,  very 
readily. 

Allyl  alcohol,  propene-l-ol-3,  (CH2 :  CH.CH2OH),  occurs  in 
crude  wood  spirits.     It  is  formed  in  several  ways  from  glycerol. 

I.  By  treating  glycerol  with  phosphorus  and  iodine,  allyl 
iodide  is  formed.  It  is  probable  that  the  first  product  of  this 
reaction  is  triiodopropane  :  — 


ALLYL  ALCOHOL  281 

H2C— OH       H2C— I  H2C— I   H2C 

HC— OH  +  PI3  =  HC— I  +  P(0H)3.  HC— I  =  HC  +  I2. 

H2C— OH       H2C— I  H2C— I  H2CI 

Glycerol  Triiodopropane  AUyl  iodide 

If  formed,  it  at  once  loses  iodine  to  form  allyl  iodide  as  shown 

above. 

Allyl  iodide  is  converted  into  the  alcohol  when  boiled  with 

water :  — 

C3H5I  +  HOH  =  CsHsOH  +  HI. 

Allyl  alcohol 

2.  AUyl  alcohol  is  also  formed  by  heating  glycerol  with 
oxalic  acid  as  in  the  preparation  of  formic  acid.  The  first 
product  of  this  reaction  is  the  acid  oxalate :  — 

H2C— OH  H2C— O— COCOOH 

HO-C=0 
HC— OH   +  I  =   HC— OH  +H2O. 

HO-C=0 
H2C— OH  H2C— OH 

Acid  oxalate 

Some  of  this  then  loses  carbon  dioxide,  giving  monoformin :  — 

H 
H2C—O— COCOOH 

H2C— O— C=0 
HC— OH  =        ■  +CO2. 

HC— OH 
H2C— OH 

H2C— OH 

Monoformin 

When  more  oxalic  acid  is  added,  as  in  the  preparation  of  formic 
acid,  formic  acid  is  set  free  from  the  monoformin  by  the  stronger 
oxalic  acid,  and  distills  over  into  the  receiver,  the  acid  oxalate 
being  regenerated :  — 

H  H2C— 0— CO.COOH 

H2C— O— C=0      HO.  CO  I  OH 

I  +  I      =  HC-OH  +      I        . 

HC— OH  HO.CO  I  HC=0 

I  H2C— OH 

H2C— OH 

Monoformin  Acid  oxalate  Formic  acid 


282  UNSATURATED   CARBON   COMPOUNDS 

If  no  more  oxalic  acid  is  added,  but  the  glycerol  and  oxalic  acid 
are  heated  to  220°-230°,  the  acid  oxalate  forms  the  neutral 
oxalate :  — 

HjC— O C=0  HaC— 0— C=0 

II  II 

HC— OH     HOC=0     =     H2O  +    HC— O— C=0. 

I  I 

H2C— OH  H2C— OH 

Acid  oxalate  Neutral  oxalate 

This  then  loses  carbon  dioxide  and  allyl  alcohol  distils  over :  — 

H2C— O— C=0  CH2 

I  I  II 

HC— 0— C=0    =    2CO2    +      CH. 

I  I 

H2C— OH  H2C— OH 

Neutral  oxalate  Allyl  alcohol 

In  making  allyl  alcohol,  therefore,  it  is  advisable  to  use  anhy- 
drous oxalic  acid. 

It  is  probable  that  some  of  the  allyl  alcohol  is  formed  by  the 
decomposition  of  the  monoformin  by  heat :  — 

H2C— O— C=0  CH2 

I  H  II 

HC— OH  =       CH     +  H2O  +  CO2, 

I  I 

H2COH  H2COH 

Monoformin  Allyl  alcohol 

as  allyl  alcohol  is  also  made  by  distilling  a  mixture  of  glycerol 
and  formic  acid. 

Allyl  alcohol  is  a  colorless  liquid  boiling  at  96.6°.  It  has  a 
disagreeable  penetrating  odor  and  is  miscible  with  water  in  all 
proportions.  Nascent  hydrogen  converts  allyl  alcohol  into 
propyl  alcohol:  — 

CH2=CH— CH2OH  +  H2  =  CH3— CH2— CH2OH. 

Propyl  alcohol 

Allyl  alcohol  forms  esters  with  acids  and  gives  the  other 
reactions  for  alcohols.     It  is,  further,  a  primary  alcohol,  as  it 


ALLYL  MUSTARD   OIL  283 

is  converted  into  the  corresponding  aldehyde  (acrolein)  and 
acid  (acrylic  acid)  by  oxidation :  — 

CHj^CHCHaOH    CH2=CHCH0    CH2=CHC00H. 

Allyl  alcohol  Acrolein  Aciylic  acid 

When  treated  with  a  i  per  cent  solution  of  potassium  per- 
manganate, allyl  alcohol  is  converted  into  glycerol. 

Potassium  permanganate  is  frequently  used  to  determine 
whether  a  substance  is  unsaturated  and  to  determine  also 
the  position  of  the  double  bond.  Unsaturated  compounds 
instantly  decolorize  a  dilute  solution  of  potassium  permanganate 
and  two  hydroxyl  groups  are  added.  The  places  taken  by  the 
two  hydroxyl  groups  indicate  the  position  of  the  double  bond. 

Allyl  alcohol  combines  with  ozone  to  give  the  ozonide :  — 

H2C  HsCO. 

/O  •     >0. 


HC     +  0<   I    =  HCO'' 
H2COH  H2COH 


Allyl  compounds.  —  Among  the  derivatives  of  allyl  alcohol 
which  are  of  interest  is  allyl  sulphide  (€3115)25.  It  is  made 
artificially  by  treating  allyl  iodide  with  potassium  sulphide :  — 

2  CsHbI  +  K2S   =   (C2H6)2S  +  2  KI. 

It  is  a  colorless,  oily  liquid  of  a  disagreeable  odor  only  slightly 
soluble  in  water. 

The  chief  constituent  of  oil  of  garlic  is  diallyl  disulphide, 
(C3H6)2S2.  When  this  is  treated  with  zinc  dust,  sulphur  is 
removed,  and  diallyl  sulphide,  (€3116)28,  results. 

AUyl  mustard  oil,  SCN.C3H6.  —  Under  thiocyanates  men- 
tion was  made  of  the  isothiocyanates  or  mustard  oils.  The 
thiocyanates  of  the  alcohol  radicals  are  made  from  potassium 
thiocyanate.  Thus,  methyl  thiocyanate  is  made  by  distilling 
potassium  methyl  sulphate  and  potassium  thiocyanate,  under 
reduced  pressure :  — 

NCSK  +  ^^>S02  =  K2SO4  +  NCSCH3. 


284  UNSATURATED    CARBON   COMPOUNDS 

The  mustard  oils  (98),  on  the  other  hand,  are  made  from 
carbon  bisulphide  and  substituted  ammonias.  The  chemical 
reactions  of  the  thiocyanates  led  to  the  conclusion  that  they 
must  be  represented  by  the  formula  NC — SR,  while  that  of  the 
isothiocyanates  or  mustard  oils  led  to  the  formula  SC — NR, 
as  representing  their  structure.  Allyl  mustard  oil  is  the  chief 
representative  of  the  class  of  compounds  known  as  mustard 
oils.  It  occurs  as  a  glucoside,  sinigrin  (530),  in  black  mustard 
seed.  From  the  glucoside  it  is  set  free  by  the  action  of  an  enzyme 
(myrosin).  It  also  occurs  in  horse-radish.  It  is  formed  by 
distilling  allyl  iodide  with  potassium  thiocyanate.  If  this 
reaction  consisted  simply  in  the  substitution  of  the  allyl  group 
C3H5,  for  potassium,  the  product  should  be  allyl  thiocyanate, 
C3H5S — CN.  As  a  matter  of  fact  it  is  the  isothiocyanate 
CsHbN — CS.  It  has  been  shown,  however,  that  the  thio- 
cyanates are  converted  into  the  isothiocyanates  by  heat, 
so  that  the  formation  of  the  isothiocyanate  in  this  case  is 
not  surprising.     It  is  made  commercially  by  this  method. 

Allyl  mustard  oil  is  a  liquid,  boiling  at  150°,  and  having  a 
very  penetrating  pungent  odor.  It  blisters  the  skin.  With 
concentrated  sulphuric  acid  it  takes  up  water,  forming  allyl- 
amine  and  carbon  oxysulphide  :  — 

C3H5NCS  +  H2O  =  C3H5NH2  +  OCS. 

Zinc  and  hydrochloric  acid  convert  it  into  allylamine,  and 
thioformic  aldehyde,  which  at  once  polymerizes  (H2CS)3 :  — 

C3H5N=C=S  +  2  H2  =  C3H5NH2  -I-  H2CS. 

These  reactions  show  that  in  allyl  mustard  oil  the  radical 
allyl  is  in  combination  with  the  nitrogen  and  not  with  the 
sulphur. 

Note  for  Student.  —  What  change  do  the  mustard  oils  in  general 
undergo  when  treated  with  nascent  hydrogen?  What  change  do  the 
thiocyanates  undergo  when  oxidized  and  when  reduced  ? 

Acrolein,  acrylic  aldehyde,  propenal,  CH2:CH.CHO.  —  Acro- 
lein can  be  made  by  careful  oxidation  of  allyl  alcohol.     It  is 


CROTONIC   ALDEHYDE  285 

formed  by  the  distillation  of  impure  glycerol  and  of  fats.  The 
glycerol  breaks  down  into  water  and  acrolein  :  — 

C3H8O3  =  C3H4O  +  2  H2O. 

It  is  best  prepared  by  heating  glycerol  with  concentrated  phos- 
phoric acid  (sp.  gr.  1.17).  Acrolein  is  a  volatile  liquid  which 
boils  at  52.4°.  It  has  an  extremely  penetrating  odor,  and  its 
vapor  acts  violently  upon  the  mucous  membrane  of  the  eyes 
and  nose,  causing  the  secretion  of  tears.  Acrolein  takes  up 
oxygen  from  the  air,  and  is  converted  into  the  corresponding 
acid,  acrylic  acid,  C3H4O2  (286).  It  takes  up  hydrogen,  and  is 
thus  converted  into  allyl  alcohol  and  w-propyl  alcohol.  It 
takes  up  hydrochloric  acid,  and  is  converted  into  |3-chloro- 
propionic  aldehyde :  — 

CH2=CHCH0  +  HCl  =  CH2CI.CH2.CHO. 

P-Chloropropionic  aldehyde 

The  first  two  reactions  are  characteristic  of  aldehydes  in 
general ;  the  last  one  is  characteristic  of  unsaturated  compounds 
of  the  ethylene  series.  Acrolein,  like  ordinary  aldehyde,  forms 
polymeric  modifications  which  can  easily  be  reconverted  into 
acrolein  by  heat.    Alkalies  resinify  it. 

It  unites  with  ammonia,  forming  acrolein  ammonia,  and  with 
other  substances  in  much  the  same  way  as  ordinary  aldehyde 
does.  With  bromine  it  forms  acrolein  dibromide,  which  when 
treated  with  barium  hydroxide  gives  ^/-fructose  (232). 

Crotonic  aldehyde,  methyl  acrolein,  CHs.CHrCH.CHO. — 
This  aldehyde  is  most  readily  made  by  distilling  aldol  (231) :  — ■ 

CH3.CH(OH).CH2CHO  =  CHj.CHiCH.CHO  +  H2O. 

Aldol  Crotonic  aldehyde 

When  oxidized  it  gives  solid  crotonic  acid  (287),  which  shows 
its  structure.     It  is  a  liquid  boiling  at  io4°-io5°. 

Crotonic  aldehyde  is  found  in  crude  wood  spirits.  It  reacts 
in  the  same  way  as  acrolein  does  with  hydrogen,  with  oxygen 
and  with  hydrochloric  acid.  Like  acrolein  it  acts  violently 
on  the  mucous  membrane  of  the  eyes  and  nose,  causing  the 


286 


UNSATURATED   CARBON  COMPOUNDS 


secretion  of  tears.     It  was  one  of  the  "  tear  gases  "  used  during 
the  World  War. 

Acids,  C„H2n-202 

Running  parallel  to  the  ethylene  hydrocarbons,  and  bearing 
the  same  relation  to  them  that  the  fatty  acids  bear  to  the  paraf- 
fins, is  a  series  of  acids  of  which  the  first  member  is  acrylic  acid, 
C3H4O2.  The  presence  of  the  double  bond  in  these  acids  makes 
them  stronger  acids  than  the  corresponding  acids  of  the  fatty 
acid  series  containing  the  same  number  of  carbon  atoms.  The 
principal  members  are  named  in  the  subjoined  table :  — 

ACRYLIC   ACID   SERIES   OR   OLEIC   ACID   SERIES 


AciDS,  C„H 

!n_2 

O2 

Melting  Point 

Boiling  Point 

Acrylic 

acid 

C3H4O2      ....           13° 

0 
140 

Crotonic 

C4H6O2      .       . 

72 

182 

Angelic 

CsHgOj    . 

45 

i8s 

Hydrosorbic 

C6Hio02     . 

Fluid 

208 

Teracrylic 

C7H1202    . 

U 

213 

Cimic 

C15H2802  . 

44 

Hypogseic 

C16H30O2  . 

33 

Oleic 

C18H3402  . 

14 

Erucic 

C22H4202  . 

•        33 

Of  most  of  the  higher  members  of  the  series  several  isomeric 
modifications  are  known.  Only  a  few  of  these  acids  will  be 
treated  of  here. 

Acrylic  acid,  propane  acid,  CH2:CH.C02H. — This  acid  has 
already  been  mentioned  in  connection  with  hydracrylic  acid, 
which,  when  heated,  breaks  down  into  acrylic  acid  and  water :  — 

CH2OH.CH2.CO2H  =  CHjrCH.COsH  +  HjO. 

Hydracrylic  acid  Acrylic  add 

Note  tor  Student.  —  This  reaction  is  analogous  to  that  which  takes 
place  when  ordinary  alcohol  is  converted  into  ethylene.  In  what  does 
the  analogy  consist?  What  acid  is  isomeric  with  hydracrylic  acid? 
How  does  it  conduct  itself  when  heated  ?  Compare  the  transformation 
of  hydracrylic  acid  into  acrylic  acid  with  that  of  malic  into  maleic  and 
fumaric  acids,  and  with  that  of  citric  into  aconitic  acid. 


CROTONIC  ACIDS  287 

Acrylic  acid  can  be  made  by  careful  oxidation  of  acrolein 
with  silver  oxide.  The  relations  between  propylene,  CjHe, 
allyl  alcohol,  C2H3CH2OH,  acrolein,  C2H3.CHO,  and  acrylic 
acid,  C2H3.CO2H,  are  the  same  as  those  between  any  hydro- 
carbon of  the  paraflSn  series,  and  the  corresponding  primary 
alcohol,  aldehyde,  and  acid.  Acrylic  acid  can  be  made  also 
by  treating  /3-iodopropionic  acid  with  alcoholic  caustic  potash :  — 

CH2I.CH2.CO2H  =  CH2:  CH.CO2H  +  HI. 

Note  por  Student.  —  Compare  this  reaction  with  that  by  which 
ethylene  is  made  from  ethyl  bromide. 

Acrylic  acid  is  a  liquid  having  a  penetrating  odor  like  that 
of  acetic  acid.     It  boils  at  140°,  and  melts  at  13°. 

Nascent  hydrogen  converts  it  into  propionic  acid.  Hydriodic 
acid  unites  directly  with  it,  forming  /3-iodopropionic  acid. 

Note  for  Student.  —  What  are  the  analogous  reactions  with  allyl 
alcohol  and  acrolein  ? 

Crotonic  acids,  butene-2-acids,  C4H6O2.  —  Two  crotonic  acids, 
the  ordinary  solid  form  and  hquid  isocrotonic  acid,  occur  in 
croton  oil  and  in  crude  pyroligneous  acid.  Ordinary  or  solid 
crotonic  acid  is  formed,  (i)  by  hydrolyzing  allyl  cyanide; 
(2)  by  distilling  |S-hydroxybutyric  acid;  (3)  by  treating 
a-bromobutyric  acid  with  alcoholic  caustic  potash ;  and  (4)  by 
heating  malonic  acid  with  paraldehyde  and  acetic  anhydride. 

Allyl  cyanide  has  been  shown  to  have  the  structure, 
CH2=CHCH2CN,  as  it  is  made  from  allyl  bromide, 
CH2^CHCH2Br,  by  replacing  the  bromine  by  the  CN  group. 
When  this  is  hydrolyzed  with  alkali  it  gives  solid  crotonic  acid :  — 

CH2=CHCH2CN  -I-  2  H2O  =  CH3CH=CHC00H  -|-  NH3. 

This  shifting  of  the  double  bond  towards  the  carboxyl  group, 
due  to  the  alkali,  is  explained  by  assuming  the  taking  up  of 
water  to  form  /3-hydroxybutyric  acid :  — 

H2C.CH— CH.C00H=H3C— CH=CH— COOH  -|-  H2O, 

I     I  I  Crotonic  acid 

HOH    H 


288  UNSATURATED   CARBON   COMPOUNDS 

and  the  splitting  off  of  water  from  the  two  middle  carbon  atoms 
to  form  ciotonic  acid  as  shown  above.  As  crotonic  acid  can 
be  made  also  from  a-bromobutyric  acid  by  splitting  off  hydro- 
bromic  acid  by  means  of  alkali,  this  leads  to  the  conclusion 
that  the  formula  is  CH3.CH=CH.C00H.  So  also  the  forma- 
tion of  crotonic  acid  from  paraldehyde  and  malonic  acid  points 
to  the  same  formula :  — 

(i)  CH3.CHO  +  H2C<^qJ2  =  CH3.CH:  C<^°^^  +  H2O; 

Aldehyde  Malonic  acid 

(2)  CH3.CH:  C<  J^'JJ  =  CH3.CH:  CH.CO2H  +  CO2. 

CU2X1 

Crotonic  acid 

Again,  when  crotonic  acid  is  fused  with  caustic  potash  with  access 
of  air,  it  gives  acetic  acid  as  the  only  product  of  the  oxidation :  — 

CH3 

CH  CH3 

+  H2O  +  O  =  2     •         ; 
CH  OCOH 

OCOH 

and,  as  it  has  been  shown  that  under  these  circumstances 
the  breaking  down  occurs  at  the  double  bond,  this  reaction 
furnishes  additional  evidence  in  favor  of  the  view  that  ordinary 
crotonic  acid  has  the  constitution  represented  above. 

As  it  has  been  shown  (see  above)  that  the  double  bond  shifts 
its  position  towards  the  carboxyl  group  in  the  presence  of  alkalies 
this  reaction  cannot  be  used  to  determine  the  position  of  the 
double  bond  in  all  cases.  Careful  oxidation  of  crotonic  acid 
with  potassium  permanganate  gives  oxalic  acid,  and  this  is  a 
proof  of  the  position  of  the  double  bond :  — 

H3CCH  OCOH 

+  7  0  =  2     I         +  H2O. 
HCCO2H  OCOH 

SoUd  crotonic  acid  melts  at  71°  and  boils  at  189°. 


OLEIC  ACID  289 

Isocrotonic  acid  contains  the  same  groups  as  cro tonic  acid, 
and  must  be  represented  by  the  same  structural  formula, 
CH3.CH:CH.C02H,  since,  like  crotonic  acid,  it  gives  «-butyric 
acid  by  reduction  and  oxalic  acid  by  oxidation  with  potassium 
permanganate.     It  melts  at  15.5°  and  boils  at  169°. 

As  will  be  shown  under  maleic  and  fumaric  acids  (290), 
the  isomerism  of  the  two  forms  of  crotonic  acid  is  due  to  the 
difference  in  the  arrangement  of  the  groups  in  space.  They 
are  stereoisomeric  (140). 

Oleic  acid,  Ci8H3402.  —  This  acid  was  referred  to  in  con- 
nection with  the  fats,  being  one  of  the  three  acids  found  most 
frequently  in  combination  with  glycerol.  Olein,  or  glyceryl 
trioleate,  is  the  liquid  fat,  and  is  the  chief  constituent  of  the 
fatty  oils,  such  as  olive  oil,  whale  oil,  etc.,  and  of  the  fats  of 
cold-blooded  animals.  It  is  contained  also  in  almost  all  ordi- 
nary fats.  In  the  preparation  of  crude  stearic  acid  for  the 
manufacture  of  candles,  the  liquid  oleic  acid  is  pressed  out 
of  the  mixture  of  fatty  acids.  It  is  separated  from  the  other 
fatty  acids  contained  in  the  liquid  by  converting  the  acids 
into  the  lead  salts  and  extracting  these  with  ether.  Lead 
oleate  is  soluble  in  ether,  the  other  lead  salts  are  not.  The 
oleic  acid  is  obtained  from  lead  oleate  by  the  action  of  acids. 

It  is  very  readily  oxidized  even  by  the  air  and  soon  turns  yel- 
low and  acquires  a  rancid  odor.  It  cannot  be  distilled  without 
undergoing  decomposition  except  in  a  vacuum. 

When  oxidized  carefully  it  gives  pelargonic  acid, 
CH3(CH2)7.COOH,  and  azelaic  acid,  HOOC.(CH2)7.COOH, 
hence  the  formula  must  be  CH3.(CH2)7.CH:CH.(CH2)7.COOH. 

Sodium  oleate  forms  a  colloidal  solution  in  water,  but  in  alco- 
hol it  forms  a  true  solution. 

Oleic  acid  is  a  colorless  oil,  insoluble  in  water,  that  solidifies 
when  cooled,  forming  crystals  that  melt  at  14°.  It  unites  with 
bromine,  forming  dibromostearic  acid.  Hydriodic  acid  converts 
it  into  stearic  acid :  — 

C18H34O2  +  H2  =  C18H36O2. 

Oleic  acid  Stearic  acid 

Hence  it  contains  a  normal  chain  (see  formula  above). 


290  UNSATURATED   CARBON   COMPOUNDS 

Oleic  acid  combines  in  the  cold  with  concentrated  sulphuric 
acid  to  give  the  sulphuric  acid  ester  of  hydroxystearic  acid, 
CH3(CH2)7CH(O.S03H)(CH2)8COOH.  When  this  is  boiled 
with  water  it  gives  hydroxystearic  acid  and  sulphuric  acid. 
These  reactions  take  place  in  the  hydrolysis  of  fats  with  con- 
centrated sulphuric  acid  (165). 

Oleic  acid  undergoes  a  remarkable  change  when  treated  with 
a  small  quantity  of  nitrous  acid.  It  is  converted  into  its  stereo- 
isomer, elaidic  acid,  melting  at  44°-45°.  Triolein  undergoes 
a  similar  change  with  nitrous  acid  and  gives  the  stereoisomer, 
trielaidin.     Trielaidin  gives  elaidic  acid  when  saponified. 

Oleic  acid  combines  very  readily  with  ozone  to  form  an  ozonide. 

Hardening  of  Liquid  Fats.  —  Liquid  fats  which  consist 
largely  of  the  glycerol  esters  of  oleic  acid  and  other  unsaturated 
acids  can  be  converted  into  solid  fats  (such  as  stearin)  by  the  I 
addition  of  hydrogen  in  the  presence  of  a  catalyst  (nickel).  As  ' 
the  solid  fats  are  much  more  valuable  than  the  liquid  fats  this 
process  is  carried  out  on  the  large  scale  and  is  known  as  the 
"hardening  of  oils."  These  hardened  oils  are  semi-solid,  like 
lard,  or  solid,  like  tallows,  according  as  the  conversion  of  the 
liquid  esters  (olein,  etc.)  into  stearin  is  partial  or  complete. 
The  lard-like  compounds  {Crisco,  Vegetal,  etc.)  are  used  as 
substitutes  for  lard  in  cooking  and  baking,  and  large  quantities 
of  oleomargarine  are  thus  made  from  the  cheap  vegetable  oils 
(cotton-seed  oil,  cocoanut  oil,  etc.).  Hardened  oils  are  also 
used  in  soap  and  candle  making. 

PoLYBAsic  Acids  of  the  Ethylene  Group 

There  are  a  few  dibasic  acids  that  bear  to  the  ethylene  hydro- 
carbons the  same  relations  that  the  members  of  the  oxalic 
acid  series  bear  to  the  paraf&ns.  They  are  to  be  regarded  as 
derived  from  the  hydrocarbons  by  the  introduction  of  two 
carboxyl  groups  in  place  of  two  hydrogen  atoms. 

Fumaric  and  Maleic  acids,  C2H2(C02H)2.  — ^  These  acids  are 
formed  by  distilling  malic  acid.  Fumaric  acid  remains  in  the 
retort ;  maleic  anhydride  distils  over :  — 


FUMARIC  AND   MALEIC   ACIDS  291 

Malic  acid  Maleic  and  Furaaric  acids 

Fumaric  acid  can  also  be  made  by  treating  bromosuccinic 
acid  with  alcoholic  potash :  — 

Bromosuccinic  acid  Fumaric  acid 

Fumaric  acid  is  frequently  found  in  the  plant  world.  Maleic 
acid  does  not  occur  in  nature.  Fumaric  acid  derives  its  name 
from  its  occurrence  in  the  sap  of  Fumaria  officinalis. 

Maleic  acid  can  be  obtained  in  good  yield  by  passing  air 
and  the  vapor  of  benzene  over  vanadium  oxide  heated  to  the 
proper  temperature :  — 

HC— CH=CH  HCCOOH 

II  I       +90=      II  +  2  CO2  +  H2O. 

HC— CH=CH  HCCOOH 

Benzene  Maleic  acid 

Fumaric  acid  is  only  slightly  soluble  in  water;  maleic  acid  is 
easily  soluble.  Both  fumaric  and  maleic  acids  are  converted 
into  succinic  acid  by  nascent  hydrogen :  — 

^  TT  ^  CO2H  „       /->  XT  ^  CO2H 

*^^"^<C02H  +  '  "  =  ^^^^<C02H' 

Maleic  or  fumaric  acid  Succinic  acid 

Both  are  converted  into  bromosuccinic  acid  by  hydrobromic 
acid :  — 

C2H2<^^;^  +  HBr  =  C2H3Br<^5«. 

Maleic  or  fumaric  acid  Bromosuccinic  acid 

When  heated  with  water  in  a  sealed  tube  both  combine  with 
water  to  form  <i/-malic  acid. 

^^«^<co;h  +  «^o  =  c^h,(oh)<^^;| 

Maleic  or  fumaric  acid  Malic  acid 


292 


UNSATURATED   CARBON   COMPOUNDS 


The  isomerism  disappears  when  the  double  bond  does.     Hence 
it  is  due  to  the  presence  of  the  double  bond. 

They  are,  therefore,  structurally  the  same,  and  both  must 

CHCO2H 
be  represented  as  ethylenedicarboxylic  acids    1 1  .    They 

CHCO2H 
are  stereoisomeric. 

An  extension  of  the  fundamental  ideas  of  stereochemistry ' 
furnishes  an  explanation  of  the  isomerism  between  maleic 
and  fumaric  acids.  According  to  these  ideas,  a  carbon  atom  in 
combination  with  four  atoms  or  groups  of  atoms 
holds  these  atoms  or  groups  by  bonds  directed  to- 
ward the  solid  angles  of  a  tetrahedron,  the  carbon 
atom  itself  being  at  the  center  of  the  tetrahedron. 
When  two  carbon  atoms  unite  in  the  simplest  way, 
the  stereochemical  model  representing  the  com- 
pound consists  of  two  tetrahedra  united  at  one 
of  the  solid  angles  of  each,  thus :  — 

When    two    carbon    atoms   unite   by  a  double  bond,  as  in 
the  ethylene  compounds,   the  model  consists  of 
two    tetrahedra   united  by  one  of   the  edges  of 
each,  thus : — 

In  case  each  carbon  is  in  combination  with  two 
unlike  atoms  or  groups,  there  are  two  ways  in 
which  these  can  be  arranged  in  space,  as  shown 
by  the  figures :  — 

M 


It  will  be  seen  that,  in  the  first  of  these  figures,  the  ^'s  are 
on  one  side,  and  the  B's  on  the  other  side ;  while  in  the  second 
figure  A  and  B  are  on  one  side  and  B  and  A  on  the  other. 

'   See  Stereochemistry,  by  A.  W.  Stewart,  p.  109. 


FUMARIC   AND   MALEIC   ACIDS 


293 


The  two  arrangements  are  different.  In  maleic  and  fumaric 
acids  each  carbon  atom  is  in  combination  with  one  hydrogen 
atom  and  one  carboxyl  group,  as  shown  in  the  above  formula. 
These  can  be  arranged  in  two  ways  in  space  corresponding  to 
the  above  figures,  thus :  — 


COOH 


COOH 


HOOC 


COOH 


The  one  having  the  carboxyl  groups  on  the  same  side  is  called 
the  cis  form,  the  other  with  the  carboxyl  groups  on  opposite 
sides  is  known  as  the  trans  form  (Lat.  cis,  on  this  side,  and 
trans,  across). 

It  is  believed  that  Figure  I  represents  the  configuration  of 
maleic  acid,  and  Figure  II  that  of  fumaric  acid.  The  main 
reason  for  this  is  the  fact  that  when  maleic  acid  is  heated  it 
loses  water  and  forms  an  anhydride,  while  fumaric  acid  does 
not  form  an  anhydride.  As  the  anhydride  is  formed  by  fehe 
interaction  of  the  two  carboxyl  groups,  a  substance  of  config- 
uration I  could  form  an  anhydride  easily  because  the  two  car- 
boxyls  are  near  enough  to  each  other  to  interact  and  give  off 
water,  while  in  the  case  of  the  substance  having  the  con- 
figuration represented  in  Figure  II  the  carboxyls  are  relatively 
much  farther  apart  and,  for  this  reason,  can  not  interact  in 
the  same  way. 

The  configurations  of  maleic  acid,  its  anhydride,  and  of 
fumaric  acid  may  be  represented  by  projection  formulas, 
thus : — 


H— C— CO2H 

II 
H— C— CO2H 

Maleic  acid 
(Cis  form) 


\r 


H— C— CO 

II  ^0 

H— C—CQ/ 

Maleic  acid 
anhydride 


H— C— CO2H 

II 
HO2C— C— H 

Fumaric  acid 
(Trans  form) 


294 


UNSATURATED   CARBON  COMPOUNDS 


Maleic  acid  gives  mesotartaric  acid  on  oxidation  with  a  i  per 
cent  solution  of  potassium  permanganate :  — 


COOH 


+  H20  +  0  = 


COOH 


Maleic  acid 


COOH 
Mesotartaric  acid 


while  f umaric  acid  gives  racemic  acid : 


HOGG 


COOH 


OH 


Fumaric  acid 


COOH  COOH 

d-  and  /-Tartaric  acids 


The  presence  of  the  double  bond  increases  the  strength  of 
the*  acids.  Thus  fumaric  acid  is  about  14  times  as  strong  as 
succinic  acid,  while  maleic  acid  is  about  12  times  as  strong  as 
fumaric  acid,  probably  because  of  the  proximity  of  the  carboxyl 
groups.  (Compare  the  strength  of  oxalic  acid  with  that  of 
malonic  and  succinic  acids.) 

The  two  crotonic  acids  already  referred  to  are  believed  to  be 
related  to  each  other  in  the  same  way  as  maleic  and  fumaric 
acids,  as  shown  by  the  projection  fomulas :  — 

CH3— C— H  CHs— C— H 


HO2C— C— H 

Crotonic  acid 
(Cis  form) 


H— C— CO2H 

Isocrotonic  add 
(Trans  form) 


Acids,  C6H6O4.  —  When  citric  acid  is  rapidly  heated,  a  dis- 
tillate consisting  of  the  anhydrides  of  two  acids  of  the  formula 
C5H6O4  is  obtained.    These  acids  are  itaconic  and  citraconic 


ACONITIC  ACID  295 

acids.  When  itaconic  anhydride  is  distilled  under  ordinary 
pressure,  it  is  converted  into  citraconic  anhydride.  When 
citraconic  anhydride  is  heated  for  some  time  with  water  at 
150°,  itaconic  acid  is  formed.  When  a  water  solution  of  citra- 
conic acid  is  treated  with  hydrochloric  or  nitric  acid  and  then 
evaporated,  a  third  acid,  mesaconic  acid,  isomeric  with  citra- 
conic and  itaconic  acid,  is  obtained. 

It  has  been  shown  that  citraconic  and  mesaconic  acids  are 
respectively  homologues  of  maleic  and  fumaric  acids,  as  repre- 
sented by  the  projection  formulas :  — 

CH3— C— CO2H  CH3— C— CO2H 

H— C— CO2H  HO2C— C— H 

Citraconic  acid  Mesaconic  acid 

(Cis)  (Trans) 

Like  fumaric  acid,  mesaconic  acid  does  not  form  an  anhy- 
dride.    Itaconic  acid  is  methylenesuccinic  acid  :  — 

CH2=C— CO2H 

I 
CH2.CO2H 

The  formation  of  itaconic  and  citraconic  anhydrides  from 
aconitic  acid,  the  first  product  formed  when  citric  acid  is  heated, 
is  shown  thus :  — 


CHC02H 

CH2 

HCCO 

•  >o 

CC02H 

ceo 
•  >o 

or       ceo     +  CO2  4-  H2O, 

CH2C02H 

H2CC0 

CHs 

Aconitic  acid 

Itaconic  anhydride 

Citraconic  anhydride 

Aconitic  acid,  CeHeOe,  €3113(00211)3.  —  Aconitic  acid  is  the 
only  tribasic  acid  of  this  group  that  need  be  mentioned.  It  is 
formed  when  citric  acid  is  heated  to  175°.  It  is  found  in  nature 
in  aconite  root,  and  in  the  sap  of  sugar  cane  and  of  the  beet. 

Nascent  hydrogen  converts  it  into  tricarballylic  acid, 
C3H6(C02H)3  (173).     Its  structural  formula  is  given  above. 


2g6  UNSATURATED   CARBON   COMPOUNDS 

Acetylene  and  its  Derivatives 

The  principal  reactions  by  means  of  which  it  is  possible  to 
pass  from  a  hydrocarbon  of  the  parafiSn  series  to  the  corre- 
sponding hydrocarbon  of  the  ethylene  series  consist  in  intro- 
ducing a  halogen  into  the  paraflSn,  and  then  treating  the  mono- 
halogen  substitution  product  with  alcoholic  caustic  potash :  — 

CzHsBr  =  C2H4  +  HBr. 

The  efiect  of  these  two  reactions  is  the  abstraction  of  two 
hydrogen  atoms  from  the  parafl&n.  The  following  questions 
therefore  suggest  themselves  :  — 

Suppose  a  dibromo  substitution  product  of  a  paraffin  should 
be  heated  with  alcoholic  caustic  potash ;  will  the  effect  be  that 
represented  by  the  equation, 

C2H4Br2  =  C2H2  +  2  HBr? 

And,  further,  suppose  a  monobromo  substitution  product  of 
an  ethylene  hydrocarbon  is  heated  with  alcoholic  potash ;  will 
the  effect  be  that  represented  by  the  equation, 

CjHsBr  =  C2H2  +HBr? 

If  so,  it  is  plain  that  we  have  it  in  our  power  to  make  a  new 
series  of  hydrocarbons,  the  members  of  which  must  bear  to  the 
ethylene  hydrocarbons  the  same  relation  that  the  latter  bear 
to  the  paraffins.  The  general  formula  of  this  series  would  be 
C„H2n-2,  that  of  the  ethylene  series  being  C„H2n,  and  that  of 
the  paraffin  series,  C„H2n+2. 

A  few  members  of  the  hydrocarbon  series,  C„H2n-2,  are  known, 
though  only  one  is  well  known,  and  this  one  alone  need  be  taken 
up  here. 

Acetylene,  ethine,  C2H2.  —  Acetylene  is  contained  in  coal 
gas  in  small  quantity.  It  is  formed  by  direct  combination 
of  hydrogen  and  carbon  when  a  current  of  hydrogen  is  passed 
between  incandescent  carbon  poles;  when  alcohol,  ether, 
methane,  and  other  organic  substances,  are  passed  through  a 
tube  heated  to  redness ;    when  coal  gas  and  some  other  sub- 


ACETYLENE,    ETHINE  297 

stances  are  burned  in  an  insufficient  supply  of  air,  as  when  a 
bunsen  burner  "strikes  back";  and  when  ethylene  bromide  is 
treated  with  alcoholic  caustic  potash :  — 

C2H4BT2  =  C2H2  +  2  HBr. 

It  is  formed  further  when  bromoform,  CHBrs,  or  iodoform, 

CHI3,  is  treated  with  sUver  or  zinc  dust.     (Write  the  equations.) 

It  is  easily  made  by  the  action  of  water  on  calcium  carbide :  — 

CzCa  +  2  H2O  =  C2H2  +  Ca(0H)2. 

This  process  is  extensively  used  on  the  large  scale  for  the 
preparation  of  acetylene  for  illuminating  and  other  purposes. 

Acetylene  is  a  colorless  gas  of  unpleasant  odor  when  impure. 
When  perfectly  pure  it  is  said  to  have  a  pleasant,  ethereal  odor. 
It  is  poisonous.  It  burns  with  a  luminous,  sooty  flame.  It  is 
somewhat  soluble  in  water,  but  more  soluble  in  organic  solvents. 
One  volume  of  acetone  dissolves  25  volumes  of  acetylene  at 
ordinary  pressure  and  300  volumes  at  12  atmospheres.  This 
solution  in  steel  cylinders  and  under  pressure  (Prestolite)  is 
frequently  used  instead  of  acetylene  itself  for  illuminating  pur- 
poses and  in  acetylene  torches.  Acetylene  when  burned  in 
specially  constructed  acetylene  burners  gives  a  very  brilliant 
light  without  smoke.  When  burned  with  oxygen  in  a  blow- 
pipe similar  to  the  oxyhydrogen  blowpipe,  it  gives  a  very  hot 
flame.  This  is  used  for  autogenous  welding  of  steel  and 
aluminium,  for  making  repairs  in  iron  and  steel  vessels,  for 
cutting  steel  and  for  glass  blowing,  especially  with  pyrex 
glass. 

When  heated  to  a  sufficiently  high  temperature,  acetylene 
is  converted  into  its  polymers,  benzene,  CeHe,  and  styrene, 
CsHg.  It  unites  with  hydrogen  to  form  ethylene  and  ethane. 
It  unites  with  nitrogen,  under  the  influence  of  the  sparks 
from  an  induction  coil,  forming  hydrocyanic  acid :  — 

C2H2  -I-  2  N  =  2  HCN. 

Acetylene  forms  some  interesting  compounds  with  metals. 
Among  them  may  be  mentioned  the  copper  compound  formed 


298  UNSATURATED   CARBON   COMPOUNDS 

by  the  action  of  acetylene  on  an  ammoniacal  solution  of  cuprous 
chloride.  This  is  used  as  a  means  of  detecting  acetylene.  It 
has  the  composition  C2CU2,  and  is  the  cuprous  salt  of  acetylene. 
It  is  a  reddish  brown  substance,  insoluble  in  water.  When  dry, 
it  explodes  violently  at  120°.  Hydrochloric  acid  decomposes  it, 
acetylene  being  evolved.     (Write  the  equations.) 

Acetylene  acts  like  a  weak  dibasic  acid.  Cuprous  carbide, 
C2CU2,  calcium  carbide,  C2Ca,  silver  carbide,  C2Ag2,  etc.,  are 
salts  of  the  acid. 

Calcium  carbide,  CaCz,  is  formed  by  heating  coal  and  lime 
together  in  the  electric  furnace. 

Acetylene  unites  with  chlorine  and  with  bromine,  forming  the 
compounds  C2H2CI4  and  C2H2Br4,  tetrachloro-  and  tetrabromo- 
ethane.  It  unites  with  hydrobromic  and  hydriodic  acids,  form- 
ing disubstitution  products  of  ethane :  — 

C2H2  +  2  HI  =  C2H4I2. 

In  the  presence  of  yellow  mercuric  oxide  and  6  per  cent 
sulphuric  acid  acetylene  combines  with  water  to  form  acetic 
aldehyde :  — 

C— H  CH3 

III  +  H2O  =       I       • 

C— H  HCO 

The  acetic  aldehyde  is  very  pure  and  can  be  oxidized  by  the  air 
in  the  presence  of  a  suitable  catalyst  (manganese  acetate)  to 
acetic  acid.  The  acetic  acid  made  in  this  way  is  free  from 
water  and  other  impurities.  Large  quantities  of  acetic  acid 
were  made  in  this  way,  from  acetylene,  in  Canada  during  the 
World  War.  The  capacity  of  the  plant  is  more  than  50  tons  of 
glacial  acetic  acid  per  day.  The  acetic  acid  was  vaporized  and 
passed  through  a  tube  heated  to  485°  containing  the  catalyst, 
hydrated  lime,  and  thus  converted  into  acetone :  — 

2  CH3COOH  =  (CH3)2CO  +  CO2  +  H2O. 

Ten  tons  a  day  of  acetone  of  great  purity  were  thus  produced. 
The    acetone  was   used   in    the  manufacture  of  cordite;    the 


ALLENE,    PROPADIENE  299 

acetic  acid  to  make  cellulose  acetate  used  as  a  varnish  for  the 
wings  of  airplanes.  It  is  said  that  monochloroacetic  acid  (63) 
is  made  on  the  large  scale  in  France  from  acetylene,  chlorine, 
and  water.  Acetylene  tetrachloride  is  first  made  (see  above). 
This  readily  loses  hydrochloric  acid  and  gives  trichloro- 
ethylene.  The  trichloroethylene  when  passed  into  go  per  cent 
sulphuric  acid  gives  monochloroacetic  acid :  — 

CCI2  HCCl  H2CCI 

C2H2Cl4=      II      +HC1.  II     +2H20=      I        +2HCI. 

HCCl  CCI2  OCOH 

Acetylene       Trichloro-  Monochloro- 

tetrachloride      ethylene  acetic  acid 

The  union  between  the  carbon  atoms  in  acetylene  is  com- 
monly represented  by  three  lines  (  =  ),  or  three  dots  (l).  Thus, 
acetylene  is  written  HC=CH  or  CH-CH.  Like  the  sign  of 
the  ethylene  condition,  the  sign  of  the  acetylene  condition 
should  not  be  interpreted  too  literally.  It  is  best  to  regard 
it  as  the  sign  of  the  condition  existing  in  acetylene.  This  con- 
dition carries  with  it  the  power  to  take  up  four  atoms  oj  a  halogen, 
or  two  molecules  oj  hydrobromic  acid  and  similar  acids. 

Most  of  the  higher  members  of  the  acetylene  series  of  hydro- 
carbons bear  to  acetylene  the  same  relation  that  the  higher 
members  of  the  ethylene  series  bear  to  ethylene. 

Allylene  or  methylacetylene,  propine  .  CHs.CiCH 

Allene,  propadiene H2C:C:CH2 

Ethylacetylene,  butine-i C2H6.C:CH, 

or  Dimethylacetylene,  hidine-z CHs.CiC.CHs 

Allylene  is  made  from  propylene  bromide.  It  resembles  acety- 
lene very  closely.  Sulphuric  acid  polymerizes  it  to  mesitylene 
(324). 

Allene,  propadiene,  H2C:C:CH2,  is  made  by  the  electrolysis 
of  itaconic  acid.  It  is  a  gas.  It  does  not  yield  copper  and 
silver  compounds  as  allylene  does.  It  is  a  diethylene  com- 
pound. 

Dimethylacetylene,  H3C.C=C.CH3,  does  not  form  copper  or 
silver  salts. 


300  UNSATURATED   CARBON  COMPOUNDS 

The  homologues  of  acetylene  may  be  divided  into  two  classes : 

1.  Those  which  are  obtained  from  acetylene  by  the  replace- 
ment of  one  or  both  of  the  hydrogen  atoms  by  saturated  radi- 
cals, such  as  methyl,  ethyl,  etc.  These  are  called  the  true 
homologues.     They  all  retain  the  condition  peculiar  to  acetylene. 

2.  Those  in  which  the  ethylene  condition  occurs  twice,  as 
in  the  hydrocarbons,  allene,  H2C:C:CH2,  and  butadiene- -i  ,t„ 
H2C:CH.CH:CH2.  These  are  called  diethylene  derivatives. 
Like  acetylene  and  its  true  homologues,  they  have  the  power 
to  take  up  four  atoms  of  a  halogen,  or  two  molecules  of  hydro- 
bromic  acid  and  similar  acids,  but  they  do  not  form  copper  and 
silver  salts.  In  fact,  not  all  true  homologues  of  acetylene  have 
this  power,  for  example,  dimethylacetylene,  HsCCiCCHj.  It 
is  necessary  that  an  acetylene  hydrogen  atom  should  be  present. 

Propargyl  alcohol,  propine-l-ol-3,  C3H4O.  —  This  primary 
alcohol  is  mentioned  merely  as  an  example  of  alcohols  which 
are  derived  from  the  acetylene  hydrocarbons.  It  is  the  hydroxyl 
derivative  of  allylene,  or  methylacetylene.  It  is  made  by 
treating  bromoallyl  alcohol,  C3H4BrOH,  with  aqueous  caustic 
potash :  — 

CH2OH  CH2OH 

=    •  -l-HBr. 

CBr^CHs         C=CH 

Like  acetylene  it  forms  copper  and  silver  salts. 
Acids,  C„H2n^02 

These  acids  are  the  carboxyl  derivatives  of  the  acetylene 
hydrocarbons,  and  hence  differ  from  the  members  of  the  acrylic 
acid  series  by  two  atoms  of  hydrogen  each,  and  from  the  mem- 
bers of  the  fatty  acid  series  by  four  atoms  of  hydrogen  each. 

Propiolic  acid,  propine  acid,  C3H2O2,  HC=CC02H.  —  The  po- 
tassium salt  of  this  acid  has  been  made  from  the  acid  potassium 
salt  of  acetylenedicarboxylic  acid,  K02CC=CC02H,  by  heating 
its  aqueous  solution,  carbon  dioxide  being  eliminated.  Acetylene- 
dicarboxylic acid  (butine  diacid)  is  formed  by  heating  dibromo- 
succinic  acid  with  a  water  solution  of  caustic  potash  :  — 


SORBIC   ACID  301 

CHBr.COaH       C.CO2H 
I  =111  +2HBr. 

CHBr.COzH       C.CO2H 

It  is  a  very  strong  dibasic  acid,  having  about  the  strength 
of  sulphuric  acid,  thus  showing  the  remarkable  effect  of  the 
triple  bond. 

Tetrolic  acid,  C4H4O2,  H3C.C=C.C02H,  is  obtained  by 
treating  ^-chlorocrotonic  acid  with  caustic  potash  :  — 

CCI.CH3         C.CH3 

II  ■    =111  +HC1. 

CH.CO2H       C.CO2H 

It  can  also  be  made  from  crotonic  acid :  — 

H3CCH:CHC02H  — >-  H3CCHBrCHBrC02H 

Crotonic  acid  Dibromobutyric  acid 

— J-HsCCiCCOzH. 

Tetrolic  acid 

Sorbic  acid,  C6H8O2,  CH3.CH:CH.CH:CH.C02H.— This  acid 
occurs  in  the  juice  of  the  unripe  sorb  apple.  It  takes  up 
hydrogen  and  yields  hydrosorbic  acid,  a  member  of  the  acrylic 
acid  series  (286).  It  also  takes  up  bromine,  the  final  product 
of  the  action  being  tetrabromocaproic  acid,  C6H7Br4C02H. 
With  hydrobromic  acid  it  forms  dibromocaproic  acid :  — 

C6H7CO2H  +  2  HBr  =  CsHgBrjCOsH. 

Dibromocaproic  acid 

It  will  be  observed  that  sorbic  acid  is  a  diethylene  derivative 
and  that  it  does  not  contain  the  acetylene  condition. 

Linolic  acid,  C17H31.CO2H,  and  linolenic  acid,  C17H29CO2H, 
occur  in  the  form  of  esters  of  glycerol  (linolin  and  linolenin) 
in  the  drying  oils  such  as  linseed  oil  and  hemp  seed  oU.  They  are 
obtained  from  these  oils  by  saponification  with  alkalies,  and 
decomposition  with  acid  of  the  soaps  formed.  They  are  oUy 
liquids,  the  most  marked  property  of  which  is  their  power  to 
take  up  oxygen  from  the  air  and  turn  into  solid  substances. 
Linseed  oil  itself  has  this  property  of  taking  up  oxygen  and 


302  UNSATURATED   CARBON  COMPOUNDS 

hardening  or  drying  in  the  air,  and  for  this  reason  it  is  very 
extensively  used  as  a  constituent  of  varnishes  and  of  oil  paints, 
and  in  the  manufacture  of  linoleum.  When  heated  alone  in 
the  absence  of  air,  linseed  oil  undergoes  polymerization  and 
becomes  thick  and  viscous.  This  litho  oil,  as  it  is  called,  is 
used  in  lithographic  printing,  and  in  the  manufacture  of  printers' 
ink. 

Both  these  acids  yield  stearic  acid  on  reduction.  With 
bromine  linolic  acid  gives  a  tetrabromide,  linolenic  acid  a 
hexabromide.  On  oxidation  linolic  acid  gives  caproic  acid, 
CH3.(CH2)4.COOH,  oxalic  acid  and  azelaic  acid,  (CH2)7(C02H)2, 
which  leads  to  the  formula :  — 

CH3.(CH2)4.CHr=CH.CH2.CH=CH.(CH2)7.COOH. 

Linolic  acid 

Linolenic  acid,  which  is  present  in  linseed  oil  in  much  larger 
quantity  than  linolic  acid,  has  been  shown  in  a  similar  manner 
to  have  the  structure  represented  by  the  formula :  — 

CH3.CH2.CH=CH.CH2.CH=:CH.CH2.CH=CH.(CH2)7.COOH 

Linolenic  acid 


Hydrocarbons,  C„H2„_4 

Hexatriene-1,  3,  5,  CeHs,  is  formed  by  heating  the  diformate 
of  divinylglycol  to  i65°-200°  :  — 

HjC-.CH.CH.O.CHO  HsC.CH.CH 

I  =  II       +CO2  +  CO  +  H2O. 

H2C:CH.CH.0.CH0  H2C:CH.CH 

Difonnate  of  divinylglycol  Hexatriene-i,  3,  5 

It  is  a  fluid  boiling  at  Tj. 5°-7g°.  It  takes  up  six  atoms  of 
bromine  to  form  a  hexabromide,  thus  showing  the  presence 
of  three  double  bonds.  When  reduced  with  hydrogen  in  the 
presence  of  nickel  it  gives  «-hexane,  CeHn.  Hydrocarbons 
isomeric  with  hexatriene  as  well  as  homologues  of  hexatriene 
are  also  known. 


HYDROCARBONS 


3°3 


Hydrocarbons,  C„H2n_6 

Dipropargyl,  hexadiine-1,  5,  CeHe,  is  made  from  diallyl 
tetrabromide  by  the  action  of  alcoholic  potash.  The  diallyl 
tetrabromide  is  made  from  diallyl,  which  in  turn  is  made  from 
aUyl  bromide  and  sodium :  — 


HjC^CHCHaBr 
H2C=CHCH2Br 

2  mols,  Allyl  bromide 


+  2  Na 


Br 


Br 


H2C — CHCH2 

I 

I12C' — •CHCH2 
Diallyl 


+  2  NaBr. 


H2C CH.  CH2 

XI2C CH.Cxl2 

Br         Br 

Diallyl  tetrabromide 


HCSC— CH2 

I 
HC=C— CH2 


Dipropargyl 


+  4  HBr. 


It  is  a  liquid  boiling  at  85.4°.  It  combines  with  bromine  with 
explosive  violence.  Like  acetylene  it  gives  copper  and  silver 
compounds,  and  from  its  method  of  formation  it  must  contain 
the  acetylene  condition  twice.  It  is  isomeric  with  benzene. 
Other  isomers  of  dipropargyl  are  also  known. 


CHAPTER   XIV 

CARBOCYCLIC  COMPOUNDS 

The  compounds  thus  far  dealt  with  may  all  be  derived  from 
marsh  gas,  or  they  are  methane  derivatives.  Most  of  them  have 
an  open  chain  formula;  a  few,  like  succinic  acid  anhydride,  the 
purine  derivatives,  etc.,  have  a  closed  chain  structure.  Besides 
the  methane  derivatives  there  is  another  great  class  of  organic 
compounds  which  have  the  closed  chain  structure,  or  are  cyclic 
compounds.  Of  these  the  simplest  are  cyclopropane,  cyclo- 
butane,  cyclopentane,  cyclohexane,  etc.,  isomeric  with  the 
olefines. 

CH2         H2C1 iCHj 

HaC'^^CHj   H2CI ^CHj 

CH2 

Cyclopropane  Cyclobutane  Cyclopentane 

They  are  made  by  the  abstraction  of  bromine  from  compounds 
like  trimethylene  bromide  and  tetramethylene  bromide  by 
sodium  or  zinc  :  — - 

CHaBr  CH2 

HjC/  +  Zn  =  ^iCA       +  ZnBra ; 

CHsBr  CH2 


Trimethylene  bromide  Cyclopropane 


H2CCH2Br  H2C 

I  +Zn   = 

H2CCri2Br  I12C 


2 


CH 

+  ZnBr2. 
CH2 


Tetramethylene  bromide  Cyclobutane 

Cyclopentane  is  most  readily  made  by  reducing  the  ketone, 
cyclopentanone,  which  results  from  the  dry  distillation  of  cal- 
cium adipate :  — 

304 


CYCLOHEXANE 


305 


H2C.CH2.CO.O 

I 
HaC.CHj.CO.O' 

Calcium  adipate 


H2C.CH2\ 
Ca — >-       I         '  >C0  • 
H2C.CH/ 

Cyclopentanone 


H2C.CH2\ 

^      I  >CH2. 

H2C.CH2/ 

Cyclopentane 


Cyclohexane  has  been  made  from  i,  6-dibromohexane  by  ab- 
stracting bromine  by  means  of  sodium  :  — 

H2CCH2CH2Br  H2CCH2CH2 

I  +  2  Na  =        I  1+2  NaBr. 

H2CCH2CH2Br  H2CCH2CH2 

1,  6-DibromohezaDe  Cyclohexane 

Cyclohexane  and  its  derivatives  are  most  readUy  formed  by 
reducing  benzene  and  its  derivatives  (328). 

These  hydrocarbons  resemble  the  paraflSns  in  their  chemical 
properties  and  hence  their  names.  The  derivatives  closely 
resemble  the  corresponding  derivatives  of  the  paraffins. 

The  cyclic  hydrocarbons  up  to  cyclooctane  have  been  made 
synthetically.  The  following  table  gives  the  boiling  points  of 
these  hydrocarbons  together  with  those  of  the  normal  hydro- 
carbons of  the  paraffin  and  olefine  series  having  the  same 
number  of  carbon  atoms. 


Paeaf^ins 

Boiling  Pi. 

Olefines 

Boiling  Ft. 

Caebocvclic 

Boiling  Pt. 

C3H8 

-44.1° 

C3H6 

-47° 

C3H6 

-34° 

C4H10 

-0-3 

C4H8 

I-I-5 

C4H8 

11-12 

C5H12 

36-4 

CsHio 

39-40 

C5H10 

50.2-50.8 

CcHh 

69 

CeHij 

67.7 

CeHi, 

80.75 

C7H16 

98.4 

C7H14 

98-99 

C7H14 

"7 

CgHis 

125-5 

CgHie 

124 

CgHie 

147 

It  will  be  noted  that,  while  the  paraffins  and  the  olefines  con- 
taining the  same  number  of  carbon  atoms  have  nearly  the  same 
boiling  points,  those  of  the  corresponding  cyclic  hydrocarbons 
are  higher  than  either. 

The  most  important  of  the  carbocyclic  compounds  are  the 
benzene  derivatives. 


CHAPTER   XV 

THE  BENZENE  SERIES  OF  HYDROCARBONS,  C„H2„_6. 
AROMATIC  COMPOUNDS 

The  hydrocarbons  of  this  series  (see  table  below)  are  all 
derived  from  benzene,  CeHo,  in  the  same  way  that  the  paraffin 
hydrocarbons  are  derived  from  marsh  gas,  i.e.,  they  are  alkyl 
derivatives  of  benzene.  When  bituminous  or  soft  coal  is  heated 
to  a  high  temperature  for  the  purpose  of  manufacturing  coal 
gas  (illuminating  gas)  or  in  the  manufacture  of  coke,  benzene 
and  several  of  its  homologues  are  formed  and  are  found  both 
in  the  gases  and  in  the  coal  tar  which  results.  Practically  all 
the  benzene  h}'drocarbons  and  some  of  their  derivatives  are 
thus  obtained  from  soft  coal,  either  as  a  by-product  of  the 
coking  ovens  or  in  the  manufacture  of  coal  gas.  In  making 
coal  gas,  the  coal  is  heated  in  sealed  retorts  and  all  the  products 
pass  through  condensers  in  which  a  thick,  black,  tarry  liquid, 
coal  tar,  collects.  This  coal  tar  was  originally  thrown  away  or 
burned  as  fuel,  until  it  was  found  to  contain  valuable  benzene 
compounds,  which  could  be  obtained  from  it  by  distillation. 
It  is  an  extremely  complex  mixture  of  aromatic  compounds 
from  which  a  great  many  substances  (mainly  hydrocarbons) 
have  been  isolated.  The  most  important  substances  obtained 
from  coal  tar  are  naphthalene  and  anthracene,  in  addition  to 
smaller  quantities  of  the  hydrocarbons  of  the  benzene  series, 
and  also  phenol,  cresols,  pyridine,  quinoline  and  carbazole.  1  he 
tar  is  distilled  from  large  fire-heated  stills. 

When  the  tar  is  distilled  completely  to  a  hard  pitch  the  distillate  is  usually 
collected  in  several  fractions  as  follows :  — 

I.   Light  oil  or  crude  naphtha  fraction  up  to  about  iio°. 
X.   Acid  oil  and  napthalene  fraction  from  iio°  to  205°. 

3.  Creosote  oil  fraction  from  205°  to  270°. 

4.  Anthracene  oil  fraction  from  270°  to  355°- 

5.  Heavy  oil  fraction  from  355°  to  450° 

306 


HYDROCARBONS  307 

The  light  oil  is  distilled  for  the  purpose  of  obtaining  benzene,  toluene,  and 
the  xylenes,  while  the  acid  oil  fraction  is  allowed  to  cool  and  the  crude 
napthalene  that  crystallizes  out  is  removed  by  means  of  centrifugals.  The 
clear  oil  is  then  treated  with  a  solution  of  sodium  hydroxide  to  remove 
acids  (phenol  or  carbolic  acid,  the  cresols,  etc.)-  The  creosote  oil  fraction 
is  used  for  the  preservation  of  wood.  The  anthracene  oil  fraction  is  cooled 
to  separate  anthracene  and  carbazole,  which  are  filtered  off,  and  the  oil 
left  is  used  for  the  same  purpose  as  the  creosote  oil. 

Most  of  the  benzene  hydrocarbons  are  now  obtained  from  the  gases  of 
the  coking  ovens.  These  gases,  after  being  separated  from  the  tar,  are 
passed  through  a  weak  solution  of  sulphuric  acid  to  remove  ammonia  (and 
pyridine)  and  then  through  large  scrubbing  towers,  in  which  they  are  brought 
into  intimate  contact  with  a  stream  of  scrubbing  oil,  flowing  counter-current 
to  the  gas.  The  scrubbing  oil  used  in  this  country  is  a  high  boiling  petro- 
leum fraction  known  as  "  straw  oil."  It  abstracts  the  aromatic  hydro- 
carbons from  the  gases.  When  saturated,  the  straw  oil  from  the  scrubbing 
towers  passes  into  a  still  in  which  steam  is  blown  through  the  oil  in  order 
to  distil  the  aromatic  hydrocarbons.  This  distillate  forms  the  crude  "gas 
benzol"  or  "coke-oven  light  oil"  of  commerce.  It  is  the  principal  source 
of  benzene,  toluene,  the  xylenes,  and  other  more  volatile  aromatic  hydrocar- 
bons. This  coke-oven  light  oil  is  distilled  through  fractionating  columns 
and  "crude  benzol,"  "crude  toluol,"  "crude  solvent  naphtha"  (mostly 
xylenes)  and  "crude  heavy  solvent  naphtha"  (mostly  trimethylbenzenes 
and  indene)  are  obtained.  The  crude  benzol,  crude  toluol,  and  crude  sol- 
vent naphtha  are  puri&ed  by  agitating  them  with  sulphuric  acid,  washing 
with  water  and  then  agitating  with  a  solution  of  caustic  soda  and  again 
washing  with  water.  They  are  finally  distilled  through  fractionating  col- 
unms  and  separated  into  the  various  grades  of  benzene,  toluene,  xylenes, 
and  refined  solvent  naptha  found  in  commerce.' 

Some  of  the  principal  taiembers  of  this  series  of  hydrocarbons 
with  their  boiling  points  and  melting  points  are  given  in  the 
table  below :  — 


Melting    Boiling 
Point        Point 


Hydrocarbons  of  the  Benzene  Series,  C„H2n-6 

Name  Formula 

Benzene                        CeHe  5-48°     80.2° 

Toluene                        CeHs.CHs  ~94-S      no.  7 

o-Xylene                        C6H4  (€113)2(0)  -4S-oo     i444 

»w-Xylene                      C6H4(CH3)2(w)  -53-6o     139. 

p-Xylene                      C6H4(CH3)2(^)  16.00    138.2 

'  See  Cod  Tar  and  Ammonia,  by  George  Lunge,  Fifth  Edition,  1916. 


308  THE   BENZENE   SERIES   OF  HYDROCARBON'S 


Name 

FORMUIA 

Melting 
Point 

Boiling 
Point 

Ethylbenzene 

C6H6.C2H5 

-93-9 

136.5 

Hemimellithene 

C6H3(CH3)3.I,2,3 

liquid 

175 

Pseudocumene 

CeH3(CH3)3.i,2,4 

-57-40 

169.5 

Mesitylene 

C6H3(CH3)3. 1,3,5 

-53-5° 

165 

Cumene 

C6H5.CH(CH3)2 

liquid 

152-9 

Durene 

C6H2(CH3)4.I,2,4,S 

80.00 

196 

Cymene  H3C.C6H4.CH(CH3)2,i,4     -73-5°    176-S 

Hexamethylbenzene     C6(CH3)6  164.00    264 

Benzene,  cyclohexatriene,  CeHe.  —  Benzene  is  separated  by 
fractional  distillation,  as  above  described,  from  the  light  oil. 
One  hundred  and  fifty  thousand  tons  were  produced  in  Germany 
in  1920,  about  half  of  which  was  used  as  fuel  in  motors.  About 
four-fifths  of  this  is  recovered  from  the  gases  of  the  coking  ovens, 
the  rest  is  obtained  from  coal  tar.  In  this  country  16,890,000 
gallons  of  refined  benzene  were  produced  in  1920,  and  55,100,000 
gallons  motor  fuel  (50  to  90  per  cent  benzene). 

Benzene  was  discovered  in  1825  by  Faraday  in  a  liquid  ob- 
tained from  compressed  oil  gas,  but  it  was  not  until  it  was 
isolated  from  coal  tar  by  A.  W.  Hofmann  in  London  in  1845 
that  its  importance  began  to  be  recognized.  In  1856  Perkin, 
a  pupil  of  Hofmann,  made  the  first  coal-tar  dye,  mauvein,  from 
anihne  a  derivative  of  benzene,  and  shorth'  after  began  its 
manufacture  on  the  large  scale.  This  was  the  beginning  of  the 
coal-tar  dyestufi  industry,  which  has  since  attained  such 
remarkable  proportions.  Some  idea  of  the  extent  of  this 
industry  may  be  formed  from  the  fact  that  over  18  million 
pounds  of  synthetic  indigo  valued  at  13^  million  dollars 
were  manufactured  in  the  United  States  in  1920,  all  from 
benzene. 

Benzene  can  be  prepared  by  distilling  benzoic  acid  with 
lime:  — 

CeHs.COOH  =  CeHe  -|-  CO2. 

Benzoic  acid  Benzene 

Note  for  Student.  —  What  is  the  analogous  method  for  the  prepa- 
ration of  marsh  gas  ? 


BENZENE,    CYCLOHEXATRIENE  309 

Benzene  was  obtained  in  this  way  by  Mitscherlich  in  1833 

from  benzoic  acid  obtained  from  gum  benzoin,  a  plant  product. 

Benzene  has  also  been  made  by  the  polymerization  of  acetylene 

by  heat  (311) :  - 

3  ^2X12  =  '-eile, 

and  also  from  cyclohexane  (310). 

To  purify  the  hydrocarbon  obtained  from  light  oU  by  frac- 
tional distillation,  it  is  crystallized  by  cooling  to  0°  and  the  fluid 
portion  removed  by  filtration.  Only  benzene  crystallizes  at 
this  temperature,  toluene  and  the  other  homologues  remain 
liquid.  When  benzene  free  from  thiophene,  C4H4S,  (a  substance 
always  present  in  coal  tar  benzene)  is  required,  it  is  boiled  with 
aluminium  chloride  and  then  distilled  from  the  chloride,  or  the 
thiophene  is  removed  by  repeated  agitation  with  concentrated 
sulphuric  acid.  The  thiophene  is  more  readUy  sulphonated  than 
benzene,  and  the  thiophenesulphonic  acid  dissolves  in  the  sul- 
phuric acid.  Perfectly  pure  benzene  can  also  be  obtained  by 
the  distillation  of  pure  benzoic  acid  with  lime. 

Benzene  is  a  colorless  liquid.  It  boils  at  80.2°  and  has  a 
peculiar,  pleasant  odor.  Several  of  the  derivatives  and  homo- 
logues of  benzene  have  an  aromatic  odor  and  hence  the  name 
aromatic  compounds  was  given  to  them  originally  to  distinguish 
them  from  the  fatty  compounds,  and  it  is  still  in  general  use. 
Benzene  is  lighter  than  water.  Its  specific  gravity  at  20° 
compared  with  water  at  4°  is  0.8799.  It  is  slightly  soluble  in 
water  and  it  dissolves  a  small  quantity  of  water.  It  is  soluble 
in  alcohol,  in  ether,  and  in  chloroform.  It  burns  with  a  bright, 
luminous,  smoky  flame.  It  crystallizes  in  orthorhombic  prisms 
which  melt  at  5.48°.  It  is  an  excellent  solvent  for  oily  and' 
resinous  substances  and  for  many  other  organic  compounds. 
It  is  used  in  making  chlorobenzene,  nitro  and  dinitrobenzene, 
and  in  making  benzene  mono  and  disulphonic  acids.  Large 
quantities  are  used  in  making  synthetic  indigo  (484).  A  large 
part  of  it  is  used  as  a  fuel  in  motors.  In  this  case  the  crude 
benzol  (50-90  per  cent  benzene)  is  used. 

Benzene  and  the  other  substances  obtained  from  coal  tar  or 
light  oil  by  distillation  are  known  as  "crudes"  or  "coal-tar 


3IO  THE   BENZENE   SERIES   OF  HYDROCARBONS 

crudes,"  while  the  products  obtained  from  these  crudes,  like 
chlorobenzene,  nitrobenzene,  aniline,  etc.,  are  called  "inter- 
mediates," as  they  are  intermediate  products  obtained  in  the 
manufacture  of  dyestufis. 

The  Chemical  Cofiduct  of  Benzene  and  Theory  Regarding  lis 
Structure.  Benzene  takes  up  six  atoms  of  h}-drogen  in  the  cold 
in  the  presence  of  finely  di\'ided  platinum  and  gives  cyclo- 
hexane : — 

CH2 

H2C/NCH2 
HjCl^yCHs 

CH2 

Cyclohexane 

It  also  takes  up  six  atoms  of  chlorine  and  six  atoms  of  bromine, 
in  the  sunUght,  forming  benzene  hexachloride  and  benzene 
hexabromide,  which  are  chlorine  and  bromine  derivatives  of 
cyclohexane :  — 

HCCl  HCBr 


cr  ^ 

^^Cl 

H>C/\C<H 

a>"\/ 

^^Cl 

B>^\/^<Br 

HCCl 

HCBr 

Benzene  hexa 

chloride 

Benzene  hexabromide 

Cyclohexane  has  been  converted  into  benzene  by  passing  it 
over  reduced  nickel  heated  to  280°  and  also  by  the  method  used 
to  prepare  unsaturated  hydrocarbons,  viz.,  by  introducing 
bromine  or  chlorine,  and  then  abstracting  hydrobromic  or 
hydrochloric  acid  by  means  of  an  alcoholic  solution  of  caustic 
potash :  — 

CsHgCls  =  CeHe  +  3  HCl. 

Trichloro-  Benzene 

cyclohexane 

Benzene  hexachloride  and  benzene  hexabromide  yield  tri- 
chlorobenzene  and  tribromobenzene  when  treated  with  an 
alcohoUc  solution  of  caustic  potash. 


BENZENE,   CYCLOHEXATRIENE  311 

HCBr  CBr 

^  ^'^+3K0H=  +3KBr  +  3HA 

i>\yc<l  Hc'^^'cBr 

HCBr  CBr 

Benzene  hexabromide  Tribromobenzene  1,3,4 

These  facts  show  that  benzene  is  a  closed  chain  or  cycUc  com- 
pound consisting  of  six  CH  groups  and  make  it  appear  probable 
that  it  contains  three  double  bonds  as  shown  in  the  formula  :  — 

CH  CH 

KCf     >,CH  Hc/\cH 


HC!k     ;CH  RCKJCB. 

CH  CH 

It  is,  therefore,  cyclohexatriene.  This  formula  for  benzene 
was  first  proposed  in  1865  by  August  Kekule,  and  it  has 
played  an  exceedingly  important  part  in  the  development  of 
the  chemistry  of  the  benzene  compounds. 

This  formula  is  also  in  accord  with  the  synthesis  of  benzene 
and  its  derivatives  from  acetylene  and  the  substituted  acety- 
lenes. Thus  three  molecules  of  acetylene  condense  to  one  of 
benzene : — 

CH  CH 

HC     "^CH  HC/^^CH 

xiC       >^CH  HC\^    y;,CH 

CH  CH 

3  molecules  Acetylene  Benzene 

This  reaction  is  a  reversible  one,  and  so  the  conversion  of  the 
acetylene  into  benzene  is  never  complete.  When  passed  through 
a  red  hot  tube,  benzene  is  partially  converted  back  into  acety- 
lene. Monobromoacetylene  polymerizes  in  the  light  to  tri- 
bromobenzene :  — 


312  THE  BENZENE  SERIES  OF  HYDROCARBONS 

CBr  CBr 

HC      '^CH  HC,|^^CH 

BrC      ^CBr  Brcl     JcBr 

CH  CH 

3  molecules  Monobromoacetylene  Tribromobenzene  i,  3,  5 

Methylacetylene  and  dimethylacetylene  give  trimethylbenzene 
and  hexamethylbenzene,  in  contact  with  sulphuric  acid  :  — 

CH3 
C.CH3  C 

H3C.C    ^C.CHs  HsC.C^^C.CHa 

III  I  II 

H3C.C      yy/Z.CH.z  H3C.C<N     yC.CH.3 

C.CH3  C 

CH3 

3  molecules  Dimethylacetylene  Hexamethylbenzene 

When  benzene  is  treated  with  chlorine  or  bromine  in  the 
presence  of  a  carrier  (iron)  it  forms  substitution  products  and 
not  addition  products,  as  might  be  expected  from  the  above 
formula.  Thus  with  bromine,  bromobenzene  and  hydrobromic 
acid  are  formed  :  — 

C6H5H  +  Br— Br  =  CeHsBr  +  HBr. 

It  seems  very  likely  that  this  apparent  contradiction  in  the 
chemical  conduct  of  benzene  is  due  to  the  fact  that  the  hydro- 
carbon first  forms  an  addition  product  with  bromine  and  that 
this  then  loses  hydrobromic  acid,  reestablishing  the  double 
bond : — 

CH  CH 

HCf^CHBr  HCf  NcBr 

+  HBr. 
HCi^yCHBr  HC'y/CH 

CH  CH 

Benzene  dibromide  Bromobenzene 


BENZENE,  ■  CYCLOHEXATRIENE  3 1 3 

This  formula  for  benzene  also  explains  the  ease  with  which 
benzene  and  its  homologues  form  nitro  compounds  with  nitric 
acid  and  sulphonic  acids  with  sulphuric  acid,  a  fact  which 
distinguishes  these  hydrocarbons  from  all  the  others  which 
have  thus  far  been  treated  of.  Thus,  with  nitric  acid  it  is 
probable  that  an  addition  product  is  first  formed  and  that 
this  then  loses  water  to  give  the  nitro  compound,  reestablishing 
the  double  bond  :  — 

CH  HCOH  CH 

HC|/\cH  HC,/'\c<H         Hc/\c.N02 

+  H0N02=  ^"'=  +H2O. 

HClJCH  HCJIJCH  KCKJCU 

CH  CH  CH 

Nitrobenzene 

With  sulphuric  acid  a  similar  reaction  is  assumed  to  take  place. 
CH  HCOH  CH 

Hc/\cH     •  Hc/\,C<^P,„     HC/Xc.SOsH 

+S03H=  ^Usti^  ^jj^Q_ 

HCl     JCH  HCs^  JCH  HC'\JCH 

CH  CH  CH 

Benzenesulphonic  acid 

It  should  be  stated  that  cyclohexane  does  not  form  nitro  com- 
pounds with  nitric  acid  or  sulphonic  acids  with  sulphuric  acid. 
It  acts  like  a  paraffin  hydrocarbon. 

The  above  examples  suggest  an  explanation  of  the  fact  that 
benzene  apparently  acts  as  a  saturated  compound  giving  sub- 
stitution products  with  various  reagents. 

Benzene  combines  very  readily  with  ozone,  giving  a  tri- 
ozonide.  As  it  has  been  shown  that  a  molecule  of  ozone 
combines  with  each  double  bond  of  an  unsaturated  compound 
(279),  it  is  evident  that  in  this  respect  benzene  acts  as  though 
it  contains  three  double  bonds. 

On  the  other  hand  the  conclusion  cannot  be  unreservedly 
drawn  that  benzene  contains  three  double  bonds,  certainly  not 
if  by  double  bond  is  meant  an  ethylene  bond. 


314 


THE  BENZENE  SERIES  OF  HYDROCARBONS 


The  fundamental  idea  intended  to  be  represented  in  the 
Kekule  formula  is  that  benzene  is  a  symmetrical  compound,  that 
all  the  carbon  atoms  and  all  the  hydrogen  atoms  hear  the  same 
relation  to  the  molecule.  If  this  formula  correctly  represents 
the  structure  of  benzene  there  should  be  but  one  monosub- 
stitution  product  possible  with  the  same  reagent,  i.e.  there 
should  be  but  one  monobromobenzene,  one  monochloro- 
benzene,  etc.  Notwithstanding  almost  innumerable  attempts 
to  make  more  than  one  monosubstitution  product  with  the 
same  reagent,  no  one  has  yet  succeeded.  Indeed,  it  has 
been  shown  that  it  is  possible  to  replace  each  of  the  six 
hydrogen  atoms  in  benzene  in  turn  by  the  same  element  (or 
substituting  group)  and  that  the  product  is  always  the  same. 
This  has  been  done  by  starting  with  ordinary  phenol,  CeHs.OH, 
which  is  hydroxybenzene,  and  treating  it  with  phosphorus 
pentabromide.  The  product  is  monobromobenzene,  CeHs.Br. 
This  can  be  converted  into  benzoic  acid,  CeHs.COOH,  by 
the  action  of  sodium  and  carbon  dioxide.  The  OH,  the 
Br,  and  the  COOH,  therefore,  replace  the  same  hydrogen 
atom  (i).  There  are  three  isomeric  hydroxybenzoic  acids, 
C6H4.OH.COOH,  known,  all  of  which  can  be  converted  into 
benzoic  acid,  and  hence  the  carboxyl  group  in  them  also 
replaces  hydrogen  (i),  while  the  OH  group  must  replace 
other  hydrogens  in   the  molecule,  say  (2),  (3),  or  (4).     Each 


CCOOH 


CCOOH 


HC 


con 


CH 

The  three  hydroxybenzoic  adds 


HC 
HC 


CCOOH 


CH 


CH 


V 

C.OH 


CH 
HCi/NcH 


HC 


V 

CH 


CH 

HC/\cH 


C.OH       HC 


CH 


+CO2 


C.OH 


BENZENE,    CYCLOHEXATRIENE  315 

of  these  three  hydroxybenzoic  acids  gives  phenol  by  splitting 
off  carbon  dioxide. 

As  the  hydroxyl  group  in  these  three  acids  occupied  the 
(2),  (3),  or  (4)  position,  it  must  occupy  these  positions  in 
phenol  itself.  But  the  phenol  obtained  in  this  way  is  iden- 
tical with  the  ordinary  phenol  with  which  we  started. 
Hence  the  four  hydrogen  atoms  (i),  (2),  (3),  and  (4)  are 
equivalent. 

In  a  similar  manner  hydrogen  atoms  (5)  and  (6)  have  been 
shown  to  be  equivalent  to  the  others.  The  facts  and  the 
theory  are  in  harmony. 

The  question  may  fairly  be  asked,  how  many  disubstitution 
products  does  the  theory  suggest? 

Numbering  the  hydrogens  in  the  formvila,'  we  have :  — 

(i)H 
(ejHC-^  \CH(2) 

I       I 

(S)HC\^   ^CH(3) 

H(4) 

The  pairs  of  hydrogens  (i)  and  (2),  (2)  and  (3),  (3)  and  (4), 
(4)  and  (s),  (s)  and  (6),  and  (6)  and  (i),  bear  the  same  relations 
to  each  other  and  to  the  molecule ;  and,  according  to  the  formula, 
whether  we  replace  (i)  and  (2),  or  (2)  and  (3),  or  (3)  and  (4),  or 
any  other  of  the  above-named  pairs,  the  product  ought  to  be  the 
same.  We  should  get  a  compound  of  which  Formula  I  is  the 
general  expression,  in  which  X  represents  any  substituting  atom 
or  group. 

In  the  second  place,  the  pairs  of  hydrogens  (i)  and  (3),  (2) 
and  (4),  (3)  and  (5),  (4)  and  (6),  (5)  and  (i),  and  (6)  and  (2), 
bear  to  each  other  the  same  relation,  but  a  different  relation 
from  that  which  the  above  pairs  do.  Replacing  any  such  pair, 
we  should  have  a  second  compound,  which  is  represented  by 
Formula  II. 

1  The  double  bonds  are  usually  omitted  for  convenience. 


X 

HC^  \CX 

1              1 

HC^^/CH 

H 

Fonnula  I. 

3l6  THE   BEXZEXE   SERIES   OF   HVDROCARBOXS 

X  X 

i  I  I  I 

HCv       /CX  HCv        /CH 

H  X 

Fonnula  II.  Formula  III. 

Finalh',  there  is  a  third  kind  of  relation.  This  is  that  between 
the  pairs  of  hydrogens,  (i)  and  (4),  (2)  and  (5),  and  (3)  and  (6) ; 
and,  by  replacing  such  a  pair,  we  should  get  a  compound  repre- 
sented b}'  Formula  III  above. 

The  theory  suggests  no  other  possibilities.  It  will  thus  be 
seen  that  tlie  theory  indicates  the  existence  of  three,  and 
only  three,  classes  of  disubstitution  products  of  benzene. 
There  ought  to  be  three,  and  onl}'  three,  dichlorobenzenes ; 
three,  and  only  three,  dibromobenzenes,  etc. 

The  disubstitution  products  have  been  studied  very  ex- 
haustively for  the  purpose  of  determining  definitely  whether 
the  conclusion  above  reached  is  in  accordance  with  the  facts ; 
and  it  may  be  said  at  once,  that  ever\-  fact  thus  far  discovered 
is  in  harmony  with  the  theor\-.  Three  weU-defined  classes 
of  isomeric  disubstitution  products  of  benzene  are  known,  and 
only  three.  They  are  called  ortho-,  meta-,  and  para-.  In  a 
similar  manner  it  can  be  shown  that  three  trisubstitution 
products,  three  tetra,  one  penta,  and  one  hexasubstitution 
product  are  possible  when  the  substituting  element  or  group 
is  the  same.  Many  examples  of  these  are  known.  Thus 
again  there  is  complete  agreement  between  the  facts  and  the 
theory. 

If  a  model  is  made  representing  the  Kekule  benzene  formula 
with  each  carbon  atom  at  the  center  of  a  regular  tetrahedron, 
it  will  be  found  that  all  the  carbon  atoms  and  all  the  hydrogen 
atoms  he  in  the  same  plane.  This  is  essential,  for  any  other 
space  formula  that  has  been  proposed  for  benzene  necessitates 
the  existence  of  optically  active  isomers,  when  two  of  the 
hydrogen  atoms  are  replaced  by  dissimilar  groups,  as  in  salicylic 
acid,  C6H4.OH.COOH.     Optically  active  compounds  of  this  type 


TOLUENE  317 

have  never  been  prepared  nor  have  they  been  observed  in 
nature.' 

The  benzene  theory  has  been  dealt  with  somewhat  fully, 
for  the  reason,  that  it  has  played  an  extremely  important  part 
in  the  study  of  the  benzene  derivatives,  and  that  its  use  serves 
greatly  to  simplify  the  study  of  these  derivatives. 

Toluene,  CyHs,  (C6H5.CH3).  —  Toluene  was  known  before  it 
was  obtained  from  coal  tar,  as  it  is  formed  by  the  dry  distil- 
lation of  Tolu  balsam,  whence  its  name.  Its  relation  to  ben- 
zene is  shown  by  its  synthesis  from  bromobenzene  and  methyl 
iodide  by  the  action  of  sodium  :  — 

CsHeBr  +  CH3I  -|-  2  Na  =  CeHB.CHj  +  NaBr  -t-  Nal. 

Another  method  for  the  preparation  of  toluene  and  other 
homologues  of  benzene  consists  in  treating  benzene  with  a 
halogen  derivative  of  a  parafEn  hydrocarbon  in  the  presence 
of  aluminium  chloride  :  — 

CeHsH  +  CICH3  =  C6H5CH3  +  HCl. 

According  to  these  syntheses,  toluene  is  methylbenzene, 
i.e.  benzene  in  which  one  hydrogen  is  replaced  by  methyl;  or 
phenylmethane,  i.e.  methane  in  which  one  hydrogen  atom  is 
replaced  by  the  radical  phenyl,  CeHs,  which  bears  the  same 
relation  to  benzene  that  methyl  bears  to  marsh  gas. 

Toluene  is  a  colorless  liquid  that  boils  at  110.8°;  it  has  the 
specific  gravity  0.8812  at  4°  compared  with  water  at  4°;  and 
has  a  pleasant  aromatic  odor. 

It  is  very  susceptible  to  the  action  of  reagents,  yielding  a 
large  number  of  substitution  products,  some  of  the  most  im- 
portant of  which  will  be  taken  up  later. 

But  one  toluene  or  methylbenzene  has  ever  been  discovered. 

It  takes  up  hydrogen  and  gives  methylcyclohexane  when 
its  vapor  mixed  with  hydrogen  is  passed  over  finely  divided 
nickel  heated  to  180°. 

Towards  oxidizing  agents  its  conduct  is  peculiar  and  inter- 
esting. The  methyl  is  oxidized,  while  the  phenyl  remains 
■  See  Stereochemistry  by  A.  W.  Stewart,  2d  ed.,  igig,  page  216. 


3l8  THE   BENZENE   SERIES   OF   HYDROCARBONS 

intact.  The  product  is  the  well-known  acid,  benzoic  acid,  which, 
as  we  have  seen,  breaks  down  readily  into  carbon  dioxide  and 
benzene.  It  has  the  composition  C7H6O2,  and  is  the  carboxyl 
derivative  of  benzene,  C6H5.CO2H.  The  oxidation  of  toluene 
is  represented  by  the  equation :  — 

CeHs.CHs  +  30  =  C6H5.CO2H  +  H2O. 

Refined  toluene  to  the  extent  of  2,740,000  gallons  was  produced 
in  the  United  States  in  1920. 

Xylenes,  CgHio  [C6H4(CH3)2].  —  That  portion  of  light  oil 
which  boils  at  about  140°  was  originally  called  xylene.  It  was 
afterwards  found  that  this  xylene  consists  of  three  isomeric 
hydrocarbons  (91-93.5  per  cent  meta,  4.8-8.1  per  cent  ortho, 
and  about  1.7  per  cent  para).  As  the  boiling  points  of  these 
three  substances  lie  near  together,  it  is  difficult  to  separate 
them  by  means  of  fractional  distillation.  By  treatment  with 
sulphuric  acid  the  ortho  and  metaxylene  dissolve  (forming 
sulphonic  acids),  while  the  para  does  not.  The  para  product 
is  then  drawn  off  and  the  ortho  and  metasulphonic  acids  are 
separated  from  each  other  by  fractional  crystallization  of  their 
sodium  salts.  The  xylenes  are  regenerated  from  their  sul- 
phonic acids  by  superheating  with  water.  They  are  known  as 
orthoxylene,  metaxylene,  and  paraxylene. 

