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\ 



^-.-.-■■^^x ... *- 



AN INTRODUCTION TO THE STUDY 



OF THE 



COMPOUNDS OF CARBON 



OB 



OKGANIC CHEMISTRY 



BY 



IRA REMSEN 

BERB8IDBNT OF THE JOHNS HOPKINS UNIVEBSITT 



FIFTH REVISION 



D. C. HEATH & CO., PUBLISHERS 
BOSTON NEW YORK CHICAGO 






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Ck)PYBiOHT, 1886, 1901, 1903, and 1909, 
By IRA REMSEN 

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PREFACE TO 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 discussed 
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 see for 
himself the reasons for adopting the prevalent 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 follow 
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." 

Without some direct contact with the compounds considered, it 
is impossible to get a clear idea regarding them and their changes. 
A course of properly selected experiments, illustrating the methods 
used in preparing the principal classes of compounds, and the funda- 
mental reactions involved in their transformations, wonderfully facili- 
^ tates the study. The attempt has been made to give directions for 
^^ such a course. More than eighty experiments which could be per- 
CO formed in any chemical laboratory are described; and it is hoped 
1^ that the plan may meet with approval. The time required to 
perform a fair proportion of these experiments is not great; and 
the results in the direction of enlarging the student's knowledge 
^^ of chemical phenomena, will, it is firmly believed, furnish a full 
^^ compensation for the time spent. 

ni 



IV PREFACE. 

The order in which the topics are taken up will be found to differ 
somewhat from that commonly adopted. The object in view was, 
however, not to find a new method, but to find one which would 
bring out as clearly as possible the beauty and simplicity of the 
relations which exist between the different classes of carbon com- 
pounds. The reasons for the method used are given in the body 
of the book. 



PREFACE TO FOURTH REVISION. 

The important advances that have been made in the field of 
organic chemistry during the past few years have made a thorough 
revision of this book necessary. The present edition gives the results 
of the revision. The principal changes and additions will be found 
in the chapters dealing with the Sugars, Stereoisomerism, the Diazo 
Compounds, and the Tei'penes. The treatment of the Aromatic 
Compounds is, in general, fuller than in the older editions. Although 
considerable has been added, the size of the volume has not been 
markedly increased, the difference between the last edition and the 
present being only about fifty pages. In addition to the changes 
indicated above, minor changes have been made throughout, and 
the author believes that the book is now fully in harmony with the 
present state of organic chemistry. 



PREFACE TO FIFTH REVISION 

Advantage has been taken of the resetting of this book to make 
a number of changes that were called for, and the author believes 
that it has been much improved. He gladly acknowledges his indebt- 
edness to Professor W. R. Orndorff of Cornell University for many 
valuable suggestions. Professor Orndorff has used the book for a 
number of years with large classes, and the author has reaped the 
benefit of his experience. 

Baltimobb, August, 1909. 



CONTENTS 

CHAPTER I 
Introduction 

PAGK 

Sonrces of compounds. — Purification of the compounds. — Deter- 
mination of the boiling-point. — Determination of the melting- 
point. — Analysis. — Formula. — Structural formula. — General 
principle of classification of the compounds of carbon . . 1 

CHAPTER II 

Methane and Bthane. — Homoloffous Series 

Methane. — Ethane 21 

CHAPTER ni 

Halogen Derivatives of Methane and Ethane 

Substitution. — Chlor-methane, Brom-methane, lodo-methane. — Di- 
iodo-methane. — Chloroform, bromoform, iodoform. — Chlor- 
ethane, Brom-ethane, lodo-ethane. — Isomerism ... 27 

CHAPTER IV 

Ozygen Derivatives of Methane and Ethane 

Alcohols. — Methyl alcohol. — Ethyl alcohol. — Fermentation. — 
Denatured alcohol. — Alcoholic beverages. — Ethers. — Ethyl 
ether. — Mixed ethers. — Aldehydes. — Formic aldehyde. — 
Acetic aldehyde. — Paraldehyde. — Metaldehyde. — Chloral. 
— Acids. — Formic acid. — Acetic acid. — Acetic anhydride. — 
Acetyl chloride, bromide, iodide. — Ethereal salts or esters. — 
Ketones or acetones 85 

CHAPTER V 

Sulphur Derivatives of Methane and Ethane 

Mercaptans. — Ethyl mercaptan. — Sulphur ethers. — Sulphonic 

acids .,,......,,, 76 



VI CONTENTS 

CHAPTER VI 
Nltrogren Derivatives of Methane and Ethane 



PAGB 



Cyanogen. — Hydrocyanic acid. — Cyanides. — Cyanuric acid. — 
Sulpho-cyanic acid. — Cyanides. — Isocyanides or carbamines. 

— Cyanates and isocyanates. — Sulpho-cyanates. — Isosulpho- 
cyanates or mustard oils. — Substituted ammonias or amines. 

— Hydrazine compounds. — Nitro-compounds. — Nitroso- and 
isonitroso-compounds. — Fulminic acid 80 



CHAPTER VII 

Derivatives of Methane and Ethane containing 
Phosphorus, Arsenic, etc. 

Phosphorus compounds. — Arsenic compounds. — Zinc ethyl. — 

Sodium ethyl. — Retrospect . . • . • • • 104 



CHAPTER Vm 

The Hydrocarbons of the Marsh-Gas Series, or Paraffins 

Petroleum. — Synthesis of parafl&ns. — Isomerism among the paraf- 
fins. — Hexanes 109 

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 alco- 
hols. — Aldehydes. — Acids. — Fatty acids. — Propionic acid. 
— Butyric acids. — Valeric acids. — Palmitic acid. — Stearic 
acid. — Soaps. — Polyacid alcohols and polybasic acids. — Di- 
acid alcohols. — Ethylene alcohol or glycol. — Dibasic acids. — 
Oxalic acid. — Malonic acid. — Succinic acids. — Pyrotartaric 
acid. — Tri-acid alcohols. — Glycerol*. — Ethereal salts of glyc- 
erol. — Fats. — Tribasic acids. — Tetr-acid alcohols. — Pent- 
acid alcohols. — Hex-acid alcohols. — Hept-acid alcohols, etc. . 121 



CONTENTS Vll 

CHAPTER X 
Mixed Compounds. — Derivatives of the Paraffins 

PAOB 

Hydroxy-acids, CnH2n08. — Carbonic acid. — Glycolic acid. — Lactic 
acids. — Hydracrylic ^cid. — Physical isomerism — Hydroxy- 
sulphonic acids. — Isethionic acid. — Lactones. — Hydroxy-acids, 
CnH2n04. — Glyccric acid. — Other Hydroxy-monobasic acids. 

— Mannonic acids. — Gluconic acids, etc. — Hydroxy-acids, 
CnH2n-206. — Tartronic acid. — Malic acids. — Hydroxy-acids, 
CnH2n-206. — Mcsoxalic acid. — Tartaric acid. — Racemic acid. 

— Inactive tartaric acid. — Hydroxy-acids, CnH2n-407. — Citric 
acid. — Hydroxy-acids, CnH2n-208. — Saccharic acid. — Mucic 
acid 157 



CHAPTER XI 

Carbohydrates 

Monosaccharides. — Trioses and te treses. — Glycerose. — Erythrose. 
— Pentoses. — Arabinoses. — Xylose. — Ribose. — Rhamnose. — 
Hexoses. — Glucose. — Fructose. — Mannose. — Galactose. — 
Gulose. — Polysaccharides or complex sugars. — Cane sugar. — 
Sugar of milk. — Maltose. — Polysaccharides that are not sugars. 
— Cellulose. — Gun cotton. — Paper. — Starch. — Glycogen. — 
Dextrin. — Gums 185 



CHAPTER Xn 

Mixed Compounds containing Nitrogen 

Amino-acids. — Amino-formic acid. — Glycocoll. — Sarcosine. — Am- 
ino-propionic acids. — Leucine. — Serine. — Cystine. — Amino- 
sulphonic acids. — Taurine. — Amino-dibasic acids. — Aspartic 
acid. — Acid amides. — Hofmann's reaction. — Amic acids. — 
Asparagine. — Succinimide. — Cyanimides. — Calcium cyan- 
amide. — Guanidine. — Creatine. — Creatinine. — Urea or carb- 
amide and derivatives. — Substituted ureas. — Ureids. — Para- 
banic acid. — Oxaluric acid. — Barbituric acid. — Sulpho urea. 
— Uric acid. — Xanthine. — Theobromine. — Caffeine. — Gua- 
nine. — Polypeptides. — Retrospect 206 



VUl CONTENTS 

CHAPTER XIII 

Unsaturated Carbon Compounds. — Distinction between 
Saturated and Unsaturated Compounds 



PAOR 



Ethylene and its derivatives. — Ethylene. — Alcohols, CnH2nO. 

— Allyl alcohol. — AUyl mustard oil. — : Acrolein. — Acids, 
CnH2n-202. — Aciylic acid. — Crotonic acids. — Oleic acid. — 
Poly basic acids of the ethylene group. — Fumaric and maleic 
acids. — Acids, C6H6O4. — Aconitic acid. — Acetylene and its 
derivatives. — Acetylene. — Propargyl alcohol. — Acids, 
CnH2n-402. — Propiolic acid. — Tetrolic acid. — Sorbic acid. — 
Linoleic acid. — Valylene. — Dipropargyl .... 228 

CHAPTER XIV 

The Benzene Series of Hydrocarbons.— Aromatic 

Compounds 

Benzene. — Toluene. — Xylenes. — Ethyl-benzene. — Mesitylene. — 
Pseudocumene. — Cymene. — Hexahydrobenzenes, naphthenes. 
— Hexamethylene.' — Tetrahydrobenzenes. — Tetrahydrotolu- 
ene. — Hydrocarbons, CioHis. — Hydrocamphene. — Menthene. 

— Dihydrobenzenes 264 

CHAPTER XV 

Derivatives of the Hydrocarbons, CnH2n-6, of the 

Benzene Series 

Halogen derivatives of benzene. — Chlor-benzene. — Brom-benzene. 

— lodo-benzene. — Phenyliodoso chloride. — lodoxy-benzene. 

— Diphenyliodonium hydroxide. — Dibrom-benzene. — Halo- 
gen derivatives of toluene. — Halogen derivatives of the higher 
members of the benzene series. — Nitro compounds of benzene 
and toluene. — Mono-nitro-benzene. — Dinitro-benzene. — Nitro- 
toluenes. — Amino compounds of benzene, etc. — Aniline. — 
Dimethyl-aniline. — Diphenylamine. — Acetanilide. — Tolui- 
dines. — Diazo compounds of benzene. — Diazo-amino com- 
pounds. — Azo-benzene. — Hydrazo-benzene. — Hydrazines. — 
Phenylhydrazine. — Methylphenylhydrazine. — Sulphonic acids 
of benzene. — Sulphanilic acid. — Helianthin. — Diphenylamine 
orange. — Phenols, or hydroxyl derivatives pf benzene, etc. ^- 



CONTENTS IX 

PAOB 

Mon-acid phenols. — Phenol. — Methyl-phenyl ether. — Tri- 
nitro-phenol. — Amino-phenols. — Phenol-sulphonic acids. — 
Phenyl mercaptan. — Cresols. — Thymol. — l)i-acid phenols. — 
Pyrocatechol. — Guaiacol. — Resorcinol. — Styphnic acid. — 
Hydroquinol. — Orcinol. — Tri-acid phenols. — Pyrogallol. — 
Phloroglucinol. — Alcohols of the benzene series. — Benzyl alco- 
hol. — Aldehydes of the benzene series. — Oil of bitter almonds. 

— Cuminic aldehyde. — Benzaldoximes. — Acids of the benzene 
series. — Monobasic acids, CnH2n-802. — Benzoic acid. — Ben- 
zoyl chloride. — Substitution-products of benzoic acid. — Nitro- 
benzoic acids. — Anthranilic acid. — Isatine. — Hippuric acid. 

— Sulpho-benzoic acids. — Toluic acids. — a-Toluic acid. — 
Oxindol. — Mesitylenic acid. — Hydro-cinnamic acid. — Hydro- 
carbostyril. — Dibasic acids, CnH2n-io04. — Phthalic acid. — 
Isophthalic acid. — Terephthalic acid. — Hexabasic acid. — Mel- 
litic acid. — Phenol-acids, or Hydroxy-acids of the benzene series. 

— Salicylic acid. — Salol. — Oxybenzoic acid. — Para-oxy ben- 
zoic acid. — Anisic acid. — Di-hydroxy-benzoic acids, C7H6O4. — 
Protocatechuic acid. — Vanillic acid. — Vanillin. — Piperonal. — 
Tri-hydroxy-benzoic acids, CtHoOs. — Gallic acid. — Tannic acid. 
Ketones and allied derivatives of the benzene series. — Quinones. 

— Pyridine bases. — Pyridine. — Lutidines. — Conyrine. — Co- 
nine. — Terpenes and camphors. — Hemiterpenes. — Terpenes. — 
Monocyclic terpenes. — Bicyclic terpenes. — Pineue. — Oil of tur- 
pentine. — Caraphene. — Camphane. — Sesqui- and polyterpenes. < 
— Caoutchouc. — Camphors. — Monocyclic camphors.- Bicyclic 
camphors.— Borneol.— Camphor.— Artificial camphor.— Geraniol 277 

CHAPTER XVI 

Di-phenyl-methane, Tri-phenyl-methane, Tetra-phenyl- 
methane, and their Derivatives 

Tri-phenyl-methane. — Trinitro-triphenyl-methane. — Triamino- 
triphenyl-methane. — Tri-phenyl-methane dyes. — Aniline dyes. 

— Para-rosaniline. — Rosaniliiie. — Hexa-methyl para-rosani- 
line. — Phthalelns. — Phenol-phthalem. — Fluorescein. — Eosin 362 

CHAPTER XVII 
Hydrocarbons, C„H2n-8, and Derivatives 

Styrene. — Styryl alcohol. — Cinnamic acid. — Nitro-cinnamic acids. 

— Amino-cinnamic acids. — Coumarin 374 



CONTENTS 

CHAPTER XVIII 
Phenyl-acetylene and Derivatives 



PAGE 



Phenyl-acetylene. — Phenyl-propiolic acid. — Ortho-nitro-phenyl- 
propiolic acid. — Indigo and allied compounds. — Indigo-blue. 
— Indigo-white. — Indol. — Skatol 380 

CHAPTER XIX 

Hydrocarbons containingr Two Benzene Residues in 

Direct Combination 

Diphenyl. — Benzidine. — Carbazol. — Naphthalene. — Derivatives 
of naphthalene. — Naphthylamines. — Naphthols. — Quinoline 
and analogous compounds. — Quinoline. — Quinaldine. — Lepi- 
dine. — Carbostyril. — Isoquinoline 386 

CHAPTER XX 

Hydrocarbons containingr Two Benzene Residues in 

Indirect Combination 

Anthracene. — Anthraquinone. — Alizarin. — Purpurin. — Phenan- 

threne 407 



CHAPTER XXI 

Glucosides. — Alkaloids, etc. 

-^Esculin. — Amygdalin. — Arbutin. — Coniferin. — Helicin. — My- 
ronic acid. — Phloridzin. — Salicin. — Saponin. — Alkaloids. — 
Quinine. — Cinchonine. — Cocaine. — Nicotine. — Stropine. — 
Tropine. — Morphine. — Codeine. — Narcotine. — Piperine. — 
Piperidine. — Strychnine. — Albumin. — Peptones . . . 415 

Index 421 



CHEMISTET 



OF THB 



COMPOUNDS OF CARBON 



-•o»- 



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, though partly on 
account of peculiarities in their chemical conduct, it is custom- 
ary to treat of these compounds by themselves. At first, 
General Cliemistry 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 compounds which form the mineral portion of 
the earth 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 compounds 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 process has no part. Gradually, however, 
this idea has been abandoned ; for, one by one, many of the 
compounds which are found in plants and animals have been 
made in the chemical laboratory, and without the aid of the 
life process. The first instance of the artificial preparation of 
an organic compound was that of urea. This substance was 
obtained by Wohler in 1828 from ammonium cyanate. When 
a water solution of the latter is evaporated on a water bath, 

1 



25 INTRODUCTION 

urea is deposited. Up to the time of Wohler's discovery, the 
formation of urea, like that of other organic compounds, was 
thought to be necessarily connected with the life process; 
but it was thus shown that it 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 oxidation, it follows that 
urea can be made from the elements. Finally, in 1856, Berthe- 
lot succeeded in making potassium formate by passing carbon 
monoxide over heated potassium hydroxide; and in making 
acetylene, a compound, the composition of which is represented 
by tjie formula C2H2, by passing an electric arc between carbon 
poles in an atmosphere of hydrogen. Since that time, every 
year has witnessed the artificial preparation, by purely chemi- 
cal 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 
carbon is not dependent upon the life process ; that they are 
simply chemical compounds governed by the same laws that 
govern other chemical compounds; and the name. Organic 
Chemistry y signifying, as it does, that the compounds included 
under it are necessarily related to organisms, is misleading. 
Organic chemistry is nothing but the Chemistry of the Com- 
pounds of Carbon, 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 silicon, 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. 



SOURCES OF COMPOUNDS 3 

This objection is of weight only as far as the carbonates 
are concerned, and it does not appear strong enough to make 
the introduction of a new name necessary. It should be men- 
tioned, however, that the name Ohemistry of the Hydrocarbons 
and their Derivatives has been suggested. The exact signifi- 
cance of this name will appear when the compounds with 
which we shall have to deal come up for consideration. 

Sources of compounds. — The compounds of carbon are, 
for the most part, made in the laboratory; but in preparing 
them we usually start with a few fundamental compounds 
that are formed by natural processes. A large number, such 
as the sugars, starch, cellulose, and the alkaloids, of which 
morphine, quinine, and nicotine are examples, occur ready 
formed in plants, but always mixed with other substances. 
Others, such as urea, uric acid, albumin, etc., occur in animal 
organisms. Petroleum^ which has been formed in nature by 
processes, the exact nature of which has not yet been satis- 
factorily explained, contains a large number of compounds con- 
sisting of only carbon and hydrogen; and these compounds 
serve as the starting-points in the preparation of a large num- 
ber of derivatives. When coal is heated for the purpose of 
manufacturing illuminating gas, a very complex mixture of 
liquid and solid products is obtained as a by-product, known 
as coal tar. This substance yields some of the most valued 
compounds of carbon. A larger number of the compounds of 
carbon are obtained from this than from any other one source. 
When bones are heated in the manufacture of bone-black, an 
oil known as hone oil is obtained. This also has proved to be 
the source of a large number of interesting compounds. In 
the preparation of charcoal by heating wood, the liquid prod- 
nets are generally condensed, and they form the source of 
several important compounds, araong which may be mentioned 
wood spirit or methyl alcohol, acetone, and pyroligneous or 
acetic add. 



4 INTRODUCTION 

Finally, we are dependent upon the process known as /er- 
mentatioii for a number of the most important compounds of 
carbon. Fermentation, as will be shown, is a general term, 
signifying any process in which a change in the composition 
of a body is effected by means of minute animal or vegetable 
organisms. The best known example of fermentation is that 
of sugar, which gives rise to the formation of ordinary alcohol. 
Alcohol in turn serves as the starting-point for the preparation 
of a large number of compounds. 

Puriflcation of the compomids. — Before the natural 
compounds of carbon can be studied chemically, they must, of 
course, be freed from foreign substances ; and before the con- 
stituents 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 difficult. If the substance is a solid, different 
methods may be used according to the nature of the substance. 
Crystallization is more frequently made use of than any other 
process. This is well illustrated, on the large scale, in the 
refining of sugar, which consists, essentially, in dissolving the 
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 crystallizor 
tion. This consists in evaporating the solution until, on cool- 
ing, 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 
successive deposits thus obtained are then recrystallized, each 
separately, until, finally, the deposits are found to be homo- 
geneous. 

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



r 



PURmCATIOS OF THE COMPOUNDS 



In fhe case of liquids, the process of distiUaiion. is used. 
The apparatus commonly used is illustrated in Fig. 1. 




The only part of the apparatus that 
tion ia the tube A. This is known as 
It is simply a straight glass 
tube, about IG"" long and 12 to 
14""" in diameter, to which is 
attached a smaller branch some- 
what inclined downward. The 
object of the tube is to accom- 
modate a thermometer B, which 
is so fixed by means of a cork, 
that it ia in the centre of the 
largertube, and its bulb directly 
below the opening of the smaller 
branch. 

For small quantities of liquids, 
the distilling flask is mucli used. 




6 INTRODUCTION 

flask, with a branch tube fitted directly to the neck, as shown 
in Fig. 2. In this apparatus, the thermometer is fitted into 
the neck of the flask in the same relation to the exit tube as 
in the larger apparatus. 

For the separation of liquids of different boiling-points, the 
process oi fractional or partial distillation is much used. "When 
a mixture of two or more liquids of different boiling-points is 
boiled, it will be noticed that the boiling-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 temperatures 
differ from each other in composition. Those obtained at the 
lower temperatures are richer in alcohol than those obtained 
at the higher temperatures, but none of them contains pure 
alcohol or pure water. In order to separate the two, therefore, 
we must proceed as follows : A number of clean, dry flasks ai'C 
prepared for collecting the distillates. The boiling is begun, 
and the point at which the first drops of the distillate appear 
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 receiver 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 different temperatures. 
In the case of alcohol and water, for example, we might have 
collected distillates from 78° to 83°, from 83° to 88°, from 88" 






PURIFICATION OF THE COMPOUNDS 7 

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 in 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 boiling this fraction the second time 
it will not all come over between these points; when 83° is 
reached some will 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 
boiling, and ponr in fraction No. 3, and so on until all the 
fractions have been subjected to a second distillation. On 
examining the new fractions, it will be found that the liquid 
tends to accumulate in the neighborhood of certain points cor- 
responding 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 effected. By 
continuing the distillation in this way, pure substances can, in 
most cases, eventually be obtained. That the fractions are 
pure can be known by the fact that the boiling-points remain 
constant. In some cases perfect separation cannot be effected 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 ren- 
dering the process of fractional distillation more rapid and 
more efficacious. One of these that has been extensively used 



8 INTRODUCTION 

with good results is the Hempel tube. This is " a wide ver- 
tical tube, filled with glass beads of special construction, and 
constricted below to prevent the beads falling out. A short, 
narrower, vertical 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 
eflB.cient.^ 

Experiment 1. Mix equal parts (about half a litre of each) of alco- 
hol and water. Distil through four or five times, and notice the changes 
in the quantities obtained in the different fractions. 

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 prop- 
erty utilized for this purpose is the boiling temperature, 
commonly called the boiling-point. This is determined by 
means of an apparatus, such as is described above as used for 
distilling. The temperature noted on the thermometer when 
the liquid is boiling is the boiling-point. When great accuracy 
is required, the point observed 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 con- 
stant boiling-point under the same barometric pressure. On 
the other hand, a constant boiling-point does not necessarily 
indicate a pure compound. 

* See " Fractional Distillation." By Sidney Young (Macmillan). 



DETERMINATION OF THE MELTING-POINT 



Determination of the melting-point. — Just as the boil- 
ing-point is a very characteristic property of liquid bodies, so 
the melting-point is an equally characteristic property of many 
solid bodies. If a substance begins to melt at a certain tem- 
perature, 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 
follows : Small tubes are prepared by heating a piece of ordi- 
nary soft glass tubing of 4™™ to 5"""* diameter, and drawing it 
out. If the parts are drawn apart about 12°"' to 
15*"™, two small tubes may be made from the nar- 
rowed portion by melting together in the middle, 
and then filing off each piece where it begins to 
grow wider near the large tube. These small 
tubes must have thin walls, and be of such inter- 
nal diameter that an ordinary pin can be intro- 
duced into them. A small quantity of the sub- 
stance 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 in a small glass flask 
containing pure sulphuric acid (see Fig. 3). The sulphuric 
acid is gently heated by a small flame until the substance 
melts. 

A convenient form of apparatus for determining melting-points 
consists of a tube about 2*^™ wide and 12'=°' long, to which a side 





10 INTRODUCTION 

bube of I*'™ diameter is so fused that it connects the lower end of 
bhe main tube with the middle (see Fig. 4). Just enough 

sulphuric acid is put into it to close the upper 
end of the side tube. The thermometer is placed 
so that the bulb is midway between the two 
openings of the side tube. On heating the tube 
at the point A, the sulphuric acid begins to circu- 
late in the apparatus in such a way that it passes 
downwards in the main tube. The instant the 
substance melts the temperature indicated by the 
thermometer is noted. This is the melting-point 
required. It is necessary, however, to correct the observed 
point in the same way as in the case of the boiling-point. 

Experiment 2. . Determine the melting-points of a few substances, 
such as urea and tartaric acid. If they do not melt at definite points, 
recrystallize them until they do. Note the melting-points observed, and 
jee how well they agree with those stated in the book. The mercury of 
the thermometer should rise slowly. 

Analysis. — Having purified the compounds, the next step 
is to determine their composition. A comparatively small 
aumber of the compounds ordinarily met with consist of car- 
bon and hydrogen only ; the largest number consist of these 
bwo elements together with oxygen; many contain carbon, 
tiydrogen, 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; 
md any metal may occur in the salts of the acids of carbon, 
rhe estimation of carbon and hydrogen is the principal prob- 
lem in the analysis of the compounds of carbon. This is 
3ffected by what is known as the combustion process. A known 
iveight of the substance is completely oxidized, the carbon 
being thus converted into carbon dioxide, and the hydrogen 
into water. These two products are collected, the water in 
jalcium chloride, the carbon dioxide in a solution of potassium 



V 



ANALYSIS 11 

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 sura 
subtracted from 100. The difference is the percentage of 
oxygen. 

A detailed description of the apparatus and of the method 
of procedure need not be given here, as it can be found in any 
book on analytical 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 furnace con- 
structed for the purpose. Ordinarily, the substance is placed 
in a narrow porcelain or platinum vessel, called a boat, which 
is introduced into the tube with granulated copper oxide. 
The tube is then connected with (1) a U-tube filled with cal- 
cium chloride; (2) a set of bulbs containing a solution of 
potassium hydroxide, and constructed so as to secure thorough 
contact of the passing gases with the solution ; and (3) a small 
U-tube half filled with solid potassium hydroxide, and the 
other half with calcium chloride. During the combustion, a 
current of pure dry oxygen is passed through the tube; and, 
finally, air is passed until the oxygen is displaced. The 
method at present used was devised by Liebig. It has con- 
tributed 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 means of 
copper oxide; then decomposing, by means of highly-heated 
metallic copper, any oxides of nitrogen which may have been 
formed, and collecting the nitrogen. The volume of the nitro- 
gen thus obtained is measured, and its weight easily calculated. 
The chief difiiculty in this method consists in removing the 
air contained in the apparatus before "the combustion is made. 
The simplest way is to pass pure carbon dioxide through the 
apparatus until the gas that passes out is completely absorbed 



12 INTRODUCTION 

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 
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 
hydroxide, leaving the nitrogen thus alone. 

The method now most extensively used is that devised by 
Kjeldahl. This consists in heating the substance with con- 
centrated sulphuric acid, potassium sulphate, and a little cop- 
per sulphate or mercury. 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 and hydrogen 
are oxidized, and the sulphur is left in the form of potassium 
sulphate, and 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. 





Percentage 


c 


62.18 


H 


13.04 





34.78 



FORMULA 13 

To get the atomic proportions, divide the figures representing 
the percentages of the elements by the corresponding atomic 
weights. We have thus : — 

At. Wt. Relative No. of Atoms 

12 = 4.35 - 2 

1 = 13.04 - 6 

16 = 2.17 - 1 

That is to say, accepting the atomic weights, 12 for carbon and 
16 for oxygen, the simplest figures representing the number of 
atoms of the three elements in the compound are 2 for carbon, 
6 for hydrogen, and 1 for oxygen. According to this, the 
simplest formula that can be assigned to a substance giving 
the above results on analysis is C2H6O. But the formula 
C4H12O2 is equally in accordance with the analytical results, 
and we can only decide between the two by determining the 
molecular weight. This is done by determining the specific 
gravity of the substance in the form of vapor. It is assumed 
that the student, who has already studied the elements of 
inorganic chemistry, is familiar with the methods used in 
determining the specific gravity of vapors, and with the con- 
nection that exists between the specific gravity and the molec- 
ular weight of the compound. A few statements in regard 
to the connection will, however, be made here, in order to 
impress upon the mind of the student its fundamental 
importance. 

Every chemical formula is intended to represent the mole- 
cule of a compound and the composition of the molecule. Our 
conception of the molecule is based almost exclusively on 
Avogadro's hypothesis, according to which equal volumes of 
all gases contain the same number of molecules under the same 
conditions of temperature and pressure. Hence, by comparing 
equal volumes of bodies in the form of gas or vapor, we get 
figures which bear to each other the same relations as the 
weights of the molecules. The figures called the specific gravi- 



14 INTRODUCTION 

ties express the relations between the weights of equal volumes. 
In the case of gases, air is taken as the standard, and the 
Weights of other gases are compared with this standard. Thus, 
if we say that the specific gravity of a gas is 0.918, we mean that 
if we call the weight of any volume of air 1, that of the same 
volume of the other gas measured under the same conditions of 
temperature and pressure is 0.918. If we assign to any com- 
pound a certain molecular weight, the molecular weights of other 
gaseous compounds can be determined without difficulty. We 
must, therefore, first select some substance, the molecule of 
which may be used as the standard. Hydrochloric acid is 
commonly taken, because hydrogen and chlorine unite with 
each other in only one proportion, and there is good evidence 
in favor of the view that it represents the simplest kind of 
combination, viz., that of onB atom of one element with one of 
another. Hydrogen and chlorine are present in the compound 
in the proportion of 1 part by weight of hydrogen to 35.4 parts 
by weight of chlorine; hence the simplest molecular weight 
that can be assigned to the compound, the atomic weight of 
hydrogen being 1, is 36.4. The molecular weight of this 
standard molecule is, therefore, taken to be 36.4, and we have 
now simply to compare the weights of other gases with that 
of hydrochloric acid in order to know their molecular weights. 
Thus to illustrate by means of the compound whose atomic re- 
lations we found by analysis to be represented by the formula* 
C2HeO, C4H12O2, etc. If this compound is converted into vapor 
and its specific gravity determined, it might be found to be 
1.6. The relation between the molecular weight of any body 
and its specific gravity is expressed by the equation 

M= d X 28.87, 

in which M is the molecular weight, and d the specific gravity 
of the substance in the form of gas or vapor. As cZ is 1.6 in 
the case under consideration, we have 

M (the unknown molecular weight) = 1.6 x '28.87 = 46.2. 



STRUCTURAL FORMULA 15 

If the formula of the compound is C2n60> ^^^ molecular weight, 
being the sum of the weights of the constituent atoms, is 

2x12 + 6x1 + 16 = 46, 

which agrees with the figure deduced from the specific gravity. 
It therefore follows that the formula CaHgO is correct. 

The molecular weight of an acid can be determined by 
analyzing its salts. To illustrate this take acetic acid. This 
is a monobasic acid, that is to say it gives but one silver salt 
and contains but one replaceable hydrogen atom. Now analysis 
of acetic acid shows that it has the composition represented by 
the formulas CHgO, C2H4O2, CgHgOg, etc. The analysis of the 
silver salt shows that it must be represented by the formula 
CgHgOgAg and not CHOAg, and hence the molecular formula 
of acetic acid is C2H4O2 and not CH2O. 

By determining the boiling-points and by determining the 
freezing-points of solutions it is possible to determine the 
molecular weights of many compounds of carbon. This is 
due to the fact that, in the case of any given solvent, weights 
of different compounds of carbon bearing to one another the 
same relation as their molecular weights cause the same ele- 
vation of the boiling-point of the liquid and the same depres- 
sion of the freezing-point. The details of these methods cannot 
be given here. 

Structural formula. — The formulas CgHgO, C2H4O2, CgHg, 
etc., tell us simply the composition of the three compounds 
represented, and tell us also the weights of their molecules. 
In studying the chemical conduct of these compounds, their 
decompositions, and the modes of preparing them, we become 
familiar with many facts which it is desirable to represent by 
means of the formulas. Thus, for example, but 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 atoms, and it is natural to conclude that it is 
held in the molecule in some way differently from the other 



16 INTROPUCTION 

three. We may, therefore, write the formula C2H3O2.H, which 
is intended to call attention to this difference. By further 
study of acetic acid, we find that the particular hydrogen, 
^hich gives to it acid properties, and which, in the above 
formula, is written by itself, is intimately associated with 
oxygen. It can be removed with oxygen by simple reactions, 
and the place of both taken by one atom of some other ele- 
ment; as, for example, chlorine. Thus, when acetic acid is 
treated with phosphorus trichloride, PClg, it is converted into 
acetyl chloride, C2H8OCI. 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 between the hydrogen and 
oxygen in the acid. Further, when acetyl chloride is heated 
with water, acetic acid is regenerated, hydrogen and oxygen 
from the water entering into the place occupied by the chlo- 
rine, as represented in this equation : — 

CaHgOCl + H2O = C2HA+HCI. 

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 lan- 
guage by the formula C2H3O.OH, which may serve as a simple 
illustration of what are called structural or constitutional for- 
mulas. 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 or 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 language in which they are written to see 
relations which might easily escape his attention without their 
aid. In order to understand them, however, the student must 



CLASSIFICATION OP COMPOUNDS OF CARBON 17 

have a knowledge of the reactions upon which they are based ^ 
and he is warned not to accept any chemical formula unless he 
can see the reasons fdr accepting it. He should ask the ques- 
tion, upon what facts is it based f whenever a formula is pre- 
sented for the first time. If he does this conscientiously, he 
will soon be able to use the language intelligently, and the 
beauty of the relations that exist between the large number 
of compounds of carbon will be revealed to him. If he does 
not, his mind will soon be in a hopeless muddle, and what he 
learns will be of little value. For the beginner, this advice is 
of vital importauQC : Study with great care the reactions of com- 
pounds; study the methods of making them, and the decomposi- 
tions which they undergo. The formulas are but the condensed 
expressions of the conclusions which are drawn from the reactions. 

General principle of classification of the compounds 
of carbon. — In considering the elements and compounds in- 
cluded under the head of Inorganic Chemistry, the fundamental 
substances are, of course, the elements. The properties 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 generallv 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 the same similarity is met 
with. Then, in turn, the oxygen and the oxygen and hydrogen 
compounds are considered, and again the resemblances in 
properties between the corresponding compounds of chlorine, 
bromine, and iodine are met with. We thus have groups of 
elements, and of the derivatives of these elements, as, — 



Cl 


CIH 


CIO.H 


Br 


BrH 


BrOsH 


I 


IH 


IO3H, etc. 



18 INTRODUCTION 

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 
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 
compounds, the system can be carried out much more perfectly; 
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 caibon 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 hydrocar- 
bons, which correspond somewhat to the different groups of 
elements. The members of one and the same series of hydro- 
carbons resemble one another more closely than the members of 
one and the same series of elements. Although we have indica- 
tions of the existence of more than ten series of these hydrocar- 
bons, 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 : (1) 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 derivatives. But the 
relations existing between any hydrocarbon and its derivatives 



CLASSIFICATION OF COMPOUNDS OF CARBON 19 

are the saine 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, is apt to feel overwhelmed by the enormous 
number of compounds 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 indicat- 
ing the extent to which the series to which they belong have bee*i 
developed. In general, the members of any series so closel^f 
resemble one another, that, if we understand the simpler mem- 
bers, 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 notion 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 two members will be treated of. 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 hydro- 
carbons and their derivatives, we may acquire a knowledge of the 
principal classes of the compounds of carbon. After these typical 
derivatives have been discussed, the entire series of hydrocar- 



20 INTRODUCTION 

bons 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 has been 
obtained, a second series will be taken up and treated in a 
similar way, and so on. But, as already stated, only a few 
of the series require much attention at the beginning. The 
first series that will be used for the purpose of illustrating the 
general principles is one of the two most important series, and 
of the onjy two that need be taken up at all fully at present. 



CHAPTER II 

METHANE AND ETHANE — HOMOLOGOUS SERIES 

If 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 with marked power 
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 remark- 
able series, the first six members of which, together with their 
formulas, are included in the subjoined table : — 

Methane (or Marsh Gas) . . . ; CH4 

Ethane CgHg 

Propane CgHg 

Butane C4Hio 

Pentane .... C5H12 

Hexane C6H14 

On examining the formulas given, it will be seen that the dif- 
ference in composition between any two consecutive members 
is represented by CHg. Thus, adding CH2 to marsh gas, CH4, 
we get ethane, C2He ; 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 CH2, is 
called an homologous series. 

Just as the members of an homologous series of hydrocarbons 
differ from one another by CHg, or some multiple of it, so 

21 



22 METHANE AND ETHANE 

also the members of any class of derivatives of these hydro- 
carbons differ from one another in the same way, and form 
homologous series. Thus, running parallel to the hydrocarbons 
mentioned above, there are two homologous series of oxygen 
derivatives, as indicated below : — 

CH4 -CH4O -CH2O2 
CgHg — C2HeO — C2H4O2 
CsHg — CsHgO — C3He02 

C4H10 — C4H10O — C4Hg02 

C5H12 — C5H12O — C5H10O2 
C(jHi4 — C6H14O — C6H12OJ 

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 
observed 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. Consider, 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 complexity as we pass from chlorine to 
iodine. Or, at least, 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 similar members of an 
homologous series. While, however, a satisfactory hypothesis 
has been offered to account for the latter fact, and experi- 



, METHANE AND ETHANE 23 

mental evidence is strongly in favor of the hypothesis, no satis- 
factory explanation of the former has been offered ; or rather 
no satisfactory experimental evidence has been furnished in 
favor of the various hypotheses which from time to time have 
been put forward to account for the similarity between members 
of the same group of elements. 

The view at present held in regard to the nature of homology 
is founded, primarily, upon the idea that carbon is quadrivalent. 
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 union 
taking place directly between the molecules CH4 and CH4, but 
we can conceive of union taking place between the molecules 
CHg and CHg, to form a molecule C2H8, which in turn is satu- 
rated. 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 
I H 

H I 

unsaturated residue H-C-, which is capable of uniting with 

I 
H 

another residue of the same kind to form the more complex 

H H 

I I 
molecule H— C~C— H, or C2HQ, which is believed to express 

I i. 
H H 

the relation existing between marsh gas, CH4, and ethane, CgHg, 
or between any two adjoining members of an homologous series. 
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 generally 



24 METHANE AND ETHANE ^ 

accepted, involves the idea that carbon atoms have the power 
of uniting with each other. And, as the explanation for the 
relation between the first and second members is, in principle, 
the same as for the relation between the second and third, the 
third and fourth, etc., it appears that this power of carbon atoms 
to unite with one another is very extensive. It is to the power 
which carbon possesses of forming homologous series, or to the 
power of the atoms of carbon to unite with each other, that we 
owe the large number of compounds of this element. 

Methane, marsh gas, fire damp, CH4. — This hydro- 
carbon 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 col- 
lected by holding the funnel over the bubbles rising from the 
bottom. It is also found in large quantities mixed with air, 
in coal mines, and sometimes issues from the earth, together 
with other gases, in the neighborhood of petroleum wells. It 
is a constituent of natural gas. 

It can be prepared 

(1) By treating aluminium carbide, C3AI4, with water : — 

C3AI4 + 12 H2O = 3 CH4 -f- 4 Al (0H)3. 

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

(3) By reduction of carbon monoxide or dioxide with calcium 
hydride. 

(4) By heating finely-divided carbon with calcium hydride. 

(5) By direct combination of carbon and hydrogen at 1150®. 
It is formed, as its occurrence in marshes indicates, by the 

decomposition of organic matter under water. In pure condi- 
tion it is made most readily by heating a mixture of sodium 
acetate and soda-lime : — 

NaCgHgOa + NaOH = CH4 + Ka-^COg. 

It will be shown hereafter that most acids of carbon break up 
in a similar way, yielding a hydrocarbon and a carbonate. 



METHANE (MARSH GAS, FIRE DAMP) 25 

Properties. Marsh gas is colorless and inodorous. It is 
slightly soluble in water, but not so much so as to prevent its 
collection over water. It burns. Its mixture with air often 
explodes when a flame is applied. This mixture is the cause 
of some of the explosions in coal mines. In ordinary language 
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. 

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

Elxperiment 3. Make marsh gas. Dehydrate some sodium acetate 
by heating it in a porcelain dish on wire gauze over a small flame. Use 
10« of sodium acetate and 20* of powdered soda-lime. Collect the gas 
over water. Bum some as it escapes from a jet. In small quantities it 
does not readily explode v^ith air. 

Reagents, in general, do not act readily upon marsh gas. 
Chlorine in diffused daylight gradually takes the place of the 
hydrogen, forming a series of compounds 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 chlor-methane or methyl 
chlonde. 

Ethane, 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 chlor-methane, CH3CI. As the cor- 
responding iodine derivative is less volatile, it is used. This 
iodo-methane^ CH3I, is treated with zinc or sodium in some 



26 METHANE AND ETHANE 

neutral medium, as, for example, anhydrous ether. The reac- 
tion which takes place is represented thus : — 

CH3I + CH3I + 2 Na = CgHe + 2 Nal. 

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

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 tetrathionic acid from sodium thiosulphate. The action is 
represented thus : — 



Na,S A j 



+^-n:s:o:>+'^^- 



Two uiol. sodium Sodium tetra- 

thiosulpliate thionate 



CHAPTER III 

HALOGEN DERIVATIVES OF METHANE AND ETHANE 

Substitution. — When methane and chlorine are brought 
together in diffused daylight, action takes place gradually; 
hydrochloric acid gas is given off, and one or more products 
are obtained, according to the length of time the action con- 
tinues. The products have been studied carefully, and four 
have been isolated. The composition of these products is rep- 
resented by the formulas CH3CI, CH2CI2, CHCI3, and CCI4. 
We see thus that the action of chlorine consists in replacing, 
step by step, the hydrogen of the hydrocarbon. The action is 
represented by the four equations : — 

(1) CH4 + CI2 = CH3CI + HCl 

(2) CHgCl + CI2 = CH2CI3 -h HCl 

(3) CH2CI2 + CI2 = CHCls + HCl 

(4) CHCI3 + CI2 = CCI4 + HCl. 

This replacement of hydrogen by chlorine is an example of 
what is known as substitution. We shall find that most hydro- 
carbons are susceptible to the influence of the halogens and 
a number of other reagents, such as nitric acid, sulphuric 
acid, etc., 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 substituted 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 

27 



28 DERIVATIVES OF METHANE AND ETHANE 

occupy the same plaxje, or bear the same relation to the carbon 
atom as the hydrogen did. 

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. The last are, however, 
not commonly called substitution-products. 

Chlor-methane, methyl chloride, CH3CI. 

Brom-methane, methyl bromide, CHgBr. 

lodo-methane, methyl iodide, CH3I. 

The chlorine and bromine products can be made by treating 
methane with the corresponding element. They can be most 
easily made by treating methyl alcohol with the corresponding 
hydrogen acids : — 

CH4O + HCl = CHgCl + H2O. 

Methyl alcohol Chlor-methane 

Di-iodo-methane, methylene iodide, CH2I2. — This sub- 
stance is the principal halogen derivative of methane containing 
two halogen atoms. It is made from iodoform or tri-iodo- 
methane, CHI3, by treating it with hydriodic acid, the latter 
acting as a reducing agent : — 

CHl3-|-HI = CH2l2+l2. 

As will be seen, this is a case of reverse substitution ; in other 
words, the action is the opposite of that described above as 
substitution. Methylene iodide is a liquid that boils at 180°, 
and has the specific gravity 3.342. 



Chloroform, CHCI3. 
Bromoform, CHBrg. 
Iodoform, CHI3. 



The best known and most exten- 
sively used of these three derivatives 
is chloroform or tri-chlor-methane. 



It is made by treating alcohol or acetone with "bleaching 



DI-IODO-ETHANB 29 

powder." The action is deep-seated, involving at least three 
different stages. It will be treated of more fully under the 
head of chloral (which see). Chloroform is a heavy liquid of 
specific gravity 1.526. It has an ethereal odor, and a some- 
what sweet taste. It is scarcely soluble in water. It boils at 
61.2°. It is one of the most valuable anaesthetics, though 
there is soihe danger attending its use. 

Experiment 4. Mix 650k bleaching powder and 1 J litres water in a 
3-litre flask. Add 33^ alcohol of sp. gr. 0.834. Heat gently on a water- 
bath until action begins. A mixture of alcohol, water, and chloroform 
will distil over. Add water, and remove the chloroform by means of a 
pipette. Add calcium chloride to the chloroform, and, after standing, 
distil on a water-bath. 

Iodoform, which is used extensively in surgery, is made by 
bringing together alcohol, an alkali, and iodine. It is a solid 
substance, soluble in alcohol and ether, but insoluble in water. 
It crystallizes in delicate, six-sided, yellow plates. Melting- 
point, 119°. 

Experiments. Dissolve 20? crystallized sodium carbonate in 1008 
water. Pour 10? alcohol into the solution, and, after heating to 60^ 
to 80°, gradually add 10? iodine. The iodoform separates from the solution. 

Tetra-chlor-methane, CCI4, is made by treating carbon bisul- 
phide with chlorine, ^nd by treating chloroform with iodine 
chloride, ICl. 

Equivalence of the hydrogen atoms in methane. Having thus 
seen that the hydrogen atoms of methane can easily be re- 
placed, the interesting question suggests itself whether these 
hydrogen atoms all bear the same relation to the carbon atom* 
We accept the conclusion that the carbon atom is quadrivalent, 
and that each of the four hydrogen atoms is in combination 

H(l) 
I 
with it, as indicated in the formula (4) H— C— H (2). Do the 

H(3) 
atoms numbered 1, 2, 3, and 4 bear the same relation to the 



80 DERIVATIVES OF METHANE AND ETHANE 

carbon or not ? If they do not, then, on replacing H (1) 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 chlor-methane and of similar 
products. This subject is an extremely difficult one to deal 
with. It can only be said that, although chlor-methane has 
been made in several ways, the product obtained' is always 
the same one ; and the same is true of all other substitution- 
products of methane. So far as evidence 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, as will be seen later. 

Chlor-^thane, ethyl chloride, CgHgCl. 
Brom-ethane, ethyl bromide, CjHgBr. 
lodo-ethane, ethyl iodide, C^Hgl. 

These substances are all liquids having pleasant ethereal odors. 
The first boils at 12^ the second at 38.8°, and the third at 72^ 
They are most readily made from alcohol, by treating it with 
the corresponding halogen acids. In case of the bromide and 
iodide, it is simpler to treat the alcohol with red phosphorus 
and the halogen. The action is similar to that involved in 
making hydrobromic acid by treating water with red phosphorus 
and bromine. It will be shown that alcohol is a hydroxide 
in which hydroxyl (OH) is in combination with the group CgHg, 
called ethyl, as represented in the formula C2H5.OH. When 
bromine is brought in contact with red phosphorus, the tribro- 
mide, PBrg, is formed, and this acts upon the alcohol thus : — 

C2H5.OH Br ' 

C2H5.OH + Br I P = 3 CgHfiBr -f- P(0H)3. 

C2H5.OH Br 

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



BEOM-ETHANE 



Experiment 8. Under a hood arrange an apparittuB as represented 
In Fig. r,. 

In the flask place lUe red phnsphoriii and 60» absolute alcohol. Put 
60* bromine in the glass- stoppered funnel, and, by nieaiia of the Btop- 




cock, let the bromine enter the flask very slowly, drop by drop. After 
allowing the mixture l« stand for two or three hours, gently heat the 
waier-hath, and the brom-ethane will diatU over. Place the distillate in 
a glasH-Btoppered cylinder, and shake it first with water to wliich soma 
caustic Boda has been added, and then two or three limes with water 
alone. Separate tlie wat«r from the brom-ethane by means of a sepa- 
rating funnel. Add two or three pieces of fused calclnm chloride the alza 
of a small marble, and let stand for a few hours. Tlien pour off into a, 
clean, dry distilling bulb, and distil, noting the boiling-point. 

Among the many halogen substitution-products of ethane 
contaiiiing more than one halogen atom, only two will be men- ■ 
tioned. These ave the two di-chlor-ethaiies, both of which are 
represented by the formula CjH,t'lf. The existence of these 
two substances, having the same composition but entirely dif- 
ferent properties, affords a good example of what is known as 
isomerism. 



32 DERIVATIVES OF METHANE AND ETHANE 

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, substances 
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 : (1) Substances may have the same 
percentage composition and the same molecular weights. Such 
bodies are said to be metameric. The di-chlor-ethanes, C2H4CI2, 
for example, are metameric. (2) Substances which have the 
same percentage composition but different molecular weights 
are said to be polymeric. Acetylene, C2H2, benzene, CgHg, and 
styrene, CgHg, are polymeric. 

The cause of isomerism is undoubtedly to be found in the 
different relations which the constituents of isomeric com- 
pounds bear to each other. 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 compounds, give us an insight into the causes of isomer- 
ism. To illustrate, let us take the two di-chlor-ethanes. One 
of these is made by treating ethane, the other by treating 
ethylene, C2H4, with chlorine. In the first case the action is 
substitution; in the second, the chlorine is added directly to 

ethylene, thus, — 

C2H4 + CI2 = C2H4CI2. 

The product from ethylene is called ethylene chloride; that 
from ethane, ethylidene chloride. It will be shown that ethylene 

CH2 
is to be represented by the formula i ; that is, that in it 

CH2 

only two hydrogen 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 equation, — 



ISOMERISM 83 

CH2 CI CH2CI 

M + = I 
CH2 CI CH2CI. 

Chlorine is taken up, and it is believed that the ethylene 
chloride obtained has the structure represented by the formula 

CH2CI 

I , the distinctive feature of which is that each of the 
CH2CI 

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 

CHCI2 
carbon atom, as represented in the formula 1 , and we 

CHa 

should be inclined to the view that this represents the structure 
of ethylidene chloride. Fortunately there is experimental evi- 
dence to support this view. It will be shown that aldehyde 

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

CHs 
phorus pentachloride, two chlorine atoms take the place of the 

oxygen. A product which must be represented by the formula 

CHCI2 
I is formed, and this is identical with ethylidene chloride. 

CHs 

Thus it will be seen that the difference between the two iso- 
meric compounds, ethylene chloride and ethylidene chloride, 
depends upon 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. 

General characteristics of the halogen derivatives of methane 
and ethane. The one characteristic to which it is desirable 
that special attention should be called is the condition of the 
halogens in the 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 



84 DERIVATIVES OF METHANE AND ETHANE 

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 chlor-methane is 
heated with silver nitrate in a sealed tube, the chlorine is 
removed. 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. 
(See " Ethane," p. 25.) 



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. 

1. Alcohols 

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



Hydrocarbons 


Alcohols 


CH4 


CH,0 


C2He 


C,H,0 



The molecule of the alcohol differs from that of the corre- 
sponding 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, methanol, CH4O. — This alcohol is also 
known as wood spirit. It is found in nature in combination 
in the oil of wintergreen. It is formed, together with many 
other substances, in the dry distillation of wood. It is hence 
contained in crude pyroligneous acid or wood vinegar. Wood 
is distilled in large quantities for various purposes; chiefly, 

85 



86 DERIVATIVES OF METHANE AND ETHANE 

however, for making charcoal. In most charcoal factories the 
distillate is collected and utilized. Wood is distilled also for 
the purpose of making pure acetic acid and its salts. 

It is not an easy matter to get pure methyl alcohol from 
crude wood spirit. Fractional distillation alone will not an- 
swer; though, if the mixture is distilled for some time, and 
the impure alcohol thus obtained then converted into some 
crystalline derivative, the latter can be purified and then 
decomposed in such a way as to yield the alcohol in pure 
condition. 

Methyl alcohol is a liquid that boils at 66.7°, and has the 
specific gravity 0.8142 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 have been caused by its 
internal use. It is an excellent solvent for fats, oils, resins, 
etc., and is extensively used for this purpose. 

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

CH40 + HBr =CH3Br +H2O; 
CH4O + HCI =CH8C1 +H2O; 
CH4O + HNO3 = CH3NO3 + H2O ; 
CH4O + H2SO4 = CH3.HSO4 + H2O. 

The action is plainly suggestive of that of metallic hydroxides 
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 of phosphorus trichloride. When phosphorus tri- 
chloride acts on methyl alcohol, the products are chlor-methane 
and phosphorous acid : — 

3 CH4O -t- PCI3 = 3 CH3CI -t- H3PO3. 

Here one atom of chlorine is substituted for an atom of 
hydrogen and an atom of oxygen, the reaction being like 



METHYL ALCOHOL 37 

that which takes place between water and phosphorus tri- 
chloride : — 

3 H2O + PCI3 = 3 HCl + H3PO3 

This fact would lead us to suspect that there is some 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 = CH3KO + 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 metallic hy- 
droxides ; the substitution of chlorine for hydrogen and oxygen ; 
and 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 reac- 
tions are due to the presence of the group called hydroxyl (OH). 
The analogy between the alcohol, a metallic hydroxide, and 
water is shown by these formulas : alcohol, CH3.OH ; hydroxide, 
K.OH ; water, H.OH. 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 group CH3 for one hydro- 
gen 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. 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 the view, we may try to make 
methyl alcohol in some way that will show us of what parts it is 
made up. Thus, we may start with marsh gas, and introduce a 



38 DERIVATIVES OF METHANE AND ETHANE 

halogen, as bromine. Now, if we bring brom^metbane together 
with a metallic hydroxide, the bromine and the metal may 
unite, leaving the hydroxyl and the group CHg, which may 
unite also, as indicated in the equation 

CHaBr + MOH = CH3.OH + MBr. 

If methyl alcohol could be made in this way, we should have 
strong evidence in favor of the view expressed in the formula 
CH3.OH. Methyl alcohol has been made by this reaction ; and 
it is indeed a general reaction for the preparation of alcohols. 

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 acid formed by oxidation has the composition expressed 
by the formula CH2O2. 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 of an import- 
ant 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 this simplest acid bears to marsh gas. 

The two most characteristic reactions of methyl alcohol are : 
(1) its power to form salt-like compounds when treated with 
acids ; and (2) its power to form an acid when oxidized. 

The neutral compounds formed with acids correspond to the 
salts of metals, only they contain the radical, or residue, methyl, 
CHg, in the place of metals. They are called ethereal salts, or 
esters. 



FERMENTATION 39 

Ethyl alcohol, ethanol, C2H6.OH. — This is the best- 
known substance belonging to the class of alcohols. It is 
known also by the name spirit of wine and ordinary alcohol. 
It occurs in small quantities widely distributed in nature. 

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

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 up of the sugar into carbon dioxide and alcohol. 
The equation 

CeHi A = 2 CgHeO + 2 CO2, 
Sugar Alcohol 

approximately expresses what takes place in the process which 
is known as alcoholic fermentation. It has been shown that 
fermentation is caused by the presence of small organized 
bodies, either animal or vegetable. These bodies, which are 
known as ferments^ are of different kinds, and cause differ- 
ent kinds of fermentation with different products. Among 
the kinds of fermentation the following may be specially 
mentioned : — 

1. Alcoholic or vinous fermentation. This is caused by a 
vegetable ferment contained in ordinary yeast. The ferment 
consists of small, round cells arranged in chains. The prod- 
ucts of its action are alcohol and carbon dioxide. 

2. Lactic acid fermentation. This is due to a vegetable 
ferment 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 which acts upon alcohol, transforming it into 
acetic acid. 

The germs of various ferments are in the air ; and, when- 
ever they find favorable conditions, they develop and produce 
their characteristic effects. They will not develop in a solution 



40 DEKIVATIVES OF METHANE AND ETHANE 

of pure sugar. The variety of sugar which is fermentable, and 
which is the one from which alcohol is obtained, is not our 
ordinary cane sugar, but one known as grape sugar, or, more 
commonly, glucose. In order that the ferments may grow, there 
must be present in the solution, besides the sugar, substances 
which contain nitrogen. These, as well as the sugar, are con- 
tained in the juices pressed out from fruits, and hence these 
juices readily undergo fermentation. 

In the manufacture of alcohol a solution containing sugar is 
first prepared from the residue of wine presses, or from some 
kind of grain or potatoes. In case the solution contains grape 
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 
ferment into grape sugar and fruit sugar, and the fermentation 
then takes place as in the first case. 

Experiment 7. Dissolve about 160* commercial grape sugar in 1 to 
IJ litres of water in a good-sized flask. Connect the flask by means of 
a bent tube with a cylinder containing clear lime water. Protect the 
latter from the air by means of a tube containing caustic potash. Now 
add to the solution of grape sugar a little brewei^s yeast ; close the con- 
nections, and allow to stand. Soon an evolution of gas will begin, and, 
as this passes through the lime water, a precipitate of calcium carbonate 
will be formed. After the action is over, place the flask in a water-bath; 
connect with a condenser, and distil over lOO'^^ of the liquid. Examine 
this for alcohol. 

A good way to detect alcohol is this : Warm the solution to be tested ; 
add a small piece of iodine and then caustic potash until the color is 
destroyed. On cooling, a yellow crystalline substance, iodoform, is de- 
posited if alcohol is present. 

To obtain alcohol from fermented liquids, these must be dis- 
tilled. The ordinary alcohol contains water, and a mixture of 

* Enzymes, substances of the character of albumin, have the powpr to bring about im- 
portant chan{fes in some of the carbohydrates. Thev are called unorganized ferments, as 
they act in general like the organized ferments or fermeuts proper. Among the important 
enzymes are diastase and invertase. 



FERMENTATION 41 

other alcohols called fusel oil. The latter can be removed partly 
by distillation, and the last portions can be got rid of by fil- 
tering through charcoal. The water cannot be removed com- 
pletely by distillation, though a product containing 95.57 per 
cent of alcohol can be obtained in this way. This mixture, 
consisting of 95.57 per cent alcohol and 4.43 per cent water, 
has a constant boiling-point (78.15°). 

Absolute alcohol is ordinary alcohol from which most of the 
water has been removed by means of some dehydrating agent, 
as quicklime or barium oxide. By continued treatment with 
freshly burned lime the quantity of water can be reduced to 
one-half a per cent, and this small quantity can be removed by 
treatment with metallic sodium. 

Experiment 8. Prepare absolute alcohol from ordinary strong alco- 
hol. For this purpose a good-sized flask is one-half to two-thirds filled 
with quicklime broken into small lumps. The alcohol is poured upon the 
lime, and allowed to stand at least twenty-four hours, when it is distilled 
off on a water-bath. If the alcohol used contains considerable water, it 
is necessary to repeat the treatment with lime. 

Pure ethyl alcohol has a peculiar, pleasant- odor. It is 
claimed, however, that perfectly anhydrous alcohol has no 
odor. It remains liquid at very low temperatures, but it 
has been converted into a solid at a temperature of — 130.5°. 
It boils at 78.3°. It burns with a non-luminous flame, which 
does not leave a deposit of soot on substances placed in it. It 
is hence used for heating purposes. 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 internally in large doses, it lowers the temperature of 
the body from 0.5° to 2°, although the sensation of warmth is 
experienced. 

Alcohol is the principal solvent for substances of organic 
origin. It is hence extensively used in the arts, as in the 
preparation of varnishes, perfumes, and tinctures of drugs. 



42 DERIVATIVES OF METHANE AND ETHANE 

Denatured alcohol. — Alcohol to which something has 
been added to make it unfit for use as a beverage can be with- 
drawn from bond for use in the industries without payment of 
the internal revenue tax on alcohol. Such alcohol is called 
denatured alcohol. Various substances are employed as dena- 
turing agents. Those authorized by the United States govern- 
ment are methyl alcohol, benzine, and pyridine bases. Ordinary 
denatured alcohol contains methyl alcohol and benzine. Com- 
pletely denatured alcohol contains methyl alcohol and pyridine 
bases (see Pyridine Bases, page 350). 

Alcoholic beverages. — Many of the beverages in common 
use depend for their efficiency upon the presence of alcohol in 
greater or smaller quantity. The milder forms of beer contain 
from 2 to 3 per cent ; light wines, such as claret, about 8 per 
cent ; while whiskey, brandy, rum, and other distilled liquors 
sometimes contain as much as 60 to 75 per cent. These dis- 
tilled liquors are ordinary alcohol with water and small quan- 
tities 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 Methyl alcohol conducts 
itself chemically like ethyl alcohol. The products formed 
contain the radical, ethyl, C2H5, instead of methyl. 

2. Ethers 

When an alcohol is treated with potassium or sodium, com- 
pounds are formed having the formulas, CHgONa, CH3OK, 
C2H5OK, CaHjONa. If one of these is treated with a mono- 
halogeu derivative of a hydrocarbon, as, for example, iodo- 
methane, CH3I, reaction takes place thus : — 

CHgONa -f CH3I = CgHeO -f NaT. 

This reaction leaves very little room for doubt in regard to 



ETHYL ETHER 43 

the structure of the compound C2H6O. It must be represented 
by the formula CHg — — CHg, or (CH3)20. Comparing 
it with methyl alcohol, it will be seen that it is obtained 
from the alcohol by replacing the hydrogen of the hydroxyl 
by methyl, CHg. Just as the alcohol is analogous to the hy- 
droxide KOH, so the new compound is analogous to the oxide, 
KoO. It is the representative of a class of bodies known as 
ethers, which are analogous to the oxides of the metals. 
Ordinary ether is the chief representative of the class. 

While the reaction above mentioned serves admirably to 
show the relations between the alcohols and ethers, it is not 
the one that is made use of in their preparation. This consists 
in treating the alcohols with sulphuric acid, and distilling. 

Ethyl ether, C4H10O = (C2H6)20. — This is the substance 
commonly known simply as ether, or sulphuric ether. The 
latter name was originally given to it because sulphuric acid 
is used in its manufacture, and plainly not because any 
sulphur is contained in it. Ether can be made from alcohol 
by making the sodium compound of alcohol, C2H50Na, and 
heating this with brom- or iodo-ethane thus : — 

CaH^ONa + C2H5I = (C2H,)20 + Nal ; 

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

2 C2H J + Ag20 = (C2H,)20 + 2 Agl. 

Ether is made on the large scale by mixing 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 : — 

C2H,0H + 2 > ^^4 = ^' J > SO4 + H2O. 
The product formed is called ethyl-sulphuric acid. 



44 



DERIVATIVES OF METHANE AND ETHANE 



Experiment 9. Slowly pour 20 to 30 «« ordinary concentrated sul- 
phuric acid into about the same volume of alcohol of 80 to 90 per 
cent. Stir thoroughly, and dilute with a litre of water. In an evaporat- 
ing dish add powdered barium carbonate until the liquid is neutral. 
Filter, and examine the clear filtrate for barium. Its presence shows 
that a soluble barium salt has been formed. This is barium ethyl- 
sulphate, Ba(C2H6S04)2. 

When ethyl-sulphuric acid is heated with alcohol, ether is 
formed, and sulphuric acid is regenerated thus : — 

C2H5OH + ^'^^ > SO4 = ^' J > + H2SO4. 

The ether thus formed distils over ; and, if alcohol is admitted 
to the sulphuric acid, ethyl-sulphuric acid will again be 
formed, and with excess of alcohol it will yield ether. The 
actual method of procedure is described in 

Experiment 10. Arrange an apparatus as shown in Fig. 6. As ether 
is veiy volatile and inflammable, it is important that the condenser be con- 
nected with the receiver by 
means of an adapter, and the 
receiver placed in a vessel con- 
taining ice. In the flask put a 
mixture of 200* alcohol, and 
3608 ordinary concentrated sul- 
phuric acid. It is better to 
mix them in another vessel, 
and allow the mixture to stand 
for some time until it is thor- 
oughly cooled down; and then 
to pour off from any deposited 




Fig. 6. 



solid as completely as possible. Now heat until the thermometer indicates 
the temperature 140°. At this point the mixture boils, and ether begins 
to pass over. As soon as this is noticed, open the stop-cock of the funnel 
A, and let a slow stream of alcohol pass into the distilling flask through 
the tube, which must reach beneath the surface of the mixture. Regulate 
this stream so that the temperature remains as near 140° as possible. In 
this way the operation can be kept up for a considerable time, the alcohol 
admitted to the flask passing out as ether, and being collected together 
with some alcohol in the receiver. After about 250 «« of alcohol has 



ETHYL ETHER 45 

been admitted, stop the operation. Pour the distillate into a glass-stop- 
pered cylinder, and add water. The ether will rise to the top, forming a 
layer, and can be removed by means of a pipette or separating funnel. 
It should be shaken in this way a few times with water ; then treated 
with a little fused calcium chloride ; and, after standing, poured off into 
a dry flask, and distilled on a water-bath. 

N.B. Never boil ether over a free flame; and, in working with it, 
always carefully avoid the neighborhood of flames. In boiling it on a 
water-bath, do not heat the water to boiling. 

Ether is a colorless, mobile liquid of a peculiar odor and 
taste. It boils at 34.9°. (Hence the necessity for the pre- 
cautions mentioned above.) Its specific gravity is 0.736 at 0°. 
(What evidence have you had that it is lighter than water?) 
It is very inflammable. 

Experiment 11. Put a few cubic centimetres of ether in a small 
evaporating dish, and apply a flame. 

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 an excellent anaesthetic, and is used extensively in this 
capacity. In consequence of its rapid evaporation, it may be 
used to produce cold. When, for example, ether is brought 
upon the skin in the form of spray, the cold produced is so 
great as to cause insensibility. 

Experiment 12. In a thin glass test-tube put 6«c water. Introduce 
the tube into a small beaker containing some ether. Force air over the 
surface of the ether by means of a bellows. The water will be frozen. 

Chemical conduct of ether. If we were dependent upon the 
decompositions and general reactions of ether for our knowledge 



46 DERIVATIVES OF METHANE AND ETHANE 

of its structure, we should be left in grave doubt as to the rela- 
tions existing between it and alcohol. Its decompositions are 
mostly deep-seated, and not easily explained. Fortunately, as 
we have seen, its synthesis from sodium ethylate, C2H50Na, and 
iodo-ethane, C2H5I, leaves us in no doubt regarding its structure. 
The simplest decompositions are these : — 

Heated with acidified water to 160° in a sealed tube, it is 
converted into alcohol : — 

(C,U,),0 + H2O = 2 CgH^OH. 

Treated with hydriodic acid at a low temperature, alcohol 
and iodo-ethane or iodo-ethane and water are formed : — 

(C2H,)20 + HI = CgH^OH + C2H5I. 

(C2H5)aO -f 2 HI = 2 CiH^I + H2O. 

Mixed ethers. — Just as ordinary or ethyl alcohol yields 
ethyl ether, so methyl alcohol yields methyl ether, (CH3)20. 
By modifying the method, a mixed ether, methyl-ethyl ether, 

H 

^TT* > 0, can be obtained. This is formed by treating sodium 
OJI3 

methylate with iodo-ethane, or by treating sodium ethylate 

with iodo-methane : — 

CHgONa -f C2H J = ^'^' >0 + Nal ; 



C2H5 

CH, 



CgH^ONa + CH3I = ^'"* > -h Nal. 

OM3 

It is formed also by distilling methyl alcohol with ethyl-sul- 
phuric acid, or ethyl alcohol with methyl-sulphuric acid : — 



CH3 , ^^Hfi Q^ C2H5 

jj>0+ H^^^^=CH3 



> O +^'^ > SO, =X' > + H2SO,; 



^"^ > -f ^^ > so, =^^^J > O + H2SO,. 

Methyl ether and methyl-ethyl ether are very similar to ordi- 
nary ether. 



ACETIC ALDEHYDE 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 proper precautions, prod- 
ucts can be obtained intermediate between the alcohols and 
acids, and differing from them in composition in that they 
contain two atoms of hydrogen less than the corresponding 
alcohols. 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 rela- 
tions in composition between the hydrocarbons, alcohols^ and 
aldehydes are shown by these formulas : — 



Hydrocarbons 


Alcohols 


Aldehydes 


CH4 


CH4O 


CHjO 


C2H8 


CgHeO 


C2H4O 


etc. 


etc. 


etc. 



Formic aldehyde, formal, miethanal, CH2O. — This alde- 
hyde is made by passing the vapor of methyl alcohol together 
with air over a heated platinum or copper spiral. When cooled 
to a low temperature it forms a liquid that boils at — 21°. It 
is manufactured on the large scale, and comes into the market 
in solution under the name of formalin. It is used in the manu- 
facture of some dyes and as a preservative and disinfectant. 
When its solution in water is evaporated, a solid substance 
having the same composition as formic aldehyde is obtained. 
This is a polymeric variety, and is represented by the formula 
(CH20)2. It is called paraformaldehyde. 

In order to gain a clear insight into the nature of the alde- 
hydes, it will be best to study the best-known representative of 
the class, which is acetic aldehyde. 

Acetic aldehyde, ethanal, O2H4O. — This aldehyde is 
formed whenever alcohol is brought in contact with an oxidizing 



48 DERIVATIVES OP METHANE AKD ETHANE 

mixture, as, for example, potassium bichromate and dilute 
sulphuric acid. 

Experiment lit. DisHolve a little potassium liichroniate in water, 
and add aulphuric acid. Now add a few cubic centimetres of alcohol, 
and notice Llie odor, which is that of aldehyde. Notice, also, the change 
of color of the aolution, showing the reduction of the bichromate. 

As aldehyde is a very volatile liquid, it is difficult to collect it. 
In preparing it, it is therefore best to pass it into some liquid 
■which will absorb it, and then afterwards separate it by some 
appropriate method. A good method is that described below. 

Experiment 14. Arrange an apparatus as shown in Pig. 7. Put 
120« granulated potassium bichromate in the fiasb A, which must have a 
capacity of IJ to 2 litres, Make a mixture of IBOe coacenlrated sulphuric 




Fig. 7. 

acid, 48W water, and 12(W alcohol. Cool Ihe mixture down to the ordi- 
nary temperature, and then pour it slowly through the funnel-tube B into 
the flask, which should stand on a water-bath containing warm water. 
The cylinders C and D are about half filled with ordinary ether, each 
one containing about 200™ ether, and placed in the large vessel F, which 



• ACETIC ALDEHYDE 49 

contains ice water. The condenser should be supplied with water of 
about 30° C. » 

Usually, when the alcohol, water, and sulphuric acid are poured upon 
the bichromate, the action begins without application of heat. At times 
it takes place rapidly, so that the liquid should always be added slowly. 
The aldehyde which is thus formed, together with some alcohol and 
water vapor, passes into the condenser-tube, where the greater part of 
the alcohol and water is condensed and returned to the flask, while the 
aldehyde, being much more volatile, passes into the ether and is there 
absorbed. After the action is over, the distilling vessel and condenser 
are removed, and, at E^ connection is made with an apparatus furnishing 
dry ammonia gas. The gas is passed into the cold ethereal solution of 
aldehyde to the point of saturation. A beautifully crystallized compound 
of aldehyde and ammonia, known as aldehyde-ammonia^ is deposited. The 
ether is poured off, and the crystals placed on filter-paper. They gradually 
undergo change in the air, becoming yellow, and acquiring a peculiar 
odor. If the crystals are placed in a flask and treated with dilute sulphuric 
acid, pure aldehyde passes over, and can be condensed by ice-cold water. 

In the process of purification of ordinary alcohol it is filtered 
through charcoal. It is thus partly oxidized to aldehyde ; and, 
when it is afterwards distilled, the first portions that pass over 
contain aldehyde, which was formerly obtained on the large 
scale by repeated distillation of these " first runnings." 

Aldehyde is a colorless liquid, boiling at 21°. It mixes with 
water and alcohol in all proportions. Its odor is marked and 
characteristic. 

From the chemical point of view, the most characteristic 
property of aldehyde is its power to unite directly with other 
substances. It unites with oxygen 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 
alkalies 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. 



50 DERIVATIVES OF METHANE AND ETHANE * 

Paraldehyde, CgHioOg — This is formed by adding a few 
drops of concentrated sulphuric acid to aldehyde, which causes 
the liquid to become hot. On cooling to 0°, the paraldehyde 
solidifies in crystalline form. It melts at 10.5°. It dissolves in 
eight times its own volume of water, and boils at 124°. When 
distilled with dilute sulphuric acid, hydrochloric acid, etc., it is 
converted into aldehyde. The specific gravity of its vapor has 
been found to be 4.583. This leads to the molecular weight 
132.4, and consequently to the formula C6H12O3. It is called a 
polymeric modification of aldehyde. It is used in medicine as 
an hypnotic. 

Metaldehyde, CgH^gOg — Metaldehyde is formed in much 
the same way as paraldehyde, but a low temperature (below 
0°) is most favorable to its formation. 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 temperature. When heated to 
120° in a sealed tube, it is converted into aldehyde. Deter- 
minations by the freezing-point method show that the molecu- 
lar weight of freshly prepared metaldehyde is the same as that 
of paraldehyde. On standing it is converted into paraldehyde 
and, probably, a substance of the formula (€21140)4. Distilled 
with dilute sulphuric acid, etc., metaldehyde is easily con- 
verted into aldehyde. 

In consequence of the tendency of aldehyde to unite with 
oxygen, it is a strong reducing agent. When added to an am- 
moniacal solution of silver nitrate, metallic silver is deposited 
on the walls of the vessel in the form of a brilliant mirror. 

Experiment 15. To a dilute solution of silver nitrate add a solution 
of ammonia until the silver oxide which is at first precipitated is nearly, 
though not quite, dissolved ; filter, warm gently in a clean test-tube, and 
add a few drops of a very dilute solution of aldehyde. A brilliant mirror 
of metallic silver will appear. This method is used in the manufacture 
of mirrors. What becomes of the aldehyde ? 



ALDEHYDE 51 

Chemical transformations of aldehyde. As aldehyde is pro- 
duced from alcohol by oxidation, so alcohol can be formed 
from aldehyde by reduction : — 

CgHeO + O =C2H40 + H20; 
C2H4O -f- H2 = C2HgO. 

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

C2H4O +0 =C2HA; 
C2H A + H2 = C2H4O + H2O. 

Treated with phosphorus pentachloride, aldehyde yields ethylr 
idene chloride, C2H4CI2 (which see). 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 
the hydroxide of ethyl, C2H3.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 which we have a 
right to ask. 

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

H2O-I-PCI5 =POCl3 + 2HCl. 

Next, th^ oxichloride, POCI3, is acted upon thus : — 

3 H2O + POCI3 = P0(0H)3 + 3 HCl. 

Or, expressing both changes in one equation, we have : — 

4 H2O + PCI5 = PO (0H)3 + 5 HCl. 

The phosphorus pentachloride gives up its chlorine and takes 
up oxygen, or oxygen and hydrogen, in its place. This is tlie 
general tendency of the chlorides of phosphorus. 



52 DERIVATIVES OF METHANE AND ETHANE 

Now, when a chloride of phosphorus is brought together 
with an alcohol, chlorine is substituted for the oxygen, two 
atoms of the former for one of the latter, thus : — 

C2H5.OH + PCI5 = C2H5CI.CIH + POClj. 

But as hydroxy 1, — — H, is univalent, its place cannot be 
taken by two atoms of chlorine and one of hydrogen, and the 
two chlorine atoms have not the power of linking the hydrogen 
to the ethyl. Hydrochloric acid is given off, and a compound is 
formed, which may be 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 or is not pres- 
ent in a compound. 

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 : — ^^^^^ ^ p^^^ ^ C,Jlfil, + POCI3. 

If the explanation above offered of the action of phosphorus 
pentachloride on alcohol is correct, it follows that aldehyde is 
not a hydroxyl compound. We can readily understand why two 
chlorine atoms should take the place of the oxygen atom, if the 
latter is in combination only with carbon as in carbon monoxide, 
CO. There is an essential difference between this kind of com- 
bination and that which we have in hydroxyl as C— 0— H. In 
the latter condition the oxygen serves to connect carbon with 
hydrogen; in the former it is in combination only with the 
carbon, and, presumably, the force 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 in a compound in the 
carbon monoxide condition, we should expect two chlorine 
atoms to take its place when the compound is treated with 



ALDEHYDE 53 

phosphorus pentachloride. Let R.CO represent any such com- 
pound ; then we should have : — 

ECO + PCI5 = R.CC1, + POCla; 

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

R.C - - H + PCI5 = R.CCl + POCl, + 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 
condition. 

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 = 0. 

According to the above reasoning aldehyde is a carbonyl 
compound, or it contains the group CO. The simplest alde- 
hyde must therefore be represented by the formula H2C = 0. 

O 

11 
Its homologue, acetic aldehyde, is CHs. C— H. The peculiar prop- 
erties of aldehyde are believed to be due to the presence of this 

O 

II 

group, C — H, which is called the aldehyde group. We do 
not know that the double line in the formula conveys a 
correct idea in regard to the relation between the carbon 
and oxygen. All that we know is that these two elements 
do occur in two different relations to each other, and the 
formulas C — — H and C = recall these relations. They 
are expressions of facts established by experiment. Our 
notions in regard to these relations are largely dependent 
upon the reactions with the chlorides of phosphorus referred 
to above. 



54 DERIVATIVES OF METHANE AND ETHANE 

Chloral, trichloraldehyde, COI3OHO. — When chlorine 
acts directly upon aldehyde, complicated reactions take place 
which need not be discussed here. If, however, water and 
calcium carbonate are present, 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 = CH8.C0H -f 2 HCl. 

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

CHs-COH + 6 CI = CCI3.COH + 3 HCl. 

In reality the aldehyde first formed acts upon the alcohol, 
forming an intermediate product which is acted upon by the 
chlorine ; and the chlorine product thus formed breaks up, form- 
ing chloral. The essential features of the reaction, however, 
are stated in the above equations. Trichloraldehyde is the 
substance commonly known as chloral. It is simply the tri- 
chlorine substitution product of aldehyde. It has all the gen- 
eral properties of aldehyde, and the conclusion is therefore 

O 
II 
justified that it contains the aldehyde group - CFT. 

Chloral is a colorless liquid, which boils at 98°, and has the 
specific gravity 1.54 at 0°. 

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

When chloral and water are brought together, they unite to 
form a crystallized compound, chloral hydrate, C2HCI3O + Hj,0, 
which is easily soluble in water, and crystallizes from the solu- 
tion in beautiful, colorless, monoclinic prisms. It melts at 57° 



FORMIC ACID 55 

and boils at 97.5°, dissociating into chloral and water. Taken 
internally in doses of from 0.6 to 2«, it produces sleep. In 
larger doses it acts as an anaesthetic. 

When treated with an alkali, chloral and chloral hydrate 
break up, yielding chloroform and formic acid : — 

CCls-COH + KOH = CHCls + KCHOg. 

Chloral Chloroform Potassium 

formate 

Similar reactions take place in the preparation of chloroform 
and iodoform from alcohol. 

Note for Student. — How is chloroform made ? How is the method 
explained? Answer the same questions for iodoform. The bleaching 
powder used in preparing chloroform furnishes chlorine. Is an alkali 
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 


Adds 


CH4 


CH4O 


CHjO 


CHA 


CaHg 


CjHeO 


C2H4O 


C2H4O2 


etc. 


etc. 


etc. 


etc. 



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

Formic acid, methanic acid, OHgOg. — This acid occurs 
in nature in red ants, in stinging nettles, in the shoots of some 
of the varieties of pine, and elsewhere. 

It can be obtained by distilling red ants, and is best pre- 
pared by heating oxalic acid with glycerol. Oxalic acid has the 
composition represented by the formula CjHgO^. When heated 



66 DERIVATIVES OF METHANE AND ETHANE 

in glycerol to 100°-110° it breaks down into carbon dioxide and 

formic acid:- c^^o. = CO, + CH,0. 

The formic acid distils over, and can be condensed. 

Experiment 16. Into a flask of 500 to 600^0 capacity put 200 to 
SOO^*^ anhydrous glycerol, and then add 30 to 40s crystallized oxalic 
acid. Connect the flask with a condenser, and insert a thermometer 
through the cork so that the bulb is below the surface of the glycerol. 
Heat gently. At 76° to 00°, carbon dioxide is evolved. Raise the tem- 
perature gradually to 112°-116°. When formic acid no longer distils 
over, add another portion of oxalic acid, and heat again. This opera- 
tion may be repeated a number of times without renewing the glycerol ; 
but, when about lOOs of oxalic acid has been decomposed, enough 
formic acid for the purpose will have been formed, and collected in 
the receiver. Dilute the distillate to about half a litre, and, while 
gently warming it in an evaporating dish, add freshly precipitated and 
washed copper oxide in small quantities until no more is dissolved. 
Then Alter, and evaporate the solution to crystallization. The beauti- 
fully crystallized salt thus obtained is copper formate. 

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 : — 

(1) By the action of carbon monoxide upon sodium hy- 
droxide : — ^Q ^ ^^^^ ^ H.COgNa. 

This method is used for the preparation of formic acid on the 
large scale, soda-lime being used instead of sodium hydroxide. 

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

2 CO2 + K2 + H2O = HCO2K + HCO3K, 
or 2 CO3H2 + K2 = HCO2K + HCO3K + H2O. 

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

C03(NH4)2+ 2 H = HCO,(NH,) + 11,0 + NH3, 
and HCOjCNH^) -H NaOH = HC02Xa + NH3 + H2O. 



FORMIC ACID 57 

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

H2CO3 = H2CO2 + 0. 

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

(4) When hydrocyanic acid is treated with an acid or an 
alkali, it breaks up, forming ammonia and formic acid. The 
reaction may be represented thus : — 

HCN + 2 H2O = H2CO2 + NHg. 

Of course, if an acid is present, the ammonium salt of the acid 
is formed ; and, if an alkali is present, the formate of this alkali 
is formed. A reaction similar to this is used very extensively in 
the preparation of the acids of the carbon, as will be shown. 

Anhydrous formic acid can be made by dehydrating either 
the copper or lead salt, and passing dry hydrogen sulphide 
over the salt placed in a heated tube, or by heating a mixture 
of dry sodium formate and acid sodium sulphate : — 

HCOgNa + NaHS04 = NagSO^ + HgCOg. 

It is a colorless liquid boiling at 99** at 760"™. It has 
a penetrating odor. Dropped on the skin, it causes extreme 
pain and produces blisters. Its specific gravity at (f is 1.22. 
When cooled down it solidifies to a mass of crystals which melt 
at 8.6°. It is a stronger acid than acetic acid. It is a power- 
ful antiseptic. 

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

H2CO2 = CO -f H2O. 

It is easily oxidized to carbonic acid. Henoe it acts as a 
reducing agent. Heated with the oxides of mercury or silver, 
they arjB reduced to the metallic condition : — 

HgO 4- H2CO2 = Hg 4- H2O 4- CO2. 
Like other acids, formic acid yields a large number of salts with 



58 DERIVATIVES OF METHANE AND ETHANE 

baseS; and ethereal salts or compound ethers with the alcohols. 
These derivatives need not be treated of here. The salts are 
all soluble in water, and some of them, as the lead, copper, and 
barium salts, crystallize very well. Some of the ethereal salts 
will be mentioned when these substances are taken up as a class. 

