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Full text of "Practical organic chemistry"

PRACTICAL 
ORGANIC CHEMISTRY 



MACMILLAN AND CO., LIMITED 

LONDON . BOMBAY . CALCUTTA . MADRAS 
MELBOURNE 

THE MACMILLAN COMPANY 

NEW YORK . BOSTON . CHICAGO 
DALLAS . SAN FRANCISCO 

THE MACMILLAN CO. OF CANADA, LTD. 

TORONTO 



C- 




'-0 



BY 



JULIUS B: COHEN, PH.D., B.Sc., F.R.S. 

PROFESSOR OF ORGANIC CHEMISTRY, THE UNIVERSITY; LEEDS 
AND ASSOCIATE OF THE OWENS COLLEGE 




MACMILLAN AND CO., LIMITED 
ST. MARTIN'S STREET, LONDON 

1920 



COPYRIGHT. 

First Edition, 1900. 

Reprinted, 1904, 1907. 

Second Edition, 1908, 1910, 1913, 1915, 1916, 1918, 1919, 1920 (twice). 



PREFACE TO THE FIRST EDITION 



THE present volume is an enlarged edition of that published 
in 1887, and has been completely rewritten. The preparations 
have all been carefully revised, some of the former ones 
omitted and many new ones introduced. The chief additions 
are the introductory chapters on organic analysis and molecular 
weight determinations, and an extension of the appendix. 

The book does not aim at being a complete laboratory guide, 
but is intended to provide a systematic course of practical in- 
struction, illustrating a great variety of reactions and processes 
with a very moderate outlay in materials and apparatus. 

The objection may be raised that the detailed description of 
processes makes no demand upon a student's resourcefulness 
or ingenuity. It must be remembered, however, that the 
manipulative part of organic chemistry is so unfamiliar to the 
elementary student that he requires minute directions in order 
to avoid waste of time and material. Until he has acquired 
considerable practical skill he cannot accomplish the experi- 
mental work requisite for research, and repeated failures will be 
apt to destroy his confidence in himself. 

To satisfy, to a legitimate extent, the prejudices of certain 
examining bodies, who still adhere to the old system of testing 
a student's knowledge of practical organic chemistry by means 
of the qualitative analysis of certain meaningless mixtures, the 
special tests for some of the more common organic substances 
have been inserted. At the same time, an attempt has been 
made at the end of the appendix to systematise the analysis of 



PREFACE TO THE FIRST EDITION 



organic substances on a broader and therefore more rational 
basis. 

The present occasion seems opportune to direct attention to 
the fact that one of the most familiar, most readily procurable 
and most cheaply produced of all organic materials is placed 
beyond the reach of many students by the heavy duty levied 
upon it. May I, in the name of teachers of organic chemistry, 
appeal to the Board of Inland Revenue, on behalf of scientific 
and technical education, to provide institutions for higher 
education in science with a limited quantity of pure alcohol 
free of duty, thereby placing schools of chemistry in this 
country in the same position as those on the Continent ? 

In conclusion I desire to thank Dr. J. McCrae, who has 
written the section on Ethyl Tartrate and the use of the Polari- 
meter, Dr. T. S. Patterson, who has been kind enough to look 
over the proofs, and Mr. H. D. Dakin, who has given me sub- 
stantial assistance in the practical work of revision. 

J. B. COHEN. 

THE YORKSHIRE COLLEGE, 
October, 1900. 



PREFACE TO THE SECOND EDITION 

IN the former edition attention was drawn to certain 
drawbacks which accompanied the study of practical organic 
chemistry, among which the heavy duty on alcohol and the 
unsatisfactory nature of the practical tests demanded by 
public examining bodies were specially emphasised. 

Teachers and students alike must welcome the changes which 
have since taken place. An excise duty on alcohol used in the 
laboratory is no longer exacted from students of science, and 
substantial reforms have been introduced into practical examina- 
tions. 

One important feature in some of the new examination 
regulations is the rec6gnition of the candidate's signed record 
of laboratory work. We are, in fact, beginning to discover an 
inherent defect in practical chemistry as an examination sub- 
ject, namely, its resistance to compression into a compact 
and convenient examination form. 

The old and drastic method by which chemistry was made to 
fit into a syllabus consisted in cutting out the core of the 
subject, or in other words, in removing all the processes which 
demanded time, skill, and some intelligence, and in reducing the 
examination to a set of exercises in a kind of legerdemain. This 
process has been to a large extent abandoned, but a residuum 
of it still remains. It is to be hoped that the kind of practical 
examination in organic chemistry, which consists in allotting 
a few hours to the identification of a substance selected from 
a particular list, will in time be superseded or accompanied 
by a scheme encouraging candidates to show, in addition 
to their note-books, evidence of skill and originality, as, for 



Aii PREFACE TO THE SECOND EDITION 

example, in submitting specimens of new or rare preparations, or 
in presenting an account of some small investigation. 

The present edition is much enlarged and contains new pre- 
parations, reactions and quantitative methods, all of which have 
been carefully revised. My object has been not to follow any 
particular syllabus, but to present a variety of processes from 
which a selection may be made to suit the special needs of 
different students. 

My thanks are due to Mr. Joseph Marshall, B.Sc., and 
several of my senior students, for their assistance in the work of 
revision. 

J. B. COHEN 
THE UNIVERSITY, LEEDS. 
July, 1908. 



CONTENTS 



ORGANIC ANALYSIS PAG B 

Qualitative examination I 

Carbon and Hydrogen I 

Nitrogen 2 

The Halogens 3 

Sulphur 3 

Phosphorus 3 

Quantitative estimation 4 

Carbon and Hydrogen 4 

Nitrogen 13 

The Halogens 22 

Sulphur 28 

Determination of molecular weight 28 

Vapour density method 29 

Cryoscopic or Freezing-point method 32 

Ebullioscopic or Boiling-point method 37 

Molecular weight of acids 43 

Molecular weight of bases 46 

PREPARATIONS 

General remarks 47 

Purification of spirit 48 

Ethyl alcohol 49 

Potassium ethyl sulphate . 50 

Crystallisation 52 

Ethyl bromide 54 



I 



CONTENTS 



PREPARATIONS PAGE 

Dehydration of liquids 56 

Determination of specific gravity 56 

boiling-point 58 

Ether 59 

Purification of commercial ether 61 

Ethylene bromide 62 

Acetaldehyde 64 

Methyl alcohol 67 

Methyl iodide 68 

Amyl alcohol 69 

Amyl nitrite 69 

Acetone 69 

Chloroform 70 

Acetoxime 71 

Melting-point determination 72 

Acetic acid . . 74 

Acetyl chloride 74 

Acetic anhydride 76 

Acetamide 77 

Heating under pressure 78 

Acetonitnle 79 

Methylamine hydrochloride (Hofmann's reaction) ... 80 

Ethyl acetate 81 

Ethyl acetoacetate 83 

Distillation in vacuo 84 

Monochloracetic acid 87 

Monobromacetic acid 89 

Glycocoll 90 

Glycocoll ester hydrochloride . . 92 

Preparation of hydrogen chloride 93 

Diazoacetic ester 94 

Diethyl malonate 96 

Ethyl malonic acid 97 

Chloral hydrate 99 

Trichloracetic acid 99 

Oxalic acid .... 100 



CONTENTS 



PREPARATIONS PAGE 

Methyl oxalate 101 

Glyoxylic and Glycollic acids 102 

Palmitic acid 104 

Glycerol 106 

Formic acid 106 

Distillation in steam 107 

Allyl alcohol 109 

Isopropyl iodide ... no 

Epichlorhydrin m 

Malic acid 112 

Succinic acid 113 

Tartaric acid 114 

Ethyl tartrate 115 

Determination of rotatory power 116 

Racemic and Mesotartaric acids 122 

Resolution of Racemic acid (Pasteur's method) ... 123 

Pyruvic acid 124. 

Citric acid 124 

Citraconic and Mesaconic acids 125 

Urea 126 

Thiocarbamide . 128 

Uric acid 128 

Alloxantin 129 

Alloxan 130 

Caffeine 131 

Creatine 132 

Tyrosine and Leucine (E. Fischer's ester method) . . . 133 

Grape sugar 135 

Benzene 136 

Purification of Benzene r 3 

Fractional distillation !3 O 

Bromobenzene 140 

Ethyl benzene . . 141 

Nitrobenzene 142 

Azoxybenzene 143 

Electrolytic reduction of Nitrobenzene 144 



CONTENTS 



PREPARATIONS PAGE 

Azobenzene 145 

Electrolytic reduction of Nitrobenzene 145 

Hydrazobenzene 146 

Benzidine 148 

Phenylhydroxylamine 148 

Nitrosobenzene 149 

/-Aminophenol 149 

Aniline 149 

Acetanilide 151 

/-Bromacetanilide 152 

/-Nitraniline 153 

w-Dinitrobenzene 154 

w-Nitraniline 154 

w-Phenylenediamine 155 

Dimethylaniline 156 

/-Nitrosodimethylaniline 157 

Thiocarbanilide 159 

Phenyl thiocarbimide 160 

Triphenylguanidine 160 

Diazobenzene sulphate 161 

Toluene from /-toluidine 163 

/-Cresol 164 

/-Chlorotoluene 165 

/-Chlorobenzoic acid 166 

j#-Bromotoluene 167 

/-lodotoluene . . 168 

Tolyliodochloride 169 

lodosotoluene 169 

p -Tolylcyanide 169 

/-Toluic acid 170 

Terephthalic acid 171 

Diazoaminobenzene 171 

Aminoazobenzene 172 

Phenylhydrazine 173 

Phenyl methyl pyrazolone (Knorr's reaction) .... 175 

Sulphanilic acid 175 



CONTENTS 



PREPARATIONS PAGE 

Methyl orange 176 

Potassium benzene sulphonate 177 

Benzenesulphonic chloride 178 

Benzene sulphonamide '. . 179 

Phenol 179 

Anisole 181 

Hexahydrophenol (Sabatier and Senderens' reaction) . 181 

o- and /-Nitrophenol 183 

Picric acid 185 

Phenol phthalein ' . . . . 186 

Fluorescein and Eosin 187 

Salicylaldehyde and ^-Hydroxybenzaldehyde (Reimer's 

reaction) 188 

Salicylic acid (Kolbe's reaction) 190 

Quinone and Quinol 192 

Benzyl chloride 194 

Benzyl alcohol 195 

Benzaldehyde 196 

a- and -Benzaldoximes 197 

Benzoic acid 199 

Nitro-, Amino-, and Hydroxy-benzoic acids 200 

wz-Bromobenzoic acid 201 

Benzoin 202 

Benzil 203 

Benzilic acid 203 

Cinnamic acid (Perkin's reaction) . . 204 

Hydrocinnamic acid 204 

Mandelic acid 205 

Phenyl methyl carbinol (Grignard's reaction) 206 

Benzoyl chloride - 208 

Benzamide . . . ; 209 

Ethyl benzoate 209 

Quantitative hydrolysis of ethyl benzoate 210 

Acetophenone (Friedel-Crafts' reaction) 210 

Acetophenoneoxime 211 

Acetophenonesemicarbazone 212 



CONTENTS 



PREPARATIONS PAGE 

Beckmann's reaction 212 

Benzoylacetone (Claisen's reaction) 212 

Diphenylmethane 213 

Triphenylmethane 214 

Malachite green 215 

Naphthalene 216 

Phthalic acid 217 

8-Naphthalenesulphonate of sodium 218 

/3-Naphthol 219 

Estimation of methoxyl (Zeisel's method) 220 

acetoxyl (A. G. Perkin's method) . . 222 

hydroxyl (Tschugaeff's method) . . . . 223 

Naphthol yellow 224 

Anthraquinone 225 

Anthraquinone /3-monosulphonate of sodium 226 

Alizarin 227 

Isatin from indigo . 229 

Quinoline 230 

Quinine sulphate from cinchona bark 231 

Phenylrnethyltriazole carboxylic acid 232 

APPENDIX. Notes on the Preparations 234 

HINTS ON THE INVESTIGATION OF ORGANIC SUBSTANCES 322 

TABLES 345 

INDEX 353 



PRACTICAL 
ORGANIC CHEMISTRY 



ORGANIC ANALYSIS 



Qualitative Examination. 

Carbon and Hydrogen. Carbon compounds are fre- 
quently inflammable, and when heated on platinum foil take 
fire or char and burn away. A safer test is to heat the substance 
with some easily reducible metallic oxide, the oxygen of which 
forms carbon dioxide with the carbon present. Take a piece of 
soft glass tube about 13 cm. (5 in.) long, and fuse it together 
at one end. Heat a gram or two of fine copper oxide in a 
porcelain crucible for a few minutes to 
drive off the moisture, and let it cool 
in a desiccator. Mix it with about 
one-tenth of its bulk of powdered sugar 
in a mortar. Pour the mixture into 
the tube, the open end of which is now 
drawn out into a wide capillary and 
bent at the same time into the form FIG. 

shown in Fig. I. This is done by 

shaking down the mixture to the closed end and revolving the 
tube in the blow-pipe flame about 2\ cm. (i in.) beyond the 
mixture until it is thoroughly softened. The tube is then 
removed from the flame, drawn out gently and bent. Make a 
file scratch across the end of the capillary and break it. When 
the tube is cold tap it horizontally at the edge of the bench, so 
as to form a free channel above the mixture. Suspend it by a 

COHEN'S ADV. p. o. c. B 



PRACTICAL ORGANIC CHEMISTRY 



copper wire to the ring of a retort stand, and let the open end 
dip into lime or baryta water. Heat the mixture gently with a 
small flame. The gas which bubbles through the lime water 
turns it milky. Moisture will also appear on the sides of the 
tube, which, provided that the copper oxide has been thoroughly 
dried beforehand, indicates the presence of hydrogen in the 
compound. Gases, or volatile substances like ether and 
alcohol, cannot, of course, be examined in this way ; but 
an apparatus must be arranged so that the gas or vapour is 
made to pass over a layer of red hot copper oxide and then 
through the lime water. 

Nitrogen. Many organic nitrogen compounds when 
strongly heated with soda-lime give off their nitrogen in the 
form of ammonia. Grind up a fragment of cheese or a few 
crystals of urea with 5 to 6 times its weight of soda-lime, pour 
the mixture into a small test-tube (preferably of hard glass) and 
cover it with an equally thick layer of soda-lime. Heat strongly, 
beginning at the top layer. Ammonia is evolved and can be 
detected by the smell, or by holding a piece of moistened 
red litmus paper at the mouth of the tube. When nitrogen is 
present in direct combination with oxygen, as in the nitro- and 
azoxy-compounds, ammonia is not evolved. The following 
general method is applicable to all compounds and is there- 
fore more reliable. The compound is heated with metallic 
potassium or sodium when potassium or sodium cyanide 
is formed. The subsequent test is the same as for cyanides. 
Pour about 10 c.c. of distilled water into a small beaker. 
Place a fragment of the substance in a small test-tube along 
with a piece of metallic potassium or sodium the size of 
a coffee bean, and heat them at first gently until the re- 
action subsides, and then strongly until the glass is nearly 
red-hot. Then place the hot end of the tube in the small 
beaker of water. The glass crumbles away, and any residual 
potassium is decomposed with a bright flash, all the cyanide 
rapidly goes into solution, whilst a quantity of carbon remains 
suspended in the liquid. Filter through a small filter into a test- 
tube. Add to the clear solution a few drops of ferrous 
sulphate solution, and a drop of ferric chloride, boil up for 
a minute, cool under the tap, and acidify with dilute hydro- 
chloric acid. A precipitate of Prussian blue indicates the 



QUALITATIVE EXAMINATION 



presence of nitrogen. If the liquid has a blue colour, let it 
stand for an hour and examine it again for a precipitate. If no 
precipitate appears and the solution remains of a clear 
yellowish-green colour, no nitrogen is present. 

If sulphur is present, an excess of alkali metal must be 
used to prevent the formation of sulphocyanide. 

The Halogens. Many halogen compounds impart a green 
fringe to the outer zone of the non-luminous flame. A more 
delicate test is to heat the substance with copper oxide 
(Beilstein). Heat a fragment of copper oxide, held in the loop 
of a platinum wire, in the outer mantle of the non-luminous 
flame until it ceases to colour the flame green. Let it cool down 
a little and then dust on some halogen compound (brom- 
acetanilide will serve this purpose, see Prep. 55, p. 152). Now 
heat again. A bright green flame, accompanied by a blue zone 
immediately round the oxide, indicates the presence of a 
halogen. The halogen in the majority of organic compounds 
is not directly precipitated by silver nitrate. Only those 
compounds which, like the hydracids and their metallic salts, 
dissociate in solution into free ions give this reaction. If, 
however, the organic compound is first destroyed, and 'the 
halogen converted into a soluble metallic salt, the test may be 
applied. Heat the substance with a fragment of metallic sodium 
or potassium as in the test for nitrogen, p. 2. The test-tube 
whilst hot is placed in cold water, the alkaline solution filtered, 
acidified with dilute nitric acid and silver nitrate solution added. 
A curdy, white or yellow precipitate (provided no cyanide is 
present), indicates a halogen. If a cyanide is present, boil with 
nitric acid until the hydrogen cyanide is expelled and add 
silver nitrate. 

Sulphur. The presence of sulphur in organic compounds 
may be detected by heating the substance with a little metallic 
sodium or potassium. The alkaline sulphide, when dissolved in 
water, gives a violet colouration with a solution of sodium nitro- 
prusside. Heat a fragment of gelatine with a small piece of 
potassium in a test-tube until the bottom of the tube is red hot, 
and place it in a small beaker of water as described in the test 
for nitrogen (p. 2). Filter the liquid and add a few drops of 
sodium nitroprusside solution. 

Phosphorua The presence of phosphorus is ascertained 

B 2 



PRACTICAL ORGANIC CHEMISTRY 



by heating the substance strongly with magnesium powder and 
moistening the cold product with water. Magnesium phosphide 
is formed and is decomposed by the water, giving phosphine 
which is readily detected by its smell. 



Quantitative Estimation. 

Carbon and Hydrogen. The principle of the method is 
that described under qualitative examination, but the substance 
and the products of combustion, viz., carbon dioxide and water, 
are weighed. The following apparatus is required. 

1. An Erlenmeyer or other form of Combustion Furnace. 
The usual length is 80-90 cm. (31-35 in.), and it is provided with 
30 to 35 burners. Flat flame burners are undesirable. 

2. A Drying Apparatus. A form of drying apparatus which 
is easily fitted together is shown in Fig. 2. It consists of four 

large U-tubes arranged side by side 
in pairs. The U-tubes are mounted 
upon a wooden stand with two up- 
rights, to which the two pairs of tubes 
are wired. The first of each pair is 
filled with soda-lime, and the second 
with pumice soaked in concentrated 
FlG 2 sulphuric acid. Each soda-lime tube 

is connected with a sulphuric acid tube 

6y well-fitting rubber corks and a bent glass tube. The two 
other limbs of the sulphuric acid U-tubes are joined by a three- 
way-tap forming a T-piece. The free end of the T-piece is 
attached to a small bulb 
tube, Fig. 3, containing a 
drop of concentrated sul- 
phuric acid to mark the 
rate at which the bubbles 
are passing through the FIG. 3 . 

drying apparatus. The 

bulb tube is connected with the combustion tube by a short 
piece of rubber tubing and a short glass tube, which passes 
through a rubber cork fixed in the end of the combustion tube. 
The rubber tubing carries a screw-clip. The open ends of 








QUANTITATIVE ESTIMATION 5 

the soda-lime (J-tubes are closed with rubber corks, through 
which pass bent glass tubes. One of these glass tubes is con- 
nected by rubber tubing to an oxygen gas-holder or to a 
cylinder of compressed oxygen, which must be furnished with 
an automatic regulating valve, and the other glass tube is 
attached to a gas-holder containing air. By turning the three- 
way tap, either oxygen or air may be supplied to the combustion 
tube. 

3. A Combustion Tube of Hard Glass. It should be about 13 
mm. inside diameter, and the walls not more than 1*5 mm. 
thick. Its length should be such that it projects at least 5 cm. 
(2 in.) beyond the furnace at either end. After cutting the 
required length, the ends of the tube are carefully heated in the 
flame until the sharp edges are just rounded. The tube is filled 
as follows. Push in a loose asbestos plug about 5 cm. (2 in.) from 



FIG. 4. 

one end. This end, to which the calcium chloride tube and potash 
apparatus are subsequently attached, may be called the front end. 
Pour in coarse copper oxide at the opposite end and shake it down 
to the plug until there is a layer about two-thirds the length of the 
tube. Keep the oxide in position by another plug of asbestos ; 
see that the plugs are not rammed too tight. Make a roll of 
copper gauze about 13 cm. (5 in.) long to slide easily into the 
back end of the combustion tube. This is done by rolling the 
gauze tightly round a stout copper wire until the requisite thick- 
ness is obtained. The projecting ends of the wire are then 
bent over into hooks as shown in Fig. 4. This roll, or spiral, 
as it is usually called, is subsequently oxidised. It is pushed 
into the tube or withdrawn as occasion requires by a piece of 
hooked wire. The combustion tube is placed on a layer of 
asbestos in the iron trough of the furnace. The arrangement of 
the tube with boat and spiral is shown in Fig. 5. 

4. A Straig fit Calcium Chloride Tube. It is inserted through a 
rubber cork and fixed in the front end of the combustion tube 
when the latter is not in use, as copper oxide is very hygro- 
scopic, and it is necessary to protect it from the moisture in 
the air. 



PRACTICAL ORGANIC CHEMISTRY 



5. A Potash Apparatus. Several forms of potash apparatus 
are made ; that of Geissler (Fig. 6), and Classen (Fig. 7) being 
perhaps most commonly employed. The latter has the advan- 
tage of being very light. The removable side tube is filled 
with granulated calcium chloride or soda-lime, with a plug of 
cotton wool at each end. The bulbs of the apparatus are filled 

5 CM Oi irt 5 CM. 

*--- SPIRAL BOAT. < CUD X > 



ASBESTOS. 



ASBESTOS. 



FIG. 5 



with a strong solution of caustic potash containing 25 grams of 
potash to 50 c.c. of water. This is done as follows. Remove 
the soda-lime tube and attach in its place a piece of rubber 
tubing. This serves as a mouthpiece. Pour the potash 
solution into a basin and dip the other end of the potash 
apparatus under the liquid. Suck at the rubber tube until the 
quantity appears sufficient to fill the bulbs. Remove the 
potash solution and continue to suck until the solution is trans- 
ferred to the bulbs. The bulbs should be nearly filled. In the 
case of Classen's apparatus, the liquid should stand half an inch 
deep in the bottom of the apparatus outside the lowest bulb. 





FIG. 6 



FIG. 7- 



Wipe the potash solution from the outside and inside of the 
inlet tube of the apparatus with filter paper. Smear a thin film 
of vaseline on the ground end of the soda-lime tube before 
replacing it, and fit to the open ends of the apparatus, stoppers 
of rubber and glass rod, which are not removed, except when 
the apparatus is in use. As the potash apparatus has to be 



QUANTITATIVE ESTIMATION 




refilled after every two combustions, it is advisable to keep a little 
stock of solution in a bottle fitted with an ordinary cork. 

6. A Calcium Chloride U- Tube. The form of calcium chloride 
tube is shown in Fig. 8. It is fitted with sieved calcium 
chloride to within 2^ cm. (i in.) of the 
side pieces, and then with coarser pieces 
to within ^ cm. (\ in.). Place a small 
plug of cotton wool in both limbs above 
the chloride to keep it in position. Two 
well-fitting corks, cut off level with the 
glass and coated with sealing-wax, pro- 
duce an effective air-tight stopper to the 
open limbs, but it is preferable to seal 

them in the blow-pipe flame. The sealing requires a little skill. 
Carefully wipe off any chloride dust which may have adhered 
to the open ends of the two limbs. Cork up one limb and 
stopper one of the side tubes. Attach a short piece of rubber 
tubing to the other side tube to serve as a mouthpiece. Now 
soften the end of the open limb in a small blow-pipe flame, and 
at the same time heat the end of a short piece of glass rod. 
With the hot end of the rod gather up the edges of the open 
limb, and whilst rotating the limb backwards and forwards in 
the flame, draw it out and seal it up. If successful, the appear- 
ance of the tube is that shown in Fig. 9. The blob of glass is 
heated in a small flame, and, by gently blowing and re-heating 
and blowing again, the blob can be 
removed, and, finally, by using a 
rather larger flame, heating and 
blowing alternately, the end is 
neatly rounded. 

7. A Porcelain or, preferably, a 
Platinum Boat. Se^ that it slips 
easily into the combustion tube. 
The boat is kept in a desiccator 
on a flat cork or support made of glass rod when not in use. 

Preparation of the Tube. Before starting the com- 
bustion it is necessary to clean and dry the combustion tube. 
This is effected by heating the whole length of the tube con- 
taining the copper oxide and spiral gradually to a dull red heat, 
and passing through it a slow stream of dry oxygen from the 




FIG. 9. 



8 PRACTICAL ORGANIC CHEMISTRY 

gas-holder or cylinder. As soon as a glowing chip is ignited at 
the front end and the moisture, which at first collects there, has 
disappeared, the gas jets are turned down and finally ex- 
tinguished. The oxygen is then stopped, and the straight 
calcium chloride tube inserted into the open end of the tube. 

Preliminary Operations. Grind up a little pure oxalic 
acid, and carefully weigh out 0*15 to o'2 gram (not more) in the 
boat. Weigh also the calcium chloride tube and potash appa- 
ratus without stoppers or other accessories. The side tube of 
the calcium chloride tube, which carries the bulb, is attached 
directly to the combustion tube with a rubber cork. This cork 
should be carefully selected, and should exactly fit the com- 
bustion tube. The bore hole should be small and smooth, and 
it is advisable to dust it with graphite or coat it with a film of 
vaseline to prevent the rubber from clinging to the glass, a 
matter of frequent occurrence unless this precaution is taken. 
The cork should be kept exclusively for the combustion. Push 
the side tube of the calcium chloride tube through the hole until 
it is flush with the opposite surface, and squeeze the cork tightly 
into the combustion tube. Attach the potash apparatus to the 
other limb of the calcium chloride tube by a well-fitting piece 
of rubber tubing about 3 cm. (i in.) long, and bring the ends 
of the glass as closely as possible together. It should be 
unnecessary to wind wire round the joint if the rubber is of the 
right diameter. A little vaseline may be used here with advan- 
tage, but only in the thinnest film. The potash apparatus 
will require to be supported upon a block or stand. Remove 
the copper spiral from the back of the tube. Introduce the 
boat and push it into position against the asbestos plug by 
means of the spiral which is placed behind it. Replace the 
rubber cork connected with the drying apparatus. The apparatus 
will present the appearance shown in Fig. 10. 

It must now be tested to see that it is air-tight. For this 
purpose, close the open end of the potash apparatus with a 
tight stopper and turn on the full pressure from either gas- 
holder. After the first few bubbles of air have passed through 
the bulbs of the potash apparatus no further movement of 
bubbles should appear in any part of the apparatus. If it 
withstands this test, the combustion may proceed. Release the 
pressure by closing the tap of the gas-holder, screwing up the 



QUANTITATIVE ESTIMATION 



clip at the back of the combustion tube, and cautiously removing 
the stopper from the potash apparatus. Then raise the three- 
way tap from its socket for a moment. 

The Combustion. Turn on the oxygen and adjust the rate 
of flow through the apparatus by means of the screw-clip so 
that 2 or 3 bubbles a second pass through the potash bulbs. 
Throw back the tiles if closed, and light the burners under the 
front layer of copper oxide to within 10 cm. (4 in.) of the boat 
and also 2 or 3 burners under the spiral behind the boat, but 
not within 5 cm. (2 in.) of the boat. Turn up the gas slowly to 
avoid cracking the tube and in a minute or two, when the tube 
is thoroughly warmed, close the tiles over the lighted burners 
and heat to a dull red heat. A vivid red heat during the 
combustion is not only unnecessary, but undesirable, as the 
glass is apt to soften and be distorted and even to blow out and 




FIG. 10. 

become perforated. A combustion tuoe carefully handled 
should last indefinitely. When the copper oxide is red hot, 
turn on the burners very gradually from the spiral towards the 
boat, but do not close the two pairs of tiles over the boat until 
the combustion is nearly terminated and the burners are all 
lighted. The first indication of the substance burning is the 
appearance of a film of moisture at the front end of the 
combustion tube and an increase in the speed of the bubbles 
passing through the potash apparatus. The front end of the 
tube, which should project 4 to 5 cm. (li to 2 in.) from the 
furnace, must be kept sufficiently hot to prevent moisture 
permanently condensing there ; but it must never be allowed to 
become so hot that there is any risk of the cork being burnt, 
and it should always be possible to place the finger and thumb 
round the part of the tube where the cork is inserted. A screen 
made from a -square piece of asbestos board, with a slit in it 



PRACTICAL ORGANIC CHEMISTRY 



slipped over the tube at the end of the furnace, may be used 
with advantage. 

The speed of the bubbles is the best indication of the progress 
of the combustion. If the rate increases so that the bubbles 
passing through the last bulb cannot easily be counted, a burner 
or burners must be lowered or extinguished until the speed 
slackens. After a time, when the air has been displaced and 
carbon dioxide largely fills the tube, the gas is nearly all ab- 
sorbed in the first potash bulb. When this occurs, the current 
of oxygen may be increased until the bubbles appear synchro- 
nously in the bulbs, when the current is again checked. If 
some copper oxide has been reduced in the first stages of the 
process, the bubbles in the potash apparatus may entirely cease 
for a time, but will reappear when the copper has been reoxi- 
dised. Here again an increased current of oxygen will hasten 
the process. The combustion is complete when a glowing chip 
held at the end of the potash apparatus is rekindled. All the 
moisture must by now have been driven over into the calcium 
chloride tube. If this is not the case, warm the end of the tube 
cautiously with a small flame, or by means of a hot tile held 
near the tube The time required to complete the combustion 
is about one-half to three-quarters of an hour from the time the 
front of the tube is red hot, but more volatile substances, which 
must be heated more cautiously, will naturally take longer. 

The combustion being complete, gradually turn down, and in 
a few minutes extinguish, the burners. Whilst the furnace cools 
the oxygen is replaced by a slow current of air. To do this the 
oxygen supply is stopped and the three-way tap is turned 
through 1 80, so as to connect the tube with the air reservoir, 
the tap of which is then opened and the stream of air regulated 
by the screw clip. 

Let the air pass through for 20 minutes whilst the furnace is 
cooling down. Then remove and stopper the potash apparatus 
and the calcium chloride tube, and after allowing them to stand 
by the balance case for half-an-hour, weigh. 

The results are calculated in percentages of carbon and 
hydrogen as follows : 

iv is the weight of substance taken. 

a is the increase in weight of the potash apparatus. 



QUANTITATIVE ESTIMATION II 

b is the increase in weight of the calcium chloride tube. 
12 x a x 100 



44 x w 

2 X b X 100 

18 x w 



= per cent, of carbon, 
per cent, of hydrogen. 



Example. 0-1510 gram of oxalic acid gave 0-1055 gram of 
COj> and o'o68 gram of H 2 O. 

12 xo'ioss; x 100 c t. 

- = 19-05 per cent, of carbon. 
44x0*1510 

2 x 0-068 x roc c , , 

. = TOO per cent, of hydrogen. 
18x0-1510 

Calculated for C 2 H 6 O : C = 19-04 per cent. ; H = 4-76 per 
cent. 

As a rule, the carbon is a little too low through loss of mois- 
ture from the potash apparatus, whilst the hydrogen is too high, 
probably through incomplete drying of the air and oxygen from 
the gas-holders. The discrepancy should not exceed o'2 per 
cent, of the theoretical amount. If the substance burns with 
difficulty it should be mixed with fine copper oxide in the 
manner described under quantitative estimation of nitrogen. 