Orihoxylene  boils  at  144.4°. 

Metaxylene  boils  at  139.2°. 

Paraxylene  boils  at  138.2°. 

These  hydrocarbons  have  also  been  obtained  from  toluene 
by  means  of  the  reactions  made  use  of  for  the  purpose  of  con- 
verting benzene  into  toluene :  — 

CIT  PIT 

C6H4<„    '  +  CH3I  -h  2  Na  =  C6H4<^„'  -I-  NaBr  +  Nal. 

3  Bromotoluenes  3  Xylenes 

C6H4<?.^'  +  CICH3  =  C6H4<  J5J'  +  HCl. 

±1  Crls 

Toluene  Xylene 

This  shows  that  they  are  all  methyltoluenes.  There  are 
three   monobromotoluenes,   known  as  ortho,  meta,  and  para 


XYLENES  319 

bromotoluene.  For  the  preparation  of  orthoxylene,  ortho- 
bromotoluene  is  used ;  metabromotoluene  yields  metaxylene, 
and  parabromotoluene  yields  paraxylene. 

Ortho,  meta,  and  paraxylene  have  also  been  obtained  from 
certain  acids,  which  bear  to  them  the  same  relation  that  ben- 
zoic acid  bears  to  benzene :  — 

CH3 

CeHs       CH3        =    C6H4(CH3)2   +  CO2. 

CO2H 

The  reaction  by  which  metaxylene  is  formed  from  mesitylenic 
acid  is  of  special  importance  in  determining  its  structure,  as  will 
be  pointed  out  (325). 

On  oxidation,  the  xylenes  undergo  changes  like  that  which 
is  illustrated  in  the  formation  of  benzoic  acid  from  toluene, 
consisting  in  the  oxidation  of  methyl  to  carboxyl.  The  first 
change  gives  monobasic  acids,  one  corresponding  to  each 
xylene.  By  further  oxidation,  these  three  monobasic  acids 
are  converted  into  dibasic  acids.  Thus,  we  have  the  three 
reactions,  all  of  the  same  kind :  — 

(i)    C6H5.CH3        +3O  =  C6H5.CO2H      +H2O; 

(2)  C6H4<^^^       +30=  C6H4<^qJjj    +  H2O; 

(3)  C6H4<^Q^'jj  +  30  =  C6H4<^°J^     +H2O. 

CTT 

The  three  monobasic  acids  of  the  formula  C6H4<  __       are 

known  as  orthotoluic,  metatoluic,  and  paratoluic  acids,  re- 
spectively; and  the  three  dibasic  acids  obtained  from  them 
are  known  as  orthophthalic,  metaphthalic,  and  paraphthalic 
acids.  Starting  thus  with  the  three  bromotoluenes,  we  get, 
first,  three  xylenes,  then  three  toluic  acids,  and  finally  three 
phthalic  acids.  In  each  case,  we  distinguish  between  the  three 
isomeric  compounds  by  the  prefixes  ortho,  meta,  and  para. 
In  a  similar  way,  all  disubstitution  products  of  benzene  are 
designated.     We   the'-efore  have   three   series   into   which   all 


320  THE   BENZENE   SERIES   OF   HYDROCARBONS 

disubstltution  products  of  benzene  can  be  arranged ;  and 
these  are  known  as  the  Ortho  series,  the  Meta  scries,  and  the 
Para  series.  In  arranging  them  in  this  way,  we  may  select  any 
prominent  disubstitution  product,  and  call  it  an  ortho  com- 
pound; and  then  call  one  of  its  isomers  a  meta  compoutid,  and 
the  other  a  para  compound.  Having  thus  a  representative  of 
each  of  the  three  classes,  the  remainder  of  the  problem  consists 
in  determining  for  each  disubstitution  product,  by  means  of 
appropriate  reactions,  into  which  one  of  the  three  representatives 
it  can  be  transformed.  If  from  a  given  compound  we  get  the 
representative  of  the  ortho  series,  we  conclude  that  the  com- 
pound belongs  to  the  ortho  series ;  if  we  get  the  representative 
of  the  meta  series,  we  conclude  that  the  compound  is  a  meta 
compound ;  and  if  we  get  the  representative  of  the  para  series, 
we  conclude  that  the  compound  is  a  para  compound.  As 
representatives,  we  may  select  either  the  three  xylenes  or  the 
three  phthalic  acids. 

This  classification  of  the  disubstitution  products  of  benzene 
into  the  ortho,  meta,  and  para  series,  by  means  of  chemical 
transformations,  is  entirely  independent  of  any  hypothesis 
regarding  the  nature  of  benzene.  We  may  now  ask,  however, 
which  one  of  the  three  general  expressions  given  above  (see 
formulas  I,  II,  and  III,  315,  316)  represents  the  relation 
of  the  groups  in  the  ortho  compounds ;  which  one  the  relation 
in  the  meta  compounds ;  and  which  one  the  relation  in  the  para 
compounds.  If  we  can  answer  these  questions  for  any  three 
isomeric  disubstitution  products  of  benzene,  the  answer  for 
the  rest  will  follow.  To  reduce  the  problem  to  simple  terms, 
therefore,  let  us  take  the  three  xylenes.  There  are  three  xylenes 
and  three  formulas ;  is  it  possible  to  determine  which  particu- 
lar formula  to  assign  to  each  xylene  ? 

As  may  be  imagined,  this  determination  is  by  no  means  a 
simple  matter;  and  it  has  been  the  occasion  of  a  great  many 
investigations.  Theoretically,  the  simplest  method  available 
consists  in  carefully  studying  the  substitution  products  of  each 
xylene,  to  discover  how  many  varieties  of  monosubstitution 
products  can  be  obtained  from  each.     The  formulas  are  :  — 


XYLENES 

CHj 

CH3 

CH3 

HC/'iVHa 

HC^i^CH 

Hc/i^CH 

HC^  ^    5CCH3 

HC<^^/CH 

H 

H 

CH3 

Formula  I. 

Formula  II. 

Fonniila  III. 

321 


Each  of  the  four  benzene  hydrogens  of  the  xylene  of  for- 
mula III  bears  the  same  relation  to  the  molecule.  It  there- 
fore should  make  no  difference  which  one  is  replaced  by  bromine, 
the  product  ought  to  be  the  same.  This  is  not  true  of  the  xylenes 
represented  by  formulas  I  and  II.  That  xylene,  whose  struc- 
ture is  represented  by  formula  III,  ought,  therefore,  to  yield 
but  one  monosubstitution  product  with  bromine.  On  study- 
ing the  xylenes,  we  find  the  one  which  boils  at  138.2°,  called 
paraxylene,  yields  but  one  monosubstitution  product;  that 
is,  we  can  get  from  it  only  one  monobromoxylene ;  only  one 
mononitroxylene,  etc.  We  therefore  conclude  that  paraxylene 
is  represented  by  formula  III  above ;  and,  further,  the  formula 
III,  on  p.  316,  is  the  general  expression  for  all  para  compounds, 
as  they  can  all  be  made  from  paraxylene  or  be  converted  into 
paraxylene. 

Examining  formula  I  in  the  same  way,  we  see  that  H  (3) 
and  H  (6)  bear  the  same  relation  to  the  molecule ;  and  that 
H  (4)  and  H  (5)  also  bear  the  same  relation  to  the  molecule, 
though  different  from  that  of  H  (3)  and  H(6).  Two  chloro- 
xylenes  of  the  formulas 

CH3  CH3 

HC/  \CCH3  HC/  \CCH3 

II  and  I  I 

HCv       /CCl  HC\       /CH 

H  CI 

ought  to  be  obtainable  from  the  xylene  of  formula  I. 

In  the  same  way  three  chloroxylenes  should  be  obtainable 
from   the  xylene  of  formula  II.     The  method,  the  principle 


322  THE  BENZENE   SERIES   OF   HYDROCARBONS 

of  which  is  thus  indicated  briefly,  while  theoretically  simple 
enough,  is  very  diiEcult  in  its  application,  except  in  the  case 
of  the  para  compound.  Other  methods  have  therefore  been 
used,  and  these  will  be  discussed  under  mesitylene,  naphtha- 
lene, and  phthalic  acid.  It  may  be  said,  in  anticipation,  that 
the  result  of  all  observations  points  to  formula  I  for  ortho- 
xylene,  to  formula  II  for  metaxylene,  and  to  formula  III  for 
paraxylene. 

Ethylbenzene,  C8Hio(C6H6.C2H6).  This  hydrocarbon  is 
isomeric  with  the  xylenes,  but  differs  from  them  in  contain- 
ing an  ethyl  group  in  the  place  of  one  hydrogen  of  benzene, 
instead  of  two  methyl  groups  in  the  place  of  two  hydrogens  of 
benzene.  It  boils  at  136.5°.  It  is  made  by  treating  a  mixture 
of  bromobenzene  and  ethyl  bromide  with  sodium :  — 

CeHjBr  -1-  CjHjBr  -t-  2  Na  =  CbHb.CzHs  -|-  2  NaBr. 

Its  conduct  towards  oxidizing  agents  distinguishes  it  from  the 
xylenes.  It  yields  benzoic  acid,  just  as  toluene  does.  In  this 
case,  as  in  that  of  toluene,  the  paraffin  radical  is  oxidized  to  car- 
boxyl.  It  has  been  found  that  no  matter  what  this  radical 
is,  it  is  oxidized  to  carboxyl,  carbon  dioxide,  and  water.  Thus, 
the  conversions  indicated  below  take  place :  — 

CeHs.CHa      gives  CeHs.COjH. 
CeHs.CjHB         "      C6H5.CO2H. 

CeHj.CsH;  "        C6H6.CO2H. 

CeHj.CsHii        "      CeHs.COaH. 
n  XT  ^C2H5       ,,      _  CO2H 

Mesitylene,  C9Hi2[C6H3(CH3)3].  Mesitylene  is  contained 
in  small  quantity  in  light  oil,  and  can  be  obtained  in  pure  con- 
dition from  this  source.  It  is  most  readily  prepared  by  treating 
acetone  with  sulphuric  acid  :  — 

3  C3H6O  =  C9H12  +  3  H2O. 


MESITYLENE 


323 


It  can  also  be  made  by  treating  methylacetylene,  CHa.C^CH, 
with  sulphuric  acid,  the  action  in  this  case  being  perfectly 
analogous  to  the  polymerization  of  acetylene  (311) :  — 

3CH;CH  =  CeHe; 
3  CHs.CiCH  =  C6H3(GH3)3. 

It  is  a  liquid  resembling  the  lower  members  of  the  series  in  its 
general  properties.     It  boils  at  165°. 

Its  conduct  towards  oxidizing  agents  shows  that  it  is  a  tri- 
methylbenzene.  When  boiled  with  dilute  nitric  acid,  it  yields 
mesitylenic  acid,  C9H10O2,  and  uvitic  acid,  C9H8O4 ;  and,  by 
further  oxidation,  trimesitic  acid,  CgHgOe,  is  formed.  By  dis- 
tillation with  lime,  mesitylenic  acid  yields  metaxylene  and 
carbon  dioxide  ;  uvitic  acid  yields  toluene  and  carbon  dioxide  ; 
and  trimesitic  acid  yields  benzene  and  carbon  dioxide.  The 
formation  and  decomposition  of  the  acids  are  represented  by 
the  equations  following :  — 

f  CH3 
C6H3(CH3)3     +30=  CeHa     CH3     +  H2O ; 

Mesitylene  1    PQ-TT 

Mesitylenic  acid 

CH3 

CO2H  +  H2O ; 
CO2H 

Uvitic  acid 


[  CH3 
C6H3   CH3    +3O 
I  CO2H 

Mesitylenic  acid 

f  CH3 

CeHs     CO2H+3O 
I  CO2H 

Uvitic  acid 

CH3 

CeHs     CH3 
I  CO2H 

Mesitylenic  acid 

f  CH3 

CeHs     CO2H 
1  CO2H 
Uvitic  acid 


=  C6H 


6X13 


[   CO2H 
C6H3       CO2H  +  H2O; 
I   CO2H 
Trimesitic  acid 

Metaxylene 


C6H6.CH3  +  2CO2; 

Toluene 


324  THE   BENZENE   SERIES   OF   HYDROCARBONS 


CfiHa 


CO2H 

CO2H        =        CeHe  +  3  CO2. 

CO2H  B^"^« 


Trimesitic  acid 

These  transformations  show  clearly  that  mesitylene  is  tri- 
methylbenzene,  but  they  do  not  show  in  what  relation  the 
three  methyl  groups  stand  to  each  other. 

An  ingenious  speculation  in  regard  to  this  relation  is  based 
upon  the  fact  that  mesitylene  is  formed  from  acetone.  It 
appears  probable  that  each  of  the  three  molecules  of  acetone 
taking  part  in  the  reaction, 

3  CaHeO  =  C9H12  +  3  H2O, 

undergoes  the  same  change.  As  the  product  contains  three 
methyl  groups,  the  simplest  assumption  that  can  be  made  is 
that  each  acetone  molecule  gives  up  water  as  represented 
thus:  — 

CHs— CO— CH3  =  CH3— C=CH  +  H2O. 

Acetone 

We  thus  have  three  molecules  of  methylacetylene, 
CH3 — -0=011,  and  these  unite  to  form  trimethylbenzene. 
The  only  way  in  which  the  union  can  be  represented,  assuming 
that  all  three  act  in  the  same  way,  is  this :  — 

OH3  OH3 

HO     "^OH  HO-^   ^OH 

III  II  I 

H3OO    ^C0H3  H3OC.      ^OOH, 

H  H 

3  mols.  Methylacetylene  Mesitylene 

According  to  this,  mesitylene  is  a  sjmimetrical  compound,  — 
that  is  to  say,  each  of  the  three  methyl  groups  bears  the  same 
relation  to  the  molecule ;   and  the  same  is  true  of  each  of  the 
three  benzene  hydrogen  atoms. 
This  view  has  been  tested  by  substituting  bromine  for  the 


PSEUDOCUMENE  325 

• 

three  hydrogen  atoms  of  the  benzene  residue  successively ;  and 
it  has  been  found  to  be  correct,  as  but  one  monobromine  sub- 
stitution product  of  mesitylene  has  ever  been  obtained.  Accept- 
ing the  formula  above  given  for  mesitylene,  an  important 
conclusion  follows  regarding  the  structure  of  metaxylene.  For 
we  have  seen  that,  by  oxidizing  mesitylene,  we  get,  as  the 
first  product,  mesitylenic  acid,  —  which  is  mesitylene,  one  of 
whose  methyls  has  been  oxidized  to  carboxyl.  As  all  the 
methyl  groups  bear  the  same  relation  to  the  molecule,  it 
makes  no  difference  which  one  is  oxidized.  The  acid  has  the 
formula :  — 

CH3  CH3 

HOaCCv        /CCH3  HC.        /CCHs 

H  H 

Mesitylenic  acid  Metaxylene  ' 

Now,  by  distilling  this  acid  with  lime,  carbon  dioxide  is  given 
off,  and  metaxylene  is  produced. 

As  the  change  consists  in  replacing  the  carboxyl  by  hydrogen, 
it  follows  that  metaxylene  must  be  represented  by  the  above 
formula,  and  consequently  that,  in  all  meta  compounds,  the  two 
substituting  atoms  or  groups  bear  to  each  other  the  relation 
which  the  two  methyl  groups  bear  to  each  other  in  this  formula 
for  metaxylene. 

Pseudocumene,  C9Hi2[C6H3(CH3)3].  —  This  hydrocarbon, 
which  is  isomeric  with  mesitylene,  occurs  in  light  oil,  from 
which  it  can  be  prepared  in  pure  condition.  Its  properties  are 
similar  to  those  of  the  lower  members  of  the  series.     It  boils  at 

169.5°- 

Pseudocumene  has  been  made  synthetically  from  3-bromo- 
paraxylene  and  methyl  iodide,  and  also  from  4-bromometa- 
xylene  and  methyl  iodide  by  heating  with  sodium.  How  this  is 
possible  will  be  understood  by  an  examination  of  the  formulas 
on  the  next  page :  — 


326  THE  BENZENE  SERIES  OF  HYDROCARBONS 


CH3 

CHs 

CH3 

Hc/i\cH 

Hc/i^CH 

1             1 

HC<^^/CBr 

HC^  ,  >CCH3 

\c/ 

HC\      /CCI 

\c/ 

CH3 

Br 

CH3 

3-BromoparaxyIene 

4-Bromometaiylene 

Pseudocumene 

Replacing  the  bromine  by  methyl,  in  either  of  the  compounds 
represented,  the  product  would  have  the  same  formula,  which  is 
that  of  pseudocumene,  or  1,3,4-trimethylbenzene. 

Hemimellithene  is  1,2,3-trimethylbenzene.  It  occurs  in 
light  oil.  It  has  been  made  from  2-bromometaxylene,  methyl 
iodide,  and  sodium :  — 


CHa 

HC^i^CBr 

1           1              +  ICH3  +  2  Na  = 

CHs 

HC^'^CCHs 

1           1             +  NaBr  +  Nal 
HC<^  ^  >CCH3 

\c/ 

H 

H 

2  -B  romometaxyl  ene 

1,2,3-Trimethylbenzene 

It  boils  at  175°. 

Mesitylene,  i,3,s-trimethylbenzene,  is  also  called  symmetrical 
trimethylbenzene  or  5-trimethylbenzene;  pseudocumene,  1,3,4- 
trimethylbenzene,  unsymmetrical  trimethylbenzene  or  w-tri- 
methylbenzene;  and  hemimellithene,  1,2,3-trimethylbenzene, 
vicinal  trimethylbenzene  or  D-trimethylbenzene.  Similarly, 
other  trisubstitution  products  of  benzene  are  designated  as 
s,  u,  and  v. 

Cumene,  isopropylbenzene,  C6H5.CH(CH3)2,  is  obtained  from 
cuminic  acid  (^-isopropylbenzoic  acid)  by  distillation  with 
lime :  — 

(CH3)2CH.C6H4COOH(^)  =  C6H6.CH(CH3)2  +  CO2. 

Cuminic  acid  Cumene 

It  is  isomeric  with  the  trimethylbenzenes  and  has  been  made 
from  bromobenzene,  isopropyl  bromide,  and  sodium :  — 

CeHjBr  -I-  (CH3)2CHBr  +  2  Na  =  CoH5.CH(CH3)2  +  2NaBr. 


METACYMENE  327 

It  has  a  pleasant  odor  and  boils  at  152.9°.     On  oxidation  it 
gives  benzoic  acid. 

paramethylisopropylbenzene,  ^°  1*  1^  s  C3H7 
This  hydrocarbon  is  of  special  importance,  on  account  of  its 
close  connection  with  two  well-known  groups  of  natural  sub- 
stances, —  the  groups  of  which  camphor  and  the  terpenes 
are  the  best  known  representatives.  It  occurs  in  the  oil  of 
caraway,  the  oil  of  thyme,  and  in  the  oil  of  eucalyptus.  The 
terpenes  are  hydrocarbons  of  the  formula  CioHie,  of  which 
oil  of  turpentine  is  the  best-known.  This  substance  easily 
gives  up  two  hydrogen  atoms  and  yields  ^-cymene  when  heated 
with  iodine.  ^-Cymene  is  best  prepared  by  heating  camphor 
with  phosphorus  pentoxide :  — 

CioHieO  =  CioHi4  -|-  H2O. 

Camphor  ^-Cymene 

It  is  a  liquid  of  a  pleasant  odor.     It  boils  at  176.5°. 
It  has  been  made  synthetically  from  parabromoisopropyl- 
benzene  and  methyl  bromide :  — 

C6H4<™^^^'^'  +  CHsBr  +  2  Na  =  C6H4<^^   +  2  NaBr, 
xJr  '^stl^ 

which  clearly  shows  its  relation  to  benzene.    When  oxidized 
it  gives  ^-toluic  and  ^-phthalic  acids  :  — 

p-Cym.ene  is  the  chief  constituent  of  spruce  turpentine,  a  by- 
product of  the  manufacture  of  sulphite  pulp. 

Metacymene,  meta-methylisopropylbenzene,  C6H4<_    '  ,    ," 

C3H.^{m) 

— This  has  been  found  in  the  products  of  distillation  of  rosin 
(rosin  spirits). 

CH3 

Tertiary    butyl-m-xylene,  /\  .  ,     , 

H3CI      ic(CH3)3'    ''    ^^^   °y 

treating  w-xylene   with  isobutyl   chloride   in  the  presence  of 


328  THE   BENZENE   SERIES  OF  HYDROCARBONS 

aluminium  chloride.      It  is  made  on  the  large  scale  by  this 
method  and  used  in  the  preparation  of  "  artificial  musk  "  (341). 

Hydroaromatic  Hydrocarbons 

Russian  petroleum,  like  American  petroleum,  consists  very 
largely  (80  per  cent)  of  saturated  hydrocarbons  (10  per  cent  aro- 
matic hydrocarbons),  but,  while  most  of  the  American  petroleums 
consist  of  paraflSns,  Russian  petroleum  is  made  up  of  satu- 
rated cyclic  hydrocarbons,  hexahydro  addition  products  of  the 
aromatic  hydrocarbons,  having  the  general  formula,  C„H2„ 
and  called  naphthenes.  They  are  isomeric  with  the  olefines,  but 
differ  from  them  in  being  saturated.  They  do  not  form  addition 
products  with  bromine  and,  unlike  the  aromatic  hydrocarbons, 
do  not  form  nitro  compounds  with  nitric  acid  or  sulphonic 
acids  with  sulphuric  acid.  They  are  readily  converted  into 
the  aromatic  hydrocarbons  by  the  loss  of  hydrogen  and  have 
been  made  from  the  benzene  hydrocarbons  by  the  addition  of 
hydrogen. 

H2C CH2 

Cyclohexane,  hexamethylene,  H2C<^       yCH2,  has,been  found 

H2C      CH2 
in  American,  Rumanian,  Galician,  and  especially  in  Russian 
petroleum.     It  has  been  made  by    reducing   iodocyclohexane 
and  also  from  i,  6-dibromohexane  by  abstracting  bromine  with 
sodium  (305). 

It  is  most  readily  obtained  by  reducing  benzene  by  passing  its 
vapor  mixed  with  hydrogen  over  finely  divided  nickel  heated  to 
180°.  It  was  made  in  this  way  during  the  World  War  and  used  in 
airplane  engines.  It  boils  at  80.85"  and  melts  at  4.7°.  Chlorine 
and  bromine  give  substitution  products.  In  its  chemical  con- 
duct it  resembles  hexane  closely,  hence  the  name  cyclohexane. 
The  higher  members  of  this  series  of  hydrocarbons  are  homo- 
logues  of  cyclohexane  and  are  made  by  the  reduction  of  the 
homologues  of  benzene.  Thus,  hexahydrotoluene  and  the 
hexahydroxylenes  are  methyl  and  dimethyl  derivatives  of 
cyclohexane.     They  are  present  in  Russian  petroleum. 


ACTION   OF  HALOGENS   ON   BENZENE  329 

Hexahydro-^-cymene,  menthane,  terpane,  C10H20,  is  especially 
important  on  account  of  its  relation  to  the  terpenes  and  camphors. 
It  will  be  taken  up  in  connection  with  these  substances. 

CH2 — CH2 — CH 
Cyclohexene,  tetrahydrobenzene,    |  1 1     >  is  made 

CIi2     CH2      CH 

from  bromocyclohexane  by  abstracting  hydrobromic  acid  with 
alcoholic  caustic  potash.  It  boils  at  82.3°  and  acts  like  the 
olefines,  forming  a  dibromide  with  bromine.  Tetrahydro tolu- 
ene and  tetrahydroxylenes,  which  are  methyl  and  dimethyl 
derivatives  of  cyclohexene  and  resemble  this  substance  very 
closely  in  their  chemical  conduct,  are  also  known.  Tetrahydro- 
toluene  occurs  in  rosin  spirits. 

Tetrahydrocymene,  CioHis,  is  a  homologue  of  tetrahydro- 
benzene and  is  related  to  the  terpenes  (441). 

Dihydrobenzenes,  CeHg,  have  been  obtained  from  the  two 
dibromocyclohexanes  by  abstracting  hydrobromic  acid  with 
alcoholic  caustic  potash.  Two  isomers  are  known,  which  re- 
semble each  other  very  closely  in  their  properties. 

CH2 
HCl    JCH 


CH2 

Cyclohexa-i,4-diene 

They  combine  with  two  and  four  atoms  of  bromine,  decolor- 
ize a  solution  of  potassium  permanganate  and  resemble  the  ole- 
fines in  their  properties. 

Dihydro-o-xylene  is  called  cantharene,  as  it  has  been  ob- 
tained by  distilling  cantharic  acid  with  lime. 

Action  of  Halogens  on  Benzene.     Addition  Products 

When  chlorine  or  bromine  acts  on  benzene,  addition  products 
are  formed :  — 

CeHe  +  6  CI  =  CeHeCU. 

B  enzenehexachloride 


33° 


THE  BENZENE  SERIES  OF  HYDROCARBONS 


This  reaction  is  much  facilitated  by  the  action  of  sunlight. 
Hexahalogen  addition  products  are  also  formed  when  the  halo- 
gens act  on  benzene  at  the  boiling  point  or,  in  the  cold,  in  the 
presence  of  a  solution  of  sodium  hydroxide.  They  are  hexa- 
halogen substitution  products  of  cyclohexane,  and  the  two  stereo- 
isomers required  by  the  Kekule  formula  are  both  formed :  — 

CI 


H 

Cis-benzenehexachloride 


R 

=C1^^ 

pCl 

W 

^ 

^Cl 

r 

CI 

Traas  -benzen  ehexachloride 

The  one  in  which  all  the  hydrogen  atoms  are  on  one  side  of  the 
plane  passing  through  the  carbon  atoms  (the  plane  of  the  paper) 
and  all  the  halogen  atoms  on  the  opposite  side  is  known  as  the 
cis  form.  The  other,  in  which  four  hydrogen  atoms  and  two 
halogens  are  on  one  side  and  four  halogens  and  two  hydrogens 
on  the  other,  is  known  as  the  trans  form.  Both  forms  of  the 
benzene  hexachloride  are  decomposed  by  alcoholic  caustic 
potash,  giving  the  unsymmetrical  trichlorobenzene  :  — 

CeHeCle  =  CeHsCla  +  3  HCl. 

That  is,  the  isomerism  disappears  when  the  benzene  condition 
is  reestablished. 

Benzene  also  combines,  in  the  dark  and  at  o°,  with  chlorine 
monoxide  to  give  the  two  benzene  hexachlorides,  and  with  hj^o- 
chlorous  acid  to  give  benzene  trichlorohydrin :  — 

CeHe  +  3  HOCl  =  C6H6Cl3(OH)3. 


Halogen  Substitution  Products  of  Benzene 

Chlorine  also  acts  on  benzene  to  give  substitution  products 
(312) :  — 

CeHs  +  CI2  =  CeHsCl  +  HCl. 


HALOGEN   SUBSTITUTION  PRODUCTS   OF  BENZENE     331 

The  reaction  is  slow  and  incomplete,  however,  unless  a  catalyst 
(iodine,  iron,  etc.)  is  present.  The  iodine  and  iron  first  form 
chlorides,  which  then  give  up  chlorine  to  the  benzene  and  are 
regenerated  by  the  action  of  more  chlorine.  They  hence  act 
as  chlorine  carriers.  Thus,  monochlorobenzene  has  been  made 
by  heating  benzene  with  ferric  chloride  :  — 

CeHe  +  2  FeCla  =  CeHjCl  +  HCl  +  2  FeClj. 

Most  of  the  elements  (I,  S,  P,  Sb,  Mo,  Sn,  Tl)  which  act  as 
chlorine  carriers,  like  iron,  form  two  chlorides.  The  exception 
to  this  rule  is  aluminium  chloride,  which  is  an  excellent  chlorine 
carrier. 

By  the  further  action  of  chlorine  on  benzene  or  on  mono- 
chlorobenzene, in  the  presence  of  a  catalyst,  ^ara-dichloro- 
benzene  is  the  main  product  of  the  reaction,  smaller  amounts 
of  the  ortho  and  7neta  products  being  formed  at  the  same  time. 
The  proportion  of  the  isomers  formed  is  influenced  by  the 
nature  of  the  catalyst.  Thus,  in  the  presence  of  aluminium 
chloride  65.7  per  cent  of  para,  29.6  per  cent  ortho,  and  4.7 
per  cent  metadichlorobenzene  are  formed,  whUe  with  ferric 
chloride  as  a  catalyst  the  percentages  are  55.5,  39.2,  and  5.3. 
Further  chlorination  gives  mainly  the  unsymmetrical  trichloro- 
benzene,  as  this  product  results  from  the  chlorination  of  all  three 
of  the  dichlorobenzenes.  It  has  already  been  stated  that  this 
trichlorobenzene  is  the  only  product  resulting  from  the 
abstraction  of  hydrochloric  acid  from  the  two  benzene  hexa- 
chlorides  with  alcoholic  caustic  potash.  The  tetrachloro- 
benzene,  which  results  from  the  further  chlorination,  is  the 
symmetrical  product,  1,2,4,5,  and  this  is  then  converted  into 
pentachloro  and  hexachlorobenzene  (CeCle)  by  more  energetic 
chlorination. 

The  chlorine  substitution  products  of  benzene  differ  mark- 
edly from  those  of  the  marsh  gas  series  in  that  the  chlorine 
can  only  be  replaced  with  great  difficulty.  Thus  it  is  not  pos- 
sible to  replace  the  chlorine  by  hydroxyl  by  heating  with  alkali 
or  by  an  amino  group  with  ammonia,  except  by  heating  to  a 
high  temperature  in  an  autoclave,  and  then  the  reaction  is 


332  THE   BENZENE   SERIES   OF  HYDROCARBONS 

incomplete.  By  heating  with  sodium  and  alcohol,  however, 
reverse  substitution  takes  place  and  the  hydrocarbon  is  re- 
generated :  — 

C6H4CI2  +  2  H2  =  CeHe  +  2  HCl. 

Monochlorobenzene,  CeHsCl,  is  made  on  the  large  scale  by 
chlorinating  benzene  in  the  presence  of  iron.  The  three  di- 
chlorobenzenes  are  always  formed  in  this  reaction  as  by-products 
(see  above),  even  when  a  large  excess  of  benzene  is  used.  The 
monochlorobenzene  is  separated  from  them  and  from  the 
excess  of  benzene  by  distillation.  Chlorobenzene  can  also  be 
made  by  the  action  of  phosphorus  pentachloride  on  hydroxj'- 
benzene  (phenol) :  — 

CeHsOH  +  PCI5  =  CsHsCl  +  HCl  +  POCI3, 

Phenol  Chlorobenzene 

but  the  reaction  does  not  take  place  as  readily  as  in  the  case  of 
alcohols,  and  it  is  simpler  and  more  economical  to  make  it  by 
the  chlorination  of  benzene.  Chlorobenzene  also  results  from 
the  decomposition  of  benzene  diazonium  chloride  (353)  by 
cuprous  chloride  or  copper  powder  :  — 

CeHsNoCl  =  CeHsCl  +  N2. 

Chlorobenzene  is  a  colorless  liquid,  having  a  pleasant  odor. 
It  boils  at  132°  and  melts  at  —45°.  It  is  used  in  large  quanti- 
ties in  the  manufacture  of  sulphur  dyes  and  in  the  preparation 
of  chloronitrobenzenes  and  other  dyestuff  intermediates.  Dur- 
ing the  World  War  picric  acid  (378)  was  made  from  chloro- 
benzene. Nearly  5,000,000  pounds  were  produced  in  1920  in 
the  United  States. 

Bromobenzene,  CeHjBr.  —  This  is  made  by  the  same  methods 
as  those  used  in  making  chlorobenzene.  It  boils  at  157°  and 
melts  at  —31° 

When  bromobenzene  in  solution  in  ether  is  treated  with 
magnesium  powder,  it  forms  phenyl  magnesium  bromide, 
CeHjMgBr.  (See  Grignard  reaction  (112).)  This  reacts  with 
methyl  bromide  to  form  methylbenzene  or  toluene,  thus :  — 

CeHsMgBr  +  BrCHs  =  CsHbCHs  +  MgBrj. 


DIPHENYLIODONIUM   HYDROXIDE  333 

Phenyl  magnesium  bromide  is  much  used  in  synthetical 
work  for  the  purpose  of  introducing  the  phenyl  group.  Thus, 
in  the  reaction  above,  the  phenyl  group  is  introduced  into 
methane.  This  reagent  is  also  used  for  the  purpose  of  sub- 
stituting iodine  for  bromine :  — 

CeHsMgBr  +  12  =  CeHjI  +  BrMgl. 

lodobenzene 

The  bromine  can  also  be  removed  from  bromobenzene  by  sodium 
(317)  and  by  nascent  hydrogen. 

lodobenzene,  CeHsI.  —  This  can  be  made  by  heating  ben- 
zene with  iodine  and  iodic  acid  in  a  sealed  tube  :  — 

S  CeHe  +  4  I  +  HIO3  =  5  CeHsI  +  3  H2O ; 

but  it  is  more  easily  made  from  the  diazonium  salt :  — 

C6H5N2CI  +  KI  =  CeHsI  +  KCl  +  N2. 

It  is  a  liquid  that  boils  at  188°,  and  melts  at  —30°. 

lodobenzene  dichloride,  CeHsIC^.  —  This  compound  is 
formed  when  lodobenzene  in  chloroform  solution  is  treated 
with  chlorine.  When  it  is  treated  with  a  solution  of  caustic 
potash,  it  is  converted  into  iodosobenzene,  CbHsIO.  This  has 
basic  properties,  and  forms  salts  that  are  derived  from  the 
hypothetical  base,  C6H6l(OH)2,  as,  for  example,  the  lodobenzene 
dichloride  given  above. 

lodoxybenzene,  C6H5IO2,  is  formed  from  iodosobenzene, 
either  by  heating  it  alone  or  by  boUing  its  water  solution :  — 

2  CsHbIO  =  CsHsI  +  C6H5IO2. 

Diphenyliodonium  hydroxide,  (C6H6)2l.OH. — This  remark- 
able substance  is  formed  when  a  mixture  of  iodoso  and  lodoxy- 
benzene is  shaken  with  silver  oxide  and  water :  — 

CeHsIO  +  C6H5IO2  4-  AgOH  =  (C6H5)2l.OH  +  AglOj. 

It  is  a  strongly  alkaline  base  and  forms  salts  that  have  many 
points  of  resemblance  with  the  thaUous  salts.  It  is  known  only 
in  solution. 


334    THE  BENZENE  SERIES  OF  HYDROCARBONS 

Diphenyliodonium  hydroxide  may  be  regarded  as  the  di- 
phenyl  derivative  of  a  hypothetical  base,  iodonium  hydroxide, 
H2l(0H),  that  bears  to  iodine  a  relation  similar  to  that  which 
ammonium  hydroxide  bears  to  nitrogen.  Similar  compounds 
of  sulphur  are  known  in  which  sulphur  plays  the  same  part 
that  iodine  plays  in  the  iodonium  compounds,  and  nitrogen 
in  the  ammonium  compounds,  such  as  trimethylsulphonium 
hydroxide  (CH3)3S.OH. 

Dibromobenzene,  C6H4Br2,  is  one  of  the  products  of  the  di- 
rect treatment  of  benzene  with  bromine  in  the  presence  of  a  car- 
rier. This  being  a  disubstitution  product  of  benzene,  it  follows, 
from  what  has  been  said  in  regard  to  isomerism  in  this  series 
of  hydrocarbons,  that  three  isomeric  varieties  of  the  substance 
ought  to  be  obtainable ;  and  the  interesting  question  suggests 
itself :  Which  one  of  the  three  possible  dibromobenzenes  is 
formed  by  direct  treatment  of  benzene  with  bromine?  The 
answer  to  the  question  is  equally  interesting.  The  main  product 
of  the  action  is  />ara-dibromobenzene,  while  there  are  always 
formed  in  smaller  quantity  some  of  the  ortho  product  and  some 
of  the  meta  product. 

In  studying  the  disubstitution  products  of  benzene,  one  of 
the  first  problems  that  presents  itself  is  the  determination  of  the 
relations  which  the  substituting  atoms  or  groups  bear  to  each 
other.  The  determination  is  made  by  transforming  the  com- 
pounds into  others,  the  relations  of  whose  groups  are  known. 
Thus,  to  illustrate,  when  benzene  is  treated  under  the  proper 
conditions  with  bromine,  three  dibromobenzenes  are  formed. 
Without  investigation,  we,  of  course,  cannot  tell  to  which  series 
these  compounds  belong.  But,  by  treating  that  product  which 
is  formed  in  largest  quantity  with  methyl  iodide  and  sodium,  we 
get  paraxylene.  In  other  words,  by  replacing  the  two  bromine 
atoms  of  the  dibromobenzene  by  methyl  groups,  we  get  a  com- 
pound which  we  know  belongs  to  the  para  series ;  and,  there- 
fore, we  have  determined  that  this  bromine  product  is  a  para 
compound.  In  a  similar  manner  the  dibromobenzenes  formed 
in  smaller  quantity  can  be  converted  into  o-xylene  and  into 
w-xylene. 


HALOGEN  DERIVATIVES  OF  TOLUENE  33S 

Halogen  Derivatives  of  Toluene 

As  toluene  contains  a  residue  of  marsh  gas,  methyl,  CH3, 
and  a  residue  of  benzene,  phenyl,  CeHs,  it  yields  two  classes  of 
substitution  products  :  (i)  Those  in  which  the  substituting  atom 
or  group  replaces  one  or  more  hydrogen  atoms  of  the  phenyl 
group  ;  and  (2)  those  in  which  the  substitution  takes  place  in  the 
methyl.  In  general,  when  treated  with  chlorine  or  bromine  in 
direct  sunlight,  or  at  the  boiling  temperature,  toluene  yields 
products  of  the  second  class  ;  while,  in  the  presence  of  iodine  or 
some  other  carrier  (331),  it  yields  products  of  the  first  class. 
Thus,  we  have  the  two  parallel  series  of  chlorine  derivatives :  — 

I 

Monochlorotoluene,  C6H4CI.CH3 

Dichlorotoluene,  C6H3CI2.CH3 

Trichlorotoluene,  C6H2CI3.CH3 

II 

Benzyl  chloride,  C6H5.CH2CI 

Benzal  chloride,  C6H6.CHCI2 

Benzo  trichloride,  CeHe.CClj 

When  a  member  of  the  first  class  is  oxidized,  the  methyl  is 
oxidized  to  carboxyl  and  the  rest  of  the  compound  remains 
unchanged,  as  in  the  case  of  toluene.  Thus,  the  first  substance 
of  class  I  yields  C6II1CI.CO2H ;  the  second,  CeHsCla-COoH,  etc. 
These  products  are  monochloro  and  dichlorobenzoic  acids.  On 
the  other  hand,  all  the  members  of  the  second  class  yield  the 
same  product  that  toluene  does;  viz.,  benzoic  acid.  Hence,  by 
treatment  with  oxidizing  agents,  it  is  easy  to  distinguish  between 
the  members  of  the  two  classes.  Further,  the  halogen  atoms 
contained  in  the  methyl  react  like  the  halogen  atoms  in  paraffin 
derivatives,  while  those  in  the  phenyl  do  not.  When,  for  ex- 
ample, benzal  chloride,  C6H6.CHCI2,  is  superheated  with  water, 
both  chlorine  atoms  are  replaced  by  oxygen,  the  product  being 
the  aldehyde  CeHo.CHO,  oil  0}  hitter  almonds,  just  as  ordinary 


336  THE   BENZENE   SERIKS   OF   HYDROCARBONS 

aldehyde  is  formed  from  ethylidene  chloride  (48)  by  the  action 
of  water.  When,  however,  the  isomeric  dichloroioluene  is 
superheated  with  water,  no  change  takes  place. 

Regarding  those  simple  substitution  products  of  toluene 
which  contain  one  halogen  atom  in  the  phenyl,  such  as  mono- 
chloro  and  monobromotoluene,  C6ll4Br.CH3,  it  will  be  seen 
that  they  are  disubstitution  products  of  benzene,  and  hence 
capable  of  existing  in  three  isomeric  varieties,  ortho,  meta,  and 
para.  The  products  formed  by  direct  treatment  of  toluene  with 
chlorine  or  bromine  are  mixtures  of  about  equal  parts  of  the 
para  and  the  ortho  compounds. 

The  determination  of  the  series  to  which  each  of  these  products 
belongs  can  be  made  by  replacing  the  halogen  by  methyl,  and 
thus  getting  the  corresponding  xylene.  One  product  of  the 
action  of  bromine  on  toluene  is  in  this  way  converted  into 
paraxylene,  and  is  therefore  parabromotoluene.  In  a  similar 
way  the  second  product  gives  orthoxylene  and  hence  is  ortho- 
bromotoluene. 

All  the  members  of  the  first  class  resemble  very  closely  the 
chlorine  substitution  products  of  benzene,  of  which  they  are 
homologues. 

Benzyl  chloride,  C6H5CH2CI,  and  benzyl  bromide,  C6H6CH2Br, 
are  made  by  chlorinating  or  brominating  toluene  at  the  boiling 
point.  The  chloride  boils  at  178°  and  the  bromide  at  198°. 
The  iodide,  CeHsCH;!,  can  be  made  from  the  bromide  by  heating 
this  with  a  solution  of  potassium  iodide.  These  compounds  are 
esters  of  benzyl  alcohol  (phenylmethyl  alcohol),  C6H.^CH20H, 
and  they  are  converted  into  this  alcohol  by  boiling  with 
potassium  carbonate  solution.  The  chlorine  in  the  side  chain 
is  easily  replaced.  Thus,  by  heating  benzyl  chloride  with 
potassium  acetate,  benzyl  acetate  is  formed ;  with  sodium 
hydrosulphide,  benzylmercaptan ;  and  with  ammonia,  benzyl- 
amine.  Toluene  derivatives  with  the  halogen  in  the  side 
chain  have  an  exceedingly  irritating  effect  on  the  mucous 
membrane  of  the  eyes  and  nose,  causing  the  secretion  of  tears. 
Benzyl  iodide  was  one  of  the  "  tear  gases  "  used  during  the 
World  War. 


NITRO   COMPOUNDS   OF  BENZENE   AND   TOLUENE      337 

Benzal  chloride,  CeHjCHCh,  and  benzotrichloride,  CsHsCCls, 
are  made  by  further  chlorination  of  toluene  at  the  boiling  point. 
Like  benzyl  chloride,  these  chlorides  are  made  on  the  large 
scale  and  are  very  important  substances.  Benzyl  chloride  is 
used  in  making  benzyl  alcohol,  and  also  in  the  manufacture  of 
certain  dyes.  Benzal  chloride  in  used  in  making  benzaldehyde 
and  as  a  synthetical  reagent.  Benzotrichloride  is  used  in  the 
manufacture  of  benzoic  acid  on  the  large  scale. 

Halogen  Derivatives  of  the  Higher  Members  of  the 
Benzene  Series 

Concerning  the  halogen  derivatives  of  the  .xylenes  it  need  only 
be  said  that  the  only  one  of  the  three  xylenes  from  which  pure 
products  can  easily  be  obtained  is  paraxylene.  When  this  is 
treated  with  bromine,  it  yields  but  one  monobromoxylene. 
The  significance  of  this  fact  has  been  discussed  above.  The 
monosubstitution  products  obtained  from  the  other  xylenes 
are  mixtures  which  it  is  very  difficult,  and  in  some  cases  im- 
possible, to  separate  into  their  constituents.  Mesitylene  and 
pseudocumene,  though  both  are  trimethylbenzenes,  conduct 
themselves  quite  differently  towards  bromine,  —  the  former 
yielding  only  one  monobromine  substitution  product ;  the 
latter,  a  mixture  of  several. 

NiTRO  Compounds  of  Benzene  and  Toluene 

In  treating  of  nitro  compounds  in  connection  with  the  paraf- 
fin derivatives  (107),  it  was  stated  that  they  are  obtained 
much  more  readily  from  the  benzene  hydrocarbons  than  from 
the  parafiSns.  Only  a  few  nitro  derivatives  of  the  paraffins  are 
known.  As  will  be  remembered,  they  cannot  readily  be  pre- 
pared by  treating  the  paraffins  with  nitric  acid,  but  must  be 
made  by  circuitous  methods,  the  principal  one  being  the  treat- 
ment of  the  halogen  derivatives  with  silver  nitrite  :  — 

H3CI  +  AgN02  =  H3C.NO2  +  Agl. 

Nitromethane 


CeHs.NOa 

+  H20 

C6H4(N02)2 

+  H20 

H3C.C6H4.N02 

+  H20 

338  THE  BENZENE  SERIES  OF  HYDROCARBONS 

The  preparation  of  a  nitro  derivative  of  a  hydrocarbon  of 
the  benzene  series  is  a  simple  matter.  It  is  only  necessary  to 
bring  the  hydrocarbon  in  contact  with  fuming  nitric  acid,  or 
better  with  a  mixture  of  sulphuric  and  nitric  acids,  when  re- 
action takes  place,  and  one  or  more  hydrogen  atoms  of  the 
hydrocarbon  are  replaced  by  the  nitro  group,  NO2,  as  repre- 
sented in  the  equations :  — 

CeHsH  -I-  HONO2 

C6H5.NO2  +  HNO3 

CeHs.CHs  +  HNO3 

H3C.C6H4.NO2  4-  HNO3        =       H3C.C6H3(N02)2    +  H2O. 

The  nitro  compounds  thus  obtained  are  not  acids,  nor  are 
they  esters  of  nitrous  acid.  If  they  were  esters  of  nitrous 
acid,  they  would  be  saponified  by  caustic  alkalies,  yielding  a 
nitrite  and  a  hydroxyl  derivative  similar  to  the  alcohols.  They 
do  not  act  in  this  way.  When  treated  with  nascent  hydrogen, 
they  are  reduced  to  amino  compounds  or  substituted  ammonias. 
Thus,  nitrobenzene,  C6H5.NO2,  gives  aniline  or  aminobenzene, 
C6H6.NH2,  which  is  a  substituted  ammonia  similar  to  methyl- 
amine  and  ethylamine.  As  in  these  the  radical  is  in  combination 
with  nitrogen,  it  is  certain  that  the  radical  is  in  combination  with 
nitrogen  in  the  nitro  compounds  also,  as  shown  in  the  formula, 
C6H6.NO2.  Everything  known  about  the  nitro  compounds  is 
in  harmony  with  this  view. 

In  making  nitro  compounds  on  the  large  scale  "  mixed  acid" 
(a.  mixture  of  concentrated  nitric  and  sulphuric  acids)  is  almost 
invariably  used.  In  the  formation  of  nitro  compounds  it  is 
highly  probable  that  an  addition  product  is  first  formed,  and 
that  water  is  eUminated  from  this  by  the  sulphuric  acid  reestab- 
lishing the  double  bond  (313).  In  order  to  form  the  addition 
product  the  un-ionized  nitric  acid  is  required,  and  this  is  present 
in  the  mixed  acid.  The  sulphuric  acid  combines  with  the 
water  formed  in  the  reaction,  and  this  prevents  the  dilution  of 
the  nitric  acid. 

Mononitrobenzene,  C6HB.NO2.  —  This  substance  is  made  on 
the  large  scale  by  treating  benzene  with  a  mixture  of  ordinary 


DINITROBENZENE  339 

concentrated  nitric  and  sulphuric  acids.  Nitrobenzene  is  a 
yellow  liquid  that  boils  at  210.9°,  melts  at  5.7°,  and  has  the 
specific  gravity  1.2 193.  Its  odor  is  similar  to  that  of  the  oil 
of  bitter  almonds,  and  it  is  hence  used  to  some  extent  instead 
of  the  latter.  It  is  known  as  the  essence  of  mirhane.  Its  vapor 
is  poisonous,  when  inhaled. 

It  is  slightly  soluble  in  water  and  the  solution  has  an  intensely 
sweet  taste.  It  mixes  in  all  proportions  with  alcohol,  ether,  and 
benzene.  An  alcoholic  solution  gives  a  red  color  with  a  solution 
of  potassium  hydroxide,  if  any  dinitrothiopkene  is  present..  It 
is  used  in  the  preparation  of  aniline,  dinitrobenzene,  chloronitro- 
benzene,  benzidine,  etc.  About  53|-  million  pounds  were  made 
in  the  United  States  in  1920. 

Chloronitrobenzenes,  C6H4(N02)C1.  —  When  monochloroben- 
zene  is  nitrated  with  mixed  acid  at  ordinary  temperatures, 
about  70  per  cent  of  ^-chloronitrobenzene  and  30  per  cent  of  the 
ortho  product  are  formed.  w-Chloronitrobenzene  is  prepared 
by  chlorinating  nitrobenzene  in  the  presence  of  a  carrier.  The 
chlorine  in  the  0-  and  ^-products  can  be  replaced  by  hydroxyl, 
methoxyl,  or  the  amino  group  by  heating  them  with  solutions  of 
the  alkalies,  with  an  alcoholic  solution  of  sodium  methylate,  or 
with  alcoholic  ammonia.  It  is  not  possible  to  replace  the 
chlorine  in  the  w-product  in  this  way. 

Dinitrobenzene,  C6H4(N02)2.  —  This  is  a  product  of  the 
further  action  of  a  mixture  of  fuming  nitric  acid  and  sulphuric 
acid  on  benzene,  or  on  nitrobenzene. 

w-Dinitrobenzene  crystallizes  in  long,  yellow  needles,  or 
thin,  rhombic  plates.  Melting  point,  89.7°.  About  2^  million 
pounds  were  made  in  the  United  States  in  1920. 

By  means  of  two  reactions,  which  will  be  described  under 
Diazo  Compounds,  it  is  a  simple  matter  to  replace  the  two 
nitro  groups  by  bromine,  thus  converting  dinitrobenzene  into 
dibromobenzene.  When  the  latter  is  converted  into  xylene, 
the  product  is  metaxylene.  Hence,  ordinary  dinitrobenzene 
is  a  meta  compound.  Small  quantities  of  o-dinitrobenzene 
and  traces  of  /(-dinitrobenzene  are  also  formed  in  the  nitra- 
tion of  benzene.     It  is  used  in  the  preparation  of  w-phenylene- 


340  THE   BENZENE   SERIES   OF  HYDROCARBONS 

diamine,  m-nitroaniline,  and  also  in  the  preparation  of  ex- 
plosives. 

Chlorodinitrobenzene,  C6H3C1(N02)2 1,2,4,  is  made  by  ener- 
getic nitration  of  chlorobenzene.  The  chlorine  in  this 
compound  is  extremely  easily  replaced,  e.g.,  when  boiled 
with  a  solution  of  sodium  carbonate  it  gives  dinitrophenol, 
C6H3(OH)(N02)2i,2,4  (377),  used  in  the  manufacture  of  sul- 
phur black.  Chlorodinitrobenzene  is  made  on  the  large  scale 
by  nitrating  o-chloronitrobenzene  and  is  an  important  dyestufif 
inteyrmediate.  Nearly  6  million  pounds  were  made  in  the 
United  States  in  1920. 

Phenylnitromethane,  C6H5CH2NO2,  is  an  example  of  a  nitro 
compound  with  the  nitro  group  in  the  side  chain,  and  is  an 
isomer  of  the  three  nitrotoluenes.  It  is  made  by  the  action  of 
benzyl  iodide  on  silver  nitrite.  It  cannot  be  hydrolyzed,  and  on 
reduction  gives  benzylamine,  C6H5CH2NH2,  and  hence  is  a  true 
nitro  compound.  When  first  prepared  the  substance  is  a  liquid, 
(b.  p.  2  25°-227°),  somewhat  soluble  in  water,  and  this  solution 
gives  no  color  with  a  solution  of  ferric  chloride.  When  dis- 
solved in  a  solution  of   sodium  hydroxide  it  forms  a  sodium 

NO 
salt,  C6H5CH<       ,  and  when  this  is  decomposed  in  the  cold 

by  hydrochloric  acid  it  gives  the  solid  modification  (m.  p.  84°), 

which  is  unstable  and  gradually  passes  over  to  the  liquid  form. 

The  solid  form  (isomeric  modification)  probably  has  a  formula, 

NO 
C6H6CH<  similar  to  that  of   the  sodium  salt,   since  its 

Oil 

aqueous  solution  gives  the  reddish  coloration  with  ferric  chloride 
solution  characteristic  of  hydroxyl  compounds  and  it  reacts 
very  readily  with  phenyl  isocyanate  (349).  Phenylnitro- 
methane belongs  to  the  class  of  pseudo  acids,  as  it  undergoes 
molecular  rearrangement  into  the  true  acid  before  it  forms 
a  salt :  — 

NO 
CeHsCHsNOz  -f-  NaOH  =  C6H5CH<^>;    +  H2O. 

UN  a 

Nitrotoluenes,  C6H4(NO;).CH3.  —  When  toluene  is  treated 
with  mixed  acid,  substitution  always  takes  place  in  the  phenyl, 


AMINO   COMPOUNDS   OF  BENZENE  341 

and,  on  the  average,  58.8  per  cent  of  the  ortho  product  is 
formed,  36.8  per  cent  of  the  para,  and  about  4.4  per  cent  of 
the  meta  by  nitration  at  0°.  A  higher  temperature  increases 
the  proportion  of  the  ortho  product  formed.  By  treatment 
with  nascent  hydrogen,  the  nitrotoluenes  are  converted  into 
the  corresponding  amino  compounds,  known  as  toluidines  (350). 

o-Nitrotoluene  melts  at  —  10.5°,  and  boils  at  218°.  /i-Nitro- 
toluene  melts  at  51°,  and  boils  at  234°.  They  are  used  in 
making  the  toluidines  and  other  dyestuff  intermediates.  Over 
6,000,000  pounds  were  made  in  the  United  States  in  1920. 

Dinitrotoluene,  C6H3CH3(N02)2, 1,2,4,  results  from  the  nitra- 
tion of  0-  or  ^-nitro toluene.  It  melts  at  69.5°,  and  on  oxi- 
dation with  nitric  acid  gives  dinitrobenzoic  acid.  On  further 
nitration  it  gives  S5rmmetrical  trinitrotoluene.  On  reduction 
it  is  converted  into  w-toluylenediamine,  which  is  used  in  the 
production  of  azo  dyestuffs  and  sulphur  colors. 

Symmetrical  trinitrotoluene,'  C6H2CH3(N02)3,1, 2,4,6,  known 
as  T.N.T.,  is  made  on  the  large  scale  by  nitrating  toluene  in 
stages  with  mixed  acid.  It  crystallizes  from  alcohol  in  needles, 
which  melt  at  8 1 . 5°  Enormous  quantities  of  this  high  explosive 
were  used  during  the  World  War. 

Trinitrotertiarybutyl-m-xylene,    (^i{'^Oi)-i<    ,   IL^.   ,  has  an 

C(CH3)3 

odor  similar  to  that  of  musk  and  is  known  as  "  artificial  musk." 


Amino  Compounds  of  Benzene,  etc. 

The  amino  derivatives  of  the  paraffins  are  made,  for  the  most 
part,  by  treating  the  halogen  derivatives  with  ammonia  (100). 
In  treating  of  these  derivatives,  however,  attention  was  called 
to  the  fact  that  the  primary  amines  can  also  be  made  by  treat- 
ing nitro  compounds  with  nascent  hydrogen  (104).  The 
latter  method  is  one  of  great  importance  in  the  benzene  series. 
It  is  used  exclusively  in  the  preparation  of  the  amino  deriva- 
tives of  the  benzene  hydrocarbons.     Several  of  these  deriva- 

'  For  information  concerning  explosives  the  student  is  referred  to 
the  book  by  Arthur  Marshall  entitled  Explosives,  2d  edition,  191 7. 


342  THE   BENZENE  SERIES   OF  HYDROCARBONS 

tives  are  well  known,  the  simplest  and  best  known  being  amino- 
benzene  or  aniline. 

Aniline,  CeHyN  (C6H6.NH2). — Aniline  was  first  obtained 
from  indigo  by  distillation.  Anil  is  the  Portuguese  and  French 
name  of  the  indigo  plant,  and  it  is  from  this  that  the  name 
aniline  is  derived.  Aniline  is  found  in  coal  tar  and  in  bone  oil, 
a  product  of  the  distillation  of  bones.  It  is  prepared  by  re- 
ducing nitrobenzene  with  nascent  hydrogen.  On  the  large 
scale  the  hydrogen  is  obtained  frohi  ferrous  chloride,  iron,  and 
water. 

The  reactions  that  take  place  are  as  follows :  In  the  presence 
of  iron  and  water,  ferrous  chloride  is  hydrohzed  to  ferrous 
hydroxide  and  hydrochloric  acid :  — 

FeCl2  +  2  H2O  =  Fe(0H)2  +  2  HCl. 

The  ferrous  hydroxide  at  once  reduces  some  of  the  nitrobenzene 
to  aniline :  — 

C6H6NO2  +  6  Fe(0H)2  +  4  H20=  6  Fe(0H)3  +  CeHsNHj, 

while  the  iron  reacts  with  the  hydrochloric  acid  set  free  to 
regenerate  ferrous  chloride  and  produce  nascent  hydrogen, 
which  reduces  more  of  the  nitrobenzene :  — 

Fe  +  2HC1  =  FeCl2  +H2; 
C6H6NO2  +  3  H2  =  CeHsNHz  +  2  H2O. 

It  wiU  be  seen  that  only  a  small  amount  of  ferrous  chloride  is 
necessary  to  bring  about  the  reduction  of  the  nitrobenzene  to 
aniline,  as  the  hydrogen  comes  from  the  water,  and  ferrous 
chloride  is  constantly  regenerated.  For  laboratory  purposes 
tin  and  hydrochloric  acid  are  frequently  used.  Other  reducing 
agents,  such  as  an  ammoniacal  solution  of  ammonium  sulphide, 
hydriodic  acid,  etc.,  also  effect  the  change. 

Aniline  is  a  colorless  liquid  that  soon  becomes  colored  brown  in 
the  air  when  not  perfectly  pure.  It  boils  at  184.32°  to  184.39°  i 
and  freezes  at  —6.24°  It  is  somewhat  soluble  in  water  (3  parts 
in  100)  and  water  dissolves  in  aniline  (5  parts  in  100).  It 
mixes  in  every  proportion  with  alcohol,  ether,  and  benzene. 


DERIVATIVES   OF  ANILINE  343 

It  is  very  hygroscopic,  absorbing  water  rapidly  from  the  air. 
The  solution  in  water  has  a  slight  alkaline  reaction.  Aniline 
is  poisonous.     Its  salts  with  strong  acids  have  an  acid  reaction. 

A  solution  of  anUine  in  water  gives  a  violet  color  with  an 
excess  of  a  solution  of  chloride  of  lime,  and  this  reaction  is  used 
as  a  test  for  aniline. 

Aniline  is  reduced  by  hydrogen  in  the  presence  of  colloidal 
platinum  to  cydohexylamine,  CsHuNHa  (b.  p.  135°)  which  acts 
like  an  amine  of  the  paraffin  hydrocarbons. 

Aniline  bears  the  same  relation  to  benzene  that  ethylamine 
or  aminoethane  bears  to  ethane.  It  is  a  substituted  ammonia, 
and  like  other  amines  it  unites  directly  with  acids,  forming 
salts.  Thus,  with  hydrochloric,  nitric,  and  sulphuric  acids  the 
action  takes  place  as  represented  below :  — 

C6H5.NH2  +  HCl      =  C6H5.NH3CI; 
C6H5.NH2  +  HNO3  =  C6H5.NH3NO3; 
C6H5.NH2  +  H2SO4  =  C6H6.NH3HSO4. 

The  hydrochloride  is  known  in  the  trade  as  aniline  salt. 
It  is  used  chiefly  in  the  production  of  aniline  black  on  the  fabric 
by  oxidation. 

The  decomposition  of  aniline  hydrochloride  by  means  of  a 
caustic  alkali  takes  place  as  represented  in  the  following  equa- 
tion :  — 

C6H5.NH3CI  +  KOH  =  CsHb.NHj  +  H2O  +  KCl. 

Aniline  is  used  in  the  preparation  of  intermediates  and  dye- 
stuffs.  Large  quantities  are  used  in  the  manufacture  of  syn- 
thetic indigo.  It  is  used  in  the  rubber  industry,  as  an  accelerator 
in  the  vulcanization  of  rubber.  Some  idea  of  its  importance  in 
the  manufacture  of  organic  chemicals  and  dyestuffs  may  be  had 
from  the  fact  that  over  39  million  pounds  were  made  in  the 
United  States  in  1920. 

Derivatives  of  Aniline.  Aniline  is  much  more  sensitive  to 
the  action  of  reagents  than  benzene,  chlorobenzene  or  nitro- 
benzene. Thus  an  aqueous  solution  when  treated  with  chlorine 
or   bromine   water  precipitates    2,4,5,-trichloro-    or   tribromo- 


344  THE   BENZENE   SERIES   OF  HYDROCARBONS 

aniline.  The  ease  with  which  chlorine  and  bromine  react  with 
aniline  is  due  to  the  fact  that  the  halogen  first  substitutes  a 
hydrogen  of  the  amino  group,  forming  phenylbromamide,  for 
example.  These  halogen  amides  are  exceedingly  unstable  and 
immediately  undergo  molecular  rearrangement,  the  halogen 
entering  the  benzene  ring  in  the  para  and  ortho  positions :  — 

CsHsNHBr — i^  BrCelh.'NB.^ip)  and  BrC6H4NH2(o). 

Phenylbromamide  ;^Bromoanilme  o-Bromoaniline 

As  there  are  two  ortho  positions  and  one  para  in  the  aniline 
m.olecule  the  reaction  stops  with  the  formation  of  2,4,6-tri- 
bromoaniline.  So  sensitive  is  aniline  to  the  action  of  oxidizing 
agents  that  it  is  frequently  necessary  to  "  protect  "  the  amino 
group.  For  example,  in  making  the  nitroanilines,  the  nitration 
is  brought  about  in  the  presence  of  large  amounts  of  sulphuric 
acid,  or  the  aniline  is  first  converted  into  acetanilide  (348). 
This  on  nitration  gives  ^-nitroacetanihde,  as  the  main  product, 
together  with  some  o-nitroacetanilide.  On  hydrolysis  with 
alkaH  or  acid  these  }'ield  p-  and  o-nitroanilines.  w-Nitro- 
aniline  is  made  on  the  large  scale  by  the  reduction  of  one  of 
the  nitro  groups  of  »«-dinitrobenzene  (339)  with  sodium  poly- 
sulphide  :  — 

C6H4<^°'  +  NasSs  +  H2O  =  C6H4<^JJ'  +  Na^SaOs- 

m-Dinitrobenzene  w-Nitroaniline 

The  nitroanilines  crystallize  in  yellow  needles.  The  ortho 
compound  melts  at  71°,  the  meta,  at  114°,  and  the  para,  at 
147°.  They  are  not  ver}-  soluble  in  water,  but  dissolve  readily 
in  alcohol.  The  0-  and  m-,  but  not  the  p-  product,  are  volatile 
with  steam,  while  the  0-  and  p-  compounds,  but  not  the  m-, 
undergo  hydrolysis  when  boiled  with  solutions  of  the  alkalies, 
giving  the  nitrophenols :  — 

O2N.C6H4.NH2  +  HOH  =  O2N.C6H4.OH  +  NH3. 

^-Nitroaniline  is  made  on  the  large  scale  and  is  used  principally 
in  the  manufacture  of  the  azo  dye  p-nitroaniline  red.     When 


DIMETHYLANILINE  345 

nitrated  with  mixed  acid  w-nitroaniline  gives  tetranitroaniline 
(T.N.A.),  C6H(N02)4NH2,  which  is  used  as  an  explosive. 
When  reduced  the  nitroanilines  are  converted  into  phenylene- 
diamines,  C6H4(NH2)2. 

Atoxyl,  H2N.C6H4.AsO (OH) (ONa),  as  the  formula  shows, 
is  a  derivative  of  aminophenylarsinic  acid.  It  is  a  valuable 
remedy  in  sleeping  sickness  and  similar  diseases.  Its  acetyl 
compound,  arsacetin,  is  also  used  for  similar  purposes. 

o-Phenylenediamine,  C6H4(NH2)2(o),  is  best  made  by  reduc- 
ing o-nitroaniline.  It  crystallizes  in  colorless  leaflets  from 
water,  melting  at  io2°-i03°,  which  rapidly  turn  brown  in  the 
air.  Its  salts,  such  as  C6H4(NH2HCl)2(o),  are  more  stable. 
It  is  much  more  soluble  in  water  than  aniline.  It  gives  a  red 
color  with  ferric  chloride,  and  is  used  in  the  nTanufacture  of 
sulphur  dyes. 

m-Phenylenediamine  is  made  on  the  large  scale  by  the  re- 
duction of  w-dinitrobenzene  with  iron,  water,  and  hydro- 
chloric acid.  It  forms  colorless  crystals  melting  at  65°, 
which  are  easily  soluble  in  water,  alcohol,  and  ether.  With 
nitrous  acid  it  is  converted  into  Bismarck  brown  (364).  Even 
traces  {-^  mg.  in  a  liter)  of  nitrous  acid  can  be  detected  by  the 
yellow  color  it  gives  with  this  base.  With  diazonium  salts  it 
gives  azo  dyes  (see  Chrysoidine,  364). 

^-Phenylenediamine,  made  by  reducing  /i-nitroaniline,  crystal- 
lizes from  water  and  melts  at  147".  It  gives  quinone  (431) 
readily  when  oxidized  with  manganese  dioxide  and  sulphuric 
acid.  It  is  used  in  the  manufacture  of  dyestuffs  and  in  coloring 
hair,  furs,  etc. 

Dimethylaniline,  C6H5N(CH3)2,  is  made  on  the  large  scale 
by  heating  aniline,  methyl  alcohol  (which  must  be  free  from 
acetone)  and  sulphuric  acid  in  an  autoclave  :  — 

H3C.OH  -t-  HO.SO2.OH  =  H2O  -I-  H3C.O.SO2.OH; 

CeHNHH  -1-  HO.SO2OCH3        =  CeHsNHCHs  -|-  H2SO4; 

Monom  ethylaniline 

C6H5N<5;^'    +  HO.SO2O.CH3   =    C6H5N(CH3)2    +  H2SO4. 

Dimethylaniline 


346  THE   BENZENE   SERIES   OF  HYDROCARBONS 

It  will  be  seen  from  the  above  reactions  that  the  process  re- 
sembles the  formation  of  ether  from  alcohol  by  the  action  of 
sulphuric  acid.  The  sulphuric  acid  first  forms  methyl  acid 
sulphate  with  the  methyl  alcohol,  which  reacts  with  the  aniline 
to  give  monomethylaniline  and  regenerates  the  sulphuric  acid. 
The  sulphuric  acid  set  free  immediately  combines  with  more 
alcohol,  and  the  methyl  acid  sulphate  combines  with  the  mono- 
methylaniline to  give  dimethylaniline  and  sulphuric  acid.  The 
technical  dimethylanUine  usually  contains  aniline  and  some 
monomethylaniline.  A  by-product  of  the  manufacture  of 
dimethylaniline  is  dimethyl  ether,  (CH3)20,  formed  by  the  action 
of  the  methyl  acid  sulphate  on  the  methyl  alcohol :  — 

H3COSO2OH  -I-  HO.CH3  =  H3COCH3  -I-  H2SO4. 

Dimethylaniline  is  an  almost  colorless  oily  fluid,  when  perfectly 
pure,  which  boUs  at  193.1°  and  melts  at  2.5°.  Its  specific 
gravity  is  0.955.  It  is  insoluble  in  water,  but  soluble  in  alcohol, 
ether,  and  benzene.  It  is  a  tertiary  amine.  The  para  hydrogen 
atom  is  extremely  easily  replaced.  Thus,  with  nitrous  acid  it 
gives  p-nitrosodimethylaniline :  — 

(CH3)2NC6H4H  +  HO.NO  =  (CH3)2NC6H4NO  +  H2O, 

which  crystallizes  in  green  leaflets  melting  at  85°  and  forms 
a  yellow  hydrochloride.  When  warmed  with  a  solution  of 
caustic  soda  it  is  hydrolyzed  quantitatively  into  ^-nitroso- 
phenol  and  dimethylamine  :  — 

(CH.O2NC6H4NO  +  HOH  =  HO.C6H4.NO  +  HN(CH3)2, 

ii-Nitrosodimethylanilme  /)-Nitrosophenol  Dimethylamine 

and  this  is  the  best  method  for  the  preparation  of  pure  dimethyl- 
amine. With  carbonyl  chloride,  dimethylaniline  gives  Michler's 
ketone  (tetramethyldiaminobenzophenone)  :  — 

CI  +  H.C6H4.N(CH3)2_^„  .C6H,N(CH3)2^    „P, 

"^"^^Cl   -t-  H.C6H4.N(CH3)2~  ^C6H4N(CH3)2'^ 

Michler's  ketone 

Dimethylaniline  combines  with  formaldehyde  (40  per  cent  solu- 


DIPHENYLAMINE  347 

tion)  in  the  presence  of  hydrochloric  acid  to  give  tetramethyl- 
diaminodiphenyknethane :  — 

HC6H4N(CH3)2  „„^C6H4N(CH3)2     ^„^ 

^=^"  +  HCeH4N(CH3).     ~    "^^<CeH4N(CH3)2    ^  ^'^^ 

Tetramethyldiaminodiphenylmethane 

When  heated  with  mixed   acid   dimethylaniline   is   converted 
into  trinitrophenylmethylnitroamine : 

H3C— N— NO2 

02N/\n02 


N02 

Tetryl 

One  of  the  methyl  groups  is  removed  by  oxidation,  its  place 
being  taken  by  a  nitro  group,  while  three  nitro  groups  enter  the 
benzene  ring.  This  compound  is  used  as  an  explosive  under  the 
name  of  Tetryl. 

Nearly  5-^  milhon  pounds  of  dimethylaniUne  were  produced 
in  the  United  States  in  1920.  It  is  a  very  important  sub- 
stance, and  is  largely  used  in  the  preparation  of  intermediates 
(Michler's  ketone  and  Michler's  hydrol,  ^-nitrosodimethyl- 
aniline,  etc.)  and  in  the  manufacture  of  dyestuffs  (Crystal  violet, 
Methyl  violet.  Malachite  green,  etc.).  It  is  also  used  as  an 
accelerator  in  the  vulcanization  of  rubber. 

Diethylaniline,  C6H5N(C2H6)2,  is  made  on  the  large  scale  from 
aniline  and  ethyl  bromide :  — 

CeHsNHj  +  2  BrCjHs  =  C6H6N(C2H6)2  +  2  HBr. 

It  is  used  in  the  manufacture  of  rhodamine  dyes. 

Diphenylamine,  (C6H5)2NH.  —  This  is  formed  from  aniline 
by  the  introduction  of  a  phenyl  group,  CeHs,  for  one  of  the 
amino' hydrogen  atoms.  It  is  prepared  on  the  large  scale,  and 
finds  extensive  use  in  the  manufacture  of  dyes  and  as  an  addition 
to  explosives  for  the  purpose  of  increasing  their  stability.  It  is 
made  by  heating  aniline  with  aniline  hydrochloride  at  22o°-23o° 
in  an  autoclave :  — 

C6H6NH2  +  CeHsNHaHCl  =  CeHsNHCsHs  +  NH4CI. 


348  THE   BENZENE   SERIES   OF  HYDROCARBONS 

It  crystallizes  in  white  laminae  from  ligroin  (m.  p.  54°,  b.  p.  302°). 
It  has  a  neutral  reaction  and  the  odor  of  flowers.  It  forms 
salts  with  strong  acids,  but  these  are  decomposed  by  water. 
MonomethylanQine  and  diphenylamine  are  examples  of  sec- 
ondary amines.  They  both  react  with  nitrous  acid,  giving 
nitrosamines :  — 

(C6H5)2NH  +  HONO     =     (C6H5)2N.NO  +  H2O. 

Nitrosodiphenylamine 

Nitrosodiphenylamine,  diphenylnitrosamine,  crystallizes  in 
yellow  plates  that  melt  at  66.5° 

The  solution  of  diphenylamine  in  concentrated  sulphuric 
acid  gives  an  intense  blue  color  with  even  traces  of  nitric  acid, 
and  this  is  a  very  delicate  test  for  nitric  acid. 

Acetanilide,  CoHs.NH.COCHa.  —  Aniline  reacts  with  acid 
chlorides  as  ammonia  does.  While  ammonia  forms  amides, 
aniline  forms  anilides.  Thus,  with  acetyl  chloride,  ammonia 
gives  acetamide,  and  aniline  gives  acetanilide :  — 

CH3.COCI  +  NHs  =  CH3.CONH2  +  HCl; 
CH3.COCI  +  NH2.C6H5  =  CHs.CO.NH.CeHs  +  HCl. 

Acetanilide  is  made  on  the  large  scale  by  boiling  aniline  with 
glacial  acetic  acid  for  several  days  and  distilling  off  the  water 
as  fast  as  it  is  formed :  — 

CH3.COOH  +  NH2.C6H5  =  CHs.CO.NH.CsHs  +  H2O. 

Acetanilide  crystallizes  from  water  in  large,  colorless  plates. 
It  melts  at  115°  and  boils  at  304°.  It  is  used  in  medicine  under 
the  name  antifebrine. 

Nearly  3  million  pounds  were  made  in  the  United  States  in 
1920.  It  is  used  technically  in  the  preparation  of  ^-nitroaniline. 
MethylacetanUide  and  ethylacetanilide  are  used  to  replace 
camphor  in  the  celluloid  industry. 

PhenyiglycocoU,  phenylglycine,  C6H5.NH.CH2COOH,  is  most 
readUy  made  by  the  action  of  monochloroacetic  acid  on 
aniline :  — 

CeHsNHH  +  CICH2.COOH  =  CeHs.NH.CHj.COOH  +  HCl. 


THIOCARBANILIDE,   DIPHENYLTHIOUREA  349 

It  is  a  very  important  intermediate  product  in  the  manufacture 
of  indigo  (485). 

Hydroxyethylaniline,  C6H5NHCH2CH2OH,  which  is  also  used 
in  the  manufacture  of  indigo,  is  made  by  combining  aniUne  with 
ethylene  chlorhydrin :  — 

CbHsNHH  +  CICH2CH2OH  =  CeHsNHCHsCHjOH  +  HCl. 

Phenyl  isocyanate,  CeHs.NCO,  made  from  carbonyl  chloride 
and  fused  aniline  hydrochloride  :  — 

CGH5NH2  +  CI2CO  =  CeHsNCO  +  2  HCl, 

is  a  mobUe  liquid,  boiling  at  163'"  and  having  a  penetrating  odor. 
Its  vapor  has  a  marked  effect  on  the  mucous  membrane  of  the 
eyes  and  nose,  producing  tears.  With  water  it  gives  diphenyl- 
urea :  — 

2  CeHjNCO  +  H2O  =  0C<S2^'w    +  CO2. 

Diphenylurea 

It  reacts  with  alcohols  and  phenols  to  form  esters  of  phenyl- 
carbamic  acid  (phenylurethanes) :  — 

C6H5.NCO  +  HO.C2H5  =  C6H6NHCO2C2H6. 

This  reaction  is  characteristic  of  the  alcoholic  and  phenolic 
kydroxyl  group,  and  is  frequently  used  to  determine  the  presence 
of  this  group  in  organic  compounds. 

Thiocarbanilide,  diphenylthiourea,  CeHsNHCSNHCeHs,  is 
made  by  the  action  of  carbon  bisulphide  on  aniline  :  — 

CS2  +  2  C6H5NH2  =  SC<JJJJ^'JJ'  +  H2S. 

Thiocarbanilide 

It  crystallizes  in  leaflets,  melting  at  151°,  which  are  scarcely 
soluble  in  water,  but  readily  in  alcohol.  It  dissolves  in  alkalies 
and  is  precipitated  from  these  solutions  by  acids,  even  by  carbon 
dioxide.  Large  quantities  are  used  as  an  accelerator  in  the 
vulcanization  of  rubber.  Over  2  million  pounds  were  manu- 
factured in  the  United  States  in  1920. 


350      THE  BENZENE  SERIES  OF  HYDROCARBONS 

Toluidines,  aminotoluenes,  H3CC6H4NH2.— The  toluidines, of 
which  there  are  three  corresponding  to  the  three  nitrotoluenes, 
are  made  from  the  latter  in  the  same  way  that  aniline  is  made 
from  nitrobenzene.  Ortho  and  paratoluidine  are  used  extensively 
in  the  manufacture  of  intermediates  and  dyes. 

The  properties  of  the  toluidines  are  much  like  those  of  aniline. 
o-Toluidine  is  a  liquid  (b.  p.  199.4°) ;  ^-toluidine  a  sohd  (m.  p. 

45°). 

The  xylidines  bear  to  the  three  xylenes  the  same  relation  that 
aniline  bears  to  benzene.  Six  isomers  are  possible  and  all  are 
known. 

Diazo  Compotuids  of  the  Benzene  Hydrocarbons 

DiAZONitJM   Salts 

When  nitrous  acid  acts  on  a  primary  amine  of  the  aliphatic 
or  aromatic  series  nitrogen  is  eliminated  and  hydroxyl  takes 
the  place  of  the  amino  group  :  — 

R.NH2  +  HO.NO  =  R.OH  +  N2  +  H2O. 

In  the  case  of  salts  of  the  aromatic  primary  amines',  intermediate 
products  containing  two  nitrogen  atoms  and  hence  first  called 
diazo  compounds  have  been  obtained.  Thus,  aniline  hydro- 
chloride, nitrate,  and  acid  sulphate  react  with  nitrous  acid,  pro- 
vided the  temperature  of  the  solution  is  kept  in  the  neighbor- 
hood of  0°,  to  form  diazonium  salts  :  — 

CeHsN^    '+         >N       =       CbHsn/       +2H2O; 
\ci         O^  \C1 

Aniline  hydrochloride  Benzenediazonium  chloride 

CbHsn/    '        +         >N=C6H6n/  -f2H20; 

\O.NO2  O^  \O.NO2 

Aniline  nitrate  Benzenediazonium  nitrate 

CeHsN^'  +        >N  =  CeHsN^  +  2  HjO. 

\O.SO2.OH  O^  \o.SO2.OH 

Aniline  add  sulphate  Benzenediazonium  sulphate 


REACTIONS  OF  THE  DIAZONIUM  SALTS  351 

These  salts  are  called  diazonium  salts,  because  they  are  sub- 
stituted ammonium  salts,  as  shown  in  the  above  formulas,  and 
the  process  by  which  they  are  formed  is  called  diazotization. 
This  property  of  forming  diazonium  salts  is  characteristic  of  the 
salts  of  the  aromatic,  primary  amines.  They  are  not  formed  from 
the  aliphatic,  primary  amine  salts,  nor  are  they  formed  from 
the  secondary  or  tertiary,  aromatic  amine  salts  (see  nitroso- 
diphenylamine  (348)  and  nitrosodimeth^daniline  (346)).  The 
diazonium  salts  are  characterized  by  their  instability  (most  of 
them  are  explosive  in  the  dry  state)  and  the  ease  with  which 
they  react  with  various  substances. 

To  prepare  a  solution  of  benzenediazonium  chloride,  aniline 
(one  mol.)  is  dissolved  in  dilute  hydrochloric  acid  (2^  to  3 
mols.)  and  ice  is  added  to  bring  the  temperature  in  the  neighbor- 
hood of  0°.  A  solution  of  the  calculated  amount  of  sodium 
nitrite  is  then  slowly  run  in  from  a  separatory  funnel.  The 
solution  must  be  kept  well  stirred  and  the  temperature  must 
not  be  allowed  to  rise  above  5°.  Owing  to  the  use  of  diazoniurh 
salts  in  the  production  of  azo  dyes  (362),  this  process  of 
diazotization  is  carried  out  on  the  large  scale.  More  than 
1000  tons  of  para-nitroaniline  are  diazotized  annually  for  the 
production  of  the  azo  dye,  paranitroanUine  red  (357). 

To  prepare  the  dry  diazonium  chloride,  aniline  hydrochloride 
is  suspended  in  a  mixture  of  glacial  acetic  acid  and  alcohol,  and 
the  calculated  amount  of  amyl  nitrite  is  then  added  to  the  well 
stirred,  ice-cold  solution.  The  aniline  hydrochloride  quickly 
goes  into  solution  as  the  diazonium  chloride.  When  ether 
is  added  to  the  ice-cold  solution  the  benzene  diazonium  chloride 
crystallizes  out  in  colorless  needles :  — 

C6H5NH3CI  +  CsHii.ONO  =  CsHsNzCl  -I-  H2O  -I-  C5H11OH. 

Amyl  nitrite  Amyl  alcohol 

Reactions  of  the  Diazonium  Salts 

I.  Replacement  of  the  Diazonium  Group  by  Hydroxyl. — When 
the  diazonium  salts  are  heated  with  water,  nitrogen  is  eliminated 
and  hydroxyl  derivatives  of  the  aromatic  hydrocarbons  (phenols) 
are  formed :  — 


352  THE   BENZENE   SERIES   OF  HYDROCARBONS 

C6H6N2SO4H  +  HOH  =  CeHs.OH  +  N2  +  H2SO4. 

Benzenediazooium  Phenol 

sulphate 

This  reaction  is  much  facilitated  by  the  action  of  light. 

In  a  similar  manner  diazonium  salts  obtained  from  the  three 
toluidines  are  converted  into  the  three  hydroxytoluenes 
(cresols) :  — 

H3C.C6H4.N2SO4H  +  HOH  =  H3C.C6H4.OH  +  N2  +  H2SO4. 

0,  m,  f, -Toluene  diazonium  0,  m,  />, -Cresols 

sulphates 

2.  Replacement  of  the  Diazonium  Group  by  Methoxyl  and 
Ethoxyl. — Heated  with  alcohols  the  diazonium  salts  undergo  a 
reaction  similar  to  that  with  water,  yielding  ethers  of  the 
phenols :  — 

CeHsNaCl  +  HOCH3       =     C6H5.OCH3  +  N2  +  HCl. 

Phenylmethylether  (Anisol) 

(o)   C6H5N2CI  +  H.OC2H6     =     C6H6.OC2H5  +  N2  +  HCl. 

Phenylethylether  (Phenetol) 

3.  Replacement  of  the  Diazonium  Group  by  Hydrogen.  —  The 
reaction  with  alcohols  is  usually  accompanied  by  another  one  in 
which  the  hydrocarbon  is  formed  and  the  alcohol  is  converted 
into  aldehyde  by  the  loss  of  two  atoms  of  hydrogen  :  — 

ib)    C6H6N2SO4H  +  H2C2H4O  =  CeHe  +  N2  +  H2SO4  +  C2H4O. 

Alcohol  Aldehyde 

In  case  of  the  benzenediazonium  salts  both  reactions  take  place 
simultaneously,  but  the  first  reaction  (a)  is  the  main  one  and 
only  a  small  amount  of  benzene  is  formed.  If  negative  groups 
are  present  in  the  benzene  ring,  then  the  second  reaction  (b) 
predominates,  e.g.  />-nitrobenzenediazonium  chloride  gives 
mainly  nitrobenzene  and  only  a  small  amount  of  /)-nitro- 
phenetol :  — 

O2N.C6H4.N2CI  +  H2C2H4O  =  C6H6.NO2  +  N2  +  HCl  +  C2H4O. 

^-Nitrobenzene-  Nitrobenzene 

diazonium  chloride 


REACTIONS   OF  THE   DIAZONIUM   SALTS  353 

4.  Replacement  of  the  Diazonium  Group  by  Halogens.  —  The 
diazonium  group  can  be  replaced  by  chlorine  by  treating  an 
aqueous  solution  of  the  diazonium  salt  with  a  solution  of 
cuprous  chloride  or  with  hydrochloric  acid  in  the  presence  of 
copper  powder :  — 

CeHsNzCl  =  CeH^Cl  +  N2. 

Chlorobenzene 

Bromobenzene  is  formed  in  a  similar  manner  by  adding  a 
solution  of  potassium  bromide  to  a  solution  of  the  diazonium 
salt  in  the  presence  of  copper  powder :  — 

C6H5N2SO4H  +  KBr  =  CeHsBr  +  N2  +  KHSO4. 

Bromobenzene 

lodobenzene  is  formed  when  a  solution  of  potassium  iodide 
is  added  to  a  solution  of  the  diazonium  salt :  — 

CeHgNzSOiH  +  KI  =  CeHsI  +  N2  +  KHSO4. 

*  lodobenzene 

In  this  case  the  decomposition  of  the  diazonium  iodide  first 
formed  takes  place  spontaneously,  no  copper  powder  being 
necessary.    This  is  the  best  method  of  preparing  lodobenzene. 

5.  Replacement  of  the  Diazondum  Group  by  Cyanogen  takes 
place  when  a  solution  of  the  diazonium  salt  is  treated  with  a 
solution  of  potassium  cuprous  cyanide :  — 

C6H5N2CI  +  KCN  =  CeHj.CN  +  N2  +  KCl. 