Acetio acid, ethanic acid, G2n402. — Acetic acid is made 

(1) By the oxidation of alcohol ; and 

(2) By the distillation of wood. 

When pure alcohol is exposed to the air it undergoes no 
change; If, however, some platinum black is placed in it, 
oxidation 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 be- 
comes sour in consequence of the formation of acetic acid. A 
great deal of acetic acid is made by exposing poor wine to the 
action of the air. The product is known as wine vinegar. 
The formation of vinegar has been shown to be due to the 
presence of a microscopic organism {Mycoderma aceti) com- 
monly known as " mother-of -vinegar." 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 spirits of wine to pass 
slowly through barrels filled with beech shavings which have 
become covered with Mycoderma aceti. The presence of the 
organism is secured by first pouring strong vinegar into the 
barrels, and allowing it to stand for one or two days in con- 
tact with the shavings. 

When wood is distilled, a very complex mixture passes over, 
one of the constituents being acetic acid. By keeping the 
temperature down comparatively low, the amount of acetic 
acid obtained is increased. The distillate is neutralized with 
soda ash, and the solution of crude sodium acetate thus ob- 
tained evaporated to dryness. It is then treated with sul- 
phuric acid, and distilled, when acetic acid passes over. ' 



ACETIC ACID 59 

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

(1) By treating sodium methylate with carbon monoxide : — 

CHjONa 4- CO = CHs-COaNa. 

(2) By treating carbon dioxide with sodium-methyl : — 

COa + CHsNa = CHa-COgNa. 

(3) By treating methyl cyanide, CH3CN, with an acid or an 
alkali : — ^j^^q^ -f 2 HgO = CH3.CO2H + NH3. 

This reaction is analogous to that involved in the formation 
of formic acid from hydrocyanic acid (see p. 57). 

To purify the acid it is passed through charcoal and dis- 
tilled. It still contains water, from which it cannot be com- 
pletely separated by distillation. When cooled to a low 
temperature it solidifies, and the water can then partly be 
poured off. By repeating the freezing, and distilling a few 
times, perfectly pure, anhydrous acetic acid can be obtained. 

Eixperiment 17. Make pure acetic acid from the commercial sub- 
stance. First distil in fractions until a portion is obtained that boils 
between 110® and 119°. Put the vessel containing this in ice. The 
liquid will solidify almost completely. Four off the little liquid which 
remains, and distil. 

Acetic acid is a clear, colorless liquid, which boils at 118**. 
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 16.7°. The pure acid which is solid at 
temperatures below 16° is known as glacial acetic acid. Its spe- 
cific gravity is 1.08 at 0°. It mixes with water in all proportions. 

Acetic acid is extensively used, chiefly in the dilute, impure 
form known as vinegar, which is an aqueous solution of acetic 
acid containing from 3 to 6 per cent of the acid, a little alcohol, 
and other substances in small quantities. It is used in calico 
printing in the form of iron and aluminium salts. With iron it 



60 DERIVATIVES OF METHANE AND ETHANE 

gives hydrogen, which is needed in the manufacture of certain 
compounds used in making dyes, as, for example, aniline. 
Glacial acetic acid is an excellent solvent for many organic sub- 
stances, and is therefore frequently used in scientific researches. 

Derivatives of acetic acid. Acetic acid yields a large num- 
ber of derivatives. They may be treated of briefly under two 
heads: (1) Those which are formed in consequence of the 
acid properties and which necessitate a loss of the acid proper- 
ties, as the salts, ethereal salts, etc. ; and (2) those in which 
the acid properties remain essentially unchanged. 

Salts of acetic add. The acetates of the alkalies were the 
first compounds of carbon ever prepared. The potassium and 
sodium salts are used in the chemical laboratory. Both crystal- 
lize, the sodium salt particularly well and easily. 

Lead acetate, (C2H802)2Pb -f- 3 H2O. This salt, which is com- 
monly known as siigar 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. 

Copper acetate, (C2H302)2Cu -f 2 H2O. This salt can be made 
by dissolving copper hydroxide or carbonate in acetic acid. It 
crystallizes in dark-blue, transparent prisms. A basic acetate, 
formed by the action of acetic acid on copper in the air, is 
known as verdigris. 

Copper aceto-arsenite, 3 CUAS2O4 + (O^^O^ju^* This double 
salt is formed by boiling verdigris and arsenic trioxide together 
in water. It has a fine bright-green color, and is used as a 
pigment and as an insecticide. It is the chief constituent of 
emerald green, Paris green, or Schweinfurt's green. 

Iron forms two distinct salts with acetic acid, the ferrous 
salt, (C2H302)2lFe + 4 H2O, and the ferric salt, (0211302)3^6. 



ACETIC ANHYDRIDE 61 

The latter is formed when sodium acetate is added to an acidi- 
fied solution of a ferric salt. At first the solution becomes 
deep-red in color ; but, on boiling, all the iron is precipitated 
as hydroxide. Hence this salt is used for the purpose of sepa- 
rating iron from manganese in analytical operations. 

Experiment 18. To a dilute solution of ferric chloride, contained 
in a small flask, add a little acetic acid and a solution of sodium acetate. 
Boil the red solution, and ferric hydroxide is precipitated, leaving the 
solution colorless. Filter, and examine the filtrate for iron. 

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 treated 
with sulphuric acid, the ether is f oirmed and can be recognized 
by its pleasant odor. This fact is taken advantage of for the 
detection of acetic acid. 

Experiment 19. To a mixture of about equal parte of acetic acid 
and alcohol, in a test-tube, add a little concentrated sulphuric acid, heat, 
and notice the odor. It is that of ethyl acetate or acetic ether. 

Acetyl chloride, O2H3OOI. 1 Just as alcohol, when 
Acetyl bromide, CgHgOBr. I treated with phosphorus tri- 
Acetyl iodide, OgHgOI. J chloride, yields a chloride of 
ethyl, so acetic acid, when treated with the same reagent, yields 
acetyl chloride. The character of the reaction is the same in 
both cases. It consists in the replacement of hydroxyl by 
chlorine : — 

3 CH3.COOH + PCI3 = 3 CH3.COCI + H3PO3. 

Acetyl chloride 

Experiment 20. Arrange a dry distilling flask, with condenser and 
dry receiver, under a hood or out of doors. Bring together 9 parts 
(say 1808) strong acetic acid and 6 parts (say 1208) phosphorus tri- 
chloride. Slightly heat the mixture on the water-bath, when acetyl 
chloride will distil over. Collect in a dry bottle. 

Acetyl chloride is a colorless liquid which boils at W^. 



62 d?;rivatives of methane and ethane 

Water acts upon it very readily, acetic and hydrochloric acids 
being formed : — 

CgHaOCl + H2O = CjHsO.OH + HCl. 

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

Acetyl chloride is a valuable reagent much used in the ex- 
amination 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 : — 

CHa-OH + C2H3OCI = CH3.O.C2H8O + 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, its composition is changed, showing that hydrogen is 
replaced by acetyl, we are justified in concluding that the sub- 
stance contains alcoholic hydroxyl. The bromide and iodide 
resemble the chloride very closely. 

Experiment 21. Treat a few cubic centimetres of absolute alcohol 
with acetyl chloride. Notice the evolution of hydrochloric acid and the 
odor of ethyl acetate. 

Acetic anhydride or acetyl oxide, O4H6O3. This is made 
by abstracting water from the acid. Like other acids, acetic 
acid contains hydroxyl, as will be shown below. It may hence 
be represented thus : C2H3O.OH. The part C2H3O is known as 
acetyl. Now when water is abstracted from the acid, the 
change takes place as represented in this equation ; — 



SUBSTITUTION-PRODUCTS OF ACETIC ACID 63 

C2H3O.OH ) __ CgHgO ^ |-| , TT |-| 

C2H3O.OH f ~ C2H3O ^ ^ "^ ^'^• 

Hence, according to this, acetic anhydride appears as the oxide 
of acetyl, while the acid itself is the hydroxide. 

It is prepared by treating sodium acetate with acetyl chlo- 
ride : — 

CgHaO.OKa -f CIC2H3O = (G2HsO)20 -f NaCl. 

Acetic anhydride is a colorless liquid which boils at 137**. 
With water it gives acetic acid. 

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

CH5OH + ^'2'^ > = CH3. OC2H3O -f CH3COOH. 
02^130 

Methyl acetate 

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

Substitution-products of acetic add. 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 sub- 
stitution of a halogen, etc., for hydrogen. Only three of the 
four hydrogen atoms of acetic acid are capable of direct 
replacement. The fourth is the one to which the acid prop- 
erties are due. Hence the substitution-products are acid. The 
best known of these products are the chlor-acetic acids which 
are made by treating the acid with chlorine. They are 
monO'Chlor-acetic, di-chlor-acetic, and tm-chlor-acetic adds. Their 
formation is represented by the following equations : — 

C2H3O.OH -h CI2 = C2H2CIO.OH -h HCl ; 
C2H2CIO.OH 4- CI2 = C2HCI2O.OH -h HCl ; 
C2HCI2O.OH -f CI2 = C2CI3O.OH + HCl. 

When treated with nascent hydrogen they are converted 



64 DERIVATIVES OF METHANE AND ETHANE 

back into acetic acid. They yield salts, ethereal salts, anhy* 
drides, etc., just the same as acetic acid itself. 

Theory in regard to the relations between the acids, alcohols, 
aldehydes, and hydrocarbons. The reactions and methods of 
f opnation 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 CaHgO-OH as the formula repre- 
senting this idea. 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 readily replaced by chlorine indicates that it is 
not present as hydroxyl, and all methods of testing for hy- 
droxyl fail to show its presence in acetyl chloride. Hence we 

may conclude that the second oxygen atom is present as car- 

O 
II 
bonyl CO. This leads us to the formula H — C — O — H f or the 

simplest acid, or formic acid. Accordingly, formic acid ap- 
pears as carbonic acid, which is commonly represented by the 

•OH 

formula O = Cv , in which one hydroxyl has been reduced 

^OH 

to hydrogen. It has already been seen that this reduction can 
be accomplished without difficulty. Many other arguments 
might be brought forward in favor of the view that the above 
formulas express the relations between formic and carbonic 
acids. Now, as acetic acid is the homologue of formic acid, 
there is every 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 con- 
firmed by the fact that acetic acid can be made from sodium 
methyl, CHgNa, and from methyl cyanide, CHg . CN. The acid 

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



RELATIONS BETWEEN COMPOUNDS OF CARBON 65 

CO<Qg'. The common constituent of the two acids is the 
O 

y 

group C — O — H or — CO. OH, which is generally known as car- 
boasyl. Acetic acid is closely related not only to formic but to 

carbonic acid. It may be regarded as carbonic acid, CO<Qg, in 

which one hydroxyl is replaced by the radical methyl. In a 
similar way we shall see that all organic acids may be regarded 
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 



C 



H fOH 



H 



1 



H 



H ^ IH 




C H C 





OH. 
LH 



LH IH 

juttiShgaS Methyl aluuuux aMiahvAa xunuiuaum 

(Methane) (Methanol) /-Mpfhanifn (Methanic acid) 



Marsh gas Methyl alcohol Jap^vaL Formic acid 



(Methanal) 

Concerning the mechanism of the changes caused by oxida- 
tion, but little can be determined by experiment. We may re- 
gard methyl alcohol as the first and simplest product of oxida- 
tion of marsh gas. Starting with methyl alcohol, we might 

expect the next change to consist in the introduction of another 

!0H 
OH 
H . But it has been found that, 
H 
except under certain peculiar conditions, one carbon atom can- 
not hold two hydroxyls in combination, and that, if such a 

compound is formed, it loses the elements of water, thus, 

OH 

O 

H + H2O. The result would be the aldehyde. 
H 

This kind of change is illustrated in the formation of carbon 
dioxide from the salts of carbonic acid. Instead of getting 



H ^ 



If, finally, the acid C 



66 DERIVATIVES OF METHANE AND ETHANE 

OH 

the acid CO<^jj, which we should naturally expect, we get 
this minus water : — 

Now, when the aldehyde is oxidized, another oxygen atom is 
introduced, and the substance thus produced is an acid, or the 
hydroxyl hydrogen can be replaced by metals, and has in gen- 
eral the characteristics of acid hydrogen. As soon as we have 
carbon in combination with oxygen as carbonyl, and also with 
hydroxyl, the substance containing the combination is an acid. 

O 

OH is oxidized, it is probable that the 

H 

same change takes place as when the alcohol is oxidized. 
That is to say, the hydrogen is probably replaced by hydroxyl, 
when a compound containing two hydroxy Is in combination 
with one carbon atom would be the result. This would be 
ordinary carbonic acid. But this breaks up into water and 
carbon dioxide, which, as we know, are the products of oxida- 
tion of formic acid. 

All the many representatives of the great classes of carbon 
compounds known as the alcohols, aldehydes, and acids are 
closely related to the three fundamental substances, methyl 
alcohol, formic aldehyde, and formic acid. Replace one of the 
hydrogen atoms of methyl alcohol by a radical, and we get a 

new alcohol, which may be represented by the formula 
rOH 

IT 

. So also a similar replacement of a hydrogen atom in 

IR fo 

formic aldehyde gives another aldehyde, C | H ; and, finally, a§ 

[r 

we have seen, the acids of carbon may be represented by the 

O ^ 

formulas C ^OH, or R.CO.OH, or C0< , which show their 

R 



C I 



ETHEREAL SALTS 67 

relations to formic and carbonic acids. Hereafter, in writing 
the formulas of members of the three great classes, the struc- 
ture 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 

Whenever an acid acts upon an alcohol, the acid is neutralized 
either wholly or partly, and a product analogous to the salts is 
formed. Thus nitric acid and ethyl alcohol give ethyl nitrate : — 

CgHa.OH + HKOa = C2H5.NO8 + HA 

just as nitric acid and potassium hydroxide give potassium 
nitrate. It has been pointed out that the radicals, methyl, CHa, 
and ethyl, C2H5, take the part of metals in the ethereal salts. 
We can thus get a series of methyl and ethyl salts with the 
various acids. 

As regards the preparation of these compounds, it should be 
remarked that the action between an alcohol and an acid does 
not take place as readily as that between an acid and a metallic 
hydroxide. Only a few of the strongest acids act directly 
without aid. Such, for example, are nitric and sulphuric acids, 
though even the latter is not completely neutralized by action 
upon alcohols, as has already been seen in the preparation of 

ethyl-sulphuric acid, ^ > SO4, for the purpose of making ether. 

Plainly ethyl-sulphuric acid is an acid ethereal salt, analogous 
to acid potassium sulphate. Both are still acid, though both 
are likewise salts. 

The methods which may be used for preparing ethereal salts 
are the following : — 

(1) Treatment of an acid with an alcohol. This is capable 
of only very limited application, as in the case of a few of the 
strongest acids. 

(2) Treatment of an acid anhydride with an alcohol. Thus 



68 DERIVATIVES OF METHANE AND ETHANE 

in the case of acetic anhydride and ethyl alcohol this reaction 
takes place : — 

n2'*nS > + CaH^OH = CH3.COOC2H5 -f CHs-COOH. 

(3) Treatment of the chloride of an acid with alcohol. This 
has been illustrated by the action of acetyl chloride, C2H8O.CI, 
upon methyl alcohol (see p. 62) : — 

CsHgOCl -fHO.CH8=C2H80.0CH3 +HC1, 
or CH8.C0C1 + H0.CH8 = CH8.COOCH8 + HCl. 

(4) Treatment of the silver salt of an acid with a halogen 
substitution-product of a hydrocarbon. For example, ethyl 
acetate can be made by treating silver acetate with brom- 
ethane : — 

CH8.C00 Ag + CaH^Br = CH3COOC2H5 + AgBr. 

This reaction is well adapted to showing the relation between 
the salt and the ethereal salt, and leaves no room for doubt that 
the two are strictly analogous. 

(5) Treatment of a mixture of an alcohol and an acid with 
dry hydrochloric acid gas or strong sulphuric acid. The forma- 
tion of ethyl acetate by this method was illustrated in Experi- 
ment 19, p. 61. The sulphuric acid facilitates the action by 
uniting with the alcohol to form ethyl-sulphuric acid, which with 
the acid gives the ethereal salt : — 

^*2«>S04 + CHa-COOH = CH3.COOC2H, + H2SO4. 
Jtl 

It is probable that the hydrochloric acid first acts upon the 
acid forming the chloride, and that this then acts upon the 
alcohol, forming the ethereal salt : — 

CH3.COOH + HCl = CH3.COCI + H2O ; 
CH8.C0C1 + C2H5OH = CH3.COOC2Hfi + HCl. 



ETHEREAL SALTS 69 

Among the more important ethereal salts of methyl and ethyl 
alcohols, the following may be mentioned : — 

Methyl-sulphuric acid, ■^> SO4, formed by mixing 

methyl alcohol and sulphuric acid. The acid itself, as well as 
its salts, is very easily soluble in water. 

Ethyl nitrate, C2H5NO3, formed by treating alcohol with 
nitric acid. Unless precautions are taken in mixing these 
reagents, complete decomposition of the alcohol will take place, 
and the action will be accompanied by a violent explosion. 

Ethyl-sulphuric acid, ^2g^> SO4. Made in the same way 

as the methyl compound. The acid and its salts are easily 
soluble in water. When boiled with water it is decomposed, 
yielding alcohol and sulphuric acid : — 

C^H^^ SO4 + H2O = H2SO4 + C^H^OH. 

Ethyl sulphate, (C2H5)2S04, is made by passing the vapor 
of sulphur trioxide into well-cooled ether : — 

(C,-E,),0 + SOs = (C2H,)2S04. 

Phosphoric acid yields ethyl phosphate, (G2Ti.5)s^04, di-ethyl-phos- 
phoric acidy (C2H5)2HP04, and ethyl-phosphoric acid, C2H5H2PO4. 

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

Of the ethereal salts which the two alcohols form with formic 
and acetic acids, methyl and ethyl acetates 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 acids 
of carbon, and many of the odors of fruits and flowers are due 
to the presence of one or another of these compounds. Many 



70 DERIVATIVES OF METHANE AND ETHANE 

of them also are used for flavoring purposes instead of the 
natural substances. 

Experiment 22. Make a mixture of 15 parts (150?) of ordinary 
concentrated sulphuric acid and 6 parts (60s) absolute alcohol. Add to 
it 10 parts (100^^) sodium acetate. Distil from a flask. Redistil the (us- 
tillate. The ethyl acetate thus formed boils at 77°. What reactions take 
place in this case ? 

Decomposition of ethereal salts. Salts of most metals ^re de- 
composed when treated with an alkaline hydroxide, as caustic 
soda or caustic potash, the result being a salt of the alkali and 
the hydroxide of the replaced metal, as seen in the case of 
copper sulphate and sodium hydroxide : — 

CUSO4 + 2 NaOH = Cu(0H)2 + Na^S04. 

So also the ethereal salts are decomposed when treated with the 
alkalies, though, as a rule, not as readily as salts. It is usually 
necessary to boil the ethereal salt with the alkali when decom- 
position 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 treated with a 
solution of caustic potash, this reaction takes place : — 

(C2H5)2S04 + 2 KOH = K2SO4 + 2 CgH^.OH ; 

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

CH8.COOC2H5 + ]SraOH= CH8.C00Na + C2H5OH. 

Experiment 23. In a 500c<: flask put 200<:c water, 50s solid caustic 
potash, and 20cc ethyl acetate. Connect with an inverted condenser, 
arranged as shown in Fig. 8. Boil gently for half an hour. Now connect 
the condenser with the flask for distilling, and again boil. Examine the 
distillate for alcohol. Acidify the contents of the flask with sulphuric 
acid, and again distil. What passes over ? 

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. 



ACETONE 



71 



As will be shown, the fata are ethereal salts, and soap-making 
consista in decomposing these fats by means of the alkalies. 
Hence, generally, to saponify an ethereal salt means to decom- 
pose it by means of an alkali into the corresponding alcohol 
and the alkali salt of the acid contained in it. 




6. Ketones or Acetones 
When an acetate is distilled, a liquid passes over which has 
the composition CaHgO, and a carbonate remains behind. The 
reaction has been carefully studied, and has been shown to take 
place in accordance with the following equation: — 
CHa-COO ., 



CH3.COO 



> Ca = CgH.O + CaCO,. 



The substance CaHaO is known as acetone. It is the best 
known representative of a class of compounds which are some- 
times called acetones, but more commonly ketones. 

Acetone, dimethylketone, propanone, CjHaO. — This 
substance has long been known as a product of the distillation 
of acetates. It is contained in considerable quantities in the 



72 DERIVATIVES OF METHANE AND ETHANE 

product obtained in the distillation of wood, and can be sepa- 
rated from the mixture after the removal of the acetic acid. 
It also occurs in the blood and in urine in small quantity. 
In certain abnormal conditions it occurs in the urine in large 
quantity as in acetonuria and in diabetes mellitus. 

It can be purified by shaking a mixture containing it with a 
concentrated solution of mono-sodium sulphite. It unites with 
the salt, forming a compound analogous to that formed with 
aldehyde. The double compound can be separated, and when 
distilled with the addition of potassium carbonate acetone 
passes over. 

Acetone is a colorless liquid having a penetrating, pleasant, 
ethereal odor. It boils at SG-S**. It is a good solvent for many 
carbon compounds, such as resins, fats, etc. 

On studying the conduct of acetone, it soon becomes evident 
that it more closely resembles the aldehydes than any other 
bodies thus far considered. It is plainly not an acid nor an 
alcohol. It acts entirely differently from either. It is not 
an ethereal salt, for on boiling with an alkali it does not yield an 
alcohol nor 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 replaced 
by two chlorine atoms thus : — 

CsHeO + PCI5 = CsHeClg + POCls; 

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 C2H8CO. The 
formation from calcium acetate leads further to the belief that 
the group C2H6 really consists of two methyls, as the simplest 
interpretation of the reaction is represented thus : — 



CH3COO _CH3 

CH3COO ^^^- CH3 



> ca = ;;;7 > co + cacOs. 

According to this, acetone is a compound of two methyl groups 



ACETONE 73 

and carbonyl, or it is carbon monoxide whose two available 
affinities have been satisfied by two methyl groups. 

We can test the correctness of this view by means of synthe- 
ses. If it is correct, it will be seen that acetone is closely re- 
lated to acetyl chloride. It is acetyl chloride in which the 
chlorine has been replaced by methyl : — 

CH3.CO.CI CH8.CO.CH3. 

Acetyl chloride Acetone 

Now, when acetyl chloride is treated with zinc methyl, Zn(CH8)2, 
it yields acetone according to this equation : — 

2 CH8.C0C1 + Zn(CH8)2 = 2 CH3.CO.CH3 + ZnClg. 

The relation between acetone and ordinary acetic aldehyde is 
similar to that of an ethereal salt to its acid ; that is, acetone 
is aldehyde, CHg.COH, in which the hydrogen has been replaced 
by methyl, CH3.CO.CH3. 

Like the aldehydes, the acetone has the power of taking up 
other substances, such as the acid sulphites, ammonia, hydro- 
cyanic acid, hydrogen, etc. This power is in some way con- 
nected with the relation of the oxygen to the carbon, which is 
the same in both compounds. Nevertheless, this condition of 
the oxygen does not always carry with it the same power as 
seen in the case of the acids which also contain carbonyl. 

By reduction with nascent hydrogen, acetone yields an alcohol 
of the formula CgHgO, known as secondary propyl alcohol, which 
when oxidized yields acetone. In other words, the relation be- 
tween this alcohol and acetone is much 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. Towards oxidizing agents, then, 
acetones (for it will be shown that other acetones conduct 
themselves in the same way) act entirely differently from the 
aldehydes. The alcohol above mentioned as related to acetone 



74 DERIVATIVES OF METHANE AND ETHANE 

is the simplest representative of a class of alcohols differing in 
some respects from the substances commonly called alcohols. 



The most important representatives of six classes of oxygen 
derivatives of the hydrocarbons have thus far been treated of, 
and, by the aid of a study of their chemical conduct and of the 
methods that may be 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 hydro- 
carbons or the hydroxides of certain groups called radicals; 
the ethers are the oxides of these same radicals ; the aldehydes 
are compounds 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 com- 
pounds consisting of carbonyl and two radicals. 

These ideas are expressed in formulas thus, R being any 
univalent radical like methyl, CHg, or ethyl, C2H5: — 

Alcohol . . . . R-O-H. 

Ether E-O-R. 

Aldehyde . . . R-C-H. 

II 


Acid R-C-O-H. 

II 


Ethereal salt . . Ac — O — R (Ac — O — H representing any 

monobasic acid). 

Ketone . . . • R — C — R. 

II 



CHAPTER V 

SULPHUR DERIVATIVES OF METHANE AND ETHANE 

1. Mercaptans 

The simplest derivatives of methane and ethane containing 
sulphur are the so-called mercaptans or sulphur alcohols. They 
can be made by a method similar to one described under the 
head of Alcohols. When a mono-halogen derivative of a hydro- 
carbon, as brom-methane, CHgBr, is treated with the hydroxide 
of a metal, as silver hydroxide, AgOH, an alcohol is formed : — 

CHaBr + AgOH = CHgOH + AgBr. 

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

CHgBr + KSH = CHsSH + KBr. 

The compound is called a mercaptan, 

Ethyl-mercaptan, CgHg.SH. — This substance can be pre- 
pared by treating iodo-ethane, C2H5I, with an alcoholic solu- 
tion of potassium hydrosulphide, KSH; also by distilling a 
mixture of the concentrated solutions of potassium ethylsul- 
phate and potassium hydrosulphide : — 

Jv 

It is a liquid of an extremely disagreeable odor; it boils at 36**; 
and is difficultly soluble in water. 

The name mercaptan was given to it on account of its 
action towards mercury. It readily forms a compound in which 
mercury takes the place of hydrogen, (C2H5S)2Hg; and the 
name has reference to this power (mercurium captans). It 

76 



76 DERIVATIVES OF METHANE AND ETHANE 

forms many other well-characterized metallic derivatives like 
this mercury compound. 

When the sodium compound of mercaptan is exposed to the 
air, it takes up oxygen. So, also, when mercaptan itself is 
treated with nitric acid, it is oxidized, the product having the 
formula C2H5.SO3H. It will thus be seen that, though in com- 
position 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. 
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 ethyl-sulphonic 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, C2H5 . SO2CI ; and, when this is treated with nascent hydro- 
gen (zinc and hydrochloric acid), it is reduced to mercaptan: — 

C2H5.SOaCl + 6H = C2H5.SH + HCl + 2HaO. 

2. Sulphur Ethers 

These are compounds similar to the ethers. They contain 
sulphur in the place of the oxygen of the ethers. Such are 
methyl sulphide, (€113)28, and ethyl sulphide, (€2115)28. These 
are made by treating brom- or iodo-methane or ethane with 
potassium sulphide : — 

2 G^il,! + K2S = (C,'R,)S + 2 KI ; 
or by treating the sodium salt of methyl or ethyl-mercaptan 
with methyl or ethyl iodide: — 

€2H5 . SNa + C^R,! = (€2H5)2S + Nal. 

They are liquids with very disagreeable odors. When oxi- 
dized they are converted into sulphones, two atoms of oxygen 

being added, thus ^^JJs > s + 0, = ^^H^ ^ g^^^ 

O2XI5 ^2"^5 



SULPHONIC ACIDS 77 

3. SuLPHONic Acids 

It was stated above, that when mercaptan is oxidized it is 
converted into an acid of the formula C2H5 . SOsH, or ethylrstd- 
phonic add. This is the representative of a large class of sub- 
stances which are commonly made by treating carbon compounds 
with sulphuric acid. These sulphonic acids can best be studied 
in connection with another series of hydrocarbons. Under the 
head of Benzene (which see) it will be shown that, when this 
hydrocarbon is treated with sulphuric acid, a reaction takes 
place that may be represented thus: — 

C«He + ^^ > SO, = ^^' > SO, + H,0. 

Benzene Benzene-snlphonic acid 

The sulphonic acid thus obtained can also be made by oxi- 
dizing the corresponding mercaptan or hydrosulphide, CeHg. SH. 
Accordingly, the sulphonic acid appears to be sulphuric acid in 
which a hydroxyl has been replaced by the radical CeH^. Rea- 
soning by analogy, which, fortunately, is supported by other 
arguments, we may conclude that ethyl-sulphonic acid formed 
from ethyl-mercaptan bears a similar relation to sulphuric acid, 

P XT 

and corresponds to the formula ^q^>^^2' So, also, methyl- 

sulphonic acid obtained by oxidation of methyl-mercaptan 

should be represented by the formula tiq'>S02 or CHs . SO2OH. 

Its relation to sulphuric acid is the same as that of ascetic acid to 
carbonic add. 

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

C^H^I-h ^>S03 = ^^^'>S03-FKI, 
or C2HJ-h^^>S02 = ^^«>S02-hKL 



78 DERIVATIVES OF METHANE AND ETHANE 

According to this reaction the sulphonic acids appear to be 
identical with the ethereal salts of sulphurous acid, but they 
do not conduct themselves like ethereal salts. The sulphonic 
acids as a class are, for example, much more stable than the 
ethereal salts as a class. It would be premature at this stage 
to discuss fully the question as to their relations. Whatever 
we may call them, 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 aie represented by the following formulas : — 

Carbonic acid, C0<^^ Sulphuric acid, ^^^<oH 

Formic acid, CO < "^ Sulphurous acid, SO2 < 

OH OH 

Acetic acid, CO < ^^» Methyl-sulphonic acid, SOj < ^' 

Any carbonic , CO < R Any sulphonic acid, SO,<J„ 
acid, > OH OH 

The difference between a sulphonic acid and an ethereal salt 
of sulphuric acid should be specially noticed. Compare for this 

C IT O 

purpose ethyl-sulphuric acid, ^ hq^^^^' ^^^ ethyl-sulphonic 

acid, HO -^^^2* Both are monobasic acids, and both contain 

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 ethyl-sulphonic acid the ethyl 
group is directly connected with the sulphur; and that in 
ethyl-sulphuric acid the connection is established by means of 
oxygen. The strongest argument in favor of this view is per- 
haps that which is founded on the formation of the sulphonic 
acids by oxidation of the hydrosulphides or mercaptans. It 
can hardly be doubted that in ethyl-mercaptan the sulphur is in 



8ULPH0KIC Acros 79 

direct combination with the ethyl ; or, to go still farther, that 
it is in combination with carbon, as represented in the formula 

H 
HsC — C — S — H. Now, by oxidation of mercaptan, three atoms 

H 
of oxygen are added, and the simplest view of the reaction 
is that the sulphur is left undisturbed in its relations to ethyl, 
but that it has taken up the oxygen, as represented in the 
formula C2H5— SOg.OH. As has been shown, the oxygen can 
be removed again by nascent hydrogen, and the result is mer- 
captan. The study of the sulphonic acids in their relations to 
sulphuric and sulphurous acids has been of considerable assist- 
ance in enabling chemists to form conceptions in regard to the 
relations of the constituents of the two latter. 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 represented 

OH H 

in the formulas S02<qtt and S02<qjj; and, further, that in 

sulphurous acid one hydrogen is in combination with sulphur 
and the other with oxygen. 



CHAPTER VI 

NITROGEN DERIVATIVES OF METHANE AND ETHANE 

The simplest compounds of carbon containing nitrogen are 
cyanogen and hydrocyanic acid. Strictly speaking, neither can 
be regarded as a derivative of a hydrocarbon, unless indeed hy- 
drocyanic acid be regarded as marsh gas, in which three hydro- 

gen atoms have been replaced by one nitrogen ^ C < and 

C I . That, however, is a mere matter of words, as there is 

nothing in the conduct of either substance, or in the methods 
of formation of hydrocyanic acid, that would lead us to suspect 
any relation between them. Though cyanogen and hydro- 
cyanic acid are therefore not to be considered as derivatives of 
the hydrocarbons, they form the starting-point for the prepa- 
ration of so many important compounds that they and their 
simpler derivatives must receive some attention at this stage. 

Cyanogen, (CN)2. — All organic compounds that contain 
nitrogen give sodium cyanide when ignited with sodium. So, 
also, potassium cyanide is formed when charcoal containing 
nitrogen is heated with potassium carbonate. Cyanogen itself 
is most 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 formed, and remains behind in the retort. It has 

80 



HYDROCYANIC ACID 81 

the same composition as cyanogen, and although its molecular 
weight is not known, it is presumably a polymeric form of 
cyanogen. 

Cyanogen (from icmvos, blue) owes its name to the fact that 
several of its compounds have a blue color. It is a colorless 
gas, which is easily soluble in water and alcohol, and is extremely 
poisonous. It burns with a purple-colored flame. 

In aqueous solution, cyanogen soon undergoes change, and a 
brown amorphous body is deposited. The solution contains 
hydrocyanic acid, oxalic acid, ammonia, carbon dioxide, and 
urea. 

The compounds containing the cyanogen group, CN, may be 
compared with those containing the halogens. In them the 
cyanogen group plays the same part as the halogen atom In the 
halides. Thus we have : — 



AgCl 


AgCN 


KCI 


KCN 


FeClj 


Fe(CN), 


etc. 


etc. 



Hydrocyanic acid, HON. — This acid, which is commonly 
called prussic acid, occurs in nature in amygdalin in combina- 
tion with other substances, in bitter almonds, the leaves of the 
cherry, laurel, etc. It is. prepared by decomposing metallic 
cyanides with hydrochloric acid, as represented in the equa- 

KCN + HCl = KCI + HCN. 

It can also be made by treating chloroform with ammonia : — 

CHClg + NHg =HCN +3 HCl, 
or CHClg + 5 ISTHg = NH^.CIT + 3 NH^Cl. 

It is a volatile liquid, boiling at 26.5°, which solidifies at — 15®. 
It has a very characteristic odor, suggesting bitter almonds. It 
is extremely poisonous. It dissolves in water in all proportions, 
and it is this solution that is known as prussic acid. Pure 



82 DEBIVATIVES OF METHANE AND ETHANE 

hydrocyanic acid does not suffer decomposition when kept. 
When water or ammonia is present, it decomposes and gives 
ammonia, formic acid, oxalic acid, and a brown substance. A 
small quantity of a mineral acid prevents this decomposition. 
By boiling with alkalies or acids it is converted into formic 
acid and ammonia (see p. 57). 

Hydrocyanic acid can be detected by the fact that when its 
solution is treated with an excess of caustic potash, and a 
solution containing a ferrous and a ferric salt is added, and the 
mixture boiled, a precipitate of Prussian blue is formed when 
the mixture is acidified ; or, by adding yellow ammonium sul- 
phide to its solution, evaporating to dryness, and then adding a 
drop of a solution of ferric chloride. If hydrocyanic acid was 
present, the solution turns a deep blood-red in consequence of 
the formation of ferric sulpho-cyanate. 

Cyanides. — Hydrocyanic, like, hydrochloric acid, forms a 
series of salts, which are called the cyanides. The cyanides of 
the alkali metals and of mercury 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 
formed by potassium cyanide, in solutions containing the heavy 
metals, are dissolved by excess of the cyanide. 

Potassium cyanide, KCN. — When anhydrous potassium 
ferrocyanide is ignited, potassium cyanide is formed according 
to this equation : — 

K^FeCCN), = 4 KCN + FeCg + ^2. 

Plainly only two-thirds of the cyanogen is thus obtained in the 
form of the potassium salt. In order to obtain a larger yield 
of cyanide it has been customary to melt together potassium 
carbonate and ferrocyanide. The reaction that takes place is 
represented thus : — 

K^FeCCN)^ + KaCOj, = 5 KCN + KCNO + CO^ + Fe. 



POTASSIUM FERROCYANIDB 83 

The product contains potassium cyanate. Potassium cyanide, 
free from the cyanate, but containing sodium cyanide, is now 
made on the large scale by heating together dehydrated potas- 
sium ferrocyanide and metallic sodium : — 

K4Fe(CN)e + 2 ISTa = 4 KCN + 2 NaCIT + Fe. 

Potassium cyanide is a violent poison. It dissolves easily in 
water. When the solution is boiled, ammonia and potassium 
formate are formed. The solution has an alkaline reaction 
due to hydrolysis : — 

KCIST + H2O = HCN + KOH. 

It is decomposed by carbon dioxide and hence when exposed 
to the air it has the odor of hydrocyanic acid. It precipitates 
cyanides from the solutions of almost all metallic salts. When 
added in excess it dissolves the precipitates, forming soluble 
double cyanides. A solution of potassium cyanide has the 
power to dissolve gold from powdered gold ores and it has 
come into extensive use for this purpose. 

Among the best-known double cyanideis are the two salts, 
potassium ferrocyanide and potassium ferricyanide. The former 
is commonly caHed yellow prussiate of potash, and the latter red 
prussiate of potash. 

Potassium ferrocyanide, 4 KCN.Pe (ON)2 + 3H20.— 
This is made on the large scale by melting together, in iron 
vessels, refuse animal substances (r.e., organic matter contain- 
ing nitrogen) with potassium carbonate and iron. The mass 
is treated with water, and the salt thus extracted then purified 
by crystallization. 

It crystallizes in large, lemon-yellow, monoclinic plates, 
soluble in about four parts of water at 15°. 

Experiment 24. ^ Make a mixture of 8 parts (1008) dehydrated 
potassium ferrocyanide and 3 parts (60^) dry potassium carbonate. Fuse 

> Experiments 24 and 26 may bo postponed until urea Is taken up, when they may be 
combined with the artlAcial preparation of urea. 



84 DERIVATIVES OF METHANE AND ETHANE 

in an iron crucible, at a low red heat, until a specimen taken out and 
placed on a stone is white when solid. Then pour out on a flat, smooth 
stone, and afterwards break up and put in a dry bottle. 

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

2[4 KCN.re(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. 

Potassium ferrocyanide is the starting-point in the prepara- 
tion of all compounds containing cyanogen. 

Potassium ferrioyanide, 3KON.Pe(ON)8.— This salt, 
known as red prussiate of potash, is prepared by oxidizing the 
ferrocyanide, either by means of chlorine or of potassium 
permanganate. 

Experiment 25. Dissolve 26s potassium ferrocyanide in 2QX)^^ cold 
water, and add S** ordinary concentrated hydrochloric acid. Into this 
pour slowly a cold solution of 2« of potassium permanganate in 300«« 
water. The oxidation is complete when a drop added to ferric chloride 
gives a brownish>red color, but no precipitate. Neutralize with chalk, 
filter, and evaporate to crystallization on a water-bath. 

Potassium f erricyanide is easily soluble in water, and crys- 
tallizes from its concentrated solutions in large, dark-red, 
orthorhombic prisms. 

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

(1) Prussian blue, (2) TumbulVs blue, and (3) soluble Prus- 
sian blue are complex double cyanides of iron represented by 
the formulas 

(1) 4 re(CN)3.3 re(C]Sr)2 or Fe;"[Fe"(C]Sr)6]3*^ 

(2) 3Fe(CN)2.2Fe(C]Sr)8 or Fe3"[Fe'"(C]Sr)6]2'", and 

(3) KCN.Fe(CN)3.Fe(CN)2 or KFe' ' '[^e" (CN)6]% respectively. 



CYANIC ACID 85 

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

Gyanosren chlorides. — 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 
CNCl. It boils at 15.5^, and its vapor acts upon the eyes, 
causing tears. It is known as liquid cyanogen chloride to dis- 
tinguish it from solid cyanogen chloride. The latter has the 
formula (C!N")8Cl3, and is formed by treating anhydrous hydro- 
cyanic 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 
known. 

Cyanic acid, NOOH. — When a cyanide of an alkali is 
treated with an oxidizing agent, it takes up oxygen and is con- 
verted into a cyanate : — 

NCK + = NCOK. 

Experiment 26.^ Dehydrate slowly 1258 potassium ferrocyanlde in 
an iron pan on a gas stove ; powder the dried salt and heat gently 1 to 2 
hours. Fuse 75s potassium bichromate, cool, powder finely, and mix 
thoroughly with the ferrocyanide. Bring the warm mixture in small 
portions with an iron spoon into a shallow iron pan which is heated suf- 
ficiently to cause the powder to glow and turn black. Stir rapidly during 
the reaction. Powder the porous mass, bring it while still warm into a 
mixture of 460^0 of 80 per cent alcohol and 50«« methyl alcohol in a litre 
balloon-fiask and heat to boiling in a water-bath. The water in the bath 
should be boiling and the alcohol warm when the mixture containing the 
cyanate is added. Boil for five minutes ; allow the undissolved part to 
settle and pour the clear solution through a plaited filter into a beaker 
standing in ice-water. The potassium cyanate separates as a heavy white 
crystalline powder. Shaking the fiask in ice-water hastens the crystal- 
lization. Let the salt settle. With the mother-liquor repeat three times 
without delay the extraction of the black mass, boiling ten minutes each 

^ See Note, p. 88. 



86 DERIVATIVES OF METHANE AND ETHANE 

time. With the aid of a pump, filter each portion as soon as obtained ; 
wash the united portions with ether; and dry in a desiccator over sul- 
phuric acid. The ferrocyanide must be anhydrous and the work must 
be done rapidly. The hot alcoholic solution must be cooled rapidly to 
prevent decomposition of the cyanate. 

Cyanic acid is readily decomposed by water yielding ammo- 
nia and carbon dioxide : — 

NCOH -f H2O = NHs + COjj. 

The potassium salt is easily soluble in water, but is decom- 
posed by it, yielding ammonia and potassium bicarbonate : — 

NCOK + 2 H2O = KHCOg + NHg. 

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 easily soluble in water; 
but, if allowed to stand in solution, or if its solution is heated, 
it is completely transformed into urea, which is isomeric with it. 
The interest connected with this transformation was referred 
to in the introductory chapter (p. 1). It will be treated of 
more fully under urea. 

Oyanurio acid, O3N3H3O3 + 2 HgO. — This acid bears a re- 
lation to cyanic acid similar to that which solid cyanogen chlo- 
ride, (CN)3Cl3, bears to the liquid variety. It is made by 
treating the solid chloride with water, and also by heating 
urea. It is a crystallized substance. 

Sulpho-cyanio acid, NOSH. — 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 sulpho-cyanates : — 

CNK + S = NCSK. 

Potassium 
sulpho-cyanate 

Experiment 27. Mix 46k dehydrated potassium ferrocyanide with 
178 dehydrated potassium carbonate, 32k sulphur, and 2s powdered char- 
coal. Fuse the mixture in an iron pan on a gas stove until the mass has 



SULPHO-CYANIC ACID 87 

become liquid, and a sample no longer precipitates Prussian blue when 
added to a solution of ferric chloride, but turns the solution blood-red : — 

K4Fe (CN)6 + K2CO8 + 8 S = 6 KCNS + FeSs + CO2 + O. 

The oxidation of the sulphur is prevented by the charcoal. Pour the fused 
mass on an iron plate, break it up into a coarse powder, and bring it into 
a flask with 250<'c alcohol. Boil with a return condenser for ten minutes, 
and finally filter the hot solution, which contains only sulpho-cyanate. On 
cooling, the salt crystallizes in long colorless prisms. Pour off the mother- 
liquor, and use it to extract the residue again for a second crystallization. 
Evaporation of the mother-liquor will yield a third crystallization. The 
dried crystals should be preserved in well-stoppered bottles, as the salt is 
very hygroscopic. 

Potassium sulpho-cyanate crystallizes in long striated prisms 
without water of crystallization. It is deliquescent. When 
dissolved in water the temperature sinks markedly. When 100 
parts of water of 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 recovered. 

Experiment 28. Dissolve some potassium sulpho-cyanate in water, 
and note the temperature before and after introducing the salt. 

Ammonium sulpho-cyanate, NCS.NH4. This salt is most 
easily prepared by treating carbon bisulphide with concen- 
trated alcoholic ammonia; — 

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

Experiment 29. Mix 240cc strong aqueous ammonia, 240«« alcohol, 
and 608 carbon bisulphide. Allow the mixture to stand for one or more 
days. Then distil down to one-third of the original volume, and filter 
while still hot the solution left in the flask. On cooling, ammonium 
sulpho-cyanate will crystallize out. 

The salt crystallizes in plates. It melts at 130°-140°, and 
at this temperature is partly transformed into the isomeric 
substance sulpho-urea. (Analogy to transformation of ammo- 
nium cyanate.) 

Having thus dealt with some of the more important simpler 
cyanogen compounds, let us now return to the nitrogen der 



88 DERIVATIVES OF METHANE AND ETHANE 

rivatives of the hydrocarbons. For convenience, these may be 
divided into three classes : — 

(1) Those which are related to cyanogen ; 

(2) Those which are related to ammonia; 

(3) Those which are related to nitric acid. 

Cyanides 

Methyl cyanide, OHg.ON. — This compound is formed by- 
distilling a mixture of potassium methyl-sulphate and potas- 
sium cyanide:-^ 

^5' > SO4 + KCN = K2SO4 + CHgCN. 

It is a liquid boiling at 82®. 

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. 

Bthyl oyanide, O2H6.ON. — Formed like the methyl com- 
pound. Also by heating chlor-ethane with potassium cya- 
nide: — 

. C2H5C1 + KCN = C2H5.CN + KC1. 

It is a liquid boiling at 98°. 

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

When methyl cyanide is treated with caustic potash, it yields 
acetic acid and ammonia : — 

CH8.cn + H2O + KOH = CH8.CO2K -f NH3. 

This reaction is strictly analogous to that which takes place 
with hydrocyanic acid, yielding formic acid (see p. 57). In 
the same way ethyl cyanide yields an acid of the formula 



ETHYL CYANIDE 89 

C8He02 (or 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. 

NoTB FOR Student. — Show how, by starting with methyl alcohol, 
acetic acid may be made by passing through the cyanide. 

/' 

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 HgC — C = N, or by the 
nitrogen atom, as represented thus, HgC — 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 it 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. 

In consequence of the close relation existing between the 
cyanides and the acids, the former are often called the nitriles 
of the acids. Thus methyl cyanide, which is converted into 
acetic acid by boiling with caustic potash, is called the nitrile 
of acetic acid, or aceto-nitrile. In the same way hydrocyanic 
acid itself may be regarded as the nitrile of formic acid, or 
formo-nitrile. 

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

C2H6 
ammonia the relation indicated by the formula N]h ; i.e., it 

H 



90 



DERIVATIVES OF METHANE AND ETHANE 



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

fC2H5 
H3C - C - N + 4 H = H3C - HgC - NH2 



or N< 



H 
H 



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 difficult 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 ethyl-amine when treated with 
nascent hydrogen, so hydrocyanic acid yields methyl-amine, 

CHs 

N^H : — 



H 



H-C-N + 4H = H8C-NHs 



or N< 



CH3 

H 

H 



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

ISOCYANIDES OR CaRBAMINES 

If, in making an ethereal salt of hydrocyanic acid from a salt, 
the silver salt is use'd, 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 carbamine. 

Ethyl isocyanide or ethyl carbamine, O2H5NO. — This 
compound is obtained when silver cyanide and iodo-ethane are 
heated together : — 

C2HJ + AgNC = C2H5NC + Agl. 

It is also formed when chloroform and ethyl-amine (see above) 
are brought together : — 

CHCI3 -I- N ] H = C2H5NC + 3 HCl. 
H 



ETHYL ISOCYANIDE 91 

It is a liquid boiling at 78.1°. It is characterized by an ex- 
tremely disagreeable odor. The methyl compound obtained by 
the same method boils 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 treated with dilute 
hydrochloric acid, they undergo an interesting cha' '*«, which 
is represented by the following equation in the case o^ ''^e 
methyl compound : — 

CHg . NC + 2 HgO = CHg - NHa + H.COgH. 

Methyl amine Formic acid 

This reaction indicates that in the isocyanides the cyanogen 
group is united to the radical by means of nitrogen, as repre- 
sented by the formula HgC — !N" — C. Hence it is, in all prob- 
ability, that when they undergo decomposition the nitrogen 
remains in combination with the radical, while the carbon of , 
the cyanogen group passes out of the compound. The conduct 
of ethyl isocyanide is represented by the equation : — 

C2H5.NC + 2 H2O = C2H5 - NHjj + H.CO2H. 

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, leads to the 
suspicion that in silver cyanide the metal may be in combina- 
tion 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 



92 DERIVATIVES OF METHANE AND ETHANE 

ethyl iodide acts upon potassium cyanide^ the principal reaction 
is direct addition : — 

KN : C + C2H5I = 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 : — 

C2H5 
AgN:C + C2HJ= 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 peculiar 
relations 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 and the cyanides, it seems not improbable that the acid is 
capable of assuming both forms represented by the formulas 
UN" : 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. A compound that can change from one iso- 
meric form to another or that reacts as though it had two 
different formulas is called a taviomeric compound. The phe- 
nomenon is called tautomerism. 

Experiment 30. The odor of the isocyanides, as has been stated, is 
extremely disagreeable, and in concentrated form it is almost unbearable. 
A vivid impression in regard to this property may be produced by the 
following experiment. In a test-tube bring together a little chloroform, 
aniline, and alcoholic potash. The reaction takes place at once. It is 
better to perfoim the experiment out-of-doors, and in such a place that 
the tube with its contents can be thrown away without molesting any 
one. The aniline used is a substituted ammonia analogous to methyl- 
amine, containing the radical CeHs in place of methyl. The isocyanide 
formed has the formula CeHs.NC. 



SULPHO-CYANATB8 93 

Cyanatbs and Isocyanates 

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

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

In the isocyanates (first called cyanates) the radical is 
believed to be united to the cyanogen by means of nitrogen, as 
represented thus, CHg — N — CO. The isocyanates are made 
by distilling potassium cyanate with the potassium salt of 
methyl- or ethyl-sulphuric acid. They can be made also by 
bringing together the iodides of radicals, or iodo-methane and 
silver cyanate. They are very volatile substances, which have 
penetrating and suffocating odors. 

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

C2H5 - N = CO -f H2O = C2H5.NH2 + CO2; 
CHs - N = CO -F H2O = CHg .NHa -f COj. 

S ULPHO-CTANATES 

The ethereal salts of sulpho-cyanic acid are easily made by 
distilling potassium sulpho-cyanate and the potassium salt of 
methyl- or ethyl-sulphuric acid : — 

^?? > SO4 + KSCN = CHgSCIsr + K2SO4. 

The ethyl compound, which is very similar to the methyl com- 
pound, is a liquid boiling at 142°. 

When boiled with nitric acid, it is oxidized to ethyl-sulphonic 
acid. Now, it has been shown above (see p. 78), that in ethyl- 
sulphonic acid the ethyl in all probability is in combination 
with the sulphur. It hence follows that, in the sulpho-cyanates 
obtained from potassium sulpho-cyanate, the radical is also 
in combination with sulphur, as indicated in the formula, 
CgH^ — S — CN. This view is supported by the fact that 



94 DERIVATIVES OF METHANE AND ETHANE 

ethyl sulphocyanate readily yields ethyl-mercaptan when 
treated with nascent hydrogen. 

The sulpho-cyanates are converted into iso-sulpho-cyanates 
or mustard-oils by heat. 

ISO-SULPHO-OYANATES OR MuSTARD-OlLS 

A number of compounds isomeric with the sulpho-cyanates 
are known. The best-known member of the class is ordinary 
mustardrOiL 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. 

NH 

This is really the ammonium salt of carbamic acid, 0C<^„^* 

Its formation is represented thus : — 

"N"TT 

C02-+-2NH3 = OC<^^^. 

Now, remembering that carbon bisulphide is similar to carbon 
dioxide, and that ethyl-amine is similar to ammonia, we can 
readily understand the reaction which takes place when these 
two substances are brought together : — 



NHC2H5 



CS2-F2NHAH.= SC< 



The product formed is the ethyl-ammonium salt of the acid 

NTTC H 

SC<„„ ^ ^, which is called ethyl-sulpho-carbamic acid. 

When the ethyl-ammonium salt is treated with silver nitrate, 

the corresponding silver salt, SC<^ ^ ^, is precipitated. 

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

2 SC < g^^'^' = 2 SC - NCgH, + HjS + Ag^S. 



ISO-SULPHO-CYANATES 



95 



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

Some of the arguments have been stated which lead to the 
view that in the sulpho-cyanates 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 ethyl-amine, carbon 
dioxide, and hydrogen sulphide : — 

SC - NCgHs + 2 H2O = C2H5NH2 + H2S -f CO2. 

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

SC - NC2H5 + 4 H = C2H5.NH2 + H2CS. 

Thus, as has been shown, the sulpho-cyanates yield mercaptans 
with nascent hydrogen, while the iso-sulpho-cyanates yield sub- 
stituted ammonias. These facts point to the relations ex- 
pressed in the formulas, R — S — CN for the sulpho-cyanates, 
and E» — N — CS for the iso-sulpho-cyanates or mustard-oils. 



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

Cyanides, R— C— N . . . 



Cyanates, R— 0— CN . . 
Sulpho-cyanates, R — S — CN" 



Isocyanides orl ^ 
Carbamines, J 



. Isocyanates, R— N— CO. 

. Iso-sulpho-cya- 
nates or Mus- 
tard-oils. 
Of these all are known except the cyanates. 



.R__N«CS. 



96 DERIVATIVES OF METHANE AND ETHANE 

Substituted Ammonias 

When brom-ethane or a similar substitution-product is 
treated with ammonia, the reactions represented by the fol- 
lowing equations take place step by step: — 

C^H.Br + NHs = NH3(C2H,)Br ; 

CgH^Br -f NH^CC^H^) = NH2(C2H5)2Br ; 
C,H,Br + NHCCaH^)^ = NH(C2H,)3Br ; 
C2H5Br + N(C2H5)3 =N(C2H,)4Br. 

The products thus formed are salts resembling ammonium 
salts. When the first three are distilled with potassium 
hydroxide they are decomposed, just as ammonium bromide 
would be. Only instead of ammonia and potassium bro- 
mide, the compounds ethyl-amine, NH2.C2H5, di-ethyl-amine, 
NH(C2H5)2, and tri-^thylramine, N (€2115)8, are obtained.- These 
substances may be regarded as derived from ammonia by the 
replacement of one, two, and three of the hydrogen atoms 
respectively by ethyl. The last product of the series of re- 
actions represented above may be regarded as ammonium 
bromide, NH4Br, in which all four hydrogen atoms are re- 
placed by ethyl groups. 

The decomposition by potassium hydroxide of the first two 
salts is represented thus : — 

NH8(C2H5) Br -f KOH = NH2(C2H5) 4- KBr -f H2O ; 
NH2(C2H5)2Br + KOH = NH(C2H5)2 + KBr + HgO. 

Methyl-amine, NH2CH3. — This compound can be pre- 
pared by treating iodo-methane with ammonia, the direct 
product of the reaction being methyl-ammonium iodide, 
NH8(CH3)I : — 

CHgl + NHg = NHgCCHg)!. 

It was first made by treating methyl isocyanate, CHg — N = CO, 
with caustic potash : — 

CH3 - N - CO + H2O = NHg. CHg + CO2. 



DI-METHYL-AMINB 97 

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

HCN + 4H = NH2.CHs. 

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

Methyl-amine is a gas that is easily condensed to a liquid. 
It smells like ammonia and fish. It burns with a yellow flame. 
It is more strongly basic and more soluble in water than am- 
monia, 1 volume of water at 12.5° taking up 1150 volumes of 
the gas. This solution acts almost exactly like a solution of 
ammonia in water. It is strongly alkaline. It precipitates 
many metallic hydroxides from solutions of their soluble salts, 
but, unlike ammonia, it does not dissolve precipitated hydrox- 
ides of nickel, cobalt, and cadmium when added in excess. It 
dissolves aluminium hydroxide. 

Methyl-amine 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 + HNOs = (NHsCHg) NOs; 
2 NH2CH3 + H2SO4 = (NH3CH8)2S04. 

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

Di-methyl-amine, NH(OH8)2. — This is formed by heating 
iodo-methane with alcoholic ammonia : — 

2 CHsI + 2 NHg = NH (CH8)2 . HI + NHJ. 

It is formed, together with methyl-amine, as a product of 
the distillation of wood. 

It is a gas which condenses to a liquid at -f 7.2®. Its prop* 
erties are much like those of methyl-amine. 



98 DERIVATIVES OF METHANE AND ETHANE 

Tri-methyl-amine, N(OH3)8. — Tri-methyl-amine is formed 
as one of the products of the treatment of iodo-methane with 
ammonia. It occurs widely distributed in nature, as in the 
blossoms of the hawthorn, the wild cherry, and the pear. It 
is contained in herring brine, and is a common product of the 
decomposition of organic substances that contain nitrogen. 
It is now obtained in large quantities from the so-called " vin- 
asse." This is the waste liquid obtained in the refining of 
beet sugar. When the "vinasse" is evaporated to dryness, 
tri-methyl-amine is given off among the volatile products. It 
is collected as the hydrochloric acid salt, N(CH3)3HC1, which, 
when heated to 260°, yields ammonia, tri-methyl-amine, and 
chlor-methane : — 

3 N(CH8)8HC1 = 2 N(CH8)3 + NHg -f 3 CH3CI. 

The chlor-methane is utilized for the purpose of producing low 
temperatures. 

Tri-methyl-amine is a liquid boiling at 9® to 10°. It has a 
strong ammoniacal and fishy odor. It is very soluble in water 
and alcohol, and is a strong base. 

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

When tri-ethyl-amine is brought together with iodo-ethane, 
the two unite, forming the compound tetrarCthyl-ammonium 
iodide, !N" (€2115)41, 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 liquid 
crystals of tetra-ethyl-ammonium hydroxide, !N" (C2H5)40H, are 
obtained. This is plainly the hypothetical ammonium hydrox- 
ide, in which the four ammonium hydrogens have been replaced 
by ethyl. Its solution acts cdmost like caustic potash. It is 
very caustic, attracts carbon dioxide from the air, saponifies 
(see p. 71) ethereal salts, and gives the same precipitates as caus- 
tic potash. It is so strong a base that neither potassium nor 



TRI-METHYL- AMINE 99 

sodium hydroxide can separate it from its salts. The reactions 
of the substituted ammonias above described make it certain 
that they are closely related to ammonia. The methods of 
formation also point clearly to the same conclusion. This 
relation is best expressed by the formulas above given. 

Another method for the formation of substituted ammonias 
in which but one radical is present, as ethyl-amine, NH2.C2H5, 
or in general NHg.R, consists in treating with nascent hydro- 
gen compounds known as nitro-compounds, which are substi- 
tution-products containing the group NO2 in the place of 
hydrogen. Thus, for example, when nitro-methane, CHg.NOj 
(which see), is treated with hydrogen, the reaction that takes 
place is represented thus : — 

CHg. NO2 -f- 6 H = CH3. NH2 -h 2 H2O. 

In connection with another series, it will be shown that this 
reaction is a most important one, from a practical as well as 
a scientific point of view. It may be said in anticipation that 
the manufacture of aniline, and consequently of all the many 
valuable dye-stuffs related to aniline, is based upon this 
reaction. 

Just as we may look upon methyl-amine 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 NHg. Owing to the frequency of the occurrence of 
this group in carbon compounds, and for the sake of simplify- 
ing the nomenclature, the group has been called the amino 
group, and the bodies containing it amino-compounds. Thus 
the compound NH2 • C2H5 may be called either ethyl-amine or 
amino-ethane, etc. 

Similarly, those substituted ammonias which contain two 
hydrocarbon residues, as direthyl-amine, NH (02115)2, are called 
imino-compounds, and the group NH the imino group. Sub- 
stituted ammonias containing one hydrocarbon residue are 



^V\^M^V 



100 DBBIVATIVBS OF METHANE AND ETHANE 

called primary ammonia bases. Those containing two residues, 
as di-ethyl-amine, NH (02115)2, are known as secondary ammonia 
bases; and those containing three residues, as tri-ethyl-amine, 
N (CHa)^, are called tertiary amrrumia bases. 

Among the most important of the reactions of amino-com- 
pounds or primary bases is that which takes place when they 
are treated with nitrous acid. Take ethyl-amine as an illus- 
tration. In order to understand what takes place when this 
compound is treated with nitrous acid, it is necessary to keep 
in mind the fact that the compound itself is a modified ammo- 
nia, and hence we may expect that its reactions will be 
modifications of those which take place with ammonia. Thus 
with nitrous acid ammonia unites directly to form ammoniiun 
nitrite : — 

NH, + HNO2 = NH4.NO2. 

So also ethyl-amine forms ethyl-ammonium nitrite : — 

NH2.C2H5 + HNO2 = NH,(C2H5).N(\. 

Ammoniiun nitrite breaks up readily into free nitrogen and 
water * ~^ 

NH4.NO2 = N, + H2O -f- H2O. 

So also ethyl-ammonium nitrite breaks up into free nitrogen^ 
water, and alcohol : — 

NHa(C2H5)N02 = N2 + HjO -f- C2H5.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, 
as is clear, it is not a convenient method of preparation ; but it 
will be shown that there are hydroxides for the preparation of 
which it is by far the most convenient method. The essential 
character of the transformation effected by it will be best under- 



NITRO-COMPOUNDS 101 

stood by comparing the formulas of the amino-compound and 
the alcohol. We have ethyl-amine, C2H5.NH2, and from it we 
get alcohol, C2H5.OH. Thus it will be seen that the trans- 
formation consists in replacing the amino group by hydroxyl. 

Hydrazine Compounds 

There is an important class of compounds, the members of 
which bear the same relation to the compound hydrazine, N2H4, 
(HjN — NH2), that the substituted ammonias bear to ammonia. 
The reactions by which they are prepared are somewhat com- 
plicated, and cannot well be discussed at this stage. The best- 
known hydrazines are those related to the hydrocarbons of the 
benzene series, as, for example, phenylhydrazine, C6H5.NH.NH2. 

NiTRO-COMPOUNDS 

Eef erence has already been made to a class of compounds con- 
taining the group NO2, and known as nitro-compounds. They 
are most readily made by treating the hydrocarbons with nitric 
acid. This method, however, is not applicable to the hydro- 
carbons methane and ethane and their homologues, as these are 
not readily changed by nitric acid. The hydrocarbon benzene, 
GeH«, is very easily acted upon by nitric acid, when the reac- 
tion represented by the following equation takes place : — 

CeHe + HONO2 = CeH5N02 + HjO. 

The action is like that which takes place between sulphuric 
acid and benzene, which gives the sulphonic acid C6H5.SO2OH 

or • * > SO2. (See p. 77.) In each case a hydroxyl of the 

acid is replaced by a residue of the hydrocarbon. The product 
in the case of the dibasic acid, sulphuric acid, is itself still 
acid, while the product in the case of the monobasic nitric 
acid is not an acid. 

The nitro-derivatives of methane have been made by a reac- 
tion which we should expect to yield ethereal salts of nitrous 



102 DERIVATIVES OF METHANE AND ETHANE 

acid ; namely, by treating iodo-metbane or ethane witb silver 
nitnte : — ^^^^ ^ ^^^^^ ^ CHaNO^ + Agl. 

Tbe compound CH8NO2, wbich is known as nitro-methane, does 
not conduct itself like tbe etbereal salts of nitrous acid. Metbyl 
nitrite, CHgO.NO, can be saponified ; nitro-methane cannot. 

Note for Student. — Compare the reaction just referred to with that 
which takes place between silver cyanide and iodo-methane ; and that 
which takes place between iodo-ethane and potassium sulphite. What 
analogy is there to the former and to the latter ? 

It bas already been stated tbat tbe nitro-derivatives are con- 
verted by nascent bydrogen into tbe corresponding amino- 
derivatives (see p. 99). 

Note for Student. — Write the equations representing the reactions 
by which methyl alcohol can be converted into methyl-amine by means 
of the nitro-compound. 

Nitroform, CH(N02)8, as tbe formula indicates, is tbe tri- 
nitro-derivative of methane, or tri-nitro-metbane. It is con- 
verted into tetra-nitro-methane, €(^"02)4, wben treated witb a 
mixture of concentrated sulpburic and fuming nitric acids. 

Nitro-chloroform, C(N02)Cl8, called also chlorpicrin and 
nitrO'trichlormethane, is formed by distilling metbyl or etbyl 
alcobol witb common salt, saltpetre, and sulpburic acid. It is 
formed from a number of more complicated nitro-compounds, 
as picric acid, by distilling tbem witb bleaching powder or 
bydrocbloric acid and potassium cblorate. 

NiTROSO- AND ISONITROSO-COMPOUNDS 

Wben a compound containing tbe group CH is treated witb 
nitrous acid, a reaction takes place, wbicb is represented tbus: — 

E3CH + HO.NO = E3C.NO -f- H^O. 

Tbe product E3C.NO, which is derived from tbe original sub- 
stance by tbe substitution of tbe group NO for a hydrogen 
atom, is called a nitroso-compound. By oxidation tbe nitroso- 



NITROSO- AND ISONITROSO-COMPOUNDS 103 

compounds are converted into nitro-compounds, and by reduc- 
tion they yield the same products as the corresponding nitro- 
compounds, that is to say, the amines. 

The isonitroso-compounds are isomeric with the nitroso-com- 
pounds. They are formed when acetones or aldehydes are 
treated with hydroxylamine, NH2.OH. The reaction may be 
represented thus : — 

CHg CHg 



CO + H2N.OH = C=N - OH + H2O. 



CHg CHg 

The hydrogen of the hydroxyl has acid properties. The 
isonitroso-compounds are readily hydrolyzed by hydrochloric 
acid, yielding, as one of the products, hydroxylamine. They 
are generally called oximes. 

As hydroxylamine reacts in this way with all aldehydes 
and with all ketones, it is a valuable reagent for compounds 
belonging to these classes. 

Fulminic acid, CNOH, according to recent investigations, 
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 prepared -by dissolving 
mercury in an excess of strong nitric acid, and adding alcohol 
to the solution. It is extremely explosive. Mixed with potas- 
sium nitrate it is used for filling percussion-caps. 

When fulminating mercury .is treated with concentrated 
hydrochloric acid, it yields hydroxylamine and formic acid. 
Fulminic acid appears, therefore, to be an isonitroso-compound. 
It is probably the oxime of carbon monoxide, and should be 
represented by the formula C = N — OH. As will be seen, 
fulminic acid is isomeric with cyanic and cyanuric acids (see 
pp. ^b and 86). 



CHAPTER VII 

DERIVATIVES OF METHANE AND ETHANE CONTAINING 

PHOSPHORUS, ARSENIC, ETC. 

Phosphorus compounds. — Corresponding to the amines 
or substituted ammonias are the phosphines, which, as the name 
implies, are related to phosphine, PHg. Methyl-phosphine, 
PHgCCHg), di-methyl-phosphine, PH(CH8)2, and tri-methyl- 
phosphine, P(CH8)8, may be taken as examples. 

These substances, like the corresponding amines, form salts 
with acids, though not as readily. The hydroxide, tetrorethyl- 
phosphonium hydroxide, P(C2H5)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, ethyl-phosphine, PH2.C2H5, 
when treated with nitric acid, is converted into ethyl-phosphinic 
add, PO(C2H5)(OH)2, a dibasic acid, bearing to phosphoric acid 
the same relation that a sulphonic acid bears to sulphuric acid. 

Note fob Student. — What is the relation? What other class of 
acids bears the same relation to carbonic acid ? 

Di-ethyl-phosphine, PH(C2H5)2, yields di-ethylrphosphinic acid, 
PO(C2H4)20H, 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 
compound containing arsenic is that which is known as cacodyl, 
a name given to it on account of its extremely disagreeable 
odor (from KaK(o&;s, stinking). It is prepared by distilling a 
mixture of potassium acetate and arsenic trioxide. The reac- 

104 



SODIUM ETHYL 105 

tions which take place are very complicated, and many products 
are formed. Chief among the products is cacodyl oxide : '■ — 

4 CHj,C02K + As A = [(CH8)2As]20 + 2 K2CO3 + 2 CO2. 

When treated with hydrochloric acid, the oxide is converted 
into the chloride (CH8)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 in all probability should be represented thus : 

(Q^i^A } • Cacodyl appears therefore as a compound analo- 
gous to the hydrazines referred to above. (See p. 101.) 
Note for Student. — In what does the analogy consist ? 

Many derivatives of cacodyl have been made, but their study 
would hardly be profitable at this stage. 

Zinc ethyl itself is made by treating iodo-ethane, C2H5I, 
with zinc alone or with zinc sodium. The reaction takes place 
in two stages. First by addition, a compound of the formula 

Zn <^ jj is formed. When this is distilled, zinc ethyl and 

zinc iodide are formed : — 

2 Zn < J, ^ = Zn(C2H5)2 +Znl2. 

It is a liquid boiling at 118°. It takes fire in the air, and bums 
with a white flame. 

Sodium ethyl, C2H6Na, can be obtained in combination 
with zinc ethyl by treating the latter with sodium. Both 
these compounds have been used to a considerable extent in 
the synthesis of carbon compounds, particularly the more com- 
plex hydrocarbons, and they will be frequently referred to in 
the following pages. 

Note for Student. — What is formed when sodium methyl and 
carbon dioxide are allowecfto act upon each other ? 



106 DERIVATIVES OF METHANE AND ETHANE 

Many of the derivatives, like the above, are volatile liquids. 
Such, for example, are mercury ethyl, Hg(C2H5)2, alumiuium 
ethyl, Al (€2115)3, tin tetrethyl, Sn(Cj}H5)4, and silicon tetrethyl, 
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 simple volatile 
compounds. 

Qrigrnard's reactions. — 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 
with great ease with a variety of substances. The reactions 
having been first described by Grrignard are known by his 
name. A simple example is that indicated below : — 

CH3l + Mg = CH3MgI. 
CHgMgl + H2O = CH4 + IMgOH. 

This particular reaction, as will be seen, affords an easy 
method of passing from methyl iodide to methane. 

■ 

Retrospect 

In the introductory chapter (p. 19) these words were used in 
describing the plan to be followed: "Of the first series of 
hydrocarbons two members will be treated of. Then the de- 
rivatives 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 each 
other. Thus by a comparatively close study of two hydro- 
carbons and their derivatives, we may acquire a knowledge of 
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 



BBTROSPECT 107 

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 (1) 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 chlor-m ethane, 
brom-ethane, etc., bear very simple relations to each other. 
"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, 
adds, ethereal salts, and ketones. The sulphur derivatives, 
some of which closely resemble the oxygen derivatives, include 
the sulphur alcohols or mercaptans, sulphur ethers, and sulphonic 
acids. 

On beginning the consideration of the nitrogen derivatives 
we found it desirable first to take up certain derivatives con- 
taining the cyanogen group, among which are cyanogen, hydro- 
cyanic acid, cyanic acid, and sulpho-cyanic acid. Many interest- 
ing carbon compounds are closely related to these fundamental 
compounds. Such, for example, are the cyanides and isocy- 
anides, the cyanates and isocyanales, the sidpho-cyanates and 
iso-sulpho-cyanates or mustard-oils. Following the compounds 
related to cyanogen, we took up the interesting compounds 
which are related to ammonia, the substituted ammonias or 
amines. Then came the nitro-derivatives ; and, finally, the 
compounds of the hydrocarbon residues or 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 treated of, which are state- 
ments in chemical language that tell us the conduct of the 
various classes of derivatives, and if he performs the experi- 



108 DERIVATIVES OF METHANE AND ETHANE 

ments that have been described, he will have a fair general 
knowledge of the kinds of relations that are met with in con- 
nection with the compounds of carbon through the whole field. 
As stated in the Introduction : " K 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 practises 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 extremely simple. Whereas, if he has failed at any 
point to catch the exact meaning, if he has failed to see the 
connection, he had better go back and faithfully review, 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, (1) show by what reactions it 
is possible to pass from marsh gas to acetic acid. (2) How 
can we pass from ordinary alcohol to ethylidene chloride, 
CH8.CHCI2? (3) What reactions enable us to make methyl- 
amine from its elements? (4) How can acetone be made 
from methyl-amine ? (5) What reactions are necessary in 
order to make ordinary ether from ethyl-amine? etc., etc. 
It is well in this sort of practice to select what appear to be the 
least closely-related compounds, and to show then how we can 
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 VIII 

THE HYDROCARBONS OF THE BIARSH-6AS SERIES, OR 

PARAFFINS 

The existence of the homologous series of hydrocarbons 
beginning with methane and ethane was spoken of before its 
first two members were discussed. A general idea of the 
extent of the series, and of the names used to designate the 
members; may be gained from the following table : — 



MARSH-GAS HYDROCARBONS 

Paraffins. — Hydrocarbons, CnHgn+j 

Boiling-point 



Methane . . 


. . CH4 . , 


. gas 


Ethane . 


. . O^Hq 


' . gas 


Propane . . 


• • CsHg . . 


' . gas 


Butane (normi 


aJ) . C4H10 . . 


. r 


Pentane " 


. C5H12 


. . 37^ 


Hexane " 


• • CeHi4 . , 


. . 69^ 


Heptane " 


• • C7H16 . . 


. . 98^ 


Octane " 


. . CgHjg . . 


. . 125^ 


Nonane " 


. . (VH20 


. . 150^ 


Dodecane " 


• • \Ji2ri2a 


. . 214^ 


Hexadeca.ne " 


• • ClgHgi . 


. . 287^ 



The explanation of the remarkable relation in composition 
existing between these members, a relation to which the name 
homology is given, has already been referred to (p. 23). . The 
number of hydrogen atoms contained in a member of this series 

109 



110 HYDROCARBONS OF THE MARSH-GAS SERIES 

bears a constant relation to the number of carbon atoms, as 
expressed in the general formula C„H2n+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 three members are gases at ordinary tem- 
peratures, while the last boils at 287°. The elevation in the 
boiling-point is to some extent regular, as will be observed. 
The difference between butane, C4H10, and pentane, C5H12, is 
37 — 1 = 36** ; that between pentane and the next member is 
69 - 37 = 32° ; between hexane and heptane it is 98 - 69 = 29° ; 
between heptane and octane, 125 — 98 = 27°; and, finally, 
between octane and nonane the difference is 150 — 125 = 25°. 
Thus it will be seen that the elevation in boiling-point caused 
by the addition of CHg decreases as we pass upward in the 
series. Other relations have been pointed out, but it would 
be premature to discuss them here. 

The chief natural source of the paraffins is petroleum ; but 
although this substance, which occurs in such enormous quanti- 
ties in nature, undoubtedly contains a number of the members 
of the paraffin series, it is an extremely difficult matter to 
isolate them from the mixture. Prolonged fractional distilla- 
tion is not sufficient for the purpose. If, however, some of the 
purest products that can thus be obtained are treated with 
concentrated sulphuric acid, and afterwards with concentrated 
nitric acid, and then washed and redistilled, they can be 
obtained in pure condition. 

Petroleum. — Petroleum occurs in enormous quantities in 
several places. Among the most important localities are 
Pennsylvania, Ohio, California, Texas, the Crimea, the Cau- 
casus, Persia, Burmah, China, Mexico, etc. In some places 
it issues constantly from the earth. Usually it is necessary 
to bore for it. When one of the cavities in which it is con- 
tained is punctured, the oil is forced out of a pipe inserted 
into the opening in a jet, in consequence of the pressure 



PETROLEUM 111 

exerted upon its surface. As first obtained, it is usually *a 
dark, yellowish-green liquid, witli an unpleasant odor. It 
varies in appearance according to the place where it is found. 
American petroleum contains the lowest members of the 
paraffin series; and when the oil is exposed to the air the 
gases are given off. 

Refining of petroleum. To render petroleum fit for use in 
lamps, it is necessary that the volatile portions should be 
removed, as they form explosive mixtures with air, just as 
marsh gas does. It is also necessary to remove the higher 
boiling portions, because they are semi-solid, and would clog 
the wicks of the lamps. The crude oil is therefore subjected to 
distillation, and only those parts which have a certain specific 
gravity or boil between certain points are used for illuminating 
purposes, under the name of kerosene. Besides being distilled, 
the oil must further be treated with concentrated sulphuric 
acid, which removes a number of undesirable substances, and 
afterwards with an alkali, and then with water. All these 
processes taken together constitute what is called the refining 
of petroleum. In the distillation, the lighter products are 
usually divided into several parts, according to the specific 
gravity or boiling-point. Thus we have the products cymogene, 
rhigolene, gasoline, naphtha, and benzine, all of which are 
lighter than kerosene. It must be distinctly understood that 
the substances here mentioned are not pure chemical indi- 
viduals. . The names are commercial names, each of which 
applies to a complex mixture of hydrocarbons. From the 
heavier products, that is, those that boil at higher tempera- 
tures than the highest limit for kerosene, paraffin, which is a 
mixture of the highest members of this series, is made. 

Owing to the danger attendant upon the use of improperly 
refined petroleum, laws have been enacted relating to the 
properties that the kerosene exposed for sale must have. 
These laws, which differ somewhat in different countries and 
different parts of the same country, relate mostly to what is 



R 




112 HYDBOCARBONS OP THE MARSH-GAS SERIES 

called the fldshing-point This is the temperature to which the 
oil must be heated before it takes fire when a flame is applied 
to it. The legal flashing-point in many parts of the United 
States is 44^. A simple and accurate instrument for deter- 
mining the flashing-point is here described : The cylinder A 
is at least 2,5*^"^ in diameter, and at least 16*^™ long. Just 

within the cork the bent tube contracts to 
a small orifice. At d it is connected with 
a hand-bellows or a gas-holder; and the 
flow of air is controlled by a pinch-cock. 
The cylinder is filled with oil to a point 
such that, when the air is running, the 
surface of the foam is about 6®" from the 
, top; and it is then put in a beaker of 

■jp water to the level of the oil. Air is now 

^^^ passed through deb, and e so adjusted that 

Fig. 9. about 0.5®" foam is kept on the surface of 

the oil. From degree to degree the test is made by bringing a 
small flame for an instant to the mouth of A, At the flashing- 
point the vapor ignites, and the bluish flame runs down to the 
surface of the oil. 

Experiment 31. Make an apparatus like the above, and determine 
the flashing-points of two or three specimens of kerosene that may be 
available. 

Synthesis of the paraffins. — Although the paraffins occur 
in nature, and a few of them can be obtained in pure condition 
from natural sources, we are dependent upon synthetical oper- 
ations performed in the laboratory for our knowledge of the 
series and the relations existing between them. 

We have already seen how ethane can be prepared from 
methane by treating methyl iodide with zinc or sodium, as 
represented in this equation : — 

CHal -f- CHgl -f- 2 Na = C.He -f- 2 Nal. 



SYNTHESIS OF THE PARAFFINS 113 

This method has been extensively used in the building up of 
higher members of the series. Thus from ethane we can make 
ethyl iodide, and by treating this with sodium get butane, 
C4H10: — 

C2H5l4-C2HJ + 2]Sra = C4HH, + 2NaI. 

But we can get the intermediate member, propane, CaHa, by 
mixing methyl iodide and ethyl iodide and treating the mixture 
with sodium : — 

CK^ + C2H5I + 2 Na = CH3.C3H5 + 2 Nal. 

By applying this method, it is plain that a large number of the 
members of the paraffin series might be made. 

Another method consists in treating the zinc compounds of 
the radicals, like zinc ethyl, Zn (02115)2, with the iodides of rad- 
icals. 'Thus zinc methyl and methyl iodide give ethane; zinc 
ethyl and ethyl iodide give butane, etc. : — 

Zn(CH8)2 + 2 CHjI = 2 CjHe + Znl^ ; 
Zn(C2H5)2 + 2 C2H5I = 2 C4H10 + Znla. 

Paraffins can be made by replacing the halogen in a substitu- 
tion-product by hydrogen. This can be effected by nascent 
hydrogen or by hydriodic acid: — 

C4Hj,I + 2 H = C4H10 + HI. 

As these halogen substitution-products can easily be made 
from the alcohols, it follows that the hydrocarbons can be made 
from the corresponding alcohols. 

Grignard's reaction may also be used for the purpose of pass- 
ing from a mono-halogen substitution-product of a paraffin to 
the paraffin itself (see p. 106). 

Finally, the paraffins can be made by heating the acids of 
the formic acid series with an alkali. This has been illus- 
trated by the preparation of marsh gas from acetic acid by heat- 



114 HYDEOCARBONS OF THE MARSH-GAS SERIES 

ing with lime and caustic potash. The reaction may be written 
thus : — CH8.CO2K + KOH = CH^ + 003X2. 

The products are a hydrocarbon and a carbonate. 

Isomerism amongr 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 discovered. This is repre- 

H H 

I I 
sented by the formula, H - C - C - H, or HaC - CHa. In ethane, 

I I 
H H 

as well as in methane, all the hydrogen atoms bear the same 
relation to the molecule, and it should make no difference 
which one is replaced by methyl. But propane is regarded as 
derived from ethane by the substitution of methyl for hydro- 
gen ; and, as it makes no difference which hydrogen is replaced, 
there is but one propane possible. Only one has ever been dis- 
covered, and this must be represented thus : — 

H H H 

I I I 
H-C-C-C-H, or CH3.CH2.CH3. 

I I I 
H H H 

Kow, continuing the process of substitution of methyl for 
hydrogen, it appears that 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 ot 



» 



ISOMERISM AMONO THE t^ARAFFms 115 

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 H8C.CH2.CH2.CH8. 

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 

III 
H - C - C - C - H, or CH3 - CH - CHj. 

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, which occurs in American petroleum, has 
been made synthetically by treating ethyl iodide with zinc : — 

2 CH3.CH2I + Zn = CH3.CH2.CH2.CH3 + Znlg. 

The method of synthesis clearly shows which of the two possi- 
ble isomerides the product is. It is known as normal butane. 
It is a gas that can be condensed to a liquid at + 1°. 

The second, or isobutane, is made from an alcohol which 
will be shown to have the structure represented by the formula 

CH3 
I 
CHa — C — OH (see Tertiary Butyl Alcohol, p. 125), by replacing 

I 
CH3 

the hydroxyl by hydrogen. It is a gas that becomes liquid 
at - 17°. 

The differences between the two butanes show themselves 
most strikingly in their derivatives. 



116 HYDKOGABBONS OF THE MARSH-GAS SERIES 

Applying the same method of reasoning to the next member 
of the series, how many isomeric varieties of pentane, C5H12, 
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 I 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 CHg groups. 
The two possible methyl derivatives of a hydrocarbon of this 
f ormrda are therefore to be represented thus : — 

H.3C.Cxi2>Cxi2>Cxi2.Cris, (1) 

and H3C.CH,.CH < ^5J». (2) 

CHs 
I 
Now, taking isobutane, HC — CHs, it will be seen that it con- 

I 
CHs 

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 CHg 

I I 

HC-CH2.CH3 (3), and H3C-C-CH3. (4) 

I I 

CSj GH3 



PENTANBS 117 

We have, therefore, apparently four pentanes. But on compar- 
ing formulas (2) and (3), it will be seen that, though written 
a little differently, they really represent one and the same 
compound. Thus the number of pentanes, the existence of 
which is indicated by the theory, is three, and these are repre- 
sented by formulas (1), (2), and (4). They are all known. 
The first is called normal pentane, the second iso-pentane, 
or di-methyl-ethyl-meth€Uie, and the third tetra-methyl- 
methane. 