The Combustion of Volatile and Hygroscopic Sub- 
stances. If the substance is a non-volatile liquid it may be 
weighed in a boat like a solid ; if it is hygroscopic the boat 
must be enclosed and weighed in a stoppered tube. If it is a 
volatile liquid a glass bulb or tube, drawn out into a neck as 
shown in Fig. n, must be used. The 
bulb is first weighed, and the liquid 
is introduced by warming the bulb 
gently to expand the air and then FlG - 

inverting the open neck under the 

liquid. The operation rnay require repeating. The tube is then 
sealed and weighed again. Before introducing the bulb into 
the tube the neck is nicked with a file and broken off. It 
is then placed in the boat and pushed into the combustion 
tube. In the combustion of a substance like naphthalene, which 
is moderately volatile, the greater part is vaporised by the 
heat of the copper oxide spiral in contact with the boat. The 



PRACTICAL ORGANIC CHEMISTRY 



burners are therefore not lighted under the boat until towards 
the close of the combustion. In the case of a highly volatile 
compound like ether, a combustion tube is used, which projects 
at least 15 cm. (6 in.) beyond the back of the furnace. The 
bulb containing the substance is then placed just outside the 
furnace, and then the spiral in contact with it. A small Bunsen 
flame is placed under the end of the spiral away from the sub- 
stance, the heat from which is sufficient to completely volatilise 
the substance at a convenient speed. 

The Combustion of Organic Substances containing 
Nitrogen. The following modification must be introduced in 
cases where the organic substances contain nitrogen. As the 
nitrogen may be liberated in the form of one or other of its 
oxides, which are liable to be absorbed in the potash apparatus, 
a source of error is introduced, which may be eliminated in the 
following way. A spiral of metallic copper is brought into the 
front end of the combustion tube, which, when red hot, reduces 
the oxides of nitrogen. The free nitrogen then passes through 
unabsorbed. About 13 to 15 cm. (5 to 6 in.) of coarse 
copper oxide is removed from the front end of the tube, and 
after inserting an asbestos plug, the space left by the oxide is 
filled with aj-oll of copper gauze 13 to 15 cm. (5 to 6 in.) 
long. The copper spiral must have a clean metallic surface, 
which is easily produced in the following way. Take a large 
test-tube or boiling tube, an inch or so longer than the spiral, 
and push down to the bottom a small pad of asbestos. Pour in 
about 5 c.c. of pure methyl alcohol. 

Have a cork at hand which fits loosely into the mouth of the 
test-tube. Wrap the tube round with a duster. Hold the cop- 
per spiral with the crucible tongs in a large blow-pipe flame until 
it is red hot throughout and slide it quickly into the test-tube. 
The methyl alcohol reduces the film of oxide on the copper and 
is at the same time oxidised to formaldehyde, the vapours of 
which attack the eyes if the tube is brought too near the face. 
The alcohol takes fire at the mouth of the test-tube. When the 
flame dies down insert the loose cork and let the tube cool. The 
spiral, which has now a bright surface, is withdrawn, and the 
excess of alcohol removed by shaking it. It must now be 
thoroughly dried. Place the spiral in a hard glass tube a few 
inches longer than the spiral and fitted at each end with a cork, 



QUANTITATIVE ESTIMATION 13 

into which short, narrow glass tubes are inserted. Attach one 
end of the tube to an apparatus for evolving carbon dioxide, 
which is thoroughly dried by passing it through concentrated 
sulphuric acid. When the air is expelled from the tube, heat it 
gently until the alcohol is removed. Then let the tube cool 
while the gas is passing through. The spiral is then removed 
and placed in the front of the combustion tube. The combustion 
is carried out in the manner already described, but a current of 
air is substituted for oxygen until all the hydrogen has been 
expelled, i.e., until water ceases to condense in the front of the 
tube. The burners under the metallic copper are then gradually 
extinquished, and the spiral allowed to cool whilst the current 
of air is replaced by oxygen. By the time the oxygen reaches 
the spiral, the latter should have so far cooled that it remains 
unoxidised. The current of oxygen is continued until a glowing 
chip is kindled at the end of the potash apparatus and the 
operation is completed by turning on the air as previously 
described. 

A convenient substance to use for analysis is acetanilide", see 
Preparation 54, p. 151. 

Combustion of Organic Compounds containing 
Halogens and Sulphur. When the halogens or sulphur 
are present in an organic compound, they are liable to be ab- 
sorbed either in the free state or in combination with oxygen in the 
potash apparatus. In this case, fused lead chromate broken up 
into small pieces must replace the coarse copper oxide in the 
combustion tube. The halogens and sulphur are retained by the 
lead, the former as the halide salt, and the latter as lead sulphate 
Special care must be taken in using lead chromate, that the 
temperature of the furnace is not too high, as otherwise the 
chromate fuses to the glass, and the combustion tube then 
cracks on cooling. 

Nitrogen (Dumas). According to this method, a weighed 
quantity of the substance is heated with copper oxide in a tube 
filled with carbon dioxide. The carbon and hydrogen form 
respectively carbon dioxide and water, and the nitrogen which 
is liberated in the form of gas is collected over caustic potash 
(which absorbs the carbon dioxide) and measured. 

The following apparatus is required : 

I. A combustion furnace of the ordinary form. 



14 



PRACTICAL ORGANIC CHEMISTRY 




FIG. 12. 



2. A short furnace of simple construction, such as used in 
Turner's method for estimating carbon in steel (Fig. 12). It 

should carry an iron trough about 
^^^^^"^7 30 cm. (12 in.) long, fixed at such 
a height that it can be heated by 
an ordinary Bunsen burner. 

3. A combustion tube, which may 
be rather longer than that used 
in the estimation of carbon and 
hydrogen. 

4. A short hard glass tube, 25 
28 cm. (10 ii in.) long, and closed at one end. 

5. A bent tube -with a bulb, blown in the centre, as shown at 
a, Fig. 13. This is attached by rubber corks to the ends of the 
long and short combustion tubes. 

6. A graduated SchijJPs Asotometer, Fig. 13. A small quan- 
tity of mercury is first poured Into the bottom of the tube so as 
to fill it 4 5 mm. above the lower side limb. A solution of 
potash (iKOH : 3H 2 O) is then poured into the glass reservoir, 
which is attached to the upper straight side limb by a rubber 
tube. By raising the reservoir and opening the tap the tube is 
filled, and remains so on closing the tap and lowering the reser- 
voir. When the tube is filled with potash solution there should 




FIG. 13. 

be sufficient mercury at the bottom to seal off the potash solu- 
tion from the bent limb, which connects with the combustion 
tube. 

7. Two flasks, 200 c.c. and 300 c.c. The necks are slightly 



QUANTITATIVE ESTIMATION 15 

constricted in the blow-pipe flame, so that .the end of the com- 
bustion tube slips in as far as the constriction (Fig. 14). The 
flasks are fitted with good corks. 

8. A spiral of copper gauze 15 cm. (6 in.) long, which is 
reduced in methyl alcohol as described on p. 12. The spiral 
should be reduced just before use when the tube is filled 
and ready. It is unnecessary to remove all the alcohol from 
the spiral by heating it in a current of carbon dioxide. It is 
sufficient to wh'Xsk it sharply through the air 

and shake off the excess of liquid. 

9. A sufficient quantity of coarse copper oxide 
to fill the combustion tube two-thirds full and a 
further quantity of fine copper oxide to occupy 
1013 cm. (4 5 in.) of the tube. 

10. Two shallow tin dishes, 10 13 cm 
(4 5 in.) in diameter for roasting copper oxide. 
These dishes can be obtained from the iron- 
monger in different sizes and are useful in the 
laboratory for a variety of purposes, such as for 
oil, metal or sand-baths. 

11. A square of copper gauze of moderate FIG. 14. 
mesh of the area of the tin dish. It is turned 

up at the edges and is used for sifting the coarse from the 
fine copper oxide after each combustion. 

12. Pure sodium bicarbonate, NaHCO 3 , in powder free from 
ammonia. 

Filling the Combustion Tube. A plug of asbestos is 
first pushed in from one end far enough to leave room for the 
copper spiral, which should lie well within the furnace. This end 
of the tube is subsequently attached to the azotometer and may 
be called the front end. The coarse copper oxide is heated over 
a Bunsen burner in one of the shallow tin dishes and the fine 
oxide in another. After about a quarter to half an hour the 
burners are extinguished and the oxides whilst still warm are 
introduced into their respective flasks with drawn-out necks, 
The flasks are closed with corks and allowed to cool. The back 
end of the combustion tube is now pushed horizontally into the 
neck of the coarse oxide flask and the oxide poured on to the 
plug by tilting the flask and tube. The tube is filled with oxide 
about two-thirds of its length. Into the flask containing the 




16 PRACTICAL ORGANIC CHEMISTRY 

fine oxide about o'2 gram of powdered substance (acetanilide 
may be conveniently used, see Prep. 54, p. 151) is weighed 
out by difference from a sample tube, which should contain the 
approximate quantity. The substance is then well mixed with 
the oxide by shaking the flask. The contents of the flask are 
carefully poured into the tube above the coarse oxide in the 
manner described and the flask is rinsed out with coarse oxide, 
which is likewise poured into the tube until it is filled to the 
full length of the furnace. A loose plug of asbestos is pushed 
in to keep the materials in position and the tube is tapped 
horizontally on the bench in order to form a channel above the 
layer of fine copper oxide. The tube is now laid in the furnace, 
which is tilted a little forwards in order to collect the moisture 
at the front end of the tube. The short closed tube is 
well packed with powdered sodium bicarbonate and tapped 
horizontally so as to form a good channel above the whole 
length of the substance. It is laid in the small furnace, which 
is also tilted forwards to drain off the water which is formed. 
The bicarbonate and the combustion tubes are connected by the 
bulb tube already described. The copper spiral is now reduced 
and pushed into the front of the tube up to the plug and finally 
the azotometer is attached by its bent tube. The arrangement 
of the tubes and their contents are shown in Figs. 13 and 15. 

The Combustion. The tap of the azotometer is opened 
and the reservoir lowered so as to empty as far as possible the 



- CtiO 



!.'?.'tt.-ttttvt;y.v;tf.iisMimgiaig 



""'I 



FIG. 15. 



graduated tube. The joints of the apparatus being well secured, 
begin by cautiously heating the bicarbonate near the closed 
end of the tube with a good burner, and concentrate the heat 
by tiles placed on each side. A rapid stream of carbon di- 
oxide is at once evolved. When it begins to slacken, push the 
burner on \ cm. or so in order to maintain a continuous and 
rapid stream. The quicker the stream of gas, the sooner is the 



QUANTITATIVE ESTIMATION 17 

air expelled, for the gas then pushes the column of air before 
it like a piston, before the latter has time to diffuse. In about 
ten minutes, the row of burners beneath the spiral and the 
coarse oxide to within 10 cm. (4 in.) of the fine oxide may be 
lighted. In another fifteen minutes, the gas which is passing 
through the tube may be tested. The current is allowed to 
slow down a little, and the graduated tube of the azotometer is 
then filled with potash solution by raising the reservoir and 
closing the tap. On gradually lowering the reservoir, a few 
bubbles will pass up the graduated tube. 

By the time they reach the top of the tube, the size of the 
bubbles should have become so minute that when collected at the 
top they occupy no appreciable volume, but appear as a fine froth. 
If this is not the case, open the tap, run out the solution and 
continue as before to drive carbon dioxide through the tube. 
Repeat the test in another five minutes. Not more than half 
the bicarbonate should have been utilised in expelling the air. 
The air being removed, the combustion of the substance is com- 
menced. The azotometer is filled with the potash solution, the 
tap closed, and the reservoir lowered as far as possible. The 
current of carbon dioxide is allowed to slacken, but it must not 
be completely stopped. The front portion of the combustion 
tube will by this time have reached a dull red heat. A few 
more burners are now lighted on both sides of the fine oxide. 
Finally, the layer of fine oxide is gradually heated and the pro- 
cess conducted in much the same manner as that described 
under the estimation of carbon and hydrogen. The combustion 
is regulated by the speed of the bubbles passing up the 
azotometer tube, which should enable them to be readily 
counted. The burners being all lighted and the tube red hot 
throughout, the "tiles above the substance are closed. The 
current of gas will shortly slacken. The residual nitrogen is 
then expelled from the tube by moving on the flame beneath 
the bicarbonate and causing a fresh stream of carbon dioxide to 
sweep through the tube. Care must be taken that the stream 
of gas is not too rapid, as otherwise the potash solution may 
become saturated and driven completely into the reservoir. The 
burners may now be extinguished and a reading of the level in 
the azotometer taken every few minutes until it remains constant 
and the bubbles are completely absorbed. Remove the 

COHEN'S ADV. p. o. c. c 



azotometer by slipping out the cork from the front of the com- 
bustion tube, and hang a thermometer beside it. Do not, 
however, stop the flow of carbon dioxide until the tube is nearly 
cold. In this way, the copper spiral remains quite bright and 
may be used for a second determination without being 
reduced. 

When the azotometer has stood for an hour in a cool place, 
adjust the level by raising the reservoir so that the liquid in the 
tube and reservoir stand at the same height. Read off the 
volume, and at the same time note the temperature and the 
barometric pressure. 

The percentage of nitrogen may be calculated as follows : 

v is the observed volume of nitrogen. 
B is the height of the barometer in mm. 
/ is the temperature. 

f is the vapour tension of the potash solution, which may be 
taken to be equal to that of water without serious error. 

The volume corrected to o and 760 mm. will be given by 
the following expression : 



(273 + ^)760 

As the weight of i c.c. of nitrogen at o and 760 mm is o'ooi26 
gram, the percentage weight of nitrogen will be given by the 
expression 

v x 273 x (B -/) 0*00126 x IPO 

(273 + /) 760 it> 

where w is the weight of substance taken. 

Example. o'2o6 gram of acetanilide gave iS'8 c.c. of moist 
N at 17 and 756 mm. [/at 17= 14-5 mm.] 

i8-8x 273 x( 75 6-i4-5)xo-T26 = fi nt< 

(273+ 17) x 760 x 0-206 
Calculated for C 8 H 9 ON ; N = 10-37 per cent. 

Instead of collecting the gas over dilute potash solution, it is often 
customary to use a very strong solution consisting of equal weights of 
potash and water. The vapour tension is practically nil. Or, again, 
the nitrogen may be transferred to a graduated tube standing over 



QUANTITATIVE ESTIMATION 



water, which gives a result free from any error arising from incorrect 
vapour tension. The manner of transferring the gas is shown in 
Fig. 16. The stem of a wide funnel is cut off and attached by rubber 
to the top- of the azotometer. This is then filled with water and the 
projecting end of the azotometer is also filled with water. A graduated 
tube is now brought over the end, and by opening the tap and raising 





FIG. 16. 

the reservoir the gas passes into the tube. The end is now closed with 
the thumb and transferred to a cylinder of water. 

The tube is held by a collar of paper, whilst the level is adjusted 
and the volume and temperature noted. 



Before commencing a second determination, the contents of 
the combustion tube are emptied on to the wire-gauze sieve, 
placed over one of the tin dishes, and the fine and coarse oxide 
separated. Both oxides are roasted in order to reoxidise any 
reduced copper, and transferred as before to their respective 
flasks. The sodium bicarbonate tube is emptied into a special 

c 2 



PRACTICAL ORGANIC CHEMISTRY 



bottle and then replenished with fresh material. Fresh caustic 
potash solution is also introduced into the azotometer, unless 
the stronger solution is used. 

Estimation, of Nitrogen, Second Method. Another method 
which dispenses with the small furnace and bicarbonate tube 
may also be used. The long combustion tube is closed at one 
end and magnesite in small lumps is introduced into the tube 
and shaken down to the closed end until there is a layer of 
about 13 15 cm. (5 6 in.). This is kept in place by a plug of 
asbestos and the tube is filled successively with 5 cm. (2 in.) of 
coarse copper oxide, then fine copper oxide mixed with the sub- 
stance, a further layer of coarse copper oxide, and finally the 



Fine COARSE 

COARSE CuO CuO CuO MAGNESITE 



|5cw. *! < ' 3cM> X 8cM -T ' 3cM> 

ASBESTOS ASBESTOS 

PLUS PLUO ^ 

FIG. 17. 



copper spiral. The contents of the tube are arranged as shown 
in Fig. 17. 

The magnesite (MgCO 3 ), which evolves carbon dioxide on 
heating, takes the place of the sodium bicarbonate in the 
previous method. The air is displaced at the beginning by 
heating the magnesite near the closed end of the tube. The 
magnesite is again heated towards the end of the combustion to 
sweep out the last traces of nitrogen. The disadvantages of 
the method are that the magnesite requires to be heated much 
more strongly than the sodium bicarbonate before it evolves 
carbon dioxide, and the length of the layer of copper oxide is 
curtailed. 

Kljeldahl's Method. The organic compound is heated 
strongly with sulphuric acid, which oxidises the organic matter 
and converts the nitrogen into ammonium sulphate. The 
ammonia is then estimated volumetrically by distilling with 
caustic soda and collecting the gas in standard acid. About 
0*5 gram of substance is accurately weighed and introduced into 
a round Jena flask (500 c.c.), together with 15 c.c. of pure con- 



QUANTITATIVE ESTIMATION 



centrated sulphuric acid and about 10 grams of anhydrous 
potassium sulphate. The object of the latter is to promote 
oxidation by raising the boiling-point of the liquid. The flask is 
clamped over wire-gauze and the contents boiled briskly until 
the liquid, which first darkens in colour, becomes clear and 
colourless or faintly yellow. When the decomposition is com- 
plete ( i hour), the flask is left to cool and the contents then 
diluted with 23 volumes of water. The flask is now attached 
to the distilling apparatus shown in Fig. 18. It is furnished 
with a double-bored rubber cork, through one hole of which a 
bulb adapter is inserted (to re- 
tain any alkali which may spirt 
upwards), the latter being con- 
nected with a condenser. The 
end of the condenser just dips 
below the surface of 25 c.c. of 
a half-normal solution of hydro- 
chloric or sulphuric acid, con- 
tained in a flask or beaker. A 
tap-funnel with a bent leg, con- 
taining about 30 grams of 
caustic soda in 60 c.c. of water, 
is inserted through the second 
hole in the cork. A few pieces 
of porous earthenware or granu- 
lated zinc are introduced into 
the flask to prevent bumping. 
After the apparatus has been 
fitted together the caustic soda 
solution is run in slowly and 

the flask shaken. The liquid is then boiled briskly until 
no more ammonia is evolved (i hour). This should 
be ascertained by testing a drop of the distillat2 with red 
litmus paper. If the operation is complete, the liquid is 
titrated with half-normal sodium carbonate solution, using 
methyl orange as indicator. 

Example. 0-5151 gram acetanilide required 17-3 c.c. NJ* 
sodium carbonate : 




2S-i7'3 = 77- 



77 xo'oo7 x 100 
0-5151 



ro'46 per cent. 



PRACTICAL ORGANIC CHEMISTRY 



The Halogens (Carius). The method of Carius, which is 
usually employed, consists in oxidising the substance with fuming 
nitric acid under pressure in presence of silver nitrate. The 
silver halide which is formed is then separated by filtration and 
weighed. 

The following apparatus is required : 

I. A piece of thick-walled soft tubing about 45 48 cm. 
(18 19 in.) long, and 12 13 mm. inside diameter, the walls 
being at least 2-5 3 mm. thick. Tubes of hard potash glass are 
also used, in which case the thickness of the walls may be rather 
less. The tube is carefully sealed at one end so that there 
is no thickening of the glass at any point into a blob. If a 
blob is formed, it may be removed by heating it and blowing 




FIG. 19. 

gently into the tube and repeating the operation if necessary. 
Tubes of soft or hard glass may be bought ready sealed at 
one end. The tube is washed out and dried before use. 

2. A narrow weighing-tube, 8 10 cm. (3 4 in.) long and 
sealed at one end, which will slip easily into the thick-walled 
tube. 

3. Pure fuming nitric acid of sp. gr. 1*5. This is prepared 
by distilling equal volumes of concentrated nitric acid (150 c.c.), 
and concentrated sulphuric acid (150 c.c.) from a litre retort, the 
neck of which has been bent in the blow-pipe flame as in Fig. 19. 
The object of this bend is to prevent acid from spirting into the 
neck and being carried over mechanically into the receiver 
during distillation. The retort is placed on a sand-bath, and 



QUANTITATIVE ESTIMATION 



attached to a condenser. The acids are poured in through 
a funnel, and a few small bits of broken unglazed pot are 
dropped in to prevent bumping. The acid is distilled with a 
moderate flame until about 70 c.c. have collected in the 
receiver, when the operation is stopped. The distillate is then 
tested for halogens by diluting largely with distilled water, and 
adding silver nitrate solution. The liquid should remain per- 
fectly clear. It should also be tested for the presence of sul- 
phuric acid, in case it is required for sulphur estimations, by 




FIG. 20. 



adding a few drops of barium chloride to a fresh portion of acid 
diluted as above. If pure, it is kept in a stoppered bottle. If it 
contains chlorine, it must be redistilled over a few crystals of 
silver nitrate. Fuming nitric acid has a sp. gr. of about i'5 at 
15, boils at about 90, and contains about 90 per cent, of 
HNO 3 . Acid of this strength can be purchased. 

4. A Tube Furnace. Various forms of furnace are used. 
Those which are heated on the principle of the Lothar Meyer 
hot-air furnace by a number of pin-hole gas jets are easily 
regulated, and can be raised to a high temperature. The 
Gattermann furnace, shown in the diagram (Fig. 20), is a very 
convenient form. 



24 PRACTICAL ORGANIC CHEMISTRY 

Filling and Sealing the Tube. By means of a thistle 
funnel with a long stem, about 5 c.c. of fuming nitric acid are first 
introduced, and the funnel carefully withdrawn so as 
not to wet the side of the tube. About o'5 gram silver 
nitrate in crystals is dropped in, and finally the narrow 
weighing-tube containing o'2 o'3 gram of substance 
is slipped to the bottom of the tube (see Fig. 21). 
Bromacetanilide (see Prep. 55, p. 152) may be used 
for this estimation. The open end of the tube is now 
sealed in the blow-pipe. This operation requires 
some care and a little skill. About two inches of the 
tube at the open end is very gradually heated by re- 
volving it for several minutes in the smoky flame of 
the blow-pipe. The tube is now grasped about the 
middle with the left hand, and inclined at an angle of 
about 45. The blast is turned on slowly, and the end 
of the tube heated and revolved until the glass begins to soften. 
The end of a glass rod, about 13 cm. (5 in.) long, held in the 
right hand, is heated at the same time. The glass rod is then 




F!G. 



used to press the edges of the glass tube together, as shown in 
Fig. 23. The subsequent operation depends upon whether 
soft or hard glass is to be manipulated. If soft glass is used, 



QUANTITATIVE ESTIMATION 



the blow-pipe flame is made as hot as possible, but reduced 
in length to about 8 to 10 cm. (3 to 4 in.). It is directed at a 
point about 2 to 3 cm. (i in.) below the open end to which 
the glass rod is attached, the glass rod now serving as a support 
whilst the tube is slowly rotated. The glass, if evenly heated 
and not drawn out, begins to thicken where the flame plays upon 
it, and the inside diameter of the tube contracts. When the 
apparent inside diameter of the tube is reduced to about 3 mm. 
( in.), the tube is quickly removed from the flame, and a 
capillary end formed by very slowly drawing out the thickened 
part of the tube (Fig. 24). When the capillary has so far cooled 
as to become rigid, it is sealed off. The tube will now have the 




FIG. 23. 



FIG. 24. 



FIG. 25. 



appearance shown in Fig. 25. The tube is kept in a vertical 
position until cold. If the tube is of hard glass, a somewhat 
different method of sealing is employed. As soon as the glass 
is sufficiently soft, it is not thickened, but drawn out at once into 
a wide capillary, about i| cm. long. By directing the flame 
below this constriction, and continuing to draw out, the capillary 
is further lengthened. When it has a length of 2 to 3 cm. 
(i in.) it is thickened by revolving it in- the flame and then 
sealed off. Hard glass is much more easily manipulated in the 
oxy-coal gas flame. When cold, the tube is transferred to the 
metal cylinder of the tube furnace. The furnace, conveniently 
isolated in case of explosions, should stand on the floor, with 
the open end raised and facing a wall. The capillary point 



26 PRACTICAL ORGANIC CHEMISTRY 

should project a little beyond the open end of the metal cylinder 
in which the sealed tube is enclosed. The temperature, indicated 
by a thermometer fixed in the top of the furnace, is carefully 
regulated. It is advisable to commence the operation in the 
morning. The temperature is gradually raised from 150 to 200 
during four hours, and then to 230 for a further four hours. The 
gas is then extinguished, and the tube allowed to cool until the 
following morning. 

Opening the Sealed Tube. The tube is drawn a little 
way out of the iron casing, so that the capillary end projects 
3 or 4 cm. The tip is then warmed cautiously in the Bunsen 
flame to expel the liquid which as a rule condenses there. The 
point is then heated until the glass softens, when the pressure 
inside perforates the glass and nitrous fumes are evolved. On no 
account must the tube be removed from the furnace before this 
operation is concluded. The tube is now taken away and 
opened. A deep file scratch is made in the wide part of the 
tube, about 3 cm. below the capillary. The end of a glass 
rod, heated to redness, is then held against the file mark. A 
crack is produced, which may be prolonged round the tube 
by touching the tube in front of the crack with the hot end 
of the glass rod. The top of the tube is now easily removed ; 
but in order to prevent fragments of glass from the broken 
edge from dropping into the acid, the tube should be held 
horizontally and the end carefully broken off. Any bits of 
glass which become detached adhere to the side of the tube, 
near the open end, and can be easily wiped off. The contents 
of the tube containing the silver halide are now carefully 
diluted by adding water a few c.c. at a time, and then washed 
into a beaker. The mixture is heated to boiling, the silver 
compound transferred to a filter, and washed with hot water 
until free from silver nitrate. The filter paper is then dried 
in a steam oven and the silver salt weighed. A simpler and 
more accurate method for filtering and weighing the silver 
halide is to use a perforated or Gooch crucible. A disc of 
filter paper is cut with a cork cutter of suitable dimensions 
to fit the bottom of the crucible, which is dried with the crucible 
in a Victor Meyer air-bath (Fig. 26) heated to 140 150 until 
constant. The air-bath consists of a jacketed copper vessel 
fixed upon a tripod. A liquid of constant boiling-point is poured 



QUANTITATIVE ESTIMATION 



27 



into the outer jacket and the vapours are condensed by an 
upright condenser or tube which is attached to the outlet tube. 
The crucible is placed within and 
covered with a metal lid. There is a 
small aperture to admit air from below 
into the inner vessel and a corresponding 
outlet in the lid. Aniline, b.p. 182, 
may be used in the outer jacket in the 
present case. The Gooch crucible is 
weighed and fitted to a filter flask and 
the silver halide filtered and washed at 
the pump. The crucible is then heated 
in the air-bath until the weight is con- 
stant ( hour) and weighed. The re- 
sult is calculated in percentage of 
halogen. 

Example. Bromacetanilide gave the 
following result : 

0-151 gram gave 0-134 gram AgBr. 
0-134x80x100, , 

188x0-151 

Calculated for C 8 H 8 BrNO ; Br = 37-38 FlG . 26 . 

per cent. 

Another Method (Piria and Schiff). There are some 
substances which are incompletely decomposed with fuming 
nitric acid under the conditions described above, and the results 
are consequently too low. In such cases the following method 
may be employed. The substance is weighed into a very small 
platinum crucible, which is then filled up with a mixture of 
anhydrous sodium carbonate (i paii) and pure powdered quick- 
lime (4 to 5 parts). The crucible is then inverted in a larger 
crucible, the space between the two being filled with the same 
mixture of sodium carbonate and lirne. The large crucible is 
now heated, first with a small blow-pipe flame, and then 
more strongly until the mass is red hot. The contents are then 
allowed to cool, and dissolved in a large excess of dilute nitric 
acid. The substance must be added slowly and the acid kept 
cool. The halogen is then precipitated with silver nitrate and 
estimated in the usual way. 




28 PRACTICAL ORGANIC CHEMISTRY 

Sulphur (Carius). The process is essentially the same as 
that described under the estimation of halogens (p. 22). The 
compound is oxidised in a sealed tube with fuming nitric acid, 
but without the addition of silver nitrate. The resulting sul- 
phuric acid is then precipitated and weighed as barium sulphate. 
The same quantities of acid and substance (diphenylthiourea 
may be used ; see Prep. 61, p. 159} are taken, and the process of 
sealing up and heating, &c., are carried out in precisely the 
same way as for the halogens. The contents of the tube, after 
heating, are cautiously diluted with water and then washed out 
into a beaker, and filtered, if necessary, from fragments of glass. 
The filter paper is then well washed with hot water and the 
filtrate diluted to at least 250 c.c. with water. The liquid is 
heated to boiling, and a few c.c. of barium chloride solution 
added. On continued heating over a small flame the liquid 
clears and the precipitate subsides. The addition of another 
drop of barium chloride will determine if the precipitation is 
complete. The liquid is then filtered through an ordinary 
Ainnel, the precipitate of barium sulphate washed with hot 
water, dried and weighed in the usual way. 

Example. Diphenylthiourea gave the following result : 

0-2518 gram gave 0-2638 gram BaSO 4 . 

0-2638x32x100 ^ 

233x0-2518 
Calculated for C 13 H 12 N 2 S ; 8=14-05. 

Determination of Molecular Weight 

According to Avogadro's law, equal volumes of all gases 
under similar conditions contain the same number of molecules. 
Consequently the weights of equal volumes or the densities of 
gases will represent the ratio of their molecular weights. If the 
densities are compared with hydrogen as the unit, the ratio 



in which W s and W h are the weights of equal volumes of 
substance and hydrogen respectively, will give the molecular 
weight of the substance compared with the molecule or two 
atoms of hydrogen or half the molecular weight compared with 



DETERMINATION OF MOLECULAR WEIGHT 



one atom of hydrogen. Consequently the observed density 
must be multiplied by two in order to obtain the molecular 
weight compared with one atom of hydrogen. 

Vapour Density Method (Victor Meyer). This 
method, which is generally employed for substances which 
volatilise without decom- 
position, is known as the 
air displacement method 
of Victor Meyer. It con- 
sists in rapidly vaporising 
a known weight of a sub- 
stance at a constant tem- 
perature at least 40 50 
above its boiling-point in 
a special form of appar- 
atus, which admits of the 
displaced air being col- 
lected and measured. The 
volume occupied by a 
given weight of the sub- 
stance under known con- 
ditions is thus ascertained 
and from these data the 
density is calculated. The 
following apparatus is re- 
quired : 

I. A Victor Meyer Ap- 
paratus as shown in 
Fig. 27. It consists of 
an elongated glass bulb 
with a narrow stem, and 
a capillary side-tube. It 
is provided with a well- 
fitting rubber cork, which 
can be pressed easily and FIG. 27. 

tightly into the open end 

of the stem. The apparatus is clamped within an outer 
jacket of tin plate or copper, which holds the boiling liquid 
required to produce a constant temperature. It is represented 
as transparent in the Fig. 




30 PRACTICAL ORGANIC CHEMISTRY 

2. Hofmann Bottles. The substance, if liquid, is introduced 
into a small stoppered glass bottle known as a Hofmann bottle 
(see Fig. 28). The dry bottle with the stopper is carefully 
weighed and then filled with liquid through a tube 
drawn out into a wide capillary. The stopper is in- 
serted and the bottle reweighed. It should hold about 
o'l gram of substance. 

3. A narrow graduated tube holding 50 c.c. and 
divided into tenths of a c.c. 

4. A large crystallising dish which serves as a gas 
FIG. 28. trough. 

5. A long and wide cylinder in which the graduated 
tube can be submerged in water. 

6. A Bunsen burner with chimney. 

The apparatus is set up as shown in Fig. 27. The Victor 
Meyer apparatus is thoroughly dried by blowing air through by 
means of a long glass tube, which reaches to the bottom of the 
bulb. A small quantity of clean dry sand previously heated in 
a crucible or a pad of asbestos is placed at the bottom of the 
bulb to break the fall of the Hofmann bottle, when it is dropped 
in. The bulb of the outer jacket is rilled two-thirds full of 
water and the displacement apparatus is clamped within it, so 
that it nearly touches the liquid. The apparatus and jacket 
must be adjusted at such a height that the capillary side limb 
dips under the water contained in the crystallising dish, placed 
on the bench. The graduated tube is filled with water and 
inverted under the water in the crystallising dish and clamped 
there until required. The burner protected from draughts by 
the chimney is lighted under the outer jacket and the displace- 
ment apparatus left open at the top. To avoid inconvenience 
arising from the steam, a split cork, into which a bent glass tube 
is inserted, is pushed loosely into the open end of the jacket. 