Phenyl  cyanide 

These  reactions  show  the  great  importance  of  the  diazonium 
salts  in  the  preparation  of  numerous  derivatives  of  the  benzene 
hydrocarbons.  By  their  means  it  is  possible  to  replace  the 
amino  group  (and  hence  the  nitro  group,  which  is  converted  into 
the  amino  group  by  reduction)  (i)  by  hydroxyl,  (2)  by  methoxyl 
or  ethoxyl,  (3)  by  hydrogen,  (4)  by  a  halogen  and  (5)  by  cyano- 
gen. As  the  cyanides  yield  acids  when  hydrolyzed  it  is  thus 
possible  to  replace  the  amino  (or  nitro)  group  by  carboxyl. 
The  reactions  of  the  diazonium  salts  have  been  used  very  exten- 
sively, especially  in  investigating  the  position  of  the  groups  in 
the  disubstitution  products  of  benzene. 


354  THE  BENZENE  SERIES   OF  HYDROCARBONS 

Note  for  Sttjdent.  —  How  can  the  position  of  the  groups  in  dinitro- 
benzeue  be  determined  by  means  of  reactions  involving  the  use  of  the 
diazonium  salts? 

The  Constitution  of  the  Diazonium  Salts.  —  The  structure  of  the 
diazonium  salts  is  based  on  the  following  facts :  In  all  the 
reactions  of  the  benzene  diazonium  salts,  compounds  containing 
a  phenyl  group  are  formed,  hence  the  diazonium  group  replaces 
but  one  hydrogen  in  benzene.  The  group  C6H6N2  acts  like 
the  metals  potassium  or  sodium,  or,  better  still,  like  a  substi- 
tuted ammonium  radical.  Thus,  with  mineral  acids  it  forms 
colorless  salts,  having  a  neutral  reaction,  similar  to  potassium  or 
ammonium  chloride.  Solutions  of  diazonium  carbonates,  how- 
ever, have  an  alkaline  reaction  due  to  partial  hydrolysis,  just 
like  the  carbonates  of  the  alkali  metals.  Conductivity  measure- 
ments made  with  solutions  of  the  diazonium  chloride,  sulphate, 
etc.,  show  that  these  salts  are  ionized  to  the  same  extent  as  solu- 
tions of  potassium  or  ammonium  chloride. 

Benzenediazonium  chloride  forms  double  salts  very  much  like 
those  formed  by  ammonium  chloride.  Thus  the  chloride 
forms  a  chloroplatinate,  (C6H5N2)2PtCl6,  and  a  chloroaurate, 
(C6H5N2)AuCli,  just  as  ammonium  chloride  does.  The  free 
base,  benzenediazonium  hydroxide,  C6H5N2OH,  is  known  only 
in  solution.  It  is  a  strong  base  with  an  alkaline  reaction. 
It  is  obtained  by  treating  a  solution  of  the  chloride  with  moist 
silver  oxide  and  filtering  off  the  silver  chloride  formed.  The 
solution  is  colorless  and  resembles  that  of  caustic  potash.  It 
neutralizes  the  strong  acids,  forming  neutral  salts.  On  standing 
it  gradually  undergoes  decomposition  with  the  formation  of 
amorphous,  resinous  substances  even  at  0°. 

DiAZO   AND   ISODIAZO    COMPOUNDS    OP    BeNZENE 

Diazobenzene  potassium  oxide,  CeHsN^N.OK.  —  When  a 
solution  of  benzenediazonium  chloride,  kept  cold  by  means  of 
ice,  is  treated  with  an  excess  of  a  concentrated  solution  of 
caustic  potash,  diazobenzene  potassium  oxide  is  formed  :  — 

C6H5N2CI  +  2  KOH  =  KCl  +  C6H5N=NOK  -f-  H2O. 


DIAZOBENZENE   POTASSIUM   OXIDE  355 

This  salt  is  also  formed  when  nitrosobenzene  is  treated  with 
hydroxylamine  in  the  presence  of  caustic  potash :  — 

CsHsNO  +  H2NOH  +  KOH  =  H20  +  C6H6N=NOK  +  H2O. 

It  crystallizes  in  colorless,  hygroscopic  .needles  and  is  readily 
soluble  in  water  and  alcohol.  It  is  extremely  unstable  and 
changes  on  standing,  partly  into  its  isomer,  and  partly  undergoes 
decomposition.  When  treated  in  the  cold  with  a  strong 
mineral  acid  it  is  at  once  reconverted  into  the  diazonium 
salt :  — 

CeHsN^NOK  +  2  HCl  =  KCl  +  CeHsNC      +  H2O. 

\ci 

With  phenols  (naphthols)  this  salt  reacts  at  once  to  form 
hydroxyazo  compounds  (374) :  — • 

C6H5N=NOH  +  HCeHi.OH  =  CsHsN^NCsHiOH  +  H2O. 

Phenol  Hydroxyazobenzene 

When  the  normal  diazobenzene  potassium  oxide  is  heated 
rapidly  to  130°-!  50°  with  a  concentrated  solution  of  caustic 
potash  it  undergoes  molecular  rearrangement  into  its  stable 
isomer,  isodiazobenzene  potassium  oxide,  C6H5N2OK.  This 
salt  can  also  be  obtained  by  diazotizing  aniline  in  alkaline  solu- 
tion :  — 

C6H5NH2  +  CsHiiONO  +  KOC2H5 

Aniline  Amyl  nitrite  Potassium  ethylate 

=  C6H5N2OK  +  CsHnOH  +  C2H6OH. 

Isodiazobenzene 
potassium  oxide 

It  crystallizes  in  colorless  leaflets,  is  readily  soluble  in  water 
and  is  quite  stable.  Like  its  isomer,  it  is  reconverted  into  the 
diazonium  salts  by  strong  mineral  acids  and  combines  in  the 
same  way  that  the  normal  salts  do,  though  more  slowly,  with 
phenols  (naphthols)  to  give  hydroxyazo  compounds.  Both 
salts  are  reduced  quantitatively  to  phenyUiydrazine  (360) 
by  nascent  hydrogen  and  both  give  benzenediazoic  acid, 
C6H5N=NO.OH,  when  oxidized  with  a  solution  of  potassium 
permanganate. 


3S6  THE   BENZENE   SERIES   OF   HYDROCARBONS 

These  reactions  and  others  indicate  that  the  two  salts  are 
structurally  identical  and  are  stereoisomeric  as  represented  in 
the  formulas :  — 

CeHsN  CeHsN 

II  •  II 

KO.N  N.OK 

Normal  diazobenzene  potassium  oxide  IsodiazobenzeDe  potassium  oxide 

(unstable,  syn  form)  (stable,  anti  fonn) 

By  way  of  explanation  of  these  formulas,  it 
should  be  said  that  they  involve  the  conception 
that  the  nitrogen  atom  exerts  its  aflSnities  in  the 
direction  of  three  edges  of  a  tetrahedron,  thus :  —   -^ 

When  combined  with  another  nitrogen  atom  by  double  union 
the  figures  representing  this  condition  would  be  :  — 

-X 


or 


There  are  two  ways  in  which  the  groups  or  atoms  X  and  Y 
can  be  arranged  in  space,  or  there  should  be  two  stereoisomeric 
forms  of  compounds  containing  a  group  of  two  nitrogen  atoms 
of  the  form  - — N=N —  combined  with  different  radicals.' 

Diazo  and  isodiazo  sulphonates  and  cyanides,  which  are  re- 
garded as  stereoisomeric,  are  also  known,  for  example :  — 

RN  RN  RN  RN 

II       and        II  II       and         II         . 

NaOaSN  N— SOsNa.  NCN  NCN 

Syn  Anti  Syn  Anti 

Paranitrobenzene  diazonium  chloride,  O2N.C6H4.N2CI  is  made 
on  the  large  scale  from  /»;nitroaniline  and  converted  into  the 
stable  sodium  salt  of  the  isodiazo  compound, 

02N.C6H4.N=N.ONa, 

•  See  Stereochemistry,  by  A.  W.  Stewart,  ad  ed.,  1919,  page  146. 


DIAZOAMINO  COMPOUNDS  357 

by  means  of  sodium  hydroxide,  for  use  of  the  dyer  in  dyeing 
cotton  goods  with  p-nitroaniline  red.  The  dyer  converts  this 
salt  into  the  diazonium  salt  by  means  of  hydrochloric  acid, 
using  ice  to  keep  the  solution  cold,  and  combines  this  with 
/3-naphthol  (500)  on  the  cotton  to  produce  the  dyestuff. 

Diazoamino  compounds.  —  When  a  diazonium  salt  is  brought 
in  contact  with  primary  or  secondary  aromatic  amines,  diazo- 
amino compounds  are  formed  :  — 

CeHsNaCl  +  HNH.CsHb  =  C6H5N=N— NHCeHs  +  HCl. 

Diazoaminobenzene 

Diazoaminobenzene  was  first  obtained  by  the  action  of  nitrous 
acid  on  aniline.  In  this  case  it  is  probable  that  diazobenzene 
hydroxide  is  first  formed  and  that  this  then  reacts  with  the 
aniline,  which  must  be  present  in  excess  :  — 

CsHsNHa  +  ONOH  =  C6H5.N=N.OH  +  H2O. 
CfiHjNN.OH  +  HNH.CoHs  =  CeHsN^N.NHCeHj  +  H2O. 

Diazoaminobenzene  crystallizes  in  golden  yellow  plates  that 
melt  at  98°.  It  is  insoluble  in  water,  but  is  readily  soluble  in 
hot  alcohol.  It  is  much  more  stable  than  the  diazonium  salts, 
but  undergoes  decomposition  when  boiled  with  water  giving 
phenol  and  aniline :  — 

C6H5.N=N.NHC6H5  +  H2O  =  CeHs.OH  +  N2  +  C6H6.NH2. 

When  treated  in  the  cold  with  nitrous  acid  in  the  presence  of 
hydrochloric  acid,  diazoaminobenzene  is  completely  converted 
into  benzenediazonium  chloride :  — 

C6H5N2NHC6H5  +  HNO2  +  2  HCl  =  2  CeHsNzCl  +  2  H2O. 

When  diazoaminobenzene,  dissolved  in  aniline,  is  treated  with 
a  small  quantity  of  aniline  hydrochloride  at  the  temperature  of 
the  water  bath,  it  is  converted  into  aminoazobenzene :  — 

CeHs.N^N.NHCeHs  =  C6H6.N=N.C6H4.NH2(/>). 

fr-Aminoazobenzeae 


358  THE   BENZENE   SERIES   OF   HYDROCARBONS 

The  aniline  hydrochloride  acts  catalytically.  This  is  a  very 
important  reaction,  and  is  carried  out  on  the  large  scale,  as 
aminoazobenzene  is  an  important  dyestuff  intermediate. 

Other  Reduction  Products  of  Nitrobenzene. — The  final  reduction 
product  of  nitrobenzene  is  aniline,  but  intermediate  products 
can  be  obtained  by  the  use  of  certain  reducing  agents. 

Nitrosobenzene,  CeHsNO,  is  the  first  product  of  the  reduction 
of  nitrobenzene,  but  it  is  not  possible  to  isolate  it,  though  its 
presence  can  be  proved  by  its  reactions,  especially  that  with 
aniline  (see  below).  It  can  be  made  by  the  action  of  nitrosyl 
chloride  on  mercury  diphenyl  dissolved  in  benzene  :  — 

CeHsHgCeHs  +  2  CINO  =  HgCU  +  2  CeHs.NO, 

or  most  readily  by  the  oxidation  of  j3-phenylhydroxylamine  (see 
below)  by  chromic  acid  :  — 

C6H6N<Qjj  +  O  =  CeHs.NO  +  H2O. 

It  forms  colorless  plates,  melting  at  68°,  and  when  melted  is  a 
green  liquid.  When  treated  with  aniline  in  acetic  acid  solution 
it  gives  azobenzene  (359) :  — 

CeHsNO  +  HjN.CeHs  =  CsHeN^NCeHs  +  H2O. 

Azobenzene 

/3-Phenylhydroxylamiiie,  C6H5.N<        ,  is  formed  when  nitro- 

OH 

benzene  is  reduced  with  zinc  dust  and  water,  especially  in  the 

presence  of  ammonium  chloride  :  — • 

C6H5.N02+H2  =  C6H6.NO+H20;  C6H6.NO+H2=C6H6NHOH. 

^-Phenylhyd^oxyl- 
amine 

If  forms  colorless  crystals  melting  at  81°.  It  undergoes 
molecular  rearrangement  in  the  presence  of  mineral  acids  to 
p-aminophenol :  — 

CeHs.NHOH  — >■  HO.C6H4.NH2(^>. 


AZOBENZENE  359 

It  reduces  Fehling's  solution,  and  this  fact  is  made  use  of  as  a 
test  for  an  aromatic  nitro  compound.  The  supposed  nitro 
compound  is  reduced  with  water  and  zinc  dust  and,  if  a  solution 
is  obtained  that  reduces  Fehling's  solution,  an  aromatic  nitro 
compound  is  present. 

O  O 


Azoxybenzene,  CeHs.N — ^N.CeHs,  or  CeHs.N^N.CeHsjismade 
in  the  laboratory  by  reducing  nitrobenzene  with  a  methyl  alco- 
holic solution  of  sodium  methylate :  — 

4  CeHsNOz+s  NaOCH3  =  2  (C6H6)2N20+3  H.COONa-l-3  H2O. 

Azoxybenzene 

It  crystallizes  in  yellow  needles,  melting  at  36°.  It  under- 
goes molecular  rearrangement  with  concentrated  sulphuric 
acid,  forming  ^-hydroxyazobenzene :  — 

O 

/\ 
CeHs.N— N.CsHs  =  C6H5.N=N.C6H4.0H(/.). 

Azobenzene,  CeHj.N^^N.CeHs,  is  made  in  the  laboratory  by 
heating  azoxybenzene  with  iron  filings :  — 

(C6H6)2.N20  -t-  Fe  =  CeHe.N^N.CeHe+FeO, 

Azobenzene 

or  better  by  oxidizing  hydrazobenzene  (see  below)  in  solution 
by  means  of  air :  — 

CsHb.N— H  CeHs.N 

1  +0=  II  +H2O. 

CeHs.N— H  CeHs.N 

Hydrazobenzene  Azobenzene 

It  has  also  been  made  from  aniline  and  nitrosobenzene  (358), 
which  shows  its  structure.  It  forms  orange-red  crystals 
melting  at  68°,  and  boils  without  decomposition  at  295°.  It  is  a 
very  stable  substance  and  can  be  nitrated  and  sulphonated  in 
the  same  way  as  a  hydrocarbon.  On  reduction  with  ammonium 
sulphide  it  gives  hydrazobenzene.     Azobenzene  can  also  be  very 


360  THE   BENZENE   SERIES   OF   HYDROCARBONS 

readily  made  by  the  electrolytic  reduction  of  nitrobcizene  in 
the  presence  of  sodium  hydroxide.  Amino  and  hydroxy  deriva- 
tives of  azobenzene  such  as 

C6H6.N=N.C6H4.NH2  and  C6H6.N=N.C6H4.0H, 

formed  by  the  action  of  the  diazonium  salts  on  aromatic  amines 
and  phenols,  are  also  well  known.  They  belong  to  the  impor- 
tant class  of  azo  dyes  (362). 

Hydrazobenzene,  CeHj.NH.NH.CeHs,  is  made  in  the  labora- 
tory by  the  reduction  of  azobenzene  with  zinc  dust  and  alkali :  — 

CeHs.N^N.CeHs  -F  H2  =  CeHj.NH— NH.CeHe. 

Pure  hydrazobenzene  crystallizes  from  alcohol  (with  the  addition 
of  some  ammonium  sulphide)  in  colorless  leaflets,  melting  at 
126°.  Mineral  acids  convert  it  quantitatively  into  benzidine 
(490) :  — 

CeHs.NHNH.CeHs  — >■  H2N.C6H4.C6H4.NH2. 

Hydrazobenzene  Benzidine 

It  is  made  on  the  large  scale  by  the  reduction  of  nitrobenzene 
with  iron  filings  and  a  solution  of  caustic  soda,  and  converted 
into  benzidine  (a  very  important  dyestuff  intermediate)  by 
the  action  of  mineral  acids. 


Aromatic  Hydrazines 

Phenylhydrazine,  C6H5.NH.NH2,  is  the  simplest  aromatic 
derivative  of  hydrazine,  H2N.NH2.  Hydrazobenzene  may  be 
regarded  as  symmetrical  diphenylhydrazine,  though  it  is  never 
called  by  this  name,  as  it  has  no  basic  properties.  Phenyl- 
hydrazine  is  made  by  the  reduction  of  benzenediazonium 
chloride,  with  the  calculated  amount  of  stannous  chloride,  in 
hydrochloric  acid ;  — 

H 
CeHs.NjCl  -h  2  H2  =  CsHs.N— NH2HCI. 

Benzenediazonium  chloride  Phenylhydrazine  hydrochloride 


METHYLPHENYLHYDRAZINE  361 

On  the  large  scale  it  is  made  by  reducing  sodium  diazo- 
benzenesulphonate  with  zinc  dust  and  hydrochloric  acid :  — 

CeHsNjCl  +  NaSOaNa  =  C6H5.N=N.S03Na  +  NaCl; 

Sodium  diazobenzenesulphonate 

C6H6N=N.S03Na  +  H2  =  CeHs-NH— NH.SOsNa. 

Sodium  phenylhydrazinesulphonate 

The  sodium  phenylhydrazinesulphonate  is  then  decomposed 
by  fuming  hydrochloric  acid,  in  which  phenylhydrazine  hydro- 
chloride is  insoluble :  — 

CeHs.NH.NH.SOsNa  +  HCl  +  H2O 

=  C6H5.NH.NH2HCI  +  NaHSOi. 

Phenylhydrazine  hydrocUoride 

The  base  is  obtained  from  the  hydrochloride  by  decomposition 
with  caustic  soda  and  is  purified  by  distillation  in  a  vacuum  :  — 

CeHj.NH.NHjHCl  +  NaOH  =  CeHj.NH.NHj  +  NaCl  +  H2O. 

Phenylhydrazine 

Phenylhydrazine,  when  perfectly  pure,  is  a  colorless  oil  that 
quickly  turns  brown  in  the  air.  It  solidifies  when  cooled  and 
the  crystals  melt  at  23°.  It  boils  at  24i"-242°  with  some 
decomposition.  It  is  volatile  with  steam,  only  slightly  soluble 
in  water,  but  miscible  with  alcohol,  ether  and  benzene.  Re- 
ducing agents  convert  it  into  aniline  and  ammonia  (214). 
Phenylhydrazine  is  an  exceedingly  valuable  reagent  for  alde- 
hydes and  ketones,  with  which  it  combines  to  form  phenyl- 
hydrazones  (106).  It  combines  with  aldoses  and  ketoses  to 
form  phenyUiydrazones  and  osazones  (223,  229).  Phenyl- 
hydrazine  is  Used  as  a  reagent  in  the  laboratory,  and  in  the 
manufacture  of  antipyrine  and  of  dyestuffs. 

Methylphenylhydrazine,  C6H6N(CH3)NH2,  is  made  from 
monomethylaniline  by  treating  it  with  nitrous  acid  and  then 
reducing  the  nitrosomethylaniline  formed  :  — 

This  hydrazine  forms  osazones  with  ketoses  and  also  with 
aldoses,  though  more  slowly. 


362  THE  BENZENE  SERIES  OF  HYDROCARBONS 

Azo  Dyes 

The  amino  and  hydroxy  derivatives  of  azobenzene  are  known 
as  azo  dyes.  They  are  of  great  technical  importance  and  are 
used  in  large  quantities  in  the  dyeing  of  silk,  wool,  and  cotton. 

Azobenzene  is  a  highly  colored  substance,  but  it  is  not  a  dye. 
To  be  a  dye  a  substance  must  not  only  be  colored,  but  the  color 
that  it  imparts  to  the  fabric  must  be  fast  to  washing  and  to 
soap.  A  gr9up  like  the  azo  group,  — N=N — ,  which  gives  color 
to  a  compound,  is  known  as  a  chromophor,  while  the  compound 
containing  the  chromophor  is  called  a  chromogen.  Thus  azo- 
benzene is  a  chromogen.  By  introducing  a  salt-forming  group, 
known  as  an  auxochrome  group,  such  as  the  NH2-group,  into  a 
chromogen  a  dye  is  obtained,  e.g.,  aminoazobenzene  is  a  dye. 

Aminoazobenzene,  C6H5.N^N.C6H4NH2(^),  is  the  simplest 
of  all  the  basic  azo  dyes.  It  is  made  on  the  large  scale  from  diazo- 
aminobenzene  by  molecular  rearrangement  (357).  It  has  been 
made  by  nitrating  azobenzene  and  reducing  the  nitroazobenzene 
formed,  which  shows  its  structure. 

Its  hydrochloride,  which  crystallizes  in  steel-blue  needles,  was 
used  at  one  time  as  a  dye  under  the  name,  aniline  yellow.  Amino- 
azobenzene crystallizes  in  orange-yellow  needles  which  melt  at 
127.4°,  and  are  insoluble  in  water,  but  soluble  in  alcohol.  The 
hydrochloric  acid  salt  can  be  diazotized  and  again  combined 
with  an  amine  to  give  disazo  dyes,  containing  two  azo  groups  :  — 

C6H6.N2.C6H4.N2CI  +  H.C6H4.N(CH3)2 

=   C6H6.N2.C6H4.N2.C6H4.N(CH3)2  +  HCl. 
Disazo  dye 

When  reduced  with  nascent  hydrogen  aminoazobenzene  gives 
aniline  and  />-phenylenediamine :  — 

C9H5.N:N.C6H4.NH2  -|-  2  H2  =  C6H6.NH2  +  H2N.C6H4.NH2. 

This  method  of  making  amino  compounds,  reduction  of  the 
basic  azo  dyes,  is  used  on  the  large  scale  to  make  ^-phenylene- 
diamine  and  other  amino  compounds.  All  azo  compounds  re- 
act in  a  similar  manner  with  nascent  hydrogen ;  the  hydrogen 
always  joins   the   doubly  bound  nitrogen  atoms.     From  the 


DIMETHYLAMINOAZOBENZENE  363 

amino  compounds  formed  by  reduction  the  structure  of  the 
azo  dye  is  determined.  Thus,  aminoazobenzene  gives  aniHne 
and  ^-phenylenediamine.  It  must  therefore  be  an  azo  com- 
pound with  the  groups  in  the  para  position  with  regard  to  each 
other,  and  it  can  be  made  from  benzenediazonium  salts  and 
aniHne.  Aminoazobenzene,  under  the  name  of  Spirit.  Yellow, 
is  used  in  coloring  alcoholic  lacquers  and  also  for  coloring' 
fats  and  cheese,  as  it  is  not  poisonous  and  is  soluble  in  these 
substances.  It  is  used  chiefly,  however,  in  the  manufacture  of 
other  dyestuifs  (Acid  yellow,  Cloth  red,  Induline,  etc.). 

Dimethylaminoazobenzene,  C6H5.N^N.C6H4.N(CH3)2.  — 
When  a  diazonium  salt  is  treated  with  dimethylaniline,  dimethyl- 
aminoazobenzene is  at  once  formed,  since  in  this  case  the  forma- 
tion of  a  diazoamino  compound  is  not  possible :  — 

C6H5.N2CI  -I-  H.C6H4.N(CH3)2  =  C6H6.N:N.C6H4.N(CH3)2HC1. 

As  the  azo  compound  here  formed  is  a  base,  it  combines  with 
the  acid  set  free  to  form  a  salt.  The  presence  of  free  mineral 
acid  usually  prevents  the  formation  of  the  azo  dyes,  so  that  the 
"  coupliiig,"  as  it  is  called,  of  a  diazonium  salt  with  an  amine  or 
a  phenol  is  frequently  brought  about  in  alkaline  solution,  or 
sodium  carbonate  or  acetate  is  added  to  get  rid  of  the  mineral 
acid  set  free  in  the  reaction.  When  reduced  with  nascent  hydro- 
gen, dimethylaminoazobenzene  gives  aniline  and  p-amino- 
dimethylaniline  (the  dimethyl  derivative  of  /j-phenylene- 
diamine) :  — 

C6H5N:NC6H4.N(CH3)2  +  2  H2  =  CeHsNHj  +  H2NC6H4N(CH3)2. 

The  main  product  of  the  action  of  a  diazonium  salt  on  an 
amine  is  always  the  para  product.  A  small  amount  of  the  ortho 
product  is  also  formed.  The  reduction  of  ^-dimethylamino- 
azobenzene forms  a  convenient  method  of  making  ^-amino- 
ditaethylaniline  and  is  used  on  the  large  scale,  as  this  base  is  an 
important  dyestufi  intermediate.  The  same  compound  is 
formed  by  the  reduction  of  /j-nitrosodimethylanUine  (356) :  — 

ON.C6H4.N(CH3)2  +  2  H2  =  H2N.C6H4.N(CH3)2(^)  +  H2O. 


364  THE  BENZENE   SERIES   OF  HYDROCARBONS 

Dimethylaminoazobenzene  crystallizes  in  yellow  leaflets, 
melting  at  117".  Under  the  name,  Butter  Yellow,  it  is  used 
to  color  butter  and  oleomargarine,  as  it  is  soluble  in  fats  and  is 
not  poisonous.     It  is  also  used  as  an  indicator. 

Chrysoiidine. — When  a  benzenediazonium  salt  is  treated 
with  metaphenylenediamine  (345),  2,4-diaminoazobenzene  is 
formed :  — 

C6H6.N2CI  +  HC6H3.(NH2)2  =  C6H6.N:N.C6H4.(NH2)2HC1. 

This  hydrochloride,  C6H6.N:N.C6H4.(NH2)2.HC1,  is  known  as 
Chrysoidine.  It  dyes  wool  and  silk  an  orange-red  color,  and 
cotton  mordanted  with  tannin  an  orange  color.  It  is  also  used 
to  color  jute,  leather,  andfats. 

Bismarck  brown  is  one  of  the  oldest  azo  dyes,  having  been 
discovered  in  1863  and  manufactured  technically  in  1866.  It 
is  made  by  the  action  of  nitrous  acid  on  a  salt  of  w-phenyl- 
enediamine  and  is  a  mixture  of  at  least  two  substances,  the 
simplest  of  which  is  triaminoazobenzene.  This  is  obtained 
when  only  one  amino  group  undergoes  diazotization,  and  the 
diazonium  salt  thus  formed  is  coupled  with  a  second  molecule  of 
the  base : — 

H2NC6H4N2CI     +     C6H4(NH2)2 

=  H2NC6H4N:NC6H3(NH2)2HC1. 

Triaminoazobenzene  bydiochloride 

By  far  the  larger  part  of  Bismarck  brown  consists  of  the 
disazo  dye  made  by  diazotizing  both  amino  groups  and  combin- 
ing the  bi-diazonium  salt  thus  formed  with  two  molecules  of 
w-phenylenediamine :  — 

N.C1+C.<™;  ^  N.N.CKI'^,, 

Bismarck  brown 

The  hydrochloride  crystallizes  in  reddish  brown  plates  and 
is  readily  soluble  m  water.  It  dyes  wool  and  tannmed  cotton 
a  red-brown  shade. 


BENZENESULPHONIC   ACID  365 

On  reduction  with  nascent  hydrogen  Bismarck  brown  gives 
w-phenylenediamine  and  1,2,4-triaminobenzene,  and  this  is  the 
best  method  of  preparing  the  latter  compound. 

Aromatic  Sulphonic  Acids 

The  aromatic  hydrocarbons  and  their  derivatives  differ 
markedly  from  those  of  the  paraffin  series  in  that  they  react 
readily  with  sulphuric  acid  to  form  sulphonic  acids  :  — 

CbHsH  +  HO.SO2.OH       =  CeHs.SOj.OH  +  H2O ; 

Benzenesulphonic  acid 

SO2.OH  SO2.OH 

C6H4<jj  ^  HO.SO2.OH  =  ^'^<S02.0H  +  ^'^' 

Benzenedisul phonic  acids 

CeH4<jj  I  HO.SO2.OH  =  '^»^<S02'0H  +  ^'-°- 

Toluenesulphonic  acids 

This  process  of  forming  a  sulphonic  acid  by  direct  treatment 
of  the  hydrocarbon  or  its  derivatives  with  concentrated  or  fuming 
sulphuric  acid  is  called  sulphonation.  The  two  processes  of 
sulphonation  and  nitration  are  of  very  great  importance  in  the 
aromatic  series  and  are  more  largely  made  use  of  than  any  others 
in  preparing  derivatives  of  these  hydrocarbons.  A  large  number 
of  coal  tar  dyes  are  sodium  salts  of  aromatic  sulphonic  acids. 

The  aromatic  sulphonic  acids  have  also  been  made  by  the 
oxidation  of  the  mercaptans  :  — 

CsHs.SH  +  30  =  CeHs.SOz.OH. 

Phenylmercaptan  Benzenesulphonic  acid 

The  bearing  of  this  method  of  formation  on  the  question  of  the 
consitution  of  the  sulphonic  acids  has  already  been  discussed 

(81). 

Benzenesulphonic  acid,  CeHe.SOjOH,  is  made  on  the  large 
scale  by  the  action  of  concentrated  sulphuric  acid  (98  per  cent) 
on  benzene,  and  in  the  laboratory  by  the  action  of  fuming  sul- 
phuric acid  on  the  hydrocarbon.  The  reaction  takes  place  very 
readily  and  without  the  aid  of  heat,  provided  that  the  benzene 
and  the  sulphuric  acid  are  thoroughly  mixed. 


366  THE   BENZENE   SERIES   OF  HYDROCARBONS 

As  in  the  case  of  the  formation  of  the  aromatic  nitro  com- 
pounds it  is  probable  that  an  addition  product  of  the  hydro- 
carbon and  the  acid  is  first  formed  and  that  this  then  loses 
water  to  form  the  sulphonic  acid  (313).  An  excess  of  sul- 
phuric acid  must  be  used  to  combine  with  the  water  formed 
in  the  reaction  and  thus  prevent  the  dilution  of  the  sulphuric 
acid.  When  fuming  sulphuric  acid  is  used  the  Jree  sulphur 
trioxide  combines  with  the  water  to  form  sulphuric  acid.  Di- 
pkenylsulphone  is  always  formed  as  a  by-product,  in  the  lat- 
ter case,  owing  to  the  action  of  some  of  the  sulphur  trioxide 
on  the  benzene : — 

2    CbHbH    +   OSO2    =    (C6H5)2S02  +  H2O. 
Diphenylsulphone 

The  benzenesulphonic  acid  is  separated  from  the  excess  of 
sulphuric  acid  by  diluting  the  mixture  with  water  and  adding 
lime.  The  excess  of  lime  and  the  calcium  sulphate  are  removed 
by  filtration,  and  the  soluble  calcium  salt  is  converted  into  the 
sodium  salt  by  treatment  with  a  solution  of  sodium  carbonate. 
A  more  modern  method  of  separating  the  two  acids  makes  use  of 
the  fact  that  benzenesulphonic  acid  is  soluble  in  benzene,  while 
sulphuric  acid  is  not.  This  process  is  much  more  economical 
than  the  "  Hmeing  out  "  process,  as  the  excess  of  sulphuric  acid 
is  recovered  and  may  be  used  over  again  by  adding  the  right 
amount  of  fuming  sulphuric  acid  to  bring  it  up  to  the  proper 
strength  (98  per  cent),  whereas  in  the  other  process  the  excess 
of  sulphuric  acid  is  converted  into  the  useless  calcium  sulphate. 
The  benzenesulphonic  acid  is  separated  from  the  benzene  by 
treatment  with  water,  in  which  it  is  very  soluble,  and  the  ben- 
zene, after  drying,  is  used  over  again.  The  sulphonic  acid  is 
then  converted  into  the  sodium  salt  by  the  action  of  sodium 
carbonate.  In  the  laboratory  the  sodium  benzenesulphonate 
is  "  salted  out  "  by  adding  the  mixture  of  concentrated  sulphuric 
acid  and  benzenesulphonic  acid  to  a  solution  of  common  salt. 

Benzenesulphonic  acid  crystallizes  from  water  in  plates  con- 
taining i^  molecules  of  water  of  crystallization.  It  is  extremely 
soluble  in  water  and  in  alcohol  and  is  a  very  strong  acid.     It 


BENZENESULPHONIC   ACID  367 

forms  salts  with  metals,  all  of  which  are  soluble  in  water.  It  is 
not  hydrolyzed  by  boiling  its  solution  with  strong  alkalies  or  by 
mineral  acids.  It  is,  however,  decomposed  into  benzene  and 
sulphuric  acid  by  distilling  in  superheated  steam  in  the  pres- 
ence of  sulphuric  acid  :  — 

C6H5SO2.OH  +  HOH  =  CeHe  +  H2SO1. 

When  the  sodium  salt  of  benzenesulphonic  acid  is  fused  with 
sodium  hydroxide  it  is  converted  into  the  sodium  salt  of 
phenol :  — 

CeHs.SOj.ONa  +  2  NaOH  =  CeHj.ONa  +  NazSOa  +  H2O. 

The  phenol  (372)  is  set  free  from  its  sodium  salt  by  treating 
the  solution  with  carbon  dioxide.  This  method  is  used  on  the 
large  scale  in  the  synthetical  production  of  phenol.  It  is  the 
most  important  method  of  introducing  the  hydroxyl  group  into 
the  aromatic  hydrocarbons  and  their  derivatives. 

When  sodium  benzenesulphonate  is  fused  with  sodium 
cyanide,  phenyl  cyanide  distils  over :  — 

CeHj.SOa.ONa  +  NaCN  =  CsHs.CN  +  NazSOs. 

Phenyl  cyanide 

Like  the  cyanides  of  the  parafiin  series,  phenyl  cyanide  is 
hydrolyzed  by  boiHng  with  dilute  mineral  acids  or  solutions 
of  the  alkalies  to  the  corresponding  acid  or  its  salts  :  — 

CeHs.CN  +  2  H2O  =  CeHs.COOH  +  NH3. 

Phenyl  cyanide  Benzoic  acid 

It  is  thus  possible  to  convert  a  sulphonic  acid  into  a  carboxylic 
acid,  or  to  introduce  a  carboxyl  group  into  an  aromatic  hydro- 
carbon or  its  derivatives.  This  transformation  can  sometimes 
be  accomplished  directly,  e.g.,  by  fusing  sodium  benzenesulpho- 
nate with  sodium  formate  :  — 

CeHs.SOa.ONa  +  H.COONa  =  CsHs.COONa  +  NaHSOj. 

The  chloride  of  benzenesulphonic  acid,  C6HB.SO2CI,  is  ob- 
tained by  treating  sodium  benzenesulphonate  with  phosphorus 
pentachloride :  — 


368  THE  BENZENE  SERIES  OF  HYDROCARBONS 

CeHs.SOjONa  +  PCI5  =  CeHs-SOjCl  +  NaCl  +  OPCI3. 

Benzenesulphonyl  chloride 

The  sulphonyl  chlorides  can  also  be  obtained  by  sulphonat- 
ing  the  aromatic  hydrocarbons  with  chlorosulphonic  acid  :  — 

CbHbH  +  HOSO2CI  =  C6H6.SO2CI  +  H2O. 

In  the  case  of  toluene  this  method  is  used  on  the  large  scale 
to  make  the  toluenesulphonyl  chlorides  (see  Saccharin,  412). 
These  chlorides  of  the  sulphonic  acids  are  usually  oily  liquids 
or  are  low  melting  solids,  having  a  disagreeable  odor,  and  are 
insoluble  in  water.  When  boiled  with  water,  however,  they  are 
converted  into  the  acids  :  — 

CeHs.SOaCl  +  HOH  =  CsHs.SOa.OH  +  HCl; 

and  when  boiled  with  alcohols  into  the  esters  of  the  sulphonic 
acids :  — 

CeHs.SOzCl  +  H.OC2H6  =  C6H5.SO2.OC2H5  +  HCl . 

Ethyl  benzenesulphonate 

With  a  strong  solution  of  ammonia  they  give  the  sulphon- 
amides :  — 

C6H5.SO2CI  +  H.NH2  =  C6H5.SO2NH2  +  HCl. 

Benzenesiilphonamide 

Owing  to  the  strong  acidifying  influence  of  the  sulphon  group, 
SO2,  the  sulphonamides  have  acid  properties,  the  hydrogen 
atoms  of  theNH2  group  being  replaceable  by  metals,  hence  they 
dissolve  in  solutions  of  the  alkalies.  They  are  well  crystallized 
solids  with  sharp  melting  points,  and  are  frequently  used  to 
identify  the  sulphonic  acids. 

Benzenedisulphonic  acids,  C6H4(S02.0H)2,  (m)  and  (p),  re- 
sult from  the  more  energetic  sulphonation  of  benzene  by  heating 
with  fuming  sulphuric  acid.  They  undergo  the  same  trans- 
formations as  the  monosulphonic  acid. 

Note  foe  Student.  —  By  what  reactions  could  the  three  benzene- 
disulphonic acids  be  converted  into  the  three  dicarboxylic  acids  (phthalic 
acids)  ?  Suppose  that  the  disulphonic  acid  obtained  in  larger  quantity 
by  sulphonating  benzene  gave  metaphthalic  acid ;  what  conclusion 
could  be  drawn  with  reference  to  the  position  of  the  two  groups  in  i.his 
disulphonic  acid? 


SULPHANILIC   ACID  369 

Benzenedisulphonic  acid  is  made  on  the  large  scale,  and  con- 
verted into  resorcinol  (385)  by  fusing  its  sodium  salt  with  sodium 
hj'droxide. 

CH 
Toluenesulphonic  acids,  C6H4 <„_,'„,     are    very     readily 

SO2OH 

formed  by  sulphonating  toluene.     At  0°,  the  average  yield  is 

53.5  per  cent  para,  3.8  per  cent  meta-,  and  42.7  per  cent  of  the 

ortho  acid,  while  at  100°  the  percentages  are  72.5,  10. i  and  17.4, 

respectively.     When  these  acids  are  oxidized  they  are  converted 

into  the  corresponding  sulphobenzoic  acids  (411). 

Nitrobenzenesulphonic  acids,  O2N.C6H4.SO2OH,  are  obtained 
by  nitrating  benzenesulphonic  acid  or  by  sulphonating  nitro- 
benzene. In  both  cases  the  meta  acid  is  the  main  product. 
Reduction  converts  these  acids  into  aminobenzenesulphonic 
acids,  H2NC6H4SO2OH. 

Metanilic  acid,  H2N.C6H4.S03H(m),  obtained  in  this  way,  is 
used  in  the  preparation  of  azo  dyes,  e.g.,  Metanil  yellow  (371). 

Sulphanilic  acid,  /)-aminobenzenesulphomc  acid, 
H2N.C6H4.SO2OH6'), 
is  the  most  important  of  the  three  sulphonic  acids  derived  from 
aniline.  It  is  always  made  from  aniline  acid  sulphate  by  the 
"  baking  "  process,  which  consists  in  baking  the  acid  sulphate 
in  an  oven  at  2oo°-2io°  from- 4  to  6  hours,  until  a  test  portion 
when  dissolved  in  water  gives  no  precipitate  (aniline)  when  made 
alkaline.  The  different  steps  in  the  process  are  indicated 
below :  — 

H2N.H2SO4  HNSO3H  NH2  NH2 

/\  /\  /XSOzOH 


H2O 


SO2OH 

Aniline  acid  sulphate    Phenylsulphonamic  acid    d-Sulpbanilic  acid         Sulphanilic  acid 

It  crystallizes  in  the  monoclinic  system  with  two  molecules 
of  water  and  is  difficultly  soluble  in  cold  water,  more  readily  in 
hot.  It  is  a  strong  acid,  decomposing  carbonates  and  forming 
salts  with  a  neutral  reaction,  such  as  sodium  sulphanilate, 
H2N.C6H4.S020Na  -|-  2  H2O.    It  does  not  form  salts  with  acids. 


370  THE  BENZENE   SERIES   OF  HYDROCARBONS 

When  fused  with  caustic  soda,  sulphaniHc  acid  gives  aniline 
and  not  ^-aminophenol  as  might  have  been  expected  :  — 

H2N.C6H4.S03Na  +  NaOH  =  CeHs.NHj  +  NajSOi. 

Aniline 

Note  foe  Student.  —  Compare  this  reaction  with  the  one  used  in 
making  marsh  gas  from  sodium  acetate  and  soda-lime. 

SulphaniHc  acid  also  reacts  with  bromine  water  in  an  unusual 
manner,  forming  2,4,6-tribromaniline  :  — 

H2NC6H4SO3H+6  Br+HzO    =   HzNCeHzBrs+HaSOi+a  HBr. 

The  sulphonic  acid  group  is  replaced  by  bromine.  By  deter- 
mining the  amount  of  sulphuric  acid  formed  in  this  reaction 
sulphanilic  acid  may  be  estimated  quantitatively. 

Sulphanilic  acid  like  taurine  (254)  is  an  inner  ammonium 
salt.  This  is  shown  by  the  fact  that  it  is  diazotized  directly 
by  nitrous  acid  to  henzenediazonium  sulphonate:  — 

N^Hs  ]SEN 

C6H4/N0  +  HONO  =  C6H4<Q>0  +  2  H2O, 
SO2  SO2 

which  crystallizes  in  colorless  needles,  sparingly  soluble  in 
water  and  shows  all  the  reactions  of  the  diazonium  salts.  It 
is  used  in  the  manufacture  of  azo  dyes  (see  below). 

Note  foe  Student.  —  What  does  henzenediazonium  sulphonate  give 
when  boiled  (i)  with  water,  (2)  with  alcohol,  (3)  with  a  solution  of 
potassium  iodide  and  (4)  with  a  solution  of  potassium  cuprous  cyanide  ? 

Sulphanilic  acid  is  a  very  important  dyestuff  intermediate 
and  is  frequently  used  in  synthetical  work.  Nearly  two  mil- 
lion pounds  were  made  in  the  United  States  in  1920. 

Helianthine,  ^-dimethylaminoazobenzene-/»-siilphoiiic  acid, 
is  formed  by  the  action  of  henzenediazonium  sulphonate  on 
dimethylaniline :  — 

JX  /N=N.C6H4N(CH3)2(^) 

C6H4<     >0+HC6H4.N(CH3)2=  C6H4< 

^  \S020H(/,) 


DERIVATI\ES   OF   BENZENE   HYDROCARBONS         371 

As  helianthine  contains  a  basic  and  an  acid  group  within  the 
same  molecule  they  are  probably  combined  in  the  form  of  an 
inner  ammonium  salt,  as  shown  in  the  formula, 

/N=N.C6H4 

C6H4<  I 

\S02.0.NH(CH3)2 

Dimethylaminoazobenzene  sulphonate 

The  sodium  salt  of  helianthine  is  known  as  methyl  orange. 
It  is  not  used  as  a  dye,  as  it  is  too  sensitive  to  alkalies,  but  is 
frequently  used  as  an  indicator  in  acidimetry  and  alkalimetry. 
It  is  not  sensitive  to  carbonic  acid,  but  gives  a  color  with  the 
weakest  alkalies,  which  is  turned  red  by  mineral  acids. 

Diphenylamine  orange,  orange  IV,  tropaeolin  OO,  is  another 
example  of  a  soluble  azo  dye.  It  is  made  by  the  action  of 
benzenediazonium  sulphonate  on  diphenylamine  in  the  pres- 
ence of  an  alkali :  — 

CeHi/No  +  HC6H4.NHC6H6  +  NaOH 


SO2 

/N=N.C6H4.NHC6H5 

=   C6H4<  +  H2O. 

\S020Na(4) 

Diphenylamine  orange 

It  dyes  wool  and  silk  an  orange  color  and  is  used  as  an  indicator. 
Metanil  yellow  is  made  in  the  same  way  from  metanilic  acid 
by  diazotizing  it  and  combining  the  diazonium  compoimd  with 
diphenylamine  in  the  presence  of  an  alkali.  It  has  the  same 
formula  as  diphenylamine  orange,  only  the  azo  and  sulphonic 
acid  groups  are  in  the  meta  position  with  reference  to  each 
other. 

Phenols  or  Hydeoxyl  Derivatives  of  the  Aromatic 
Hydrocarbons 

Derivatives  of  the  aromatic  hydrocarbons  in  which  the 
hydrogen  of  the  benzene  nucleus  is  replaced  by  hydroxyl  are 
called  phenols,  after  the  first  and  simplest  member  of  the  series, 
phenol,  or  hydroxybenzene. 


372  THE  BENZENE   SERIES   OF  HYDROCARBONS 

COH 


It  will  be  seen  from  this  formula  for  phenol  that  it  contains  the 
tertiary  alcohol  group,  =C — OH(135),  and  it  acts  like  an 
alcohol  to  some  extent.  In  its  conduct  towards  oxidizing 
agents  phenol  acts  like  the  tertiary  alcohols,  as  it  gives  neither 
aldehydes  nor  ketones,  but  breaks  down  at  once  to  acids  con- 
taining a  smaller  number  of  carbon  atoms.  The  phenols  are, 
however,  more  acid  than  the  alcohols  and  dissolve  readily  in 
solutions  of  the  caustic  alkalies,  forming  phenolates,  such  as 
sodium  phenolate,  CeHs.ONa.  They  are  designated  as  monacid, 
diacid,  or  triacid  phenols  according  to  the  number  of  hydroxyl 
groups  they  contain. 

Monacid  Phenols 

Phenol,  carbolic  acid,  CeHs.OH,  occurs  normally  in  small 
amounts  in  the  urine  of  men  and  other  animals.  It  is  also  found 
in  the  distillation  products  of  wood,  coal  and  bones  and  is 
obtained  from  coal  tar.  Together  with  the  cresols  (hydroxy- 
toluenes)  and  xylenols  (hydroxyxylenes)  it  is  isolated  from  the 
acid  oU  (306)  by  agitation  with  a  lo  per  cent  solution  of  caustic 
soda.  The  phenols  are  precipitated  from  this  solution  by  carbon 
dioxide,  and  phenol  is  separated  by  fractional  distillation  from 
the  cresols  and  xylenols. 

Phenol  can  also  be  made  synthetically  from  benzene  by  the 
steps  indicated  below :  — 

CeHe  — ^  CsHsNOj  ^  CeHjNHj  —^  CeHsNHjCl 

Benzene  Nitrobenzene  Aniline  Aniline  salt 

^  C6H5N2CI  -^-  C6H5OH  ; 

Diazotuum  salt  Phenol 

or  by  fusing  sodium  benzenesulphonate  with  caustic  soda 
(367) : — 

CsHe  — >-  CeHsSOsH  -^  CsHsSOsNa  — >-  CeHsOH. 

Benzene       Benzenesulphonic  acid    Sodium  benzenesulphonate  Phenol 


MONACID    PHENOLS  373 

During  the  World  War  large  quantities  of  phenol  were  made 
by  the  latter  method.  Phenol  also  results  from  the  three 
hydroxy-benzoic  acids  by  distilling  them  with  lime  (314) :  — 

HOC6H4COOH(o)(w)(^)  =  CeHsOH  +  CO2, 

Hydroxybenzoic  acids  Phenol 

and  it  has  been  made  in  small  quantity  by  the  direct  oxidation 
of  benzene  with  hydrogen  peroxide  in   the  presence  of  iron 

salts : — 

CeHe  +  0  =  CeHsOH. 

Benzene  is  oxidized  to  phenol  in  the  animal  organism. 

Phenol,  when  pure,  crystallizes  in  colorless,  orthorhombic 
needles  which  melt  at  40.8°  and  it  boils  at  181.6°.  In  the 
presence  of  light  and  air  the  crystals  soon  turn  red,  due  to  oxida- 
tion. Phenol  has  a  characteristic,  penetrating  odor  and  is 
hygroscopic.  A  small  amount  of  water  lowers  the  melting  point 
of  phenol,  so  that  the  mixture  is  liquid  at  ordinary  temperatures. 
8.2  parts  of  phenol  dissolve  at  15°  in  100  parts  of  water  and  100 
parts  of  phenol  at  15°  dissolve  37.4  parts  of  water.  At  84° 
phenol  is  miscible  with  water  in  all  proportions.  It  mixes  in 
all  proportions  with  alcohol,  ether,  and  benzene  and  is  poisonous. 
Saccharate  of  lime  or  sodium  sulphite  is  used  as  an  antidote  in 
cases  of  poisoning  with  phenol.  Phenol  is  a  valuable  disin- 
fectant and  antiseptic,  though  its  use  for  this  purpose  is  di- 
minishing, as  OT-cresol  has  been  found  to  have  greater  disin- 
fecting power  and  to  be  less  poisonous.  Phenol  is  a  weak  acid 
having  about  the  same  strength  as  hydrocyanic  acid.  It  is 
set  free  from  its  solution  in  ammonia  or  the  alkahes  by  carbon 
dioxide  and  hence  is  not  soluble  in  solutions  of  the  alkaline 
carbonates.  Towards  methyl  orange  and  phenolphthalein 
phenol  acts  like  a  neutral  substance,  but  it  acts  as  a  monobasic 
acid  towards  Poirrier*s  blue.  When  reduced  with  hydrogen  at 
160°  in  the  presence  of  nickel  as  a  catalyst,  phenol  is  quanti- 
tatively reduced  to  cyclohexanol,  CeHnOH,  a  secondary  alcohol, 
boiling  at  161°,  and  melting  at  i6°-i7°.  When  platinum  black 
is  used  as  a  catalyst  cyclohexane  is  formed.     When  cyclohexanol 


374  THE   BENZENE   SERIES   OF  HYDROCARBONS 

is  oxidized  it  gives  cyclohexanone,  CeHioO,  a  ketone,  thus  show- 
ing that  it  is  a  secondary  alcohol.  (Write  the  equations  in- 
volved in  all  these  transformations.) 

Most  of  the  phenol  is  used  in  the  manufacture  of  picric  acid 
(378),  sahcylic  acid  1,420),  dyes  and  synthetic  remedies.  Large 
quantities  are  now  used  in  making  synthetic  resins  (for  phono- 
graph records,  bakehte,  etc.)  by  combining  phenol  with  formal- 
dehyde. Synthetic  tanning  materials  are  also  now  made  from 
phenol,  formaldehyde,  and  sulphuric  acid  or  sulphites.  Tri- 
phenyl  phosphate  is  now  made  on  the  large  scale  from  phenol 
and  used  as  a  substitute  for  camphor  in  the  manufacture  of 
pyroxyline  plastics  (376) . 

Like  aniline  phenol  is  extremely  susceptible  to  the  action  of 
reagents.  The  hydrogen  of  the  hydroxyl  group  is  first  replaced 
by  the  substituting  group  or  element,  which  then  enters  the 
benzene  ring,  hydrogen  taking  its  place.  Thus,  a  solution  of 
phenol  in  water  gives  a  precipitate  of  tribromophenol  bromide, 
C6H3Br3.0Br,2,4,6,  when  treated  with  bromine  water,  and 
dilute  nitric  acid  converts  it  into  ortho-  and  paranitrophenol. 
The  best  test  for  phenol  (in  the  absence  of  cresols)  is  the  pre- 
cipitate it  gives  with  bromine  water.  One  part  of  phenol  in 
44, coo  parts  of  water  gives  a  perceptible  precipitate  at  once  with 
this  reagent.  Millon's  reagent  gives  a  yellow  precipitate  with 
phenol  solutions,  and  this  test  is  said  to  be  more  delicate  than 
the  reaction  with  bromine  water.  A  solution  of  ferric  chloride 
gives  a  blue-violet  color  with  neutral  solutions  of  phenol.  Like 
aniline  and  its  derivatives  phenol  and  its  derivatives  react 
readily  with  benzenediazonium  salts  to  form  azo  dyes.  In 
alkaline  solution  it  gives  p-hydroxyazobenzene  and  a  small  amount 
of  the  (7-compound  :  — 

HO.C6H4H  +  CIN2.C6H5  =  HO.CeHi.NiNCeHs  -1-  HCl. 

Phenol  Benzenediazonium  ^-Hydroxyazobenzene 

chloride 


^-Hydroxyazobenzene  crystallizes  in  orange  colored,  rhombic 
prisms  melting  at  152°,  and  is  a  yellowish  red  dyestuff.  It  is 
also  formed  by  the  molecular  rearrangement  of  azoxybenzene 


ETHYLPHENYL  ETHER,  PHENETOL        375 

(359)  with  sulphuric  acid  and  by  heating  ^-nitrosophenol  with 
aniline  acetate  at  100° :  — 

HO.C6H4.NO  +  H2N.C6H6  =  HO.C6H4.N=N.C6H6  +  H2O. 

This  last  reaction  shows  the  structure  of  the  compound. 

/»-Hydroxyazobenzene  is  no  longer  used  as  a  dye.  Large 
quantities  of  it  are  made,  however,  from  phenol  and  diazotized 
aniline  for  the  manufacture  of  ^-aminophenol.  For  this  pur- 
pose the  ^-hydroxyazobenzene  is  reduced  with  iron  and 
hydrochloric  acid  (write  the  equation),  and  the  aniline  formed 
is  separated  from  the  /"-aminophenol  by  distillation  in  steam 
and  is  used  over  again. 

Like  the  alcohols  phenol  forms  ethers  and  esters. 

Methylphenyl  ether,  anisol,  C6H5.O.CH3,  was  first  obtained 
from  anisic  acid  (methoxybenzoic  acid)  by  distilling  it  with 
barium  oxide,  and  hence  the  name.  It  is  best  made  by  treating 
a  solution  of  sodium  phenolate  with  dimethyl  sulphate  :  — 

CeHs.ONa  +  (CH30)2S02  =  CeHj.O.CHs  +  NaO.SO2.OCH3. 

Anisol 

It  is  a  pleasant  smelling  liquid  melting  at  —37.8°  and  boiling  at 
153.9°.  It  was  used  during  the  World  War  as  a  delousing 
agent.  It  is  used  as  a  solvent,  in  '  the  preparation  of  trinitro- 
anisol  and  of  methoxyacetophenone  (fojrmed  by  the  action  of 
acetyl  chloride  on  anisol  and  used  in  the  manufacture  of  per- 
fumes). 

Ethylphenyl  ether,  phenetol,  C6H5.O.C2H6,  is  made  from  so- 
dium phenolate  and  ethyl  bromide  :  — 

CeHs.ONa  +  BrCzHj  =  CgHb.O.CzHs  -|-  NaBr. 

Phenetol 

It  is  a  liquid  with  a  pleasant  odor,  melting  at  —33.5°  and 
boiling  at  i7i.5°-i72.s''. 

Note  for  Student.  —  Compare  these  two  substances  with  the  mixed 
ethers  (46).  What  method  analogous  to  the  one  used  in  the  prepara- 
tion of  phenetol  is  used  in  the  preparation  of  mixed  ethers?  Does 
phenol  act  like  an  alcohol?  How  are  these  phenol  ethers  made  from 
aniline  ? 


376  THE   BENZENE  SERIES   OF  HYDROCARBONS 

Diphenyl  ether,  CeHs.O.CeHs,  is  made  on  the  large  scale  by  the 
action  of  bromobenzene  on  potassium  phenolate  in  the  presence 
of  finely  divided  copper  at  210°.  (Write  the  equation.)  It  melts 
at  28°  and  boUs  at  252°-2S5°  and  has  an  odor  similar  to  that  of 
the  geranium.     It  is  used  in  the  manufacture  of  perfumes. 

Phenyl  acetate,  CeHj.O.CO.CHs,  is  formed  when  phenol  is 
treated  with  acetyl  chloride  or  when  a  benzenediazonium  salt 
is  boiled  with  glacial  acetic  acid  :  — 

C6H5.N2NO3  +  H0.C0.CH3=  CsHs.O.CO.CHs  +  N2  +  HNO3. 

Phenyl  acetate 

It  is  a  liquid  boiling  at  195°. 

Note  por  Student.  —  Write  the  equation  of  the  reaction  that  takes 
place  when  acetyl  chloride  acts  on  phenol. 

Phenol  also  forms  esters  of  the  inorganic  acids,  e.g. :  — 
Phenylsulphuric  acid,  C6H5.HSO4.  —  This  is  present  in  human 

urine  in  the  form  of  the  potassium  salt. 
Triphenyl  phosphate,  OP(OC6H5)3,  is  made  by  the  action  of 

phosphorus  oxychloride  on  phenol :  — 

OPCI3  +  3  HOCeHs  =  OP(OC6H6)3  +  3  HCl. 

Triphenyl  phosphate 

Triphenyl  phosphate  melts  at  45°.  It  is  used  as  a  substitute 
for  camphor  in  the  manufacture  of  pyroxyline  plastics. 

Substitution  Products  or  Phenol 

^-Nitrosophenol,  HO.C6H4.NO  (/>),  or  quinone  oxime, 
0:C6H4:NOH,  is  made  by  the  action  of  nitrous  acid  on 
phenol :  — 

HO.C6H4H  +  HONO  =  HO.C6H4.NO  +  H2O, 

P-Nitrosophenol 

or  by  the  action  of  solutions  of  the  alkalies  on  ^-nitrosodimethyl- 
aniline  (346).  Since  it  is  also  formed  by  the  action  of  hydroxyl- 
amine  hydrochloride  on  quinone  (433) :  — 

0:C6H4:0  +  H2NOH  =  0:C6BU:N0H  +  H2O, 

Quinone  Quinoneojome 


DINITROPHENOL  377 

it  is  highly  probable  that  it  is  an  oxime  of  quinone  as  shown 
above.  It  crystallizes  in  yellowish  needles,  is  fairly  soluble 
in  water,  readily  in  alcohol,  ether,  and  acetone,  and  the  solutions 
have  a  bright  green  color.  Like  the  oximes  it  has  acid  properties, 
the  hydrogen  of  the  =NOH  group  being  replaceable  by  metals 
and  radicals.  When  reduced  with  sodium  sulphide  it  gives 
/>-aminophenol  and,  when  oxidized,  ^-nitrophenol.  (Write  the 
equations.)  It  is  made  on  the  large  scale  from  phenol  and  is 
used  in  the  manufacture  of  the  hydron  dyes  (especially  hydron 
blue),  the  sulphur  dyes,  and  of  /i-aminophenol. 

Nitrophenols,  HO.C6H4.NO2.  —  Nitration  of  phenol  with  di- 
lute nitric  acid  produces  about  equal  quantities  of  ortho-  and 
paranitrophenol,  which  are  separated  by  distillation  in  steam, 
the  ortho  product  being  volatile.  o-Nitro phenol  crystallizes  in 
yellow,  orthorhombic  needles,  having  a  characteristic  penetrat- 
ing odor  and  a  sweet  taste.  It  is  slightly  soluble  in  cold  water, 
readily  in  alcohol  and  ether,  melts  at  44.5°  and  boils  at  214°. 
On  reduction  it  gives  o-aminophenol.  Its  salts  with  the  metals 
have  a  red  color.  Together  with  ^-nitrophenol  it  is  made  on 
the  large  scale  by  nitrating  phenol,  and  is  used  in  making 
(7-nitroanisol,  o-aminophenol,  dianisidine,  etc.,  and  in  the  man- 
ufacture of  azo  and  sulphur  dyes.  p-Nitro phenol  crystallizes 
in  colorless  needles,  melting  at  114°  It  is  fairly  soluble  in  hot 
water,  readily  in  alcohol,  and  its  salts  with  the  metals  have  a 
yellow  color.  On  reduction  it  gives  ^-aminophenol.  It  is  used 
in  the  manufacture  of  ^-aminophenol,  />-nitrophenetol,  sulphur 
dyes  (Vidal  black),  and  also  in  the  laboratory  as  an  indicator. 

m-Nitrophenol  is  made  from  m-nitroaniline  (344)  by  diazotiz- 
ing  its  hydrochloride  and  decomposing  the  diazonium  salt  with 
water.  The  nitrophenols  are  stronger  acids  than  phenol,  e.g., 
they  decompose  carbonates,  forming  salts  and  setting  carbon 
dioxide  free. 

Dinitrophenol,  C6H3(OH)(N02)2, 1,2,4,  is  made  by  boiling 
i-chloro-2,4-dinitrobenzene  (340)  with  sodium  carbonate,  and 
is  used  in  making  sulphur  dyes.  When  nitrated  it  gives  picric 
acid  (378).  On  reduction  it  gives  2,4-diaminophenol,  used  as 
a  photographic  developer  under  the  name  of  amidol. 


378  THE   BENZENE   SERIES   OF  HYDROCARBONS 

s-Trinitrophenol,  picric  acid,  HO .C6H2.(N02)3,i, 2,4,6,  is  made 
on  the  large  scale,  for  use  as  an  explosive,  by  dissolving  phenol 
in  concentrated  sulphuric  acid  and  treating  the  phenolsulphonic 
acids  formed  (381)  with  nitric  acid  (sp.  gr.  i.  4)  :  — 

HO.C6H4.SO3H  +  3  HNO3     =     HO.C6H2(N02)3+H2S04  +  2  H2O. 

Picric  add 

Note  for  Student.  —  Compare  this  reaction  with  that  of  bromine  on 
sulphanilic  acid  (370).  What  does  sulphanilic  acid  give  when  fused 
with  caustic  soda? 

During  the  World  War  large  quantities  of  picric  acid  were 
made  from  chlorobenzene.  This  when  nitrated  gives  i-chloro- 
2,4-dinitrobenzene,  which  is  converted  into  2,4-dinitrophenol 
by  boiling  with  soda  solution.  This  gives  picric  acid  when 
nitrated.  Picric  acid  also  results  from  the  oxidation  of  i-tri- 
nitrobenzene  with  potassium  ferricyanide :  — 


OH 

OsN/NnOz 

+  0  = 

OjN/NnOs 

NO2 

NO2 

s-Trinitrobenzene 

Picric  acid 

This  reaction  and  the  fact  that  picric  acid  is  obtained  by  the 
nitration  of  0-  and  /»-nitrophenol,  but  cannot  be  made  by  the 
nitration  of  w-nitrophenol,  determines  its  structural  formula. 
Picric  acid  is  also  formed  by  the  action  of  nitric  acid  on  silk, 
leather,  various  resins,  indigo,  and  aniline.  Picric  acid  crystal- 
lizes from  water  in  yellow  leaflets  which  melt  at  122.5°.  There 
are  two  modifications  of  picric  acid,  one  yellow,  the  other  color- 
less. The  solution  in  water  has  a  deep  yellow  color  and  contains 
the  yellow  form,  while  the  solution  in  ligroin  is  colorless.  When 
the  sodium  salt  of  picric  acid  is  reduced  with  sodium  hydro- 
sulphide,  picramic  acid,  C6H2(N02)2-NH2(OH)  (4,6-dinitro- 
2-aminophenol),  is  formed.  This  crystallizes  in  red  needles, 
melting  at  i68°-i69°.  It  is  used  in  the  manufacture  of  azo  dyes. 
Picric  acid  is  a  strong  acid,  comparable  with  the  mineral  acids, 
and  hke  the  strong  acids  undergoes  considerable  ionization  in 


AMINOPHENOLS  379 

aqueous  solution.  The  presence  of  the  three  nitre  groups  has 
a  remarkable  influence  on  the  phenol  hydroxyl  group,  so  that  in 
its  reactions  picric  acid  resembles  the  carboxylic  acids,  e.g., 
it  gives  picryl  chloride,  C6H2(N02)3C1  (trinitrochlorobenzene) 
with  phosphorus  pentachloride,  which  can  also  be  made  by  the 
nitration  of  chlorobenzene.  This  reacts  like  the  chloride  of 
an  acid,  giving  picric  acid  when  boiled  with  water ;  picramide, 
C6H2(N02)3NH2  (trinitroaniline),  with  ammonia;  and  esters 
with  alcohols,  such  as  trinitroanisol,  C6H2(N02)30CH3,  which 
can  also  be  obtained  by  nitrating  anisol.  (Write  all  the  equa- 
tions.) Picric  acid  forms  well  crystallized  salts.  The  am- 
monium salt,  which  is  used  as  an  explosive,  exists  in  a  yellow 
and  a  red  modification.  Picric  acid  is  one  of  the  oldest  dyes, 
having  been  first  used  in  dyeing  silk  in  1849.  It  dyes  wool, 
sUk  and  the  human  skin  an  intense  yellow.  It  is  no  longer 
used  as  a  dye.  Picric  acid  has  an  extremely  bitter  taste  and 
hence  the  name  (Gr.  pikros,  bitter).  With  bleaching  powder 
picric  acid  gives  chloropicrin,  CCI3NO2,  one  of  the  "poison 
gases "  used  during  the  World  War.  Under  the  name  of 
lyddite,  picric  acid  is  used  as  a  high  explosive.' 

Aminophenols,  HO.C6H4.NH2. — -The  aminophenols  are 
formed  by  the  reduction  of  the  nitrophenols. 

0- Amino  phenol  crystallizes  in  colorless  scales  which  melt  at 
174°  and  quickly  turn  brown  in  the  air  due  to  oxidation.  It 
is  soluble  in  water,  alcohol,  and  ether  and  has  basic  properties 
forming  a  hydrochloride,  HO.C6H4.NH2.HCI,  crystallizing  in 
colorless  needles.  The  methyl  ether,  H3CO.C6H4.NH2,  known 
as  o-anisidine,  is  made  by  the  reduction  of  o-nitroanisol  and  is 
used  in  the  preparation  of  azo  dyes  and  in  the  manufacture  of 
guaiacol  (384). 

Salvarsan,  a  valuable  remedy  in  sleeping  sickness,  syphilis, 
and  similar  diseases,  is  the  hydrochloride  of  diaminodihydroxy- 
arsenobenzene, 

AsCeHsOHNHa 

II 

ASC6H3OHNH2 

'  See  Explosives,  by  Arthur  Marshall,  2d  edition,  1917. 


380         THE  BEXZEXE  SERIES   OF  HYDROCARBONS 

771- Amino  phenol  is  made  on  the  large  scale  by  heating  resor- 
cinol  (385)  with  a  strong  solution  of  ammonia  under  pressure 
in  an  autoclave :  — 

HO.C6H4.OH  +  HNH2  =  HO.C6H4.NH2  +  H2O, 

Resorcinol  ffl-Aminophenol 

or  by  fusing  metaniUc  acid  (369)  with  caustic  soda. 

ffl-Aminophenol  melts  at  i22°-i23°,  is  soluble  in  water, 
alcohol,  and  ether,  and  is  stable  in  the  air.  It  has  basic  proper- 
ties and  forms  a  hydrochloride  melting  at  229°. 

Diethyl-m-aminoplmiol,  HO.CiH^.NiCJS^i,  is  made  on  the 
large  scale  from  diethylaniline  (347)  by  first  con^'erting  it  into  the 
w-sulphonic  acid  (by  sulphonating  in  the  presence  of  a  large  excess 
of  sulphuric  acid)  and  then  fusing  this  with  caustic  soda.  (Write 
the  equations.)     It  is  used  in  making  the  rhodamine  dyes  (364). 

p-Atnino phenol  forms  leaflets  melting  at  184°,  easily  soluble 
in  water  and  alcohol  and  very  readily  oxidized.  Chromic  acid 
converts  it  into  /"-benzoquinone  (476).  It  is  made  on  the  large 
scale  by  the  electrolytic  reduction  of  nitrobenzene  in  sulphuric 
acid.  jS-PhenyUiydroxylamine  (358)  is  first  formed  and  is 
immediately  converted  into  />-aminophenol  by  the  sulphuric 
acid.  It  is  also  made  by  the  reduction  of  /)-nitrosophenol  and 
of  ^-hydroxyazobenzene  (374).  It  is  used  in  the  manufacture 
of  dyes,  in  coloring  hair  and  furs,  and  under  the  name,  rhodinal, 
as  a  photographic  developer. 

Methyl-/>-aminophenol,  CH3NHC6H40H(/»),  is  made  by  heat- 
ing hydroquinol  (387)  with  a  solution  of  methylamine  in  an 
autoclave :  — 

HO.C6H4.OH  -I-  HNH.CH3  =  HO.C6H4.NHCH3  -I-  H2O. 

Hydroquinol  Methyl-#-amiDophenol 

The  sulphate,  (CH3NHC6H40H)2H2S04,  is  used  as  a  photo- 
graphic developer  under  the  name,  7netol. 

^-Phenetidine,  C2H5O.C6H4.NH2,  the  ethyl  ether  of  p-zxamo- 
phenol,  is  made  by  the  reduction  of  ^-nitrophenetol  with  iron 
and  hydrochloric  acid,  and  is  used  in  the  manufacture  of  dyes 
and  synthetic  remedies. 


CRESOLS,   HYDROXYTOLUENES,   CRESYLIC  ACIDS      381 

Dulcine  or  Sucrol,  C2H6.O.C6H4.NH.CO.NH2,  is  made  by 
heating  ^-phenetidine  with  urea :  — 

C6H6O.C6H4.NH2  +  CO(NH2)2 

if-Phenetidine 

=  C2H6O.C6H4.NH.co.NH2  +  NH3. 

Dulcine 

It  is  200  times  as  sweet  as  cane  sugar  and  was  used  during  the 
World  War  as  a  sweetening  agent  in  place  of  sugar. 

Phenacetine,  C2H5O.C6H4.NH.COCH3,  made  from  ^-pheneti- 
dine  by  heating  with  glacial  acetic  acid  (see  Acetanilide,  348), 
is  used  in  medicine  as  an  antipyretic  and  antineuralgic.  It  is 
said  to  be  less  poisonous  than  acetanilide. 

Phenolsulphonic  acids,  HO.C6H4.SO2OH.  —  Phenol  is  sul- 
phonated  much  more  readily  than  benzene.  It  forms  0- 
and  p-phenolsulpkonic  acids  when  treated  with  sulphuric  acid 
at  ordinary  temperatures.  o-Phenolsulphonic  acid  is  unstable 
and  goes  over  into  the  para  acid  when  heated.  Even  heating  its 
aqueous  solution  transforms  it  into  a  solution  of  the  para  acid. 
When  phenol  is  sulphonated  at  100°  the  para  acid  is  therefore 
the  main  product.  These  acids  are  the  intermediate  products  in 
the  manufacture  of  picric  acid  (378).  Aseptol  is  a  ^^^  per  cent 
aqueous  solution  of  0-  and  ^-phenolsulphonic  acids  and  is  used 
as  an  antiseptic. 

m- Phenolsulphonic  acid  is  obtained  by  fusing  benzene- 
disulphonic  acid  (368)  with  caustic  soda :  — 

Na03S.C6H4.S03Na  +  NaOH  =  HO.C6H4.S03Na  +  NazSOa. 

It  is  an  intermediate  product  in  the  manufacture  of  resorcinol 
(385). 

Cresols,  hydroxy  toluenes,  cresylic  acids,  HO.C6H4.CH3. — 
The  three  cresols  are  present  in  the  acid  oil  and  naphthalene 
fraction  (306)  obtained  in  distilling  coal  tar,  and  are  separated 
from  phenol  (372)  and  the  xylenols  by  fractional  distillation. 
The  cresols  are  also  present  in  pine  wood  and  beech  wood  tars. 
The  coal  tar  cresol  is  a  mixture  of  35  to  40  per  cent  ortho-, 
35  to  40  per  cent  meta-,  and  25  per  cent  para-cresol.  Nearly 
pure  o-cresol  can  be  obtained  from  this  mixture  by  careful 


382  THE   BENZENE   SERIES   OF  HYDROCARBONS 

fractional  distillation.  The  remaining  mixture,  containing 
60  per  cent  meta-  and  40  per  cent  para-cresol,  is  separated  by 
treating  it  with  three  times  the  quantity  of  fuming  sulphuric 
acid  (20  per  cent  SO3).  Sulphonation  takes  place  in  the  cold. 
Water  is  then  added  so  that  the  boiUng  point  of  the  solution  is 
i25°-i30°.  When  superheated  steam  is  run  in,  the  w-cresol- 
sulphonic  acid  is  hydrolyzed  and  w-cresol  distils  over  with  the 
steam.  After  all  the  w-cresol  has  distilled  over,  the  ^-cresol- 
sulphonic  acid  is  hydrolyzed  at  a  higher  temperature  with 
superheated  steam  and  the  /»-cresol  distils  with  the  steam.  The 
pure  cresols  can  also  be  obtained  from  the  corresponding  tolui- 
dines  (350,  353)  or  from  the  toluenesulphonic  acids  by  fusing 
the  latter  with  caustic  soda. 

Note  por  Student.  —  Write  the  equations  representing  the  reactions 
involved  in  these  transformations. 

The  cresols  resemble  the  phenols  closely  in  their  properties. 
They  are  weaker  acids,  but  are  stronger  antiseptics  than  phenol. 
m-Cresol  is  the  most  efl&cient  bactericide  and  the  least  poisonous. 
o-Cresol  melts  at  31°  and  boils  at  188°.  w-Cresol  melts  at  4° 
and  boils  at  203°,  while  /»-cresol  melts  at  36.5°  and  boils  at  202°. 
Both  the  m-  and  the  ^-cresol,  but  not  the  ortho,  give  a  blue  color 
with  a  solution  of  ferric  chloride.  Artificial  resins  are  made 
from  the  cresols  by  condensing  them  with  formaldehyde.  The 
resin  made  from  o-cresol  is  without  odor  and  is  used  as  a  sub- 
stitute for  shellac.  Synthetic  tanning  materials  are  also  made 
from  the  cresolsulphonic  acids  by  combining  them  with  formal- 
dehyde. 

Thymol,  />-isopropyl-7n-cresol,  H3CC6H3(OH)CH(CH3)2, 
occurs  in  various  essential  oils,  especially  in  the  oil  of  thyme, 
whence  the  name.  On  the  large  scale  it  is  obtained  from  Ajowan 
oil  by  shaking  it  with  a  10  per  cent  solution  of  caustic  soda.  The 
aqueous  alkaline  solution  of  the  thymol  is  separated  from  the 
^-cymene  and  terpenes  present  in  the  oil,  and  the  thymol  is 
precipitated  by  acid  and  purified  by  recrystallization.  It  forms 
large  transparent,  hexagonal  crystals  melting  at  51.5°,  and  it  boils 
at  232°.     It  is  used  in  medicine  and  as  an  antiseptic.     When 


PYROCATECHOL  383 

heated  with  phosphorus  pentoxide,  it  yields  w-cresol  and  propy- 
lene, while,  when  distilled  with  phosphorus  pentasulphide,  it 
gives  cymene.  These  two  reactions  show  that  thymol  is  p-iso- 
propyl-»j-cresol.     (Write  the  equations.) 

When  treated  with  iodine  and  a  solution  of  caustic  soda,  thymol 
gives  a  diiododithymol,  a  derivative  of  diphenyl.  Under  the 
name  aristol  this  substance  is  used  as  a  substitute  for  iodoform. 

Carvacrol,  />-isopropyl-o-cresol,  H3CC6H3(OH)CH(CH3)2, 
occurs  in  the  oil  of  thyme  and  in  camphor  oil.  It  constitutes 
about  80  per  cent  of  the  oil  of  Origanum  hirtum.  It  is  obtained 
from  its  isomer,  carvone,  which  is  the  chief  constituent  of  the 
oil  of  caraway,  by  heating  this  ketone  with  glacial  phosphoric 
acid.  It  is  closely  connected  with  camphor  and  can  be  obtained 
by  heating  camphor  with  iodine.  It  has  also  been  made  from 
cymenesulphonic  acid  by  fusing  it  with  caustic  soda.  When 
pure  it  is  a  colorless  liquid  melting  at  about  1°,  and  boiling  at 
236°-237°.  It  is  distinguished  from  its  isomer,  thymol,  by 
the  fact  that  it  gives  a  green  color  with  a  solution  of  ferric 
chloride.  With  phosphorus  pentoxide  it  gives  o-cresol  and 
propylene,  while  with  the  pentasulphide  it  gives  /i-cymene. 
These  two  reactions  show  its  structure. 

DiAciD  Phenols 

The  three  dihydroxybenzenes,  C6H4(OH)2,  are  well  known  and 
all  are  important  substances.  w-Dihydroxybenzene,  resorcinol, 
is  the  most  important. 

Pyrocatechol,  o-dihydroxybenzene,  C6H4(OH)2,  occurs  in 
raw  beet  sugar  and  was  first  made  by  the  distillation  of  catechin 
{Mimosa  catechin),  whence  the  name  pyrocatechin  formerly 
used.  Many  other  resins  give  pyrocatechol  when  distilled  or 
when  fused  with  caustic  alkalies.  It  is  made  on  the  large  scale 
from  phenol.  When  chlorine  is  passed  into  phenol  the  main 
product  is  o-chlorophenol.  This  is  converted  into  pyrocatechol 
by  heating  with  a  solution  of  caustic  alkali :  — 

HO.CeHi.CKo)  +  NaOH  =  HO.CaHi.OHCo)  +  NaCl. 

0-Chlorophenol  Pyrocatechol 


384  THE   BENZENE   SERIES   OF   HYDROCARi;ONS 

Note  for  Student.  —  Can  chlorine  be  removed  from  chlorobenzene 
by  boiling  it  with  a  solution  of  an  alkali?  What  is  the  effect  of  heating 
the  three  chloronitrobenzenes  with  aqueous  alkali?  AVhat  does  picryl 
chloride  give  when  boiled  with  water? 

Pyrocatechol  crystallizes  in  monoclinic  prisms.  It  melts  at 
104°  and  boils  at  245°  and  is  soluble  in  water,  alcohol  and  ether. 
Like  phenol  it  combines  with  sulphuric  acid  to  form  an  acid 
sulphate  and  in  this  form  it  is  a  constant  constituent  of  the  urine 
of  horses.  It  is  more  susceptible  to  the  action  of  reagents  than 
phenol,  e.g.,  it  reduces  a  solution  of  silver  nitrate  in  the  cold  and 
Fehling's  solution  on  warming.  Its  aqueous  solution  becomes 
green  on  the  addition  of  a  solution  of  ferric  chloride,  and  this 
color  changes  to  a  violet  when  a  solution  of  soda  or  sodium 
acetate  is  added.  Lead  acetate  gives  a  precipitate  of  the  lead 
salt,  and  calcium  chloride,  in  the  presence  of  ammonia,  crystals 
of  the  calcium  salt.  These  reactions  distinguish  pyrocatechol 
from  its  isomers,  resorcinol  and  hydroquinol.  The  alkaline 
solution  turns  brown  in  the  air  due  to  oxidation. 

Pyrocatechol  is  used  as  a  photographic  developer  and  in  the 
manufacture  of  guaiacol  and  adrenalin. 

Guaiacol,  HO.C6H4.0CH3(o),  occurs  in  guaiac  resin  and  in 
beech  wood  tar  and  was  formerly  obtained  from  this  source. 
It  was  then  made  on  the  large  scale  from  an  alkaline  solution  of 
pyrocatechol  and  sodium  meth}'l  sulphate.  (Write  the  equa- 
tion.) At  present  it  is  made  by  diazotizing  a  salt  of  o-anisidine 
and  boiling  the  product  with  water :  — 

H3CO.C6H4.NH2 — s-H3CO.C6H4.N2Cl — ^  H3CO.C6H4.OH. 

It  forms  colorless  crystals  that  melt  at  28.5°,  and  it  boils  at 
205°.  It  has  a  characteristic  odor  and  a  sweet  taste.  It  is 
somewhat  soluble  in  water  and  readily  in  alcohol  and  ether. 
The  alcoholic  solution  gives  a  blue  color  with  a  solution  of  ferric 
chloride,  which  soon  turns  green  and  then  yellow.  When 
heated  with  hydriodic  acid  it  gives  pyrocatechol,  and  when  dis- 
tilled with  zinc  dust,  anisol.  (Write  the  equations.)  The  car- 
bonate OC(O.C6H4.0CH3)2  and  some  other  derivatives  have 
been  recommended  as  remedies  for  tuberculosis. 


RESORCINOL  385 

Note  for  Stxjdent.  —  How  can  guaiacol  carbonate  be  made  ?  How 
is  diethyl  carbonate  made  ? 

Guaiacol  is  used  in  making  vanUlin  (426)  synthetically  and 
in  medicine. 

Veratrol,  C6H4(OCH3)2,  is  the  dimethyl  ether  of  pyrocatechol 
and  is  made  from  guaiacol  by  the  action  of  methyl  iodide  and 
alkali.  It  was  first  made  by  the  distillation  of  veratric  acid, 
(CH30)2.C6H3.COOH,  whence  the  name. 

Resorcinol,  m-dihydroxybenzene,  C6H4(OH)2(m),  gets  its 
name  from  the  fact  that  it  was  first  obtained  from  the  resins, 
galhanum  and  asafastida,  by  fusion  with  caustic  alkalies.  It  is 
made  on  the  large  scale  by  fusing  crude  sodium  benzene- 
disulphonate  with  caustic  potash.  (Write  the  equation.)  This 
crude  salt  contains  sodium  benzene-/i-sulphonate  as  well  as  the 
w-compound.  Both  are  converted  into  resorcinol  by  fusion 
with  alkalies,  as  the  ^-sulphonate  undergoes  molecular  rear- 
rangement by  the  action  of  the  fused  alkali.  Resorcinol  forms 
colorless  crystals  that  melt  at  118°,  and  it  boils  at  276.5° 
It  is  soluble  in  water,  alcohol,  ether,  and  not  very  soluble  in 
benzene,  insoluble  in  chloroform  and  carbon  bisulphide.  Its 
aqueous  solution  has  an  intensely  sweet  taste.  It  reduces  an 
ammoniacal  solution  of  silver  nitrate  and  Fehling's  solution 
when  heated.  With  a  solution  of  ferric  chloride  it  gives  a  dark 
violet  color.  It  is  very  readily  reduced  by  boiling  its  aqueous 
solution  with  sodium  amalgam  to  dihydroresorcinol,  which  acts 
like  a  tautomeric  substance  (see  phloroglucinol,  389) :  — 

CH2 
-^  HzC/NcHa 

f—  oclJco 

CH2 

m-DiketocycIohexane 

Dihydroresorcinol  is  a  strong  acid,  as  it  decomposes  car- 
bonates, forming  salts  (influence  of  the  double  bond  and  of  the 
carbonyl  group).  It  also  reacts  as  a  dike  tone,  forming  a  di- 
oxime  with  hydroxylamine.     (Write  the  equations.) 


CH2 

H2C/\CH2 

HOC^  JCO 
CH 

m-Hydroxyketotetrahydrobenzene 

386  THE   BENZENE   SERIES   OF  HYDROCARBONS 

Note  for  Student.  —  Notice  the  ease  with  which  resorcinol  is  reduced 
by  nascent  hydrogen  to  a  derivative  of  cyclohexane.  From  the  first 
formula  given  for  dihydroresorcinol  what  would  it  give  with  bromine? 
It  acts  like  an  unsaturated  compound. 

Resorcinol  is  extremely  readily  acted  upon  by  reagents,  e.g., 
with  bromine  water  it  gives  a  precipitate  of  2,4,6-tribromo- 
resorcinol  and  with  nitric  acid  2,4,6-trinitroresorcinol  (styph- 
nic  acid),  both  of  which  act  as  dibasic  acids  (compare  with 
picric  acid).     With  nitrous  acid  it  gives  2,4-dinitrosoresorcinol 

CO 
HC/\C:N0H 
Hcl      IcO 

C:NOH 

Dinitroso  resorcinol 

which  is  a  quinone  dioxime  (compare  with  nitrosophenol).  It 
is  used  as  a  dye  under  the  name.  Fast  green  O.  Carboxylic 
acids  of  resorcinol  are  formed  by  simply  boiUng  its  aqueous 
solution  with  potassium  bicarbonate  :  — 

C6H4(OH)2  +  KHCO3  =  (HOaCeHaCOOK  +  H2O. 

2,4-  and  2,6-Dihydroxybenzoic  acids 

Like  w-phenylenediamine  (345)  resorcinol  reacts  readily  with 
benzene diazonium  salts  to  form  azo  compounds.  In  alkaUne 
solution  it  gives  w-dihydroxyazobenzene  :  — 

C6H4(OH)2  +  CeHe.NzCl  =  (HO)2.C6H3.N2C6H5  +  HCl. 

m-Dibydroxyazobenzene 

This  is  used  to  color  alcoholic  lacquers  and  fats  under  the  name 
of  Sudan  G.  Resorcinol  when  fused  with  phthaUc  anhydride 
gives  fluorescein  (475),  and  this  reaction  is  used  as  a  test  both 
for  resorcinol  and  for  phthalic  acid  (415) .  Neither  pyrocatechol 
nor  hydroquinol  gives  fluorescein  with  phthalic  anhydride. 
When  heated  with  sodium  nitrite,  resorcinol  is  converted  into  a 
blue  dye,  called  Lacmoid  from  its  resemblance  to  litmus,  as  its 
solution  is  turned  blue  by  alkalies  and  red  by  acids.  It  is  used 
as  an  indicator  in  acidimetry  and  alkalimetry. 


ORCINOL  387 

Resorcinol  is  used  in  the  manufacture  of  fluorescein  and 
other  dyestufifs. 