It would lead too far to discuss all the methods of prep- 
aration and the properties of these hydrocarbons. It will 
be seen that the methods of preparation show what the 
structure of a hydrocarbon is. Di-methyl-ethyl-methane, for 
example, is made from an alcohol which can be shown to 
have the formula 

^TT ^ Cxi.CH2*^I^2^II; 

by replacing the hydroxyl by hydrogen. Hence its structure is 
that represented above by formulas (2) and (3). 

Tetra-methyl-methane 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 
CHj — CO — CHg. It has also been shown that, by treating 
acetone with phosphorus pentachloride, the oxygen is replaced 
by chlorine, giving a compound of the formula CHg— CCI2— CHg. 
Now, by treating this chloride with zinc-methyl, the chloride is 

replaced by methyl thus : — 

CH3 

I 
CH3 - CCI2 - CHj -t- Zn(CH8)2 = CHj - C - CHa + ZnCl^. 

I 
CH3 

The product is tetra-methyl-methane, and this synthesis 
shows clearly what the structure of the product is. 



118 HYDROCARBONS OP THE MARSH-GAS SERIES 

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. Only the names and 
formulas of these will be given here : — 



1. Normal hexane, CHg. CHj. CHj. CHj. CH^. CHj. 

2. Iso-hexane, CH8.CH2.CH2.CH< 



CH3 



CHs 

3. Methyl-di-ethyl-methane, CH3.CH<|^?!''^^*. 

4. Tetra-methyl-ethane, :^'^ > HC - CH < ^f:^ 

JI3O i^jig 

CHs 

I 
6. Tri-methyl-ethyl-methane, H3C — C — CH2. CHg. 

I 
CH3 

Passing upward, we find that nine heptanes are possible 
according to the theory, while but Jive have thus far been dis- 
covered ; and that, while theory indicates the possibility of the 
discovery of eighteen hydrocarbons of the formula CgHig, but 
five are known. The theoretical number of isomeric varieties 
of the highest members of the series is very great, but our 
knowledge in regard to these highest members is quite limited, 
and it is impossible to say whether the theory will ever be 
confirmed by facts. It may be that there is some law limiting 
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 
members of the series is all that is necessary for the 
present. 

On examining the formulas used to express the structure of 



HEXANBS 119 

the hydrocarbons, we find that they can be divided into three 
classes : — 

(1) Those in which there is no carbon atom in combination 
with more than two others ; as, — 

Propane .... CHg.CHa.CHa; 
Normal butane . . CHg . CHg . CHj . CHg ; 
Normal pentane . . CHg. CHg. CHg. CHg. CHg; 
and Noripal hexane . . CHg.CHa.CHg.CHa.CHg.CHg. 

(2) Those in which there is at least one carbon atom in 
combination with three others ; as, — 

CH 
Isobutane .... CH3.CH<^,j.^; 

Oils 



Isopentane . . . CHg.CHj.CH <^tt'; 



CH 

Isohexane. . . . CH8.CH2.CH2.CH<^„*; 

OJtlg 

H P CH 

and Tetra-m ethyl-ethane, ^^^ > CH — CH < ^^. 

MgO dig 

(3) Those in which there is at least one carbon atom in 
combination with four others ; asj — 

CHg 

Tetra^methyl.) ^ .cHg-i-CHg; 
methane ) , 

CHg 

CH, 

and Tri-methyl-ethyl- [ c,H, - C - CH, 
methane ) i 

CHg 

The members of the first class are called normal paraffins; 
those of the second class, iso-paraffins; and those of the third 
elass, neo-paraffins. 



120 HYDROCARBONS OF THE MARSH-GAS SERIES 

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 iso-paraffins; 
but, on comparing the boiling-points and other physical prop- 
erties of normal paraffins with those of the iso- or neo-paraffins, 
no such simple relations are observed. 

Begarding 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 we get the 

IC2H6 
g ; tri-methyl-methane 
H fCHs 

p '; tetra-methyl-methane, cJ «, etc. 
H lCH« 



CHAPTER IX 

OXYGEN DERIVATIVES OF THE HIGHER MEMBERS OF 

THE PARAFFIN SERIES 

We are now to take up the derivatives of the higher mem- 
bers of the parafi&n series, just as we took up the derivatives of 
methane and ethane. 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. 

1. Alcohols 

Normal propyl alcohol, propanol, CgHyOH. — When 
sugar undergoes fermentation, a little propyl alcohol is always 
formed, and is contained in the "fusel oil." From this it can 
be separated by treating those portions which boil between 
85° and 110° with phosphorus and bromine. The bromides of 
the alcohols present are thus formed (what is the reaction?), 
and these are separated by fractional distillation. The bro- 
mide corresponding to propyl alcohol is then converted into 
the alcohol (how can this be done?). 

It is a colorless liquid with a pleasant odor. It boils at 97° 
(compare with the boiling-points of methyl and ethyl alcohol). 
It conducts itself almost exactly like the first two members of 
the series. By oxidation it is converted into an aldehyde, 
CgHeO, and an acid, CgHeOg, which bear to it the same relations 
that acetic aldehyde and acetic acid bear to ethyl alcohol. 

Secondary propyl or Isopropyl alcohol, C3H7OH. — 

The reasons for regarding the alcohols as hydroxyl derivatives 

121 



122 DERIVATIVES OF THE PARAFFINS 

of the hydrocarbons have been given pretty fully. As the six 
hydrogen atoms of ethane are all of the same kind; but one 
ethyl alcohol appears to be possible, and only one is known. 
But just as there are two butanes or methyl derivatives of pro- 
pane, so there are two hydroxyl derivatives of propane ; or, in 
other words, two propyl alcohols. The first is the one obtained 
from " fusel oil,'' the other is the one called secondary propyl 
alcohol. This has already been referred to under the head of 
Acetone (see p. 73), where it was stated that acetone is con- 
verted into secondary propyl alcohol by nascent hydrogen. 
We are, in fact, dependent upon this method for the prepara- 
tion of the alcohol. 

It is, like ordinary propyl alcohol, a colorless liquid. It 
boils at 81°. While all its reactions show that it is a hydrox- 
ide, under the influence of oxidizing agents it conducts itself 
quite differently from the alcohols thus far considered. It is 
converted first into acetone, CsHeO, which is isomeric with the 
aldehyde obtained from ordinary propyl alcohol; by further 
oxidation, it however does not yield an acid of the formula 
CsHgOa, as we should expect it to, but breaks down, yielding 
two simpler acids; viz., formic acid, CHjOa, and acetic acid, 
C2H4OJ. 

Secondary alcohols. — Secondary propyl alcohol is the 
simplest representative of a class of alcohols known as 
secondary alcohols. They are made by treating the ketones 
with nascent hydrogen, and are easily distinguished from other 
alcohols by their conduct toward oxidizing agents. They 
yield acetones containing the same number of carbon atoms, 
and then break down, yielding acids containing a smaller num- 
ber 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 



SECONDARY ALCOHOLS 123 

represented by the formula CHg — CO — CHg. The simplest 
change that can take place in this compound under the influence 
of hydrogen is that represented in the following equation : — 

CHs - CO - CHa + Ha = CHs - CH.OH - CH3. 

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 equation. On the other hand, the easy transfor- 
mation of primary propyl alcohol into propionic acid, which can 
be shown to contain ethyl, shows that in the alcohol ethyl is 
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 di-methyl deriva- 
tive of methyl alcohol, as represented by the formulas : — 



C 



C 



CH2*CH3 

H 

H 

OH 

Methyl alcohol Ethyl-methyl alcohol or Dimethyl-methyl alco- 

ordinary propyl hoi or secondary 

alcohol propyl alcohol 



rH 
H 
H 
OH 



CH3 
CHg. 
H 
OH 



Primary propyl alcohol is methyl alcohol in which one hydrogen 
is replaced by a radical, while secondary propyl alcohol is 
methyl alcohol 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. The alco- 
hols of the first class, like methyl, ethyl, and ordinary propyl 
alcohols, which are derived from methyl alcohol by the substitu- 
tion of one radical for one hydrogen, are caWed primary alcohols. 
Another way of stating the difference between primary and 
secondary alcohols is this : Primary alcohols contain the group 



124 DERIVATIVES OF THE PARAFFINS 

CHgOH ; secondary alcohols contain the group CHOH. These 
statements necessarily follow from the first ones. 

A primary alcoholy 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 and 
then an acid or acids containing a smaller number of carbon 
atoms. 

Becalling what was said regarding the nature of the changes 
involved in passing from an alcohol to the corresponding alde- 
hyde and acid, it will be seen that the formation of the acid is 
impossible in the case of a secondary alcohol. In the case of 
a primary alcohol, we have : — 



H 
H 
OH 

Alcohol Aldehyde Add 



1 




c 



CR 
OH. 




In fhe case of the secondary alcohol, we have : — 



t 



C 



B 
B 
H 
OH 

Secondary alcohol Ketone 



10 



Further introduction of 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, 
making four butyl alcohols in all. They are all known. Two 
are primary alcohols. 



BUTYL ALCOHOLS 125 

1. Normal butyl alcohol, CH8.CH2.CH3.CH3OH. 

CH 

2. Isobutyl alcohol, (3 jj*>CH.CH20 H. 

The third is a derivative of normal butane, and is a secondaiy 
alcohoL 

3. Secondary butyl alcohol, CH3.CH2.CH<^^ . This 

alcohol is prepared by treating ethyl-methyl ketone with nas- 
cent hydrogen : — 

CH8.CH2-CO-CH8 + H2 = CH,.CHj.CH<^2 * 

CH3 

(Compare this with the reaction for making secondary propyl 
alcohol.) CHs 

I 

4. Tertiary butyl alcohol, CHs - C - OH. The fourth butyl 

I 
CHs 

alcohol has properties that distinguish it from the primary 
and secondary alcohols. When oxidized it yields neither an 
aldehyde nor an acetone, but breaks down at once, yielding 
acids containing a smaller number of carbon atoms. Assum- 
ing that every primary alcohol contains the group CHjOH, 
and that every secondary alcohol contains the group CHOH, 
it follows that 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 

CHs 

I 
the formula CHs — C — OH, as this represents the only other 

I 
CHs 

arrangement of the constituents possible, according to our 
theory. This formula represents a condition which does not 
exist in either the primary or secondary alcohols. It is 
methyl alcohol in which all the hydrogen atoms, except that 
of the hydroxyl, are replaced by methyl groups. It con- 
tains the group C — (OH). Such an alcohol is known as a 



126 



DERIVATIVES OF THE PARAFFINS 



tertiary alcohol, and the one under consideration is called ter^ 
tiary hviyl alcohol. It is the simplest derivative of a class of 
which but few members are known. 

Tertiary butyl alcohol is made by treating acetone with 
methyl magnesium bromide, CHgMgBr (Grignard's reagent), 
and then treating the product with water : — 



(CH8)2CO + CHgMgBr = 



CHs 
CHg 
CHa 
OMgBr 



+ H2O 



= C 



rcHg 

cJcHg. 
^ CHs' 
I OMgBr 

fCHs 

CHs 

CHs + Mg < 

OH 



Br 

oh' 



By using other ketones and magnesium compounds contain- 
ing other radicals, other tertiary alcohols can be obtained. 

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. 

To what was said above regarding the conduct of primary 
and secondary alcohols we can now add: Tertiary alcohols 
yield neither aldehydes nor acetones containing the same 
number of carbon atoms, but generally break down, yielding 
simpler acids. 

The formulas representing the three classes of alcohols are : — 





R 


R 






R 


[3- 


H 
H 




and 


c. 


R 
R 




.OH 


OH 






OH 


Pr 


Imary 


Secondary 




Tei 


rtlary 



Pentyl alcohols, C^Hn-OH. — Eight of these are possible, 
and all are known. Only the two aniyl alcohols need be taken 
up here. 



AMYL ALCOHOLS 127 

Inactive amyl alcohol, ^5^>CH-CH2-CH20H.— 

This alcohol, together with at least one other of the same com- 
position, forms the chief part of " fusel oil.'' By fractional 
distillation of this, ordinary amyl alcohol is obtained, as a 
colorless liquid, having a penetrating odor, and boiling at 131° 
to 132**. This can be separated by other methods into two 
isomeric alcohols, one of which is inactive amyl alcohol and 
the other active amyl alcohol. The names refer to the behav- 
ior of the substances towards polarized light, the former 
having no action upon it, the latter turning the plane of polar- 
ization to the left. 

When treated with oxidizing agents inactive amyl 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.CO2H. Therefore, the alcohol has 

CH 
the structure represented by the formula ^>CH.CH2.CH20H. 

Active amyl alcohol, CH3.CH2.CH<^^q— .— This, as 

has been stated, is obtained, together with the inactive alcohol, 
from fusel oil. It is a primary alcohol as represented. 

A list of some of the more important remaining 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 methyl-carbinol, di-ethyl-carbinol, etc., which 
convey at once an accurate idea concerning the structure of 
the substances. A few illustrations will suffice. Take the 
alcohols considered above: — 



Ethyl alcohol is methyl-carbinol, 




128 



DBBIVATIVBS OF THE PABAFFINS 



Primary propyl alcohol is ethyl-carbinol, 



f CH2CH3 



H 
OH 



Secondary propyl alcohol is dirmethyU 
carMnol, 



fCH, 



Tertiary butyl alcohol is tri-methyl-carbinol, C 



H 
OH 

CHj 
CH 



3. 



CH3* 
LOH 



Inactive amyl alcohol is isobutyl-carbijiol, C 



CH2. CH< ^ 
H 



H 

OH, etc., etc., 

a name given to it on account of the presence in it of the 
isobutyl group CH2.CH < ^^» . 

The following table will give an imperfect idea of the extent 
to which the series of alcohols derived from the paraffins has 
been investigated. There are fourteen hexyl alcohols and 
thirteen heptyl alcohols known. 

Cetyl alcohol, CjeHgs.OH, is the chief constituent of sper- 
maceti. 

Ceryl alcohol, CjeHgs.OH, is found in Chinese wax. 

Myricyl alcohol, CaoHa.OH, occurs in beeswax and in Car- 
nauba wax. 

Of most of the higher members but one variety is known. 
They are not important, except in so far as they indicate the 
possibility of the discovery of other alcohols. 



ALDEHYDES 129 

« 

ALCOHOLS OF THE METHYL ALCOHOL SERIES 

Series CnHgn+i . OH 

Methyl alcohol CHg . OH 

Ethyl " C2H5.OH 

Propyl " C3H7.OH 

Butyl " C4H9.OH 

Pentyl « C^Hn-OH 

Hexyl « CeHia.OH 

Heptyl « ......... C7H15.OH 

Octyl " CgHiy.OH 

Nonyl « C9H19.OH 

Cetyl « CieHas.OH 

Ceryl " 0,^^^,011 

Myricyl " CaoHa.OH 

2. Aldehydes 

In general, it follows from what has been said concerning 
the properties of primary alcohols, that there should be an 
aldehyde corresponding 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 noticed. 
It consists in distilling a mixture of a formate and a salt of 
some other acid. Thus, when a mixture of an acetate and a 
formate is distilled, acetic aldehyde is formed as represented 
by the equation : — 

^5 ■ r nnU = ^^3 . COH + M,CO,. 

Jl . COOM Aldehyde 



130 DERIVATIVES OF THE PARAFFINS 

This method has been used to a considerable extent in making 
the higher members of the series. 

Experiment 32. Mix about equal weights of dry calcium formate 
and dry calcium acetate. Distil from a small flask. Collect some of the 
distillate in water, and determine whether aldehyde is formed. 

3. Acids 

Formic and acetic acids are the first two members of an 
homologous series of similar, acids, generally called the fatty 
acids because several of them occur in large quantities 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 been given, and need not here be re- 
stated : — 

FATTY ACIDS 

Series CnHa^+i . CO2H, or G^2S>% 

Formic acid H.CO^H 

Acetic « CHs.COgH 

Propionic" C2H5.CO2H 

Butyric " C8H7.CO2H 

Valeric « C4H9.CO2H 

JP^^.^^^^., 1 C,Hn.C02H 

Hexoic acids 



C«Hi« . COoH 



'e^^ia 



C7H11C . COoH 



(Enanthylic or 
Heptoic acids 

Caprylic or 
Octoic acids 

Pelargonic or 
Nonoic acids 

Capric acid CgHjg . CO2H 

Laurie '* CuHjb.COjH 



CjjTliy • CO2H 



PROPIONIC ACID 131 

Myristic acid CisHgj.COgH 

Palmitic « CisHai.COgH 

Margaric " CieHgg.COaH 

Stearic " . CuHss-COJI 

Arachidic " C^U^. GO Jtl 

Behenic " CaH^.COjH 

Hyenic « C24H49.COSH 

Cerotic « CaeH^g.COjjH 

Melissic " C^H^j.COaH 

Although, as will be seen, a large number of fatty acids are 
known, most of those included in the list are at present merely 
curiosities, and need not be specially studied. Not more than 
six in addition to formic and acetic acids will require attention. 

Propionic acid, propanic acid, OaHeOaCOaHjj.OOaH).— 
Propionic acid is formed in small quantity (1) by the distil- 
lation of wood; (2) by the fermentation of various organic 
bodies, particularly calcium lactate and tartrate ; (3) by treat- 
ing ethyl cyanide (propio-nitrile) with caustic potash : — 

C2H5 . CN + KOH + H2O = C2H5 . CO2K + NH3 ; 

and (4) by oxidizing normal propyl alcohol. This last method 
is used on the large scale. 

Other methods for preparing it are the following : — 

(1) By reducing lactic acid with hydriodic acid. (This will 
be explained under the head of Lactic Acid, which see.) 

(2) By the action of carbon dioxide upon sodium ethyl : — 

CO2 + NaC2H5 = C2H5 . C02Ka. 

It is a colorless liquid with a penetrating odor somewhat 
resembling that of acetic acid. It boils at 141**. (Compare 
with boiling-points of formic and acetic acids.) 



132 DERIVATIVES OF THE PAEAFFLN8 

It yields a large number of derivatives corresponding to those 
obtained from acetic acid. 

IfoTB FOR Stddbnt. — What 18 pFopionyl ohloride ? and how can it be 
prepared? It is analogous to acetyl chloride. 

The simple substitution-products of propionic acid present 
an interesting and instructive case of isomerism. There are 
two chlor-propionic acids, two brom-propionic acids, etc. Those 
products which are obtained by direct treatment of propionic 
acid with substituting agents are called a-products, and the 
isomeric substances ^-products. Thus we have a-chlor-propionic 
and a-bromrpropiomc acid, made by treating propionic acid with 
chlorine and bromine; and p-ddor-propionia acid and ^brom- 
propiomc add, made by indirect methods. The difference be- 
tween these two series of derivatives is due to difEerent relations 
between the constituents. The usual method of representation 
indicates the possibility of the existence of two isomeric chlor- 
propionic acids, and of similar mono-substitution products of 
propionic acid. The acid is represented thus : — 

CH3.CHj.COjH. 

Now, if chlorine should enter into the compound, as represented 
by the formula CHiCl.CHa.COjH, (1) we should have one of 
the chlor-propionie acids ; while, if it should enter as indicated 
in the formula CHj.CHCl.COsH, (2) we should have the iso- 
meric product. We have thus two chlor-propionic acids actu- 
ally known, and our theory gives ua two formulas. How can 
we tell which of the formulas represents a-chlor-propionic acid, 
and which the j8-acid ? Only by carefully studying all 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 mono-substitution products of propionic 
acid. a-Chlor-propionie acid can be transformed into a lactic 
acid, the structure of which is represented by the formula 
CHg. CH(OH) . CO2H, and by replacing the hydroxyl of this 



BUTYRIC ACIDS 133 

lactic acid by chlorine, a-chlor-propionic acid is formed. It 
therefore follows that formula (2) above given is that of a-chlor- 
propionic acid, and formula (1) that of ^-chlor-propionic acid. 
Further, any mono-substitution product of propionic acid that 
can be made directly from a-chlor-propionic acid, or converted 
directly into this acid, is an a-product, and has the general 

formula CHa.CHX.CO.H; 

and, similarly, the j8-products have the general formula 

CI12X • Cxl2 . CO2H, 

in which X represents any univalent atom or group. 

Butyric acids, butanic acids, O^HgOgCOaHy.OOgH). — 
Normal butyric acid, CH3.CH2.CH2.CO2H. When butter is 
boiled with 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 the alka- 
lies, are decomposed, yielding alcohol and alkali salts of acids 
(saponification). In the case of butter and of nearly all other 
fats, the alcohol formed is glycerol. Butyric acid occurs also 
in many other fats besides butter. 

It is most readily made by fermentation of sugar by what is 
known as the butyric add ferment. This ferment probably is 
contained in putrid cheese. Hence, to make the acid, sugar 
and tartaric acid are dissolved in water, and, after a time, 
putrid cheese and sour milk are added, and also some powdered 
chalk. At first the sugar is converted into glucose : — 

C12H22O11 -f- H2O = 2 C6Hi20e. 

Cane sugar Glucose ^'^, 

The glucose breaks up, yielding lactic acid, CsHeOj:— ' . ^;. " 

CgHiaOg = 2 CsHgOa. 

Glucose Lactic acid 



134 DERIVATIVES OF THE PARAFFINS 

And, finally, the lactic acid is converted into butyric acid: — 

2 CsHA = C4H8O2 + 2 CO2 + 4 H. 

Other methods for the preparation of butyric acid are : — 

(1) By oxidation of normal butyl alcohol ; and 

(2) By treating normal propyl cyanide, CH8.CH2.CH2CN, 
with caustic potash. 

' The acid is a liquid having an acid, rancid odor, like that of 
rancid butter. It boils at 163**. (Compare with the preceding 
acids.) Like the lower members of the series it mixes with 
water in all proportions. 

Ethyl bvtyrate, C8H7.CO2C2H5, has a pleasant odor resembling 
that of pineapples. It is used under the name of essence of 
pineapples, 

OH 
Isobutyrio acid, methyl-propanic aoid,Q„^>OH.002H. 

— From the two propyl alcohols the two chlorides, propyl chlo- 

ride, CH8.CH2.CH2CI, and isopropyl chloride, ^jj'^>CHCl, can 

be made, and from these the corresponding cyanides, — 

Propyl cyanide CH3.CH2.CH2CN, 

CH 
and Isopropyl cyanide .... ^^j^ > CHCN. 

. When boiled with caustic potash, the former is converted into 
normal butyric acid, as stated above ; while the latter yields 

CH 

isobutyric acid, ^j^'^>CH.C02H. This acid can also be pre- 

pared by oxidizing isobutyl alcohol, ^g^>CH.CH20H. It is 

found in nature in the carob bean. 

Isobutyric acid is a liquid which boils at 154**. Its odor is 
less unpleasant than that of the normal acid. 

Valeric acids, 05Hio02(04Hj).002H). — Four carboxyl de- 
rivatives of the butanes are possible. Four acids of the 
formula C^HipOg are known. 



STEARIC ACID 135 

Inactive or ordinary valeric acid, q„^>0H.0H2.0O2H. 

— This acid is made by oxidizing inactive amyl alcohol. It 
can also be made (and this reaction reveals the structure of 

the acid) by starting with isobutyl alcohol, ^„'>CH.CH20H, 

converting this first into the chloride and then into the cya- 

CH 

nide, and, finally, transforming the cyanide, ^^>CH.CH2CN, 

into the acid. It occurs in valerian root, whence its name. It 

is an unpleasant smelling liquid, boiling at 174**. It requires 

thirty parts of water for solution. 

Amyl valerate, C4H9.CO2C5H11, has the odor of apples, and is 

used under the name of essence of apples, 

OH 
Active valeric acid, p-^-i>OH.OH2.0H3 — This acid 

is prepared by oxidation of active amyl alcohol. Although the 
alcohol turns the plane of polarization to the left, the acid 
turns it to the right. The alcohol is said to be kevo-rota^tory, 
and the acid dextro-rotatory. 



The higher acids of the series are, for the most part, found 
in various fats. They are difficultly soluble in water. The 
highest members are solids. The two best known, because 
occurring in largest quantity, are palmitic and stearic acids. 
These are contained in combination with the alcohol, glycerol, 
in all the common fats. The fats will be treated under the 
head of Glycerol. 

Palmitic acid, O15H31.OO2H, can be made by saponifying 
many fats, as palm oil, olive oil, and bayberry tallow. The 
last-named fat consists of about one-fifth part of palmitin, four- 
fifths being free palmitic acid and a little lauric acid and laurin. 

It crystallizes in needles which melt at 62.6°. 

Stearic acid, G17H35. OO2H, is the acid contained in that 
particular fat known as stearin. The so-called "stearin can- 



136 DERIVATIVES OP THE PARAFFINS 

dies" consist of stearic acid mixed with palmitic acid and a 
little paraffin, and from them stearic acid can be separated in 
pure form by long-continued fractional crystallization from 
ether and alcohol. 

It crystallizes from alcohol in needles or laminae which melt 
at 69.3^ 

Soaps. — In speaking of the decompositions of ethereal salts 
by boiling with 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 an alkali, as caustic 
soda, the alcohol is liberated, and the alkali salts of the acids 
are formed. These salts are the soaps. They are in solution 
after the process of saponification is completed, and can be 
separated by adding a solution of common salt, in which they 
are insoluble. 

Experiment 33. In an iron pot boil about 25s of lard with a solution 

of caustic soda for two hours. After cooling, add a strong solution of 

sodium chloride. The soap will separate and rise to the top of the solution, 

where it will finally solidify. Dissolve some of the soap thus obtained in 

water, and filter. Add hydrochloric acid, when the free fatty acids, 

mainly palmitic and stearic acids, will separate as solids, which will rise 

to the top. The hydrochloric acid simply decomposes the sodium palmi- 

tate and stearate, giving free palmitic and stearic acids and sodium 

chloride : — 

Ci6H8i.C02Na + HCl = C16H81.CO2H + NaCl, 
Sodium palmitate Palmitic acid 

and Ci7H86.C02Na + HCl = C17H86.CO2H + NaCl. 

Sodium stearate Stearic acid 



The remaining derivatives of the higher members of the 
paraffin series include the ethers, ketones, ethereal salts, 
mercaptans, sulphur ethers, sulphonic acids, cyanides and 
isocyanides, cyanates and isocyanates, sulpho-cyanates and 
iso-sulpho-cyanates, substituted ammonias and analogous com- 
pounds, metal derivatives, and nitro-derivatives. 



ETHYLENE ALCOHOL 137 

A great many substances belonging to these classes, and 
containing residues of the higher hydrocarbons, have been pre- 
pared and studied ; but, in the main, they so closely resemble 
the simpler substances which have already been described that 
we should gain nothing by taking them up here individually. 
The student, however, is earnestly advised to apply the princi- 
ples discussed in the first part of the book to a few other cases. 
Thus, let him take propane and butane, and not only write the 
formulas of the derivatives which can be obtained from them, 
but, above all, write the equations representing the action in- 
volved in their preparation, and the transformations of which 
they are capable. 

POLYACID ALCOHOLS AND POLYBASIC ACIDS 

1. Di-AciD Alcohols 

The alcohols thus far treated of are of the simplest kind. 
They correspond to the simplest metallic hydroxides, as potas- 
sium hydroxide, KOH. Just as these simplest metallic hydrox- 
ides are called mon-acid bases, so the simplest alcohols are 
called mon-acid alcohols,^ expressions which are suggested by 
the term mono-basic add. But, as is well known, there are 
metallic hydroxides, like calcium hydroxide, Ca(0H)2, barium 
hydroxide, Ba(0H)2, etc., which contain two hydroxy Is, and 
are hence known as di-acid bases; and so, too, there are di-acid 
alcohols which bear to the mon-acid alcohols the same relation 
that the di-acid bases bear to the mon-acid bases. Only one 
alcohol of this kind, derived from the parafl&n hydrocarbons, is 
well known. 

Ethylene alcohol or glycol, ethandiol, 02H6O2[02H4(OH)2]. 
— Glycol is made by starting with ethylene, a hydrocar- 
bon of the formula C2H4. When 'this is brought together 
with bromine, the two unite directly, forming ethylene bromide, 

^ The expression monatomic alcohols is used by some writers, but, as it Is conftising, 
it is giving way to the more rational expression above used. 



138 DERIVATIVES OF THE PARAFFINS 

C2H4Br2. By replacing the two bromine atoms by bydroxyl, 
ethylene alcohol or glycol is formed. 

It is a colorless, inodorous, somewhat oily liquid, that boils 
at 197.6**. It has a sweetish taste, and is hence called glycol 
(from yXvKw, sweet). Hence, further, the other alcohols of this 
series are also called glycols. 

The derivatives of ethylene alcohol are not as numerous as 
those of the better-known members of the methyl alcohol series, 
but those which are known are of the same general character. 
The reactions of the alcohol are the same as those of the mon- 
acid alcohols, but it presents more possibilities. In most cases 
in which a mon-acid alcohol yields one derivative, ethylene 
alcohol yields two. Thus, with sodium, the two compounds, 

ONa ONa 

sodium glycol, C2H4< , and di-sodium glycol, C2H4< , 

oil OM& 

can be formed ; from these, by treating with ethyl iodide, the 
two ethers, ethylrglycol ether, C2H4< ^ , and dUethyUglycol 

OP H 

ether, C2H4< , are made. By treatment with hydrochloric 

OC2H5 

CI 
acid, the chloride, C2H4< , known as ethylene chlorhydrine, is 

OH 

formed; and this, by treatment with phosphorus trichloride, 
can be converted into ethylene chloride, C2H4CI2, etc. 

Its conduct towards acids is like that of a di-acid base. It 
forms neutral and cdcoholic salts, of which the acetates may serve 
as examples. Thus we have the 

Mono-acetate, C^H^K ^S?^^^, 

OH 

and the Di-acetate, C2H4< ^^^^^^ ; 

the former still containing alcoholic hydroxyl and corresponding 
to a basic salt ; the latter being a neutral compound. 

The formation of the di-acetate is a step in one of the methods 
of preparing ethylene alcohol. This method consists in treat- 
ing ethylene bromide with potassium acetate in alcoholic solu- 



ETHYLENE ALCOHOL 139 

tion, separating the acetates of ethylene thus formed, and 
decomposing these by means of barium hydroxide. The re- 
actions involved are represented by the following equations : — 

<'*<B:+Ko:c:iI:o-'^"'<o:SSo+'^^' 

The alcohol can also be made by treating ethylene bromide 
with potassium carbonate : — 

C2H,<^^ + 5^>CO + H20 = C2H,<^JJ-|.2KBr + CO,; 
Br KO OH 

and by treating ethylene bromide with silver oxide : — 

C2H, < 5^ + Ag^O + H2O = C^H, < ^ 5 + 2 ^g^^- 
Br OH 

These methods of formation show clearly what ethylene 
alcohol is. 

When acetyl chloride acts upon the alcohol at ordinary tem- 
perature, the product has the formula CzH^Kqi^^^. This 

is also formed by the action of hydrochloric acid gas on the 
di-acetate. It seems probable, therefore, that the action of 
acetyl chloride should be represented by two equations, thus : — 

CjH, < Q JJ + 2 CAOCl = C,H, < '^^Q + 2 HCl ; 
and C,H, < ^^^'^ + HCl = C,H, < ^J^*""^ + C,H A- 

There are two ways in which the structure of a compound 
of the formula C2H4(OH)2 can be represented. They are, — 

CHaCOH) 
(1) I , in which each hydroxyl is represented in combi- 

CHo(OH) 0IT(OH)2 . 

nation with a different carbon atom ; and (2) I , in which 

CHs 



140 DERIVATIVES OF THE PARAFFINS 

both hydroxyls are represented in combination with the 
same carbon atom. The question suggests itself, to which of 
these formulas does ethylene alcohol correspond ? To answer 
this question, we must recall what was said regarding the two 
dichlor-ethanes, known as ethylene chloride and ethylidene 
chloride. The former of these corresponds to the formula 
CHgCl.CHgCl, while the latter, which is formed from aldehyde 
by replacing the carbonyl oxygen by two chlorine atoms, is 
represented by the formula CHCI2.CH8. When the chlorine 
atoms of ethylene chloride are replaced by hydroxyl, ethylene 
alcohol is produced. Hence, the alcohol has the formula 
(HOjHaC — CH2(0H), or each of the hydroxyls is in combina- 
tion with a different carbon atom. When oxidized ethylene 

CH2OH 
alcohol gives, first, glycolic acid, I , and then oxalic acid, 

COOH COOH 

I • This furnishes independent evidence that the alcohol 
COOH 

contains two primary alcohol groups and it must therefore be 

CH2OH 
represented by the formula | 

CH2OH 

All attempts to make the isomeric di-acid 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 I , have failed. Instead of getting ethylidene 

CHs 

alcohol, aldehyde is generally obtained. Aldehyde is ethyli- 
dene alcohol minus water : — 

CHs - CH(0H)2 = CHs - CHO + HA 

It is believed that one carbon atom cannot, under ordinary 
circumstances, 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, C0<^„, 
can be. So, too, the simplest di-acid alcohol conceivable, 



ETHYLENE ALCOHOL 141 

viz., methylene alcohol, CH2(OH)2, cannot exist, but would 
break up, if formed at all, into water and formic aldehyde : — 

CH2(OH)2 = H2O + H.CHO. 

(See discussion regarding the transformation of alcohol into 
aldehyde, pp. 65-67.) 

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 mon-acid 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 we take away two atoms of hydrogen from methane and 
ethane, we have left the residues or radicals CH2 and C2H4. 
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 may be regarded as ethane in which 
two hydrogen atoms are replaced by 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-O-C2H4-O-H 

Two molecules water Ethylene alcohol 



The higher member of the series of di-acid alcohols will not 
be taken up here. 

2. Dibasic Acids 

Just as there are^di-acid alcohols derived from the paraffins, 
so there are dibasic acids which may also be regarded as deriva- 
tives of the paraffins. We have seen that the simplest acids, 
the monobasic fatty acids, are closely related to formic and 



142 DERIVATIVES OF THE PARAFFINS 

carbonic acids ; that they may 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 group carboxyl, 
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 
derived from two molecules of carbonic acid by the replacement 
of two hydroxyls by the bivalent radical CHg : — 

OTT 

Two molecules carbonic acid Dibasic acid 

The general methods of preparation available for the building 
up of the series of dibasic acids are modifications of those used 
in making the monobasic acids. They are : — 

1. Oxidation of di-add primary alcohols. Just as a mon- 
acid primary alcohol, R.CH2OH, yields by oxidation a mono- 
basic acid, so a di-acid primary alcohol, R"(CH20H)2, yields a 
dibasic acid, E"(C02H)2. 

2. Treatment of the dicyanides, R"(CN)2, with caustic alkalies, 

3. Oxidation of the hydroxy-acids or alcohol acids. These 
are compounds which are at the same time alcohol and acid; 
as, for example, hydroxy-acetic 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 

CH2OH 
formula | • When this is oxidized, the alcoholic portion, 

COoH 

CH2OH, is converted into carboxyl, and a dibasic acid is formed. 

4. From the cyanogen derivatives of the monobasic acids, 



OXALIC ACID 143 

ON 
such as cyan-acetic acid, CH2<^^ „, by the transformation of 

the cyanogen group into carboxyl. 

DIBASIC ACIDS, C„H2n-204 

Oxalic acid (C02H)2. 

Malonic " CH2(C02H)2. 

Succinic " C2H4(C02H)o. 

Pyrotartaric " C3H6(C02H)2. 

.Adipic " C4H8(C02H)2. 

Pimelic " C5H,o(C02H)2. 

Suberic " C6Hi2(C02H)2. 

Azelaic " C7Hh(C02H)2. 

Sebacic " C8Hi6(C02H)2. 

Brassylic " C9Hi8(C02H)2. 

Eoccellic " Ci5H3o(C02H)2. 



Of the many acids included in this list only four or five can 
be said to be well known. We may confine our attention to the 
first four members. 

Oxalic acid, C:.Ho04[(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 hydro- 
carbon by replacement of hydrogen by carboxyl; nor is it 
derived from two molecules of carbonic acid by replacement of 
two hydroxy Is by a bivalent radical. Still it is in other respects 
so closely allied to the members of the series, and has so many 
things in common with the other members, that it would be a 
mere act of pedantry to consider it in any other connection. 

Oxalic acid occurs very widely distributed in nature ; as in 
certain plants of the oxcUis varieties, in the form of the acid 



144 DERIVATIVES OF THE PARAFFINS 

potassium salt; as calcium salt in many plants; 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 
so-called carbohydrates, such as starch, cellulose, etc. 

Experiment 34. To be carried out under a hood. In a good-sized 
flask pour half a litre of ordinary concentrated nitric acid (of specific 
gravity 1.245) upon 60b of sugar. Heat gently until the reaction begins. 
Then withdraw the flame, when the oxidation will proceed with some 
violence, and accompanied by a copious evolution of red fumes. When 
the action has ceased, evaporate the liquid to one-«ixth the original 
volume, and let it cool, when oxalic acid will crystallize out. Recrystal- 
lize from water the acid thus obtained, and with the pure substance 
perform such experiments as will exhibit its properties. For example, 
(1) Heat a specimen at 100°, and notice loss of water; (2) Heat some in 
a small flask with sulphuric acid, and prove that both oxides of carbon 
are formed. 

On the large scale, oxalic acid is made by heating wood 
shavings or sawdust with caustic potash and caustic soda to 
240° to 260°. The mass is extracted with water, and the solu- 
tion evaporated to crystallization, when sodium oxalate is 
deposited. 

Other methods, which are interesting from a purely scientific 
point of view, are the following : — 

1. The spontaneous transformation of an aqueous solution of 

cyanogen : — 

CN COgH 

1 +4H20= I +2NH3; 
CN CO2H 

CN COsCNH^) 

or, really, | + 4 HgO = | 

CN C02(NH4) 

2. Treatment of carbon dioxide with sodium : -^ 

2 CO2 + 2 Na = C204Na2. 

3. Heating sodium formate : — 

2 H . COoNa = CaO^Nag + 2 H. 



MALONIC ACID 145 

Oxalic acid crystallizes from water in monoclinic prisms con- 
taining two molecules of water (C2H2O4 -f 2 HgO). It loses 
this water at 100°, and then melts at 189°. It sublimes just 
above the melting-point, but, if heated higher, it breaks up 
into carbon monoxide, carbon dioxide, and formic acid : — 

2 C2H2O4 = 2 CO2 + CO + HCO2H + H2O. 

Sulphuric acid decomposes it into carbon monoxide, carbon 
dioxide, and water. Heated with glycerol to 100°, carbon 
dioxide and formic acid are formed (see Formic Acid): — 

C2H2O4 = CO2 + HCO2H. 

It is an excellent reducing agent, and is used to standardize 
solutions of potassium permanganate. 

Bxpeiiment 35. Try the action of a solution of potassium perman- 
ganate on a solution of oxalic acid. Why is it best to have the solution 
of the permanganate acid ? 

Oxalic acid is an active poison. It is used in calico printing. 

Salts of oxalic acid. Like all dibasic acids, oxalic acid forms 
acid and neutral salts with metals. All the salts are insoluble 
except those containing the alkalies. Among those most com- 
mon are the acid potassium salt, C2O4HK, which is found in the 
sorrels or plants of the oxalis variety; the ammonium salt, 
0204(^114)2, of which some urinary calculi are formed; and 
calcium oxalate, C204Ca, which, being insoluble in water and 
acetic acid, is used as a means of detecting calcium in the pres- 
ence of magnesium, and of estimating calcium and oxalic acid. 

Malonic acid, C3H404[CH2(C02H)2]. — This acid was first 
made by oxidation of malic acid (which see), and is hence 
called malonic axiid. It can best be made by starting with 
acetic acid. The necessary steps are : (1) making chlor-acetic 
acid ; (2) transforming chlor-acetic acid into cyan-acetic acid ; 
(3) heating cyan-acetic acid with an alkali. 

Note for Student. — Write the equations representing the three 
steps mentioned. 



146 DERIVATIVES OF THE PARAFFINS 

It is a solid that crystallizes in larainaB. It breaks up at a 
temperature above 132°, which is its melting-point, into carbon 
dioxide and acetic acid : — 

CHj < p^ -J. = CH3CO2H + CO2. 

NoTB FOR Student. — What simple method for the preparation of 
marsh gas and other paraffins is this reaction analogous to ? 

Succinic acids, 04H«O4[02H4(CO2H)2].— Regarding these 
acids as derived from ethane by substituting two carboxyls for 
two hydrogens, it is clear that two are possible, one corre- 
sponding to ethylene" chloride and another corresponding to 
ethylidene chloride. Two are actually known. One is the 
well-known succinic acid ; the other is called isosuccinic acid. 

Succinic acid, ethylene-succinic acid, i . — 

CH2*C02S 

This acid occurs in amber (hence its name, from Lat. succinum, 
amber); in some varieties of lignite ; in many plants ; and in 
the animal organism, as in the urine of the horse, goat, and 
rabbit. 

It is formed under many circumstances, especially by oxida- 
tion of fats with nitric acid, by fermentation of calcium malate, 
and, in small quantity, in the alcoholic fermentation of sugar. 
Among the methods for its preparation are : — 

CHg.CN 

1. Treatment of ethylene cyanide, | , with a caustic 
alkali : — CHs . CN 

CHgCK CH2. CO2K 

I +2KOH + 2H20= I -f2NH3. 

CH2CN CH2. CO2K 

2. Similarly, by treatment of )8-cyan-propionic acid with an 
alkali. (What is ^-cyan-propionic acid ?) 



ISOSUCCINIC ACID * l47 

3. Reduction of tartaric and malic acids by means of hy- 
driodic acid. These well-known acids will be shown to be 
closely related to succinic acid, and the reaction here mentioned 
will be explained. The methods actually used in the prepara- 
tion of succinic acid are: (1) the distillation of amber, and 
(2) the fermentation of calcium malate. 

The acid crystallizes in monoclinic prisms, which melt at 
182° (try it). 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 chloroform. It is converted into succinic acid by boiling 
with water. When boiled with alcohols it yields the corre- 
sponding ester acids. For example, with ordinary alcohol 
mono-ethyl succinate is formed. 

C2H4<^^>0 + C2H5OH = ^2^4<QQQjj^ • 

Among the salts basic ferric succinate, C4H4O4. 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 
aluminium from manganese, zinc, nickel, and cobalt quanti- 
tatively, 

BxperlmeDt 36. Make a neutral solution of ammonium succinate 
by neutralizing an aqueous solution of the acid, and boiling off all excess 
of ammonia. Add some of this solution to a solution known to contain 
manganese and iron m the ferric state. A brown-red precipitate will be 
formed. Filter and wash, and examine the filtrate for iron. 

CH(C02H)2 
Isosuccinic acid, ethylidene-succinic acid, I 

CH3 

This acid is made by treating a-cyan-propionic acid with an 
alkali. (What is a-cyan-propionic acid ?) 

Isosuccinic acid forms crystals that melt at 130°. Heated 



148 DERIVATIVES OF THE PARAFFINS 

above its melting-point it breaks up into propionic acid and 
carbon dioxide: — 

CH(C02H)2 CH2CO2H 

I = I +C0^ 

CHj CH3 

Isosacdnic acid Propionic acid 

NoTB FOR Studbnt. — NoticB carefully the difference between the two 
succinic acids, as shown by their conduct when heated. What is the 
difference ? 

Acids of the formula 05H8O4[C3H6(CO2H)2]. — Four 
acids of the formula C5H8O4 are known, only one of which, 
however, need be mentioned here. This is, — 

CH3. CS> CO2S 
P3n:'otartaric acid, J — As the name indi- 

cates, this acid may be made by dry distillation of tartaric acid. 

Tri-acid Alcohols 

The existence of mon-acid alcohols corresponding to the mon- 
acid bases, like potassium hydroxide, and of di-acid alcohols 
corresponding to the di-acid bases, like calcium hydroxide, sug- 
gests the possible existence of tri-acid alcohols corresponding to 
tri-acid bases, like ferric hydroxide. There is only one alcohol 
of this kind derived from the paraffin hydrocarbons that is at all 
well known. This is the common substance glycerin or glycerol. 

Glycerol, glycerin, propantriol, CgHgOg. — As has been 
stated repeatedly, glycerol occurs very widely distributed as the 
alcoholic or basic 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 mem- 
ber of another series. 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 in 



GLYCEROL 149 

the case of the glycerol compounds of palmitic and stearic acids 

are these : — 

Formation 

C,H,(OH)3+3 HO . OC . Ci5Ha=CaH5(0 . OC . C^Ha)3+3 HA 

Glycerol Palmitic acid Glyceryl tri-palmitate, 

or Falmitin 

C,H,(OH),+ 3 HO . 00 . C,jH«= CjH,(0 . 00 . Ci,H„)s+3 H^O. 

Glycerol Stearic acid Glyceryl tri-stearate, 

or Stearin 

SaponijicaUon 
CaH^CO . OC . C^H8i)3 + 3 KOH = C8H,(OH)3 + 3 Q^Ti^ . CO^ 

Palmitin Glycerol Potassiam pahnitate 

0^,(0 . 00 . C„H85)3 + 3 KOH = C8H5(OH)8 + 3 C„Ha, . OOjK. 

Stearin Glycerol Potassiam stearate 

The fats are also decomposed by superheated steam, yield- 
ing free glycerol and the free acids, and this method is used 
on the large scale, a little lime being added to facilitate the 
process. Lead oxide decomposes fats yielding a mixture of 
glycerol and the lead salts of the acids. The mixture is known 
in medicine as " lead plaster." 

Glycerol is formed in small quantity by the alcoholic fer- 
mentation of sugar. 

It has been made synthetically from propylene chloride, 
CsHeClj. The necessary steps are: (1) treatment with chlo- 
rine, giving CgHfiCls ; (2) treatment of the tri-chlorine deriva- 
tive with water, thus replacing the three chlorine atoms by 
hydroxyl. Another synthesis of glycerol has been effected by 
starting with formic aldehyde. When this is treated with 

r CH2OH 
nitromethane, a compound of the formula O2NC < CH2OH 

( CH2OH 
is formed. By reduction this gives the substance 

( CH2OH 
HOHNC \ CH2OH. 
( CH2OH 

From this in turn by elimination of the constituents of methyl 



150 DERIVATIVES OF THE PARAFFINS 

alcohol the oxime, HONC | CH2OH jg fanned. By substi. 

' \ CH2OH' -^ 

tuting oxygen for the oxime group NOH, dihydroxyacetone 

CH2OH 

CO , results, and by reduction this is easily converted into 
I 
CH2OH 

glycerol. 

Glycerol is a thick colorless liquid, with a sweetish taste 
(compare with glycol). It mixes with alcohol and water in 
all proportions but is insoluble in ether. It attracts moisture 
from the air. At low temperatures it solidifies, forming 
deliquescent crystals which melt at 28°. Pure glycerol boils at 
290° without decomposition. If salts are present it undergoes 
decomposition at the boiling temperature. Under diminished 
pressure it can be distilled ; but, when heated to its boiling-point 
under the ordinary atmospheric pressure, it undergoes decom- 
position. It is volatile with water vapor. 

Glycerol is used to some extent in medicine, but its chief 
use is in the manufacture of nitro-glycerin, 

Experiment 37. Heat a little commercial glycerol in a dry vessel, 
and try to boil it. What evidence have you that it undergoes decomposi- 
tion ? Put 20«« to 30CC glycerol in 400^^ to 500«« water in a flask ; connect 
with a condenser, and boil. Does glycerol pass over with the water vapor ? 

The reactions of glycerol all clearly lead to the conclusion 
that it is a tri-acid alcohol. 

(1) The three hydroxy 1 groups can be replaced successively 
by chlorine, giving the compounds, — 

f CI 
CMorhydririf CgHs-j ,qjjv ; 

Dichlorhydrm, CsHa-j rvA; 
and Trichlorhydnny CsHjClg. 

The last compound is really trichlorpropane. 



GLYCEROL 151 

(2) It forms three classes of ethereal salts containing one, 
two, and three acid residues respectively. For example, with 
acetic anhydride these reactions take place : — 

( OH ( OC2H3O 

1. CsHJ oh + (C2H80)20 = CshJ oh + C^HA. 

(OH (OH 

( OH ( OC2H3O 

2. CsH J OH + 2 (C2H30)20 = C3H5 ] OC2H3O + 2 C2H4O2. 

(OH (OH 

r OH ( OC2H3O 

3. C3H, ■] OH -I- 3 (C2H30)20 = C3H5 ] OC2H3O 4- 3 CgH A- 

( OH ( OC2H3O 

In regard to the relations of the hydroxyl groups to the parts of 
the radical C3H5, it appears highly probable that each hydroxyl 
is in combination with a diiferent carbon atom as represented 

CH2OH 

in the formula CHOH . 

I 
CII2OH 

In the first place, it has been shown that compounds con- 
taining two hydroxyls in combination with the same carbon 
are unstable. They readily lose water. It would follow from 
this that the simplest tri-acid alcohol must contain at least 
three atoms of carbon, just as the simplest di-acid alcohol 
must contain at least two atoms of carbon. We have seen 
that the simplest tri-acid alcohol known does contain three 

atoms of carbon. 

CH2OH 
I 
Further, if the formula of glycerol is CHOH , it contains two 

I 
CH2OH 

primary alcohol groups, CH2OH, and one secondary alcohol 
group, CHOH, and we have seen that the group CH2OH is 
converted into carboxyl under the influence of oxidizing agents ; 
and the group CHOH into carbonyl CO. Therefore, we should 



152 DBBIVATIVBS OF THE PABAFFINS 

expect by oxidizing glycerol to get products of the f ormulasy 
CO,H CO2H COOH 

I I I 

CHOH , CHOH, and CO . Products of these formulas actually 

I I I 

CH2OH CO2H COOH 

are obtained, the first being glyceric acid (which see), the second 

tartronic acid (which see), and the third mesoxalic acid (which 

see). 

Just as ethyl alcohol is regarded as water in which one 

C H ) 

hydrogen is replaced by the univalent radical C2H5, as ^^ > O ; 

and glycol is regarded as water in which two hydrogen atoms 
of two molecules of water are replaced by the bivalent radical 

C2H4, as C2H4^ ; so also glycerol may be regarded as water 
H ^^ 

in which three hydrogen atoms of three molecules are replaced 
.by the trivalent radical C3H5, thus : — 



HOH 




roH 


HOH 


C,H, 


OH. 


HOH 




OH 


Three molecules water 


Olyoi 


erol 



Ethereal salts or esters of glycerol. — Among the im« 

portant esters of glycerol are the nitraies. Two of these 

fONOa 
are known ; viz., the mono-nitrate, CsHs OH , and the tri- 

OH 

nitraie, G^s{O^O^S9 t^6 latter being the chief constituent of 
nitro-glycerin, Nitro-glycerin is prepared by treating glycerol 
with a mixture of concentrated sulphuric and nitric acids. It 
is a pale yellow oil that is insoluble in water. At — 20® 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, and 
Iree nitrogen. As heat is evolved the gases expand and, 



BUTTER 153 

in fact, they occupy 10,000 times that of the nitro-glycerin. 
This accounts for the enormous explosive power of the 
substance. Dynamite is infusorial earth impregnated with 
nitro-glycerin. Mixed with nitrocellulose (which see) it 
forms smokeless powder. It is the active constituent of other 
explosives. 

When treated with a caustic alkali, nitro-glycerin is saponi- 
fied, yielding glycerol and a nitrate. This shows that it is an 
ester of nitric acid, and not a nitro-compound. 

Fats. — The relation of the fats to glycerol has already 
been stated. Most fats are mixtures of the three neutral 
esters that glycerol forms with palmitic, stearic, and oleic 
acids, known by the names paXmitin, stearin, and olein. Olein 
is liquid, and the other two fats are solids, stearin having the 
higher melting-point. Therefore, the larger the proportion of 
olein contained in a fat, the softer it is, while the greater the 
proportion of stearin, the higher its melting-point. Among 
the fats that are particularly rich in stearin may be men- 
tioned mutton tallow, heef tallow, and lafd. Human fat and 
palm oil are particularly rich in palmitin. Sperm oil and cod- 
liver oil are rich in olein. Fats occur very widely distributed 
in naturd, both in plants and animals. They are of the highest 
importance from the physiological point of view, forming one 
of the three great classes of food-stuffs. 

Butter consists of ethereal salts of glycerol and the follow- 
ing acids : myristic, palmitic, and stearic acids, which are not 
volatile, and butyric, caproic, caprylic, and capric acids, which 
are volatile with water vapor. All the acids mentioned are 
members of the fatty acid series. Some of these acids are sol- 
uble and some are insoluble in water. The percentage of in- 
soluble fatty acids contained in butter has been found to be 
88 per cent. As the proportion of insoluble fatty acids con- 
tained in artificial butters, such as the so-called oleo-margarin^ 



154 DERIVATIVES OF THE PARAFFINS 

is greater than that contained in butter, it is not a difficult 
matter to distinguish between the two by determining the 
amount of these acids contained in them. 

Tri-basic Acids 

Tri-oarballylio acid, C8H6(C02H)8. — This acid can be 
made from trichlorhydrin, C3H5CI8 (which see), by replacing 
the chlorine by cyanogen, and heating with an alkali the tri- 
cyanhydrin thus obtained. It can be made also by treating 
aconitic acid (which see) with nascent hydrogen. It crystal- 
lizes from water in orthorhombic prisms which melt at 166°. 

Tetr-acid Alcohols 

Brythrol, enrthrite, C4Hio04[C4H6(OH)4]. — The sub- 
stance occurs in one of the algae {Protococcua vulgaris) and in 
several lichens. It crystallizes from water in quadratic prisms. 
It has a very sweet taste. The fact that the simplest tetr-acid 
alcohol contains four atoms of carbon should be specially noted. 



There is no well-known tetra-basic acid derived from the 
hydrocarbons of the paraffin series. 



Pent-acid Alcohols 



One pent-acid alcohol occurs in nature in Adonis vemalis, 
and it is hence called adonite. It is also formed by reduction 
of ribose (which see). 

By reduction of xylose (which see) a pent-acid alcohol, called 
xylite, is formed; and by reduction of arabinose (which see) 
another called arabite is formed. 

All the above-named alcohols have the formula C5H12O5 
[05117(011)5]. There are three modifications of arabite — two 
optically active, and one inactive. There is still another pent- 
acid alcoliol known as rhamnite, formed by reduction of rham- 



% 



HEX-ACID ALCOHOLS 155 

nose (which see). This has the composition represented by 
the formula C6HiA[CH8.C5Hfl(OH)5]. ' 



Two pentabasic acids have been made, but they are of no 
special importance. 

Hex-acid Alcohols 

There are several hex-acid 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 hex- 
<icid alcohols contain six carbon atoms each. 

Mannitol, mannite, C6H8(OH)6. — Mannite is very widely 
distributed in the vegetable kingdom. It occurs most abun- 
dantly in manna,^ which is the partly dried sap of the manna-ash 
{Fraxinus omus), 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 mushrooms 
and in celery, in olives, and in the leaves of syringa (mock 
orange) and in many other plants. It forms 20 per cent of 
dried Agaricus integer. 

Mannite is formed in the lactic acid fermentation of sugar. 
It is formed also by the action of nascent hydrogen on fructose 
and mannose. It crystallizes in needles, or rhombic prisms, 
easily soluble in water and in alcohol. It has a sweet taste. 

Nitric acid converts mannite into manno-saccharic add 
(which see). When boiled with concentrated hydriodic acid, 
it is converted into secondary hexyl iodide, CeHjgl. 

Mannite hexa-nitrate (nitro-mannite), C6H8(O.N02)6, is 
formed by treating mannite with a mixture of concentrated 
sulphuric and nitric acids. It is a solid substance and is very 
explosive. (Analogy with nitro-glycerin.) 

1 The maQDa of the Scriptures was probably obtained ftrom the branches of Tammaria 
QaUica, It contains no mannite, but a fermentable sugar. 



156 DERIVATIVES OP THE PARAFFINS 

Mannite hex-acetate, C6H9(O.C2H30)e, is formed by treat- 
ing mannite with acetic anhydride. Its formation, as well as 
that of the hexa-nitrate, shows that mannite is a hex-acid 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 mannite — the ordinary, known as 
dextro-mannite, and, further, levo-mannite, and inactive mannite. 

Dulcite, OeHgCOH)^^. — This occurs in a kind of manna 
obtained from Madagascar, the source of which, however, is 
unknown. It is formed by treating sugar of milk or galactose 
with nascent hydrogen (compare with mannite in this respect). 

Nitric acid oxidizes dulcite, forming mucic acid (which see), 
isomeric with manno-saccharic acid, which is formed from 
mannite. Like mannite, when boiled with hydriodic acid it 
yields secondary hexyl iodide, CgHijI. 

Sorbite, 06H8(OH)6+ liH20. — Ordinary sorbite occurs in 
the berries of the mountain ash, sorb apple, and other fruits, 
as plums, cherries, apples, etc. It is formed by reduction of 
glucose, and also together with mannite by the reduction of 
fructose. This variety is known as dextro-sorbite, because it 
is formed from glucose, which is dextro-rotatory. Lcevo^orbite 
is also known, having been obtained by the reduction of laevo- 
gulose. 

There are no hexorhasic acids known belonging to this series. 



Hept-acid Alcohols, etc. 

Perseite, 07H9(OH)7, occurs in the fruit and leaves of 
Laurus persea, and has been made artificially from dextro- 
mannose, by treating it with hydrocyanic acid, converting the 
nitril thus formed into the corresponding acid, and reducing 
this acid. It is also called dextro-mannoheptite. By similar 
reactions an oct-acid and an alcohol with nine hydroxyls have 
been made from glucose. 



CHAPTER X 

MIXED COMPOUNDS— DERIYATIVES 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 which are at the same time alcohols 
and acids. There are others which are at the same time alco- 
hols and aldehydes, alcohols and ketones, acids and ketones, 
etc. Fortunately, for our purpose, the number of compounds 
of this kind actually known is comparatively small, though 
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 commonly called oxy-a/cids or hydroxy-acids. 

HyDROXY-ACIDS, CnHgnOs 

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 corre- 
sponding fatty acid by one atom of oxygen, or by containing 
one hydroxyl in the place of one hydrogen, thus : — 

Fatty acids Hydroxy-acids 

H.COjH HO.COjH. 

CH,.CO,H CH,<2Jjj. 

C2H5.CO2H C2H4 < ^^ g • 

etc. etc. 

167 



158 DERIVATIVES OF THE PARAFFINS 

The first member of the scries, which by analogy would be 
called hydroxy-formic add, is nothing but the ordinary hypo- 
thetical 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 peculiar structure, it is a dibasic acid which the 
other members 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 proper. 

Carbonic acid, H2CO3 f CO <Q„j It is believed that 

this body exists in solutions of carbon dioxide in water. All 
that is known about it is that it is a feeble dibasic acid, and 
breaks up into water and carbon dioxide whenever it is set 
free from its salts. We have seen that this instability is 
generally met with in compounds containing two hydroxyls in 
combination with one carbon atom. 

Among the derivatives of carbonic acid that should be 
mentioned here are the ethereal salts. These may be made : — 

1. By treating silver carbonate, CO<^.^j with the iodides 
of alcohol radicals ; as, for example, — 

CO<^^| + 2C.H,I = CO<^^;| + 2AgI. 

2. By treating the alcohols with carbonyl chloride, COCI2: — 

COCI2 4- 2 C2H5OH = CO(OC2H5)2 + 2 HCl. 

CI 
Ethyl chlor-carbonate, OC < ^^ „ . — This compound is 

made by treating alcohol with carbonyl chloride : — 

COCI2 + C2H5OH = OC < l' + HCl. 

It may be regarded as the ethyl ester of mono-chlor-formio 
acid, CI . COOH ; and, properly speaking, should be called ethyl 
chlor-formcUe, 



ETHYL CHLOR-CARBONATB 159 

Carbon bisulphide acts like carbou dioxide towards alkar 
lies and alcohols, and thus a number of ether acids and 
ethereal salts containing sulphur can be made. Thus, when 

carbon bisulphide is added to a solution of caustic potash in 

OC H 

alcohol, a potassium salt of the formula SC < ^^ ' is formed. 

This is called potassium xanthogenate. Free xanthogenic acid 
is very unstable, breaking up into alcohol and carbon bisul- 
phide. The formation of the salt is represented by the follow- 
ing equation : — 

CS2 + KOH + C2H5OH = SC < ^^^' + H2O. 

A similar salt made from ordinary amyl alcohol has been used 
for the purpose of destroying phylloxera, the insect which is so 
destructive to grape-vines, particularly in the wine districts of 
!France. 

General methods for the preparation of hydroxy-acids. The 
methods available for making the hydroxy-acids are modifica- 
tions of those used for making alcohols and acids. 

Starting with a mon-acid alcohol, a hydroxy-acid can be 
made by the same methods that were used in making an acid 
from a hydrocarbon. Suppose, for example, that it is desired 
to make acetic acid from marsh gas. The reactions that may 
be used are: (1) the preparation of a halogen derivative; 
(2) conversion of the halogen derivative into the cyanogen 
derivative ; and (3) conversion of the cyanogen derivative into 
the acid. The results of these operations are described by 
saying that carboxyl has been introduced. By similar opera- 
tions carboxyl can be introduced into methyl alcohol, and the 
product is hydroxy-acetic acid. 

It is, however, generally better to start with an acid, and 
introduce hydroxyl. This can be done in several ways : — 

1. By treating a halogen derivative of an acid with water or 
silver hydroxide : — 



160 DERIVATIVES OF THE PARAFFINS 

CH, < ^J^^jj + HHO = CH, < Jjjjj + HBr. 

Brom-acetic acid 

2. By treating an amino derivative of an acid with nitrous 
acid (see page 100) : — 

ISTTT OTT 

CH, < J^^ + HNO, = CH, < ^"^jj + N, + H,0. 

Amino-acetic acid 

3. By treating a salt of a avlphonioadd derivative of an acid 
with caustic potash : — 

CHj < ^^ ^ + KOH = CH2 < ^Q TT- + K2SO3. 

Sulpho-acetic acid 

The first two of these reactions have been described and 
mentioned as affording methods for the introduction of hy- 
droxy 1 into hydrocarbons. It will be seen that the only dif- 
ference between the reactions used in making alcohols and 
those used in making hydroxy-acids is that in one case we 
start with the hydrocarbons, while in the other we start with 
the acids. 

Glycolic acid, hydroxy-acetic acid, oxy-acetic acid, 
ethanolic acid, 02H4O3f0H2<QQ ^j. — Glycolic acid is 

found in nature in unripe grapes, and in the leaves of the wild 
grape (Ampelopsis hederacea). 

It can be made from glycocoll, which is amino-acetic acid (see 
reaction 2, above), from brom- or chlor-acetic acid and water 
(see reaction 1, above), and by the oxidation of glycol: — 

CH2OH CO2H 

I +02= I +H2O. 

CH2OH CH2OH 

Glycol Glycolic acid 

This consists in transforming one of the primary alcohol groups, 
CH2OH, contained in glycol, into carboxyl. (What would be 



GLYCOLIC ACID, ETC. 161 

formed by conversion of both the primary alcohol groups of 
glycol into carboxyl ?) It can also be made by careful oxida- 
tion 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 forms crystals that are easily soluble in water, 
alcohol, and ether. 

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: — 

^^» < CO,Ag + ^'^'^ = ^^' < COAH5 "^ ^^^- 

In this reaction, as well as in the formation of salts of glycolic 
acid, the alcoholic hydroxyl remains unchanged. 

As an alcohol, glycolic acid forms ethers of which ethyl- 

glycolic acid, G^2<qq^9 niay serve as an example. It will 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 160°. Ethyl-glycolic 
acid is a liquid that boils at 206"* to 207"*. Finally, as an 
alcohol, 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 H O 

CH2<CpQ I, ' . As will be seen, this bears the same relation 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 



162 DERIVATIVES OP THE PARAFFINS 

heated to 100°. This substance is plainly an ester, an alcohol, 
and an acid. 

When glycolic acid is heated to 250°-280° it yields glycoUde, 
which is believed to be derived from the acid as represented in 
this equation : — 

OH CH2-O-CO 

It is plainly a double ester resulting from the interaction of 
the alcoholic 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, glycolide is converted into glycolic 
acid. 

Lactic acids, hydroxy-propionic acids, oxy-propionic 
acids, CzB%03\C2Ra<^q^' — In speaking of propionic 

acid, it was pointed out that two series of substitution-products 
of the acid are known, which are designated as the a- and fi- 
series. Accordingly we should expect to find two hydroxy- 
propionic acids, the a- and the )3-acid. Two lactic acids have 
been known for a long time. One of these is ordinary lactic 
add; the other a variety that is found in meat, and hence 
called sarco-lactic acid. But, strange to say, a thorough in- 
vestigation of these two acids has proved that both must be 
represented by the same structural formula, as both conduct 
themselves in exactly the same way towards reagents. Further, 
two other hydroxy-propionic acids are certainly known. The 
facts then are these: four acids are known, all of which are 
hydroxy-propionic acids. Our ordinary theory enables us to 
foretell the existence of only two. Before discussing this 
apparent discrepancy let us briefly study the acids themselves. 



LACTIC ACIDS 163 

1. Lactic acid, inactive ethylidene-lactic acid, a-hy- 
droxy-propionic acid, CH3.0H<^q„. — Lactic acid is 

made by the fermentation of sugar, as has already been de- 
scribed under Butyric Acid (which see). The process is car- 
ried out best by dissolving cane sugar and a little tartaric acid 
in water; then adding putrid cheese, milk, and zinc carbonate, 
the object of which is to prevent the solution from becoming 
acid, as the presence of free acid is fatal to the ferment. Lac- 
tic acid can also be made by fermentation of sugar of milk, 
and is hence contained in sour milk; by boiling a-chlor-pro- 
pionic acid with alkalies, — 

CH3.CH < co^H + ^^H = CH3.CH< ^^^.f KCl; 

and by treating alanine (a-amino-propionic acid) with nitrous 
acid, — 

CH3.CH < ^^^ 4- HN02=CH3.CH < ^ J jj -f N2 -h HA 

Lactic acid is a thick liquid that mixes with water and with 
alcohol in all proportions. 

When commercial lactic acid of specific gravity 1.21 is dis- 
tilled under much diminished pressure (1 mm. of mercury) and 
the distillate allowed to stand in a freezing-mixture for a time, 
it takes the form of crystals that melt at 17°.5-18®. 

Treated with hydriodic acid, it is reduced to propionic acid, 

OTT 
CHs-CH < ^ J^^ -h 2 HI = CH3.CH2.CO2H + H2O + 1,. 

2. Sarco-lactic acid, dextro-ethylidene-lactic acid, 

OH 
CH3CH< QQ -CT* — This acid occurs in the liquids expressed 

from meat. It is therefore contained in "extract of meat," 
and can be obtained most readily from this source. 

Its properties are, for the most part, like those of inactive 



164 DERIVATIVES OF THE PARAFFINS 

lactic acid, and its conduct towards reagents is in all respects 
the same. Its salts are somewhat more easily soluble than 
those of ordinary inactive lactic acid. The chief difference 
between the two is observed in the action towards polarized 
light. Dextro-lactic acid turns the plane of polarization to the 
right. Its salts are all levo-rotatory. On the other hand, 
neither inactive lactic acid nor its salts exert any action upon 
polarized light.* 

OH 
3. Levo-lactio acid, 0H8.0H< QQg^ — A third variety 

of ethylidene-lactic acid, that turns the plane of polarization 
to the left, is formed from cane sugar by the action of a certain 
bacillils found in a spring-water. By fractional crystallization 
of the strychnine salt of ordinary inactive lactic acid two kinds 
of crystals are obtained. The acid separated from one kind is 
sarco-lactic, or dextro-lactic, acid; while that separated from 
the other kind is levo-lactic acid. This method of splitting 
the inactive acid into the two active varieties is applicable to 
many other similar cases. The relations between these three 
acids are of the same kind as those existing between the three 
varieties of tartaric acid (which see). 



OH^OH 



CH2.CO2H 



4. Hydracrylio acid, 

^-hydroxy-propionic acid, 

Hydracrylic acid is made by boiling ^-iodo-propionic acid with 
water or silver oxide and water:— 

CH2I CH2.OH 

I +HHO= I +HL 

CH2.CO2H CH2.CO2H 

CHa 

It is made also by starting with ethylene, || . When this 

CH2 

hydrocarbon is treated with hy pochlorous acid, HOCl, it is con- 

> See active and inactive amyl alcohols, p. 127. 



HYDRACHYLIC ACID 165 

CH2CI 
verted into ethylene-chlorhydrine, | (which §ee). By 

CH2OH 

replacing the chlorine with cyanogen, and boiling the cyan- 

CH2CN 
hydrine, | , thus obtained, with an alkali, hydracrylic acid 

CH2OH 

is obtained. 

These reactions clearly show that hydracrylic acid is an 
ethylene compound, and, as it is made from j8-iodo-propionic 
acid by replacing the iodine with hydroxyl, it follows further 
that the j8-substitution-products of propionic acid are ethylene 
products, and that the a-products are ethylidene products (see 
p. 132). 

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 accylic acidy CH2:CH.C02H 
(which see). 

The difference in conduct between ethylidene-lactic acid and 
ethylene-lactic acid, when heated, is interesting and suggestive. 
When ethylidene-lactic acid is heated, both its acid and alco- 
holic properties are destroyed, both the alcoholic and acid 
hydroxyls taking part in the reaction. Whereas, when 
ethylene-lactic acid is heated, only the alcoholic properties are 
destroyed, the carboxyl remaining intact. 

There are then more hydroxy-propionic acids known than our 
theory of linkage in its simplest form can account for. Other 
cases of this kind are known, and one very marked and 
especially interesting one will be taken up when tartaric acid 
is treated of. It will be shown that just as there are two 
active lactic acids and an inactive one, so there are two active 
tartaric acids and an inactive one, which conduct themselves in 
the same way towards reagents, and must hence be represented 
by the same structural formula. 

We have here to deal with a new kind of isomerism. Com- 
pounds may conduct themselves chemically m the same way, 



166 



DERIVATIVES OP THE PARAFFINS 



and yet differ in some of their physical properties, as in their 
action towards polarized light. To distinguish this kind of 
isomerism from ordinary chemical isomerism it has been called 
physical isomerism. 

An ingenious hypothesis has been put forward by way of 
explanation of that particular kind of physical isomerism which 
shows itself in the action of compounds upon polarized light. 
It must be remembered that our ordinary 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 one carbon atom 
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 Fig. 10. 

If these groups are all different in kind, and only in this 
case, it is possible to arrange them in two ways with reference 
to the carbon atom. The difference between the two arrange- 





Fig. 10. 



Fig. 11. 



ments is that which is observed between either one and its 
reflection in a mirror. Imperfectly the second arrangement 
is shown in Fig. 11.^ 

A carbon atom, in combination with four different kinds of 
atoms or groups, is called an asymmetrical carbon atom. When- 
ever, therefore, a compound contains an asymmetrical carbon 
atom, there are two possible arrangements of its parts in space 



* This can be made clear only by means of models. These can easUy be made of stout 
wire and wooden balls. 



ISETHIONIC ACID 167 

which correspond to the two complementary tetrahedrons, viz., 
the right-handed and the left-handed tetrahedron. 

In ethylidene lactic acid there is an asymmetrical carbon atom, 
as shown by the ordinary formula, which may be written thus : 
H 

I 
CHa — C — OH, the central carbon atom appearing in combination 
I 
CO2H 

with (1) hydrogen, (2) hydroxyl, (3) carboxyl, and (4) methyl. 
Hence, according to the hypothesis just stated, there ought to 
be two possible arrangements of the constituents of this com- 
pound, one corresponding to the right-handed tetrahedron, the 
other to the left-handed tetrahedron. Both would be ethylidene- 
lactic acids. The inactive variety is formed by the combination 
of the two active varieties, and must, therefore, have a greater 
molecular weight than these. 

The branch of chemistry that has to deal with the kind 
of isomerism just referred to is called stereo-chemistry. The 
phenomena of stereo-chemistry have been the subject of exten- 
sive investigation, and the facts established furnish a strong 
foundation for the theory briefly expounded above. 

Hydroxy-sulphonio acids. — It has been pointed out that 
the sulphonic acids and the carbonic acids are analogous : that, 
for example, methyl-sulphonic acid, CHg.SOsH, is analogous to 
methyl-carbonic or acetic acid, CHg. CO2H. Now, just as the 
hydroxy-acids already treated of are derived from the carbonic 
acids by the introduction of hydroxyl, so there are hydroxy- 
acids derived in a similar way from the sulphonic acids. 
Only one such acid is well known. It is — 

OH 

Isethionio acid, CJ3.^<^^ „, also called ^-hydroxy-ethyl- 

sidphonic acid. In composition it is analogous to the hydroxy- 
propionic acids. It is prepared by passing sulphur trioxide into 
well qogled alcohol or ether and boiling the product with 



168 DERIVATIVES OF THE PARAFFINS 

water; and also by treating taurine (which see) with nitrous 
acid: — 

CH2.NH2 CH2OH 

I +HN02= I +H20 + N^ 

CHj-SOgH CH2.SO3H 

Lactones 

The monohydroxy-monobasic acids of the paraffin series are 
designated as a-, fi-, y-, S-, etc., 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 
the hydroxyl is united with the next carbon atom in the chain 
the product is called a j8-hydroxy-acid, etc. The following 
examples will make this clear : — 

Acids of the formulas 

CH2(OH).C02H, CH8.CH(OH).C02H, CH3.CH2.CH(OH).C02H 

are a-hydroxy-acids. 

Acids of the formula 

CH2(OH).CH2.C02H, CH3.CH(OH).CH2.C02H, 

CH3.CH2.CH(OH).CH2.C02H are ^hydroxy-acids. 

Acids of the formulas 

CH2(OH).CH2.CH2.C02H, etc., 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 8-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-hydroxy-butyric 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 



HYDROXY-ACIDS 169 

y-hydroxy-butyrate and hydrochloric acid is represented by the 
following equation : — 

CHaCOH) .CH2.CH2.C02Na + HCl 

= CH2.CH2.CH2.CO + NaCl 4- H2O. 

I i 

The change from the free acid to the lactone may be repre- 
sented thus : — 



CHa.CHaCOH) CH2.CH 

I = I 

CH2.CO.OH CH2.CO 



"No + H2O. 



The reaction is similar to that which takes place when suc- 
cinic acid is heated : — 

CH2.CO.OH CH2.COV 

I = I >0 + H20. 

CH2.CO.OH CH2.CO/ 

The product in this case is an anhydride. The lactones may 
be defined as anhydrides of hydroxy-acids. They are neutral, 
but they form the salts of the corresponding hydroxy-acids 
when they are boiled for some time with bases in solution. 

Hydroxy-acids, CnH2n04 

The acids just treated of are called monohydroxy-monohdsic 
acids. Similarly, there are dihydroxy-monohasic acids, which 
are derived from the monohydroxy-acids by the introduction of 

CO H 

a second hydroxy 1. Thus, if into lactic acid, CHg.CH <pwTT > 

a hydroxyl should be introduced into the methyl, the product 

CH2.OH 

I 
would have the formula CH.OH. This is the best-known 

I 
CO2H 

dihydroxy-monobasic acid of the paraffin series. 



170 DERIVATIVES OF THE PARAFFINS 



Glyceric acid, propandiolic acid, C3H6O4 



CH2OH 

CHOH 

CO.H 



This acid has been referred to as the first product of the oxida- 
tion of glycerol. It is prepared by allowing glycerol and nitric 
acid to stand together at the ordinary temperature for some 
time, and then heating on the water-bath. It can also be made 
by treating j8-chlor-l actio acid with water. 

An optically active variety of glyceric acid has been obtained 
from the inactive variety. It will be seen that the acid con- 
tains an asymmetric atom. 

Glyceric acid is a thick syrup that mixes with water and 
alcohol. When treated with very concentrated hydriodic acid, 
it is converted into ^-iodo-propionic acid. This conversion 
involves two reactions: — 

CH2OH CH2I 

I I 

(1) CHOH -h HI = CHOH -f HA and 

I I 

CO2H CO2H 

CH2I CH2I 

I I 

(2) CHOH + 2 HI = CH2 + H2O -f 2 1. 

I ■ I 

CO2H CO2H 

Other Hydroxy-monobasic Acids 

Just as by oxidation of the tri-acid alcohol, glycerol, a dihy- 
droxy-monobasic acid can be formed, so by oxidation of the 
tetr-acid alcohol, erythrol, a trihydroxy-monobasic acid can be 
formed. This is erythritic add. Its relation to erythrol is 
like that of glyceric acid to glycerol : — 



MANNONIC ACIDS 



171 



CHjOH 

1 


CH2OH 

1 


CHjOH 

1 


CH2OH 

1 


CHOH 

1 


CHOH 
1 


CHOH 
1 


CHOH 

1 


CHjOH 

Glycerol 


CO2H 

Glyceric acid 


CHOH 

1 
CH2OH 

Erythrol 


CHOH 

1 
CO,H 

ErytbrlUc acid 



Similarly from the pent-acid alcohols tetrahydroxy-mono- 
basic acids, and from the hex-acid alcohols, pentahydroxy- 
monobasic acids can be made. The latter are of special 
importance on account of their connection with the sugars. 

Mannonic acids, CgHi2O7(C5H6(OH)50O2H).— Three acids 
are included in this group. They are the dextro, the Zevo, 
and the inactive varieties, or d-^ mannonic^ P mannonic^ 
ir^ mannonic acids. They are related to the three mannites 
and the three mannoses. As will be shown further on, the 
mannoses are pentahydroxy-aldehydes and the relations here 
referred to are represented by the following formulas : — 



CH2OH 

I 
CHOH 

I 
CHOH 

I 
CHOH 

I 
CHOH 

I 
CH2OH 

Mannite 



CH2OH 

I 

CHOH 

I 
CHOH 

I 
CHOH 

1 

CHOH 
I 
COH 

Mannose 



CH2OH 

I 

CHOH 

I 
CHOH 

I 
CHOH 

I 
CHOH 

I 
CO2H 

Mannonic acid 



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 complementary forms, while the inactive 



1 Instead of using the prefixes dextro- and levo-, and the wordinactive, it is customary 
to use the letters (2-, 1-, and i-, as they are here used. 



172 DERIVATIVES OF THE PARAFFINS 

variety is formed by a combination of the dextro and levo 
varieties. 

Gluconic acids, 0gHi2Oy[0^Hg(OH)^0O2HJ. — The gin- 
conic acids are related to the three glucoses in the same way 
that the mannonic acids are related to the mannoses. Dextro- 
gluconic acid is formed by the oxidation of glucose and of cane 
sugar. When heated with quinoline to 140°, it is partly con- 
verted into d-mannonic acid. Similarly d-mannonic acid is 
partly converted into c?-gluconic acid by the same process. 
Three Qulonic acids and three Galactonic acids of the 
same composition and structure as the mannonic and the glu- 
conic acids are also known. 

The existence of so many acids of the formula 

C,He(0H),C02H 

is due to the fact that a substance made up as represented in 

the formula 

CH2OH 

I 
CHOH 

I 
CHOH 

I 
CHOH 

I 
CHOH 

I 
CO2H 

contains four asymmetric carbon atoms. The total number 
of isomers possible, according to the theory, is sixteen — eight 
dextro and eight levo, besides eight racemic. 

. HyDROXY-ACIDS, CnH2n_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 



HYDROXY-SUCCINIC ACIDS 173 

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 malic acid. 

Tartronic acid, OoH.oJCHCOHX^^aHy _rrhis acid 

is prepared by an indirect method from tartaric acid. It can 
be made, — 

(1) By boiling brom-malonic acid with silver oxide and 
water : — 

CHBr< ^^^2 + AgOH = CH(OH)< ^^^ + AgBr ; 

(2) By treating brom-cyan-acetic acid with caustic potash ; — 
CHBr< ^^ „ + 2 KOH + H,0 

\jKJ2tL 

= CH(OH) < ^^^ + NH, + KBr. 

Tartronic acid is a solid that crystallizes in prisms. It is 
• easily soluble in water, alcohol, and ether. The anhydrous 
acid melts at 185-187** with evolution of carbon dioxide and 
water, and forms glycolide (which see) : — 

(1) CH(OH)<CO«H = CH,<OH^ + CO, 

Glycolic acid 

OTT CH,-0-CO 

(2) 2CH,<^^ = I I +2 HA 

Olycolide 

Note- FOR Student. — Compare reaction (1) with that which takes 
place when iso-succinic acid is heated, and note the analogy. 

Hydroxy-succinic acids, O^HgO^^OaHaCOHX^^^^) 

V OO2H/ 

Three hydroxy-succinic acids have been described, the priu« 
cipal one being ordinary malic acid. 



174 DERIVATIVES OF THE PARAFFINS 

/OH(OH) .OO^Hx 
Malic acid, CMfil \ __ „ ). — This acid is very 

widely distributed in the vegetable kingdom, as in the berries 
of the mountain ash, in apples, cherries, etc. 

It is best prepared from the berries of the mountain ash 
which have not quite reached ripeness. The berries are pressed 
and boiled with milk of lime. The acid passes into solution as 
the calcium salt, and this is purified by crystallization. 

It can also be made by treating aspartic acid, which is amino- 

CO H 

succinic acid, C2H8(NH2)<^q^„, with nitrous acid, and by treat- 
ing tartaric acid with hydriodic acid. This latter reaction will 
be explained when tartaric acid is treated of. Tartaric and 
malic acids are closely related to each other, and both are 
related to succinic acid, as will appear from the reactions. 

Malic acid is a solid substance that crystallizes with diffi- 
culty. It is very easily soluble in water and in alcohol. Its 
solutions twn the plane of polarization to the right or to the lefty 
according to the concentration. 

When heated it loses water and yields fumaric acid and 
male'ic anhydride (which see). Pumaric and maleic acids 
are isomeric, and both are represented by the formula 

CO H 

C2H2<p,Q^TT. The reaction mentioned is represented by the 
following equation: — 

xjr-«« «-«^ Fumaric or 

Malic acid ^^^1^5^ ^i^ 

Note for Student. — Compare this reaction with that which takes 
place when hydracrylic acid is heated, and note the analogy. 

When treated with hydriodic acid, malic acid is reduced to 
succinic acid. 

Note for Student. — Compare this reaction with the conduct of 
lactic and glyceric acids when treated with hydriodic acid. 



IKACTIVE MALIC ACID ' 175 

Treated with hydrobromic acid, malic acid is converted into 
inono-brom-succinic acid. 