Whilst the water is boiling steadily and-*not too violently, the 
substance is weighed. Chloroform, b.p. 61, or pure and dry 
ether, b.p. 34'5 (see Prep. 3, p. 59), may be used for the 
experiment, as their boiling-points lie well below that of water. 
Before introducing the bottle and liquid, the apparatus must 
be tested to ascertain if the temperature is constant. As 
a rule hour's boiling suffices. Push in the rubber cork and 
note if within the next minute or two any bubbles escape. If 



DETERMINATION OF MOLECULAR WEIGHT 31 

not, slip the graduated tube over the end of the side tube, and 
carefully remove the rubber cork so that no water enters the 
stem through the capillary. Remove the stopper of the 
Hofmann bottle before dropping it in, and at once push in the 
cork. Very shortly a stream of air bubbles will ascend the 
graduated tube. When, in the course of a minute or two, the 
bubbles cease, remove the cork from the apparatus and extin- 
guish the burner. The graduated tube is transferred to the 
large cylinder of water by closing the open end with the thumb. 
Leave the tube in the water with a thermometer beside it 
for J hour. Lift the graduated tube, and whilst holding it 
by a collar of paper adjust the levels inside and out. Read off 
the volume and note the temperature and barometric pressure. 

The density is calculated as follows : 

If v is the volume, / the temperature, B the barometric 
pressure, and f the vapour tension of water at f, then the 
corrected volume is given by the formula 

v x (B-f) x 273 
760 x (273 + /) 

This multiplied by 0-00009, the weight of i c.c. of hydrogen, 
gives the weight of hydrogen occupying the same volume as 

the vaporised substance, from which the density A= ? is 

w h 

obtained. 

Example. The following result was obtained with ether : 
0-1146 gram of ether gave 36*3 c.c. at 11 and 752 mm. /= 10 
mm. at I i c . 

36-3 x (752 - 10) x 273 x 0-00009 = 0-00.06 
760 x 284 



0-1 = 
0-00306 J/ 
Calculated for C 4 Hi O ; A = 37. 

If substances of higher boiling-point have to be vaporised, 
the water in the outer jacket is replaced by other liquids of 
correspondingly higher boiling-point, such as xylene, b.p. 140, 
aniline, b.p. 182, ethyl benzoate, b.p. 211, amyl benzoate, b.p. 
260, diphenylamine, b.p. 310', c. A Lothar Meyer air-bath 



PRACTICAL ORGANIC CHEMISTRY 



(Fig. 29) is, however, much more convenient for obtaining con- 
stant temperatures up to 600. It consists of three concentric 
metal cylinders, the outer one being coated with non-conducting- 
material. They are so arranged that the heated- air from a 

movable ring burner passes be- 
tween the two outer cylinders 
(shown in section in the Fig.), 
and descends to the bottom of 
the central cylinder, into which 
it has access through a ring 
of circular holes. The hot air 
is thoroughly mixed by this zig- 
zag flow, and the temperature 
is equalised. The bulb of 
the displacement apparatus is 
clamped in the interior cylinder, 
and a thermometer is fixed be- 
side it. 

The vapour density of freshly 
distilled aniline, b.p. 182, may 
FIG. 29. be determined, the temperature 

of the air-bath being adjusted 

to about 240. The adjustment is made by raising or lowering 
the flame, or by altering the position of the movable ring 
burner. 

Example. 0*1229 of aniline gave 31 c.c. at 7*5 and 750 mm. 

A = 45-87. 
Calculated for C 6 H r N ; A = 46'5 

The Cryoscopic or Freezing-point Method (RaoultX 
This method depends upon the fact, first demonstrated by 
Raoult, and afterwards confirmed on theoretical grounds by 
van't Hofif, that the original freezing-point of a given quantity 
of liquid is lowered the same number of degrees by dissolving 
in it different substances whose weights are proportional to 
their molecular weights. This rule does not, however, apply to 
salts, acids, &c., which appear to dissociate in certain solvents, 
nor to substances which form molecular aggregates or associate 
in solution. Supposing the freezing-point of 100 grams of a 




DETERMINATION OF MOLECULAR WEIGHT 33 

solvent to be lowered i by dissolving i, 2, 3 and 4 grams 
respectively, of four different substances, the molecular weights 
of these substances will be in the ratio of i : 2 : 3 : 4. In ordei 
to convert these ratios into true molecular weights, the numbers 
must be multiplied by a coefficient which depends upon the 
nature of the particular solvent selected, and may be deter- 
mined empirically by means of substances of known molecular 
weight or by calculation from thermodynamical data. 1 

If w is the weight of substance and W the weight of solvent, 
d the depression of the freezing-point, and k the coefficient for 
the solvent determined for the standard conditions, t.e. t for the 
weight of substance, which produces i depression in 100 grams 
of solvent, the molecular weight M is given by the following 
expression : 

\ookw. 



M = 



dW 



The values of k for some of the common solvents with their 
melting-points are given in the following table : 



m.p. 
o 
5 '3 
5'4 

i? 

40 
/-Toluidine ... i 42-5 



Water... 
Nitrobenzene ... 
Benzene 
Acetic acid 
Phenol.. 



18-5 
70-0 
50-0 
39-0 
72-0 
51-0 



It should be remembered that nitrobenzene, phenol, and acetic acid 
are hygroscopic. 

The following apparatus is required : 

A Beckmann Freezing-point Apparatus. The form of appar- 
atus is shown in the accompanying Fig. 30. It consists of a 
glass jar standing on a metal tray and furnished with a stirrer. 
The cover of the jar has a wide slit to admit the stirrer, and a 
circular aperture with clips to hold a wide test-tube. 

Within the wide test-tube is a narrower one, which is held in 
position by a cork. The narrow test-tube is sometimes 

1 Vide van't Hoff, Ztschr. fhys. ChtiK. , I. p. 481 ; Ostwald, Outlines of General 
Chemistry, chap. vi. p. 130 ; J. Walker, Introduction to Physical Chemistry, chap, 
xviii. p. 176. 

COHEN'S ADV. p. o. c. D 



34 



PRACTICAL ORGANIC CHEMISTRY 



furnished with a side tube, for introducing the substance, but it is 
not necessary. It is provided with a stirrer. A Beckmann 
thermometer completes the apparatus. This is fixed through a 

cork so that the bulb 
nearly touches the bottom 
of the tube, a wide slit 
being cut in the side of 
the cork for moving the 
stirrer. The Beckmann 
thermometer is of special 
construction and requires 
explanation. As the 
method involves merely 
an accurate determination 
of small differences of 
temperature, it is not re- 
quisite to know the exact 
position on the thermo- 
meter scale. The Beck- 
mann thermometer regis- 
ters 6 degrees, which are 
divided into hundredths. 
The little glass reservoir 
at the top (a, Fig. 30) 
serves the purpose of 
adjusting the mercury 
column to different parts 
of the thermometer scale 
by adding or removing 
mercury from the bulb. 



Freezing-point De- 
termination. In the 
example to be described, 
pure benzene (see p. 136) 
is used as the solvent. 

Carefully dry the inner tube. Fit it with a cork and weigh it 
together with the cork suspended by a wire to the arm of the 
balance. Introduce sufficient benzene to cover the bulb of the 
Beckmann thermometer when it is pushed nearly to the bottom 
of the tube. About 10 c.c.will be found to be sufficient. Insert 




DETERMINATION OF MOLECULAR WEIGHT 35 

the cork and weigh the tube and benzene. Fill up the outer jar 
with water and small lumps of ice and stir from time to time. 
Whilst the benzene is cooling in the apparatus the Beckmann 
thermometer may be adjusted. 

Adjustment of the Beckmann Thermometer. 
Determine first the value of the mercury thread in degrees 
between the top of the scale and the orifice of the reservoir. 
This may be done by warming the bulb in a water-bath along 
with an ordinary thermometer. As soon as sufficient mercury 
has collected at the orifice, the burner is removed, the water 
well stirred, and the little bead of mercury detached by gently 
tapping the head of the thermometer without removing the bulb 
from the water. The temperature on the ordinary thermometer 
is nottd and is again read off when the mercury in the Beck- 
mann thermometer has subsided to the top of the scale. Sup- 
posing, then, the value of the thread above the scale to have 
been determined and equivalent to 2, and the freezing-point of 
benzene to be about 4, the thermometer degrees may in this case 
be made to coincide with the Beckmann degrees, which will bring 
the thread of mercury well up the scale. The bulb of the thermo- 
meter will therefore require to be at a temperature of 6 + 2 = 8 
before removing the excess of mercury. It will, however, be 
necessary to introduce more mercury into the bulb. This is 
done by inverting the thermometer and tapping it gently on the 
palm of the hand, so as to detach a bead of mercury, which 
slips down to the orifice of the capillary. By warming the bulb 
the mercury is driven to the top and coalesces with that in the 
reservoir, so that on cooling the additional mercury runs into 
the bulb. When sufficient mercury has been added the thermo- 
meter is cooled to 8, and the excess detached as described above 
The zero should now coincide approximately with that of ice- 
cold water. If the thermometer is to be adjusted to any other 
temperature it i-s placed in water and warmed to that tempera- 
ture + the number of degrees on the scale above that point 
+ the value of the thread above the scale. The excess of 
mercury is then detached. The thermometer being adjusted, 
insert it through the cork so that the bulb is well covered by the 
benzene, and let the benzene cool well below its freezing-point 
before stirring. Tap the head of the thermometer occa- 
sionally with a pencil. Now stir briskly for a moment. As soon 

D 2 



36 PRACTICAL ORGANIC CHEMISTRY 

as crystals of the solvent begin to separate the mercury thread 
will shoot up. Keep stirring occasionally and tapping the 
thermometer, and read off the maximum point reached by means 
of a lens. This gives a rough indication of the freezing-point 
of the benzene. Take out the inner tube and melt the crystals 
by warming the tube in the hand, and replace it in the apparatus. 
Repeat the experiment, cooling the solvent not more than 0*2 
below its freezing-point before stirring. Make two or three 
determinations in this way. The results should not differ by 
more than o'oi. Fuse some naphthalene in a bas,in and break 
it up into small lumps or mould into pellets (p. 39). Weigh a 
piece of about o'i to 0*2 gram on a watch-glass. Raise the cork 
of the inner tube and drop the naphthalene in. Let it dissolve 
and then determine the freezing-point of the benzene as ifefore. 
Repeat the process by dropping one or two fresh pieces of 
naphthalene into the same solvent. At the end of the operation 
remove the thermometer and stirrer, and weigh the benzene in 
the inner tube with the cork. After deducting the weight of 
naphthalene, the weight of the benzene will be approximately 
the mean of the first and final weighings. 

Example. Using the same solvent and adding successively 
three lots of substance (naphthalene), the following results were 
obtained : 

w. W. a. M. Mean. 



0-0985 
0^0729 
0-1193 



97 



0-403 
0-305 
0-486 



126 

I23'2 J-125'3 

I26- 



Calculated for C, n H 8 : M = I28. 



In determining the molecular weight of liquids the apparatus 
shown in Fig. 82 (p. 210) is convenient for weighing and trans- 
ferring the liquid to the tube. 

The Eykman Depressimeter. For rapid but less 
accurate determinations the apparatus of Eykman may be used, 
which is shown in Fig. 31. It consists of a small vessel, into 
the neck of which a thermometer is ground. The thermometer 
is of the Beckmann type but divided into twentieths of degrees. 
Phenol, m.p. 42-5, is usually employed as the solvent. The 
vessel and thermometer are dried and weighed. Phenol melted 
on the water-bath is poured in to within about 5 c.c. of the neck, 



DETERMINATION OF MOLECULAR WEIGHT 



37 



the thermometer inserted, and the apparatus weighed again. 
The melting-point of the phenol must now be ascertained. 
Warm the metal over a small flame on a sand-bath so as to 
melt the phenol, leaving, however, a few crystals floating in the 
liquid, and place the vessel in the cylinder, at the bottom of 
which is a wire spring or pad of cotton wool. A perforated 
cork at the top keeps the stem of the tnermometer in position. 
Let the phenol cool down well below iis freezing-point, and 
then shake the cylinder until solidification commences. This 
will give a first approximation to the freezing- 
point. The phenol is now warmed gently as before 
until only a few crystals remain unmelted. The 
vessel is replaced in the cylinder and the liquid 
cooled o'5 to i below the point previously ascer- 
tained. It is now shaken until crystallisation sets 
in, and then occasionally until the maximum point 
is reached. The operation is repeated as often 
as requisite. The substance is now introduced, a 
sufficient quantity being taken to produce a depres- 
sion of at least o - 5. In order to effect this the 
phenol is melted and the neck warmed with a 
small flame until the thermometer -is loosened and 
can be withdrawn. As much phenol as possible 
is allowed to drain off the neck and off the ther- 
mometer, and the weighed quantity of substance 
introduced. The thermometer is replaced, and any phenol which 
may have run out is wiped off from the outside of the vessel, which 
is then re-weighed. The freezing-point is determined as before. 

The Ebullioscopic or Boiling-point Method 
(Raoult). The boiling-point of a liquid is found to be affected 
by the presence of a dissolved substance in a similar manner 
to the freezing-point, that is, the boiling-point of a given quantity 
of a liquid is raised the same number of degrees by dissolving in 
it the same number of molecules of different substances, or, in 
other words, such weights of these substances as represent the 
ratio of their molecular weights. These facts were first clearly 
demonstrated by Raoult. 

Statical Method. The most convenient form of apparatus 
for determining molecular weight by this method is Beckmann'u 
boiling-point apparatus shown in Fig. 32. 




FIG. 31. 



PRACTICAL ORGANIC CHEMISTRY 



It consists of a boiling-tube, through the bottom of which a 
stout platinum wire is sealed, which is intended to conduct 

external heat to the 

B li( l uid 

Y)i\ bles 

Above the wire 
layer, about an 



and form bub- 
one point. 
is a 
inch 

deep, of glass beads. 
The object of the 
beads is to break up 
the bubbles and so pre- 
vent superheating and 
irregular boiling. To 
the side limb a reflux 
condenser is attached 
to condense the va- 
pours given off during 
the boiling. A Beck- 
mann thermometer is 
f\ inserted through the 
1 1 mouth of the tube. 
This thermometer is 
similar in construction 
to that used for freez- 
ing-point determina- 
tions, but it has a 
smaller bulb. The 
boiling-tube is placed 
in the central cavity 
of a hollow glass or 
porcelain jacket, which 
contains the same 
liquid as the boiling- 
tube and is also pro- 
vided with a condenser. 
This jacket prevents 
radiation from the boil- 
ing-tube. It is pro- 

vided with two windows of mica. The jacket is clamped on a 
gauze ring supported on a square tray of asbestos placed upon a 




FIG. 32. 



DETERMINATION OF MOLECULAR WEIGHT 39 

tripod. In the figure the lower part of the porcelain jacket and 
the asbestos tray are made transparent to show the position of 
the burners and the concentric rings of asbestos below the tray. 
The asbestos has a circular hole in the centre, which admits 
the lower end of the boiling-tube. Two asbestos chimneys 
are fixed upright at the diagonal corners of the tray to carry 
off heated air and two burners are placed below the other two 
corners. The boiling-point of the solvent is first ascertained. 
For this purpose benzene may be used. The Beckmann 
thermometer must be adjusted so that, when in the boiling liquid, 
the thread occupies the lower half of the scale. In order to 
adjust it, the bulb must be placed in water warmed gradually 
6 7 above the boiling-point of benzene, and the bead then 
detached as already explained in the description of the freezing- 
point method. 

The boiling-tube is carefully dried and weighed with the 
beads. Sufficient benzene is poured in to cover the bulb of the 
thermometer, which is pushed down a little way into the beads. 
The condenser is attached to the side limb. A layer of I 2 cm. 
of benzene is poured into the outer jacket, and the condenser 
fixed in position. The same water supply may be made to 
traverse both condensers. The two burners under the tray are 
lighted and the temperature regulated so that the benzene in the 
outer jacket boils briskly, whilst at the same time sufficient heat 
finds its way to the boiling-tube, through the gauze ring outside 
the concentric screens of asbestos below the tray, to keep the 
benzene in the state of steady ebullition. In about hour from 
the time the benzene boils in the inner tube the first reading may 
be made, and a fresh reading every five minutes until the 
temperature is constant, i.e., does not vary more than 0*01. As 
the atmospheric pressure may produce considerable variations in 
the reading, it is important to observe the barometer occasionally 
during the experiment, and to make a correction, which is about 
O'O43 for every I mm. below 760. 

The temperature being constant, a pellet (o'i o'2 gram) of 
fused naphthalene is carefully weighed and dropped into the boil- 
ing-tube through the condenser without interrupting the boiling. 
These pellets are conveniently made in a small bullet-mould. 

The boiling-point will rise and after a few minutes will remain 
stationary. The temperature is noted. A second and third 



PRACTICAL ORGANIC CHEMISTRY 



determination may be made by introducing fresh pellets of 
naphthalene. 

When the observations are complete, the apparatus is 
allowed to cool and the weight of benzene ascertained by 
weighing the boiling-tube and benzene. 

As in the freezing-point method, the molecular weight is 
calculated from the weight of substance required to raise the 
boiling-point of too grams of solvent i, and the result multiplied 
by a coefficient which depends upon the nature of the solvent. 
The following is a list of solvents commonly employed and 
their coefficients and boiling-points : 



bp. 
78 

79 
100 
118 
184 

The molecular weight is determined from the formula 
100 kw 





b.p. 


*. 




Ether 


35 


2I'I 


Ethyl alcohol 


Acetone 


56 


I7-I 


Benzene ... 


Chloroform 


61 


3 6-6 


Water 


Methyl alcohol ... 


66 


8-S 


Acetic acid 


Ethyl acetate 


77 


26-8 


Aniline 



k. 

"'5 

26-1 



32'2 



M = 



dW 



in which TV is the weight of substance, W that of the solvent, 
d the rfse of boiling-point, and k the coefficient. 

Example. Using the same solvent and adding successively 
four pellets of naphthalene, the following results were 
obtained : 

Mean. 



-128-3 



A simpler and more convenient form of Beckmann apparatus, 
requiring much less solvent and giving equally accurate results, 
is shown in Fig. 33. It consists of a boiling-tube furnished with 
two side pieces, one of which is stoppered and serves to 
introduce the substance and the other acts as a condenser. The 
boiling-tube stands on an asbestos pad and is surrounded by 
two short concentric glass cylinders surmounted by a mica plate. 
The other parts of the apparatus are similar to those in the older 
form and the process is conducted in the same way. 



w W. d. M. 


I 


o 1866 


21-313 


0-185 


126-6 


2 


o'i893 




0-185 


128-3 


3 


o - i86o 


,, 


0-185 


126-0 


4 


0-1901 


,, 


0-180 


132-4 


Calculated for C 10 H 8 ; M = 128. 



DETERMINATION OF MOLECULAR WEIGHT 



Example Ten c.c. of benzene were used and two pellets of 
naphthalene were added. 

iv. W. d. M. Mean. 



0-2072 
0-2072 



874 
874 



0-483 
0-485 



131-1 
127-6 



129-3 



Dynamical Method. A third, somewhat different and 
less accurate, method for determining the boiling-point is one 
devised by Sakurai and 
modified by Lands- 
berger and later by 
Walker and Lumsden. 
The apparatus of 
Walker and Lumsden 
is shown in Fig. 34, 
and consists of three 
vessels, a boiling flask, 
A, a tube, B, graduated, 
in c.c. and an outer 
jacket of glass, c. The 
boiling flask is pro- 
vided with a safety 
tube, D, and a bent 
tube, E, which is con- 
nected with another 
bent tube, F, passing 
through a cork to the 
bottom of the gradu- 
ated tube, B. A ther- 
mometer graduated in 
tenths is inserted 
through a second hole 
in the same cork. There is a small hole at G in the graduated 
tube below the cork through which the vapour of the boiling liquid 
escapes into the outside jacket, and is condensed by a condenser 
not shown in the diagram. The outer jacket, C, is attached by a 
cork surrounding B. A small quantity of solvent (510 c.c.) is in- 
troduced into the tube B and a larger quantity of the same solvent 
into the boiling flask, A. The vapour from A passes into B and 
raises it to the boiling-point, which is read off. The excess 
of liquid which has condensed is poured out. The weighed 




FIG. 33. 



42 



PRACTICAL ORGANIC CHEMISTRY 



substance is introduced and the boiling continued. When 
a steady temperature is reached, the new boiling-point is 
determined ; the tube is immediately disconnected from the 
flask, the flame removed, and the volume of the solvent is 
read off as accurately as possible-- By repeating the process, 

several determina- 
tions may be car- 
ried out with the 
same solvent and 
the same material. 
The weighing of 
fresh solvent for 
each estimation of 
new portions of 
substance is also 
avoided. The main 
precautions to be 
taken are (i) to 
ensure steady boil- 
ing in the flask, A, 
by introducing frag- 
ments of porous pot, 
and (2) to conduct 
the boiling at such 
a rate that the drops 
fall slowly and re- 
gularly from the 
FIG. 34. condenser. The in- 

accuracies of the 

method arise from constant change of concentration throughout 
the operation and from impurity in the solvent, the boiling-point 
of which will have a tendency to rise as the distillation proceeds. 
Examples. 

w. Volume of solvent.^ d. M. Mean. 




o'Siog grm. (urea) 
0-8109 ,, 



1 7 '5 c.c. (alcohol) 



i '04 
0-52 



Calculated for CON 2 H 4 ; M = 6o. 



1 The constants for liquids at the boiling-point ( constant divided by the specific 
gravity of the solvent at the boiling-point) are as follows : 

Alcohol 15 '60 Acetone 22^20 

Ether 3'3 Chloroform ... 26'co 

Water 5^40 Benzene 3 2 ' 8 



MOLECULAR WEIGHT OF ORGANIC ACIDS 43 

Although the boiling-point method is able to dispose of a 
greater number of convenient solvents than are suitable for 
freezing-point determinations, it is never so accurate, mainly on 
account of the difficulty of avoiding fluctuations in the boiling- 
point, due to radiation, to the dripping of cold liquid from the 
condenser, to impure solvent, and to barometric fluctuations. 



Molecular Weight of Organic Acids 

Determination by means of the Silver Salt. The 
basicity of an organic acid being known, the molecular weight 
can be determined by estimating the amount of metal in one of 
its normal salts. The ratio of metal to salt will be that of the 
atomic weight of the metal to the molecular weight of the salt. 
The silver salts are usually selected for these determinations, 
since they are, as a rule, normal, i.e. neither acid nor basic ; 
they are only slightly soluble in water, and are consequently 
readily obtained by precipitation, and finally they rarely contain 
water of crystallisation. On the other hand they are very 
unstable, being quickly discoloured when exposed to light, and 
often decomposing with slight explosion when heated. Silver 
benzoate may be prepared by way of illustration. Weigh out 
roughly 2 3 grams of benzoic acid into a flask, and add about 
20 c.c. of water and an excess of dilute ammonia. Boil the 
solution until the escaping steam has nearly lost the smell of 
ammonia, and then test the liquid from time to time until it is 
neutral to litmus. Cool the flask under the tap, and add an excess 
of silver nitrate solution (3 4 grams AgNO 3 ). Filter with the 
filter-pump. 

Filtration under Reduced Pressure. A filter-pump is 
an essential part of a laboratory fitting. It consists of a good 
water-jet aspirator (see Fig. 35), which is fixed to the water-tap 
by a stout piece of rubber tubing well wired at both ends. The 
joint is wrapped round with cloth or leather wired on to the 
rubber. The side tube of the aspirator is connected by pump 
tubing to an empty filter flask or bottle by means of a glass tap. 
A second glass tube or side piece is put in connection with the 
filter flask by means of rubber tubing. The object of inserting 
a vessel between the pump arid the filter flask is to prevent 



44 



PRACTICAL ORGANIC CHEMISTRY 



water running back when the aspirator is stopped. Before 
stopping the pump, close the glass tap. Turn off the water, and 
then lift the tap out of its socket for a moment to equalise the 
pressure. 

Use a porcelain funnel and filter flask, different sizes of which 
are shown in Fig. 36. The bottom of the funnel is covered with 
a disc of filter paper. After filtering, wash three or four times 

with a little cold water, 
press the precipitate 
well down and let it 
drain. Remove the 
precipitate and spread 
it on a piece of porous 
plate, and place it in 
a vacuum-desiccator 
over sulphuric acid. 
There are several use- 
ful forms of vacuum- 
desiccator, two of 
which are represented 
in Fig. 37. 

The ground rims 
are greased with vase- 
line or a mixture of 
bees-wax and vaseline, 
and the air is exhausted 
by attaching the tube 
of the water-pump to 
the glass tap of the 
desiccator. 

If the substance is left overnight in the desiccator it will be 
dry by the next day. The silver salt should be protected as far 
as possible from the light. When the precipitate is thoroughly 
dry, weigh about 0*3 gram into a weighed porcelain crucible. 
Cover with the lid and heat, at first gently, over a small flame. 
When the first reaction is over, heat the crucible for a few 
minutes to a dull red heat, and then allow it to cool in a desic- 
cator. The silver salt will be completely decomposed and leave 
a dull white residue of silver. The crucible is now weighed and 
the weight of silver determined. 




FIG. 35. 



MOLECULAR WEIGHT OF ORGANIC ACIDS 45 




FIG. 36. 




FIG. 37. 



46 PRACTICAL ORGANIC CHEMISTRY 

If W is the weight of salt, w the weight of silver, and n the 
basicity of the acid, the molecular weight of the silver salt is 
determined from the following formula : 



The molecular weight of the acid is then obtained by deduct- 
ing atoms of silver and adding n atoms of hydrogen. 

Example 0*3652 grm. silver benzoate gave 0*1720 grin. 
silver. 



= I22 . 2 . 



0-1720 
Calculated for C 7 H 6 O 2 ; M = 122 

Molecular "Weight of Organic Bases 

Determination by means of the Platinum Salt. 
The organic bases form, like ammonia, crystalline chloroplati- 
nates with platinic chloride of the general formula B 2 H 2 ,PtCI 6 . 
By estimating the amount of platinum present in the salt, it is 
possible to calculate the molecular weight of the platinum com- 
pound, and consequently that of the base. 

Dissolve about I gram of an organic base (brucine, strych- 
nine, quinine, &c.) in 10 c.c. of a mixture of equal volumes of 
concentrated hydrochloric acid and water. To the clear hot 
solution add excess of platinic chloride and let it cool. Yellow 
microscopic crystals of the chloroplatinate of the base separate. 
(If the chloroplatinate of the base is very soluble in water, such 
as aniline, it must be washed with strong hydrochloric acid, 
pressed on a porous plate and dried in a vacuum-desiccator over 
solid caustic potash.) 

Filter on the porcelain funnel with the pump and wash three 
or four times with small quantities of cold water. Press the 
precipitate down and dry on a porous plate in the vacuum-desic- 
cator. When thoroughly dry, weigh out about o - 5 to I gram of 
the compound into a porcelain or platinum crucible, and heat 
gently with the lid on, and then more strongly until the organic 
matter is completely burnt away; Cool the crucible in the desic- 
cator and weigh. 



MOLECULAR WEIGHT OF ORGANIC BASES 47 

The molecular weight of the salt is calculated from the weight 
w of the platinum, and W of the salt, according to the formula 
(the atomic weight of platinum being 195) : 
W*. 195 

w 

To determine from this the weight of the base, it is necessary 
to deduct from the molecular weight of the salt that of H 2 PtCl 6 , 
and as two molecules of the base are contained in the salt, 
the result is halved. 

Example 07010 grm. of aniline chloroplatinate, 

(C 6 H 6 NH 2 ) 2 H 2 PtCl 6 , 
gave 0*2303 grm. platinum. 

07010 x 195 = M.W. of the salt. 

0-2303 

594-2- 409-9 - 9ri , 

2 

Calculated for C 6 H 7 N ; M = 93. 

Preparations 

General Remarks. Carefully read through the method. 
References to the process are given under each heading. Be 
clear as to the objects of the various steps described and the 
nature of the materials employed. It cannot be too strongly urged 
that in all cases where any doubt exists as to the nature of an 
operation, a preliminary trial should be made in a test-tube with a 
small quantity of the substance. This is especially necessary in 
crystallisation where the quantity and character of the solvent are 
unknown. A vast amount of time and material is thereby saved. 
A small stock of clean and dry test-tubes (5 x and smaller sizes) 
should always be at hand for this purpose ; also watch-glasses 
for microscopic examination of solid substances. 

The yield of either the crude or purified product should 
always be ascertained, and the purity of the product determined 
either by the boiling-point or melting-point. A small rough 
balance with celluloid pans, for use on the bench, is indispensable. 

Select vessels of a size appropriate to the quantities dealt 
with. Never use beakers for boiling or evaporating liquids, but 
flasks and basins. Use ordinary, carefully selected, corks rather 



48 PRACTICAL ORGANIC CHEMISTRY 

than rubber stoppers (which are attacked by many organic 
liquids), and soften them well before use. The reactions 
described at the end of each preparation are to be done in test- 
tubes, and should not be neglected. 

Above all, work with suitable, compact and clean apparatus 
on a dean bench. The best results are usually obtained when the 
preparation is carried out with something of the care and 
accuracy of a quantitative analysis. 

Where the asterisk occurs, it signifies that the operation must 
be conducted in the fume cupboard. 

Whilst the preparation is in progress, utilise the spare minutes 
in reading the notes in the Appendix. 

To facilitate reference to general manipulative processes, 
which are described as they occur in conjunction with different 
preparations, the following table is added. 

Solids. Page. 

Filtration ... ... ... ... ... 53 

Filtration under reduced pressure ... ... 43 

Crystallisation ... ... 52 

Fractional crystallisation ... ... ... 122 

Sublimation ... ... ... ... ... 226 

Determination of melting-point ... ... 72 

Liquids. 

Dehydration... ... ... ... ... 56 

Determination of boiling-point ... ... 58 

Distillation under reduced pressure ... 84 

Distillation in steam ... ... ... 107 

Fractional distillation ... ... ... 136 

Determination of specific gravity ... ... 56 

Liquids and Solids. 

Heating under pressure ... ... 24, 78 

Determination of rotatory power ... ... 116 

Mechanical stirring ... ... ... 9 J 47 

Purification of Methylated Spirit and Spirits of Wine 
Methylated spirit, or spirits of wine 6070 " over-proof, " may 
generally replace the more costly absolute alcohol as a solvent 
after undergoing a process of purification. The methylated 
spirit must be of the old kind, consisting of a mixture of 9 parts 
spirit of wine and i part purified wood-spirit, without the 



ETHYL ALCOHOL 



49 



addition of paraffin i.e., it should give a clear solution with 
water. It is, however, preferable to use rectified spirits 60-70 
over-proof which can be bought free of duty by teaching institu- 
tions on application to the Inland Revenue Board. 

Methylated spirit contains, in addition to ethyl and methyl 
alcohols, water, fusel-oil, acetalde- 
hyde, and acetone. It may be 
freed from aldehyde by boiling 
with 2 3 per cent, solid caustic 
potash on the water-bath with an 
upright condenser for one hour, or 
if larger quantities are employed, 
a tin bottle is preferable, which 
is heated directly over a small 
flame (see Fig. 38). It is then 
distilled with the apparatus shown 
in Fig. 39. The bottle is here 
surmsunted with a T-piece hold- 
ing a thermometer. The distil- 
lation is stopped when most of the 
spirit has distilled and the ther- 
mometer indicates 80. A further 
purification may be effected by 
adding a little powdered perman- 
ganate of potash and by a second 
distillation, but this is rarely ne- 
cessary. The same method of 
purification may be applied to 
over-proof spirit, which will hence- 
forth be called spirit as distinguished from the purified product 
or absolute alcohol. 