Hydroquinol,  ^-dihydroxybenzene,  C6H4(OH)2,  was  first  ob- 
tained by  the  distillation  of  quinic  acid,  whence  the  name.  It 
is  sometimes  found  in  plants,  as  arbutin,  a  glucoside,  which 
yields  hydroquinol  on  hydrolysis.  It  is  made  on  the  large 
scale  by  oxidizing  aniline  with  sodium  bichromate  and  sulphuric 
acid  to  ^-benzoquinone  (431)  and  then  reducing  this  to  hydro- 
quinol by  means  of  sulphur  dioxide. 

CeHsNHa  — >■   CsHjNHOH  — >-  HOC6H4NH2 

Aniline  Phenylhydroxylamine  ^-Aminophenol 

— >-  0:C6H4:0  — >  HO.CeH^.OH. 

^-Benzoquinone  Hydroquinol 

It  crystallizes  from  water  in  colorless,  hexagonal  prisms  which 
melt  at  169°-! 70°  and  have  a  sweet  taste.  It  is  easily  soluble 
in  alcohol,  ether  and  hot  water.  The  alkaline  solution  soon 
turns  brown  in  the  air,  due  to  oxidation.  It  reduces  an  am- 
moniacal  solution  of  silver  nitrate  on  warming,  and  Fehling's 
solutien  in  the  cold.  Oxidizing  agents  convert  it  into  p-henzo- 
quinone  (431),  and  this  reaction  distinguishes  it  from  its  two 
isomers.  It  has  also  been  obtained  by  fusing  ^-iodophenol  with 
caustic  potash,  and,  together  with  phenol  and  pyrocatechol,  by 
oxidizing  benzene  with  hydrogen  peroxide  in  the  presence  of 
iron  salts. 

Note  for  Student.  —  What  reactions  used  in  the  preparation  of 
hydroquinol  prove  that  it  is  a  para  compound? 

It  is  used  in  photography  as  a  developer  and  also  in  the  manu- 
facture of  intermediates  (quinizarin,  etc.). 

Orcinol,  s-dihydroxy toluene,  H3C.C^3.(OH)2-l,3,5,  is  found 
in  several  lichens  and  results  from  the  fusion  of  aloes  with 
alkalies.  It  has  been  made  synthetically  from  1,3,5-chloro- 
toluenesulphonic  acid  by  fusing  with  caustic  soda,  which  proves 
its  structure.  In  this  reaction  the  chlorine  as  well  as  the  sul- 
phonic  acid  group  is  replaced  by  hydroxyl.  Orcinol  crystallizes 
with  a  molecule  of  water  in  colorless,  monoclinic  prisms  which 
rapidly  turn  red  in  the  air  due  to  oxidation.    They  are  readily 


388  THE   BENZENE   SERIES  OF  HYDROCARBONS 

soluble  in  water,  alcohol  and  ether  and  melt  at  56°.  The 
anhydrous  substance  melts  at  107°  and  boils  at  287°-290°.  A 
solution  of  ferric  chloride  gives  a  violet-black  color.  Like 
resorcinol,  when  heated  with  phthalic  anhydride  it  gives  phtha- 
leins.  Orcinol  is  converted  into  a  mixture  of  dyes  called  orcein 
when  allowed  to  undergo  oxidation  in  the  air  in  the  presence  of 
ammonia. 

Litmus  is  obtained  from  lichens  of  the  Roccella  and  Lecanora 
variety  by  treating  them  in  the  powdered  form  with  ammonium 
carbonate,  potassium  carbonate,  chalk  and  water,  and  allowing 
the  mixture  to  ferment.  Commercial  litrnus  is  made  by  mixing 
the  concentrated  solution  of  the  potassium  salts  with  chalk  and 
gypsum.  It  contains  several  coloring  matters.  In  the  free 
condition  these  are  red,  while  their  salts  are  blue,  hence  the  use 
of  litmus  as  an  indicator  in  acidimetry  and  alkalimetry. 

Teiacid  Phenols 

The  three  trihydroxybenzenes  are  all  known.  Of  these  the 
most  important  is  pyrogaUol. 

Pyrogallol,  pyrogallic  acid,  w-trihydroxybenzene, 

C6H3(OH)3-l,2,3,  was  first  obtained  by  the  dry  distillation  of 
gallic  acid  (428)  whence  the  name :  — 

(HOa.CeHj.COOH  =  CeHaCOH),  +  CO2. 

Gallic  acid  Pyrogallol 

It  is  a  constituent  of  some  important  natural  dyes,  such  as 
haematoxylin  and  ellagic  acid,  and  its  dimethyl  ether  is  present 
in  the  creosote  from  beech  wood  tar.  It  is  made  on  the  large 
scale  by  heating  gallic  acid  with  half  its  weight  of  water  in 
an  autoclave  to  175°  The  crude  product  is  purified  by  dis- 
tillation or  sublimation.  Pyrogallol  crystallizes  in  needles 
melting  at  i32.s°-i33°  It  has  been  made  from  1,2,3-chloro- 
phenolsulphonic  acid  by  fusion  with  caustic  potash,  and  this 
synthesis  shows  the  position  of  the  hydroxyl  groups.  It  sub- 
limes readily  and  distils  under  730  mm.  pressure  at  293°-294°, 
with  slight  decomposition.  It  is  readily  soluble  in  water,  alcohol, 
and  ether,  and  reduces  gold,  silver,  and  mercury  salts.     The 


PHLOROGLUCINOL  389 

solution  in  alkalies  absorbs  oxygen  from  the  air  and  turns  brown, 
and  is  used  in  gas  analysis  for  the  determination  of  oxygen.  It 
is  poisonous.  It  does  not  combine  with  hydroxylamine.  When 
its  aqueous  solution  is  boiled  with  potassium  bicarbonate  it 
gives  pyrogallolcarboxylic  acid,  isomeric  with  gallic  acid,  and 
gallic  acid.  It  gives  a  blue  color  with  a  solution  of  a  mixture 
of  ferrous  and  ferric  salts.  It  is  used  as  a  photographic  de- 
veloper, in  gas  analysis,  in  the  preparation  of  colloidal  solutions 
of  the  metals,  and  in  the  manufacture  of  dyes  (gallein,  coerulein, 
etc.). 

Phloroglucinol,  s-trihydroxybenzene,  C6H3(OH)3 -1,3,5,  was 
first  obtained  from  the  glucoside,  phloridzin  (529).  It  is  most 
readUy  prepared  by  boiling  the  hydrochloric  acid  salt  of 
1,3,5-triaminobenzene  or  2,4,6-triaminoberLzoic  acid  with 
water. 

Note  for  Student.  —  Write  the  equations.  What  must  be  the  struc- 
ture of  phloroglucinol,  from  these  methods  of  formation?  Note  the 
ease  with  which  the  amino  groups  are  replaced  by  hydroxyl.  How  is 
phenol  made  from  aniline  ? 

Phloroglucinol  is  also  formed  when  resorcinol  is  fused  with 
caustic  potash  in  the  air  or  by  fusing  1,3,5-benzenetrisulphonic 
acid  with  caustic  alkalies.  (Write  the  equations.)  Phloro- 
glucinol crystallizes  from  water  in  rhombic  plates  containing  two 
molecules  of  water  of  crystallization,  which  melt  at  ii3°-ii6°. 
The  anhydrous  product  melts  at  2i']°-2ig°  It  is  readily  soluble 
in  water,  alcohol,  and  ether.  It  has  a  sweet  taste.  It  reduces 
Fehling's  solution,  gives  a  blue-violet  color  with  a  solution  of 
ferric  chloride,  and  its  alkaline  solution  absorbs  oxygen  from  the 
air,  but  not  as  readily  as  pyrogallol  does.  Its  aqueous  solution 
gives  phloroglucinolcarboxylic  acid  when  heated  with  potassium 
bicarbonate.  Phloroglucinol  acts  like  a  tautomeric  substance. 
It  dissolves  in  solutions  of  alkalies,  forming  salts,  C6H3(OK)s, 
and  these  solutions  give  a  trimethyl  ether,  C6H3(OCH3)3,  insol- 
uble in  alkalies,  when  treated  with  methyl  iodide.  With  acetyl 
chloride  it  gives  a  triacetate,  C6H3(OCOCH3)3.  These  reactions 
and  the  methods  of  making  the  substance  show  that  it  is  1,3,5- 
trihydroxybenzene  (see  formula,  next  page) .    When  treated  with 


390    THE  BENZENE  SERIES  OF  HYDROCARBONS 

hydroxylamine,  however,  it  gives  a  trioxime,  C6H6(NOH)3, 
a  derivative  of  cyclohexane.  This  reaction  shows  that  phloro- 
glucinol  contains  three  carbonyl  groups,  i.e.,  that  it  is  5-triketo- 
cyclohexane. 

CH  CH2 

HO.C|'^\c.OH  — >-  OC/NCO 

HCL     IJCH  -« —  HzCl      JCH2 

C.OH  CO 

Trihydroxybenzene  1,3,5  j-Triketocydohexane 

It  will  be  seen  that  the  second  formula  is  derived  from  the 
first  by  the  migration  of  the  hydrogen  atoms  of  the  hydroxyl 
groups  to  the  carbon  atoms,  and  the  elimination  of  the  three 
double  bonds.  Phloroglucinol  has  no  technical  application.  It 
is  used  to  determine  the  amount  of  pentosans  in  plants.  When 
substances  containing  pentosans  are  boiled  with  hydrochloric 
acid  they  give  furfural  (or  methyl  furfural,  318)  which  combines 
with  phloroglucinol  to  form  an  insoluble  compound.  From  the 
amount  of  this  compound  formed  the  amount  of  pentosans 
present  can  be  calculated.  Phloroglucinol  is  also  used  to 
determine  the  presence  of  wood  pulp  in  paper.  Such  paper 
gives  a  purplish  red  color  when  treated  with  a  solution  of  phloro- 
glucinol containing  hydrochloric  acid. 

Hydroxyhydroquinol,  u-trihydroxybenzene,  C6H3(OH)3-l,2,4, 
is  formed  by  fusing  hydroquinone  with  caustic  alkalies  in  the 
air:  — 

OH  OH 

+         0  -  '       ^OH 


Its  triacetate,  C6H3(OCOCH3)3,  is  formed  by  heating  ^-benzo- 
quinone  (431)  and  acetic  anhydride  with  a  small  amount  of 
sulphuric  acid.  When  hydrolyzed  with  hydrochloric  acid  this 
gives  hydroxyhydroquinol.  It  crystallizes  in  monoclinic  leaflets 
melting  at  140.5°. 

Note  for  Student.  —  How  many  monohydroxyhydroquinols  are 
possible  and  known? 


benzyl  alcohol  391 

Aromatic  Alcohols,  Aldehydes,  and  Ketones 

The  phenols  resemble  the  tertiary  alcohols  of  the  paraffin 
series  in  some  respects,  but  differ  from  them  in  others. 
Aromatic  alcohols,  which  are  completely  analogous  to  the 
alcohols  of  the  paraffin  series,  are  also  known.  The  simplest  of 
these  is  benzyl  alcohol,  CeHs.CHjOH,  or  phenylmethyl  alcohol 
(phenylcarbinol) ,  isomeric  with  the  cresols.  This  is  a  primary 
alcohol,  as  it  yields  benzoic  aldehyde  and  benzoic  acid  when 
oxidized :  - — ■ 

C6H5.CH2OH  CeHs.CHO  CeHj.COOH. 

Benzyl  alcohol  Benzoic  aldehyde  Benzoic  acid 

Secondary  alcohols,  such  as  diphenylcarbinol,  (C6H6)2.CHOH, 
formed  by  the  reduction  of  benzophenone,  CeHe.CO.CeHs 
(diphenyl  ketone),  and  tertiary  alcohols  like  triphenylcarbinol, 
(C6H6)3C.OH,  are  also  known.  The  aromatic  alcohols  are  all 
derivatives  of  the  alcohols  of  the  paraffin  series. 

Benzyl  alcohol,  C6H6.CH2OH,  is  found  in  the  oil  of  tuberose, 
ylang-ylang,  cloves,  and  cassia  flowers,  and  in  the  form  of  the 
acetate,  benzoate,  or  sahcylate  in  the  oils  of  tuberose,  ylang- 
ylang,  hyacinth,  jasmine,  gardenia,  and  in  Peru  and  Tolu 
balsam.  It  has  been  known  as  a  constituent  of  these  two 
balsams  for  a  long  time,  but  it  is  only  since  its  discovery  in  the 
essential  oils  of  the  flowers  used  in  perfumery  that  its  importance 
has  been  realized  and  that  it  has  been  manufactured  on  the  large 
scale.  Lately  it  has  come  into  prominence  in  medicine.  For 
use  in  the  manufacture  of  perfumes  it  is  made  from  benzalde- 
hyde  (394)  by  the  action  of  concentrated  solutions  of  the 
alkalies :  — 

2  CeHs.CHO  +  KOH  =  CeHs.CHjOH  +  CeHs.COOK. 

Benzaldehyde  Benzyl  alcohol  Potassium  benzoate 

A  similar  reaction  takes  place  with  formaldehyde :  — ■ 
2  H.CHO  +  KOH  =  H3C.OH  +  H.COOK. 

Formaldehyde  Methyl  alcohol      Potassium  formate 

It  will  be  seen  from  these  reactions  that  one  molecule  of  the 
aldehyde  oxidizes  another  molecule  to  the  acid  and  is  itself 


392  THE  BENZENE  SERIES  OF  HYDROCARBONS 

reduced  to  the  alcohol.  Benzaldehyde  is  the  phenyl  derivative 
of  formaldehyde. 

Benzyl  alcohol  is  also  made  on  the  large  scale  from  benzyl 
chloride  (336)  by  boiUng  it  with  water  and  freshly  precipitated 
lead  oxide :  — 

CeHs.CHzCl  +  HOH  =  C6H5.CH2OH  +  HCl. 

Benzyl  chloride  Benzyl  alcohol 

The  benzyl  alcohol  manufactured  in  this  way  is  apt  to  contain 
chlorine  compounds  which  give  the  alcohol  a  disagreeable  odor 
and  render  it  unfit  for  use  in  perfumery.  Benzyl  alcohol  is  a 
colorless  liquid.  It  has  a  faint  aromatic  odor  when  pure,  but 
soon  acquires  the  odor  of  oil  of  bitter  almonds  on  standing  in  the 
air  in  consequence  of  the  formation  of  some  benzaldehyde  by 
oxidation.  It  boils  at  205.5°-2o6°,  and  is  readily  soluble  in 
organic  solvents.  It  is  not  very  soluble  in  water  (i  vol.  in  35  of 
water) . 

Benzyl  alcohol  is  the  phenyl  derivative  of  methyl  alcohol 
and  hence  is  completely  analogous  to  that  alcohol  in  its  re- 
actions ;  e.g.,  it  gives  esters  with  acids,  such  as  benzyl  chloride 
and  bromide  (336)  and  benzyl  acetate  with  acetic  anhydride. 
(Write  the  equations.)  It  also  forms  ethers,  of  which  the 
methyl  ether,  C6H6CH2.O.CH3  (made  from  benzyl  chloride  and 
sodium  methylate),  and  the  benzyl  ether,  C6H6CH2.O.CH2C6H6, 
are  examples. 

Note  for  the  Student. — ^What  would  benzyl  alcohol  give  when 
treated  with  sodium?  What  would  this  product  give  when  treated  with 
benzyl  chloride? 

It  differs  from  the  cresols  in  being  insoluble  in  solutions  of  the 
alkaHes  and  also  in  the  products  which  it  gives  on  oxidation. 
Benzoic  aldehyde  and  benzoic  acid  are  formed  from  benzyl 
alcohol  by  oxidation,  while  the  cresols  give  the  hydroxy- 
benzoic  acids  (420).  Substitution  products,  such  as  chlo- 
robenzyl  alcohols,  CI.C6H4.CH2OH,  nitrobenzyl  alcohols, 
NO2.C6H4.CH2OH,  etc.,  cannot  be  made  by  direct  treatment 
of  the  alcohol  with  chlorine  or  nitric  acid,  as  these  reagents 


PHENYLETHYL  ALCOHOL  393 

oxidize  the  alcohol.  They  are  made  from  the  chloro toluenes, 
CI.C6H4.CH3,  or  the  nitro toluenes,  NO2.C6H4.CH3,  by  chlori- 
nation  at  the  boiling  point  and  the  conversion  of  the  chloro- 
benzyl  chlorides,  CI.C6H4.CH2CI,  or  nitrobenzyl  chlorides, 
NO2.C6H3.CH2CI,  into  the  corresponding  alc(5hols  by  boiling 
with  water.  (Write  the  equations.)  These  substituted  benzyl 
alcohols  are  converted  into  the  corresponding  benzoic  acids  by 
oxidation : — 

CI.C6H4.CH2OH  +02    =    CI.C6H4.COOH  +  H2O. 

Chlorobenzyl  alcohols  Chlorobenzoic  acids 

NO2.C6H4.CH2OH  +  02  =  NO2.C6H4.cooH  +  H2O. 

Nitrobenzyl  alcohols  Nitrobenzoic  acids 

Homologues  of  benzyl  alcohol  such  as  a-phenylethyl  alcohol, 
CeHs.CHOH.CHa,  and  (3-phenylethyl  alcohol,  C6H5.CH2CH2OH, 
one  a  secondary  and  the  other  a  primary  alcohol,  are  well  known. 
Homologues  are  also  known,  derivatives  of  the  xylenes,  cumene, 
mesitylene,  etc.,  in  the  same  way  that  benzyl  alcohol  is  derived 
from  toluene,  such  as  tolyl  carbinol,  H3C.C6H4.CH2OH,  which  is 
known  in  three  forms,  ortho-,  meta-,  and  para-,  and  cuminyl 
alcohol,  ^-isopropyl  benzyl  alcohol,  C3H7.C6H4.CH20H(/'), 
made  by  reducing  cuminol,  C3H7.C6H4.CHO  {p),  an  aldehyde 
found  in  the  oil  of  cumin  (398). 

Phenylethyl  alcohol,  C6H5.CH2.CH2OH,  occurs  in  the  attar 
of  roses  and  in  neroli  oil  both  in  the  free  state  and  combined  with 
benzoic  acid  and  with  phenylacetic  acid  in  the  form  of  esters. 
It  is  made  on  the  large  scale  in  France  by  the  reduction  of  ethyl 
phenyl  acetate  with  sodium  and  absolute  alcohol :  — 

C6H6.CH2.CO.OC2H6  +  2H2  =  C6H5.CH2.CH2OH  +  CjHsOH. 

Ethyl  phenyl  acetate  Phenylethyl  alcohol 

In  this  country  it  is  made  commercially  by  the  Grignard  re- 
action from  ethylene  oxide  and  phenylmagnesium  bromide  in 
ether  solution :  — 

'  I  No  +  CeHs.Mg.Br  =  CeHg.CHa.CHa.OMgBr. 
H2C/ 

Ethylene  oxide        Phenyl  magnesium 
bromide 


394  THE  BENZENE  SERIES  OF  HYDROCARBONS 

CeHe.CHj.CHs.OMgBr+HjO  =  C6H6.CH2.CH20H+Mg<Qjj- 

Phenylethyl  alcohol 

Phenylethyl  alcohol  is  a  colorless  liquid  boiling  at  22o°-222'' 
(740  mm.),  having  a  faint  aromatic  odor,  readily  soluble  in  all 
the  ordinary  organic  solvents  and  somewhat  soluble  in  water 
(i  in  60).  It  is  readily  oxidized,  even  by  the  air,  to  phenyl- 
acetic  aldehyde  and  hence  soon  acquires  the  hyacinth  odor  of 
that  substance.  Chromic  acid  oxidizes  it  to  phenylacetic 
aldehyde  and  phenylacetic  acid.  It  is  used  in  the  manufacture 
of  perfumes. 

Phenylpropyl  alcohol,  C6H6.CH2.CH2.CH2OH,  is  found  as 
the  ester  of  cinnamic  acid  in  Sumatra  benzoes,  in  Styrax  and 
in  other  balsams  and  resins.  It  is  made  synthetically  by  the 
reduction  of  ethyl  cinnamate  with  sodium  and  absolute 
alcohol :  — 

CsHe.CH:  CH.CO2C2H5+2  H2=C6H6.CH2.CH2.CH20H+C2H60 

Ethyl  cinnamate  Phenylpropyl  alcohol 

It  is  a  colorless  liquid  having  an  odor  somewhat  similar  to  the 
hyacinth  and  boiling  at  235°.  Oxidized  with  chromic  acid 
it  gives  hydrocinnamic  acid.  It  is  used  in  the  manufacture  of 
perfumes.. 

Aromatic  Aldehydes 

The  aromatic  aldehydes  resemble  the  aliphatic  aldehydes. 
They  result  from  the  oxidation  of  the  primary  aromatic  alcohols, 
and  give  these  alcohols  on  reduction.  The  simplest  and  most 
important  is  the  oil  of  bitter  almonds  or  benzoic  aldehyde, 
CeHs.CHO. 

Oil  of  bitter  almonds,  benzaldehyde,  CeHs.CHO,  as  its  name 
indicates  was  first  obtained  from  bitter  almonds  in  which  it 
occurs  as  amygdalin,  a  glucoside  (528).  This  is  also  present  in 
cherry  kernels  and  in  cherry-laurel  leaves.  It  is  hydrolyzed  by 
emtdsin,  an  enzyme  present  in  the  bitter  almonds,  or  by  dilute 
mineral  acids,  into  benzoic  aldehyde,  hydrocyanic  acid  and 
glucose :  — 

C20H27NO11  +  2  H2O  =  CeHs.CHO  +  HCN  +  2  CeHijOe. 

Amygdalin  Benzoic  aldehyde  Glucose 


OIL   OF  BITTER   ALMONDS  39S 

The  natural  oil  of  bitter  almonds,  therefore,  contains  hydro- 
cyanic acid  and  is  poisonous.  Benzaldehyde  was  first  made 
artificially  by  oxidation  of  benzyl  alcohol.  It  has  also  been 
made  by  other  methods  used  in  the  preparation  of  aldehydes, 
e.g.  by  the  distillation  of  a  mixture  of  calcium  benzoate  and 
formate :  — 

P  IT  POO 

g^QQ>Ca  =  C6H5.CHO  +  CaCOs. 

By  reducing  benzoyl  chloride  (404)  with  nascent  hydrogen : 
CeHs.CO.Cl  +  H2  =  CeHs.CHO  +  HCl, 

Benzoyl  chloride 

and  by  heating  benzal  chloride  (337)  with  water  in  the  presence 
of  small  amounts  of  iron  or  iron  salts :  — 

CeHs.CHClj  +  H2O  =  CeHs.CHO  +  2  HCl. 

Benzal  chloride  Benaaldehyde 

Note  for  the  Student.  —  Show  how  acetic  aldehyde  can  be  made  by 
methods  analogous  to  those  given  above.  What  is  the  action  of  caustic 
alkalies  on  acetic  aldehyde  and  on  benzoic  aldehyde  ? 

On  the  large  scale  benzaldehyde  is  made  from  toluene  by 
direct  oxidation.  Toluene  and  65  per  cent  sulphuric  acid  are 
thoroughly  stirred  while  finely  powdered  manganese  dioxide  is 
added,  the  temperature  being  kept  at  40°.  After  the  reaction 
is  over,  benzaldehyde  and  unchanged  toluene  are  driven  over  by 
steam :  — 

C6H5.CH3  +  02  =  CeHs.CHO  +  H2O. 

Another  method  involves  the  conversion  of  the  toluene  into  a 
mixture  of  benzal  chloride  and  benzotrichloride  by  the  action  of 
chlorine  at  the  boiling  point  of  toluene,  and  the  heating  of  this 
product  with  water  in  the  presence  of  small  amounts  of  iron  or 
iron  salts  to  9o°-95°.  The  hydrochloric  acid  formed  in  the 
reaction  (see  above)  is  very  pure  and  is  collected  in  water  and 
utilized.  After  the  reaction  is  over,  milk  of  lime  is  added  and 
the  benzaldehyde  removed   by  steam  distillation.    After  fil- 


396  THE  BENZENE  SERIES  OF  H\'DROCARBONS 

tration  of  the  residue  the  benzoic  acid  present  in  the  filtrate  in 
the  form  of  the  calciiim  salt,  is  recovered  by  the  addition  of 
hydrochloric  acid.  The  benzaldehyde  made  in  this  way  usually 
contains  small  quantities  of  chlorobenzaldehyde,  which  comes 
from  a  small  amount  of  chlorobenzal  chloride  unavoidably 
formed  in  the  chlorination  of  toluene.  When  a  chlorine-free 
benzaldehyde  is  required,  as  in  the  manufacture  of  perfumes, 
it  is  manufactured  by  the  direct  oxidation  of  toluene.  Benzyl 
chloride  can  be  converted  into  benzaldehyde  by  boiling  it  with 
an  aqueous  solution  of  lead  nitrate :  — ■ 

2  CeHs.CHzCl  +  Pb(N03)2  =  PbCl2  +  2  CeHj.CHO  +  2HNO2. 

In  this  reaction  benzyl  alcohol  is  first  formed  and  is  then  con- 
verted into  the  aldehyde  by  the  nitric  acid  set  free.  (Write  the 
equation.)  This  method  was  used  at  one  time  for  the  manufac- 
ture of  benzaldehyde.  The  crude  benzaldehyde  is  purified  by 
treating  it  with  aqueous  sulphurous  acid  which  dissolves  the 
benzaldehyde  (forming  a  compound  with  the  sulphurous  acid 
soluble  in  water)  leaving  the  impurities.  When  this  solution  is 
boiled  sulphur  dioxide  is  given  off  and  is  recovered  and  used  over 
again,  and  the  pure  benzaldehyde  is  set  free. 

Benzaldehyde  is  a  liquid  having  the  odor  of  bitter  almonds. 
It  melts  at  26°  and  boils  at  179.1°.  It  is  difficultly  soluble  in 
water  (i  part  in  600)  but  very  readily  soluble  in  alcohol  and 
ether.  It  is  not  poisonous.  Like  the  aliphatic  aldehydes  it  is 
very  readily  oxidized  even  by  the  oxygen  of  the  air  (especially 
in  the  sunlight)  forming  benzoic  acid.  It  reduces  an  ammoniacal 
solution  of  silver  nitrate  ;  forms  an  addition  product  with  sodium 
bisulphite ;  combines  with  hydrogen  to  form  benzyl  alcohol,  with 
ammonia  and  with  hydrocyanic  acid.  With  hydroxylamine  it 
gives  an  oxime  (109)  and  with  phenylhydrazine  a  phenyUiydra- 
zone,  melting  at  152°  When  treated  with  hydrazine  sulphate 
it  gives  henzylideneazine,  C6H5.CH=N — N^CH.CeHs,  which 
melts  at  93°.  With  phosphorus  pentachloride  it  gives 
benzal  chloride.  (Write  all  the  equations  representing  these 
transformations.)     Benzaldehyde  undergoes   condensation  (see 


OIL   OF   BITTER  ALMONDS  "  397 

aldol  condensation),  when  boiled  with  an  alcoholic  solution  of 
potassium  cyanide,  forming  benzoin :  — 

CeHs.CHO  +  HCO.CeHs  =  CeHs.CHOH.CO.CeHs. 

Benzoin 

Benzoin  is  a  ketone  alcohol,  as  it  takes  up  hydrogen,  forming 
hydrobenzoin,  CeHs.CHOH.CHOH.CeHs,  and  on  oxidation  gives 
benzil,  CeHs.CO.CO.CeHs,  a  diketone.  Benzoin  contains  the 
group  — ^CHOH.CO —  characteristic  of  the  sugars.  Like  the 
sugars  it  reduces  Fehling's  solution  and  gives  a  phenylosazone 
with  phenylhydrazine.     (Write  the  equations.) 

When  heated  with  the  sodium  salts  of  the  fatty  acids  and 
acetic  anhydride,  benzaldehyde  gives  unsaturated  acids : — 

CeHs.CHO  +  H2CH.COOH  =  CeHe.CH:  CH.COOH  +  H2O. 

Cinnamic  acid 

This  reaction  (which  is  called  Perkin's  synthesis)  is  supposed  to 
be  preceded  by  the  formation  of  the  addition  product, 
CeHs.CHOH.CHs.COONa  (aldol  condensation)  from  which  the 
acetic  anhydride  splits  oS  water  to  give  cinnamic  acid.  Benz- 
aldehyde also  reacts  in  a  simUar  manner  with  primary  aromatic 
amines.  Thus,  with  aniline  it  first  gives  the  addition  product, 
CeHs.CHOH.NHCeHB,  which  then  gives  benzylideneaniline , 
C6H5.CH=NC6H5,  by  the  loss  of  water. 

With  tertiary  aromatic  amines  benzaldehyde  combines  very 
readUy,  giving  substituted  amino  derivatives  of  triphenyl- 
methane  (463) :  — 

C6H6.CHO+  2  C6H4.N(CH3)2  =  C6H5.CH(C6H4.N(CH3)2)2+H20. 

Dimethyl  aniline  Tetramethyldiaminotriphenyl- 

raethane 

Like  other  benzene  derivatives  benzaldehyde  can  be  nitrated 
and  sulphonated.  The  meta  products  are  the  ones  formed  in 
largest  quantity  by  the  direct  action  of  nitric  or  sulphuric  acid. 
When  chlorinated  at  the  boiling  point  the  chlorine  goes  into  the 
side  chain  with  the  formation  of  benzoyl  chloride,  CeHj.CO.Cl 
(404). 


398  THE  BENZENE   SERIES   OF   H\'DROCARBONS 

Benzaldehyde  is  used  in  the  manufacture  of  the  triphenyl- 
methane  dyes  (malachite  green,  etc.)  and  in  the  manxifacture  of 
perfumes.  Over  702,000  pounds  were  made  in  the  United  States 
in  1920. 

Phenylacetic  aldehyde,  C6H5.CH2.CHO,  has  the  odor  of 
hyacinth  and  is  used  in  the  manufacture  of  perfumes.  It  is 
made  from  cinnamic  acid  by  treating  it  with  hypochlorous 
acid :  — 

C6H5.CH=CH.COOH  +  HOCl  =  CeHs.CHOH.CHCl.COOH. 

Cinnamic  acid  Phenyl-a-chlorolactic  acid 

This  product  when  heated  with  dilute  sulphuric  acid  gives 
phenylacetic  aldehyde :  — 

CeHs.CHOH.CHCl.COOH  =  CsHj.CHj.CHO  +  HCl  +  CO2. 

Phenyl-a-chlorolactic  acid  Phenylacetic  aldehyde 

It  is  a  colorless  fluid,  which  colors  the  skin  yellow.  It  boils  at 
75°  (s  mm.  pressure),  polymerizes  readily,  and  is  easily  oxi- 
dized to  phenylacetic  acid.  On  reduction  it  gives  phenylethyl 
alcohol,  C6H6.CH2.CH2OH,  and  it  can  be  made  by  the  oxidation 
of  this  alcohol. 

Cuminic  aldehyde,  cuminol,  ^-isopropylbenzaldehyde, 
C3H7.C6H4.CHO(^),  occurs  together  with  cymene  in  the  oO  of 
cumin,  whence  the  name.  It  has  a  pleasant  aromatic  odor, 
boils  at  232°  and  resembles  benzaldehyde  closely  in  its  properties. 
Dilute  nitric  acid  oxidizes  it  to  cuminic  acid  (/)-isopropyl- 
benzoic  acid)  while  chromic  acid  converts  it  into  terephthalic 
acid.  Nascent  hydrogen  reduces  it  to  cuminyl  alcohol, 
C3H7.C6H4.CH20H(/»),  and  distillation  with  zinc  dust  gives 
cymene  (^-isopropylmethylbenzene).    (Write  aU  the  equations.) 

Benzaldoximes,  C6H5.CH:N.OH.  ^  Hydroxylamine  reacts 
with  benzoic  aldehyde  forming  benz-anti-aldoxime :  — 

CeHs.CHO  +  H2NOH  =  CeHs.CHtN.OH  +  H2O. 

This  appears  first  as  an  oil,  but  when  purified  it  forms  long, 
lustrous  prisms,  melting  at  35". 

When  hydrochloric  acid  gas  is  conducted  into  an  ether  solu- 
tion of  the  above  oxime,  a  hydrochloride  is  precipitated,  and 


BENZALUOXlMES  399 

when  this  is  treated  with  sodium  carbonate,  benz-syn-aldoxime, 
isomeric  with  the  above,  is  obtained.  This  crystallizes  from 
ether  in  thin,  lustrous  needles,  and  melts,  when  rapidly  heated, 
at  125°.  By  long-continued  heating,  however,  it  is  converted 
into  the  oxime,  melting  at  35°. 

These  two  oximes  are  stereoisomeric.  In  terms  of  the  con- 
ceptions of  stereochemistry  they  are  represented  by  the  for- 
mulas :  — 

CeHs— C— H     and      CeHj— C— H 

II  II 

HO— N  N— OH 

CeHs 


and 


OH 


[For  an  explanation  of  the  significance  of  these  space  formulas, 
especially  as  far  as  the  nitrogen  atom  is  concerned,  see  356.] 

The  one  with  the  hydrogen  atom  and  the  hydroxyl  on  oppo- 
site sides  of  the  plane  passing  through  the  doubly  bound  carbon 
and  nitrogen  atoms  is  called  benz-anti-aldoxime;  the  one  with 
the  hydrogen  atom  and  the  hydroxyl  on  the  same  side  is  called 
benz-syn-aldoxime.  The  one  that  melts  at  125°  loses  water 
and  forms  phenyl  cyanide  or  benzoniti;il,  CeHsCN,  when  heated 
with  acetic  anhydride.  The  other  gives  an  acetate.  The  one 
that  loses  water  and  yields  the  nitril  when  heated  with  acetic 
anhydride  is  the  syn-aldoxime,  as  in  this  form  the  hydrogen  and 
hydroxyl  are  so  situated  that  they  can  unite  to  form  water, 
whereas  this  is  not  the  case  in  the  anti  form.  According  to  this 
the  stable  form,  the  one  most  easily  obtained,  is  the  anti  oxime. 
The  following  scheme  shows  how  the  anti  can  be  converted  into 
the  syn  oxime  and  vice  versa :  — 
Benz-anti-aldoxime+HCl — >-Benz-anti-aldoxime  hydrochloride 

+  I 

Benz-syn-aldoxime-< — HCl  —  Benz-syn-aldoxime  hydrochloride 


400         THE  BENZEXE  SERIES  OF  HYDROCARBONS 

Aromatic  Ketones 

These  are  of  two  kinds,  the  mixed  ketones,  of  which  aceto- 
phenone  (methylphenyl  ketone),  CeHs.CO.CHs,  is  the  simplest 
example,  and  the  aromatic  ketones,  such  as  benzophenone 
(diphenylketone),  CsHs.CO.CeHe. 

Acetophenone,  CeHs.CO.CHj,  is  formed  from  benzene  and 
acetyl  chloride  in  the  presence  of  aluminium  chloride  (Friedel 
and  Crafts  reaction) :  — 

CsHb.H  +  CI.CO.CH3  =  C6H5.CO.CH3  +  HCl. 

It  forms  crystals  that  melt  at  20.5°  and  it  boils  at  202°.,  It  is 
present  in  coal  tar.  It  has  an  agreeable  odor,  is  only  slightly 
soluble  in  water  and  is  volatile  with  steam.  It  shows  all  the 
reactions  characteristic  of  the  aliphatic  ketones.  It  was  for- 
merly used  as  a  soporific  under  the  name  Hypnone. 

Note  for  the  Student.  —  Give  the  reactions  of  acetophenone  with 
hydroxylamine,  with  phenylhydrazine  and  with  semicarbazide.  What  does 
acetophenone  give  when  reduced  with  nascent  hydrogen? 

Benzophenone,  diphenylketone,  CeHs.CO.CeHs,  is  formed 
when  calcium  benzoate  is  distilled :  — 

Sh!  CO  O^*^^  =  CeHs.CO.CeHs  +  CaCOs, 

Calcium  benzoate  Benzophenone 

or  by  the  action  of  benzoyl  chloride  on  benzene  in  the  presence 
of  aluminium  chloride :  — ^ 

CeHa.CO.Cl  +  H.CeHs  =  CeHs.CO.CeHs  +  HCl 

Benzoyl  chloride  Benzophenone 

It  is  dimorphous.  The  stable  modification  melts  at  49°.  When 
distilled  it  gives  the  unstable  modification,  melting  at  26°,  which 
gradually  changes  (more  rapidly  on  the  addition  of  a  crystal  of 
the  stable  form)  to  the  stable  modification.  It  boils  at  305.7" 
(754  mm.),  is  insoluble  in  water,  easily  soluble  in  alcohol,  ether, 
and  in  glacial  acetic  acid.  It  acts  like  the  aliphatic  ketones, 
e.g.,  it  gives  an  oxune  melting  at  140°  and  a  phenylhydrazone 
melting  at  105°. 


BENZOPHENONE,  DIPHENYLKETONE       401 

One  of  the  derivatives  of  benzophenone,  Michler's  ketone, 
/>-/)-tetramethyldiaminobenzoplienone, 

(/>)(CH3)2=N.C6H4.CO.C6H4.N=(CH3)2(/') 

is  of  great  importance  in  the  manufacture  of  the  triphenyl- 
methane  dyes.  It  is  made  by  conducting  phosgene,  0=C:^Cl2, 
into  dimethylaniline  until  the  increase  in  weight  shows  that  a 
half  molecule  of  the  gas  has  been  absorbed.  The  crystal  mass 
formed  consists  of  dime  thy  laminobenzoyl  chloride  and  di- 
methylaniline hydrochloride :  — 

(CH3)2N.C6H4.H  +  C1.C0.C1=  (CH3)2.N.C6H4.C0.C1  +  HCl; 
C6H5N(CH3)2  +  HCl  =  C6H5.N(CH3)2.HC1. 

This  mixture  is  heated  for  some  time  on  the  water  bath  in  a 
closed  vessel  until  the  reaction  is  complete :  — 

(CH3)2N.C6H4.C0.C1  +  H.C6H4.N(CH3)2  = 

(CH3)2NC6H4.CO.C6H4N(CH3)2  +  HCl. 

A  solution  of  sodium  hydroxide  is  then  added  to  neutralize  the 
hydrochloric  acid,  and  the  unchanged  dimethylaniline  is  removed 
by  distillation  in  steam.  The  ketone  is  purified  by  dissolving  in 
hydrochloric  acid,  filtering  the  solution,  and  precipitating  it 
with  sodium  hydroxide.  If  necessary  it  is  further  purified  by 
crystallization  from  alcohol.  It  crystallizes  in  almost  colorless 
leaflets  that  melt  at  174°  and  are  readily  soluble  in  alcohol  and 
ether.  On  reduction  it  gives  tetramethyldiaminobenzhydrol, 
((CH3)2NCeH4)2CHOH,  Michler's  hydrol. 

The  tetraethyl  compound,  (C2H6)2N.C6H4.CO.C6H4.N(C2H5)2, 
is  made  in  a  similar  manner  from  diethylaniline  and  is  used  in 
the  manufacture  of  dyes  (light  blue,  alkali  violet  6B,  etc.) 

Mixed  aromatic  ketones,  such  as  phenyltolyl  ketone, 
C6H6.CO.C«H4CH3,  give  stereoisomeric  ketoximes.  The  con- 
figuration of  these  isomers  is  determined  from  the  products 
formed  in  the  Beckmann  rearrangement',  brought  about  by  sul- 
phuric acid,  phosphorus  pentachloride,  etc.     In  this  molecular 

'  See  Stereochemistry,  by  A.  W.  Stewart,  2d  Ed.  1919,  page  135. 


402  THE   BENZENE  SERIES   OF  HYDROCARBONS 

rearrangement  of  the  ketoximes,  the  hydroxyl  group  and  alphyl 
group  on  the  same  side  of  the  plane  passing  through  the 
doubly  bound  carbon  and  nitrogen  atoms,  exchange  places, 
thus :  — 

CeHj — C — C6H4.CH3 — >-HO.C — C6H4.CH3 

II  II 

HO— N  CsHsN 

— s-C6H5HN.OC.C6H4.CH3, 

Phenyltolyl-syn-ketoxime  Intermediate  product  Anilide  of  toluic  acid 

and  this  intermediate  product  goes  over  to  the  more  stable 
substituted  amide  of  the  acid  as  shown  above  and  below : 

C6H6.C.C6H4CH3 — ^-CeHs.C.OH  — >-  CeHs.CO.NHCeHjCHa. 

II  II 

N.OH  N.C6H4CH3 

Phenyltolyl-anti-  Intermediate  product  Toluidide  of  benzoic  acid 

ketoxime 

Acids  of  the  Benzene  Series 

The  simplest  of  these  acids  is  benzoic  acid,  which  bears  to 
benzene  the  same  relation  that  acetic  acid  bears  to  marsh  gas. 
It  is  the  carboxyl  derivative  of  benzene.  The  homologous 
acids  are  carboxyl  derivatives  of  the  homologous  hydrocarbons. 
There  are  monobasic,  dibasic,  tribasic,  and  even  hexabasic  acids. 

Monobasic  Acids,  C„}i2n-s02 

Benzoic  acid,  C6H5.CO2H.  —  Benzoic  acid  occurs  in  gum 
benzoin,  in  the  balsams  of  Peru  and  Tolu,  in  cranberries,  and  in 
combination  with  aminoacetic  acid  or  glycine  as  hippuric  acid 
(410)  in  the  urine  of  herbivorous  animals.  It  is  present  in  coal 
tar.  It  can  be  made  in  many  ways,  the  most  important  of  which 
are  given  below :  — 

I.  By  oxidation  of  benzyl  alcohol  or  any  alcohol  which  is  a 
phenyl  derivative  of  an  alcohol  of  the  methyl  alcohol  series. 
The  common  condition  in  all  these  alcohols  is  the  presence  of 
the  difficultly  oxidizable  residue,  CeHs,  in  combination  with  an 
easily  oxidizable  residue  of  an  alcohol  of  the  marsh  gas  series :  — 


BENZOIC  ACID  403 

C6H5.CH2OH  gives  CeHs.COzH ; 

C6H6.CH2.CH2OH  "      CeHs.COaH ; 

C6H6.CH2.CH2.CH2OH     "     CeHs.COzH,  etc. 

2.  By  oxidation  of  benzoic  aldehyde,  and  the  aldehydes  of  the 
other  alcohols  referred  to  in  the  preceding  paragraph. 

3.  By  oxidation  of  all  benzene  hydrocarbons  which  contain 
but  one  residue  of  the  marsh  gas  series.  Attention  has  already 
been  called  to  this  fact  (319). 

4.  By  hydrolyzing  cyanbenzene  (phenyl  cyanide,  benzo- 
nitril)  with  dilute  sulphuric  acid :  — • 

CeHsCN  +  2  H2O  =  C6H6.CO2H  +  NH3. 

5.  By  treating  benzene  with  carbonyl  chloride  in  the  pres- 
ence of  aluminium  chloride :  — 

CeHs  +  COCI2     =      CeHB.COCl  +  HCl ; 
CbHs.COCI  +  H2O  =  C6H6.CO2H  +  HCl. 

6.  By  treating  benzene  with  carbon  dioxide  in  the  presence 
of  aluminium  chloride :  — 

CsHe  +  CO2  =  C6H6.CO2H. 

This  and  the  preceding  method  are  of  special  interest  from  the 
scientific  point  of  view,  for  the  reason  that  they  clearly  show 
that  benzoic  acid  is  the  carboxyl  derivative  of  benzene. 

Note  fob  the  Student.  — Which  of  the  methods  above  given  are  of  gen- 
eral application  for  the  preparation  of  the  organic  acids  ?  How  is  benzene 
made  from  benzoic  acid  ? 

Up  to  1877  benzoic  acid  was  made  on  the  large  scale  from 
the  urine  of  horses  and  cattle  by  hydrolysis  of  the  hippuric 
acid  (410),  C6H6.CO.NH.CH2.COOH,  contained  therein.  This 
method  is  no  longer  used.  A  small  quantity  of  benzoic  acid, 
principally  for  medicinal  uses,  is  made  at  the  present  time  from 
gum  benzoin.  Most  of  the  benzoic  acid  is  now  made  from  toluene 
either  by  direct  oxidation  with  manganese  dioxide  and  sul- 
phuric acid  or  by  chlorinating  the  toluene  at  the  boiling  point 


404  THE  BENZENE  SERIES  OF  HYDROCARBONS 

to  benzotrichloride  and  heating  this  with  milk  of  lime  and  a 
small  amount  of  iron  powder :  — ■ 

C6H5.CCI3  +  2  H2O  =  CeHs.COOH  +  3  HCl. 

Note  for  the  Student.  —  What  does  chloroform  give  when  heated 
with  a  solution  of  an  alkali?  Of  what  aliphatic  compounds  are  benzo- 
trichloride and  benzoic  acid  derivatives  ? 

The  benzoic  acid  made  by  the  last  method  generally  contains  a 
trace  of  chlorobenzoic  acid  due  to  the  presence  of  a  small  amount 
of  chlorobenzotrichloride  in  the  benzotrichloride.  Consider- 
able benzoic  acid  is  obtained  as  a  by-product  in  the  manufacture 
of  benzaldehyde  (396). 

Benzoic  acid  forms  lustrous  laminae  or  needles  that  melt  at 
121°.  It  boils  at  250°  It  is  comparatively  easily  soluble  in 
hot  water,  but  difficulty  soluble  in  cold  water.  It  is  volatile 
with  steam,  and  is  purified  by  steam  distillation.  Its  vapor 
acts  upon  the  mucous  membrane  of  the  respiratory  passages, 
and  causes  coughing.     It  sublimes  very  readily. 

Benzoic  acid  is  about  t,.^  times  as  strong  as  acetic  acid,  owing 
to  the  influence  of  the  negative  phenyl  group.  It  is,  however, 
a  weaker  acid  than  formic  acid.  When  heated  with  lime,  benzoic 
acid  breaks  down,  giving  benzene  and  carbon  dioxide. 

With  sodium  amalgam  and  water  it  yields  benzyl  alcohol. 
With  hydriodic  acid,  it  gives  toluene  and  hydrogen  addition 
products  of  toluene. 

Sodium  benzoate  is  extensively  used  as  a  preservative.  Over 
800,000  lb.  were  made  in  the  United  States  in  1920. 

The  ethereal  salts  of  benzoic  acid  can  be  made  by  any 
of  the  general  methods  used  in  the  preparation  of  esters  (67). 

Di-,  tetra-,  and  hexahydro  addition  products  of  benzoic  acid 
have  been  made.  Hexahydrobenzoic  acid,  CeHuCOOH,  is 
the  carboxyl  derivative  of  cyclohexane.  It  is  found  in  Russian 
petroleum.  It  gives  cyclohexane  when  distilled  with  lime.  It 
has  a  rancid  odor  hke  that  of  capric  acid. 

Benzoyl  chloride,  CeHs.COCl,  is  made  from  benzoic  acid  by 
the  action  of  phosphorus  pentachloride.  On  the  large  scale  it 
is  made  from  benzoic  aldehyde  by  treating  it  with  chlorine :  — 


BENZANILIDE  405 

CeHs.CHO  +  CI2  =  CeHs.COCl  +  HCl. 

It  is  more  stable  than  the  chlorides  of  the  fatty  acids,  but 
undergoes  the  same  kinds  of  change.  It  is  insoluble  in  water 
and  is  only  slowly  hydrolyzed  by  water.  It  is  a  colorless  liquid, 
boiling  at  i93.9°-i94.i°,  and  has  a  characteristic  pungent 
odor. 

Benzoyl  chloride  when  heated  with  alcohols  and  phenols, 
amino  and  imino  compounds  acts  upon  them  in  the  same  way 
that  acetyl  chloride  does,  and  forms  benzoyl  compounds :  — 

CeHs.OH  +  CeHs.COCl  =  CeHs.CO.OCeHs  +  HCl. 

Phenol  Phenyl  benzoate 

When  benzoyl  chloride  is  treated  with  an  aqueous  solution 
of  a  phenol  or  an  alcohol  containing  sodium  hydroxide,  it  gives 
a  benzoate : — 

CeHsOH  +  CeHsCOCl  +  NaOH 

=  CeHs.COOCeHs  +  NaCl  +  H2O. 

This  Baumann-Schotten  reaction,  as  it  is  called,  furnishes  a 
valuable  method  for  detecting  alcoholic  or  phenolic  hydroxyl 
groups. 

Benzamide,  C6H6.CONH2,  is  made  by  treating  benzoyl 
chloride  with  ammonia :  — 

CeHs.CO.Cl  +  H.NH2  +  NH3  =  CeHs.CO.NHa  +  NH4CI. 

It  crystallizes  in  plates,  melting  at  130°,  and  is  soluble  in  hot 
water.  It  acts  as  a  weak  acid  and  dissolves  in  alkalies,  as  the 
hydrogen  atoms  of  the  amino  group  are  replaceable  by  metals, 
owing  to  the  influence  of  the  benzoyl  group.  When  distilled 
with  phosphorus  pentoxide  benzamide  gives  benzonitrile :  — 

C6H6.CO.NH2  =  CeHs.CN  +  H2O. 

Benzanilide,  CeHs.CO.NH.CeHs)  analogous  to  acetanilide,  is 
made  by  the  action  of  benzoyl  chloride  on  aniline. 


4o6  THE  BENZENE  SERIES  OF  HYDROCARBONS 

Benzoyl  cyanide,  CeHsCOCN,  is  made  by  distilling  potassium 
cyanide  and  benzoyl  chloride : 

CeHs.COCl  +  KCN  =  CeHs.COCN  +  KCl. 

On  hydrolysis  benzoyl  cyanide  gives  the  acid  C6H6.CO.CO2H. 
This  is  known  as  henzoyljormic  acid.  It  is  of  interest,  for  the 
reason  that  one  of  its  derivatives  is  closely  related  to  indigo. 
(See  Isatin,  409.) 

Substitution  Products  of  Benzoic  Acid 

Benzoic  acid  readily  yields  substitution  products  when  treated 
with  the  halogens,  and  with  nitric  and  sulphuric  acids.  The 
products  obtained  by  direct  substitution  belong  to  the  meta 
series.  Thus,  when  chlorine  acts  upon  benzoic  acid,  the  main 
product  is  meta-chlorobenzoic  acid;  nitric  acid  gives  mainly 
meta-nitrohenzoic  acid;  and  sulphuric  acid  gives  mainly  meta- 
sulphohenzoic  acid. 

Note  for  the  Stddent.  —  Compare  this  with  the  result  of  the  direct 
action  of  the  same  reagents  on  toluene  and  on  nitrobenzene. 

Substituted  benzoic  acids  can  be  made,  also,  by  oxidizing  the 

corresponding  substituted  toluenes.     Thus,  the  chloro toluenes 

give  chlorobenzoic  acids ;  nitrotoluenes  give  nitrobenzoic  acids, 

etc:  — 

C6H4CI.CH3       give   C6H4CI.CO2H; 

C6H4(N02)CH3       "        C6H4(N02)C02H. 

The  three  nitrobenzoic  acids  and  the  corresponding  amino- 
benzoic  acids  may  serve  as  examples  of  the  mono-substitution 
products. 

Ortho-nitrobenzoic  acid,  NO2C6H4COOH.  —  Ortho-nitro- 
benzoic  acid  is  formed,  together  with  a  large  quantity  of  the 
meta  acid  and  some  of  the  para  acid,  by  treating  benzoic 
acid  with  nitric  acid.  It  is  best  made  by  oxidizing  ortho-nitro- 
toluene  with  potassium  permanganate,  and  by  oxidizing  ortho- 
nitrocinnamic  acid.  It  crystallizes  in  needles,  melts  at  147°, 
and  has  an  intensely  sweet  taste. 


ANTHRANILIC   ACID  407 

Meta-nitrobenzoic  acid,  NO2C6H4COOH,  is  the  chief  prod- 
uct of  the  action  of  nitric  acid  on  benzoic  acid.  It  crystallizes 
in  laminae,  or  plates,  and  melts  at  140°  to  141°. 

Para-nitrobenzoic  acid,  NO2C6H4COOH,  is  best  prepared 
by  oxidizing  para-nitrotoluene.  It  crystallizes  in  laminae, 
melts  at  238°,  and  is  much  less  soluble  in  water  than  the  ortho 
and  meta  acids. 

The  nitrobenzoic  acids  are  much  stronger  acids  than  benzoic 
acid,  owing  to  the  influence  of  the  nitro  group.  The  ortho  acid 
is  the  strongest  of  the  three,  while  the  meta  and  para  acids  have 
about  the  same  strength. 

The  determination  of  the  series  to  which  these  three  acids 
belong  is  effected  by  transforming  them  into  the  amino  acids ; 
and  these,  through  the  diazonium  compounds,  into  the  corre- 
sponding hydroxy  acids  of  the  formula  HOCeHuCOOH. 

Note  for  the  Stitdent.  — ■  Give  the  equations  representing  the  re- 
actions involved  in  passing  from  toluene  to  ortho-hydroxybenzoic  acid 
(salicylic  acid)  by  the  method  above  referred  to.     See  below. 

In  a  similar  way,  Hnes  of  connection  have  been  established 
between  the  three  hydroxy  acids  and  the  chloro-,  bromo-,  and 
iodobenzoic  acids. 

Note  for  the  Stxtoent.  —  What  are  the  reactions  ? 

The  three  hydroxy  acids,  on  the  other  hand,  have  been  made 
by  methods  that  connect  them  directly  with  the  three  dibasic 
acids  of  benzene,  C6H4(C02H)2,  which,  in  turn,  have  been  made 
from  the  three  xylenes. 

Anthranilic  acid,  ortho-aminobenzoic  acid,  HjNCeHiCOOH. — 
This  acid  can  be  made  by  reducing  ortho-nitrobenzoic  acid 
with  tin  and  hydrochloric  acid.  It  is  made  on  the  large  scale 
from  phthaUmide  by  Hofmann's  reaction  (257) :  — 

C(\  /CONH2 


C6H4/   ^NH  -I-  NaOH  =  CeHi/ 


^CQ/  \COONa 

PhthaUmide  Sodium  salt  of  phthalamic  acid 

CONH2  +  CI2  _    „       NH2  +  CO2 -I- H2O 

^""^^COONa  -I-  2  NaOH  ~       '^"^COONa  +  2  NaCl ' 


4o8  THE   BENZENE   SERIES  OF  HYDROCARBONS 

o-Nitrotoluene  is  converted  into  anthranilic  acid  by  boiling  with 
solutions  of  alkalies :  — 

It  is  also  formed  by  boiling  indigo  with  caustic  potash.  It  has 
already  been  stated  that  indigo  yields  aniline.  Now,  as  ortho- 
aminobenzoic  acid  is  also  obtained,  and  this  breaks  down  into 
anihne  and  carbon  dioxide, 

C6H4<„_  „=  C6H6NH2  +  CO2, 

it  seems  probable  that  the  aniline  is  a  secondary  product. 

Anthranilic  acid  melts  at  145°  It  is  soluble  in  water  and 
alcohol,  and  yields  salts  with  acids  and  with  bases  (compare 
with  aminoacetic  acid).  The  methyl  ester  is  a  constituent  of  the 
oil  of  orange  blossoms,  neroli  oU,  and  oil  of  jasmine.  It  is  made 
on  the  large  scale  from  anthrarulic  acid,  and  is  used  in  the  manu- 
facture of  perfumes. 

Like  other  amino  acids,  anthranilic  acid  is  an  inner  ammonium 

salt  and  should,  accordingly,  be  represented  by  the  formula 

CO 
C6H4<  _j.  >0.      When  it  is  diazotized  it  yields  an  inner  diazo- 

CO 

nium  salt  of  the  formula  C6H4< -^  >0.     When  this  is  boiled 

N2 

with  water  it  yields  salicyhc  acid :  — 

C6H4<^°>0  +  H20  =  CeH4<^2°^   +N2. 
iN2  Ori{0) 

The  solutions  of  anthranilic  acid  have  a  sweet  taste  and  a 
blue  fluorescence  which  is  characteristic  of  the  substance. 
Anthranihc  acid  is  reduced  when  treated  in  solution  in  amyl 
alcohol  with  sodium  to  hexahydroanthranihc  acid,  hexahydro- 
benzoic  acid  and  »-pimelic  acid,  HOOC.(CH2)5.COOH  (157). 
Anthranilic  acid  was  at  one  time  used  in  the  manufacture 
of   artificial    indigo.     It  is   used   in   the  manufacture  of  azo 


ISATIN  409 

dyes,  thiosalicylic  add,  and  of  the  methyl  ester  of  anthranilic 

acid. 

CO 
When  benzenediazonium  carboxylate,  C6H4<       >0,  which 

is  completely  analogous  to  benzenediazonium  sulphonate  (370) 
is  treated  with  dimethylaniline  it  forms  an  azo  compound :  — 

CO 

C6H4<jr>0+C6H5.N(CH3)2  =  HOOC.C6H4.N2.C6H4.N(CH3)2. 

2  Dimethylaminoazobenzenecarboxylatc 

This  azo  compound  is  known  as  Methyl  Red  and  is  a  very  valu- 
able indicator  in  acidimetry  and  alkalimetry.  It  is  used  espe- 
cially in  the  Kjeldahl  determination  of  nitrogen. 

CO 

Isatin,  C6H4<        >C0.  —  Isatin  is  obtained  by  the  oxidation 

of  indigo,  and  from  ortho-nitrobenzoic  acid  as  follows :  — 

The  nitro  acid  is  converted  into  the  acid  chloride,  the  chloride 
into  the  cyanide,  and  this  into  the  corresponding  carboxyl 
derivative,  which  is  the  ortho-nitro  derivative  of  benzoyl- 
formic  acid.  The  ortho-nitrobenzoylformic  acid  is  then  reduced 
to  the  amino  compound,  and  this  loses  water  and  gives  isatin. 
The  changes  are  indicated  thus :  — 


elii^ 


COOH  xCOCl  yCO.CN 

— >-  C6H4<'  — >-  CgKj^ 

NO2  \N02  \N02 


,CO.COOH  /CO.COOH 


C6H4<^  >■  CeHlv 


C6H4/      ^C.OH      or      C6H4/ 


NO2  \NH2 

/COk  /CO 


CO. 

N  ^  \NH/ 

The  formula  given  for  isatin  represents  it  as  an  anhydride 
of  ortho-aminobenzoylformic  acid.  The  formation  of  anhydrides 
of  dibasic  acids  is  a  characteristic  of  ortho  compounds.  Neither 
the  meta  nor  para  acid  gives  up  water.    We  shall  find  that  this 


4IO  THE   BENZENE   SERIES   OF  HYDROCARBONS 

fact  is  illustrated  in  the  case  of  the  dibasic  acids  of  benzene, 

the  only  one  that  yields  an  anhydride  being  ortho-phthalic  acid, 

COOTT  CO 

C6H4<  p^j-.TT, . ,  which  gives  phthaUc  anhydride,C6H4  <       >  O. 

This  ready  formation  of  anhydrides  from  ortho  compounds, 
taken  together  with  the  fact  that  the  meta  and  para  compounds 
do  not  yield  anhydrides,  is  an  argument  in  favor  of  the  view 
that  in  the  ortho  compounds  the  two  substituting  groups  are 
actuall)'  nearer  together  than  in  the  meta  and  para  compounds. 
(See  Maleic  acid,  293.) 

Isatin  crystaUizes  in  reddish  yellow,  monoclinic  prisms  melt- 
ing at  201°,  sparingly  soluble  in  water,  but  readily  in  alcohol. 
When  heated  with  phosphorus  pentachloride  it  gives  isatin 

chloride,  C6H4<^  - .  '^C.Cl,  and  when  this  is  reduced  with  zinc 

dust  and  acetic  acid  it  gives  indigo. 

Isatin  illustrates  the  phenomenon  of  tautomerism  (96). 
Towards  some  reagents  it  reacts  as  though  it  contained  hydroxyl ; 
towards  others  as  though  it  contained  the  imino  group  NH,  as 
represented  by  the  two  formulas :  — 

/ca  /CO. 

C6H4<         >C.OH      and      C6H4<  >C0. 

The  first  of  these  formulas  is  known  as  the  lactitn,  the  second 
as  the  lactam  formula.  The  evidence  is  in  favor  of  the  lactam 
formula  for  isatin,  but  derivatives  of  the  lactim  formula  are  also 
known.     Isatin  is  a  pseudo  acid  (340),  as  the  sodium  salt  has 

the  formula  C6H4<(*^^C0Na. 

Meta-  and  Para-aminobenzoic  acids  are  made  from  the  cor- 
responding nitro  acids  by  reductiojj.  The  ethyl  ester  of  ^-amino- 
benzoic  acid  has  anaesthetic  properties  and  is  called  afmsthesin. 
Novocaine,  a  very  valuable  local  anaesthetic,  is  the  diethylamine 
derivative  of  anaesthesin,  H2NC6H4C02C2H4N(C2H6)2HC1. 

Hippuric  acid,  benzoylaminoacetic   acid,  CH2<S^^J?^^  -a 

JNHOCCeHs, 

occurs  in  the  urine  of  herbivorous  animals.     A  small  quantity 


SULPHOBENZOIC  ACIDS  41 1 

is  found  in  normal  human  urine.     If  toluene  or  benzoic  acid 
is  taken  with  the  food,  it    appears   as  hippuric   acid  in  the 
urine,  whUe  derivatives  of  benzoic  acid  appear  as  derivatives 
of  hippuric  acid. 
Hippuric  acid  has  been  made  synthetically : 
I.   By  heating  glycine  with  benzoic  acid  to  160° :  — 


CeHs.COlOH 


jHlHN  NH.CO.C6H5 

Hippuric  acid 

2.  By  heating  benzamide  with  chloroacetic  acid :  — ■ 
C6H6.CO.NHH  +  Ho2>CH2  =  ^^^'•^2^>CH2  +  HCl. 

Hippuric  acid 

3.  By  heating  glycine  with  benzoyl  chloride :  — ■ 
CH,<^^2  +  C1.0CCeH5=  CH,<^;^0^«^^  +  HCl. 

Hippuric  acid 

Hippuric  acid  crystallizes  from  water  in  long,  orthorhombic 
prisms  which  melt  at  187". 

It  is  hydrolyzed  into  benzoic  acid  and  glycine  by  boiling 
with  aUsahes,  and  more  readily  by  boiling  with  dilute  acids  :  — 

CH2<„|-.TT  +H2O  =  CH2<„„  „  +  CeHj.COjH. 

Note  for  the  Student.  —  What  relation  does  hippuric  acid  bear  to 
benzamide  ?  What  is  the  effect  of  boiling  acid  amides  with  alkalies  ?  Write 
the  equation  for  the  hydrolysis  of  benzamide,  and  compare  it  with  that  for 
the  hydrolysis  of  hippuric  acid. 

COOH 

Sulphobenzoic  acids,  C6H4<  . —  When  sulphuric  acid 

SO2OH 

or  sulphur  trioxide  acts  upon  benzoic  acid  the  principal  product  is 

meta-sulphobenzoic  acid.    The  ortho  and  para  acids  are  made 

by  oxidizing  ortho-  and  para-toluenesulphonic  acids :  — ■ 

^'^<  SO2OH  -^'-^<  SO2OH  • 


412  THE  BENZENE   SERIES   OF  HYDROCARBONS 

o-Sulphohenzoic  acid  when  anhydrous  mehs  at  130°.  It  re- 
sembles phthahc  acid  (415)  in  its  reactions.  Thus  it  forms  an 
anhydride,  melting  at  129.5°,  ^i^d  ^^  imide  (see  below).  With 
phosphorus  pentachloride  it  gives  two  dichlorides,  melting  at 

CO  CI 

40°   and    79°,  which    have    the    symmetrical,   C6H4<        ' 

bUjCi 

<CC12V 
^O,  formulas  (417). 
SO2/ 

When  the  anhydride  or  the  chlorides  of  o-sulphobenzoic  acid 

are  heated  with  phenols  they  give  the  phenol  sulphonphthaleins, 

which  are  completely   analogous  to  the  phthaleins  (472)  and 

are  largely  used  as  indicators  and  in  determining  hydrogen-ion 

concentration. 

When  the  amide  of  o-toluenesulphonic  acid,  H3CC6H4SO2NH2, 

is  oxidized  with  potassium  permanganate  it  gives  the  potassium 

salt  of  o-sulphaminobenzoic  acid,  KOOCC6H4SO2NH2.     When 

the   solution  is  acidified    the    o-sulphaminobenzoic  acid  first 

formed  loses  a  molecule  of  water  and  gives  benzoic  sulphinide, 

CO 
C6H4<   •    >NH,  which  is  the  imide  of  o-sulphobenzoic  acid, 
0O2 

CO 
analogous  to  succinimide,  C2H4<    _>NH. 

Benzoic  sulphinide  has  about  five  hundred  times  the  sweeten- 
ing power  of  cane  sugar,  and  in  consequence  it  has  come  into 
extensive  use  as  a  sweetening  agent.  It  has  no  food  value  and 
is  eliminated  unchanged  from  the  body  by  the  kidneys.  In 
commerce  it  is  known  as  saccharin.  It  is  a  crystallized  sub- 
stance rather  difficultly  soluble  in  water,  but  readUy  soluble 
in  alcohol  and  ether.  It  is  soluble  in  acetone,  and  crystallizes 
beautifully  from  this.     It  melts  at  223°-2  24° 

On  the  large  scale  benzoic  sulphiiiide  is  made  as  foUows: 
Toluene  is  treated  with  chlorosulphonic  acid,  and  a  mixture 
of  about  equal  parts  of  the  /»-toluenesulphonyl  chloride  and 
the  ortho  product  is  obtained.  The  ortho  chloride  is  liquid  and 
can  be  separated  from  the  sohd  para  chloride.  When  treated 
with  ammonia  it  gives  o-toluenesulphonamide.     This  is  con- 


a-TOLUIC   ACID,   PHENYLACETIC    ACID  413 

verted  into  the  amide  of  o-sulphobenzoic  acid  by  oxidation  with 
sodium  bichromate  and  sulphuric  acid,  and  by  loss  of  water  this 
gives  the  sulphinide. 

CbHbCHj — ^H3CC6H4S02Cl(o) — J-H3CC6H4S02NH2(o) 

CO 
— >-HOOCC6H4S02NH2(o)  — >■  QH4<cr;  >NH. 

bU2 

The   hydrogen   atom  of  the   imino   group   has   acid   prop- 

CO 

erties.    The  sodium  salt  C6H4<_  >NNa  is  soluble  in  water 

0U2 

and  is  known  as  soluble  saccharin.  Commerical  saccharin 
contains  only  a  trace  of  para-sulphaminobenzoic  acid.  Over 
half  a  million  pounds  of  saccharin  were  produced  in  the  United 
States  in  1919. 

Toluic  acids,  C8H8O2.  —  There  are  four  acids  of  this  formula 
known,  viz.,  the  three  carboxyl  derivatives  of  toluene,  in  which 
the  carboxyl  replaces  a  hydrogen  atom  in  the  benzene  ring, 
H3CC6H4COOH,  and  an  acid  obtained  from  toluene  by  sub- 
stituting carboxyl  for  a  hydrogen  atom  of  the  methyl, 
C6H5.CH2.CO2H.  Ortho-,  meta-,  and  para-toluic  acids  are  made 
by  oxidizing  the  corresponding  xylenes  with  nitric  acid :  — 

CeH4<^^^  +  30  =  C^<qqI^  +  H2O. 

They,  as  well  as  their  derivatives,  of  which  many  are  known, 
have  been  studied  carefully.  The  substituted  toluic  acids  can 
be  made  either  by  direct  treatment  of  the  acids  with  reagents 
or  by  oxidizing  substituted  xylenes :  — 

C6H3(N02)<^JJ'  +  30  =  C6H3(N02)<^2'^  +  H2O. 

Nitroxylenes  Nitrotoluic  acids 

o-Toluic  acid,  phenylacetic  acid,  C6H6.CH2.CO2H.  —  Just  as 
benzoic  acid  is  regarded  as  phenylformic  acid,  so  a-toluic  acid 
is  phenylacetic  acid.  It  is  obtained  by  reducing  mandelic  or 
phenylglycolic  acid,  C6H6CH(OH)COOH,  which  is  formed  when 
amygdalin  is  treated  with  hydrochloric  acid.  It  is  prepared 
from  toluene  by  converting  it  into  benzyl  chloride,  from  which 


414  THE   BENZENE   SERIES  OF  HYDROCARBONS 

the  cyanide  is  made  by  boiling  with  potassium  cyanide.  The 
cyanide  is  then  hydrolyzed  and  yields  the  acid :  — 

CsHs.CHs        +  CI2       =  C6H5.CH2CI         +  HCl ; 

Soiling  toluene  Benzyl  chloride 

C6H5.CH2CI    +  KCN  =  CeHs.CHjCN       +  KCl; 

Benzyl  cyanide 

C6H5.CH2CN  +  2  H2O  =  C6H6.CH2.cO2H  +  NH3. 

a-Toluic  acid 

The  acid  crystallizes  in  thin  laminae,  and  melts  at  76.5°. 

Note  for  the  Student.  —  What  would  you  expect  o-toluic  acid  to 
yield  when  oxidized?  (403.)  What  would  you  expect  it  to  yield  when 
distilled  with  lime?  \^'hat  would  you  expect  the  three  toluic  acids, 
HaCCjHjCOOH,  to  yield  by  oxidation,  and  when  distilled  with  lime? 
(319.) 

CH 
Oxindol,  C6H4<         >CO,    is    obtained    by    reduction    of 

isatin  and  of  dioxindol  (487) ;  and  also  from  o-amino- 
a-toluic  acid  by  loss  of  water,  in  the  same  way  that  isatin  is 
formed  from  o-aminobenzoylformic  acid.  It  melts  at  120°. 
When  a-toluic  acid  is  treated  with  nitric  acid,  the  para- 
and  ortho-nitro  acids  are  formed.  The  latter  is  reduced  by 
means  of  tin  and  hydrochloric  acid,  when  oxindol  is  at  once 
obtained:  — 

c»H^<m£r''  =  c^«^<m>co  +  H20. 

Or  thoamin 0-0- toluic  acid  Oxindol 

Mesitylenic  acid,  (CH3)2C6H3COOH.  —  This  acid  has  already 
been  referred  to  as  the  first  product  of  oxidation  of  mesitylene. 
It  is  the  only  monobasic  acid  that  has  been  obtained  by  the 
oxidation  of  mesitylene ;  and  it  is  the  only  one  possible.  By 
distillation  with  lime,  it  yields  metaxylene.  Further  oxidation 
converts  it  into  uvitic  and  trimesitic  acids  (323). 

Note  for  the  Sttjdent.  —  Of  what  special  significance  is  the  forma- 
tion of  metaxylene  from  mesitylenic  acid?  How  many  monobasic  acids 
does  pseudocumene  give  when  oxidized  ?  How  many  does  hemimelUthene 
give?    What  do  these  acids  give  when  distilled  with  limp? 


PHTHALIC  ACID,   ORTHO-PHTHALIC  ACID  415 

Hydrocinnamic     acid,    P-phenylpropionic     acid,     CeHs.CHz. 

CH2.CO2H.  —  This  acid  is  obtained  by  treating  cinnamic 
acid  with  nascent  hydrogen :  — 

CeHs.CHrCH.COzH  +  H2  =  C6H5.CH2.CH2.CO2H. 

cinnamic  acid,  Hydrocinnamic  acid, 

/3-Phenylacrylic  acid  ^-Phenylpropionic  acid 

It  is  also  made  by  starting  with  ethyl  benzene,  C6H6.C2H6, 
and  carrying  out  the  same  reactions  that  are  necessary  to  trans- 
form toluene  into  a-toluic  acid  (414).  It  is  a  product  of  the 
putrefaction  of  several  proteins,  such  as  albumin  and  fibrin  and 
of  the  brain  substance.  It  crystallizes  from  water,  in  long 
needles,  which  melt  at  48°.  It  yields  benzoic  acid  when  oxidized 
with  chromic  acid,  and  ethylbenzene  when  distilled  with  lime. 

Ortho-aminohydrocinnamic  acid,  H2NC6H4.CH2CH2CO2H. — 
This  acid  is  prepared  from  hydrocinnamic  acid  in  the  same  way 
that  ortho-amino-a-toluic  acid  is  made  from  a-toluic  acid.  It 
is  not  known  in  the  free  state,  but,  like  the  ortho-amino  deriv- 
atives of  benzoyKormic  and  of  a-toluic  acids,  it  loses  water,  and 
forms  an  anhydride,  hydrocarbostyril. 

!^  *^C.OH,  is  made  by  treating 

ortho-nitrohydrocinnamic  acid  with  tin  and  hydrochloric  acid. 
It  crystallizes  in  prisms,  melting  at  160°.  It  is  interesting 
chiefly  for  the  reason  that  it  is  closely  related  to  the  important 
compound  quinoline  (507).  When  heated  with  phosphorus 
pentachloride,  hydrocarbostyril  is  converted  into  dichloro- 
quinoline,  which  gives  quinoUne  on  reduction. 

Dibasic  Acids,  C„H2,^io04 

The  simplest  acids  of  this  group  are  the  three  phthalic  acids, 

which  are  the  dicarboxyl  derivatives  of  benzene,  belonging  to 

the  ortho,  meta,  and  para  series. 

CO  H 
Phthalic  acid,  ortho-phthalic  acid,  C6H4<  _ _  ^_.    .  — PhthaHc 

C02H(o) 

acid  was  the  first  of  the  three  acids  of  this  composition  dis- 
covered;   and,  as  it  was  obtained  from   naphthalene,  it  was 


41 6  THE   BENZENE  SERIES   OF  HYDROCARBONS 

named  phthalic  acid.  It  is  manufactured  on  the  large  scale  by 
oxidizing  naphthalene  by  means  of  concentrated  sulphuric  acid 
in  the  presence  of  a  little  mercuric  sulphate  at  a  temperature  of 
220°-30o°.  (See  equation  below.)  It  can  be  made  from  alizarin 
andpurpurin;  and  from  ortho-toluic  acid,  HsCCeH^COOHCo), 
by  oxidation  with  potassiiun  permanganate. 

PhthaUc  acid  forms  orthorhombic  crystals,  which  melt  at 
213°  or  lower,  for,  when  heated,  it  breaks  down  gradually, 
even  below  the  melting  point,  into  water  and  the  anhydride, 
which  melts  at  131°.  Distilled  with  lime,  it  yields  benzene; 
though,  by  selecting  the  right  proportions,  benzoic  acid  can  be 
obtained :  — 

^  „  ^COaH  _  CeHe  „  „     .CO2H  _  CeHs.CO^H 

^'^^COaH  ~  +  2  CO2'   '^'^^C02H  +  CO; 

Phthalic  acid  is  a  much  stronger  acid  than  either  of  its  isomers 
(compare  oxalic  acid  and  its  homologues).  It  is  about  20  times 
as  strong  as  benzoic  acid. 

By  boiling  orthoxylene  with  nitric  acid  it  yields  ortho-toluic 

acid,  H3CC6H4COOH(o) ,  and  this  is  oxidized  to  phthalic  acid 

by  treatment  with  potassium  permanganate. 

CO 
Phthalic  anhydride,  C6H4<>0,    is    formed    by    heating 

phthaHc  acid.  It  forms  long  needles,  which  melt  at  131°. 
Heated  with  phenols,  it  forms  the  compounds  known  as  phthal- 

CH 

eins  (472).     On   reduction   it   gives  phthalid,  C6H4<    ^>0. 

This  is  the  anhydride  or  lactone  of  o-hydroxymethylbenzoic 
acid,  HOCH2C6H4COOH. 

Phthahc  anhydride  is  now  made  in  this  country  on  the  large 
scale  by  passing  the  vapor  of  naphthalene  and  air  over  a  catalyst 
(vanadium  oxide)  heated  to  the  proper  temperature :  — 

+  90=  >0  +  2  C02  +  2  H2O. 

Naphthalene  Phthalic  anhydride 


ISOPHTHALIC  ACID,   META-PHTHALIC  ACID  417 

Nearly  800,000  pounds  were  made  in  the  United  States  in  1920 
by  this  method.  It  is  used  in  the  manufacture  of  the  phthalein 
dyes,  of  anthraquinone,  and  of  phenolphthalein. 

Phthalyl   chloride   is   formed  by   the  action   of  phosphorus 
pentachloride  on  phthaUc  anhydride.     It  is  known  in  two  forms : 

COCl  /CCI2 

C6H4<^Q^j  and  CeH,^^  >0. 

I.  j-Phthaly]  chloride  z.   H-Phthalyl  chloride 

The  melting  point  of  i  is  i5°-i6°,  that  of  2  is  88°-89°.  The  two 
forms  are  very  readily  converted  into  one  another;  thus,  merely 
warming  with  aluminium  chloride  converts  the  symmetrical 
(i)  into  the  unsymmetrical  chloride  (2),  while  heating  on  the 
water  bath  for  several  hours  transforms  the  unsymmetrical  into 
the  symmetrical  chloride. 

Phthalic  anhydride  resembles  succinic  anhydride  (162)  closely. 
Thus,  when  heated  with  alcohols  it  gives  the  acid  phthalates :  — 

<  POOO  TT 

>0  +   HO.C2H6    =    C6H4<p^QTT  , 

and  with  ammonia  it  yields  phthalimide :  — ■ 

/CO  /CO 

CeH/    >0  +  H2N.H  =  CbH/    >NH  +  H2O. 

\co  \co 

Phthalimide 

Diethyl  phthalate,  C6H4(COOC2H5)2,  made  by  heating  phthahc 

anhydride  with  a  3  per  cent  solution  of  hydrochloric  acid  in  ethyl 

alcohol,  is  used  in  denaturing  alcohol  for  the  manufacture  of 

perfumes,  lotions,  etc.     It  is  a  liquid,  boiling  at  295°. 

COOK 
Potassium  acid  phthalate,  C6H4<„„„„,  is  used  in  making 

standard  solutions  in  acidimetry  and  alkaUmetry  and  in  de- 
termining hydrogen-ion  concentration. 

CO  H 

Isophthalicacid,meta-phthalicacid,  C6H4<  ,      ,isformed 

C02H(ni) 

by  oxidizing  either  metaxylene  or  meta-toluic  acid  with  chromic 


41 8  THE  BENZENE  SERIES  OF  HYDROCARBONS 

acid;  by  distilling  meta-benzenedisulphonic  acid  with  potas- 
sium cyanide,  and  boiling  the  resulting  dicyanide  with  £ 
solution  of  alkaU. 

Note  for  the  Student.  —  Write  the  equations  representing  the  reac- 
tions involved  in  passing  from  meta-benzenedisulphonic  acid  to  isophthalic 
acid.  Into  which  dihydroxybenzene  is  this  same  disulphonic  acid  con- 
verted by  fusing  it  with  caustic  potash? 

The  acid  is  formed,  further,  by  heating  the  potassium  salt 
of  meta-sulphobenzoic  acid  with  sodium  formate :  — 

C6H4<^5*'f-.   .  +H.C02Na  =  C6H4<^°'^  ,   ,  +  HKSO3. 
S03K(w)  L02Na(w) 

Potassium  sulpho-  otassium  sodium 

benzoate  isophthalate 

This  reaction  is  of  importance,  for  the  reason  that  the  same 
sulphobenzoic  acid,  which  is  thus  converted  into  isophthalic 
acid,  can  also  be  converted  into  one  of  the  three  hydroxy- 
benzoic  acids;  and  thus  connection  is  established  between  the 
latter  and  isophthalic  acid  and  metaxylene. 

Isophthalic  acid  crystallizes  in  fine  needles  from  water.  It 
melts  above  300°,  and  is  not  converted  into  an  anhydride. 

CO2H 

Terephthalic    acid,    para-phthaUc    acid,    C6H4<_,_^„,  ,. — 

C02H(^) 

Terephthahc  acid  is  formed  by  oxidation  of  the  oU  of  tur- 
pentine,' p-cymene,  paraxylene,  and  para-toluic  acid;  and  by 
heating  a  mixture  of  potassium  para-sulphobenzoate  and  so- 
dium formate :  — 

^^«^<Sk(^)  +  «-C«^Na   =  C^4^^^^^^^  +  HKSO3. 

Potassium  para-  Potassium  sodium 

sulphobenzoate  terephthalate 

Para-sulphobenzoic  acid  is  converted  into  one  of  the  three 
hydroxybenzoic  acids  by  caustic  potash.  In  the  para  as  well 
as  the  meta  series,  the  lines  of  connection  indicated  below  have 
been  established :  — 

'  The  prefix  lere  is  derived  from  the  Latin  terebinthinus,  turpentine. 


PHENOL  ACIDS  41 9 

^'^''^  co^  '*~  ^'^<  SO3H  9^^<  chI 

j:     CO.H      L  CH3 


t 


CeH4<Qjj    ^-    C6H4<gQ^jj 

Terephthalic  acid  is  a  solid  that  is  practically  insoluble  in 
water.  It  sublimes  without  melting  and,  like  isophthaUc  acjd, 
yields  no  anhydride. 

Hydrophthalic  Acids 

Di-,  tetra-,  and  hexa-hydrophthalic  acids  have  been  made 
from  all  three  phthalic  acids  by  reducing  them  with  sodium 
amalgam.  The  di-  and  tetra-hydro  acids  act  like  the  un- 
saturated acids,  whUe  the  hexahydro  acids  resemble  the  satu- 
rated fatty  acids. 

Hexabasic  Acid 

Mellitic  acid,  C6(C02H)6.  — ^This  acid  occurs  in  nature  in  the 
form  of  the  aluminium  salt,  as  the  mineral  honey-stone  or  mellite. 
The  mineral  is  rare,  and  is  found  in  beds  of  Hgnite.  Mellitic 
acid  has  been  made  by  direct  oxidation  of  graphite  with  potas- 
sium permanganate,  and  by  oxidation  of  hexamethylbenzene, 
C6(CH3)6.  By  heating  with  sodahme  it  is  converted  into  ben- 
zene and  carbon  dioxide :  — 

CeCCOalTle  =  CeHs  +  6  CO2. 

Phenol  Acids,  or  Hydroxy  Acids  of  the  Benzene  Series 

It  will  be  remembered  that  the  alcohol  acids  or  hydroxy  acids 
of  the  parafl&n  series  form  an  important  class,  including  such 
compounds  as  glycoUc,  lactic,  malic,  tartaric,  and  citric  acids. 
The  peculiarity  of  these  compounds  is  their  double  character. 
They  are  at  the  same  time  alcohols  and  acids,  though  the  acid 


420  THE   BEXZENE   SERIES   OF  HYDROCARBONS 

properties  are  more  prominent  than  the  alcoholic.  The  hy- 
droxy acids  of  the  benzene  series  bear  the  same  relations  to  the 
benzene  hydrocarbons  that  the  hydroxy  acids  already  studied 
bear  to  the  paraffins.  The  simplest  are  those  which  contain  one 
hydroxyl  and  one  carboxyl,  having  the  formula  HOCeHjCOOH. 

MONO-HYDROXYBENZOIC   ACIDS,    CvHeOs 

Salicylic  acid,  ortho-hydroxybenzoic  acid,  HOC6H4COOH(o), 

in  the  form  of  the  methyl  ester  is  present  in  the  oU  of  wintergreen, 
prepared  from  the  blossoms  of  Gaultheria  procumbens.  It  gets 
its  name  from  the  glucoside  saUcin,  present  in  the  bark  and 
leaves  of  the  willow  (Salix).  It  is  formed  in  a  niunber  of  ways, 
among  which  the  following  should  be  specially  mentioned : 

1.  By  converting  ortho-aminobenzoic  acid  into  the  inner 
diazonium  salt,  and  boiling  with  water  (408). 

Note  for  the  Student.  —  Give  the  equations  representing  the  re- 
actions. 

2.  By  fusing  the  potassium  salt  of  ortho-sulphobenzoic  acid 
with  caustic  potash. 

Note  for  the  Student.  —  Write  the  equation. 

3.  Salicylic  acid  is  manufactured  by  heating  dry  sodium  phe- 
nolate  in  an  autoclave  with  carbon  dioxide  under  a  pressure  of 
8  to  10  atmospheres  at  ioo°-i45°  At  100°  the  carbon  dioxide 
is  rapidly  absorbed,  with  the  formation  of  sodium  phenyl  car- 
bonate, CeHjO.CO.ONa,  which  then  undergoes  molecular  re- 
arrangement into  sodium  salicylate :  — 

O.COONa  r  H  ^OH 

Sodium  phenyl  carbonate  Sodium  salicylate 

the  -COONa  group  entering  the  benzene  ring,  and  the  displaced 
hydrogen  atom  taking  its  place  as  shown  above. 