The reactions just described show clearly that malic acid is 
hydroxy-succinic acid. Nevertheless, if hydroxy-succinic acid 
is made by treating brom-succinic 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 IT 

Inactive malic acid, 02H3(OH)< r^r^Tr- — Inactive malic 

acid can be made not only by the method first mentioned, but 
by several others, which indicate that the relation between it 
and succinic acid is that expressed in the formula given. It, 
like ordinary malic acid, is unquestionably a hydroxy-succinic 
acid, and both are derived from ordinary succinic acid. 

Other reactions for the preparation of inactive malic acid 
are: — 

(1) By treating dichlor-propionic acid with potassium cyanide, 
and boiling the product with caustic potash : — 

CH2CI.CHCI.CO2H + KCN 

CH2CN 

= I +k:ci; 

CHCI.CO2H 
CHjCN 
and I +2 KOH -|- H2O 

CHCI.CO2H 

CH2.CO2K 
= I +KCI + NH3. 

CH(0H).C02H 

(2) By heating fumaric acid with water : — 

C2H2 < ^^j2 + H2O ±= C2H3(OH) < ^2^2 ; and 

(3) By reducing racemic acid with hydriodic acid. Race- 
mic acid has the same composition as tartaric acid. The latter, 
when treated with hydriodic acid, yields active malic acid. 



176 DEEIVATIVES OF THE PARAFFINS 

The properties of inactive malic acid are very much like 
those of active malic acid. As regards their chemical conduct 
they are almost identical. The principal difference between 
them is observed in their conduct towards polarized light. 
They present a new case of physical isomerism of the same 
kind as that referred to in connection with the lactic acids 
(which see). 

Dextro-malic 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, two 
different salts are obtained. One of these is derived from 
ordinary levo-malic addf while the other is derived from the 
isomeric deoctro-malic add, 

Hydroxy-acids, CnHjn^gOe 

These are di-hydroocy-dibasic adds. The chief members of 
the group are mesoxalic acid and the different modifications of 
tartaric acid. 

Mesoxalic acid, 08H406(o(OH)2<^q'^). — This acid 

is obtained by indirect and rather complicated reactions from 
uric acid (which see). It has been made also by boiling di- 
brom-malonic acid with baryta-water and by oxidizing glycerol 
(see p. 152). 

Note for Student. — Explain this reaction. 

The acid forms deliquescent needles. When its aqueous 
solution is boiled, glyoxylic acid, which is an aldehyde and 
acid related to oxalic acid, is formed : — 

CO TT CHO 

C(OH),<^Xw= I +CO, + H,0. 

Qlyoxylic acid 



DI-HYDROXY-SUCCINIC ACIDS 177 

Mesoxalic acid affords an example of a rare condition ; viz., 
the existence of a compound in which two hydroxy Is are in 
combination with one and the same carbon atom. This same 
condition exists in chloral hydrate. The acid readily loses 
water and passes over into the form C0(C00H)2. 

(CO UN 
02H2(OH)2 < QQ^^-^I' 

OH(OH) . OO2H 
1. Tartaric acid, I • — Ordinary tartaric acid 

OH(OH) . OO2H 

^ occurs widely distributed in fruits, sometimes free, sometimes 
in the form of the potassium or calcium salt ; as, for example, 
in grapes, berries of the mountain ash, potatoes, cucumbers, 
etc., etc. 

It can be made by the following methods : — 

(1) By oxidizing sugar of milk with nitric acid ; 

(2) By oxidizing cane sugar, starch, glucose, and other 
similar substances. 

Tartaric acid is prepared from "tartar," which is impure 
acid potassium tartrate. When grape juice ferments this 
salt is deposited. It is purified by crystallization, converted 
into the calcium salt by treating it with chalk and calcium 
chloride, and the salt then decomposed by means of sulphuric 
acid. 

The acid crystallizes in large monoclinic prisms, which are 
easily soluble in water and in alcohol. It melts at 170°. Its 
solution turns the plane of polarization to the right. 

Treated with hydriodic acid, tartaric acid yields, first, malic 
acid, and then ordinary succinic acid : — 

(1) C3H,(OH),<^^^JJ + 2HI 

= C,H,(OH) < ^^'J + H,0 + 1,; 

Malic acid 



178 DERIVATIVES OF THE PARAFFINS 

(2) C,U,(OK) < ^^'^ + 2 HI 

= C2H4 <QQY{'^ "^^O "^ ■'■** 

Buccinic acid 

While malic acid is mono-hydroxy-succinic acid, ordinary 
tartaric acid appears to be di-hydroxy-succinic acid. But, just 
as the malic acid prepared from mono-brom-succinic acid is 
optically inactive, and therefore different from natural, active 
malic acid, so, too, the tartaric acid prepared from di-brom-suc- 
cinic acid is optically inactive, and therefore different from 
ordinary tartaric acid. The relations between the natural and 
the artificial acids will be more fully dealt with below. 

Tartrates, Among the salts the following may be mentioned : 

Mono-potassium tartrate^ KH . C4H4O6. This is the chief con- 
stituent of tartar. In pure form, as used in medicine, it is 
known as cream of tartar. 

Sodium-potassium tartrate, KNa . C4H4O6 + 4 HgO. This salt 
crystallizes beautifully. It is known as Bochelle salt or 
Seignette salt, Seidlitz powders consist of (1) a mixture of 
Rochelle salt and sodium bicarbonate, and (2) tartaric acid. 
These are dissolved separately and then brought together, when 
a rapid evolution of carbon dioxide takes place. 

Calcium tartrate, Ca . C4H40g + 4 HgO. This salt occurs in 
senna leaves and in grapes. It forms a crystalline powder or 
rhombic octahedrons insoluble in water. 

Potassium-antimonyl tartrate, K (SbO) . C4H4O6 4- ^ H2O. This 
is known as tartar emetic. It is prepared by digesting anti- 
monic oxide with mono-potassium tartrate. It crystallizes in 
rhombic octahedrons. It loses its water of crystallization at 
100°, and at 200 to 220° is converted into an antimony potas- 
sium salt of the formula KSb . C4H2O8. 

2. Racemic acid, (C4H606)2 • 2 HoO. — Kacemic acid occurs, 
together with tartaric acid, in many kinds of grapes, and, on 



BACEMIO ACID 179 

recrystallizing the crude tartar, acid potassium racemate, being 
more soluble than the tartrate, remains in the mother liquors. 
Eacemic acid is formed by boiling ordinary tartaric acid with 
water, or with hydrochloric acid. If tartaric acid is heated 
with water in sealed tubes at 175% it is almost completely 
transformed into racemic acid. It is formed further by oxida- 
tion of dulcite, mannite, cane sugar, gum, etc., with nitric acid. 
It is formed, together with a third variety of tartaric acid known 
as inactive tartaric acid, when di-hrom-succinic acidHs treated 
with silver oxide and water. 

Racemic acid differs from tartaric acid in many ways. It 
crystallizes differently, and contains water of crystallization. 
It is less soluble than tartaric acid. It produces precipitates in 
solutions of lime salts, while tartaric acid does not. Racemio 
add is optically inactive, while tartaric acid is dextro-rotatory. 
On the other hand, racemic and tartaric acids conduct them- 
selves towards most reagents exactly alike. 

The relations between racemic and tartaric acid are the same 
as those which have already been referred to as existing between 
inactive malic acid and dextro-malic acid, and between inactive 
lactic and dextro-lactic acid. This case is, however, of special 
Interest, as it was the first one of the kind studied. The relations 
were discovered by means of the experiment described below. 

When a solution of the ammonium-sodium salt of .racemic 
acid, (NH4)Na . C4H4O6, is allowed to evaporate spontaneously, 
beautiful large crystals are deposited. On examining these 
carefully, they are found to be of two kinds. On the crystals 
of one kind certain hemihedral faces are developed, while on 
the crystals of the other kind the complementary hemihedral 
faces are developed ; so that if a crystal of one kind is placed 
in front of a mirror, its reflection will represent the arrange- 
ment of the hemihedral faces occurring on a crystal of the 
other kind. The crystals can be separated into right-handed, or 
those which have the right-handed hemihedral faces, and left- 
handed, or those which have the left-handed hemihedral faces. 



ISO DERIVATIVES OF THE PARAFFIKS 

On separating the acid from the right-handed crystals it is 
found to be ordinary dextro-rotatory tartaric acid; while the acid 
from the left-handed crystals is an isomeric substance called 
levo-rotatory tartaric acid. When these two varieties of tartaric 
acid are brought together in solution, they unite, the action being 
attended by an elevation of temperature, and the result is ra- 
cemic acid. These phenomena were first observed by Pasteur. 

By crystallizing cinchonine racemate from alcohol it can be 
resolved into the dextro and levo varieties, from which the 
corresponding active acids can be obtained. 

It will thus be seen that racemic acid consists of two opti- 
cally active substances in combination, one of which, ordinary 
tartaric acid, is dextro-rotatory, and the other levo-rotatory. 

As has already been stated, both inactive malic acid and in- 
active lactic acid have been resolved into two active varieties, 
one of which is dextro-rotatory, and the other levo-rotatory, 

3. Inactive tartaric acid, mesotartario acid, anti- 
tartaric acid, G4H6O6 + H2O, is similar to racemic acid. It 
is formed together with racemic acid by treating di-brom- 
succinic acid with silver oxide and water. It is optically in- 
active. Unlike racemic acid it cannot be resolved into the 
optically active forms, and it is believed that the inactivity is 
due to " internal compensation." 

The following explanation will serve to make the relations 
between the four tartaric acids clear: Tartaric acid contains 
two asymmetrical carbon atoms (see p. 166), each one of which 
is in combination with (1) a hydrogen atom, (2) a hydroxyl, 
(3) a carboxyl, and (4) the group, CH(OH).COaH: — 

H 

I 
HO-C-COgH 

I 
HO-C-CO2H 

I 
H. 



HYDROXY-ACIDS 181 

There are two ways in which these four groups can be arranged 
around each asymmetrical carbon according to the hypothesis 
already explained under the lactic acids (which see). One 
arrangement makes the substance dextro-rotatory, the other 
makes it levo-rotatory. Now, if the arrangement around both of 
the carbon atoms is the same, the substance will be optically 
active. Thus the existence of the dextro-acid and of the levo- 
acid can be explained. The racemic modification, in this case 
racemic acid, being formed by combination of the dextro-acid 
with the levo-acid is inactive. But, further, if in one half of 
the molecule there is the right-handed arrangement, and in the 
other half the left-handed arrangement, the substance will be 
inactive by "internal compensation," and will not be capable 
of resolution into two optically active products. This is be- 
lieved to be the condition in mesotartaric acid. These rela- 
tions cannot be made entirely clear by words and formulsis. 
Models, which can be easily constructed of stiff wire and 
wooden balls, are necessary to make them clear. Formulas 
may, however, be used to recall the arrangements in space that 
are represented in the models. The following formulas are 
used to show the difference between the two active acids and 
mesotartaric acid : — 

CO2H CO2H CO2H 

I I I 

HO-C-H H-C-OH HO-C-H 

I II 

H-C-OH HO-C-H HO-C-H 

I I I 

CO2H. CO2H. CO2H. 

Levo-tartaric acid Dextro-tartaric acid Inactive mesotartaric acid 



Hydroxy-acids, C„H2„_407 

These are mono-hydroxy-tribasic acids. Citric acid is the 
only one known. 



182 DERIVATIVES OP THE PARAFFINS 

/ • f 002H\ 

Citric acid, OgHsOt + H2O ( OaHiCOH) 4 OO2H . — Citric 

^ 1 002H>^ 

acid, like malic and tartaric acids, is widely distributed in 

nature in many varieties of fruit, especially in lemons, in 
which it occurs in the free condition. It is found in currants, 
whortleberries, raspberries, gooseberries, etc., etc. 

It is prepared from lemon juice, and also by the fermenta- 
tion of glucose by dtromyces pfefferianua and a few other fer- 
ments. After the fermentation the mass is treated with lime. 
The calcium salt thus obtained in the form of a precipitate, is 
collected, and decomposed with sulphuric acid. One hundred 
parts of lemons yield 5^ parts of the acid. 

Citric acid crystallizes in rhombic prisms which are very 
easily soluble in water. The crystallized acid melts at 100°, 
the anhydrous at 153° to 154°. Heated to 175° it loses water 
and yields aconitic acid (which see) : — 

C3H4(OH)(C02H)3 = C3H3(CO,H)3 + H^O. 

Aconitic acid 

Aconitic acid takes up hydrogen, and is transformed into 
tricarballylic acid (which see). Thus a clear connection be- 
tween tricarballylic acid and citric acid is traced; the latter 
is hydroxy-tricarballylic acid. Citric acid can be made from 
dichloracetone by first converting this into acetone-dicarbonic 
acid : — 

QQ ^ CH2CI QQ CH2CN QQ CH2CO2H 

CH2CI CH2CN CH2CO2H • 

The acetone-dicarbonic acid is then treated with hydrocyanic 
acid and the nitril thus formed hydrolyzed as shown below : — 

CH2 . CO2H CH2 . CO2II 

I I ^OH 

CO + HCN=C<^,xT » 

I I ^^ 

CH2. CO2H CH2. CO2H 



HYDROXY-ACIDS 183 



CI12 . CO2H CIi2 . CO2H. 

CH2 . CO2H CH2. CO2H 



This synthesis shows that the hydroxy 1 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, then loses water and carbon dioxide 
and gives itaconic anhydride (see itaconic acid). This 
anhydride is then partly converted into citraconic anhydride 
(see citraconic acid) by the action of heat. 

Citrates, A few of the salts of citric acid are : — 

Mono-potassium citrate^ KHg . CgHgOj + 2 H2O ; 

Di-potassium citrate, K2H . CgHjOj ; 

Tri-potassium citrate, K3 . CeHgOy + H2O. All these potas- 
sium salts are easily soluble in water. 

Calcium citrate, Q>^i>z{Q^fi^)2-\-^^j^' This salt is formed 
by mixing a citrate of an alkali with calcium chloride. It is 
more easily soluble in cold than in hot water ; hence boiling 
causes a precipitate in dilute solutions. 

Magnesium citrate, Mg3(C6H507)2 + 14 II2O. This is made by 
dissolving magnesia in citric acid. It is used in medicine. 

HyDROXY-ACIDS, CnH2n_208 

It has been pointed out that the hex-acid alcohols are 
converted by oxidation into pentahydroxy-monobasic acids. 
By further oxidation these pentahydroxy-monobasic acids 
are converted into tetrahydroxy-dibasic acids. Thus sorbite, 
CH20H(CHOH)4CH20H, when oxidized, yields, first, glu- 
conic acid, CH20H(CHOH)4C02H, and then saccharic acid, 
C02H(CHOH)4C02H, a tetrahydroxy-dibasic acid. Corre- 
sponding to each gluconic acid there is a saccharic acid. So 
also the mannonic acids yield mannosaccharic acids, which are 
dibasic and isomeric with the saccharic acids ; and galactonic 



184 DERIVATIVES OF THE PARAFFINS 

acid yields mucic add. The best-known members of this 
group are saccharic and mucic acids. 

Saoohario acid, OeHioOs (o4H4(OH)4 < qo'h)* ~ "^^^ 
dextro variety is formed by the oxidation of cane sugar, 
d-glucose, sugar of milk, or starch with nitric acid. 

It is an amorphous mass that becomes solid only with diffi- 
culty. When treated with hydriodic acid it is reduced to 
adipic acid, a member of the oxalic acid series (see table, page 
143): — 

Saccharic acid Adipic acid 

Mucic acid, 06Hio08(o4H4(OH)4 < ^q'^). — This is 

formed by the oxidation of sugar of milk, the gums, dulcite, 
or galactose with nitric acid. It is best prepared from sugar 
of milk. 

It is a crystalline powder that is very difficultly soluble 
in cold water. Hydriodic acid reduces it to adipic acid (see 
above, under Saccharic acid). 

When heated with pyridine to 140°, mucic acid is changed 
to the isomeric form, allomucic acid. 



CHAPTER XI 

CARBOHYDRATES 

Among the mixed compounds are the important substances 
commonly known as carbohydrcUes, This name was originally 
given to them because they consist of carbon in combination 
with hydrogen and oxygen, which two elements are generally 
contained in them in the proportion to form water, as shown 
in the formulas, for glucose, CeHjaOe, starch, CeHioOj, 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 sub- 
stance, for example, is rhamnose, CgHigOa. Further, there are 
some carbon compounds, as, for example, formic aldehyde, 
CH2O, acetic acid, C2H4O2, and lactic acid, CgHgOa, that con- 
tain hydrogen 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 : — 

1. Monosaccharides or simple sugars, — Examples of these 
are glucose, fructose, arabinose, and mannose. 

2. Polysaccharides or complex sugars. — Examples are cane 
sugar, sugar of milk, maltose, and isomaltose. 

3. Polysaccharides, that are not sugars, — Examples are cel- 
lulose, starch, and gums. 

The monosaccharides are the simplest carbohydrates. Those 
which are best known have the composition CgHigOe, and are 
related to the hex-acid alcohols, sorbite and mannite, C6H8(OH)6. 
There are, however, simpler ones, such as arabinose, C^H^O^^ 

185 



186 CARBOH YD RATES 

erythrose, C4H8O4, and glycerose, CgHgOs; and some that are 
more complex, as heptose, C7H14O7, octose, CgHjeOg, and nonose, 
CgHigOg. The monosaccharides, therefore, fall into classes 
which are called trioses, tetroses, pentoses, hexoses, etc., accord- 
ing to the number of oxygen atoms contained in them. 

By methods that will be explained below, it has been shown 
that the monosaccharides or simple sugars are aldehyde-alcohols 
(aldoses) or ketone-alcohols (ketoses). 

1. Monosaccharides 

A. Trioses and Tetroses 

Glycerose, O3H6O3. — This sugar deserves special mention 
because it is the simplest member of the group of monosacchar- 
ides, and because it has been obtained artificially. It is formed 
by treating glycerol with mild oxidizing agents, as, for example, 
bromine and sodium hydroxide. It is a mixture of glyceric 
aldehyde and dioxyacetone, the relations of which to glycerol 
are shown by the following formulas : — 

CH(0H)<^|2« CH(OH)<CHO^, CO<^H;OH 

Glycerol Glyceric aldehyde Dioxyacetone 

Glycerose is a syrup that undergoes fermentation and reduces 
alkaline solutions of copper salts, acting thus like many of the 
sugars. Glyceric aldehyde is a simple example of an aldose 
or aldehyde-alcohol, and dioxyacetone is the simplest example 
of a ketose or ketone-alcohol. 

When the mixture of these two substances is treated with 
caustic soda it is converted into i-acrose, a sugar of special 
importance, as it forms the starting point in the synthetical 
operations that lead to the formation of all the members of 
the glucose group. 

Erythrose, C4H8O4, has been obtained from erythrite in 
the same way that glycerose is obtained from glycerol. 



MONOSACCHARIDES 187 

B. Pentoses 

Arabinoses, OsHioOs. — Ordinary arabinose is obtained from 
gum arabic and cherry gum by boiling with dilute sulphuric 
acid. This variety is called levo-arabinose on account of its re- 
lation to levo-glucose and levo-mannose, although it turns the 
plane of polarization to the right. Dextro-arabinose and in- 
active arabinose have also been obtained, the latter by com- 
bination of the levo and dextro varieties. 

Xylose, O5H10O5, is obtained from wood gum by boiling 
with dilute acids. 

Bibose, O5H10O5, yields adonite (which see) by reduction. 
It is stereoisomeric with arabinose. 

Bhamnose, O6H12O5, has been obtained by the breaking 
down of a number of natural substances, such as quercitrin. 
It has been shown to be a methyl derivative of a pentose, and 
is therefore to be represented by the formula CH3.C5H9O5. 

. C. Hexoses 

Glucose, grape sugar (dextrose), O6H12O6+H2O.— Glucose 
occurs very widely distributed in the vegetable kingdom, 
especially in sweet fruits, in which it is found together with 
an equivalent quantity of fructose or fruit sugar. It is also 
found in honey, together with fructose; and, further, in the 
blood, in the liver, and in the urine. In the disease Diabetes 
mellitics the quantity contained in the urine is largely in- 
creased, reaching as high as 180 to 360 grams per day. 

Glucose is formed from several of the carbohydrates of the 
formulas C12H22O11 and CgHioOa, by boiling them with dilute 
mineral acids, or by the action of enzymes. The formation 
from cane sugar takes place according to this equation, equiva- 
lent quantities of glucose and fructose being formed: — 

Ci2H220n + H2O = CgHigOe + C6Hi20e. 

Cane sugar Glucose Fructose 



I 



188 CARBOHYDRATES 

Starch, cellulose, and dextrin yield glucose according to 
this equation: — 

CeHioO^ + H2O = CeHi20^ 

Finally, glucose occurs in nature, in combination with a 
number of carbon compounds, in the so-called glucosides. 
These break up easily when treated with dilute mineral acids 
or ferments, and yield glucose as one of the products (see 
Glucosides). Examples of the glucosides are amygdalin, 
aesculin, salicin, etc. 

Glucose is prepared on the large scale from corn starch in 
the United States, and from potato starch in Germany. The 
transformation is usually effected by boiling with dilute sul- 
phuric acid. The acid is then removed by treating the 
solutions with chalk, and filtering. The filtered solutions are 
evaporated down either to a syrupy consistency, and sent into 
the market under the names " glucose," " mixing syrup," etc., 
or to dryness, the solid product being known in commerce as 
"grape sugar." By evaporating the solutions down to such 
a concentration that they contain from 12 to 15 per cent of 
glucose, crystals are formed that closely resemble those of 
cane sugar. They consist of anhydrous grape sugar. Their 
formation is facilitated by adding a little of the crystallized 
substance to the concentrated solutions. Glucose crystallizes 
from concentrated solutions, usually in crystalline masses con- 
sisting of minute six-sided plates which contain one molecule 
of water. The mass, as seen in commercial "granulated grape 
sugar," looks like granulated sugar. It crystallizes from 
alcohol in monoclinic crystals: The sweetness of glucose is 
to that of cane sugar as 3 to 6. Its solutions turn the plane of 
polarization to the right. 

If in the treatment of starch with sulphuric acid the trans- 
formation is not complete, and this is usually the case, the prod- 
uct is a mixture of glucose, maltose, and dextrin. The longer 
the action continues, the larger the percentage of glucose. 



GLUCOSE 189 

Gluoose is easily oxidized, reducing the salts of silver and 
copper. When treated with nascent hydrogen, it yields sorbite 
(which see). Under the influence of yeast it ferments, yielding 
mainly alcohol and carbon dioxide. Putrid cheese transforms 
it first into lactic acid and then into butyric acid by the so- 
called lactic acid fermentation. 

Glucose forms compounds with metals and salts. Among 
the better known compounds of this kind are those mentioned 
below : — 

Sodium glucose •....• CeHuOe . N"a ; 

Sodium chloride glucose . . 2 CgHjaOe . NaCl + H2O ; 

also CfiHiaOe . NaCl + ^Hg 0, and GeHuOa . 2 NaCl. 

These compounds, with sodium chloride, crystallize well, and 
can be easily obtained in pure condition. 

Cupric oidde glucose • • • • CeHigOe . 5 CuO. 

By treatment with acetic anhydride, glucose yields a product 
containing five acetyl groups, pent-acetyl-glucose, 

^6^17(021130)503. 

Note fob Student. — What does the formation of this compound 
Indicate? 

It is often important to know the quantity of glucose con- 
tained in a given liquid ; as, for example, in the urine in a case 
of suspected diabetes. For the purpose of making the estima- 
tion, advantage is taken of the action of glucose towards an 
alkaline solution of copper sulphate. The solution commonly 
used is that known as FeMing^s solution. It is prepared by 
dissolving 34.64*^ crystallized pure copper sulphaie in 200*" 
water, adding a solution of 160* potassium tartrate, and 90* 
sodium hydroxide, and diluting so that the whole makes one 
litre. 

Experiment 38. . Make half the quantity of Fehling^s solution above 
mentioned, and put in a bottle with a glass stopper. In a test-tube boil 
about 10"'' of this solution, and then add a few drops of a dilute solution 



190 CARBOHYDRATES 

of glucose. Continue to boil, and add a little more of the glucose solution; 
and so on, until, on removing the tube from the lamp, a dark-red uniform- 
looking precipitate settles, leaving the liquid above it perfectly clear and 
colorless. This precipitate is cuprous oxide. By taking proper precau- 
tions, the exact amount of glucose present in a solution can be estimated 
in this way. 

Ordinary glucose is known as c2-glucose on account of its 
dextro-rotatory power. Both ^glucose and i-glucose have been 
made. 

Fructose, fruit sugar (levulose), CgHjaOe. — This sugar 
occurs together with glucose, and in equivalent quantities, in 
fruits ; and is formed by the action of dilute mineral acids, or 
invertase, on cane sugar. Pure fructose is obtained by heating 
inulin, a carbohydrate of the formula C12H20O10, with very dilute 
acids. It is also formed with mannose by careful oxidation of 
d-mannite. 

Ordinary fructose is called c^f ructose, although it turns the 
plane of polarization to the left. The reason for this is that it 
is related to other substances that are dextro-rotatory. 

Fructose can be obtained in the form of crystals. It is about 
as sweet as cane sugar, and has been proposed as a substitute 
for this in diabetes. 

^-Fructose has been made artificially in three ways : — 

1. By polymerization of formic aldehyde, CHgO, by means 
of bases ; 

2. By successive treatment of acrolein with bromine and 
baryta water ; 

3. By the action of dilute alkali on glycerose, which is 
formed by oxidation of glycerol. 

It will be observed that formic aldehyde has the same per- 
centage composition as fructose. 

When acrolein is treated with bromine, two atoms of the 
latter are added directly to the former : — 

CHg: CH . COH + 2 Br = CHjBr . CHBr . COH, 



FRUCTOSE 191 

When this di bromide is treated with baryta water, hydroxy 1 
is first substituted for bromine, and glyceric aldehyde and 
dihydroxyacetone are the first products. These are then con- 
densed and form i-f ructose : — 

CHgBr . CHBr . COH + Ba(0H)2 

= CH2OH . CHOH . COH + BaBrg. 

Glyceric aldehyde is, however, not the only product of this 
reaction. Dihydroxyacetone, CHgOH — CO — CHgOH, is also 
formed, as is shown by the reactions of the product. The 
formation of i-fnictose from glycerose takes place as repre- 
sented in the following equation: — 

CHjOH - CHOH - CHO + CHgOH - CO - CHgOH 

= CH2OH - CHOH - CHOH - CHOH - CO - CHgOH. 

The oxygen atom of the aldehyde group, CHO, unites with a 
hydrogen atom of one of the CH2 groups of the dihydroxy- 
acetone, forming hydroxyl, and this makes possible the union 
of the residue of the glyceric aldehyde with that of the 
dihydroxyacetone. 

This reaction is known as the aldol condensation, because the 
product first obtained in this way was called aldol. This is 
formed by condensation of ordinary aldehyde thus : — 

CH3 . CHO + CH3 . CHO = CH3 . CHOH . CH2 . CHO. 

Aldol 

Aldol is really )8-hydroxbutyric aldehyde. 

On account of the formation of i-fructose from acrolein, it 
was called ojcrose. It was later shown to be the inactive 
variety of fructose, and the name acrose became unnecessary, 
though it is still used. 

When i-fructose is treated with . yeast, it is partly trans- 
formed by the ferment into alcohol and carbon dioxide. It is 
the cZ-fructose contained in it that undergoes the change, while 
the ^fructose remains unchanged, and can be obtained free 
from the other two varieties. 



192 CAEBOHYDRATES 

Constitution of glucose and fructose, — Two reactions have 
been of special value in the determination of the constitution 
of the members of the group of monosaccharides. 

a. When either an aldehyde or an acetone is treated with 
hydrocyanic acid an addition-product is formed thus: — 

H H 

I I OH 

CH,.C=0 + HCN = CH3.C<);^; 

and ^|>C = + HCH = ^«;>C<^^. 

The products can be converted into corresponding acids by 
the change of the cyanogen group into carboxyl. Thus the 
nitril from aldehyde yields a-hydroxypropionic (or lactic) 
acid: — 

H H 

CH3.C <CN +2 H,0 = CH3.C <^QQjj+NH,; 
while the nitril from acetone yields o-hydroxy isobutyric acid : — 

By the aid of these reactions it has been shown that glucose 
is an aldose, and fructose a ketose, of these formulas : — 

(1) CHO - CHOH - CHOH - CHOH - CHOH ~ CH2OH. 

Glucose 

(2) CH2OH - CO - CHOH - CHOH - CHOH - CHjOH. 

Fructose 

By adding hydrocyanic acid to a compound of formula (1) a 
nitril of the following formula would be formed : — 



HO 



> CH - CHOH - CHOH - CHOH - CHOH - CHgOH. 



GLUCOSE AND FRUCTOSE 193 



This would yield an acid of the formula 

HOOC 
HO 



> CH - CHOH - CHOH - CHOH - CHOH - CHgOH. 



By treating this with hydriodic acid it should be reduced to 
the acid 

H02C.CH2»^"2* CH2.CH2. Cxl2.Cll8. 

The acid obtained from glucose by means of the above re- 
actions has the structure represented by this formula, and it 
hence follows that glucose itself must have the structure 
represented by formula (1) above, or it must be an aldose. 

By subjecting fructose to the same processes, the product 
obtained has the structure 

CO2H 
I 
CH3 . CH . CH2 • CH2 . CH2 . CH3 f 

and it follows from this that fructose must have the structure 
represented by formula (2) above, or it must be a ketose. 

b. When an aldehyde or a ketone is treated with phenyl- 
hydrazine, CgHa.NH.NHj, a reaction takes place, as repre- 
sented in this equation: — 

H H 

I I 

ECO + H2N . NHCeHfi = R . CN . NHCeH^ + HgO. 

The products thus formed are called phenylhydrazones. 
The sugars form hydrazones when treated with phenyl 
hydrazine. Thus glucose and fructose give the products 

(1) CHjOH.CHOH. CHOH. CHOH. CHOH. CH 



N.NHCeHg, 

Phenylhydrazone of Glucose 

(2) CH2OH. CHOH. CHOH. CHOH. C.CH2OH 

II 
N.NHCfiHj. 

PhenylhyclrMOD^ of |*rncto«« ^ 



19i CARBOHYDRATES 

If the sugars are boiled with an excess of phenylhydraziiie a 
second reaction takes place. In the case of glucose, the CHOH 
group adjoining the carbon atom with which the residue of 
phenylhydrazine is combined, loses two hydrogen atoms and is 
converted into the ketone group CO. Then phenylhydrazine 
reacts with this, and forms a product of the formula 

CH2OH . CHOH . CHOH . CHOH . C • CH 

II II 
CeH^HN.N N.NHCeHfi. 

This is called phenylgluoosazone. 

In the case of fructose, the primary alcohol group, CH2OH, 
adjoining the carbon atom with which the residue of phenyl- 
hydrazine is combined is changed to the aldehyde group, CHO, 
and then phenylhydrazine reacts with this in the usual way, 
giving a product of the formula 

CH2OH . CHOH . CHOH . CHOH . C . CH 

II II 
CeH^HN.NN.NHCfiHs. 

This is the phenylfruotosazone. Phenylglucosazone and 
phenylfructosazone are identical. 

The osazones are in general difficultly soluble in water and 
have characteristic properties whereby they can be recognized. 
The sugars themselves are easily soluble and it is hard to 
separate them, and until the discovery of the phenylhydrazine 
reaction the investigation of the sugars advanced very slowly. 
This reaction in the hands of one of the most skilful experi- 
menters, Emil Fischer, has greatly advanced our knowledge of 
the sugar group within a few years past. 

The formation of the osazones makes it possible to recognize 
the different sugars, but it does not give the sugars themselves. 
The regeneration of the sugars from the osazones is of great 
importance. The principal reactions available for the purpose 
are the following : — 

1. The osazone is heated for a short time with fuming 



GALACTOSE 195 

hydrochloric acid, when it yields phenylhydrazine hydrochlo- 
ride and an osone, thus : — 

CH2OH . (CH0H)3 . C . CH + 2 H2O + 2 HCl 

II II 
CeHfiHN.N N.NHCeHg 

= CH20H(CHOH)3CO . CHO + 2 CeH^ . NH . NHj . HCl. 

Osone 

2. The osone can be isolated and reduced by means of acetic 

acid and zinc dust, when it is converted into the corresponding 

ketose : — 

CH20H(CHOH)8CO . CHO + 2 H 

= CH20H(CHOH)3 . CO . CH2OH. 

Whether the original sugar was an aldose or a ketose, the 
final product of the above series of reactions is a ketose. The 
aldoses cannot, therefore, be regenerated in this way. On 
the other hand, any aldose can be converted into a ketose by 
this means. 

Mannose, 06Hi206- — c^Mannose is one of the products of 
oxidation of d-mannite, and is obtained by the action of dilute 
acids on some kinds of cellulose. The shavings formed in the 
manufacture of buttons from vegetable ivory are rich in the 
cellulose which yields d-mannose. 

I-Mannose and i-mannose have also been prepared. 
The mannoses are aldoses, and are stereoisomeric with 
glucose. 

Galactose, 06Hi206- — d-Galactose is formed by treatment 
of sugar of milk with dilute acids, d-glucose being formed at 
the same time. Other carbohydrates also yield it. I- and 
i-Galactoses are known. By reduction d- and /-galactoses are 
transformed into dulcite* By oxidation all three galactoses 
yield mucic acid. 



196 CARBOHYDRATES 

Gulose, CeHuOe* — The three guloses have been made arti- 
ficially. They are aldoses corresponding to the three sorbites, 
and are stereoisomeric with the glucoses. 

The method by which ^gulose was made is of special inter- 
est, as it is based upon reactions that may be used for passing 
from any aldose to one containing one carbon atom more. It 
consists in adding hydrocyanic acid to the aldose, converting 
the nitril thus obtained into the corresponding acid, and then re- 
ducing the acid. Thus in the case of ^gulose the starting-point 
is xylose, and the steps may be briefly represented thus : — 

Xylose -> (HCN) 2 hydrocyanides ^ '-^'^""^^ ^'^}-> 
, , „ ^idonic acid ) 

(reduction) ^^^°«« 
^ldose. 

TcUoae and idose are isomeric with glucose. They have only 

been made artificially. 

2. Polysaccharides or Complex Sugars 

The polysaccharides, or complex sugars, are found in nature, 
as, for example, cane sugar and sugar of milk, or are formed 
from more complex carbohydrates, as, for example, maltose 
from starch. Their most characteristic property is their power 
to break down into monosaccharides under the influence of 
dilute acids or enzymes. The reaction involves the addition 
of the elements of water, and is called hydrolysis. A simple 
example of this kind of action is the conversion of maltose 
into d-glucose: — 

C12H22O11 + H2O = 2 Q^i^Qf, 

Maltose d-GIucose 

In most cases the hydrolysis of a polysaccharide gives more 
than one monosaccharide. Cane sugar, for example, gives 
(2-glucose and c2-f ructose : — 

C12H22O11 -f H2O = C6H12OJ -f- CeHigOe ; 

Cane sugar d-QIucose {/-Fructose 



CANE SUGAR 197 

sugar of milk gives d-galactose and c^glucose : — 

Ci2H220n + HgO = CeHigOe + CgHiaOe. 

cf-Galactose (2-61ucos6 

Polysaccharides that give two monosaccharides when hydro- 
lyzed are known as saccharobioses ; those that give three, as 
saccharotrioses. 

Cane sugar, saccharose, Ci2H220u' — This well-known 
variety of sugar occurs very widely distributed in nature, in 
sugar cane, sorghum, the Java palm, the sugar maple, beets, 
madder root, coffee, walnuts, hazel nuts, sweet and bitter 
almonds ; in the blossoms of many plants ; in honey, etc., etc. 

It is obtained mainly from the sugar cane and from beets. 
In either case the processes of extraction and refining are 
largely mechanical. When sugar cane is used, this is macer- 
ated with water to dissolve the sugar. Thus a dark-colored 
solution is obtained. This is evaporated, and then passed 
through filters of bone-black which remove the coloring mat- 
ter. The solution is evaporated in the air to some extent, and 
then in large vessels called vacuum pans, from which the air 
is partly exhausted, so that the boiling takes place at a lower 
temperature than would be required under the ordinary 
pressure of the atmosphere. The mixture of crystals and 
mother liquors obtained from the vacuum pans is freed from 
the liquid by being brought into the centrifugals. These 
are funnel-shaped sieves which are revolved very rapidly 
the liquid being thus thrown by centrifugal force through the 
openings of the sieve, while the crystals remain behind and 
are nearly dried. The final drying is effected by placing the 
crystals in a warm room. 

When beets are used, the process is essentially the same, 
though there are some differences in the details. 

The mother liquors which are obtained from the centrifu- 
gals are further evaporated, and yield lower grades of sugar; 



198 CARBOHYDRATES 

and, finally, a syrup is obtained which does not crystallize. 
This is molasses. Molasses is sometimes brought into the 
market as such ; sometimes, particularly when obtained from 
beet sugar, it is allowed to ferment for the purpose of making 
alcohol. The spent wash, or waste liquor, " vinasse," is now 
evaporated to dryness and calcined for the purpose of getting 
the alkaline salts contained in the residues. The products of 
distillation are collected, and from them tri-methyl-amine is 
separated (see p. 98). 

Sugar crystallizes from water in well-formed, large mono- 
clinic prisms. It is dextro-rotatory. When heated to 210° to 
220®, cane sugar loses water, and is converted into the sub- 
stance called caramelf which is more or less brown in color, 
according to the duration of the heating and the temperature 
reached. Boiled with dilute mineral acids, cane sugar is split 
into equal parts of glucose and fructose, as has been stated. 
The mixture of the two is called invert-sugar. The process is 
called inversion. It takes place, to some extent, when impure 
sugar is allowed to stand. Hence invert-sugar is contained in 
the brown sugars found in the market. The enzyme, invertin 
(see p. 185), formed by yeast, gradually transforms cane sugar 
into glucose and fructose, and these then undergo fermentation. 
Cane sugar itself does not ferment. 

Cane sugar does not reduce an alkaline solution of copper 
sulphate. If the two are boiled together for some time, the 
sugar is to some extent inverted, and to this extent reduction 
of the copper salt takes place. 

Experiment 39. Prepare a dilute solution of cane sugar by dissolv- 
ing U to 2k in 200c« water. Test this with Fehling's solution, as in Exp. 
38. Now add to the sugar solution 10 drops concentrated hydrochloric 
acid, and heat for half an hour on the water-bath at 100^ ; exactly neu- 
tralize the acid with a dilute solutioi) of sodium carbonate, and test with 
Fehling's solution. 

Oxidizing agents readily convert cane sugar into oxalic acid 
(see Exp. 34) and saccharic acid. 



SUGAR OF MILK 199 

Like glucose, cane sugar forms compounds with metals, 
metallic oxides, and salts. Among these the following may 
be mentioned : — 

Sodium sucrate CiaHaOu . !N"a, 

Sodium-chloride sucrate . • C12H22O1X . NaCl, 

Calcium sucrate C12H20O11 . Ca, 

and Lime sucrate C12H22OU • 2 CaO. 

These derivatives are not sweet. 

An oct-a^tate of the formula Ci2Hi4(C2H30)80ii has been made 
by treating sugar with sodium acetate and acetic anhydride. 

Cane sugar is in some way made up by a combination of a 
molecule of c2-glucose and a molecule of d-fructose, with elimi- 
nation of a molecule of water. The resulting compound does 
not react with phenylhydrazine nor with Fehling's solution, 
and, therefore, it probably does not contain a carbonyl group 
CO. The artificial preparation of cane sugar from c2-glucose 
and d-fructose has not been effected. 

Sugar of milk, lactose, C12H22O11 + H2O. — This sugar oc- 
curs in the milk of all mammals, and is obtained in the manu- 
facture of cheese. The casein is separated from the milk by 
means of rennet; the sugar of milk remains in solution, is 
separated by evaporation, and purified by recrystallization. It 
crystallizes in rhombic crystals. That which comes into the 
market has been crystallized on strings or wood splinters. It has 
a slightly sweet taste ; is much less soluble in water than cane 
sugar, and is dextro-rotatory. It reduces Fehling's solution. 
Oxidized with nitric acid, it yields mucic and saccharic acids. 
Kascent hydrogen converts sugar of milk into mannite, dulcite, 
and other substances. Like glucose and cane sugar, it forms 
compounds with bases, dissolving lime, baryta, lead oxide, etc. 

Sugar of milk ferments under certain circumstances, and is 
thus converted into lactic acid. The souring of milk is a result 
of this fermentation. The lactic acid formed coagulates the 
casein i hence the thickening. 



200 CABBOHYDRATES 

Maltose, C12H22OU . H2O. — This carbohydrate is formed by 
the action of Tnalt on starch. Malt^ which is made by steeping 
barley in water until it germinates, and then drying it, con- 
tains a substance called diastasey which has the power of effect- 
ing changes similar to some of those effected by the ferments. 
Thus, it acts upon starch, and converts it into dextrin and 
maltose : — 

starch Maltose Dextrin 

Maltose is also formed by the action of dilute sulphuric acid 
upon starch, and is hence contained in commercial glucoses. 
By further treatment with sulphuric acid it is converted into 
glucose. Maltose crystallizes in fine needles; is dextro-rota- 
tory; reduces Fehling's solution; and ferments with yeast, 
being first converted into monosaccharides by mcUtase, which 
is an enzyme contained in, or formed by, yeast. 

3. POLYSAGCHABIDES THAT ABE NOT SuGABS 

Cellulose, (C6Hio05)-b. — Cellulose is the chief constituent of 
the cell membranes of all vegetable tissues. It presents dif- 
ferent appearances and different properties, according to the 
source from which it is obtained; but these differences are 
due to substances with which the cellulose is mixed; and 
when they are removed, the cellulose left behind is the same 
thing, no matter what its source may have been. The coarse 
wood of trees, as well as the tender shoots of the most delicate 
plants, all contain cellulose as an essential constituent. Cot- 
ton-wool, hemp, and flax consist almost wholly of cellulose. 
It also occurs in the animal kingdom. Thus the tunica of 
the Ascidia is chiefly composed of cellulose. 

For the preparation of cellulose, either Swedish filter-paper 
or cotton-wool may be taken. 

Experiment 40. Treat some cotton-wool successively with ether, 
alcohol, water, a caustic alkali, and, finally, a dilute acid. Then wash 
with water. 



GUN COTTON 201 

Cellulose is amorphous ; insoluble in all ordinary solvents ; 
soluble in an ammoniacal solution of cupric oxide. It dis* 
solves in concentrated sulphuric acid. If the solution is 
diluted and boiled, the cellulose is converted into dextrin and 
glucose. It will thus be seen that rags, paper, and wood, 
which consist largely of cellulose, might be used for the 
preparation of glucose, and consequently of alcohol. 

Experiment 41. Dissolve a sheet or two of filter-paper in as small a 
quantity of concentrated sulphuric acid as will suffice ; dilute with water 
to about half to three-quarters of a litre, and boil for an hour. Hemove 
the sulphuric acid by means of chalk; filter; evaporate; and test for 
glucose by means of Fehling's solution. 



Gun cotton, pyroxylin, nitro-oellulose. — Cellulose has 
some of the properties of alcohols ; among them the power to 
form ethereal salts with acids. Thus, when treated with 
nitric acid, it forms several nitrates, just as glycerol forms the 
nitrates known as nitro-glycerin (which see). 

When cotton is exposed for some time to the action of a 
warm mixture of nitre and sulphuric acid, soluble gun cotton or 
soluble pyroxylin is formed. This consists of the lower nitrates 
(the di-, tri-, and tetra-nitrates), which are soluble in ether 
containing a little alcohol, and in acetone. 

The solution is called collodion solution. When poured upon 
the surface of a solid, such as glass, the ether and alcohol 
rapidly evaporate and leave a thin coating of the nitrates. It 
finds extensive application in surgery and in photography. 

When treated with a mixture of nitric and sulphuric acids, 
cotton yields the higher nitrates (tetra-, penta-, and hexa- 
nitrates), which are not soluble in alcohol and ether. These 
are called gun cotton or pyroxylin. They are extensively used 
as explosives. Gun cotton forms the active constituent of 
some of the smokeless powders now so extensively used. In 
the manufacture of these powders the gun cotton is gelatinized 
by treating it, in finely divided condition, with acetone or some 



202 CAUBOIIYDUATES 

other similar solvent. Under these circumstances the gun 
cotton does not dissolve, but it swells up and forms a gelati- 
nous mass. From this the solvent is removed by pressure and 
evaporation, and the residual mass cut into laminae, or powdered 
by appropriate methods. The name "explosive gelatin '' is 
given to the substance prepared as above. 

A solution of soluble cotton in molten camphor gives ceUiUoid, 
As it is plastic at a slightly elevated temperature, it can easily 
be moulded into any desired shape. When it cools it hardens. 

Paper. — Paper in its many forms consists mainly of cellu- 
lose. The essential features in the manufacture of paper are, 
first, the disintegration of the substances used. This is effected 
partly mechanically, and partly by boiling with caustic soda. 
The mass is converted into pulp by means of knives placed on 
rollers. The pulp, with the necessary quantity of water^ is 
then passed between rollers. Rags of cotton or linen are 
chiefly used in the manufacture of paper; wood and straw 
are also used. 

Starch, (CeHioO^),. — Starch is found everywhere in the 
vegetable kingdom in large quantity, particularly in all kinds 
of grain, as maize, wheat, etc. ; in tubers, as the potato^ arrow- 
root, etc. ; in fruits, as chestnuts, acorns, etc. 

In the United States starch is manufactured mainly from 
maize ; in Europe, from potatoes. 

The processes involved in the manufacture of starch are 
mostly mechanical. The maize is first treated with warm 
water; the softened grain is then ground between stones, a 
stream of water running continuously into the mill. The thin 
milky fluid which is carried away is brought upon sieves of 
silk bolting-cloth, which are kept in constant motion. The 
starch passes through with the water as a milky fluid^ and 
this is allowed to settle when the water is drawn off. The 
starch is next treated with water containing a little alkali 
(caustic soda, or sodium carbonate), the object of which is 



STARCH 203 

to dissolve gluten, oil, etc. The mixture is now brought into 
shallow, long wooden runs, where the starch is deposited, 
the alkaline water running off. Finally, the starch is washed 
with water, and dried at a low temperature. 

Starch has a granular structure, the grains as seen under 
the microscope having a series of concentric markings, with a 
nucleus. 

Starch in its usual condition is insoluble in water. If ground 
with cold water, it is partly dissolved. If heated with water, 
the membranes of the starch-cells are broken, and the contents 
form a partial solution. On cooling, it forms a jelly called 
starch paste. 

With iodine, starch paste gives a deep blue color; with 
bromine, a yellow color. 

Kxperiment 42. Make some starch paste thus : Put a few grammes 
of starch! in an evaporating dish; pour enough cold water upon it to 
cover it ; grind it under the water with a pestle, and then pour 200<^ to 
300«c hot water upon it. When this is cool, add a few drops to a litre 
of water, and then add a few drops of potassium iodide. As long as 
the iodine is in combination with the potassium no change of color 
takes place ; but if the iodine is set free by the addition of a drop or 
two of chlorine water, or of strong nitric acid, the entire liquid turns 
a beautiful dark blue. The cause of this color is the formation of a 
very unstable compound of starch and iodine. The color is easily 
destroyed by a slight excess of chlorine water (try it in a test-tube) ; 
by alkalies (try it) ; by sulphurous acid (try it) ; by hydrogen sulphide 
(try it) ; etc. It is also destroyed by heating. (Heat some of the 
solution in a test-tube, and let it stand.) The color reappears on cooling. 

Experiment 43. Use some of the starch paste in studying the effect 
of bromine upon it. Use dilute solutions. The bromine must be in the 
free condition. 

Starch is converted into dextrin, maltose, and glucose by 
dilute acids; diastase converts it into dextrin, maltose, and 
isomaltose. 

' The purest form of starch ^o be found in the market Is that made from arrowroot 
Ordinary starch contains other substances which sometimes interfere with the reactions. 



204 GABBOHYDBATES 

Experiment 44. Add 20^ concentrated hydrochloric acid to 200<» of 
the starch paste already made, and heat for two hours on the water- 
bath, connecting the flask with an inverted condenser (see Fig. 8). 
Then examine with Fehling^s solution. Test, also, some of the original 
starch paste with Fehling's solution. 

When starch is treated for a few days with cold, dilute 
mineral acids, it is converted into "soluble starch," which 
dissolves in water without the formation of a paste. 

Starch is used extensively in laundries, as a food, and in 
making glucose (grape sugar). 

Glycogren, (OeHioOs)*. — This is a carbohydrate resembling 
starch that occurs in the animal organism. It is found in 
the tissues of nearly all animals as a reserve material, but 
disappears during exercise or hunger. It is especially abun- 
dant in the liver of healthy animals. It yields dextrin, 
maltose, and c^-glucose when hydrolyzed. 

Dextrin, OeHioOs* — Dextrin is formed by treating starch 
with dilute acids or diastase. It is converted by further treat- 
ment with acids into glucose. The substance ordinarily called 
dextrin has been shown to be a mixture of several isomeric sub- 
stances which resemble each other very closely. The mixture 
is an uncrystallizable solid. It is strongly dextro-rotatory; 
gives a red color with iodine, and does not reduce Fehling's 
solution. It is used extensively as a substitute for gum. 

Gums. — Under this head are included a number of sub- 
stances which occur in nature. One of the best known is gum 
arabic, which is obtained in Senegambia from the bark of trees 
belonging to the Acacia variety. Its formula, like that of 
cane sugar, is C12HJJ2O11. Other gums are wood gum, obtained 
from the birch, ash, beech, etc. ; bassorin, the chief constituent 
of gum tragacanth, etc. 

Our knowledge of the chemistry of these gums is very 
limited. 



CHAPTER XII 

MIXED COMPOUNDS CONTAINING NITROGEN 

In speaking of the preparation of dibasic acids from mono- 
basic acids, reference was made to cyan-acetic and the two 
cyan-propionic acids. These are simple cyanogen substitution- 
products analogous to chlor-acetic and the two chlor-propionic 
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 for Student. — How can malonic be made from acetic acid ; 
and the two succinic acids from propionic acid? Give the equations. 

The chief substances to be considered under the head of 
mixed compounds containing nitrogen are the amino-cbcids and 
the add 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, glycocoll, etc., be- 
longing 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 
hydrocarbon to the hydrocarbon. That is to say, it may be re- 
garded as the acid in which a hydrogen has been replaced by 
the amino group, NH2. Thus, amino-acetic acid is represented 

205 



206 MIXED COMPOUNDS CONTAINING NITROGEN 

NH 

by the formula CH2<^q^tt ; while amino-methane, or methyl- 

amine, is represented thus: CH3.NH2. The reasons for regard- 
ing methyl-amine as a substituted ammonia have been stated. 
The formula is based upon the reactions of the substance; 
that is, upon its chemical conduct and the methods used in its 
preparation. The same arguments lead in the same way to the 
view that the amino-acids are substituted ammonias, and, at 
the same time, acids. The simplest method for their prepara- 
tion consists in treating halogen derivatives of the acids with 
ammonia. Thus amino-acetic acid can be made by treating 
brom-acetic acid with ammonia: — 

CH, < ^^^g + 2 NH3 = CH2 < ^^^ + NH^Br. 

Note for Student. — Compare this reaction with that made use of 
for making methyl-amine. 

NH2 
Axnino-formic acid, carbamic acid, I . — This acid 

CO2H 

is not known in the free condition. Its ammonium salt, 

NH2 

I , is formed when carbon dioxide and ammonia are 

CO2NH4 

brought together, and it is therefore contained in commercial 

ammonium carbonate : — 

NH2 

I 
C02 + 2NH3=C02NH4. 

The other carbamates are prepared from the ammonium 
salt. They are decomposed, yielding carbonates and ammonia. 
Thus, when potassium carbamate is warmed in water solution, 
decomposition takes place, as represented in the equation, — 

NH2 . CO2K + H2O = NH3 + HKCO3. 

The ethereal salts of carbamic acid, called urethanesj are 



GLYCOCOLL 207 

readily made by treating the ethereal salts of chlor-f ormic acid 
(see p. 158) with ammonia : — 

CI NH2 

I I 

CO2C2H5 + 2 NH3 = CO2C2H5 + NH4CI. 

Amino-formic 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. 

GlyooooU glycine. 1 o,H.NO, ( OH,<^^M. - In the 
amino-acetio acid, J ^*^^^^^ \ - CO2H/ 

bile are contained two complicated acids, which are known as 
glycocholic and taurocholic acids. When glycocholic acid is 
boiled with hydrochloric acid, it breaks up, 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 up into benzoic acid and glycocoll. 

When uric acid is treated with hydriodic acid, glycocoll is 
one of the products. Further, glycocoll is formed when glue is 
boiled with baryta water or dilute sulphuric acid. Its forma- 
tion from brom-acetic acid and ammonia, mentioned above, gives 
the clearest indication in regard to its relation to acetic acid. 

Amino-acetic acid is soluble in water, insoluble in alcohol or 
ether. It has a sweetish taste, and is sometimes called gelatin 
sugar. 

Amino-acetic acid has both acid and basic properties. It 
unites with acids, forming weak salts ; and it acts upon bases, 
giving salts with metals, — the amino-acetates. It also unites 
with salts, forming double compounds. 

Examples of the compounds with acids are the 

Hydrochloride • • • • CH2 < r^r\TT ' 

^.1. .r. ^TT NH2.HNO3 

and the Nitrate CH2 < ^^ ^r > 

of the salts with metals, 



208 MIXED COMPOUNDS CONTAINING NITROGEN 

Zinc amino-acetate . . Zii(C2H4N02)2 + HgO, 
and Copper amino-acetate • Cu (02114^02)2 + H2O ; 

of the compounds with salts, the double salt of 

Copper nitrate 1 CufNO ) . Cu(C H4NO ) + 2 H 0. 

and Copper amino-acetate, J ^ ^^^' \ 2 *^ 2/2 2 • 

Treated with nitrous acid, glycocoU is converted into hydroxy- 
acetic acid. With soda-lime it gives methyl-amine. 

Note for Student. — Write the equation representing the reaction 
that takes place when glycocoU is treated with nitrous acid. 

It seems probable that amino-acetic acid and other similar 
compounds are really salts formed by the union of the acid con- 
stituent, carboxyl, with the basic constituent, NH2. In accord- 
ance with this view the formula should be written thus : — 

CH2<^^«>0. 
Saroosine, methyl-firlyoocoU, 03H7NO2f0H2<QO2H • 

NH2 . OHgv 

or 0H2\ /^ )• — When brom-acetic acid is treated with 

CO ^ 

methyl-amine instead of with ammonia, a reaction takes place 

similar to that which takes place with ammonia, the product 

being methyl-glycocoll or sarcosine : — 

CH, < ^J^ + 2 CH, . NH, = C H, < ^^^ ' + NH3(CH,)Br. 

Sarcosine 

Sarcosine is a product of the decomposition 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. 

Amino-propionio acids, O8H7NO2. — These acids bear to 
propionic acid relations similar to that which amino-acetic acid 



CYSTINE 209 

bears to acetic acid. There are two, corresponding to a- and 
)8-chlor-propionic acids, from which they are made. Their 
properties are much like those of glycocoll. a-Amino-propionic 
acid, which is also called alanin, is widely distributed in nature. 
Among the amino derivatives of the higher members of the 
fatty acid series, two are of special importance. These are 
leucine and isoleucine. 

Leucine, ^a-aminoisobutylacetic acid, 

^„* > CH . CH, . CH(NHj) . COOH, 

is a frequent product of decomposition of vegetable and 

animal albuminoid substances. The inactive variety has 

been made artificially by starting with isovaleric aldehyde, 

CH 

^>CH . CH2.CHO, and by means of hydrocyanic acid convert- 
CHs 

ing this into the amino acid of the above formula. When this 

inactive acid is split into its optically active components, the 

levo variety is found to be identical with the leucine obtained 

from natural sources. 

Isoleucine, <^a-amino-i8-methyl-i8-ethyl-propionio acid, 

CH CH 

' * ^> CH . CHCNHa) . COOH, like leucine, is a frequent prod- 
CH3 

uct of decomposition of vegetable and animal albuminoid sub- 
stances. It is dextro-rotatory. 

Serine, which is obtained from silk by boiling with dilute 
acids, has been shown to be a-amino-)8-hydroxy -propionic acid, 
CHgCOH) . CH(NH2) . COOH. 

Cystine, C6H12K2O4S2, a substance that is sometimes found 
as a crystalline sediment in the urine of human beings and 
dogs, is a derivative of a-amino-propionic acid. Tin and 
hydrochloric acid reduce it to cysteine C3H7KO8S. The two 



210 MIXED COMPOUNDS CONTAINING NITROGEN 

substances bear to each other the relation represented by these 
formulas : — 

CH2 . SH CH2 . S S . H2C 

I I I 

CH.NHj CH.NH2 HjiN.HC 

I I I 

COOH COOH HOOC 

Cy stein Cystine 

Among the amino derivatives of the higher members of the 
fatty acid series, that of caproic acid should be specially men- 
tioned. 

Amino-sulphonic Acids 

Just as there are amino derivatives of the carboxyl acids, 
so, too, there are amino derivatives of the sulphonic acids. 
The most important of these is 

^-Amino-ethyl-sulphonio acid, f C2H7NSO3 (^'^2M4< -^^^ y 

Taurine is found in combination with cholic acid in taurocholic 
acid, in ox bile, and the bile of many animals, as well as in 
other animal liquids. It has been made synthetically from 

OH 

isethionic acid, C2H4 < gQ jj, by treating the acid successively 
with phosphorus pentachloride and ammonia : — 

OTT PI 

C,H, < g^^^jj + 2 PCI, = C,H, < g^^^j + 2 POCl, + 2 HCl ; 

Isethionic acid Ghlor-ethyl-sulphon-chloride 

CI CI 

^*^* < SO2CI + ^'^ = ^'^' < SO,OH + ^^^ 5 

Chlor-ethyl-sulphonic acid 

C2H4 < so OH + ^ ^^' = ^'^* < S(?H + ^^*^^- 

Taurine 

Taurine crystallizes in large monoclinic prisms. It is a very 
stable substance, and can be boiled with concentrated acids 



ACID AMIDES 211 

without 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 

ammonium salt as represented by the formula C2H4<4.^*>0. 

Amino-dibasic Acids 

Aspartic acid, { c^j^-^Q.iCJI.C^H,) < ^ J?! 

A m ino-succinic acid, \ * ^ 4v 2 sv 2>f -^ COgH 

or HO2C . H2C - CH(NH2) . CO2H. 

Aspartic acid occurs in pumpkin seeds, and is frequently 
met with as a product of boiling various natural compounds 
with dilute acids. Thus, for example, it is formed when casein 
and albumin are treated in this way. It is formed also when 
asparagine (which see) 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 levo-rotatory. A cold solution is dextro-rotatory. 
It contains an asymmetric carbon atom, and the three varieties 
(d-, Z-, and i-) 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 body distils over which is known as acetamide. 
The reaction is represented by the following equation : — 

CH3 . COONH4 = CHs . CONH2 -f H2O. 

The substance obtained has neither acid nor basic properties. 
An examination of the ammonium salts of other acids that 
contain carboxyl shows that the reaction is a general one, and 
a class of neutral bodies, known as the acid amides, can thus 
be obtained. As no one of the acid amides of the fatty acid 



212 MIXED COMPOUNDS CONTAINING NITROGEN 

series is of special importance, a few words of a general char- 
acter in regard to the class will suffice. 

Besides the reaction above given, 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 am- 
monia ; thus, when ethyl acetate is treated with ammonia, this 
reaction takes place : — 

CH3 . CO AH5 + NH, = CH3 . CONH2 + CsHgO. 

The other reaction consists in treating the acid chlorides with 
ammonia. Thus, to get acetamide, we may treat acetyl chloride 
(see p. 62) with ammonia : — 

CH3 . COCl + 2 NH3 == CH3. CONH2 + NH4CI. 

This last reaction is perhaps most frequently used. It shows 
the relation that exists between acetic acid and acetamide. 
For acetyl chloride is made from acetic acid by treatment with 
phosphorus trichloride, and is, therefore, as has been pointed 
out, 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 preparation 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 : — 









II 


II 


CHj. C - OH 


CH,-C-NH» 


Acetic acid 


Acetamide 



As the acid hydrogen of the acid is replaced, the amide is not 
an acid. On the other hand, the basic properties of the 
ammonia are destroyed by the presence of the acid residue as 
a part of its composition. This latter fact may be stated in 
another way ; viz., when an ammonia residue is in combination 



ACID AMIDES 213 

with carbon, which in turn is in combination with oxygen, its 
basic properties are destroyed. 

The amides are converted into ammonia and a salt when 
boiled with strong bases : — 

CHs. CONH2 + KOH = CHsCOjK + NH^. 

They are converted into cyanides by treatment with phos- 
phorus pentoxide, P2O5: — 

CHs . CONH2 == CHs . GN + H2O. 

As the substance obtained in this way is identical with methyl 
cyanide, which is formed by heating the potassium salt of 
methyl-sulphuric acid with potassium cyanide, 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 represented in the formula CHg— C — N. 

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 : — 

E . C00NH4->R . CONHj-^R . CN, 
and R . CN->R . CONHa-^R. COONH4. 

As acetamide is made by treating ammonia with the chloride 
of acetic acid, so, by treating ammonia with the chloride of any 
acid, the corresponding amide can be made. Similarly, by 
treating acid amides with acid chlorides, more complicated com- 
pounds can be obtained. Of these dirocetamide, NH(C2H30)2, 
and tri-acetamide, N(C2H80)8, may serve as examples. The re- 
lations of these substances to ammonia and to acetic acid are 
shown by the formulas, ordinary or mon-acetamide being 
NHa.CaHsO or CH3.CO.NH,. 



214 



MIXBD COMPODSDS CONTAINING NITROGEN 



Experiment 45. Arrange an apparatiiB aa shown in Fig. 12. In 
flank A put dO* oxalic acid (deliyd rated at 100°) and Ti^ absolute alcohol ; 
iiiid, in flask S, 60" absolute alcohol. Heat the bath D to 100° ; and then 
lieat llie alcohol in flMk B to boiling, and continue to pass the vapor 
from flaflk B into tlie mixture in flask A, meanwhile allowing the tem- 
perature of the oil-bath to riae to 125°-130°. A mixture of alcohol And 
ethyl ozalata will distil over, while the ethyl oxalate will be mostlj' in 




Pig. 13, 
flask A. Add concentrated ammonia to some of the ethyl oxalate. 
Oxamide ia thrown down as a white powder. What reactions have 
taken place ? Write the equations. Filter off the oxainide, and wash 
it with water. See whether it conducts itself like an acid. Has it an 
acid reaction? Boil with caustic potash (not too much), and notice 
whether ammonia is given off. Why does It dissolve ? How can the 
oxalic acid be extracted from the solution ? 

Hoftnann's reaction. — When an acid amide is treated 
with sodium hydroxide and bromine, three reactions take place, 
as represented in the equations : — 

CH,.C0NH, + Br,= CH3.C0NHBr-|-HBr; 
CHj. CONHBr + NaOH = CH^N : C : O + NaEr + HjO ; 
CHj.N : C : O + HaO = CH3NHJ+ CO^ 



ASPARAGINB 215 

It is thus possible by starting with any acid to pass to the 
primary amine containing the same radical as the acid. In the 
case of acetic acid the three stages are represented below : — 

CHg. COOH-^CHg.CONHa-^CHs.NHa. 

Acetic acid Acetamide Methylamine 

This reaction has become of great practical importance in 
connection with the artificial preparation of indigo (which see). 

Amic acids. — When the amide of a poly basic acid is boiled 
with ammonia, and under some other circumstances, partial de- 
composition takes place, and a substance is formed which is 
both amide and acid. Thus, in the case of oxamide, the prod- 

CO2H 
uct is oxamic acid, | . This acid forms well-characterized 

CONH2 

salts and other derivatives such as are obtained from acids in 
general. There is one acid of this kind which is a well-known 
natural substance. It has already been referred to in connec- 
tion with aspartic acid, which is closely related to it. It is 

Aspara^ne, amino-succinamic acid, 

/CH2.CONH2 \ 

C4H8N2O3 -f- H20( I 1. — Asparagine is found 

^CH(NE[2) . COOH/ 

in many plants, as in asparagus, liquorice, beets, peas, beans, 

vetches, and in wheat. It can be made by treating mon-ethyl 

amino-succinate with ammonia. 

Note for Student. — What reaction takes place ? Write the equa- 
tion. 

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. — Notice 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. 



216 MIXED COMPOUNDS CONTAINING NITROGEN 

Nitrous acid converts asparagine into malic acid. 

Asparagine contains an asymmetric carbon atom, and two 
of the three theoretically possible stereoisomeric varieties are 
known. The levo-rotatory variety is found in the seeds of 
many plants, in asparagus, in beets, in peas, beans, and in 
vetch sprouts. The dextro variety is also found in vetch 
sprouts. 

CO 

Suooinimide, OaH4 < ^Q > NH. — This compound deserves 

attention in this connection, as it represents a not uncommon 
class known as the cuM 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 : — 

CHj.CONHa CHj.COv 
I = I >NH + NHa. 

CH2.CONH2 CH2.CO/ 

Succinamlde Succinimlde 

The hydrogen atom of the imide is replaceable by some 
metals, or the imide has the properties of a weak acid. 

Cyan-amides, ON2H2. — In speaking 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 NgCgClg. When the former is treated with ammonia, 
it is converted into an amide, XC.NHg, which bears to cyanic 
acid, NC . OH, the relation of an amide. Like the other simple 
compounds of cyanogen, cyan-amide readily undergoes change. 
Heated to 150° or when allowed to stand, it is converted into 
di-cyan-diamide, C2N4H4; while, when heated to above 150°, a 
violent reaction takes place, and trircyan-triamide, CgNgHg, is 
formed. The latter compound is also called melamine and 
cyanuramide, and from certain methods of formation it is 
poncluded that it is the amide of cyanuric acid. It is a strong 



CREATINE 217 

m on-acid base. The formation of these compounds is particu- 
larly interesting, as illustrating the tendency on the part of 
the simpler cyanides to undergo change under slight provo- 
cation. 

Calcium cyanaxnide, CNsCa. — This compound has come 
into prominence as a fertilizer. It furnishes the nitrogen 
necessary to the growth of plants. It is made by passing 
nitrogen over calcium carbide heated to TSO^-IOOO** in an 
electric furnace, when the reaction represented in this equation 
takes place: — 

CaCa + N2 = CNaCa + C. 

The nitrogen used is obtained by fractional distillation of 
liquid air. 

Guanidine, ONaHg. — This substance, which is closely 
related to cyan-amide, is formed by the oxidation of guanine 
(which see), and this in turn is obtained from guano. It can 
also be made by treating cyanogen iodide with ammonia: - 

NCI-f2NH3 = HN:C<^2* ^^, 

the product being the hydriodic acid salt of guanidine. As 
will be seen, guanidine is cyan-amide plus ammonia : — 

NC .NH2 + NHs=:HN : C <r:t:'. 

JS1I2 

It is a strongly alkaline base. Boiled with dilute sulphuric 
acid or baryta water, it yields urea and ammonia : — 

CN3H5 + H2O = CON2H4 + NH3. 

Goanidine Urea 

_ « 

Creatine, O4H9N3O2. — This substance is found in the 
muscles of all animals. It is closely related to guanidine 
and also to sarcosine (see p. 208). It has been made syn- 
thetically by bringing cyan-amide and sarcosine together. 



218 MIXED COMPOUNDS CONTAINING NITROGEN 

The reaction is analogous to that made use of for the prepara- 
tion of guanidine : — 

N = C-NH2+ I =HN:C< p^. p^^„ 

Cyan-amide Sarcoslne Creatine 

Creatinine, O4H7N3O, is in small quantity a constant con- 
stituent of urine. It can be made from creatine by evap- 
orating its solutions, especially if acids are present. In 
contact with alkalies it gradually takes up the elements of 
water and forms creatine. It is a strong base, forming with 
acids well-crystallized salts. Its relation to creatine is repre- 
sented thus: — 

^^ '* ^\>. .CH2.COOH ^^ • ^\j.^CH, . CO. 

CH3 ^CH3 

Creatine Creatinine 



Urea, or carbamide, and derivatives. — Closely related 
to the nitrogen compounds just considered is urea, or the 
amide of carbonic acid. Its importance and certain peculiari- 
ties distinguish it from the other acid amides, and it is there- 
fore treated of by itself. 

Urea is found in the urine and blood of all mammals, and 
particularly in the urine of carnivorous animals. Human 
urine contains from 2 to 3 per cent ; the quantity given off by 
an adult man in 24 hours being about 30^. Urea can be made 
by the following methods: — 

(1) By treating carbonyl chloride with ammonia : — 

COCI2 + 2 NH3 = CON2H4 + 2 HCl. 
(What is the analogous reaction for the preparation of acetamide ?) 



UREA 219 

(2) By heating ammonium carbamate : — 

CO <Q^^ = CON2H4 + 2 H2O. 

(3) By treating ethyl carbonate with ammonia : -^ 

C0< ^'^' + 2 NH, = CONjH^ + 2 G,U,0. 

(What is the analogous reaction for preparing oxamide ?) 

(4) By the addition of water to cyan-amide : — 

CN . NH2 + H2O = CON2H4. 

(5) By evaporation of ammonium cyanate in aqueous solu- 
tion : — 

CN(0NH4) = CON2H4. 

This reaction is of special interest, for the reason that it is the 
first example of the formation, by artificial methods from in- 
organic substances, of an organic compound found in the ani- 
mal body (see p. 1). 

Urea is most readily obtained from urine. 

Experiment 46. Evaporate four or five litres fresh urine to a thin, 
syrupy consistence. After cooling add ordinary concentrated nitric acid, 
when crystals of urea nitrate are obtained. Filter^ wash, and recrys- 
tallize from moderately concentrated nitric acid. When the crystals of 
urea nitrate are white, dissolve again in water, and add finely-powdered 
barium carbonate. The nitric acid forms barium nitrate, and the urea is 
left in free condition. Evaporate to dryness, and from the residue extract 
the urea with strong alcohol. 

Experiment 47. Make potassium cyanate as directed in Experi- 
ments 24, p. 83, and 26, p. 86. Extract the cyanate with cold waterj and 
add a solution of ammonium sulphate containing as much of the salt 
as there was used of potassium ferrocyanide in the preparation of the 
cyanate. Evaporate to a small volume, and allow to cool. Potassium 
sulphate will crystallize out. Filter this off, and evaporate to dryness. 
Extract with alcohol. The urea will crystallize from the alcoholic solu- 
tion when it is brought to proper concentration. Give all the reactions 



220 MIXED COMPOUNDS CONTAINING NITROGEN 

involved in passing from potassium ferrocyanide to urea. Compare the 
urea made artificially with that made from urine. 

Urea crystallizes from alcohol in large^ rhombic prisms, 
which melt at 132^. 

Expe^ment 48. Determine the melting-points of both the natural 
and artificial specimens of urea. 

Urea is easily soluble in water and alcohol. Heated with 
water in a sealed tube to 180**, or boiled with dilute acid or 
alkalies, it breaks up into carbon dioxide and ammonia : — 

CON2H4 + HsO = CO, + 2 NHg. 

The same decomposition of the urea takes place spontaneously 
when urine is allowed to stand. Hence the odor of ammonia 
is always noticed in the neighborhood of urinals that are not 
kept thoroughly clean. This decomposition is due to the action 
of an organism known as micrococcus urece. This change is a 
good example of the way in which nature converts useless 
material into useful ones. Urea is a waste-product of the life- 
process. After it has left the body it ceases to be of value, 
whereas carbon dioxide and ammonia are essential to the life 
of plants. 

Sodium hypochlorite or hypobromite decomposes urea into 
carbon dioxide, nitrogen, and water : — 

COCNjjH^) + 3 NaOCl = CO, + 3 NaCl + N2 + 2 H^O. 

The carbon dioxide is absorbed by the solution which contains 
sodium hydroxide, and the nitrogen then 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. 

Experiment 49. To a solution of 20e sodium hydroxide in 10(V^ 
water add about 5<^ bromine, and shake well. Make a solution of urea 
in water, and add this to the solution o| the hypobromite. An evolution 
of gas will be noticed, showing that the urea is decomposed. 



SUBSTITUTED UREAS 221 

Nitrous acid acts in a similar way j. — 

CON2H4 + 2 HNOs = CO2 + 2 Na 4- 3 HjO. 

When heated, urea loses ammonia, and yields first biuret 
and finally cyanuric add (see p. 86) : — 



0C< 



NHo /NH 



^2 



2 



Urea Biuret 

3 C0(NH2), = CgHgO^, + 3 NH^ 

Cyanuric acid 

Biuret in alkaline solution gives a beautiful violet-red reaction 
with a little copper sulphate. This biuret-reaction is charac- 
teristic of the more complicated polypeptides (which see). 

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, ^^"^nh ^ ' ' ^^^ 
ethyl-urea, CO < ^ *, are examples. 

Among the compounds with acids, the following may be 
mentioned : urea hydrochloride, CH4K2O . HCl ; urea nitrate, 
CH4N2O.HNO3; and urea phosphate, CH4N2O . H8PO4. With 
metals it forms such compounds as that with mercuric oxide, 
2HgO.CH4N20; with sUver, CH2N20.Ag2, etc. With salts it 
forms such compounds as 2 CO(NH2)2 . Hg(N08)2 . 3 HgO, etc. 

Substituted ureas — that is, those derivatives of urea 
which contain hydrocarbon residues in place of one or all the 
hydrogen atoms — can be made from the cyanates of substi- 
tuted ammonias. The fundamental reaction is the spontaneous 
transformation of ammonium cyanate into urea : — 

CN.ONH4 = CO(NH2)2. 



222 MIXED COMPOUNDS CONTAINING NlTliOGEN 

In the same way, cyanates of substituted ammonias are 
transformed into substituted ureas: — 

CN.ONHaCH^ = CO < ^ JJ^^"^' ; 

CN . ONHaCCaHs)^ = CO < ^^'"^'^', etc. 

The urea derivatives which contain acid radicals are made 
by treating urea with the acid chlorides: — 

CO < '^ + C^sOCl = CO < ^ J! • ^^^"^ + HCl. 

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, 0C<^„* ' ^, is a simple ureid. The rela- 
tion between the acid and urea in the ureid is like that between 
the acid and ammonia in the amide : — 

CH3. COOH + HHglSr = CH3. CONH2 + H2O 5 

Acid Amide 

CHs.COOH + HHN^„-. CH,.COHN^ _^^„^ 

Acid Urea Ureid 

The ureids of dibasic acids resemble in the same way the 
amides 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.HNv 

I >C0= I >CO + 2H20. 

COOH + HHN/ CO . HN/ 

Oxalic acid Urea Ureid uf oxalic acid 



BARBITURIC ACID 223 

There are several compounds of this kind that are of 
importance : — 



Parabanic acid, 
Oxalyl-urea, \ CaHgNgOg 

Oxal-ureid, 



CO.HNv 

I >C0 



.—This is 



formed by boiling uric acid with strong nitric acid and with 
other oxidizing agents, and by treating a mixture of oxalic acid 
and urea with phosphorus oxy chloride. It acts like an acid, 
the hydrogen of the imide group being replaceable by metals, 
as in succinimide. Its salts readily pass over into salts of 
oxaluric acid when treated with water : — 

CO.HNv COOH 

I >C0 + H20= I 

CO . HN/ CO . HN . CONHa 



/CO . OH \ 

UVOO.HN.OO.NHg/, 



/CO . OH 

Oxaluric acid, 03H4N2O4\0O.HN.0O.NH2y, 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 m human urine. With 'phosphorus oxychloride it 
gives parabanic acid. 

Barbituric acid, malonyl-urea, 

C,H,N,03+2H20(CH2<g2*.NH^^^)' ^'^® parabanic 
acid, is obtained from uric acid. It has been made artificially 
by treating a mixture of malonic acid and urea with phosphorus 
oxychloride. Treated with an alkali, it breaks up into malonic 
acid and urea. 



Diethylbarbituric acid, C(02H,)2< ggjjg >0O. made 

by the action of the diethyl ester of diethylmalonic acid upon 
urea, is an excellent soporific. It is known as veronal. 



224 MIXED COMPOUNDS CONTAINING NITROGEN 

Sulpho-urea, thio-urea, OS(NH2)2. — This substance is 
formed by heating ammonium sulpho-cyanate, the reaction 
being analogous to that by which urea is formed from am- 
monium cyanate : — 

NCSNH4 = SC(NHjV 

It forms rhombic prisms melting at 172®. It combines with 
one equivalent of acids, forming salts. 

A number of derivatives of sulpho-urea have been made. 
They resemble those obtained from urea. 

CTrio acid, G5H4N4O3. — Uric acid occurs in human urine 
in small quantity, in the urine of carnivorous animals, and in 
the excrement of birds and of reptiles. The excrement of 
reptiles consists almost wholly of ammonium urate. In gout, 
uric acid is deposited in the joints, under the skin, and in the 
bladder as calculi, in the form of insoluble acid salts. 

Uric acid forms colorless, crystalline scales, and is almost 
insoluble in water. It acts like a weak dibasic acid. 

By treating the lead salt of uric acid with methyl iodide, 
two isomeric methyl-uric acids can be obtained, and these can 
be further converted into a tetra-methyl-uric acid, which is 
derived from uric acid by the substitution of four methyl 
groups for the four hydrogen atoms, €5(0113)4X403. When 
this is decomposed, all the methyl groups are given off in 
combination with nitrogen in the form of methyl-amine. This 
shows that uric acid contains four imino groups, as shown in 
the formula C5(NH)408. Other transformations show that the 
constitution of the acid must be represented by the formula 

NH-CO 

I I 

CO C-NH. 

I II >C0. 

According to this, uric acid contains two urea residues com- 



XANTHINE 226 

CO 

bined in different ways with the group C . It is to be re- 

II 
C 

garded as a diureid of a hypothetical trihydroxyacrylic acid, 

C(0H)2 : C(OH) . CO2H. That this view is correct has been 

shown by the artificial preparation of 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). 

Uric acid and related compounds are regarded as derived 
from a compound of the formula 

(1) N = CH(6) 

I I (7) 
(2)HC (5)C-NHv 

II II ^H(8) 

(3) N - C-N^^ 

(4) (9) 

to which the name purin has been given. 

A careful study of uric acid has shown that it is a tauto- 
meric compound. It may be represented by either one of the 
two formulas, 

NH-CO N = C.OH 

II II 

CO C-NH\ or HO.C C-NH\ 

I II >C0 II II >C.OH. 

According to the latter formula it is a 2, 6, 8-trihydroxypurin. 

Xanthine, 2, 6-dihydroxypurin, O4H4N4O2, 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 : — 

CsH^N.O + HNO2 = C5H4N4O2 + H2O 4- Nj. 

In this case the nitrous acid causes a substitution of an 
hydroxyl group for an amino group, ^ 



226 MIXED COMPOUNDS CONTAINING NITROGEN 

SS^eSrTianthine. } 0,H,N.O.[0.H.(CH3).N,OJ, is a 
substance found in chocolate prepared from the seed of the 
cacao tree. It has been made by treating the lead compound 
of xanthine with methyl iodide. 

Caffeine, theine, trimethyl-xanthine, 

O8H10N4O2 + H2O[06H(CH8)3N4O2 + H2O], is the active con- 
stituent of coffee and tea. It has been made from theo- 
bromine by the introduction of a third methyl group. 

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-aniino, 6-hydroxypurin, 

06H6N6O[06H3(NH2)N4O], is found principally in guano, 
from which it is prepared. Nitrous acid converts it into 
xanthine. Oxidizing agents convert it into guanidine, CNgH^ 
(see p. 217). 

Polypeptides. — These are compounds which have been 
prepared from amino-acids and acid amides. The simplest 
example is glycyl-glycine, a compound of glycine of the con- 
stitution NH2.CH2.CO.NH.OH2.CO2H. As will be seen, 
it contains the glycyl group, NH2.CH2.CO, and this has taken 
the place of one of the hydrogen atoms of the amino group of 
another molecule of glycine. From this by treatment, first 
with chloracetyl chloride, and then ammonia, the tripeptide, 
diglycyl-glycine, NH2 . CHg . CONH . CHg. CO . NH . CHg. COgH, 
is formed. Many polypeptides have thus been prepared, among 
them being one containing eighteen carbon atoms. Some poly- 
peptides have been obtained by decomposition of natural albu- 
mins. Most of them are easily soluble in water and difficultly 
soluble in alcohol. The more complicated polypeptides give 
the biuret-reaction (see p. 221). All polypeptides are hydro- 
lyzed, yielding the constituent amino acids. These compounds 
are of special importance because of their relations to the 
Deptones (which see). 



RETROSPECT 227 

Eetrospect 

All the compounds we have thus far had to deal with may 
be regarded as derived from the marsh-gas hydrocarbons or 
paraffins. These are, (1) the substitution-products of the hydro- 
carbons; (2) alcohols, of which there are three classes : (a) the 
primary, (b) the secondary, and (c) the tertiary alcohols; (3) 
aldehydes; (4) ketones; (5) a/iids. 

Acids and alcohols act upon each other, forming (6) ethereal 
salts, and alcohols can be converted into (7) ethers. 

Corresponding to the oxygen derivatives, there are com- 
pounds containing sulphur, as (8) the sulphur alcohols or mer- 
captans; (9) the sulphur ethers ; and (10) the sulphonic acids. 

Under the head of compounds containing nitrogen occur 
cyanogen and the allied compounds hydrocyanic, cyanic, and 
sulpho-cyanic ax^ids. Related to these are (11) the cyanides, 
and (12) the isocyanides; (13) the cyanates, and (14) the iso- 
cyanates; (15) the sulpho-cyanates, and (16) the iso-sulpho- 
cyanates or mustard-oils. 

Finally, there are (17) compounds containing metals in com- 
bination with radicals. 

Then there are poly-acid alcohols and poly-basic acids. 

Under the head of mixed compounds were found compounds 
which belong at the same time to two or more of the funda- 
mental classes, as the hydroxy-acids, the carbo-hydrates, and the 
amino-adds. A study of the amino-acids and the acid amides 
led naturally to urea and its derivatives, to uric acid and its 
derivatives, and to the polypeptides. 

We turn now to a new class of compounds, known as unsatu- 
rated compounds. 



CHAPTER XIII 

UNSATURATED CARBON COHPOUNDS— DISTINCTION BE- 
TWEEN SATURATED AND UNSATURATED COMPOUNDS 

Most of the compounds thus fax studied are generally called 
saturcUed compounds. This is slu. appropriate name so far as 
the hydrocarbons themselves and some of the classes of their 
derivatives are concerned. The expression " saturated " is in- 
tended 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 
example, must first displace hydrogen before it can enter into 
combination : — ^H^ + Br^ = CHsBr + HBr. 