FIG. 38. 






Ethyl Alcohol, C 2 H 5 .OH 



Commercial absolute alcohol may be used for the preparations 
which follow. It is obtained by distilling crude spirits of wine 
over quicklime, and usually contains about 0*5 per cent, of 
water. 

Properties. Pure ethyl alcohol boils at 78-3, and has a 
sp. gr. of 0793 at J 5- It mixes with water in all proportions 

COHEN'S ADV. p.o.c. E 



PRACTICAL ORGANIC CHEMISTRY 



Reaction. A delicate test for ethyl alcohol is the iodoform 
reaction. Pour a few drops of alcohol into a test-tube and add 
about 5 c.c. of a solution of iodine in potassium 1 iodide, and then 
dilute caustic soda solution until the iodine colour vanishes. 
Shake up and warm very gently to about 60. If no turbidity 
or precipitate appears at once, set the test-tube aside for a 
time. Yellow crystals of iodoform will ultimately deposit, which 
have a peculiar odour, and a characteristic star shape when 
viewed under the microsco'pe. The same reaction is given with 




FIG. 39. 

other substances, such as acetone, aldehyde, &c., but not with 
methyl alcohol. 

PREPARATION i. 
Potassium Ethyl Sulphate, C 2 H 6 O.SO,.OK 

Dabit Ann. Chim. Phys. 1800, (i) 34, 300 ; Claesson, /. prakt. 
Chem. 1879 (2} 19, 246. 

70 grins. (87 c.c.) absolute alcohol. 1 
50 (27 c.c.) cone, sulphuric acid. 

The alcohol is poured into a round flask (| litre) and the 
-sulphuric acid is slowly added and well mixed by shaking. A 

1 For the preparation of methyl potassium sulphate the same quantity of methyl 
alcohol is used ; in other respects the two processes are identical. The yield is 
45 50 grams. 



POTASSIUM ETHYL SULPHATE 



considerable amount of heat is developed in the process. The 
flask is now fitted with a reflux condenser (see Fig. 40) placed 
upon the water-bath and heated for 2 3 hours. The product 
now contains in addition to ethyl hydrogen sulphate, free sul- 
phuric acid and unchanged alcohol. The liquid on cooling is 
poured into i litre of cold water m a large basin and well stirred. 
It is neutralised by adding chalk ground into a thin paste with 
water. This precipitates the free sulphuric acid as calcium sul- 
phate and converts the ethyl hydrogen sulphate into the soluble 




FIG. 40. 

calcium salt. The mixture is heated and filtered through a 
large porcelain funnel (see Fig. 36) at the filter-pump, and the 
precipitate pressed well down. The clear filtrate is heated on 
the water-bath and a solution of potassium carbonate (about 50 
grams) is added in small quantities until the liquid is slightly 
alkaline. To ensure complete precipitation a little of the clear 
liquid should be tested with a solution of potassium carbonate 
before proceeding. 

The calcium salt is thereby converted into the soluble potas- 
sium salt and calcium carbonate is precipitated. The latter is 
removed by filtration, as before, and the filtrate concentrated on 
the water-bath to a small volume until a drop of the liquid, re- 
moved on the end of a glass rod, crystallises at once on cooling 

E 2 



52 PRACTICAL ORGANIC CHEMISTRY 

The potassium ethyl sulphate is filtered and washed with a 
little spirit or methylated spirit. 1 

Crystallisation. The substance should now be recrystal- 
lised. The success of many operations in practical organic 
chemistry depends upon skill in crystallisation. The first essen- 
tial is to select a suitable solvent, that is, one which dissolves 
much more of the substance at a high than at a low temperature. 
To discover a suitable solvent a small quantity of the substance 
(o' i gram is sufficient) is placed in a test-tube and a few drops 
of the solvent poured in. The common solvents are water, 
methyl and ethyl alcohol, ethyl acetate, acetic acid, acetone, benz- 
ene (also toluene and xylene) nitrobenzene, petroleum spirit and 
ligroin, chloroform and carbon tetrachloride. If the substance 
dissolves on shaking without warming or does not visibly 
diminish on boiling, it may be discarded as unsuitable. If it 
dissolves on heating or boiling and crystallises on cooling in 
considerable quantity, it may be employed. Sometimes solutions 
can be supercooled. In such cases, rubbing the sides of the 
test-tube with a glass rod will cause the substance to deposit. A 
convenient method of crystallisation may be occasionally em- 
ployed by using two miscible solvents in one of which the 
substance is soluble and in the other insoluble. The substance 
is then dissolved in a small quantity of the first solvent and 
the second added gradually until a turbidity appears. Alcohol 
and water, and benzene and petroleum spirit are often used in 
conjunction in this way. If a substance of low melting-point is 
to be crystallised care should be taken that sufficient solvent 
is present to prevent the substance separating at a temperature 
at which it is still liquid. The interval of temperature may be 
increased after the solution has reached the ordinary tempera- 
ture, by cooling it in a freezing mixture, when some of the 
solid will be deposited. 

In the present instance spirit or methylated spirit (purified) 
will be found an efficient solvent for potassium ethyl sulphate. 
The following is the mode of procedure when a volatile or in- 
flammable solvent is used : the substance is placed in a round 
flask attached to an upright condenser and heated on the water- 
bath. The form of apparatus is that already described (see Fig. 

1 I{ methylated spirit is used it must be purified according to the method described 
on D. 48 



POTASSIUM ETHYL SULPHATE 



53 



40.) Small quantities of spirit are added and kept boiling until 
a solution is obtained. A small quantity of impurity may remain 
undissolved. The hot solution is at once decanted or filtered 




CL 





FIG. 41. 

through a fluted filter (Fig. 41) or hot water funnel (Fig. 42) 
into a beaker and allowed to cool. 

A fluted filter is made by first folding a large circular filter 
paper in the ordinary way. It is then half opened out and the 
two quadrants folded towards the middle line (see a, Fig. 41), 
This makes three creases with the hollows on the same side. 
The filter is now turned over and each section folded down the 




FIG. 42. 



centre so that the hollows of the four new creases alternate 
with the ridges of the three others as shown at b. The paper 
when opened now appears like c. The two rectangular flutings 
indicated by an asterisk have still to be divided by a crease 



54 PRACTICAL ORGANIC CHEMISTRY 

down the middle. The filter is now pushed well into the 
funnel, the stem of which is cut off short as shown at d. 

A hot-water funnel is shown in Fig. 42. It consists of a 
jacketed metal funnel, with a projecting metal tube. The vessel 
is partly filled with water which is boiled by placing a small 
burner under the end of the tube. The glass funnel is placed 
within the metal-jacket. By keeping the liquid hot, crystallisation 
in the filter is thus prevented. 

Before filtering an inflammable liquid such as alcohol the flame 
must be removed. The potassium ethyl sulphate is dried on a 
plate of unglazed earthenware or on a thin pad consisting of 
three or four sheets of filter paper, with another sheet over the 
crystals to keep out the dust. On concentrating the mother 
liquors on the water-bath, a further quantity of crystals may be 
obtained. Yield 35 40 grams. The following equations 
express the chemical reactions which occur : 

1. C 2 H 5 OH + II 2 SO 4 = C 2 H 5 SO 4 H + HjO 

Ethyl hydrogen sulphate. 

2. 2C 2 H 5 SO 4 H + CaCO 3 = (C 2 H B SO 4 ).,Ca + H,O + CO 2 

Calcium ethyl sulphate. 

3. (C,H.S0 4 ),C* + K 8 C0 3 = 2C 2 H 8 S0 4 K + CaCO 3 . 

Potassium ethyl sulphate. 

Properties. Colourless, foliated crystals ; easily soluble in 
water and dilute alcohol, less soluble in absolute alcohol. 

Reactions, i. Dissolve a little of the recrystallised salt in water, 
and add barium chloride solution. There is no precipitate, as 
the barium salt of ethyl hydrogen sulphate is soluble in water. 
2. Boil a little of the solution of the salt with a few drops 
of dilute hydrochloric acid for a minute and add barium chloride. 
A precipitate of barium sulphate is formed, as, on boiling ethyl 
hydrogen sulphate in aqueous solution, it is decomposed into 
sulphuric acid and alcohol (see Appendix, p. 234). 

PREPARATION 2. 

Ethyl Bromide (Monobromethane), C 2 H 6 Br. 
De Vrij, Jahresber., 1857, 441. 
loo grms. potassium bromide. 
100 (54 c.c.) cone, sulphuric acid 
60 j? (75 c - c )- absolute alcohol 



ETHYL BROMIDE 



55 



Fit up the apparatus as shown in Fig. 43. The distilling 
flask should have a capacity of not less than i litre, and is 
attached to a long condenser. An adapter is fixed to the end of 
the condenser, dipping into a conical flask (250 c.c.), which 
serves as receiver. The alcohol and sulphuric acid are mixed 
in the distilling flask and cooled to the ordinary temperature 
under the tap. The potassium bromide, coarsely powdered, is 
then added. The flask, which is closed with a cork, is fixed to 
the condenser and heated on the sand-bath. A sufficient quan- 
tity of water is poured into the receiver to close the end of the 
adapter. After a short time the liquid in the flask begins to 
boil and froth up, and the ethyl bromide, in the form of heavy 




FIG. 43. 

drops of colourless liquid, distils and collects at the bottom of 
the receiver. If the liquid threatens to froth over, the flask must 
be raised from the sand-bath for a moment. The distillation is 
continued until no further drops of oil appear at the end of 
the condenser. As the ethyl bromide has a low boiling point 
(38-39 c ), it is desirable to surround the receiver with ice during 
this operation. The distillate is now removed and poured into 
a separating funnel (Fig. 44), and the lower layer of ethyl bro- 
mide separated. The water is thrown away and the ethyl 
bromide poured back together with about an equal bulk of dilute 
sodium carbonate solution and shaken up. The ethyl bromide 
is withdrawn, as before, and again shaken up with water. 
Finally, it is carefully separated from the water and run into a 
dry distilling flask. The small quantity of water which remains. 



PRACTICAL ORGANIC CHEMISTRY 



and renders the liquid turbid, is removed by adding a dehydrat- 
ing agent. 

Dehydration. Moisture can be readily removed from liquids 
by adding a solid hygroscopic substance which does not act 
chemically upon the liquid. The common 
dehydrating agents are calcium chloride, 
potassium carbonate, sodium sulphate 
(anhydrous), quicklime, &c. Alkalis can- 
not of course be used for dehydrating or- 
ganic acids, nor can calcium chloride be 
employed in conjunction with alcohols or 
organic bases, with which it combines. In 
the present instance it can be used. A few 
small pieces of the granulated or fused 
calcium chloride are added to the liquid. 
The flask is corked and left to stand for 
some hours until the liquid becomes 
clear. It is then distilled. A ther- 
mometer is inserted into the neck of 
the flask with the bulb just below the 
.side tube. The flask is attached to a con- 
denser and heated gently on the water- 
bath, so that the liquid distils at a moderate speed (2 3 drops 
a second). The temperature is noted and the portion boiling at 
35 43 collected in a separate flask. This consists of ethyl 
bromide which may contain a little ether. Yield 75 80 grams. 

HOH + H 2 S0 4 = C,H,.H.S0 4 + H 2 O. 

Ethyl hydrogen sulphate. 

KBr = C 2 H 5 Br + KHSO 4 . 

Ethyl bromide. 

Properties Colourless liquid ; b. p. 38 '8 ; sp. gr. 1*47 at 15" 
(see Appendix, p. 234). 

Determination of Specific Gravity. A simple method 
for determining the specific gravity of liquids is as follows : A 
pyknometer, or small glass bottle, is used of about 20 to 30 c.c. 
capacity, with narrow neck, upon which a mark is etched and 
which is closed by a ground glass stopper (Fig. 45). 

The bottle is thoroughly cleaned and dried by warming and 
aspirating air through it, after which it is allowed to cool and 
weighed. It is then filled with the liquid, which is poured in 




FIG. 44- 



C 25 

Alcohol. 



C 2 H 5 .H.SO 4 



ETHYL BROMIDE 



57 



through a funnel, the stem of which is drawn out so as to pass 

through the narrow neck. The bottle is placed in a mixture of 
snow or pounded ice and left a quarter to half an 
hour, until the contents have a temperature of o. 
The meniscus is now adjusted until it coincides 
with the mark on the neck of the bottle. If 
more liquid has to be added, this may be 
done from a small pipette with capillary de- 
livery tube ; if some of the liquid has to be 
removed, a thin roll of filter paper may be 
inserted which will absorb it. The bottle is 
then stoppered, dried on the outside, left in the 
balance case for a quarter of an hour, and 
weighed. It is then emptied, cleaned, and 
dried, and filled with distilled water previously 
boiled. The water is cooled to o, the meniscus 
adjusted and the bottle weighed, the same 
process being repeated as that just described. 

The following expression will give the specific gravity of the 

liquid at o compared with water at o : 




FIG. 45. 



Where w l = weight of empty bottle, 

w. 2 = bottle and water at o, 
iti z = bottle and liquid at o ; 

or. if compared with water at 4, the above number must be 
multiplied by the density at o = o - 999S73. 

A very delicate and useful piece of apparatus, which is 
readily made with the blow-pipe, is Perkins' modification of 
Sprengel's pyknometer. 1 It is especially adapted for small quan- 
tities of liquid and for the more volatile ones. The apparatus 
(Fig. 46) consists of a U-tube to hold from 2 to 10 c.c., drawn 
out at each end into a fine capillary. The one capillary limb, a, is 
bent outwards and is furnished with a small bulb ; the other, b, 
is bent at a right angle with the first. On the limb a, between 
the bulb and the top of the U-tube a mark is etched. The 

1 Trans. C^tem. Sac. 1884, 45, 421. 



PRACTICAL ORGANIC CHEMISTRY 



tube is dried and weighed, and the liquid drawn in through the 
limb b, until it half fills the small bulb on the limb a. The 
apparatus is cooled in ice and water, and the meniscus adjusted 
to the mark on a by tilting the tube until the limb b has a hori- 
zontal position. To the end of this limb a piece of filter paper 
is applied, until the liquid sinks to the desired position in the 




Flo 46. 

limb a. The U-tube is then brought to the vertical position, 
loose glass caps placed over the ends of the two limbs, the 
apparatus carefully dried, and allowed to stand and weighed. 
The operation is then repeated with distilled water. 

Example An experiment with ethyl bromide gave the fol- 
lowing result : 

Weight of tube empty ......... 6^242 grams 

+ ethyl bromide at o . . 9*472 
-K water at o ...... 8'4i7 



A =0-999873 x . - r4 8 5 . 

Determination of the Boiling-point. A correct deter- 
mination of the boiling-point of a liquid is made with a standard 



ETHER 59 

thermometer, i.e., one that has been calibrated, and the o and 100 
points carefully determined. An ordinary thermometer corrected 
by a standard thermometer at Kew will serve equally well. 
Correction must also be made for barometic pressure. This is 
approximately o'O43 for every i mm. below 760 (Landolt). A 
further correction is required for the thread of mercury, which 
may project above the vessel. For this correction the following 
formula may be used : 

N(T-/)o-oooi54. 

Where T = apparent temperature in degrees. 

/ = temperature of a second thermometer, the bulb 
of which is placed at half the length N above 
the vessel. 
N = length of the mercury column in degrees from 

above the vessel to T. 
o'oooi 54 = apparent expansion of mercury in glass. 

This correction may be avoided by using short (Anschiitz) 
thermometers, in which the mercury thread is entirely immersed 
in the vapour. A rough correction for points above 100 may 
be made by determining the boiling points of pure organic 
substances, such as naphthalene, 2i6'6, &c. 

PREPARATION 3. 
Ether (Diethyl Ether, Diethyl Oxide), (C 2 H 5 ) 2 O 

V. Cordus (1544) ; Journ. Pharm., 1815, 1, 97 ; Williamson, 
Phil. Mag. 1850, (3) 37, 350. 

150 grms. (80 c.c.) cone, sulphuric acid. 
85 ( 1 10 c.c.) absolute alcohol. 

A distilling flask (\ litre) is fitted with a double-bored cork. 
Through one hole a thermometer is inserted, the bulb of which 
must be covered by the liquid in the flask and through the 
other a tap-funnel passes. The side-tube of the distilling flask 
is fixed by a cork into the upper end of a long condenser. An 
adapter is fitted to the lower end and passes through the neck 
of a flask, which is surrounded by ice. The apparatus is shown 



6o 



PRACTICAL ORGANIC CHEMISTRY 



in Fig 47. The sulphuric acid and alcohol are cautiously 
mixed together in the distilling flask, which is then placed upon 
a sand-bath and attached to the condenser. The mixture is 
heated to 140 and alcohol is run in from the tap-funnel at the 
same speed as the liqaid distils (about three drops a second). 
The temperature must be kept constant at 140 145. When 
about twice the quantity of alcohol contained in the original 
mixture has been added and converted into ether, the distillation 
is stopped. The receiver now contains, in addition to ether, 
alcohol, water and sulphurous acid. The liquid is poured into 




FIG. 47. 

a large separating funnel and a small quantity (30 40 c.c.) of 
dilute caustic soda added and well shaken. After settling, 
the caustic soda solution is drawn off below, and about the 
same quantity of a strong solution of common salt added, 
and the process of shaking and drawing off repeated. The 
ether, which is now free from sulphurous acid and from 
most of the alcohol, still contains water. It is therefore 
poured into a large dry distilling flask and some pieces 
of solid calcium chloride added. It is allowed to stand 
loosely corked overnight. The distilling flask is now attached 
to a long condenser and heated on the water- bath. The 
ether, which distils, still contains traces of alcohol and water, 
which it obstinately retains and from which it can only be freed 



ETHER 61 

by a further treatment with metallic sodium. A few very thin 
slices of sodium are dropped into the receiver and the vessel 
closed with a cork, through which an open calcium chloride tube 
is inserted to allow any hydrogen to escape and to prevent the 
entrance of moisture. 

When the sodium produces no further action, the ether is 
decanted from the sodium residues into a distilling flask and 
distilled on the water-bath. A thermometer is placed in the 
neck of the flask to indicate the boiling-point, which should be 
constant at 35. 

C 2 H 6 OH + H 2 SO 4 = C 2 H 5 SO 4 H + H 2 O. 
C 2 H 5 SO 4 H + C 2 H 5 OH - C 2 H 5 .O.C 2 H 5 + H 2 SO 4 . 

Properties. Colourless, mobile liquid ; b.p. 35 ; sp. gr. 0*720 
at 15 ; burns with a luminous flame ; not miscible with water ; 
9 parts of water dissolve I part of ether, and 35 parts of ether 
dissolve I part of water at the ordinary temperature. See 
Appendix, p. 236. 

Commercial Ether is made from methylated spirit and 
contains alcohol, water, and other impurities, and for many 





FIG. 48. FIG. 49. 



reactions requires to be purified. The following method of purifi- 
cation may be employed. The ether is distilled over a little 
coarsely powdered caustic potash, then placed in contact with solid 
calcium chloride for several hours, and finally decanted and 
treated with metallic sodium. It is convenient to use a sodium 
knife (Fig. 48) or press (Fig. 49) for preparing the sodium. 
In the former the metal can be cut into very thin slices, and 
in the latter it is pressed into fine wire thfough a circular steel die, 



62 PRACTICAL ORGANIC CHEMISTRY 

It must be remembered that ether is highly inflammable, and 
also exceedingly volatile, and great care should be taken that 
no flame is in the neighbourhood of the liquid. It must on no 
account be distilled over the bare flame, but always from the 
water-bath, and then with a long well-cooled condenser. The 
distillation of large quantities should be avoided as far as 
possible. In such cases it is convenient to employ a distilling 
flask of moderate size (250 c.c.), and to add, as the liquid distils, 
a fresh supply of ether or ethereal liquid from a tap-funnel 
inserted through the neck of the flask, which can be done 
without interrupting the distillation. 

PREPARATION 4. 
Ethylene Bromide. CH 2 Br. CH 2 Br. 

Balard, Ann. Chim. Phys. 1826 (2), 32, 375 ; Erlenmeyer. 
Bunte, Annalen, 1873, 168, 64. 

25 grms. (30 c.c.) absolute alcohol. 
150 (80 c.c.) cone, sulphuric acid. 
200 (65 c.c.) bromine (which must be measured 

out in the fume-cupboard). 
300 of a mixture of 100 grms. (124 c.c.) alcohol 

and 200 grms. (108 c.c.) cone, sulphuric 

acid. 

Fit up an apparatus as shown in Fig. 50 . It consists of a 
round flask (2 litres), which is furnished with a double-bored 
cork. A tap-funnel is inserted through one hole and a delivery 
tube through the other, by which it is connected with two 
wash-bottles with safety tubes. A useful form of wash-bottle is 
that shown in Fig. 50 and in section at a. Otherwise a three- 
necked Woulff bottle will serve, with a long tube inserted through 
the central neck. The wash-bottles are one-third filled with 
caustic soda solution. The two ordinary wash-bottles standing 
in the trough of water contain the bromine. The first contains 
about 50 c.c. of bromine and i c.c. of water and the second about 
1 5 c.c. of bromine and i c.c. of water. The latter is attached to 
a wide U tube or cylinder containing pieces of soda-lime. If a 
cylinder is used a layer of glass fragments or marbles should 



ETHYLENE BROMIDE 



form a layer round the orifice of the inlet tube with the soda- 
lime above. 

The joints being tight, the mixture of 25 grams of alcohol and 
150 grams of sulphuric acid is run into the large flask containing 
a little dry sand and heated with a small flame on the sand-bath 
until a steady stream of gas is evolved. When this occurs the 
mixture of alcohol and sulphuric acid is dropped in slowly from 
the tap-funnel. It is important to moderate the temperature 
to prevent excessive frothing and the separation of carbon, 
which, however, cannot altogether be avoided. A considerable 
quantity of sulphur dioxide which is evolved with the ethylene 




FIG. 50. 

is removed by the caustic soda in the wash-bottles. If the 
water surrounding the bromine bottles becomes warm, small 
lumps of ice should be thrown in. The caustic soda should 
be occasionally renewed, otherwise sulphur dioxide may pass 
into the bromine and reduce it to hydrobromic acid. If the 
pressure in the apparatus causes a back rush of bubbles 
through the tap-funnel attached to the flask, the difficulty is 
met by inserting the stopper in the tap-funnel. After a 
few hours the bromine in both vessels is decolourised or at 
least changes to a straw colour. The crude ethylene bromide 
is removed and shaken with dilute caustic soda solution, then 
with water, separated from the aqueous layer and dehydrated 



64 PRACTICAL ORGANIC CHEMISTRY 

over small pieces of calcium chloride. It is decanted or 
filtered from the calcium chloride and distilled. The distillate is 
collected at 130 132. The yield is nearly equal to the 
weight of bromine taken. 

C 2 H 5 (OH)-H 2 O = C 2 H 4 
C 2 H 4 + Br 2 = Cjjt^Br^ 

Properties. Colourless liquid, which solidifies, at o to a 
crystalline mass and melts at 9 ; b.fx 131 '5 ; sp.gr. 2' 19 at 15. 

Reaction. Attach a 100 c.c. flask to a short upright con- 
denser (see Fig. 86) and to the upper end of the condenser 
attach a vertical delivery tube, dipping into an ammoniacal 
cuprous chloride 1 solution. Pour 2 3 c.c. of ethylene bromide 
into the flask with 4 times its volume of strong methyl alcoholic 
potash, which is prepared by boiling methyl alcohol with excess 
of caustic potash on the water-bath with upright condenser. On 
gently heating, a rapid evolution of acetylene occurs and the 
characteristic brown copper compound (C 2 H 2 Cu 2 ,H 2 O) is pre- 
cipitated from the cuprous chloride solution. 



Acetylene. 

See Appendix, p. 237. 

PREPARATION 5. 

Acetaldehyde, CH 3 .CO.H 

Liebig, Annalen, 1835, 14, 133 ; Staedeler, J. prakt. Chem., 
1859, (i) 76, 54- 

100 grms. potassium bichromate 
420 c.c. water. 

A mixture of 100 grms. (125 c.c.) absolute alcohol 
and 140 grms. (75 c.c.) cone, sulphuric acid. 

100 c.c. methylated ether, which has been left to 
stand over solid caustic potash for a few hours, and 
then distilled off from the water-bath. 
A round flask (i^ litre) is provided with a double-bored cork. 

1 Ammoniacal cuprous chloride is made as follows : Boil up copper oxide and 
metallic copper with cone, hydrochloric acid for a short time until the liquid 
is nearly colourless, and pour the liquid into water. The white cuprous chloride is 
washed once or twice by decantation and dissolved in a strong solution of ammonium 
chloride. When required a little ammonia is added sufficient to give a clear blue 
solution. 



ACETALDEHYDE 



A bent tube, which passes through one hole, connects the flask 
with a condenser and receiver. A tap-funnel is inserted through 
the other hole. The flask is placed upon a sand-bath, and the 
receiver is cooled in ice. It is important that all the corks 
should be tight, as a small leak will considerably diminish the 
yield. The potassium bichromate in small pieces and the 
420 c.c. of water are placed in the flask and gently warmed. 
The flame is then removed, and the mixture of alcohol and 




Fie. 51. 

sulphuric acid, which may be used warm, is slowly added from 
the tap-funnel. The flask is occasionally shaken. A consider- 
able rise of temperature occurs and the liquid darkens, whilst 
aldehyde, with a little water and alcohol, distils. When the 
mixture has all been added, the flask is heated on the sand-bath 
until all the aldehyde has distilled (about 150 c.c.), which may 
be determined by removing the cork from the flask and noticing 
if the smell of aldehyde is still perceptible. The distillate is now 
redistilled on the water-bath in the apparatus shown in Fig. 51. 
COHEN'S ADV. p. o. c. F 



66 



PRACTICAL ORGANIC CHEMISTRY 



The flask is attached to an upright condenser in which the 
water is kept at a temperature of 30 35. Alcohol and aqueous 
vapour condense in the condenser ; the aldehyde, on the other 
hand, passes by a tube attached to' a 100 c.c. pipette into two 
narrow (TOO c.c.) cylinders, one-third filled with the dry ether, 
and cooled in ice-water. The aldehyde readily dissolves in the 
ether and is rapidly absorbed. If the ethereal solution is now 
saturated with dry ammonia gas, the whole of the aldehyde 
separates out in the form of colour- 
less crystals of aldehyde-ammonia, 
CH 3 .CH.OH.NH 2 . The apparatus 
for preparing the dry ammonia is 
shown in Fig. 52. The flask contain- 
ing strong ammonia solution is heated 
by a small flame, when the gas is 
readily evolved and passes up the 
tower, which is filled with soda-lime 
or quicklime. The ethereal solution 
is saturated with the gas, and is then 
allowed to stand for an hour. 

The ether is then decanted from 
the crystals, which are drained at 
the filter-pump, washed with a little ether, and finally dried in 
the air on filter-paper. Yield of aldehyde-ammonia, 25 30 
grams. It may be used for the reactions described on p. 67. 

Pure aldehyde may be prepared from the aldehyde-ammonia 
as follows : The crystals are dissolved in an equal weight 
of water and distilled on the water-bath with a mixture 
of 1 5 parts of concentrated sulphuric acid and 2 parts of water, 
the receiver being well cooled in ice. The temperature of the 
water-bath is gradually raised until the water begins to boil, 
and the distillation is then interrupted. The distillate is de- 
hydrated over an equal bulk of calcium chloride, from which it 
is distilled in the water-bath, heated to 30. The anhydrous 
aldehyde is kept in a well-stoppered bottle. 

3C 2 H 6 (OH) + K 2 Cr 2 O 7 + 4H 2 SO 4 = 3C 2 H 4 O + K 2 SO 4 + 

Cr 2 (S0 4 ) 3 + 7 H 2 

C 2 H 4 O + NH 3 = CH 3 CH.OH.NH 2 

2CH 3 CH.OH.NH 2 + H 2 S0 4 = 2CH 3 .CO.H + (NH 4 ) 2 SO 4 . 




IMG 5 a. 



METHYL ALCOHOL 67 

Properties. Colourless liquid with a distinctive smell ; b.p. 
21 ; sp. gr. 0*807 at cr ; soluble in water, alcohol and ether. 

Reactions. Acetaldehyde and many of the aliphatic aldehydes 
are characterised by the following reactions : 

1. Prepare a little ammonio-silver nitrate by adding dilute 
ammonia drop by drop to silver nitrate solution until the pre- 
cipitate just dissolves. Add to a third of a test-tube full of the 
ammonia-silver nitrate solution about i c.c. of aldehyde, and 
place it in a beaker of hot water. A mirror of metallic silver is 
deposited. Ag 2 O + C 2 H 4 O = Ag 2 + C 2 H 4 O 2 (acetic acid). 

2. To i c.c. of aldehyde add 2-3 times its volume of a cold 
saturated solution of sodium bisulphite and shake up. The 
additive compound, CH 3 CH.OH.SO 3 Na, crystallises out on 
standing. A crystal of the substance introduced into the liquid 
will hasten its formation. The bisulphite solution is prepared 
either by dissolving sodium metabisulphite in water, or by 
passing sulphur dioxide into soda crystals covered with a layer 
of water. It forms an apple-green solution, smelling strongly 
of sulphur dioxide. The sulphur dioxide is conveniently obtained 
from a bottle of the liquid which can be purchased, or by dropping 
concentrated sulphuric acid on to solid sodium sulphite. 

3. A solution of magenta decolourised by sulphur dioxide 
becomes violet on the addition of a drop of aldehyde (Scruff). 
Prepare a weak solution of magenta by dissolving a crystal in 
half a test-tube of water and bubbling in sulphur dioxide until 
the colour disappears. Now add a few drops of aldehyde. 

4. Boil a few drops of aldehyde with I 2 c.c. of caustic 
potash solution. The liquid becomes yellow and a brown 
resinous precipitate is formed. 

5. Add a drop or two of concentrated sulphuric acid to I c.c. 
of aldehyde. The mixture becomes hot in consequence of the 
aldehyde undergoing polymerisation to paraldehyde (C 2 H 4 O) 3i 
b.p. 124", which separates as an oil on adding water. See 
Appendix, p. 238. 

Methyl Alcohol. CH,,OH 

Commercial methyl alcohol is obtained by purifying wood spirit. 
It often contains a little acetone, which may be detected by the 
iodoform reaction (see p. 50). It may, if necessary, be purified by 
boiling it, using an upright condenser, with 3 4 per cent, of solid 

F 2 



68 PRACTICAL ORGANIC CHEMISTRY 

caustic potash on the water-bath, and then distilling. It is 
freed from water by standing for twenty-four hours in a flask 
one-third filled with freshly-burnt quicklime, and re-distilling 
from the water-bath, using a thermometer. 

Properties. Colourless liquid ; b. p. 66 67 ; sp. gr. 0796 
at 20. 

PREPARATION 6. 

Methyl Iodide (lodomethane), CH 3 I 
Dumas and Peligot, Annalen, 1835, 15, 20. 

1 8 grms. methyl alcohol. 
5 red phosphorus 
50 iodine 

Attach a flask (250 c.c.) to an upright condenser, and bring 
into it the methyl alcohol and red phosphorus. Add the iodine 
gradually by detaching the flask for a moment from the con- 
denser. A considerable evolution of heat occurs. When the 
iodine has been added the flask is left attached to the condenser 
over night, and the contents then distilled from the water-bath 
using a similar apparatus to that of Fig. 43, p. 55. The dis- 
tillate is shaken up with dilute caustic soda in a separating 
funnel, to remove iodine and hydriodic acid. If sufficient 
caustic soda has been used the lower layer of methyl iodide will 
be colourless. Separate the methyl iodide, add a few pieces of 
solid calcium chloride, and after standing until clear, distil from 
the water-bath with thermometer. Yield 45 grams. Ethyl 
iodide and the other alkyl iodides are prepared in precisely the 
same fashion. 

5CH 3 OH + P + 5! = sCH 3 I + H 3 PO 4 + H 2 O. 

Properties. Colourless, highly refractive liquid ; b. p. 45 ; 
sp. gr. 2*27 at 1 5. 