4.  By  heating  phenol  with  tetra-chlorome thane  and  an  alco- 
holic solution  of  potassium  hydroxide  :  — 

C6H5OH  +  CCI4  +  6  KOH  =  C6H4<^Q  J.  +  4  KCl  +  4  H2O, 


SALICYLIC   ACID,   ORTHO-HYDROXY BENZOIC   ACID      421 

Chloroform  acts  on  phenol  in  alkaline  solution  to  give  sali- 
cylic aldehyde  and  ^-hydroxybenzaldehyde  :  — 

(i)   HO.C6H4H  +  CI.CHCI2      =HO.C6H4.CHCl2  +  HCl 

(2)  HO.C6H4.CHCI2+2  NaOH  =  HO.C6H4.CH(OH)2+  2  NaCl 

(3)  HO.C6H4.CH(OH)2  =HO.C6H4.CHO  +  H2O. 

Salicylic  aldehyde  and 
^-hydroxybenzaldehyde 

The  two  aldehydes  are  separated  by  distillation  in  steam,  the 
ortho  aldehyde  being  volatile  in  steam  whUe  the  para  product 
is  not.  This  reaction  (the  Tiemann  and  Reimer  reaction)  is 
used  for  the  purpose  of  introducing  an  aldehyde  group  into 
phenols.  From  the  aldehydes  the  acids  can  be  obtained  by 
oxidation. 

5.  By  saponifying  the  methyl  salicylate  found  in  oU  of  winter- 
green  :  — 

CsH4<2q^j^jj^  +  KOH  =  C6H4<°Q^^  +  CH3OH. 

Salicylic  acid  crystallizes  from  hot  water  in  fine  needles.  It 
melts  at  159°.  When  heated  with  sodalime,  it  breaks  down 
into  phenol  and  carbon  dioxide  :  — • 

C6H4<°Q  jj=    C6H5.OH  +  CO2. 

Heated  alone  it  gives  phenyl  salicylate  (salol)  and  xanthone :  — 
OT-T  01T 

Phenyl  salicylate  (salol) 

^'^^^COOCeHs  =  CeH4<^Q>CeH4  +  H2O. 

Xanthone 

With  ferric  chloride,  its  aqueous  solution  gives  a  characteristic, 
dark  violet-blue  color,  provided  no  free  mineral  acid  is  present. 
Free  salicylic  acid  is  antiseptic,  preventing  putrefaction  and 
fermentation.  It  is  therefore  used  for  preserving  foods.  It  is 
also  used  extensively  in  medicine,  especially  in  rheumatism, 
and  as  an  antipyretic. 


422  THE  BENZENE  SERIES  OF  HYDROCARBONS 

With  bromine  water,  salicylic  acid  gives  a  precipitate  of 
tribromophenol  bromide,  C6H2Br3(OBr), 2,4,6,  and  this  reaction 
is  used  for  the  quantitative  determination  of  salicylic  acid :  — 

HO.C6H4.COOH  +  8  Br  =  (BrO).C6H2Br3  +  CO2  +  4  HBr. 

When  reduced  in  amyl  alcohol  solution  with  metallic  sodium 
salicylic  acid  is  converted  into  pimeUc  acid,  HOOC(CH2)6COOH. 

The  methyl  ester  of  salicylic  acid,  HO.C6H4.CO.OCH3,  is  the 
chief  constitutent  of  oil  of  wintergreen.  It  is  made  artificiaOy 
by  heating  two  parts  of  salicylic  acid,  two  parts  of  methyl 
alcohol,  and  one  part  of  sulphuric  acid,  and  is  used  in  perfumery 
and  in  flavoring  confectionery,  chewing  gums,  etc.  About 
900,000  pounds  were  made  in  the  United  States  in  1919. 

Large  quantities  of  salicylic  acid  are  used  in  medicine  and  in 
the  preparation  of  synthetic  remedies  {Aspirin,  Salol,  etc.)  and 
of  the  artificial  oil  of  wintergreen.  Nearly  3  million  pounds 
of  the  U.  S.  P.  grade  of  salicyHc  acid  were  made  in  the  United 
States  in  1920.  The  technical  sahcylic  acid,  of  which  nearly 
4  million  pounds  were  made  in  the  United  States  in  1920,  is 
used  in  the  manufacture  of  azo  dyes  {Alizarin  Yellow,  Chrysamine 
G,  Cotton  Yellow,  etc.)  and  in  the  preparation  of  aminosalicylic 

acid,   H2N.C6H3<^TT      ,    used   in   the    manufacture    of   the 

valuable  diamond  black. 

Salicylic  acid  forms  salts  of  the  general  formula  HOC6H4COOM ; 
and,  with  the  alkalies,  compounds  in  which  both  the  phenol 
hydrogen  and  the  acid  hydrogen  are  replaced   by  metals,  as 

KOCeHiCOOK.  The  basic  calcium  salt,  C6H4<^_  >Ca+H20, 

CO2 

is  very  difficultly  soluble  in  water,  and  is  converted  by  carbon 

dio3dde  into  the  soluble  salt  fC6H4<        J  Ca.     Salicylic  acid 

forms  ethereal  salts  of  the  general  formula  HOCeliiCOOR,  of 
which  methyl  salicylate,  HOC6H4COOCH3,  is  the  best-known 
example.  It  forms,  also,  ether  adds  of  the  general  formula 
ROC6H4CO2H ;  and,  finally,  ether  esters  of  the  general  formula 
ROC6H4CO2R. 


PHENYL  SALICYLATE  423 

Acetylsalicylic  acid  is  used  in  medicine  under  the  name  aspirin. 
It  is  made  by  heating  salicylic  acid  with  acetic  anhydride. 
1,708,000  pounds  were  made  in  the  United  States  in  1920. 

Phenyl  salicylate  (salol),  HOC6H4CO2C6H5,  is  formed  when 
salicylic  acid  is  heated  alone  to  2oo°-22o°  (421)  and  when 
sodium  salicylate,  sodium  phenolate,  and  phosphorus  oxychloride 
are  heated  to  i2o°-i25° :  — 

2  CeHsONa  +  2  HOC6H4COONa  +  OPCI3 

=  3  NaCl  +  NaPOs  +  2  HOC6H4COOC6H5. 

It  is  a  solid  that  melts  at  43°  It  is  extensively  used  as  an 
antiseptic,  antipyretic,  and  antirheumatic. 

That  salicyhc  acid  belongs  to  the  ortho  series  is  clear  from  the 
following  facts : 

Ortho-toluenesulphonic  acid  has  been  converted  into  ortho- 
sulphobenzoic  acid,  and  this  into  salicyhc  acid.  Further,  the 
same  toluenesulphonic  acid  has  been  converted  into  ortho- 
toluic  acid,  which,  by  oxidation,  yields  phthalic  acid :  — 

Ortho-toluenesulphonic  Ortho-sulphobenzoic 

acid  acid 

Potassium  salicylate 

^3)  CeH.<so^^(^)    +  KCN  =  CeH.<^^;^^      +  K.SO3 ; 

Ortho-tolyl  cyanide 

(4)     C6H4<^JJ'  +  2  H20=  C6H4<^Q^'jj^^^     +  NH3; 

Ortho-toluic  acid 

(s)  c.^^<coko)  +  ^  ^    =  ^^^^<cSS(.)  +  H^o- 

Phthalic  acid 


424  THE   BENZENE   SERIES   OF   HYDROCARBONS 

Thiosalicylic  acid,  HS.C6H4.COOH(o),  is  made  from  anthra- 
nilic  acid  by  diazotizing  it  and  decomposing  the  diazonium 
carboxylate  with  sodium  disulphide :  — 

2  C6H4<^0  +  NajSz  =  C6H4/         \C6H4.COONa  +  2  N2. 


Yo  ^COONa 

When  this  dithio  acid  is  reduced  it  gives  thiosalicylic  acid :  — 

<S — S\  /SH 

\C6H4.COONa  +  H2    =    2  C6H4< 
COONa  \COONa 

ThiosaUcylic  acid  crystallizes  in  sulphur  yellow  plates  melting 
,  at  i63°-i64°  and  soluble  in  hot  water.  When  oxidized  it  gives 
o-sulphobenzoic  acid.  It  is  made  on  the  large  scale  by  the  above 
method  and  is  used  in  making  thioindigo. 

Meta-hydroxybenzoic  acid,  oxybenzoic  acid,  HOC6H4C02H(m) . 
—  This  acid  is  made  from  meta-aminobenzoic  and  meta-sulpho- 
benzoic  acid  by  the  usual  reactions. 

It  crystallizes  from  water  in  needles  united  to  form  wart- 
like masses.  It  gives  no  color  with  ferric  chloride.  Its  con- 
nection with  meta-phthalic  (isophthalic)  acid  and  metaxylene 
is  shown  by  means  of  the  transformations  already  referred 
to  (419) ;  that  is  to  say,  the  same  sulphobenzoic  acid  which, 
by  fusing  with  caustic  potash,  yields  hydroxybenzoic  acid,  by 
fusing  with  sodiiun  formate  yields  isophthalic  acid.  Therefore 
oxybenzoic  acid  is  a  meta  compound. 

Para-hydroxybenzoic  acid,  HOCeHjCOOHC/*)  -1-  H2O,  is 
formed  from  the  corresponding  amino  and  sulphobenzoic  acids ; 
by  treating  various  resins  with  caustic  potash;  from  anisic 
acid  (425)  by  heating  with  hydriodic  acid;  and  by  heating 
potassium  phenolate  in  a  current  of  carbon  dioxide  to  220°. 

Note  for  the  Student.  —  Note  the  fact  that,  while  sodium  phenolate, 
when  heated  in  carbon  dioxide,  yields  salicylic  acid,  potassium  phenolate, 
under  the  same  circumstances,  yields  para-hydroxybenzoic  acid. 

The  reasons  for  regarding  para-hydroxybenzoic  acid  as  a  mem- 
ber of  the  para  series  are  similar  to  those  which  show  that  oxy- 


PROTOCATECHUIC   ACID  425 

benzoic  acid  is  a  meta  compound.  The  same  sulphobenzoic  acid 
that  yields  para-oxybenzoic  acid  also  yields  terephthaUc  acid. 

Anisic  acid,  ^-methoxybenzoic '  acid,  H3COC6H4C02H(/i)  is 
formed  by  the  o.xidation  of  anethol,  HsCOCeHiCHrCHCHs, 
the  chief  constituent  of  the  oil  of  anise  seed.  It  is  also  made 
by  heating  para-hydroxybenzoic  acid  with  caustic  potash  and 
methyl  iodide  and  saponifying  the  methyl  ester  thus  formed. 
As  the  formula  indicates,  it  is  the  methyl  ether  of  para- 
hydroxybenzoic  acid.  It  is  isomeric  with  methyl  salicylate. 
By  boiling  with  a  solution  of  caustic  alkali  the  latter  is  sapon- 
ified, while  anisic  acid  is  not.  When  anisic  acid  is  distilled  with 
lime,  anisol  is  formed. 

DiHYDROXYBENZOIC  ACIDS,   C7H6O4 

Protocatechmc  acid,  3,4-dihydroxybenzoic  acid, 
(HO)2C6H3C02H, 

is  a  frequent  product  of  the  fusion  of  resins  with  alkali.  The 
following  substances,  among  others,  yield  it :  oil  of  cloves, 
piperic  acid,  catechin,  gum  benzoin,  asafoetida,  vanillin,  etc. 
It  is  made  from  sulpho-w-hydroxybenzoic  acid,  and  from 
sulpho-^i-hydroxybenzoic  acids  by  fusing  with  caustic  potash. 

Note  for  the  Stxtoent.  —  What  analogy  is  there  between  the  fact 
that  protocatechuic  acid  is  formed  from  sulpho-OT-hydroxybenzoic  acid 
and  from  sulpho-^-hydroxybenzoic  acid,  and  the  fact  that  pseudocumene 
is  formed  from  bromometaxylene  and  from  bromoparaxylene  ?  What  con- 
clusion may  be  drawn  regarding  the  relations  of  the  two  hydroxyl  groups, 
and  the  carboxyl  in  protocatechuic  acid  ? 

It  is  made  synthetically  together  with  2,3-dihydroxybenzoic 
acid  by  heating  pyrocatechol  with  a  solution  of  ammonium 
carbonate. 

By  distillation  with  lime,  protocatechuic  acid  breaks  down 
into  pyrocatechol  and  carbon  dioxide :  — 

(HO)2C6H3C02H=  C6H4(OH)2  -t-  CO2. 

Pyrocatechol 

'  Methoxy  is  derived  from  methoxyl,  the  name  given  to  the  ether  group, 
OCHa.     In  a  similar  way  OC2H6  is  called  e«Aoa:yi;  OCiHi,phenoxyl,  etc. 


426  THE   BENZENE   SERIES   OF  HYDROCARBONS 

Adrenaline,  suprarenine,  C9H13O3N,  is  found  in  the  medulla 
of  the  suprarenal  capsules  of  all  vertebrates  and  is  characterized 
by  its  remarkable  effect  on  the  blood  pressure.  As  small  an 
amount  as  0.000002  gram  injected  intravenously  produces  a 
noticeable  effect  on  the  blood  pressure.  It  is  usually  made  from 
the  suprarenal  glands  of  the  sheep  or  other  animals  by  extract- 
ing them  with  dilute  acid  and  precipitating  the  base  with  am- 
monia. It  is  an  unstable,  weak  base  which  decomposes  rapidly 
when  in  aqueous  solution,  but  is  fairly  stable  in  the  solid  state 
or  in  the  form  of  the  hydrochloride,  in  which  form  it  is  generally 
sold.  It  is  distinguished  readily  by  the  green  color  it  gives  with 
a  solution  of  ferric  chloride.  (Compare  with  pyrocatechol.)  It 
yields  protocatechuic  acid  on  oxidation  and,  when  distilled 
with  sodalime,  methylamine.  When  benzoylated  with  benzoyl 
chloride  it  forms  a  tribenzoate.  It  is  made  synthetically  from 
pyrocatechol :  (I)  This  is  first  condensed  with  monochloro- 
acetic  acid  in  the  presence  of  phosphorus  oxychloride  to  chloro- 
acetyl  pyrocatechol  (II)  which  gives  the  methylamino  com- 
pound of  the  ketone  (III)  when  treated  with  methylamine.  By 
means  of  sodium  amalgam  the  ketone  is  then  reduced  to 
^/-adrenaline  (IV)  :  — 

OH  OH  OH  OH 


lOH   (    \0H        (    ^OH  {    ^OH 

I  II  III 

CO.CH2C1    CO.CH2NHCH3  HCOH.CH2NHCH3 


©■ 


The  synthetic  product  is  optically  inactive;  the  natural  product 
is  levorotatory  and  is  much  more  active  physiologically  than 
the  dextroproduct  or  the  optically  inactive  base.  By  means 
of  the  salt  with  (f-tartaric  acid,  the  levorotatory  adrenaline  is 
separated  from  the  synthetic  product  and  is  used  in  medicine  and 
in  surgery. 

Vanillin,  the  monomethyl  ether  of  protocatechuic  aldehyde, 

rcHO(i) 

CeHs    OCH3(3), 
^0H(4) 


PIPERONAL,   HELIOTROPIN  427 

is  very  widely  distributed  in  the  plant  world,  usually,  however, 
in  small  quantity.  It  is  the  characteristic  constituent  of  the 
vanilla  bean,  which  contains  about  2  per  cent.  It  is  made  on 
the  large  scale  by  oxidizing  isoeugenol  with  ozone  or  other  oxi- 
dizing agents :  — ■ 

/OH  /OH 

CeHsf-OCHa  +03  =  CeHs^OCHs  +  CH3.COOH. 

\CH=CH.CH3  \CHO 

Isoeugenol  Vanillin 

The  isoeugenol  is  made  from  eugenol,  the  chief  constituent  of 
the  oil  of  cloves,  by  heating  it  with  a  solution  of  caustic  soda, 
which  causes  the  shifting  of  the  double  bond  in  the  side  chain. 
(See  allyl  cyanide  and  crotonic  acid.) 

/OH  /OH 

CeHsf-OCHj  — =>-    CeHs^OCHs 

\CH2CH=CH2  \CH=CH.CH3 

Eugenol  Isoeugenol 

It  has  been  made  synthetically  from  guaiacol  by  treating  it 
with  chloroform  and  a  solution  of  an  alkali.  (Analogous  to  the 
preparation  of  salicylic  aldehyde.) 

/OCH3      /OCH3       /OCH3      /OCH3 

C6H4^H(o)s^C6H3f-OH      ^CeHs^OH      ^CeHa^OH   . 

\CHCI2  \CH(0H)2  \CHO 

It  crystallizes  in  colorless  needles  melting  at  8o°-8i°,  which  are 
somewhat  soluble  in  water.  The  aqueous  solution  gives  a 
blue  color  with  ferric  chloride.  It  gives  an  oxime  melting  at 
i2i°-i22°  and  an  acetyl  compound  melting  at  71°,  and  these 
compounds  are  used  to  identify  vanillin.  Large  quantities  of 
vanillin  are  used  in  the  manufacture  of  chocolate,  ice  cream, 
confectionery,  and  vanilla  extract.  It  is  also  used  in  the  manu- 
facture of  perfumes. 
Piperonal,  heliotropin,  the  methylene  ether  of  protocatechuic 
/CHO 
aldehyde,  C6H3^0-^(-,jj^^  j^  ^^^^  ^^  ^^^  j^^.^^  ^^^j^  ^^  ^^^j^. 


428  THE   BENZENE  SERIES  OF  HYDROCARBONS 

ing  isosafrol,  which  is  obtained  from  safrol  by  molecular  re- 
arrangement with  solutions  of  the  alkalies :  — 

CeH^O^^H^  ^C6h/o>^^^  ^CeH/o>*^^^ 

XCHsCH^CHj  \CH=CH.CH3  \CHO 

Safrol  Isosafrol  Piperonal 

Safrol  is  the  chief  constituent  of  the  oil  of  sassafras  and  of  cam- 
phor oil.  Helio tropin  has  also  been  made  by  treating  an  alkaline 
solution  of  protocatechuic  aldehyde  with  methylene  iodide.  It 
forms  colorless  crystals,  having  the  odor  of  heUotrope,  which 
melt  at  3S"-36°.  It  is  made  on  the  large  scale  from  safrol  and 
is  used  in  the  manufacture  of  perfumes. 

Vanillic  acid,  ^-hydroxy-m-methoxybenzoic  acid, 

[  OCH3  (3) 
CeHs  \  OH  (4)     ,  is  formed  by  oxidation  of  vanillin,  which  is  the 

I  CO2H  (i) 
corresponding  aldehyde.      It  is  the  mono  methyl  ether  of  proto- 
catechuic acid,  and  gives  guaiacol  when  distilled  with  lime. 

Trihydroxybenzoic  Acids,  CtHoOs 

Gallic  acid,  3,4,5-trihydroxybenzoic  acid, 

(HOsCeHz.COOH  +  H2O. 

—  GalUc  acid  occurs  in  nutgaUs,  sumach,  Chinese  tea,  and  in 
many  other  plants.  It  is  formed  by  boiling  tannin  or  tannic  acid 
with  dilute  sulphuric  acid  and  by  fusing  bromoprotocatechuic 
acid  or  bromo-3,5-dihydroxybeiizoic  acid  with  caustic  potash :  — 

[Br 
CeHs     (OH),  +  KOH  =  (HOsCeHsCOaH  +  KBr. 
I  CO2H 

Bromoprotocatechuic  acid  Gallic  acid 

Gallic  acid  is  also  obtained  together  with  its  isomer,  pyro- 
gallolcarboxylic  acid,  by  heating  a  solution  of  pyrogallol  with 
potassium  bicarbonate. 

Note  for  the  Sttjdent.  —  Deduce  the  structure  of  gallic  acid  from 
these  methods  of  synthesis  of  the  acid.  See  note  on  page  390.  What  is 
the  structure  of  pyrogallolcarboxylic  acid  ? 


TANNINS,   TANNIC  ACID'S  429 

Gallic  acid  is  prepared  on  the  large  scale  from  the  mother  liquors 

obtained  in  extracting  tannin  from  nutgaUs  (see  below).    These 

are  inoculated  with  certain  microorganisms  {penicillmm  glaucum, 

aspergillus  niger,  etc.)  which  hydrolyze  the  tannin  to  glucose  and 

gaUic  acid.    After  the  fermentation  has  ceased,  the  gallic  acid 

is  filtered  off  and  purified  by  recrystaUization  from  water. 

Gallic  acid  is  difficultly  soluble  in  cold  water,   easily  in  hot 

water,  alcohol,  and  ether.     Its  solution  gives,  with  a  little  ferric 

chloride  solution,  a  blue-black  precipitate,  which   dissolves  in 

excess  of  ferric  chloride,  forming  a  dark  green  solution  (iron  ink) . 

It  is  readily  oxidized,  reduces  Fehling's  solution  and  salts  of  the 

noble  metals,  and  its  alkaline  solution  absorbs  oxygen.     It  is 

not  precipitated  by  gelatin  solution  (distinction  from  tannin). 

When  distilled,  it  yields  pyrogallol  (pyrogallic  acid)  and  carbon 

dioxide :  — 

(HO)3CaH2C02H  =  CeHsCOH),  +  CO2. 

Gallic  acid  is  used  in  making  pyrogaUol,  in  the  manufacture 
of  anthraquinone  dyes,  medicinal  remedies,  and  writing  inks. 

Tannins,  tannic  acids,  are  widely  distributed  in  the  plant 
world  and  are  largely  used  for  the  purpose  of  converting  hides 
into  leather'  (tanning).  The  name  is  applied  to  a  group  of  sub- 
stances which  act  as  weak  acids,  have  an  astringent  taste,  give  a 
blue-black  or  green  color  with  ferric  salts,  and  precipitates  with 
solutions  of  gelatin,  proteins  and  the  alkaloids.  They  are  closely 
related  to  the  hydroxy  aromatic  acids  and  give  one  or  more 
of  these  acids  on  hydrolysis.  The  tannin  of  Chinese  nutgalls, 
when  hydrolyzed  with  dilute  sulphuric  acid,  gives  gallic  acid  and 
glucose  in  the  proportion  of  ten  molecules  of  the  acid  to  one  of 
glucose,  and  is  closely  related  to,  or  identical  with,  a  penta- 
digaUoylglucose  made  synthetically  by  EmU  Fischer  from  gallic 
acid  and  glucose :  — 

C6H706[(HO)3.C6H2.CO.OC6H2.(OH)2CO.]6  or  C76H62O46. 

Pentadigalloylglucose 

This  substance,  which  contains  five  residues  of  digallic  acid, 
(HO)3C6H2CO.OC6H2(OH)2COOH, 
'  See  Industrial  Chemistry,  edited  by  Allen  Rogers,  3d  ed ;  p.  1092. 


43°  THE   BENZENE   SERIES   OF   HYDROCARBONS 

in  place  of  the  five  hydroxyl  hydrogen  atoms  of  glucose,  bears  a 
remarkable  resemblance  to  the  tannin  obtained  from  Chinese 
nutgalls  and  gives  all  the  reactions  characteristic  of  that  sub- 
stance. Like  the  natural  tannin  it  is  optically  active  and  gives 
the  same  amount  of  glucose  and  gallic  acid  when  hydrolyzed  with 
dilute  sulphuric  acid. 

The  commercial  gallo tannin,  obtained  by  evaporating  aqueous 
extracts  of  nutgalls,  is  a  white,  or  yellowish,  amorphous  powder, 
readily  soluble  in  water  and  alcohol,  but  insoluble  in  ether, 
chloroform,  and  benzene.  It  is  a  typical  colloid  and  is  precipi- 
tated from  its  aqueous  solutions  by  hydrochloric  and  sulphuric 
acids  and  by  sodium  and  potassium  chlorides.  Animal  skin 
removes  it  completely  from  its  aqueous  solutions,  and  it  gives 
precipitates  with  solutions  of  gelatin,  egg  albumen,  and  the 
alkaloids.  It  decomposes  carbonates  and  is  a  weak  acid.  With 
solutions  of  ferric  salts  it  gives  a  bluish-black  coloration  or  a 
precipitate  according  to  the  concentration. 

It  is  used  in  medicine,  as  a  mordant  in  dyeing,  and  in  the 
manufacture  of  writing  inks.      It  is  not  used  as  a  tanning  agent. 

Depsides.  —  The  digallic  acid,  mentioned  above  as  a  con- 
stituent of  Fischer's  artificial  tannin,  is  an  example  of  a 
class  of  compounds  caUed  depsides  (Gr.  depsein,  to  tan).  The 
simplest  of  these  is  derived  from  />-hydroxybenzoic  acid, 
HO.C6H4.COOH(^).  The  acid  is  first  treated  in  aqueous, 
alkaline  solution  with  methyl  chlorocarbonate  to  obtain  the 
carbomethoxy  compound :  — 

H3CO.CO.Cl-f  NaO.C6H4.COONa 

=  HsCO.CO.O.CeHi.COONa  +  NaCl. 

The  phenol  group  in  the  acid  is  thus  protected  or  rendered 
inactive.  The  carbomethoxy  compound  is  then  treated  with 
phosphorus  pentachloride  and  the  chloride  formed  is  combined 
with  another  molecule  of  ^-hydroxybenzoic  acid  in  aqueous, 
alkaUne  solution :  — 

H3CO.CO.OC6H4.COCI  +  NaO.CeHi.COONa 

=  H3CO.CO.OC6H4.CO.OC6H4COONa  +  NaCl, 


QUINONES  431 

When  this  product  is  saponified  by  cold,  dilute  alkali  it  gives 
methyl  alcohol,  carbon  dioxide,  and  the  sodium  salt  of  the 
depside  of  ^-hydroxybenzoic  acid,  HO.C6H4.CO.OC6H4.COOH, 
in  which  the  ^-hydroxybenzoyl  group  replaces  the  hydrogen 
of  the  phenol  hydroxyl  group.  As  this  substance  contains  two 
residues  of  ^-hydroxybenzoic  acid,  it  is  called  a  di-depside, 
while  those  containing  three  and  four  residues  are  known  as 
tri-  and  tetra-depsides.  The  di-depsides  of  gallic  acid  and  of 
protocatechuic  acid  give  precipitates  with  dilute  solutions  of 
gelatin  analogous  to  those  obtained  with  tannin.  All  the 
depsides  are  hydrolyzed  by  heating  with  solutions  of  the  alkalies 
and  yield  salts  of  the  hydroxy  aromatic  acids. 

QuiNONES 

The  quinones  are  compounds  formed  by  the  oxidation  of  the 
0-  and  p-  dihydroxy  derivatives  of  the  aromatic  hydrocarbons :  — ■ 

C6H4(OH)2  +  O    =   C6H4O2  +  H2O. 

Dihydroxybenzene  Quinone 

The  simplest  one,  and  the  best-known,  is  called  quinone  or 
^-benzoquinone,  from  the  fact  that  it  was  first  obtained  by  the 
oxidation  of  quinic  acid,  hexahydrotetrahydroxybenzoic  acid, 
C6H7(OH)4COOH. 

^-Benzoquinone,  C6H4O2,  results  from  the  oxidation  of  para- 
derivatives  of  benzene,  such  as  /)-phenylenediamine,  ^-amino- 
phenol,  sulphanilic  acid,  and  ^-phenolsulphonic  acid.  It  is 
usually  made  by  the  oxidation  of  anUine  by  means  of  chromic 
acid  mixture  (387) .  As  hydroquinol  is  now  a  commercial  prod- 
uct, quinone  is  most  conveniently  made  from  it  by  oxidation. 

It  crystallizes  in  yellow,  monoclinic  prisms,  which  melt  at 
115.7°,  s-nd  have  a  penetrating,  characteristic  odor  resembling 
that  of  chlorine.  It  turns  brown  when  exposed  to  the  Ught,  and 
the  aqueous  solution  colors  the  skin  brown.  It  sublimes  in 
golden,  yellow  needles  and  is  volatUe  with  steam,  though  with 
slight  decomposition.  When  heated  with  acetic  anhydride  in 
the  presence  of  sulphuric  acid  quinone  gives  the  tri-acetate  of 
hydroxy  hydroquinol :  — 

C6H4O2  +  2  (CH3CO)20  =  C6H3(OCOCH3)3  +  CH3COOH. 


CH 

CO 

HC/^CH 

HC/^CH 

HCs  ^CH 
CH 

■^HCIJCH 
CO 

Benzene 

Quinone 

432  THE  BENZENE  SERIES  OF  HYDROCARBONS 

With  hydroquinol,  quinone  forms  an  addition  product,  C6H4O2 
+  C6H4(OH)2,  known  as  quinhydrone.  It  crystallizes  in  green 
prisms  having  a  metallic  luster  and  is  also  formed  as  an  inter- 
mediate product  in  the  oxidation  of  hydroquinol  or  in  the 
reduction  of  quinone. 

When  benzene  is  oxidized  by  passing  air  saturated  with 
benzene  vapor  over  heated  vanadium  oxide  it  gives  quinone 
and  maleic  acid :  — 


H.C.COOH 

+  302=       II  +2CO2. 

H.C.COOH 

Maleic  acid 

Reducing  agents  (hydriodic  acid,  sulphurous  acid,  hydroxyl- 
amine,  etc.)  convert  it  into  hydroquinol :  — 

C6H4O2  +  H2SO3  +  H2O    =   C6H4(OH)2  +  H2SO4. 
Quinone  Hydroquinol 

When  reduced  with  hydrogen  in  the  presence  of  finely  divided 
nickel  heated  to  the  proper  temperature,  quinone  first  gives 
hydroquinol,  which  then  takes  up  six  atoms  of  hydrogen  to  form 
cyclohexa-i,4-diol  (quinitol)  I:  — 

HCOH  CO 

H2C/NCH2  H2C/NCH2 

H2CI  y  CH2  HzCl^  CH2 

HCOH  CO 

This  substance  conducts  itself  like  a  saturated,  secondary  alco- 
hol, e.  g.,  it  gives  a  diketone,  cyclohexa-i,4-dione  II,  on  oxidation, 
and  it  has  also  been  made  by  the  reduction  of  this  diketone. 

Quinone  is  an  unsaturated  compound,  and  in  solution  in 
chloroform  combines  with  two  and  four  atoms  of  bromine  to 
form  a  di-  and  a  tetra-bromide,  C6H402Br2  and  C6H402Br4. 

The  fact  that  quinone  can  only  be  obtained  from  para  com- 
pounds by  oxidation  and  that  it  yields  hydroquinol  (^-dihydroxy- 


0-BENZOQUINONE  433 

benzene)  on  reduction  leads  to  the  conclusion  that  the  oxygen 
atoms  are  in  the  para  position  to  each  other,  as  shown  in  the 
structural  formula  given  above. 

According  to  this  view  of  the  structure  of  quinone  it  is 
a  para-diketodihydrobenzene,  and  is  a  derivative  of  cyclo- 
hexa-i,4-diene  (329),  in  which  four  para  hydrogen  atoms  are 
replaced  by  two  oxygen  atoms.  Like  cyclohexa-i,4-diene  it  is 
unsaturated  and  takes  up  two  and  four  atoms  of  bromine,  and 
like  the  diketones  it  forms  a  monoxime,  CeH^OCNOH),  and  a 
dioxime,  C6H4(NOH)2,  with  hydroxylamine  hydrochloride.  The 
monoxime  is  identical  with  /)-mtrosophenol  (376)  obtained  by 
the  action  of  nitrous  acid  on  phenol. 

Homologues  of  />-benzoquinone  are  also  known,  such  as  tolu- 
quinone,  CeHsOjCHa,  and  xyloquinone,  C6H202(CH3)2.  The 
latter  compound  is  made  synthetically  by  the  action  of  solutions 
of  the  alkalies  on  diacetyl :  — 

H3C.C.CO.CH 

II         II 

O  ^2  H3C.C.CO.CH 

II  II  +2H2O. 

H2      O  HC.CO.C.CH3 

Xyloquinoae 

HC.C0.C.CH3 

2  mols.  Diacetyl 

They  are  all  colored  compounds  which  are  reduced  to  colorless 
dihydroxy  derivatives  of  the  aromatic  hydrocarbons  by  nascent 
hydrogen. 
o-Benzoquinone,  CO 

HC/NCO, 
HCI     icH 

CH 

isomeric  with  ^-benzoquinone,  has  been  obtained  by  oxidizing 
pyrocatechol  in  ethereal  solution  with  silver  oxide.  It  crystal- 
lizes in  red  plates,  is  unstable  and  decomposes  when  heated  to 
6o°-7o°.  It  differs  from  /)-benzoquinone  in  being  non-volatile 
with  steam  and  having  no  odor.     It  is  reduced  to  pyrocatechol 


434  AROMATIC  COMPOUNDS 

by  sulphurous  acid.     It  is  the  diketo  derivative  of  cyclohexa- 
1,3-diene  (329). 

Qujnones  in  which  the  oxygen  atoms  are  in  the  meta  position 
to  each  other  are  unknown. 

FURAN,   TmOPHENE,   PyREOL 

These  three  substances  have  been  shown  to  be  related  struc- 
turally to  benzene  as  indicated  in  the  formulas  below :  — 


HC 
HC 


CH       HC 


\/ 


CH       HC 


CH       HC 
CH       HC 


CH 


\/ 


CH 


O  S  NH 

Furan  Tbiophene  Pyrrol 

Furan  is  regarded  as  benzene  in  which  an  oxygen  atom  has  been 
substituted  for  the  group  — HC=:CH — .  Similarly,  thiophene 
is  derived  from  benzene  by  the  substitution  of  a  sulphur 
atom,  and  pyrrol,  by  the  substitution  of  an  imino  group,  NH, 
for  two  of  the  ^CH —  groups. 

Derivatives  of  all  three  compounds  are  formed  from  mucic 
acid  (206)  H02C(CHOH)4C02H.  When  distilled  this  gives 
pyromucic  acid,  which  is  a  carboxyl  derivative  of  furan ;  when 
the  ammonium  salt  of  mucic  acid  is  distilled,  pyrrol  is  obtained ; 
and,  when  mucic  acid  is  distilled  with  barium  sulphide,  a  car- 
boxyl derivative  of  thiophene  is  obtained.  Fural,  furfural, 
C4H3O.CHO,  is  obtained  from  pentoses  by  distilling  them  with 
hydrochloric  acid.  The  yield  is  quantitative,  and  this  fact  is 
taken  advantage  of  for  the  purpose  of  determining  the  amounts 
of  pentoses  present  in  various  substances  (218).  Large  quan- 
tities of  fural  may  be  made  from  corn  cobs.  It  is  a  liquid  boil- 
ing at  162°. 

Thiophene,  C4H4S,  occurs  in  coal  tar  benzene  and  resembles 
benzene  very  closely.  It  can  be  made  synthetically  in  a  num- 
ber of  ways. 

Pyrrol,  C4H4NH,  is  contained  in  coal  tar  in  small  quantity; 
in  larger  quantity  in  Dippel's  oil,  formed  when  bones  are  dis- 


PYRIDINE   BASES  435 

tilled.  Many  substances  occurring  in  nature  are  related  more 
or  less  closely  to  pyrrol. 

Pyridine  Bases,  C„H2„_6N 

Pyridine  was  first  isolated  from  bone  oil,  a  product  resulting 
from  the  heating  of  bones  in  closed  retorts  for  the  purpose 
of  making  bone  black  or  ivory  black.  Besides  pyridine,  bone 
oil  contains  higher  homologues,  most  of  which  are  methyl 
derivatives  of  pyridine.  These  pyridine  bases  are  also  found  in 
the  distillation  products  of  wood,  coal,  lignite,  and  bituminous 
shales.  At  present  they  are  obtained  from  coal  tar,  although 
this  substance  contains  only  0.05  to  o.i  per  cent  of  these  bases.' 
They  form  an  homologous  series  analogous  to  the  hydrocarbons 
of  the  benzene  series :  — 

Pyridine CsHsN 

Picolines CeHrN 

Lutidines C7H9N 

Collidines CgHuN 

Parvolines C9H13N 

etc.  etc._ 

Soon  after  the  discovery  of  the  pyridine  bases  in  bone  oil  they 
were  found  among  the  products  formed  when  cinchonine,  an 
alkaloid  present  together  with  quinine  in  cinchona  bark,  is  dis- 
tilled with  caustic  alkalies.  At  the  present  time  it  is  known  that 
a  large  number  of  the  plant  alkaloids,  some  of  which  are  valuable 
medicinal  remedies,  are  derivatives  of  these  bases.  The  forma- 
tion of  pyridine  bases  when  bones  are  heated  is  due  to  the  pres- 
ence of  fats  and  proteins  in  the  bones,  for  when  the  fats  are 
removed,  no  pyridine  bases  are  formed.  The  fats  give  acrolein 
on  heating  and  the  proteins  (gelatin,  etc.)  form  ammonia, 
methylamine,  etc.  These  substances  react  with  one  another 
at  the  high  temperature  to  form  the  pyridine  bases.     Homo- 

'  See  Coal  Tar  and  Ammonia,  by  G.  Lunge,  sth  ed.  1916,  Part  II,  Coal 
Tar,  p.  895. 


436  AROMATIC   COMPOUNDS 

logues  of  pyridine  are  formed  whenever  the  compounds  of  the 
aldehydes  of  the  fatty  series  with  ammonia  (aldehyde  ammonias) 
are  heated  either  alone  or  with  aldehydes.  Thus,  acetic  alde- 
hyde ammonia  gives  as  the  chief  product,  2-methyl-5-ethyl- 
pyridine :  — 

4  CH3.CHO  +  NH3  =  C5H3(CH3)(C2H6)N  +  4  H2O. 

While  acrolein  ammonia  gives  /3-picoline  :  — 

2  HaCiCH.CHO  +  NH3  =  C6H4(CH3)N  +  2  H2O. 

(3-Picoline  is  also  formed  by  the  distillation  of  strychnine  and 
brucine  with  lime. 

Pyridine  and  its  homologues  are  formed  in  considerable 
quantity  by  distilling  glycerol  with  ammonium  phosphate. 

Pyridine,  CsHbN,  is  a  colorless  liquid,  with  a  characteristic 
penetrating  odor.  It  boils  at  115.1°.  It  has  been  obtained 
pure  by  fractional  distillation  of  bone  oil  and  of  the  bases  from 
coal  tar,  but  is  best  made  by  distillation  of  its  carboxylic  acid 
with  lime :  — 

C5H4N.COOH  =  CsHsN  +  CO2. 

>  Nicotinic  acid  Pyridine 

This  acid,  which  bears  the  same  relation  to  pyridine  that 
benzoic  acid  bears  to  benzene,  is  obtained  by  the  oxidation  of 
the  alkaloid  nicotine,  found  in  tobacco.  Pyridine  is  present  in 
crude  ammonia.  It  is  miscible  with  water  in  all  proportions 
and  the  mixture  having  the  composition  CbHjN  +  3H2O  has 
the  boiUng  point  92°-93°.  Pyridine  is  a  weak,  monacid  base, 
forming  salts  like  CsHsN.HCl,  C5H5N.HNO3,  C6H6N.H2SO4, 
etc.  The  ferrocyanide  is  only  sparingly  soluble  in  cold  water 
and  is  used  to  separate  it  from  its  homologues  and  to  identify  it. 
It  does  not  turn  litmus  blue.  Commercial  pyridine  is  used  in 
denaturing  alcohol  and  in  synthetical  work.  It  is  also  used  in 
making  piperidine  on  the  large  scale.  It  is  a  tertiary  amine, 
since  it  does  not  give  an  acetyl  derivative  with  acetyl  chloride 
and  combines  with  methyl  iodide  to  form  methyl  pyridonium 


PYRIDINE  437 

iodide,  C6H6N<-.      •     A  solution  of  this  iodide  in  water  gives 

p"LT 

methylpyridonium  hydroxide,  C6H5N<  „„  ,  when  treated  with 

silver  oxide,  and  this  hydroxide  is  a  strong  base.  Pyridine  is  a 
remarkably  stable  substance,  even  more  stable  than  benzene. 
It  may  be  boiled  with  nitric  or  chromic  acids  without  undergoing 
any  change,  and  this  fact  is  made  use  of  in  purifying  it.  The 
homologues  of  pyridine  are  oxidized  to  pyridinecarboxylic,  or 
picolinic,  acids,  just  as  the  homologues  of  benzene  give  the 
carboxylic  acids  of  benzene  on  oxidation :  — 

C6H4NCH3  +  30  =  C6H4N.COOH  +  H2O. 

Picolines  Picolinic  acids 

In  its  conduct  towards  reagents  it  acts  remarkably  like  benzene, 
but  it  does  not  form  substitution  products  as  readily  as  benzene 
does.  Thus  it  forms  a  sulphonic  acid  only  when  heated  to  a  very 
high  temperature  with  sulphuric  acid,  and  a  nitre  compound  only 
when  heated  to  300°  with  mixed  acid  (308) .  The  sodium  salt  of 
the  sulphonic  acid  gives  a  hydroxypyridine  when  fused  with  caus- 
tic soda,  and  this  compound  acts  like  a  phenol.  Nitropyridine 
on  reduction  is  converted  into  aminopyridine,  which  resembles 
aniline  closely.  It  can  be  diazotized  like  aniline  and  the  di- 
azonium  salt  combines  with  phenols  and  amines  to  form  azo 
compounds.  With  chlorine  and  bromine  pyridine  forms  halogen 
substitution  products. 

Pyridine  has  been  made  synthetically  from  trimethylene 
bromide  (304)  by  first  converting  this  into  the  cyanide  and  the 
cyanide  into  pentamethylenediamine  by  reduction  with  sodium 
in  alcoholic  solution :  — 

CHsBr  _^  „  ^  .  CH2CN  _^  XT  p  ^  CH2CH2NH2 
^^^  <  CH^Br  ~^  ^'^  <  CH2CN  ~^  ^'^  <  CH2CH2NH; 

TrimethyleDe  Trimethylene  Pentamethylene- 

bromide  cyanide  diamine 

When  the  hydrochloride  of  this  base  is  distilled  it  gives  piperi- 
dine  (hexahydropyridine)  and  this,  when  oxidized  by  heating  it 
with  concentrated  sulphuric  acid  to  300°,  gives  pyridine :  — 


438  AROMATIC   COMPOUNDS 

/CH2CH2NH2HCI  .CH2.CH2 

H2C<  =  H2C<  >NH  +  NH4CI. 

\CH2CH2NHH  \CH2.CH2 

PentamethylenediMaine  Piperidine 

hydrochloride 

/CH2.CH2  /CH=CH\ 

H2C<  >NH  +  30=  HC/  >N  +  3  H2O. 

\CH2.CH2  ^CH-CH^ 

Piperidine  Pyridine 

Piperidine  hydrochloride  also  results  when  an  aqueous  solution 
of  s-chloroamylamine  is  heated  on  the  water  bath : — 

/CH2CH2CI  /CH2CH2 

H2C<  =  H2C<  >NH.HC1. 

\CH2CH2NH.H  \CH2CH2 

S-Chloroamylamine  Piperidine  hydrochloride 

When  the  boiling  alcoholic  solution  of  pyridine  is  treated  with 
sodium,  piperidine  is  formed :  — 

/CH=CH.  /CH2CH2 

HC^'  >N  +  6  H  =  H2C<  >NH. 

^CH-CH^  \CH2CH2 

Pyridine  Piperidine 

It  will  be  seen  from  the  above  reactions  that  the  relation  between 
pyridine  and  piperidine  is  the  same  as  that  between  benzene  and 
cyclohexane.  Another  method  of  formation  of  pyridine,  which 
throws  light  on  its  structure,  is  from  quinoline,  a  base  which 
is  also  present  in  coal  tar  and  whose  structure  is  known 
(507).  Quinoline  when  oxidized  gives  quinolinic  acid  (pyridine- 
dicarboxylic  acid) :  — 

+  9°  =  QcoSh+^C02  +  H20, 

N  N 

Quinoline  Quinolinic  acid 

analogous  to  the  formation  of  phthalic  acid  by  the  oxidation  of 


PYRIDINE  '  439 

naphthalene.  QuinoHnic  acid  when  distilled  with  lime  gives 
pyridine,  just  as  phthalic  acid  gives  benzene :; 

N 

Quinolinic  acid 

According  to  these  methods  of  formation  and  the  reactions  of 
pyridine  it  is  benzene  in  which  a  nitrogen  atom  takes  the  place 
of  one  CH  group. 


N 

This  formula  is  in  accord  with  the  remarkable  stability  of  the 
substance  and  with  the  fact  that  it  is  a  tertiary  amine,  but  gives 
a  hexahydro  addition  product,  piperidine,  on  reduction  ,which 
is  a  secondary  amine.  According  to  this  formula  of  pyridine  it 
is  in  a  sense  a  monosubstitution  product  of  benzene  and  should 
yield  three  monosubstitution  products  corresponding  to  the 
ortho-,  meta-,  and  para-  disubstitution  products  of  benzene. 
For  example,  there  should  be  three  methylpyridines  or  picolines, 
three  pyridinecarboxylic  acids,  etc.  The  three  picolines,  all  of 
which  are  present  in  coal  tar  and  in  bone  oil,  are  represented 
by  the  following  formulas :  — 


They  are  designated  a-,  (3-,  and  y-picoline  or  2-,  3-,  and  4-picoline 
according  to  the  position  of  the  methyl  group,  a-  and  y-Picoline 
but  not  the  /3-product  are  formed  when  methylpyridonium  iodide 


44°  AROMATIC   COMPOUNDS 

is  heated  in  a  sealed  tube  to  about  300°  and  the  hydroiodides 
formed  are  distilled  with  a  solution  of  an  alkali :  — 


CH3 

CH3 

\^CH3 

/\ 

/\              ^\ 

and            — 

¥-        \\          and 

^ycH3        ^y 

HNI 

HNI 

N                       N 

a-Picoline 

■y-Picoline 

a-Picoline                   v-PicoUne 

.  hydroiodide 

hydroiodide 

INCH3 

Methylpyri- 
donium  iodide 

When  oxidized  a-picoUne  gives  picoUnic  acid,  while  /3-picoUne 
yields  nicotinic  acid  (first  obtained  by  the  oxidation  of  nicotine, 
whence  the  name)  and  y-picoline  gives  isonicotinic  acid.  When 
distilled  with  lime  all  these  acids  give  pyridine. 

Lutidines,  C6H3(CH3)2N.  —  The  six  dimethylpyridines  (2,  3 ; 
2,4;  2,  s ;  2,  6 ;  3,4;  and  3,  5)  predicted  by  the  theory  are  all 
known  and  are  present  in  coal  tar.  When  oxidized  they  are 
first  converted  into  monobasic  acids,  C5H3N.CH3.COOH  and 
then  into  dibasic  acids,  C6H3N(COOH)2.  The  monobasic  acids 
give  the  three  picolines  when  distilled  with  Ume,  while  the  dibasic 
acids  yield  pyridine. 

P-Ethylpyridine,  C6H4NC2H5,  isomeric  with  the  lutidines,  is 
formed  in  the  distillation  of  cinchonine  with  potash,  or  of 
brucine  with  lime.     It  gives  nicotinic  acid  on  oxidation. 

Conyrine,  2-propylpyridine,  C5H4(CH2CH2CH3)N,  is  obtained 
from  its  hexahydride,  conine  (442),  by  distillation  of  its  hydro- 
chloride with  zinc  dust.  It  boils  at  i66°-i68°.  It  is  converted 
into  picolinic  acid  by  oxidation  and  into  inactive  conine  on  re- 
duction with  hydriodic  acid. 

Collidine,  2,4,6-trimethyl-pyridine,  C6H2(CH3)3N,  isomeric 
with  conyrine,  is  obtained  from  coUidinedicarboxylic  acid  ester 
by  distillation  with  sodalime.  The  ester  is  made  from  aceto- 
acetic  ester,  acetic  aldehyde  and  ammonia :  — 

CH3 

C2H6O.CO.CH2      OCH        H2C.CO.OCSH5 

I       +    +       +      I  -3H20  = 

H3C.CO         NH3  OC.CH3 


PIPERIDINE,  HEXAHYDROPYRIDINE  441 

CH3  CH3 

CH  C 

CjHsO.OC.c/Nc.CO.OCaHs     CjHeO.OC.c/Nc.CO.OCzHe 

HaCcll    JIC.CH3  —>-  HaC.cll      Jc.CHs 

^  (Oxidation  ^ 

Dihydrocollidinediethyl        With  N2O3)        2,4,6-Triinethylpyridine 
dicarboxylate  methyl  dicarboxylate 

CH3  CH3 

c  c 

CsHBO.OC.c/^C.CO.OCaHs  H.c/%C.H     +2CO2. 

H3C.cllic.CH3  -*"  H3C.cllic.CH3  +  2  C2H4 

N  N 

Collidinedicarboxylic  add  ester  2,4,6-CoUidine 

It  boUs  at  1 71°-!  7  2°  and  is  fairly  soluble  in  cold  water,  but 
only  slightly  soluble  in  hot  water. 

Piperidine,  hexahydropyridine,  CbHuN,  was  first  obtained 
from  piperine,  the  alkaloid  of  pepper.  Piperine  is  piperyl- 
piperidine,  and  when  hydrolyzed  it  gives  piperidine  and 
piperic  acid.  Piperidine  is  now  made  on  the  large  scale  from 
pyridine  by  reducing  it  in  a  boiling  solution  in  ethyl  alcohol  with 
sodium.  It  is  a  colorless  liquid  having  a  strong  ammoniacal 
odor  and  also  the  odor  of  pepper.  It  is  mlscible  with  water  in 
all  proportions.  It  has  a  very  caustic  taste  and  is  a  very  much 
stronger  base  than  pyridine,  turning  litmus  blue.  It  solidifies 
at  —13°,  boils  at  106.2°  and  is  very  poisonous.  It  is  a  secondary 
amine,  as  it  gives  an  acetyl  compound  with  acetyl  chloride  and 
a  nitroso  compound  with  nitrous  acid.  When  the  benzoyl  deriv- 
ative of  piperidine  is  treated  with  phosphorus  pentabromide  it 
gives  a  dibromo  product  which  when  distilled  decomposes  into 
pentamethylene  dibromide  and  phenyl  cyanide :  — 

CH2  CH2  CH2 

H2C^CH2  H2C/NCH2  HzC/NcHj 

H2CIJCH2  H2CI      JCH2  H2CIJCH2 

NH  N.COCsHb  N.CBraCeHs 


442  AROMATIC  COMPOUNDS 

CH2 
HjC/NcHa 


n- 


+  CeHsCN. 
BrHsC       CHzBr 

This  is  the  best  method  of  making  pentamethylene  dibromide. 

•CH2.CH2 
Conine,    2-propylpiperi(iine,    HjCy  >NH,  occurs  with 

other  bases  in  spotted  hemlock  {conium  macidatum).  It  is  a 
colorless  liquid,  having  a  stupefying  odor  and  boiling  at  167°. 
It  is  but  slightly  soluble  in  water  and  is  extremely  poisonous. 
Both  the  dextro-  and  levorotatory  forms  occur  in  nature. 
(Does  it  contain  an  asymmetric  carbon  atom?)  The  d-form  is 
the  one  used  in  medicine.  It  was  the  first  alkaloid  to  be  made 
synthetically.    The  steps  taken  are  as  follows :  — 

L     lea,  +  OCH.CH3  =  L     ]lCH=CH.CH3  +  H2O. 

N  N 

a-Picoline  Ald^yde  a-Propenylpyridine 

CH2 

HjC/NcHa 
■^yCH=CH.CH3  +  4  H2  =  H2CI     JCH.CH2.CH2.CH3. 

N  NH 

a-Propenylpyridine  Inactive  conine 

The  synthesis  of  pyridine  from  triinethylene  bromide  (437)  and 
of  a-picoline  from  pyridine  (439)  have  already  been  given.  The 
inactive  conine  can  be  resolved  into  the  two  active  forms  by 
means  of  the  salts  formed  with  d-tartaric  acid. 

Terpenes  and  Camphors 

Most  of  the  hydrocarbons  occurring  in  the  volatile  oils,* 
obtained  from  plants  or  parts  of  plants  (leaves,  roots,  flowers, 
fruits,  rinds)  by  distillation  with  steam,  have  the  composition 

'  See  Volatile  Oils,  by  E.  Gildemeister,  2d  ed.  Translated  by  E.  Kremers, 
1913- 


HEMITERPENES  443 

and  molecular  weight  represented  by  the  formula,  CioHie.  The 
best  known  representative  of  this  class  of  hydrocarbons  is  pinene, 
the  chief  constituent  of  the  oil  of  turpentine  (see  footnote,  418). 
For  this  reason  they  were  called  Terpenes.  At  the  present  time 
terpenes  are  known  having  the  formula,  CsHg,  such  as  isoprene 
found  among  the  products  of  the  dry  distillation  of  rubber,  and 
these  are  designated  Hemiterpenes.  More  complicated  terpenes 
having  the  formula,  C16H24,  and  hence  called  Sesquiterpenes, 
are  also  constituents  of  many  volatile  oils.  Finally  there  are 
terpenes,  (CsHs),,  such  as  rubber  and  gutta  percha,  whose 
molecular  weights  are  unknown,  and  these  are  called  Poly- 
ierpenes.  All  of  these  terpenes  are  unsaturated  compounds. 
Some  contain  one  double  bond  and  unite  with  one  molecule  of 
hydrochloric  acid  or  two  atoms  of  bromine,  others  contain  two 
double  bonds  and  combine  with  two  molecules  of  hydrochloric 
acid  or  four  atoms  of  bromine.  Several  of  them  combine  with 
water  to  form  hydrates.  The  hemiterpenes  and  terpenes  are 
readily  polymerized  by  heat  or  the  action  of  sulphuric  acid, 
and  several  of  the  polyterpenes  are  depolymerized  by  the  action 
of  heat.  Many  of  the  terpenes  are  closely  related  to  the  hydro- 
gen addition  products  of  ^-cymene  and  can  be  converted  into 
/»-cymene  by  mild  oxidation,  whUe  more  energetic  oxidation 
gives  ^-toluic  and  terephthalic  acids.  A  few  contain  the 
OT-cymene  nucleus,  sylvestrene  for  example. 

Hemiterpenes 

Isoprene,  2-methyl-i,3-butadiene,  CsHg,  is  the  best-known 
representative  of  this  class.  It  is  formed  in  small  quantity  as 
one  of  the  products  of  the  distillation  of  natural  rubber  and  by 
the  decomposition  of  turpentine  or  dipentene  at  a  dull  red  heat. 
It  is  a  colorless  liquid,  boiling  at  37".     It  has  been  shown  to  be 

.  CH3 

/3-methyldivinyl  or  2-methyl-i,3-butadiene,  I 

H2C  ;C — CH:CH2, 

XT  p 

as  it  gives  a  dibromide,         >CBr.CH2.CH2.Br,  when    treated 
XI3U 

with  hydrobromic   acid,   identical   with    that   obtained   from 


444  AROMATIC   COMPOUNDS 

dimethylaUene,      !?'^>C:C:CH2,    by    the    addition    of     two 

molecules  of  hydrobromic  acid.  This  dibromide,  made  from 
dimethylallene,  gives  isoprene  when  treated  with  alcoholic 
caustic  potash :  — 

HaCv  CHs 

>CBr.CH2.CH2Br  =  |  +  2  HBr. 

HsC/  HaC^C— CH=CH2 

Isoprene 

When  heated  to  300°,  isoprene  undergoes  polymerization  to 
dipentene  (446) :  — 

CH3  Clla 


II     + 

c 

H2C/\CH  . 

H2C  I        y  CH2  ' 

CH 

I 

H-,C— C— CH2 

2  mols.  Isoprene 

HsC— C=CH2 

Dipentene 

and  dipentene  is  depolymerized  to  isoprene  when  its  vapor  is 
passed  over  a  red-hot  platinum  spiral. 

The  chief  interest  attached  to  isoprene  is  the  fact  that 
when  heated  to  100°  with  glacial  acetic  acid,  it  is  polymerized 
to  an  amorphous  substance,  said  to  be  identical  with  natural 
rubber.  This  product  is  vulcanized,  just  as  natural  rubber  is, 
when  heated  with  sulphur.  The  artificial  rubber  is  far  inferior, 
however,  to  the  natural  product  and  lacks  many  of  its  funda- 
mental properties. 

Cyclic  Terpenes 

The  terpenes  of  this  group  are  classified  as  monocyclic  and 
bicyclic  according  as  they  contain  one  or  two  rings  of  carbon 
atoms. 

Monocyclic  Terpenes 

These  terpenes  are  closely  related  to  />-cymene  and  its  hydro- 


LIMONENE  445 

gen  addition  products.     The  carbon  atoms  in  the  formula  of 
p-cymene  are  numbered  as  follows :  — 

O  CH3 


C 
HjC/NcH 

H2C  s,^       J  CH2 

CH 
»C— C— C"  H2C=C— CH3 

Limonene 

and  the  position  of  a  double  bond  between  two  or  more  carbon 
atoms,  as  in  the  formula  of  limonene  given  above,  is  indicated 
by  the  Greek  letter  A  with  the  numbers  of  the  carbon  atoms 
between  which  the  double  bonds  occur  as  exponents.  Thus, 
limonene  is  A^-^®>  menthadiene. 

Hexahydro-^-cymene  is  designated  menthane,  as  it  is  a  satu- 
rated hydrocarbon  and  can  be  readily  obtained  by  the  reduc- 
tion of  its  hydroxyl  derivative,  menthol.  It  is  not  a  natural 
product,  but  is  made  from  ^-cymene  by  passing  its  vapor  mixed 
with  hydrogen  over  finely  divided  nickel  heated  to  180°  It  is 
a  liquid  boiling  at  i68°-i69°. 

Limonene  (carvene,  citrene),  CioHie,  occurs  very  widely  dis- 
tributed in  nature  both  in  the  dextro-  and  levo-  forms  and 
in  the  dl-iorm,  which  is  called  dipentene.  d-Limonene  occurs 
most  abundantly  in  the  oils  of  orange,  lemon,  bergamot,  manda- 
rin, and  in  a  number  of  other  oils.  l-Limonene  occurs  in  pine 
needle  oil,  in  pine  cone  oil  and  in  other  oils.  Both  limonenes  are 
liquids  of  an  agreeable  lemon-like  odor,  boiling  at  175"-!  76°. 
They  yield  the  same  derivatives,  which  differ  only  in  the  direction 
in  which  they  rotate  polarized  light.  When  equal  quantities  of 
d-  and  Z-limonene  are  mixed,  dipentene  is  formed,  and  dipentene 
also  results  when  either  of  the  limonenes  is  heated  to  a  high 
temperature  or  when  they  are  heated  with  acids.  In  the  cold, 
acids  frequently  cause  the  hydration  of  limonene  to  terpineol 
and  terpin  hydrate :  — 


446  AROMATIC   COMPOUNDS 

CH3  CH3 

CH  CH 

H2C=C.CH3  H3C.C.OH 

Liraonene 

CH3 

Terpineol 

CH3  CH3 

C.OH  C.OH 

H2C/\CH2   ,   H  O  =  H2C/\|CH2 
H2CI     JcHj         '         HjCl      'CHjOH 

CH  CH2 

H3C.C.OH  H3C.C.OH 

CH3  CH3 

Terpin  Terpin  hydrate 

Concentrated  sulphuric  acid  changes  limonene  to  p-cymene. 
The  Umonenes  take  up  four  atoms  of  bromine  and  yield  optically 
active  tetrabromides  that  melt  at  io4°-io5°.  They  also  take 
up  two  molecules  of  hydrochloric  acid,  forming,  however,  a 
dihydrochloride  of  dipentene,  melting  at  50°. 

Dipentene  (inactive  limonene),  occurs  frequently  in  nature  and 
is  found  in  Swedish  turpentine  oU  and  in  a  number  of  other 
volatile  oils. 

It  has  been  made  synthetically  by  the  polymerization  of 
isoprene  (444),  and  it  is  formed  together  with  isoprene  when 
caoutchouc  is  distilled.  It  results  also  when  pinene,  limonene, 
and  pheUandrene  are  heated  to  2So°-3oo°.  Its  synthesis  from 
the  alcohols,  linalool  and  geraniol  (459)  determines  its  structure 
and  that  of  the  Umonenes :  — 


iviiLi^  1  jujjj  447 


CHs 

CH3 

C 

COH 

H2C/^CH2 
H2CI        CH2' 

CH2 

CH 

H3C.C.CH3 

H3C.C.OH 

Geraoiol 

CH3 

Terpin  hydrate 

CH3 

CH3 

COH 

C 

HiC^       CH2    _  2  jj  0  — 
H2CIV      JCH2 

HjC/^CH 

H2CI       y'CHj 

CH 

CH 

H3C.COH 

H2C— C     CH3 

CH3 

Terpin 

Dipentene 

-  H20  = 


This  change  is  brought  about  by  shaking  with  dilute  sulphuric 
acid. 

Note  for  Student.  —  Does  the  formula  for  dipentene  contain  an 
asymmetric  carbon  atom? 

Dipentene  dififers  from  limonene  only  in  being  optically 
inactive  and  in  giving  optically  inactive  derivatives. 

Monocyclic  Alcohols  and  Ketones 

Menthol,  C10H19OH  (peppermint  camphor),  is  present  in  the 
peppermint  oils,  of  which  /-menthol  is  the  principal  constituent 
together  with  its  acetate  and  isovalerate.  On  cooling,  menthol 
separates  from  the  oil  of  peppermint  in  colorless,  hexagonal 
needles  having  the  characteristic  odor  of  oil  of  peppermint.     It 


448  AROMATIC   COMPOUNDS 

melts  between  43.5"  and  44.5°,  and  boils  at  215.5°.  It  is  usee 
as  an  antiseptic  and  anaesthetic.  When  heated  with  coppei 
sulphate  it  gives  ^-cymene.  Menthol  is  a  saturated,  secondarj 
alcohol  derived  from  menthane,  as  it  yields  menthane  (hexa- 
hydro-/>-cymene)  on  reduction  with  hydriodic  acid  and  phos- 
phorus, and  the  ketone,  menthone,  on  oxidation  with  chromic 
acid :  — 

CH3  CH3  CH3  CH3 

CH  CH  CH 

I'CHa  HaC/NcHz  HsC/NcHa    HC 

CH2  HsCl      JCHOH     HaCl     Jc=0  HC 

CH  CH  CH 

H3C.C.CH3       H3C.C.CH3  H3C.C.CHS       H3C.C.CH3 

H  H  H  H 

Menthane  Menthol  Menthone  Thymol 

The  position  of  the  OH  group  is  determined  by  the  fact  that 
when  menthone  in  chloroform  solution  is  treated  with  bromine 
it  gives  a  crystalline  dibromomenthone,  CioHi6Br20  (m.p.  79°- 
80°)  from  which,  by  heating  with  quinoUne,  thymol  (see  above) 
is  formed.  Menthol  is  made  artificially  by  the  reduction  of 
menthone  and  of  pulegone.     (See  below.) 

d-Pulegone,  CioHieO,  occurs  in  European  pennyroyal  oil 
and  also  in  other  labiate  oils,  sometimes  together  with  men- 
thol and  menthone.  It  is  a  colorless  liquid  having  a  sweetish, 
peppermint-like  odor,  resembling  that  of  menthone.  It  boils 
at  224°. 

It  is  an  unsaturated  ketone,  as  it  combines  with  bromine 
to  form  a  hquid  dibromide  and  with  a  molecule  of  hydrobromic 
acid  to  form  a  crystalline  hydrobromide,  and  forms  a  semi- 
carbazone  with  semicarbazide.  When  reduced  in  alcoholic 
solution  with  sodium  it  gives,  first,  the  corresponding  second- 
ary alcohol,  pidegol,  and  then  Z-menthol :  — 


L,AKVUiNi!-  449 

CH3  CH3  CH3 

CH  CH  CH 

H2c/\ch2  ,  jj  ^HsC/NcHj       ,  „  ^HaC/NcHa 
HaC^CO  ^    '     HaCliCHOH^    '    HaCi      icHOH. 

C  C  CH 

H3C.C.CH3  H3C.C.CH3  H3C.C.CH3 

Pulegone  Pulegol 

H 

/-Menthol 

When  reduced  with  hydrogen  at  180°,  nickel  being  used  as  a 
catalyst,  pulegone  gives  menthone.  When  it  is  superheated 
with  water  pulegone  gives  acetone  and  1,3-methylcyclohexa- 
none : — 


CH3 

CH3 

CH 

CH 

H2C(         CH2  1    TT  r\ 

kAJco  +^^° 

c 

CH2 

H3C.C.CH3 

Pulegone 

1,3-MethyI- 
cyclohexanone 

This  reaction  determines  the  position  of  the  double  bond  in 
pulegone. 

c?-CaTvone,  C10H14O,  is  present  in  the  oil  of  caratvay  and  in 
dill  oil,  of  which  it  constitutes  from  50  to  60  per  cent.  It  is  a 
colorless  liquid  having  the  odor  of  the  oil  of  caraway  and  boiling 
at  23o°-23i°  It  is  an  unsaturated  ketone  and  forms  an  oxime 
with  hydroxylamine. 

This  oxime  also  results  when  limonene  is  treated  with 
nitrosyl  chloride,  and  hydrochloric  acid  is  eliminated  from 
the  addition  product  thus  formed :  — 


45° 


CH3 


AROMATIC   COMPOUNDS 
CH3 
C— CI 


HjC/^CH 


u; 


HsCiyCHs 
CH 

Limonene 

CH3 


+   ONCl    = 


H2C 


HjCl      JCH2 
CH 


NOH 


-  HCl 


H2C — C — CH3 

Limonenenitroso- 
chloride 


CH3 


H2NOH 

-< — 


H2C=C— CH3 

Carvoxime 


c 

HC,^^|CO 

H2C'xJCH2. 

CH 
H2C=C— CHs 

Carvone 


When  heated  with  phosphoric  acid  or  with  solutions  of  the 
alkalies  carvone  is  converted  into  carvacrol  (383),  and  this 
reaction  determines  the  position  of  the  oxygen  atom :  — 


CH3 


CH3 


c 

HC^^CO 
H2C  L      )  CH2 

CH 

>■ 

c 

HC^NCOH 
HC^  JCH 

C 

H2C— C    CH3 

H3C— C— CHs 

Carvone 

H 

Carvacrol 

When  treated  in  alcoholic  solution  with  sodium,  carvone  is  not 
reduced  to  carveol,  C10H15OH,  but  takes  up  four  atoms  of 
hydrogen  to  form  dihydrocarveol :  — 


4SI 

CHs  CH3 

C  CH 

HC.^CO        4.     ,H       =  HjC/NcHOH 

CH  CH 

HjC^C— CH3  H2C=:C— CH3 

Carvone  Dihydrocarveol 

Cineol  (eucalyptol),  CioHisO,  is  very  widely  distributed  in 
nature.  It  is  the  principal  constituent  of  the  oil  of  Eucalyptus 
globulus,  of  cajeput  oil,  niaouli  oil  and  of  the  oil  of  wormwood 
{Oleum  cinae),  and  is  found  in  a  very  large  number  of  other  oils. 
It  is  a  colorless  liquid,  optically  inactive,  and  has  an  odor  re- 
sembling that  of  camphor.  It  solidifies  at  about  1°  and  boils  at 
i76°-i77°.  The  oxygen  in  cineol  is  not  present  in  the  form  of 
hydroxyl  or  as  a  ketone  group,  since  sodium  does  not  act  upon 
it  and  it  does  not  react  with  either  hydroxylamine  or  phenyl- 
hydrazine.  Since  it  is  formed  by  the  elimination  of  a  molecule 
of  water  from  cis-terpin  it  is  regarded  as  an  oxide :  — 


-     H2O 


H3C— C- 

H2C/\CH2 
H2CI      JCH2   O. 


(CH3)2C— OH  (CH3)2C 

cis-Terpin  Cineol 

Note  for  Student.  —  Does  cineol  contain  an  asymmetric  carbon  atom? 

Cineol  has  basic  properties  and  forms  oxonium  salts  with 
hydrochloric  and  other  acids. 

Terpineol,  CioHisO,  occurs  in  the  (/-form  in  the  oil  of  orange 
and  in  the  /-form  in  lignaloe  oil.  The  commercial  liquid, 
terpineol,  is  formed  by  the  action  of  dilute  sulphuric  acid  on 
terpin  hydrate :  — 


452  AROMATIC  COMPOUNDS 

CHs  CH3 

C 

2       -7TTn  =  "^^'"l        |CH  ^H2C 
CH2OH        '       H^cL    JCH2   H2C 


H3C.C.OH 
CH3 

Terpineol 


CH3 


+H2O. 


CH3 

Terpin  hydrate 


Terpinolene 


The  a-terpineol  is  a  solid  melting  at  35°  and  boiling  at  2i7°-2i8°. 
The  commercial  liquid  product,  which  is  a  mixture  of  isomers, 
has  an  odor  resembling  that  of  the  lilac,  and  is  used  in  perfumery. 
When  the  optically  active  terpineols  are  boiled  with  a  solution 
of  oxalic  acid  they  lose  a  molecule  of  water  and  give  optically 
inactive  terpinolene,  as  shown  above. 

Note  for  Student.  —  Does  the  formula   for   terpinolene  contain  an 
asymmetric  carbon  atom?     Does  that  of  terpineol? 


BicYCLic  Terpenes 

The  two  most  important  members  of  this  group  are  pinene 
and  camphene. 

a-Pinene,  C10H16,  is  remarkably  widely  distributed  in  nature 
and  occurs  in  the  d-,  1-,  and  dl-  forms.  It  forms  the  principal 
constituent  of  the  distillate  from  the  oleoresins  obtained  from 
several  species  of  pine,  and  known  commercially  as  turpentine 
oils.  French  and  Spanish  turpentine  consist  for  the  most  part 
of  i-a-pinene,  while  in  the  Greek  and  American  oil  the  (i-a-pinene 
forms  the  largest  part.  There  are  also  American  turpentines 
which  are  levo  rotatory  or  nearly  inactive.  It  is  a  colorless, 
mobile  liquid  boiUng  at  i5s"-i56°.  Like  most  of  the  terpenes, 
a-pinene  takes  up  oxygen  from  the  air  and  partly  resinifies.  It 
is  very  readily  converted  into  other  terpenes.  When  heated  to 
25o°-27o°  it  is  changed  to  dipentene,  and  it  is  converted  into 


TERPIN   HYDRATE 


453 


terpinolene  by  means  of  alcoholic  sulphuric  acid.  a-Pinene  is 
an  unsaturated  hydrocarbon  with  one  double  bond.  When 
dry  hydrochloric  acid  gas  is  passed  into  the  well-cooled  and  dried 
a-pinene  one  molecule  of  hydrochloric  acid  is  taken  up  and 
bornyl  chloride  results. 

This  substance  used  to  be  called  pinene  hydrochloride, 
CioHieHCl,  and  on  account  of  its  odor,  which  resembles  that 
of  natural  camphor,  "  artificial  camphor.''  It  is  also  made 
from  borneol  (455)  by  the  action  of  phosphorus  pentachloride 
or  by  the  action  of  hydrochloric  acid,  and  hence  arose  the 
name :  — 


HoC CH — CH2 


H3C.C.CH3  +  HCl 


CH3 

a-Pinene 


HoC CH— CH2 


H2C 


CH 


H3C      CI 

Intermediate  hydrochloride 


XI2C        CH      CH2 


H3C.C.CH3      H 


H2C C C— CI 


Ho  C         CH         C  H2 


H3C.C.CH3         H 


H2C C C— OH 


CH3 

Bornyl  chloride 


CH3 

Borneol 


The  formula  now  given  to  a-pinene  represents  it  as  containing 
a  hexamethylene  and  a  tetramethylene  ring.  It  wiU  be  seen 
from  the  above  formulas  that  in  the  conversion  into  bornyl 
chloride  molecular  rearrangement  takes  place  with  the  forma- 
tion of  the  more  stable  pentamethylene  ring.  When  bornyl 
chloride  is  heated  with  aniline  it  gives  camphene. 

Terpin  hydrate,  CioHi8(OH)2  +  H2O,  is  formed  very  readily 
from  oil  of  turpentine  by  allowing  it  to  stand  for  several  days 
with  dilute  sulphuric  acid :  — 


454 


HaC- 


H 

-c- 


AROMATIC   COMPOUNDS 
H 

H2C — c- 


-CH2 


HC 


H3C.C.CH3 

=C — 
CH3 

a-Pinene 


-CH2 

+  2  H2O  = 

CH  H2C 


H3C.C.CH3 
OH 


+  H20  = 


HO^ 


\     -CH2 
^CHs 


H2C- 


-CH2 

H3C.C.CH3 
OH 


Terpin 

CH2OH 


H2C- 


-CH2 


HO/       \CH3 

Terpin  hydrate 

Terpin  hydrate  is  made  in  this  way  on  the  large  scale,  and  is 
converted  into  the  liquid  terpineols  by  the  action  of  dilute 
sulphuric  acid  for  use  in  perfumery.  When  heated  in  acetic 
acid  solution  with  benzenesulphonic  acid  a-pinene  takes  up 
only  one  molecule  of  water,  breaking  the  tetramethylene  ring 
and  forming  terpineol :  — 


H2C- 


H 

-c- 


HC 


H3C.C.CH3 
=C — 
CH3 

a-Pinene 


CH2  H2C' 

+  H2O  = 


H 

-c- 


-CH2 


CH 


HC 


H3C.C.CH3 
OH 


CH2 


CH3 

Terpineol 


This  reaction  establishes  the  position  of  the  double  bond  in 
a-pinene. 


BORNEOL 


455 


Camphene,  CioHie,  is  the  only  solid  hydrocarbon  of  this  for- 
mula occurring  in  nature.  Both  the  d-  and  the  I-  forms  have  been 
found  in  the  oils  of  lemon  and  other  volatile  oils.  Artificially 
camphene  is  obtained  from  bornyl  chloride  (made  from  pinene 
or  from  borneol)  by  the  elimination  of  hydrochloric  acid  (453). 
It  forms  a  colorless  crystalline  mass  having  a  faint  camphor- 
like odor  and  it  sublimes  very  readily.  It  is  much  more  stable 
towards  light  and  air  than  the  other  terpenes.  It  melts  at  about 
50°  and  boils  at  about  160°.  The  structural  formula  for  cam- 
phene, 


H2C CH C(CH3)2 

CH2 
H2C CH C=CH2 

Camphene 


H2C-^ CH- 


H2C- 


C(CH3)2 

CH2 

-CH C— CHs 


Dihydrocamphene 


H 


is  in  accord  with  the  fact  that  it  forms  a  dibromide,  CioHi6Br2 
(m.p.  9i°-9i.5°),  andcombines  with  one  molecule  of  hydrochloric 
acid.  On  reduction  with  hydrogen  in  the  presence  of  platinum 
it  gives  dihydrocamphene  (see  above)  isomeric  with  camphane 
(456).  When  it  is  heated  with  glacial  acetic  acid  and  50  per 
cent  sulphuric  acid  for  2-3  hours  at  5o°-6o°  it  is  converted 
into  isobornyl  acetate,  from  which  isoborneol  (457)  can  be 
obtained  by  saponification.  On  oxidation  with  chromic  acid 
camphene  is  converted  into  camphor. 

Bicyclic  Alcohols  and  Ketones 

Borneol,  Borneo  camphor,  CioHisO,  from  the  camphor  tree 
(Dryobalanops  camphora)  growing  in  Borneo,  Sumatra,  etc.,  is 
the  d-iorm.  The  Ngai  camphor  consists  of  the  /-borneol.  Both 
forms  are  present  also  in  various  volatile  oils.  The  artificial 
borneol  obtained  by  the  reduction  of  d-  or  /-camphor  in  alco- 
holic solution  by  sodium  is  a  mixture  of  d-  or  /-borneol  and  its 
stereoisomer    isoborneol.      The  pure  rf-borneol  crystallizes  in 


4S6 


AROMATIC   COMPOUNDS 


hexagonal  plates  that  melt  at  203°-204°  and  boil  at  212°.  Like 
camphor  it  volatilizes  at  ordinary  temperatures.  It  has  an 
odor  similar  to  that  of  camphor  and  ambra.  It  is  a  saturated, 
secondary  alcohol  and  gives  the  saturated  ketone,  camphor,  on 
oxidation :  — 


H2C 


H2C 


+  0  = 


CHOH 


H,C 


H2C 


+   H2O. 


C=0 


CH3 

Borneol  and  Isoborneol 


CH3 

Camphor 


Borneol  gives  optically  active  bornyl  iodide  with  hydriodic  acid 
(identical  with  pinene  hydroiodide)  and  this  when  reduced  with 
zinc  dust  and  hydriodic  acid  in  glacial  acetic  acid  yields  the 
optically  inactive  camphane :  — 


H2C 


H2C 


+  H2 


CHI 


H2C 


HoC 


CH, 


CH2 


+  HI. 


CH3 

d-  and  /-Bornyl  iodide 


CH3 

Camphane 


The  optically  inactive  camphane  is  obtained  from  both  d-  and 
I-  bornyl  iodide. 

Note  tor  Student.  —  Does  camphane  contain  an  asymmetric  carbon 
atom?  Explain  the  fact  that  borneol  and  isoborneol  both  give  camphor 
on  oxidation  and  that  camphor  on  reduction  gives  both  borneol  and  iso- 
borneol.    WTiat  does  fructose  give  on  reduction  ? 

With  phosphorus  pentachloride  borneol  gives  bornyl  chloride, 
identical  with  a-pinene  hydrochloride  (463) ,  and  this  gives  cam- 
phene  when  boiled  with  aniline :  — 


Z)-CAMPHOR 


457 


HaC 


H2C 


HC 

or 

H2C 

Bornyl  chloride 


CCH3 


HC 


\ 


CH2 


-C=GH2 


-CH2    C(CH3)2  +  HC1. 
— ^CH2 


H2C 

Camphene 

Isoborneol  is  always  formed  together  with  borneol  in  the 
reduction  of  camphor.  It  is  easily  obtained  from  camphene  in 
the  form  of  its  acetic  acid  ester,  isobornyl  acetate,  by  warming 
it  to  5o°-6o°  for  some  hours  with  glacial  acetic  acid  and  50 
per  cent  sulphuric  acid.  On  saponification  of  the  ester  iso- 
borneol results.  This  crystallizes  in  leaflets  of  the  hexagonal 
system,  which  melt  at  212°  in  a  sealed  tube.  It  volatilizes  very 
readily  and  is  more  soluble  than  borneol.  Isobornyl  chloride 
is  identical  with  camphene  hydrochloride.  Like  borneol,  iso- 
borneol is  a  saturated  secondary  alcohol,  and  gives  camphor 
on  oxidation.  Hence,  it  is  a  stereoisomer  of  borneol.  It 
differs  from  borneol  in  its  action  towards  dehydrating  agents, 
such  as  zinc  chloride.  Borneol  is  very  stable,  while  isoborneol 
yields  camphene. 

d-Camphor,  CioHieO,  generally  called  Japanese  or  laurus 
camphor  to  distinguish  it  from  Borneo  camphor,  is  obtained  on 
the  large  scale  together  with  camphor  oil  by  distilling  the  finely 
cut  wood  of  the  Cinnamomum  camphor  a  with  steam.  It  has 
also  been  found  in  several  volatile  oils.  The  I-  and  dl-  forms 
likewise  occur  in  some  volatile  oils.  Both  d-  and  /-camphor  are 
formed  artificially  by  the  oxidation  of  the  corresponding  opti- 
cally active  borneols  with  nitric  acid  or  of  camphene  with  chromic 
acid.     Camphor  crystallizes  in  the  hexagonal  system.     It  has  a 


4S8  AROMATIC   COMPOUNDS 

characteristic  odor  and  sublimes  even  at  ordinary  temperatures. 
It  melts  at  175°,  boils  at  204°,  and  is  readily  soluble  in  organic 
solvents.  Small  pieces  of  camphor  when  placed  on  water  rotate 
in  a  very  lively  manner. 

Camphor  is  a  saturated  ketone.  It  yields  an  oxime  with 
hydroxylamine,  and  on  reduction  in  alcohoUc  solution  with 
sodium  it  gives  both  borneol  and  isoborneol  (456).  Oxidized 
with  nitric  acid  it  gives  the  dibasic  camphoric  acid :  — 

CH3                                                      CH3 
H2C C C=0  H2C C COOH 


H3C.C.CH3 


+  3O 


H3C.C.CH3 


H2C CH — CH2  H2C CH — COOH 

Camphor  Camphoric  acid 

Phosphorus  pentoxide  converts  camphor  into  />-cymene :  — 
CioHieO  =  C10H14  +  H2O ; 

Camphor  ^-Cymene 

while  the  action  of  iodine  results  in  the  formation  of  carvacrol :  — 
CioHieO  +  I2  =  C10H14O  +  2  HI. 

Camphor  Carvacrol 

As  the  hydroxyl  group  in  carvacrol  (383)  is  in  the  ortho  position 
to  the  methyl  group,  it  follows  that  the  ketone  group  in  camphor 
is  also  ortho  to  the  methyl  group. 

Approximately  9  million  pounds  of  camphor  are  produced 
annually.  Two-thirds  of  this  is  used  in  the  celluloid  industry 
(in  the  manufacture  of  celluloid  articles,  motion-picture  films, 
etc.);  the  rest  is  used  in  the  manufacture  of  smokeless  pow- 
der, explosives,  and  for  disinfection  and  medicinal  purposes. 
Camphor  is  now  manufactured  artificially  from  the  oil  of  tur- 
pentine. The  pinene  is  first  converted  into  bornyl  chloride 
by  the  action  of  dry  hydrochloric  acid,  and  the  bornyl  chloride 
is  then  heated  with  bases.  This  gives  camphene.  The  cam- 
phene  is  then  converted  into  camphor  by  oxidation  with 
chromic  acid  mixture,  in  which  case  bornyl  and  isobornyl  chro- 
mates  are  formed  as  intermediate  products.     Another  method 


LINALOOL  459 

converts  camphene  into  isobornyl  acetate  (457),  and  this  is 
hydrolyzed  to  isoborneol,  which  on  oxidation  gives  camphor 
(456).     The  synthetic  camphor  is  optically  inactive.' 

Isomeric  with  camphor  or  borneol  are  three  important  sub- 
stances, geraniol,  linalool,  and  geranial,  which  are  termed  ole- 
fine  camphors,  to  distinguish  them  from  camphor  and  borneol. 

Geraniol,  CioHisO,  is  the  principal  constituent  of  palmarosa 
oil  and  of  the  German  and  Turkish  rose  oils.  It  is  also  found  in 
considerable  quantities  in  the  oils  of  geranium,  citronella,  and 
lemon  grass.  Pure  geraniol  is  a  colorless  oily  liquid  with  a 
pleasant  rose-like  odor,  that  boils  at  229°-23o°.  It  is  optically 
inactive  and  is  a  primary  alcohol,  as  it  gives  geranial,  CioHieO, 
an  aldehyde,  on  oxidation,  and  has  been  made  by  the  reduction 
of  this  aldehyde.     It  has  been  shown  to  have  the  structure  :  — 

(CH3)2C=CH.CH2.CH2.C=:CH.CH20H  = 

CHa 

Geraniol 

(CH3)2C=CH.CH2.CH2.C=C=CH2  +  HjO. 
CH3 

Anhydrogeraniol 

It  yields  anhydrogeraniol,  CioHie  (see  above),  when  heated  with 
dehydrating  agents,  and  is  converted  into  dipentene  by  the 
action  of  dilute  sulphuric  acid  (447). 

Linalool,  CioHigO,  is  isomeric  with  geraniol  and  forms  the 
chief  constituent  of  lignaloe  oil.  It  boils  at  i98°-i99°  and  is 
readily  converted  into  geraniol  by  the  action  of  organic  acids. 
It  is  optically  active  and  is  a  tertiary  alcohol.  It  has  been 
shown  to  have  the  structure  :  — 

CH3 

(CH3)2C=CH.CH2.CH2.C— CH=CH2. 

OH 

Linalool 

'  See  article  cm  Camphor  in  Thorpe's  Dictionary  of  Applied  Chemistry, 
latest  edition. 


460  AROMATIC   COMPOUNDS 

Both  geraniol  and  linalool  are  very  readily  converted  into  the 
terpenes  and  their  oxygen  derivatives  (447). 