The compound 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, thus: — 

PCl3 + Cl2 = PCV 
Ammonia is unsaturated, for it can take up an equivalent of 
an acid : — ^^ jj^ _^ jj^.^ ^ 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 ammonia, hydrocyanic acid, 
and other substances. 

Second. The ketones also act like unsaturated compounds, 
though their power in this way is less marked than that of the 
aldehydes. 

Third, The substituted ammonias are unsaturated, in the 
same sense that ammonia itself is unsaturated. 

22s 



UNSATURATED CARBON COMPOUNDS , 229 

F(mrth, The cyanides take up hydrogen directly, and are 
therefore unsaturated also. 

In the substituted ammonias the un saturation is due to the 
same cause as that in ammonia. In them the nitrogen is tri- 
valent. In contact with acids it becomes quinquivalent, and 
saturates itself. 

In the cyanides carbon and nitrogen are probably 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: — 

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 probably changed 
to the hydroxyl condition. The changes are usually repre- 
sented by formulas such as the following: — 

(CH,),C = + HCN = (CH,),C<^Q J- 

In carbonyl the oxygen is represented as held by two bonds 
to the carbon atom, while in hydroxyl it is represented as held 
by one bond. The signs may be used if not too literally inter- 
preted. There are undoubtedly two relations which carbon 
and oxygen bear to each other in carbon compounds. These 
relations may be called the hydroxyl relation, represented by 
the sign C — — , and the carbonyl relation, represented by the 
sign C = O. 

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 comr 
pounds are spoken of. 



230 UNSATURATED CARBON COMPOUNDS 

The kind of relation between the carbon atoms in all the 
saturated hydrocarbons is, so far as we know, the same as that 
which exists between the two carbon atoms of ethane, and 
this is represented by the formula HgC — CHg. This formula 
signifies simply that the two carbon atoms are held together 
by the forces which in marsh gas enabled each methyl group to 
hold one hydrogen atom. Abstracting one hydrogen atom from 
marsh gas, union is effected between the carbon atoms. What 
would result if two hydrogen atoms were to be abstracted, and 
union between the carbons then effected ? Theoretically we 
should get a compound made up of two groups CH2, thus 
CH2.CH2, 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 which differs markedly from 
ethane. It shows the property of unsaturation very clearly. 
This is olejiant 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 the paraffins ; 
though of these, as well as of the hydrocarbons, very few 
are known as compared with the number of the paraffin 
derivatives. 

ETHYLENE AND ITS DERIVATIVES 

Hydrocarbons, CnH2n, the Olefines 

The principal hydrocarbons of this series are included in 
the subjoined table : — 

Ethylene, Ethene C2H4. 

Propylene, Propene CgHg. 

Butylene, Butene C4H8. 

Amylene, Pentene C5H10. 

Hexylene, Hexene CqHw 

Heptylene, Heptene C7II14. 



UNSATURATED CARBON COMPOUNDS 231 

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. 

Ethylene, oleflant gas, 02H4(OH2 = OHg). — This gas is 
formed when many organic substances are subjected to dry 
distillation. The two principal reactions which yield it are : — 

(1) The action of an alcoholic solution of potassium hydrox- 
ide on ethyl chloride, bromide, or iodide : — 

CgH^Br + KOH = C2H4 + KBr + HgO. 

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 substances belonging to 
other classes. By means of it it is possible to pass from 
any saturated compound to the corresponding unsaturated com- 
pound of the ethylene series. Thus we can pass from ethane, 
C2H6, to ethylene, C2H4, by first introducing bromine, and then 
abstracting hydrobromic acid from the mono-bromine substi- 
tution-product. By treating the mono-bromine substitution- 
products of other saturated compounds in the same way, the 
corresponding unsaturated compounds can be made. 

(2) The action of sulphuric acid and other dehydrating agents 

upon alcohol : — 

C2H5.0H = C2H4-|-H20. 

Experiment 51. In a flask of 2< to 3^ capacity put a mixture of 
258 alcohol and ISO* ordinary concentrated sulphuric acid. Heat to 160° 
to 170°, and add gradually through a funnel tube about 600*'*' of a mixture 
of 1 part of alcohol and 2 parts of concentrated sulphuric acid. Pass the 
gas through three wash bottles containing, in order, sulphuric acid, 
caustic soda, and sulphuric acid. Then pass it into bromine contained in 
a cylinder, provided with a cork with two holes. If the cylinder has a 
diameter of about S^™, let the layer of bromine be about 6<"" to 7*"" deep. 
Upon it pour a somewhat deeper layer of water. Place the cylinder in 
a vessel containing cold water. Pass the gas into the bromine until it is 
completely decolorized. (See note, next page.) 



232 UNSATURATED CARBON COMPOUNDS 

Ethylene is a colorless gas which can be condensed to a 
liquid. It burns with a luminous flame. With oxygen it 
forms a mixture which explodes when ignited. Its most chaV' 
acteristic property is its power to unite directly with other sub- 
stances, particularly with the halogens and with the hydrogen axiids 
of the halogens. Thus it unites with chlorine and bromine, and 
with hydriodic and hydrobromic acids : — 

C2H4 + CI2 = C2H4CI2 1 
C2H4 + Br2 =C2H4Br25 
CgH^ + HBr =C2H5Br; 
C2H4 -\- HI = C2H5I. 

The products formed with chlorine and bromine are called 
ethylene chloride and ethylene bromide. They have been men- 
tioned 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. 

Note. — The addition of bromine to ethylene is illustrated by the 
experiment last performed, in which ethylene bromide is formed. To 
purify the product, put a little dilute caustic soda in the cylinder, and shake. 
Remove the upper layer of water, and repeat the washing with dilute 
caustic soda. Then wash with water two or three times, each time remov- 
ing the water with the aid of a separating funnel. Finally, put the oil in a 
!flask, add a few pieces of granulated calcium chloride, and allow to stand. 
Pour off into a dry distilling-bulb, and distil, noting the temperature. 

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, CHg, and CH? Is it to be represented by the 
formula CHg. CHg 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 
evidence is in favor of 'the view that aldehyde is correctly 

represented by the formula CH3.C<^jj. Hence, as has been 



ALCOHOLS 233 

pointed out, the chloride obtained from it 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 has 

CH2 CHg 

the formula I , and not I • 

CH2 CH 

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, II or CH2: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 ethylene, the compound in whose 
formula it is written having the power to take up two atoms of 
bromine, a molecule of hydrobromic acid, etc. 

The homologues of ethylene bear the same relation to it that 
the homologues of ethane bear to this hydrocarbon. Propylene 

CH . CH3 

is methyl-ethylene, II , just as propane is methyl-ethane, 

CH2.CH8 CH.CHg C(CH8)2» 



I . Butylene is dimethyl-ethylene, 11 , or II 

CHg QTT Q o CH.CHs CH2 

or ethyl-ethylene, II . That is to say, in the hydro- 

CH2 

carbons of the ethylene series the ethylene condition between 
carbon atoms occurs only once. 

Alcohols, CnHj^O 

These alcohols bear to the ethylene hydrocarbons the same 
relation that the alcohols of the methyl alcohol series bear to 
the paraffins. Only one is well known. This is the second 
member, corresponding to propylene. 



234 UNSATURATED CARBON COMPOUNDS 

Allyl alcohol, CsHeOCCHstCH.CHoOH). — This alcohol 
is formed in several ways from glycerol. 

1. By introducing two chlorine atoms into glycerol in the 
place of two hydroxyls, thus getting dichlorhydrin, C3H5CI2.OH : 

CH2OH CH2CI 

CHOH + f:^! = CHCl + 2 H,0 ; 
I ^^^ I 

CHjOH CHjOH 

and treating the dichlorhydrin with sodium, which extracts the 
chlorine : — 

CHgCl CHj 

I II 

CHCl + 2 Na = CH +2 NaCl. 

I I 

CH2OH CH2OH 

2. By treating glycerol with the iodide of phosphorus. This 
gives allyl iodide, CsHgl. By treating the iodide with silver 
hydroxide it is converted into the alcohol. 

3. Most readily by heating glycerol with oxalic acid, as in 
the preparation of formic acid. The mixture is heated to 260°, 
when allyl alcohol passes over. The first product formed in 
this case is an ethereal salt of formic acid with glycerol, 
HOH2C.CHOH.CH2O.COH. At a higher temperature this 
breaks down, yielding allyl alcohol, HOHgC . CH : CHg, carbon 
dioxide and water. 

Allyl alcohol is a colorless liquid boiling at 96.5°. It has a 
disagreeable penetrating odor and is miscible with water in all 
proportions. 

Nascent hydrogen does not act upon it, or at least the action, 
if any, takes place with difficulty. As far as composition is 
concerned, the relation between allyl alcohol and propyl alco- 
hol is the same as that between ethylene and ethane : — 

C3H5. OH + H2 = C3H7 . OH. 



ALLYL MUSTARD-OIL 236 

Allyl alcohol forms esters with acids and gives the other re- 
actions for alcoholic hydroxyl. It is, further, a primary 
alcohol, as it is converted by certain oxidizing agents into the 
corresponding aldehyde (acrolein) and acid (acrylic acid). 

When treated with a dilute solution of potassium permanga- 
nate it is converted into glycerol : — 

CH2 CH2OH 

II I 

CH + + H2O = CHOH. 

I I 

CH2OH CH2OH 

Allyl compounds. — Among the derivatives of allyl alcohol 
which are of special interest is allyl sulphide (03115)28, which 
is the chief constituent of the oil of garlic. It can be made 
artificially by treating allyl iodide with potassium sulphide : — 

2 CaH,! + K2S = (Q,TL,\ S + 2 KI. 

It is a colorless, oily liquid of a disagreeable odor, only slightly 
soluble in water. 

Allyl mustard-oil, SON . CsHs. — Under the head of Sulpho- 
cyanates mention was made of a series of isomeric compounds 
called isosulpho-cyanates or mustard-oils. The sulpho-cyanates 
of the alcohol radicals are made from potassium sulpho- 
cyanate. Thus, methyl sulpho-cyanate is made by mixing 
together potassium methyl-sulphate and potassium sulpho- 
cyanate, and distilling: — 

NCSK + ^^fz > SO, = KsS04 + KCSCHs. 

The mustard-oils, on the other hand, are made by a com- 
plicated reaction from carbon bisulphide and substituted 
ammonias. The conduct of the sulpho-cyanates led to the 
conclusion that they must be represented by the formula 
NC — SR, while that of the isosulpho-cyanates or mustard-oils 



236 UNSATURATED CARBON COMPOUNDS 

led to the formula SC — NR, as representing their structura 
AUyl mustard-oil is the chief representative of the class of 
bodies known as mustard-oils. It occurs as a glucoside (which 
see) in mustard seed. From the glucoside it is formed by 
the action of an enzyme. It also occurs in horse-radish. It is 
formed by treating allyl iodide with potassium sulpho-cyanate. 
If this reaction consisted simply in the substitution of the allyl 
group, CgHi, for potassium the product should be allyl sulpho- 
cyanate, C3H5S — CN. As a matter of fact it is the isosulpho- 
cyanate CaHgN — CS. As has already been pointed out (see 
p. 94), the sulpho-cyanates are converted into the isosulpho- 
cyanates by heat, so that the formation of the isosulpho- 
cyanate in this case is not surprising. 

Allyl mustard-oil is a liquid, boiling at 150.7°, and having a 
very pungent odor. 

Zinc and hydrochloric acid convert it into allyl-amine, 
NH2.C3H5, and thioformic aldehyde, HgCS. This reaction 
indicates that in allyl mustard-oil the radical allyl is in com- 
bination 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 
sulpho-cyanates undergo when oxidized? 

Acrolein, acrylic aldehyde, C3H40(CH2:CH.COH). — 

Acrolein can be made by careful oxidation of allyl alcohol. It 
is formed by the dry distillation of impure glycerol, which 
breaks up into water and acrolein : — 

It is, hence, formed also by heating the ordinary fats, the 
peculiar penetrating odor noticed when fatty substances are 
heated to a sufficiently high temperature being due to the 
formation of acrolein. It is prepared best by heating glycerol 
with boric acid. 



CROTONIC ALDEHYDE 237 

Experiment 52. In a test-tube mix anhydrous glycerol (1 part) 
and boric acid (2 parts), and heat the mixture. Pass the vapors through 
a bent tube into water contained in another test-tube. Notice the odor. 
Try the effect on a dilute solution of nitrate of silver. What is the mean- 
ing of this redaction ? 

Acrolein is a volatile liquid which boils at 62.4°. It has an 
extremely penetrating odor, and its vapor acts violently upon 
the eyes, causing the secretion of tears. 

Acrolein takes up oxygen from the air, and is converted into 
the corresponding acid, acrylic acid, C3H4O2 (which see). 

It takes up hydrogen, and is thus converted into allyl alcohol. 

It takes up hydrochloric acid, and is converted into j8-chlor- 
propionic aldehyde: — 

C2H3 . COH + HCl = CH2CI . CHa . COH. 

9 ^-Ghlor-propionic aldehyde 

The first two reactions are characteristic of aldehydes in 
general ; the last one is characteristic of unsaturated compounds 
belonging to the ethylene group. Acrolein, like ordinary alde- 
hyde, forms polymeric modifications which can easily be 
reconverted into acrolein. 

It unites with ammonia, forming acrolein-ammonia, and with 
other substances in much the same way as ordinary aldehyde 
does. It unites with bromine to form acrolein dibromide, which 
when treated with barium hydroxide gives i-f ructose (which see). 

Crotonio aldehyde, C4H60(CH8.CH: CH. COH). — This 

aldehyde is most readily made by distilling aldol (which see). 
The starting-point is acetic aldehyde. By treatment with 
potassium carbonate in aqueous solution the acetic aldehyde is 
condensed (aldol condensation) to aldol or ^-hydroxy-butyric 
aldehyde, CH3.CH(OH).CH2.COH. By distillation this breaks 
down into crotonic aldehyde and water : — 

CH3.CH(OH).CH2.COH = CH3.CH;CH,C0H + HjO. 



238 UNSATURATED CARBON COMPOUNDS 

Acids, CnHjn.gO, 

Banning parallel to the ethylene series of hydrocarbons, and 
bearing the same relation to it that the fatty acid series bears 
to the paraffins, is a series of acids of which the first member 
is acrylic acid, C3H4O2. Several members of the series are 
known. The principal members are named in the subjoined 
table: — 

ACRYLIC ACID SERIES 
Acids, Cnllgn-'A 

Acrylic acid C3H40^ 

Crotonic " C4II6O2. 

Angelic " 'C^HgOa. 

Hydrosorbic i^ CgHioOa. 

Teracrylic " ........ C7H12O2. 

Cimic " CwHasOa. 

Hypogaeic " CieH^Oa. 

Oleic « ........ C18H34O2. 

Erucic " C22H42O2. 



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, C3H402(CH2:CH.C02H). — This acid has 
already been mentioned in connection with hydracrylic acid, 
which, when heated, breaks up into acrylic acid and water : — 

CH2OH . CH2. CO2H = CH2 : CH . CO2H + H2O. 

Hydracrylic acid Acrylic acid 

Note for 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 239 

Acrylic acid can be made by careful oxidation of acrolein 
with silver oxide. The relations between propylene, CgHe, 
allyl alcohol, C3H5.OH, acrolein, C2H3.COH, and acrylic acid, 
C2H3.CO2H, are the same as those between any hydrocarbon 
of the paraffin series, and the corresponding primary alcohol, 
aldehyde, and acid. 

Acrylic acid can be made further by treating j8-iodo-propionic 
acid with alcoholic caustic potash : — 

CH2l.CH2.C02H = CH2:CH.C02H + HI. 

Note for Student. — Compare this reaction with that by which 
ethylene is made from ethyl bromide. 

Acrylic acid is a liquid having a pungent odor. It boils at 
140^ and melts at 13°. 

Nascent hydrogen converts it into propionic acid. Hydriodio 
acid unites directly with it, forming )8-iodo-propionic acid. 

Note for Student. — What are the analogous reactions with allyl 
alcohol and acrolein ? 

Crotonio acids, O4H6O2. — Two crotonic acids, the ordi- 
nary solid form and isocrotonic acid, occur in croton oil and 
in crude pyroligneous acid. Ordinary or solid crotonic acid 
is formed, (1) by hydrolyzing allyl cyanide ; (2) by distilling 
j8-hydroxy-butyric acid; (3) by treating a-brom-butyric acid 
with alcoholic caustic potash; (4) by heating malonic acid 
with paraldehyde and acetic anhydride. 

Allyl cyanide has been shown to have the structure 
CHg.CH: CH.CN, although it is formed from allyl bromide, 
which must have the structure CH2 : CH . CH2Br, because this 
is formed by the action of hydrobromic acid on allyl alcohol. 
It follows that the structure of crotonic acid should be repre- 
sented by the formula CHg.CH : CH. COgH. The formation of 
crotonic acid from a-brom-butyric acid, CH8.CH2.CHBr.CO2H, 
by the abstraction of hydrobromic acid leads to the same 



240 UNSATURATED CARBON COMPOUNDS 

conclusion. So also the formation of crotonic acid from 
paraldehyde and malonic acid points to the formula 

CHj. CH : CH . COgH for crotonic acid : — 
(1) CHs.CHO + CH,<^^^^ = CH3.CH:C<^^^^ + H20; 

Aldehyde Malonic acid 

(2) CHj.CH : C < ^""^ = CHg.CH : CH.COjH + C0» 

Crotonic acid 

Again, when crotonic acid is fused with caustic potash, it gives 
only acetic acid : — 

C4H A + H2O + O = 2 C2H4O2 ; 

and, as it has been shown that under these circumstances the 
breaking down takes place at the place where the double bond 
occurs, this reaction furnishes additional evidence in favor of 
the view that ordinary crotonic acid has the constitution 
represented by the formula CH3.CH : CH.CO2H. 

Isocrotonic acid contains the same groups as crotonic acid, 
and is also to be represented by the formula 

CH3.CH:CH.C02H. 

As will be shown under maleic and fumaric acids (which see), 
the difference between the two f orm^ of crotonic acid is proba- 
bly due to the difference in the arrangement of the groups in 
space. 

Oleic acid, C18H34O2. — This acid was referred to in con- 
nection with the fats, it being one of the three acids found, 
most frequently in combination with glycerol. Olein, or 
glyceryl tri-oleate, is the liquid fat, and is the chief con- 
stituent 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 ordinary fats. In the preparation of stearic acid 
for the manufacture of candles, the oleic acid is pressed out 



POLYBASIC ACIDS OF THE ETHYLENE GROUP 241 

of the mixture of fatty acids. To prepare the acid, ole'm is 
saponified, and the soap then decomposed with hydrochloric 
acid. 

Note for Student. — Give the equations representing the reactions 
involved in passing from olein, or glyceryl tri-oleate, to oleYc acid. 

OleXc acid is a colorless oil that solidifies when cooled, form- 
ing crystals that melt at 14°. It unites with bromine, forming 
dibromstearic acid. Hydriodic acid converts it into stearic 
acid: — 

C18H34O3 + H2 = Ci8Hg802. 

Oleic acid Stearic acid 

PoLYBAsic Acids op the Ethylene Group 

There are a few dibasic acids that bear to the ethylene 
hydrocarbons the same relations that the members of the 
oxalic add series bear to the paraffins. They may be regarded 
as derived from the hydrocarbons by the introduction of two 
carboxyl groups. 

Acids, C2H2(C02H)2. — There are two acids of this formula, 
fumaric and male'ic acids, both of which are formed by the 
distillation of malic acid. Fumaric acid remains in the retort j 
male'ic anhydride distils over. 

Fumaric acid can also be made by treating brom-succinic 
acid with alcoholic potash. 

Both fumaric and male'ic acids are converted into succinic 
acid by nascent hydrogen, and into the same brom-succinic 
acid by hydrobromic acid. Both combine with water to form 
the same malic acid. They are, therefore, structurally the 
same, and both must be represented as ethylene-dicarbonio 

CH . CO2H 

acids II . They are hence stereo-isomeric : — 

CH.CO2H 

C2H8(OH) < QQ^ = C2H2 < (JO H "^ ^^^ ' 

Malic acid MaleTc or Famaric acid 



242 



UNSATURATED CAKIJON COMPOUNDS 



C,H,Br<^Q^jj 

Brom-Bucclnic acid 

Maleic or Fumaric acid 



C,H,<^^g + HBr; 

Fumaric acid 
Succinic acid 



An extension of the fundamental ideas of stereochemistry 
furnishes a plausible explanation of the relation 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 toward the solid 
angles of a tetrahedron, the carbon atom itself 
being at the centre of the tetrahedron. When two 
carbon atoms unite in the simplest way, the stereo- 
chemical model representing the compound consists 
of two tetrahedrons 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 tetrahedrons 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 arra-iged 
in space, as shown by the figures : — 





I. 



II. 





POL YB ASIC ACIDS OF THE ETHYLENE GROUP 243 

It will be seen that, in the first of these figures, the A'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. 
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 ordinary 

CH . CO2H 
formula |1 . These can be arranged in two ways cor- \ 

CH . CO2H 
responding to the above figures, thus : — 

T. II. 

COOH Hr :7C00H 





COOH HOOO 



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 th^ 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 the 
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 give off water, while 
in the case of the substance having the configuration repre- 
sented in figure II. this would not appear to be possible. 

The configurations of maleic and fumaric acids can be repre- 
sented by formulas, thus : — 

H - C - CO,H H - C - COjH 

II II 

H - C - CO2H CO2H - C - H 

Maleic acid Fumaric acid 



244 UNSATUBATED CARBON COMPOUNDS 

MaleXc anhydride similarly can be represented thus: — 

H - C - C0> 



II >0 

-. n - no/ 



H - C - CO 

This extension of the theory of stereochemistry applies to a 
large number of phenomena and furnishes a satisfactory ex- 
planation of a number of cases of isomerism for which no other 
explanation has been found. 

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 formulas : — 

CH3-C-H CH3-C-H 

II II 

COjH-C-H H-C-CO2H 

Crotonic acid Isocrotonic acid 

Acids, C5H6O4. — When citric acid is rapidly heated, a dis- 
tillate consisting of the anhydrides of two acids of the formula 
C5H8O4 is obtained. These acids are itaconic and citraconic 
Cicids. 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 anhydride is treated with hydrochloric or nitric acid and 
then evaporated, a third acid, memconic acid, isomeric with 
citraconic 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 formulas : — 

CHs - C - CO2H CH3 - C - CO2H 

II II 

H - C - CO2H CO2H - C - H 

Citraconic acid Mesaconic acid 

Like fumaric acid, mesaconic acid does not form an anhy- 



ACETYLENE 245 

dride. Itaconic acid is not a methyl derivative of maleic or 
fumaric acid, but corresponds to the formula 

CH2=C-C02H 
I 

The formation of itaconic and citraconic anhydrides from 
aconitic acid is shown thus : — 

CH . COjH CH, CH . COv 

u II n >0 



C.COsH . C.CO V C.CO 



\- 



I I ^0 or I 

CHj . CO,H CH, . CO/ CH, 

Aconitic acid Itaconic anhydride Citraconic anhydride 

Aconitic acid, [C6H606(C8H8(C02H)8)]. — Aconitic acid is 
the only tri-basic acid of this group that need be mentioned. 
As has been stated, 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 tri-carballylic acid, 
C3H5(C02H)3. The relation between citric and aconitic acid is 
shown above. 

Acetylene and its Derivatives 

The principal reactions by means of which it is possible to 
pass from a hydrocarbon of the paraffin series to the corre- 
sponding hydrocarbon of the ethylene series consist in intro- 
ducing a halogen into the paraffin, and then treating the 
mono-halogen substitution-product with alcoholic caustic 
potash : — 

C,H,Br = C2H4 -t- HBr. 

The effect of these two reactions is the abstraction of two 
hydrogen atoms from the paraffin. The following questions 
therefore suggest themselves : — 



246 UNSATUBATED GAKBON COMPOUNDS 

Suppose a dibrom substitution-product of a paraffin should be 
heated with alcoholic caustic potash ; will the effect be that rep- 
resented by the equation 

CgH^Bra = CgHa + 2 HBr ? 

And, further, suppose a mono substitution-product of an 
ethylene hydrocarbon be treated with alcoholic potash; will 
the effect be that represented by the equation 

CsjHaBr^CjjHa + 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 
CnH2n_2, that of thc ethylene series being CJlsm and that of 
the paraffin series, CnH2n+2- 

A few members of the hydrocarbon series, CnHgn-a a-^® 
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 carbon poles which are incandescent in consequence 
of the passage of an electric current; when alcohol, ether, 
methane, and other organic substances are passed through a 
tube heated to redness; when coal gas and some other sub- 
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 : — 

C2H4Br2=C2H2 + 2HBr. 

It is formed further when bromoform, CHBr^j, or iodoform, 

CHIg, is treated with silver or zinc dust. 

It is easily made by the action of water on calcium 

carbide * ^^ 

CaCa + 2 H2O = C2H2 + Ca(0H)2. 



«M 



ACETYLENE 



This process is estensively used on the large scale for the 
preparation of acetylene for ilhimiiiating purposes. 

Experiment 63. In a WoulfT's flask or an ordiDBry Florence 
prorided with a dropping funnel and an outlet tube, put a few plE 
calcium carbide about the size of half-Inch cubes. When the water frout 
the funnel la allowed lo drop ou the carbide the gas la given oS at once, 
and the rapidity of the current can be regulated by regulating the drop- 
ping of the water. After the operation has been in progress long enough 
to drive the air out of the apparaiaa, connect a burner with the delivery 
lube at A, and set fire to tlie gaa. Unless the burner is an "acetylene 
burner" the flame gives a great deal of soot and it should not be allowed 
to bum long. In the test-tube S is a strong solution of ainmoniacal 
cuprous chloride prepared as follows : Make a saturated solution of 1 part 
common salt and 2^ parts crystallized copper sulphate. Saturate with 
sulphur dioxide. Filter, and wash with acetic acid. Dissolve the whits 



<t the ^^1 
e flask ^^1 




I 



Fig. 13. 

ti'iii riiL I I (\kiiL Mill lie absorbed by the cojipcr .sdlutiiin, and a pre- 
cipitate formpd (Bee Fxp 54). 

Acetylene is a colorless gas of unpleasant, leeky odor. It U 
poisonouB. It burns with a luminouB, sooty flame. 




248 UNSATURATED CARBON COMPOUNDS 

When heated to a sufficiently high temperature, it is cou' 
verted into the polymeric substances, benzene, GqH.^ and sty- 
rene, CgHg. 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 + 2N = 2HCK 

Acetylene forms some curious compounds with metals and 
metallic oxides. Among them may be mentioned the copper 
compound obtained in Exp. 53. This has the composition 
C2CU2, which ia 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. 

'Experiment 54. Filter off the precipitate obtained in Exp. 53, 
and wash it until the wash-water runs through colorless. Bring the 
precipitate, together with a little water, into a flask furnished with a 
funnel-tube and a deliv.ery-tube. Slowly add concentrated hydrochloric 
acid, and notice the evolution of gas. Collect some of it in a small 
cylinder over water, and burn it. 

Acetylene acts like a weak dibasic acid. Cuprous carbide, 
C2CU2, calcium carbide, C2Ca, silver carbide, C2Ag2, etc., are 
salts of the acid. 

Calcium carbide, CaC2, is formed by heating coal and lime 
together in the electric furnace. With water it gives acetylene 
and calcium hydroxide. It is used extensively for illuminat- 
ing purposes. 

Acetylene unites with bromine, forming the compound 
C2H2Br4, tetra-brom-ethane. It unites with hydrobromic and 
hydriodic acids, forming substitution-products of the saturated 
hydrocarbons : — 

C2H2 + 2 HI = C2H4T2. 

The union between the carbon atoms in acetylene is com- 
monly represented by three lines (=), or three dots (•). 



ACETYLENE 249 

CH 

Thus, acetylene is written III or CHiCH. Like the sign of 

CH 

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 condi- 
tion carries with it the power to take up four atoms of a halogen^ 
or two molecules of hydrobromic acid and similar acids, and to 
form metallic derivatives like those of acetylene above referred to. 
Most of the higher members of the acetylene series of hydro- 
carbons bear to acetylene the same relation that the higher mem- 
bers of the ethylene series bear to ethylene. The first one is 

Allylene or methyl-acetylene . • . CHg.CiCH; 
the second is 

Ethyl-acetylene C2H5.C:CH, 

or Dimethyl-acetylene CHg.CiC.CH^ 

It should be noticed in this connection that there is a hydro- 
carbon of the formula C4H6, which, strictly speaking, is not 
a homologue of acetylene, though it is closely related to 

CH : CH2 
dimethyl-acetylene. It has the formula I 

CHtCHa 

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 
radicals, such as methyl, ethyl, etc. These are called the t'ime 
homologues. They all retain the condition peculiar to acetylene. 

2. Those in which the ethylene condition occurs twice, as 
in the hydrocarbons of the formulas 

CH:Ch/ G:CJI^ 

These may be called diethylene derivatives. These, like acety- 
lene and its true homologues, have the power to take up four 



250 UNSATURATED CARBON COMPOUNDS 

atoms of a halogen, or two molecules of hydrobromic acid and 
similar acids, but they do not form copper and silver salts. 

Propargyl alcohol, G8H4O. — This alcohol is mentioned 
merely as an example of alcohols which are derived from the 
acetylene hydrocarbons. It is the hydroxyl derivative of 
allylene, or methyl-acetylene. It is made by treating brom- 
allyl alcohol, C3H4Br.OH, with alcoholic caustic potash:-^— 

CH2OH CH2OH 

I = I +HBr. 

CBr = CH2 C = CH 

Acids, CnH2„_402 

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. 

/OH N 

Propiolic acid, C3H202( III ). — The potassium salt of 

VC.CO2H/ 

this acid has been made from the acid potassium salt of acety- 

C.COgK 

lene-dicarbonic acid, ||| , by heating its aqueous solution. 

C.COjH 

Acetylene-dicarbonic acid is formed by heating dibrom-succinic 
acid with a water solution of caustic potash : — 

CHBr.COgH C.COgH 

I =111 +2HBr. 

CHBr.COgH C.CO2H 

/ C . CH3 \ 
Tetrolic acid, C4H402( ||| ), is obtained by treating 

VC.CO^H/ 
/3-chlor-crotonic acid with caustic potash : — 

CCI.CH3 C.CH3 

II = III + HCl. 
CH . CO,H C . CO,H 



VALYLENB 251 

Sorbio acid, OeHgOaCCHs . CH : OH . OH : OH . OO2H) . — 
This acid occurs in the unripe berries of the mountain ash. 
It takes up hydrogen and yields hydrosorbic acid, a member of 
the acrylic acid series (see table, p. 238). It also takes up 
bromine, the final product of the action being an acid of the 
formula C5H7Br4.C02H. With hydrobromic acid it forms 
dibrom-caproic acid : — 

C5H7 . CO2H + 2 HBr = CfiHgBra. COjH. 

Dibrom-caproic acid 

It will be observed that sorbic acid is a diethylene derivative 
and that it does not contain the acetylene condition. 

Linoleic acid, Ci8H32O2(0i7H3i0O2H). — This acid occurs 
in the form of an ethereal salt of glycerol in drying oils. It 
can b^ obtained from linseed oil by saponification. It is an 
oily liquid, one of the most marked properties of which is its 
power to take up oxygen from the air, and turn into a solid 
substance. Linseed oil itself has this property of hardening 
or drying. It is the principal substance belonging to the class 
of drying oils. The oil is used extensively as a constituent of 
varnishes and of oil paints. 

The relations between linoleic, oleic, and stearic acids as far 
as their composition is concerned are shown by the following 
formulas : — 

Ci8Hg602 C18H54O2 Vyi8H32v)2 

stearic acid Oleic acid Linoleic acid 



Valylene, OsHg. — We have thus far had to deal with three 
series of hydrocarbons of the general formulas CnH2n+2, CnH2n, 
and CnH2n-2» We naturally inquire whether there is a series of 
the general formula C„H2n_4. A few members of the series have 
been prepared by abstracting hydrogen from certain of the 
acetylene hydrocarbons by the action of alcoholic potash on the 



252 UNSATURATED CARBON COMPOUNDS 

bromine derivatives. Thus, valylene, CgHe, has been made by 
treating valerylene bromide, CgHgBra, with alcoholic potash : — 

C5ll8Br2 = C5He + 2HBr. 

It is a liquid. Its most characteristic property is its power 
to unite with bromine to form the saturated compound CsHjBrg. 

Dipropargyl, CeHe- — I>ipropargyl (boiling point 85*^ is 
obtained from the compound diallyl-tetrabromide, CeHioBr4, by 
boiling with alcoholic caustic potash : — 

C6HioBr4 = C6He + 4HBr. 

It unites very readily with bromine, forming, as the final 
product of the action, the compound CeHgBrg, which is an octo- 
bromine substitution-product of hexane, C^^^. 



The unsaturated hydrocarbons and their derivatives thus far 
treated of are obtained by simple reactions from the saturated 
compounds, and they all have the power to take up bromine, 
hydrobromic acid, etc., readily, and thus to pass back to the 
saturated condition. Whatever the re^al nature of the relation 
between the carbon atoms in all these unsaturated hydrocarbons 
may be, it is easily changed to the condition that exists in the 
saturated compounds. There are several hydrocarbons, how- 
ever, which are unsaturated but are not easily converted into 
derivatives of the saturated hydrocarbons. Although under 
some circumstances they with difficulty unite directly with the 
halogens, they do not take up enough to convert them into 
derivatives of the paraffins ; and the products formed are un- 
stable, easily giving up the halogen atoms with which they 
united. The simplest hydrocarbon of this kind is the well- 
known benzene, which is isomeric with dipropargyl. Before 
proceeding to the study of benzene and its derivatives, it will 
be well to inquire whether the abstraction of hydrogen by 
the reaction chiefly used can be pushed further than it has 
thus far been pushed. Can we, in other words, by means of 
this reaction get hydrocarbons of the formula CnHgn-g which 



UNSATURATED HYDROCARBONS 253 

have the power to unite directly with ten atoms of bromine ? 
Such hydrocarbons have not been prepared. Hydrocarbons of 
the formula CnH2n_8 are known ; but they are not made from 
the paraffins by abstracting hydrogen, and they are not con- 
verted into substitution-products of the paraffins by the 
addition of halogens and halogen acids. 

The compounds which have been treated of fall under five 
general heads, according to the formulas of the hydrocarbons. 
These heads are : — 

1. Hydrocarbons, CnHgn+g, the paraffins and their derivatives. 

2. Hydrocarbons, CnHan, or olefins and their derivatives. 

3. Hydrocarbons, CaHa^.a, or the acetylene hydrocarbons and 

their derivatives, 

4. Hydrocarbons, CnH2n_4, and their derivatives. 

5. Hydrocarbons, CnH2n_6, and their derivatives. 

This classification, while strictly correct, is misleading, inas- 
much as it conveys no idea in regard to the relative importance 
of the compounds of the different classes. As we have seen, the 
only compounds whose treatment required much time are those 
of the first class. These compounds stand out prominently, 
and are distinguished by the frequency of their occurrence and 
their great number. The compounds of the second class are 
much less numerous, and but a small number of them are familiar 
substances. While a few substances belonging to the third 
class are known, our knowledge in regard to the class is much 
more limited than even that of the second class. Finally, as 
regards the fourth and fifth classes, the few representatives 
of them that a?e known are at present scientific curiosities. 
Thus, after we leave the paraffin derivatives, our knowledge 
dwindles away very rapidly when we pass to the following 
classes, until it ends with a single coinpound in the fifth class. 

Let us now pass to the consideration of a new group, the 
importance and number of whose members entitle it to rank 
with the group of paraffin derivatives. 



CHAPTER XIV 

THE BENZENE SERIES OF HYDROCARBONS.^ 

AROMATIC COMPOUNDS 

The fundamental substance of this group is benzene, C^Ti^, 
which bears to the group the same relation that marsh gas 
bears to the group of paraffin derivatives. Benzene, together 
with some of its homologues, is a product of the distillation of 
bituminous coal, and is, therefore, contained in coal tar. As 
coal tar is the raw material from which all benzene derivatives 
are obtained, it will be well briefly to describe the conditions 
of its formation and the method of obtaining pure hydrocar- 
bons from it. 

Coal tar is a thick, black, tarry liquid, which is obtained in 
the manufacture of illuminating gas from bituminous coal. 
The coal is heated in retorts, and all the products passed 
through a series of tubes called condensers. These are kept 
cool, and in them the liquid and volatile solid products are con- 
densed, forming together the coal tar. It is an extremely com- 
plex mixture, from which a great many substances have been 
obtained. Among those most readily obtained from it are the 
hydrocarbons of the benzene series, as well as the hydrocarbons 
naphthalene and anthracene, both of which are important sub- 
stances. 

When the tar is heated, of course the most volatile liquids 

pass over first. These are collected in vessels containing water. 

The first portions of the distillate float on water, and constitute 

what is called the light oil. After a time hydrocarbons and 

other substances of greater specific gravity than the light oil 

pass over. These portions sink under water, and constitute 

the heavy oil. 

254 



BENZENE SERIES 265 

The light oil is treated with caustic soda, which removes 
phenol (carbolic acid) and similar substances, and with sul- 
phuric acid, which removes certain basic compounds and olefins. 
The residue is then subjected to fractional distillation, by 
which means the first two members of the series can be ob- 
tained in very nearly pure condition. As these hydrocarbons 
form the basis of a number of important industries, they are 
separated from coal tar on the large scale. 

The principal members of the series are named in the table 
belovir 

HYDROCARBONS, C^HgaHi 

Benzene Series 

Benzene CJl^ 

Toluene CjHg. 

Xylenes CgHjo. 

Mesitylene ] p -rr 

Pseudocumene J 

Durene 1 >-, tt 

Cymene . 

Hexa-methyl benzene Cu^is* 

Benzene, CgHg. — Benzene is prepared, as above described, 
from the light oil obtained from coal tar. A large part of the 
benzene now used is obtained from the gas formed in the coke 
furnaces. It is also prepared by heating benzoic acid with lime, 
when the acid breaks up into carbon dioxide and benzene : — 

C7Hg02 = CgHg + CO2. ■ 

Note for Student. — What is the analogous method for the prepara- 
tion of marsh gas ? 

Benzene has been made further by simply heating acetylene:— 

3 C2H2 = CgHg. 

To purify the hydrocarbon obtained by fractional distillation 



256 BENZENE SERIES OF HYDROCARBONS 

from light oil, it is cooled down to a low temperature, and that 
which does not solidify is poured off. The crystals are pressed 
in the cold between layers of bibulous paper, and are then very 
nearly pure benzene. This can be further purified by treat- 
ment with sulphuric acid, which removes a small quantity of a 
substance containing sulphur, and known as thiophene, C4H4S. 
Perfectly pure benzene is obtained by distilling pure benzoic 
acid with lime. 

Experiment 55. Mix intimately 60s benzoic acid and 100s quick- 
lime, and distil from a flask connected with a condenser. See that the 
materials and apparatus are dry. Add a little calcium chloride to the 
distillate ; and, after it has stood for an hour or two, redistil it from a 
distilling-bulb of proper size, noting the temperature at which it boils. 
Put the redistilled hydrocarbon in a test-tube, and surround it with a 
freezing mixture. 

Experiment 56. In most places where there are gas-works it will 
not be difficult to get a quantity of light oil. The separation of some 
of this into benzene and toluene, and the purification of the two hydro- 
carbons, is the best possible introduction to a study of the aromatic 
compounds. The benzene and toluene thus obtained may be used in the 
preparation of a number of tjrpical derivatives according to methods 
which will be described. In fractioning the light oil, it will be observed 
that there is a tendency to an accumulation of the distillates in the parts 
boiling near 80.6*^ (the boiling-point of benzene) and 110*^ (the boiling- 
point of toluene). The final purification of the benzene should be effected 
by freezing and pressing, as described above. The toluene should be dis- 
tilled until its boiling-point is not changed by redistillation. 

Benzene is a colorless liquid boiling at 80.5®. It has a 
peculiar, pleasant odor. Several of the homologues of benzene 
have a similar odor. Hence the name aromatic compounds was 
given to them originally, and it is still in general use. Ben- 
zene is lighter than water, its specific gravity being 0.899 at 0^ 
It is insoluble in water, soluble in alcohol and chloroform. It 
bums with a bright, luminous, smoky flame. 

• 

Experiment 57. Pour a layer of benzene on water in a small 
evaporating-dish. Set fire to it. 



BENZENE SERIES 257 

Benzene crystallizes in orthorhombic prisms when cooled to 
0°, These melt at 6®. It is an excellent solvent for oily and 
resinous substances.^ 

Chemical conduct of benzene, and hypothesis regarding its 
structure. In the light of the knowledge already gained in 
studying hydrocarbons which contain a smaller proportion of 
hydrogen than the paraffins, we should naturally expect to find 
that benzene can easily be converted into a derivative of 
hexane. We should expect to find that it unites with bromine, 
just as dipropargyl does, to form an octo-brom-hexane thus, — 

C6He + Br3 = C6HeBr8; 

with hydrobromic acid to form tetra-brom-hexane thus, — 

C6H« + 4HBr = CeHioBr4; 
and probably with hydrogen to form hexane, — 

^6^6 + 8 H = CeHi4. 

But none of these reactions takes place. Hydrobromic acid, 
which combines so readily with all the unsaturated compounds 
hitherto considered, does not act at all upon benzene. Bromine 
acts readily enough, but the action which usually takes place 
is like that which takes place with the saturated paraffins. It 
is substitution, and not addition. Thus, bromine forms mono- 
brom-benzene, CeHgBr, under ordinary circumstances. If, 
however, the action takes place in the direct sunlight, a 
product is formed which has the formula CgHgBrg, known as 
benzene hexabromide, and to this no more bromine can be added. 

Benzene takes up six atoms of hydrogen and yields a hydro- 
carbon of the composition CgHxa. This is not a member of the 
ethylene series. (See Hexamethylene.) 

The facts mentioned show clearly that benzene differs in 
some way fundamentally from all the hydrocarbons which 

1 Benzene, the chemical individual of the definite formula CeHs, must not be confounded 
with ** benzine,** the commercial substance obtained in the refining of petroleum (see p. 
111). 



258 BENZENE SERIES OF HYDROCARBONS 

have been treated of thus far. But these facts are not suffi- 
cient to enable us to form an hypothesis in regard to its struc- 
ture. On studying the many substitution-products of benzene, 
however, facts of a different order and of the highest impor- 
tance are revealed. 

It will be remembered that the theory in regard to the rela- 
tions of the paraffins to each other is based upon the fact, that 
only one mono-substitution product of marsh gas can be ob- 
tained with any given substituting agent. There is but one 
chlor-methane, but one brom-methane, etc. This fact leads to 
the belief that each hydrogen atom of marsh gas bears the 
same relation to the carbon atom, or that marsh gas is a sym- 
metrical compound. A similar conclusion has been reached 
in regard to benzene; and it is based upon a thorough 
study of the substitution-products. Notwithstanding almost 
innumerable efforts to prepare isomeric mono-substitution 
products of benzene, no such isomeric substances have been 
prepared. There is but one mono-brom-benzene, but one mono- 
chlor-benzene, etc. Further, mono-brom-benzene has been pre- 
pared by substituting bromine for each of the six hydrogen 
atoms of benzene successively ; and the product has been found 
to be the same, no matter which hydrogen is replaced. As this 
fact is of fundamental importance, it will be well to point out 
how it is possible to replace the six hydrogens successively, and 
to know that in each case a different hydrogen atom is replaced. 
While it would lead too far to follow this subject in detail, the 
principle made use of can be made clear in a few words : — 

We have a compound, the formula of which is CgHg. Write 

12 3 4 5 6 

it thus, CgHHHHHH, numbering the hydrogen symbols to fa- 

1 
cilitate reference to them. The problem is to replace, say H, 

2 

by bromine ; in a second case, to replace H by bromine ; in a 

8 

third, H, etc. ; and to compare the six mono-brom-benzenes thus 
obtained. Suppose we treat benzene with bromine. We get 



BENZENE SEIMES 269 

a mono-brom-benzene, and we know that one of the hydrogen 
atoms is replaced by bromine, but of course we cannot tell 
which one. We may assume that it is any one of the six 
represented in the above formula. For the sake of the argu- 

1 ^ 8 8 4 5 6 

ment, call it H. Our compound is therefore CgBrHHHHH. 
Now treat this compound with something else which has the 
power to replace the hydrogen, say nitric acid. A second 
hydrogen atom is replaced by the nitro group NOg. Again, 
we do not know which one of the hydrogen atoms is replaced 
in this operation, but we do Tcnow that it is a different one 
from that which was replaced by the bromine in the first 

operation. Call it H. We have, therefore, the compound 

8 4 5 6 

CeBr(N02)HHHH. By treating this compound with nascent 

hydrogen, two reactions take place, the chief one for our 

present purpose being the replacement of the bromine by 

1 
hydrogen. In other words, H is put back into the com- 

1 8 4 5 6 

pound again, and we have C8H(NH2)HHHH. By means 
of two reactions which will be studied farther on it is a 
simple matter to replace the amino group by bromine. This 

1 8 4 5 6 

done, we have the compound CgHBrHHHH, or a mono-brom- 
benzene, in which the bromine certainly replaces a different 
hydrogen atom from that replaced by direct substitution. The 
two products are, however, identical. The above explanation 
will serve to make clear the principle that is involved in the 
study of the relations which the hydrogen atoms contained in 
benzene bear to the molecule. The principle has been applied 
successively to all the hydrogen atoms, and, as already stated, 
the result is the proof that all these hydrogen atoms bear the 
same relation to the molecule. The same is true of the carbon 
atoms, as the compound is symmetrical. 

How can we imagine six carbon atoms and six hydrogen 
atoms arranged so that all these shall bear the same relation 
to the molecule ? The simplest conception is that each carbon 



260 BENZENE SERIES OP HYDROCARBONS 

is in combination with one hydrogen, and that the six carbon 
atoms are arranged in the form of a ring, and not, as in the 
paraffins, in the form of an open chain, or a chain with branches. 
Using our ordinary method of representation, this conception 
is symbolized in the formula 




or, as the curved lines have no special significance, the expres- 
sion becomes 

H 

I I 

HCv .CH 

H 

This symbol, then, is the expression of a thought suggested by 
a study of the chemical conduct of benzene. Before we can 
accept it as probable, it must be tested by all the facts known 
to us. If it is not in accordance with all of them, if it sug- 
gests possibilities which are not realized, then it must be dis 
carded. 

In the first place, then, does it account for the addition 
products, benzene hexabromide, hexa-hydro-benzene, etc.? The 
formula represents each carbon atom as trivalent, and we should 
expect, therefore, each one to have the power to take up an 
additional univalent atom, forming, in the case of bromine, 
a compound of the formula 



BENZENE 261 

HBr 
BrHCj/ \cHBr 



BrHCv yCHBr 

HBr 

in which each carbon atom is acting as a quadrivalent atom. 
Unless the ring form of combination between the carbon atoms 
is broken up, it is impossible for the compound to take up 
more bromine. Hence, the last product of the addition of 
bromine to benzene should be benzene hexabromide. The 
facts and the hypothesis are in harmony. 

Again, we may inquire : Of how many isomeric di-substitu- 
tion products of benzene does the hypothesis suggest the exist- 
ence ? Numbering the hydrogens in the f ormula, we have : — 

(1)H 
(6)HC/ \jH(2) 
(6)H0^^H(3) 

H(4) 

The hydrogens (1) and (2), (2) and (3), (3) and (4), (4) and 
(6), (5) and (6), and (6) and (1), bear the same relations to 
each other ; and, according to the formula, whether we replace 
(1) 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 the following is the general 
expression, in which X represents any substituting atom oi 
group: — X 

HC/ \3X 

I I 

H 

Formols I. 



262 BENZENE SERIES OF HYDROCARBONS 

In the second place, the hydrogens (1) and (3), (2) and (4), 

(3) and (5), (4) and (6), (5) and (1), 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 the 

general formula 

X 

I I 

HCv yCX 

H 

Formala II. 

Finally, there is a third kind of relation, which is that 
between hydrogens, (1) and (4), (2) and (5), and (3) and (6) ; 
and, by replacing such a pair, we should get a compound 
represented by the general formula 

X 

I I 

HC. yCR 

X 

Formula III. 

The hypothesis suggests no other possibilities. We see thus 
that the hypothesis indicates the existence of three, and only 
three, classes of di-substitution products of benzene. There 
ought to be three, and only three, di-chlor-benzenes ; three, 
and only three, di-brom-benzenes, etc. 

The di-substitution 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 every fact thus far discovered 
is in harmony with the hypothesis. Three well-marked classes 



BENZENE 



263 



of isomeric di-substitution products of benzene are known, and 
only three ; and many representatives of the three classes have 
been studied carefully. There are many other facts of less 
importance known which furnish arguments in favor of the 
benzene hypothesis expressed in the formula above discussed, 
but this is not the place to discuss them. Let it suffice, for 
the present, to recognize that the hypothesis is in accordance 
with the most important facts known to us. 

There is one point that has not been touched upon, and that 
is the relation of the carbon atoms to each other. The formula 
is commonly written thus : — 

H 

HC^ \CH 

I II 

H 

which indicates that the carbon atoms are joined together alter- 
nately by single and by double bonds. This formula, however, 
expresses something about which we know little, and concern- 
ing which it is difficult, at present, to form any conception. 
Another formula that has been suggested is this : — 




OH 



CH 



CH 



In each of these, as will be seen, an attempt is made to account 
for the fourth bond of each carbon atom. The question in- 
volved is an extremely difficult one to investigate, and it is 
not surprising that chemists do not agree as to the formula 
to be preferred. 



264 BENZENE SERIES OF HYDKOCAEBONS 

The simple formula 

H 

Hc/ \:)H 

I I 

Ha >CH 

H 

leaves the question as to the relation between the carbon atoms 
entirely open, and suffices for most purposes. 

The benzene hypothesis has been treated of somewhat fully, 
for the reasons, 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 th^se derivatives. 

Benzene and its homologues form nitro compounds and sul- 
phonic acids by direct treatment with nitric and sulphuric 
acids, respectively. This distinguishes them from the paraffins 
and other hydrocarbons hitherto treated of. 

Toluene, OtHsCObHs.OHs). — Toluene was known before 
it was obtained from coal tar, as it is formed by the dry dis- 
tillation of Tolu balsam, whence its name. Its relation to 
benzene is shown by its synthesis from brom-benzene and 
methyl iodide : — 

CaH^Br + CHsI + Na^ = CeH^. CHa + NaBr + Nal. 

Note for Student. — Compare this reaction with that used in the syn- 
thesis of ethane from methane, of propane from ethane and methane, etc. 

According to this synthesis, toluene appears as methyl-heiizenef 
or benzene in which one hydrogen is replaced by methyl ; or 
as phenyl-methane, or methane in which one hydrogen atom is 
replaced by the radical phenyl, CeHg, which bears the same 
relation to benzene that methyl bears to marsh gas. 

Toluene is a colorless liquid that boils at 110°; it has the 
specific gravity 0.8824 at 0°; and has a pleasant aromatic 
odor. 



XYLENES 265 

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 farther on. 

But one toluene or methyl-benzene has ever been discovered. 

Towards oxidizing agents its conduct is peculiar and inter- 
esting. The methyl is oxidized, while the phenyl remains 
intact. The product is a well-known acid, benzoic acid, which, 
as we have seen, breaks up readily into carbon dioxide and 
benzene. It has the composition C7He02, and is the carboxyl 
derivative of benzene, C6H5.CO2H. The oxidation of toluene 
is represented by the equation 

C6H5.CH3 + 30 = CgHs-COgH -f- HjO. 

Xylenes, C8Hio[C6H4(CH3)2].— That portion of light oil 
which boils at about 140*^ was originally called xylene. It was 
afterwards found that this coal-tar xylene consists of three 
isomeric hydrocarbons. As the boiling-points of these three 
substances lie quite near together, it is impossible to separate 
them by means of fractional distillation. By treatment with 
sulphuric acid, however, they can be separated, and thus ob- 
tained in pure condition. They are known as ortho-xylene, 
metorxylene, and parorxylene, 

Ortho-xylene resembles benzene and toluene in its general 
properties, but boils at 142°. 

Meta-xylene boils at 137°. It is the principal constituent 
of commercial xylene. 

Para-xylene boils at 136° to 137^ 

These hydrocarbons have also been obtained from toluene 
by means of the reaction made use of for the purpose of con- 
verting benzene into toluene : — 

CgH4 < g"' + CH3I + 2 Na = CeHi < ^Jj» + NaBr + NaL 



266 BENZENE SERIES OP HYDROCARBONS 

This shows that they are all methyl-toluenes. There are 
three mono-brom-toluenes, known as ortho-, meta-, and parar 
brom-toluene. For the preparation of ortho-xylene, ortho- 
brom-toluene is used; meta-brom-toluene yields meta-xylene, 
and para-brom-toluene yields para-xylene. 

Ortho- and meta-xylene have also been obtained from certain 
acids, which bear to them the same relation that benzoic acid 
bears to benzene : — 

fCHa 
GeHA CH3 = C«H4(CHs), + CO,. 
ICOsH 

The reaction by which meta-xylene is formed from mesitylenio 
add is of special importance, as will be pointed out. 

By oxidation, the xylenes undergo changes like that which 
is illustrated in the formation of benzoic acid from toluene, 
consisting in the transformation of methyl into carboxyl. 

The first change gives acids of the formula C6H4<^^^_, one 

C/U2H 

corresponding to each xylene. By further oxidation, these 
three monobasic acids are converted into dibasic acids of the 

CO H 

formula C6H4< J^ Thus, we have the three reactions, all 
of the same kind: — 

(1) C6H,.CH3 -f-30 = C6H5.C02H -|- H^O; 

(2) CeH,<^JJ« +30 = CeH,<^^Jj-|.H,05 
and (3) CeH^ < ^^'^ -(- 3 = CeH, < ^ JJJ + HA 



CH 

The three monobasic acids of the' formula C6H4< ^ are 

CU20. 

known as ortho-toluic, metortoluic, and parortoluic acids re- 
spectively; and the three dibasic acids obtained from them 
are known as ortho-phtkaliCf meta-phthalic, and para-phthaUe 
acids. Starting thus with the three brom-toluenes, we get, 



XYLENES 267 

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 orthoy meta, and 
para. In a similar way, all di-substitution products of ben- 
zene are designated. We therefore have three series into 
which all di-substitution products of benzene can be arranged ; 
and these are known as the Ortho-series,' the MetOrseries, and 
the Para-series, In arranging them in this way, we may 
select any prominent di-substitution product, and call it an 
ortho compound; and then call one of its isomerides a meta 
compound, 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 di-substitution 
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 compound 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. 
Now, to repeat, any di-substitution product of benzene which 
can be converted into ortho-xylene or into ortho-phthalic acid 
is regarded as an ortho compound, etc. 

This classification of the di-substitution 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., pp. 261, 262) 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 di-substitution products, the answer for the rest will 



268 BENZENE SERIES OF HYDROCARBONS 

follow. To reduce the problem to simple terms, therefore, 
let us take the three xylenes. We have three xylenes and 
three formulas: How can we determine which particular for- 
mula 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 mono-substitution 
products can be obtained from each. The formulas are : — 

CII3 CH3 CH3 

... 

(4)HC'^ ^C.CHj (4)HC^ ^CH(1) (4)HC^ ^CH(l) 



I I I 

(3)HC^ /CH(1) (3)HC,^ /CCH3 (3)HCs^ /CH(2) 

(2) (2) ^^' 

Formula I. Formula II. Formula III. 

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, 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 kind of mono-substitution product. On studying the 
xylenes, we find the one which boils at 136° to 137**, called 
para-xylene, yields but one kind of mono-substitution products ; 
that is, we can get from it only one mono-brom-xylene ; only 
one mono-nitro-xylene, etc. We therefore conclude that para- 
xylene is represented by formula III. above ; and, further, that 
formula III., on p. 262, is the general expression for all para 
compounds. 

Examining formula I. in the same way, we see that H (1) 
and H (4) bear the same relation to the molecule; and that 



ETHYL-BENZENE 269 

H (3) and H (2) also bear the same relation to the molecule, 
though different from that of H (1) and H (4). Two chlor. 
xylenes of the formulas 

CH3 CH, 

I I and I I 

HCv /CCl HCv /CH 

H CI 

ought to be obtainable from the xylene of formula I. 

In the same way three mono-substitution products should be 
obtainable from the xylene of formula IL The method, the 
principle of which is thus indicated briefly, while theoretically 
simple enough, is very difficult in its application, except in the 
case of the para compounds. Other methods have therefore 
been used, and these will be discussed under mesitylene and 
naphthalene. It may be said, in anticipation, that the result 
of all observations point to formula I. for ortho-xylene, to 
formula II. for meta-xylene, and to formula III. for para- 
xylene. 

Ethyl-benzene, OgHioCOeHs.OaH^). — This hydrocarbon is 
isomeric with the xylenes, but differs from them in that it con- 
tains 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 is made by treating a mixture of brom-benzene 
and ethyl bromide with sodium : — 

CeHfiBr -f- CgH^Br + 2 Na = CeH^ . C2H5 + 2 NaBr. 

Its conduct toward 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 



270 BENZENE SERIES OF HYDROCARBONS 

is, it is oxidized to carboxyl, carbou dioxide, and water. 
Thus, the conversions indicated below take place: — 

C6H5.CH3 gives CeHs.COjH. 

C6H5.C2H5 « CeHj.CO^H. 

CflH^.CaHy " C6H5.CO2H. 

Mesitylene,09Hi2[OeH8(OH8)8]. — 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 CgHgO = C9H12 + 3 H2O. 

It can also be made by treating methyl-acetylene, CHg.C =CH, 
with sulphuric acid, the action in this case being perfectly 
analogous to the polymerization of acetylene : — 

3CH:CH = CeHe; 
3 CH3. C : CH =: 0^118(0113)3. 

It is a liquid resembling the lower members of the series in its 
general properties. It boils at 163°. 

Its conduct towards oxidizing agents shows that it is a tri- 
metkyUbenzene. When boiled with dilute nitric acid, it yields 
mesitylenic acid, O9H10O2 and uvitic acid, O9H8O4; and, by 
further oxidation, trimesitic acid, O9H6O6, is formed. By dis- 
tillation with lime, mesitylenic acid yields meta-xylene 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 may be represented 
by the equations following : — 



MESITYLENE 



271 



CHaCCHg), +30 

MeBltylene 

(CH3 

CgH,]CH, +30 
(COsH 

Mesitylenic acid 

(CH3 

C,H3.]C0sH + 30 
(CO2H 

ITTitic acid 

^CHs 
CgHgK CHg 
(COjH 

Mesitylenic acid 

(CHg 
CgHg-jCOjH 
(CO2H 

tTviUc acid 

( COjH 

CgHg ] CO2H 

(.OOsH 

Trimesltic acid 



CHg 
CgHg { CHg + H.0 ; 
COjH 

Mesitylenic acid 

(CHg 
CgHg ] CO^H + HjO ; 
(cOjH 

Uvitlc acid 

(COjH 
CHgjCOaH + HjOj 
(.COjH 

Trimesitic add 



= CgHi 



(CHg 
ICHg 



+ C0,; 



Meta-xylene 



CH.. CHg + 2 CO,; 

Toluene 



CgHg -f- 3 CO2. 

Benzene 



These transformations show clearly that mesitylene is tri- 
methyl-benzene, but they do not show in what relation the 
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 
appeal's probable that each of the three molecules of acetone 
taking part in the reaction, 

3 CsHgO = 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: — 



272 BENZENE SERIES OF HYDROCAEBONS 

CHs- CO - CH3= CH3 - C = CH + HA 

Acetone 

We thus have three molecules of methyl acetylene, 
CH3 — C = CH, 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 : — 



CH 



8 



HC/ ^CH 

II I 

XI3O • Cv jy<j • 01x3 

H 

According to this reasoning, mesitylene is a symmetrical com- 
pound, — 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 replacing the three hydrogen 
atoms of the benzene residue successively by bromine ; and it 
has been found to be correct, as but one mono-bromine substi- 
tution-product of mesitylene has ever been obtained. Accept- 
ing the formula above given for mesitylene, an important 
conclusion follows regarding the structure of meta-xylene. 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 converted into 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 

I I 

CO2H . Cv yfC . CH3 

\c/ 

H 



PSEUDOCUMENB 273 

Now, by distilling this acid with lime, carbon dioxide is given 
off, and meta-xylene is produced. 

As the change consists in removing the carboxyl, and re- 
placing it by hydrogen, it follows that meta-xylene must be 
represented by the formula 



CH 



3 



I I 

H 

and consequently that, in all meta compounds, the two substi- 
tuting atoms or groups bear to each other the relation which 
the two methyl groups bear to each other in this formula for 
meta-xylene. 



Pseudooumene, Q^^^Q^JSjB^^* — This hydrocarbon, 
which is isomeric with mesitylene, occurs in coal-tar oil, from 
which it can be made in pure condition. Its properties are 
similar to those of the lower members of the series. It boils 
at 169.8°. 

Pseudocumene has been made synthetically from brom-para- 
xylene and methyl iodide, and also from brom-meta-xylene and 
methyl iodide. How this is possible, will be understood by an 
examination of the formulas below : — 

CHg CH3 

Hc/ \CH HC/ \CH 

II II 

HCv XBr HCv .CCHj 

CH3 ^r 

Brom-i»rE-xyl«M» Brom-meta-xylene 



274 BENZENE SERIES OF HYDROCARBONS 

Replacing the bromine by methyl, in either of the compounds 
represented, the product would have the formula 

CHs 

I 1 

CH3 
which is that of pseudocumene. 

Oymene, -i^ „ (Q-a^OB.^^.^ 

Para-methyl-isopropyl-benzene, / ^^ u\^«^^ O^J 
This hydrocarbon is of special importance and interest, on 
account of its close connection with two well-known groups of 
natural substances, — the groups of which camphor and oil of 
turpentine are the best-known representatives. It occurs in 
the oil of caraway and the oil of thyme. The terpenes are 
hydrocarbons of the formula CioHje, of which oil of turpentine 
is the best known. This substance easily gives up two hydro- 
gen atoms and yields cymene when heated with iodine. Proba- 
bly the simplest way to prepare cymene is to treat camphor 
with phosphorus pentasulphide, zinc chloride, or phosphorus 
pentoxide. 

It is a liquid of a pleasant odor. It boils at 175°. 

It has been made synthetically from para-brom-toluene and 
isopropyl bromide : — 

CeH, < ^' + CsH^Br + 2 Na = CeH^ < ^ h + ^ ^^^''^ 

which cleai'ly shows its relation to benzene. As the final 
product of its oxidation, it yields para-phthalic (terephthalic) 
acid: — 

6H4 < * gives C«Hi < ^^^jj ; 

see page 270. 



TETRAHtDROBENZENES 275 

Hexahydrobenzenes, Naphthenes 

Caucasian petroleum consists principally of a mixture of 
hydrocarbons that have been found to be hydrogen addition- 
products of members of the benzene series. They are oils that 
can be converted into members of the benzene series by passing 
them through tubes heated to a red heat. They do not react 
with concentrated nitric or sulphuric acid, and in this respect 
they differ markedly from the benzene hydrocarbons. They 
. are called naphthenes. 

Hexamethylene, hexanaphthene, 0H2< -,__^" __^>OHn. 

(Jxi2 • Uxi2 

— This is found not only in Caucasian petroleum but in the 

petroleum from other sources. American petroleum contains 

it in small quantity. It can be made artificially by reducing 

CTT PIT 
iodo-cyclohexane, IHC<^Tj.^' ^Tj^>CH2. ^^ ^s formed by 

reducing benzene with hydrogen in the presence of hot, finely 
divided nickel. The product formed when benzene is treated 
with concentrated hydriodic acid is methyl-pentamethylene, 

<CH2. CH2 
I . 
CH2 • Cxij 
Other hydrocarbons of this series are hexahydrotoluene or 

CH CH 
heptanaphthene, CHg . CH < ^^ ' ^^ > CH2, hexahydroxylene 

O JI2 . 0X12 

or octonaphthene, (CH8)2C6Hio, etc. 

Tetrahydrobenzenes 
The simplest hydrocarbon of this group is tetrahydrobenzene, 

Cxl2 • Cxi2 . CIl 

I II . It is formed from brom-cyclohexane by elim- 

CH2 . CH2 . CH 

inating hydrobromic acid. 

Tetrahydrotoluene, CHs . GeH^, is contained in the essence 
of resin. 



276 BENZENE SERIES OF HYDROCARBONS 

Hydrocarbons, OioHig. — There are several hydrocarbons 
of the formula CioHig known that belong to the series of tetra- 
hydrobenzenes. The principal ones are related to the terpenes 
(which see). 

DiHYDBOBENZENES 

A number of the members of this group have been made, as, 
for example, dihydrobenzene, CeHg, dihydrotoluene, C7H10, di- 
hydroxylenes, CgHig, etc. 

Dihydro-o-xylene, or cantfiarene, (C'H.^)2GJi^f is formed by 
heating cantharic acid, C10H12O4, with lime. 



CHAPTER XV 

DERIVATIVES OF THE HYDROCARBONS, CaHgo-e, 
OF THE BENZENE SERIES 

Recalling what has been learned under the head of De- 
rivatives of the Paraffins, we should naturally look for repre- 
sentatives of all the classes of compounds there met with. 
The derivatives of the paraffins were classified as: — 

1. Halogen derivatives. 

2. Oxygen derivatives, including the Alcohols, Aldehydes, 

Acids, etc. 

3. Sulphur derivatives, including the Mercaptans, Sulphonic 

Acids, etc. 

4. Nitrogen Derivatives, including Cyanides, Amines, Nitro 

compounds, etc. 
6. Metallic derivatives. 

The derivatives of the benzene hydrocarbons may be classi- 
fied in the same way, but a change in the order of treatment 
will be somewhat more convenient, owing to many points of 
analogy between the halogen substitution-products, the nitro 
compounds, and the sulphonic acids. All these three classes 
of derivatives of the benzene hydrocarbons are made by direct 
treatment of the hydrocarbons with the substituting agents, 
and in some respects resemble one another, so that they will 
be studied in connection. As the amino derivatives of this 
series are made almost exclusively from nitro compounds by 
reduction, they will be^taken up in connection with the nitro 
compounds; and, further, by treatment of the amino com- 
pounds with nitrous acid, a new class of nitrogen derivatives, 

277 



278 DERIVATIVES OF THE BENZENE SERIES 

known as diazo compounds, not commonly met with in connec- 
tion with the paraffins, is formed. These will be taken up 
after the amino compounds. 

After these classes have been studied, the oxygen derivatives, 
which include the phenols or simple hydroxyl derivatives of 
the hydrocarbons, the alcohols, aldehydes, acids, and ketones 
will be taken up in turn ; and, finally, the hydroxy-acids, which 
are strictly analogous to the hydroxy-acids of the paraffin series. 

There are thus the following classes : — 

1. Halogen derivatives, 5. Sulphonic acids, 9. Acids, 

2. Nitro compounds, 6. Phenols, 10. Ketones ( and 

3. Amino compounds. 7. Alcohols. Quinones), 

4. Diazo compounds. 8. Aldehydes, 11. Hydroxy-acids. 

The relations of most of these classes to the hydrocarbons 
are the same as those of the corresponding derivatives of the 
paraffin series to the paraffins ; and the general methods of 
preparation, as well as the reactions, are the same. Hence, 
most of the knowledge acquired in the first part of the course 
may be applied to the series now under consideration. 

An enormous number of derivatives of the benzene hydro- 
carbons have been prepared and studied, but only very few 
need to be studied in order to make the chemistry of all of 
them clear. In the following a few of the more important 
representatives of each class will be presented, mainly with 
the object of illustrating general facts and general relations. 

Halogen Derivatives of Benzene 

Very little need be said in regard to these derivatives. By 
direct action of bromine or chlorine upon benzene the hydrogen 
atoms are replaced one after another, until, as the final products, 
hexorchlor-henzene, CgCle, and hexa-brom-henzene, CeBrg, are ob- 
tained. When the action takes plfice in direct sunlight, 
addition-products, CeHeClg and CgHeBre, are formed. Benzene 



HALOGEN DERIVATIVES OF BENZENE 279 

hexachloride, CeHgCle, is formed also when chlorine is con- 
ducted into boiling benzene. The addition-products are decom- 
posed, yielding tri-substitution products of benzene and halogen 
acid: — 

CeHeBrg = CeHaBrg -f- 3 HBr. 

The substitution-products are very stable. They are, as a 
rule, formed more easily than the halogen derivatives of the 
paraffins, and, as a rule, they do not give up the halogens as 
readily. Thus, while it is possible in the paraffin derivatives 
to replace chlorine and bromine by hydroxyl, the amino group, 
etc., these replacements cannot easily be effected in the benzene 
derivatives. The halogens can be removed by sodium, as 
shown in the synthesis of hydrocarbons : — 

CfiHaBr -f CH3I 4- 2 Na = CgHs . CH3 -f- NaBr + Nal, etc. 

They can also be removed by nascent hydrogen, the hydrocar- 
bons being regenerated : — 

CeH^Cla -F 4 H = CeHg -f- 2 HCl. 

This kind of reverse substitution is easily effected by means of 
alcohol and metallic sodium. 

. Chlor-benzene, CeHsGl. — Chlor-benzene can be made by 
treating benzene with chlorine, but the action is slow. The 
action is much hastened by adding a little iodine or ferric 
chloride. These substances act as carriers, and are found prac- 
tically unchanged at the end of the operation. Chlor-benzene 
can also be made by boiling a diazonium salt (which see) with 
hydrochloric acid : — 

CeH^lSr.Cl 4- HCl = CeHfiCl -F Ng -f- HCl. 

Brom-benzene, OeHsBr. — This is made by the same meth- 
ods as those used in making chlor-benzene. 

When brom-benzene in solution in ether is treated with mag- 
nesium powder, it forms a compound of the formula CaHgMgBr 



280 DERIVATIVES OF THE BENZENE SERIES 

(see Grignard's reactions, p. 106). This reacts with methyl 
bromide to form methyl-benzene or toluene, thus : — 

CeH^MgBr + BrCHg = CeH^.CHs + MgBr^. 

lodo-benzene, CgHsI. — This can be made by treating ben- 
zene with iodine and iodic acid : — 

5C«H6 + 4I + HI08 = 5C6H5l+3H20; 

but it is most easily made through the diazonium salt. It is a 
liquid that solidifies at — 30°. 

Phenyliodoso chloride, OeH5lCl2. — This compound is 
formed when iodo-benzene in chloroform solution is treated with 
chlorine. When it is treated with caustic potash, it is converted 
into iodoso-benzene, OgHsIO. This has basic properties, and 
forms salts that are derived from the hypothetical base, 
C6H5l(OH)2, as, for example, C6H5l(O.CO.CH3)2. 

lodoxy-benzene, GeH5l02, is formed from iodoso-benzene, 
either by heating it alone or by boiling its water solution : — 

2 CeHJO = CeHJ + 0^11,10^ 

Diphenyliodoniuin hydroxide, (06H6)2l.OH. — This Re- 
markable substance is formed when a mixture of iodoso- and 
iodoxy-benzene is shaken with silver oxide and water : — 

CeHJO + C6H5IO2 4- AgOH = (C6H5)2 1 . OH + AglO^. 

It is strongly alkaline and forms salts that have many points 
of resemblance with the salts of thallium. 

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. Compounds of the 
same order are known in which sulphur plays the same part 
that iodine plays in the iodonium compounds, and nitrogen in 
the ammonium compounds. 



HALOGEN DERIVATIVES OF TOLUENE 281 

Dibrom-benzene, 06H4Br2, is one of the products of the di- 
rect treatment of benzene with bromine in the presence of a car- 
rier. This being a di-substitution 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 dibrom-benzenes is formed 
by direct treatment of benzene with bromine ? The answer to 
the question is equally interesting. The main product of the 
action is jparo-dibrom-benzene, while there is always formed in 
much smaller quantity some of the ortho product. The reason 
why these products are formed, and. not the meta compound, is 
imknown ; nor has any plausible hypothesis been suggested to 
account for the fact. 

In studying the substitution-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, as has been stated, by 
transforming the compounds into others, the relations of whose 
groups are known. Thus, to illustrate, when benzene is treated 
imder the proper conditions with bromine, two dibrom-benzenes 
are formed. Without investigation, we, of course, cannot tell 
to which series these compounds belong. But, by treating 
that product which is formed in larger quantity with methyl 
iodide and sodium, we get a para-xylene. In other words, by 
replacing the two bromine atoms of the dibrom-benzene by 
methyl groups, we get a compound which we know belongs 
to the para series; and, therefore, we have determined that 
the bromine product is a para compound. In the following the 
chief reactions made use of for effecting the transformations 
of the derivatives will be discussed. 

Halogen Derivatives op Toluene 

As toluene is made up of a residue of marsh gas, methyl, 
CHa, and a residue of benzene, phenyl, CeHg, it yields two 



282 DEUIVATIVES OK THE BENZENE SERIES 

classes of substitution-products: (1) Those in which the sub- 
stituting 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 tem- 
perature, toluene yields products of the second class ; while, 
when treated in the dark, or at ordinary temperatures, in the 
presence of iodine or some other carrier (see page 279), it yields 
products of the first class. Thus, we have the two parallel 
series of chlorine derivatives : — 



I 


II 


0^11401.0113. 


OgHa. OM2OI. 


06H3C12.CH3. 


OgHs.OHOla. 


03112013. 0H3. 


O6I13.OOI3. 



When a member of the first class is oxidized, the methyl is 
changed, and the rest of the compound remains unchanged, 
as in the case of toluene. Thus, the first substance of class I. 
yields the product OgH401.OO2H; the second, O6H3OI2.OO2H, 
etc. These products are substituted benzoic acids. On the 
other hand, all the members of the second class yield the same 
product that toluene does ; viz., benzoic acid. Hence, by treat- 
ment 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 benzene ring do not. When, for 
example, the compound O6H5.OHOI2, which is called benzal 
chloride, is superheated with water, both chlorine atoms are 
replaced by oxygen, the product being the aldehyde OoHj-OHO, 
which, as we shall see, is the familiar substance, oil of bit- 
ter almonds. When, however, the isomeric di-chlor-toluene, 
O6H3OI2.CH3, 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- 



NITRO COMPOUNDS OF BENZENE AND TOLUENE 283 

brom-toluene, C6H4Br.CH3, we see that they are di-substi- 
tution products of benzene, and hence capable of existing in 
three isomeric varieties, ortho, meta, and para. The prod- 
ucts formed by direct treatment of toluene with chlorine or 
bromine are mixtures of the para and the ortho com- 
pounds. 

The determination of the series to which one of these products 
belongs can be made by replacing the halogen by methyl, and 
thus getting the corresponding xylene. The main product of 
the action of bromine on toluene is thus converted into para- 
xylene, and is therefore para-brom-toluene. 

Halogen Derivatives op the Higher Members op 

THE Benzene Series 

Concerning the. halogen derivatives of xylene, it need only be 
said that the only one of the three xylenes from which pure 
products can easily be obtained is para-xylene. When this is 
treated with bromine, it yields but one mono-brom-xylene. The 
significance of this fact has been discussed above. The mono- 
substitution products obtained from the other xylenes are 
mixtures which it is very difficult, and in some cases impos- 
sible, to separate into their constituents. Mesitylene and 
pseudocumene, though both are tri-m ethyl-benzenes, conduct 
themselves quite differently towards bromine, — the former 
yielding only one mono-bromine product ; the latter, a mixture 
of several. 

Nitro Compounds op Benzene and Toluene 

In speaking of nitro compounds in connection with the paraf- 
fin derivatives (see p. 101), it was stated that they are obtained 
much more readily from the benzene hydrocarbons than from 
the paraffins. Only a few nitro derivatives of the paraffins are 
known. As will be remembered, they cannot be prepared by 
treating the paraffins with nitric acid, but must be made by 



284 DERIVATIVES OF THE BENZENE SERIES 

circuitous methods, the principal one being the treatment of 
the halogen derivatives with silver nitrite : — 

CjHsBr + AgNOj = CgH^CNOa) + AgBr. 

Nitro-ethane 

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 strong nitric acid, when 
reaction takes place, and one or more hydrogen atoms of the 
hydrocarbon are replaced by the nitro group NOj, as repre- 
sented in the equations : — 

CeH^ + HNO = CeH^ . NO2 + H,0 ; 

CeH^.NOa + HNOg = C^HXNOa)^ +H2O; 

CeH^.CHg 4- HNO3 = CeH^ < ^^2 +H2O; 



CeH^ < g^2 + HNO3 = C6H3 < (^)' + HA 



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 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, nitro-benzene, CeH^ . NOo, gives aniline or amino-benzene, 
CgHs.NHg, which is a substituted ammonia similar to methyl- 
amine and ethyl-amine. As in these the radical is in com- 
bination with nitrogen, it is probable that the radical is in 
combination with nitrogen in the nitro compounds also, as 
shown in the formula, CgHs.NOj. Everything known about 
these nitro compounds is in harmony with this view. The 
formation of a nitro compound by the action of nitric acid on 
a hydrocarbon is represented thus : — 

CeH^ + HO . NO2 = CeH^ . NO3 + HaO. 



DLNITRO-BENZENB ' 285 

Mono-nitro-benzene, OeHg . NO2. — This substance is made 
by treating benzene with fuming nitric acid, or with a mixture 
of ordinary concentrated nitric and sulphuric acids. In the 
latter case, the sulphuric acid facilitates the reaction, probably 
by preventing the dilution of the nitric acid by the water 
necessarily formed. 

Experiment 57. Make a mixture of ||75<^ ordinary concentrated 
sulphuric acid, and 75<:<: ordinary concentrated nitric acid. Let it cool to 
the room temperature. Put the vessel containing it in water, and add 
about 15<:<' to 20<:<' benzene, a few drops at a time, waiting each time until 
the reaction is complete. Shake well until the benzene is dissolved, thea 
pour slowly into about a litre of cold water. A yellow oil will sink to the 
bottom. This is nitro-benzene. Pour off the acid and water ; wash two 
or three times with water ; separate the water by means of a pipette, and 
dry by adding a little granulated calcium chloride. After standing for 
some time, pour off from the calcium chloride, and distil from a proper 
sized distilling-bulb, noting the boiling temperature. 

Nitro-benzene is a liquid that boils at 209**, melts at 6**, and 
has the specific gravity 1.2. Its odor is like that of the oil of 
bitter almonds, and it is hence used in many cases instead of 
the latter. It is known as the essence ofmirbane. It is manu- 
factured on the large scale, and used principally in the prepa- 
ration of aniline. Its vapor is poisonous. 

Dinitro-benzene, 06H4(NO2)2 — This is a product of the 
further action of nitric acid on benzene, or on nitro-benzene. 

Experiment 58. Make a mixture of 50'^^ concentrated sulphuric 
acid, and SO^c fuming nitric acid. Without cooling add very slowly about 
10<»' benzene from a pipette with a fine opening. After the action is 
over, boil the mixture for a short time ; then pour into about half a litre 
of water. Filter off the solid substance thus precipitated, press it between 
layers of filter-paper, and crystallize from alcohol. 

Dinitro-benzene crystallizes in long, fine needles, or thin, 
rhombic plates. Melting-point, 90**. 

By means of two reactions, which will be described under 
the head of Diazo Compounds, it is a simple matter to replace 



286 DERIVATIVES OF THE BENZENE SERIES 

the two nitro groups by bromine, thus converting dinitro-ben- 
zene into dibrom-benzene. When the latter is converted into 
xylene, the product is meta-xylene. Hence, ordinary dinitro- 
benzene is a meta compound. 

Nitro-toluenes, OeHiCNOa) . OHs. — When toluene is treated 
with nitric acid, substitution always takes place in the phenyl. 
Over 50 per cent of the ortho product is formed, about 40 per 
cent of the para, and about 4 per cent of the meta. The 
higher the temperature, the larger the proportion of the ortho 
product formed. 

Note for Student. — What mono-bromine products are formed by 
direct treatment of toluene with bromine ? Given a mono-nitro-toluene, 
how is it possible to determine whether it belongs to the ortho, the meta, 
or the para series ? 

By treatment with nascent hydrogen, the nitro-toluenes are 
converted into the corresponding amino compounds, called 
Toluidines (which see). 

Amino Compounds op Benzene, etc. 

The amino derivatives of the paraffins are made, for the most 
part, by treating the halogen derivatives with ammonia : — 

CgHfiBr + NH3 = C2H5 . NH2 + HBr. 

In speaking of these derivatives, however, attention was called 
to the fact that they can also be made by treating nitro com- 
pounds with nascent hydrogen. The latter method is one of 
great importance in the benzene series. It is used exclusively 
in the preparation of the amino derivatives of the benzene 
hydrocarbons. Several of these derivatives are well known, 
the simplest and best known being amino-benzene or aniline. 

Aniline, OgH7N(0(.H6.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, 



ANILINE 287 

a product of the distillaticn of bones. It is prepared by re- 
ducing nitro-benzene with nascent hydrogen. On the large 
scale the hydrogen is obtained from hydrochloric acid, iron, and 
water. Only a small quantity of acid is required. After the 
reaction has started, the iron acts upon the water in the presence 
of ferrous chloride, yielding hydrogen and ferric hydroxide : — 

CeHsNOg 4- 2 Fe + 4 H2O = CeH^lSrHa + 2 Fe(0H)3. 

For laboratory purposes tin and hydrochloric acid are perhaps 
best. Other reducing agents, such as an ammoniacal solution 
of ammonium sulphide, hydriodic acid, etc., also effect the 
change, which is represented by the following equation : — 

CeH,. NO2 + 6H = C6H5.NH2 + 2H2O. 

Experiment 59. Arrange a litre flask with a stopper and a straight 
glass tube from two to three feet long. Put in the flask 85^^ granulated 
tin and about 4008 ordinary concentrated hydrochloric acid. Now add 
slowly 508 nitro-benzene. After the action is over, add enough water to 
dissolve the contents of the flask, then add sodium hydroxide until the 
precipitate first formed is nearly all dissolved. Distil, when aniline and 
water will pass over. Separate by means of a separating funnel. 

Aniline is a colorless liquid that soon becomes colored in 
the air. It boils at 182.5°. It solidifies at a low temperature 
and melts at — 8° ; it is easily soluble in alcohol, but slightly 
soluble in water. The solution in water has only a slight alka- 
line reaction. Aniline is poisonous. Its salts with strong 
acids have an acid reaction. 

Bxperlment 60. To an aqueous solution of a little of the aniline 
obtained in Exp. 59, in a test-tube, add a filtered solution of bleaching 
powder (calcium hypochlorite). A beautiful violet color is produced. 