Reaction. Shake a few drops of methyl iodide with an 
alcoholic solution of silver nitrate. A white precipitate of a 
compound of silver iodide and silver nitrate is deposited, which is 
decomposed and gives yellow silver iodide on adding water. 
See Appendix, p. 240. 



AMYL ALCOHOL 69 



Amyl Alcohol, C 6 H n .OH. 

Commercial amyl alcohol is contained in fusel oil from fer 
mentation and consists mainly of isobutyl carbinol together 
with about 13 per cent, of secondary butyl carbinol, which 
renders the liquid optically active. It turns the plane of polar- 
isation to the left (see p. 116). 

Properties. Colourless, highly refractive liquid with a burning 
taste and penetrating smell ; b. p. 131 132 sp. gr., o'8ii3 at 
19 ; dissolves in 39 parts of water at i6'5. 

PREPARATION 7. 
Amyl Nitrite, C 5 H U O.NO. 

Balard ; Guthrie, Quart. J. C. S., 1858, 11, 245 ; Rennard, 
Jahresb., 1874, p. 352. 

30 grms. (37 c.c.) amyl alcohol. 

30 sodium nitrite (finely powdered). 

18 (10 c.c.) cone, sulphuric acid. 

The amyl alcohol and sodium nitrite are mixed in a flask 
(500 c.c.), and whilst the mixture is cooled in ice-water, the 
cone, sulphuric acid is added drop by drop from a funnel with 
constant shaking. Towards the end of the process a more 
vigorous reaction sets in, when care must be taken to add the 
sulphuric acid more slowly. When the whole of the acid has 
been added, the top layer of amyl nitrite is decanted into a 
separating-funnel. A little water is then added to the residue 
and, after shaking, a further quantity of amyl nitrite separates 
and is decanted as before. The whole of the amyl nitrite 
is then separated from water, dehydrated over calcium chloride 
and distilled. The liquid boiling at 95 100 is collected 
separately. Yield, 30 35 grams. 

C 5 H n OH + NaNO 2 + H 2 SO 4 = C 5 H n O.NO+NaHSO 4 + H 2 O. 

Properties. Yellow-green liquid with a peculiar penetrating 
and sweet smell, which, on inhaling, causes a rush of blood to 
the head ; b. p. 96 ; sp. gr. 0-902. See Appendix, p. 240. 

Acetone (Dimethyl ketone), CH 3 .CO.CH 3 . 
Commercial acetone is obtained from the products of the 
distillation of wood. To purify it, it is shaken with a saturated 



70 PRACTICAL ORGANIC CHEMISTRY 

solution of sodium bisulphite (see Reaction 2, p. 67). The crystal- 
line mass, C 3 H c ONaHSO 3 , is filtered and well drained and then 
distilled with sodium carbonate solution. The distillate is 
dehydrated over solid calcium chloride and finally distilled. 

Properties. Colourless liquid with a pleasant colour ; b. p. 
56'3 ; sp. gr. 0792 at 15 ; soluble in water. 

Reactions. i. Acetone gives the iodoform reaction like ethyl 
alcohol (p. 50). 2. Dissolve a few crystals of ^-bromophenyl- 
hydrazine or ^-nitrophenylhydrazine in a few drops of glacial 
acetic acid, dilute with about I c.c. of water and add a drop of 
acetone. The bromo- or nitro-phenylhydrazone of acetone 
separate as crystalline precipitates. 



PREPARATION 8. 
Chloroform (Trichloromethane), 

Liebig, Pogg. Ann., 1851, 23, 444 ; Dumas, Ann. Chim. 
1834, 56, 115. 

200 grms. bleaching powder (fresh). 

800 c.c. water. 

40 grms. (50 c.c.) acetone. 

A large round flask (4 litres) is fitted with a cork, through 
which a bent tube passes connecting the flask with a long con- 
denser and receiver. The flask is placed upon a large sand- 
bath. Grind the bleaching powder into a paste with 400 c.c. of 
water and rinse it into the flask with the remaining 400 c.c. 
Add the acetone and attach the flask to the condenser. Heat 
cautiously until the reaction sets in, which is indicated by the 
frothing of the liquid. Remove the flame for a time, and when 
the reaction has moderated, boil the contents until no more 
chloroform distils. This is easily determined by collecting the 
distillate in a test-tube and observing if any drops of heavy 
liquid are present. The distillate is shaken with dilute caustic 
soda solution in a separating funnel and the lower layer of 
chloroform run into a distilling flask. A few pieces of solid 
calcium chloride are added and left until the liquid is clear, 
when it is distilled from the water-bath with a thermometer 
inserted into the neck of the flask. Yield about 40 grams. 



ACETOXIME 71 



The bleaching powder acts as though it consisted of a 
compound of calcium hydrate and chlorine, and the process 
probably occurs in two stages. 

1. CH 3 .CO.CH 3 +3C1 2 = CH 3 .CO.CC1 3 + 3HC1. 

2. 2CH 3 .CO.CCl 3 + Ca(OH) 2 = (CH 3 .COO) 2 Ca + 2CHCl s . 

Trichloracetone is first formed, which is then decomposed by 
the lime into calcium acetate and chloroform. 

Properties. Colourless liquid possessing a sweet smell, b. p. 
60 62; sp.gr. 1*498 at 15; veiy slightly soluble in water; 
non-inflammable. As chloroform slowly decomposes in presence 
of air and sunlight into phosgene, it is usual to add a little 
alcohol to the commercial product, which arrests the change. 
Pure chloroform is neutral to litmus, has no action on silver 
nitrate solution and does not discolour concentrated sulphuric 
acid when shaken with it for an hour or left for a day. 

Reactions. i. Heat a few drops with double its volume of 
methyl alcoholic potash. On the addition of water a clear 
solution is obtained. Potassium formate and chloride are 
formed. CHC1 3 + 4KOH = 3KC1 + HCO.OK + 2H 2 O. 

2. Bring into a test-tube two drops of chloroform, one drop of 
aniline and I c.c. of alcoholic potash and warm in the fume 
atpboard. Note the intolerable smell of phenyl carbamine 
(carbamine reaction), CHC1 3 + C C H 5 NH 2 + 3KOH = C 6 H 6 NC-|- 
3KC1 + 3H 2 O. Wash out the contents of the test-tube in the 
fume cupboard. 

PREPARATION 9. 
CH, 

Acetoxime, C:NOH 

i 

CH 3 
V. Meyer, Fanin, Ber., 1882, 15, 1324. 

5 grms. hydroxylamine hydrochloride in 10 c.c. water 
3 caustic soda in 10 c.c. water 

6 (7'6 c.c.) pure acetone. 

Add the acetone to the mixture of the hydroxylamine 
hydrochloride and caustic soda in a small flask. The flask is 
then corked and left for twenty-four hours, during which the 



72 PRACTICAL ORGANIC CHEMISTRY 

crystalline oxime separates. The presence of any free hydroxyl- 
amine is then tested in a few drops of the liquid with Fehling's 
solution, or by merely adding a drop or two of copper sulphate, 
then a sufficient quantity of caustic soda to produce a clear blue 
solution and warming. An orange-red precipitate of cuprous 
oxide indicates uncombined hydroxylamine. If no free 
hydroxylamine is present, the liquid is shaken up with an equal 
volume of ether, in which the acetoxime dissolves. The 
ethereal solution is separated and the process repeated twice 
with fresh ether. The united ethereal extract is filtered, if 
necessary, through a dry filter into a distilling flask. The 
greater part of the ether is distilled off on the water-bath. The 
remaining liquid is poured into a glass basin and the rest of the 
ether left to evaporate in the air, the last traces being removed 
by heating for a few minutes on the water-bath. The acetoxime 
separates out on cooling in colourless needles. It is dried on 
a porous plate and recrystallised from a little petroleum spirit 
m. p. 6162. Yield 4 5 grams. 

CH 3 .CO.CH 3 + NH 2 OH.HC1 + NaOH 

= CH 3 .C:NOH.CH 3 + NaCl + 2H 2 O 

Properties. Colourless needles ; m. p. 60. 

Reaction. Boil a small quantity for a few minutes with dilute 
hydrochloric acid, and test with Fehling's solution. The oxime 
is decomposed into acetone and hydroxylamine, 

CH 3 .C(NOH).CH 3 +H 2 O = CH 3 .CO.CH 3 +NH 2 OH. 

Melting-point Determination. For this purpose the 
following apparatus is used (Fig. 53). A small sample of finely 
powdered substance, which has been carefully dried, is introduced 
into a capillary tube of about i mm. inside diameter sealed at 
one end. The tube is made from soft thin-walled glass tubing, 
about 15 mm. diameter, by rotating it in the blow-pipe flame until 
the glass softens, and then quickly drawing it out. The long 
capillary is then broken into lengths of about 7 cm. (T\ in.) by 
scratching across with a writing diamond, and each short tube 
is sealed at one end. To introduce the substance, it is con- 
venient to scoop up the finely powdered material off a watch 
glass with the open end. By tapping the closed end on 
the bench, the powder is shaken down. The quantity intro- 
duced should occupy a length of about 2 3 mm. when tightly 



MELTING-POINT DETERMINATION 



73 



packed. The tube is attached to a thermometer (preferably with 
a very small bulb) so that the substance is level with the bulb. The 
attachment may be made by a narrow rubber ring or by simply 
moistening the side of the capillary with the thermometer bulb, 
which has been dipped in the liquid in the bath, and then 
pressing it against the thermometer stem. The thermometer 
passes through a cork inserted into a round flask with a long 
neck, the bulb of which is three-quarters filled with concentrated 
sulphuric acid, glycerol, or castor oil. The flask is clamped to a 




FIG. 53. 

retort stand and is heated very gradually by a small flame. In- 
stead of clamping the flask to a retort stand, it can be fixed in a 
small brass tripod, shown in Fig. 53, which fits on to an ordinary 
laboratory tripod and from which it can be removed when not 
required. 1 When a certain temperature is reached the substance, 
if pure, melts suddenly within one or two degrees. When 
approaching the melting-point, it is desirable to remove the 
flame or turn it very low so that the rise of temperature is very 
gradual. If the liquefaction is protracted, it is an indication 
that the substance is not pure. The melting-point, obtained in 
this way, to be quite accurate, must be corrected for the 

1 The apparatus (flask and stand) can be purchased from Mr. J. Watkinson, Physics 
Department, The University, Leeds, price 25. yi. t postage included. 



74 PRACTICAL ORGANIC CHEMISTRY 

temperature of the thread of mercury outside the liquid, the 
same formula being used as in the correction for the boiling- 
point (see p. 58). When the acid becomes discoloured, a crystal 
of potassium nitrate will remove the colour on warming. 

Acetic Acid, CH 3 .CO.OH. 

Commercial acetic acid is manufactured from pyroligneous 
acid obtained in the destructive distillation of wood. The latter 
is neutralised with lime, and separated by distillation from wood- 
spirit and acetone. The crude calcium acetate, which has a 
dark colour, is then distilled with the requisite quantity of con- 
centrated hydrochloric acid. Anhydrous or glacial acetic acid 
is obtained by distilling fused sodium acetate with concentrated 
sulphuric acid. 

Properties. Colourless liquid with pungent smell ; b. p. 
119 ; m. p. 167 ; sp. gr. 1*055 at I 5- It should not decolorise 
a solution of permanganate. The vapour of the boiling acid is 
inflammable. 

Reactions. Add a few drops of alcohol to the same quantity 
of acetic acid, and an equal volume of concentrated sulphuric 
acid. Warm gently and notice the fruity smell of ethyl acetate. 
Neutralise a few drops of acetic acid by adding excess of 
ammonia and boiling until neutral. Let cool and add a drop 
of ferric chloride. The red colour of ferric acetate is produced. 
On boiling, basic ferric acetate is precipitated. 

Heat a very small quantity of potassium acetate with an equal 
bulk of arsenious oxide. The disagreeable and poisonous vapour 
of cacodyl oxide is evolved. 

4CH 3 .COOK + As 2 3 = As 2 (CH 3 ) 4 O + 2CO 2 + 2K 3 CO t 

PREPARATION 10. 
Acetyl Chloride, CH 3 .CO.C1. 

Gerhardt, Ann. Chim. P/iys., 1853, (3) 37, 285 ; Bechamp 
Compt. rend., 1855, 40, 944, and 1856, 42, 224. 
50 grms. glacial acetic acid. 
40 phosphorus trichloride. 

Fit up the apparatus shown in Fig. 54. It consists of a distilling 
flask (250 c.c.), which is attached to a condenser. A small 



ACETYL CHLORIDE 



75 



filter flask serves as receiver, the side tube being attached 
to a' calcium chloride tube. The distilling vessel is provided 
with a cork, through which a tap-funnel is inserted. The flask 
is cooled in cold water in the water-bath (outlined in Fig. 54), 
whilst the phosphorus trichloride is slowly run in from the tap- 
funnel.* When the phosphorus chloride has been added, the 
water in the water-bath is warmed to 40 50, until the evolu- 
tion of hydrochloric acid gas, which at first is very rapid, begins 
to abate. The water-bath is then heated to boiling until 




FIG. 54- 

nothing further distils. The distillate is no.v redistilled as 
before, but with a thermometer, and the distillate collected 
at the boiling-point of acetyl chloride (53 56). Yield 45 
grams. 

3CH 3 .COOH + 2PC1 3 = 3CH 3 .COC1 + P 2 O 3 +3HC1. 

Properties. Colourless liquid with a pungent smell : it fumes 
in contact with moist air ; b. p. 55 ; sp. gr. 1*105 at 2O - 

Reactions, i. Add a few drops of acetyl chloride to about 
5 c.c. of water in a test-tube. The acetyl chloride sinks to the 
bottom of the test-tube, but on shaking rapidly dissolves, and 
heat is evolved. The acetyl chloride is converted into acetic acid 
and hydrochloric acid. 

CH 3 .COC1 + H 2 O = CH 3 .CO.OH + HC1. 

2. To about i c.c. of ethyl alcohol in a test-tube, add I c.c. 
of acetyl chloride drop by drop, cooling under the tap. Then 



76 PRACTICAL ORGANIC CHEMISTRY 

add about i c.c. of a solution of common salt. Ethyl acetate, 
recognised by its fragrant smell, separates out on the surface of 
the liquid. 

CH 3 .COC1 + C 2 H 5 OH = CH 3 .CO.OC 2 H 5 + HC1. 

3. Add two drops of acetyl chloride to a drop of aniline. A 
vigorous action occurs, and a solid separates. This is acetanilide, 
and may be obtained in larger crystals by dissolving in boiling 
water and cooling slowly. 

CH 3 .COC1 + C 6 H 6 NH 2 = C 6 H 5 NH.CO.CH 3 + HC1. 
See Appendix, p. 241. 

PREPARATION n 

Acetic Anhydride (Diacetyl Oxide), CR 3 CO/ ' 
Gerhardt, Ann. Chim. Phys., 1853, (3) 37, 311. 

55 grms. sodium acetate (fused). 
40 acetyl chloride. 

A retort (250 c.c.) is attached to a short condenser and 
receiver, which is furnished, as in the previous preparation, with 
a calcium chloride tube. The tubulus of the retort is closed by 
a cork, through which a tap-funnel is fixed. The fused sodium 
acetate is prepared by fusing crystallised sodium acetate, 
(CH 3 .COONa + 3H 2 O). The sodium acetate (100 grams) is 
placed in a shallow tin and heated over a Bunsen burner. 
It first melts in the water of crystallisation, after which it 
becomes solid, and finally melts again as the temperature rises. 
When completely melted it is allowed to cool, powdered, and 
introduced into the retort. The acetyl chloride is gradually 
added through the tap-funnel, the retort being cooled in water.* 
When the acetyl chloride has been added, the contents of the 
retort are well stirred by means of a thick glass rod pushed 
through the tubulus. The retort is now closed by an ordinary 
cork or stopper, and heated over a small flame, which should 
be moved about to prevent the retort cracking. When nothing 



ACETAMIDE 77 



further distils, the retort is allowed to cobl somewhat, and the 
distillate poured back and redistilled. Finally it is distilled 
from a distilling flask with a thermometer, and collected at 
130 140. Yield 40 grams. 

CH 3 .COC1 + CH 3 .CO.ONa = (CH 3 .CO) 2 O + NaCl. 

Properties Colourless liquid with an irritating smell ; b. p. 
138 ; sp. gr. roS at 15. 

Reactions Repeat the three experiments described under 
acetyl chloride. The result is the same in each case ; but as 
the acetic anhydride reacts less readily than acetyl chloride, the 
mixture requires to be warmed. 



2. 3 ' + C 2 H 6 H = CH 3 .CO.OC 2 H 6 + CH 3 .COOH. 



In Reaction 2, combination is not complete, even on boiling, 
and a little dilute caustic soda must be added to decompose the 
unchanged acetic anhydride. In Reaction 3, the product remains 
liquid until water is added, when it becomes solid, and on 
heating dissolves. See Appendix^ p. 242. 

PREPARATION 12. 
Acetamide, CH-j.CO.NHjj. 

Hofmann, Ber., 1882, 15, 981 ; Rosanoff, Gulick, and Larkin, 
/. Amer. Chem. Sac., 1911, 33, 974. 

100 grms. ammonium acetate. 

Acetamide may be obtained by boiling 100 grams of am- 
monium acetate with 120 grams of glacial acetic acid for 5 6 
hours with reflux condenser and then distilling the product in 
the ordinary way. A considerable quantity of* water, and 
acetic acid distils, and when the temperature reaches 180 the 
apparatus shown in Fig. 55 is used in which the condenser is 



PRACTICAL ORGANIC CHEMISTRY 



replaced by a straight wide tube. The distillate solidifies, and 
consists mainly of acetamide. The yield is about 60 grams. 
A good result is also obtained by first heating the ammonium 




FIG. 55. 



acetate in sealed tubes. The ammonium acetate, if not procur- 
able, may be prepared by adding to 70 grms. glacial acetic acid, 
warmed in a basin on the water-bath, about 80 grms. powdered 
ammonium carbonate until the acid is neutralised, which is re- 
cognised by diluting a sample with a little water, and testing 
with litmus. 

Heating under Pressure. Two tubes are made from the 
usual thick-walled tubing by sealing one end (see p. 24). These 
are gently warmed, and the melted acetate poured in until they 
are about half full. They are then sealed in the manner described 
on p. 24. The tubes are then placed in a tube furnace (p. 23) 
and gradually heated to 200, at which temperature they are 
maintained for 5 6 hours. Without removing the tubes from the 
furnace they are allowed to cool, and the capillary end opened by 
holding a Bunsen burner to the tip until fused, when the pressure 
within perforates the glass. If a deep file scratch is then made 
about an inch below the sealed end and the end of a red-hot glass 
rod held against the scratch, a deep crack is produced and the end 
easily removed. After heating, the tubes contain a clear, oily- 
looking liquid, which consists of an aqueous solution of acetamide, 
together wit^ some unchanged acetate. The contents are poured 
into a distilling flask and distilled with a straight tube as 
condenser, and the portion boiling above 180 collected in a 



ACETONITRILE 79 



small beaker. This distillate, on standing, almost completely 
solidifies to a colourless crystalline mass. It is freed from 
mother-liquor by spreading on a porous plate, and purified by a 
second distillation. The acetamide has then a nearly constant 
boiling-point. Yield, about 40 grams. 

CHj.CO.ONH 4 = CH 3 .CONH 2 + H 2 O. 

Properties. Colourless, rhombohedral crystals, having a 
peculiar smell of mice. This is due to impurity, which may be 
removed by recrystallising from benzene ; m.p. 82 ; b.p. 222 ; 
easily soluble in water and alcohol. 

Reaction. i. Boil a small quantity of acetamide with caustic 
soda solution. Ammonia is evolved, and sodium acetate is found 
in solution, CH 3 .CONH 2 + NaOH = CH 3 .CO.ONa + NH 3 . 
See Appendix, p. 243. 

PREPARATION 13. 

Acetonitrile (Methyl cyanide), CH 3 .CN. 
Dumas, Malaguti and Leblanc, Annalen, 1848, 64, 332. 

10 grms. acetamide 

15 phosphorus pentoxide. 

The phosphorus pentoxide is introduced into a small dis- 
tilling flask (200 c.c.) attached to a short condenser. As the 
pentoxide absorbs moisture rapidly and becomes sticky, it is 
convenient to push the neck of the distilling flask through a 
cork which fits the phosphorus pentoxide bottle, and then to 
shake in the oxide until the required weight is obtained. The 
powdered acetamide is immediately introduced and shaken up, 
and the mixture distilled over a small flame, which is constantly 
moved about. Add to the distillate about half its volume 
of water, and then solid potassium carbonate, until no more 
dissolves. The upper layer of liquid, which consists of methyl 
cyanide, is separated and distilled over a little fresh phosphorus 
pentoxide with thermometer. Yield, about 5 grams. 

CH 3 .CO.NH 2 - H 2 O = CH 3 CN. 

Properties. Colourless liquid with peculiar smell ; b. p. 82. 
Reaction. Boil a few grams of the acetonitrile with three 



So PRACTICAL ORGANIC CHEMISTRY 

times its weight of a mixture of 2 vols. water and 3 vols. con- 
centrated sulphuric acid for an hour with a long upright tube 
or air-condenser. Distil a few c.c. of liquid, and test the distillate 
for acetic acid, 2CH 3 .CN + H 2 SO 4 + 4H 2 O = 2 CH 3 .COOH + 
(NH 4 ) 2 SO 4 . See Appendix, p. 244. 

PREPARATION 14. 
Methylamine Hydrochloride, CH 3 .NH 2 .HC1. 

Wurtz, Compt.rend., 1848, 28, 223 ; Hofmann, er., 1882, 14, 
2725, and Ser., 1883, 15, 407 and 762. 

20 grms. acetamide 

54 (18 c.c.) bromine 

56 caustic potash. 

The dry acetamide and bromine are mixed in a flask ( litre), 
and whilst the mixture is cooled in water, a 10 per cent, 
solution of caustic potash (about 20 grams KOH) is added, 
until the dark brown liquid changes to a deep yellow colour. 
The solution, which now contains potassium bromide and 
acetmonobromamide, is slowly added from a tap-funnel in- 
serted, together with a thermometer, into the neck of a distilling 
flask (i litre). The flask contains a concentrated solution of 
caustic potash (56 grams in 100 c.c. of water), heated to 60 70. 
Heat is evolved, and care must be taken that the rise of tem- 
perature does not greatly exceed the above limits. The reaction 
goes on quietly, and the yellow solution is gradually decolourised. 
The mixture is then digested for a short time at the above 
temperature until the yellow colour completely disappears. A 
few bits of broken pot are now introduced into the flask, which 
is closed with an ordinary cork, and the liquid distilled over 
wire-gauze. The vapours of methylamine and ammonia, which 
are cooled, are passed by means of a bent adapter, attached to 
the end of the condenser, into dilute hydrochloric acid contained 
in the receiver. Care must be taken that the adapter does not 
dip too far into the acid, or liquid may be sucked back into the 
condenser and distilling flask. When the distillate is no longer 
alkaline, and consequently all the methylamine has been driven 
over, the hydrochloric acid solution is evaporated to dryness on 



Si 



the water-bath, and the colourless crystalline residue extracted 
repeatedly with small quantities of absolute alcohol, which 
dissolves out the methylamine salt from the ammonium chloride. 
From the hot alcoholic solution foliated crystals separate out 
on cooling. 

CH 3 .CONH 2 + Br 2 + KOH = CH 3 .CONHBr + KBr + H,O 

Acetamide. Acetmonobromamide. 

CHs-CONHBr + KOH = CH 3 .N:CO + KBr + H 2 O 

Methylisocyanate 

CH 3 .N:C:O + 2KOH - CH 3 .NH 2 + K 2 CO 3 

Methylamine. 

Properties. Large deliquescent tablets, which melt at 227, 
and sublime above that temperature, with slight decomposition. 
The base is liberated on warming with caustic soda, as an in- 
flammable gas with strong ammoniacal smell. See Appendix, 
p. 245. 

PREPARATION 15. 
Ethyl Acetate (Acetic Ether), CH 3 .CO.OC 2 H 5 . 

Scheele, Chemical Essays, 1782, p. 307; Frankland, Duppa, 
Phil Trans., 1865, 156, 37 ; Pabst, Bull. Soc. Chim., 1880 33, 
35- 

50 c.c, cone, sulphuric acid. 

50 c.c. absolute alcohol. 1 

Mixture of equal volumes of glacial acetic acid (100 c.c.) 
and s.bsolute alcohol (100 c.c.). 

A distilling flask ( litre) is attached to a condenser and 
receiver. The flask is provided with a cork, through which a 
separating funnel is inserted. The mixture of 50 c.c, of con- 
centrated sulphuric acid and 50 c.c. of absolute alcohol is 
poured into the flask, which is then heated in a bath of paraffin 
wax or fusible metal 2 to 140, and kept at this temperature. 
The mixture of equal volumes of acetic acid and alcohol is 

1 Methyl acetate may be made in precisely the same way, using methyl alcohol. 
The product is then fractionated and collected at 57 63". 

2 A fusible metal bath has the advantage over -an oil-bath of neither smelling nor 
being liable to catch fire. It is made by melting in a small cooking pan one part 
of lead and two parts of bismuth. This alloy is fluid above 120. 

COHEN'S ADV. p. o. c. G 



82 PRACTICAL ORGANIC CHEMISTRY 

now added, drop by drop, from the tap-funnel at the speed at 
which the liquid distils, as in the preparation of ether (p. 59) 
When all the mixture has been added, the distillate, which con- 
tains the ester, and also acetic acid, alcohol, ether, and 
sulphurous acid, is shaken in a separating funnel with a strong 
solution of sodium carbonate (50 c.c.) until the upper layer of 
ethyl acetate ceases to redden blue litmus. The lower layer is 
removed as completely as possible, and a strong solution of 
calcium chloride (50 grams in 50 c.c. of water) added, and the 
shaking repeated. The lower layer of calcium chloride is run 
off, and the ethyl acetate carefully decanted from the mouth of 
the funnel into a dry distilling flask. A few pieces of solid 
calcium chloride are added, and, after standing over night, the 
ethyl acetate is distilled from the water-bath with a thermo- 
meter in the neck of the flask. The portion distilling below 
74 contains ether, that boiling at 74 79 is mainly ethyl 
acetate, and is separately collected. Yield, 80 per cent, of 
the theory. 

C 2 H 5 (OH) + H 2 S0 4 = C 2 H 6 .H.S0 4 + H,O. 
C 2 H 6 HSO 4 + CH 3 .CO.OH = CH 3 .COOC 2 H 6 +~H 2 SO 4 . 

Properties. Colourless liquid, with an agreeable fruity smell ; 
b. p. 77; sp. gr. 0-9068 at 15; soluble in about 11 parts of 
water ; miscible in all proportions with alcohol, ether, and acetic 
acid, 

Reaction. Weigh out 20 grams of ethyl acetate, and heat in a 
round flask with three times its volume of aqueous potash 
(iKOH : 3H 2 O) with upright condenser over wire-gauze. Add 
a small piece of porous pot to prevent bumping. After an hour 
or so the upper layer of ethyl acetate will have disappeared. Distil 
the product with a thermometer until the temperature reaches 
100. Add solid potassium carbonate to the distillate until no 
more dissolves. Separate the top layer of alcohol and dehydrate 
over fresh potassium carbonate or quicklime. Distil with a 
thermometer and weigh the distillate. Neutralise the alkaline 
liquid, from which the alcohol was first distilled, with dilute sul- 
phuric acid, and evaporate to dryness on the water-bath. Break 
up the solid residue, and distil with concentrated sulphuric acid 
(20 c.c.) until the thermometer marks 130. Redistil and collect 



ETHYL ACETOACETATE 83 

between 115 and 120. Weigh the distillate. This process 
furnishes an example of hydrolysis or saponification, 

CH 3 .COOC 2 H 5 + H 2 O = CH 3 .COOH + C 2 H 5 OH. 
See Appendix, p. 247. 

PREPARATION 16, 

Ethyl Acetoacetate (Acetoacetic Ester), 
CH 3 .CO.CH 2 .CO.OC 2 H 5 . 

Geuther, Jahresb., 1863, p. 323 ; Frankland, Duppa, Phil. 
Trans., 1865, 156, 3> , Wislicenus, Annalen, 1877, 186, 161. 

200 grms. ethyl acetate. 
20 sodium. 

The ethyl acetate, carefully dehydrated as described in the 
previous preparation, is introduced into a round flask ( litre) 
connected with a long upright condenser. 20 grams well pressed 
sodium, cut into thin slices, are quickly added, and the flask 
cooled in water. After a short time a brisk reaction sets in, and 
ultimately the liquid boils. When the first action is over, and 
no further evolution of heat occurs, the mixture is heated on the 
water-bath, without detaching the condenser, until the sodium is 
completely dissolved. A 50 per cent, acetic acid solution is at 
once added and well shaken, until the liquid is acid (about 
100 c.c.), and then an equal volume of concentrated brine. The 
liquid divides into two layers ; the upper one, consisting of 
acetoacetic ester and unchanged ethyl acetate, is carefully 
separated. It is distilled over wire-gauze until the thermometer 
marks 100, and all the ethyl acetate has been removed. The 
distillate is now collected in five fractions (100 130, 130 135, 
165175, 175185, 185200). The fraction distilling at 
175 185 is nearly pure acetoacetic ester. Yield 30 40 grams. 
A further quantity may be obtained by redistilling the other 
fractions ; but it is undesirable to repeat the process frequently, 
as acetoacetic ester gradually decomposes at the boiling point. 
It is for this reason that Gattermann recommends the fractional 
distillation to be carried out in -vacua. 

The brown residue remaining in the distilling flask solidifies, 
on cooling, to a crystalline mass consisting chiefly of dehy- 

G 7. 



84 PRACTICAL ORGANIC CHEMISTRY 

dracetic acid C 8 H 8 O 4 . It is converted into the sodium salt by 
boiling with soda solution with the addition of animal char- 
coal. The sodium salt crystallises from the filtrate. On 
adding dilute sulphuric acid, the free acid is obtained as colour- 
less needles ; m. p. 109. 

1. 2(^H 8 OH + Naj, = 2NaOC 2 H 5 + H 2 

/ONa 

2. CII 3 CO.OC 2 H 5 + NaOC 2 H 5 = CH 3 .C^OC 2 H 5 

\OC 2 H 5 

/ONa 

3. CII 3 .C^OC 2 H 5 + CH 3 .CO.OC 2 H 5 = CH 3 .C(ONa):CH.CO.OC 2 H 5 

X OC 2 H 5 

+ 2C 2 H 5 OH. 

4. CII 3 . C(ONa) :CH. CO. OC 2 H 5 + C 2 II 4 O 2 = CH 3 . CO. CH 2 . CO. OC 2 H 5 

+ CH 3 .CO.ONa 



The formation of ethyl acetoacetate occurs, according to 
Claisen, in four steps. The presence of a small quantity of 
alcohol gives rise to sodium ethylate, which forms an additive 
compound with ethyl acetate. The latter unites with a second 
molecule of ethyl acetate yielding the sodium salt of ethyl aceto- 
acetate, and splitting off alcohol, which reacts with fresh metallic 
sodium. The sodium salt on acidifying passes into the tauto- 
meric (ketonic) form of acetoacetic ester. 

Properties. Colourless liquid possessing a fruity smell ; b. p, 
181; sp. gr. I '03 at 15. Boiled with dilute caustic potash, 
the ester decomposes into alcohol, carbon dioxide, and acetone 
(ketonic decomposition), with strong or alcoholic caustic potash, 
sodium acetate and alcohol are formed (acid decomposition). 

Reactions. I. Add a drop of ferric chloride dissolved in alcohol 
to a few drops of the ester ; a deep violet coloration is produced. 

2. Add i c.c. of a saturated alcoholic solution of cupric acetate 
to a few drops of the ester, a bluish-green crystalline precipitate 
of copper acetoacetic ester, (C 6 H 9 O 3 ) 2 Cu, is formed. See 
Appendix, p. 248. 