Geranial,  citral,  CioHieO,  is  the  chief  constituent  of  lemon 
grass  oil.  It  is  a  hght  yeUow  liquid,  optically  inactive,  having 
the  odor  of  lemon.  It  boils  at  110°  to  111°  (12  mm.).  As  it 
gives  geraniol  when  reduced,  and  geranic  acid,  containing  the 
same  number  of  carbon  atoms,  when  oxidized,  it  has  the  follow- 
ing structure :  — 

(CH3)2C=CH.CH2.CH2.C=CH.CHO. 
CH3 

Citral 

When  heated  with  potassium  hydrogen  sulphate  citral  is  con- 
verted into  p-cymene.  Citral  readily  condenses  with  acetone  to 
form  ionone,  C13H20O,  which  has  the  odor  of  violets  and  is  manu- 
factured on  the  large  scale.  ^ 

POLYTERPENES 

Caoutchouc,  (CjHs),,  generally  known  as  rubber  or  indiarub- 
ber,  is  the  coagulated  latex  or  milky  juice  of  certain  tropical 
plants,  especially  of  Hevea  Braziliensis.  It  can  be  obtained  pure, 
in  the  form  of  a  white,  amorphous  mass,  by  dissolving  the  crude 
product  in  benzene,  precipitating  with  alcohol  and  extracting 
this  product  with  acetone.  Analyses  of  this  product  give  results 
agreeing  with  the  formula,  CsHg.  Rubber  is  a  colloid  of  high 
molecular  weight  belonging  to  the  class  of  terpenes.  It  com- 
bines with  bromine  to  form  a  tetrabromide  (CioHi6Br4)^,  and 
with  hydrochloric  acid  to  form  a  dihydrochloride  (CioHie  2  HCl),. 
When  heated  with  a  small  amount  of  sulphur  under  pressure 
or  when  treated  with  sulphur  chloride  in  the  cold,  it  undergoes 
mdcanization.  This  process  of  vulcanization  by  heating  with 
sulphur  is  much  facihtated  by  the  presence  of  accelerators 
(such  as  lead  oxide,  zinc  oxide,  thiocarbanilide,  etc.).  It  in- 
creases the  strength,  elasticity,  durability,  and  usefulness  of 

'  See  Volatile  Oils,  by  E.  Gildemeister,  2d  ed.,  translated  by  E.  Kramers 
page  464. 


CAOUTCHOUC  461 

rubber.  Unvulcanized  rubber  becomes  sticty  at  30°  and  loses 
its  elasticity  completely  at  0°.  When  heated  with  a  larger 
amount  of  sulphur  and  to  a  higher  temperature,  hard  rubber, 
ebonite  or  vulcanite  is  formed. 

When  crude  rubber  is  subjected  to  dry  distillation  both 
isoprene  (444)  and  dipentene  are  formed,  and  an  artificial 
rubber  has  been  made  by  the  polymerization  of  isoprene  by  heat 
and  other  polymerizing  agents.  This  artificial  rubber  can  be 
vulcanized  like  the  natural  rubber.  Owing  to  the  great  com- 
mercial importance  of  rubber  many  attempts  have  been  made  to 
prepare  it  artificially  by  the  polymerization  of  isoprene,  but 
so  far  the  process  has  not  been  a  commercial  success  and  the 
production  of  an  artificial  rubber  completely  identical  in 
all  its  properties  with  the  natural  product  has  not  yet  been 
attained.  The  world's  production  of  plantation  rubber  in  1920 
was  304,000  tons.'  The  value  of  the  rubber  industry  in  1919 
was  $1,122,000,000.  Gutta  percha  and  balata  seem  to  be 
isomeric  with  rubber. 

'  See  article  on  Rubber  in  Thorpe's  Dictionary  of  Applied  Chemistry  and 
in  /.  Ind.  and  Eng.  Chem.,  May,  1922. 


CHAPTER  XVI 

DIPHENYLMETHANE,  TRIPHENYLMETHANE,  TETRA- 
PHENYLMETHANE,  AND   THEIR  DERIVATIVES 

As  we  have  seen,  toluene  may  be  regarded  either  as  methyl- 
benzene  or  phenyhnethane.  Of  course,  according  to  all  that 
is  known  regarding  similar  substances,  the  two  views  are  identi- 
cal.    Regarding  it,  for  our  present  purpose,  as  phenyhnethane, 

CeHs 

TT 

we  may  write  its  formula  thus :  C  |  „ 

H 

This  suggests  the  possibility  of'  the  existence  of  such  sub- 
stances as  Diphenylmethane,  Triphenylmethane,  and  Tetra- 
phenylmetkane :  — 


fCeHs 
P  I  CeHs 
^'^  IH 

H 


Cells  fCeHs 


(! 


CeHs  p  I  CjHs 

CeHs     '  I  CeHs 

H  [  CeHe 


All  these  hydrocarbons  are  known.  The  derivatives  of  di- 
and  triphenylmethane  are  of  special  interest  and  importance. 
Only  di-  and  triphenylmethane  wiU  be  treated  of  here. 

There  is  one  reaction  by  means  of  which  these  hydrocarbons 
can  be  made  very  readily.  It  has  also  been  used  for  the  synthesis 
of  many  other  aromatic  hydrocarbons  and  their  derivatives.  It 
depends  upon  the  remarkable  fact  that,  when  an  aromatic  hydro- 
carbon is  brought  together  with  a  compound  containing  chlorine, 
and  anhydrous  aluminium  chloride  then  added,  hydrochloric  acid 
is  evolved,  and  union  of  the  two  residues  is  effected,  the  alumin- 
ium chloride  not  entering  into  the  composition  of  the  product 
(Friedel-Crafts  reaction).  Thus,  when  benzene  and  benzyl 
chloride,  C6H6.CH2CI,  are  brought  together,  no  action  takes 

462 


DIPHKNYLMETHANE  463 

place;  but,  if  some  anhydrous  aluminium  chloride  is  added, 
•reaction  takes  place  according  to  the  following  equation :  — 

CeHs.CHjCl  +  CeHe  =  CeHs.CHj.CeHs  +  HCl, 

Diph  enylmethane 

and  diphenylmethane  is  formed. 

Similarly,  when  chloroform  and  benzene  are  brought  together 
in  the  presence  of  aluminium  chloride,  triphenylmethane  is 
formed  accdrding  to  this  equation :  — 

CHCI3  +  3  CeHe  =  CH(CeH6)3  +  3  HCl. 

Triphenylmetliane 

Another  method  by  which  these  hydrocarbons  can  be  made, 
consists  in  heating  a  chloride  and  a  hydrocarbon  together  in  the 
presence  of  zinc  dust.  Thus,  benzyl  chloride  and  benzene  give 
diphenylmethane  when  boiled  with  zinc  dust;  and  benzal 
chloride,  C6H6.CHCI2,  and  benzene  give  triphenylmethane :  — 

C6H5.CHCI2  +  2  CeHe  =  CH(C6H6)3  +  2  HCl. 

Diphenylmethane,  H2C(C6H6)2,  is  most  readily  made  from 
benzyl  chloride,  benzene,  and  aluminium  chloride.  It  can  also 
be  obtained  from  methylene  chloride  and  benzene  in  the  pres- 
ence of  aluminium  chloride :  — 

H2CCI2  +  2  CeHe  =  H2C(C6H6)2  +  2  HCl. 

Methylene  Benzene         Diphenylmethane 

chloride 

Diphenylmethane  and  its  homologues  are  also  formed  from 
the  ahphatic  aldehydes  and  the  aromatic  hydrocarbons  by  the 
action  of  concentrated  sulphuric  acid :  — 

H2C=:0  +  2  CeHe  =  H2C(C6H6)2  +  H2O. 

Formaldehyde  Benzene  Diphenylmethane 

Acetic  aldehyde  gives  diphenyle thane,  H3C.CH(C6H6)2.  Di- 
phenylmethane crystallizes  in  colorless  needles  that  have  the 
odor  of  oranges  and  melt  at  26°.  It  is  readily  soluble  in  alcohol 
and  ether  and  distils  at  262°. 


464  DIPHENYLMETHAXE,   ETC. 

/i-Diaminodiphenylmethane,  (H2NC6H4)2CH2,  is  obtained 
by  heating  anhydroformaldehydeaniline,  C6H6N=;CH2  (made 
by  the  action  of  formaldehyde  on  aniline),  with  aniline  and 
aniline  salt.    A  nhydro-p-aminobenzyl  alcohol,  H — N — -€6114 — CH; 


is  formed  as  the  intermediate  product :  — 

H— N— C6H4CH2  +  HC6H4.NH2  =  H2C(C6H4NH2)2. 

I 1 

It  is  used  in  the  preparation  of  fuchsine  (469).  Its  tetramethyl 
derivative  is  obtained  from  dimethylaniline  and  formalde- 
hyde :  — 

H2CO  +  2  HC6H4.N(CH3)2    =  H2C(C6H4N(CH3)2)2  +  H2O. 

Tetramethyl-^-diarainodiphenyl- 
methane 

Benzhydrol,  diphenylcarbinol,  (C6H5)2.CHOH,  is  made  from 
diphenylmethyl  bromide,  (C6H6)2CHBr  (from  diphenyl- 
methane  and  bromine) ,  by  heating  with  water.  It  is  also  formed 
by  the  reduction  of  benzophenone  (400)  and  gives  benzophenone 
on  oxidation.  It  can  also  be  obtained  by  the  action  of  phenyl 
magnesium  bromide  on  benzaldehyde :  — 

H 

CsHs.MgBr  +  C6H5.CHO  =  (C6H5)2C— O— MgBr, 
(C6H6)2C— OMgBr  +  H2O  =   (C6H5)2.CHOH  +  Br.Mg.OH. 

Benzhydrol 

H 

Tetramethyl-/i-diaminobenzhydrol,  ((CH3)2NC6H4)2CHOH,  is 
obtained  by  the  oxidation  of  tetramethyl-/>-diamino-diphenyl- 
methane  and  also  by  the  reduction  of  Michler's  ketone  (401). 
It  crystallizes  in  colorless  prisms,  which  dissolve  in  glacial  acetic 
acid  with  an  intense  blue  color.  It  is  known  as  Michler's 
hydrol,  and  is  used  in  the  synthesis  of  many  dyestuffs. 

Triphenylmethane,  CH(C6H5)3.  —  This  hydrocarbon  can  be 
made,  as  above  described,  from  benzal  chloride  and  benzene, 
and  from  chloroform  and  benzene.  It  is  best  obtained  from 
triphenylmethyl    chloride    (made    from   carbon    tetrachloride, 


TETRAMETHYLDIAMINOTRIPHENYLMETHANE        465 

benzene,  and  aluminium  chloride)  by  the  action  of  zinc  dust  and 
glacial  acetic  acid :  — 

(C6H5)3CC1  +  H2   =   (C6H6)3CH  +  HCl. 

Ifforms  lustrous,  thin  laminas,  that  melt  at  93°.  It  is  insoluble 
in  water ;  easily  soluble  in  benzene,  ether,  and  chloroform.  It 
is  crystallized  best  from  hot  alcohol. 

With  bromine  triphenyhnethane  gives  triphenylmethyl  bro- 
mide, (C6H5)3C— Br,  and  this  is  converted  into  triphenyl- 
carbinol,  (C6H6)3C — OH,  by  simply  boiling  with  water.  Tri- 
phenylcarbinol  melts  at  159°.  It  can  also  be  prepared  by  the 
oxidation  of  triphenylmethane  in  glacial  acetic  acid  solution 
with  chromic  acid.  It  has  been  made  synthetically  from 
benzophenone  by  the  action  of  phenyl  magnesium  bromide  :  — 

(C6H5)2CO — ^  (C6H5)3C— OMgBr — ^  (C6H5)3COH. 

On  reduction  with  zinc  and  acetic  acid  it  is  converted  into  tri- 
phenylmethane. 

Triphenylmethyl,  (C6H5)3C,  is  the  name  given  to  a  compound 
obtained  by  Gomberg  by  the  action  of  molecular  silver  on 
triphenylmethyl  chloride  in  solution  in  benzene  :  — 

(C6H5)3C-C1  +  Ag   =   AgCl  +   (C6H5)3C. 

Triphenylmethyl 

It  is  characterized  by  its  remarkable  chemical  activity.  It 
combines  at  once  with  oxygen  when  brought  in  contact  with  the 
air  to  form  the  colorless  peroxide,  (C6H6)3CO — OC(C6H5)3,  and 
unites  quantitatively  with  iodine  to  form  triphenylmethyl 
iodide,  (C6H6)3CI.  Molecular  weight  determinations  by  the 
freezing  point  method  show  that  it  has  the  formula,  (€(06115)3)2. 
According  to  this  it  is  hexaphenylethane,  (C6H6)3C — C(C6H6)3. 
When  first  dissolved  in  benzene  the  solution  is  colorless,  but  it 
soon  becomes  orange-yellow.  When  this  solution  is  shaken  with 
air  the  color  disappears,  owing  to  the  formation  of  the  peroxide, 
but  it  reappears  when  the  solution  is  allowed  to  stand. 

Tetramethyldiaminotriphenylmethane,  leucomalackite  green, 
C6H5CH(C6H4N(CH3)2)2,   is  formed  when   benzaldehyde   and 


466  DIPHENYLMETHANE,  ETC. 

dimethylaniline  are  heated  with  a  dehydrating  agent  or  witl 
hydrochloric  acid :  — 

CeHsCHO  +  2  HC6H4N(CH3)2 

Benzaldebyde  Dimethylaniline 

=  C6HbCH(C6H4N(CH3)2)2  +  HaO 
Tetramethyldiamino- 
triphenylmethane 

It  crystallizes  from  alcohol  in  colorless,  trichnic  plates  meltin; 
at  93°-94°.  As  it  is  a  colorless  compound  and  results  from  th( 
reduction  of  malachite  green  it  is  called  leucomalachite  greet 
(Gr.  leukos,  white).  It  is  a  basic  substance  and  forms  colorlesi 
salts  with  acids.  When  oxidized  with  lead  dioxide  it  gives  th( 
carbinol,  CeHsCCOH) (C6H4N(CH3)2)2.  This  is  also  a  colorless 
crystalline  substance  (m.p.  132°)  which  dissolves  in  acids  in  thi 
cold  without  color.  On  heating,  however,  water  is  split  off  an( 
the  green  salt  is  formed :  — 

.C6H4N(CH3)2  C6H4N(CH3)2 

'1  \C6H4N(CH3)2   =  CeHsC:/     \n(CH3)2  +  H2O. 
/\  \z=/     I 


OH 

H     CI  CI 

Colorless  salt  Colored  salt 

The  structure  of  the  colored  salt  is  similar  to  that  of  ^-quinon 
(431),  and  for  this  reason  the  formula  is  called  a  "  quinoid 
formula.  It  will  be  shown  later  that  many  other  dyes  have  th 
quinoid  structure.  (See  salts  of  phenolphthalein  (474)  an^ 
fuchsin  (469)).  The  dye,  malachite  green,  is  either  the  doubl 
salt  of  zinc  chloride  with  the  above  colored  salt,  3  C23H26N2C 
+  2  ZnCl2  +  2  H2O,  or  the  oxalate,  2  C23H26N2  +  3  H2C2O 
On  reduction  malachite  green  takes  up  hydrogen  and  is  cor 
verted  into  the  colorless  tetramethyldiaminotriphenylmethan 
(leucomalachite  green),  just  as  the  colored  quino"ne  is  converte 
into  the  colorless  hydroquinol  by  reduction :  — 

^C6H4N(CH3)2  +  H2 

'   ^<(^^)>:N(CH3)2  =  C6H6CH(C6H4N(CH3)2)2  +  HC 
01 

Green  salt  Leucomalachite  green 


TRIPHENYLMETHANE   DYES  467 

When  a  solution  of  sodium  hydroxide  is  added  to  a  solution  of 
malachite  green,  the  colorless  tetramethyldiaminotriphenyl- 
carbinol  is  precipitated,  as  the  colored  base  first  formed  is  un- 
stable and  goes  over  into  the  colorless  carbinol,  which  is  insoluble 
in  water :  — 

/C6H4N(CH3)2 
CeHeC/    /=zv  — ^     C6H6C=(C6H4N(CH3)2)2. 


OH 
OH 


^^^^N(CH3)2 


Colored  base  Colorless  carbinol 

Somewhat  over  654,000  pounds  of  malachite  green  (oxalate)  were 
made  in  the  United  States  in  1920. 

^-Trinitrotriphenylmethane,  HC(C6H4N02)3,  is  formed  by 
treating  triphenylmethane  with  fuming  nitric  acid.  It  crys- 
tallizes in  scales  that  melt  at  203°  On  reduction  it  gives 
triaminotriphenylmethane,  HC(C6H4NH2)3,  which  is  called />ara- 
leucaniline,  as  it  is  also  formed  by  the  reduction  of  pararqs- 
aniline,  HOC(C6H4NH2)3,  and  is  converted  into  pararosaniline 
on  oxidation.  It  crystallizes  in  leaflets  that  melt  at  148°. 
When  trinitrotriphenyhnethane  is  oxidized  with  chromic  acid 
it  gives  trinitrotriphenylcarbinol,  HOC(C6H4N02)3,  and  when 
this  is  reduced  with  zinc  dust  and  acetic  acid,  pararosaniHne 
is  formed. 

Triphenylmethane  Dyes 

Many  of  the  triphenylmethane  dyes  are  salts  of  pararos- 
aniline, C19H19N3O,  and  of  its  homologue,  rosaniline, 
Ci9Hi8(CH3)N30,  and  their  derivatives.  PararosanUine  is 
formed  when  aniline  and  paratoluidine  are  oxidized  with  arsenic 
acid  or  with  nitrobenzene :  — • 

2  CeHeNHa  +  H3C.C6H4.NH2  -}-  3  O 

Aniline  ^-Toluidine 

=  HOC(C6H4NH2)3  +  2  H2O. 

Pararosaniline 

Rosaniline  is  formed  'by  oxidizing  aniline  and  a  mixture  of 
ortho  and  paratoluidine :  — 


468  DIPHENYLMETHANE,   ETC. 

CeHsNHj  +  H3C.C6H4.NH2  +  H3C.C6H4.NH2  +  3  O 
Aniline  ^-Toluidlne  o-Toluidine 

=  Hoc<r        NH2    +  2  H20 

Rosaniline 

Rosaniline  is  formed  only  when  orthotoluidine  is  present,  and 
from  the  above  method  of  formation  it  will  be  seen  that  it  is  a 
methyl  derivative  of  pararosaniUne.  As  rosaniline  contains 
a  residue  of  orthotoluidine,  it  follows  that  the  methyl  group  is 
in  the  ortho  position  to  the  amino  group  in  this  substance. 

By  treating  pararosanUine  with  a  reducing  agent  it  is  con- 
verted into  paraleucaniline,  which  has  been  shown  to  be  ^-tri- 
aminotriphenylmethane :  — ■ 

HOC(C6H4NH2)3  +  H2  =  HC(C6H4NH2)3  +  H2O, 

Pararosaniline  Paraleucaniline 

while  rosaniline  when  reduced  gives  leucaniUne  :  — 

^(C6H4NH2)2  ^(C6H4NH2)2 

Rosaniline  Leucaniline 

It  will  be  seen  from  these  facts  that  pararosaniline  is  a  derivative 
of  triphenyhne thane  and  that  rosaniline  is  derived  from  its 
homologue,  diphenyltolylmethane,  (C6H5)2CH(C6H6CH3).  This 
was  first  conclusively  shown  by  diazotizing  paraleucaniline 
and  decomposing  the  diazonium  salt  formed  with  alcohol  when 
triphenylmethane  was  obtained :  — 

HC(C6H4NH2H2S04)3 ^  HC(C6H4N2HS04)3  — ^  HC(C6H6)3. 

Leucanihne  by  similar  treatment  gave  diphenyltolylmethane. 
Pararosaniline  was  then  made  synthetically  from  triphenyl- 
methane :  — 

HC(C6H6)3  -^  HC(C6H4N02)3  — ^  HC(C6H4NH2)3 

Paraleucaniline 

^-^HOC(C6H4NH2)3. 

Pararosaniline 


TRIPHENYLMETHANE   DYES  469 

In  the  commercial  preparation  of  fuchsine  or  magenta,  a  mixture 
of  aniline,  ortho-  and  paratoluidine  is  oxidized  with  nitro- 
benzene. Both  pararosaniline  and  rosaniline  are  formed.  (See 
467,  468.)  When  these  colorless  bases  are  treated  with  hydro- 
chloric acid  they  form  colored  salts  by  the  elimination  of 
water,  as  in  the  case  of  the  formation  of  malachite  green  (465) , 
thus :  — 

/C6H4NH2  /=s. 

HO— C^C6H4NH2    =   H20-|-(H2NC6H4)2C=(        >=NH2C1. 
\C6H4NH2HCl  \=/ 

Pararosaniline  hydrochloride  Parafuchsine,  quinoid 

(colorless)  (colored) 

When  parafuchsine  (I)  is  treated  with  solutions  of  the  alkalies 
it  is  first  converted  into  an  unstable,  colored,  substituted  am- 
monium hydroxide  (II)  and  this  gradually  goes  over  into  the 
insoluble,  colorless  carbinol  base,  pararosaniline  (III) :  — ■ 

C(C6H4NH2)2  C(C6H4NH2)2  HO— C(C6H4NH2)2 

A 

H2NCI  H2N— OH  NH2 

Parafuchsine  Colored  base  Pararosaniline 

Another  method  for  the  preparation  of  parafuchsine  consists  in 
the  oxidation  of  diaminodiphenylmethane  (463)  and  aniline  in 
the  presence  of  hydrochloric  acid  :  — 

(H2N.C6H4)2CH2  +  H.C6H4.NH2  +  O2 

=  (H2N.C6H4)3COH  +  H2O. 

The  commercial  fuchsine  or  magenta  is  a  mixture  of  the  colored 
(quinoid)  chlorides  of  pararosaniline  and  rosanUine.  It  forms 
green  crystals  which  dissolve  in  water  with  a  red  color.  It  dyes 
silk  and  wool  directly  a  bluish  red  color,  cotton  only  after 
mordanting  with  tannin  and  tartar  emetic.  Somewhat  over 
284,000  pounds  of  fuchsine  or  magenta  were  produced  in  the 
United  States  in  1920. 


47°  DIPHENYLMETHANE,   ETC. 

Dyeing.  Silk  and  woolen  fabrics  can  generally  be  dyed 
directly  by  placing  them  in  a  solution  of  a  dye,  cotton  only  in 
the  case  of  certain  substantive  dyes  (Congo  red  for  example). 
Vegetable  fabrics  require  as  a  rule  previous  treatment  with  a 
mordant.  Aluminium,  ferric  and  chromic  hydroxides,  obtained 
by  saturating  the  fabric  with  the  acetates  of  these  metals  and 
then  steaming,  are  used  as  mordants  with  acid  dyes,  while 
tannin  is  employed  with  basic  dyes. 

Acid  fuchsine  is  a  mixture  of  the  acid  sodium  salts  of  the  di- 
and  trisulphonic  acids  of  rosaniline  and  pararosardline,  made  by 
the  action  of  fuming  sulphuric  acid  on  these  bases  and  convert- 
ing the  sulphonic  acids  formed  into  the  acid  sodium  salts.  It 
is  more  soluble  in  water  than  fuchsine  and  is  a  valuable  dye. 

Derivatives  of  Parajrosaniline  and  Rosaniline 

By  the  introduction  of  methyl  or  ethyl  groups  into  fuchsine  in 
the  place  of  the  amino  hydrogens  the  red  color  of  the  dye  is 
changed  to  violet,  the  intensity  of  the  latter  color  depending  on 
the  number  of  alkyl  groups  introduced. 

Methyl  violet  is  made  by  oxidizing  dimethylaniline  with  copper 
sulphate,  phenol,  and  sodium  chloride.  The  methane  carbon 
atom  necessary  to  combine  the  three  phenyl  residues  is  spUt  off 
from  part  of  the  dimethylaniUne.  Consequently  methyl  violet  is 
essentially  a  mixture  of  pentamethylparafuchsine  and  hexa- 
methylparafuchsine.  It  dyes  silk  and  wool  a  violet  color,  the 
shade  being  bluer  the  more  methyl  groups  the  dye  contains. 
Over  600,000  pounds  of  methyl  violet  were  produced  in  the 
United  States  in  1920. 

Crystal  violet  is  hexamethylparafuchsine.  It  is  one  of  the 
constituents  of  methyl  violet  and  is  characterized  by  its  re- 
markable power  of  crystallization,  whence  the  name.  It  is 
made  by  the  action  of  dimethylaniUne  (i)  on  Michler's  ketone 
(401)  or  (2)  on  Michler's  hydrol  (401) :  — 

(cS'nSh!^*^^  +  H.C6H4N(CH3)2=  HO.C(CeH4N(CH3)2)3. 

Michler's  Dimethylaniline  Hexamethyltriamino- 

ketone  triphenylcarbinol 


ANILINE   BLUE  47 1 

When  the  carbinol  is  treated  with  hydrochloric  acid,  water 
splits  off,  giving  crystal  violet, 

((H3C)2NC6H4)2=C=/"^=N(CH3)2C1. 
Crystal  violet 

When  Michler's  hydrol  is  used  the  leuco  base  is  first  formed :  — 

Michler's  hydrol  Dimethylaniline 

=    HC(C6H4N(CH3)2)3  +  H2O. 
Leucobase  of  crystal  violet 

The  leucobase  is  then  oxidized  to  the  dye  base  (carbinol)  with 
lead  peroxide  as  in  the  case  of  the  preparation  of  malachite 
green  (466),  and  the  carbinol  is  combined  with  hydrochloric 
acid. 

Aniline  blue.  —  When  pararosaniline  or  rosaniline  is  heated 
with  aniline  and  benzoic  acid,  ammonia  is  eliminated  and  the 
triphenyl  derivative  is  formed  :  — 

HO.C(C6H4NH2)3  +  3  H2N.C6H5 

Pararosaniline 

=  HO.C(C6H4NHC6H5)3  +  3  NH3. 

Triphenylpararosaniline 

As  the  anhydro-chloride  of  this  base, 

(C6H6HNC6H4)2=C=<'^N=NHC6H6, 

CI 

Aniline  blue 

is  insoluble  in  water,  it  has  to  be  used  in  alcoholic  solution. 
Triphenylpararosaniline  is  usually  converted  into  sulphonic 
acids  (mono-,  di-,  or  trisulphonic  acid)  by  the  action  of  fuming 
sulphuric  acid  in  order  to  render  it  soluble.  The  sodium  salts 
of  these  acids  are  called  Soluble  blue,  Alkali  blue,  Cotton  blue,  etc. 
About  783,000  pounds  of  Alkali  blue  and  Soluble  blue  were 
produced  in  the  United  States  in  1920. 


47-  DIPHENYLMETHANE,   ETC. 

Phthaleins 

When  a  phenol  is  heated  with  phthaUc  anhydride  and  a 
dehydrating  agent,  water  is  ehminated  and  a  phthalein  is  formed. 

Phenolphthalein,  C20H14O4,  is  the  simplest  of  all  the  phthaleins. 
It  is  formed  by  heating  phenol  and  phthahc  anhydride  with 
concentrated  sulphuric  acid  or  with  some  other  dehydrating 
agent : — 


/CO  /CCCeHiOH) 


2 


C6H4<:        )>0  +   2  HC6H4.OH    =    C6H4<'      ^O  +H2O. 

Phenolphthalein 

After  the  reaction  is  completed  the  mass  is  boiled  with  water  to 
remove  the  sulphuric  acid,  unchanged  phenol  and  phthahc 
anhydride,  and  the  phenolphthalein  dissolved  in  a  solution  of 
caustic  soda.  The  solution  is  filtered  to  remove  fluoran  (476), 
the  phenolphthalein  precipitated  by  the  addition  of  an  acid  and 
recrystallized  from  methyl  alcohol.  It  cr},-staUizes  in  the  mono- 
clinic  system,  is  insoluble  in  water,  and  melts  at  2So°-253°. 
It  dissolves  in  alkahes  with  a  red  color  and  is  precipitated 
from  this  solution  colorless  by  acids.  It  is  used  as  an  indicator 
in  acidimetry  and  alkalimetry.  It  is  made  on  the  large  scale 
and  is  used  as  a  purgative.  It  is  not  a  dye  but  is  converted 
into  a  dye  by  introducing  nitro  groups.  (Compare  with  phenol 
and  picric  acid.) 

Phenolphthalein  has  been  shown  by  Baeyer  to  be  a  derivative 
of  triphenylmethane  by  means  of  the  following  reactions.  When 
phthalic  anhydride  is  treated  with  phosphorus  pentachloride  it 
gives  phthalyl  chloride  (417) ,  and  this  when  heated  with  benzene 
in  the  presence  of  aluminium  chloride  gives  diphenylphthalide : — 

/C=Cl2  /C(C6H6)2 

C6H4<^  )o       +  2  HCeHe  =  C6H4<^   )>0         -f  2  HCl. 
^CO  XO 

«-Phthalyl  chloride  Benzene  Diphenylphthalide 

Diphenylphthalide  when  boiled  with  a  concentrated  solution 


PHTHALEINS  473 

of   caustic  soda  gives    the   sodium  salt  of    triphenylcarbinol- 
carboxylic  acid :  — 

(^(C,li,h  HO-7C(C6H6)2 


/"^y^eo-sh  HO- 

C6H4<r    yo  +    HONa    =    C6H4< 


^CO  ^COONa 

DiphenylphthaEde  or  anhydride  Sodium  salt  of  triphenyl- 

of  triphenylcarbinolcarboxylic  acid  carbinolcarboxylic  acid 


This  sodium  salt  undergoes  reduction  to  the  sodium  salt  of 
triphenylmethanecarboxylic  acid  when  its  solution  is  boiled 
with  zinc  dust :  — ■ 

HOC(C6H6)2  HC(C6H6)2 

C6H4/  +  Ha  =  C6H4/  +  H2O. 

\COONa  ^COONa 

Sodium  triplienyl-  Sodium  triphenyl- 

carbinolcarboxylate  methanecarboxylate 

The  triphenylmethanecarboxylic  acid,  obtained  from  the 
sodium  salt,  by  decomposing  it  with  acids,  gives  triphenyl- 
methane  when  heated  with  barium  hydroxide :  — 

HC(C6H6)2 

CeHi/  =  (C6H6)3CH  +  CO2. 

^COOH 

Triphenylmethane-  Triphenylmethane 

carboxylic  acid 

Having  thus  shown  that  diphenylphthalide  is  a  derivative  of 
triphenylmethane  Baeyer  then  made  phenolphthalein  syntheti- 
cally from  it.  On  heating  with  nitric  acid  dinitrodiphenyl- 
phthalide  (II)  was  made.  This  was  then  converted  into  diamino- 
diphenylphthalide  (III)  by  reduction,  and  this  when  diazotized 
and  boiled  with  water  gave  phenolphthalein :  — ■ 

fCeHs  fC6H4N02            fC6H4NH2           [CeHiOH 

CeHs  pICeHiNOz  p   C6H4NH2  p   C6H4OH 

C6H4— CO  *--  C6H4— CO  ^  CeHi— CO  •"  C6H4— CO 

0_ 1  [O 1  ■  [0 L  [o 1 

Diplienylphthalide  II  III  PlieBolphtiialein 

From  this  synthesis  of  phenolphthalein  it  will  be  seen  that  it  is 
dihydroxy  diphenylphthalide. 


474 


DIPHENYLMETHANE,  ETC. 


When  phenolphthalein  dissolves  in  solutions  of  the  alkalies 
it  gives  a  red  color,  due  to  the  formation  of  the  red  sodium  salt 
of  the  quinoid  modification  of  phenolphthalein :  — 


HO 


OH 


HO 


Phenolphthalem 
Cactoid  formula) 


HO 


+  KOH  = 


OH 


Potassium  salt  of  the  carbinol- 

carboxylic  acid  (colorless, 

unstable) 


+  H,0. 


COOK 


Colored  potassium  salt  of 

phenolphthalein  (quinoid 

formula) 


It  wUl  be  noted  that  in  alkaline  solution  water  splits  off  to  give 
the  colored,  quinoid  salt,  as  in  the  case  of  the  formation  of  para- 
fuchsine  from  pararosaniline  and  hydrochloric  acid  (469). 

When  acid  is  added  to  the  solution  of  this  colored  quinoid 
salt  of  phenolphthalein,  the  reverse  changes  take  place,  and 
phenolphthalein  is  precipitated :  — 


HO 


=0 


COOK 


Colored  salt  of  phenolphthalein 
(quinoid  formula) 


HO 


+  H.0  = 


HO 


+  HC1  =  KCH- 


OH 


COOH 


Colorless  carbinolcarboxylic 
add  (unstable) 


COOH 


Quinoid  form  of  phenolphthalein 
(unstable) 


HO 


-HsO  = 


Free  phenolphthalein 
(lactoid  formula) 


PHTHALEINS  475 

It  will  be  noted  that  in  acid  solution  water  splits  off  to  form 
the  lactone  ring. 

When  an  excess  of  alkali  is  added  to  the  colored  solution  of  the 
potassium  salt  it  becomes  colorless.  This  is  due  to  the  formation 
of  the  tripotassium  salt  of  the  carbinolcarboxylic  acid,  which  is 
colorless :  — 

HOr'    >        ^"V"  KOr^  ^       (^  >0K 

+  H2O 


Colored  potassium  salt  of  Colorless  tripotassium  salt  of 

phenolphthalein  the  carbinolcarboxylic  acid 

Alcohol  also  decolorizes  the  colored  solution  of  the  potassium 
salt  of  phenolphthalein  in  consequence  of  the  formation  of  the 
salt  of  the  carbinolcarboxylic  acid :  — 

HOf'  ^  (    >0H 


l-^COOK 

Colored  potassium  salt  of  Colorless  monopotassium  salt 

phenolphthalein  of  the  carbinolcarboxylic  acid 

Note  for  the  Student.  —  Note  that  all  carbinols  are  colorless ;    color 
appears  only  when  water  splits  off  and  the  quinoid  condition  is  established. 

Recent  investigations  have  shown  that  the  formation  of  phenol- 
phthalein and  other  phthaleins  takes  place  in  two  stages :  first 
the  phthalic  anhydride  combines  with  a  molecule  of  phenol  to 
give  ^-hydroxybenzoyl-o-benzoic  acid : " — 

/CO  /CO.C6H4.0H(/>) 

C6H«<(      >0    +    HC6H4OH    =    C6H4< 

Vo  \C00H(<?) 

^-Hydroxybenzoyl-o-benzoic  acid 

and  this  then  combines  with  another  molecule  of  phenol  to 
give  phenolphthalein  and  water :  — 


476  DIPHENYLMETHANE,   ETC. 

HOC6H4C— OH  HO.C6H4.C.C6H4OH 

CeH4<(yO     +  HC6H4.OH  =         C6H4<(y>0  +  H2O. 

CO  CO 

f-Hydroiybenzoyl-  Phenol  Phenolphthalein 

o-benzoic  acid 
(lactone  form) 

The  formation  of  phenolphthalein,  which  is  a  dipara  compound, 
is  always  accompanied  by  that  of  fluoran,  which  is  removed  from 
the  phenolphthalein  by  dissolving  it  in  solutions  of  the  alkalies 
in  which  fluoran  is  insoluble.  Fluoran  has  been  shown  to  be 
the  anhydride  of  diorthophenolphthalein :  — 


Diorthophenolphthalein  Fluoran 

(unknown) 

It  is  called  fluoran  as  it  is  the  mother  substance  of  the  fluorescein 
dyes. 

Fluorescein,  anhydroresorcinolphthalein,  CsoHuOs  +  H2O,  is 
made  on  the  large  scale  by  heating  resorcinol  and  phthalic 
anhydride  with  zinc  chloride  to  200° :  — 

HO 

/CO 

C6H4^     >  O  +   2  C6H4(0H)2(W)  = 

Vo 


Phthalic  anhydride  Resorcinol  Fluorescein 

The  formation  of  fluorescein  is  analogous  to  that  of  phenol- 
phthalein. The  phthahc  acid  residue  enters  the  two  molecules 
of  resorcinol  in  the  para  position  to  one  of  the  hydroxyl  groups 
and  ortho  to  the  other ;  and  then  the  two  hydroxyls  in  the 
ortho  position  lose  a  molecule  of  water  as  in  the  formation  of 
fluoran.  (See  above.)  The  quinoid  structure  is  given  to  fluores- 
cein because  it  is  a  colored  compound  and  contains  a  carboxy) 


TETRAETHYLRHOD AMINE  477 

group.  It  dissolves  readily  in  solutions  of  the  alkalies  or  alkaline 
carbonates,  and  these  solutions  are  wonderfully  fluorescent 
(yellow  by  transmitted  light  and  yellowish  green  by  reflected 
light).  The  color  of  the  solution  is  perceptible  even  when  only 
one  part  of  the  salt  is  present  in  16  million  parts  of  water.  The 
formation  of  fluorescein  is  therefore  used  as  a  test  for  resor- 
cinol  or  phthalic  acid.  Uranine  is  the  disodium  salt  of  fluores- 
cein. Fluorescein  dyes  silk  and  wool  yellow,  but  is  not  used  as 
a  dye.     Its  halogen  derivatives,  however,  are  important  dyes. 

Eosin  is  tetrabromofluorescein  made  by  brominating  fluores- 
cein :  — ■ 

Br       „      Br 


Quinoid  formula  Lactoid  formula 

(colored)  (colorless) 

It  crystallizes  from  aqueous  alcohol  in  flesh-colored  crystals, 
which  may  be  a  mixture  of  the  colorless,  lactoid  form,  and  of 
the  colored,  quinoid  form.  The  alcoholic  solution  is  reddish 
yellow.  On  the  addition  of  even  a  trace  of  alkali  a  yellowish- 
green  fluorescence  makes  its  appearance.  The  colored  di- 
sodium or  dipotassium  salt  forms  the  soluble  eosin  of  commerce. 
Eosin  is  used  in  dyeing  wool,  silk  and  cotton.  Nearly  86,000 
pounds  were  made  in  the  United  States  in  1920. 

The  Rhodamine  dyes  are  closely  related  to  fluorescein. 

Tetraethylrhodamine  is  formed  by  fusing  phthaHc  anhydride 
and  diethyl-w-aminophenol  with  a  condensing  agent :  — 

/CO  xm 

CeH/     'yO+2CiR/  =  2H,o  + 


^CO  ^N(C2H6)2 


Tetraethylrhodamine 
(colorless  base) 


478  DIPHENYLMETHANE,   ETC. 

The  base  itself  is  colorless  and  therefore  has  the  lactoid  formula 
as  given  above.  When  it  is  dissolved  in  hydrochloric  acid  it 
gives  the  colored  tetraethybhodamine  hydrochloride :  — 

,    ^      ^       N(C,H5),Cl  /V*''N«^N»N{C,H5),C1 


COOH  (    >COOCjHis 


Rhodamine  B  Rhodamine  3B 

This  forms  green  crystals  which  dissolve  in  water  and  alcohol 
with  a  bluish  red  color.  It  dyes  silk  a  magnificent  red  with  an 
intense  greenish  yellow  fluorescence.  Rhodamine  3B  is  the  ethyl 
ester  of  rhodamine  B.  It  is  formed  by  esterifying  rhodamine 
B  by  heating  it  with  alcohoUc  hydrochloric  acid.  This  reaction 
shows  the  presence  of  the  free  carboxyl  group  in  rhodamine  B. 

SULPHONPHTHALEINS 

These  compounds  are  completely  analogous  to  the  phthaleins. 
They  are  formed  by  heating  the  phenols  with  the  anhydride  of 
o-sulphobenzoic  acid  (412)  or  with  the  chlorides  of  that  acid. 

Phenolsulphonphthalein  is  a  bright  red  crystalUne  powder 
somewhat  soluble  in  water,  more  so  in  alcohol.  From  the  fact 
that  it  is  a  colored  compound,  while  its  tetrabromo  derivative  is 
colorless,  they  are  given  the  following  formulas :  — ■ 


Ho/\ 


Phenolsulphonphthaldn  Tetrabromophenolsulphonphthalein 

(colored)  (colorless) 

(quinoid  formula)  (lactoid  fonnula) 

Phenolsulphonphthalein  is  used  in  medicine  as  a  functional 
test  for  the  kidneys  and  in  diagnosing  diseases  of  the  kidneys. 
Under  the  names  phenol  red  and  bromophenol  bltie  it  and  its 
tetrabromo  derivative  are  used  as  indicators. 


CHAPTER  XVn 

PHENYLETHYLENE  AND   DERIVATIVES 

Styrene,  phenylethylene,  C6H6.CH=CH2. — This  hydrocarbon 
is  found  in  the  resin,  liquid  storax,  and  in  coal  tar.  It  is  formed 
when  cinnamic  acid  (479)  is  heated  to  its  boiling  point :  — 

C6H6.CH=CH.COOH  =  C6H5.CH=CH2  +  CO2, 

Cinnamic  acid  Styrene 

and  by  the  polymerization  of  acetylene :  — 

4  C2H2    =   CgHg. 

Acetylene  Styrene 

It  is  a  liquid  with  a  pleasant  odor,  boiling  at  i45.5°-i46°,  in- 
soluble in  water  but  miscible  with  alcohol  and  ether  in  all  pro- 
portions. When  heated  or  even  when  allowed  to  stand  it  under- 
goes polymerization  to  the  solid,  tnetastyrene.  Styrene  like  ethyl- 
ene (277)  combines  with  chlorine  and  bromine,  forming  a  dichlo- 
ride,  C6H6.CHCI.CH2CI,  and  a  dibromide,  CeHs.CHBr.CHiBr. 
With  hydrobromic  acid  it  forms  phenylethylbromide, 
CeHj.CHBr.CHs.  Chromic  acid  converts  it  into  benzoic  acid 
(322).  Homologues  of  styrene,  such  as  phenylpropylene, 
phenylbutylene,  etc.,  have  been  prepared. 

Cinnamyl  alcohol,  styryl  alcohol,  C6H5.CH:CH.CH20H, 
occurs  in  the  form  of  the  ethereal  salt  of  cinnamic  acid  in  liquid 
storax,  and  also  in  the  balsam  of  Peru.  It  crystallizes  in  needles 
that  melt  at  33°.  It  is  somewhat  soluble  in  water,  has  an  odor  of 
hyacinths,  and  boils  at  254°-255°.  When  oxidized  with  platinum 
black  it  gives  cinnamic  aldehyde,  C6H6.CH=CH.CHO,  the 
chief  constituent  of  the  oil  of  cinnamon ;  and  by  further  oxida- 
tion cinnamic  acid. 

Cinnamic  acid,  phenylacrylic  acid,  C6H5.CH=CH.COOH, 
occurs  partly  free  and  partly  in  combination  in  the  form  of  esters 
in  many  balsams  and  resins  (storax,  balsams  of  Peru  and  Tolu, 

479 


48o  PHENYLETHYLENE  AND   DERI\'ATIVES 

etc.).  It  can  be  made  by  heating  benzaldehyde  with  sodium 
acetate  and  acetic  anhydride  (Perkin's  synthesis  (397)) :  — 

CsHb.CHO  +  H2CH.COOH  =  C6H5.CH=CH.COOH  +  H2O; 

or  by  treating  benzal  chloride  with  sodium  acetate :  — 

C6H6.CHCI2  +  H2CH.COOH  =  C6H5.CH:CH.(X)OH  +  2  HCl. 

It  crystallizes  from  hot  water  in  monoclinic  prisms  which  melt 
at  134°.  When  rapidly  distilled  it  boils  at  300°,  but  when 
distUled  slowly  it  decomposes  into  styxene  and  carbon  dioxide. 
Oxidizing  agents  convert  it  first  into  benzaldehyde,  and  then  into 
benzoic  acid.  It  combines  with  nascent  hydrogen  to  form 
hydrocinnamic  or  phenylpropionic  acid,  C6H6.CH2CH2.COOH 
(416),  and  with  bromine  to  form  cinnamic  acid  dibromide, 
CeHs.CHBr.CHBr.COOH.  The  ordinary  cinnamic  acid  is  the 
trans-form :  — 

CeHs.C — H  H — C — CeHs 

II  II 

H— C— COOH  H— C— COOH 

Trans  Cis 

It  is  converted  into  the  cis-form  by  the  action  of  ultraviolet 
light. 

When  nitrated  cinnamic  acid  gives  ortho-  and  paranitro- 
cinnamic  acids,  which  are  converted  into  the  corresponding  amino 
cinnamic  acids  by  reduction.     The  orthoaminocinnamic  acid, 

/CH:CHCOOH 
C6H4^  ,  loses  water  when  set  free  from  its  salts, 

\NH2(o) 
and  forms  the  anhydride,  carbostyril  (a-hydroxyquinoHne) :  — 

.CH=CH  ^CH=CH 

C6H4<'  I  C6H4<'  I 

\nH— CO  \n==C— OH 

Lactam  formula  Lactim  formxila 

Carbostyril  is  a  tautomeric  substance.  In  the  free  state  ii 
probably  has  the  lactam  structure,  while  the  sodium  salt  ii 


«JUUMAK1J\  481 

derived  from  its  tautomeric  form,  o-hydroxyquinoline  (509) 
which  acts  like  a  phenol. 

Coumarin,  C6H4^  |     ,  is  the  anhydride  of  the  cis  form 

X) CO 

of  orthohydroxycinnamic  acid.  It  is  found  in  tonka  beans  and 
is  the  odoriferous  principle  of  woodruff  (Asperula  odorata).  It 
is  also  found  in  dates,  in  Peru  balsam,  and  is  very  widely  dis- 
tributed in  nature.  Synthetically  it  was  first  obtained  by 
Perkin  from  saUcylic  aldehyde,  sodium  acetate,  and  acetic 
anhydride :  — 

/CHO                                               /CH=CH 
CcHZ              +  H2CH.COOH  =  CsH/  I     +  2  H2O. 

NDH  (0)  ^0 CO 

Salicylic  aldehyde  Coumarin 

It  crystallizes  in  rhombic  prisms,  has  a  pleasant  spicy  odor,  and  a 
bitter  taste.  In  very  great  dilution  it  has  the  odor  of  new-mown 
hay.  It  melts  at  6g°-'jo°,  is  difficultly  soluble  in  water,  readily 
in  alcohol  and  ether.  When  boiled  with  a  solution  of  concen- 
trated caustic  potash  it  is  hydrolyzed  to  a  salt  of  orthocoumaric 
acid,  which  is  stereoisomeric  with  coumarinic  acid :  — 

HO.C6H4.CH  HC.CeHiv  HC.C6H4.OH 

II  II  >  II 

HC.COOH  HC.CO  /  HC.COOH 

0-Coumaric  acid  Coumarinic  acid 

(trans)  (cis) 

Coumarinic  acid  itself  is  not  known.  As  soon  as  it  is  set  free 
from  its  salts  it  forms  the  anhydride,  coumarin.  o-Coumaric 
acid  is  converted  into  coumarin  by  the  action  of  acetic 
anhydride.  Coumarin  is  made  on  the  large  scale  from  o-cresol, 
and  is  used  in  perfumery  and  in  the  preparation  of  flavoring 
extracts. 


CHAPTER  XVIII 

PHENYLACETYLENE   AND    DERIVATIVES 

Phenylacetylene,  C6H5.C=CH,  can  be  made  from  styrene  ir 
the  same  way  that  acetylene  is  made  from  ethylene :  — 

CeHs.CH^CHa  +  Bra  =  CeHs.CHBr.CHjBr. 

Phenylethylene  Phenylethylene  bromide 

CeHs.CHBr.CHjBr  +  2  KOH  =  C6H6.C;CH+  2  KBr+  2  HjO, 

Phenylacetylene 

It  is  most  readily  obtained  by  the  distillation  of  phenylpropiolic 
acid :  — 

CeHs.C^C.COOH  =  CeHs.C^CH  +  CO2. 

Phenylpropiolic  acid  Phenylacetylene 

It  is  a  hquid  boiUng  at  142°.  Like  acetylene  it  gives  a  silver 
compound,  C6K6.C=CAg,  and  combines  with  four  atoms  oi 
bromine. 

Phenylpropiolic  acid,  CeHs.C^C.COOH,  is  made  from  cin- 
namic  acid  in  the  same  way  that  phenylacetylene  is  made  from 
styrene :  — 

HC — CeHs  BrHCCeHj  C — CeHs 

HC— COOH  BrHCCOOH  C— COOh' 

It  crystallizes  in  needles  that  melt  at  i36°-i37°.  When  heated 
it  loses  carbon  dioxide  and  forms  phenylacetylene. 

Orthonitrophenylpropiolic  acid,  02N.C6H4.C=C.COOH,  is 
made  from  orthonitrocinnamic  acid  in  the  same  way  that 
phenylpropioUc  acid  is  made  from  cinnamic  acid.  It  crystal- 
lizes in  colorless  needles  which  decompose  at  i55"-i56°.  When 
heated  with  water  it  loses  carbon  dioxide  and  gives  o-nitro- 
phenylacetylene.     It  is  of  special  interest  because  of  the  ease 

482 


INDIGO  BLUE,  INDIGOTIN  483 

with  which  it  can  be  converted  into  indigo.  When  heated  in 
alkaline  solution  in  the  presence  of  a  mild  reducing  agent,  such 
as  glucose,  it  yields  indigo :  — 

C=C.COOH,      ^ 

2  CeH4<^Q^^^^  +  2  H, 


(7-Nitrophenylpropiolic  acid 


C0\  /COs 


C6H4<  >C:C<  XeHi  +  2  CO2  +  2  H2O. 

Indigo 


Indigo  and  Related  Compounds 

Indigo  is  the  oldest  and  most  valuable  dye  known.  Mummy 
cloth  which  is  at  least  4000  years  old  has  been  shown  to  be  dyed 
with  it.  Eighteen  million  pounds  (20  per  cent  paste),  valued 
at  about  $13,500,000,  were  produced  in  the  United  States 
in  1920.  Until  recently  all  the  indigo  was  obtained  from 
the  indigo  plants  (such  as  Indigofera  sumatrana  and  /.  arrecta) 
which  were  grown  on  the  large  scale  in  India,  Java,  China, 
Japan,,  and  in  South  America,  but  most  of  that  now  used 
is  made  synthetically  from  benzene.  Indigo  is  present  in  the 
plant  in  the  form  of  a  glucoside,  indican,  C14H17NO6  +  3  H2O, 
which  occurs  chiefly  in  the  leaves.  The  plant  also  contains  an 
enzyme,  which  in  the  presence  of  water  hydrolyzes  the  indican 

yNH 
to  glucose  and  indoxyl,  C6H4^   ^^-^'  ^"^^  '-^^  indoxyl  is  then 

^C— OH 
oxidized  to  indigo  by  the  air,  lime  being  added  to  render  the 
solution  alkaline.  (See  below.)  The  natural  indigo  of  commerce 
contains  indiglucin,  indigo  brown,  indirubin,  and  other  impuri- 
ties in  addition  to  the  blue  dye  indigotin.  The  synthetic  dye 
is  practically  pure  indigotin. 

Indigo  blue,  indigotin,  C16H10N2O2,  is  a  dark  blue  powder 
which  when  rubbed  takes  on  a  coppery  luster.  It  sublimes  in 
copper-red  prisms  and  is  insoluble  in  most  solvents.  It  can  be 
crystallized  from  hot  aniline  or  nitrobenzene.     It  does  not  dis- 


484  PHENYLACETYLENE  AND   DERI\ATI\ES 

solve  in  solutions  of  the  alkalies  or  acids.  Its  vapor  density  is  in 
accord  with  the  formula,  C16H10N2O2,  and  not  with  the  formula, 
CgHsNO,  originally  given  it.  The  vapor  of  indigo  has  a  pur- 
plish red  color.  Its  solution  in  aniline  is  blue  ;  in  paraffin,  red. 
Oxidizing  agents  convert  indigo  into  isatin  (409),  while  dis- 
tillation with  caustic  potash  gives  aniline.  When  boiled  with 
a  solution  of  caustic  potash  and  manganese  dioxide,  anthranilic 
acid  (407)  is  formed.  Indigo  is  readily  reduced  to  the  leuco- 
compound,  indigo  white,  C16H12N2O2  (485),  a  colorless  crystal- 
line substance,  soluble  in  alcohol  and  ether  and  also  in  solutioris 
of  the  alkalies  (owing  to  the  presence  of  phenol  hydroxyl  groups). 
When  the  alkaline  solution  is  oxidized  by  the  air  insoluble  indigo 
blue  separates,  and  this  is  one  of  the  methods  used  to  determine 
the  value  of  commercial  indigo.  As  indigo  is  insoluble,  in  order  to 
fix  it  on  the  fabric  it  is  first  reduced  in  alkaline  solution  with  the 
sodium  salt  of  hyposulphurous  acid,  Na2S204,  to  indigo  white, 
which  is  soluble  in  alkalies  and  which  has  an  affinity  for  the 
fabric.  The  fabric  is  soaked  in  the  vat  containing  the  solution 
of  indigo  white  and  then  exposed  to  the  air,  which  converts  the 
indigo  white  by  oxidation  to  indigo  blue.  This  is  called  "  vat 
dyeing,"  and  indigo  is  the  most  important  of  the  "  vat  dyes." 
The  colors  produced  by  the  vat  dyes  are  exceedingly  fast.  They 
resist  the  action  of  light,  and  soap,  and  washing,  and  are  the 
most  valuable  dyes  known. 

The  Constitution  of  Indigotin.     The  formula  for  indigotin  is 
C16H10N2O2,  and  as  it  gives  isatin,  C8H6NO2  (409),  on  oxidation 

/CO 
it  must  contain  two  residues  of  isatin,  C6H4<'    /CO,  united  in 

some  way.  Baeyer  proved  this  view  to  be  correct  by  making 
indigotin  from  isatin.  He  first  converted  isatin  into  the  chloride 
by  the  action  of  phosphorus  pentachloride.  On  reduction  this 
gives  indigotin :  — 

/CO  yCO         /CO 

2  C6H4^  ^CC1-|-2H2  =  C6H4<'    >C:C^  >C6H4+2HC1. 

Isatin  chloride  Indigotin 


SYNTHETIC   INDIGO  485 

This  formula  not  only  explains  the  ease  with  which  indigotin 
is  oxidized  to  isatin :  — 

/CO  /CO  /CO 

C6H4<'    /C=C<^  )>CeH4  +  O2  =  2  CcH/  >C0, 

Indigotin  Isatin 

and  the  fact  that  it  is  formed  practically  quantitatively  by  the 
oxidation  of  indoxyl  (see  below),  but  is  in  accord  -with  its 
entire  chemical  conduct. 

Indigo  white,  as  stated  above,  is  the  product  of  reduction  of 
indigo  blue :  — 

/C0\  _     /CO. 

C6H4<  yC — C<.  /C6H4  +  H2 

Indigo  blue 

/C— OH  ^C— OH 
=  CbH/   )C-Cf  )>C6H4. 
^NH         ^NH 

Indigo  white 

Synthetic  indigo  is  now  manufactured  on  the  large  scale  from 
aniline.  There  are  three  methods  which  are  of  importance. 
In  the  first  of  these  aniline  is  condensed  with  monochloroacetic 
acid  to  form  phenylglycine  :  — 

CsHb.NHH  +  CICH2.COOH  =  CfiHs.NH.CHj.COOH  +  HCl. 

Phenylglycine 

Phenylglycine  is  then  heated  with  sodium  amide,  when  indoxyl 
is  formed  by  the  elimination  of  water :  — 

/NH. 
CeHs.NH.CHz.COOH  =  CeH/  >CH2  +  H2O. 

\co/ 

Indoxyl 
Phenylglycine  (tautomeric  form) 

The  indoxyl  is  then  oxidized  in  alkaline  solution  by  air  to  indigo- 
tin:— 

/CO  /CO  /CO 

2  CsH/   >CH2  +  02  =  CbH/  )>C=C<'  ^C6H4  +  2  H2O. 
^NH  ^NH         ^NH 

3  mols.  of  Indoxyl  Indigotin 


486  PHENYLACETYLENE   AND   DERIVATIVES 

The  second  process  differs  from  the  first  only  in  the  method 
used  to  convert  aniline  into  phenylglycine.  From  that  point 
on  the  methods  are  the  same.  In  this  method  anihne  is  con- 
densed in  aqueous  solution  with  the  sodium  bisulphite  com- 
pound of  formaldehyde :  — 

CeHs.NHH  -f-  HOCHaSOsNa  =  CeHs.NH.CHzSOsNa  +  H2O. 

The  resulting  product,  which  is  sodium  to-methylanilinesul- 
phonate,  reacts  in  aqueous  solution  with  sodium  cyanide  to 
give  the  nitrUe  of  phenylglycine :  — 

CeHs.NHCHjSOsNa  +  NaCN  =  CsHs.NH.CHaCN  +  NajSOs ; 

and  this  on  hydrolysis  gives  phenylglycine  :  — 

CeHs.NH.CHaCN  +  2  H2O   =   CeHj.NH.CHz.COOH  +  NH3. 

All  these  reactions  take  place  practically  quantitatively  in 
aqueous  solutions,  and  only  the  phenylglycine  is  isolated. 

The  third  method  depends  upon  the  fact  that  aniline  combines 
with  ethylene  chlorohydrin  (152)  to  form  anOinoethyl  alco- 
hol (349) :  — 

CeHs.NHj  +  ClCa.CHaOH  =  CeHj.NH.CHz.CHsOH  +  HCl. 

Ethylene-  AnOinoethyl  alcohol 

chlorohydrin 

This  product  is  converted  into  indoxyl  by  fusion  with  caustic 
potash :  — 

/NH 
C6H4.NH.CH2.CH2OH  +  02  =  CsH/  ^CHj  +  2  H2O, 

XO 

Anilinoethyl  alcohol  Indoxyl 

and  the  indoxyl  is  oxidized  to  indigotin  in  the  usual  manner. 

When  indigo  is  sulphonated  it  gives  a  disulphonic  acid  in  which 
the  two  sulphonic  acid  groups  are  in  the  para  positions  to  the 
imino  groups.  The  disodium  salt  of  this  acid,  which  is  readily 
soluble  in  water,  is  the  indigo  carmine  of  commerce  formerly 
much  used  in  dyeing  wool  and  silk.  It  is  now  used  in  the  manu- 
facture of  writing  inks.  The  bromoindigos  made  by  the  direct 
bromination  of  indigo  are  very  important  and  valuable  val 
dyes.     The  dibromoindigo,  made  synthetically,  in  which  the  twc 


DIOXINDOL  487 

bromine  atoms  are  in  the  para  positions  to  the  carbonyl  groups 
has  been  found  to  be  identical  with  the  purple  of  antiquity 
(Tyrian  purple).  It  was  obtained  by  the  Phoenicians  from  the 
mollusc,  Murex  hrandaris. 

A  number  of  compounds  closely  related  to  indigo  were  ob- 
tained by  Baeyer  in  the  course  of  his  investigation  of  the 

/CO 
reduction  products  of  isatin,  C6H4<^    ^  CO  (409). 

HCOH 

Dioxindol,  C6H4<^^CO,   which  is   the   anhydride  of   ortho- 

^^  /CHOH.COOH 

aminophenylglycolic  acid,  C6H4<f  ,  is  formed  by 

\NH2(o) 

reducing  isatin  with  zinc  dust  and  hydrochloric  acid :  — 
CO  HCOH 

CeHi/NcO  +  Ha  =  C6H4<(\cO. 
NH  NH 

Isatin  Dioxindol 

It  is  formed  also  by  the  reduction  of  o-nitrophenylglycolic  acid 
with  zinc  dust  in  acetic  acid  solution :  — 

/CHOH.CO2H  /CHOH.CO2H 

C6H4<  —>-  C.B./  — H2O    — ^ 

^nOjCo)  \nh2(<7) 

/CHOH 
C6H4<(  ^CO. 

It  yields  isatin  on  oxidation  and  can  also  be  obtained  by  the 
oxidation  of  oxindol.  It  crystallizes  in  colorless  prisms  which 
melt  at  i67"-i58°  and  are  readily  soluble  in  water,  alcohol,  and 
ether.  On  reduction  with  sodium  amalgam  in  mineral  acid 
solution  it  gives  oxindol  (414) :  — 

HCOH  CH2 

C6H4<^CO  +  H2  =  C6H4<^0  +  HjO. 

NH  NH 

Dioxindol  Oxmdol 


488  PHENYLACETYLENE   AND   DERIVATIVES 

.COH 
Indoxyl,  C6H4<^    /CH,  isomeric  with  oxindol,  results  from  the 

fusion  of  indigo  with  caustic  potash,  and  is  the  intermediate 
product  in  the  formation  of  indigo,  both  the  natural  and  the 
synthetic.     It  acts  as  a  tautomeric  substance  and  yields  deriv- 

/CO 
atives  of  the  pseudo  form,  C6H4\^   /CHa.     It  occurs  in  yellow 

crystals  melting  at  85°,  is  soluble  in  hot  water,  with  a  yellow- 
green  fluorescence,  and  is  volatile  with  superheated  steam.  It 
dissolves  in  concentrated  hydrochloric  acid,  with  a  red  color.  It 
is  an  extremely  unstable  substance  and  resinifies  very  readily. 
It  is  oxidized  almost  quantitatively  in  alkaline  solution  by  the 
air  to  indigo.  It  forms  a  nitroso  compound  and  hence  contains 
an  imino  group.  On  heating  with  potassium  pyrosulphate, 
K2S2O7,  it  forms  potassium  indoxyl  sulphate,  CaHsNOSOsK, 
a  constituent  of  the  urine  (urine  indican).  This  reaction  shows 
the  presence  of  the  hydroxyl  group. 
CH 
Indol,  C6H4\^CH,  was  first  obtained  by  distilling  oxindol 

NH 

with  zinc  dust :  — 

CH2  CH 

C6H4<)>CO  +  H2  =  C6H4<()'CH  +  H2O. 
NH  NH 

Oxindol  Indol 

It  is  also  formed  from  o-amino-/3-chlorostyrene  by  the  elimina- 
tion of  hydrochloric  acid :  — 

yCH=CHCl  yCH 

C6H4<'  =       CeO/  JCU  +  HCl, 

^NH2(o)  ^NH , 

o-Amino-^-chlorostyrene  Indol 

and  this  s)Tithesis  establishes  the  structure  of  the  substance. 
It  is  present  in  coal  tar  in  small  quantity  and  may  be  isolated 


TRYPTOPHAN  489 

from  the  fraction  boiling  between  240°  and  260°.  It  is  also 
present  in  the  oil  of  jasmine  and  in  neroli  oil.  It  crystallizes 
in  white  leaflets  which  melt  at  52.5°,  and  is  volatile  with  steam. 
The  impure  product  has  a  very  disagreeable  fecal  odor.  The 
pure  substance,  however,  has  a  pleasant  floral  odor  and  is  used 
in  perfumery.     It  forms  indigo  when  oxidized  with  ozone. 

/3-Methylindol,  skatol  (Gr.  skatos  =  feces),  C6H4\'   ^CHa   , 

has  been  found  in  civet,  and,  with  indol,  in  the  wood  of  the  tree 
Celtis  reticulosa.  It  also  occurs  in  human  feces  and  is  the  cause 
of  its  disagreeable  odor.  It  is  formed  together  with  indol  in  the 
putrefaction  of  the  proteins  and  also  by  fusing  the  proteins  with 
caustic  soda.  It  crystallizes  in  colorless  leaflets  which  melt  at 
95°,  and  when  impure  it  has  a  strong'odor  of  feces.  Like  indol, 
skatol  is  made  artificially  and  is  used  in  the  manufacture  of 
floral  perfumes. 

Trjrptophan,  a  product  of  the  hydrolysis  of  the  proteins,  is 
^-indolalanine, 

/C— CH2.CH(NH2)  .COOH. 

C6H4S  y-CH 

It  has  also  been  made  synthetically.     The  synthetic  product  is 
optically  inactive ;  the  tryptophan  from  the  proteins  is  levo- 
rotatory. 
Note  foe  Student.  —  Does  it  contain  an  asymmetric  carbon  atom  ? 


CHAPTER  XEX 

HYDROCARBONS    CONTAINING    TWO    BENZENE    RESIDUES 
IN   DIRECT   COMBINATION 

Just  as  the  marsh  gas  residue,  methyl,  CH3,  unites  with  methyl 
to  form  ethane,  H3C.CH3,  so  the  benzene  residue,  phenyl,  CeHs, 
unites  with  phenyl  to  form  the  hydrocarbon  diphenyl, 
HsCe.CeHs,  and  residues  of  toluene  and  of  the  higher  mem- 
bers of  the  series  unite  in  a  similar  way  to  form  homologues 
of  diphenyl. 

Diphenyl,  CviH.io,(CeH.i.CeH.i). — This  hydrocarbon  is  made 
by  treating  bromobenzene  with  sodium :  — 

2  CeHjBr  +  2  Na  =  C12H10  +  2  NaBr ; 

and  by  conducting  benzene  through  a  tube  heated  to  redness :  — 

2  CeHe  =  CiaHio  +  H2. 

It  forms  large,  lustrous  plates.  It  melts  at  70.5°,  and  boils 
at  254°.     It  is  easily  soluble  in  hot  alcohol  and  ether. 

Diphenyl  is  an  extremely  stable  substance.  It  resists  the 
action  of  ordinary  oxidizing  agents,  but  with  strong  ones  it 
yields  benzoic  acid.  A  large  number  of  derivatives  of  diphenyl 
have  been  studied. 

Substitution  products  of  diphenyl.  —  Substituting  agents,  as 
the  halogens,  nitric  and  sulphuric  acids,  act  upon  diphenyl 
much  in  the  same  way  as  they  do  upon  toluene.  Of  the  mono- 
substitution  products,  three  varieties,  ortho,  meta,  and  para, 
are  possible.  Of  these  the  para  derivatives  are  most  easily 
obtained  by  direct  action.  At  the  same  time  ortho  derivatives 
are  formed  to  some  extent.  By  further  action  ortho-para 
products  and  di-para  products  are  formed.  In  the  latter  the 
substituting  atoms  or  groups  occupy  the  positions  indicated 
on  the  next  page  :  — ■ 

490 


BENZIDINE   DYES  49 1 


cx 


CeHi.NHjC/.). 
Benzidine,  |  —  This    is    diparadiaminodiphenyl. 

C6H4.NH2(/>) 

It  is  formed  by  the  reduction  of  diparadinitrodiphenyl,  and 
also  from  hydrazobenzene  (360)  made  by  the  reduction  of  nitro- 
benzene in  alkaline  solution.  When  this  is  treated  with  mineral 
acids  it  is  transformed  into  benzidine  :  — ■ 

CeHe.NH  CeHi.NHs 

CsHs.NH  C6H4.NH2' 

Hydrazobenzene  Benzidine 

Benzidine  is  manufactured  on  the  large  scale  by  this  method. 
It  crystallizes  from  hot  water  in  leaflets  that  melt  at  127.5°- 
128°.  It  is  difficultly  soluble  in  water,  more  readUy  in  alcohol 
and  ether.  It  boilsat  4oo°-4oi°.  The  sulphate,  C12H12N2H2SO4, 
and  the  chromate,  Ci2Hi2N2H2Cr04,  both  difficultly  soluble  in 
water  and  alcohol,  are  characteristic  salts.  The  sulphate 
crystallizes  in  scales  and  is  used  to  estimate  benzidine  or  stil- 
phuric  acid  quantitatively.  The  chromate  has  a  deep  blue  color 
and  crystallizes  in  needles.  Over  2,000,000  pounds  of  benzidine 
were  made  in  the  United  States  in  1920. 

Benzidine  dyes.  —  Benzidine  and  its  homologues  (o-tolidine, 
Ci2H6(CH3)2(NH2)2,  made  from  o-nitro toluene,  etc.)  are  of  great 
importance  in  the  manufacture  of  azo  dyes.  When  the  di- 
hydrochloride  is  diazotized  with  nitrous  acid  it  gives  diphenyl- 
tetrazonium  chloride :  — 

C6H4NH2HCI  C6H4N2CI 

■    I  ^1 

C6H4NH2HCI  C6H4N2CI, 

and    this   reacts   readily   with   phenol   acids,   naphthylamine- 


492  TWO   BENZENE   RESIDUES,   ETC. 

sulphonic  acids  (506)  and  naphthol  sulphonic  acids  (502)  to 
form  valuable  disazo  dyes  that  dye  cotton  directly  without  the 
use  of  a  mordant.  They  are  therefore  called  direct  or  substantive 
dyes.  The  first  dye  of  this  class  was  called  Congo  red  (506). 
Chrysamine  G,  an  important  disazo  dye,  is  made  by  the  action  of 
diphenyltetrazonium  chloride  on  sodium  salicylate  in  alkaline 
solution :  — 


/> 


Na  .OH 


C6H4N2CI      C6H4COONa      C6H4N2C6H3COONa 
■I  +        •  =1  +2  NaCl. 

C6H4N2CI      C6H4COONa      C6H4N2C6H3COONa 

\)Na  \dH 

Diphenyltetrazonium-    Sodium  salicylate  Chrysamine  G 

chloride  (2  mols.) 

C6     4V 

Carbazole,  |        /NH,  the  imide  of  diphenyl,  is  found  in  coal 
C6H4/ 

tar  and  is  obtained  from  the  anthracene  fraction  by  distilling  it 
with  sodium  and  potassium  hydroxides.  The  carbazole  forms 
a  non- volatile  potassium  or  sodium  salt  with  the  fused  alkalies, 
in  which  the  hydrogen  of  the  imide  group  is  replaced  by  the 
metal,  while  anthracene  and  the  other  hydrocarbons  distil. 
The  alkali  salt  of  carbazole  is  then  decomposed  by  water,  the 
carbazole  and  alkali  recovered,  and  the  carbazole  purified  by 
sublimation.  It  is  formed  by  passing  the  vapor  of  o-amino- 
diphenyl  over  red  hot  lime  or  the  vapor  of  diphenylamine 
through  a  red  hot  tube  (compare  with  the  formation  of  diphenyl 
from  benzene) :  — 

CeHjy  06X14^ 

^NH  =   I        ^NH  +  H2. 

Diphenylamine  Carbazole 

It  crystallizes  in  colorless  leaflets  that  melt  at  238°  and  are 
sparingly  soluble  in  alcohol,  ether,  and  benzene.  It  distils  at 
338°,  sublimes  readily,  and  is  exceedingly  stable.  It  yields  an 
acetyl  and  a  nitroso  compound,  and  a  potassium  salt,  (C6H4)2NK., 
when  fused  with  caustic  potash,  showing  the  presence  of  the 


NAPHTHALENE  493 

imide  group.  It  is  used  in  the  manufacture  of  Hydron  blue, 
a  valuable  vat  dye. 

Naphthalene,  CioHg.  —  This  hydrocarbon  is  the  constituent 
of  coal  tar  which  is  present  in  largest  amount,  about  6-15  per 
cent  of  the  tar  being  naphthalene.^  It  crystallizes  out  of  the 
fractions  boiling  between  iio°-27o°,  and  after  it  is  freed  from 
oil  by  centrifuging  and  pressure,  is  purified  by  washing  it  with 
small  amounts  of  sulphuric  acid  and  distilling  in  steam  or  sub- 
liming it.  Large  quantities  of  naphthalene  are  now  obtained 
from  the  gases  of  the  coking  ovens.  Naphthalene  is  also  formed 
when  marsh  gas,  ethylene,  acetylene,  or  the  vapors  of  alcohol, 
ether,  acetic  acid,  benzene,  toluene,  etc.,  are  passed  through  a 
red-hot  tube.  It  crystallizes  in  colorless,  monochnic  plates  that 
melt  at  80°  and  are  insoluble  in  water,  but  dissolve  readily  in 
hot  alcohol  and  benzene.  It  boils  at  218°,  is  volatUe  with  steam 
and  sublimes  very  readily.  It  has  a  characteristic  tarry  odor. 
It  gives  phthalic  anhydride  (416)  on  oxidation,  which  shows 
that  it  is  an  ortho  derivative  of  benzene.  Its  structural  formula 
is  based  on  the  following  syntheses  from  benzene  derivatives : — 

I.  When  o-xylylene  dibromide  is  heated  with  the  disodium 
compound  of  the  ethyl  ester  of  symmetrical  ethanetetracar- 
boxylic  acid  it  forms  ethyl  tetrahydronaphthalenetetracarboxy- 
late :  — 

/CHjBr  Na— C=(COOC2H6)2 

C6H4<  +  I 

^CHjBrCo)      Na— C=(COOC2H6)2 

/CH2C=(COOC2H6)2 
=  C6H4<  I  +  2  NaBr. 

x:h2C=(cooc2H6)2 

When  this  ester  is  saponified  it  loses  two  molecules  of  carbon 
dioxide  (160),  forming  tetrahydronaphthalenedicarboxylic  acid, 
and  the  silver  salt  of  this  acid  when  heated  gives  naphthalene 
and  the  anhydride  of  the  acid :  — 

/CH2.CH(C00Ag) 
2C6HZ  I  =  2C02  +  4Ag  +  H20-|- 

\CH2.CH(C00Ag) 

'  See  Lunge's  Coal  Tar  and  Ammonia,  Fifth  ed.  IQ16. 


494  TWO   BENZENE   RESIDUES,   ETC. 

/CH=CH  /CH2CH.CO 

CeHZ  I        +    CeHZ  I        >0. 

\CH=CH  \CH2CH.CO 

Naphthalene  Anhydride 

The  anhydride  of  the  acid  also  yields  naphthalene  when  its 
vapor  is  passed  through  a  red-hot  tube.     (Write  the  equation.) 

2.  Phenylbutylene  dibromide  gives  naphthalene  when  its 
vapor  is  passed  over  lime  heated  to  a  red  heat :  — 

yCH2 — CH2  yCH:=^CH 

CeH/  I  =  CeHZ  I       +  2  HBr  +  H2. 

BrH2C.CHBr  \CH=CH 

Naphthalene 

3.  y-Phenylisocrotonic  acid,  C6H6.CH=CHCH2.COOH, 
loses  water  when  heated  and  is  converted  into  a-naphthol,  a 
hydroxyl  derivative  of  naphthalene :  — 


HO      CH 

CH       CH 

Hcl^^CH^CHu 

^  ^"r^I^"" -t-H,o 

HC  OCOH 

CH     COH 

■y-Phenylisocrotonic  acid 

a-Naphthol 

When  heated  with  zinc  dust  a-naphthol  gives  naphthalene. 

According  to  these  syntheses  naphthalene  is  made  up  of  two 
benzene  residues  having  two  ortho  carbon  atoms  in  common,  and 
this  formula  is  in  accord  with  the  entire  chemical  conduct  of 
the  substance.  It  resembles  benzene  very  closely,  e.g.,  it  forms 
nitro  compounds  with  nitric  acid  and  sulphonic  acids  with 
sulphuric  add,  the  nitro  compounds  undergo  reduction  to  amino 
derivatives  of  naphthalene  and  these  can  be  diazotized  in  ex- 
actly the  same  way  that  aniline  is.  The  sulphonic  acids  are 
converted  into  hydroxynaphthalenes  by  fusing  with  alkalies, 
and  these  substances  (called  naphthols)  resemble  the  phenols 
closely. 

The  presence  of  two  benzene  rings  in  naphthalene  has  also 
been  shown  in  the  following  manner :  Nitronaphthalene, 
obtained  by  the  direct  action  of  nitric  acid  on  naphthalene, 
yields  nitrophthalic  acid  on  oxidation  with  chromic  acid :  — 


I   II  n  1  ^  I    I   "°003 


JNAl'tliHAl^Jl.NE  495 

NOa     _  NO2 

IcOOH 

which  can  also  be  prepared  by  the  direct  nitration  of  phthalic 
acid.  Hence  the  ring  into  which  the  nitro  group  has  entered 
is  a  benzene  ring.  If,  however,  nitronaphthalene  is  reduced  to 
aminonaphthalene  and  this  is  oxidized  with  potassium  perman- 
ganate, phthahc  acid  is  formed :  — 

HOOCrf^'^ 


^ » "  ■ 


^- 


It  follows,  therefore,  that  the  second  ring  in  naphthalene  is  also 
a  benzene  ring.  Further,  it  has  been  shown  that  naphthalene- 
sulphonic  acid  yields  both  sulphophthalic  acid  and  phthalic 
acid  on  oxidation. 

The  hydrogen  addition  products  of  naphthalene  are  also  in 
accord  with  the  above  formula.  When  treated  with  metallic 
sodium  in  alcoholic  solution  naphthalene  takes  up  two  atoms  of 
hydrogen  to  form  dihydronaphthalene,  CioHio,  and  this  com- 
pound like  dihydrobenzene  (329)  acts  like  an  unsaturated  com- 
pound, taking  up  bromine  with  great  ease.  In  addition  to  this 
dOiydride,  which  is  called  A^  to  indicate  the  position  of  the 
double  bond,  a  second  dihydride  A^  has  been  made  by  heat- 
ing A^  with  sodium  ethylate.  It  is  also  characterized  by  the 
ease  with  which  it  combines  with  bromine.  These  two  di- 
hydrides  are  exactly  analogous  to  the  two  dihydrobenzenes  and 
are  the  only  ones  possible  according  to  the  theory :  — 


CH       CH  CH      CHj 

CH       CHj  HO     CHj 

Ai  Naphthalene  dihydrides  A" 


On  further  reduction  naphthalene  forms  a  tetrahydride,  CioH^, 
and  the  final  product  is  a  decahydride,  CioHis,  which  acts  like 
a  saturated  hydrocarbon  of  the  paraflSn  series :  —  ' 


496  TWO   BENZENE   RESIDUES,   ETC. 

CH       CHj  HjC  HCHa 

HCf^^Nr      ^CHj  HjC|''^C''^CH» 

CH      CHi  HjCHCHj 

Naphthalene  tetrahydiide  Naphthalene  decahydride 

Naphthalene  tetrahydride  and  decahydride  are  now  made  on  the 
large  scale  by  reducing  naphthalene  with  hydrogen  in  the  pres- 
ence of  nickel  as  a  catalyst.  They  are  both  liquids,  and  are 
used  as  fuel  in  gas  engines  in  place  of  gasolene.  They  are 
known  in  the  trade  as  tetralin  and  decalin. 

Over  37  million  pounds  of  naphthalene  were  produced  in  the 
United  States  in  1920,  almost  one-third  of  which  was  from  the 
gases  of  the  coking  ovens.  The  most  important  uses  of  naph- 
thalene are  in  making  derivatives,  which  are  used  in  very  large 
quantities  in  the  manufacture  of  azo  dyes ;  and  for  the  prepara- 
tion of  phthaUc  anhydride,  which  is  used  in  making  the  phthalein 
dyes,  anthraquinone,  and  phenolphthalein.  Large  quantities 
are  used  in  the  manufacture  of  lampblack  and  for  heating 
purposes.  It  is  used  in  preserving  wood,  hides,  and  furs,  and 
as  a  fuel  in  motors.  It  is  also  used  as  an  antiseptic  and  an 
insecticide.    The  well  known  moth  balls  are  naphthalene. 

Isomerism  of  the  substitution  products  of  naphthalene. 

aHC      CHa 
aHC      CHa 

The  number  of  substitution  products  obtained  from  naphthalene 
is  much  greater  than  that  obtained  from  benzene  and  corresponds 
with  the  number  theoretically  possible  for  the  above  formula. 
Two  series  of  monosubstitution  products  are  possible  according 
as  the  a-or  |8-hydrogen  atoms  are  replaced,  and  both  are  known. 
Those  in  which  the  hydrogens  i,  4,  5,  or  8  are  replaced  are  called 
a-derivatives,  while  those  resulting  from  the  replacement  of 
2,  3,  6,  or  7  are  designated  |8-derivatives.  For  the  disubstitution 
products,  where  the  substituents  are  the  same,  the  number  of 
isomers  is  10,  while  it  is  14  when  they  are  different.  The  10 
isomers  are  designated  by  the  numbers :   1,2  ;  1,3  ;  1,4 ;  1,5  ;  1,6 ; 


SUBSTITUTION    PRODUCTS    OF   NAPHTHALENE         497 

1,7  ;  1,8  ;  2,3  ;  2,6  ;  and  2,7.  Ten  dichloronapkthalenes  are  known, 
and  the  structure  of  each  has  been  determined.  In  the  case  of  the 
a-  and  j3-naphthylaminemonosulphonic  acids,  H2N.C10H6.SO3H, 
the  14  isomers  are  all  known,  and  the  same  is  true  of  the  14 
isomeric  trichloronaphthalenes  predicted  by  the  theory.  The 
substitution  of  all  the  hydrogen  atoms  in  naphthalene  by  dif- 
ferent substituents  would  theoretically  give  rise  to  10,766,600 
derivatives.  Disubstitution  products  in  which  the  substituents 
are  in  the  1,8  positions  are  called  "peri"  compounds.  They 
resemble  the  ortho  derivatives  of  benzene  and  naphthalene  in 
many  respects,  e.g.,  peri-naphthalenedicarboxylic  acid. 


HOOC  COOH  ^iCr nCHa 


CO 


Naphthalic  acid  Acenaphthene 

forms  an  anhydride  just  as  o-phthalic  acid  does,  and  hence  is 
called  naphthalic  acid.  It  is  made  by  the  oxidation  of  ace- 
naphthene, a  constituent  of  coal-tar. 

The  method  of  determining  the  position  of  the  substituents  in 
naphthalene  is  similar  to  that  used  in  the  benzene  series.  For 
example,  the  mononitronaphthalene  which  results  from  the 
direct  nitration  of  naphthalene  and  which  was  originally  called 
a-nitronaphthalene  merely  to  distinguish  it  from  its  isomer, 
j3-nitronaphthalene  (499)  obtained  from  |3-naphthylamine,  can 
be  converted  into  a-naphthol  in  the  same  way  that  nitrobenzene 
is  converted  into  phenol  (351).  The  position  of  the  hydroxyl 
group  in  a-naphthol  is  fixed  by  its  synthesis  from  y-phenyl- 
isocro tonic  acid  (494).  Therefore,  the  nitro  group  in  a-nitro- 
naphthalene must  occupy  one  of  the  positions  i,  4,  5,  or  8,  and  in 
/3-nitronaphthalene,  2, 3, 6,  or  7.  Any  monosubstitution  product 
that  can  be  converted  into  a-naphthol  or  a-nitronaphthalene, 
or  can  be  made  from  these  substances,  is  called  an  a-com- 
pound,  and  this  fixes  the  structure,  while  its  isomer  must  be  the 
^-compound.  Another  method  consists  in  the  oxidation  of 
the  naphthalene  derivative  to  a  benzene  derivative  of  known 


498  TWO   BENZENE   RESIDUES,   ETC. 

Structure.     Thus    a-nitronaphthalene    gives     the     1,2,3-nitro- 
phthalic  acid  on  oxidation :  — 

NOj  NOs 

r^S^^  r^cooH 

+  90=  o  +2COa+H,0. 

k/^^  k^COOH 

and  must  have  the  nitro  group  in  one  of  the  positions  i,  4,  5,  or  8. 

Substitution  Products  of  Naphthalene 

Homologues  of  naphthalene,  methyl,  ethyl,  and  propyl  deriva- 
tives, etc.,  are  unimportant.  They  can  be  made  synthetically  by 
the  Friedel  and  Crafts  method  or  by  other  methods  used  in 
preparing  the  homologues  of  benzene.  a-Methylnaphthalene 
(b.p.  24o°-242°),  and  /3-methylnaphthalene(m.  p.  32°),  are  both 
present  in  coal  tar.  On  oxidation  they  give  the  corresponding 
a-naphthoic  or  /S-naphthoic  acid,  compounds  which  resemble 
benzoic  acid  very  closely  in  their  properties.  They  are  both 
converted  into  naphthalene  when  distilled  with  lime. 

a-Chloronaphthalene,  C10H7CI  (a),  and  a-bromonaphthalene, 
CioHTBr  (a),  are  formed  by  the  action  of  chlorine  or  bromine  on 
naphthalene  in  the  presence  of  iron  as  a  catalyst.  i-Chloro- 
naphthalene  is  a  fluid  boiling  at  263°.  i-Bromonaphthalene 
is  also  liquid  and  boils  at  279.5°.  Addition  products,  such  as 
naphthalene  dichloride,  C10H8CI2,  and  naphthalene  tetrachloride, 
CioHsCU,  similar  to  naphthalene  dihydride  and  tetrahydride 
(495,  496),  are  formed  in  the  cold  when  no  carrier  is  present. 
When  heated  or  treated  with  bases  these  substances  lose  hydro- 
chloric acid,  giving  monochloro-  and  dichloronaphthalenes.  The 
j3-monohalogen  derivatives  can  not  be  obtained  by  direct  action 
of  the  halogens  on  naphthalene,  but  are  prepared  from  /3-com- 
pounds,  such  as  ;S-naphthol  and  |8-naphthylamine,  by  the 
methods  used  in  the  benzene  series  to  replace  hydroxyl  and  the 
amino  group  by  a  halogen.  The  monohalogen  derivatives  oi 
naphthalene,  both  a-  and  /3-,  can  be  prepared  readily  from  the  a 
and  /3-naphthalenesulphonic  acids  (499)  by  treating  them  witl 
phosphorus  pentachloride  or  pentabromide.  The  chlorides  0: 
bromides  of  the  sulphonic  acids  are  first  formed,  and  these  b'^ 


NAPHTHALENESULPHONIC  ACIDS  499 

the  further  action  of  the  phosphorus  compounds  give  mono- 
halogen  derivatives  of  naphthalene  :  — 

C10H7.SO2CI  +  PCI5  =  C10H7CI  +  OSCI2  +  OPCI3. 

a-or  ^-Naphthalene-  a-  or  (3-Chloro-      Thionyl 

sulphuryl  chloride  naphthalene         chloride 

This  reaction,  which  is  peculiar  to  the  naphthalene  series,  also 
takes  place  with  derivatives  of  the  sulphonic  acids.  i-Chloro- 
naphthalene  is  used  in  the  preparation  of  chlorosulphonic  acids 
of  naphthalene  and  in  making  Naphthalene  green  V. 

a-Nitronaphthalene,  CioH7N02(a),  is  formed  by  the  direct 
nitration  of  naphthalene  with  mixed  acid  at  4S°-5o°.  No  /3- 
product  is  formed  even  when  the  nitration  is  carried  out  at  a 
higher  temperature  (see  Naphthalenesulphonic  acids  below). 
It  crystallizes  from  alcohol  in  yellow  needles  that  melt  at  61°. 
Its  boiling  point  is  304°  It  dissolves  in  concentrated  sulphuric 
acid  with  a  blood-red  color  and  when  nitrated  in  this  solu- 
tion gives  1,5-  and  1,8-dinitronaphthalene.  It  is  oxidized  by 
chromic  acid  to  nitrophthalic  acid  (1,2,3)  ^.nd  gives  a-naphthyl- 
amine  on  reduction.  It  is  poisonous.  When  treated  with 
phosphorus  pentachloride,  the  nitro  group  is  eliminated  and 
a-chloronaphthalene  is  formed.  This  is  a  reaction  peculiar  to 
the  naphthalene  series.  It  does  not  take  place  in  the  benzene 
series.  Di-,  tri-,  and  tetranitronaphthalenes  are  used  in  the 
manufacture  of  explosives.  Nitronaphthalene  is  used  in  the 
preparation  of  a-naphthylamine  and  of  i-nitronaphthalene- 
5-sulphonic  acid  and  of  other  intermediates. 