To a solution of aniline in concentrated sulphuric acid add a small 
grain of potassium bichromate. A blue color is produced. 

Aniline bears to benzene the same relation that ethyl-amine 
or amino-ethane bears to ethane. It is a substituted ammonia, 
and, like other bodies of the same class, it unites directly with 



288 DERIVATIVES OF THE BENZENE SERIES 

acids, forming salts. Thus, with hydrochloric, nitric, and sul- 
phuric acids the action takes place as represented below : — 

CeH^.NHg + HCl = (C6H5.NH8)C1 ; 
CeH, . NH2 + HNOa = (CeH, . NH8)N08 ; 
CgH^ . NH2 + H2SO4 = CeH^ . NH3HSO4. 

The hydrochloride is known in the trade as aniline salt 
The decomposition of aniline hydrochloride by means of 

a caustic alkali takes place as represented in the following 

equation : — 

CeHfi . NHgCl + KOH = G,1I, . NHg + KjO + KCl. 

Derivatives of Aniline. — Aniline is much more sensitive 
to the action of reagents then benzene or its halogen or nitro 
derivatives. Substitution takes place easily, but there is danger 
that the aniline will be decomposed by the substituting agent. 
Among the substitution-products that find extensive applica- 
tion is one of the sulphonic acids. 

Dimethyl-aniline, 06H5N(CH3)2. — When aniline is treated 
with methyl bromide and similar halogen derivatives of the 
paraffins, residues of the paraffins are introduced into the 
aniline in place of the ammonia hydrogen atoms : — 

C6H5.NH2 4-CH3Br= (C6H5.NHCH3).HBr; 
CgHs .NH2 + 2 CHsBr = [CeH^ . N(CH3)2] . HBr + HBr. 

Of the compounds obtainable by this method, dimethyl-aniline 
is the most important from the technical point of view. It is 
prepared by a modification of the above method — by heating 
aniline with hydrochloric or sulphuric acid and methyl alcohol 
in a closed vessel : — 

CeHg . NH2. HCl 4- CH3OH = CeHs . NHg -f CH3CI + HjO ; 
CeHfi . NH2 + CHgCl = CgH^ . NH(CH8) . HCl ; 
C6H5.NH(CH8).HC1 4- CH3OH = C6H5.]Sr(CH3)2.HCl + HjO. 

It is a liquid that boils at 192°, and solidifies at 0.5°. 



TOLUIDINES 289 

Diphenylamine, (C6H5)2NH.— This is another example 
of the possibilities presented by aniline. As will be seen, 
diphenylamine is formed from aniline by the introduction of a 
phenyl group, CgHg, for one of the ammonia hydrogen atoms. 
It is prepared on the large scale, and finds extensive use in 
the manufacture of dyes. The reaction made use of consists 
in heating aniline with aniline hydrochloride at 200°: — 

CeHfi. NH2 + CeHs . NH^ . HCl = CgH^ . NH . CeHg + NH^Cl. 

It is a solid that crystallizes in white laminae from ligroin. 
It melts at 54° and boils at 302°. It forms salts with strong 
acids, but these are decomposed by water. 

Aoetanilide, CeH^ . NH . COCH3. — 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 . COCl + NH3 = CH3. CONH2 + HCl ; 
CH3 . COCl + NH2 . Ceils = C H3 . CO . NH . CgH^ + HCl. 

Acetanilide is more easily prepared by boiling aniline with 
glacial acetic acid for 24 hours : — 

CH3. COOH + NH2. CeHs = CH3. CO.NH. CfiHa + H2O. 

Acetanilide crystallizes from water in large, colorless plates. 
It meits at 115° and boils at 304°. It is used in medicine 
under the name antifebnne, 

Toluidines, amino-toluenes, C6H4< ij^ ' "~The toluidines, 

of which there are three corresponding to the three nitro- 
toluenes, are made from the latter in the same way that aniline 
is made from nitro-benzene. As para-nitro-toluene is the best 
known of the three nitro-toluenes, so para-toluidine is the best 
known of the three toluidines. 

The properties of the toluidines are much like those of 
aniline. 



290 DERIVATIVES OF THE BENZENE SERIES 

Treated with various oxidizing agents, a mixture of aniline 
and the toluidines is converted into a compound known as 
rosaniline. This is the mother substance of the large group 
of compounds known as the aniline dyes, Eosaniline and its 
derivatives, the aniline dyes, will be treated under Tri-phenyJr 
methane (which see). 

Nitrous acid converts the salts of the toluidines into diazo- 
nium compounds analogous to those formed from aniline salts 
(see Diazo Compounds). 

The xylidines bear to the three xylenes the same relation 
that aniline bears to benzene. It is not a simple matter to get 
any one of them in pure condition. 

DiAzoNiuM Compounds of Benzene 

The usual action of nitrous acid on amino compounds is 
represented by the equation, — 

E.NH2 + HN02 = E.0H + H2O + N2. 

When an amino derivative of a hydrocarbon of the benzene 
series is treated with nitrous acid at low temperatures, a prod- 
uct is obtained which contains two nitrogen atoms, and which 
is, therefore, called a diazo compound. Thus, in the case of 
aniline sulphate, the action is represented by the equation, — 

CeHfiNHg. H2SO4 + HNO2 = CeH^Na. HSO4 + 2 HgO. 

Aniline sulpliate Benzene-diazoniam sulphate 

So, also, with the nitrate we have, — 

CeHaNHa. HNOa + HNOg = CgH^Na. NO^ + 2 H^O. 

Aniline nitrate Benzene-diazonium nitrate 

The salts thus formed are called diazonium salts for reasons 
which will presently be given. The method here given for 
the preparation of benzene-diazonium nitrate is not the one used 
by the discoverer. He passed nitrogen trioxide into an emul- 
sion of the amino compound in alcohol. If a solution of the 
diazonium salt is wanted, which is generally the case, the eaJ- 



DIAZONIUM COMPOUNDS OF BENZENE 291 

Ciliated quantity of sodium nitrite is added in water solution 
and then the calculated quantity of hydrochloric acid to de- 
compose the sodium nitrate. Thus action is secured between 
the aniline salt and the nitrous acid as it is set free. If the 
dry diazonium salt is wanted, the salt to be diazotized may be 
suspended in glacial acetic acid or absolute alcohol and ainyl 
nitrite slowly added. Here too the nitrous acid acts as it is 
set free from the amyl nitrite. For the purposes of study the 
sulphate may be used. 

Experiment 61. Dissolve 15s aniline in 9-10 times this weight of ab- 
solute alcohol (in any case this should not be of less strength than 95 per 
cent) ; add slowly 208 concentrated sulphuric acid. A thick paste of aniline 
sulphate separates at first, but on further and somewhat more rapid addi- 
tion of the rest of the sulphuric acid the precipitate first formed passes again 
into solution. The solution thus obtained is allowed to cool down at least 
to the temperature of the room, but it should not be cooled so low as to 
cause a separation of aniline sulphate. Now add 20s amyl nitrite, which 
is a little more than the calculated quantity. During the process the tem- 
perature rises only slightly, and even this can be prevented by cooling the 
vessel in water. In 10-15 minutes the benzene-diazonium sulphate separates 
in beautiful needles, and the whole mass solidifies, forming a crystalline 
paste. Filter with the aid of a pump and wash with a little alcohol and 
ether. If, after the addition of the amyl nitrite, the crystalline paste is 
not formed in about 16 minutes, add a few drops of ether. The reaction 
involved is represented by the following equation : — 

C6H6N.SO4H + CfiHiiNOg = C6H5N.SO4H + CsHiiOH -h H2O. 

Ill III 

Ha N 

Aniline sulphate Amyl Benzene-diazonium Amyl 

nitrite sulphate alcohol 

With the benzene-diazonium sulphate thus obtained perform the ex- 
periments described below. 

(a) Dissolve a little of the salt in water at the ordinary temperature, 
and allow the solution to stand. Decomposition, indicated by change of 
color, and a marked change in odor will take place. 

(b) Boil a little with water in a test-tube, and notice the odor of 
phenol or carbolic acid. 



292 DERIVATIVES OP THE BENZENE SERIES 

(c) Boil a few grains with alcohol in a test-tube, and notice the ease 
with which the decomposition takes place. The chief product is ethyl- 
phenyl ether or phenetol, CcHg. O. C2H6. 

(d) Boil some with concentrated hydrochloric acid. Chlor-benzene is 
formed, which sinks to the bottom when water is added. 

In all these experiments a gas is evolved which can be shown to be 
nitrogen. Collect some, and show that it does not support combustion. 

(e) Heat a very little of the compound, dried by pressing in filter- 
paper, on platinum foil and note the detonation. 

The above experiments serve to indicate the instability of 
benzene-diazonium sulphate. This same instability is charac- 
teristic of all diazonium salts, and it is the ease with which 
they undergo a variety of changes that makes them so valu- 
able. The principal changes are : — 

1. That illustrated in Exp. 61 (6), which is brought about 
by boiling with water. The action is represented thus : — 

C6H^2.S04H -f- H2O = CeH^.OH -f N^ -f- H2SO4. 

Phenol 

2. That illustrated in Exp. 61 (c), which is effected by boil- 
ing with alcohol : — 

C6H5N2.SO4H -f C2H5.OH = CeHfi.O.CaHfi + 1^2 + H2SO4. 

Phenetol 

In some cases alcohol reacts in another way, thus : — 
EN2CI + C2H5OH = RH -f N2 + C2H4O + HCl. 

The result of this is the substitution of hydrogen for the 
diazo group. Sometimes both reactions take place with alcohol. 

3. That effected by hydrochloric acid as illustrated in Exp. 

C6H5N2 . NOa + HCl = CeH^Cl -f- N2 + HNOa- 

Mono-chlor-benzene 

This reaction is much facilitated by the addition of cuprous 
chloride (Sandmeyer's reaction). 



CONSTITUTION OF THE DIAZONIUM SALTS 293 

Benzene-diazonium chloride reacts with potassium iodide as 
shown in the equation : — 

CeH^NaCl + KI = CeH^I + KCl + N^. 

Changes similar to the last are effected by hydrobromic and 
hydriodic acids, the chief products being brom-benzene and 
iodo-benzene respectively. Here also the corresponding cuprous 
salts are of great assistance. 

From the above it follows that, if we have a compound con- 
taining a nitro group, we can, by making the diazonium salt, 
transform it (1) into the corresponding hydroxyl derivative; 
(2) into the corresponding chlorine, bromine, or iodine deriva- 
tive; or (3) we can make ethers containing such groups as 
C2H5O, CHgO, etc. These reactions involving the use of the 
diazonium salts have been used very extensively in the inves- 
tigation of the substitution-products of the benzene series. 

Note for Student. — How can the relation of the groups in dlnitro- 
benzene be determined by using the diazonium reactions ? 

Constitution of the Diazonium Salts. — The salts 
formed by the action of nitrous acid on aniline salts are 
salts of a strong base which are to be compared with the alkali 
salts. It has been shown by determinations of the freezing 
point and of the electrical conductivity of the solutions of 
these salts in water that they are broken down into ions in the 
same way as salts of strong bases. This suggests that they 
are analogous to ammonium salts, and the view that is most 
in accordance with all the facts is that represented by such 
formulas as the following: — 

CeH^.N - CI; CeH,. N -NO3; CeH^-N - HSO4. 

Ill III III 

As the salts are analogous to ammonium salts, they are called 
diazonium salts. According to this view they are to be regarded 



294 DERIVATIVES OF THE BENZENE SERIES 

as aniline salts into which a nitrogen atom has been introduced 
in place of three hydrogen atoms : — 



Ha N 

C6H,-N-N0, — ^ CeHj-N-NOa. 



H3 N 

Metallic Derivatives of Diazo-benzene and of Isodiazo- 
benzene. — When a diazonium salt is treated in the cold with 
caustic potash a potassium salt of the formula CgHs . N2 . OK is 
formed. When this is treated with ethyl iodide it gives an 
ether of diazo-benzene, CeH^ . No . OC2H5. The fact that the 
ethyl in this compound is in combination with oxygen is shown 
by the character of the products formed when it is decomposed. 
It does not yield ethylamine as it would if the ethyl were in 
combination with nitrogen. When the above-mentioned potas- 
sium salt is treated with phenols (which see), it reacts with 
them at once, forming azo compounds (which see). 

When the ordinary potassium salt of diazo-benzene is heated 
with concentrated caustic potash at 130°, it is converted 
into the isomeric compound, potassium iso-diazo-henzene oxide, 
by molecular rearrangement. This does not easily give azo 
compounds with phenols. With ethyl iodide it gives a com- 
pound in which the ethyl is in combination with nitrogen. It 

C H 
is a nitroso compound of the formula CgHfi.N < '^^ \ 

The facts above stated suggest that the ordinary or normal 
potassium diazo-benzene oxide has the structure represented by 
the formula CgHg — N^ — OK, that the isomeric compound has 
the formula CeHg — NK.NO, and that they are derived from 
the two compounds : — 

CgHfi . N2 . OH ; CeHfi . NH . NO. 

Diazo-benzene hydroxide Phenyl nitrosamine 



DIAZO-AMINO COMPOUNDS 



295 



It has been suggested that the two potassium salts and 
other similar salts are stereoisomeric, as represented in the 
formulas : — 



an. - N 



an, - N 

II 



'6 



KO.N 

Normal potassiuiii-diozo-benzene oxide 



N.OK 

Potassium iso-diazo-benzene oxide 



By way of explanation of these formulas, it should be said 
that they involve the conception that the nitrogen atom exerts 
its affinities 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 : — 




or 




There are two ways in which the groups or atoms X and Y 
can be arranged in space, or there should be two isomeric forms 
of compounds containing a group of two nitrogen atoms of the 
form — N= N — . 

Further evidence is necessary to determine which of the two 
views presented is correct. 



Diazo-amino Compounds. — When a diazonium salt reacts 
with an amino compound a diazo-amino compound is formed, 



/ 



296 DERIVATIVES OF THE BENZENE SERIES 

as, for example, when benzene-diazonium chloride acts upon 
aniline : — 

As will be seen, the residue of the diazonium salt takes the place 
of one of the hydrogen atoms of the amino group. Diazo-amino- 
benzene forms golden yellow laminae or prisms. It is insoluble 
in water, but readily in hot alcohol. When heated with aniline 
hydrochloride it is transformed into aminoazo-benzene : — 

CeH, . N2 . NH . CeH, -^ QH^ . Ng . C6H4 . NHj, 

Other diazo-amino compounds act in the same way. The 
product formed in the above case is an amino derivative of 
a compound, CeHg . !N"2 . CeH^, known as azo-benzene. 

Azo-benzene, CgHg • Ng • CeH^, is formed by partial reduc- 
tion of nitro-benzene in alkaline solution, as by treating with 
an alcoholic solution of caustic potash. It crystallizes from 
alcohol in orange-red, orthorhombic crystals. Reducing agents 
convert it into hydrazo-benzene, CgHg . NH . NHCgHg. Azo cotw- 
pounds are, in general, highly colored, and many of them are 
used as dyes. Those that are useful in this way are deriva- 
tives of the simple azo compounds, especially those containing 
the amino and hydroxyl groups. Some of them will be treated 
of in other connections. 

Hydrazo-benzene, OgHg . NH . NH . OgHg, is formed by re- 
duction of azo-benzene. It is made by reduction of nitro- 
benzene by means of zinc dust in alkaline solution, without 
isolating the azo-benzene which is formed as an intermediate 
product. It forms colorless laminae, is scarcely soluble in 
water, but easily in alcohol and ether. Under the influence 
of mineral acids, hydrazo-benzene is transformed into the iso- 
meric benzidine J 

C«H,.NH CgH^.NHg 

I — ^ I 
CeHs . NH CgH^ . NHg. 

Uydrazo-b«nzen« Beuzidina 



PHENYLHYDRAZINE 297 

Reduction-products of nitro-benzene. — The final re- 
duction-product of nitro-benzene is amino-benzene or aniline^ 
but by regulating the conditions, a number of intermediate 
products can be obtained. In addition to those already men- 
tioned there are two others, azoxy-benzene^ CgHa . NgO . CeHg, and 
phenylrhydroxylamine, CgHa . NH (OH). 

The following table will serve to emphasize the relations be- 
tween most of these products : — 

CeH^.NOa C6H5.NV CeH^.N CeH^.NH CeH^.NH, 

I >0 II I 

Nitro-benzene Azoxy-benzene Azo-benzene Hydrazo-benzene Aniline 

These compounds are representatives of classes of similar 
structure and properties. 

Hydrazines 

Hydrazo-benzene is a derivative of hydrazine, NHg . NHg, and 
may be called symmetrical diphenylhydrazine in view of the 
fact that the two phenyl groups contained in it are symmetric- 
ally distributed, as shown by the formula, CeHa . NH . NH . CeHg. 
The simplest representative of the class of aromatic hydrazines 
is phenylhydrazine, CgHs . NH . NHg, a compound which, as has 
been seen, has played an important part in the investigation of 
the sugars. 

Phenylhydrazine, OeH^. NH. NHg — This is formed by 
the reduction of diazonium salts : — 

CeH^ . NgCl + 4 H = CeH^ . NH .NH^ . HCl. 

Benzene-diazonium chloride Phenylhydrazine hydrochloride 

CeHs . NH . NH2 . HCl + NaOH = CeH^ . NH . NH, + NaCl + 

H2O. 

It is a yellow oil which, when cooled, forms crystals that melt 
at 23°. It boils at 233°. It finds extensive application in 



298 DERIVATIVES OF THE BENZENE SERIES 

the manufacture of antipyrine, a somewhat complicated com- 
pound much used in medicine. 

Phenylhydrazine is a monacid base, and forms well-charac- 
terized salts. It reacts with aldehydes and with ketones, form- 
ing phenylhydrazones, and with aldoses and ketoses, forming 
phenylosazones (see p. 194). 

Methylphenylhydrazine, OgHj . NOH3 . NHg, is made by 
treating methylaniline with nitrous acid and reducing the 
nitroso compound thus formed: — 

It reacts with ketoses to form osazones, but with aldoses it 
does not form osazones, and, therefore, it can be used to dis- 
tinguish between these two classes of sugars. 

SuLPHONic Acids of Benzene, etc. 

The methods of preparation of the sulphonic acids, and the 
relations of these acids to the hydrocarbons, were pretty fully 
discussed in connection with the paraflB.ns. Three general 
methods for their preparation were given. These are : — 

1. Oxidation of the mercaptans ; thus, ethyl-sulphonic acid 
is formed by oxidation of ethyl-mercaptan : — 

CgH, . SH + 3 = C2H5 . SO3H. 

2. Treatment of a halogen substitution-product with a sul- 
phite : — 

CgH^Br -f NagSOg = C2H5 . SOgNa + NaBr. 

3. Treatment of a hydrocarbon with sulphuric acid. This 
method is not applicable to the paraffins, but is the one used 
almost exclusively in the case of the benzene hydrocarbons. 
This reaction is characteristic of the aromatic compounds 
Benzene-sulphonic acid is formed thus : — 

CeHe + H2SO4 = CeH5 . SOgH + H^O. 



BENZENE-SULPHONIC ACID * 299 

Toluene-sulphonic acid is formed thus : — 

CfiHj . CH3 + H2SO4 = C6H4 < ^^ „ + H2O. 
The constitution of sulphonic acids is discussed on p. 77. 

Benzene-sulphonio acid, OeHgSOg ( ^^^ > SO2) . — This 

acid is made by treating benzene with sulphuric acid. Simi- 
larly, and more easily, toluene-sulphonic add, C7H7 . SO3H, is 
made from toluene. 

Experiment 62. In a flask bring together about 60^ toluene and 
100''*' concentrated sulphuric acid (ordinary). Heat on a water-bath and 
shake until most of the toluene is dissolved. Pour the contents of the 
flask into a large evaporating dish of at least 8^ to 10^ capacity, contain- 
ing 41 to 51 water. Heat gently, and add gradually, stirring meanwhile, 
finely-powdered chalk, until the solution has become neutral. Pass 
through a muslin filter attached to a wooden frame, and wash thor- 
oughly with hot water. Afterwards refilter the filtrate through a paper 
filter. Evaporate to quite a small volume (say 500«« to 700«c), and filter 
from gypsum. In solution there is now the calcium salt of the sulphonic 
acid. Add just enough of a solution of sodium carbonate to precipitate 
exactly the calcium ; filter off from the calcium carbonate, and evaporate 
to dryness, finally, on the water-bath. To prevent caking it is necessary 
to stir the thick, syrupy mass. When it is nearly dry, it is best to 
powder it, and complete the drying at 100° to 120° in an air-bath. The 
sodium salt can be used for a number of experiments. 

Experiment 68. In a dry evaporating dish mix thoroughly 20s of 
sodium toluene-sulphonate with 258 of phosphorus penta-chloride, by 
means of a dry pestle. The mass becomes semi-liquid and hot, and 
hydrochloric acid is given off, in consequence of the action of the 
moisture of the air on the chlorides of phosphorus. Hence, the experi- 
ment should be performed under a hood or out of doors. The reaction 
is represented by the equation, — 

C7H7 . SOaONa + PCls = C7H7. SO2CI + POCls + NaCl. 

After the action is over, and the mass cooled down to the ordinary 
temperature, add about a litre of cold water. Everything will dissolve 
except the sulphon-chloride, C7H7 . SO-iCl, which will remain as a heavy 
oil at the bottom of the vessel. Four off the water, add about 600®" of 



300 DERIVATIVES OF THE BENZENE SERIES 

strong ammonia, and let stand. The chloride will thus be converted into 
the corresponding sulphon-amide, thus : — 

C7H7. SO2CI + 2 NHg = C7H7. SO2NH2 + NH4CI. 

After cooling, filter off the sulphon-amide ; wash well with cold w^ter, 
and crystallize from water. 

Note for Student. — Refer back to what was said regarding the acid 
chlorides and acid amides, paying particular attention to the general 
methods of preparation and their decompositions. 

Experiment 64, Mix 208 potassium cyanide with an equal weight 
of dry potassium toluenensulphonate, and distil from a small retort. The 
distillate is impure tolyl cyanide, C7H7.CN : — 

Put the tolyl cyanide in a flask of 300«« to 400«o capacity, and add a mix- 
ture of 60co water and 150'''' ordinary concentrated sulphuric acid. Heat 
on a sand-bath until the tolulc acid begins to appear in the form of fine, 
white needles in the neck of the fiask. On cooling, the acid will crystal- 
lize out. Pour off the liquid, and wash with cold water. Now crystal 
lize the acid once or twice from water. When pure, paratoluic acid 
melts at 177°. The reaction is represented by the following equation : — 

C7H7. CN -f 2 H2O = C7H7 . CO2H + NHs. 

Benzene-sulphonic acid itself is a very easily soluble sub- 
stance. It is a strong acid^ and yields a series of salts and 
other derivatives. 

When fused with potassium hydroxide, benzene-sulphonic 
acid is converted into phenol (Exp. 65, p. 304) : — 

CeH,. SOgK + KOH = CeH^. OH + K2SO3. 

By further treattaent of benzene with fuming sulphuric acid 
a benzene-disulphonic acid is formed. This is capable of the 
same transformations as the mono-sulphonic acid. 

Note for Student. — By what reaction could benzene-disulphonio 
acid be transformed into the corresponding dicarbonic acid, C6H4(C02H)2? 
Suppose the product obtained were meta-phthalic acid, what conclusion 
could be drawn with reference to the relation of the two sulpho groups, 
SO9H, in the disulphonic acid ? 



HELIANTHIN 301 

Sulphanilic acid, C^Bi4<^^ L.. — Concentrated sulphurio 

acid converts aniline into aniline sulphate, CgHgNHg . HSO4. 
When this is heated to 180° — 200® it is converted into the 

para-sulphonic acid, C6H4 < «/-i It/ v : — 

"NTT 
C6H5.NH3.HS04 = C6H4<g^^ + HA 

Sulphanilic acid is difficultly soluble in cold water, more easily 
in hot water. It crystallizes from a solution in water in ortho- 
rhombic plates. 

Like taurine, it is an inner ammonium salt, and should, 

therefore, be represented thus, C6H4< ^^ ^>. It is, however, 

a strong acid, while taurine is neutral. This is accounted for 
by the fact that aniline is a much weaker base than ethylamine. 
In taurine the basic portion has the power completely to neu- 
tralize the acid portion, while in sulphanilic acid this is not 
the case. Sulphanilic acid finds extensive application in 
the manufacture of dyes. 



Helianthin, orange III, tropaBolin D, is an example of 
the azo dyes already referred to. It is formed by the action 
of benzene-diazonium sulphonate on dimethyl-aniline. The 
benzene-diazonium sulphonate is made from sulphanilic acid : — 

SalphaniUo acid Benzene-diazonium sulplionat. 

^"» \S03-NH(CHs), 

Benzene-diazonium Dimethyl- Dlmethyl-amino-azo-benzene 

sulphonate aniline sulphonate 

The godium salt of this product is orange III or heliau* 



302 DERIVATIVES OF THE BENZENE SERIES 

thin. It is not used as a dye as it is very sensitive to acids 
and alkalies, but it is used as an indicator in acidimetry and 
alkalimetry. It reacts with the weakest alkalies and is not 
affected by carbonic acid. 

Diphenylamine orange, tropsBolin OO, is another ex- 
ample of the azo dyes. It is made by the action of diazotized 
sulphanilic acid on diphenyl-amine in alkaline solution : — 

^«^*<qA > + ?S' >NH+NaOH=CeH,<f^-^«^^^^C^^^ 
SO3 GeP-s SOgNa + HgO. 

Diphenyl-amine orange 

Phenols, or Hydroxyl Derivatives of Benzene, etc. 

The hydroxyl derivatives of the paraffins are called alcohols. 
As will be remembered, they are of three kinds, each of which 
is well characterized. These are : — 

1. Primary alcoholSy of which ordinary ethyl alcohol is the 
commonest example, and which, when oxidized, yield aldehydes 
and then acids containing the same number of carbon atoms. 

2. Secondary alcohols, which by oxidation yield acetones and 
then acids containing a smaller number of carbon atoms. 

3. Tertiary alcohols, which by oxidation yield neither alde- 
hydes nor acetones, but break down at once, yielding acids 
with a smaller number of carbon atoms. 

The primary alcohols were shown to correspond to the 




formula C^ ^ 5 the secondary to C< ; and the tertiary to 

R 

^ ; or, in other words, the primary alcohols contain the 

I HO 

group CH2-OH; the secondary, the group CH.OH; and the 
tertiary, the group C . OH. 



MON-ACID PHENOLS 303 

Now, the simplest hydroxyl derivative of the members of 
the benzene series is phenol, CeHa.OH, or benzene in which 
one hydrogen is replaced by hydroxyl. Eepresenting this 
compound in terms of the accepted benzene hypothesis, we 
have the formula 

OH 

Hc/ \:jh 

I I 

HCv yCK 

H 

According to this, phenol appears to be allied to the tertiary 
alcohols, as it contains the group C . OH, and not CHgOH nor 
CH.OH. We shall see that, in fact, phenol conducts itself 
towards oxidizing agents like the tertiary alcohols. It yields 
neither aldehydes nor ketones. 

All compounds which contain hydroxyl in the place of the 
benzene-hydrogen atoms of benzene and its homologues are 
called phenols. As in the case of alcohols, there are phenols 
containing one hydroxyl, or mon-acid phenols; those contain- 
ing two hydroxyls, or di-acid phenols; those containing three 
hydroxyls, or tri-acid phenols, etc. Some of these are familiar 
substances. 

MoN-AciD Phenols 

Phenol, carbolic acid, OeHeOCOeHsOH). — Phenol is found 
in small quantities in the urine. It is formed by the distilla- 
tion of wood, coal, and bones. Hence, it is a constituent of 
coal tar, and from this it is prepared. For this purpose the 
heavy oil (see p. 254) is treated with an alkali which dissolves 
the phenol. From the solution it is precipitated by hydro- 
chloric acid. It is purified by distillation. 

Phenol can also be made by converting nitro-benzene into 
aniline; then into diazo-benzene ; and boiling this with water 



304 DERIVATIVES OF THE BENZENE SERIES 

(see Exp. 61 (&)) ; and by fusing a salt of benzene-sulphonic 
acid with potassium hydroxide. 

Experiment 65. In a silver (or iron) crucible, or evaporating dish, 
melt 40s to 50s potassium hydroxide, after adding a few cubic centimetres 
of water. Now add gradually lOs finely-powdered sodium toluene-sulpho- 
nate, obtained in Exp. 62, stirring constantly with a silver (or iron) spatula. 
Do not heat to a very high temperature. After the mass has been kept in 
a state of fusion for one-quarter to one-half an hour, let it cool. Dissolve 
in 200<=° to 260<5c water, and acidify with hydrochloric acid. Notice the 
odor of the gases given off. What gas do you detect ? When the liquid 
has cooled down, extract with ether in a glass-stoppered cylinder. From 
the ether extract distil the ether on a water-bath. The residue is impure 
cresol (p. 300). Phenol can be detected by the following reactions, for 
which a solution in water should be prepared : — 

(a) A few drops of ferric chloride solution gives a beautiful blue color. 

(&) Add one-fourth volume of ammonia, and then a few drops of a 
dilute solution of bleaching powder. A blue color is produced. 

(c) Bromine water gives a yellowish-white precipitate of tri-brom- 
phenol. 

The reaction which takes place in fusing potassium hydrox- 
ide and potassium benzene-sulphonate together is represented 
by the equation, — 

CeH^ . SOsK + KOH = CfiH^ . OH + K^SOs. 

It effects the replacement of the group, SO3K, by hydroxyl. 
Phenol is made by this method on the large scale. 

Phenol, when pure, crystallizes in beautiful colorless ortho- 
rhombic needles that melt at 42®. The presence of a little 
water prevents it from solidifying. It has a peculiar, 
penetrating odor; boils at 181°; is difficultly soluble in 
water (1 part in 15 parts water at ordinary temperature); 
mixes with alcohol and ether in all proportions; and is 
poisonous. It is a valuable antiseptic, and finds extensive 
application as a disinfectant and in the manufacture of picric 
acid. 

An aqueous solution of phenol is colored violet by a little 
ferric chloride. 



DIPHENYL-ETHER 305 

Bromine water gives a precipitate of tri-brom-phenol when 
added to a water solution of phenol. 

Phenol is not soluble in alkaline carbonates. Its acid prop- 
erties are not strong enough to enable it to decompose these 
carbonates. On the other hand, it forms salts with the alkalies 
and with several strong bases. Among these may be men- 
tioned the following : — 

Potassium phenolate, CeHj . OK, made by dissolving potassium 
in phenol, and by treating phenol with a solution of caustic 
potash. 

Barium phenolate, (C6H50)2Ba + 2 HgO, made by dissolving 
phenol in baryta water. 

Basic lead salt of phenol, CeH^OPbOH, made by dissolving 
lead oxide in phenol. 

Phenol also forms ethers, of which the methyl, ethyl, and 
diphenyl ethers may serve as examples : — 

Methyl-phenyl ether, OyHgO (S^*>o). —This substance, 

also called anisol, is obtained from anisic acid (methoxy- 
benzoic acid) by boiling with baryta water. It is made also 
by treating potassium phenolate, CeHgOK, with methyl 

iodide : — P tj 

CgH^OK + CH3I = ^g^^ > + KL 

It is a liquid of a pleasant odor. 

Note for Student. — Compare this substance with ordinary ether. 
What method analogous to that above mentioned can be used in the 
preparation of ordinary ether ? 

Bthyl-phenyl ether, OgHioO (^«^^>o), is called ph^etol 

Diphenyl ether, Ci2HioO(^«^*>o)- — This bears to 

phenol the same relation that ordinary ether bears to alcohol. 
With acids, phenol, like the alcohols, yields ethereal salts in 
which the phenyl group, CgH,, takes the place of a metal. 



DEEIVATIVBS OP THE BENZENE SERIES 



Among the compounds of this class which phenol forms with 
organic acids, the following may be mentioned: — 

Phenyl acetate, OgHsOsCOHs- CO,. OeHj,). — This is formed 

by treating phenol with acetyl chloride. 

NoTB FOR Student. — What use is acetyl chloride put to as a reagent 
in organic chemiBtry ? Explain Its use. Wbat concluaioD can be drawn 
from the fact that acetyl chloride acts upon pbenol, replacing one hydrogen 
by acetyl, CiHjO? 

SvbstitutioTirproduela of phenol. Phenol is very susceptible 
to the action of various reagents, and a large nunlber of substi- 
tution-products have been made from it. 

Bromine acta upon it readily. If, for example, bromine 
water ia added to a water solution of phenol, tri-brom-phenol 
is formed and -precipitated. 



^ N0,\ 



■ Dilute nitric 



Nitro-phenolB. C^HsNO, (^ C^H^ < q^'J 
acid acts upon phenol, yielding two mono-nitro-phenols, one 
of which belongs to the ortho series, the other to the para 



a of E 






Kxperlmeut 66. Add 208 phenol to 
40" ordinary concentrated nitric acid (sp. gr. 1.34), Stir, and, after a 




TRI-NITRO-PHENOL 307 

time, pour off the dilute acid from the oil. Wash with water, and then 
put it into a flask, with about a litre of water, arranged as shown in 
Fig. 14. Flask A holds nothing but water ; while the oil, together with 
water, are in B, From A a current of steam is passed into i5, which is 
heated by means of a lamp. Yellow crystals pass over and appear in the 
receiver, while a non-volatile substance remains behind in flask B, The 
volatile substance is ortho-nitro-phenol ; the non-volatile is para-nitro- 
phenol. 

Tri-nitro-phenol, picric acid, 06H3N307(06H2<^^2)8y 

This is formed very easily by the action of strong nitric acid 
on phenol. 

Experiment 67. Add IOr phenol slowly to lO^ concentrated nitric 
acid. When the action is over, add 30s fuming nitric acid and boil for 
some minutes. Extract the picric acid by means of hot water, and purify 
by dissolving in potassium carbonate, and evaporating to crystallization. 

Picric acid crystallizes in yellow leaflets or prisms, has a 
very bitter taste (whence the name, from Trt/cpos, bitter), is 
poisonous, decomposes with explosion when heated rapidly. 
It dyes wool and silk yellow. 

Note for Student. — Is there any analogy between tri-nitro-phenol 
and tri-nitro-glycerin ? What is the essential difference between them ? 

It is extensively used as an explosive under the name lyddite. 

One of the most interesting properties of tri-nitro-phenol is 
its power to form salts. It acts like a strong acid. It will 
thus be seen that, while the substance CeHj.OH has only very 
slight acid properties, the same substance, with three of its 
hydrogens replaced by nitro groups, C6H2(N02)8. OH, has 
strong acid properties. In the salts, which have the general 
formula C6H2(N02)s. OM, the metal replaces the hydrogen of 
the hydroxyl. Among them may be mentioned the potassium 
salt which was obtained in Exp. 67 ; this explodes when heated 
and when struck. Ammonium picrate, C6H2(N02)3.0NH4, ia 
used as a constituent of explosives. 



808 DERIVATIVES OP THE BENZENE SERIES 

OS 

A m ino-phenols, O6H4 < jx-aj — The amino-phenols are 

formed by reducing the nitro-phenols by means of tin and 
hydrochloric acid. Met-amino-phenol and some of its deriva- 
tives are used in the preparation of the rhodamine dyes. 

Par-amino-phenol, used under the name of rhodinol as a 
developer in photography, yields an ethyl ether, p-pJienetidiney 

CeH4<2Sf^'. The acetyl derivative of this, CeH4<2Sf^'U ^xr ' 

NH2 NH.CO.CHs 

is extensively used in medicine under the name phenacetin as 
an antipyrotic and antineuralgic. 

OH 

Phenol-sulphonicacids, 06H4<g^TT» — When phenol is 

treated with sulphuric acid, the ortho and para sulphonic acids 
are formed. At low temperatures the ortho acid is formed in 
larger quantity than the para acid. The ortho acid is readily 
converted into the para acid by heat, so that, at a compara- 
tively high temperature, the para acid is the principal product. 
The change of the ortho acid to the para takes place even when 
its water solution is boiled. A mixture of the ortho and the 
para acids is used in water solution as an antiseptic under the 
name aseptol. 

Phenyl-mercaptan, 1 

Phenyl hydrosulphide, [^ OeHeSCOeHfi.SH).— This bears 

Thiophenol, ) 

the same relation to phenol that mercaptan bears to alcohol. 
It can be made by reducing benzene^sulphon-chloride. This 
reduction is effected by first making the sulphon-chloride, 
C6H5.SO2CI (Exp. 63), and then treating this with nascent 
hydrogen. 

Note for Student. — What is the effect of oxidizing the mercaptans? 

It can be made, also, by treating phenol with phosphorus 
pentasulphide, the effect of this reagent being to substitute 
sulphur for oxygen. 



THYMOL 309 

Note for Student. — What analogy is there between the action of 
phosphorus pentachloride and of phosphorus pentasulphide on compounds 
containing oxygen ? 

Phenyl-mercaptan is a liquid, with a very disagreeable odor. 
It forms a crystallized mercury compound, (CeH5S)2Hg. 

Gresols, CjHsOf C6H4 < ^ ). — There are three cresols, 

r*TT 
or hydroxyl derivatives of toluene, of the formula C6H4 < . 

They are all found in coal tar, and the tars from pine and beech 
wood. When mixed together, it is difficult to separate them. 
To obtain them in pure condition, it is therefore best to make 
them from the three toluidines, or from the three sulphonic 
acids of toluene. 

Note for Student. — Give the equations representing the reactions 
involved in passing from the three toluidines to the cresols, and from the 
three toluene-sulphonic acids to the cresols. 

The cresols resemble phenol very closely. 

Creosote is a mixture of chemical compounds contained in 
wood tar. It contains the cresols. Coal-tar creosote consists 
largely of phenols. 

Thymol, propyl-meta-cresol, OioHi40(C6H3-| OHW ).— 

This phenol is contained in oil of thyme, together with cy- 
mene, and is made artificially from nitro-cuminic aldehyde, 

rCHO 
CgHs \ NO2 ("»). When this is reduced it gives an amino deriva- 

l C8H7(p) 

> Formulas of this kind serve very well to indicate the relations of the groups and 
atoms contained in benzene derivatives. This one, for example, indicates that the 
hydroxy] is in the meta position (m) to methyl; while the propyl is in the para 
position (/>) to methyl. For di-substitution products, such formulas may also 

CH 

be used. Thus, the three toluidines may be represented by CeH4 < ,„ * , .t 

CH, CH, ^"•^''^ 



310 D£BIVATIV£S OF THB BBNZENE SERIES 

rCHs 

tive of cymene, C^Hg -j NHa , which can be converted into thymol 

ICsHt 
through the diazo compound. It forms large monoclinic crys- 
tals, which melt at 50°. It has a pleasant odor, like that of 
the oil of thyme. Treated with phosphorus pentoxide, it 
yields meta^sresol and propylene, C8H«; while, when treated 
with phosphorus pentasulphide, it yields cymene. These two 
reactions indicate that the groups contained in thymol bear to 
each other the relations indicated by the formula given above. 
It is one of the tv70 theoretically possible hydroxyl derivatives 
of cymene. The other one, carvacrol, has the hydroxyl in the 
ortho position relative to methyl. It has been made from 
the corresponding cymene-sulphonic- acid ; is found in nature 
in the ethereal oil of Origanum hirtum; and can be made from 
carvone, or the oil of caraway, by heating it with glacial phos- 
phoric acid or with caustic potash. 

Di-AciD Phenols 

The three theoretically possible di-hydroxyl benzenes, 

OH 
C6H4<^^, are all well known. 

Pyrocatechol, IrTTn/rTT^^^ ^ 

Ortho-di-hydroxy-benzene, i ^^'^''^^V''^'^ OR(,o) y ~ 

This substance is a frequent product of the dry distillation of 

natural substances, — as of catechu, morintannic acid, etc., — 

and of the melting of resins with caustic potash. It can be 

made by fusing ortho-chlor-phenol or ortho-phenol-sulphonio 

acid with caustic potash. It forms crystals, which melt at 

104°. It is easily soluble in water, alcohol, and ether. 

The dilute solution in water gives with ferric chloride a 
dark green color, which becomes violet on the addition of a 
little of a very dilute solution of sodium carbonate. 

It reduces silver nitrate in solution in cold water. It is 
used in photography. 



DI-ACID PHENOLS 311 

OCHT 
Guaiacol, monomethyl-pyrooatechol, ^6H4<q„ ^. — 

This substance was first found in guaiac resin. Hence its 
name. It is formed in considerable quantity in the distilla- 
tion of wood, especially beech wood. It is made syntheti- 
cally by introducing methyl into pyrocatechol. Guaiacol is a 
liquid that solidifies at 28.5° and boils at 205°. The carbon- 
ate, CO(OC6H4 . OCH8)2, has been recommended as a remedy in 
tuberculosis. 

9 

Veratrol, dimethyl-pyrooateohol, O6H4 < ^^__^ ^s formed 
by treating the potassium salt of pyrocatechol with methyl 

r CO2H 

iodide and by distilling veratric acid, CeHs -j OCHs, with lime. 

Resorcinol, Irim I nrt ^ OB. \ 

Meta-di-hydroxy-benzene, i '^^^^^ V ' * ^ OH(m) ) ' ~ 

Resorcinol is formed by the melting of a number of resins with 

caustic potash, as of galbanum, sagapenum, asafoetida, etc. 

It is made, also, by melting meta-iodo-phenol or meta-benzene- 

disulphonic acid with caustic potash. 

It crystallizes from water, usually in thick, orthorhombic 
prisms. Melting-point, 118°. 

With ferric chloride, the water solution gives a dark violet 
color. Heated for a few minutes with phthalic anhydride in a 
test-tube, a yellowish-red mass is formed. When this is added 
to dilute caustic soda, a solution with remarkable fluorescence 
is obtained. The explanation of this reaction will be given 
under the head of Tri-phenyl-methane, when the phthaleins 
will be described. 

Resorcinol is used largely in the manufacture of certain dyes, 
and is therefore manufactured on the large scale. 

Heated with sodium nitrite resorcinol gives a deep blue 
dye. This is soluble in water and the solution is turned 



{ 



312 DERIVATIVES OF THE BENZEJSE 8E1UES 

red by acids. It is called lacmoid and is used as an indi« 
cator. 

compound is formed by the action of nitric acid on resorcinol, 
and on those resins which give resorcinol when treated with 
caustic potash. It closely resembles picric acid. Heated with 
bromine and acetic acid, it yields the substance known as 
brompicririy which has the formula C(N02)Br3. 

Hydroquinol, \ rrr n Inrx ^ ^^ ^ 

Para-di-hydroxy-benzene, f ^«^«^H "^^OHcp)/" ~ 

Hydroquinol is formed by the oxidation of quinic acid, by 

reduction of quinone (which see), by means of sulphur dioxide, 

by fusing para-iodo-phenol with caustic potash, etc. 

It is a crystallized substance which melts at 169''; easily 
soluble in alcohol, ether, and hot water. 

Oxidizing agents, such as ferric chloride, chlorine, etc., convert 
it into quinone. It is used in photography as a " developer." 



It would lead too far to discuss here the reactions which 
have been made use of for the purpose of determining to which 
series each of the three di-hydroxy-benzenes belongs. The 
principle involved, however, is simple. Either these substances 
must be converted, directly or indirectly, into others, in regard 
to the relation of whose groups we have evidence; or sub- 
stances, the relation of whose groups is known, must be con- 
verted into the di-hydroxy-benzenes. The reactions employed 
for effecting the conversions are mainly those which have 
already been studied ; viz., the formation of amino compounds 
from nitro compounds by reduction; the formation of diazo com- 
pounds from amino compounds ; the formation of (1) hydroxyl 
derivatives, (2) chlorine, bromine, or iodine derivatives, from 
the diazo compounds ; and the formation of hydroxyl deriva- 
tives from sulphonic acids. 



TRI-ACID PHENOLS 313 



Orcinol, 
Di-hydroxy-toluene 



jCzHgO, 



— There are 



fCH3 
CeHs OH(w) 

lOH(m) J 

two coloring matters, known as archil and litmus, which are 
made from different lichens by exposing them in powdered 
condition in ammoniacal solution to the action of air. Archil 
contains a substance called orcein, which can be made from 
orcinol by treating it with ammonia in contact with the air. 
Orcinol is contained in several lichens. It is formed, also, by 
melting aloes with caustic potash, and by melting 1, 3, 5-chlor- 
toluene-sulphonic acid with caustic potash. The last reaction 
shows that orcinol is 1, 3, 5-di-hydroxy-toluene. 

Orcinol crystallizes in large, colorless, monoclinic prisms 
which turn red in the air. Ferric chloride colors the aqueous 
solution a blue violet. 

Treated with ammonia in moist air, it is converted into 
orcein, C28H24N2O7, a substance which dissolves in alkalies, 
forming beautiful red solutions. 

Orcinol is manufactured on the large scale, and then con- 
verted into orcein, which is used as a dye. 

Litmus is obtained from the lichens Roccella and Lecanora by 
treating them with ammonia and potassium carbonate. Com- 
mercial litmus is made by mixing the concentrated solution 
of the potassium salt with chalk or gypsum. 



Tri-acid Phenols 



Pyrogallol, pyrogallio acid, 



fOH(l)] 
CeHs OH(2). 
iOH(3)J 



Tri-hy droxy-benzene, J ^e-^^^s 

Pyrogallic acid is formed by dry distillation of gallic acid, the 
reaction being analogous to that by which benzene is produced 
by distillation of benzoic acid : — 

C6H,.C02H = C6H6 + C02 5 

Benzoic acid Benzene 



S14 DERIVATIVES OF THE BENZENE SEBIES 



C,H,{ Ws = CeH,(OH), + CO,. 



2 Pyrogallol 

Gallic acid 



It is formed also when one of the chlor-phenol-sulphonic acids 
is fused with caustic potash : — 



fOH (1) jj-ojj 
C,H, CI (2)+jj.Qjj = C,H,. 
lS0sK(3) 



fOH 

OH + KCl + KjSO^ 
OH 



Potassium chlor-phenol- Pyrogallol 

Bolphonate 

It crystallizes in laminae or needles ; melts at 132-133** ; is 
easily soluble in water, ether, and alcohol. In alkaline solu- 
tion it absorbs oxygen rapidly and becomes brown. On account 
of this power to absorb oxygen it is used in gas analysis. It 
is poisonous. With a solution containing a ferrous and a ferric 
salt it gives a blue color. 

Most of the phenols give color reactions with ferric chloride, 
and most of them change color in the air. These changes in 
color are undoubtedly due to the action of oxygen. Towards 
oxidizing agents they are all unstable, most of them breaking 
down readily and yielding as the chief product of oxidation, 
carbon dioxide. In general, the larger the number of hydroxyl 
groups contained in a phenol, the less stable it is. It will be 
seen that these same statements hold good for the hydroxy- 
acids of the benzene group, of which gallic acid and salicylic 
acid are examples. 

fOH(l)l 



Phlorogluoinol, aH„(OH) 



. — This phenol 



CeHg OH(3) 
lOH(5) 

was first obtained from phloretin, which is one of the products 
of decomposition of a glucoside (see Glucosides), phloridzin. 
It can be obtained also from other glucosides, and from several 
resins. Resorcinol gives it when fused with potassium hydrox- 
ide, as does 1, 3, 5-benzene-trisulphonic acid. 
In some of its reactions phloroglucinol acts like a tri-hydroxy 



ALCOHOLS OF THE BENZENE SERIES 315 

benzene, in others it acts as if it contained three carbonyl 
groups, CO. Thus, for example, on the one hand, it gives a 
tri-niethyl-ether, 06^3(00113)3, and, on the other hand, with hy- 
droxylamine it gives a trioxime, 06H6(NOH)8. In the present 
state of our knowledge we can only conclyde that in contact 
with some reagents it actually is tri-hydroxy-benzene, while in 
contact with others it is tri-keto-hexa-methylene. The two 
conditions are represented by the formulas : — 

H 

C CH2 

HO . C 11^^ . OH OC|^\cO 

Hcl JcH HacljcHa 

C CO 

OH 

Trl-hydroxy-benzene Tri-keto-hexa-methylene 

This is another example of tautomerism already illustrated 
by hydrocyanic acid and by uric acid. 

Alcohols op the Benzene Series 

The phenols are those hydroxyl derivatives of the benzene 
hydrocarbons, which contain the hydroxyl in the place of one 
or mote of the six benzene hydrogens. But just as there are 
two classes of halogen substitution-products of toluene, in one 
of which the substitution has taken place in the benzene resi- 
due, and in the other in the marsh-gas residue, as indicated in 
the two formulas, — 

OeH^Ol . OHg and CJI, . OH^Cl, 

so, also, there are two classes of hydroxyl derivatives : (1) the 
phenols, and (2) those in which the hydroxyl is in the marsh- 
gas residue. The simplest example of the second class corre- 
sponds to the formula, OeH^ . OH2 . OH. It is isomeric with the 
cresols, C6H4 . OH . CH3, and has entirely different properties. 
While the cresols are the true homologues of phenol, the new 
substance is methyl alcohol in which one of the hydrogens 



316 DERIVATIVES OF THE BENZENE SERIES 

of the raethyl has been replaced by phenyl, CeH^. It may 



be represented by the formula, ^ i„ ^ Which makes its 




analogy to ethyl alcohol, C 



fCHs 
^ , apparent. 



H 
OH 

Benzyl alcohol, C^HgOCCgH^-CHaOH). — Benzyl alcohol 
or phenyl carbinol is found in nature in the balsams of Peru 
and Tolu, and in storax. In these substances it is, for the 
most part, in combination with benzoic or cinnamic acid. It is 
made by treating the oil of bitter almonds, which is the corre- 
sponding aldehyde, with nascent hydrogen : — 

CeHs . CHO + H2 = CeHj . CHg . OH. 

Oil of bitter almonds Benzyl alcohol 

It is also made by replacing the chlorine in benzyl chloride, 
CeHfi . CHgCl, by hydroxy 1, just as methyl alcohol is made from 
methyl chloride by a similar replacement. In the case of 
benzyl chloride this can be effected even by boiling for a long 
time with water : — 

CfiH, . CH2CI + H2O = CeHj . CH2OH + HCl. • 

Benzyl alcohol is a colorless liquid with a pleasant odor. It 
boils at 206.5**. It dissolves with difl&culty in water, and is 
soluble in alcohol and ether. 

Note for Student. — Notice the great difference between the boiling- 
point of methyl alcohol and that of phenyl-methyl alcohol. 

Oxidizing agents convert the alcohol, first, into the oil of 
bitter almonds or benzoic aldehyde, and then into benzoic acid. 
The relations between the three substances are like those be- 
tween any primary alcohol and the corresponding aldehyde 
and acid, as shown by the formulas : — 

C6H5 . CH2OH ; CeHj . CHO ; CeH, . CO2H. 

Benzyl alcohol Benzoic aldehyde Benzoic acid 



BENZYL ALCOHOL 317 

Hydriodic acid converts benzyl alcohol into toluene: — 
CflHfi. CH2OH + 2HI = CgH, . CH3 + H2O + 2 1. 

Benzyl alcohol conducts itself, in most respects, like the 
primary alcohols of the methyl alcohol series. A large number 
of its derivatives have been made and studied. Among them 
are ethereal salts, of which benzyl acetate, CII3 . CO . OC7H7, and 
benzyl nitrate, NO2 . OC7H7, may serve as examples ; ethers, of 
which the methyl ether, CgHa.CHa.O.CHg, and the phenyl etJier, 
CgHj. CH2 . OCqHs, are good examples ; and substitution-products, 
of which chlor-benzyl alcohol, C6H4CI . CH2OH, and nitro-benzyl 
alcohol, C6H4(N02) . CH2OH, are examples. 

These substitution-products are not made by direct treatment 
of the alcohol with the substituting agents, but by starting with 
the corresponding substituted toluene. Thus, chlor-benzyl 
alcohol is made from chlor-toluene, CeH4Cl.CHa, by first con- 
verting this into chlor-benzyl chloride, CeH4Cl . CH2CI, and then 
replacing the chlorine of the group CH2CI by hydroxy 1. By 
oxidation the substituted benzyl alcohols yield the correspond- 
ing substituted benzoic acid: — 

C«^H4C1.CH20H + O2 =CeH4Cl.C02H + HA 

Ghlor-benzoic acid 

C8H4(NOs).CHsOH +0,= CeH4(N02)C02H + H,0. 

Nitro-benzoic acid 

Very few of the alcohols analogous to benzyl alcohol have 
been prepared. Plainly, the homologues may be of two kinds : 

1. Those which are phenyl derivatives of the alcohols of the 
methyl alcohol series. Of this class, phenyl-ethyl alcohol, 
C6H5.CH2.CH20H,the isomeric substance CeHg.CH. OH. CHg, 
and phenyl-propyl alcohol, C6H5.CH2.CH2.CH2OH, are exam- 
ples. Phenyl-propyl alcohol is of special interest on accoimt 
of its connection with cinnamic acid (which see), which has 
come into prominence since it has been shown to be closely re- 
lated to the interesting substances of the indigo group. It 



318 DERIVATIVES OF THE BENZENE SERIES 

occurs in storax in the form of an ethereal salt, which will be 
treated of more fully under the head of Cinnamic Acid. 

2. Those which are derivatives of xylene, mesitylene, etc., 
in the same sense that benzyl alcohol is a derivative of toluene. 
The following belong to this class : — 

Tolyl^arbinol ^«^*^CH OH' 

and Cuminyl alcohol .... CJi^K^^^^, 

which is made from cuminol, an aldehyde found in the oil of 
cumin. 

Aldehydes op the Benzene Series 

The aldehydes of this group are closely related to the alco- 
hols just considered. The simplest one is the oil of bitter 
almonds, or benzoic aldehyde, C7HeO. 

iL°oi^S:hyS°°'''}^'H,O(0.H. . OHO). -This sub- 

stance occurs in combination in amygdalin, which is found in 
bitter almonds, laurel leaves, cherry kernels, etc. Amygdalin 
belongs to the class of bodies known as glucosidesy which break 
up into a glucose and other substances. Amygdalin itself, 
under the influence of emulsin, which occurs with it in the 
plants, breaks up into benzoic aldehyde, hydrocyanic acid, and 
dextrose : — 

C^oHg^NOn + 2 H2O = C^HeO + CNH + 2 CeHiA- 

Amygdalin Benzoic aldehyde Glucose 

Benzoic aldehyde can be made : 

1. By oxidizing benzyl alcohol : — 

CeH^ . CH2OH + = CgHs . CHO + H2O. 

2. By distilling a mixture of calcium benzoate and calcium 
formate : — 



CUMINIC ALDEHYDE 319 



OA.COIOM 
H.ICOOM 



= CeH5.CHO + M2C08. 



3. By treating benzoyl chloride with nascent hydrogen : — 

CfiH, . COCl + Ha = CeHs . CHO + HCl. 

4. By treating benzal chloride with water and milk of lime 
under pressure : — 

CfiH, . CHClj +H2O = CeH^ . CHO + 2 HCl. 

Note for Student. — Refer to the general methods for the prepara- 
tion of aldehydes. Which of the above reactions are used for the 
preparation of aldehydes in general ? Which of the reactions throw light 
upon the nature of aldehydes, and their relation to alcohols ? 

Benzoic aldehyde is prepared either from bitter almonds, 
which yield about 1.5 to 2 per cent ; or from benzal chloride. . 
On the large scale it is prepared by treating benzyl chloride 
with lead nitrate : — 

2 CeHfi . CH2CI + Pb(N08)2 = PbCla + 2 CflH^.CHO + 2 HNO^; 

or from benzal chloride (see reaction 4 above). 

Benzoic aldehyde is a liquid having a pleasant characteristic 
odor. It boils at 179° ; is difl&cultly soluble in water ; is not ' 
poisonous. 

It unites with oxygen to form benzoic acid ; with hydrogen 
to form benzyl alcohol; with hydrogen sulphide, ammonia, 
ammonium sulphide, alcohols, acids, anhydrides, and ketones. 
In short, its powers of combination with other substances are 
almost unlimited. ' Hence, a very large number of derivatives 
are known. 

Guminic aldehyde, cuminol, doHigOf C6H4 <S^?P V 

This aldehyde occurs in oil of cumin, from which it is made. 
It is a liquid with the odor of the oil of cumin. Its reactions 
are like those of benzoic aldehyde. 



820 DERIVATIVES OF THU BENZENE SERIES 

Benzaldoximes, CcHj . CH : N . OH. — Hydroxylamine re* 
acts with benzoic aldehyde as it generally reacts with aldehydes, 
forming an oxime : — 

CeHfi. CHO + H2NOH = CgHa . CH : N . OH + HjO. 

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 
when this is treated with sodium carbonate, a new oxime, 
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 regarded as stereoisomeric. In terms 
of the conceptions of stereochemistry they should be represented 
by the formulas : — 

CgH^ - C - H and CgH, - C - H 

II II 

HO - N N - OH 



CeHnK :7H CeH 




or Xr^ and 



HO 




[For an explanation of the significance of these formulas, 
especially as far as the nitrogen atom is concerned, see p. 295.] 

The one with the hydrogen atom and the hydroxyl on oppo- 
site sides is called henz-antiraldoxime ; the one with the hydro- 
gen atom and the hydroxyl on the same side is called henT^- 
syn-aJldoxime. The one that melts at 125'' easily loses water 
and forms phenyl cyanide or benzonitril, CeHjCN. The other 
does not. It is believed that the one that loses water and 



BENZOIC ACID 321 

yields the nitril when heated with acetic anhydride is the syn- 
oxime, as in this form the hydrogen and hydroxyl appear to be 
so situated that they can unite to yield 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. Phe- 
nomena of this kind have been extensively studied and the 
ideas here set forth rest upon a broad foundation of experi- 
mental evidence. 

Acids of the Benzene Sebies 

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 derivatives of the homologous hydrocarbons. There 
are monobasic, dibasic, tribasic, and even hexabasic acids, but 
the number actually known is small. 

Monobasic Acids, CnHgn-sOj 

Benzoic acid, CyHgOgCCeHi . COgH) — Benzoic acid occurs 
in gum benzoin, in the balsams of Peru and Tolu, and in 
combination with amino-acetic acid or glycine in the urine of 
herbivorous animals. It can be made in many ways, the most 
important of which are given below : — 

1. 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 difl&cultly oxidizable residue, CqHs, in combination with an 
easily oxidizable residue of an alcohol of the marsh-gas series : — 

CeHfi . CH2OH gives CgHs . CO2H ; 

CeH, . CH2 . CH2OH « CfiH^ . CO2H ; 

CgHfi . CH2 . CHg . CH2OH « CgHs . CO2H, 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 



322 DERIVATIVES OF THE BENZENE SERIES 

but one residue of the marsh-gas series. Attention has already 
been called to this fact (see p. 270). 

4. By treating cyan-benzene (phenyl cyanide, benzo-nitril) 
with sulphuric acid (see Exp. 64, p. 300) : — 

CeH^CN + 2 H2O = CfiHs • CO2H -f- NHg. 

5. By treating benzene with carbonyl chloride in the pres- 
ence of aluminium chloride : — 

CeHe + COCI2 = CfiHfi • COCl + HCl ; 

CgHfi . COCl + H2O = CflHfi . CO2H -f- HCl. 

A reaction similar to this is of extensive application in the 
preparation of some hydrocarbons. It will be treated of more 
fully under the head of Tri-phenyl-methane. 

6. By treating benzene with carbon dioxide in the presence 
of aluminium chloride : — 

CgHe + CO2 = CgHj • CO2H. 

This and the preceding methods are of special interest from the 
scientific point of view, for the reason that they clearly show 
the relation between benzoic acid, on the one hand, and ben- 
zene and carbonic acid, on the other. 

Note for Student. — Which of the methods above given are of gen- 
eral application for the preparation of the acids of carbon ? 

Benzoic acid is prepared on the large scale: (1) from gum 
benzoin by sublimation ; (2) from the urine of horses and cows 
by treating the hippuric acid with hydrochloric acid ; (3) from 
toluene, best, by converting it into benzyl chloride, and oxidiz- 
ing this with dilute nitric acid. 

Experiment 68. If the material m obtainable, evaporate a quantity 

of the urine of horses or cows to about one-half or one-third its volume. 

4.dd hydrochloric acid. On cooling, hippuric acid will be deposited. Re- 

ystallize this several times from dilute nitric acid. Boil the hippuric acid 



BENZOIC ACID 323 

for about a quarter of an hour with ordinary concentrated hydrochloric 
acid. By this means the hippuric acid is decomposed, yielding glycine 
(aminp-acetic acid) and benzoic acid : — 

C9H9NO8 + H2O = C7H6O2 + CH, < ^ "I- . 

Hippuric acid Benzoic acid ^^20. 

^^ Glycine 

Benzoic acid forms lustrous laminae or needles, which melt 
at 121°. It boils at 250^ 

Experiment 69. Determine the melting-point of the benzoic acid 
which you have made from hippuric acid. If it is not as stated above, 
recrystallize from water until the melting-point is not changed by further 
crystallization. Those specimens which are least pure can be purified by 
recrystallizing them from dilute nitric acid. 

The acid is comparatively easily soluble in hot water, but 
difficultly soluble in cold water. It is volatile with steam. 

Experiment 70. Put some in a one-litre flask, with about 700<^<^ to 
800«« water. Connect with a condenser, and boil dovm to about 200*'*'. 
Neutralize the distillate with ammonia, and evaporate down to a small 
volume. Acidify, when benzoic acid VTill be throvni down. 

Its vapor acts upon the mucous membrane of the respiratory 
passages, and causes coughing. 
It sublimes very easily. 

Experiment 71. Put some dry benzoic acid in a small, dry crystal- 
lizing dish, and put the dish in a sand-bath. Over the mouth of the dish 
put a paper cone made from filter-paper, arranged as shown in Fig. 16. 
Heat with a small flame. The benzoic acid will be deposited on the paper 
in beautiful lustrous needles. 

Or another form of apparatus, which is useful for subliming small 
quantities of substance, consists, essentially, of two watch-glasses which 
are of exactly the same size. The edges of the glasses are ground to 
secure a good joint when they are brought together. In using this appa- 
ratus, put the substance to be sublimed in one of the glasses ; stretch a 
round piece of filter-paper over it, and then place the other glass upon it. 



DERIVATIVES OP THE BENZENE SEEIE8 



Clamp the glaaaes tc^etlier by means of a thin hrasa clamp. Now put the 
glasses on a sand-bath, and warm gently, when the substance will slowly 




pass through the paper and appear in crjstale in the upper watch-glass. 
It is well to keep a small pad of moist filter-paper on the upper glasB during 
th'e operation. 

When heated with lime, benzoic acid breaks up into benzene 
and carbon dioxide (see Exp. 64) : — 

C,H A = CsH, -I- COr 

With sodium amalgam, it yields benzyl alcohol and other re- 
duction-products. With hydriodie acid, it yields toluene, and 
then hydrogen addition-products of toluene. 

A great many derivatives of benzoic acid are known. 

Nearly all its salts are soluble in water. 



BENZOYL CYANIDE 325 

Sodium benzoate in small quantities is extensively used as a* 
preservative. 
The ethereal salts can be made by any of the general 

« 

methods already described. 

Experiment 72. To 50^^ benzoic acid, add 100^^ absolute alcohol and 
108 concentrated gulphuric acid and boil for 3 hours under a return con- 
denser. Now add three or four volumes of water, when ethyl benzoate 
will separate as an oil. Wash with water and a little sodium carbonate ; 
and, finally, dry. Yield 658 or 90 per cent of the calculated. 

Benzoyl chloride, OeHj.OOOl, and bromide, CeHs.COBr, 
are made from benzoic acid in the same way that acetyl chlo- 
ride is made from acetic acid. On the large scale the chloride 
is made from benzoic aldehyde by treating it with chlorine : — 

CeH^.COH + CI2 = CsH^.COCl + HCl. 

They are more stable than the corresponding compounds of 
the fatty acids, but undergo the same kinds of change. 

Benzoyl chloride acts upon alcohols and phenols, amino and 
imino compounds in the same way that acetyl chloride does, 
and forms benzoyl compounds : — 

CeHj.OH + CeH^.COCl = CeH^.CO.OCeHs + HCl. 

The reaction is much aided by the addition of caustic potash 
(Baumann-Schotten reaction). An example of this is repre- 
sented thus : — 

C6H50H+C6H5COCl4-NaOH=C6H5.COOC6H5+]SraCl+H20. 

The Baumann-Schotten reaction furnishes a valuable method 
for detecting hydroxy 1, amino, and imino groups. 

Benzoyl cyanide, OgHs.OO.ON, is made by distilling 
mercuric cyanide and benzoyl chloride: — 

2 CeH^ . COCl + Hg(CN)2 = 2 CeH^ . COCN + HgCl,. 



326 DERIVATIVES OF THE BENZENE SERIES 

The cyanogen can be converted into carboxyl, and thus an acid 
of the formula CcH^ . CO . CO2H obtained. This is known as 
benzoylformic acid. It is of interest, for the reason that one of 
its derivatives is closely related to indigo (see Isatine). 

SubstitutiorirProducts 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 mostly to the 
meta series. Thus, when chlorine acts upon benzoic acid, the 
main product is meta-chlor-benzoic acid ; nitric acid gives mainly 
metornitro-benzoic acid ; and sulphuric acid gives mainly metor 
sulpho-benzoic acid. 

Note for Student. — Compare this with the result of the direct 
action of the same reagents on toluene. 

Substituted benzoic acids can be made, also, by oxidizing the 
corresponding substituted toluenes. Thus, chlor-toluene gives 
chlor-benzoic acid ; nitro-toluene gives nitro-benzoic acid, etc. : — 

CeH^Cl . CH3 gives C6H4CI . CO2H ; 

C6H4(N02)CH3 « C6H4(N02)C02H. 

The three nitro-benzoic acids and the corresponding amino- 
benzoic adds may serve as examples of the mono-substitution 
products. 

Ortho-nitro-benzoic acid, O7H5NO4 ( O6H4 < ^J^ ). — 

Ortho-nitro-benzoic acid is formed, together with a large quan- 
tity of the meta acid and some of the para acid, by treating 
benzoic acid with nitric acid, by oxidizing ortho-nitro-toluene 
with potassium permanganate, and by oxidizing ortho-nitro- 
cinnamic acid. It crystallizes in needles, melts at 147°, and 
has an intensely sweet taste. 



ANTHRANILIC ACID 327 



OO2H 



Meta-nitro-benzoic acid, O6H4 < ^^ , 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°. 

CO TT 

Para-nitro-benzoic acid, 06H4< , is prepared best * 

by oxidizing para-nitro-toluene. It crystallizes in laminae, 
melts at 238°, and is much less easily soluble in water than 
the ortho and meta acids. 

The determination of the series to which these three acids 
belong is effected by transforming them into the amino-acids ; 
and these, through the diazo compounds, into the corresponding 

OH 

hydroxy-acids of the formula C6H4< 

Note for Student. — Give the equations representing the action 
involved in passing from toluene to ortho-hydroxy-benzoic acid (salicylic 
acid) by the method above referred to. 

In a similar way, lines of connection can be established 
between the three hydroxy-acids and the chlor-, brom-, and 
iodo-benzoic acids. 

Note for Student. — 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 

CO H 

acids of benzene, C6H4<^, which, in turn, have been made 
from the three xylenes. 

Ortho-amino-benzoic acid,] / OO2H 



07H7N02f06H4<j^g 



2(o), 



Anthranilic acid. 
This acid is made by reducing ortho-nitro-benzoic acid with 
tin and hydrochloric acid, and, on the large scale, from phthal- 
imide by Hofmann's reaction (see p. 214): — 



828 DERIVATIVES OF THE BENZENE SERIES 

^«H^<n;S^ +2NaBr + C02 + H20. 
COOisa, 

It is also formed by boiling indigo with, caustic potash. It has 
already been stated that indigo yields aniline. Now, as ortho- 
amino-benzoic acid is also obtained, and this breaks up easily 
into aniline and carbon dioxide, 

C^4 < ^Q |j = CeH^H, + C0« 

it seems probable that the aniline is a secondary product. 

Like other amino acids, anthranilic acid is probably an inner 
.salt and should, accordingly, be represented by the formula 

CO 

C6H4 < j^jj >. When it is diazotized it yields an inner dia- 

co 
zonium salt of the formula C6H4 < j^^ >. When this is boiled 

Hi 

N 
with water it yields salicylic acid : — 

N OH 



Isatine, C8H5NO2('06H4 < ^^ ^ O . OH or O6H4 < ^H -^ ^^\ 

— Isatine is obtained by the oxidation of indigo, and from 
ortho-nitro-benzoic acid as follows : — 

The nitro-acid is converted into the 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-nitro-benzoyl-formic acid is then 
reduced to the amino compound and this loses water and gives 
isatine. The changes are indicated thus : — 



ISATINE 329 

pxT .COOH p„^COCl p„ .CO.CK 
^xT^CO.COOH p„ .CO.COOH rn ^^^-^rnrr 

orCeH,<^?^>CO. 
NH 

The formula given for isatine represents it as an anhydride 
of ortho-amino-benzoyl-formic acid. The formation of anhy- 
drides of aromatic acids is a characteristic of ortho compounds. 
Neither the meta nor para acids give up water. We shall find 
that this fact is illustrated in the case of the dibasic acids, the 
only one that yields an anhydride being ortho-phthalic acid, 

C6H4 < QooH ' which gives phthalic anhydride, C6H4 < pQ>0. 

This ready formation of anhydrides from ortho compounds, 
taken together with the fact that the meta and para compounds 
do not yield anhydrides, has been regarded as an argument in 
favor of the view that in the ortho compounds the two substi- 
tuting groups are actually nearer together than in the meta 
and para compounds. 

Isatine illustrates the phenomenon of tautomerism (see p. 
92). 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 : — 

C,H,<^^^C.OH and C,H,^^^CO. 

The first of these formulas is known as the Icuitim, the second 
as the lactam formula. 

The relation of isatine to indigo will be discussed briefly 
under the head of Indigo. 

Meta- and Para-amino-benzoic acids are made from the 
corresponding nitro acids by reduction. 



830 DERIVATIVES OP THE BENZENE SERIES 

• Hippuric acid, benzoyl-amino-acetic acid, 
O9H9NO3 (CuHs . CONH . OH2CO2H). 

Hippuric acid, as has already been seen (Exp. 68), occurs in 
the urine of herbivorous animals, as the cow, horse, camel, and 
sheep. Some hippuric acid is found in human urine under 
ordinary circumstances. If benzoic acid is taken with the 
food, it appears as hippuric acid in the urine, while derivatives 
of benzoic acid appear as derivatives of hippuric acid. 

Hippuric acid can be made synthetically from benzoic acid 
and acetic acid : 

1. By heating glycine with benzoic acid to 160** : — 

c.h..co;oh:+'|^J>ch,=ch,<^^jjC^-^<'^«+h,o. 

IIip[>uric acid 

2. By heating benzamide with chlor-acetic acid : — 

CeH, . CO . NHH + ^^^^ > CU, = ^«^* ' ^^0 C ^ ^^' + ^^^' 

Hippuric acid 

3. By heating glycine with benzoyl chloride : — 

CH, < ™ + CI . OCCeH, = CH, < ^q^^^'^' + HCl. 

Hippuric acid crystallizes from water in long, orthorhombic 
prisms which melt at 187°. 

It is decomposed into benzoic acid and glycine by boiling 
with alkalies, and more readily by boiling with dilute acids 
(Exp. 68) : — 

CH2 < nQ ^ ' ^ + H'i^ = ^^2 < (jQ j£ + ^eHs . COgH. 

NoTB FOR Student. — What relation does hippuric acid bear to ben- 
zamide ? What is the effect of boiling acid amides with alkalies ? Write 
the equation for the decomposition of benzamide, and compare it with 
that for the decomposition of hippuric acid. 



TOLUIC ACIDS 331 

COOTT 
Siilpho-benzoic acids,- C6n4 < . — When sulphuric 

acid or sulphur trioxide acts upon benzoic acid the principal 
product is generally meta-sulpho-benzoic acid. The ortho- and 
para-acids can be made by oxidizing ortho- and para-toluene- 
sulphonic acids : — 

CH3 COOH 

^'^'^ SO^OH"^ ^^^*^ SO^OH- 
When the amide of ortho-sulpho-benzoic acid is oxidized with 
potassium permanganate it gives the potassium salt of a com- 

co 

pound of the formula, C6H4<g^ >NH, which has been called 
benzoic sulpMnidej and on acidifying, this is precipitated : — 

CH, . ^ XT . CH3 n XT ^ CH3 



^'^^ ^ SO2OH "^ ^'^' ^ SO2CI "^ ^'^^ ^ SO^NHa 

Benzoic sulphinide has five hundred times the sweetening 
power of cane sugar, and in consequence it has come into ex- 
tensive use as a sweetening agent. In commerce it is known 
as saccharin. It is a crystallized substance rather difficultly 
soluble in water. It is soluble in acetone, and crystallizes 
beautifully from this. 

Toluic acids, C8H8O2. — There are four acids of this formula 
known ; viz., the three carboxyl derivatives of toluene in which 

the carboxyl enters into the benzene ring, C6H4< ' , and an 

acid obtained from toluene by replacing a hydrogen of the 
methyl by carboxyl, thus, CgHj . CHo . CO2H. Ortho-, metor, 

CH 

and para-toluic acids, C6H4< ' , are made by oxidizing the 
corresponding xylenes with nitric acid : — 



C6H4 < ^^ 4-30 = C6H4 < -f HjjO, 



332 DERIVATIVES OF THE BENZENE SERIES 

They, as well as their derivatives, of which many are known, 
have been studied carefully. The substituted toluic acids can 
be made either by treating the acids with strong reagents or 
by oxidizing substituted xylenes : — 

Nitro-xylene Nitro-toluic acid 

benzoic acid may be regarded as phenyl-formic acid, so op-toluio 
acid may be regarded as phenyl-acetic acid. It is obtained by re- 
ducing mandelic or phenyl-glycolic acid, CgHj. CH(OH) . COgH, 
which is formed when amygdalin is treated with hydrochloric 
acid. It is prepared from toluene by converting this into 
benzyl chloride, from which the cyanide is made by boiling with 
potassium cyanide. The cyanide is then treated with an alkali| 
and yields the acid : — 

CeH^.CHg +01, =C6H,.CHjCl +Ha5 

Boiling toluene Benzyl chloride 

CjH, . CHjCl + KCN = C,H, . CHjiCN + KCl ; 

Benzyl cyanide 

C6H5 . CHaCN + 2 H2O = CgH, . CH, . CO,H + NH,. 

a-Toluio add 

The acid crystallizes in thin laminae ; and melts at 76.6®. 

Note for Student. — What would you exx>ect a-toluic aCid to yield 
when oxidized ? (See p. 270.) What would you expect it to yield when 
distilled with lime? What would you expect the three toluic acids, 

C6H4 < ^^\„ to yield by oxidation, and when distilled with lime ? (See 
p. 824.) 

Oxindol, OgHrNO (Ojft < ^"E" > Oo) . — Oxindol is obtained 

by reduction of isatine (see p. 328) ; and also from ortho-amino- 
o-toluic acid by loss of water, in the same way that isatine 



HYDRO-CINNAMIC ACID 333 

is formed from ortho-amino-benzoyl-formic acid. When a-toliiic 
acid is treated with nitric acid, the para- and ortho-nitro acids 
are formed. The latter is reduced by means of tin and hydro- 
chloric acid, when oxindol is at once obtained:— 

Ortho-amino-a-toluic acid Oxindol 



Mesitylenio acid, OsHioOafOeHg < ^^^ ) . — 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 from mesitylene; and, according to the accepted 
hypothesis, it is the only one possible. By distillation with 
lime, it yields meta-xylene. Further oxidation converts it 
into uvitic and trimesitic acids (see p. 270). 

Note for Student. — Of what special significance is the formation of 
meta-xylene from mesitylenic acid ? 

?leS^^pSl^:^. }C.H.O,(O.H,.CH..OH..CO^. 

— Hydro-cinnamic or ^-phenyl-propionic acid is obtained by 
treating cinnamic acid with nascent hydrogen : — 



C0M5 . CH : C H , CO2H + H2 = CgH5 • CII2 . CH2 . COjH. 

Cinnamic acid, Hydro-cinnamic acid, 

/3-Phenyl-acrylic acid ^-Phenyl-propionic acid 



It is also made by starting with ethyl-benzene, CeHg . O2H5, 
and cariying out the same reactions that are necessary to 
transform toluene into a-toluic acid (see p. 332). It is a 
product of the decay of several animal substances, such as 
albumin, fibrin, brain, etc. It crystallizes from water, in long 
needles, which melt at 48°. It yields benzoic acid when oxi- 
dized. 



834 DERIVATIVES OF THE BENZENE SERIES 

Ortho-amino-hydro- j. n h < ^^^ ' ^^ * OOgH 

cinnamic acid, ) * * NHgjo) 
acid is prepared from hydro-cinnamic acid in the same way 
that ortho-amino-a-toluic acid is made from a-toluic acid. It 
is not obtained in the free state; but, like the ortho-amino 
derivatives of benzoyl-formic and of o^toluic acids, it loses 
waterj and forms the anhydride. 

Hydro-carbostyril, O6H4 < TT ^ O . OH. — Hy dro-carbo- 

styril is made by treating ortho-nitro-hydro-cinnamic acid with 
tin and hydrochloric acid. It is a solid that crystallizes in 
prisms, melting at 160**. It is interesting chiefly for the reason 
that it is closely related to the important compound quhwline 
(which see). When treated with phosphorus pentachloride, 
hydro-carbostyril is converted into di-chlor-quinoline. The 
significance of this reaction will appear later. 

Dibasic Acids, C„H2n_io04 

The simplest acids of this group are the three phthalic acids, 
which are the di-carboxyl derivatives of benzene, belonging to 
the ortho, meta, and para series. 

SSh^coid. } OAO(OA<«°D. - Phtt».ic 

acid was the first of the three acids of this composition dis- 
covered; and, as it was obtained from naphthalene, it was 
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 tem- 
perature of 220°-300**. It can further be formed from alizarin 

and purpurin; and from ortho-toluic acid, ^e^4"^nQ^^ f^7 
oxidation with potassium permanganate. 



ISOPHTHALIC ACID 836 

Experiment 78. Mix 40«^ naphthalene and 80s potassium chlorate, 
and add this mixture gradually to 400s ordinary concentrated hydro- 
chloric acid. Naphthalene tetra-chloride, CioHgCU, is formed in this 
reaction. Wash with water. Oradually add 400« ordinary concentrated 
nitric acid (sp. gr. 1.45), and boil in a large retort with upright neck. 
When all is dissolved, evaporate the nitric acid ; and, finally, distil the 
residue. Phthalic anhydride passes over. Recrystallize from water, 
'i his will be used for other experiments. 

Phthalic acid forms orthorhombic crystals, which melt at 
213° or lower, according to circumstances, for, when heated, it 
breaks up gradually, even below the melting-point, into water 
and the anhydride which melts at 128**. Distilled with lime, 
it yields benzene ; though, by selecting the right proportions, 
benzoic acid can be obtained : — 

(1) C,H, < ^^^ = CeH, + 2 CO. ; 

(2) C.H, < ^^*JJ = CeH, . CO,H + CO^ 

Phthalic acid is oxidized by chromic acid to carbon dioxide 
and watel*. Hence it cannot be made from ortho-xylene by 
oxidation with chromic acid. By boiling ortho-xylene with 

nitric acid, however, it yields ortho-toluic acid, 0.114 <^^' , 

cu2n(o) 

and this can be oxidized to phthalic acid by treatment with 
potassium permanganate. 

CO 

Phthalic anhydride, OeH^ < ^q > O, is formed by heat- 
ing phthalic acid. It forms long needles, which melt at 128**. 
Heated with phenols, it forms the compounds known as pJUhal- 
eins (which see). 

Isophthalio acid, \ mj ^^OgH f^^^^^A u^ ^^; 

•\r^Z ^T-xT- T -J y ^6-ti.4 < i^^ TT » IS lormed by oxi- 
Meta-phthalic acid, J ®. * COgHdn)' '^ 

dizing either meta-xylene or meta-toluic acid with chromic 



336 DERIVATIVES OP THE BENZENE SERIES 

acid; by distilling meta-benzene-disulphonic acid with potas- 
sium cyanide, and boiling the resulting dicyanide with an 
alkali. 

Note for Student. — Write the equations representing the action 
involved in passing from meta-benzene-disulphonic acid to isophthalic 
acid. Into which dihydroxy-benzene is this same disulphonic acid con- 
verted by melting it with caustic potash ? 

The acid is formed, further, by heating the potassium salt 
of meta-sulpho-benzoic acid with sodium formate : — 



CfiH, < ^X'^/^x + H • COaNa = CeH, < ^XC/^x + HKSO3. 



Potassium sulpho- Potasslnm sodinm 

benzoate isophthalate 



This reaction is of importance, for the reason that the same 
sulpho-benzoic 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 meta-xylene. 

Isophthalic acid crystallizes in fine needles from water. It 
melts above 300°, and is not converted into an anhydride. 

Sr.SSSSot&, }0A<°g^,.-Te.pUha.,. acid 

is formed by oxidation of the oil of turpentine,^ cymene, para- 
xylene, and para-toluic acid ; by heating a mixture of potas- 
sium para-sulpho-benzoate and sodium formate : — 

Potassium para- Potassium sodium 

Bulpho-benzoate terephthalate 

Para-sulpho-benzoic acid is converted into one of the three 
hydroxy -benzoic acids by caustic potash. In the para as well 

1 The prefix fere is derived firom the Latin terehirUhinua^ turpentine. 



PHENOL-ACIDS OF THE BENZENE SERIES 337 

as the meta series, the lines of connection indicated below have 
been established : — 



COM " *^SO,H r ' CH 



I \ i 

I 

p XT ^ OH nzT ^ SO3H 

^6^4 < OH ""^ ^'^' ^ SO3H 

Terephthalic acid is a solid that is practically insoluble in 
water. It sublimes without melting and, like isophthalic acid, 
yields no anhydride. 

Hexabasic Acid 

Mellitio acid, OisHeOiaCOgCOOgEOe]. — This acid occurs in 
nature in the form of the aluminium salt, as the mineral 
honey-stone or melUte, The mineral is rare, and is found in 
beds of lignite. Mellitic acid has been made by direct oxida- 
tion of carbon with potassium permanganate, and by oxidation 
of hexa-methyl-benzene, C6(CH3)6. By ignition with soda-lime 
it is converted into benzene and carbon dioxide : — 

Ce(C02H)e = CeHe + 6 COg. 