Distillation in vacuo. The apparatus is shown in Fig. 56. 
The distilling flask is provided with a thermometer and attached 
to a short condenser and receiver. The receiver consists of a 



DISTILLATION IN VACUO 



second distilling flask, which is tightly attached to the end of 
the narrow condenser tube, figured at a and connected by the 
side limb by means of pump-tubing to a water-jet aspirator and 




FIG. 56. 

mercury-gauge. Some small bits of porous pot are placed in 
the flask, which is heated in a paraffin bath, and the apparatus 
exhausted to about 35 40 mm. pressure. At this pressure ethyl 
acetoacetate boils at about gcr. The following table gives the 
temperatures corresponding to different pressures : 



/. 

74 . 


mm. 

. 14 


t. 

94 


mm. 

4? 


7Q 


" 18 


Q7 . 


. SO 


QC 


. 20 


100. 


. 80 



The chief inconvenience which attends distillation in vacua is 
the bumping of the liquid in the distilling flask. This may be 
moderated or removed by various devices, such as the introduc- 
tion of porous pot, capillary glass tubes, &c., or by driving a 
rapid stream of fine air-bubbles through the liquid. For this 
purpose a Claisen flask (Fig. 57 ), may be used with advantage. 
A tube is drawn out into a fine capillary and is open at both 
ends, the wide end being attached to a short piece of rubber 
tubing and screw-clip. This tube is inserted through a cork lA 



86 



PRACTICAL ORGANIC CHEMISTRY 



the straight neck of the flask, whilst the thermometer is fixed 
in the second neck, which is attached to the condenser. The 
stream of air-bubbles is regulated by the clip. Instead of the 

C 




FIG. 58. 



FIG. 57. 




FIG. 59. 



long manometer shown in Fig. 56, a more compact, and, for 
low pressures, a more convenient form is shown in Fig. 58. 
If the distillate has to be separated into fractions, it is unde- 
sirable to interrupt the boiling. Various forms of apparatus 
for effecting this object are shown in Figs. 59 61. The 
apparatus (Fig. 59) consists of a double receiver a and b ; c and 
e are ordinary two-way taps, whilst d is a three-way tap pierced 
lengthwise and crosswise as shown in section at f. The 





FIG. 60. 



FIG. 61. 



aspirator is attached to the limb marked with the arrow. During 
the distillation the taps c and d connect the apparatus with the 
aspirator whilst e is closed. The distillate collects in a. When 
this fraction is to be removed, c is closed and e is opened. The 



MONOCHLORACETIC ACID 87 

liquid is thereby transferred to the second receiver b ; e is now 
closed, c is opened and d turned so as to let air into b ; b may 
now be removed and replaced by a similar vessel and the pro- 
cess repeated. Fig. 60 needs little explanation. There are two 
or more receivers on one stem. By rotating the stem the dis- 
tillate falls into one or other receiver. Fig. 61 consists of a 
vacuum vessel containing a series of test-tubes which can be 
moved in turn, under the end of the condenser, by means of a 
vertical axis. It is often preferable to heat the distilling flask 
in an oil or metal bath instead of using wire-gauze. Distilling 
flasks above 250 c.c. capacity should not be used for low pres- 
sures, as they may collapse. For high boiling liquids, or for 
substances which may solidify in the condenser, a condenser 
tube without water-jacket is used. A convenient form of con- 
denser tube is shown at a, Fig. 56. It consists of straight tube 
fused on to a short narrower tail-piece. In certain cases it is 
found convenient to insert the side- tube of the distilling flask 
directly into the neck of the receiver (see p. 94). 

PREPARATION 17. 

Monochloracetic Acid, CH 2 C1.CO.OH. 
R. Hofmann, Annalen, 1857, 102, i ; Auger, Behal, Bull. Soc. 
CAtm., 1889, (3) 2, 145- 

100 c.c. glacial acetic acid. 
10 grms. red phosphorus. 

Fit up the apparatus shown in Fig. 62.* It consists of a stone- 
ware jar one-third full of pyrolusite in lumps, and fitted with exit 
tube and tap-funnel. It is heated on a sand-bath over a small 
flame, whilst concentrated hydrochloric acid is allowed to drop 
in from the tap-funnel. A rapid current of chlorine is thus 
evolved, which is dried by passing through concentrated sul- 
phuric acid in the Woulff bottle. The Woulff bottle has a safety 
and exit tube, the latter being connected with a straight tube 
passing to the bottom of the retort. The retort is tilted upwards 
. and connected with an upright condenser, which is furnished 
with an open calcium chloride tube. The acetic acid and phos- 
phorus are placed in the retort, and heated on the water-bath. 
The retort and contents are weighed at the commencement of 
the operation on a rough balance. A rapid current of chlorine 



88 



PRACTICAL ORGANIC CHEMISTRY 



is then passed through for six to twelve hours, and the retort 
occasionally weighed, until the increase in weight (50 grams) 
roughly corresponds to the formation of monochloracetic acid. 
The operation is stopped when a sample solidifies on cooling 
and on rubbing with a glass rod. The action of the chlorine is 
greatly facilitated by sunlight. The yellow liquid in the retort 
is poured into a distilling flask, and distilled over wire-gauze. 
Some acetyl chloride and unchanged acetic acid first distil, 




JMG. 62. 

after which the temperature rises and the fraction boiling at 
150 190 is collected separately. It is advisable to run the 
water out of the condenser when the temperature approaches 
170, as the acid may solidify and block the condenser-tube. 
The distillate solidifies on cooling. Any liquid is drained off 
at once, and the solid is redistilled and collected at 180 190. 
It is nearly pure chloracetic acid. Yield 80 100 grams. 

CH 3 .CO.OH + Cl s = CH 2 C1.CO.OH + HC1. 

The phosphorus acts as a "chlorine carrier" by forming 
probably phosphorus pentachloride, and then reverting to the 
state of trichloride. 

Properties. Colourless crystals ; m. p. 63 ; b. p. 185 187 ; 
readily soluble in water, and deliquescent in moist air. It 
causes blisters on the skin. See Appendix, p. 252. 



MONOBROMACETIC ACID 



89 



PREPARATION 18. 
Monobromacetic Acid, CH,Br.COOH. 

Hell, fier., 1881, 14, 891 ; Volhard, Annalen, 1887, 242, 
141 ; Zelinsky, Ber., 1887, 20,J2O26. 

30 grms. (30 c.c.) glacial acetic acid. 
IO 5 (35 c - c -) bromine. 
5 red phosphorus. 

All the above substances must be dry. The acetic acid is frozen in 
ice, and any liquid drained off, and the red phosphorus is washed 
with water to free it from phosphoric acid, dried in the steam oven, 
and kept over sulphuric acid in a desiccator until required. The 
bromine is placed in a separating funnel with half its volume of 
concentrated sulphuric acid overnight, and 

then separated. The apparatus is shown in 
Fig. 63 . It consists of a round flask (250 c.c.) 
attached to an upright condenser, which is 
provided with a cork. A tap-funnel con- 
taining the bromine passes through one 
hole, and a wide bent tube, attached at its 
lower end to a funnel, passes through the other. 
As a large quantity of hydrobromic acid is 
evolved in the reaction, the funnel is made to 
touch the surface of water contained in a 
beaker, whereby it is completely absorbed. 
The phosphorus and acetic acid are placed 
in the flask, and bromine dropped in from the 
tap-funnel.* A vigorous reaction occurs, and 
the liquid becomes very warm. After half 
the bromine has been added the action 
moderates, and the remainder may be run in 
more quickly. When the whole has been 
added, the liquid is boiled gently until the colour of the 
bromine disappears. It is now allowed to cool, and the 
liquid decanted into a distilling flask for distillation in vacua. 
Care must be taken not to touch the substance with the hands, 
as even a small quantity produces very unpleasant sores. The 
apparatus for distilling in vacua is shown in Fig. 56 (p. 85). 




FIG. 63. 



90 PRACTICAL ORGANIC CHEMISTRY 

The distilling flask is provided with a thermometer, and attached 
to a short condenser and receiver. The receiver consists of a 
second distilling flask, which is tightly attached to the end of the 
condenser and connected by the side limb with pump-tubing to 
a water-jet aspirator and mercury manometer. Some small 
bits of of porous pot are placed in the flask, and the apparatus 
exhausted to about 50 60 mm. pressure. The liquid distils at 
a nearly constant temperature (about 50 53), and consists of 
nearly pure bromacetylbromide. The calculated quantity of 
water is added to convert it into bromacetic acid, when the liquid 
forms a solid crystalline mass.* It may be purified by distilla- 
tion at atmospheric pressure with condenser-tube only, the 
portion boiling above 165 being collected separately. 

3CH,.COOH + P + iiBr = 3CH 2 Br.COBr + HPO 3 + 5HBr. 

Bromacetvl bromide. 



CH 2 Br.COBr. + H 2 O = Ch 2 Br.CO.OH + HBr. 

Broinacetic acid. 

Properties. Colourless crystals; m. p. 50 51; b. p. 208. 
See Appendix, p. 252. 

PREPARATION 19. 
G-lycocoll (Glycine, Aminoacetic Acid). C 

Braconnot, Ann. Chim. Phys., 1820, (2) 13, 114; Perkin, 
Duppa, Trans. Chem. Soc., 1859, 11, 22 ; Kraut, Annalen, 1891, 
266, 292. 

50 grms. chloracetic acid. 

50 c.c. water. 

600 c.c. ammonia, 26'$ per cent. (sp. gr. o'9O7 at 14). 
Fit up the apparatus shown in Fig. 64. It consists of a large 
wide-necked bottle, in which the ammonia solution is placed. 
The solution is stirred by a mechanical stirrer, rotated by means 
of a water-turbine. The solution of the chloracetic acid in 50 
c.c. water, is dropped in from a tap-funnel. After standing 
24 hours the liquid is poured into a flask, and the excess of 
ammonia is removed by passing in a current of steam, and 
evaporating at the same time on the water-bath until the last 
traces of ammonia disappear. The solution now contains gly- 



GLYCOCOLL 



cocoll and ammonium chloride. Precipitated carbonate of copper 
is added to the hot liquid until no further effervescence occurs, 
and some carbonate remains undissolved. It is filtered and 
evaporated down on the water-bath until crystallisation sets in. 
This is determined by removing and cooling a small portion in 
a test-tube or watch-glass. The blue needles of copper glycocoll, 
(C 2 H 4 NO 2 )2Cu.H 2 O, are filtered and washed, first with dilute and 
then with stronger spirit. The mother liquor may be further eva- 
porated, and a fresh quantity of crystals obtained. The copper 
salt is dissolved in water and precipitated hot with hydrogen 
sulphide, the free glycocoll passing into solution. The pre- 
cipitate is filtered and well washed, and the filtrate evaporated 





FIG. 64. 

to a small bulk on the water-bath. Crystals of glycocoll 
separate out. Yield 15-20 grams. The loss is due to the 
formation of di- and triglycolaminic acid, NH(CH,.COOH) 9 
and N(CH 2 COOH) 3 . 

CH 2 C1.COOH + 2NH 3 = CH 2 NH 2 .COOH + NH 4 C1. 

Properties. Large monoclinic crystals ; discoloured at 228 ; 
m.p. 232-236 ; scarcely soluble in alcohol and ether, readily 
soluble in water (i part glycocoll in 4 parts water). 

Reaction. i. Add a drop of copper sulphate to a solution of 
glycocoll, and notice the blue colour of the copper salt. 

2. Add a drop of ferric chloride to the solution. It gives a 
deep red colour. See Appendix, p. 254. 



92 PRACTICAL ORGANIC CHEMISTRY 



PREPARATION 20. 

CH 2 .NH 2 .HC1 
Glycocoll Ester Hydrochloride, | 

CO.OC 2 H 6 

Klages, Her., 1903, 36, 1506, Hantzsch and Silberrad, Ber,, 
1900, 33, 70. 

250 c.c. formaldehyde solution (40 per cent.). 

90 grams ammonium chloride (powdered). 
no potassium cyanide (in 200 c.c. water). 

63 c.c. glacial acetic acid. 

The first part of the process consists in the preparation of 
methyleneamino-acetonitrile. 



= CH 2 :N.CH 2 CN + 2H 2 O. 

The formaldehyde and ammonium chloride are mixed in a 
wide-necked glass jar cooled in a freezing mixture and 
stirred by means of a stirrer as shown in Fig. 64. When the 
temperature falls to 5 the potassium cyanide solution is slowly 
run in from a tap-funnel during three hours, the temperature 
being maintained below 10. When half the cyanide solution 
has been added the ammonium chloride will have com- 
pletely dissolved. Whilst 'the second half of the solution is 
being added, 63 c.c. of glacial acetic acid are dropped in from 
another tap-funnel at about the same rate, whilst the tempera- 
ture is kept below 15. As soon as the acetic acid is 
added a white crystalline substance begins to separate and 
gradually fills the liquid. The stirring is continued for another 
hour after the solutions have been added. The crystalline mass is 
filtered, washed with water and dried. The yield is 60 70 grams. 
Methyleneamino-acetonitrile melts at 129. Itmayberecrystallised 
from alcohol, but is usually pure enough for further treatment. 

On hydrolysis in presence of alcohol it breaks up into glycocoll 
ester hydrochloride, ammonium chloride and formaldehyde. 

CH 2 :N.CH 2 CN + 2H 2 O + C 2 H 5 OH + HC1 = (HC1)NH 2 .CH 2 .COOC 2 H 5 
+ NH 4 C1 + CH 2 O. 

Twenty-five grams methyleneamino-acetonitrile are added to 
170 c.c. of absolute alcohol previously saturated in the cold 
with hydrogen chloride. 




GLYCOCOLL ESTER HYDROCHLORIDE 93 

Preparation of Hydrogen Chloride. A filter flask 
(^ litre) is fitted with a rubber cork, through which a tap- 
funnel is inserted. The flask is filled one-third full of con- 
centrated hydrochloric acid and is attached to a wash-bottle 
containing a little concentrated sulphuric acid. A delivery 
tube is attached to the wash-bottle. The hydrogen chloride is 
generated by dropping concentrated sul- 
phuric acid from the tap-funnel into the 
flask containing the hydrochloric acid. 
As the gas is rapidly absorbed by the 
alcohol and may in consequence run 
back into the wash-bottle, it is advis- 
able to run in the acid rather more 
quickly at the beginning than is neces- 
sary later on and to generate the gas 
for a short time before passing it into 
the alcohol. The apparatus is shown 
in Fig. 65. 

When saturated, the mixture is boiled FIG. 65. 

for an hour with reflux condenser on 

the water-bath and filtered hot from the ammonium chloride 
which remains undissolved. On cooling, the greater portion of 
the ester hydrochloride crystallises. A further quantity may be 
obtained by concentrating the mother liquors. Yield 30 35 
grams. 

Properties, Colourless needles ; m. p. 144, soluble in hot 
alcohol, very soluble in water. 

Glycocoll Ester Hydrochloride from Gelatine. 

Mix 100 grams commercial gelatine or size with 300 c.c. con- 
centrated hydrochloric acid and shake until the gelatine is nearly 
dissolved ; then add a few fragments of porous pot and boil 
over wire gauze with reflux condenser for four hours. The 
dark coloured product is. now evaporated on the water-bath 
under diminished pressure in the apparatus shown in Fig. 66. 

It consists of two distilling flasks (i litre) fitted together by 
rubber corks, the one acting as distilling flask and the other as 
receiver. The receiver which is cooled by a stream of water 
is attached to a water-jet aspirator. A long capillary, which 
nearly touches the bottom of the flask, is inserted through the 



94 



PRACTICAL ORGANIC CHEMISTRY 



cork of the distilling vessel. It serves to agitate the liquid 
by introducing a stream of fine air-bubbles which keep it 
in constant motion. When the water is removed as far 
as possible, the residue, which forms, on cooling, a thick 
viscid mass, is mixed with 500 c.c. absolute alcohol. It is 
heated on the water-bath with reflux condenser for a short time 
with the addition of a little animal charcoal and filtered. The 
alcoholic solution is cooled in ice and saturated with dry 
hydrogen chloride (see p. 93). The liquid is then boiled for 




FIG. 66. 

half an hour on the water bath, cooled, and, after dropping in a 
crystal of the substance, left overnight. Glycocoll ester hydro- 
chloride crystallises in colourless needles (m. p. 144) and is 
filtered and washed with a little alcohol. Yield 1015 grams. 

PREPARATION 21. 

CH/H 
Diazoacetic Ester, X N 

COOC 2 H 5 

Curtius, J. prakt. Chem.^ 1888, 38, 401 ; Silberrad, Trans. 
Chem. Sac., 1902, 81, 600. 

25 grams glycocoll ester hydrochloride (in 50 c.c. of water). 
1 8 ,, sodium nitrite in fine powder. 



DIAZOACETIC ESTER 95 

The glycocoll ester and sodium nitrite are shaken together in 
a separating funnel (250 c.c.) until the nitrite is dissolved, a 
little water being added if necessary. Fifteen c.c. of ether are 
poured into the funnel, and when the temperature has sunk to 
about 5, two or three drops of a ten per cent, sulphuric acid 
solution are added. The mixture is now well shaken for a 
minute and the aqueous layer drawn off into a flask standing in 
ice whilst the yellow ethereal solution, separated as completely 
as possible from water, is poured from the neck of the funnel 
into a dry flask. The aqueous pottion cooled to 5 is returned 
to the funnel and the process is repeated five or six times with 
fresh quantities of ether, a few drops of sulphuric acid being 
added each time before shaking, and the yellow ethereal layer 
separated, until the ether is only slightly coloured. 

The united ethereal extracts are shaken with very small 
quantities of sodiam carbonate solution until no more carbon 
dioxide is evolved and the solution remains alkaline. The 
ether solution is then thoroughly dehydrated over calcium 
chloride over-night and the ether carefully removed on the 
water-bath, which should not be heated to boiling. When most 
of the ether has been distilled off, the flask is taken from the 
water-bath and the remainder of the ether removed by blowing 
air over the surface of the liquid. Yield about 15 grams. 

HCI. NH,C H 2 . COOC 2 H 6 + NaNO 2 = N,C H. COOC 2 H 8 + NaCl + 2lI 2 O. 

Properties. Deep yellow liquid which explodes on boiling ; 
but distils undecomposed under diminished pressure. 

Reactions. Add a drop of the diazoacetic ester to con- 
centrated sulphuric acid. It decomposes explosively. Heat a 
few c.c. of the ester in turn with water and alcohol. Nitrogen 
is evolved with the formation of glycollic ester in the first case 
and ethyl glycollic ester in the second. 

N 2 CH.COOC 2 H 5 + H 2 O = CH,OH.COOC 2 H 6 + N* 

5 + C 2 H 5 OH = CH 2 OC 2 H 6 .C00 2 H 5 + N 2 . 



Add an ethereal solution of iodine. Nitrogen is evolved and 
iodacetic ester is formed. Heat a little of the ester with 
concentrated hydrochloric acid. Nitrogen is evolved and 
chloracetic ester is formed. Gradually add five grams of the 
diazoacetic ester to a solution of 8 grams of caustic soda 



96 PRACTICAL ORGANIC CHEMISTRY 

dissolved in 12 c.c. of water heated on the water-bath. A 
vigorous reaction occurs and yellow crystals of sodium bis- 
diazoacetate are deposited. Cool, add 10 c.c. of spirit, and 
filter and wash with spirit. 

/ N = N \ 
2CHN 2 . COOC 2 H 5 + 2NaOH = COONa. CH< >CH. COONa 

\N = N/ 
+ 2C 2 H 6 OH. 
See Appendix, p. 255. 



PREPARATION 22. 
Diethyl Malonate. C 



Conrad, Anna/en, 1880, 204, 126; W. A. Noyes, Amer. 
Chem.J., 1896, 18, 1105. 

50 grms. chloracetic acid (in 100 c.c. water) 
28 sodium carbonate (anhydrous) 
28 sodium cyanide (in powder) 

The solution of chloracetic acid is poured into a wide basin 
(20 cm. diam.), and whilst the mixture is heated to 5560 sodium 
carbonate (28 grms.) is added until the evolution of carbon di- 
oxide ceases and the liquid is neutral. A solution of sodium 
chloracetate is thus obtained. Sodium cyanide (28 grms.) is 
now added, the mixture gently heated and well stirred.* Vigorous 
effervescence occurs and the flame is removed. When the re- 
action is over, the conterits of the basin are rapidly evaporated 
on the sand-bath, whilst the mass is continuously stirred with a 
thermometer until the temperature reaches 135. The brown 
semi-fluid mass is allowed to cool and stirred whilst solidifying, 
and then quickly broken up into coarse powder and introduced 
into a round flask (\ litre). The sodium cyanacetate which has 
been formed is now converted into the ester, and at the same 
time hydrolysed by boiling with sulphuric acid. Absolute 
alcohol (20 c.c.) is added, and the flask is then mounted on a 
water-bath and attached to a reflux condenser. A cold mixture 
of 80 c.c. absolute alcohol and 90 c.c. concentrated sulphuric 
acid is added in the course of about ten minutes, and the flask 
heated for two hours on the water-bath. The mixture is cooled 
quickly, 100 c.c, of water added, and any insoluble matter 



ETHYL MALONIC ACID 97 

filtered off. The filter is washed several times with small 
quantities of ether, and the filtrate shaken up with the ether and 
separated. The filtrate is shaken up again with fresh ether when 
the;ester is completely separated, and the united ethereal extracts 
freed from acid by shaking with water and then with a strong 
solution of sodium carbonate until the latter remains alkaline. 
The ether extract is then separated, dehydrated with calcium 
chloride, and the ether removed on the water-bath. The residual 
ester is distilled under reduced pressure. Yield 45 50 grams. 
CH 2 C1. COONa H- NaCN = CH 2 CN.COONa + NaCl 

CHgCN. COONa + 2C 2 H 6 OH + aH 2 SO 4 = CH 2 (COOC 2 H 5 ) 2 + NaHSO 4 
+ NH 4 HSO 4 . 

Properties. Colourless liquid ; b. p. 195 ; sp. gr. ro68 at 18 
See Appendix, p. 256. 

PREPARATION 23. 
Ethyl Malonic Acid, C 2 H 5 .C 
Conrad, Annalen, 1880, 204, 134. 

1 6 grms. ethyl malonate 

25 (32 c.c.) absolute alcohol 

2'3 sodium 
20 ethyl iodide. 

Sodium ethylate is first prepared by dissolving 2'3 grams 
sodium in 25 grams alcohol, and the reaction completed, if 
necessary, on the water-bath as described on p. 83. Whilst 
the product is still slightly warm, 16 grams malonic ester are 
added from a tap-funnel. The liquid remains clear at first, but 
before the ester has all been added a white crystalline body 
(sodium ethyl malonate) separates out, and soon the whole 
solidifies. To the solid mass 20 grams ethyl iodide are slowly 
added. The mass softens and, after continued shaking, com- 
pletely liquefies with evolution of heat. The product is now 
heated on the water-bath, when it becomes turbid from the 
separation of sodium iodide in the form of a fine powder. After 
one and a half hours the liquid ceases to be alkaline and the 
reaction is complete. The alcohol is distilled off from a brine- 
bath (water saturated with common salt* On the addition of 

COHEN'S ADV. P. O. C. K 



PRACTICAL ORGANIC CHEMISTRY 



water to the residue an almost colourless oil separates out. The 
oil is removed by extraction with ether, dehydrated over calcium 
chloride and distilled. When the ether has been driven off, 
almost the whole of the residue (ethyl diethyl malonate) passes 
over at 206 208". Yield about 1 5 grams. 

CH 2 .(CO.OC 2 H 5 ) 2 + NaOC 2 H 5 = CHNa(CO.OC 2 H 5 ) 2 + C 2 H 5 OH 

Sodium ethyl malonate. 

CHNa(CO.OC 2 H 5 ) 2 +C 2 H 5 I = CH(CoH 5 )(CO.OC 2 H 5 ) 2 + Nal 

Ethyl malonic ester. 

Properties. Colourless liquid with an agreeable fruity smell ; 
b. p. 207, sp. gr. roo8 at 18. 

To obtain the free acid, the ester is hydrolysed with 
caustic potash. To 15 grams caustic potash in strong 
aqueous solution, 10 grams of the ester are slowly added 
from a tap-funnel. At first an emulsion forms, which soon 
solidifies to a white mass. This is heated on the water- 
bath with frequent shaking for about three-quarters of an 
hour, until i it becomes completely liquid. The hydrolysis is 
then complete. The product is diluted with a little water, 
neutralised with concentrated hydrochloric acid, and the free 
acid precipitated with a strong solution of calcium chloride 
as the calcium salt. This is separated from the solution by 
filtration and concentrated hydrochloric acid added to the 
calcium salt. From the acid solution the free ethyl malonic 
acid is extracted by shaking with ether. After evaporating 
off the ether, the acid remains behind as a syrup, which 
solidifies when cold. This is redissolved in water, boiled 
with a little animal charcoal to free it from any adhering 
colouring matter, filtered, and evaporated to syrupy con- 
sistency on the water-bath. The colourless acid crystallises 
on cooling. Yield about 5 grams. 

C 2 H 5 CH(CO.OC 2 H 5 ) 2 + 2KOH = C 2 H 5 CH(CO 2 K) 2 + 2C 2 H 5 OH 
C. 2 H 5 CH(CO 2 K) 2 + 2HC1 = C,H 5 CH(CO 2 H) 2 + 2KCL 

Ethyl malonic acid. 

Properties. Rhombic prisms ; m. p. ui'5, easily soluble in 
water, alcohol, and ether. 

Reaction. i. Heat a gram or two of the acid in a test- 
tube over a small flame and have at hand a second test-tube 
one-third full of lime water. The acid decomposes at i6o c 



TRICHLORACETIC ACID 99 

into butyric acid and carbon dioxide. When the effervescence 
begins to slacken, decant the gas downwards into the test- 
tube of lime-water, shake up and notice the turbidity. The 
acid which remains will have a strong smell of butyric acid, 

C 2 H 5 CH(CO 2 H) 2 = C 3 H 7 CO.OH + CO 2 
See Appendix, p. 256. 

Chloral Hydrate, CC1 3 .C 

Liebig, Annalen, 1832, 1, 189 ; Dumas, Ann. Chint. Phys. 
1834, 56, 123. 

Chloral hydrate is obtained by the action of chlorine upon 
ethyl alcohol. The solid chloral alcoholate is formed, 
CC1 3 .CHOH.OC 2 H 6 , which, when decomposed with sulphuric 
acid, yields chloral, CC1 3 .COH, a liquid which combines with 
water to form the crystalline hydrate. 

Properties. It crystallises in prisms, which dissolve easily in 
water, alcohol, and liquid hydrocarbons. It has a peculiar 
smell ; m. p. 57 ; b. p. 97'5. It volatilises on evaporating its 
aqueous solution. 

Reactions. i. Add a few drops of a solution of chloral 
hydrate to a little ammonio-silver nitrate solution and warm. 
Metallic silver will be deposited. 

2. Add a little caustic soda to a solution of chloral and warm 
gently. The heat of the hand is sufficient for the purpose. A 
smell of chloroform is at once apparent, CCl 3 .CH(OH) 2 -f 
NaOH = CHCl 3 -|-HCO.ONa + H 2 O. Sodium formate remains 
in solution. 

3. Add a few drops of ammonium sulphide solution and warm 
gently. A brown colouration or precipitate is formed. 

PREPARATION 24. 
Trichloracetic Acid, CC1 3 .CO.OH. 

Dumas, Compt. rend., 1838, 8, 609 ; Clermont, Ann. Chim. 
Phys., 1871, (6), 6, 135- 

25 grms. chloral hydrate 

20 fuming nitric acid ; sp. gr. i '5 (see p. 20). 

H 2 



100 PRACTICAL ORGANIC CHEMISTRY 

The chloral hydrate is melted in a distilling flask (250 c.c.) and 
the fuming nitric acid added.* The mixture is heated carefully 
over a small flame until the reaction sets in. After a few 
minutes red fumes are evolved, consisting mainly of nitrogen 
tetroxide. The reaction proceeds without the application of 
heat, and is complete when, on warming the liquid, nitrous 
fumes cease to come off. The product is now distilled ; below 
123 excess of nitric acid distils ; between 123 and 194 a 
mixture of trichloracetic acid and a small quantity of nitric acid 
pass over, and at 194 196 nearly pure trichloracetic acid 
collects in the receiver and solidifies on cooling. It is advisable 
to distil the last fraction with a condenser-tube only. The 
fraction boiling at 123 190 is treated with a fresh quantity of 
fuming nitric acid (10 c.c.), and the product purified as before. 
Yield, 10 15 grams. 

CC1 3 .CO.H + O = CC1 3 .CO.OH. 

Properties. Colourless, rhombohedral crystals ; m. p. 52 ; 
b. p. 195. See Appendix, p. 257. 

PREPARATION 25. 

CO.OH 

Oxalic Acid, | +2H 2 O 

CO.OH 

Scheele (1776), Naumann, Moeser, Lindenbaum, J. prakt. 
Chem. 1907, 75, 146. 

140 c.c. cone, nitric acid. 

20 grms. cane sugar. 

o'l grm. vanadium pentoxide. 

The nitric aciu is warmed gently on the water-bath in a large 
flask (i litre) with the addition of the vanadium pentoxide. It is 
then placed in the fume cupboard and the cane sugar at once 
added. As soon as torrents of brown fumes begin to be evolved, 
the flask is placed in cold water. After the reaction has ceased the 
liquid is left for twenty-four hours when colourless crystals of 
the acid separate. A further small quantity may be obtained 
from the mother liquor on standing. The crystals are drained on 
a small porcelain funnel without filter paper, and recrystallised 
from a very small quantity of water. Yield, 15 20 grams. 



METHYL OXALATE 101 

Properties. Colourless crystals, which, on heating to 100, 
lose their water of crystallisation, melt, and then partly sublime 
and partly decompose, giving off carbon dioxide and formic 
acid. M. p. of the hydrated crystals ioi'5. Soluble in water 
and in alcohol, very slightly soluble in ether. 

Reactions. i. Boil a little of the acid with ammonia solution 
until neutral, and add calcium chloride solution. A white pre- 
cipitate of the calcium salt is obtained, which is insoluble in 
acetic acid. 

2. Add to a solution of the acid a few drops of dilute 
sulphuric acid, and warm gently. On adding permanganate 
solution it is immediately decolourised, 5C 2 H 2 O 4 + 2KMnO 4 4- 
3H 2 SO 4 =ioCO 2 +8H 2 O + K 2 SO 4 + 2MnSO 4 . 

3. Heat two or three grams of the crystals with about 5 c.c. con- 
centrated sulphuric acid. Rapid effervescence occurs, and the 
gas may be ignited at the mouth of the tube, C 2 H 2 O 4 H 2 O = 
CO + CO 2 . See Appendix, p. 257. 



PREPARATION 26 

CO.OCH 3 
Methyl Oxalate, | 

CO.OCHg 

Dumas, Peligot,^. Chim. Phys., 1836, 58, 44 ; Erlenmeyer, 
Rep. Pharm. (:>), 23, 432. 

70 grms. crystallised oxalic acid 
50 (63 c.c.) methyl alcohol. 

The oxalic acid is powdered and heated in a basin on a water- 
bath, which is kept boiling briskly, until no more water is given off 
(one to two hours). It must be occasionally stirred and powdered 
up. It is then heated to 1 10 120 in an air-bath or in a Victor 
Meyer drying apparatus (see p. 27) until it loses the weight 
corresponding to two molecules of water. If the Victor Meyer 
apparatus is used, amyl alcohol, b. p. 132, should be placed in 
the outer jacket. 

The dehydrated and powdered oxalic acid is mixed with the 



PRACTICAL ORGANIC CHEMISTRY 



methyl alcohol, and the mixture heated on the water-bath for 
two hours with an upright condenser. The liquid is then distilled 
with a thermometer. When the temperature rises to 100 the 
receiver is replaced by a beaker, and the water-jacket of the 
condenser removed. The thermometer rises rapidly to the 
boiling-point of methyl oxalate, 160 165, and the distillate 
solidifies in the receiver. It is drained at the pump and dried. 
It may be recrystallised from spirit. Yield, 2025 grams. 



Properties. Colourless plates ; m. p. 54 ; b. p. 163. 
Reactions. For this purpose the alcoholic mother liquor from 
the crystals may be used. 