/3-Nitronaphthalene  is  made  from  /3-naphthylamine  hydro- 
chloride by  diazotizing  and  treating  the  diazonium  salt  with 
sodium  nitrite  in  the  presence  of  cuprous  oxide  :  — 

C10H7N2CI  +  NaNOz  =  C10H7NO2  +  N2  -I-  NaCl. 

It  crystallizes  in  yellow  needles  that  melt  at  79°  and  have  an 
odor  similar  to  that  of  cinnamon.  When  reduced  it  gives 
i8-naphthylamine,  and  this  gives  j3-naphthol  when  its  salt  is 
diazotized  and  boiled  with  water. 

Naphthalenesulphonic  acids,  C10H7SO3H,  are  formed  by 
sulphonation   of   naphthalene.     The    i-acid   results   in   larger 


SOO  TWO   BENZENE   RESIDUES,   ETC. 

quantity  at  lower  temperatures,  the  2-acid  at  higher  tempera- 
tures. Thus  at  ioo°  with  concentrated  sulphuric  acid  95  pei 
cent  of  the  i-acid  and  5  per  cent  of  the  2-add  are  formed,  while 
at  160°,  18  per  cent  of  the  i-acid  and  82  per  cent  of  the  2-acid 
are  obtained.  They  are  separated  by  recrystaUization  of  the 
calcium  salts,  the  calcium  salt  of  the  2-acid  being  more  difS- 
cultly  soluble  in  water,  and  are  converted  into  the  sodium  salts 
by  means  of  sodium  carbonate.  From  the  sodium  salts  a-  and 
|3-naphthols  are  obtained  by  fusing  with  alkalies  :  — 

CioHjSOsNa  +  NaOH  =  CioHjOH  +  NajSOs, 

and  the  a-  and  ;3-cyannaphthalenes  by  fusing  with  sodium 
cyanide :  — 

CioHjSOsNa  -f-  NaCN  =  C10H7CN  +  NazSOs. 

These  cyannaphthalenes  give  the  two  naphthoic  acids  (498) 
when  hydrolyzed.  The  difference  in  the  conduct  of  the  two 
naphthalenesulphonic  acids  towards  sodium  amalgam  is  im- 
portant. The  sulphoxyl  group  in  the  a-position  is  replaced  by 
hydrogen,  while  in  the  |8-position  it  is  unattacked.  The  a-acid 
is  also  converted  into  naphthalene  by  boiling  with  dilute  sul- 
phuric acid, 

C10H7SO3H  -I-  H2O  =  CioHs  +  H2SO4, 

while  the  |8-acid  undergoes  no  change. 

Naphthols,  C10H7OH.  —  a-  and  /3-Naphthols  are  present  in 
coal  tar,  but  are  always  made  from  the  two  monosulphonic  acids 
by  fusing  with  alkalies.  They  can  also  be  made  from  the  two 
naphthylamines  by  diazotizing  and  boiling  their  diazonium  salts 
with  water. 

a-Naphthol  is  sometimes  made  on  the  large  scale  from  a-naph- 
thylamine  by  heating  it  with  dilute  sulphuric  acid  in  an  autc 
clave  to  200° :  — 

C10H7NH2  -I-  HOH  =  C10H7OH  -f  NH3. 

This  method  gives  a-naphthol  free  from  even  a  trace  oi 
^-naphthol,     It  crystallizes  in  monoclinic  needles,  which  melt  at 


|8-NAPHTH0L  501 

94°.  It  boils  at  278°-28o°,  is  only  slightly  soluble  in  water,  but 
dissolves  readily  in  alcohol,  ether,  and  benzene.  With  ferric 
chloride  it  gives  a  violet  color  and  a  flocky  precipitate.  It  has 
an  odor  somewhat  Uke  that  of  phenol  and  acts  chemically  like 
phenol,  although  the  hydroxyl  group  reacts  more  readily  than 
that  in  phenol.  For  example,  it  is  readily  converted  into 
naphthylamine  by  heating  with  the  zinc  chloride  or  the  calcium 
chloride  compound  of  ammonia :  — ■ 

C10H7.OH  +  HNH2    =    CioHyNHz  +  H2O, 

and  is  converted  into  the  ethyl  ether,  C10H7OC2H6,  merely  by 
boiling  with  alcohol  and  a  mineral  acid.  This  ether,  curiously 
enough,  although  it  does  not  contain  a  free  hydroxyl  group, 
combines  with  diazonium  salts  in  the  same  way  that  a-naphthol 
does  to  form  azo  compounds :  — 

CeHsNaCl  +  HCioHeOCsHj  =  CeHsNadoHeOCaHs  +  HCl. 

a-Naphthol  is  used  in  the  preparation  of  a  number  of  dyes, 
but  most  of  it  is  converted  into  a-naphtholsulphonic  acids, 
which  are  very  important  dyestuff  intermediates.  It  is  also 
used  to  prepare  Martins  yellow  and  Naphthol  yellow  S. 

<CM2 — CH2 
I      ,  formed  by 
CH2— CH2 

reducing  a-naphthol  in  solution  in  amyl  alcohol  with  sodium, 
shows  in  its  chemical  conduct  a  very  close  resemblance  to  phenol, 
e.g.,  it  is  soluble  in  alkalies  and  is  precipitated  from  this  solution 
by  carbon  dioxide,  just  as  phenol  is.  Like  phenol  it  also  com- 
bines with  diazonium  salts  to  form  hydroxyazo  compounds.  It 
is  called  "  aromatic  "-tetrahydro-a-naphthol,  abbreviated  as 
shown  above,  to  indicate  that  it  acts  like  an  aromatic  compound. 
/3-Naphthol  is  always  made  synthetically  from  naphthalene- 
2-sulphonic  acid  by  fusing  with  caustic  soda.  It  crystallizes  in 
nearly  inodorous,  monoclinic  leaflets  that  melt  at  123°,  and  it 
boils  at  285°-286°.  It  sublimes  very  readily  and  is  volatile 
with  superheated  steam.  It  is  difficultly  soluble  in  cold  water, 
more  readily  in  hot,  and  in  ether,  alcohol,  and  benzene.     Ferric 


502  TWO   BENZENE   RESIDUES,   ETC. 

chloride  gives  first  a  faint  green  color  and  then  a  white  floc- 
culent  precipitate.  Like  a-naphthol  the  /S-compound  is  readily 
converted  into  ethers  with  alcohols  and  hydrochloric  acid. 

P-Naphthylmethyl  ether,  C10H7OCH3,  has  an  odor  similar  to 
that  of  neroli  oil.  It  is  made  synthetically  on  the  large  scale 
and  is  used  in  perfumery  under  the  name,  nerolin. 

With  ammonia,  or  more  readily  with  ammonium  sulphite  and 
ammonia,  naphthol  is  converted  into  /3-naphthylamine :  — 

C10H7.OH  +  HNH2  =  C10H7.NH2  +  H2O, 

and  this  is  the  technical  method  for  the  production  of  j3-naphthyl- 
amine. 

/CH2.CHOH 

ac-Tetrahydro-p-naphthol,  C6H4\  |  ,  is  formed  to- 

\CH2.CH2 
gether  with  a  small  amount  of  the  ar-tetrahydro  product  by  the 
reduction  of  /3-naphthol  with  sodium  and  amyl  alcohol.  It  acts 
like  a  secondary  alcohol,  while  the  ar-compound  acts  like  a 
phenol.  It  is  called  "  alicyclic  "  (abbreviated  to  ac)  to  show 
that  it  acts  like  the  aliphatic  and  cyclic  compounds. 

Enormous  quantities  of  /3-naphthol  are  used  in  making  azo 
dyes  and  dyestuff  intermediates.  Large  quantities  are  also 
converted  into  /8-naphthylamine.  About  12  million  pounds 
were  made  in  the  United  States  in  1920. 

Naphtholsulphonic  acids  are  obtained  by  sulphonation  of  the 
naphthols  or  from  the  naphthylaminesulphonic  acids.  Thus, 
i-naphthol-4-sulphonic  acid  was  for  a  long  time  made  by  di- 
azotizing  naphthionic  acid  (i-naphthylamine-4-sulphonic  acid) 
and  boiling  the  diazonium  salt  with  water.  This  method  is  no 
longer  used,  since  naphthionic  acid  can  be  more  readily  con- 
verted into  the  hydroxy  acid  by  heating  with  sodium  bisulphite 
and  an  alkali.  Ammonia  splits  off,  and  the  sodium  salt  of  a 
sulphurous  acid  ester  of  i-naphthol-4-sulphonic  acid  is  first 
obtained  and  then  saponified  by  the  alkali :  — 

NaSO3.C10H6.NH2  — >-  NaS03.CioH60S02Na 

— >-  NaSO3.C10H6.OH. 


AMINONAPHTHOLS  503 

The  acid  is  also  made  technically  by  heating  i-chloronaphtha- 
lene-4-sulphonic  acid  with  dilute  caustic  soda  solution  under 
pressure  to  200°,  when  the  chlorine  is  replaced  by  the  hydroxyl 
group.  a-Naphthol  gives  a  mixture  of  the  ortho  and  para  acids 
when  sulphonated.  If,  however,  the  hydroxyl  group  is  rendered 
inactive,  only  the  para  acid  is  formed.  Thus  a-naphthyl- 
ethyl  ether  gives  only  the  4-sulphonic  acid.  i-Naphthol- 
4.-sulphonic  acid  is  used,  in  the  form  of  its  sodium  salt,  in  the 
manufacture  of  azo-dyes  and  is  known  as  Neville  and  Winther's 
acid.  The  2,6-  and  2,8-/3-naphtholsulphonic  acids  made  by 
sulphonating  /3-naphthol  are  also  important  dyestuff  interme- 
diates. The  first  is  called  Schdffer's  acid  and  the  second  crocein 
acid,  because  of  its  use  in  the  manufacture  of  crocein  scarlet 
(made  by  diazotizing  aminoazobenzenesulphonic  acid  and 
combining  it  with  the  crocein  acid  in  alkaline  solution).  The 
|3-naphtholdisulphonic  acids  (2,3,6  and  2,6,8),  known  in  the 
form  of  their  sodium  salts  as  R-salt  and  G-salt,  because  one 
gives  red  (rot)  and  the  other  yellow  (gelb)  azo  dyes  with  di- 
azonium  salts,  are  important  dyestuff  intermediates.  Chromo- 
tropic  acid  (i,8-dihydroxynaphthalene-3,6-disulphonic  acid) 
made  from  the  i-amino-8-naphthol-3,6-disulphonic  acid  (H- 
acid),  by  heating  with  a  concentrated  solution  of  caustic 
potash,  is  also  of  technical  importance. 

Nitronaphthols  analogous  to  the  nitrophenols  are  formed 
by  the  nitration  of  the  naphthols.  For  example,  2,4-dinitro- 
a-naphthol  is  made  by  nitrating  a-naphthol  mono-  or  disulphonic 
acid,  the  sulphonic  acid  groups  being  displaced  by  the  nitro 
groups,  and  2,4-dinitro-a-naphthol-7-sulphonic  acid  by  nitrat- 
ing a-naphtholtrisulphonic  acid  (1,2,4,7).  In  this  case  the 
sulphonic  acid  groups  in  positions  2  and  4  are  replaced  by  nitro 
groups,  while  that  in  7  is  not  attacked.  The  sodium  salts  of 
these  nitro  compounds  are  yellow  dyes  known  as  Martius 
yellow  and  Naphihol  yellow  S,  respectively. 

Aminonaphthols  are  made  by  the  reduction  of  the  nitro- 
naphthols, and  like  the  aminophenols  readily  undergo  oxidation 
in  the  air.  The  i-amino-8-naphthol-3,6-disulphonic  acid  is 
known  as  H-acid  and  is  largely  used  in  the  manufacture  of 


504  TWO   BENZENE  RESIDUES,   ETC. 

azo  dyes.  The  sodium  salt  of  the  i-amino-2-naphthol-6-sul- 
phonic  acid,  known  as  eikonogen,  is  used  as  a  photographic 
developer. 

a-Naphthylamine,  CioH7NH2(a),  is  made  on  the  large  scale  by 
reducing  a-nitronaphthalene  in  the  same  way  that  aniline  is 
made  from  nitrobenzene.  It  can  also  be  made  by  heating 
naphthalene  to  its  boiling  point  with  sodium  amide,  NaNHj, 
hydrogen  being  evolved.  It  crystallizes  from  alcohol  in  color- 
less needles,  melts  at  50°,  and  boUs  at  301°.  It  is  very  difficultly 
soluble  in  water,  has  a  disagreeable,  fecal  odor,  and  sublimes 
readily.  Like  aniline  it  turns  brown  in  the  air,  due  to  oxidation. 
Chromic  acid  oxidizes  it  to  a-naphthaquinone  (506).  Its 
hydrochloride  is  sparingly  soluble  in  water  and  is  converted  into 
the  diazonium  salt,  C10H7N2CI,  by  the  action  of  nitrous  acid. 
When  boiled  with  water  this  gives  a-naphthol,  and  it  combines 
with  phenols  or  naphthols  and  with  aromatic  amines,  in  the 
same  way  that  the  benzene  diazonium  salts  do,  to  form  azo 
dyes.  When  heated  with  sodium  amide  (and  naphthalene)  to 
230°  it  gives  1 ,5-naphthylenediamine,  CioH6(NH2)2. 

a-Naphthylamine  is  used  in  making  dyes  and  intermediates. 
Most  of  it  is  converted  into  naphthionic  acid.  Over  5  million 
pounds  were  made  in  the  United  States  in  1920. 

/CH2.CH2 
ar-Tetrahydro-a-naphthylamine,  H2NC6H3<(^  | 

\CH6.CH2, 

is  formed  by  the  action  of  sodium  on  the  amyl  alcohol  solution 
of  a-naphthylamine.  It  resembles  aniline  in  its  chemical  conduct, 
e.g.,  it  can  be  diazotized,  and  the  diazonium  salt  is  converted 
into  ar-tetrahydro-a-naphthol  by  boiling  with  water. 

P-Naphthylamine,  CioH7NH2(P),  is  made  on  the  large  scale  by 
heating  /3-naphthol  (501)  with  20  per  cent  ammonia  and  am- 
monium sulphite  under  pressure.  It  crystallizes  in  leaflets, 
melts  at  112°,  boils  at  306°,  and  differs  from  a-naphthylamine  in 
being  odorless.  It  is  more  stable  than  the  a-compound  and  is 
not  colored  by  oxidizing  agents. 

|8-Naphthylamine  is  used  in  making  dyes  and  intermediates. 
It  is  not  as  important  as  the  a-compound. 


CONGO  RED  505 

.CH2.CHNH2 
ac-Tetrahydro-P-naphthylamine,  CeRt^  \  ,  formed 

\CH2.CH2 

by  reducing  |3-naphthylamine  with  sodium  and  amyl  alcohol, 
cannot  be  diazotized.  With  nitrous  acid  it  forms  a  very  stable 
nitrite.  It  resembles  piperidine  in  its  odor  and  properties  and 
is  a  strong  base.  It  contains  an  asymmetric  carbon  atom  and 
has  been  separated  into  a  dextro  and  a  levo  modification. 

Naphthylaminesulphonic  acids  are  made  by  sulphonation  of 
the  naphthylamines.  The  most  important  of  these  is  i-naphthyl- 
amine-4-sulphonic  acid,  (i)H2N.CioH6.S03H(4)  {naphihionic 
acid),  which  is  made  by  roasting  a-naphthylamine  acid  sulphate 
in  the  same  way  that  sulphanilic  acid  (369)  is  made  from  aniline 
acid  sulphate.  It  resembles  sulphanilic  acid  very  closely.  Like 
sulphanilic  acid  it  is  diazotized  directly  by  nitrous  acid,  and 
the  diazonium  sulphonate  combines  with  phenols,  naphthols, 
atid  aromatic  amines  to  form  valuable  azo  dyes.  It  is  a  very 
important  intermediate,  nearly  4,000,000  pounds  having  been 
made  in-  the  United  States  in  igao. 

Azo  dyes  of  the  naphthalene  series  are  of  great  technical 
importance.  They  are  produced  by  the  action  of  diazonium 
salts  on  the  naphthylamines  and  naphthols  or  their  sulphonic 
acids. 

Congo  red  is  made  by  the  action  of  diphenyltetrazonium 
chloride  (491)  on  naphthionic  acid  in  alkaline  solution :  — 

CIN2.C6H4— C6H4.N2CI  +  2  CioH6(NH2)S03Na  +  2  NaOH 

=  2  H2O  +  2  NaCl, 

(4)Na03S\  2  2  /S03Na(4) 

>CioH6N:NC6H4.C6H4N:NCioH6< 

(i)NH2/  \NH2(i) 

Congo  red 

It  is  an  important  substantive  dye  for  cotton,  over  i^  million 
pounds  having  been  made  in  the  United  States  in  1920.  The 
free  acid  is  blue  and  the  salts  are  red.  It  acts  as  an  indicator, 
the  reverse  of  litmus,  as  in  alkaline  solution  it  is  red,  in  acid 
blue.     Benzopurpurin,  made  by  substituting  tolidine  (491)  for 


5o6  TWO   BENZENE  RESIDUES,   ETC. 

benzidine,  is  a  dimethyl  derivative  of  Congo  red  containing  a 
methyl  group  attached  to  each  of  the  benzene  residues  of  the 
diphenyl  group.  A  few  of  the  simpler  azo  dyes  of  this  series 
are:  — 

Orange  II,  NaS03.CcH4N2CioH60H(P),  made  by  diazotiz- 
ing  sulphardlic  acid  and  combining  it  in  alkaline  solution  with 
j3-naphthol,  is  an  important  azo  dye  containing  a  benzene 
and  a  naphthalene  residue.  Nearly  2,000,000  pounds  were 
made  in  the  United  States  in  1920. 

Ponceau,  2  R,  (CH3)2C6H3.N=N.CioH40H(S03Na)2,  made 
from  diazotized  xyHdine  hydrochloride  and  R-salt  (603)  is  an 
important  red  azo-dye.  Over  1,000,000  pounds  were  made  in 
the  United  States  in  1920. 

Fast  red,  NaSOs.CioHe— N=N— CioH5(OH).S03Na,  made  by 
diazotizing  naphthionic  acid  and  combining  it  with  i ,  4-naphthol- 
sulphonic  acid,  is  an  example  of  a  red  azo  dye  containing  two 
naphthalene  residues.'  Nearly  500,000  pounds  were  made  in 
the  United  States  in  1920. 

Quinones  of  the  naphthalene  series.  —  Three  isomeric  qui- 
nones,  CioHgOs,  are  known.  They  are  called  a-,  /3-,  and  amphi- 
according  to  the  position  of  the  ketone  groups. 

a-Naphthaquinone  is  made  by  the  oxidation  of  naphthalene, 
a-naphthylamine,  1,4-dihydroxynaphthalene  and  other  disub- 
stitution  products  of  naphthalene  having  the  groups  in  the  i  ,4 
position,  with  chromic  acid.  It  crystallizes  in  yellow,  triclinic 
needles  that  melt  at  125°,  and  resembles  ordinary />-benzoquinone 
closely  m  its  properties.  It  has  a  similar  odor,  is  volatile  with 
steam,  and  gives  a  dioxime  with  hydroxylamine.  It  is  reduced 
by  sulphurous  acid  to  1,4-dihydroxynaphthalene  and  there- 
fore has  the  two  carbonyl  groups  in  the  1,4  position,  or  it  is  a 
para  quinone  (I) :  — 

CO  _       CO 

I.  a-Naphthaquinone  II.  ^-Naphthaquinone  m.  amphi-Naphthaquinone 

'  See  Synthetic  Dyesttiffs,  by  J.  C.  Caine  and  J.  T.  Thorpe,  for  further 
information  regarding  these  dyes. 


QUINOLINE  507 

P-Naphthaquinone  resembles  o-benzoquinone  in  that  it  is  not 
volatile  with  steam  and  has  no  odor.  It  is  obtained  by  the 
oxidation  of  i-amino-2-naphthol  or  ofj  1,2-dihydroxynaphtha- 
lene,  and  is  reduced  to  this  latter  compound  by  sulphurous  acid. 
Hence  it  is  a  1,2  or  ortho  quinone  (II).  It  crystallizes  in  red 
needles,  which  decompose  at  115°,  and  forms  a  dioxime  with 
hy  droxylamine . 

am^Ai-Naphthaquinone  or  2,6-naphthaqulnone  is  made  by 
oxidizing  2,6-dihydroxynaphthalene  in  benzene  solution  with 
lead  peroxide  and  yields  this  dihydroxynaphthalene  on  re- 
duction. Hence  the  structure  (III) .  It  crystallizes  in  yellowish 
red  prisms,  is  not  volatile  with  steam  and  has  no  odor.  It  is  a 
strong  oxidizing  agent. 

Naphthazarin,  5,6-dihydroxy-a-naphthaquinone,  is  a  dye  that 
resembles  alizarin,  whence  the  name.  It  is  made  from 
1,5-dinitronaphthalene  by  heating  it  with  a  solution  of  sulphur 
in  fuming  sulphuric  acid.  It  is  ordinarily  called  Alizarin  black 
in  the  trade  and  is  a  valuable  mordant  dye. 

Nitroso-P-naphthol  is  |8-naphthaquinone-a-oxime.  It  is  made 
by  the  action  of  nitrous  acid  on  /J-naphthol.  (Compare  with  the 
formation  of  nitrosophenol  or  quinone  monoxime.)  It  crystal- 
lizes in  orange  brown  prisms  that  melt  at  110°  It  is  used  in 
analytical  chemistry,  especially  to  detect  and  determine  cobalt 
and  as  a  dye  under  the  name  Gambine  Y. 

QuiNOLINE   AND  ISOQUINOLINE  AND  ThEIR  DERIVATIVES 

Quinohne  and  isoquinoline  are  basic  substances,  resem- 
bling pyridine,  found  in  coal  tar  and  bone  oil.  They  are  of 
importance  because  of  their  close  connection  with  the  alka- 
loids. Thus,  quinine  gives  quinoline,  a-methylquinohne  (lepi- 
dine),  and  ^-methoxyquinoUne,  when  fused  with  caustic  potash, 
and  papaverine  gives  derivatives  of  isoquinoline. 

Quinoline,  C9H7N,  has  been  isolated  from  coal  tar  and  bone  oil. 

It  is  difi&cult,  however,  to  obtain  it  pure  from  these  sources  or 

from  the  alkaloids.    When  required  pure  it  is  usually  made  syn- 

,  thetically  by  Skraup's  method   (509,510).     It  is  a  colorless, 


508  TWO   BENZENE   RESIDUES,   ETC. 

highl}-  refracting  liquid,  having  a  very  characteristic  odor.  It 
boUs  at  238°,  solidifies  at  -22.6°  and  is  heavier  than  water.  It  is 
a  monacid,  tertiary  base  like  pyridine,  and  forms  well  character- 
ized salts  with  acids.  The  dichromate  (C9H7N)2H2Cr207,  is  diffi- 
cultly soluble  in  water.     It  combines  with  methyl  iodide  just  as 

/CH3 
pyridine  does,  forming  methyl  quinolonium  iodide,  C9H7N<' 

\I 
When  oxidized  with  potassium  permanganate  quinofine  gives 
quinolinic  acid,  C5H3N(COOH)2,  just  as  naphthalene  gives 
phthalic  acid.  Like  phthalic  acid,  quinolinic  acid  yields  an 
anhydride  when  heated,  and  hence  the  two  carboxyl  groups 
are  in  the  ortho  position  to  each  other.  When  distilled  with 
lime  quinolinic  acid  gives  pyridine,  just  as  phthalic  acid  gives 
benzene : — 

'^K     =    I    I  +  =  ^*- 

N 

Quinolinic  acid 

Quinolinic  acid  is,  therefore,  a  pyridinedicarboxylic  acid  with 
the  carboxyl  groups  in  the  ortho  position  to  each  other.  It  has 
been  shown  to  be  a,/3-pyridinedicarboxylic  acid,  as  it  loses 
carbon  dioxide  and  is  converted  into  /3-pyridinemonocarboxylic 
acid  (nicotinic  acid)  when  heated,  and  has  been  made  by  the 
oxidation  of  a,/3-dimethylpyridine.  Quinoline,  hence,  con- 
tains a  pyridine  ring.  When  a-methylquinoline,  which  can 
be  made  from  quinoline,  is  oxidized  it  gives  an  acetyl  derivative 
of  o-aminobenzoic  acid :  — 


CH=:CH  /COOH 

+  50   =  C6ll4<  +  CO2. 

\xrTT  rnrrjJn^ 


H  ( 

^N^C— CH3        '  ^NH.COCHsW 

a-Metliylquinoline  Acetylaminobenzoic  acid 


Hence  quinoline  must  also  contain  a  benzene  ring.  From 
these  facts  it  is  concluded  that  quinoline  contains  a  benzene 
ring  and  a  pyridine  ring  with  two  ortho  carbon  atoms  in  com- 
mon: — 


t^UJU^UJ^lJNE  509 

H  H 

HC^  \c^    '^CH 

I  II  I 

H 

It  will  be  seen  from  the  above  formula  that  quinoline  is  naphtha- 
lene in  which  one  of  the  CH-groups  in  the  a-position  (i,  4,  5  or 
8)  is  replaced  by  nitrogen.  It  therefore  bears  the  same  relation 
to  naphthalene  that  pyridine  bears  to  benzene.  This  formula 
has  been  confirmed  by  the  following  syntheses  from  aniline 
or  ortho  substitution  products  of  aniline :  — 

1.  o-Aminocinnamic  aldehyde,  obtained  by  the  reduction  of 
o-nitrocinnamic  aldehyde,  loses  water  and  gives  quinoline, 

,CH=CH  /CH— CH 

C6H4/        OCH  =  CgH/  I      +  H2O, 

\nh2(o)  \n=ch 

Quinoline 

while  carbostyril  (a-hydroxyquinoline  (512))  is  formed  from 
o-aminocinnamic  acid :  — 

,CH=:CH  /CH=CH 

C6H4/        OCOH  =  CbH/  I  +  H2O. 

\NH2(o)  \n=C-OH 

Carbostyril 

2.  0-Aminobenzaldehyde  condenses  very  readily  with  alde- 
hydes or  ketones  in  the  presence  of  dilute  caustic  soda  to  form 
quinoline  and  its,  derivatives :  — 

/CHO         H2=CH  /CH=CH 

CbH/  +  1       =  C6H4<  I        +  2  H2O. 

\NH2(o)        0=CH  \N=CH 

Acetone  gives  a-methyl quinoline  (quinaldine). 

3.  The  most  important  synthesis  of  quinoline  and  its  deriva- 
tives and  the  one  used  to  prepare  these  substances  in  the  pure 
state  is  that  due  to  Skraup.    It  consists  in  beating  aniline, 


Sio 


TWO   BENZENE   RESIDUES,   ETC. 


glycerol,  and  concentrated  sulphuric  acid  with  an  oxidizing  agent, 
such  as  nitrobenzene  or  arsenic  acid :  — 

/H  HOCH2.CHOH 

CeH/  +  I  +0 

\NH2  CH2OH 

/CH=CH 
=  C6H4<  I        +  4  H2O. 

\N=^CH 

Quinoline 

Acrolein,  CH2=CH.CH0,  is  formed  here  as  an  intermediate 
product  and  combines  with  the  aniline  to  form  /3-phenylamino- 
propionic  aldehyde,  C6H6.NH.CH2.CH2.CHO,  which  is  then 
oxidized  to  quinoUne.  Homologues  of  aniline  give  homologues 
of  quinoline,  and  derivatives  of  aniline  give  derivatives  of 
quinoline  in  which  the  substituting  group  is  in  the  benzene 
portion  of  the  quinoline. 

The  hydrogen  addition  products  are  also  in  accord  with  the 
above  formula  for  quinoline.     It  takes  up  four  hydrogen  atoms 

<CH2.CH2 
I  , 
NH.CH2 
which  acts  as  a  secondary  base.  The  N-methyl  derivative  of 
this  base  is  kairoline,  which  is  used  as  an  antipyretic.  The 
final  product  of  the  reduction  of  quinoline  is  quinoline  deca- 
hydride :  — 


H,C 


H,C 


This  is  a  strong,  secondary  base  having  the  character  of  an 
aliphatic  amine.  It  absorbs  carbon  dioxide  from  the  air  and 
has  a  stupefying  odor  similar  to  that  of  conine.  It  has  been 
separated  into  its  optically  active  modifications. 

The  number  of  substitution  products  obtained  from  quinoline 


LEPIDINE,  7-METHV:LQUIN0LINE 


511 


is  very  large  and  is  in  accord  with  the  number  theoretically 
possible.  Thus,  there  are  7  monosubstitution  products  possible, 
as  will  be  seen  by  an  examination  of  the  formula  :•= — 


ana 


para 


meta 


ortho 


A  substituting  group  or  atom  may  take  the  place  of  any  one  of 
the  hydrogen  atoms  indicated  by  the  numbers  2,  3,  4,  5,  6,  7,  8, 
each  of  which  bears  a  different  relation  to  the  nitrogen  atom. 
Seven  monomethyl  derivatives  are  known,  and  these  are  con- 
verted into  the  seven  possible  monocarboxylic  acids  by  oxida- 
tion. The  seven  monochloro  derivatives  are  also  all  known. 
Another  method  of  designating  the  hydrogen  atoms  in  quinoline 
is  shown  above.  Those  in  the  pyridine  ring  are  marked  a,  fi,  and 
7  as  in  pyridine,  while  those  in  the  benzene  ring  are  designated 
ortho-,  meta-,  para-,  and  ana-. 


HOMOLOGUES  AND   DERIVATIVES   OF   QuiNOLINE 

Quinaldine,  a-methylquinoline,  C9H6(CH3)N,  is  present  in 
coal  tar  and  in  the  crude  quinoline  obtained  from  coal  tar.  It  is 
a  liquid  having  the  odor  of  quinoline  and  boiling  at  246°  to  248°. 
It  has  been  made  synthetically  (see  method  2  above)  from 
acetone,  and  also  from  quinoline  by  the  method  used  to  make 
a-methylpyridine  (439)  from  pyridine.  When  oxidized  with 
chromic  acid  it  gives  quinaldinic  acid,  CgHeN.COOH,  which  is 
converted  into  quinoline  by  heating  with  lime.  The  a-position 
of  the  methyl  group  is  proved  by  the  formation  of  acetyl- 
o-aminobenzoic  acid  by  oxidation  with  potassium  perman- 
ganate (508). 

Lepidine,  Y-methylquinoline,  C9H6(CH3)N,  is  present  in  coal 
tar  and  is  formed  by  distilling  cinchonine  with  caustic  potash. 
It   boils   at   258°-26o°.    The   position   of   the  methyl   group 


512  BENZENE  RESIDXJES,   ETC. 

follows  from  its  oxidation  with  potassium  permanganate  to 
7-methylpyridine-a-;8-dicarboxylic  acid. 

o-Hydroxyqiiinoline,  C9H6(OH)N,  is  made  from  o-amino- 
phenol  by  Skraup's  synthesis,  and  also  from  quinoline-o-sul- 
phonic  acid  by  fusing  with  alkalies.  It  crystallizes  from 
alcohol  in  colorless  prisms,  melts  at  7S°-76°  and  resembles 
a-naphthol,  e.g.  it  gives  o-aminoquinoline,  when  heated  with 
the  ammonia  compound  of  zinc  chloride. 

a-Hydroxyquinoline,  carbostyril,  is  formed  by  the  elimination 
of  water  from  the  cis-  form  of  o-aminocinnamic  acid  (480). 
It  is  more  readily  prepared  from  quinoUne  by  the  action  of 
bleaching  powder  and  an  alkali :  — 

/CH=CH     HOCl  /CH=CH       NaOH 

C6H4<  I  — ^  C6H4/  t  — >• 

\n=ch  \nci— CHOH 

.CH=CH  .CH— CH 


C6H4/  I  or      C6H4/  I 

^NH— CO  \N^=C 


COH 

It  crystaUizes  from  water  with  a  molecule  of  water,  from  alcohol 
in  the  anhydrous  form,  which  melts  at  i99°-2oo°.  It  acts  as  a 
tautomeric  substance  (see  formulas  above)  and  gives  both  N- 
and  O-  alkyl  ethers.  With  phosphorus  pentachloride  it  is  con- 
verted into  a-chloroquinoline,  and  this  on  reduction  with 
hydriodic  acid  yields  quinoline. 

Isoquinoline  was  first  found  in  coal  tar  and  then  made  syn- 
thetically from  homophthalic  acid :  — 


CH2 

t^CHj.COOH 

JcOOH          ^ 

/NcHsCO 

.   J  cod 

NH3 

— >■ 

/V^co 

^1,NH 

Homophthalic  acid 

Anhydride 

CO 

Homophthalimide 

CH 
'^'^'^COH     OPCI3 

CH 

^Y^cci 

HI 

CH 

/y^cH 

COH 

Homophthalimide 

CCl 

DichloroisoquinoUoe 

— »- 

CH 

Isoquinoline 

ISOQUINOLINE  513 

Isoquinoline  is  also  formed  directly  from  homophthalimide  by 
distillation  with  zinc  dust  in  an  atmosphere  of  hydrogen. 

A  simpler  synthesis  is  that   from   formaminomethylphenyl 
carbinol  by  the  loss  of  water :  — 

/CHOH.CH2  /CH=CH 

CeHs^  I         =  CsHZ  1       +  2  H2O. 

OHC— NH  \CH=N 

Isoquinoline 

The  constitution  of  isoquinoline  as  a  derivative  of  naphthalene 
in  which  a  )3-CH  group  is  replaced  by  nitrogen  follows  from  the 
syntheses,  and  from  the  fact  that  on  oxidation  it  gives  phthalic 
acid  and  cinchomeronic  acid,  i.e.  an  ortho  dicarboxylic  acid  of 
benzene  and  an  ortho  dicarboxylic  acid  of  pyridine  (/3,7-acid,  iso- 
meric with  quinolinic  acid).  Isoquinoline  melts  at  24°-25°  and 
boils  at  240.5°.  Its  odor  is  similar  to  that  of  benzaldehyde.  It 
is  a  basic  substance  and  resembles  quinoline  in  its  chemical 
conduct.  The  alkaloids,  papaverine,  narcotine,  laudanosine,  and 
hydrastine  are  derivatives  of  isoquinoline  or  its  tetrahydride. 


CHAPTER    XX 

ANTHRACENE   AND    PHENANTHRENE   AND    SOME   OF 
THEIR   DERIVATIVES 

Anthracene  (Gr.  anthrax,  coal),  C14H10,  together  with  its 
isomer,  phenanthrene,  and  other  h}'drocarbons  and  carbazole, 
is  present  in  the  anthracene  oil  obtained  in  the  distillation  of 
coal  tar.'  Coal  tar  is  the  only  source  of  anthracene,  although 
it  contains  only  0.2  to  0.5  per  cent  of  this  hydrocarbon.  It  is 
separated  from  the  anthracene  oil  by  slow  cooUng  and  centrifug- 
ing  the  crude  anthracene  which  crystallizes  out.  This  product, 
which  contains  from  25  to  40  per  cent  anthracene,  is  further 
purified  by  washing  with  solvent  naphtha,  in  which  anthracene  is 
practically  insoluble,  to  remove  oil  and  the  major  portion  of  the 
phenanthrene  and  other  hydrocarbons  present.  The  dried  ma- 
terial (50-60  per  cent  anthracene)  is  then  fused  with  a  mixture 
of  caustic  potash  and  caustic  soda  at  26o°-2  7o°,  and  subjected  to 
sublimation  in  superheated  steam.  This  removes  the  carbazole 
(492)  which  forms  a  non-volatile  sodium  or  potassium  salt, 
(C6H4)2=NK.  The  subhmed  anthracene  is  again  extracted  with 
solvent  naphtha  to  remove  the  remainder  of  the  phenanthrene, 
etc.,  and  resubUmed.  This  product  (90-95  per  cent  anthra- 
cene) is  then  converted  into  anthraquinone  by  oxidation. 
The  determination  of  the  amount  of  pure  anthracene  in  the 
crude  product  is  made  by  oxidizing  it  with  chromic  acid  to 
anthraquinone,  which  is  then  purified  and  weighed.  This  is 
known  as  the  Hochst  anthracene  test. 

Anthracene  crystallizes  in  colorless,  monoclinic  plates  which 
when  absolutely  pure  show  a  bluish  fluorescence.  It  melts  at 
213°  and  boils  at  about  360°,  with  slight  decomposition.  It  is 
insoluble  in  water  and  difficultly  soluble  in  most  organic  solvents. 
Benzene  and  its  higher  homologues  dissolve  it  to  some  extent  at 

'  See  Coal  Tar  and  Ammonia,  by  G.  Lunge,  sth  ed.  1916. 
S14 


ANTHRACENE  51 5 

their  boiling  points.  The  pure  product  is  best  obtained  by  the 
reduction  of  pure  anthraquinone.  Anthracene  forms  an  addition 
product  with  picric  acid  crystallizing  in  ruby-red  needles  that 
melt  at  138°.  This  is  used  as  a  test  for  anthracene.  Direct 
sunlight  converts  anthracene  into  a  polymeric  modification, 
dianthracene,  C28H20,  melting  at  243°  In  the  dark  or  when 
heated  to  its  melting  point  dianthracene  is  reconverted  into 
anthracene.  Over  700,000  pounds  of  anthracene  (100  per  cent) 
were  produced  in  the  United  States  in  1920,  and  a  considerable 
quantity  was  imported.  The  entire  quantity  is  converted  into 
anthraquinone  for  the  purpose  of  making  the  anthraquinone 
dyes. 

The  constitution  of  anthracene  has  been  determined  from 
its  syntheses  from  benzene  or  ortho  derivatives  of  benzene,  some 
of  the  more  important  of  which  are  as  follows :  — 

1.  Benzene  when  heated  with  symmetrical  tetrabromoethane 
in  the  presence  of  aluminium  chloride  gives  anthracene :  — 

/H    BrCHBr    H.  /CH. 

C6H4<     +      I         +      >C6H4  =  CcHZ  i       >C6H4+4  HBr. 
^H    BrCHBr    W  \CH/ 

Anthracene 

2.  0-Bromobenzylbromide  in  solution  in  ether  when  treated 
with  sodium  gives  a  mixture  of  dihydroanthracene  and  anthra- 
cene :  — 

/Br(o)  BrCHj 

C6H4<  +  \C6H4  -t-  4  Na 

\CH2Br       (o)Br/ 

CH2\ 


=  C6H4<  >C6H4  +  4  NaBr. 

Dihydroanthracene 

When  this  mixture  is  heated  on  a  water  bath  with  sulphuric  acid 
the  dihydroanthracene  is  oxidized  to  anthracene.  That  anthra- 
cene as  well  as  dihydroanthracene  is  formed  in  this  reaction  is 
explained  by  the  ease  with  which  dihydroanthracene  loses  hydro- 
gen and  is  converted  into  anthracene. 


;i6 


ANTHRACENE  AND  PHENANTHRENE 


3.   Phthalic  anhydride  combines  with  benzene  in  the  presence 
of  aluminium  chloride  to  form  o-benzoylbenzoic  acid :  — 


C6H4. 


/ 


COv  yCO.CsHs 

4^  /O  +  HCeHs  =  C6H4<'  , 

\C0/  \COOH  (0) 

and  this  yields  anthraquinone  by  the  action  of  sulphuric  acid :  - 


CcH4  +   H2O. 


xCOCeHs  yCO. 

C6H4<'  =    C6H4<' 

\COOH(o)  \C0 

Anthraquinone 

Anthraquinone  when  heated  with  zinc  dust  is  reduced  to 
anthracene : — 


C6H4< 


/ 


CO 


,\ 


CH. 


AnthraquinoDe 


C6H4  +  6  H  =  C6H4<r    I      ^CeHi  +  2  H2O. 


Anthracene 


From  these  syntheses  and  from  the  fact  that  anthracene  gives 
anthraquinone  on  oxidation,  the  constitution  of  which  is  de- 
termined by  synthesis  3,  it  will  be  seen  that  anthracene  con- 
tains two  residues  of  benzene  joined  by  means  of  the  group 
C2H2.  According  to  synthesis  i  these  two  middle  carbon  atoms 
are  joined  to  each  other,  and  according  to  the  other  syntheses 
they  take  in  each  benzene  residue  the  ortho  position  to  each 
other,  as  shown  in  the  formula  below :  — 


According  to  this  formula  there  should  be  three  series  of  mono 
substitution  products  possible  according  as  hydrogen  atoms  a, 
j3,  or  7  are  replaced.  As  a  matter  of  fact  three  monochloro- 
anthracenes,  three  monohydroxyanthracenes  and  three  mono- 


HYDROXYANTHRACENES 


517 


aminoanthracenes,  etc.,  are  all  known.     When  anthracene  is 
oxidized  to  anthraquinone, 


aHC 


CO  CHa 


cHC 


CHy3 


CO  CHa 

Anthraquinone 


however,  it  will  be  seen  that  the  7-hydrogen  atoms  disappear 
and  that  only  two  series  of  mono  derivatives,  a  and  /3,  are 
possible.  Here  again  the  formula  is  in  accord  with  the  facts. 
Two  monosulphonic  acids,  two  mononitro  derivatives,  etc.,  of 
anthraquinone  are  known  and  only  two. 

The  reduction  products  of  anthracene  are  also  in  accord  with 
the  theory.  Dihydroanthracene,  whose  formula  is  determined 
by  synthesis  2,  is  formed  very  readily  from  anthracene  by  re- 
duction* with  sodium  and  alcohol.  Further  reduction  with  more 
powerful  reducing  agents  gives  C14H16  and  finally  C14H24.  (Write 
out  the  formulas.)- 

Chlorine  and  bromine  first  form  7-addition  products  with 

.CHCk 
anthracene,  such  as  anthracene  dichloride,  C^'Ri^'  ^C6H4. 

\CHCF 
Halogen  acid  then  splits  off,  giving  a  7-monohalogen  substitution 

/CCk 
product,  e.g.  C6H4^    |       yC^Ht.     This  takes  up  more  chlorine 

\ch/ 

<CCl2     ^ 
/>C6H4,  from  which 
CHCK 
by  the   elimination   of    hydrochloric    acid    the    9,10-dichloro- 

.CCL 
anthracene,  C6H4<'    |        )>C6H4  results. 
\CCK 

Hydroxyanthracenes,  C6H4.C2H2.C6H30H,a,  and  p,  are  called 
anthrols.     They  are  made  by  fusing  a-  or  )3-anthracenesulphonic 


Sl8       ANTHRACENE  AND  PHENANTHRENE 

acid  with  alkali  or  by  reducing  a-  or  j8-hydroxyanthraquinone 
(521).  They  resemble  the  phenols  and  especially  the  naphthols 
in  their  chemical  conduct. 

■y-Hydroxyanthracene  or  anthranol  is  obtained  by  reducing 
anthraquinone.     (See  below.) 

The   most   important   derivative   of   anthracene   is   anthra- 
quinone. 

/CO. 

Anthraquinone,  C6H4\  >C6H4,  is  farmed  by  the  distilla- 

tion  of  calcium  phthalate :  — 
COO. 


^'"'\coo/^'  /CO. 

/-r>n  =  C6H4<  /CeEU  +  2  CaCOj. 

C.H/''''Va  ^CO/ 


COO^ 

Anthraquinone 

This  method,  which  is  the  one  used  for  making  ketones,  indicates 
that  anthraquinone  is  a  diketone. 

On  the  large  scale  two  methods  are  used  to  make  anthraqui- 
none, which  is  a  very  important  dyestufE  intermediate,  (i)  direct 
oxidation  of  anthracene,  and  (2)  synthesis  from  phthalic  anhy- 
dride and  benzene  (516).  As  phthalic  anhydride  (416)  is  made 
from  naphthalene,  this  is  a  method  for  making  anthraquinone 
from  naphthalene. 

In  the  oxidation  of  anthracene  two  processes  are  used, 
(i)  oxidation  with  sodium  bichromate  and  sulphuric  acid,  and 
(2)  oxidation  of  the  anthracene  in  the  form  of  vapor  with  air 
in  the  pr.esence  of  a  catalyst,  such  as  vanadium  oxide.  This 
method  is  analogous  to  that  used  technically  to  make  phthalic 
anhydride  from  naphthalene. 

Anthraquinone  crystallizes  in  yellow,  orthorhombic  prisms 
which  melt  at  285°  (cor.).  It  sublimes  in  yellow  needles  and 
boils  at  382°.  It  dissolves  when  heated  with  concentrated  sul- 
phuric acid  at  100°  and  is  precipitated  from  this  solution  un- 
changed by  water.  This  is  the  method  made  use  of  on  the  large 
scale  to  purify  anthraquinone.     The  impurities  are  converted 


ANTHRAQUINONE  519 

into  sulphonic  acids,  which  are  soluble  in  water.  It  is  difficultly 
soluble  in  most  organic  solvents,  but  dissolves  in  hot  glacial 
acetic  acid  and  benzene.  Towards  oxidizing  agents  it  is  exceed- 
ingly stable.  Anthraquinone  differs  from  the  para  quinones  of 
the  benzene  and  naphthalene  series  in  several  respects,  and 
exhibits  many  of  the  properties  of  the  diketones,  e.g.  it  does  not 
have  the  characteristic  quinone  odor,  is  not  volatile  with  steam, 
and  is  not  reduced  by  sulphurous  acid.  About  540,000  pounds 
of  anthraquinone  were  produced  in  the  United  States  in  1920, 
a  considerable  part  of  which  was  made  synthetically  from 
phthalic  anhydride  and  benzene.  It  is  all  used  in  the  prepara- 
tion of  the  anthraquinone  dyes. 
When  fused  with  caustic  potash  it  gives  potassium  benzoate :  — 

CcHZ         }C,Ui  +  2  KOH  =  2  CsHb.COOK. 

\co/ 

Hydriodic  acid  reduces  it  to  anthracene  and  dihydroanthracene. 
When  reduced  in  glacial  acetic  acid  with  tin  and  hydrochloric 
acid  antkrone  is  formed  :  — 

/CO.  /CO  . 

CeHZ  >C6H4  +  2  H2  =  CeH/  >C6H4  +  H2O. 

\co/  ^cn/ 

Anthraquinone  Anthrone 

This  substance  has  also  been  obtained  by  the  action  of  sulphuric 
acid  on  benzyl-o-benzoic  acid  (made  by  the  reduction  of 
benzoyl-o-benzoic  acid) :  — 

/CH2.C6H5  yCH2. 

CeH/  =  CeH/  >C6H4  +  H2O. 

\COOH(o)  \C0  / 

Benzyl-tJ-benzoic  acid  Anthrone 

It  forms  colorless  crystals,  melting  at  i54°-i5S°,  and  is  insol- 
uble in  cold  solutions  of  the  alkalies.  When  heated  to  boiling 
with  a  dilute  solution  of  caustic  soda  it  dissolves.  If  this 
solution    is    cooled    quickly  to  -5°    and    acidified,  anikranol, 

C6H4<^  I       J?C6H4,   isomeric  with    anthrone,    is    precipitated. 

\ch/ 


520  ANTHR.\CEXE   AND    PHENAXTHRENE 

This  substance  crystallizes  in  brownish  yellow  leaflets,  which 
melt  at  once  when  brought  into  a  bath  heated  to  120°.  It 
dissolves  in  glacial  acetic  acid  with  a  yellow  color.  When  this 
solution  is  boiled  the  color  fades,  and  on  the  addition  of  water 
anthrone  crystallizes  out.  Anthranol  is  completely  soluble  in 
cold  aqueous  alkalies,  and  its  solutions  in  organic  solvents  show 
a  marked  bluish  fluorescence,  while  those  of  anthrone  are  non- 
fluorescent. 

Anthraquinone  when  reduced  with  zinc  dust  and  caustic  soda 

/C(OH) 
solution  gives  anthrahydroquinol,  CeHis^     />C6H4.      This  crys- 

^C(OH) 
taUizes  in  flat,  brown  crystals  melting  at  180°,  readily  soluble 
in  alcohol,  the  solution  having  a  yellow  color  and  strong  greenish 
fluorescence.  Iodine  or  bromine  oxidizes  it  instantaneously  to 
anthraquinone.  It  is  completely  soluble  in  cold  aqueous  alkali 
with  a  deep  red  color  and  readily  undergoes  oxidation  to  anthra- 
quinone in  this  solution  by  air.  It  is  converted  to  some  extent 
into  its  isomer,  7-hydroxyanthrone,  in  the  cold  by  3  per  cent 
alcoholic  hydrochloric  acid.     7-  Hydroxyanthrone  (oxyanthranol) 

CO 
C6H4<^"^C6H4,   is  best  made,   however,   by  the  hydrolysis  of 
HCOH 

CO 
bromoanthrone,   C6H4  <'    "^C6H4   (made    by   brominating   an- 

HCBr 
throne).  It  crystallizes  in  yellowish  white  needles  melting  at 
167'^  which  are  colorless  when  powdered.  Unlike  its  isomer, 
anthrahydroquinol,  iodine  and  bromine  are  without  action  on  it 
in  the  cold  and  its  solutions  in  organic  solvents  do  not  fluoresce. 
It  is  also  insoluble  in  cold  aqueous  alkalies.  It  is  converted  into 
its  isomer,  anthrahydroquinol,  to  the  extent  of  97  per  cent  by 
alcoholic  hydrochloric  acid. 

/CO. 
Anthraquinone-P-sulphonic  acid,  C6H4<  ^CeHs.SOsHCP),  is 

\co/ 

obtained  by  sulphonating  anthraquinone  with  fuming  sulphuric 


ALIZARIN  521 

acid  at  160°.  Its  sodium  salt,  which  is  difficultly  soluble 
in  cold  water  and  has  a  silvery  luster,  is  known  in  the  trade  as 
"  silver  salt." 

Anthraquinone-a-sulphonic  acid  is  formed  by  sulphonating 
anthraquinone  in  the  presence  of  mercury  salts. 

a-  and  P-Hydroxyanthraquinones  are  obtained  from  these  acids 
by  heating  them  with  a  20  per  cent  solution  of  caustic  soda  under 
pressure. 

2-Aminoanthraquinone  is  obtained  by  heating  sodium  anthra- 
quinone-/3-sulphonate  with  25  per  cent  ammonia  under  pres- 
sure :  — 

CeH/        >C6H3.S03Na  +  2  NH3 

\co/ 

=  CeHZ         >C6H3.NH2  +  NaNH4S03. 

\co/ 

It  is  the  substance  from  which  the  very  valuable  indanthrene 
vat  dyes  are  made.^  These  dyes  are  the  fastest  and  among  the 
most  important  vat  dyes  known.  Most  of  them  are  imported  at 
the  present  time. 

There  are  ten  possible  dihydroxyanthraquinones,  and  all  are 
known.     Alizarin  is  the  only  one  of  commercial  importance. 

/CO. 
Alizarin,  l,2-dihydroxyanthraqviinone,C6H4<'  />C6H2.(OH)2 

\co/ 

is  the  chief  constituent  of  the  red  dye  (Turkey  red)  obtained 
from  madder  root  {Rubia  tinctorium)  and  known  for  centuries. 
The  dye  was  not  isolated  from  the  madder  root,  but  the  whole 
root  was  used,  after  it  had  been  dried  and  could  be  ground 
finely.  It  is  present  in  madder  root  as  a  glucoside,  ruberythric 
acid,  C26H28O14,  which  is  hydrolyzed  by  dilute  mineral  acids  or 
by  the  action  of  an  enzyme  contained  in  the  madder  root,  to 
alizarin  and  glucose :  — 

C26H28  0i4  +  2  H2O  =  C14H8O4  +  2  CeHizOe. 

'  See  Synthetic  Dyestuffs,  by  J.  C.  Caine  and  J.  T.  Thorpe,  sth  ed.  1920, 
p.  127. 


52  2  ANTHRACENE   .AND   PHENAXTHRENE 

In  Europe  large  tracts  of  land  were  devoted  to  growing  madder, 
especially  in  Holland  and  France.  The  annual  production  of 
madder  root  exceeded  in  value  $15,000,000.  The  discovery  of 
the  artificial  preparation  of  alizarin  from  coal  tar  in  1869,  the 
first  of  the  natural  dyes  to  be  made  synthetically,  destroyed 
this  industry  and  released  the  land  for  the  growing  of  food- 
crops. 

Alizarin  is  now  made  on  the  large  scale  by  heating  the  sodium 
salt  of  anthraquinone-^-sulphonic  acid  with  a  concentrated 
solution  of  caustic  soda  and  some  potassium  nitrate  in  an  auto- 
clave to  180°: 

C6H4<'        ^CeHsSOsNa  +  3  NaOH  -f  O? 

/CO. 
=  C6H4<         >  C6H2''ONa)2  +  Na2S04  +  2  H2O. 

\co/ 

In  this  reaction  not  only  is  the  sulphonic  acid  group  replaced 
by  hydroxyl,  but  the  a-hydrogen  is  also  oxidized  to  hydroxyl. 
The  dye  is  set  free  from  the  solution  of  the  sodium  salt  by  an 
acid  and  brought  into  the  market  in  the  form  of  a  20  per  cent 
paste. 

Alizarin  crystallizes  in  red,  orthorhombic  needles  that  melt 
at  289°-290°.  It  sublimes  in  orange-red  needles.  It  is  only 
sHghtly  soluble  in  water,  but  dissolves  readily  in  organic  solvents. 
In  solutions  of  the  caustic  alkalies  it  dissolves  with  character- 
istic colors.  The  concentrated  solutions  are  purplish  red,  having 
a  purple-blue  color  by  reflected  light.  On  dilution  the  color 
changes  to  a  bluish  violet. 

Alizarin  is  a  mordant  dye  and  gives  different  colors  with 
different  mordants,  red  with  aluminium  and  tin,  violet-black 
with  iron,  reddish  brown  with  chromium,  and  blue  with  calcium. 
In  dyeing  cotton  with  alizarin  (Turkey  red  dyeing),  in  order  to 
produce  bright  red  shades  with  the  aluminium  mordant,  the 
fabric  is  treated  with  Turkey  red  oil  (made  by  treating  castor 
oil  with  sulphuric  acid  and  neutralizing  the  product  with  soda). 


ALIZARIN  523 

sumac,  and  precipitated  chalk,  it  having  been  shown  that  the 
presence  of  calcium  is  necessary  to  produce  pure  red  shades. 

When  distilled  with  zinc  dust  alizarin  gives  anthracene,  and 
it  is  this  reaction  that  led  to  the  discovery  that  alizarin  is  a 
derivative  of  anthracene,  and  to  its  artificial  preparation  from 
that  hydrocarbon. 

Constitution  of  alizarin.  —  The  preparation  of  alizarin  from 
anthraquinone-/3-sulphonic  acid  and  the  fact  that  it  gives  a 
diacetate  shows  that  alizarin  is  a  dihydroxyl  derivative  of 
anthraquinone.  Since  it  has  been  made  by  the  oxidation  of 
a-hydroxyanthraquinone  and  also  by  the  oxidation  of  /3-hydroxy- 
anthraquinone,  the  two  hydroxyl  groups  must  be  in  the 
a,/3-positions.  Its  formation  from  phthalic  anhydride  and 
pyrocatechol  by  heating  with  sulphuric  acid  to  150°, 


+  H2O, 
CO 

Phthalic  anhydride      Pyrocatechol 

proves  that  both  hydroxyl  groups  are  in  the  same  benzene  ring 
and  in  the  ortho  position  to  each  other.  Hence  alizarin  is 
1,2-dihydroxyanthraquinone.  This  formula  for  alizarin  is 
also  in  accord  with  the  fact  that  it  gives  two  nitro  products 
(1,2,3  ^^'^  ij2,4)  and  that  it  gives  purpurin,  trihydroxy- 
anthraquinone  (1,2,4)  on  oxidation.  Purpurin  also  results 
from  the  oxidation  of  quinizarin  (1,4-dihydroxyanthraquinone, 
formed  from  phthalic  anhydride  and  hydroquinol) ,  and  hence 
must  have  the  hydroxyl  groups  in  the  1,2,4  positions. 

3-Nitroalizarin,  alizarin  orange,  is  made  on  the  large  scale 
by  nitrating  alizarin,  and  is  a  valuable  mordant  dye.  On 
reduction  it  gives  3-aminoalizarin.  It  is  also  used  in  making 
alizarin  blue. 

Alizarin  blue  is  made  by  heating  alizarin  orange,  3-amino- 
alizarin and  glycerol  with  sulphuric  acid  (see  Skraup's  syn- 
thesis of  quinoline  (509)) :  — 


524 


ANTHRACENE  AND  PHENANTHRENE 


CO  OH  CO   OH  HO      CO  OH 

/YYNOH    /\^\^0H      /N^N^NoH 

CO 


Alizarin  orange 


Alizarin  blue 


Alizarin  green 


It  is  a  valuable  mordant  dye.  It  undergoes  oxidation  when 
treated  with  fuming  sulphuric  acid  to  Alizarin  green.  (See  for- 
mula above.) 

Purpurin,  1,2,4-trihydroxanthyraquinone,  is  one  of  the  dyes 
found  in  madder  root  together  with  alizarin  and  is,  there- 
fore, present  in  natural  alizarin.  It  can  be  made  from  alizarin- 
4-sulphonic  acid  by  heating  with  alkaUes  and  also  by  the  oxida- 
tion of  either  alizarin  or  quinizarin  with  manganese  dioxide  and 
sulphuric  acid.    Like  alizarin  it  is  a  valuable  mordant  dye. 

Anthragallol  (anthracene  brown)  is  1,2,3-trihydroxyanthra- 
quinone.  It  is  not  made  from  anthraquinone,  but  by  heating 
gaUic  acid  and  benzoic  acid  with  sulphuric  acid :  — 


COOH 


+ 


HOOC 


CO  HO 


OH+^H.O. 


Benzoic  acid 


Gallic  acid 


CO 

Anthragallol 


When  galUc  acid  alone  is  heated  with  sulphuric  acid  it  gives 
hexahydroxyanthraquinone  (rufigallol) : ' 

HO     CO 


OH 

ho/\h         HOOC /\  oh  _  ho 

Hol     JcOOH+         hI      JoH~HO 

OH 

3  mols.  Gallic  acid 

which  is  also  used  as  a  mordant  dye. 

'  See  Synthetic  Dyestuffs,  by  J.  C.  Caine  and  J.  T.  Thorpe,  for  other  dye- 
stuffs  derived  from  anthraquinone. 


OH 
OH 

CO   OH-I-2H2O, 

Rufigallol 


PHENANTHRENE  525 

ACRIDINE 

Acridine,  C13H9N,  is  present  in  crude  anthracene  and  also  in 
crude  diphenylamine.  It  is  formed  synthetically  by  heating 
diphenylamine  and  formic  acid  or  formyldiphenylamine  with 
zinc  chloride :  — 

H— C=0  /CH. 

CeHsy   I   /CeHe     =     CeH,/  |      ^CsHi  +  H2O. 

Formyldiphenylamine  Acridine 

It  crystallizes  from  hot  water,  in  which  it  is  difi&cultly  soluble, 
in  colorless  needles.  It  melts  at  107°,  sublimes  very  readily 
even  at  100°,  and  boils  at  345°-346°.  It  is  characterized  by  the 
bluish  fluorescence  of  its  dilute  solutions.  On  oxidation  it 
gives  acridinic  acid  (a,/3-quinolinedicarboxylic  acid) :  — 

CH 

'^  .   »  «  f''''^V'''^COOH 

.  ^     ^  k   V\     JCOOH 

Acridine  Acridinic  acid 

The  constitution  of  acridine  as  a  derivative  of  anthracene  in 
which  one  of  the  7-CH  groups  is  replaced  by  nitrogen  follows 
from  the  above  synthesis  and  from  the  fact  that  it  gives  acridinic 
acid  on  oxidation. 

Chrysaniline  or  phosphine,  a  valuable  yellow  dye,  used  largely 
for  dyeing  leather,  is  a  mixture  of  the  salts  of  diaminophenyl- 

C6H4<'  I  ^CeHaNHj 
acridine,  ^C'^  ,  and  its  homologues. 

C6H4NH2 

PHENANTHRENE 

Phenanthrene,  C14H10,  isomeric  with  anthracene,  is  found  in 
anthracene  oil  and  hence  in  crude  anthracene  (514).  It  has  been 
obtained  by  distUling  morphine  with  zinc  dust.  It  crystallizes 
from  alcohol  in  colorless,  monoclinic  leaflets,  that  melt  at  100.35°. 


526       ANTHRACENE  AND  PHENANTHRENE 

Its  boiling  point  is  340°  (cor.).  It  is  more  readUy  soluble  in 
alcohol  than  anthracene  and  its  solutions  show  a  bluish 
fluorescence.  The  pure  substance  is  best  prepared  by  the 
reduction  of  pure  phenanthraquinone  (527) .  Oxidizing  agents 
convert  it  into  phenanthraquinone  and  into  diphenic  acid, 
C6H4— COOH  (0) 

I  a    diorthodicarboxylic    acid  of   diphenyl.     It 

C6H4— COOH(o), 

has  been  made  by  conducting  dibenzyl,  stilbene,  or  o-ditolyl 
through  a  red-hot  tube  :  — 

CeHs — CH2     CeHs — CH     C6H4 — CH3(o)     C6H4 — C — H 

I  II  I  I  II 

CeHs — CH2     CeHj — CH     C6H4 — CH3(o)     C6H4 — C — H 

Dibenzyl  Stilbene  o-Ditolyl  Phenanthrene 

It  will  be  seen  from  the  above  formulas  that  the  change  con- 
sists in  the  loss  of  hydrogen  and  the  union  of  the  residues,  as  in 
the  formation  of  diphenyl  from  benzene  and  of  o-ditolyl  from 
toluene.  In  a  similar  manner  benzil  is  converted  into  phen- 
anthraquinone when  heated  with  aluminium  chloride :  — 

CeHs— C=0       CeKi— C=0 

I  =1  I  +H2. 

CeHs— C=0      C6H4— C=0 

Benzil  Phenanthraquinone 

The  ormation  of  phenanthrene  from  stilbene  and  from  o-ditolyl, 
as  well  as  the  fact  that  it  gives  diphenic  acid  on  oxidation  proves 
that  phenanthrene  is  a  derivative  of  diphenyl,  containing  a 
— CH^CH —  group  joined  to  two  ortho  carbon  atoms,  as  shown 
in  the  formula :  — 


It  will  be  noted  from  this  formula  that  phenanthrene  contains 
three  benzene  rings,  and  that  five  monosubstitution  products 
with  the  same  substituent  are  possible  (i,  2,  3, 4,  and  9).     Five 


rnJLivfui  X njv/iv^UINONE  527 

mononitrophenanthrenes  are  known.  Phenanthrene  is  of  interest 
mainly  because  of  its  close  connection  with  the  very  valuable 
opium  alkaloids,  morphine,  codeine,  and  thebaine.  These 
alkaloids  undoubtedly  contain  a  phenanthrene  nucleus.  Phen- 
anthrene is  at  present  of  little  practical  importance,  though 
some  dyes  are  made  from  phenanthraquinone. 

Phenanthraquinone  is  formed  by  the  oxidation  of  phen- 
anthrene with  chromic  acid  mixture  :  — 

C6H4 — CH  C6H4 — CO 

I  11+30=1  I      +  H2O, 

C6H4 CH  06X14 — CO 

or  from  benzil  (526) . 

It  crystallizes  in  orange-yellow  needles,  that  melt  at  206.5° 
to  207.5°.  It  sublimes  in  orange-red  plates.  It  is  somewhat 
soluble  in  hot  water,  more  so  in  alcohol,  and  in  glacial  acetic  acid. 
It  dissolves  in  a  warm  solution  of  sodium  bisulphite,  from  which 
it  is  precipitated  by  acids  or  alkalies.  This  conduct  is  made  use 
of  to  separate  it  from  anthraquinone,  which  is  insoluble  in  a 
solution  of  sodium  bisulphite.  Oxidizing  agents  convert  it  into 
diphenic  acid : 

C6H4.CO  C6H4.COOH(o) 

I         I     +  H2O  +  O  =  I 
C6H4.CO  C6H4.COOH(o) 

When  distilled  with  zinc  dust  it  is  reduced  to  phenanthrene. 


CHAPTER   XXI 


GLUCOSIDES ' 


The  Methylglucosides.  —  When  glucose  is  dissolved  in  cold 
methyl  alcohol  saturated  with  dry  hydrochloric  acid  gas,  and 
the  solution  is  allowed  to  stand  for  several  hours,  it  is  con- 
verted into  a  mixture  of  a-methylglucoside  and  /3-methyl- 
glucoside,  which  are  separated  by  fractional  crystallization. 
a-Methylglucoside  melts  at  165°  and  is  dextrorotatory  (+157°) ; 
iS-methylglucoside  melts  at  104°  and  is  levorotatory  (-33°). 
When  hydrolyzed  the  a-compound  yields  a-glucose,  and  the 
/3-product  /3-glucose.  The  rotatory  power  of  these  glucosides 
is  the  same  in  a  freshly  prepared  solution  as  it  is  in  one  that  has 
been  kept  for  some  time,  which  is  not  the  case  with  glucose. 
The  methylglucosides  do  not  give  reactions  characteristic  of  the 
aldehydes.  They  are  regarded  as  stereoisomeric  and  have  the 
following  formulas :  — 


H3CO— C— H 


H— C— OCH; 


HOCH 


HCOH 


HOCH 


HCOH 


H2COH 

a-Methylglucoside 


H2COH 

3-Methylglucoside 


It  will  be  noted  that  the  methylglucosides  are  methyl  derivatives 
of  the  two  stereoisomeric  forms  of  li-glucose  (221).     The  only 

'  See  E.  Frankland  Armstrong :  Simple  Carbohydrates  and  Glucosides,  3d 
ed.  1919. 

S28 


AMYGDALIN  529 

difference  between  them  is  in  the  space  arrangement  of  the 
hydrogen  atom  and  the  methoxyl  around  the  upper  carbon  atom. 
These  synthetic  glucosides  are  completely  analogous  to  the 
natural  glucosides.  Like  them  they  are  hydrolyzed  to  glucose 
and  an  alcohol  by  the  action  of  dilute  mineral  acids  or  by  enzymes. 
Thus,  maltase  hydrolyzes  the  a-  but  not  the  /3-compound,  and 
emulsin  the  /3-  but  not  the  a-product,  the  action  of  the  enzymes 
being  specific.  The  natural  glucosides  occur  in  plants  especially 
in  the  fruit,  roots,  and  bark  and  they  are  accompanied  by  the 
enzyme  that  hydrolyzes  them  to  a  sugar  (generally  d-glucose) 
and  an  alcohol,  aldehyde,  phenol,  acid,  etc.  All  these  glucosides 
are  ethers  of  glucose  having  the  general  formula :  — 

RO— CH(CHOH)2.CH.CHOH.CH20H 

I O I 

where  R  represents  the  residue  of  the  alcohol,  aldehyde,  phenol, 
acid,  etc.  which  may  be  present.  As  most  of  the  natural  gluco- 
sides are  hydrolyzed  by  emulsin,  but  not  by  maltase,  they  are 
regarded  as  having  a  structure  similar  to  that  of  ^-methyl- 
glucoside,  in  which  the  methyl  group  is  replaced  by  some  other 
radical.  Maltose,  which,  like  a-methylglucoside,  is  readily 
hydrolyzed  by  maltase  but  not  by  emulsin,  is  an  a-glucoside 
and  has  a  configuration  similar  to  that  of  the  a-methylgluco- 
side, a  glucose  residue  taking  the  place  of  the  methyl  group.  It 
has  been  shown  in  several  cases  that  the  enzyme  can  effect  the 
synthesis  of  the  compound  it  hydrolyzes.  Thus,  a  mixture  of 
maltose  and  isomaltose  has  been  made  from  glucose  by  the 
action  of  maltase.  Invertase,  lactase,  emulsin  and  the  lipases 
also  act  synthetically.  The  reactions  are  reversible  and  stop 
when  equilibrium  is  established. 

A  few  of  the  more  important  glucosides  are  given  below. 

Aesculin,  CiBHieOg  -|-  1^  H2O,  occurs  in  the  bark  of  the  horse- 
chestnut  tree  {Aesculus  hippocastanum)  and  yields  glucose  and 
aesculetin  (dihydroxycoumarin)  on  hydrolysis. 

Amygdalin,  C20H27O11N  -|-  3  H2O,  is  found  in  bitter  almonds, 
in  the  leaves  of  the  cherry  laurel,  and  in  the  kernels  of  apricots. 


53°  GLUCOSIDES 

peaches,  plums,  cherries,  etc.  It  is  hydrolyzed  by  mineral  acids 
or  by  emulsin,  an  enzyme  present  in  bitter  almonds,  to  benzalde- 
hyde,  glucose,  and  hydrocyanic  acid  (394). 

Arbutin,  C10H16O7,  and  methylarbutin,  Ci2Hi6(CH3)07,  are 
both  present  in  the  leaves  of  the  bearberry  {Arbutus  uva  ursi). 
They  yield  glucose  and  hydroquinol  or  the  monomethyl  ether 
of  hydroquinol  on  hydrolysis.  Methylarbutin  has  been  made 
synthetically  by  the  action  of  acetochloroglucose  on  the  potas- 
sium silt  of  the  monomethyl  ether  of  hydroquinol  in  alcoholic 
solution :  — 

HCCl  +  KOCelWCIhip)         HCOC6H4.0CH3(/') 

"I  /I 

O  (HC0Ac)2  0:;(HC0H)2 

CH  +  4  C2H6OH         =  CH  +  KCl 

I  i 

HCOAc  HCOH  +  4  CHsCOOCjHb. 

I  I 

H2COAC  H2COH 

Acetochloroglucose  Methylarbutin 

The  acetochloroglucose  is  formed  by  the  action  of  acetyl  chloride 
on  glucose.  Both  an  a-  and  a  j3-acetochloroglucose  are  now 
known.  It  is  only  the  j3-compound  that  gives  glucosides,  as 
the  a-product  is  converted  into  the  j3-acetochloroglucose  by  the 
action  of  alkalies. 

Coniferin,  C16H22O8  +  2  H2O,  is  the  glucoside  found  in  the 
conifers.  It  gives  glucose  and  coniferyl  alcohol  on  hydrolysis, 
and  the  latter  is  converted  into  vanillin  by  oxidation.  It  was 
used  at  one  time  in  the  preparation  of  vanillin  on  the  large  scale. 

Helicin,  Ci.jHieOy  +  f  H2O,  does  not  occur  in  nature.  It  is 
made  by  the  oxidation  of  salicin  (see  below)  with  dilute  nitric 
acid  or  by  the  action  of  /3-acetochloroglucose  on  the  potassium 
salt  of  salicylic  aldehyde  in  alcoholic  solution.  It  is  hydrolyzed 
by  emulsin  to  glucose  and  salicylic  aldehyde. 

Phloridzin,  C01H24O10,  is  found  in  the  root  bark  of  fruit  trees. 
It  yields  glucose  and  phloretin,  C15H14O5,  when  hydrolyzed  with 
acids.     Phloretin  gives  phloretic   acid,   C9H10O3,   and  phloro- 


SINIGRIN,    POTASSIUM   MYRONATE  531 

glucinol  (389)  on  hydrolysis.  Phloridzin  has  the  remarkable 
power  of  prpducing  glycosuria  when  injected  subcutaneously. 

Salicin,  CisHisOy,  occurs  in  willow  bark  and  also  in  poplars. 
It  is  used  in  medicine  as  a  remedy  for  rheumatism  and  as  a 
febrifuge.  It  has  been  made  synthetically  from  /3-acetochloro- 
glucose  and  salicylic  alcohol.  It  is  hydrolyzed  by  emulsin  to 
glucose  and  salicylic  alcohol.  When  treated  with  benzoyl 
chloride  it  gives  a  benzoyl  derivative  in  which  the  benzoyl  group 
is  in  the  glucose  residue.  This  product  is  identical  with  the 
natural  glucoside,  populin,  found  in  the  bark  of  a  number  of 
species  of  poplar  (Populus). 

Saponins,  C„H2a-80io,  form  a  group  of  closely  related  gluco- 
sides,  widely  distributed  in  nature,  whose  aqueous  solutions 
froth  like  soap  solutions  when  shaken.  They  yield  sugars  and 
sapogenin,  C18H23O8,  on  hydrolysis. 

Sinigrin,  potassium  myronate,  C10H16O9NS2K,  occurs  in  black 
mustard  seed.  It  is  hydrolyzed  by  the  enzyme,  rnyrosin,  which 
is  also  present  in  the  seed,  to  allyl  isothiocyanate  (mustard  oil), 
glucose,  and  monopotassium  sulphate :  — 

C10H16O9NS2K  +  H2O  =  C3H5NCS  +  CeHiaOe  +  KHSO4. 

Mustard  oil  Glucose 

A  number  of  important  glucosides,  such  as  the  tannins,  indican, 
and  ruberythric  acid  have  already  been  mentioned.^ 

The  red  and  blue  coloring  matters  of  fruits  and  flowers  are 
termed  anthocyanins  (Gr.  anthos,  flower,  kuanos,  blue).  These 
anthocyanins  are  glucosides.  They  undergo  hydrolysis  with 
dilute  mineral  acids,  yielding  glucose  and  the  free  coloring  matters 
termed  anthocyanidins.  The  blue  coloring  matter  of  the  corn- 
flower is  due  to  the  presence  of  a  potassium  salt  of  an  antho- 
cyanin.  The  same  anthocyanin  is  the  cause  of  the  red  color  of 
the  rose  and  the  geranium,  in  which  it  is  present  in  the  form  of  a 
red  oxonium  salt. 

1  See  Simple  Carbohydrates  and  Glucosides,  by  E.  F.  Armstrong,  for  the 
function  of  the  carbohydrates  and  glucosides  in  plants. 


CHAPTER  XXII 
PLANT   ALKALOIDS' 

The  alkaloids  are  complex,  basic,  nitrogenous  organic  com- 
pounds found  in  plants.  Some  of  them  are  aliphatic  compounds, 
such  as  caffeine  and  theobromine  (270),  and  have  already  been 
treated  of.  Others  have  been  shown  to  be  derived  from  pyridine, 
quinoline,  or  isoquinoline.  On  account  of  their  physiological 
action  on  the  animal  organism  they  form  an  extremely  important 
class  of  compounds  and  many  of  them  constitute  the  active 
principles  of  the  common  vegetable  drugs  used  in  medicine. 
Almost  all  the  plants  yielding  alkaloids  belong  to  the  class  of 
dicotyledons,  and  it  is  seldom  that  the  plant  contains  only 
one  alkaloid.  Generally  several  are  present  and  they  are 
chemically  and  often  physiologically  closely  related.  Alkaloids 
rarely  occur  in  plants  in  the  free  condition,  but  almost  always 
combined  with  acids  in  the  form  of  salts.  The  acids  with  which 
they  are  combined  are  those  usually  found  in  plants,  oxalic, 
malic,  succinic,  citric,  tannic,  etc.,  or  special  acids  character- 
istic of  the  plant  (quinic  acid  with  the  quinine  alkaloids,  meconic 
acid  with  the  opium  alkaloids,  aconitic  acid  with  aconite  alka- 
loids). A  few  of  the  alkaloids  contain  only  carbon,  hydrogen, 
and  nitrogen  and  are  liquid,  volatile  compounds,  e.g.  conine  and 
nicotine;  most  of  them,  however,  contain  oxygen  in  addition  to 
the  above  named  elements  and  are  crystalline,  non-volatile 
bases.  They  are  nearly  all  optically  active  and  usually  levo- 
rotatory.  A  few  like  conine  are  secondary  bases,  but  most  of 
them  are  tertiary  amines.  Some  like  betaine  (251)  are  inner 
ammonium  salts.  The  alkaloids  are  precipitated  from  solutions 
of  their  salts  by  certain  alkaloid  reagents,  such  as  tannic  acid  and 
phosphomolybdic  acid,  gold  and  platinum  chlorides,  a  solution  of 
iodine  in  potassium  iodide,  a  solution  of  potassium  mercuric 

'  See  The  Plant  Alkaloids,  by  T.  A.  Henry,  1913. 
S32 


NICOTINE  533 

iodide,  etc.  They  are  also  generally  characterized  by  their 
bitter,  astringent  taste  and  physiological  action.  Many  of 
them  give  characteristic  color  reactions  with  chlorine  water, 
nitric  or  sulphuric  acids,  etc.  which  serve  to  identify  them. 

The  alkaloids  are  usually  isolated  from  the  plants  by  extraction 
with  alcohol  or  water,  in  which  their  salts  occurring  in  plants  are 
generally  soluble.  When  they  occur  in  the  form  of  salts  in- 
soluble in  these  solvents,  the  ground  plant  is  mixed  with  lime 
or  magnesia  and  then  extracted  with  some  solvent  in  which  the 
base  is  soluble.     They  are  then  purified  by  recrystallization. 

Only  a  few  of  the  more  important  alkaloids  derived  from 
pyridine,  quinoline  or  isoquinoline  will  be  dealt  with  here. 

Alkaloids  Derived  from  Pyridine 

Conine  (442)  and  piperidine  (441)  have  already  been  presented. 

Piperine,  C17H19NO3,  is  found  in  the  fruits  of  black  and  white 
pepper  {Piper  nigrum).  It  gives  piperidine  and  piperic  acid  on 
hydrolysis :  — 

CitHisNOs  +  H2O    =   C5H11N  +  C12H10O4, 
Piperine  Piperidine  Piperic  acid 

and  has  been  made  synthetically  from  the  chloride  of  piperic 
acid  and  piperidine,  hydrochloric  acid  being  eliminated.  Hence 
piperine  is  piperylpiperidine,  CeHioN.CisHgOa.  Both  piperi- 
dine and  piperic  acid  have  been  made  synthetically. 

Nicotine,  C10H14N2,  is' the  principal  alkaloid  found  in  tobacco 
leaves  (Nicotiana  tabacum),  in  which  it  occurs  in  combination 
with  citric  and  malic  acids.  It  is  a  colorless,  oily  base  which 
rapidly  turns  brown  in  the  air  and  is  extremely  poisonous.  Its 
solution  in  water  is  levorotatory  and  it  is  a  ditertiary  base. 
On  oxidation  with  potassium  permanganate  it  gives  nicotinic 

acid  (/3-pyridinecarboxylic  acid  „ 

(440))  and  hence  it  is  a  /3-de-  '  ^ 

rivative  of  pyridine.  It  has 
been  made  synthetically  and 
shown  to  be  /3-pyridyl-a-N- 
methylp3TroUdine :  — 

Nicotine 


534  PLANT   ALKALOIDS 


SOLANACEOUS   ALKALOIDS 


Only  three  of  these  alkaloids  are  used  in  medicine,  atropine, 
hyoscyamine,  and  scopolamine.  They  are  characterized  by 
their  mydriatic  action,  that  is,  their  power  of  dilating  the  pupil 
of  the  eye  when  the  aqueous  solutions  of  their  salts  are  dropped 
into  the  eye. 

Atropine,  C17H23NO3,  is  seldom  found  in  plants.  It  is  made 
from  its  stereoisomer,  hyoscyamine,  by  the  action  of  dilute  alka- 
lies. Hyoscyamine  is  the  chief  constituent  of  Atropa  belladonna, 
Datura  stramonium,  Hyoscyamus,  etc.  It  crystallizes  from  dilute 
alcohol  in  needles  (m.  p.  108.5°),  ^'^d  is  levorotatory.  Its  sul- 
phate, (Ci7H23N03)2.H2S04,  is  readily  soluble  in  water,  has  a 
bitter  taste,  and  a  neutral  reaction.  Like  atropine  it  causes 
dilation  of  the  pupU  of  the  eye.  It  is  readUy  converted  into  its 
racemic  modification,  atropine,  by  treating  its  alcoholic  solution 
with  a  small  quantity  of  alkali ;  this  is  the  commercial  method 
of  preparing  atropine.  Atropine  crystallizes  in  colorless  prisms 
(m.  p.  115.5°).  The  aqueous  solution  is  bitter  to  the  taste,  has 
an  alkaline  reaction  and  is  optically  inactive.  The  sulphate, 
(Ci7H23N03)2H2S04  +  HjO,  is  the  salt  generally  used  in  medicine. 
It  is  principally  used  owing  to  its  property  of  causing  dilation  of 
the  pupil  of  the  eye,  and  this  property  may  be  used  for  its  de- 
tection. A  drop  or  two  of  an  aqueous  solution,  i  part  of  atro- 
pine in  130,000  parts  of  water,  when  introduced  into  the  eye  of 
a  cat  is  sufficient  to  produce  this  effect.  The  formula  for  both 
atropine  and  hyoscyamine  is  represented  thus :  — 


H2C CH CH: 

.ooc.ch/ 

^CeH, 


I  I  /CH2OH 

NCH3        CH.OOC.CH<: 


I12C  CH  CI12 

Atropine 


It  will  be  seen  from  this  formula  that  atropine  is  an  ester  of 
tropine  with  the  acid,  C6H5.CH<    ^      ,    called    tropic  acid. 


QUININE  S3S 

H2C CH CH2 

I  I 

NCH3        CHOH 

H2C CH C  H2 

Tropine 

Both  tropine  and  tropic  acid  have  been  made  synthetically. 

Coca  Alkaloids 

Cocaine,  Ci7H2iN04,  is  the  most  important  of  the  alkaloids 
found  in  coca  leaves  {Erythroxylon  coca).  Its  hydrochloride, 
C17H21NO4.HCI,  is  used  in  surgery  as  a  local  anaesthetic.  The 
base  crystallizes  from  alcohol  in  prisms  (m.  p.  98°),  is  soluble  in 
hot  water  and  is  levorotatory.  The  aqueous  solution  is  alka- 
line to  litmus  and  produces  the  characteristic  numbness  when 
applied  to  the  tongue.  When  hydrolyzed  with  acids  or  alkalies 
cocaine  gives  ecgonine,  benzoic  acid,  and  methyl  alcohol,  and  is 
therefore  the  methyl  ester  of  benzoylecgonine.  Ecgonine  has 
been  shown  to  be  tropinecarboxylic  acid :  — 

H2C— CH— CH.COOH       H2C— CH— CH.COOCH3 


NCH3  CHOH 


NCHaCHO.COCeHs 


H2C — CH — CH2  H2C — CH — CH2 

Ecgonine  Cocaine 

It  is  obtained  by  the  hydrolysis  of  the  residues  found  in  coca 
leaves,  after  extracting  the  cocaine,  and  is  converted  into  cocaine 
by  first  benzoylating  it  with  benzoic  anhydride,  and  then  methyl- 
ating  the  benzoylecgonine  in  alkaline  solution  with  methyl 
iodide. 

Like  morphine  cocaine  is  a  habit-forming  drug. 

Alkaloids  Derived  from  Quinoline 

Cinchona  Alkaloids 

Quinine,  C20H24N2O2  -f-  3  H2O,  is  the  most  important  of  all 
the  alkaloids.  It  occurs  together  with  cinchonine  and  other 
alkaloids  in  the  bark  of  cinchona  trees  indigenous  to  South 


536  PLANT   ALK.\LOrDS 

America.  Most  of  the  cinchona  bark  now  comes  from  the 
island  of  Java  and  from  Bengal,  where  the  trees  are  grown 
in  Government  plantations.  The  world's  annual  production  of 
quinine  sulphate,  (C2oH24N202)2.H2S04  +  8  H2O,  is  over  250,000 
kilograms.  It  is  largely  used  as  a  specific  for  malaria  and  as  a 
prophylactic  against  this  disease.  It  is  also  used  as  a  febrifuge 
and  as  a  tonic. 