Phenol-acids, or Hydroxy-acids op the Benzene Series 

It will be remembered that the alcohol acids or hydroxy- 
acids of the paraffin series form an important class, including 
such compounds as glycolic, 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 properties are more prominent than the alco- 
holic. The hydroxy-acids of the benzene series bear the same 
relations to the benzene hydrocarbons that the hydroxy-acids 



338 DERIVATIVES OP THE BENZENE SERIES 

already studied bear to the paraffins. The simplest are those 
which contain one hydroxyl and one carboxyl in benzene^ 

OH 

having the formula C^RaK^q h* 

MONO-HYDROXY-BENZOIC AciDS, CjB^O^ 



Salicylic acid, 



OH 



Ortho-hydroxy-benzoic acid. l^^'^002H(o) — Salicylic 
acid is found in the form of an ethereal salt of methyl, in the 
oil of wintergreen, prepared from the blossoms of Gaultheria 
procumbens. It is formed in a number of ways, among which 
the following should be specially mentioned : — 

1. By converting ortho-amino-benzoic acid into the diazo 
compound, and boiling with water (see p. 328). 

Note for Student. — Give the equations representing the reactions. 

2. By fusing a salt of ortho-sulpho-benzoic acid with caustic 
potash. 

Note for Student. — Write the equation. 

3. By treating sodium phenolate with carbon dioxide. The 
sodium salt is first saturated with carbon dioxide under press- 
ure in closed vessels. This gives sodium phenyl carbonate, 
CeHs.O.COgNa. By heating this to 120-130° under pressure 
it is converted into sodium salicylate : — 

CeH, . . CO^Na = CeH^ < ^^^ . 

COaNa 

4. By heating phenol with tetra<5hlor-methane and an alco- 
holic solution of potassium hydroxide : — 

OK" 
CfiH^ . OH + CCI4 + 6 KOH = CeH,< ^ J^ -F 4 KCl-F 4 HgO. 

5. By saponifying the methyl salicylate found in oil of 
wintergreen : — 

OH OH 

O6H4 < ^^ ^jj -1- KOH = C6H4 < (iQ ^ + CH3OH. 



SALICVLIC ACID 



339^H 



Kxperlment 74> Boil 30°' to 40" oil of wintergreen v 
ately strong caustic potasli in a flask ooniiecied with an inyerted oon- 
denser. When it ia dissolved, acidify witb hjdrooliloric acid. Filter oS 
the salicylic acid which separates, and lecrystallize from water. 

Experiment 75. Dissolve 8CK sodium hydroude and iOt phenol in 
130" water in a litre flask, arranged as in Fig. 18. If the mixture is cool, 
heat to 50-00°, and remove the flame. SloiBly add 60b cliloroforiii, shak- 
ing the mixture for several minutes after each addition. The mixture 
gradually becomes dark colored. An hour or more may be required 




Ui complete the addition of all tlie chloroform, 
boil for an hour, and then distil off tbe excess of chloroform on the water- 
bath. Acidify witli dilute hydrochloric acid, when a thick reddish brown 
oil Qomes down. Distil in steam as in Exp. 67, until tbe distillate no 
longer appears in milky drops. A light-colored oil consisting of salicylic 
aldehyde and phenol settles in tbo receiver. Decant the sapemataat 
Extract with ether, and concentrate the extract by evaporation 
■bath. To the concentrated extract add a saturated solution 
•sodium sulphite (freshly prepared by dissolving 40a sijiiium 




SiO DERIVATIVES OF THE BENZENE SERIES 

sulphite in 76«« hot water, cooling the solution, and saturating with 
sulphur dioxide) . Shake the mixture 8 or 10 times, 2 or 3 minutes at a 
time, for half an hour ; then allow it to stand for several hours. The 
aldehyde unites with the sulphite, forming small, glistening, white 
crystals, while the phenol remains in solution in the ether. Filter with 
the aid of a pump, and wash the crystals with alcohol. Then treat the 
crystals on the water-bath with hydrochloric acid, when salicylic alde- 
hyde is thrown down. Extract completely with ether, separate the two 
solutions, and evaporate the ether. 

In an iron or silver dish, melt 25^^ caustic potash ; remove the lamp ; 
and add the salicylic aldehyde drop by drop, stirring constantly. The 
potassium salt of salicylic acid is thus formed. After the mass is cooled, 
dissolve in water, ^nd precipitate the salicylic acid with dilute hydro- 
chloric acid. Filter, wash with cold water, and purify by recrystallizing 
from water. 

* 

The action of chloroform on phenol in the presence of caustic 

soda is analogous to that of tetra-chlor-methane. It will be 
understood with the aid of the following equations : — 

(1) CeH, . OH + CHCla = C,U, < ^^^^ + HCl; 

OFT OFT 

(2) CoH,<^JJ^^^ + 2NaOH = C,H,<^^^^^^^.^2NaCl; 

(3) CeH, < (.^(OH)^ = ^^' ^ CHO + ^^^• 

This reaction is of general application to phenols, and affords 
a very convenient method for the preparation of the phenol- 
aldehydes and from these the acids. 

Salicylic acid crystallizes from hot water in fine needles. It 
melts at 159^ 

When heated with soda-lime, it breaks up into phenol and 
carbon dioxide : — 

OTT 
CA < ^J„ = CoH, . OH + CO^ 

Heated alone it gives phenyl salicylate (salol) and xanthone:— 



PHENYL SALICYLATE 341 

(1) 2W<0H^jj = C.H,<0H^^^^^+C0. + H,0; 

Phenyl salicylate (salol) 

(2) C.H,<2J^^^jj^ = CeH,<0^>CeH, + HA 

Xanthone 

With ferric chloride, its aqueous solution gives a characteristic 
dark violet-blue color. Free salicylic acid is antiseptic, pre- 
venting decay and fermentation. It is therefore used for pre- 
serving foods. It is also used extensively in medicine, 
especially in rheumatism. 

Acetylaalicylic acid is used in medicine under the name 

OH 
Salicylic acid forms salts of the general formula C6H4< ; 

and, with the alkalies, compounds, in which both the phenol 
hydrogen and the acid hydrogen are replaced by metals, as 

C6H4<^^ _. The basic calcium salt, C6H4<^^ >Ca 4-1120, is 
UU2IV C/U2 

very difficultly soluble in water, and is converted by carbon 

dioxide into the salt (^«^*<co ) ^** Salicylic acid forms 

OH 
ethereal salts of the general formula C6H4<^q , of which 

OH 

methyl salicylate, C6H4<p^ ^ , is the best-known example. 

OR 
It forms, also, ether-acids of the general formula C6H4<p^ ; 

OR 

and, finally, compounds of the general formula C6H4<^q • 

Phenyl salicylate (salol), O6H4 < ^5in,^ tt • — This is 

formed when salicylic acid is heated alone to 200-220*^, and 
when salicylic acid, phenol, and phosphorus oxychloride are 
heated together. It is a solid that melts at 43^ It is exten- 
sively used as an antiseptic. 



342 DERIVATIVES OF THE BENZENE SERIES 

That salicylic acid belongs to the ortho series is clear from 
the following facts : — 

Ortho-toluene-sulphonic acid has been converted into ortho- 
sulpho-benzoic acid, and this into salicylic acid. Further, the 
same toluene-sulphonic acid has been converted into ortho- 
toluic acid, which, by oxidation, yields phthalic acid. 

■ Ortho-toluene-sulphonic Ortho-sulpho-benzoic 

acid acid 

(2) C«H4<g^^^^ +KOH = CeH«<^^»^ +K^0,; 

Potassium salicylate 

(3) C,H,<gJ^'^^ +KCN = CeH«<^^» +K,S03; 

(4) CeH,<^J» +2HjO = C«H,<^^» +NH,; 

Ortho-toluic acid 
Phthalic acid 

Oxybenzoio acid, I CH <^^ This 

Meta-hydroxy-benzoic acid, / ^ * COgH^^j* 

acid is made from meta-amino-benzoic and meta-sulpho-benzoic 
acid by the usual reactions. 

It crystallizes from water in needles united to form wart- 
like-looking masses. It gives no color with ferric chloride. 
Its connection with meta-phthalic (isophthalic) acid and meta- 
xylene is shown by means of the transformations tabulated on 
p. 337; that is to say, the same sulpho-benzoic acid which, by 
fusing with caustic potash, yields oxy ben zoic acid, by fusing 
with sodium formate yields isophthalic acid. Therefore oxy. 
benzoic acid is a meta compound. 



DI-HYDROXY-BENZOIC ACIDS 343 

Para-oxybenzoio acid, \ C H < ^^ + H O 

Para-hydroxy-benzoio acid, j ^ ^ CO^jH^^ ^ 

Para-oxybenzoic acid is formed from the corresponding amino- 

and sulpho-benzoic acids; by treating various resins with 

caustic potash ; from anisic acid (see below), by heating with 

hydriodic acid; by heating potassium phenolate in a current 

of carbon dioxide to 220°. 

Note for Student. — Notice the fact that, while sodium phenolate, 
when heated in a current of carbon dioxide, yields salicylic acid, potas- 
sium phenolate, under the same circumstances, yields para-oxybenzoic 
acid. 

Its aldehyde is formed, together with salicylic aldehyde, by 
treating phenol with chloroform and caustic soda* (see Exp. 75). 

The reasons for regarding para-oxybenzoic acid as a member 
of the para series are similar to those which show that oxyben- 
zoic acid is a meta compound. The same sulpho-benzoic acid 
that yields para-oxybenzoic acid also yields terephthalic acid. 

Anisic acid, \ O H < ^^"^^ Anisic 

Para-methoxy-benzoic^ acid, / ^ * COgH, >* 

OCH 
acid is formed by the oxidation of anethol, C«H4 < ^ tt ^j a 

phenol ether contained in anise oil. It is made by heating 
para-oxybenzoic acid with caustic potash and methyl iodide 
and saponifying the di-methyl ether thus formed. As the 
formula indicates, it is the methyl ether of para-oxybenzoic 
acid. As will be seen, it is isomeric with methyl salicylate. 
By boiling with caustic alkali the latter is saponified, while 
anisic acid is not. When anisic acid is distilled with lime, 
anisol is formed. 

Dl-HYDROXY-BENZOIC AciDS, C7H6O4 

Protocatechuic acid, CgHg | ^, is a frequent product 

* Meihoxy Is derived from methoasyl, the name given to the ether g^oup, OCH3. In a 
•imilar way 0C|Hb is called ethoxyl; OGeHf, phenoxyl, etc. 



344 DEBIVATIVES OF THE BENZENE SEBIES 

of the fusion of organio substances with caustic potash. Thus, 
the following substances, among others, yield it : oil of cloves, 
piperic acid, catechin, gum benzoin, asafcetida, vanillin, etc 
It is made from sulpho-oxybenzoic acid, and from sulpho-para- 
oxybenzoic acids by fusing with caustic potash. 

Note fob Student. — What analogy is there between the fact that 
protocatechuic acid is formed from sulpho-oxybenzoic acid and from 
solpho-para-oxybenzoic acid, and the fact that pseudocnmene is formed 
from brom-meta-xylene and from brom-para-xylene ? What conclusion 
may be drawn regarding the relations of the two hydroxyl groups, and 
the carboxyl in protocatechuic acid ? 

By distillation with lime, protocatechuic acid breaks up into 
pyrocatechol and carbon dioxide : — 

rOH 

I. CO2H Pyrocatechol 

fOOHs 
Vanillic €tcid, CgEEg-j OH , is formed by oxidation of 

I0O2H 

vanillin, which is the corresponding aldehyde. It is the mono- 
methyl ether of protocatechuic acid. 

Vanillin, OgHgOgI O^ < OH ), is the active constituent 

^ iCHO>' 

of the vanilla bean. It is made artificially by treating the 
ether, guaiacol, CeH.<^^^ with chloroform and caustic soda. 

(o) 

rCHO 
Piperonal, OgHg j 0^^„ . — This is formed by .oxidizing 

piperic acid, which is itself a product of the decomposition of 
piperine, a complex compound that is found in different 



GALLIC ACID 345 

varieties of pepper. Piperonal is the methylene ether of 
protocatechuic aldehyde. It can be made artificially, and is 
used in perfumery under the name heliotropine. The relations 
between protocatechuic aldehyde, vanillin, and piperonal are 
shown by the following formulas : — 

/CHO(l) (CHO (1) (CHO (1) 

CeHs i OH (3) CeHa ] OCH3 (3) C^, i O ^ pxx (^^ 

(OH (4) (OH (4) (O '(4) 

Protocatechuic Vanillin Piperonal 

aldehyde (Heliotropine) 



Tri-htdroxt-benzoio Acids, CyHflO^ 

QaUio acid, 07H6O, + H2o(06H2<^^^« + H2o).— Gallic 

acid occurs in nutgalls, sumach, Chinese tea, and in many 
other plants. It is formed by boiling tannin or tannic acid 
with dilute sulphuric acid; by melting brom-protocatechuic 
acid with caustic potash: — 

CeHa \ (0U\ + KOH = CeH^ < ^^^' + KBr. 
( CO,H ^^'^ 

Brom-protocatechuic Gallic acid 

acid 

It is best prepared from gall nuts by hydrolysis of the 
tannin contained in them. 

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 dis- 
solves in excess of ferric chloride, forming a dark green 
solution. It. readily reduces gold and silver salts in solution. 
When distilled, it yields pyrogallol (pyrogallic acid) and 
carbon dioxide: — 

CeH, < f^^ = C6H3(OH)3 +C0,. 



346 DERIVATIVES OF THE BENZENE SERIES 

Tannic acid, tannin, C14H10O9 + 2 H2O. — This substance 
occurs in gall nuts, from which it is extracted in large quan- 
tities. It is an amorphous powder. It is markedly astringent. 
It is soluble in water, the solution giving, with ferric chloride, a 
dark blue-black color. Tannin is used extensively in medicine, 
in dyeing, and in the manufacture of ink and leather (tanning). 
It combines with gelatin, forming an insoluble substance. Its 
relation to gallic acid is indicated by the following equation : — 

2 CyHgOs = Ci4H,o09 + H2O. 
Gallic acid Tannin 

Ketones and Allied Derivatives op the Benzene Series 

The ketones of the benzene series are strictly analogous to 
those of the paraffin series, and they are made in the same 
way. Acetone is made by distilling calcium acetate : 



CHa.COlO ^ 
CHal CO ^ 



CH3 
CH3 



=;,;;'> CO +caco8. 

Acetone 



So, also, benzophenone or diphenyl-ketone is made by distill- 
ing calcium benzoate : — 



CeH,.co:0 



Benzuphenone 



Further, by distilling mixtures of the salts of two fatty acids^ 
mixed ketones are obtained : — 



CH3 . COiOM; CHs 



C2H,. iCOOMl - C2H, >^^'^ ^^COg. 



Ethyl-methyl 
ketone 



And, similarly, mixed ketones containing one residue of a 
benzene hydrocarbon and one of a paraffin, or two different 
residues of benzene hydrocarbons, can be obtained thus : — 



QUINONES 347 

w CH3.COOM - CH3 ^^^ + ^'^^'' 

Phenyl-methyl ketone, 
Acetophenone 



C«H,.COOM 
GH3 
COOM 



(2^ CH^GH, =^«JJ»>C0 + M,C03. 



Phenyl-tolyl-ketone 

Interesting results have been readied through a study of the 
oximQs of the aromatic ketones. It has been shown that while 
the symmetrical ketones, like benzophenone, CeHa.CO.CaHg, 
give but one oxime, some of the unsymmetrical ketones, like 
phenyl-tolyl-ketone, C6H5.CO.C6H4.CH3, give two. This is 
quite in accordance with the views already set forth in regard to 
the stereochemistry of nitrogen compounds (see Benzaldoxime, 
page 320). In the terms of stereochemistry the two formulas 



CgHs . C . CgHg 




CgHj.C.CgHj 


II 


and 


II 


HO.N ■ 




N.OH 



are identical, so that a symmetrical ketone can give but one 
oxime. On the other hand the formulas 

II and II 

HO.N N.OH 

are different, so that an unsymmetrical ketone can give two 
oximes. 

QUINONES 

The quinones are peculiar compounds which in some ways are 
allied to the ketones. The simplest example of the class, and 
the one best known, is called quinone. Its formula is C6H4O2, 
and it therefore appears to be benzene in which two hydrogen 
atoms are replaced by two oxygen atoms. All quinones bear 
this relation to the hydrocarbons, of which they may be regarded 
as derivatives. 



348 DERIVATIVES OF THE BENZENE SERIES 

Quinone, O6H4O29 is formed by the oxidation of quinic acid, 
hydroquinol, para-diainino-benzene, and some other benzene 
derivatives in which two substituting groups occupy the para 
position relatively to each other. 

It is usually made by oxidizing aniline with sodium bi- 
chromate and sulphuric acid. In the laboratory it is most 
convenient to make it by oxidizing hydroquinol. 

It forms long, yellow prisms; sublimes in golden-yellow 
needles ; is volatile with steam ; and has a peculi^ penetrating 
odor. 

Sulphurous acid reduces quinone to hydroquinol : — 

CeH A + H2SO3 + H,0 = C6H4(OH)2 + H2SO4. 

The easy transformation of hydroquinol into quinone, and 
the opposite transformation of quinone into hydroquinol, as 
well as the formation of quinone from other para compounds, 
force us to the conclusion that the oxygen atoms in quinone 
are in the para position relatively to each other. Quinone 
appears, therefore, as benzene containing two oxygen atoms in 
the para position as represented in the formula:— 

CO 
HC/NCH 



HC 



ICH 



CO 

As quinone forms a monoxime, C6H40(NOH), and a dioxime, 
C6H4(NOH)2, and takes up four atoms of bromine and of 
chlorine, it is generally regarded as a di-ketone of the formula — 

CO 
HC/\CH 



HC 



CO 



CH 



ORTHO-BEN ZOQUINONB 



349 



According to this view quinone is not, strictly speaking, a 
derivative of benzene, but is derived from dihydrobenzene : — v 

CHa 
HC/\CH 

Hcl JcH 
CHa 

If the di-ketone formula is correct, quinone may be regarded 
as derived from a dibasic acid in the same way that a simple 
ketone is derived from a monobasic acid. Thus, the calcium 

COOH 

salt of an acid of the formula ^^^^<qqqyi ought, according 
to this view, to yield quinone by distillation : — 






CO 



C,H,<COiO ; 



= C2H2 <QQ> C2H2 + 2 CaCOs. 



Several quinones have been studied. Under the head of 
Anthracene we shall meet with an important one called anthror 
quinone, which has been made by reactions that prove it to be 
a di-ketone in the sense in which this expression is explained 
above. 



Ortho-benzoquinone, isomeric with the well-known para 
compound, has recently been prepared from pyrocatechol. 
It is probably to be represented by the formula : — 

CO 

Hc/Nco 



HC 



CH 



CH 



360 DERIVATIVES OF THE BENZENE SERIES 

Pyridine Bases, C,H2„_5N 

The pyridine bases are formed in the distillation of bones, 
certain bituminous shales, and coal, and were first isolated from 
bone oil, which is a complex mixture of many substances. At 
present these bases are obtained principally from coal tar. The 
principal members of the group are pyridine, picoline, lutidine, 
and coUidine. They form an homologous series : — 

Pyridine CfiHsN 

Picoline CeH^N 

Lutidine C7H9N 

CoUidine CgHuN 

The formation of these bases in the distillation of bones is 
due to the presence of acrolein, ammonia, methylamine, etc., 
and their action upon one another at high temperatures. 
Members, of the series are formed whenever aldehydes of the 
fatty series are heated with ammonia. For example, ordinary 
aldehyde and ammonia give methyl-ethyl-pyridine, CsHuN, 
[C^3(CH3)(CA)N]:- 

and acrolein and ammonia give /8-picoline : — 

2C8H4O H-NH8 = CeHyN + 2H,0. 

Pyridine and picoline are also formed when glycerol is 
distilled with ammonium sulphate and sulphuric acid. 

An interesting synthesis of pyridine is effected by passing 
acetylene and hydrocyanic acid together through a heated 
tube. This is analogous to the synthesis of benzene from 
acetylene:- 3C,H, = CeHe; 

2 C2H2 H- HON = C5H5N. 

Pyridine can also be made from penta-methylene-diamine by 
first subjecting the hydrochloric acid salt of this substance to 
dry distillation and heating the product thus formed with sul- 
phuric acid : — 



• PYRIDINE 



351 



CH2< 



CHa . CHg . NHgCl. 
CH2 • CH.2 . Nxi2 



^il.2 . vyll.2 



^^^CH-CH^^ 



Pyridine, OgHgN. — Pyridine is found in commercial am- 
monia, and is formed, as stated above, in the distillation of 
bones, of certain bituminous shales, and of coal. It has been 
prepared from a number of its carboxyl derivatives, as, for 
example, from nicotinic acid, C5H4N" . COgH, which is formed 
when nicotine is oxidized with nitric acid. The formation of 
pyridine from quinolinic acid, a dicarboxyl derivative of pyri- 
dine, is of special importance, as it leads very clearly to a con- 
ception of the constitution of pyridine. Quinoline (which see) 
will be shown to have the constitution represented by the 
formula — 

HC CH 

JO. 




When it is oxidized it gives the dibasic acid above referred to, 
quinolinic acid, 



HC 
HC 



v^ 



CO,H 



When this is distilled with lime it loses carbon dioxide and 
gives pyridine : — 

CH r.r. XX CH 

^/\CH 



^^ysQ/^0^ HC 




+ 2C0j. 



CO,H HC^CH 



362 DERIVATIVES OF THE BENZENE SEBIES 

According to this, pyridine is benzene containing a nitrogen 
atom in place of one of the CH groups. The question in re- 
gard to the linkage of the groups and atoms in pyridine is a 
difficult one to deal with, and it need not be discussed here. 
Suffice it to say that the above hypothesis, as to the relation 
between benzene and pyridine, is in accordance with all the 
facts known. 

Pyridine is a liquid with a peculiar, sharp, characteristic 
odor. It is miscible with water in all proportions. It boils 
at 115**. It acts like a monacid base, forming salts like 
C5H4N . HCl, CfiHsN . HNOa, C5H5N . H2SO4, etc. It unites with 
alkyl iodides like methyl iodide, ethyl iodide, etc. When 
these compounds are treated with silver hydroxide, they form 
the corresponding hydroxides, which are strong bases. The 
compounds with the alkyl iodides are converted by heat into 
salts of homologues of pyiidine. For example, the ethyl iodide 
addition-product of pyridine is transformed at 290° into ethyl- 
pyridine hydriodide : — 

C^H^ . C2H J = C2H5 . C5H4N . HI. 

The view above presented has suggested various lines of in- 
vestigation. Thus, if the above formula represents the rela- 
tions between benzene and pyridine, it is clear that the existence 
of three isomeric mono-substitution products of pyridine ought 
to be possible. For example, there should be three methyl- 
pyridines or picolines, three pyridine-carbonic acids, etc. The 
three picolines should correspond to the formulas 

H H CH, 

HC^ \CH HC/' \c.CHs UG^ \CH 

II 11^ II 

\n/ \n/ \n/ 

Ortho-picoline Meta-picoline Para-picoline 

All three picolines are known ; and, by oxidation, they are 



CONINE 353 

converted into the three pyridine-carbonic acids, C5H4N . COgH ; 
and these, when distilled with lime, yield pyridine and carbon 
dioxide. 

Lutidines, 05H8(OH3)2N. — No less than six isomeric vari- 
eties of dimethylpyridine are possible according to the theory. 
Five of these have been prepared in pure condition. By oxida- 
tion they yield, first, monobasic acids, and then dibasic acids. 
When the monobasic acids are distilled with lime, they yield 
picolines. The dibasic acids give pyridine : — 

NC5H,<^^»jj = NC,H4 . CH3 + CO, ; 

NC,H8<^^^J = NC,H, + 2 CO^ 

Oonsrrine, propylpsrridine, NC^H^-OgHy. — This base is 
formed when conine is heated with zinc chloride or when the 
hydrochloride of conine is heated with zinc dust. It is con- 
verted into picolinic acid by oxidation, and is reduced to conine 
by hydriodic acid. 

The pyridine bases unite with two, four, or six atoms of 
hydrogen. Some of the alkaloids are derivatives of the addi- 
tion-products thus formed. 

Piperidine, CgHjiN. — This base is formed from piperine, a 
constituent of pepper. It has been made by adding hydrogen 
to pyridine by means of sodium and alcohol : — 

C5H5N + 6 H = C^HnN. 



Oonine, propylpiperidine, CHj ^NH . — This 



^, OR, 
base occurs together with others in hemlock {Conium maculatum). 



XJH, - CH - O3H, 
X!H„ - OH. 



354 



DERIVATIVES OF THE BENZENE SERIES 



It is a colorless liquid, and is a violent poison. This is the 
first alkaloid that was prepared artificially, and it is therefore 
of special interest. The steps taken are indicated below : — 



CH2OH 

I 
CH . 

II 

CHa 

AUyl 
alco 



CHjBr 

I 



lyl 
hoi 



■»- CH - 

II 
CH, 

Ailyl bromide 



CHjBr 

I 
CH, - 

I 
CHjBr 




CH,CN 



Tri-methylene Tri-methylene 



bromide 



7 



cyanide 



ivi 
de 



CHj . CONH, CHjCHjjNH 

I 
CHj 

I 
CH^.CONHj 



a 
I 
CHj — 

I 
CHjCHjNH, 

Penta-methylene diamine 



CH2 

! 
CH, 

I 
CH, 



CH 



CH 




NH 



Piperidine 



N 
HC/NCH 



HC 



CH3-N-I 
Hc/\CH 



CH 



HC 



CH 



CH 

Pyridine 

N 
Hc/\c.CH = CH.CH 



N 
HC/\C.CH. 



)CH 



HCl 



CH 



HC 



3 



CH 

NH 
HoOr iCH . CHo . CMo . Cxl« 



\y 

CH 



ICH 



H,C 



)CH, 



CH, 

Inactive conine 



The change from picoline to allyl-picoline is effected by 
means of paraldehyde. The conine thus obtained is optically 
inactive, whereas that obtained from hemlock is dextro-rotatory. 
By means of the salt with c^-tartaric acid, the inactive conine 
can be resolved into the two active varieties. The (i-conine 
thus obtained is identical with natural conine. 

[Is there an asymmetric carbon atom in conine ?] 



HEMITEBPENBS 355 

Tbrpenes and Camphors 

Terpenes are hydrocarbons found in various coniferous trees 
and in plants of the citrus varieties. The so-called ethereal 
oils are obtained from such plants and their fruits by distilla- 
tion with water vapor. Some of these ethereal oils are mixtures 
of hydrocarbons of the formula CioHm with other compounds 
containing oxygen. The principal terpenes have the for- 

mula CioHie and are related to hexahydrocymene, C6Hio<^ * . 

Others are related to tetrahydrocymene, and still others to 
dihydrocymene. Some take up one molecule of hydrochloric 
acid or two atoms of bromine, others take up two molecules of 
hydrochloric acid or four atoms of bromine. They also com- 
bine with water to form hydrates. They are easily polymer- 
ized by heat or by shaking with sulphuric acid or boron 
fluoride. Many are converted into cymene by gentle oxi- 
dation, and by more energetic oxidation into 2>-toluic and 
terephthalic acids. 

The broadest classification of the terpenes is into (1) Hemi- 
terpenes, CgHg; (2) Terpenes, CioHje; (3) Sesquiterpenes, GisHn] 
(4) Diterpenes, C20H32 ; (5) Polyterpenes, (CioHjg),;. 

(1) Hemiterpenes 

Isoprene, C^H.^. — This is formed in the distillation of caout- 
chouc or india rubber. It has been shown to be fi-methyl-divinyl, 
H2C = C(CH8) — CH = CH2. It is also formed from methyl-pyr- 
rolidine, a tetrahydrogen addition-product of one of the pico- 
lines. When heated to 100** in a sealed tube with glacial 
acetic acid it gives a product that appears to he identical with 
india rubber, 

(2) Terpenes 
These are classified into Monocyclic and Bicydic Terpenes, 



356 DBBIVATIVES OF THB BENZENE SERIES 



A. Monocyclic Terpenes 

The characteristic property of these is the power to take 
up four atoms of bromine or two molecules of the halogen 
acids. The principal ones are limonene and dipentene, the 
latter being the inactive variety of the two optically active 
limonenes. 

Limonene, OiqH,^ — The dextro variety is found in oil of 
lemon, oil of bergamot, and a number of other ethereal oils. 
Oil of orange is almost entirely (i-limonene. With bromine it 
forms a tetra-bromide, CioHjeBr^, m. p. 104°-105°. ^Limonene 
is found in the oil of fir needles {Pinus sylvestris) and in oil of 
fir, together with ^pinene. Inactive limonene or dipentene 
occurs with cineol in Oleum cince, and is formed by heating 
pinene and camphene to 250°-300°, and is therefore contained 
in Eussian and Swedish oil of turpentine. 



B. Bicydic Teipenes 

These combine with one molecule of hydrobromic acid and 
with two atoms of chlorine or of bromine and with one mole- 
cule of water. The two most important members of this group 
are pinene and camphene. 

Pinene, CjoHie. — This is the principal ingredient of the vari- 
ous kinds of oil of turpentine obtained from different varieties of 
pine. Heated to 250^-270** it is converted into limonene. It is 
known in three varieties — dextro, levo, and inactive, (i-Pinene 
is obtained from American, German, and Swedish oil of turpen- 
tine"; ^pinene from the French. The inactive variety is formed 
by combination of the two active varieties. The evidence 
points to the following formula as the most probable for 
pinene : — 



BICYCLIC TERPENES 367 

CH2 — Crl — CHj 

I 

CH3 — C — CH3 
CH = G - CH 
5H3 
This significance of the adjective "bicyclic" will be apparent. 



k 



cf-Pinene hydrochloride, bornyl chloride, C10H17CI, is 
formed by conducting diy hydrochloric acid gas into pinene. 
It is a crystalline solid with an odor like that of ordinary cam- 
phor. When heated alone, or with bases, hydrochloric acid is 
split off and camphene which is isomeric with pinene is formed. 

Oil of Turpentine. — When incisions are made in the trunk 
of various conifers, a liquid exudes that is known as turpen- 
tine. Most of that which comes into the market is obtained 
from Pinus australis, growing in North America. The .volatile 
constituent of turpentine is oil of turpentine. The non-volatile 
constituent is abietic acid, C20H30O2. These are separated by 
distillation. If the distillation is carried on without the a4di- 
tion of water, the residue is ordinary rosin (colophony). 

Oil of turpentine dissolves sulphur, phosphorus, and caout- 
chouc, and is used in the preparation of varnishes and oil 
colors. 

Camphene, OioHjg. — This is formed from bornyl chloride 

(which see) and also from bomeol. From d-bornyl chloride 

(Camphene is obtained ; and from ^bornyl chloride Camphene. 

Camphene has been shown to have the formula given below. 

It is therefore clear that in passing from pinene to camphene 

I 
the connecting link HsC — C — CHs changes from the meta to 

I 
the para linking. 

Oamphane, CioHig, is formed from bornyl chloride or iodide 
by reduction. Whether formed from dr or from Z-bornyl iodide 



358 



DERIVATIVES OF THE BENZENE SERIES 



the camphane is inactive. Hence the camphane molecule must 
be symmetrical. This is shown by the formula below, which 
also shows the relation between camphene and camphane : — 



CH2 - CH - CH 

I 
CHs — C — CHj 

I 

CHj - C - CH 

I 
CH, 

Camphene 



CH2 — CH — CHj 

1 

CH3 — C — CH3 

I 

CH2 — C CHj 

I 

CH, 

Camphane 



(3) Sesqui- and Polytbrpenbs 

Caoutchouc, (CioHig)^,. — This is commonly known as india 
rubber. It is the hardened milky juice of the tropical euphor- 
biacese, apocyneae, etc., especially of Siphonia (ficus) elasHca 
of Brazil. By dissolving the crude material in chloroform 
and precipitating with alcohol it can be obtained pure, in the 
form of a white, amorphous mass. By treatment with sul- 
phur it is vulcanized, the product being much harder than the 
caoutchouc itself. Treated with ozone and water it is split into 
two molecules of levulinic aldehyde, CH3.CO.CH2.CH2.CHO. 
Now it has been shown that the effect of treatment with ozone 
is to add two atoms of oxygen to each pair of carbon atoms 
united by double bonds and to cause a breaking down at these 
parts of the molecule. In this case the action is indicated 
thus : — 





CHfl.C 



•CH2.CH2.CH^ O 



rt.^H.CHj.CH/ 




C . CH«. 



Further, it has been pointed out that isoprene (which see) is 
easily polymerized to caoutchouc. These formulas will be 
helpful in this connection : — 



SESQUI- AND POLYTERPENES 369 

^CH2 CH2^CHv /CH2 . CHa . CH,x 

HsC.Cf >C . CHs -> CHs . C^ ^.CHg. 

XIHrrCHa H2C^ ^CH . CH2 . CHa^ 

Isoprene Caoutchouc 



Camphors 

Ordinary camphor is the best known example of these. 
They are either ketones or alcohols. By reduction with alco- 
hol and sodium the ketone camphors are converted into alcohol 
camphors, and the alcohol camphors are converted into ketone 
camphors by oxidation. The hydroxyl group of the alcohol 
camphors can be replaced by halogen, and the compounds thus 
obtained, when treated with alcoholic alkali, give up the halo- 
gen and hy drogen and yield terpenes. Thus borneol, C10H17 . OH, 
gives bornyl chloride, C10H17CI, and this in turn gives camphene 
(which see). 

A. Monocyclic Camphors 

These are derived from the monocyclic terpenes. The prin- 
cipal one is 

i-Mehthol, CioHjgOH, a solid, melting at 42** and boiling at 
212°, which is the principal ingredient of the oil of pepper- 
mint. It has been shown to be a hydroxyl derivative of 
hexahydrocymene, C10H20. 



B. Bicydic Camphors 

The principal members of this group are related to camphene 
and camphane. They are borneol and laurinol. 

Borneol, Borneo camphor, C,oHi80[CioH,-(OH)]. — Borneo 
camphor occurs in cavities in a tree (Dryobalanops camjyhora) 
found in Borneo, Sumatra, etc. This variety is dextro-rota- 
tory. The levo-rotatory variety is found in the camphor 



360 DERIVATIVES OF THE BENZENE SERIES 

from valerian oil, and inactive borneol is formed by bring- 
ing together d- and ^borneol. Borneol is much like ordinary- 
camphor or laurinol, but its odor resembles that of pepper. 
Treated with sodium and alcohol, laurinol gives d- and ^borneol. 
Both the active varieties give laurinol by oxidation; treated 
with phosphorus pentachloride borneol gives bornyl chloride, 
C10H17CI, identical with pinene hydrochloride. 



Camphor, laurinol, CioHigO. — This is the substance ordi- 
narily called camphor. It is obtained in China and Japan 
from different species of the genus Camphora of the Lauras 
family by distilling the finely cut wood with water vapor. It 
is purified by sublimation. It is a colorless mass that can be 
crystallized from alcohol and sublimes in lustrous prisms. The 
ordinary form is dextro-rotatory. Both the other possible 
stereo-isomeric forms are known. Camphor is reduced to 
borneol by hydrogen from sodium and alcohol. It can be 
made by oxidizing borneol or camphene. When distilled with 
phosphorus pentoxide, camphor gives cymene. The same de- 
composition is effected by heating it with concentrated hydro- 
chloric acid to ITO"*. 

The reactions of camphor show that it is a saturated ketone. 
The ease with which it is converted into cymene makes it 
highly probable that a methyl group and an isopropyl group 
are present in the compound in the para position in a ben- 
zene ring. When heated with iodine it gives carvacrol by 
loss of two atoms of hydrogen. Carvacrol is isomeric with 
thymol, the hydroxyl being in the ortho position to the 
methyl group. This makes it appear highly probable that 
the oxygen in camphor is ortho to methyl. Other facts 
that have been brought to light in investigations of the 
oxidation-products of camphor indicate that the group, 
C(CH3)2, formed from isopropyl is united with two para 
carbon atoms of the benzene ring. All this is shown by 



BICVCLIC CAMPHORS 



861 



the formula for camphor given below, now generally accepted 
by chemists. 



H2C — CH — CH2 IS.2C — CH — CH2 



I 
HsC.C.CHs 

I 
H2C — C — CH2 

I 
CHs 

Camphane 



I 
HsC.C.CHs 

I 
HgC - C - CH(OH) 

I 
CHs 

Borneol 



H2C — CH — CH2 

I 
H3C . C . CHs 

I 

H2C - C - CO 

I 

CHs 

Camphor 



Artificial Camphcr. — Camphor is now manufactured from 
pinene. The steps involved are (1) addition of hydrochloric 
acid and formation of bornyl chloride; (2) treatment of the 
bornyl chloride with bases and formation of camphene; 
(3) oxidation of camphene and formation of camphor. The 
product differs from ordinary camphor in being optically 
inactive. 



Although not closely related to the terpenes, two substances 
of similar composition may be mentioned in this connection. 
These are the hydrocarbon anhydrogeraniol and the oxygen 
compound geraniol. 

Anhydrogeraniol, CjoHis, is formed from geraniol, CjoHigO, 
by elimination of water. It probably has the structure repre- 
sented by the formula, — 

(0113)20 = OH . OH2 . 01x2 . 0(0113) = = CH2» 

Geraniol, CioHigO, is contained in Indian oil of geranium 
and a number of other ethereal oils. It is a primary alcohol, 
giving an aldehyde geraniol, OioHigO, and an acid, geranic acid^ 
OioHiflOg, by oxidation. Geranial loses water and gives cymene. 



CHAPTER XVI 



DI-PHENYI^METHANE, TRI-PHENYI^METHANE, TETRA- 
PHENYL-METHAITE, AND THEIR DERIVATIVES 

As we have seen, toluene may be regarded either as methyl- 
benzene or phenyl-methane. Of course, according to all that 
is known regarding similar substances, the two views are identi- 
cal. Eegarding it, for our present purpose, as phenyl-methane, 

CeHs 

we may write its formula thus : c ' 



H 

H 

LH 



This suggests the possibility of the existence of such sub- 
stances as 

CeHs 



Di-phetiyl-methane C 



Ih 



Tri-phenyl-metJiane C 



rCeH, 

H 



and Tetra-phenyl-methane C' 



CeH5 
CeHg 



All these hydrocarbons are known. The derivatives of tri- 
phenyl-methane are of special interest and importance. 

There is one reaction by means of which these hydrocai'bons 



TRI-PHENYL-METHANE 363 

can be made very readily. It has also been used for the synthe- 
sis of many other hydrocarbons. It depends upon the remark- 
able fact that, when a hydrocarbon is brought together with a 
compound containing chlorine, and anhydrous aluminium chlo- 
ride then added, hydrochloric acid is evolved, and union of the 
two substances is effected, the aluminium chloride not entering 
into the composition of the product. Thus, when benzene and* 
benzyl chloride, CgHg . CHgCl, are brought together under ordi- 
nary circumstances, no action takes place ; but, if some solid 
aluminium chloride is added, reaction takes place according to 
the following equation : — 

CgHg . CH2CI + CgHg = CgHg. CH2 . CgHg + HCl, 

Di-phenyl-methane 

and di-phenyl-methane is formed. 

Similarly, when chloroform and benzene are brought together 
in the presence of aluminium chloride, tri-phenyl-methane is 
formed according to this equation : — 

CHCI3 + 3 CgHe = CH (C6H,)3 + 3 HCl. 

Tri-phenyl-methane 

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 
di-phenyl-methane when boiled with zinc dust; and benzal 
chloride, CeHg .CHCI2, and benzene give tri-phenyl-methane : — 

CeH, . CHCI2 + 2 CeHe = CH(C6H,)3 + 2 HCl. 
Only tri-phenyl-methane will be treated of here. 

Tri-phenyl-methane, Ci9Hi6[CH(C6H5)3]- — This hydrocar- 
bon can be made, as above described, from benzal chlo- 
ride and benzene, and from chloroform and benzene. It 
can also be made from benzal chloride and mercury diphenyl, 
HgCC^H,),:- 



36-1 DI-PHBNYL-MBTHANE, ETC. 

CeH^ .CHCI2 + Hg(CeH,)2 = CH(CeH,)3 + HgCl^. 

It forms lustrous, thin laminae, which melt at 92°. It is 
insoluble in water ; easily soluble in ether and chloroform. It 
is crystallized best from alcohol. 

Towards reagents it is very stable. Thus, ordinary concen- 
trated sulphuric acid does not act upon it. fCeHg 

I r\ TT 

Oxidizing agents convert it into tri-phenyl-carbinol, C \ ^*^« 

lOH 
That the oxidation-product is really tri-phenyl-carbinol appears 
probable, from the fact that whenever aromatic hydrocarbons 
that contain paraffin residues are oxidized, the paraffin resi- 
dues are first attacked, while, as a rule, the benzene residue is 
unacted upon. Further, it gives an acetate with acetyl chlo- 
ride; and with phosphorus pentachloride it gives a chloride 
which is decomposed by boiling water, giving the carbinol 
again. A bromide is formed by treating it with hydrobromic 
acid, and this gives the carbinol when boiled with water. 



Trinitro-triphenyl- 1 Ci9H,3(N02)8[CH(CeH,NO,)8], is 
metnane, J 

formed by treating triphenyl^m ethane with nitric acid; and 
also by treating a mixture of nitro-benzene and chloroform 
with aluminium chloride : — 

CHCI3 -f- 3 CfiH,. NO2 = CH(C6H4. N02)3 + 3 HCl. 

This reaction shows that in the tri-nitro product one nitre 
group is contained in each benzene residue. 



Triamino-triphenyl-inethane, para-leuoaniline, 

Ci9Hi3(NH2)8[CH(C6H4. NH2)3] — 

The tri-araino compound is made by reduction of the tri-nitro 
compound, and also by reduction of para-rosaniIine» It is 
converted into para-roganiline by oxidation, 



PARA-ROSANILINB 



365 



Tri-phenyl-methane Dyes 

The well-known substances included under the head of Tri- 
phenyl-methane Dyes are more or less simple derivatives of 
the two compounds called rosaniline and para-rosaniline. 

When mixtures of aniline with ortho- and para-toluidines 
are heated with oxidizing agents, such as arsenic acid, stannic 
chloride, mercuric chloride, etc., several substances are formed,- 
the principal of which are the two above named. Pararrosan- 
iline, C19H19N3O, is formed from para-toluidine and aniline, 
according to the equation, — 

2 CfiHylSr + CjK^ -f- 3 = CigHi^tTgO -f- 2 ILjO. 

Aniline /7-Toluidine Para-rosaniline 

Bosaniline, C20H21N3O, is formed in a similar way : — 
CeRjN + 2 C7H9N + 30 = C20H21N3O -f- 2 H2O. 

Aniline o- and /7-Toluidine Rosaniline 

The composition and modes of formation of the two sub- 
stances show that rosaniline is a homologue of para-rosaniline, 
the relation between the two substances being represented by 
the formulas C19H19N3O and Ci9H,8(CH3)!N"30. 

By treating para-rosaniline with a reducing agent, it is con- 
verted into para-leucaniline, which has been shown to be tri- 
amino-triphenyl-methane : — 



CigHigNgO + Ha = CigHj^Nj 

Para-rosaniline Para-leuc- 

aniline 



CeH^ . NH2 
CH \ CeH^ . NH2 
CeH^.NHj 



+ H2O. 



It will thus be seen that pararrosaniline and rosaniline, which 
are the fundamental compounds of the group of aniline dyes, 
are derivatives of the hydrocarbon tri-phenyl-methane. 

Para-rosaniline, OigHigNgO. — The formation of this sub- 
stance by oxidation of para-leucaniline and of a mixture of 
toluidiae and auilijie was mentioned above. The relation 



366 DI-PHBNYL-METHANE, ETC. 

between para-rosaniline and para-leucaniline is expressed by 
the following formulas : — 

f CgHj f CeH, . NHj f CgH, . NH, 

CHJCgH, CHJCeH4.NHii C(OH) CH^-NHj. 
ICeH, [C8H,.NH, iC8H,.NH, 

Trl-phenyl- Triamlno-trlphenyl-methane, TriAmino-trlphenyl-carbinol, 
methane or Para-leucaniline or Para-roeaniline 

Bosaniline, O20H21N3O. — This is the principal constituent 
of commercial f uclisine. It is formed by oxidizing a mixture of 
aniline with ortho- and para-toluidines : — 

CeHyN 4- 2 C^HoN + 30 = CaoHj^NsO + 2 HgO. 

Experiment 76. In a dry test-tube put a little dry mercuric chlo- 
ride and a few drops of commercial aniline. Heat over a small flame. 
Dissolve the product in alcohol, with the addition of a little hydrochloric 
or acetic acid. The beautiful color of the solution is due to the presence 
of the hydrochloride or acetate of rosaniline. 

On the large scale, the oxidizing agent used is arsenic acid. 
Care is taken to remove all arsenic acid from the product, but 
it is nevertheless sometimes found in the products obtained in 
the market. Nitro-benzene is also used as the oxidizing agent. 
In this case there is, of course, no arsenic in the product., 
Rosaniline crystallizes in needles or plates. It is very slightly 
soluble in water; more readily soluble in alcohol. It forms 
three series of salts with monobasic acids. With hydrochloric 
acid it forms the salts C2oHiyN3 . HCl and CaoHiaNg . 3 HCl. 
Fuchsine or magenta is a mixture of the hydrochlorides of 
rosaniline and para-rosaniline. The formation of the salts of 
para-rosaniline takes place as represented in the following 
equation : — 

CeH^.NHg 
C (OHXCgH^ . NH2)3 + HCl = C CcH4 . NHg + H^O 

Para-rosaniline [ C,H4 . NH . HCl 



Para-rosaniline hydrochloride 



ROSANILINE 367 

Instead of the formulas here given for the salt two others 
have been suggested. In one of these the salt is represented 
as derived from the base triamino-triphenyl-carbinol or para- 
rosaniline, as potassium chloride is formed from potassium 
hydroxide : — 



NHg . CeH^ 
NH^.CeHJ 



NHg.CeH; 
C(OH) . NH2 . C6H4 [ CCl. 

NH2 . CeH^ 

According to the other view the salt and all the colored salts 
derived from para-rosaniline and similar bases have a constitu- 
tion similar to that of quinone, as shown thus for the hydro- 
chloric acid salt of para-rosaniline : — 

HjN . H^Cev yCeH4 . NII2 

II 

c 

Hc/\CH 

or (C6H^H2)2C : CgH^ : NH2CI. 

HCv yCH 

C 

II 
NH2CI 

Fuchsine and the other salts of rosaniline dye wool and silk 
directly. For dyeing cotton cloth, however, a mordant is gen- 
erally necessary. 

Dyeing. Animal fibres, in general, are colored directly by 
dyes ; that is to say, they have the power of forming with the 
dyes stable compounds which adhere to the fibres. This is not 
generally true of vegetable fibres, as cotton cloth and linen. 
Hence, in order to dye the latter, something must be added 
that, with the dye, forms a compound which adheres to the 
fibres. Substances which act in this way are called mordants. 
Among the substances used as mordants are aluminium acetate, 
ferric acetate, and some salts of tin. 



368 DI-PHENYL-METHANE, ETC. 

Experiment 77. Make a dilute solution of picric acid by dissolving 
2K to 3« in 200«c to 300c« water. In a portion of it suspend a few pieces of 
white yarn or flannel. The woollen material will be strongly dyed yellow. 
In another portion suspend a piece of ordinary cotton cloth. 

It should be noted that some dyes are applicable to cotton 
without mordants. These are called substantive dyes. 

Acid fachsine is a sulphonic acid of rosaniline. It is 
formed by treating rosaniline with concentrated sulphuric acid 
at 120°. It is soluble in water, and is a valuable dye. 

Aniline dyes. — By introducing various hydrocarbon resi- 
dues into para-rosaniline or rosaniline, in place of some or all 
of the hydrogen atoms of the amino groups, dyes of other 
colors are formed. The general effect of introducing methyl 
groups is to form dyes of a violet color. As the number of 
methyl groups increases, the product has a deeper blue tint. 

Hexamethyl-para-rosaniline. — The hydrochloric acid 
salt of this is the well-crystallized dye, crystal violet j 
[C6H4.N(CH3)2]2C:C6H4:N(CH3)2C1. It is one of the prin- 
cipal constituents of methyl violet. Some of the methods used 
in preparing this dye are of special interest. It is made — 

(1) By the action of para-tetra-methyl-diamino-benzophenone 
on dimethyl-aniline in the presence of dehydrating agents — 

(CntN.cS > ^^ + CeH,.N(CH3),HCl = 
C,9H,2N3(CH3)eCl + HjO. 

(2) By lieating dimethyl-aniline with carbonyl chloride and 
aluminium chloride or zinc chloride : — 

C0Cl, + 2 CaH,.N(CH3),= CO<^«JJ^;^|^^»|* + 2 HCl; 

C„H^N,(CH3)gCl + H,0. 



PHTHALE'iNS 369 

Methyl violet consists of crystal violet mixed with products 
containing a smaller number of methyl groups. 

Methyl green is an addition-product formed by the action of 
methyl chloride on an alcoholic solution of crystal violet. 

Hofmann^s violet (Dahlia) is either the hydrochloric acid or 
acetic acid salt of tri-methyl-rosaniline. It is made by heating 
together a salt of rosaniline, methyl iodide, and methyl alcohol. 

Aniline blue is the hydrochloride of tri-phenyl-rosaniline. It 
is formed by heating salts of rosaniline with aniline and some 
benzoic acid. 

Soluble blue is a sulphonic acid of aniline blue. 

Phthaleins 

In speaking of phthalic anhydride, it was stated that when 
this substance is treated with phenols, phthaleins are formed ; 
and, in speaking of resorcinol, a markedly fluorescent body 
was mentioned as being formed when phthalic anhydride and 
resorcinol are heated together. 

Phenol-phthale'in, O20H14O4. — This substance is formed by 
heating a mixture of phenol and phthalic anhydride with sul- 
phuric acid or some other dehydrating agent ; — 

2 CeHeO + CgHA = C^ll,,0,+^,0. 

Phenol Phthalic Phenol- 

anhydride phthalein 

The mass is boiled with water to remove the sulphuric acid, 
dissolved in caustic soda, and the phenol-phthale'in precipitated 
by the addition of an acid. It forms a granular crystalline 
powder. Its solution in alkalies is red or violet, according to 
the thickness of the layer. Acids destroy the color. Hence it 
is used as an indicator in acidimetry and alkalimetry as a sub- 
stitute for litmus. It is used in medicine as a purgative. 

Phenol-phthalein, like rosaniline, is a derivative of tri-phenyl- 
methane, as has been shown by the following somewhat compli- 
cated reactions : -^ 



370 DI-PHENYL-METHANB, ETC. 

By treating phthalic anhydride with phosphorus pentachlo- 
ride, phthalyl chloride, C8H4O2CI2, is formed. When this is 
treated with benzene in the presence of aluminium chloride, the 
reaction represented in the following equation takes place : — 

CgH ACI2 + 2 CeHe = CgH ACCeH,)^ + 2 HCl. 

Phthftlyl chloride Diphenyl-phthalide 

The substance thus formed is known as diphenyl-phtJuUide. 
Its conduct towards water and bases is such as to show that it 
is the anhydride of an acid : — 

CsH A(C6H5)2 + KOH = C;H,0 < 9?^, . 

When this salt is reduced by means of zinc dust it loses 
oxygen : — 

C7H5O I /Q u \ + Hjj = C7H5 j n ^ \ H" H2O. 

And, finally, when the acid is distilled with baryta, it loses 
carbon dioxide and yields tri-phenyl-methane : — 

( CO H ( *^ 

C7H5 ■) /p It N = CH ■} CeHfi + CO2. 
^ (,^6"5;2 ( C H 

We have thus passed from phthalic anhydride to triphenyl- 
methane, and the reactions just referred to are in all prob- 
ability correctly represented by the following formulas and 
equations : — 



C 



+ KOH = C 



CeHfi 



CeH^.CO 

lo 1 



CeHg 

C6H4.CO2K. 
I OH 



Diphenyl-phthalide, or an- Potassium tri|)henyl- 

hydride of triphenyl-car- carbiuol-carbonate 

binol-carbonic acid 



PHENOL-PHTHALEIN 



371 



C 



C6H4.CO0K + H2 
LOH 



= C 



CeHs 
LH 

Potassium triphenyl« 
methane-carbonate 



c- 



C6H4 . C02H 
H 



= C 



+ C0, 



CeHg 
H 

Triphenyl-methane 

Now, by making dinitro-diphenyl-phthalicle, reducing it, and 
boiling the diazo compound with water, the product obtained is 
phenol-phthalein. Hence, the latter compound appears to be 
the dihydroxy derivative of diphenyl-phthalide : — 



C 



CeH^ . CO 
10— 



c 



I 



C6H4.NH2 

CeH^.NHg 
CgH^ . CO 

10 J 



c 



C6H4 . OH 
CfiH^.OH 
CeH4 . CO • 
10 i 



Phenol-phthalein 

The formula for phenol-phthalein may also be written 
thus : — 

C6H4 . OH p C6H4 p^ 
CeH^.OH^^^O >^^' 

the curious arrangement of the carbonyl group being simply 
the sign of the anhydride condition between carboxyl and 
hydroxy 1, of which the simplest expression is 



OH 



O 



^^COOH = ^< ' +^^^- 

This plainly is the characteristic grouping of the lactones 
(see p. 169). 

There is reason to believe that when a phthalein is treated 
with a base and converted into a salt the constitution is essen- 



372 FLUOEESCBiN 

tially changed, the resulting salt having a quinone-like struc- 
ture, as shown thus: — 



HO r^ r>0H o = 





COOK 



Free phenol-phthaleln Mono-potaBBiam salt of phenol-phthalein 

(lactoid formula) (quinoid formula) 

Note for Student. — Although the reactions above briefly described 
may at first sight appear to be difficult to comprehend, they are in reality 
simple enough. The student is earnestly recommended not to slight them 
on account of the long names and complex formulas involved. They afford 
an excellent example of the methods upon which we rely for determining 
the nature of complex substances. Notice that all appears dark until the 
well-known substance tri-phenyl-methane is obtained, which suggests that 
all the substances are derivatives of this fundamental hydrocarbon ; and 
how easily, when this conception has once been formed, the interpretation 
of all the reactions follows. 

Among the other phthaleins that deserve special mention is 
that which is formed with resorcinol. 

Fluorescein, resorcinol-phthalein, OjjuHijjOg + HjO. — 

This beautiful substance is formed by heating together resor- 
cinol and phthalic anhydride to 200° : — 

2 CeH4(OH)2 + CgH A = C^Hi^O^ + 2 H^O. 

Its solutions in alkalies are wonderfully fluorescent. The sub- 
stance, which is sold under the name "wranin" for the purpose 
of exhibiting the phenomenon of fluorescence, is the di-sodium 
salt of fluorescein. 

From the solutions of its salts fluorescein is precipitated as a 
yellow powder of the composition, CjoHiA. Heated to 130** 
this loses water and forms the compound, C^HiaOs, which is 
yellowish red. The fact that the compound is colored has led 
to the belief that it has the quinoid structure in the free con- 
ditions as well as in its salts. 



EosiN 373 

The reaction that takes place between resorcinol and phthalic 
anhydride, when fluorescein is formed, is of the same kind as 
that which takes place between phenol and the anhydride to 
form phenol-phthalein. We should therefore expect to find 
that fluorescein has the formula: — 

HO 




COOH 



It is found, however, that in reality fluorescein corresponds to 
the above formula less one molecule of water ; and it is believed 
that the structure should be represented thus : — 

HO 




COOH 



Eosin, tetra-brom-fluorescein, 02oH6Br405B[2, is formed 
by treating fluorescein with bromine, and then with potassium 
carbonate. Its dilute solutions have an exquisite, delicate pink 
color which suggests a color often seen in the sky at the dawn 
of day. Hence the name of eosin, from yuiq, dawn. It is 
fluorescent, and is used as a dye. Its relation to fluorescein 
is shown by this formula : — 

Br Br 




COOK 



CHAPTER XVII 

HYDROCARBONS, CnH^n-s, AND DERIVATIVES 

The hydrocarbons thus far considered are of three classes. 
They are: (1) parafBins^ or saturated hydrocarbons of the 
marsh-gas series ; (2) unsaturated hydrocarbons related to the 
paraflRns ; and (3) hydrocarbons which contain residues of the 
saturated parafBins and of benzene. 

We now pass to a brief consideration of a hydrocarbon which 
is made up of a residue of benzene and of an unsaturated par- 
afi&n. It bears to ethylene the same relation that toluene bears 
to marsh gas ; that is to say, it is phenyl-ethylene. 

Styrene, phenyl-ethylene, OgHgCOcHs.OHiOHa).— This 

hydrocarbon is contained in liquid storax — a fragrant, honey- 
like substance which exudes from various plants, as the liquid- 
ambar — and in coal-tar xylenes. It is formed by distilling 
cinnamic acid with lime: — 

C9H8O2 = CgHg + CO2. 

Note for Student. — What does this reaction suggest with regard to 
the relation between cinnamic acid and styrene ? 

It is also formed from phenyl-ethane, CgHg.CsHg, in the same 
way that ethylene is formed from ethane : — 



I 



C,H, H-Bfj =C8H,Br +HBr 

CjHjBr +KOH = C2H4 +KBr + H20' 

CH.. CsHg + Bij = C,H,. CjHiBr + HBr; 
CgHj. CjHiBr + KOH = CeHj. C^Hj + KBr + H,0, 

Styrene 

374 



CINNAMYL ALCOHOL 875 

Its formation by heating acetylene was mentioned on page 
246: — 

4 C2H2 = CgHg. 

NoTB FOB Student. — What other polymeric product is obtained by 
heating acetylene ? 

Styrene is a liquid of an aromatic odor; boils at 140°; 
insoluble in water; miscible with ether and alcohol in all 
proportions. 

When heated alone up to 300°, or even when allowed to stand 
at ordinary temperatures, it is converted into a polymeric modi- 
fication called metorstyrene, which is a solid. This same change 
is readily effected by several reagents, such as iodine and con- 
centrated sulphuric acid. Styrene unites directly with chlorine 
and bromine in the same way that ethylene does (see p. 232) : — 

CeHg. CH: CHj + 2 Br = CeH,. CHBr . CHaBr. 

It unites with hydrobromic acid, forming phenyl-ethyl 
bromide : — 

CeHg. CH : CHg + HBr = CeHg. CHg . CH^Br. 

Hydriodic acid reduces it to phenyl-ethane : — 

CeH,.CH:CH2 + 2HI = C6H5.CH2.CH3 + 2L 

Chromic acid and other oxidizing agents convert styrene into 
benzoic acid (see remarks, p. 269). Some higher members of 
this series have been prepared, such as phenyl-propylene, phenyl- 
butylene, etc. ; but at present they are not of sufficient impor- 
tance to make their consideration necessary. 

Styrene is closely related to cinnamic acid, from which the 
interesting and important compounds of the indigo group are 
obtained. 

sSSl°Scohol, ^ ' J CJ9HioO(C6H5 . OH : OH . OH2OH). - 

This alcohol occurs in nature in the form of an ethereal salt of 
cinnamic acid in liquid storax, and also in balsam of Peru. 



376 HYDEOCARBONS, CnHgQ.g AND DERIVATIVES 

It forms long, thin needles, which melt at 33°. It is fairly- 
soluble in water ; has the odor of hyacinths ; and boils at 250°. 
Nascent hydrogen converts it into phenyl-propyl alcohol, 
CeH^.CHa.CHa.CHgOH (see p. 317): — 

Cglig . CH : CH . CH2OM + H2 = CgHj. CH2. CH2. CH2OII. 

Hydriodic acid converts it into propenyl-benzene (phenyl- 
propylene), CcHa.CHiCH.CHg, and toluene. 

When oxidized with platinum black it is converted into the 
corresponding aldehyde, cinnamic aldehyde, the chief con- 
stituent of the oil of cinnamon; and, by further oxidation, 
into cinnamic acid. The relations between the three sub- 
stances are the familiar ones of a primary alcohol, and the 
corresponding aldehyde and acid: — 

C6H5.CH:CH.CH20H. C6H5.CH:CH.CHO. 

Styryl alcohol Cinnamic aldehyde 

C6H5.CH:CH.C02H. 

cinnamic acid 

These compounds are the )3-phenyl derivatives of allyl alcohol, 
acrolein, and acrylic acid : — 



CH2:CH.CH20H. 


CH2:CH.CH0. 


CH2:CH.C02H. 


Allyl alcohol 


Acrolein or 
acrylic aldehyde 


Acrylic acid 



pS.nySlor?Uo acid. ) ©.HsO^CCH, . OH : CH . COaH). - 

Cinnamic acid is found in liquid storax, partly in the free con- 
dition, and partly in the form of an ethereal salt in combina- 
tion with styryl alcohol, as styryl cinnamate, in the balsams of 
Tolu and Peru. It can be made synthetically : — 

1. By heating together benzoic aldehyde and acetyl chlo- 
ride : — 

CeH^. COH + CH3. COCl = CfiH^ . C2H2. CO2H 4- HCl. 



CINNAMIO ACID 377 

This reaction will be better understood by writing it in two 
equations : — 

(1) CeH,. CHiO; + C1H21H . COCl = CeH^. CH : CH . COCl + HgO ; 

Cinnamyl chloride 

(2) CeHg.CH : CH.COCl + H^O = C6H5.CH:CH.C02H + HCl. 

Cinnamyl chloride 

The kind of action represented in equation (1) is not un- 
common. We have already met with it in the formation of 
mesitylene from acetone (see p. 270), in which case two hydro- 
gens from each of three methyl groups unite with an oxygen 
atom from each of the three carbonyl groups. The product is 
called a condensation-product, and the action is known as con- 
densation. It has already been referred to under the head of 
cUdol condensation (see p. 191). 

2. By heating together benzoic aldehyde, sodium acetate, and 
acetic anhydride (Perkin's re|U3tion) ; — 

H H 

C6H5.C:0 + HCH2.C02Na = C6H5-C-OH. 

I 
CH2 . COgNa 

The acetic anhydride acts as a dehydrating agent and con- 
verts the product first formed into sodium cinnamate : — 

H 
CeHfi.C-OH =C6H5.CH:CH.C02Na-fH20. 
CHg.COgNa 

3. By treating benzal chloride with sodium acetate : — 

CeH, . CHlClgi-f CiHglH. C02Na==C6H5. CH : CH . C02Na+ 

Cells . CH : CH . COgNa + HCl = CeH^ . CH : CH . CO2H + NaCl. 

The acid is now manufactured on the large scale by the last 
method. 

Cinnamic acid is a solid which crystallizes in monoclinic 



378 HYDROCARBONS, CnHgn-s AND DERIVATIVES 

prisms. It melts at 133^ and boils at 300* to 400^ It is 
easily decomposed into styrene and carbon dioxide : — 

CeHg . CH : CH . COgH = C^H, . CH : CHa + CO,. 

Oxidizing agents convert it first into benzoic aldehyde and 
then into benzoic acid. Nascent hydrogen converts it into 
hydro-cinnamic or phenyl-propionic acid, CeHg . CHj. CHj. CO2H 
(p. 333). It unites with hydrochloric, hydrobromic, and hydri- 
odic acids: — 

CgHg . CgHg . CO2H + HCl := Cglis . C2I13CI . COjH. 

Pbenyl-chlor-propionic acid 

Bromine yields the addition-product CgHa . C2H2Br2 . CO2H. 
Treated with substituting agents, such as nitric acid, etc., it 
yields substitution-products in which the entering atoms or 
groups are contained in the benzene residue, in the ortho and 

para positions relatively to the acrylic acid residue, C2H2. CO2H. 

» 

Nitro-cinnamic acids, aH, j ^2^2- OO^H _ rpj^^ ^^^^ 

and para acids are formed by dissolving cinnamic acid in nitric 
acid. 

Note for Student. — What are the products when toluene is treated 
with nitric acid ? When benzoic acid is treated in the same way ? To 
which case is the above analogous ? 

A m ino-oinnamio acids, CgH^ ] ^^ • 2^ — These acids 

are formed by treating the nitro-acids with reducing agents. 
The ortho acid loses water when set free from its salts, and forms 

/CH = CH XH = CH 

the anhydride carbostyril, C«h/ I or C^h/ I 

® *\NH-CO * *\ N = C(OH) 

analogous to hydro-carbostyril (p. 334). 

Ooumarin, C^B.fi2{^Cf;HA^'^^^^\ is a compound found 
in Tonka beans and in many other plant substances. It is 



COUMARIN 879 

made synthetically from salicylic aldehyde, sodium acetate, and 
acetic anhydride, just as cinnamic acid is made from benzoic 
aldehyde, sodium acetate, and acetic anhydride. The first 
product of this action is probably ortho-hydroxy-cinnamic acid, 

or coumaric acid, C6H4 1 * ' * , from which, by treatment 

with hydrobromic acid, coumarin is formed. This has a pleas- 
ant odor, like that of sweet clover, and is used in perfumery. 
In very great dilution it has the odor of nefuymown hay. 
Treated with bases, it yields salts of coumaric acid. 

The coumaric acid made artificially is the trans variety, that 
is to to say, the one that has the hydroxyl and carboxyl groups 
on the opposite sides of the molecule as represented in the 

H - C - C6H4OH 
formula, n . Treatment with hydrobromic acid 

HO2C-C-H 

H-C-C6H4OH ^. ^ ^ 
transforms this into the da variety, n , which then 

H-C-COaH 
TT — P — P FT 

loses water, forming coumarin, n No. 

H-C-CO ^ 



\ 



CHAPTER XVIII 

PHENYL-ACETYLENE AND DERIVATIVES 

Phenyl-aoetylene, aoetenyl-benzene, OeHgCiOH, bears 
to acetylene the same relation that styrene, or phenyl-ethylene, 
bears to ethylene. It is made from styrene in the same way 
that acetylene is made from ethylene : — 

(1) C2H4 +Bv, ^C^U.Bv,', 

(2) CgH^Brg +2KOH = C2H2 +2KBr + 2H20. 
CgHg . C2H3 4" Br2 = CgHg . C2H8Br2 ; 

CgHs . C2H3Br2 + 2 KOH = CeU, . C2H + 2 KBr + 2 HgO- 

Phenyl-acetylene 

It is a liquid that boils at 142°. It unites directly with four 
atoms of bromine, forms metallic derivatives, and, in general, 
conducts itself like acetylene (which see). 

Phenyl-propiolio acid, OgHgOaCOeHg . CiO . CO2H). — This 

acid is a carboxyl derivative of phenyl-acetylene, bearing to it 
the same relation that cinnamic acid bears to phenyl-ethylene. 
It is made from cinnamic acid, by treating the dibromine addi- 
tion-product with alcoholic potash. The reaction takes place 
in two stages : — 

CeHg . CHBr . CHBr . CO2H = CeH^ . CH : CBr . COgH + HBr ; 
CeHs . CH : CBr . COgH = CgH, . C i C . COjH + HBr.* 

It forms long needles, which melt at 136** to 137**. When 
heated with water to 120°, it breaks up into carbon dioxide and 
phenyl-acetylene. 

380 



INDIGO AND ALLIED COMPOUNDS 381 

Ortho-nitro-phenyl-propiolio acid, C^H^\^^ ^, is 

made from the dibromide of ortho-nitro-cinnamic acid, in the 
same way that phenyl-propiolic acid is made from the dibromide 
of cinnamic acid (see preceding paragraph). It is of special 
interest, for the reason that it can easily be transformed 
into indigo. The transformation is most readily effected by 
boiling it with alkalies and grape sugar, or some other mild 
reducing agent. The reaction is represented by the following 
equation : — 

2 CeH, [ 5n^^'^ + ^^ = CigHioN A + 2 CO^ + 2 H^O. 

^ -^ ^2(0) Indigo 

Ortho-nitro-phenyl- 
propiolic acid 

Indigo and Allied Compounds 

Indigo is the oldest dye known. A mummy cloth 4000 
years old has been shown to be dyed with it. The value 
of the world's annual production of this dye is estimated at 
$20,000,000. Until recently all the indigo used was made 
from the indigo plants, but most of that now used is manu- 
factured by artificial methods. 

In several plants, Indigofera tinctoria, Isatis tinctoria, etc., 
there occurs a glucoside, indican, which, under the influence of 
dilute mineral acids or certain enzymes, breaks up, yielding a 
member of the glucose group and a substance which by oxida- 
tion is converted into indigo-blue. The indigo of commerce 
was formerly all prepared in the East and West Indies, in 
South America, Egypt, Bengal, and other warm countries. In 
brief, the process is this : — 

At the proper stage the plants are cut off down to the ground, 
put in a large tank, and covered with water. Enzyme action 
takes place, the indican breaking up and yielding indoxyl 
(which see), as above stated. The liquid becomes green, and 
then blue. When the fermentation is finished, the liquid is 



382 PHBNYL-ACETYLBNB AND DERIVATIVES 

drawn off into a second tank. This liquid contains indigo- 
white or possibly indoxyl in solution. In contact with the air 
it is oxidized, forming indigo, which, being insoluble, is thrown 
down. In order to facilitate the precipitation of the indigo, 
the liquid is thoroughly stirred. Finally, the liquid is drawn 
off, the precipitated indigo pressed and dried, and then sent 
into the market. 

The substance prepared as above has a dark-blue color, and 
contains other coloring matters besides indigo-blue. Its value 
depends upon the amount of the definite compound, indigo-blue, 
contained in it 

IndifiTO-blue, indigotin, GieHioNsO,. — Indigo-blue is ob- 
tained from commercial indigo by reducing it to indigo-white, 
and then exposing the clear colorless solution to the air, when 
indigo-blue is precipitated. 

Experiment 78. Into a test-tube pat a small quantity of powdered 
indigo ; add fine zinc filings or zinc dust and caustic soda. When the 
mixture is heated the solution becomes colorless. When this result has 
been reached, pour some of the solution into a small evaporating dish. 
Contact with the air colors it blue. 

Indigo-blue can be made artificially by a number of methodsi 
among which the two following are the principal ones : — 

1. By boiling ortho-nitro-phenyl-propiolic acid (which see) 
with an alkali and grape sugar. 

2. From ortho-amino-benzoic (anthranilic) acid by treating 
it with chlor-acetic acid and fusing the product thus obtained 
with caustic potash : — 

(1) CH, < ^^^ + CICH, . CO,H = C.H« < ^0^^* ' ^^*^ 

+ HC1; 

(2) C,H,<^^^-^H,.COOH =c.H,<^^jj>C.COOH 

(3) C.H,<^^jj>C.COOH =C,H,<^^jj>CH+CO, 



INDIGO-WHITE 883 

The compound of the formula C6H4<_^ l^>CH is called 

COH 

indoxyl. When oxidized by air in alkaline solution this is con- 
verted into indigo-blue : — 

(4) 2 CeH4< ^^^ >CH+03=CeH,< ^q > ^ * ^ < CO ^ ^'^' 

This method is now used on the large scale very successfully. 
The anthranilic acid is prepared from phthalic anhydride, 
which is obtained from naphthalene by oxidizing it with con- 
centrated sulphuric acid in the presence of a little mercury. 
The conversion of phthalic anhydride into anthranilic acid is 
effected by means of Hofmann's reaction (see Anthranilic acid 
and Methylamine). The history of the attempts to prepare 
indigo synthetically is full of interest. At present the artifi- 
cially prepared product is driving natural indigo out of the 
market. 

Indigo-blue crystallizes from aniline in dark-blue crystals. 
It sublimes in rhombic crystals. Its vapor has a purple-red 
color. It is insoluble in water, alcohol, and ether ; soluble in 
aniline and chloroform. Oxidizing agents convert it into isa- 
tine (which see). * Heated with solid caustic potash, it yields 
carbon dioxide and aniline ; boiled with a solution of caustic 
potash and finely powdered manganese dioxide, it is converted 
into ortho-amino-benzoic acid (anthranilic acid). 

Indigo-white, O16H12N2O2, is formed by reduction of indigo- 
blue, as above described. Its solutions in alkalies rapidly turn 
blue in the air, in consequence of the formation of indigo-blue. 

When indigo is oxidized with nitric acid, isatine, CgHjNOj, 
is formed : — 

CieHioN A + 0, = 2 CeH^ <.^^ > CO. 



384 PHENYL-ACETYLENE AND DERIVATIVES 

When isatine is treated with sodium amalgam, it takes up 
hydrogen, and yields dioxindol, C8H7NO2 : — 

Isatine Dioxindol 

By further reduction, dioxindol loses an atom of oxygen, yield- 
ing oxindoly CgHyNO : — 

CeH, < ^J^jj > CO + H, = CeH, < ^^ > CO + HA 

Dioxindol Oxindol 

By distilling oxindol with zinc dust, indol is formed : — 

Indol 

Constitution of indigo. — The constitution of indigo is de- 
duced from a consideration of a number of facts. In the first 
place, its vapor density shows that it has the molecular weight 
represented by the formula C16H10K2O2. 

CO 
Its relations to isatine, C6H4 < > CO, make it probable 

C 
that indigo contains two groups, C6H4 < -kt > C : , united. It 

can be made, for example, by reducing isatine chloride, 

CO 
C6H4< ^CCl, a reaction that can be most readily inter- 
preted thus : — 

2C6H4<g^>CCl-t-4H = C6H4<§^>C:C<g-^>CeH4 

+2 HCl. 

Further, indigo can be made from di-o-nitro-di-phenyl-di- 

acetylene, C6H4 < ^^ ^^ > C6H4, a fact that shows that 

the union between the two halves of the indigo molecule is 
between carbon atoms. The presence of two imino groups is 



METHYL-INDOL 385 

shown by introducing radicals, and then decomposing the 
ethers thus formed. It is found that the radicals are given 
off in combination with nitrogen in the form of substituted 
ammonias. 

All these facts, and all others that have been established by 
the investigations on indigo, are in harmony with the view 
expressed by the formula for indigo already given : — 

CeH,<^^>C:C<^^>CeH,. 

Indol, C8H7N(c6H4<Q2>CHy — The mother substance 

of indigo and related compounds is indol. As stated above, it 
is formed from oxindol by heating it with zinc dust. It is also 

formed from ortho-amino-chlor-styrene, C6H4 < ^xt^ PTTm ^^ 
elimination of hydrochloric acid : — ' 

^"^^ < CH L CHCl = ^^"^^ < CH > ^^ "^ ^^^ 
It is a crystalline substance of peculiar odor. 

p-Methyl-indol, skatol, C6H4<^^>CHa.— This occurs in 

I 
CH3 

P 

human faeces and is largely responsible for the characteristic 

penetrating odor of the faeces. 



CHAPTER XIX 

HYDROCARBONS CONTAINING TWO BENZENE RESIDUES 

IN DIRECT COMBINATION 

Just as the marsh-gas residue, methyl, CH^ unites with methyl 

CHa 
to form ethane, I 9 so the benzene residue, phenyl, CeHj, 

CH, C.H. 

unites with phenyl to form the hydrocarbon diphenyl, I , and 

C5H5 . 

residues of toluene and of the higher members of the series 

unite in a similar way to form homologues of diphenyl. 

Diphenyl, CiaHioCCeHs.CeHs). — This hydrocarbon is made 
by treating brom-benzene with sodium : — 

2 CeH^Br + 2 Na = CiaHw + 2 NaBr ; 

and by conducting benzene through a tube heated to redness : — 

» 

2 CgHg = C12H10 + ^2. 

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 

S80 



BENZIDINE • 387 

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 

below : — 

H H H H 

C C CO 

C C CO 

H H H H 

0,H4.NH2(p) 
Benzidine, I . — This is diparardiamino-diphenyl. 

It is formed by reduction of dinitro-diphenyl, and also by the 
reduction of azobenzene in acid solution. In the latter case 
hydrazobenzene, which is isomeric with benzidine, is first 
formed, and this is then transformed into benzidine in the 
presence of acids (see hydrazobenzene) : — 

CeH,.NH C6H4.NH, 

Hydrazobenzene Benzidine 

Benzidine is manufactured on the large scale by this method. 
It is a solid that melts at 122°. 

The amino groups are in the two para positions in benzidine. 

Benzidine dyes. — Benzidine, being an amino derivative of an 
aromatic hydrocarbon, is readily diazotized, and the final prod- 
uct of the action of nitrous acid is a compound containing two 
diazo groups or a tetrazo compound. Thus the chloride gives 
a tetrazo chloride : — 

CeH^ . NH2 . HCl CeH^ . N2CI 

CeH^ . NH2 . HCl C6H4 . N2CI 

The tetrazo compound reacts with great ease with aromatic 



1 



388 HYDROCARBONS WITH TWO BENZENE RESIDUES 

amino-sulplioiiic acids, hydroxy-acids, and phenol-sulphonic 
acids, forming valuable dyes that have the power to unite 
directly with cotton. They are called substantive dyes. The 
first dye of this kind that came into use was known as Congo 
red. This is made by treating diphenyltetrazonium chloride 
with sodium napMhionate, Naphthionic acid, as will be shown 
further on, is a derivative of naphthalene (see below). 

Chrysamin G, is made by the action of sodium salicylate ou 
diphenyltetrazonium chloride : — 



OH ^TT XT ^XT .OH 

NTa 

2HC1. 



C.H,.M CeH,<^^^^^CeH,.K,C.H3<^^^ 

OH "" ' OH 

C^.N,C1 CeH,<(.^^^ C,H,.N..CeH3<co^a 



Carbazol, I ^NH, is a curious derivative of diphenyl 

that is found in coal tar in small quantity. It has been shown 
to be a substituted ammonia containing a residue of diphenyL 
It is properly designated by the name diphenyl-imide, and is 
represented by the above formula. It has been made syn- 

C*H' 

through a red-hot tube, a reaction taking place which is analogous 
to that mentioned above as taking place when benzene is treated 
in the same way, the product in the latter case being diphenyl. 

Naphthalene, CioHg. — While the relations of diphenyl to 
benzene are clearly shown by its simple synthesis from brom- 
benzene, the relations of naphthalene to benzene have been 
discovered through a careful study of its chemical conduct. 
The facts can \e best interpreted by assuming that the mole- 
cule of naphthalene is formed by the union of two benzene 
residues in such a way that they have two carbon atoms in 
common, as represented in the formulas 



NAPHTHALENE 



389 



HC - CH - C - CH - CH 

I I I 

HC - CH - C - CH - CH 



H H 

c c 

HC^ ^C^ ^CH 
and I II I 



H H 
How this conception was reached will be shown below, after 
the properties and the reactions of naphthalene shall have been 
discussed. 

Naphthalene is a frequent product of the heating of organic 
substances. Thus, it is formed by passing the vapors of alco- 
hol, ether, acetic acid, volatile oils, petroleum, benzene, toluene, 
etc., through red-hot tubes ; and, also, by treating ethylene and 
acetylene in the same way. It is therefore found in coal tar, 
and in gas-pipes used for gas made by heating naphtha, 
gasolene, etc., to high temperatures. It has been made 
synthetically : — 

1. By treating o-xylylene bromide with the di-sodium com- 
pound of the ethyl ester of symmetrical ethane-tetra-carboxylic 
acid; saponifying the ester thus formed; and distilling the 
silver salt of the resulting acid: — 

H 

C ^CHgBr 



HC 
HC 



C 

c 



\ 



CHoBr 



C 
H 

H 

C ^ CHa 

Hc/YNcCCOaCgH^) 



NaC(C0AH,)2 
+ I 

NaCCCOAHa), 



HC 



5/8 



"xA/CCCO^C^H,), 



-f. 2 NaBr. 



c 
C C 



H 



H, 



390 HYDBOCABBONS WITS IVfO BENZENE BBSIDDUS 



<CH, - C( 
1 
CH, - C( 

<Hj — 
1 
H,- 



CH2 0(00202115)2 

I 
C(CO,CJI,), 

/CH, - CH(COJEI) 

I 
CH(CO,H) 



/CH, - C(CO^), 

c.h/ I 

X!H, - C(CO,H), 



/CH - CH 
II 
CH 



CaH/ II 

x;h- 



2. By conducting phenyl-butylene bromide over heated 
lime: — 

<H-CH 
II * 
H-CH 

3. When yphenylisocrotonic (phenyl vinylacetic) acid, 
C«Hj.CH = CH.CH,.COOH, is heated, it loses water and 
gives a-naphthol, a hydroxyl derivative of naphthalene: — 



H 
C 



H 
C 



HO 
HO 




H 
H 



CH 
OH 



H H 

Hcrir^CH 



HO 



90 

OH 



V^^v^CH 



O 
H 



By reduction with zinc dust a-naphthol gives naphthalene. 

The above syntheses give a clew to the constitution of naph- 
thalene, but they do not clear it up entirely. A study of the 
chemical conduct of naphthalene has, however, led to a solution 
of the problem. 

Naphthalene is prepared on the large scale from those por- 
tions of coal tar which boil between 180° to 250°. This material 
is treated with caustic soda, and then with sulphuric acid, and 
distilled with water vapor. 

It forms colorless, lustrous, monoclinic plates. It melts at 
80°, and boils at 218°. It has a tarry odor; is volatile with 
steam, and sublimes readily. It is insoluble in water ; easily 



NAPHTHALENE 391 

soluble in boiling alcohol, from which it can be crystallized. 
Oxidizing agents convert it into phthalic acid (see Exp. 73). 
On the large scale phthalic acid is made from it by oxidizing 
with sulphuric acid, as has already been stated. It is used as 
an antiseptic and insecticide. The well-known moth baUs, for 
example, are made of naphthalene. 

The ease with which naphthalene yields phthalic acid, sug- 
gests that the hydrocarbon is probably a di-derivative of benzene 
containing two hydrocarbon residues ; such, for example, as is 

{C H 
CH' Such a substance, how- 
ever, contains unsaturated paraffin residues, and hence ought 
readily to take up bromine, hydrobromic acid, etc. Bromine 
and chlorine are indeed taken up easily, but the products thus 
obtained act rather like the addition-products of benzene than 
the addition-products of the unsaturated paraffins. They break 
up readily, and yield stable substitution-products of naphtha- 
lene. 

We have seen that a hydrocarbon containing a benzene 
residue and an unsaturated paraffin residue, as, for example, 
styrene or phenyl-ethylene, CeH^ . C2H3, and phenyl-aceiylene, 
CeH5.C2H, when treated with bromine or hydrobromic acid, 
takes them up as readily as ethylene and acetylene, and this 
action takes place before substitution. According to this, 
naphthalene ought to take up bromine and especially hydro- 
bromic acid with avidity before substitution of its hydrogen 
takes place. 