1. Add a little caustic potash solution. Crystals of potassium 
oxalate are deposited. The ester is hydrolysed. 

2. Add a few drops of concentrated ammonia. A white 
crystalline precipitate of oxamide is formed, C 2 O 2 (OCH 3 ).,+ 
2NH 3 =C 2 O 2 (NH 2 ) 2 



PREPARATION 27. 

Glyoxylic Acid, CHO.COOH + H,O. 
Glycollic Acid, CH 2 OH.COOH. 

Tafel and Friedrichs, Ber., 1904, 37, 3187 ; Centralblatt ; 1905 
II, 1699. 

20 grms. oxalic acid (in fine powder). 
loo c.c. sulphuric acid (10 per cent.). 

The process is one of electrolytic reduction and the apparatus 
is similar to that shown in Fig. 77, p. 144. It consists of a small 
porous cell (8 cm. x 2 cm. diam.) surrounded by a narrow beaker 
(n cm. x 6 cm. diam.). The oxalic acid, mixed with 100 c.c. 
10 per cent, sulphuric acid (titrated against standard baryta 
solution) forms the cathode liquid and is placed in the 
beaker. The porous cell is filled with the same strength of 
sulphuric acid and forms the anode liquid. The electrodes are 
made from ordinary clean sheet lead. The anode consists of a 
thin strip projecting about two inches from the cell and the 



GLYOXYLIC ACID 103 



cathode is made from a rectangular piece 10x15 cm - with a 
long tongue, the square portion being bent into the form of a 
cylinder surrounding the porous cell, and the projecting tongue 
serving as attachment to the circuit (see Fig. 77, p. 144). It is 
advisable to reverse the current before use so as to produce a 
metallic surface. 

The whole apparatus is placed in a good freezing mixture. 
The electrodes are connected in circuit with an ammeter and 
resistance as described on p. 1 44. The reduction requires theoreti- 
cally 9 ampere-hours and the strength of current may vary 
between moderately wide limits (2 6 amperes) per 100 sq. cm. 
of cathode surface. The cathode liquid should be frequently 
stirred so as to bring the suspended oxalic acid into solution, 
and, as the yield of glyoxylic acid depends on efficient cooling, 
ii is important that the temperature should not exceed 10. If 
the temperature is allowed to rise, glycollic acid is formed. 
The glyoxylic acid is separated as the calcium salt. The 
cathode liquid is poured into a basin and the sulphuric and 
unchanged oxalic acid precipitated with standard baryta solution. 
The mixture is filtered and the filtrate is concentrated in vacua 
at 60 (see p. 94), neutralised in the cold with calcium 
carbonate, boiled up for a short time and filtered. As calcium 
glyoxylate is only slightly soluble in cold water (i part in 140 
of water at 18) the greater portion crystallises on cooling. If 
calcium glycollate, which is much more soluble, is present, it 
may be separated from the filtrate by concentrating the solu- 
tion on the water-bath and precipitating with spirit. To obtain 
free glyoxylic acid, the calcium salt is dried and suspended 
in water, the calculated quantity of oxalic acid added and the 
mixture filtered. The filtrate is evaporated in a vacuum 
desiccator, when the glyoxylic acid remains as a viscid liquid 
which may crystallise on long standing, 

COOH.COOH + H 2 = CHO'COOH + H 2 O. 

. Crystallises in rhombic prisms ; very soluble in 



water. 

Reactions. i. Adda few drops of the acid solution or solu- 
tion of the calcium salt to a few c.c. of ammonia-silver nitrate 
and warm in hot water. A silver mirror is deposited. 

2. To the acid, neutralised with potassium carbonate, or to the 



104 PRACTICAL ORGANIC CHEMISTRY 

solution of the calcium salt, add a solution of phenylhydrazine 
acetate and a little sodium acetate. 1'lie phenylhydrazone 
separates on standing in minute yellow crystals, which can be 
recrystallised from alcohol. The neutral salts also combine 
with sodium bisulphite and hydroxylamine. 

Glycollic Acid. If it is required to convert the oxalic acid 
completely into glycollic acid, the same method is employed as 
described above, but the temperature is raised to 35 and the 
number of ampere-hours is doubled. The separation is effected 
as the calcium salt and precipitated with alcohol as already 
described. 

COOH.COOH + 2H 2 = CH 2 OH + COOH + H 2 O 

Properties. Crystals m. p. 79 80 ; very soluble in water. 
The air-dried calcium salt contains three molecules of water of 
crystallisation and is soluble in 80 parts of water 15, and in 19 
parts at 100. See Appendix, p. 258. 

PREPARATION 28. 

Palmitic Acid, C 15 H 31 CO.OH. 

Fremy, Annalen, 1840, 38, 44. 

30 grms. palm oil. 

24 caustic potash. 

The caustic potash is dissolved in its own weight of water. 
The palm oil is melted in a large basin on the water-bath, 
and the potash solution added with constant stirring. The 
mixture is heated for half an hour. Half a litre of boiling 
water is poured in, and, after stirring well, 75 c.c. concentrated 
hydrochloric acid are gradually added, and the heating con- 
tinued until the palmitic acid separates out as a transparent 
brown oil on the surface of the liquid. It is allowed to cool, and 
the cake of impure acid removed and pressed between filter- 
paper. The acid is now melted in a small basin on the water- 
bath and decanted, from any water which may have separated, 
into a retort (250 c.c.). It must be distilled in vacua. The 
neck of the retort is fixed into a small filtering tube, which serves 
as receiver, as shown in Fig. 67. A few small pieces of unglazed 



PALMITIC ACID 105 




pot are dropped into the retort, the tubulus of which is closed 
with a cork holding a thermometer. Before commencing the 
distillation the apparatus should be tested to see that it is air- 
tight. It is then evacuated with the water pump (See Fig. 35, 
p. 44), and the distillation commenced. 
During the distillation it is advisable 
to hold the Bunsen and to heat the 
retort with the bare flame. Under a 
pressure of 36 mm. the acid distils at 
245. The pale yellow oil which col- 
lects in the receiver is poured out 
into a basin whilst hot and allowed to 
cool. The cake of acid is spread on 
a porous plate and left to drain, 
when it becomes nearly colourless, FIG. 67. 

and, ^after one or two crystallisations 

from small quantities of spirit, is pure, and melts at 62. 
Yield about 20 grams. 

The aqueous portion from which the cake of acid is removed 
contains free hydrochloric acid, potassium chloride, and glycerol. 
The lafter may be obtained by evaporating to dryness on the 
water-bath, and extracting the residue with small quantities of 
alcohol, which dissolves out the glycerol. On evaporating the 
alcohol impure glycerol is left. 

CH 2 .O.CO.C 15 H 31 

CH.O.COC 15 H 31 + 3KOH = 3 C 16 H 31 COOK + C 3 H 5 (OH) 3 

Potassium palmitate. Glycerol. 

CH 2 .p.CO.C 15 H 31 

Palmitin. 

C 16 H 31 COOK + HC1 = C 15 H 31 COOH + KC1. 

Properties. Crystallises in tufts of colourless needles ; m. p. 
62 ; soluble in alcohol and ether ; insoluble in water. 

Reactions. i. Dissolve a small quantity of the acid in caustic 
soda solution and add salt. Sodium palmitate separates as a 
curdy white precipitate. 

2. Boil another portion of the acid with caustic soda and let it 
cool. Pour off the liquid from the crust of sodium palmi- 
tate, which forms on the surface, wash once or twice with 



io6 PRACTICAL ORGANIC CHEMISTRY 

a little cold water, and dissolve the sodium salt in hot 
water. On cooling, a thick gelatinous mass of sodium 
palmitate separates. See Appendix, p. 258. 

Glycerol (Glycerin), CH 2 (OH).CH(OH).CH 2 (OH) 
Scheele, Opusc., 1779, 2, 175. 

Glycerol is obtained by the hydrolysis of fats and oils, and 
purified by distillation under reduced pressure \vith superheated 
steam. 

Properties. A viscid, colourless liquid, with a sweet taste ; m. p. 
17, b. p. 290. It boils, under ordinary pressure, with partial 
decomposition forming acrolein ; sp. gr. 1-269 at I2 > miscible 
with water and alcohol ; insoluble in ether and the hydrocarbons. 

Reactions. i. Heat a few drops of glycerol with some powdered 
potassium hydrogen sulphate. The irritating smell of acrolein 
is at once perceptible. 

2. Make a borax bead and dip it into a solution of glycerol 
and bring it into the flame. A green colouration due to boric 
acid is produced. 

PREPARATION 29. 
Formic Acid, H.CO.OH. 

Berthelot, Ann. Chim. Phys., 1856, (3) 46, 477 ; Lovin, Bull. 
Soc. Chim., 1866, (2) 5, 7 ; 1870, (2) 14, 367. 

50 grms. anhydrous glycerol. 
200 oxalic acid (in four portions of 50 grams). 

The glycerol is dehydrated by heating it gently in a basin on 
a sand-bath until a thermometer with the bulb immersed in the 
liquid indicates 175. Fifty grams of commercial crystallised 
oxalic acid and 50 grams of glycerol are heated in a retort 
(250 c.c.) over wire-gauze, with condenser and receiver. A 
thermometer is fixed through the tubulus with the bulb in the 
liquid. The reaction begins at about 80, and at 90 proceeds 
briskly, carbon dioxide being evolved. The temperature is main- 
tained at 105 i 10 until the evolution of gas has slackened. 
Some aqueous formic acid has meanwhile collected in the 



FORMIC ACID 



107 



receiver. The contents of the retort are now cooled to 
about 80 and a further 50 grams of oxalic acid added. The 
reaction recommences on heating with the formation of aqueous 
formic acid, which becomes more concentrated with each fresh 
addition of oxalic acid until the distillate eventually contains 56 
per cent, of acid. The other portions of oxalic acid are added 
in the same way. In order to regain the formic acid which 
remains as monoformin in the retort, the contents are trans- 
ferred to a round flask, diluted with about 250 c.c. of water 
and distilled in steam, until the distillate has only a faintly acid 
reaction (about 250 c.c.). 

Distillation in Steam. The apparatus for distilling in 
steam is shown in Fig. 68. A large flask, or, preferably, a i gallon 




FIG. tS. 

tin is closed by a double bored cork. A safety-tube passes 
through one hole, and a bent tube which terminates below the 
cork passes through the second hole, and is attached by rubber 
tubing to the inlet-tube of the distilling flask (i litre). The 
flask is sloped to prevent the contents being splashed over 
into the condenser. It is heated on the sand-bath or asbestos 
board to boiling, and steam passed in. The united distillates 
are poured into a basin and neutralised by adding lead car- 
bonate until, on heating, no further effervescence occurs. The 
liquid is now left for a moment to settle, and t^e clear solution 
decanted, whilst hot, through a fluted filter. The residue in the 



io8 PRACTICAL ORGANIC CHEMISTRY 

basin is boiled up again with a volume of water equal to that 
decanted, and again a third and fourth time, and filtered hot 
each time until no more lead formate is dissolved. The lead 
formate will have now passed into solution and the liquid is then 
evaporated down on a sand-bath or ring- 
burner (see Fig. 69), until crystals appear 
on the surface, when the liquid is put on 
one side to cool. Lead formate crystal- 
lises out in long white needles. Yield 
about 150 grams. In order to obtain 
pure formic acid, hydrogen sulphide is 
passed over tne heated lead salt. It is 
carried out as follows : 

The powdered salt, dried on the water- 
bath, is introduced in a long layer into a sloping wide tube, 
loosely stopped at the lower end by a plug of glass wool or 
asbestos.* To the lower end of the tube a receiver, in the form 
of adistilling-flask, is attached, which is protected from moisture 
by a drying-tube. The salt is heated gently by moving a flame 
along the tube whilst hydrogen sulphide, washed through water, 
and dried by passing through a U-tube containing calcium chlor- 
ide, is led over the salt in not too rapid a stream. The lead 
formate blackens, and is slowly converted into lead sulphide and 
formic acid, which drops into the receiver. The acid, which retains 
a strong smell of hydrogen sulphide, is freed from the latter by 
distillation over a little dry lead formate. Yield is nearly 
theoretical. 




C 3 H 5 (OH) 3 + C 2 H 2 4 = CaftjcH + CO 2 + H A 

Glycerol raonoformin. 

+ H P = HCO.OH + C 3 H 5 (OH) 3 . 

Formic acid. 

Properties. Colourless liquid, with a penetrating smell re- 
sembling sulphurous acid: b. p. 100; sp. gr. T223 at o; solidifies 
below oto colourless crystals ; m. p. 8 "6 ; soluble in water and 
alcohol. 

Reactions. Fftr the following tests use a neutral solution pre- 
pared as follows : Boil a little lead formate with a solution of 



ALLYL ALCOHOL 109 

sodium carbonate, filter, add a slight excess of nitric acid, boil a 
minute, add dilute ammonia and boil until neutral. I. Add 
a drop of ferric chloride. A red colouration is produced, 
which, on boiling, becomes turbid from the formation of basic 
ferric formate. (Compare acetic acid, p. 74.) 

2. Add to the solution a few drops of a solution of silver 
nitrate and warm. Metallic silver is deposited as a black powder. 

3. Add to the solution a few drops of a solution of mercuric 
chloride and warm. White mercurous chloride is deposited. 

4. Add concentrated sulphuric acid to a little formic acid, 
solid lead formate, or other salt and heat. Carbon monoxide 
is evolved, and may be lighted at the mouth of the test-tube. 
(HCOO) 2 Pb + H 2 SO 4 = PbSO 4 + 2H 2 O + 2CO. See Appendix 
p. 259. 

PREPARATION 30. 

Allyl Alcohol, CH^CH.CHgOH. 
Tollens, Henninger, Annalen, 1870, 156, 129. 

50 grms. oxalic acid. 
200 glycerol. 

ammonium chloride. 

A mixture of the above substances is heated in a retort 
( litre) over wire-gauze with condenser and receiver.* A rapid 
evolution of carbon dioxide at first occurs, and the temperature, 
indicated by a thermometer dipping into the liquid, remains for 
some time stationary at about 130. As the temperature slowly 
rises the evolution of gas slackens, and after a time (at about 
180) entirely ceases. When the temperature has reached 195 
the receiver, which contains aqueous formic acid, is changed. 
At 200 210 carbon dioxide is again given off, and oily streaks 
are observed to run down the neck of the retort ; at the same 
time a disagreeable penetrating smell is perceptible. By gently 
heating the contents of the retort, a temperature of 220 230 is 
maintained for some time, and when it has finally risen to 260 
the distillation is stopped. The distillate is a mixture of allyl 
alcohol and water, and there is also present allyl formate, 
glycerol, and acrolein. Excess of glycerol remains in the 
retort and may be used again by repeating the operation with a 
smaller quantity of oxalic acid (30 40 grams) until the residue is 



I io PRACTICAL ORGANIC CHEMISTRY 

too small or has become dark-coloured and thick. The distil- 
late is submitted to a second distillation, which is continued 
until no oily layer separates from the latter portions which distil 
on treating with solid potassium carbonate. This occurs when 
the temperature reaches about 105. On adding solid potassium 
carbonate to the distillate, the allyl alcohol settles out as an oil. 
This is separated and distilled. Yield about 15 grams boiling 
at 92 96. 

C 2 H 2 O 4 + C 3 H 8 O 3 = C 3 H 6 (OH) 2 .O.CO.H + H 2 O + CO 2 

Glycerol monoformin. 

C 3 H 5 (OH) 2 .O.CO.H = C 3 H 6 OH + H 2 O + CO 2 

Allyl alcohol. 

Properties. Colourless liquid, with a pungent odour ; b. p. 
96-5 ; sp. gr. 0-858 at 15. 

Reaction. Add bromine water to a little of the allyl alcohol. 
It is immediately decolourised, C 3 H 5 OH + Br 2 = C 3 H 6 Br 2 OH. 
See Appendix, p. 259. 

PREPARATION 31. 
Isopropyl Iodide, CH 3 .CHI.CH 3 
Markownikoff, Annalen, 1866, 138, 364. 

60 grms. iodine. 

40 glycerol. 

32 water. 

ii yellow phosphorus. 

The iodine, glycerol, and water are placed together in a retort 
(250 c.c.), standing over wire-gauze and attached to a condenser 
and receiver. The phosphorus is cut up under a layer of water 
into small pieces, the size of a pea, and, with crucible tongs, 
dropped gradually into the retort. The introduction of the 
phosphorus generally produces at the beginning a violent re- 
action, often accompanied by a vivid flash. If no reaction 
occurs on adding the first few pieces of phosphorus, the retort 
must be warmed gently. The last two-thirds of the phosphorus 
may be added more quickly. The contents of the retort are 
now distilled as long as any oily liquid passes over. The distil- 
late is poured back into the retort and redistilled. The liquid 
is then shaken up with dilute caustic soda solution in a separating- 



EPICHLORHYDRIN 



funnel, the isopropyl iodide separated, dried over calcium 
chloride, poured off and fractionated in a distilling flask. It 
distils entirely at 88 89". Yield 30 35 grams. 

1. PI 3 + 3 H 2 = 3 HI + H 3 P0 3 . 

2. CH 2 OH CH,I 

CHOH + 3HJ = CHI + 3H 2 O 
CH 2 OH CH,I 

Propenyl triiodide. 

3 CHJ CH 3 

* I - ! 

CHI + 2HI = CHI +2l 2 

i i 

CH 2 I CH 3 

Isopropyl iodide. 

Propenyl triiodide is probably formed as an intermediate pro- 
duct, though it does not exist in the free state. 

Properties. Colourless liquid ; b. p. 89'5 ; sp. gr. 1744 at - 
See Appendix, p. 260. 

PREPARATION 32. 

CH 2 C1.CH.CH 2 
Epichlorhydrin, \O/ 

Reboul, Annalen, Spl., 1861, 1, 221. 

200 grms. glycerol. 

160 c.c. glacial acetic acid. 

The glycerol, which must be dehydrated (see p. 106), is mixed 
with an equal volume of glacial acetic acid. Hydrochloric acid 
gas (see Fig. 65, p. 93) is passed into the cold liquid for about 
two hours, when it ceases to be absorbed. The mixture is now 
heated on the water-bath, and, after standing twenty-four hours, 
the current of gas is continued for about six hours more. The 
liquid is distilled with a thermometer.* Hydrochloric acid is 
first given off, together with acetic acid. As the temperature 
rises, the dichlorhydrin and acetodichlorhydrin distil. The 
portion distilling at 160210, consisting mainly of dichlorhydrin, 
is collected separately and used for the preparation of epichlor- 



PRACTICAL ORGANIC CHEMISTRY 



hydrin. Yield of dichlorhydrin about 120 grams. Epichlor- 
hydrin is obtained by the action of aqueous potash solution 
upon the dichlorhydrin. A solution of 100 grams of caustic 
potash in 200 c.c. of water is well cooled and poured slowly, with 
constant stirring, into the dichlorhydrin. Rise of temperature 
must be carefully avoided. The epichlorhydrin is separated 
from the product by adding ether, which dissolves out the 
epichlorhydrin. The upper layer is separated, shaken up 
with a little water, and again separated. It is then dehydrated 
over calcium chloride and decanted into a round flask. The 
ether is first removed on the water-bath. The residue is then 
fractionally distilled. This is effected by attaching a fractionat- 
ing column to the flask (see p. 137). The portion boiling 
at 115 125 is epichlorhydrin, and is collected separately. The 
portion boiling above this temperature consists mainly 01 
acetodichlorhydrin. Yield 25 30 grams. 

CH 2 OH.CHOH.CH 2 OH + HC1 = CH 2 C1.CHOH.CH 2 OH + H 2 O. 

a-Monochlorhydrin. 

CH 2 C1.CHOH.CH 2 OH + HC1 = CH 2 C1.CHOH.CH 2 C1 + H,O. 

oa-Dichlorhydrin. 

CH 2 C1.CHOK.CH 2 C1 + KOH = CH 2 .CH.CH 2 C1 + KC1 + H 2 O. 

NN O/ 

Epichlorhydrin. 

Properties. Mobile liquid, with an ethereal smell ; b. p. 
117 ; sp. gr. 1-203 at o. 

Reaction. Warm a little of the epichlorhydrin with caustic 
potash solution. It dissolves, forming glycerol. See Appendix, 
p. 260. 

CH(OH).COOH 
Malic Acid, | 

CH 2 .COOH 

Malic acid is prepared from the juice of the mountain ash 
berries by precipitation as the calcium salt. 

Properties. It is soluble in water and alcohol, but not in 
ether. On heating, it loses water and is converted into fumaric 
and maleic acids (see p. 125). On oxidation it gives malonic acid 
and on reduction succinic acid. 

Reactions. I. Make a strong neutral solution, add calcium 
chloride solution and boil. The calcium salt is precipitated. 



SUCCINIC ACID 



2. Mix about o'5 gram each of powdered malic acid and 
resorcinol, and add I c.c. of concentrated sulphuric acid. 
Warm the mixture for a moment over the flame until it 
begins to froth. On cooling and adding water and caustic soda 
solution, anintense blue fluorescence is produced(vonPechmann). 

PREPARATION 33. 

Succinic Acid (Ethylenedicarboxylic Acid), 

COOH.CH 2 .CH 2 .COOH. 
Schmitt, Annalen, 1860, 114, 106. 

10 grms. malic acid. 
30 hydriodic acid. 
2 red phosphorus. 

The hydriodic acid is conveniently prepared, according to 
Gattermann, as follows : A small round flask (100 c.c.) is 
provided with a tap- funnel and delivery-tube, the latter being 
attached to a U-tube as shown in Fig. 70. The U-tube is filled 
with broken glass or pot, which 
has been coated with amor- 
phous phosphorus by rubbing 
it in the phosphorus slightly 
moistened with water. The 
flask is first detached from the 
U-tube and funnel, and 44 
grams of iodine introduced.* 
Four grams of yellow phos- 
phorus, cut in small pieces, are 
then added. The phosphorus 
must be cut under water, 
brought on to filter-paper with 
crucible tongs, pressed for a moment, and transferred with* 
tongs to the flask. Each piece of phosphorus as it drops in 
produces a flash. When the phosphorus has been added a dark 
coloured liquid is obtained, which solidifies on cooling, and 
consists of PI 3 . The flask, when cold, is closed with its cork, 
and the delivery tube from the U-tube is inserted loosely into 
the neck of a small flask containing 50 c.c. of water, so that 
the open end of the delivery-tube is above the surface of the 
water. It is kept in position by a wedge of cork fixed in the 

COHEN'S ADV. P. o. c. i 




FIG. 70. 



114 PRACTICAL ORGANIC CHEMISTRY 

neck. Ten c.c. of water are now added gradually from the tap- 
funnel. Hydriodic acid is evolved, and, after being freed from 
iodine in the U- tu be, is absorbed by the water. When the water 
has been added, the liquid is gently heated over a small flame 
until no more fumes issue from the delivery-tube. The aqueous 
solution of hydriodic acid is distilled with a thermometer, and 
the portion boiling at 125 and above is collected separately. It 
consists .of strong hydriodic acid solution, containing about 
57 per cent, of HI. The malic acid is dissolved in the 
hydriodic acid and poured into a stout-walled tube for 
sealing. The red phosphorus is added, and the tube sealed 
in the usual way (see p. 24). It is heated in the tube-furnace 
for six hours at 120. On removing the tube it is found to be 
filled with crystals of succinic acid mixed with iodine. The 
contents are poured into a basin and evaporated to dryness on 
the water-bath. The residue, when cold, is stirred with a little 
chloroform to dissolve the free iodine, which is then decanted, 
and the process repeated if necessary. After warming to drive 
off the chloroform, the substance is dissolved in hot water and 
set aside to crystallise. Succinic acid crystallises in long prisms. 
Yield 5 grams. 

' COOH.CHOH.CH 2 .COOH + aHI = COOH.CH 2 .CH2.COOH 
+ H 2 O + I 2 . 

Properties. Colourless prisms ; m. p. 180. On distillation, 
the acid loses water and is converted into the anhydride. 

Reaction. i. Make a neutral solution by boiling with an 
excess of ammonia, and add to one portion, calcium chloride ; 
no precipitate is formed ; to another portion add a drop or 
two of ferric chloride ; a brown precipitate of ferric succinate 
is thrown clown. See Appendix, p. 261. 

CH(OH).COOH 
Tartaric Acid (Dihydroxysuccinic Acid), | 

CH(OH).COOH 
Scheele (1769). 

The acid potassium or calcium tartrates are found in many 
plants ; but the chief source of tartaric acid is the impure acid 
potassium salt, which separates out as wine-lees, or argol from 
grape-juice in process of fermentation. 

Properties. The acid crystallises in monoclinic prisms, 



ETHYL TARTRATE 115 



soluble in alcohol and water, but not in ether. It turns the 
plane of polarisation to the right ; m. p. 167 170. 

Reactions. i. Heat a crystal of the acid. It gives an odour 
resembling burnt sugar. Carefully neutralise a solution of tar- 
taric acid with caustic soda, and make the following tests : 

2. Add calcium chloride and stir with a glass rod. A crystal- 
line precipitate of calcium tartrate, C 4 H 4 O 6 Ca + 4H 2 O, is formed 
which dissolves in acetic acid and caustic alkalis. Repeat the 
foregoing test, but add a few drops of acetic acid before the cal- 
cium chloride. There is no precipitate. Calcium sulphate also 
gives no precipitate with tartaric acid or neutral tartrates, 
(compare reactions for oxalic acid, p. 100). 

3. Add silver nitrate solution. The white precipitate is the 
silver salt. Add two or three drops of dilute ammonia until the 
precipitate is nearly dissolved, and place the test-tube in a 
beaker of hot water. A silver mirror will be deposited. 

4. Add a few drops of acetic acid and a little ammonium or 
potassium acetate solution to a moderately strong solution of 
tartaric acid or a neutral tartrate. On stirring with a glass rod, 
the acid potassium or ammonium tartrate will be precipitated. 

5. To a solution of tartaric acid or a tartrate in water add 
a drop of ferrous sulphate solution and a few drops of hydrogen 
peroxide and make alkaline with caustic soda. A violet colora- 
tion is produced (Fenton's reaction). 

PREPARATION 34. 

CH(OH).CO.OC 2 H 6 
Ethyl Tartrate, | 

CH(OH).CO.OC 2 H 5 . 

Anschiitz, Pictet, Ber., 1880, 13, 1176. 
30 grms. tartaric acid. 
1 60 c.c. absolute alcohol. 

The tartaric acid is finely powdered and mixed with half the 
above quantity (80 c.c.) of absolute alcohol. The mixture is 
heated on the water-bath with upright condenser until dissolved. 
The flask is immersed in cold water, and the well-cooled 
solution saturated with dry hydrochloric acid gas (prepared in 
the usual way by dropping cone, sulphuric acid into cone, 
hydrochloric acid, see Fig. 65, p. 93). After standing for an 

I 2 



ii6 PRACTICAL ORGANIC CHEMISTRY 

hour or two (or preferably overnight), the hydrochloric acid, 
excess of alcohol and water are expelled by evacuating the 
flask and distilling in vacua on the water-bath. The re- 
maining half of the alcohol is added to the residue, and the 
mixture again saturated in the cold with hydrochloric acid gas. 
After standing, the acid, alcohol and water are removed as 
before, and the residue fractionated from an oil or metal bath in 
vacuo. The ethyl tartrate distils as a clear viscid liquid. After 
a second distillation in vacuo the substance is pure. 

At II mm. it boils at 155. 
,, 20 J6 4- 

The yield is 80 per cent, of the theory. See Appendix, p. 262. 

Determination of Rotatory Power. The rotatory power 
of ethyl tartrate, which is an optically active substance, is 
determined by means of a polarimeter. One of these instru- 
ments known as Laurent's polarimeter is shown in Figs. 
71 and 72. 

The monochromatic light of a sodium flame is used in these 
determinations and is obtained by suspending in a Bunsen 
flame a platinum wire basket containing fused sodium chloride 
or the more volatile bromide. The latter gives a brighter flame, 
but the basket requires replenishing more frequently. The 
light from the flame passes through a cell B, containing a 
solution of potassium bichromate (or a crystal of this substance), 
which deprives it of blue or violet rays. It then passes through 
the polarising nicol prism P. A plate of quartz cut parallel to 
the optic axis covers half the opening D, and is of such a thick- 
ness that it produces a difference of a half-wave length (or an 
exact odd multiple of a half-wave length) between the two rays, 
which it gives by double refraction. The light then passes 
through the substance placed in the tube T and entering at E 
strikes the analysing nicol N. The telescope OH is focussed on 
the edge of the quartz plate at D. When N is turned, a pointer 
moves over the graduated circle C and its position can be read 
by means of the lens L. 

The Theory of the Instrument may be explained as 
follows : If, after passing through the nicol P, the plane of 
vibration is in the direction OB, Fig. 73 a, then in the half of the 
field to the right, uncovered by the quartz plate, it passes on un- 



ROTATORY POWER 




FIG. 71- 




FIG. 72. 



n8 



PRACTICAL ORGANIC CHEMISTRY 



changed. When it strikes the quartz the ray is broken up into 
the two components Oy and Ox. These traverse the quartz 
with different velocities, and since one ray is retarded half a 
wave-length in respect of the other, the vibration of one com- 
ponent will be represented by Oy, but the other must be re- 
presented by Ox' instead of Ox. These two combine on 
emerging to a plane polarised ray vibrating in the direction 
OB' so that the angle AOB' is equal to the angle AOB. 

If now (the tube containing water or other non-rotating 
liquid) the nicol N be so placed that it is parallel to nicol P, 
then the light, in the half of the field to the right, will pass 
through unchanged, but only a portion of the light which has 




FIG. 73 

passed through the quartz diaphragm with its plane of vibration 
in the direction OB', will pass through N and consequently there 
will be different intensities of illumination in the two halves 
of the field, Fig. 73 b (if the angle a is 45 then the angle BOB 
will be 90, and the light in the left half of the field will be com- 
pletely obscured). Similarly if the plane of the nicol N be made 
parallel to OB' there will be a greater intensity of illumination 
in the left half of the field, Fig. 73 c. Between the two positions 
of the nicol N there must necessarily be one which gives 
uniform illumination of the whole field, and this is the zero 
point of the instrument, Fig 73 d. 

If the tube T, containing the active substance, be interposed 
between the two nicols, then both rays OB and OB' will be 
rotated through equal angles, and to re-establish uniform 



MOLECULAR ROTATION iig 

illumination in the two halves of the field, the nicol N must 
be turned through an angle equal to the angle of rotation, which 
is then measured on the divided circle. 

When the angle a is small, i.e. when the plane of 
vibration of the polarised light is almost parallel to the optic 
axis of the quartz, the greatest degree of sensitiveness is 
attained, for then a very small change in the position of N 
causes a great difference in the respective illuminations in the 
two halves of the field. As a increases, the sensitiveness 
diminishes, but a greater total intensity of illumination is ob- 
tained. By moving J (Fig. 71) the position of the nicol P may 
be altered. For clear colourless liquids the angle a may be 
made comparatively small ; but in the case of coloured liquids 
it is necessary to have a larger, and so obtain a greater intensity 
of light at the cost of sensitiveness. 

Calculation of Results ; Homogeneous Liquids. 
The angle of rotation, represented by an (for sodium light), varies 
with the length of the column of substance through which the 
light passes. One decimetre has been chosen as unit of length. 
The angle also varies with the temperature, which must conse- 
quently be determined for each observation. 

For the comparison of the rotary power of different substances, 
use is made of the constant specific rotation^ which may be defined 
as the angle of rotation, produced by I gram of active substance 
in i c.c. by a layer I dm. in length. This is obtained by dividing 
the observed angle of rotation by the product of the length in 
decimetres, and the density of the substance at the temperature 
at which the observation was made. 



/ x d 



Molecular Rotation is the above quantity multiplied by 
the molecular weight M of the compound, and divided by 100 to 
avoid unwieldy numbers, and is represented thus 






It expresses the angle of rotation of i mm. of active substance 
containing i gram-molecule in i c.c. 