Quinine  crystallizes  in  needles  melting  at  57°  or  when  an- 
hydrous at  177°.  It  is  a  strong  ditertiary,  diacid  base,  has  an 
intensely  bitter  taste,  and  is  levorotatory.  The  neutral  sulphate 
in  dilute  solution  shows  a  blue  fluorescence,  which  is  character- 
istic.    The  following  formula  has  been  assigned  to  quinine:  — 

H 

— C CH— -CH, 


H5CO 


m 

N 


OH     N— CHo— CHo— CH 

CH2 CH— CH=CH: 

Quinine 


and  is  in  accord  with  the  following  facts:  Quinine  is  an  un- 
saturated compound,  it  combines  with  two  atoms  of  hydrogen  to 
form  hydroquinine,  and  with  two  of  bromine  to  form  a  dibromide. 
This  is  believed  to  be  due  to  the  presence  of  the  vin^'l  group, 
— CH=CH2.  Quinine  is  converted  into  a  ketone,  quininone, 
C20H22N2O2,  on  oxidation,  and  hence  must  contain  a  secondary 
alcohol  group.  With  stronger  oxidizing  agents  it  gives  quininic 
acid  (^-methoxyquinoline-7-carboxylic  acid),  which  shows  that 
it  is  a  /(-methoxy  derivative  of  quinoline,  and  that  the  second 
half  of  the  molecule  replaces  the  7-hydrogen  of  quinoline. 
Fusion  with  alkalies  gives  />-methoxyquinoline  from  the  first 
half  of  the  molecule,  and  /S-ethylpyridine  from  the  second  half. 

Cinchonine,  Ci9H2i(OH)N2,  is  also  present  in  cinchona  bark 
and  resembles  quinine  in  its  physiological  action,  but  is  weaker. 
It  is  derived  from  quinine  by  replacing  the  methoxyl  group  by 
hydrogen.  It  also  gives  a  ketone,  cinchoninone,  C19H20ON2, 
on  oxidation,  showing  the  presence  of  the  secondary  alcohol 


MORPHINE  537 

group,  and  with  stronger  oxidizing  agents,  cinchoninic  acid 
(7-quinolinecarboxylicacid).  When  fused  with  caustic  potash 
it  gives  quinoline  and  /3-ethylpyridine.  Like  quinine  it  is 
unsaturated  and  forms  a  crystalline  dibromide. 

Strychnos  Alkaloids 

Strychnine,  C21H22O2N2,  and  brucine,  C23H26O4N2,  both  occur 
in  the  seeds  of  Strychnos  nux  vomica.  Strychnine  crystallizes  in 
colorless  rhombohedra  that  melt  at  268°.  It  is  slightly  soluble 
in  water,  more  so  in  alcohol  and  readily  in  chloroform.  It  is 
levorotatory.  The  aqueous  solution  has  an  alkaline  reaction 
and  an  extremely  bitter  taste,  one  part  in  700,000  parts  of  water 
being  recognizable  by  the  bitter  taste.  The  nitrate,  sulphate 
and  hydrochloride  are  used  in  medicine,  principally  as  a  tonic. 
On  account  of  its  poisonous  properties  strychnine  is  frequently 
used  to  exterminate  rodents  and  other  vermin. 

Although  strychnine  contains  two  nitrogen  atoms  it  acts  as  a 
monacid  base.  When  fused  with  caustic  potash  it  yields  both 
quinoline  and  indol,  and  when  distilled  with  sodalime,  carbazole. 
Hence  strychnine  must  contain  residues  both  of  quinoline  and 
carbazole.     Its  structural  formula  is  not  yet  known. 

Brucine  is  strychnine  with  two  hydrogens  replaced  by  two 
methoxy  groups.     It  is  less  poisonous  than  strychnine. 

Alkaloids  Derived  from  Isoquinoline 

Morphine,  C17H19NO3  +  H2O,  is  the  most  important-  of  the 
opium  alkaloids,  and  the  first  alkaloid  ever  isolated.  Opium  is 
the  sun-dried  latex  of  the  unripe  fruit  of  the  opium  poppy 
{Papaver  somniferum)  and  has  been  used  for  centuries.  Twenty- 
five  alkaloids  have  been  isolated  from  opium,  but  the  only  ones 
used  in  medicine  are  morphine  and  its  methyl  ether,  codeine. 
Morphine  crystallizes  from  alcohol  in  colorless,  triclinic  prisms 
containing  a  molecule  of  water  of  crystallization.  It  melts  with 
decomposition  at  254°,  has  a  bitter  taste  and  is  sparingly  soluble 
in  most  solvents.  The  salt  most  commonly  used  in  medicine 
is  the  sulphate,  (Ci7Hi9N03)2H2S04  -|-  5  H2O.    In  small  doses 


538  PLANT   ALKALOIDS 

it  acts  as  a  sedative,  producing  sleep  and  relieving  pain.  It 
is  a  habit-forming  drug.  In  doses  of  0.2  to  0.3  gram  it  is  fatal  to 
man. 

Although  a  large  amount  of  work  has  been  done  on  morphine 
and  its  derivatives,  its  structural  formula  has  not  yet  been  clearly 
established.  On  distillation  with  zinc  dust  it  gives  phenanthrene. 
It  contains  two  hydroxyl  groups,  as  with  acetic  anhydride  it 
gives  a  diacetate,  heroin,  used  in  medicine.  Of  the  two  hydroxyl 
groups  one  acts  as  a  phenol  group,  as  morphine  is  soluble  in  a 
solution  of  caustic  alkali  and  gives  the  methyl  ether,  codeine, 
insoluble  in  alkali,  when  methylated.  The  second  hydroxyl  is 
present  in  the  form  of  a  secondary  alcohol  group,  as  codeine, 
C18H21NO3,  gives  a  ketone,  codeinone,  CigHwNOs,  on  oxida- 
tion. 

Codeine  is  made  on  the  large  scale  by  methylating  morphine 
in  alkaline  solution  with  dimethyl  sulphate.  It  resembles 
morphine  in  its  physiological  action,  but  is  less  narcotic. 

Over  600,000  pounds  of  opium  valued  at  $5,387,855  were 
imported  into  the  United  States  in  1920. 

Narcotine,  C22H23NO7.  —  When  opium  is  extracted  with  water 
to  obtain  morphine,  etc.,  most  of  the  narcotine  remains  in  the 
insoluble  residue  from  which  it  is  extracted  with  dilute  hydro- 
chloric acid.  It  crystallizes  from  alcohol  in  colorless  needles 
(m.  p.  176°).  It  is  levorotatory  and  is  a  weak  monacid,  tertiary 
base.  In  its  physiological  action  it  resembles  codeine,  but  is 
less  depressant.  It  is  much  less  poisonous  than  either  morphine 
or  codeine.  It  is  little  used  in  medicine.  It  has  been  made 
synthetically  and  shown  to  have  the  following  formula :  — 


H3CO  HC 

— CH 1 

-O^Y^NCH, 

6.0c  ^ 

'°\A/^^^ 

H^CO^^ 

H2C< 

CH2  0CH3 

It  will  be  noted  that  it  is  a  derivative  of  tetrahydroiso- 
quinoline  and  that  it  contains  three  methoxy  groups  and  a 
lactone  ring. 


PROTEINS  539 

The  Proteins 

The  nitrogenous,  organic  substances  found  in  living  matter 
and  produced  by  it  are  called  proteins  (Gr.  proteios,  the  first). 
Like  the  fats  and  carbohydrates  they  are  found  only  in  living 
matter  or  in  the  products  of  the  action  of  living  matter.  The 
food  of  animals  consists  of  proteins,  fats,  and  carbohydrates,  and 
of  these  the  proteins  are  the  most  important.  An  animal  can 
exist  for  a  long  time  without  fats  or  carbohydrates,  but  it  dies 
when  deprived  of  proteins.  The  proteins  are  also  essential 
constituents  of  all  living  cells  and  are  therefore  of  the  first  im- 
portance for  the  phenomenon  of  life.  They  are  absolutely 
necessary  for  the  growth  and  development  of  living  cells.  They 
consist  of  carbon,  hydrogen,  nitrogen,  oxygen,  and  some  sulphur. 
Sometimes  they  contain  phosphorus.  The  amount  of  these 
constituents  varies  somewhat  in  the  different  proteins  and  is 
approximately  C —  50  per  cent,  H —  7  per  cent,  N — 16  per  cent, 
O — 25  percent,  S — 0.2  to  3  percent,  P  —  o  to  3  per  cent.  Those 
which  are  soluble  in  water  form  colloidal  solutions  and  do  not 
difiuse  through  parchment  paper,  and  this  fact  is  taken  advantage 
of  to  free  them  from  salts  and  crystalloids.  These  solutions  are 
levorotatory.  Most  of  the  proteins  are  amorphous  substances 
without  a  definite  melting  point,  that  carbonize  on  heating  and 
give  off  gas.  Some  have  been  obtained  crystalline,  e.g.,  the 
albumins,  haemoglobin,  edestin  from  hemp  seed,  etc. 

Many  of  the  proteins  can  be  "  salted  out  "  from  their  aqueous 
solutions  by  sodium  chloride  or  magnesium  sulphate,  and  almost 
all  of  them  are  precipitated  unchanged  by  saturating  their  solu- 
tions with  ammonium  sulphate.  Alcohol  also  precipitates  proteins 
unchanged  from  aqueous  solutions,  while  strong  alcohol  coagu- 
lates them.  Heat  coagulates  the  proteins,  and  the  temperature 
at  which  coagulation  takes  place  is  characteristic  for  the  different 
proteins.  These  coagulated  proteins  can  be  brought  into  solu- 
tion again  by  the  action  of  dilute  acids  or  alkalies,  but  these 
solutions  are  no  longer  coagulable  by  heat.  They  are  called 
metaproteins  and  are  precipitated  by  neutralizing  their  solutions. 
The  proteins  are  also  precipitated  by  copper  sulphate,  ferric 


540  PROTEINS 

chloride,  mercuric  chloride,  etc.,  and  by  the  alkaloid  precipitat- 
ing agents,  especially  phosphotungstic  acid.  They  give  certain 
color  reactions,  which  are  used  as  tests  for  proteins,  such  as :  — 

1.  The  biuret  reactio?!  {26i:). 

2.  Millon's  reaction.  This  consists  in  the  formation  of  a 
red  color  when  a  protein  is  heated  with  a  mixture  of  mercuric 
nitrate  and  nitrite  (Millon's  reagent). 

3.  Xanthoproteic  reaction.  Most  proteins  develop  a  yellow 
color  when  heated  with  nitric  acid.  This  changes  to  an  orange 
when  the  solution  is  made  alkaline. 

Chemically  most  of  the  proteins  have  weak  acid  and  basic 
properties,  like  the  amino  acids.  They  are  digested  by  certain 
enzymes  and  hydrolyzed  by  mineral  acids  to  mixtures  of  amino 
acids.  They  are  regarded  as  composed  of  residues  of  these  amino 
acids  combined  with  one  another  in  the  same  way  as  in  the 
pol)^eptides  (271).  These  polypeptides  give  many  of  the  re- 
actions characteristic  of  the  proteins,  and  several  of  them  have 
been  found  among  the  products  of  the  hydrolysis  of  the  proteins. 
Little  is  known  regarding  the  molecular  weight  of  the  proteins 
except  that  it  must  be  very  large.  Determinations  of  the 
osmotic  pressure  of  solutions  of  the  albumin  of  the  hen's  egg, 
for  example,  have  given  results  which  point  to  a  molecular 
weight  of  about  12,000  for  that  substance.  The  percentage  of 
iron  in  haemoglobin,  assuming  that  the  molecule  contains  one 
atom  of  iron,  indicates  a  molecular  weight  of  about  16,500  for 
this  substance. 

The  following  classification  of  the  proteins  has  been  adopted 
by  the  American  Society  of  Biochemists  : '  — 

Proteins  are  defined  as  nitrogenous,  organic  substances  con- 
sisting wholly,  or  in  part,  of  amino  acids,  united  by  their  carboxyl 
and  amino  groups.     They  are  divided  into  three  main  classes :  — 

1.  Simple  proteins, 

2.  Compound  or  conjugated  proteins, 

3.  Derived  proteins. 

The  first  two  classes  are  natural  proteins ;  the  last  includes 
the  artificial  proteins  and  proteins  modified  by  reagents. 

'  See  p.  112,  Physiological  Ckemisiry,  by  .\.  P.  Mathews,  3d  ed.,  1921 . 


CONJUGATED    PROTEINS  541 

I.  The  simple  proteins.  —  These  are  proteins   occurring  in 

nature  which  when  treated  with  enzymes  or  acids  break  down, 
yielding  only  a-amino  acids  or  their  derivatives.  They  differ 
from  the  conjugated  proteins  in  that  the  latter  not  only  break 
down  into  a-amino  acids  but  also  into  other  non-protein  sub- 
stances. The  simple  proteins  are  separated  into  the  following 
groups  by  their  solubilities  and  other  properties. 

A.  Albumins.  Simple  proteins,  coagulable  by  heat,  soluble 
in  water  and  dilute  salt  solutions.     Ovalbumin,  serum  albumin. 

B.  Globulins.  Simple  proteins,  coagulable  by  heat,  insoluble 
in  water,  but  soluble  in  dilute  solutions  of  salts  of  strong  bases 
and  acids.     Serum  globulin,  edesiin. 

C.  Glutelins.  Simple  proteins,  coagulable  by  heat,  insoluble 
in  water  or  dilute  salt  solutions,  but  soluble  in  very  dilute  acids 
or  alkalies.    Gluienin  of  wheat. 

D.  Prolamines.  Simple  proteins,  insoluble  in  water,  soluble 
in  80  per  cent  alcohol.    Gliadin,  hordein,  zein.     Found  in  cereals. 

E.  Albuminoids.  Simple  proteins,  insoluble  in  dilute  acid, 
alkali,  water  or  salt  solutions.     Elastin,  keratin,  collagen. 

F.  Histones.  Simple  proteins,  not  coagulable  by  heat, 
soluble  in  water  and  in  dilute  acid ;  strongly  basic,  and  insoluble 
in  ammonia.      Histone  from  birds'  corpuscles  and  from  thymus. 

G.  Protamines.  Simple  proteins,  strongly  basic,  non-coagu- 
lable  by  heat,  soluble  in  ammonia  and  yielding  large  amounts  of 
diamine  acids  on  hydrolysis.  Sturin,  salmin,  clupein.  Found 
in  ripe  sperm  of  fishes. 

II.  Conjugated  proteins.  —  These  are  compounds  of  simple 
proteins  with  some  other  non-protein  group.  The  other  group 
is  generally  acid  in  nature.  They  are  subdivided  into  the  fol- 
lowing classes : — 

A.  Hcemoglobins.  The  prosthetic  group  (Gr.  prostheses, 
additional)  is  colored.  It  may  be  hematin  as  in  haemoglobin  or 
the  colored  radicals  of  phycoerythrin  or  phycocyan.  Hcemo- 
globin,  hcemocyanin,  phycoerthrin,  phycocyan. 

B.  Gluco proteins.  The  prosthetic  group  contains  a  carbo- 
hydrate radical.  In  mucin  and  cartilage  it  may  be  chondroitic 
acid.     Mucin,  ichthulin,  mucoids. 


542  PROTEINS 

C.  Phosphoproteins.  Proteins  of  the  c>'toplasm.  The  pros- 
thetic group  is  not  known.  It  contains  phosphoric  acid,  but  not 
in  the  form  of  nucleic  acid  or  a  phosphohpin.     Casein,  vitdlin. 

D.  Nticleo proteins.  Proteins  of  the  nucleus.  The  chro- 
matins. The  prosthetic  group  is  nucleic  acid.  Xuclein, 
nudeo-histone. 

E.  Lecithoproteins.  Found  in  the  cytoplasm  and  limiting 
membrane.  The  prosthetic  group  is  lecithin  or  a  phospholipin. 
No  lecithoprotein  has  yet  been  isolated.     They  probably  exist. 

III.  Derived  proteins.  —  This  group  is  an  artificial  one.  It 
includes  all  the  various  cleavage  products  of  the  proteins 
occurring  in  nature,  which  are  produced  by  the  action  of 
reagents  or  enzymes,  or  physical  agents,  such  as  heat ;  and 
also  artifically  synthesized  proteins.  It  is  divided  into  various 
groups  according  to  solubility  and  also  somewhat  according  to 
the  degree  of  hydrolysis. 

A .  Primary  Protein  Derivatives. 

a.  Proteans.  Derived  proteins.  The  first  products  of  the 
action  of  acids,  enzymes  or  water  on  simple  proteins.  Insoluble 
in  water.     Edestan,  myosan. 

b.  Metaproteins.  The  further  action  of  acids  and  alkalies 
produces  metaproteins.  These  are  soluble  in  weak  acids  or 
alkahes,  but  insoluble  in  neutral  solutions.  Acid  albumin, 
{acid  metaprotein) ;   alkali  albumin. 

c.  Coagulated  proteins.  Insoluble  protein  products  produced 
by  the  action  of  heat  or  alcohol. 

B.  Secondary  Protein  Derivatives. 

a.  Proteoses.  Hydroly tic  cleavage  products  of  proteins.  Sol- 
uble in  water,  not  coagulable  by  heat,  precipitated  by  saturating 
their  solutions  with  ammonium  sulphate. 

b.  Peptones.  Hydrolytic  cleavage  products  of  proteins ;  solu- 
ble in  water,  not  coagulable  by  heat,  not  precipitated  by  satura- 
tion with  ammonium  sulphate.  Generally  diffusible  and  giving 
the  biuret  reaction. 

c.  Peptides.  These  are  compounds  of  the  amino  acids,  of 
which  the  composition  is  known.  Many  are  synthetic.  The 
amino  acids  are  united  through  the  amino  and  carboxyl  groups. 


DERIVED    PROTEINS  543 

They  may  or  may  not  give  the  biuret  reaction.  They  are  not 
coagulable  by  heat.  They  are  called  di-,  tri-,  tetra-,  penta- 
peptides,  etc.,  according  to  the  number  of  residues  of  amino 
acids  contained  in  the  molecule.  (See  Polypeptides  (271).)  For 
further  details  concerning  these  substances  the  student  is  referred 
to  textbooks  on  Physiological  Chemistry. 


INDEX 


Acchroodextrin,  243 

Acetamide,  255 

Acetanilide,  348 

Acetates,  59 

Acetic  acid,  3,  4,  35,  56,  63,  143, 

glacial,  58 

halogen  substitution  products, 
Acetic  aldehyde,  48,  152,  165 
Acetic  anhydride,  61 
Acetic  ether,  60,  71 
"Acetin,"  168 
Acetoacetic  acid,  207 
Acetoacetic  ester  synthesis,  210 
Acetochloroglucose,  530 
Acetolysis,  245 
Acetone,  4,  35,  72,  133,  2g8 
AcetonitrUe,  93 
Acetophenone,  400 
Acetyl,  61 

chloride,  60 

oxyde,  6i 
Acetylene,  296 

Acetylene-dicarboxylic  acid,  300 
Acetyl-glycolic  acid,  181 
Acetyl-salicylic  acid,  420 
Acetyl  urea,  264 
Acid  albumin,  542 

alcohols,  176 

amides,  255 

fuchsine,  470 

hydrolysis,  208 

imides,  259 

metaprotein,  542 

oil,  306 
Acids,  54 

acetylenic  series,  300 

acrylic  series,  286 

alcohol,  156 

amic,  258 

amino,  247 

amino  dibasic,  254 


62 


aminosulphonic,  254 

aromatic  sulphonic,  365 

benzoic  series,  402 

dibasic,  155 

dibasic  aromatic,  415 

dihydroxy  dibasic,  196 

dihydroxy  monobasic,  189 

fatty,  38,  143 

hexabasic,  175 

hexabasic  aromatic,  419 

hydroxy,  176 

hydroxy  aromatic,  419 

ketone,  206 

monobasic  aromatic,  402 

monohydroxy  dibasic,  192 

monohydroxy  monobasic,  189 

monohydroxy  tribasic,  203 

oleic  series,  286 

oxy,  176 

pentabasic,  174 

pentahydroxy  monobasic,  191 

phenol,  419 

polybasic,  150 

polybasic  ethylenic,  290 

pseudo,  340 

tetrabasic,  173 

tetrahydroxy  monobasic,  191 

tribasic,  173 

trihydroxy  monobasic,  190 
Aconitic  acid,  295 
Acridine,  525 
a-Acritol,  175 
Acrolein,  284 
a-Acrose,  232 
i^crylic  acid,  286 
Acrylic  aldehyde,  284 
Active  compounds,  136 
Active  principles,  532 
Adipic  acid,  157 
Adonitol,  173 
Adrenaline,  426 


S4S 


546 


INDEX 


Aesciilin,  529 
After  damp,  23 
d-.\lanme,  252 
Albumin,  3,  541 
Albuminoids,  541 
Alcohol,  absolute,  40 

denatured,  41 

ordinary,  39 
Alcohol  acids,  156,  176 
Alcohols,  3,  35,  105,  129 

acid,  176 

aldehyde,  213 

aromatic,  391 

bicydic,  455 

diacid,  150 

ethylene,  280 

Geneva  nomenclature,  141 

heptacid,  175 

hexacid,  174 

ketone,  213 

monacid,  150 

monocyclic,  447 

pentacid,  173 

polyacid,  150 

primary,  132 

secondary,  131 

tertiary,  135 

tetracid,  173 

thio,  76 

triacid,  163 
Aldehyde,  48 

acids,  206 

alcohols,  213 

aromonia,  49,  52 

bisulphite  compounds,  49,  52 

group,  52 

hydrocyanide,  49,  52 
Aldehj'des,  47,  142 

aromatic,  394 
Aldohexoses,  219 
Aldol,  231 

condensation,  231 
Aldopentoses,  216 
Aldoses,  213 
Aldotetroses,  216 
Aldotriose,  213 
Aldoximes,  109 
Alicyclic  compounds,  502 
Alizarin,  521 


black,  507 

blue,  523 

green,  524 

orange,  523 
-\lkali  albumin,  542 

blue,  471 
Alkaloid  reagents,  532 
^Alkaloids,  532 

cinchona,  535 

foca,  S3S 

isoquinoline,  537 

pyridine,  533 

quinoline,  535 

solanaceous,  534 

strychnos,  537 
Alkyl,  43 
Alkylenes,  275 
Allene,  299,  300 
AUomucic  acid,  206 
AUose,  227 
.-Ulyl  alcohol,  280 

isothiocyanate,  98 

mustard  oil,  283 

sulphide,  283 
Allylene,  299 
.\ltrose,  227 
Aluminium  ethyl,  112 
Amic  acids,  258 
Amides,  acid,  255 
Amidol,  377 
.Amines,  104 
Amino-acetic  acid,  249 
Amino  acids,  247 
2-Anunoantliraquinone,  521 
Amino-azobenzene,  362 

-benzene,  342 

-benzenesulphonic  acids,  369 
)w-Aminobenzoic  acid,  410 
o-.Aminobenzoic  acid,  407 
/>-Aminobenzoic  acid,  410 
.Amino-butane  diacid,  254 
Amino  compounds,  104 
Amino  dibasic  acids,  254 
/>-Aminodimethylaniline,  363 
-Vminoethane,  104 

acid,  249 
/3-Aminoethylsulphonic  acid,  254 
Aminoformic  acid,  248 
o-Aminohydrociimamic  acid,  415 


INDEX 


547 


2-Amino-6-hydroxypurine,  271 
Z-a-Aminoisobutyric  acid,  252 
d-a-  Amino  -  0  -  methyl  -  /3  -  ethyl- 

propionic  acid,  253 
1,8-  Aminonaphthol  -  3 , 6  -  disulf  onic 

acid,  503 
Aminonaphthols,  503 
I  -  Amino  -  2  -  naphthol  -  6  -  sulphonic 

acid,  504 
w-Aminophenol,  380 
o-Aminophenol,  379 
^-Aminophenol,  380 
Amino-phenylarsinic  acid,  345 

-propionic  acids,  252 

-succinamic  acid,  259 

-succinic  acid,  254 

-sulphonic  acids,  254 

-toluenes,  350 
Ammonias,  substituted,  100 
Ammonium  cyanate,  90 

oxalate,  159 

thiocyanate,  90 
ow^&'-Compounds,  506 
Amygdalin,  529 
Amyl  alcohol,  active,  136,  137 

fermentation,  136 
Amylene,  275 
Amylopectin,  242 
Amylopsin,  239 
Amylose,  242 
Anaesthesin,  410 
Analysis,  9 
Anethol,  3,  425 
Angelic  acid,  286 
Anhydro-^-aminobenzyl  alcohol,  464 

-resorcinolphthalein,  476 
Anilides,  348 
Aniline,  342 

blue,  471 

salt,  343 

yellow,  362 
Anisic  acid,  425 
o-Anisidine,  379 
Anisol,  37S 
Anthocyanidins,  531 
Anthocyanins,  531 
Anthracene,  514 

brown,  524 

oil,  306 


Anthragallol,  524 
Anthrahydroquinol,  520 
Anthranilic  acid,  407 
Anthranol,  518,  519 
Anthraquinone,  518 

-sulphonic  acids,  520 
Anthrols,  517 
Anthrone,  519 
flH/f-Compounds,  356 
Antifebrine,  348 

Antimonyl  potassium  tartrate,  200 
Apples,  essence  of,  147 
Arabans,  217 
Arabinoses,  217 
Arabitol,  173 
Arabonic  acids,  191 
Arachidic  acid,  143 
Arbutin,  387,  530 
Argol,  199 
Aristol,  383 

Aromatic  compounds,  306,  309 
Arrack,  70 
Arsacetin,  345 

Arsenic  derivatives  of  methane,  no 
Asparagine,  259 
Aspartic  acid,  254 
"Asphalt  base"  crudes,  118 
Aspirin,  420 

Asymmetric  carbon  atom,  138 
Atoxyl,  345 
Atropine,  534 
Auxochrome,  362 
Azelaic  acid,  157 
Azo-benzene,  359 
Azo  dyes,  362 

dyes  of  the  naphthalene  series,  505 
Azoxybenzene,  359 
Azulmic  acid,  84 

Bacterium  aceti,  3,  39,  57 

lactis,  39 
Bakelite,  47,  374 
Baking  powders,  199 

process,  369 
Balata,  461 
Ballistite,  171 
Banana  oil,  artificial,  146 
Barbituric  acid,  267 
Baumann-Schotten  reaction,  405 


548 


INDEX 


Beckmann  rearrangement,  401 

Beef  tallow,  172 

Beer,  42 

Beet  sugar,  23s 

Behenic  acid,  143 

Benzal  chloride,  335,  337 

Benzaldehyde,  394 

Benzaldoximes,  398  1 

Benzamide,  405 

Benzanilide,  405 

Benzene,  41,  307,  308 

amino  compounds,  341 

diazo  compounds,  350,  354 

-diazonium  chloride,  354 

-diazonium  hydroxide,  354 

-diazonium  sulphonate,  370 

-disulphonic  acids,  368 

halogen  addition  products,  329 

halogen  substitution  products,  330 

hexachlorides,  329 

hydrocarbons,  306 

isodiazo  compounds,  354 

nitro  compounds,  337 

series,  18,  117 

-sulphonamide,  368 

-sulphonic  acid,  365 

-sulphonyl  chloride,  368 

trichlorohydrin,  330 
Benzhydrol,  464 
Benzidine,  491 

dyes,  491 
Benzil,  397 
Benzine,  41 
Benzoic  acid,  402 

adds,  substituted,  406 

sulphinide,  412 
Benzoin,  397 
Benzophenone,  400 
Benzopurpurin,  505 
p-BenzoquLnone,  433 
/"-Benzoquinone,  431 
Benzotrichloride,  335,  337 
Benzoyl-aminoacetic  acid,  410 

chloride,  404 

cyanide,  406 

-ecgonine  methyl  ester,  535 

-formic  acid,  406 
Benzyl  alcohol,  391 

bromide,  336 


Benzyl  chloride,  335,  336 
Benzylidene-aniline,  397 

-azine,  396 
Betaine,  251 
Beverages,  Alcoholic,  42 
Bismarck  brown,  364 
Bitter  almonds.  Oil  of,  394 
Biuret,  264 

reaction,  264,  540 
Bivalent  radicals,  155 
Blasting  gelatin,  171 
Boat,  10 

Boiling  point,  determination  of,  7 
Bone-black,  4 

oil,  4,  435 
Borneo  camphor,  455 
Bomeol,  455 
Bomyl  chloride,  453 
Brandy,  42 
Brassylic  add,  157 
British  gum,  243 
Bromo-benzene,  332 

-ethane,  30 
Bromoform,  28 
Bromethane,  26 
a-Bromonaphthalene,  498 
Bromophenol  blue,  478 
a-Bromopropionic  acid,  144 
/3-Bromopropionic  add,  144 
Brucine,  537 
Bueb  process,  87 
Butadiene-1,3,  300 
Butane,  19,  116,  123,  126 

acid,  146 

diacid,  161 
Butanes,  122 
Butane-tetrol,!, 2,3,4,  i73 

-triol-2,3,4-als,  216 

-triol-i,3,4-one-2,  216 
Butanol-i,  133 
Butanol-2,  134 
Butanone,  74 

-3-acid,  207 
i-Butene,  275,  280 
2-Butene,  280 
Butene-2-adds,  287 
Butine-i,  299 
Butine-2,  299 
Butine  diacid,  300 


INDEX 


549 


Butter,  146,  171,  172 
Butyl  alcohol,  133,  142 
Butylene,  134,  275,  280 
Butylenes,  278,  280 
Butyric  acid,  143,  146,  172 

Cacodyl,  no 

chloride,  in 

oxide.  III 
Caffeine,  3,  270 
Calcium  acetate,  59 

carbide,  29S 

citrate,  205 

cyanamide,  260 

oxalate,  159 

racemate,  201 

tartrate,  igg 
Camphene,  454 

dibromide,  455 
(i-Camphor,  3,  457 

"artificial,"  453 

Borneo,  455 

Japanese,  457 

Laurus,  457 

peppermint,  447 
Camphors,  442 

olefine,  459 
Cane  sugar,  23s 
Cantharene,  329 
Caoutchouc,  3,  460 
Capric  acid,  143,  172 
Caproic  acid,  143,  172 
Caprylic  acid,  143,  172 
Caramel,  237 
Carbamic  acid,  98,  248 
Carbamide,  262 
Carbazole,  492 
Carbinol,  35,  132 
Carbocyclic  compounds,  304 
Carbohydrates,  212 
Carbolic  acid,  372 
Carbon  bisulphide,  178 

estimation  of,  9 

monoxide,  88 

suboxide,  161 

tetrachloride,  28 
Carbonic  acid,  176,  177 
Carbonyl,  51 

chloride,  177 


Carbostyril,  480,  512 
Carboxyl,  64 
Carbylamines,  94 
Carvacrol,  383 
Carvene,  445 
d-Carvone,  449 
Casein,  3,  542 
Cellubiose,  245 
Celluloid,  246 
Cellulose,  3,  244 

acetate,  246 

nitrates,  246 

xanthic  acid,  246 
Cerotene,  275 
Cerotic  acid,  143 
Ceryl  alcohol,  141,  142 
Cetyl  alcohol,  141,  142 

palmitate,  148 
Charcoal,  4 
Chardonnet  silk,  246 
Chloral,  53 

hydrate,  53 
Chlorine  carrier,  29,  331 
Chloro-acetic  acid,  299 

benzene,  332 

-dinitrobenzene,  340 

-ethane,  30 
Chloroform,  27 
Chloromethane,  26,  103 
a-Chloronaphthalene,  498 
Chloronitrobenzenes,  339 
Chlorophyll,  232 
Chloropicrin,  108,  379 
a-Chloropropionic  acid,  144 
/3-Chloropropionic  acid,  144 
Chlorotoluene,  335 
Choke  damp,  23 
Chromogen,  362 
Chromophor,  362 
Chromotropic  acid,  503 
Chrysamine  G,  492 
Chrysanihne,  595 
Chrysoidine,  364 
Cimic  acid,  286 
Cinchona  alkaloids,  535 
Cinchonie,  536 
Cineol,  451 
Cinnamic  acid,  479 

aldehyde,  479 


550 


INDEX 


Cinnamyl  alcohol,  479 

ctj-Compounds,  293,  330 

Citraconic  acid,  294 

Citral,  460 

Citrates,  204 

Citrene,  445 

Citric  acid,  3,  203 

Citromyces  pfefferianus,  203 

Classification      of      carbon      com- 
pounds, IS 

Clupein,  541 

Coagulated  proteins,  542 

Coal  gas,  4,  87 
tar,  4,  306 

"Coal-tar  crudes,"  309 

Coca  alkaloids,  535 

Cocaine,  535 

Cocoa  butter,  172 

Codeine,  538 

"Coke-oven  light  oil,"  307 

Collagen,  541 

Collidines,  435,  440 

Collodion  cotton,  246 

Colloidal  polysaccharoses  or  polyoses, 
212,  240 

Column  stills,  7 

Combustion  process,  9 

Complex  sugars,  212,  234 

Compound  ethers,  68 

Condensite,  47 

Congo  red,  505 

Coniferin,  530 

Conine,  442 

Constitution  of  organic  compounds, 
14 

Conyrine,  440 

Cordite,  171,  298 

Com  sugar,  221 

Cotton,  244 
blue,  471 
soluble,  246 

Cotton  seed  oil,  3 

Coumarin,  481 

■'Coupling,"  363 

"Cracking  distillation,"  118 

"Cream  of  tartar,"  199 

Creatine,  262 

Creatinine,  262 

Creosote  oU,  306 


Cresols,  381 

Cresylic  acids,  381 

Crisco,  290 

Crocein,  503 

Crotonic  acids,  286,  287 

aldehyde,  285 
"Crudes,"  309 
Crystallization,  5 

fractional,  5 
Crystal  violet,  470 
Cumene,  308,  326 
Cuminic  acid,  326 

aldehyde,  398 
Cuminol,  398 
Cupric  acetates,  59 

acetoarsenite,  59 
C}an-acetic  acid,  156 
C)an-amide,  260 
Cyanic  acid,  89 
Cyanides,  85,  91 
Cyanogen,  83 

chlorides,  89 
Cyanuramide,  89 
Cyanuric  acid,  90 

chloride,  89 
Cyclic  compounds,  304 
Cydobutane,  304 
Cyclohexadienes,  329 
Cyclohexa-i,4-diol,  432 
Cyclohexa-i,4-dione,  432 
Cyclohexane,  304,  305,  328 
Cydohexanol,  373 
Cydohexatriene,  308 
Cydohexene,  329 
Cydohexylamine,  343 
Cydopentane,  304 
Cyclopropane,  304 
Cylinder  oils,  iiS 
OT-Cymene,  327 
^-CjTuene,  308,  327 
Cymogene,  123 
Cystein,  253 
Cystine,  253 

Decalain,  496 
Decane,  116 
Decene,  275 
Decylene,  275 
Denatured  alcohol,  41 


INDEX 


551 


Depsides,  430 

Dextrins,  243 

Dextrorotatory  compounds,  137 

Dextrose,  219,  221 

Diacetamide,  257 

Diacetin,  168 

Diallyl  disulphide,  283 

2,4-Diaminoazobenzene,  364 

Diaminodihydroxyarsenobenzene, 

379 
Di-^-diaminodiphenyl;  491 
^-Diaminodiphenylmethane,  464 
2,4-DiaminophenoI,  377 
Dianthracene,  515 
Diastase,  40,  239 
Diazo-acetic  ester,  250 

-aminobenzene,  357 

-amino  compounds,  357 

-benzene  compounds,  350,  354 

-benzene  potassium  oxide,  354 

-methane,  251 
Diazonium  salts,  350 
Diazotization,  351 
Dibromo-benzene,  334 

-indigo,  486 

-methane,  27 

-methone,  448 
Dichloro-acetic  acid,  62 

-acetone,  204 

-ethanes,  31,  164 

-hydrin,  167 

-methane,  26 

-propionic  acid,  19s 

-toluene,  335 
Dicyandiamide,  260 
Dicyanogen,  84 
Diethylamine,  104 

-OT-aminophenoI,  380 

-aniline,  347 

-barbituric  acid,  267 

glycol  ether,  152 

malonate,  160 

-phosphine,  no 

-phosphinic  acid,  no 

-phosphoric  acid,  70 

phthalate,  417 

sulphate,  70 
Diethylene  derivatives,  300 
Digallic  acid,  429,  430 


Dihydro-benzenes,  329 

-phthalic  acids,  419 

-resorcinol,  3S5 
Dihydroxyacetone,  213,  215 
1,2-Dihydroxyanthraquinone,  521 
w-Dihydroxyazobenzene,  386 
m-Dihydroxybenzene,  385 
o-Dihydroxybenzene,  383 
^-Dihydroxybenzene,  387 
3,4-Dihydroxybenzoic  acid,  425 
Dihydro-o-xylene,  329 
1 ,8-Dihydroxynaphthalene-3,6-di- 

sulphonic  acid,  503 
5,6-Dihydroxy-a-naphtha-quinone, 

507 
2,6-Dihydroxypurine,  270 
Dihydroxysuccinic  acids,  197 
i-Dihydroxy toluene,  387 
Diiodo-methane,  27 

-thymol,  383 
«j-Diketocyclohexane,  385 
^-Diketodihydrobenzene,  433 
Dimethyl,  23 

-acetylene,  299 

-amine,  100,  102,  346 

-aminoazobenzene,  363 

-aminoazobenzene  carboxylate,  409 
p  -  Dimethylaminoazobenzene  -p-  sul- 

phonic  acid,  370 
Dimethyl-aniline,  345 

-butanes,  127 

carbinol,  132,  141 
Dimethylene,  278 
Dimethyl  ether,  44,  346 

-ethylene,  280 

-ethylm  ethane,  124 

-hydrazine,  106 

-isopropylmethane,  126,  127 

ketone,  72 

oxide,  43 

-phosphine,  no 
2,2-Dimethylpropane,  124,  127 
Dimethyl-propylmethane,  125 

-pyridines,  440 

sulphate,  69 

-xanthines,  270 
4,6-Dinitro-2-aminophenol,  378 
Dinitrobenzene,  339 
2,4-Dinitro-a-naphthol,  503 


552 


INDEX 


J  ,4-Dmitro-a-naphthol-  7-sulphonic 

add,  503 
-',4-Dinitrophenol,  377 
2,4-Diiutrosoresorcinol,  386 
Dinitro-thiophene,  33q 

-toluene,  341 
Dioleostearin,  172 
Dioxindol,  487 
Dipentene,  446 
Dipeptide,  271 
Diphenyl,  490 

-amine,  347 

-amine  orange,  371 

-carbinol,  464 

ether,  376 

-iodonium  hydroxide,  333 

ketone,  400 

-methane,  462,  463 

-nitrosamine,  348 

substitution  products,  490 

-sulphone,  366 

-thiourea,  349 
Dippel's  oil,  434 
Dipropargyl,  303 
Disaccharoses,  234 
Disazo  dyes,  362 
Disodium  glycol,  152 
Distillation,  5 

fractional  or  partial,  5 
Distilled  liquors,  42 
Docosane,  116 
Dodecane,  116 
Dodecylene,  275 
Dotriacontane,  116 
"Driers,"  149 
Drying  oils,  301 
Dulcine,  381 
Dulcitol,  17s 
Durene,  308 
Dye,  362 
Dyeing,  470 
Dyes,  Azo,  362 

Benzidine,  491 

Direct,  492 

Indanthrene  vat,  521 

Naphthal  azo,  505 

Substantive,  492 

Triphenylmethane,  467 
Dynamite,  170 


Ebonite,  461 
Edestan,  542 
Edestin,  541 
Eicosane,  116 
Eikonogen,  504 
Elaidic  acid,  290 
Elastin,  541 
Emerald  green,  60 
Emulsin,  394 

End  tautomeric  form,  210 
Enzymes,  40 
Eosin,  477 
Erucic  acid,  286 
Erythrite,  173 
Erythritol,  173 
Erythrodextrin,  243 
Erythronic  acids,  190 
Erythroses,  216 
Erythrulose,  216 
Esteriiication,  67 
Esters,  38,  67 
Ethanal,  48,  66 

acid,  206 
Ethane,  19,  23,  66,  116 

halogen  derivatives,  25 

nitrogen  derivatives,  83 

oxygen  derivatives,  35 

phosphorus  derivatives,  no 

sulphur  derivatives,  76 
Ethane  acid,  56,  66 

amide,  255 

diacid,  157 

-diol,  150 

nitrile,  91 

-2-ol-i-sulphonic  acid,  187 

-thiol,  76 
Ethanol,  39,  66 

acid,  180 
Ethene,  275,  276 
Ethenol,  280 
Ether,  44 

Ethereal  salts,  38,  67 
Ethers,  43 

compound,  68 

mixed,  46 

thio,  78 
Ethane,  296 
Ethoxyl,  425 
Ethyl,  31,  42,  155 


INDEX 


55c 


acetate,  60,  70,  71 

acetoacetate,  208 

-acetylene,  299 

alcohol,  39,  133,  140,  142 

-amine,  104 
Ethylates,  43 
Ethyl-benzene,  308,  322 

bromide,  30 

butyrate,  146 

carbinol,  132,  141 

carbylamine,  94 

chloride,  30 

chlorocarbonate,  178 

chloroformate,  178 

cyanide,  91 

diazoacetate,  250 

-dithiocarbamic  acid,  98 
Ethylene,  275,  276 

alcohol,  150 

alcohols,  280 

chloride,  32,  152,  154 

chlorohydrin,  151,  152 

-dicarboxylic  acids,  292 

-lactic  acid,  187 

oxide,  152 

ozonide,  279 

radical,  155 

-succinic  acid,  161 
Ethyl  ether,  44 

ethylene,  280 

formate,  70 

glycolate,  180 

glycol  ether,  152 

-glycolic  acid,  181 

P-hydroxycrotonate,  211 
EthyUdene  chloride,  31,  32,  154 

-lactic  acid,  182 

oxide,  152 

-succinic  acid,  163 
Ethyl  iodide,  30 

isocyanide,  94 

mercaptan,  76 

methane,  128 

mustard  oil,  99 

nitrate,  69 

nitrite,  69 

-phenyl  ether,  375 

-phosphine,  iro 

-phosphonic  acid,  no 


Ethyl-phosphoric  acid,  70 
;3-Ethylpyridine,  440 
Ethyl  sulphide,  78 

-sulphonic  acid,  79 

-sulphuric  acid,  44,  69,  81 

thiocyanate,  97 

-urea,  264 
Eucalyptol,  3,  451 
Eugenol,  3 
External  compensation,  148,  202 

Fabrikoid,  140 
Fast  green  O,  386 

red,  506 
Fats,  2,  3,  171 
Fatty  acids,  38,  143,  164 
Fehling's  solution,  200,  223 
Feld  process,  87 
Fermentation,  3,  39,  165 

acetic  acid,  39 

alcoholic  or  vinous,  39,  184 

amyl  alcohol,  136 

lactic  acid,  39,  182 
Ferments,  39 
Ferric  acetate,  60 

ferrocyanide,  89 

succinate,  basic,  162 

thiocyanate,  91 
Ferrous  acetate,  60 
Filter  paper,  244 
Fire  damp,  22 
Fluoran,  472,  476 
Fluorescein,  476 
Formaldehyde,  47 
Formalin,  47 
Formic  acid,  38,  54,  64,  86,  143 

aldehyde,  47,  64 
Formonitrile,  93 
Formose,  231 
Formula,  constitutional,  14 

determination  of,  11 

space,  197 

structural,  13 
Friedel-Crafts  reaction,  400,  462 
(ii-Fructose,  40,  227 
ii-Fructose,  231 
Fuchsine,  469 

acid,  470 
Fucitol,  173 


554 


INDEX 


Fucose,  2ig 
Fuel  oils,  ii8 
Fulminating  mercury,  109 
Fulminic  acid,  log 
Fumaric  acid,  290 
Fural,  434 
Furan,  434 
Furfural,  434 
Furfuraldehyde,  218 
Fusel  oil,  40,  120,  133,  136 

Galactonic  acids,  192 
Galactoses,  226 
Gallic  acid,  3,  428 
Gallotannin,  430 
Gambine  Y,  507 
"Gas  benzol,"  307 
Gas  oils,  118 
Gasolene,  4,  118 
Gelatin  dynamites,  171 

sugar,  249 
Gelignites,  171 
Geneva  nomenclature  of  alcohols,  141 

nomenclature  of  the  parafEns,  128 
Geranial,  460 
Geraniol,  459 
Glacial  acetic  acid,  58 
GlanzstofF,  246 
Gliadin,  541 
Globulins,  541 
Gluconic  acids,  191 
Glucoproteins,  541 
(/-Glucose,  40,  219 
"  Glucose,"  commercial,  220,  243 
/-Glucose,  222 
rf-Glucose  hydrate,  221,  225 
i-Glucose  phenyUiydrazone,  223 
Glucosides,  528 
Glucosone,  230 
Glutaric  acid,  157,  163 
Glutdins,  541 
Glutenin,  541 
Glyceric  acid,  189 

aldehyde,  213 
Glycerin,  164 
Glycerol,  146,  164 

esters  or  ethereal  salts,  1 70 

nitrates,  170 
Glycerose,  213,  233 


Glycerxl  trioleate,  289 

tripahnitate,  164 

tristearate,  164 
Glsxine,  249 
Glycocholic  acid,  249 
GlycocoU,  249 
Glycogen,  244 
Glycol,  150 

diacetate,  153 
Glycolic  acid,  1 76,  180 

aldehyde,  233 

anhj'dride,  181 
Glycolide,  181 
Glycol  monoacetate,  153 
Glycols,  152 
Glycylglycine,  271 
Glyoxj'lic  acid,  206 
Grain  alcohol,  39 
Grape  sugar,  40,  219,  221 
"Gray  acetate  of  lime,"  59 
Grignard  reaction,  112 
G-salt,  503 
Guaiacol,  384 
Guanase,  271 
Guanidine,  261 
Guanine,  271 
Gulonic  acids,  192 
Guloses,  226 
Gun  cotton,  246 
Gutta  percha,  461 

H-acid,  503 
Haemocyanin,  541 
Haemoglobins,  541 
Hardening  of  liquid  fats,  290 
Hard  rubber,  461 
Heavy  oil,  306 
Hefner  lamp,  140 
Helianthine,  370 
Helicin,  530 
Heliotropin,  427 
Hemimellithene,  308,  326 
Hemiterpenes,  443 
Hemp,  246 

Hempel  distilling  tube,  7 
Hemp  seed  oil,  301 
Heneicosane,  116 
Hentriacontane,  116 
Heptacosane,  116 


INDEX 


555 


Heptadecane,  ii6 
Heptane,  ii6,  126 
Heptanes,  126 
Heptene,  275 
Heptoic  acid,  143 
Heptyl  alcohol,  142 
Heptylene,  275 
Heroin,  538 
Hexachloroethane,  33 
Hexacontane,  116 
Hexacosane,  116 
Hexadecane,  116 
Hexadecylene,  275 
Hexadiene-i,s,  303 
Hexahydroxyanthraquinone,  524 
Hexahydro-benzoic  acid,  404 

-^-cymene,  329,  445 

-phthalic  acids,  419 

-pyridine,  441 

-toluene,  328 

-xylenes,  328 
Hexamethylbenzene,  308 
Hexamethylene,  328 
Hexamethylparafuchsine,  470 
Hexane,  19,  116,  125,  126 

-hexol-i,2,3,A,s,6,  174 

-pentol-i,2,3,4,s,  173 

-pentol-2,3,4,s,6-als,  219 
Hexanes,  125 
Hexasaccharoses,  235 
Hexatriene-1,3,5,  302 
Hexene,  275 
Hexodioses,  234 
Hexoic  acid,  143 
Hexonic  acids,  205 
Hexoses,  213,  219 

synthesis  of,  233 
Hexotriose,  234 
Hexyl  alcohol,  142 
Hexylene,  275 
Hippuric  acid,  3,  249,  410 
Histones,  541 
Hofmann's  reaction,  257 
Homologous  series,  19,  115 
Honey,  219 
Honey-stone,  419 
Hordein,  541 
Human  fat,  172 
Hydracrylic  acid,  182,  186 


Hydrazines,  aromatic,  360 

substituted,  106 
Hydrazobenzene,  360 
Hydroaromatic  hydrocarbons,  328 
Hydrobenzoin,  397 
Hydrocarbons,  16 

benzene,  306 

hydroaromatic,  328 

Marsh  gas,  115 

saturated  paraffin,  117 

unsaturated,  302,  303 

unsaturated  normal,  275 

with  two  benzene  residues,  490 
Hydrocarbostyril,  415 
Hydrocinnamic  acid,  415 
Hydrocyanic  acid,  84,  88 
Hydroferricyanic  acid,  87 
Hydroferrocyanic  acid,  87 
Hydrogen,  estimation  of,  9 
Hydrophthalic  acids;  419 
Hydroquinol,  387 
Hydrosorbic  acid,  286,  301 
Hydroxyacetic  acid,  156,  180 
Hydroxyanthracenes,  517 
Hydroxyanthraquinones,  521 
■y-Hydroxyanthrone,  520 
/J-Hydroxyazobenzene,  374 
Hydroxybenzene,  371 
m-Hydroxybenzoic  acid,  424 
o-Hydroxybenzoic  acid,  420 
/"-Hydroxybenzoic  acid,  424 
y-Hydroxybutyric  acid,  188 
/3-Hydroxybutyric  aldehyde,  232 
Hydroxyethylaniline,  349 
^-Hydroxy ethylsulphonic  acid,  187 
Hydroxy-formic  acid,  177 

-hydroquinol,  390 
m-Hydroxyketotetrahydrobenzene, 

38s 
Hydroxyl,  37 
p-Hydroxy-»t-methoxybenzoic    acid, 

428 
a-Hydroxypropionic  acid,  182 
8-Hydroxypropionic  acid,  182,  186 
Hydrox}T)ropionic  acids,  181 
a-Hydroxyquinoline,  480 
Hydroxy-quinolines,  512 

-succinic  acids,  193 

-sulphonic  acids,  187 


556 


INDEX 


Hydroxy-toluenes,  381 

-tricarballylic  acid,  203 
Hyenic  acid,  143 
Hyoscyamine,  534 
Hypnone,  400 
Hypog£eic  acid,  286 

Ichthulin,  541 
Iditol,  175 
Idonic  acids,  192 
Idosaccharic  acid,  206 
Idoses,  227 
Imides,  acid,  259 
Imino  compounds,  104 
Inactive  compounds,  136,  148 

resolution  into  active  components, 
201 
Indanthrene  vat  dyes,  521 
Indian  com,  241  _ 
India  rubber,  460 
Indican,  483 
Indigo,  483 

blue,  483 

carmine,  486 

synthetic,  485 

white,  484 
Indigotin,  483 
Indol,  488 
/3-Indolalanine,  489 
Indoxyl,  488 
"Intermediates,"  310 
Internal  compensation,  202 
Inulase,  244 
Inulin,  243 
Inversion,  237 
Invertase,  40,  21Q,  237 
Invert  sugar,  219,  237 
lodo-benzene,  333 

dichloride,  333 
lodoethane,  30 
Iodoform,  28 
/3-Iodolactic  acid,  190 
lodome thane,  26 
3-Iodopropane  acid,  190 
i8-Iodopropionic  acid,  186,  190 
lodosobenzene,  333 
lodoxybenzene,  333 
lonone,  460 
Isatin,  409 


Isethionic  acid,  187 
Isoamyl  acetate,  140 

alcohol,  inactive,  136,  141 

isovalerate,  147 

nitrite,  140 
Isobomeol,  457 
Isobutane,  123,  127 
Isobutyl  alcohol,  133 

carbinol,  136,  141 
Isobutjrric  acid,  146 
Isocrotonic  acid,  289 
Isocyanates,  96 
Isocyanides,  94 
Isodiazo  benzene  compounds,  354 

potassium  oxide,  355 
Isohexane,  127 
Isoleucine,  253 
Isomaltose,  240 
Isomerism,  31,  121,  144,  496 

spatial,  137,  292,  330,  356 
Isonitroso  compounds,  108 
Isoparaffins,  127 
Isopentane,  124,  127 
Isophthalic  acid,  417 
Isoprene,  443 
Isopropyl  alcohol,  129 
^-Isopropylbenzaldehyde,  398 
Isopropylbenzene,  326 
/)-Isopropylbenzoic  acid,  326 
Isopropyl  chloride,  146 
^-Isopropyl-m-cresol,  382 
^-Isopropyl-o-cresol,  383 
Isopropyl  cyanide,  146 
Isoquinoline,  507,  512 

alkaloids,  537 
Isorhamnose,  219 
Isorhodeose,  219 
Isosuccinic  acid,  163 
Isothiocyanates,  98 
Isovaleric  acid,  147,  161 
Itaconic  acid,  294 
Ivory  black,  4 
Ivory  nut,  225 

Japanese  camphor,  457 
Jute,  246 

Kairoline,  510 


INDEX 


SS7 


Keratin,  541 
Kerosene,  4,  118 
Ketohexose,  219 
Ketone  hydrolysis,  208 
Ketones,  72 

Aromatic,  400 

Bicyclic,  455 

Mixed,  400 

Monocyclic,  447 
Ketone  tautomeric  form,  210 
Ketoses,  213 
Ketotetrose,  216 
Ketotriose,  213 
Ketoximes,  109 

Lacmoid,  386 
Lactam  compounds,  410 
,  Lactase,  220,  238 
i-Lactic  acid,  185 
dl-hactic  acid,  3,  176,  182 
/-Lactic  acid,  185 
Lactic  acids,  181 
Lactide,  185 
Lactim  compounds,  410 
Lactobionic  acid,  239 
Lactoid  compounds,  474 
Lactone?,  187 
Lactose,  238 
Lamp  oUs,  118 
Lard,  3,  172 
Laurie  acid,  143 
Laurus  camphor,  457 
Lead,  Sugar  of,  59 
acetate,  59 
"plaster,"  149 
Lecithoproteins,  542 
Lepidine,  511 
Leucine,  252 

Leucomalachite  green,  465 
Levorotatory  compounds,  137 
Levulic  acid,  211 
Levulose,  219,  228 
Liebig  combustion  process,  10 
Light  oU,  306 
Limonene,  445 
Linalool,  459 
Linen,  246 
Linolenic  acid,  301 
Ijnolenin,  301 


Linolic  acid,  301 
Linolin,  301 
Linseed  oil,  3,  301 
Lipase,  165,  172 
Liquors,  distilled,  42 
Litho  oil,  302 
Litmus,  388 
Liver  starch,  244 
Lubricating  oils,  4 
Lutindines,  435,  440 
Lyddite,  379 
Lyxonic  acids,  191 
Lyxose,  218 

Magenta,  469 
Magnesium  citrate,  205 

Methyl  iodide,  22 
Maize,  241 
Malachite  green,  466 
Maleic  acid,  290 
(i-Malic  acid,  196 
J/-Malic  acid,  195 
i-Malic  acid,  3,  193 
Malonic  acid,  156,  159 

"ester  synthesis,"  160 
Malonyl  urea,  267 
Maltase,  220 
Maltobionic  acid,  240 
Maltose,  239 
Malt  sugar,  239 
Mannite,  174 
Mannitol,  174 

hexacetate,  175 

hexanitrate,  174 
i-Mannoheptitol,  175 
Mannonic  acids,  191 
Mannosaccharic  acid,  205 
Mannosans,  225 
Mannoses,  225 
Maple  sugar,  235 
Margaric  acid,  143 
Marsh  gas,  19,  22,  64 

gas  hydrocarbons,  115 
Martins  yellow,  503 
Mauvein,  308 
Medinal,  267 
Melamine,  260 
Melene,  275 
Melissic  acid,  143 


558 


INDEX 


Mellite,  419 

Mellitic  acid,  419 

Melting  point,  determination  of,  8 

i,8(9)-Menthadiene,  445 
Menthane,  329,  445 
Menthol,  447 
Mercaptans,  76 
Mercaptides,  77 
"Mercerized"  cotton,  245 
Mercuric  fulminate,  109 
Mercury  ethyl,  112 
Mesaconic  acid,  295 
Mesitylene,  308,  322 
Mesitylenic  acid,  323,  414 
Mesotartaric  acid,  197,  202 
Mesoxalic  acid,  196 
Meta  benzene   disubstitution   prod- 
ucts, 316,  320 
Metaldehyde,  49 
Metamerism,  31 
Metanilic  acid,  369 
Metanil  yellow,  371 
Metaproteins,  539,  541 
Metastyrene,  479 
Methanal,  47,  64 
Methane,  19,  22,  29,  116 

Arsenic  derivatives,  no 

Halogen  derivatives,  25 

Nitrogen  derivatives,  83 

Oxygen  derivatives,  35 

Phosphorus  derivatives,  no 

Sulphur  derivatives,  76 
Methane  acid  54,  64 

nitrile,  93 

-thiol,  76 
Methanol,  35,  64 
^-Methoxybenzoic  acid,  425 
Methoxyl,  425 
Methyl,  21,  38 

-acetylene,  299 

acrolein,  285 

alcohol,  35,  41,  64,  132,  142 

-amine,  100,  loi 

-^-aminophenol,  380 

-ammonium  salts,  100 

-arbutin,  $3° 
Methylates,  43 
Methyl-benzene,  317 

bromide,  26 


2-Methyl-i,3-butadiene,  443 
2-Methylbutane,  124,  127 
2-Methylbutanol-i,  137 
3-Methylbutanol-i,  136 
Methyl  carbinol,  39,  140 

carbylamine,  94 

chloride,  26 

cyanide,  91 

diethylmethane,  126 
/3-Methyldivinyl,  443 
Methylene,  278 

bromide,  27 

chloride,  26,  28 

iodide,  27 

-succinic  acid,  295 
Methylethylene,  280 
Methyl  ethyl  ether,  46 

ethyl  ketone,  74 

-glucosijes,  528 

-glycocoU,  251 

-hydrazine,  106 

hydroxide,  37 
0-Methylindol,  489 
Methyl  iodide,  26 

isocyanide,  94 

-isopropylbenzenes,  327 

-raercaptan,  76 

-naphthalenes,  498 

orange,  371 
2-Methylpentane,  127 

-phenyl  ether,  375 

-phenylhydrazine,  361 

-phenyl  ketone,  400 

-phosphine,  iro 
2-Methylpropane,  123,  127 
Methylpropane  acid,  146 
Methylpropanols,  133 
2-Methylpropene,  280 
Methyl-pyridonium  hydroxide,  437 

-pyridonium  iodide,  436 

-quinolines,  511 
N-Methylquinoline  tetrahydride,  510 
Methyl  Red,  409 

salicylate,  422 

sulphide,  78 

-sulphonic  acid,  80 

-sulphuric  acid,  68 

-toluenes,  318 

violet,  470 


INDEX 


559 


Metol,  380 

Michler's  hydrol,  401,  464 

Ketone,  401 
Micrococcus  ureae,  263 
Milk,  Sugar  of,  3,  238 
Millon's  reaction,  540 
Mirbane,  Essence  of,  :i:ig 
"Mixed  acid,"  338 

"base"  crudes,  118 

compounds,  176,  247 

ethers,  46 
Molecular  weight,  determination  of, 

12 
Monoacetin,  168 
Monochloro-acetic  acid,  62 

-hydrin,  167 

-hydrin  dinitrate,  168 
Monoethyl  sulphate,  44 
Monosaccharoses,  212,  213 
Monoses,  212,  213 
Mordant,  470 
Morphine,  3,  537 
Moth  balls,  496 
"  Mother-of-vinegar,"  57 
Mucic  acid,  206 
Mucin,  541 
Mucoids,  541 
"  Musk,  Artificial,"  341 
Mustard  gas,  79,  153 

oils,  98 
Mutarotation,  222 
Myosan,  542 
Myricyl  alcohol,  141,  142 
Myristic  acid,  143,  172 
Myrosin,  284 


Naphtha  fraction  of  coal  tar,  306 
Naphthalene,  493 

fraction  of  coal  tar,  306 

hydrides,  495 

-sulphonic  acids,  499 
^-Naphthaquinone-a-oxime,  507 
Naphthaquinones,  506 
Naphthas,  118 
Naphthazarin,  507 
" Naphthenic  base "  crudes,  iiS 
Naphthenes,  117,  328 
Naphthionic  acid,  505 


Naphthols,  500 

0-Naphtholdisulphonic  acids,  503 
Naphthol-sulphonic  acids,  502 

yellow  S,  503 
Naphthylamines,  504 
i-Naphthylamine-4-sulphonic     acid, 

505 
Naphthylaminesulphonic  acids,  505 
/3-Naphthylmethyl  ether,  502 
Narcotine,  538 
Neoparafifins,  127 
Neopentane,  128 
Nerolin,  502 

Neville  and  Winther's  acid,  503 
Nicotine,  3,  533 
Nicotinic  acid,  508 
"Nitre,  Sweet  spirit  of,"  69 
Nitriles,  91,  93 
3-Nitroalizarin,  523 
/>-Nitroaniline  red,  524 
Nitro-anilines,  344 

-benzene,  107,  338 
/>-Nitrobenzenediazonium      chloride, 

356 
Nitro-benzenesulphonic  acids,  369 

-benzoic  acids,  406 

-cellulose,  246 

-chloroform,  108 

compounds,  104,  107 
Nitroform,  108 
Nitrogen,  estimation  of,  10 

absolute  method,  10 

Kjeldahl  method,  11 
Nitro-glycerin,  170 

-mannite,  174 

-methane,  107 

-naphthalenes,  499 

-naphthols,  503 

-phenols,  377 
o-Nitrophenylpropiolic  acid,  482 
Nitroso-benzene,  358 

compounds,  105,  108 
^-Nitrosodimethylaniline,  346 
Nitrosodiphenylamine,  348 
Nitroso-/3-naphthol,  507 
^-Nitrosophenol,  376 
Nitro-starch,  242 

toluenes,  340 

-trichloromethane,  108 


56o 


INDEX 


Nomenclature  of  alcohols,  140 

Geneva,  141 
Nomenclature  of  the  paiaffins,  127 

Geneva,  128 
Nonadecane,  116 
Nonane,  116 
Nonene,  275 
Nonic  acid,  143 
Nonyl  alcohol,  142 
Nonylene,  275 
Normal  hydrolj'sis,  208 
Normal  paraffins,  127 
Nuclein,  542 
Nucleo-histone,  542 
Nucleoproteins,  542 

Octadecane,  116 
Octadecylene,  275 
Octamethylsucrose,  237 
Octane,  116 
Octene,  275 
Octoic  acid,  143 
Octyl  alcohol,  142 
Octylene,  275 
Oenanthylic  acid,  143 
defiant  gas,  275,  276 
define  camphors,  459 
defines,  117,  275,  305 
Oleic  acid,  164,  172,  286,  289 
Olein,  171,  289 
Oleomargarin,  172,  290 
Oleopalmitobutyrin,  171 
Olive  oil,  3,  172,  289 
Optical  activity,  136 
Orange  II,  506 

IV,  371 
Orcein,  388 
Orcinol,  387 
Organic  chemistry,  j. 
Orthoacetic  acid,  207 
Ortho  benzene  disubstitution    prod- 
ucts, 316,  320 
Ovalbumin,  541 
Oxalates,  159 
Oxalic  acid,  156,  157 
Oxalyl  urea,  266 
Oxalureid,  266 
Oxaluric  acid,  267 
Oxamic  acid,  258 


Oximes,  109 
Oxindol,  414 
0.\\acetic  acid,  180 
Oxyanthranol,  520 
Oxybenzoic  acid,  424 
Oxypropionic  acids,  181 
Ozonides,  279 

Palmitic  acid,  143,  148,  164,  172 
Palmitin,  164 
Paper,  246 
Parabanic  acid,  266 
Para   benzene    disubstitution    prod- 
ucts, 316,  320 
Paracyanogen,  83 
"Parafiin  base"  crudes,  118 
Parafiins,  115,  305 

Isomerism  among,  121 

mixed  compound  derivatives,  176 

normal,  127 

oxygen  derivatives  of  the  higher, 
129 

synthesis  of,  1 20 
Paraffin  series,  18 

wax,  4,  118 
Paraformaldehyde,  48 
Paratuchsine,  469 
Paraldehyde,  49,  52 
Paraleucaniline,  467 
Pararosaniline,  467 
Parchment  paper,  245 
Paris  green,  60 
Parvolines,  435 
Pelargonic  acid,  143 
Penicillium  gkucum,  202 
Pentadecane,  116 
Pentadecylene,  275 
Pentadigalloylglucose,  429 
Pentamethylene  dibromide,  441 
Pentane,  19,  116,  124,  126 

diacid,  163 

-pentol-i, 2,3,4,5,  I73 
Pentanes,  123 

Pentane-tetrol-2,3,4,s-als,  216 
Pentanone-4-acid,  211 
Pentasaccharoses,  235 
Pentatriacontane,  116 
Pentene,  275 
Pentosans,  390 


INDEX 


561 


Pentoses,  213,  216 
Pentyl  alcohol,  142 
Pentyl  alcohols,  136 
Peppermint  camphor,  447 
Pepsin,  272 
Peptides,  542 
Peptones,  542 

Perkin's  synthesis,  397,  480 
Perseitol,  175 
Petrohol,  130 
Petrolatum,  118 
Petroleum,  4,  115,  117 

ether,  125 
Phenacetine,  381 
Phenanthraquinone,  527 
Phenanthrene,  525 
^-Phenetidine,  380 
Phenetol,  375 
Phenol,  367,  372 
Phenolates,  372 
Phenol-phthalein,  472 

red,  478 
Phenols,  371 

diacid,  383 

triacid,  388 
Phenol-sulphonic  acids,  381 

-sulphonphthaleins,  412,  478 
Phenoxyl,  425 
Phenyl,  317 

acetate,  376 

-acetic  acid,  413 

-acetic  aldehyde,  398 

-acetylene,  482 

-acrylic  add,  479 

-carbamic  esters,  349 

carbinol,  391 
Phenylenediamines,  345 
Phenyl-ethyl  alcohol,  393 

-ethylene,  479 
(f-Phenylglycosazone,  224 
Phenyl-glycerosazone,  214,  215 

-glycine,  348 

-glycocoU,  348 

-hydrazine,  106,  360 

-hydrazones,  106 
)3-Phenylhydroxylamine,  358 
Phenyl  isocyanate,  349 

magnesium  bromide,  332 

-methane,  317 


-methyl  alcohol,  391 

-nitromethane,  340 

-propiolic  acid,  482 
;3-Phenylpropionic  acid,  415 
Phenyl-propyl  alcohol,  394 

salicylate,  423 

-sulphuric  acid,  376 

tolyl  ketone,  401 

-urethanes,  349 
Phloretin,  530 
Phloridzin,  530 
Phloroglycinol,  389 
Phosgene,  177 
PliDsphine  (dye),  525 
Phosphines,  substituted,  no 
Phosphoproteins,  542 
Phthaleins,  472 
m-Phthalic  acid,  417 
o-Phthalic  acid,  415 
^-Phthalic  acid,  418 
Phthalic  acids,  31  q 

anhydride,  416 
Phthalid,  416 
Phthalyl  chlorides,  417 
Phycocyan,  541 
Phycoerthrin,  541 
PicoUnes,  43-5,  439 
Picramic  acid,  378 
Picramide,  379 
Picric  acid,  4,  378 
Picryl  chloride,  379 
Pimelic  acid,  157 
Pineapples,  essence  of,  146 
Pinene,  443 
a-Pinene,  452 
Pinene  hydrochloride,  453 
Piperidine,  441 
Piperonal,  427 
Piperine,  533 
Piperylpiperidine,  533 
Plant  alkaloids,  532 
Plastics,  47 
Poirrier's  blue,  373 
Polymerism,  31 
Polyoses,  212,  234 

colloidal,  212 
Polypeptides,  271 
Polysaccharoses,  212,  234 

colloidal,  2X2,  240 


562 


INDEX 


Polyterpenes,  443,  460 
Ponceau,  2  R,  506 
Populin,  531 
Potassium  acetate,  59 

citrates,  205 

ferric  ferrocyanide,  89 

ferricyanide,  87,  88 

ferrocyanide,  87 

myronate,  531 

oxalate,  acid,  159 

phthalate,  acid,  417 

tartrate,  acid,  199 

thiocyanate,  90 

xanthate,  178 
Prestolite,  72,  297 
Primary  alcohols,  132 

amines,  104 
Prolamines,  541 
Propadiene,  299 
Propane,  19,  116,  126 

acid,  144 

diacid,  159 

-diol-2,3-acid,  189 

-diol-2,3-al,  213 

-diol-i,3-one,  215 

nitrile,  91 

-triol-1,2,3,  164 
Propanol-2-acid,  182 

-3-acid,  186 

diacid,  192 
Propanols,  129 
Propanone,  72 

acid,  207 
Propargyl  alcohol,  300 
Propenal,  284 
Propene,  275 

acid,  286 

-1-0I-3,  280 
Propine,  299 

acid,  300 

-1-0I-3,  300 
Propiolic  acid,  300 
Propionic  acid,  143,  144 
Propyl  alcohol,  129,  132,  141,  142 

chloride,  146 

cyanide,  146 
Propylene,  130,  275,  278,  280 

chloride,  165 
2-Propylpiperidine,  442 


2-Propylpyridine,  440 
Protamines,  541 
Proteans,  542 
Proteins,  539 

compound  or  conjugated,  541 

derived,  542 

simple,  541 
Proteoses,  542 
Protocatechuic  acid,  425 
Prussian  blue,  88 

soluble,  89 
Prussiate  of  potash,  red,  88 

yellow,  88 
Prussic  acid,  84 
Pseudo  acids,  340 
Pseudocumene,  308,  325 
Pseudosymmetrical  carbon  atom,  1 73 
Pseudouric  acid,  269 
Ptyalin,  239 
Pulegol,  448 
d-Pulegone,  448 

Purification  of  organic  compounds,  4 
Purine,  269 
Purpurin,  524 
Pyrene,  29 
Pyridine,  435,  436 

alkaloids,  533 

bases,  41,  435 
^-Pyridinecarboxylic  acid,  508 
Pyridine  derivatives,  117 
a,/3-Pyridinedicarboxylic  acid,  508 
/S-Pyridyl-n-N-methylpyrrolidine,  533 
Pyrocatechin,  383 
Pyrocatechol,  383 
Pyrogallic  acid,  388 
Pyrogallol,  388 
Pyroracemic  acid,  207 
Pyrrol,  434 
Pyruvic  acid,  207 

"Quick-vinegar  process,"  57 

Quinaldine,  511 

Ouinhydrone,  432 

Quinine,  3,  535 

Quinitol,  432 

Quinoid  compounds,  466,  474 

QuinoUne,  507 

alkaloids,  535 

derivatives,  117 


INDEX 


563 


Quinoline  hydrides,  510 
Quinolinic  acid,  508 
Quinone,  431 

oxime,  376 
Quinones,  431 

of  the  naphthalene  series,  506 
Quinovose,  219 

Racemic  acid,  197,  200 

Radical,  38 

Raffinose,  234 

Reicher-Meissl  number,  172 

Residue,  38  , 

Resins,  Synthetic,  47,  374,  382 

Resolution  o£   inactive   compounds, 

201 
Resorcinol,  385 
Reverse  substitution,  27 
Revertose,  240 
Rhamnitol,  173 
Rhamnose,  218 
Rhodamme  B  and  3B,  478 
Rhodeitol,  173 
Rhodeose,  219 
Rhodinal,  380 
Ribonic  acids,  191 
Riboses,  218 

Ribotrihydroxyglutaric  acid,  205 
RocceUic  acid,  157 
Rochelle  salt,  igg 
Rock  oil,  117 
Rosaniline,  467 
Rosin,  3 

spirits,  327 
R-salt,  503 
Rubber,  3,  460 

Hard,  461 
Rufigallol,  524 
Rum,  42 

Artificial,  70 

Saccharic  acid,  205 
Saccharin,  412 
Saccharomyces,  39 
Saccharose,  235 
Safrol,  3 
Salicin,  531 
Salicylic  acid,  420 
Salmin,  541 


Salol,  423 

"Saltmg  out"  process,  149 
Salvarsan,  379 
Saponification,  71 
Saponins,  531 
Sarcolactic  acid,  3,  185 
Sarcosine,  251 
Saturated  compounds,  273 

paraffin  hydrocarbons,  117 
Schaffer's  acid,  503 
Schweinfurt  green,  60 
Schweitzer's  reagent,  244 
Sebacic  acid,  157 
Secondary  alcohols,  131 

amines,  104 

butyl  alcohol,  134 

butyl  carbinol,  137 

propyl  alcohol,  129,  132,  141 
Seidlitz  powders,  199 
Seignette  salt,  199 
Semicarbazide,  265 
Semicarbazones,  265 
Serine,  253 
Serum  albumin,  541 

globulin,  541 
Sesquiterpenes,  443 
Silicon  tetraethyl,  112 
Silk,  artificial,  246 

Chardonnet,  246 
"Silver  salt,"  521 
Simple  sugars,  212 
Sinigrin,  284,  534 
Skatol,  489 
Skraup  synthesis,  509 
Smokeless  powders,  246 
Soaps,  149 
Sodium  acetate,  59 

ammonium  tartrate,  199 

benzoate,  404 

cyanide,  85 

ethyl,  III 

ferricyanide,  89 

ferrocyanide,  87 

glycol,  152 

methyl,  58 

potassium  tartrate,  igg 
Solanaceous  alkaloids,  534 
Soluble  blue,  471 

cotton,  246 


S04 


rXDEX 


Soluble  eosin,  477 

Prussian  blue,  89 

saccharin,  413 

starch,  241 
Sorbic  acid,  301 
Sorbitol,  175 

Sources  of  organic  compounds,  i 
Space  formulas,  197 
Spatial    isomerism,    137,   292,   330, 

356 
Spermaceti,  141,  148 
Spindle  oils,  118 
Spirit  of  wine,  39 

Yellow,  363 
Spruce  turpentine,  327 
Starch,  2,  241 

Soluble,  241 

paste,  242 

sugar,  243 
Stearic  acid,  143,  148,  164,  172 
Stearin,  164 

candles,  148 
Stereochemistry,  140 
Stereoisomerism,  289,  292,  330,  356 
"Straw  oil,"  307 

Structure  of  organic  compounds,  14 
Strychnine,  3,  185,  537 
Strychnos  alkaloids,  537 
Sturin,  541 
Styphnic  acid,  386 
Styrene,  479 
Styryl  alcohol,  479 
Suberic  acid,  157 
Substituted  ammonias,  100 

hydrazines,  106 

phosphines,  no 

ureas,  265 
Substitution,  25 

Reverse,  27 
Succinic  acids,  156,  161 

anhydride,  162 
Succinimide,  259 
Sucrol,  381 
Sucrose,  235 

octoacetate,  237 
Sudan  G, 386 
Sugar,  2,  23s 

beet,  235 

cane,  235 


Sugar  maple,  235 
Sugars,  complex,  212,  234 

simple,  212 

synthesis  of,  233 

"sand,"  193 
Sulphanilic  acid,  369 
Sulphides,  alkyl,  117 
Sulphoacetic  acid,  187 
o-Sulphobenzoic  acid  dichlorides,  412 
Sulphobenzoic  acids,  411 
Sulphonal,  78 
Sulphonaraides,  368 
Sulphonation,  365 
Sulphones,  78 
Sulphonic  acids,  79 

acids,  aromatic,  365 
Sulphonphthaleins,  478 
Sulphonyl  chlorides,  368 
Sulphoxyl,  80 
Sulphuric  ether,  44 
Suprarenine,  426 
"Sweet  spirit  of  nitre,"  69 
Syrrmietrical  benzene  trisubstitution 

products,  326 
iVH-Compounds,  356 
Synthesis,  24 

Talitol,  17s 
Tallow,  3 

Talomucic  acid,  206 
Talonic  acids,  192 
i-Talose,  227 
Tannic  acids,  429 
Tannins,  3,  429 

Synthetic,  374,  382 
"Tartar,"  199 

emetic,  200 
d-Tartaric  acid,  3,  197,  198 
dZ-Tartaric  acid,  197,  200 
Z-Tartaric  acid,  197,  202 
Tartronic  acid,  192 
Taurine,  254 

Taurocholic  acid,  249,  254 
Tautomcrism,  96,  211,  410 
Teracrylic  acid,  286 
Terephthalic  acid,  418 
Terpane,  329 
Terpenes,  442 

Bicyclic,  452 


INDEX 


565 


Terpenes,  Cyclic,  444 

Monocyclic,  444 
Terpineol,  451 
Terpin  hydrate,  453 
Tertiary  alcoliols,  135 

amines,  104 

butyl  alcohol,  134,  141 

butyl-OT-xylene,  321 
Tetrabromophenolsulphonphthalein, 

478 
Tetracosane,  116 
Tetradecane,  116 
Tetradecylene,  27s 
Tetraethyl-ammonium       hydroxide, 
103 

ammonium  iodide,  103 
p,^-Tetraethyldianiinobenzophenone, 

401 
Tetraethyl-phosphonium   hydroxide, 
no 

-rhodamine,  477 
Tetrahydro-benzene,  329 

-cymene,  329 
or-Tetrahydro-a-naphthol,  501 
o<;-Tetrahydro-/3-naphthol,  502 
<2»'-Tetrahydro-a-naphthylamine,  504 
or-Tetrahydro-^-naphthylamine,  505 
Tetrahydro-phthalic  acids,  419 

-toluene,  329 
Tetrahydroxylenes,  329 
Tetrahydroxydipic  acids,  205 
Tetralin,  496 

Tetramethyl-ammonium    hydroxide, 
103 

-diaminobenzhydrol,  401 

-^-dlaminobenzhydrol,  464 

-diaminobenzophenone,  401 
/',/'-Tetramethyldiaminobenzophe- 

none,  401 
Tetramethyl-^-diaminodiphenylmeth- 
ane,  464 

-diaminotriphenylcarbinol,  466 

-diaminotriphenylmethane,  465 

-methane,  124,  127 
Tetranitro-aniline,  345 

-methane,  108 
Tetraphenylmethane,  462 
Tetrasaccharoses,  235 
Tetrolic  acid,  310 


Tetroses,  213,  216 
Tetryl,  347 
Theine,  270 
Theobromine,  3,  270 
Theophylline,  270 

Thiele-Dennis  melting  point  appara- 
tus, 9 
Thioalcohols,  78 
Thiocarbanilide,  349 
Thiocyanates,  97 
Thiocyanic  acid,  90 
Thiodiglycol,  153 
Thio  ethers,  78 
Thiophene,  309,  434 
ThiosaUcyhc  acid,  424 
Thiourea,  90,  267 
Threonic  acids,  190 
Thymol,  382 

Tiemann  and  Reimer  reaction,  421 
Tin  tetraethyl,  112 
T.  N.  A.,  345 
T.  N.  T.,  4,  341 
Toluene,  307,  317 

halogen  derivatives,  335 

nitro  compounds,  337 

sulphonic  acids,  369 
Toluic  acids,  319,  413 
Toluidines,  350 
Toluquinone,  433 
<ra»j-Compounds,  293,  330 
Triacetamide,  257 
Triacetin,  168 
1,2,4-Triaminobenzene,  365 
Triaminotriphenylmethane,  467 
Tributyrin,  172 
Tricarballylic  acid,  1 73 
Trichloraldehyde,  53 
Trichloro-acetic  acid,  62 

-hydrin,  167 

-propane,  167 

-toluene,  335 
Tricosane,  ii6 
Tricyan-hydrin,  173 

-triamide,  260 
Tridecane,  116 
Tridecylene,  275 
Trielaidin,  290 
Triethyl-amine,  104 

phosphate,  70 


566 


ESTDEX 


Triethyl-phosphine,  no 

-phosphine  oxide,  no 
1,2,4-Trihydroxyanthraqumone,  524 
i,3,S-Trihydroxybenzene,  390 
Trihydroxybenzenes,  388 
3,4,S-Trihydroxybenzoic  acid,  428 
Trihydroxyglutaric  acids,  205 
2,6,8-Triliydroxypurine,  270 
i-Triketocyclohexane,  390 
Trimesitic  acid,  323 
Trimethyl-amine,  100,  102 

-benzenes,  326 

carbinol,  134,  141 

-ethylmethane,  126,  127 

-glycine,  231 

-methane,  128 

-phosphine,  no 
2,4,6-Trimethylpyridine,  439 
1,3,7-Tiimethylxanthine,  270 
i-Trinitroaniline,  379 
i-Trinitrochlorobenzene,  379 
Trinitromethane,  108 
i-Trinitrophenol,  378 
Trinitrophenyhnethylnitroamine,  347 
2,4,6-Trinitroresorcinol,  386 
Trinitro-toluene,  341 

-tertiarybutyl-»i-xylene,  341 
/i-Trinitrotriphenylmethane,  467 
Triolein,  171 
Trional,  79 
Trioses,  213 
Tripalmitin,  171,  172 
Triphenyl-carbinol,  465 

-methane,  462,  464 

-methane  dyes,  467 

-methyl,  465 

-methyl  bromide,  465 

-methyl  peroxide,  465 

phosphate,  376 
Trisaccharose,  234 
Tristearin,  171 
Trivalent  radical,  169 
Tropaeolin,  303,  371 
Tropine  tropate,  S34 
Trypsin,  272 
Tryptophan,  489 
TumbuU's  blue,  88 
Turpentine,  3 

oil  of,  327,  443,  4S2 


Twitchell's  reagent,  165 
Tynan  purple,  487 

Undecane,  116 

Undecylene,  275 

Univalent  radical,  155 

Unsaturated  carbon  compounds,  273 

normal  hydrocarbons,  275 
Unsynmietrical     benzene     trisubsti- 

tution  products,  326 
Uranine,  477 
Urea,  i,  3,  90,  262 
Ureas,  Substituted,  265 
Urease,  264 
Ureids,  266 
Urethanes,  248 
Uric  acid,  3,  267 
Uvitic  acid,  323 

Valeric  acid,  143 
Valeric  acids,  147 
Vanillin,  426 
Vanillic  acid,  428 
Vaseline,  4,  118 
"Vat  dyeing,"  484 
Vegetol,  290 
Veratrol,  385 
Verdigris,  59 
Veronal,  267 

Vicinal  benzene  trisubstitution  prod- 
ucts, 326 
"Vinasse,"  103 
Vinegar,  3 

cider  or  wine,  57 
Vinyl  alcohol,  280 
Viscose,  246 
Vitellin,  542 
Vulcanite,  461 
Vulcanization,  460 

Weizmann  process,  j«,   133 
MThale  oil,  289 
Whey,  238 
Whisky,  42 
Williamson's  blue,  88 
Wine,  Spirit  of,  39 
Wines,  42 

Wintergreen,  oil  of,  422 
Wood,  dry  distillation  of,  35 


INDEX 


567 


Wood  alcohol,  4,  35 

spirit,  35 
sugar,  217 

Xanthic  acid,  178 
Xanthine,  270 
Xanthoproteic  reaction,  540 
Xylans,  217 
Xylenes,  307,  318 
Xylidines,  350 
Xylitol,  173 


Xylonic  acids,  191 
Xyloquinone,  433 
Xyloses,  217 
Xylotrihydroxyglutaric  acid,  205 

Yeast,  39 

Zapon,  140 
Zein,  541 
Zinc  ethyl,  iii 
Zymase,  40 


INGJl,  DEAD 

Professor  of  Organic  Chemistry 

Succumbs  After  Protracted 

Illness 


Professor  "W.  R. ,  Orndoffi,  Professor 
of  Organic  Chemistry,  died  at  his 
home  at  8  o'clock  yesterday  mornlns. 
having  heen  in  ill  health  for  nearly 
tvro  years. 

Professor  Orndoff  was  born  in  Bal- 
timore, Md.,  on  September  9,  1862. 
Hf.  studied  at  Baltimore  City  College 
and  at  Johns  Hopkins,  having  re- 
ceived degrees  of  N.  B.  and  Ph.  D. 
After  that  he  studied  in  the  universi- 
ties of  Griefswald,  Berlin,  Heidelberg, 
and  Munich. 

At  Cornell  he  began  his  work  as  an 
assistant  Instructor  in  chemistry.  In 
1890  he  became  assistant  professor 
and  in  1902  was  made  a  professor. 

He  was  a  member  of  the  Interna- 
tional Jury  of  Awards  at  the  Paris 
Exposition  in  1899,  the  St.  Louis  Ex- 
position in  1904,  and  the  Panama  Ex- 
position  in    1915. 

Among  Professor  Orndoff's  greatest 
works  was  the  writing  of  several 
chemistry  texts  and  laboratory  books 
and  the  translating  oiE  Salkowskl's 
"Physiological  Chemistry." 

He  was  a  member  of  the  American 
Chemical  Society,  Nu  Sigma  Nu,  and 
Sigma  Xi. 

Services  will  be  held  at  his  home 
at  802  Bast  Seneca  Street,  at  3 
o'clock   tomorrow   afternoon. 


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