While it does take up four atoms of chlorine or of bromine, 
it does not take hydrochloric or hydrobromic acid, a fact that 
makes it improbable that naphthalene contains unsaturated 
hydrocarbon residues. 

f C H 

The formula C6H4 \ ^^^ and similar ones being thus rendered 

L ^2112 

extremely improbable, the next thought that suggests itself is 
that the two groups 0^112 may be united, as represented in the 



392 HYDROCARBONS WITH TWO BENZENE RESIDUES 

fCH.CH 

formula C^U^ i \ . Assuming, further, that the two groups 

I CH.CH 

are united to two carbon atoms of the benzene residue which 

are in the ortho relation to each other, we may whte this same 

formula thus : — U 

Hc/ \:;-CH-CH 

H 

or, what is the same thing, — 

H H 

^11 I • 

HCv /^v /CH 

H H 

This formula represents naphthalene as made up of two 
benzene residues united in such a way that they have two 
carbon atoms in common. This, as has been stated, repre- 
sents the hypothesis at present held in regard to the structure 
of naphthalene. 

As regards the assumption that the two residues are united 
through carbon atoms which are in the ortho position relatively 
to each other, it should be said that this assumption is made 
because phthalic acid is the product of oxidation ; and the facts 
already considered have shown that terephthalic acid must be 
represented by the formula 

CO2H 

xx' ' 

CO,H 



NAPHTHALENE 393 

and isophihalic acid by 

CO2H 



HCv .CCO2H 

H 

and hence, in terms of the accepted hypothesis, the third pos- 
sible formula must be given to phthalic acid, viz., — 

H 

HC/ \c . CO2H 

I I 

HCv .C.CO2H 

H 

Are there any facts besides those above mentioned which 
make the hypothesis appear probable ? 

By a different line of reasoning, based upon other facts, the 
conclusion is reached that naphthalene is made up of two ben- 
zene residues which have two carbon atoms in common, and 
the only formula that represents this conception is the one 
already given. The facts which lead to this conclusion are the 
following : — 

When nitro-naphthalene is oxidized it yields nitro-phthalic 
acid. This shows that the nitro group is contained in a 
benzene residue; and we may represent it by the formula 

C C H 
CeH8.N02 j ^^ , the oxidation taking place as indicated thus : — 

By reducing this same nitro-naphthalene, amino-n'aphthalene 
is obtained; and, when this is oxidized, phthalic acid is 
formed : — 



894 HYDROCARBONS WITH TWO BENZENE RESIDUES 



CgH^I 



C,H . NH, 

C2H2 



+ 12 



^=^•^{00* 



COsH 
H 



+ 2 CO, + HNOs + H,0. 



These two reactions show (1) that the part of nitro-naphtha- 
lene in which the nitro group is situated is a benzene residue ; 
(2) that there is another benzene residue in the compound into 
which the nitro group has not entered. 

These transformations may be represented thus: — 



H H 

C Q G 



Hc/\/^CH 



HC 



CH 



C^ c 

H NOa 

Nitro-naphthalene 



H 
C 



Hc/Nc - CO,H 

CHv Jc - CO2 H 

C 

NOa 

Nitro-phthalio acid 



H H 

C y>, C 

H NH2 

Amino-iiaphthnVnc 



H 
C 



Hc/\c « COjP 
Hcl Jc - COjflL 

H 

Fhthalio acid 



It has been noticed^ also^ that by oxidation of a naphthalene- 
sulphonic acid, both sulpho-phthalic and phthalic acid itself 
are obtained. 

It follows, from these facts, that naphthalene is made up of 
two benzene residues, and the only way in which a hydrocarbon 
of the formula CioHg can be thus made up, is by having two 
carbon atoms common to the two residues, as represented in 
the formula already given : — 



DEBIVATIVEiS OF NAPHTHALENE 395 

H H 

HC/ \i^ \CH 

I I I 

H H 

The proof just given for this formula is independent of any 
notions regarding the ortho, meta, and para relations in ben- 
zene. As phthalic acid is the product of oxidation, it follows 
that the carboxyl groups in the acid must bear to each other 
the relation expressed by the formula 

H 

HC/ Nu-COjH 
I I 

HCv yC - COjfl[ 

H 

and, therefore, that in all ortho compounds the substituting 
groups bear this same relation to each other. Hence, by start- 
ing with the above formula of phthalic acid, — and to this, it 
must be remembered, we are led independently of any facts 
connected with the formation of the acid from naphthalene, — 
the accepted formula of naphthalene follows naturally. 

Derivatives of Naphthalene 

An interesting fact that has been discovered by a study of the 
mono-substitution-products of naphthalene is this, — that two, 
and only two, varieties can be obtained. There is an a- and a 
/8-chlor-naphthalene, an a- and a ^-brom-naphthalene, etc., etc. 
This fact is quite in harmony with the views held regarding the 
constitution of naphthalene, as will readily be seen by examin- 
ing the formula somewhat more in detail. There are two, and 
only two, kinds of relations which the hydrogen atoms bear to 
the molecule; all those marked with an a being of one kind, 
and all those marked with a p being of another kind; — 



396 HYDKOCAKBONS WITH TWO BE^ZENB RESIDUES 

a H a H 



/3 HC. .a .CH p 

a M a li 

Here, again, a problem presents itself like that presented by 
the di-substitution-products of benzene. The theory gave us 
three formulas, and three compounds are known. The problem 
was to determine which formula to assign to each compound. 
Here we have two formulas for two brom-naphthalenes and 
other mono-substitution-products of naphthalene, and we 
actually have two compounds ; and the question arises, which 
of the two formulas must we assign to a given compound ? The 
method adopted is simple, and can be explained in a few words. 
That nitro-derivative of naphthalene which is known as a-nitro- 
naphthalene yields nitro-phthalic acid by oxidation ; and the 
relation of the nitro group to the carboxyl groups, in this acid, 
has been determined. It is expressed by the formula, 

HC/ \c-CO2H 

I I 

HCv /C-CO2H 

H 

Formula I. 

while the formula of the other nitro-phthalic acid is 

H 

NOsC/^ \c-COsH 

I I 

HCv .C-CO2H 

H 

Formula II. 



AMINO-NAPHTHALENE 397 

As a-nitro-naphtlialene yields the acid of formula I., it fol- 
lows that in it the nitro group must occupy the position of one 
of the hydrogen atoms marked a in the above formula for naph- 
thalene. Those substitution-products of naphthalene which 
belong to the same series as a-nitro-naphthalene are called a 
derivatives. In the fi compounds the substituting group or 
atom must occupy the place of one of the hydrogen atoms 
marked p. 

According to the theory in every case in which the two 
substituting atoms or groups are the same, there are ten di- 
substitution-products of naphthalene possible. For example, 
there are ten di-chlor-naphthalenes possible. AU ten are haown 
and no more. The relations between the two substituting 
atoms can be followed by the aid of the figure below : — 

8 1 
7/\/\2 



6 



\/\/ 



3 



The numbers mark the positions of the eight hydrogen atoms 
in naphthalene. Two substituting atoms or groups may bear 
to each other the relations 

1,2; 1,3; 1,4; 1,6; 1,6; 1,7; 1,8; 2, 3; 2, 6; 2,7. 

Further, there are fourteen tri-substitution-products possible 
in which the three substituting atoms or groups are the same. 

There are fourteen tri-chlor-napMhalenes possible and all are 
known. 

a-Amino-naphthalene, a-naphthylamine, a-CioHy.NHa.— 

This is formed by the reduction of a-nitro-naphthalene, which 
is the chief product of the treatment of naphthalene with nitric 
acid in the cold. It melts at 50°. It is also formed from the 
corresponding hydroxy 1 compound, a-naphthol, by heating it 



898 HYDROCARBONS WITH TWO BENZENE RESIDUES 

with the ammonia compound of zinc chloride. It turns red in 
contact with the air. It has a fecal-like odor. 

P-Aminonaphthalene, P-naphthylamine, P-G10H7.NH29 is 
made from /8-naphthol by treating it with the ammonia com- 
pound of zinc chloride.^ It melts at 112® and has no odor. 

Several of the sulphonic acids derived from the naphthyl- 
amines are of value for the preparation of dyes. 

Naphthionic acid, 1, 4-naphth7laniine-sulphonic acid. 

— It is the sodium salt of this acid that gives Congo red when 
brought together with diphenyltetrazonium chloride in the 
presence of sodium hydroxide (see Benzidine) : ^ 

C.H4.N,.C.oH,<?2f* 

Congo red -'^ -"-8 

When j3-naphthylamine is treated with sulphuric acid, four 
mono-sulphonic acids are formed. 

Naphthols^ O10H7 . OH. — Both of the naphthols occur in 
coal tar. They act in general like the phenols, though the 
hydroxyl group reacts more readily than that in the phenols. 
It has already been seen that the amino group can be substi- 
tuted for the hydroxyl group of the naphthols. The naphthols 
are made by fusing the corresponding sulphonic acids with 
caustic potash : — 

C10H7 . SO3K + KOH = C10H7. OH + KaSO^ 

Both sulphonic acids are formed when naphthalene is treated 
with sulphuric acid. At low temperatures (80°) the a-acid is 



NAPHTHOLS 399 

the chief product. At higher temperatures (160°) the /8-acid 
is formed in larger quantity. Indeed, the a-variety is converted 
into the /8-variety when heated with sulphuric acid. 

The synthesis of o-naphthol by heating y-phenylisocrotonic 
acid has already been referred to (see page 390). 

a-Naphthol is difficultly soluble in water^ crystallizes in lus- 
trous needles, and melts at 95°. 

P-Naphtlicl is easily soluble in water, crystallizes in leaflets, 
and melts at 122°. 

Naphtholr8ulphonic acids. — Many of these are known, and 
are used in the preparation of azo dyes. The 1, 4-naphthol- 
sulphonic acid is the one principally used. 

Among the azo dyes derived from naphthalene the following 
may be mentioned : — 

a-Naphthol orange, formed by the action of a-naphthol on ben- 
zene-diazonium sulphonate in alkaline solution. It is repre- 
sented by the formula CioHe < J^*^*^^"^*^^^ ; 

Biehricli scarlet, made from diazoazobenzenedisulphonic acid, 

C H <f * ^ 

I SOs , and )8-naphthol. This dye may serve as an ex- 
Na.C6H4.SO8H 

ample of the possibilities presented by the azo compounds. Its 
formula is 

K PIT ^SOsH 
CxoHe < ^^^•^^ < Na . CeH, . SOaH. 

P'NapMhol orange is formed by treating benzene-diazonium 
sulphonate (see sulplianilic acid) with )8-naphthol in alkaline 

solution. Its formula is CioHe < J^* J^* ' ^^'^* • 

Some of the simpler derivatives of naphthalene are used as 
dyes. Among these the following may be mentioned : — 

2, JirDi-mitro^-naphiliol, CioH5(N02)20H, which is used in the 
form of the sodium salt under the name of Martins^ Yellow ; 



400 HYDROCARBONS WITH TWO BENZENE RESIDUES 



Di-nitronaphtholaulphonic acid, C10H4 



r (N02)2(2, 4) 
S08H(7) , which in 

lOH(l) 

the form of the sodium salt is used under the name NapMhol 
TeUow S. 



o-Naphtho-quinone, OioHg02. — This compound is obtained 
by oxidizing naphthalene with chromic acid ; also by oxidizing 
a-amino-a-naphthol and other di-substitution-products of naph- 
thalene in which the two substituting groups are in the 1, 4 
position relatively to each other. It bears to naphthalene the 
same relation that ordinary quinone bears to benzene ; that is, 
it is naphthalene in which two hydrogen atoms are replaced 
by two oxygen atoms. 

It forms yellow needles, which melt at 125®. Like ordinary 
quinone, it is volatile with water vapor. Sulphurous acid con- 
verts it into a-napJitho-hydro-quinone : — 

CoHeOj + Hj = C,oHe(OH), (1, 4). 

Note for Student. — Compare with the action of reducing agents on 
ordinary quinone. 

It gives a dioxime with hydroxylamine. 

jS-Naphtho-quinone, O10H6O2. — This quinone is formed by 
oxidizing )8-amino-a-naphthol with ferric chloride. When re- 
duced with sulphurous acid it gives 1, 2-di-hydroxy-naphthalene. 
It consists of red needles that decompose at 115-120**. It is 
inodorous and is not volatile. While in a-naphtho-quinone the 
two oxygen atoms are in the 1, 4 (para) position to each other, 
as they are in ordinary benzoquinone (see Quinone), in fi- 
naphtho-quinone the oxygen atoms are ortho to each other. 
a-Naphtho-quinone in general resembles ordinary quinone; 
j8-naphtho-quinone does not. The formulas of the two naph« 
tho-quinoues are here given : — 



QUINOLINE AND ANALOGOUS COMPOUNDS 401 



CHnCO CHpCO 



C V" ^" C 



HC 
HC 



^\/\ 



CH HC 



.^X\ 



CO 



[jCCO C^CH 



H H 

a-Naphtho*quinone ^-Naphtho-quinone 

Di-hydroxy-naphtho-quinone, OioH4{q ^, is a dye 

known by the name naphthazarin, on account of its resem- 
blance to alizarin (which see). 

Homologues of naphthalene — like methyl- and ethyl-naph- 
thalene — have been prepared, a- and )8-methyl-naphthalene 
have been found in coal tar. 

QUINOLINE AND ANALOGOUS COMPOUNDS 

When quinine or cinchonine is distilled with caustic potash, 
a basic substance of the formula C9H7N is formed. This is 
called quinoline. It occurs in coal tar together with an iso- 
meric substance isoquinoline, and some homologues. Among 
the compounds homologous with quinoline are the following : — 

Quinaldine, a-Methyl-quinoline .... CioHgN. 
Lepidine, y-Methyl-quinoline .... C10H9N". 
Cryptidine CuHuN. 



Qmnoline, O9H7N. — Quinoline is formed by the distillation 
of quinine, cinchonine, or strychnine, with caustic potash; is 
fdrmed from certain derivatives of benzene; and is found in 
coal tar. 

1. By passing allyl-aniline over heated lead oxide : — 
CeH^.NH,CH:CH.CH3-hOj5 = C9H7N-l-2HA 



402 HYDBOGABBONS WITH TWO BENZENE BESIDUBS 

This synthesis is similar to that of naphthalene from phenyl* 
butylene (see p. 390). 

2. By heating together glycerol, aniline, nitro-benzene, and 
sulphuric acid. In this case acroleiCn is probably first formed 
from the glycerol by the action of the sulphuric acid : ^ 

CHjOH CH, 

I II 

CHOH = CH +2H,0. 

I I 

CHjOH CHO 

This acrole][n then combines with aniline thus : — 

H H 

C ^NH, C ^^ 

^5^ +OHC.CH = CH, = ^YY i^ + HA 

HCLJCH HClJCH .CH 

CH CH HC^ 

H 

The nitro-benzene now acts as an oxidizer, and removing two 
hydrogen atoms gives quinoline : — 

H 

H H H 

The nitro-benzene in acting as an oxidizing agent is itself 
reduced, and the aniline thus formed enters into reaction to- 
gether with the other aniline present. The whole change can 
be represented as below : — 

2 CeH,NH, + CeH^NO^ + 3 C^H A = 3 CgH,N + 11 H,0. 



QUINOLIKE AND ANALOGOUS COMPOUNDS 



403 



3. From o-amino-cinnamio aldehyde by loss of water : — 



C.H, 



/ 



CH=:CH.CHO 



CH = CH 



\ 



or 



NHj 



CH Q NH, 



= C«Hy I +H,0} 



CH^N 



^''^^\l + ^'>- 




This simple synthesis shows very clearly the constitution of 
quinoline. It is analogous to naphthalene in a way. Just as 
the latter is made up of two benzene rings united by two com- 
mon carbon atoms, so quinoline is made up of a benzene ring 
and a pyridine ring united in the same way. This hypothesis 
is in harmony with all the facts known in regard to quinoline. 

4. Another synthesis of quinoline is effected by starting with 
hydrocarbostyril (which see). When this is treated with phos- 
phorus pentachloride it is converted into dichlor-quinoline, and 
by reduction with hydriodic acid this gives quinoline : — 



c.h/ 



I 

COH 



G,n/ 



CH = CC1 

I 

N = CC1 



C«H,/ 



CH = CH 



I 
N = CH 



Quinoline is a colorless liquid with a penetrating odor, and 
is a powerful antiseptic. It boils at 239°. Potassium per- 
manganate converts it into quinolinic acid, which is a pyridine- 
dicarbonic acid, CjH3N(C0sH)j. The formation of this acid is 
analogous to the formation of phthalic acid from naphthalene : -~- 



NpCH 

H(/V^m 



HC 



Sk^Tt 



CH 



HC 
HC 



NPC0,H 



CH 



cVo^O,H 



404 HYDUOCAUBONS WITH TWO BENZENE RESIDUES 

CH ri CH CH /^ f^r\ TT 



HC 



CH HO 



CH^CH (jyCX^OgH 

It has already been pointed out that quinolinic acid gives 
pyridine when distilled with lime and that the accepted hypoth- 
esis in regard to the constitution of pyridine is based on this 
fact and the formation of quinolinic acid from quinoline (see 
pyridine). 

Quinoline forms well-characterized salts with acids. In 
these salts it acts like a mon-acid base. The number of sub- 
stitution-products derivable from quinoline is large. Thus 
there are seven mono-substitution-products possible, as will be 
seen by an examination of the figure below s — 

(1) 

chq-r 

(2) HCi^ Y Vh (a) 

W (7) 

A substituting atom or group may take the place of any oile 
of the hydrogen atoms indicated by the letters a, p, and y, and 
the numbers 1, 2, 3, 4, each of which bears a different relation 
to the nitrogen atom. According to i^is there are seven possi- 
ble mono-methyl derivatives. All of these are known. So also 
there are seven possible mono-chlor derivatives, and all of these 
are known. 

The methyl derivatives are designated by the letters a, fi, y, 
and the numbers 1, 2, 3, 4. 

a-Methyl-quinoline, quinaldine, C9H6(CH8)N. — This 
occurs in coal tar, and can be made by digesting aniline, 
pai'aldehyde, and hydrochloric acid: — 



HYDUOXY-QUINOLIKE 405 

/CH = CH 

N N = C(CH8) 

and by treating o-amino-benzoic aldehyde with acetone : — 

/CHO CH3 /CH = CH 

CeH / + I = CeH / I + 2 H^O. 

\NH2 CO-CH3 \ N = C-CH3 

•y-Methyl-quinoline, lepidine, 09H6(OH3)N. — This occurs 
together with quinoline and quinaldine in coal tar, and it is 
formed by distilling cinchonine with caustic potash. When 
this is brought together with iso-amyl iodide an addition- 
product is formed, and when the latter is treated with caustic 
potash the substance known as cyanin is formed : — 

2 CioHeN . CH^I = CgoH^Ngl + HI. 

Cyanin forms monoclinic prisms with a metallic green lustre. 
Its solution in alcohol is deep blue. This color is destroyed 

by acids and restored by alkalies. 

/ N=CH 
1-Hydroxy-quinoline, CcHaCOH)^ I , is formed from 

X5H=CH 

1-quinoline-sulphonio acid by fusing it with caustic potash. 

a-Hydroxy-quinoline, carbostyril, is formed by the elimi- 
nation of water from o-amiuo-cinnamic acid. It has either the 
hydroxyl or the keto group in the pyridine ring : — 

CH p CH CH p CH 

hc^Wh HC^^V^CH 



HC 



■>- 




.. >. CO HC^ Jl J^(^^) 



H 



2 



Hydrogen addition-products of quinoline and its derivatives. — 
Quinoline, like naphthalene, takes up hydrogen quite easily. 
Tin and hydrochloric acid convert it into tetra-hydro-quinoline, 
in which the hydrogen has been added to the pyridine ring : — 



406 HYDROCARBONS WITH TWO BENZENE RESIDUES 

•C JI2 — Cri2 

C^4< I . 

^NH - CH, 

The tydrochloride of l-hydroxy-methyl-tetra-hydro-quino- 
line is used as a febrifuge under the name kairine. 

The sulphate of 4-raethoxy-tetra-hydro-quinoline, called thai' 
line, is also used as a febrifuge. 

The final product of the addition of hydrogen to quinoline 
is deca-hydro-quinoline, CjHjyN. 

CHqCH 

CufY^N 
Isoquinoline, . — A base isomeric with quino- 



C 



CH^CH 



line is found with it in coal tar. This base, which is called 
isoquinoline, can be made by methods that show that the 
isomerism with quinoline is due to a difference in the position 
of the nitrogen atom. In it the nitrogen atom is not directly 
connected with the benzene ring, but it is in the )8-position as 
shown in the above formula. It can be made, for example, 

from the imide of an acid of the formula ^^^<nf\r\^ 
(homophthalio acid). This imide has the formula 

CH, - CO 






x;o - NH 

When treated with phosphorus oxychloride it gives dichlor- 

yCH =CC1 
isoquinoline, C6H4< | , and this when reduced by means 

\CC1=N CH = CH 

of zinc dust gives isoquinoline, C6H4<^ | . Isoquinoline 

melts at 23® and boils at 240.5®. It resembles quinoline in its 
general properties. 

Several alkaloids are derivatives of tetra-hydro-isoquinoline, 
such, for example, as papaverine, narcotine, and hydrastine. 



CHAPTER XX 

HYDROCARBONS CONTAINING TWO BENZENE RESIDUES 

INDIRECTLY COMBINED 

DiPHENTL and naphthalene have been shown to consist of two 
benzene residues in direct combination. Diphenyl-methane is 
an example of a hydrocarbon consisting of two benzene resi- 
dues in indirect combination, CeHa.CHa.CeHg. As diphenyl- 
methane is closely related to toluene, it was treated of in 
connection with the hydrocarbons of the benzene series. 
There are some hydrocarbons which have been shown to con- 
sist of two benzene residues united by means of residues of 
unsaturated paraffins. The most important of these is the 
well-known anthracene. 

Anthracene, C14H10. — Anthracene is formed under condi- 
tions similar to those which give rise to the formation of 
naphthalene, especially by heating organic substances to a 
high temperature, and is hence found in coal tar. 

It has been made synthetically from benzene derivatives by 
a number of methods : — 

1. By heating ortho-brom-benzyl bromide with sodium : — 



C,H,| 






(o) 



^ __ ( CHoBr , Br ) ^ ^-^ ^ ^-^ 



.CHv 



= CgHy I >C6H4 -f 4 NaBr + 2 H. 



407 



408 HYDBOCAKBO>'S Wiril TWO BENZENE RESIDUES 

2. By treating a mixture of benzene and acetylene tetra^ 
bromide with aluminium chloride : — 



BrCHBr .CHv 

CfiHe + I + CeHe = CeH/ | NCeH^ + 4 HBr. 



Anthracene is prepared in large quantity from those portions 
of coal tar which boil between 340° and 360°. The distillate 
is redistilled, and that which distils after the temperature has 
reached 340° is treated with liquid sulphur dioxide to remove 
the impurities. When pure it forms laminae, or monoclinic 
plates, showing a beautiful blue fluorescence. It melts at 213°, 
and boils at 351°. 

Anthracene takes up hydrogen, forming di-hydro-aiithraceney 
C14H12, and hexa-hydrcHinthraceney C14H16. It takes up bromine 
and chlorine, forming first addition-products and then substi- 
tution-products. 

Oxidizing agents convert anthracene into anthra-quinone, 
C14H8O2, just as they convert naphthalene into naphtho- 
quinone. 

The formation of anthracene from ortho-brom-benzyl bromide 
and from benzene and acetylene tetrabromide (see above) fur- 
nishes strong proof in favor of the view that anthracene con- 
sists of two groups, C6H4, united by the group, CgHg; thus, 
C6H4 . C2H2 . C6H4. It hence appears as a diphenylene ^ deriva- 
tive of ethane, C2H2 (€6114)2, analogous to diphenyl-ethane, 
C2H4(CeH5)2. This conception may also be expressed thus: — 

a a 

H H 

pnc^ \c-cH-c/ \iJip 

^HCv .C-CH-Cv yCHfi 

H ^ H . 

a a 

iPlieiiylen«aC«H4. 



ANTHRAQUINONE 409 

This is the formula commonly accepted for anthracene. It is 
in harmony with a large number of facts, and has been an 
efficient aid in investigations on anthracene and its derivatives. 
The Greek letters, a, p, y, show the three different positions of 
the hydrogen atoms, and indicate that there are three possible 
raono-substitution-products of anthracene. 

Anthraqiiinone, ChHsOz ( OeHi < qq > OgHi] . — Anthra- 
quinone is formed 

1. By direct oxidation of anthracene : — 

^14^10 + O3 = C14H8O2 + H2O. 

2. By distilling calcium benzoate : — 

CeH4 < jj jjQOG ^ ^^^ ~ ^^A "^ CO ^ ^^A + ^ ^aO- 

3. By treating phthalic anhydride with benzene in the 
presence of aluminium chloride. The first product is ortho- 
benzoyl-benzoic acid : — 

CftH4 < ^^ > O + CfiHg = C6H4 < QQQ jj • 

Ortho-benzoyl-benzoic acid 

The ortho-benzoyl-benzoic acid thus formed is converted into 
anthraquinone when heated with phosphorus pentoxide : — 

C6H4<^^^jj = C6H4 < ^^ > C6H4 -f- HgO. 

4. By distilling calcium phthalate : — 

e.H.{§»>c.: 

= CaH, < ^^ > CeH, + 2 CaCO» 



( COiO ! 

^•*^* 1 :C00 ^ \ 



Experiment 79. — Dissolve 5« commercial anthracene in 220<» hot 
glacial acetic acid. Slowly add to the boiling solution 50s chromic acid 



410 HYDROCARBONS WITH TWO BENZENE RESIDUES 

in 60<^ acetic acid (50 p. c). Boil for some hours. After cooling, add 
760<^ water ; filter ; wash ; dry ; and sublime. 

Anthraquinone forms rhombic crystals, melting at 285®. It 
sublimes in yellow needles ; is insoluble in water, but slightly 
soluble in alcohol and ether. It is an extremely stable com- 
pound, resisting the action of alcoholic potash and oxidizing 
agents. Fused with solid potassium hydroxide, it yields ben- 
zoic acid : — 

CeH4 < CO > C6H4 + 2 KOH = 2 C^,.COOK 

Reducing agents convert it successively into oxanthranolj 
CmHioOj, anthranoly C14H10O, and anthracene, CmHi©.. These 
changes may be represented thus: — 

C,H, < ^^ > C A + H, = C,H, < CO ^^^ > ^'^ ' 

Ozanthranol 

C,H, < ^^^^^ > C^4 + H, = C,H4 < I > C,H4 + H,0 ; 

^ CH 

Anthranol 

CeH4<p2^^>CeH4 + H, =CeH4< I >CeH4 + H,0. 
^^ CH 

When heated with zinc dust, it yields anthracene. A great 
many derivatives of anthraquinone have been made. Among 
the best known are the hydroxyl derivatives, some of which 
are much-prized dyes and are manufactured in great quantities. 

The hydroxyl derivatives of anthraquinone can be made by 
melting either the bromine derivatives or the sulphonic acids 
with caustic potash. 

Di-hydroxy-anthraquinone, i ^^^^^^^l^^^^^^^ (OH)J.- 
Alizarin is the well-known dye that was originally obtained 
from madder root. The substance found in the root is ntbe' 



ALIZARIN 411 

rythric add, a glucoside of the formula CaeHagOn. When this 
is treated with dilute acids or alkalies or ferments, it is decom- 
posed, yielding alizarin and a glucose : — 

^26^28014 + 2 H2O = C14H8O4 + 2 C6H12OC. 

Alizarin Glucose 

It is formed by fusing dichlor- or dibrom-anthraquinone or 
the sodium salt of anthraquinone-monosulphonic acid * with 
caustic soda and potassium chlorate : — 

C14H7O2 . SOsNa + NaOH + = Ci4He02 (0H)2 + NajSOj. 

Alizarin is now manufactured from anthracene on the large 
scale, and large tracts of land that were formerly used for 
cultivating madder are now used for other purposes. 

Experiment 80. Dissolve 20? anthraquinone in a small quantity of 
faming sulphuric acid, heating gradually to 260°. Dissolve the product 
in a litre of water. Neutralize with finely powdered chalk ; filter. Pre- 
cipitate with a solution of sodium carbonate ; filter ; and finally evaporate 
to dryness. The salt thus obtained is impure sodium anthraquinone-mono- 
sulphonate. In an iron crucible mix 10? of the sulphonate, 40? sodium 
hydroxide, and 8? potassium chlorate, and heat for several hours at 166*^ 
to 175°. The formation of alizarin, during the melting, is shown by the 
dark purple color of the mass. When a little of this is dissolved in water, 
it should form a beautiful purple-red solution. Continue the melting until 
the mass acts in this way. Dissolve the mass in f^ to 1^ water, and acidify. 
Alizarin is thrown down in brown amorphous flakes. Filter off, dry, and 
sublime between watch-glasses. 

Alizarin forms red needles, which melt at 289**. It dissolves 
in alkalies, forming dark purple-red solutions. When heated 
with zinc dust, it yields anthracene. It was this reaction 
which gave the first clew to the nature of alizarin, and led, 
soon after, to its synthesis. 

The two hydroxyl groups in alizarin are in the a and fi posi- 
tions in one benzene ring, as shown in the formula 



412 HYDllOCAltliONS WITH TWO BENZENE KESIDUES 

CH^CO^,C(0H) 
HC/YY^ (OH) 
hJ. i 1 JcH 

The evidence in favor of this view is this: Alizarin is 
formed by beating pjrocatecliol and phthalic anliydiide with 
sulphuric acid. This shows that the two hydroxy! groups are 
in the ortho position with reference to each other. It is only 
necessary to show that one of the hydroxyls is in the a position 
to make the evidence complete. A second di-hydroxy-anthra- 
quinone known aa quinizarin is formed from phthalic anhydride 
and hydroquinol. In quinizarin, therefore, the hydroxyl groups 
are in the para position with reference to each other, — 
CH 00 C(OH) 



CH 

ck^0'o'^c"(OH) 

When quinizarin is oxidized, a third hydroxy! group is intro- 
duced, and putpurin, a trihydroxy-anthraquinone, is formed. 
The same is true of alizarin. It follows therefore that in 
alizarin the hydroxy] groups are in the a and p positions : — 

CH CO C(Oll) 




,,C0 C(OH) 
^y^|0(OH) 

''CO<'C(.OH) 



ALIZARIN 413 

There are ten possible di-hydroxy-arithraquinones. Nine of 
these are known. Those in which the hydroxyl groups are in 
the ortho relation to each other have coloring power. 

Tri-hydSjxy-anthraquinone, } Oi4H805[ChH50,(OH)3].- 
Purpurin is contained in madder root, and is therefore found 
in madder alizarin. It can be made by melting alizarin-sul- 
phonic acid with caustic potash, by melting tri-bromanthra- 
quinone with caustic potash, and also by oxidizing alizarin or 
quinizarin with manganese dioxide and sulphuric acid. 

It dissolves in water, forming solutions that are pure red. 
With alumina mordants it gives a beautiful scarlet red. 

Anthrapurpurin, isopurpurin, 0i4H5O2(OH)8, is found in 
artificial alizarin. 

Phenanthrene, OhHio, which is isomeric with anthracene, 
is also found in the higher boiling parts of coal tar. It is 
found further in "stupp," a mixture of substances obtained 
in the distillation of mercury ores in Idria. It is formed from 
dibenzyl and from o-ditolyl by passing their vapors through 
red-hot tubes: — 



C6H5.CH2 
I 

I 
C6H4.CH8 



C6H4 . CH 

H II 

CeH4 . CH 



When oxidized, phenanthrene is converted into diphenic acid 

which has been shown to be a di-ortho carboxyl derivative of 

diphenyl, — 

CqH.^, CO2H. 

I 

C6H4 CO2H. 
In this process pheiianthraquiuone is formed as an inter me- 



414 HYDBOGABBONS WITH TWO BENZENB BESIDUES 

diate product. This bears to phenanthrene the same relation 
that anthraquinone bears to anthracene. The facts mentioned 
and all other facts known in regard to phenanthrene make 
it clear that this hydrocarbon is made up as shown in the 
formula 

CH CH 
CHC/=VvCCH 

CHCH^ ^CHCH 

It is a derivative of diphenyl, and consists of three benzene 
rings. The formation of phenanthraquinone and of diphenic 
acid by oxidation of phenanthene is easily explained on this 
assumption. 



CHAPTER XXI 

GLUCOSIDES, ALKALOIDS, ETC.— CONCLUSION 

Under the head of the sugars, reference was made (see p. 188) 
to a class of compounds called glucosides, that occur in plants. 
These substances break down under the influence of dilute 
acids or enzymes into some variety of sugar and other com- 
pounds. ThuS; salicin breaks down^ according to the equation 

CeH4(OH)CH2(OC«Hu05) + H,0 
= C«Hi,Oe + C6H4(OH)CH,OH 

OlucoBe Salicylic alcohol 

into glucose and salicylic alcohol, the alcohol corresponding 
to salicylic acid. Some of the more important glucosides are 
mentioned below. 

^sculin, Gi5HieOi9 + ll H2O, occurs in the bark of the 
horse-chestnut tree {j^sculus hippocastanum). It breaks down 
into glucose and sesculetin : — 

Ci5Hie09 + HjO = CgHijOe + C9He04. 

jEscuUn Glucose jEsculetin 

Its water solution shows blue fluorescence. 

Amygdalin, O20H27NO11 + 3 H2O, occurs particularly in 
bitter almonds; also in the kernels of apples, pears, peaches, 
plums, cherries, etc. With emulsin, an enzyme contained in the 
aqueous extract of almonds, amygdalin is broken down into 
benzoic aldehyde, hydrocyanic acid, and glucose: — 

CaoHg^NOu + 2 H2O = GjUfi + CNH + 2 C«HiaO«. 

415 



416 GLUCOSIDES, ALKALOIDS, ETC. 

Arbutin, CiaHigOy, and Methyl-arbutin, OigHigOy, occur in 
the leaves of some varieties of the grape. They break down 
into glucose and hydroquinol or methyl-hydroquinol. 

Coniferin, C16H22O8 4- 2 HgO, occurs in the cambium layer of 
the conifers. It breaks down into glucose and coniferyl alco- 
hol. It yields vanillin when oxidized, and was at one time 
used in the preparation of vanillin on the large scale. 

Helicin, GisHieO? + H2O, is formed by the action of nitrous 
acid on salicin (which see). It has also been made artificially 
by mixing an alcoholic solution of acetochlorhydrose with the 
potassium compound of salicylic aldehyde : — 

CeH,C105(C2H30)4 + CH.O^K + 4 C^HeO 
= CisHiqOj + KCl + 4 C2H5. C2H3O2. 

Acetochlorhydrose is formed by heating glucose with an 
excess of acetyl chloride. 

Helicin breaks up into glucose and salicylic aldehyde. 

Myronic acid, C10H19NS2O10, is found in the form of the 
potassium salt in black mustard seed. When treated with 
myrosin, which is contained in the aqueous extract of mustard 
seed, potassium myronate is converted into glucose, allyl 
mustard oil, and acid potassium sulphate: — 

C10H18NS2O10K = CeHi^Oe + C3H,. NCS + KHSO4. 

Phloridzin, O21H24O10, is a crystalline substance found in the 
root bark of fruit trees. It yields glucose and Phloretin, 
CiaHi405, which gives phloretic acid, C9H10O3, and phloroglucinol 
(which see). 

Salicin, Cis'H.igOj, occurs in willow bark, and in the bark 
and leaves of poplars. Its decomposition into salicylic alcohol 
and glucose has been referred to (see preceding page). 



ALKALOIDS OF PERUVIAN BARK 417 

Saponin, CnH2n_80io, is found in soap root {SaponaHa 
offlcinalis). Its water solution forms a lather like that formed 
by soap. 

Alkaloids 

The alkaloids are compounds occurring in plajnts, frequently 
constituting those parts of the plants which are most active 
when taken into the animal body. They are hence sometimes 
called the active principles of the plants. Many of these sub- 
stances are used in medicine. As regards their chemical char- 
acter, they are basic in the sense that ammonia is basic ; they 
contain nitrogen, and form salts, just as ammonia does, i.e., by 
direct addition to the acids. These and other facts lead to the 
belief that the alkaloids are related to ammonia — that they 
are substituted ammonias. It has been shown that several of 
the alkaloids are related to pyridine (see p. 351) and quinoline 
(see p. 401). Only a few of the more important alkaloids need 
be mentioned here. 

Alkaloids of Peruvian Bark ^ 

Quinine, C20H24N2O2 + 3 H2O. — This valuable substance is 
obtained from the outer bark of the Cinchona varieties. When 
oxidized, it yields derivatives of pyridine. In view of the 
interest connected with quinine, the discovery of its relation 
to pyridine and quinoline has led to a large number of investi- 
gations on the derivatives of these two bases, and it is probable 
that in time it will be possible to make quinine synthetically 
in the laboratory. 

The salts of quinine are formed by direct addition of the 
base to the acids. Examples are 

Quinine hydrochloride . C20H24N2O2.HCI; 
Quinine nitrate , , . . C20H24N2O2.HNO8; 
Quinine sulphate . . . C2oH24N20a.H2SO^ etc., etc. 



418 GLUCOSIDES, ALKALOIDS, ETC. 

Cinchonine, Ci9H22N20, Cinchonidine, dsHnNsO, and 
other bases occur with quinine in Peruvian bark. 

Cocaine, C17H21NO4, is found in coca leaves {Erythroxyhn 
coca). It melts at 98° and is levo-rotatory. Its hydrochloric 
acid salt, Ci7HaN04.HCl, has recently come into prominence 
in medicine, owing to the fact that it is a powerful anaesthetic. 

Nicotine, G10H14N2, occurs in tobacco leaves in combination 
with malic acid. Potassium permanganate converts it into 
nicotinic acid; which is one of the possible pyridine-monocar- 
bonic acids. 

Atropine, C17H28NO8, is found in many varieties of Solanum 
together with hyoscyamine, with which it is isomeric. It is 
produced from this by treating it with alcoholic potassium 
hydroxide. Atropine gives tropine and tropic acid (which see) 
when boiled with baryta water. Tropic acid has been shown to 
be a-phenyl-hydracrylic acid, 

CHaCOH - CH - CO3H. 

I 

Tropine, CsHisNO, the basic constituent of atropine^ has 
been prepared artificially. 

Alkaloids of Opium 

Opium is the evaporated sap which flows from incisions in 
the capsules of the white poppy (Papaver somniferum) before 
they are ripe. The three principal alkaloids contained in 
opiumv are morphine, code'ine, and narcotine. 

Morphine, C17H19NO8 + H2O, is a crystallizable solid which 
is difficultly soluble in water, alcohol, and ether. When de- 
composed, it yields pyridine, trimethylamine, and phenan- 
threne, together with other products. It is important as a 
soporific. 



STRYCHNINE 419 

Codeine, C18H21NO3, is a mono-methyl derivative of mor- 
phine and can be prepared from it. Like morphine it is exten- 
sively used in medicine. 

Narcotine, O22H28NO7, has been shown to contain three 
methyl groups, which are split off, as methyl chloride, when 
the substance is heated with hydrochloric acid. It is a deriva- 
tive of tetra-hydro-isoquinoline. 

Piperine, OnHuNOs, is contained in black pepper. When 
treated with alcoholic potash^ it breaks down into piperidine 
and piperic acid : — 

Ca^Hi^NOa + H2O = C^HuN + C12H10O4. 

Piperidine Piperic acid 

Piperidine, CgHnN, which, as just stated, is formed by the 
decomposition of piperine, has been made synthetically by 
treating pyridine with nascent hydrogen : — 

C5H,N + 6H = C5HnN. 

Pyridine Piperidine 

It is therefore Tiexorhydropyridine (see p. 353). 

Strychnine, C21H22N2O2, and bruoine, O28H26N2O4 + 4 H2O, 
are two alkaloids that occur in nux vomica. Strychnine is a 
most violent poison. 

In the animal body occur a large number of complicated sub- 
stances, the study of which, at this stage, would hardly be 
profitable. Thus, there are the albumins, caseins, and fibrin ; 
the coloring matters of the blood, oxyhsemoglobin, haemoglobin, 
etc. A knowledge of these substances is of great importance 
for physiology, and much progress has been made in this field. 

The study of the composition of animal substances, such 
as milk, urine, etc., and of the relations of the chemical sub- 
stances occurring in the body to the processes of life, is the 
object of physiological chemistry. Without a good knowledge 
of the general chemistry of the compounds of carbon, how- 
ever, the subjects treated of under the head of Physiological 
Chemistry cannot be understood. 



420 GLUCOSIDES, ALKALOIDS, ETC. 

Albumins, etc. 

The albumins form the most important part of the organism. 
They enter into the composition of protoplasm and of all the 
nutritive liquids of the body. They are for the most part pre- 
cipitated by heat, by strong mineral acids and by many me- 
tallic salts, such as cupric sulphate, lead acetate, mercuric 
chloride ; • by alcohol and tannic acid. With sodium hydroxide 
and very little cupric sulphate they give a violet color. This 
is the biuret-reaction referred to on page 221. 

The different varieties of albumin have approximately the 
same composition. All contain carbon, hydrogen, oxygen, 
and sulphur. 

Hydrolytic agents such as hydrochloric or sulphuric acid, 
baryta water, potassium hydroxide, and also certain enzymes, 
as, for example, pancreas enzyme, break down the albumins 
and give many simpler products, prominent among which are 
amino-acids. Several of these products have been treated of 
in the proper places. Those which should receive special 
mention are : 

Glycine, alanine, amino-valeric acid, leucine, isoleucine, 
phenyl-alanine, aspartic acid, glutamic acid ; serine, tyrosine, 
cystine, cysteine ; diamine- valeric acid (ornithine), diamino- 
caproic acid (lysine) ; urea, ammonia. 

The amino-acids are linked together in the albumins, forming 
very complex molecules. The polypeptides (which see) are 
intermediate between the amino-acids and the albumins. 

Peptones. — These are products formed by the action of the 
juices of the stomach (pepsin) and of the pancreas enzyme on 
the albumins. The first products of the action are anti- and 
hemi-albumose. These then pass over into peptone. The pep- 
tones are easily soluble in water, and are not coagulated by 
heat. Further, they are not precipitated by most of the 
reagents that precipitate albumin. The peptones appear to be 
closely related to the artificially prepared polypeptides (see 
p. 226). 



INDEX 



Abietic acid, 357. 
Acctamide, 211. 
Acet-amino-phenol, 308. 
Acetanilide, 289. 
Acetates, 60. 
Acetenyl-benzene, 380. 
Acetic acid, 3, 55, 58, 
130. 

aldehyde, 47. 

anhydride, 61. 

ether, 61. 
Acetochlorhydrose, 416. 
Acetone, 3, 71. 
Acetones, 71. 
Aceto-nitrile, 89. 
Acetophenone, 346. 
Acetyl bromide, 61. 

chloride, 61. 
Acetylene, 246. 

-dicarbonic acid, 250. 
Acetyl-glycolic acid, 
161. 

iodide, 61. 

oxide, 61. 

-urea, 221. 
Acid amides, 205, 211. 

fuchsine, 368. 

imides, 216. 
Acids, 55. 

Alcohol, 157. 

Benzene, 321. 

Dibasic, 141, 334. 

Fatty, 38, 130. 

Hexabasic, 337. 

Hydroxy-, 157. 

Oxy-, 157. 

Sulphonic, 77, 298. 

Tribasic, 154. 

Unsatiirateii, 238, 250. 
Aconitic acid, 182, 245. 



Acrolein, 236. 
Acrose, 186, 191. 
Acrylic acid, 165, 238. 

acid series, 238. 

aldehyde, 236. 
Active compounds, 127. 

principles, 417. 
Adipic acid, 143, 184. 
Adonite, 154. 
iEsculetin, 415. 
iEsculin, 415. 
Alanine, 163, 208. 
Albumins, 419, 420. 
Alcohols, 35, 121. 

Acid, 157. 

Benzene, 315. 

Di-acid, 137. 

Hex-acid, 155. 

Hept-acid, 156. 

Mon-acid, 137. 

Monatomic, 137. 

Pent-acid, 154. 

Primary, 123. 

Secondary, 122. 

Sulphur, 75. 

Tertiary, 126. 

Tetr-acid, 154. 

Tri-acid, 148. 

Unsaturated, 233. 
Aldehyde, 47. 

-alcohols, 186. 

ammonia, 49. 

hydrocyanide, 47. 
Aldehydes, 47, 129. 

Benzene, 318. 
Aldol, 191. 

condensation, 191. 
Aldoses, 186. 
Alizarin, 410. 
Alkaloids, 417. 
AUomucic acid, 184. 
Alloxan, 225. 

421 



Allyl alcohol, 234. 
-aniline, 401. 
isosulpho-cy&nate, 

236. 
mustard-oil, 235. 
sulphide, 235. 
Allylene, 249. 
Alimtiinium ethyl, 106. 
Amic acids, 215. 
Amines, 96. 

Amino-acetic acid, 160; 
207. 
-acids, 205, 420. 
-azo-benzene, 296. 
-benzene, 286. 
-benzoic acids, 327. 
-cinnamic acids, 378. 
-cinnamic aldehyde, 

403. 
compounds, 99. 
-dibasic acids, 211. 
-ethane, 99. 
-ethyl-sulphonic acid, 

210. 
-formic acid, 206. 
-hvdrocinnamic acid, 

334. 
-hydroxy-propionic 

acid, 209. 
-hydroxypurin, 226. 
-isobutylacetic acid, 

209. 
-methyl-ethyl-propi- 

onic acid, 209. 
-naphthalenes, 397. 
-naphthpl, 400. 
-phenols, 308. 
-propionic acid, 163^ 

209. 
-propionic acids, 208. 
-succinamic acid, 
215. 



422 



INDEX 



Amino-succinic acid, 
174, 211. 

-sulphonic acids, 210. 

-toluenes, 289. 
z' Ammonia bases, 100. 

Ammonias, substituted, 

96. 
Ammonium cyanate, 86. 
Amygdalin, 318, 415. 
Amyl alcohols, 126. 

valerate, 135. 
Amylene, 230. 
Analysis, 10. 
Anethol, 343. 
Angelic acid, 238. 
Anhydrogeraniol, 361. 
Anilides, 289. 
Aniline, 286. 

blue, 369. 

dyes, 290, 368. 

salt, 288. 
Anisic acid, 305, 343. 
Anisol, 305. 
Anthracene, 407. 
Anthranilic acid, 327. 
Anthranol, 410. 
Anthrapurpurin, 413. 
Anthraquinone, 408, 
409. 

-sulphonic acid, 411. 
Anti-albumose, 420. 
Antifebrine, 289. 
Antipyrine, 298. 
Antitartaric acid, 180. 
Apple essence, 135. 
Arabic, gum, 204. 
Arabinoses, 185, 187. 
Arabite, 154. 
Arachidic acid, 131. 
Arbutin, 416. 
Archil, 313. [256. 

Aromatic compounds, 
Arsenic compounds, 104. 
Aseptol, 308. 
Asparagine, 215. 
Aspartic acid, 174, 211. 
Aspirin, 341. 
Asymmetrical carbon 

atom, 166. 
Atropine, 418. 
Azelaic acid, 143. 



Azo-benzene, 296. 

-compounds, 296. 
Azoxy-benzene, 297. 



Barbituric acid, 223. 
Bassorin, 204. 
Beef tallow, 153. 
Behenic acid, 131. 
Benzal chloride, 282. 
Benzaldoximes, 320. 
Benzene, 254, 255. 

-diazonium salts, 290. 

-disulphonic acid, 300. 

hexabromide, 257. 

hexachloride, 278. 

series, 254. 

-sulphonic acid, 299. 
Benzidine, 296, 387. 

dyes, 387. 
Benzine, 111, 257. 
Benzoic acid, 265, 321. 

aldehyde, 318. 

sulphinide, 331. 
Benzophenone, 346, 
Benzoyl-amino-acetic 
acid, 330. 

benzoic acid, 409. 

bromide, 325. 

chloride, 325. 

cyanide, 325. 

-formic acid, 326. 
Benzyl alcohol, 316. 

chloride, 316. 

cyanide, 332. 

ethers, 317. 

salts, 317. 
Beverages, alcoholic, 

42. 
Biebrich scarlet, 399. 
Bitter-almond oil, 282, 
Biuret, 221. [318. 

Bivalent radicals, 141, 
Boiling-point, 8. 
Bone oil, 3, 350. 
Borneo camphor, 359. 
Borneol, 359, 
Bomyl chloride, 357. 
Brassylic acid, 143. 



Brom-benzene, 279. 

-ethane, 30. 

-methane, 28. 

-naphthalenes, 395. 

-picrin, 312. 

-propionic acids, 132. 

-protocatechuic acid, 
345. 
Bromoform, 28. 
Brucine, 419. 
Butane, 21, 109, 115. 
Butanes, 115. 
Butanic acids, 133. 
Butene, 230. 
Butter, 153. 
Butyl alcohol, 125, 129. 

alcohols, 124. 
Butylene, 230, 233. 
Butyric acid, 130, 133. 

acid ferment, 133. 

acids, 133. 



Cacodyl, 104. 

chloride, 105. 

oxide, 105. 
Caffeine, 226. [217. 

Calcium cyanamide, 
Camphanes, 357. 
Camphene, 357. 
Camphor, 359. 

Artificial, 361. 

Borneo, 359. 
Cane sugar, 197. 
Cantharene, 276. 
Caoutchouc, 358. 
Capric acid, 130. 
Caproic acid, 130. 
Caprylic acid, 130. 
Caramel, 198. 
Carbamic acid, 94, 206. 
Carbamide, 218. 
Carbamines, 90. 
Carbazol, 388. 
Carbides, 248. 
Carbinol derivatives^ 

127. 
Carbohydrates, 185. 
Carbolic acid, 303. 
Carbonic acid, 158. 



\ 



INDEX 



428 



Carbonyl, 53. 
Carbostyril, 378, 405. 
Carboxyl, 65. 
Carvacrol, 310, 360. 
Casein, 419. 
Celluloid, 202. 
Cellulose, 200. 

nitrates, 201. 
Cerotic acid. 131. 
Ceryl alcohol, 128, 129. 
Cetyl alcohol, 128, 129. 
Chlor-acetic acids, 63. 
Chloral, 54. 

hydrate, 54. 
Chlor-benzene, 279. 

-benzoic acid, 326. 

-benzyl alcohol, 317. 

-ethane, 30. 

-fonnic acid, 158. 
Chlorhvdrin. 150. 

« 

Chlor-me thane, 25, 28. 

-naphthalenes, 395. 

-picrin, 102. 

-propionic acids, 132. 
Chloroform, 28. 
Cholic acid, 210. 
Chrysamine, 388. 
Cimicic acid, 238. 
Cinchonidine, 418. 
Cinchonine, 418. 
Cinnamic acid, 376. 

aldehyde, 370. 
Cinnamyl alcohol, 375. 

chloride, 377. 
Citraconic acid, 244. 

anhydride, 183, 245. 
Citrates, 183. 
Citric acid, 182. 
Classification of carbon 

compounds, 17. 
Coal tar, 3, 254. 
Cocaine, 418. 
Codeine, 419. 
Cod-liver oil, 153. 
Collidine, 350. 
Collodion, 201. 
Colophony, 357. 
Combustion process, 11. 
Congo rod, 388, 398. 
Coniferin, 416. 
Conines, 353. 



Constitution of com- 
pounds, 16. 
Constitutional formulas, 

16. 
Conyrine, 353. 
Coumaric acid, 379. 
Coumarin, 378. 
Cream of tartar, 178. 
Creatine, 217. 
Creatinine, 218. 
Creosote, 309. 
Cresols, 309. 
Crotonic acid, 238, 239. 

acids, 239. 

aldehyde, 237. 
Cryptidine, 401. 
Crystal violet, 368. 
Crystallization, 4. 
Cuminic aldehyde, 319. 
Cuminol, 319. 
Cuminyl alcohol, 318. 
Cyan-acetic acid, 143. 

-amides, 216. 
Cyanates, 93. 
Cyanic acid, 85. 
Cyanides, 82, 88. 
Cyanin, 405. 
Cyanogen, 80. 

chlorides, 85. 
Cyan-propionic acid, 

146, 147. 
Cyanuramide, 216. 
Cyanuric acid, 86, 221. 
Cymene, 255, 274. 
Cymogene, 111. 
Cystein, 209. 
Cystine, 209. 






Dahlia, 369. 
Deca^hydro-quinoline, 

406. 
Denatured alcohol, 42. 
Dextrin, 204. 
Dextro compounds, 136. 
Dextrose, 187. 
Di-acetamide, 213. 

-amino-diphenyl, 387. 
Diastase, 40, 200. 



Diazo-amino-benzene, 
296. 
-amino compoimd8» 

295. 
-benzene compounds, 

290. 
-benzene. Potassium, 
294. 
Diazonium salts, 290. 
Di-brom-benzene, 281. 
Dichlor-acetic acid, 63. 

-ethanes, 31. 
Dichlorhydrin, 150. 
Dichlor-isoquinoline, 
406. 
-toluene, 282. 
Di-cyan-diamide, 216. 
Di-ethylene derivatives, 

249. 
Di-ethyl-amine, 96. 
-glycol ether, 138. 
-phosphine, 104. 
-phosphinic acid, 104. 
-phosphoric acid, 69. 
Diglycyl-glycine, 2126. 
Dihydro-anthracene, 
408. 
-benzenes, 276. 
-toluene, 276. 
Dihydroxy-acids, 169. 
-anthraquinone, 410. ^ 
-benzenes, 310. 
-benzoic acids, 343. 
-dibasic acids, 176. 
Dihydro-xylenes, 276. 
Dihydroxy-naphthoqui« 
none, 401. 
-purin, 225. 
Dihydroxy-succinic 
acids, 177. 
-toluene, 313. 
Diiodo-methane, 28. 
Dimethyl-acetylene, 
249. 
-amine, 97. 
-amino-azo-benzene 
sulphonate, 301. 
-aniline, 288. 
-carbinol, 128. 
-ethylene, 233. 
-ethyl-methane, 117. 



424 



INDEX 



Dimethyl- ketone, 7 1 . 

-methyl alcohol, 123. 

-phosphine, 104. 

-pyrocatechol, 311. 

-xanthine, 226. 
Dinitro-benzene, 285. 

-di-phenyl-di-acety- 
le'ne, 384. 

-naphthol, 399. 

-naphtholsulphonic 
acid, 400. 
Dioxindol, 384. 
Dioxyacetone, 186. 
Dipentene, 356. 

Diphenic acid, 413. 
Diphenyl, 386. 
Diphenyl-amine, 289. 

-amine orange, 302. 

ether, 305. 

-imide, 388. 

-iodonium hydroxide, 
280. 

ketone, 346. 

-methane, 362. 

-phthalide, 370. 

-tetrazonium chlo- 
ride, 387. 
Dipropargyl, 252. 
Di-sodium glycol, 138. 
Distillation, 5. 
Diterpenes, 355. 
Dodecane, 109. 
Drying oils, 251. 
Dulcite, 156. 
Durene, 255. 
Dynamite, 153. 
Dyeing, 367. 
Dyes, aniline, 368. 

benzidine, 387. 

substantive, 368, 388, 

tri-phenyl-methane, 
365. 

E 

Emerald green, 60. 
Emulsin, 415. 
Enzymes, 40. 
Eosin, 373. 
Erucic acid, 238. 
Erythrite, 154. 
Erythritic acid, 170. 



Erythrol, 154. 
Erythrose, 186. 
Esters, 38, 67. 
Ethanal, 47. 
Ethandiol, 137. 
Ethane, 21, 25, 109. 
Ethanic acid, 58. 
Ethanol, 39. 
Ethanolic acid, 160. 
Ethene, 230. 
Ether, 43. 

Ethereal salts, 38, 67. 
Ethers, 42. 

Mixed, 46. 

sulphur, 76. 
Ethine, 246. 
Ethyl acetate, 61, 69. 

-acetylene, 249. 

alcohol, 39, 129. 

-amine, 89, 96. 

-ammonium nitrite, 
100. 

-benzene, 269. 

bromide, 39. 

butyrate, 134. 

carbamine, 90. 

carbinol, 128. 

chlor-carbonate, 158. 

chlor-formate, 158. 

chloride, 30. 

cyanide, 88. 
Ethylene, 230, 231. 

alcohol, 137. 

bromide, 137, 232. 

chlorhydrin, 138. 

chloride, 32, 232. 

cyanide, 146. 

-dicarbonic acids, 241. 

glycol, 137. 

lactic acid, 165. 

series, 230. 

succinic acid, 146. 
Ethyl-ethylene, 233. 

ether, 43. 

-glycol ether, 138. 

glycolate, 161. 

-glycolic acid, 161. 
Ethyh'dene chloride, 32, 

51. 
d-Ethylidene-lactic 
acid, 163. 



t-Ethylidene-lactic 

acid, 163. 
^Ethylidene-lactic 

acid, 164. 
Ethylidene succinic 

acid, 147. 
Ethyl iodide, 30. 
isocyanide, 90. 
isosulphocynate, 94. 
-mercaptan, 75. 
-methyl alcohol, 123. 
-mustard oil, 94. 
nitrate, 69. 
-phenyl ether, 292, 

305. 
phosphate, 69. 
phosphine, 104. 
phosphinic acid, 104. 
phosphoric acid, 69. 
sulphate, 69. 
sulphide, 76. 
-sulpho-carbamic 

acid, 94. 
-sulphonic acid, 76, 77. 
-sulphuric acid, 43, 

69. 
-urea, 221. 



Fats, 153. 
Fatty acids, 38. 
Fehling's solution, 189. 
Fermentation, 4, 39. 

Acetic acid, 39. 

Alcoholic or vinous, 
39. 

Lactic acid, 39. 
Ferments, 39. 

Unorganized, 40. 
Ferric succinate, Basic, 

147. 
Ferricyanides, 83. 
Ferrocyanides, 83. 
Fibrin, 419. 
Fire damp, 24. 
Flashing-point, 112. 
Fluorescein, 372. 
Formal, 47. 
Formalin, 47. 



INDEX 



425 



Formic acid, 55, 130. 

aldehyde, 47. 
Formo-nitrile, 89. 
Formula,Constitiitional, 
16. 

Determination of, 12. 

Structural, 15. 
Fractional crystalliza- 
tion, 4. 

distillation, 6. 
Fructosazone, 194. 
d-Fructose, 190. 
i-Fructose, 190. 
^Fructose, 191. 
Fruit sugar, 190. 
Fuchsine, 366. 
Fulminating mercury, 

103. 
Fulminic acid, 103. 
Fumaric acid, 174, 241. 
Fusel oil, 41, 121, 127. 

G 

Galactonic acids, 172. 
Galactoses, 195. 
Gallic acid, 345. 
Garlic oil, 235. 
Gasoline, 111. 
Gelatin, Explosive, 202. 

sugar, 207. 
Geranial, 356. 
Geranic acid, 356. 
Geraniol, 361. 
Glacial acetic acid, 59. 
Gluconic acids, 172. 
Glucosazone, 194. 
Glucose, 40, 187. 
Glucosides, 188, 415. 
Glyceric acid, 152, 170. 

aldehyde, 186. 
Glycerin, 148. 
Glycerol, 133, 148. 

esters, 152. 

nitrates, 152. 
Glycerose, 185. 
Glyceryl tri-oleate, 240. 

tri-palmitate, 149. 

tri-stearate, 149. 
Glycine, 207. 
Glycocholic acid, 207. 



GlycocoU, 160, 207. 
Glycogen, 204. 
Glycol, 137. 
salts, 138. 
Gly colic acid, 160. 
Glycolide, 161. 
Glycols, 138. 
Glycyl-glycine, 226. 
Glyoxylic acid, 176. 
Grape sugar, 40, 187, 
Grignard's reactions, 

106. 
Guaiacol, 311. 
Guanidine, 217. 
Guanine, 226. 
Gulonic acids, 172. 
Guloses, 196. 
Gums, 204. 
Gun cotton, 201. 

H 

Haemoglobin, 419. 
Heavy oil, 254. 
Helianthin, 301. 
Helicin, 416. 
Heliotropine, 345. 
Hemi-albumose, 420. 
Hemiterpenes, 356. 
Hempel tube, 8. 
Hepta-naphthene, 275. 
Heptanes, 109. 
Heptene, 230. 
Heptoic acid, 130. 
Heptose, 186. 
Heptyl alcohols, 129. 
Heptylene, 230. 
Hexa-brom-benzene, 

278. 
Hexach lor-benzene, 

278. 
Hexadecane, 109. 
Hexahydro-anthracene, 
408. 

-benzenes, 275. 

-cymene, 355. 

-methyl-benzene, 255. 

-methylene, 275. 

-methyl-pararosani- 
linei^ 368. 

-naphthene, 275. 



-pyridine, 419. 

-toluene, 275. 

-xylene, 275. 
Hexane, 21, 109, 118. 
Hexanes, 118. 
Hexene, 230. 
Hexoic acid, 130. 
Hexoses, 186, 187. 
Hexyl alcohols, 129. 
Hexylene, 230. 
Hippuric acid, 207, 

330. 
Hofmann's reaction, 
214. 

violet, 369. 
Homology, 21. 
Homophthalic acid, 406. 
Honey stone, 337. 
Human fat, 153. 
Hydracrylic acid, 164. 
Hydrastine, 406. 
Hydrazines, 101, 297. 
Hydrazo- benzene, 

296. 
Hsrdrazones, 193. 
Hydrocarbons, 18. 
Hydro-carbostyril, 334. 

-cinnamic acid, 338. 
Hydrocyanic acid, 81. 
Hydrolysis, 196. 
Hydro-naphthoqui- 

none, 400. 
Hydroquinol, 312. 
Hydrosorbic acid, 238, 

251. 
Hydroxy-acetic acid, 
160. 

acids, 157. 

-benzoic acids, 337. 

-butyric aldehyde, 
191. 

-cinnamic acid, 379. 

-dibasic acids, 172. 

-ethyl-sulphonic acid, 
167. 

-formic acid, 158. 
Hydroxyl, 37. ^ 

Hydroxylamine, 103. 
Hydroxy-methyl-tetra- 
hydro-quinoline, 
406. 



426 



INDEX 



a^Hydroxy-propionic 

acid, 163. 
/3-Hydroxy-propionic 

add, 164. 
Hydroxy-propionic 

acids, 162. 
Hydroxy-quinolines, 
405. 
-succinic acids, 173. 
-sulphonic acids, 167. 
-tribasic acids, 181. 
Hyenic acid, 131. 
Hyoscyamine, 418. 
Hypogsic acid, 238. 



Idonic acid, 196. 
Idose, 196. 

Imino compounds, 99. 
Inactive compounds, 
India rubber, 355. [127. 
Indican, 381. 
Indigo, 381. 
Indigo-blue, 382. 

-white, 383. 
Indigotin, 382. 
Indol, 384, 385. 
Indoxyl, 383. [180. 

Internal compensation, 
Inulin, 190. 
Inversion, 198. 
Invert sugar, 198. 
Invertase, 40. 
lodo-benzene, 280. 

-cyclohexane, 275. 

-ethane, 30. 

-methane, 28. 
Iodoform, 28. [280. 

lodonium hydroxide, 
lodoso-benzene, 280. 
lodoxy-benzene, 280. 
Isatine, 328. 
Isethionic acid, 167. 
Isobutane, 115. 
Isobutyl alcohol, 125. 

-carbinol, 128. 
Isobutyric acid, 134. 
Isocrotonic acid, 239. 
Isocyanates, 93. 
Isocyaoides, 90. 



Isodiazo-benzene, 294. 

-benzene-oxide, 294. 
Isohexane, 118. 
Isoleucine, 209. 
Isomerism, 31. 

Physical, 166. 
Isonitroso compounds, 

102. 
Iso-paraffins, 119. 
Isopentane, 117. 
Isophthalic acid, 

335. 
Isoprene, 355. 
Isopropyl alcohol, 

121. 
Isopurpurin, 413. 
Isoquinoline, 401, 406. 
Isosuccinic acid, 147. 
Isosulphocyanates, 94. 
Itaconic acid, 244. 

anhydride, 183, 245. 

K 

Kairine, 406. 
Kerosene, 111. 
Ketone alcohols, 186. 
Ketones, 71, 340. 
Ketoses, 186. 



Lacmoid, 312. 

Lactam compounds, 329. 

Lactic acid, 163. 

acids, 162. 
Z-Lactic acid, 164. 
Lactim compounds, 329. 
Lactones, 168. 
Lactose, 199. 
Lard, 153. 
Laurie acid, 130. 
Laurinol, 360. 
Lead plaster, 149. 

sugar of, 60. 
Lepidine, 401, 405. 
Leucine, 209. 
Levo compounds, 135. 
Levulose, 190. 
Light oil, 251. 
Limonenes, 356. 



LinoleTc acid, 251. 
Litmus, 313. 
Lutidines, 350, 353. 
Lyddite, 307. 

M 

Maleic acid, 174, 241. 

anhydride, 244. 
c^Malic acid, 176. 
t-Malic acid, 175. 
^-Malic acid, 174. 
Malonic acid, 143, 145. 
Malonyl urea, 223. 
Malt, 200. 
Maltase, 200. 
Maltose, 200. 
Mandelic acid, 332. 
Manna, 155. 
Mannite, 155. 

hex-acetate, 156. 

hexa-nitrate, 155. 
Mannitol, 155. 
Mannoheptite, 156. 
Mannonic acids, 171. 
Manno-saccharic acid, 
Mannoses, 195. [155. 
Margaric acid, 131. 
Marsh gas, 21, 24. 

series, 109. 
Martius' yellow, 399. 
Melamine, 216. 
Melissic acid, 131. 
Mellite, 337. 
Mellitic acid, 337. 
Melting-points, 9. 
Menthadiene, 355. 
Menthane, 355. 
Menthene, 355. 
Menthol, 359. 
Mercaptans, 75. 
Mercury ethyl, 106. 

fulminate, 103. 
Mesaconic acid, 244. 
Mesitylene, 255, 270. 
Mesitylenic acid, 270, 

333. 
Meso tartaric acid, 180. 
Mesoxalic acid, 176. 
Meta-amino-benzoic 
acid, 329. 



INDEX 



427 



Meta-di-hydroxy-ben- 
zene, 311. 

-hydroxy-benzoic 
acid, 342. 
Metaldehyde, 50. 
Metamerism, 32. 
Meta^phthalic acid, 335. 

-series, 267. 

-styrene, 375. 
Methanal, 47. 
Methane, 21, 24, 29, 

109. 
Methanic acid, 55. 
Methanol, 35. 
Methoxy-benzoic acid, 
305, 343. 

-tet ra-hyd ro-quino- 
line, 406. 
Methyl acetate, 69. 

-acetylene, 249. 

alcohol, 3, 35, 129. 
, alcohol series, 129. 

-amine, 90, 96. 

-ammonium salts, 97. 

-arbutin, 416. 

-benzene, 264. 

bromide, 28. 

-carbinol, 128. 

chloride, 25, 28. 

cyanide, 88. 

-diethyl-methane, 
118. 

-divinyl, 356. 
Methylene iodide, 28. 
Methyl ether, 46, 

-ethylene, 233. 

ethyl ether, 46. 

-ethyl-pyridine, 350. 

-glycocoll, 208. 

green, 369. 

-indol, 385. 

iodide, 28. 

-isopropyl-benzene, 
274. 

-naphthalenes, 401. 

-peiitamethylene, 
275. 

-phenyl ether, 305. 

-phenylhydrazine, 
298. 

-phosphine, 104. 



-propanic acid, 134. 

-pyrocatechol, 311. 

-quinolines, 401, 404. 

sulphide, 76. 

-sulphuric acid, 69. 

-toluenes, 266. 

violet, 369. 
Milk sugar, 199. 
Mirbane, Essence of, 

285. 
Mixed ethers, 46. 
Mixing syrup, 188. 
Molasses, 198. 
Molecular weights, de- 
termination of, 13. 
Monosaccharides, 185. 
Mordants, 367. 
Morphine, 418. 
Moth balls, 391. 
" Mother-of- vinegar," 

58. 
Mucic acid, 184. 
Mustard-oils, 94. 
Mutton tallow, 153. 
Mycoderma acetif 58. 
Myricyl alcohol, 128, 

129. 
Myristic acid, 131. 
Myronic acid, 416. 
My rosin, 416. 



N 

Naphtha, 111. 
Naphthalene, 388. 
Naphthazarin, 401. 
Naphthenes, 275. 
Naphthionic acid, 398. 
Naphthols, 398. 

oranges, 399. 

Hsulphonic acid, 399. 

yellow S, 400. 
Naphthoquinones, 400. 
Naphthylamines, 397. 

-sulphonio acid, 398. 
Narcotine, 406, 419. 
Neo-paraflBuis, 119. 
Nicotine, 418. 
Nicotinic acid, 351. 
Nitriles, 89. 



Nitro-benzene, 285. 

-benzoic acids, 326. 

-benzyl alcohol, 317. 

-cellulose, 201. 

-chloroform, 102. 

-cinnamic acids, 378. 

compounds, 99, 101. 

-cuminic aldehyde, 
309. 
Nitroform,^ 102. 
Nitrogen, estimation of, 

11. 
Nitro -glycerin, 150, 152. 

-mannite, 155. 

-methane, 102. 

-naphthalene, 394. 

-phenols, 306. 

-phenyl-propiolic 
acid, 381. 
Nitroso compoimds, 

102. 
Nitro-toluenes, 286. 

-trichlormethane, 102. 
Nonane, 109. 
Nonoio acid, 130. 
Nonose, 186. 
Nonyl alcohol, 129. 
Normal paraffins, 119. 
Nux vomica, 419. 

O 

Octane, 109. 
Octoio acid, 130. 
Octonaphthene, 275. 
Octose, 186. 
Octyl alcohol, 129. 
CEnanthylic acid, 130. 
Oils, Drymg, 251. 
Olefiant gas, 230, 231. 
Olefines, 230. 
Olefin-terpenes, 357. 
Oleic acid, 148, 240. 
Olein, 153, 238, 240. 
Oleomargarin, 153. 
Opium alkaloids, 418. 
Optical activity, 127. 
Orange III, 301. 
Orcein, 313. 

Orcinol, 313. [acid, 327. 
Ortho-amino-benzoic 



428 



INDEX 



Ortho-benzoquinone, 
349. 

-di-hydroxy-benzene, 
310. 

-hydroxy-benzoic 
acid, 338. 

-phthalic acid, 334. 

-series, 267. 
Osazones, 194. 
Osones, 195. 
Oxalates, 145. 
Oxalic acid, 143. 
Oxal-ureid, 223. 
Oxaluric acid, 223. 
Oxalyl-urea, 223. 
Oxamic acid, 215. 
Oxanthranol, 410. 
Oximes, 103. 
Oxindol, 332, 384. 
Oxy-acetic acid, 160. 

-acids, 157. 

-benzoic acid, 342. 

-hsBHioglobin, 419. 

-propionic acids, 162. 



Palmitic acid, 131, 135. 
Palmitin, 149, 153. 
Papaverine, 406. 
Paper, 202. 
Para-amino-benzoic 

acids, 329. 
Parabanic acid, 223. 
Para-cyanogen, 80. 

-di-hydroxy-benzene, 
312. 
Paraffin, 111. 
Paraffins, 109. 
Paraformaldehyde, 47. 
Para-hydroxy-benzoic 

acid, 343. 
Paraldehyde, 50. 
Para-leucaniline, 364. 

-methyl-isopropyl- 
benzene, 274. 

-nitro-toluene, 284. 

-oxybenzoic acid, 343. 

-phthalic acid, 336. 

-rosaniline, 365. 

-sericj 267. 



Para-toluidine, 289. 
Paris green, 60. 
Partial distillation, 6. 
Pelargonic acid, 130. 
Pent-acety 1-^ lucose, 

189. 
Penta-methylene-di- 

amine, 350. 
Pentane, 21, 109, 117. 
Pentanes, 116. 
Pentene, 230. 
Pentoses, 186, 187. 
Pentyl alcohol, 129. 

alcohols, 126. 
Peptones, 420. 
Peruvian bark alka- 
loids, 417. 
Petroleum, 3, 110. 
Phenacetin, 308. 
Phenanthraquinone, 

413. 
Phenanthrene, 413. 
Phenetidine, 308. 
Phenetol, 292. 
Phenol, 302. 
Phenolates, 305. 
Phenol-acids, 337. 

-phthalein, 369. 
Phenols, 302. 

Mon-acid, 302. 

Di-acid, 310. 

Tri-acid, 313. 
Phenol-sulphonic acids, 
' 308. 
Phenyl acetate, 306. 

-acetic acid, 332. 

-acrylic acid, 376. 

-acetylene, 380. 

-butylene, 375. 

-carbinol, 316. 
Phenylene, 408. 
Phenyl-ethyl alcohol, 
317. 

-ethylene, 374. 
Phenylfructosazone, 

194. 
Phenylglucosazone, 194. 
Phenyl-glycolic acid, 

332. 
Phenylhydrazine, 297. 
Phenylhydrazones, 193. 



Phenyl hydrosulphiole, 
308. 

-hydroxyl-amine, 297. 
Phenyl-iodoso chloride, 
280. 

-ketones, 346. 

-mercaptan, 308. 

-methane, 264, 362. 

-methyl ketone, 346. 

-propiolic acid, 380. 

-propionic acid, 333. 

-propyl alcohol, 317. 

-propylene, 375. 

-salicylate, 341. 

-tolyl ketone, 346. 

-vinylacetic acid, 390. 
Phloretic acid, 416. 
Phloretin, 314, 416. 
Phloridzin, 314, 416. 
Phloroglucinol, 314. 
Phosphines, 104. 
Phosphorus compounds, 

104. 
Phthaleins, 335, 369. 
Phthalic acid, 334. 

acids, 226, 334. 

anhydride, 335. 
Physiological chemistry, 

419. 
Picolines, 350, 352. 
Picrates, 307. 
Picric acid, 307. 
Pimelic acid, 143. 
Pineapple essence, 134. 
Pinene hydrochloride^ 

357, 358. 
Pinenes, 356. 
Piperic acid, 407. 
Piperidme, 353, 419. 
Piperine, 419. 
Piperonal, 344. 
Polymerism, 32. 
Polypeptides, 226. 
Polysaccharides, 185, 

196, 200. 
Polyterpenes, 355. 
Potassium cyanide, 82. 

ferricyanide, 83. 

ferrocyanide, 84. 
Primary alcohols, 123. 

ammonia basesi 100. 



INDEX 



429 



Propandiolic acid, 170. 
Propane, 21, 109. 
Propanic acid, 131. 
Propanol, 121. 
Propanone, 71. 
Propantriol, 148. 
Propargyl alcohol, 250. 
Propene, 230. 
Propiolic acid, 250. 
Propionic acid, 130, 131. 
Propyl alcohol, 73, 121, 
129. 

-meta-cresol, 309. 

-piperidine, 353. 

-pyridine, 353. 
Propylene, 230, 233. 
Protocatechuic acid, 

343. 
Prussian blue, 84. 
Prussiates of potash, 

83. 
Prussic acid, 81. 
Pseudocuniene,255, 273. 
Purification of com- 
pounds, 4. 
Purin, 225. 
Purpurin, 413. 
Pyridine, 350, 351. 

bases, 350. 

-dicarbonic acid, 403. 
Pyrocatechol, 310. 
Pyrogallic acid, 313. 
Pyrogallol, 313. 
Pyroligneous acid, 3. 
Pyro tartaric acid, 143, 

148. 
Pyroxylin, 201. 

Soluble, 201. 

Q 

* ' Quick- vinegar pro- 
cess," 58. 

Quinaldine, 401, 404. 

Quinine, 417. 

Quinizarin, 412. 

Quinoline, 334, 401. 

Quinolinic acid, 351, 
403. 

Quinone, 348. 

Quinones, 347. 



R 

Racemic acid, 178. 
Radicals, 38, 141, 152. 
Re4 prussiate of pot- 
ash, 83. 
Residues, 38. 
Resorcinol, 311. 
Resorcinol-phthalein, 
Rhamnite, 154. [372. 
Rhamnose, 187. 
Rhigoline, 111. 
Rhodamine dyes, 308. 
Rhodinol, 308. * 
Ribose, 187. 
Roccellic acid, 143. 
Rochelle salt, 178. 
Rosaniline, 290, 365, 366. 
Rosin, 357. 
Ruberythric acid, 410. 



S 



Saccharic acid, 184. 
Saccharin, 331. 
Saccharobioses, 197. 
Saccharose, 197. 

oct-acetate, 199. 
Saccharotrioses, 197. 
SaUcm, 415, 416. 
Salicylic acid, 338. 

aldehyde, 339. 
Salol, 341. 
Saponification, 70. 
Saponin, 417. 
Sarco-lactic acid, 163. 
Sarcosine, 208. 
Saturated compounds, 

228. 
Schweinf urth's green,60. 
Sebacic acid, 143. 
Secondary alcohols, 122. 

ammonia bases, 100. 

butyl alcohol, 125. 

propyl alcohol, 73, 121 . 
Seldlitz powders, 178. 
Seignette salt, 178. 
Serine, 209. 
Sesquiterpenes, 355. 
Silicon tetrethyl, 106. 
Skatol, 385. 



Smokeless powder, 153, 

201. 
Soaps, 136. 

Sodium chloride glucose, 
189. 

ethyl, 105. 

glucose, 189. 

glycol, 138. 

methyl, 59. 
Soluble blue, 84, 369. 

cotton, 201. 

starch, 204. 
Sorbic acid, 251. 
Sorbite, 156. 
Sources of compoimds, 

3. 
Specific gravities and 
molecular weights, 
13. 
Spem. oil, 153. 
Spirit of wine, 39. 
Starch, 202. 
Stearic acid, 131, 135. 
Stearin, 149, 153. 

candles, 135. 
Stereo-chemistry, 167. 
Structural formulas, 15. 
Structure of compoimds, 

16. 
Strychnine, 419. 
Stupp, 413. 
Styphnic acid, 312. 
Styrene, 374. 
Styryl alcohol, 375. 
Suberic acid, 143. 
Substantive dyes, 368. 
Substituted ammonias, 

96. 
Substitution, 27. 
Succinamide, 216. 
Succinate, Basic ferric, 

147. 
Succinic acid, 143, 146. 

acids, 146. 

anhydride, 147. 
Succinimide, 216. 
Sucrates, 199. 
Sugar of lead, 60. 

of milk, 199. 
Sugars, 185. 
Sulphanilic acid, 301. 



430 



INDEX 



Sulpho-benzoic acids, 
326, 331. 

-cyanates, 87, 93. 

-cyanic acid, 86. 
Sulphones, 76. 
Sulphonic acids, 77, 298. 
Sulpho-urea, 87, 224. 
Sulphur alcohols, 75. 

ethers, 76. 
Sulphuric ether, 43. 
Synthesis, 26. 



Tallows, 153. 
Talose, 196. 
Tannic acid, 346. 
Tannin, 346. 
"Tartar,'' 177. 

Cream of, 178. 

emetic, 178. 
d-Tartaric acid, 177. 
i-Tartaric acid, 180. 
i-Tartaric acid, 180. 
Tartrates, 178. 
Tartronic acid, 152, 173. 
Taurine, 168, 210. 
Taurocholic acid, 210. 
Tautomerism, 92. 
Teracrylic acid, 238. 
Terecamphene, 359. 
Terephthalic acid, 336. 
Terpanes, 357. 
Terpenes, 355. 
Tertiary alcohols, 126. 

ammonia bases, 100. 

butyl alcohol, 125. 
Tetra-brom-fluorescein, 
373. 

-chlor-methane, 
29. 

-ethyl-ammonium hy- 
droxide, 98. 

-ethyl-ammonium 
iodide, 98. 

-ethy 1-phosphonium 
hydroxide, 104. 
Tet rahy d ro-ben zenes, 
275. 

isoquinoline, 406. 

-quinolino, 405. 

-toluene, 275. 



Tetra-hydroxy-dibasic 

acids, 183. 
Tetra-methyl-ethane, 
118. 

-methyl-methane, , 
117. 

-nitro-methane, 102. 

-phenyl-methane, 
362. 
Tetrolic acid, 250. 
Tetroses, 186. 
Thalline, 406. 
Theine, 226. 
Theobrorbine, 226. 
Thiophene, 256. 
Thiophenol, 308. 
Thio-urea, 224. 
Thymol, 309. 
Tin tetrethyl, 106. 
Toluene, 255, 264. 

-sulphon-amide, 300. 

-sulphon-chloride,299. 

-sulphonic acid, 299. 
a-Toluic acid, 332. 
Toluic acids, 266, 300, 

331. 
Toluidmes, 289. 
Tolyl-carbinol, 318. 

-cyanide, 300. 
Tri-acetamide, 213. 

-amino-triphenyl-car- 
binol, 366. 

-amino-triphenyl-me- 
thane, 364. 

-brom-phenol, 306. 

-carballylic acid, 154. 

-chloracetic acid, 63. 

-chloraldehyde, 54. 
Trichlorhydrin, 150. 
Tri-chlor-methane, 28. 

-chlor-propane, 150. 

-cyanhydrin, 154. 

-cyan-triamide, 216. 

-ethyl-amine, 96. 
Trihy d roxy-anthraquin- 
one, 413. 

-benzene, 313. 

-benzoic acids, 345. 

-purin, 225. 
Tri-keto-hexamethyl- 
ene, 315. 



Trimesitic acid, 270. 
Trimethyl-amine, 98. 

-benzene, 270. 

-carbinol, 128. 

-ethyl-methane, 118. 

-phosphine, 104. 

-xanthine, 226. 
Trinitro-methane, 102. 

-phenol, 307. 

-resorcinol, 312. 

-triphenyl-methane, 
364. 
Trioses, 186. 
Triphenyl-carbinoi, 364. 

-carbinol-carbonic 
acid, 370. 

-methane, 362, 363. 

-methane dyes, 365. 
Trivalent radicals, 152. 
Tropaeolin D., 301. 
TropsBolin OO, 302. 
Tropic acid, 418. 
Tropine, 418. 
TumbuU's blue, 84. 
Turpentine, 357. 

U 

Univalent radicals, 141. 
Unsaturated com- 

poimds, 228. 
Uranin, 372. 
Urea, 86, 218. 

salts, 221. 

Substituted, 221. 
Ureids, 222. 
Urethanes, 206. 
Uric acid, 224. 
Uvitic acid, 270. 



Valeric acid, 130, 134. 
Valylene, 251. 
Vanillic acid, 344. 
Vanillin, 344. 
Veratric acid, 311. 
Veratrol, 311. 
Verdigris, 60. 
Veronal, 223. 
Vinasse, 98, 198. 
Vinegar, 59. . 



INDEX 



431 



W 

Wine, spirit of, 39. 

vinegar, 58. 
Wintergreen oil, 338. 
Wood gum, 204. 

spirits, 3, 35. 



Xanthine, 225. 
Xanthogenic acid, 158. 
Xanthone, 340. 
Xylenes, 255, 265. 
Xylidines, 290. 
Xylite, 154. 
Xylose, 187. 



Yellow prussiate of pot- 
ash, 83. 



Z 



Zinc ethyl, 105. 



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