PRACTICAL ORGANIC CHEMISTRY 



Rotation of Ethyl Tartrate. Fill a 200 mm. polarimeter- 
tube with the tartrate prepared. Whilst it is settling determine 
the zero of the instrument, and if it does not coincide with the 
zero of the graduated circle, a corresponding correction must be 
introduced in the subsequent observations. The tube is then 
placed in the instrument, and the angle of rotation determined 
by turning the analyser N until equality of illumination is estab- 
lished in the two halves of the field. In making polarimetric 
observations reliance should not be placed on a single setting of 
the instrument, but at least five or six readings should be made, 
which, with a good instrument, should not differ by more than 
four or five minutes. The temperature at the time of observa- 
tion must be noted, and the density determined either at that 
temperature or at two or three other temperatures, and the 
required density found by extrapolation. 

Example : 



Temp. 


Length. 


a 


d 


[a] D 


20 


199-85 mm. 


1 8 28' 


1-2059 


7-66 



[o]g = 7-66 
M{? = 7-47 
[a]jf = 7-27 

MB = 7-07 

[a] = 6-86 
[a]{ = 6-66 



Anschiitz, Pictet, Ber., 1880, 13, 1177. 



By extrapolation. 



Rotation of Tartaric Acid. The specific rotation of a 
dissolved substance can be calculated from the rotation of the 
solution if the concentration is known. The formula to be used 
for this purpose is : 



where a is the angle of rotation of solution, / the length of the 
tube, and c the concentration, i.e., the weight in grams of the 
dissolved substance contained in 100 c.c. of solution. The 



formula [a] D = 



Ip a 



may also be used (it is, in fact, identical), 



where p is the percentage (by weight) of substance in solution, 



ROTATION OF TARTARIC ACID 



and d the density of the solution. The specific rotation of dis- 
solved substances varies with the concentration and with the 
temperature. 

Heat some tartaric acid in an air-bath to 1 10, until it is quite 
dry. Weigh accurately about 20 grams of the dry acid and 
dissolve in water ; then make up the solution to exactly 100 c.c. 
Determine the rotation of the solution in a 200 mm. tube, and 
note the temperature at which the observation is made. 

Take 50 c.c. of the solution and dilute it to 100 c.c. Deter- 
mine the rotation of this solution at the same temperature as 
that at which the first rotation was observed. 

Dilute 50 c.c. of the second solution to 100 c.c., and again 
determine the rotation at the same temperature. 

The same process can be repeated once or twice more. Cal- 
culate the specific rotation of the tartaric acid, using the first 
formula. Plot the results on squared paper, making the ordi- 
nates specific rotation and the abscissae concentration. 

Example : 



Temp. 


Concentration. 


Length of tuKe. 


Angle of Rotation. 


Spec. Rot. 122. 


IO 
IO 


40 
20 


2OO mm. 



6 
3 59' 


+ 7'5 
+ 9-96 


10 


10 





2 II' 


+ 10-91 



(Krecke, Bischoff, Stereocheniie, p. 228.) 

The following table shows the influences of temperature on 
the specific rotation of an aqueous solution containing 20 grams 
of tartaric acid in 100 c.c. 



Temp. 


Length of tube. 


Angle of Rotation. 


Specific Rotation. 


O 


200 mm. 


3 28' 


+ 8-66 


10 




3 5' 


+ 9-96 


2O 




4 38' 


+ 11-57 


40 




5 28' 


+ 13-66 


60 




6 28' 


+ 16-16 


80 




7 21' 


+ 18-38 


1 00 




8 36' 


+ 21-50 



(Thomsen, /. prakt. Cli [2] 32, 211.} 



PRACTICAL ORGANIC CHEMISTRY 



PREPARATION 35 
Eacemic Acid and Mesotartaric Acids. 

CH(OH).COOH 

+ H 2 
CH(OH).COOH 

Pasteur, Ann. Chim. Phys., 1848, (3)24, 442 ; 1850, (3) 28, 56 ; 
Dessaignes, Bull. Soc. Chim., 1863, 5, 356 ; Jungfleisch, Bull. 
Soc. Chim., 1872, 18, 201 ; Hollemann, Rec. trav. chim. Pays-Bas^ 
1898, 17, 66. 

100 grms. tartaric acid. 

350 caustic soda (in 700 c.c. water). 

Boil the tartaric acid and caustic soda solution for three hours 
in a round flask (i litre), or preferably in a tin bottle furnished with 
reflux condenser. The use of a tin vessel obviates certain diffi- 
culties of filtration which the solution of the silica by the action 
of the alkali on the glass entails. The liquid, after boiling, is 
carefully neutralised with cone, hydrochloric acid (it is advis- 
able to remove a little of the solution beforehand in case of 
overshooting the mark) and an excess of calcium chloride solu- 
tion is added to the hot liquid. The mixture is left overnight, 
and the calcium salts filtered off at the pump, washed with 
water, and well pressed. 

The calcium salts are well dried on the water-bath, or a frac- 
tion of the whole weight of the moist salts is taken and dried, 
and the total dry weight estimated. The substance is then sus- 
pended in boiling water and the calculated quantity of sulphuric 
acid added, after which the mixture is boiled for an hour. The 
calcium sulphate is removed by filtration, well washed with hot 
water, and the precipitate pressed down. The filtrate is concen- 
trated on the water-bath until crystallisation begins. Racemic 
acid crystallises first, and after dehydrating on the water-bath 
melts at 205. A further quantity is obtained on evaporation. 
Yield 5060 grains. 

The last mother liquors contain mesotartaric acid, m. p. 143 
144, which is much more soluble in water than racemic acid. 
To obtain a pure specimen repeated crystallisation is necessary. 



RACEMIC ACID AND MESOTARTARIC ACID 123 

The yield varies with the period of boiling, but usually does not 
exceed 10 grams. 

Resolution of Racemic Acid. The racemic acid is dis- 
solved in water (250 c.c.) and divided into two equal volumes. 
Half of the solution is carefully neutralised with caustic soda 
and the other half with ammonia, and the two solutions then 
mixed. 

The liquid is concentrated and poured into a crystallising dish. 
If, on cooling, the crystals are small and massed together, the 
solution has been too concentrated, and must be diluted so that 
small, well-defined crystals deposit. A dozen or so of these are 





FIG. 74. 



picked out, dried, and put on one side. The remaining crystals 
are re-dissolved and left to cool in a room of fairly even tempera- 
ture. 

When the solution is just cold the crystals, previously re- 
moved, are sown evenly over the bottom of the dish at distances 
of I 2 cms. apart and left for two days. The crystals will have 
now grown to a size which will enable the facets to be readily 
recognised. Each crystal is dried and carefully examined with 
a pocket lens in order to determine the position of the hemi- 
hedral facets, and placed in separate heaps. These facets lie 
to the right or left hand of the central prism face, as shown in 
Fig. 74. The crystals should be weighed, dissolved, and the 
solution diluted and examined in the polarimeter. The specific 
rotation may then be calculated. See Appendix, p. 264. 



124 PRACTICAL ORGANIC CHEMISTRY 

PREPARATION 36. 
Pyruvic Acid, CH 3 .CO.CO.OH. 
Doebner, Annalen, 1887, 242, 268. 

200 grms. potassium hydrogen sulphate. 
100 tartaric acid. 

The potassium hydrogen sulphate and tartaric acid must be 
finely powdered and intimately mixed. The mixture is distilled 
in a round flask (i litre), attached to a moderately long condenser 
tube, from a paraffin bath heated to 220.* The mass at first 
froths up, and it is necessary to interrupt the heating when the 
flask is not more than half full of froth, as otherwise it may 
boil over. When the temperature of the bath has fallen to 
about 120, the heating may be recommenced. The distillation 
is carried on until no more liquid distils. The distillate, which 
consists of water and pyruvic acid, and has a yellow colour, is 
fractionated in vacua. It is collected at 68 70 at a pressure 
of 20 mm., and is quite colourless. Yield 15 20 grams. It 
may be fractionated at the ordinary pressure, but is difficult to 
obtain colourless in this way. 

CO.OH.CHOH.CHOH.COOH = CH 3 .CO.COOH + CO 2 +H 2 O 

Properties. Colourless liquid ; b. p. 165 at atmospheric 
pressure ; m. p. 10 11 ; polymerises on keeping. 

Reaction. Dissolve a drop of phenylhydrazine in two drops 
of glacial acetic acid, dilute with about I c.c. of water, and add 
a drop of pyruvic acid. A yellow crystalline precipitate of the 
phenylhydrazone, CH 3 .C:(N.NH.C 6 H 5 ).CO.OH, is formed. 

CH 2 .COOH 
Citric Acid, C(OH).COOH + H 2 O 

CH 2 .COOH 
Scheele (1784). 

Citric acid occurs in the free state, as well as in the form of 
the calcium and potassium salt?, associated with malic and tar- 



CITRACONIC AND MESACONIC ACID 125 

taric acid, in many plants. It is prepared principally from 
lemon juice, from which it is precipitated as the calcium salt on 
boiling with chalk and also by the citric fermentation of 
glucose. 

Properties. The acid, which contains I molecule of water, 
crystallises in prisms ; soluble in water, alcohol, and also mo- 
derately soluble in ether ; m. p. 100. The anhydrous acid melts 

at 153 154- 

Reactions. i. Heat a little of the acid and notice the irri- 
tating vapours. 

Make a neutral solution of sodium citrate by adding caustic 
soda to a solution of the acid. 

2. Add lime water. There is no precioitate of the calcium salt, 
(C 6 H 6 O 7 ) 2 Ca 3 + 4H 2 O, until the solution is boiled. 

3. Add calcium chloride solution and boil, and, to another 
portion, silver nitrate solution. Note the results and compare 
the reactions with those of tartaric acid (p. 115). 



PREPARATION 37. 

Citraconic and Mesaconic Acids. 
(Methyl fumaric and Methyl maleic acid). 

CH 3 .C(COOH):CH(COOH). 

Kekule, Lehrbuch, 2, 319 ; Fittig, Anna/en, 1877, 188, 73. 
250 grms. citric acid (crystallised). 

Heat the crystallised citric acid, without powdering, in a porce- 
lain basin to a temperature not exceeding 150. The water of 
crystallisation is expelled, and the crystals become pasty and 
then fluid. When cold, the solid mass is removed from the 
basin by gently warming, and is coarsely powdered. The anhy- 
drous acid is rapidly distilled in portions of 100 grams, from a 
retort (250 c.c.) with bent neck (see Fig. 19, p. 22), fitted to a con- 
denser, the receiver being a separating funnel. The distillate 
consists of two layers. The lower layer of impure citraconic 
anhydride is run off, and the upper layer, consisting of water and 
citraconic acid, is fractionated, the portion distilling at 190 210 
being collected and mixed with the previous lower layer. 



126 PRACTICAL ORGANIC CHEMISTRY 

The citraconic anhydride is now distilled in -vacua and col- 
lected at no 114 under a pressure of 30 mm. Yield 30 35 
grams. 

CH 2 .COOH CH 3 

C(OH).COOH = C.CO\ + CO 2 + 2H 2 O. 

! II \o 

CH 2 .COOH CH.CO/ 

Properties. Colourless liquid; b. p. 213 214 (ordinary 
pressure). To convert the anhydride into citraconic acid the 
calculated quantity of water is added (i mol. acid : I mol. water), 
and the mixture well stirred. The whole solidifies, on standing, 
to a mass of colourless crystals of citraconic acid, which are 
dried on a porous plate ; m. p. 8486. 

MESACONIC ACID. To a saturated solution of citraconic acid 
in ether (4 parts citraconic acid require about 5 parts of anhy- 
drous ether), about I part of chloroform is added, and a few 
drops of a moderately strong solution of bromine in chloroform. 
The mixture is placed in strong sunlight, when mesaconic acid, 
which is insoluble in ether and chloroform, begins at once to 
deposit on the side of the vessel nearest the light. Drops of 
bromine are added from time to time until no further precipita- 
tion occurs. The pasty mass is then filtered, washed with ether, 
and dried on a porous plate. Yield 73 per cent, of the citraconic 
acid ; m. p. 202 : . See Appendix, p. 265. 

PREPARATION 38. 
Urea (Carbamide), 



Wohler, Pogg. Ann., 1828, 12, 253; Clemm, Annalen, 1848, 
66, 382. 

50 grms. potassium cyanide (98 99 per cent). 
140 red oxide of lead. 
25 ammonium sulphate. 

The potassium cyanide is heated in an iron dish over a 
large burner until it begins to fuse, when 140 grams of red 
oxide of lead are gradually added in small quantities and 
stirred in. The heat of the reaction causes the mass to melt 



UREA 127 

and froth up.- When it fuses quietly, the dark coloured liquid 
mass is poured on to an iron plate and allowed to cool. 
It solidifies and is powdered and separated from the solid 
cake of metallic lead. 200 c.c. of cold water are poured on 
to the crude cyanate and, after standing an hour, filtered 
through a fluted filter and washed with a little cold water. 
A concentrated solution of 25 grams of ammonium sulphate 
is immediately added to the filtrate, which is evaporated to 
dryness on the water-bath, the mass being stirred occa- 
sionally to prevent the formation of a surface crust. The 
cooled residue is powdered and the urea extracted with alcohol 
by boiling on the water-bath, using a reflux condenser and 
adding successively small quantities of spirit until the extract 
leaves only a small residue on evaporation on a watch-glass. 
The greater part of the alcohol is distilled off on the water- 
bath, and the residue poured out into a beaker to crystallise. 
Yield about 15 grams. 

1. 4KCX + Pb;jO 4 = 4CONK + 3?b 

2. (NH 4 ) 2 SO 4 + 2CONK = 2CON.NH 4 + K 2 SO 4 

3. CON.NH 4 = CO(NH 2 ) 2 

Properties. Colourless prisms ; m. p. 132; very soluble in 
water ; soluble in hot alcohol. 

Reactions. I. Add to a strong solution of urea in water a 
drop of concentrated nitric acid, and to another portion a 
concentrated solution of oxalic acid ; the crystalline nitrate 
CO(NH 2 ) 2 HNO 3 and oxalate (.CO(NH 2 ) 2 ) 2 C 2 H 2 O 4 are deposited. 

2. Melt a few crystals of urea over a small flame and heat 
gently for a minute, so that bubbles of gas are slowly evolved. 
Cool and add a few drops of water, then a drop of copper sul- 
phate solution, and finally a tew drops of caustic soda. A violet 
or pink coloration is produced, depending upon the quantity of 
bittret formed. 

2CO(NH 2 ) 2 NH/CO.NH 2 + ^ 

Biuret. 

3. Add a few drops of sodium hypochlorite, or hypobromite, 
to a solution of urea in water. Nitrogen is given off, 
CO(NH 2 ) 2 + 3NaOCl = N 2 + 2H 2 O + sNaCl + CO 2 (which 
dissolves in the alkaline solution"). 



128 PRACTICAL ORGANIC CHEMISTRY 

4. Add to a solution of urea a few drops of hydrochloric acid 
and a solution of sodium nitrite. Effervescence occurs and 
nitrogen and carbon dioxide are evolved. 

CO(NH 2 ) 2 + 2HO.NO = 2N 2 + CO 2 + 3H 2 O. 

5. Heat a little urea with soda-lime. Ammonia is evolved. 
See Appendix, p. 267. 

PREPARATION 39. 
Thiocarbamide (Thiourea), SC^SS 2 " 

\IN rl 2 

Reynolds, Trans. Chem. Sot:., 1869, 22, i ; Volhard, J. prakt. 
Chem., 1874, (2), 9, 10. 

50 grms. ammonium thiocyanate. 

The ammonium thiocyanate is melted in a round flask in a 
paraffin-bath, and kept at a temperature at which the mass re- 
mainsjust liquid (140 145) for 5 6 hours. The cooled melt is 
powdered and ground with half its weight of cold water, which 
dissolves unchanged ammonium thiocyanate, but little of the 
thiourea. By dissolving the residue in a little hot water, pure 
thiourea is obtained, on cooling, in colourless, silky needles. 
Yield 7 8 grams. 

CNS.NH 4 = CS(NH 2 ) 2 . 

Properties Colourless, rhombic prisms (from dilute aqueous 
solution), long silky needles (from concentrated solutions) ; m. p. 
172. Very slightly soluble in cold water (i part of thiourea dis- 
solves in about 1 1 parts of water at the ordinary temperature). 

HN CO L 

Uric Acid, CO C NH 

I || >CO 
HN C NH 

Scheele (1776). 

Uric acid is a product of the metabolism of the animal 
organism. It is usually prepared from guano, which is treated 
first with dilute hydrochloric acid to remove phosphate of cal- 
cium. The uric acid is then dissolved out with hot caustic soda 
and the clear alkaline solution precipitated with acid. 



ALLOXANTIN 129 



Properties. Uric acid forms microscopic crystals of a charac- 
teristic shape. It is insoluble in water, but dissolves in the 
presence of many organic substances. On dry distillation it 
yields ammonia, cyanuric acid, and urea. 

Reactions. Evaporate a little of the acid with a few c.c. of 
dilute nitric acid to dryness on the water-bath. An orange or 
red residue remains. On cooling, add ammonia. A fine purple 
colour is produced (murexide test) ; see also Reaction for 
alloxan (p. 130). 

PREPARATION 40. 

Alloxantin, C 8 H 4 N 4 O 7 + sH 2 O 

Liebig, Wohler, Annalen, 1838, 26, 262. 

10 grms. uric acid. 

20 (18 c.c.) cone, hydrochloric acid diluted with an 

equal weight of water. 

21 potassium chlorate. 

The hydrochloric acid is poured over the uric acid. The 
mixture is heated to 35, and the potassium chlorate, finely 
powdered, is added in small quantities at a time with constant 
shaking. When about two grams of the chlorate have been 
added, the uric acid will have nearly dissolved, and the liquid 
has a faint yellow colour. It is diluted with double its volume 
of water, allowed to stand for about an hour, and filtered. The 
filtrate is saturated with hydrogen sulphide, and yields, 
after being left for 12 hours, crystalline crusts, often of a 
reddish tint, of alloxantin mixed with sulphur. It is filtered 
and washed with cold water, and the alloxantin dissolved in a 
small quantity of hot water, and filtered from the residue of 
sulphur. On cooling the filtrate, colourless crystals separate 
out. Yield 7 8 grams. 

C 5 H 4 N 4 O 3 + O + H 2 O = C 4 H 2 N 2 O 4 + CON 2 H 4 . 

Uric acid. Alloxan. Urea. 

2C 4 H 2 N 2 O 4 + H 2 S = C 8 H 4 N 4 O T + S + H 2 O. 

Alloxantin. 

Properties. Hard, colourless crystals, slightly soluble in coki. 
more readily in hot water. 
COHEN'S ADV. p. o. c. K 



130 PRACTICAL ORGANIC CHEMISTRY 

Reactions. I. Add to the solution of alloxantin a little baryta 
water ; a violet colouration is produced. 

2. Add ammonio-silver nitrate solution and warm ; metallic 
silver is deposited. 

3. Boil the solution with mercuric oxide ; a violet solution of 
murexide is formed. 



PREPARATION 41. 
Alloxan (Mesoxalylurea), CO ' 



Liebig, Wohler, Annalen, 1838, 26, 256. 

5 grms. alloxantin. 

S 11 (3'S c - c -) cone, nitric acid (sp. gr. 1*4). 
10 (7 c.c.) fuming (sp. gr. 1-5). 

The finely powdered alloxantin is added to a mixture of the 
strong and fuming nitric acid, and left to stand. Slight evolu- 
tion of nitrous fumes occurs, and the alloxantin, which at first 
remains at the bottom of the vessel, slowly changes into the 
more bulky crystals of alloxan, which gradually fill the liquid. 
The reaction lasts about two days, and is complete when a 
sample dissolves readily and completely in cold water. The 
crystalline mass is spread upon a porous plate, thoroughly dried 
in the air, and freed from traces of nitric acid by heating in a 
basin on the water-bath, until the smell of the acid disappears. 
Alloxan may be obtained in large crystals by dissolving the dry 
product in the smallest quantity of hot water, and allowing the 
solution to evaporate slowly in a desiccator over sulphuric acid. 
The crystals are liable to effloresce. 

C 8 H 4 N 4 O 7 -1- O = 2C 4 H 2 N 2 O 4 . 

Alloxantin. Alloxan. 

Properties. Colourless crystals, containing 4 molecules of 
water of crystallisation. 

Reactions. i. A small quantity of the alloxan solution is 
evaporated to dryness on the water-bath in a porcelain basin. 
A reddish residue is left, which turns purple on the addition of 
Ammonia (murexide). See Appendix, p. 268. 



CAFFEINE 



PREPARATION 42. 



CH,.N CO 



Caffeine (Trimethyl xanthine), 



COC N(CH 3 ) 

i ii \ 

iCH 



CH.N C 



100 grms. tea. 

Digest the tea with 500 c.c. boiling water for a quarter of an 
hour, and filter through cloth into a basin placed over a ring 
burner (see p. 108), so that the liquid in the filter is kept hot. 
Moderately fine unsized cotton cloth is used, and is wetted and 
stretched on a wooden frame as shown in Fig. 75. Wash with 
a further 250 c.c. of boiling water. Add to the filtrate a solu- 
tion of basic lead acetate (made by boiling acetate of lead 
solution with excess of litharge, and then filtering) until no more 




FIG. 75. 

precipitate is formed. Filter hot through a large fluted filter 
from precipitated albumin, and wash with water. To the boil- 
ing filtrate add dilute sulphuric acid until the lead is precipitated 
as sulphate. Filter or decant from the sulphate of lead, and 
concentrate the solution with the addition of animal charcoal 
to 250 300 c.c. Filter and extract the filtrate three times with 
small quantities (50 c.c.) of chloroform. Distil off the chloro- 
form on the water-bath, and dissolve the residue in a small 
quantity of hot water. On allowing the solution to evaporate 
very slowly, long silky needles of caffeine separate, which may 
have a slightly yellow tint, in which case they should be drained, 
re-dissolved in water, and boiled with the addition of animal 
charcoal. The needles contain one molecule of water, which 
they lose at 1 00 and melt at 234*5. Yield about i'5 grams. 
See Appendix, p. 269. 

K 2 



PRACTICAL ORGANIC CHEMISTRY 



PREPARATION 43. 

/N(CH 3 ).CH 2 .CO.OH 

Creatine. HN:C<; +H.O 

\NH 2 

Neubauer, Annalen, 1861, 119, 27. 
500 grms. meat. 

The meat, separated as far as possible from fat, is put through 
a sausage machine, or finely chopped and digested with \ iitre 
of water at 50 60, and well stirred from time to time. It is 
filtered through cloth (see Fig. 75, p. 131), and is then digested 
with a further 250 c.c. of water in the same way, filtered, and 
the cloth removed from the frame and squeezed out. The 
filtrate is heated to boiling to coagulate the albumin, and, on 
cooling, filtered. Basic acetate of lead is carefully added, just 
sufficient to precipitate the soluble albumin. The liquid is 
again filtered through a fluted filter, and the lead removed with 
hydrogen sulphide, which is passed into the warm liquid. 
The filtrate from the sulphide of lead is concentrated to a thin 
syrup on the water-bath and then transferred to a vacuum 
desiccator, where it is left over sulphuric acid. In a short time, 
especially on the addition of a crystal of creatine, needle-shaped 
crystals begin to separate, and when no further crystallisation 
is observed, the crystals, which have a brown colour, are 
brought on to a porcelain funnel, and washed with a little 
spirit. They are recrystallised from a little hot water, with the 
addition of animal charcoal. Yield about I gram. The filtrate 
r'rom the creatine contains hypoxanthine and sarcolactic acid, 
but the small quantity of these two constituents render them 
difficult to extract 

Properties. Small rhombic prisms ; with difficulty soluble 
in cold water, readily soluble in hot water. On warming with 
alkalis, it decomposes into urea and sarcosine, 

/N(CH 3 ).CH 2 .COOH 
HN:C< 

\NH, 
NH(CH 3 ).CH,.COONa. 



TYROSINE LEUCINE -133 

PREPARATION 44. 

Tyrosine, (OH).C 6 H 4 .CH 2 .CH(NH 2 ).COOH 

CH 3 \ 
Leucine, >CH.CH 2 .CH(NH 2 ).COOH 

CU/ 

Beyer, Zeit., 1867, 436 ; E. Fischer, Ser., 1901, 34, 433. 
100 grms. hoof or horn shavings (washed free from dirt). 



2 5 55 ( 1 3& c - c -) cone, sulphuric acid (in 750 c.c. water). 

The shavings and acid are heated in a round flask (i litres) on 
the water-bath until the greater part is dissolved, and then boiled 
with reflux condenser over wire-gauze for about 20 hours, until the 
solution no longer gives the biuret reaction (p. 127). Add to a 
little of the liquid two drops of copper sulphate solution and make 
alkaline with caustic soda ; if the colouration is violet or pink 
instead of blue, continue to boil. After boiling, the dark 
coloured liquid is poured into a large basin and neutralised whilst 
hot with slaked lime. The hot liquid is filtered and the residua! 
calcium sulphate replaced in the basin and extracted twice with 
300 c.c. of hot water. The united filtrates are concentrated and 
made up to a litre. The total quantity of oxalic acid (about 20 
grams) required to precipitate the dissolved calcium salts is 
determined by a preliminary estimation with 50 c.c. of the solution. 
The liquid is boiled before adding the acid and filtered hot from 
the precipitated calcium oxalate. The precipitate is extracted 
twice with 250 c.c. of water and concentrated (to about 250 c.c.) 
until crystals appear on the surface. 

Tyrosine. On cooling, a brown, crystalline crust of impure 
tyrosine separates. It is filtered, dissolved in the least quantity 
of boiling water, boiled with a little animal charcoal, and 
filtered. On cooling, long, white, silky needles of tyrosine are 
deposited. Yield about 2 grams. 

Reactions. Warm a small quantity of the substance with a 
drop of strong nitric acid and add ammonia. A yellow solution 
is produced in the first case, which changes to deep orange with 
ammonia (xanthoproteic reaction). Warm with a solution of 
mercury in strong nitric acid (Millon's reagent). The liquid 
turns red, and a red precipitate is then formed. 

Leucine. The filtrate from the tyrosine is further con- 
centrated on the water-bath to a small bulk, when on cooling a 



134 



quantity (about 20 grams) of crude leucine in the form of a brown 
crystalline crust separates, and is collected on a filter and 
dried on a porous plate. It is converted into the ester 
hydrochloride as follows : the dry material is dissolved in 
1 20 c.c. absolute alcohol and saturated with hydrogen chloride 
(p. 93). The alcohol is removed by distilling under reduced 
pressure at a temperature not exceeding 40 in the apparatus 
shown in Fig. 66 (p. 94). The same quantity of alcohol is added, 
saturated with hydrogen chloride, and removed as before. The 
residue, which consists of the ester hydrochloride of leucine and 
small quantities of other amino-acids, is converted into the free 
ester in the following way : it is dissolved in about one-quarter 
its volume of water, to which an equal volume of purified ether 
is then added. The liquid is well cooled in a freezing mixture 
and a cooled 33 per cent, solution of caustic soda is slowly added 
until the liquid is just alkaline, and then an equal volume of a 
saturated solution of potassium carbonate. The mass is now 
well shaken and the ether decanted. In this way the ester, 
which is rapidly hydrolysed by alkali at the ordinary tempera- 
ture, is liberated from the hydrochloride without decomposition 
and dissolves in the ether. The residue is kept in the freezing 
mixture, a fresh quantity of ether, more caustic soda solution, and 
sufficient solid potassium carbonate to form a pasty mass are 
added in succession, shaken up thoroughly and the ether de- 
canted. The residue is extracted two or three times with fresh 
ether and the united extract, freed as far as possible from water, 
is shaken up for a minute with solid potassium carbonate and 
then dehydrated overnight with anhydrous sodium sulphate. 
The ether is removed on the water-bath and the residue distilled 
at a pressure not exceeding 1 5 mm. The colourless liquid, which 
distils at 80 100, has an ammoniacal smell and is nearly pure 
leucine ester. Yield 10 15 grams. The ester is readily 
hydrolysed by boiling five times its weight of water with reflux 
condenser until the alkaline reaction disappears (about an 
hour). The liquid is then concentrated on the water-bath until 
crystals separate on the surface and cooled. The leucine 
may be recrystallised from dilute alcohol or dissolved in 
the smallest quantity of hot water and alcohol added until 
a turbidity appears. It forms small glistening plates, which 
melt and sublime at 170. See Appendix, p. 270. 



GRAPE SUGAR 13$ 

PREPARATION 45. 

Grape Sugar. (Glucose, Dextrose.) 

Soxhlet, J.prakt. Ch., 1880, (2) 21, 245. 

CH 2 OH.CHOH.CHOH.CHOH.CHOH.CO.H 

250 grms. cane sugar. 
750 c.c. spirit. 
30 c.c. cone, hydrochloric acid. 

The spirit and acid are mixed and warmed to 45 50, whilst 
the finely powdered cane-sugar is gradually added and stirred. 
When the sugar has dissolved the solution is cooled, and a few- 
crystals of anhydrous grape-sugar added. On standing for a 
day or two the grape-sugar deposits in the form of fine crystals, 
which continue to increase in quantity. When no further de- 
position is observed, the crystals are filtered and washed with 
spirit. The sugar may be purified by dissolving in a little 
water to a syrup, and adding hot methyl alcohol until a turbidity 
appears. On cooling, the grape-sugar crystallises out. 

C^H^Oii "*" ^O = C 6 H ]2 O 6 + C 6 H 12 O 6 . 

Cane sugar. Glucose. Fructose. 

Properties. Colourless crystals ; m. p. 146 ; soluble in hot 
and cold water, insoluble in alcohol. 

Reactions. I. Add to a little of the solution of glucose a few 
drops of caustic soda, and warm. The colour changes from 
yellow to brown. 

2. Add to 2 or 3 c.c. of the solution two or three drops of copper 
sulphate, and then caustic soda, until a clear blue solution is 
obtained, and heat to boiling. Red cuprous oxide is precipi- 
tated. 

3. Add a few drops of glucose solution to half a test-tube 
of ammonio-silver nitrate solution and place the test-tube in 
hot water. A mirror of metallic silver is formed. 

4. Dissolve about o'5 gram of glucose in 5 c.c. of water, and 
add a solution of phenylhydrazine acetate, made by dissolving 
i gram of phenylhydrazine in the same weight of glacial acetic 
acid, and diluting to 5 c.c. Mix the solutions and warm in the 



136 PRACTICAL ORGANIC CHEMISTRY 

water-bath. In a few minutes the yellow crystalline phenyl- 
glucosazone (m. p. 204 205) is deposited. 

5. Mix a few drops of a glucose solution with a few drops of 
an alcoholic solution of a-naphthol and pour slowly down the side 
of the test-tube a few drops of cone, sulphuric acid. A violet 
colouration is produced. (Molisch's reaction.) See Appendix, 
p. 271. 

Benzene. 

Pure Commercial Benzene, obtained from coal-tar 
naphtha, should distil within one degree (80 8r), and solidify 
completely when cooled to o. Other tests are as follows : 
shaken with concentrated sulphuric acid for a few minutes, the 
acid should not darken, and a drop of bromine water should 
not be immediately decolourised. A single distillation over a 
few small pieces of sodium, which absorb any traces of water, is 
usually a sufficient purification. If the benzene impart a brown 
or black colour to the sulphuric acid, it must be repeatedly 
shaken with about 20 per cent, of the acid until the latter 
becomes only slightly yellow on standing. This is done in a 
stoppered separating funnel, and after shaking for a few minutes 
the mixture is allowed to settle, and the lower layer of acid 
drawn off. The benzene is then shaken two or three times with 
water to free it from acid, carefully separated from the aqueous 
layer, and left in contact with fused calcium chloride until the 
liquid becomes clear. It is then decanted, frozen in ice, and 
any liquid (carbon bisulphide, paraffins) carefully drained off, 
and the benzene finally distilled over sodium. 

Properties. Mobile, colourless liquid ; m. p. 5*4 ; b. p. 80*4 ; 
sp. gr. 0*874 at 2O - Coal-tar benzene usually contains a little 
thiophene, C 4 H 4 S, which may be detected by dissolving a few 
crystals of isatin (see p. 229) in concentrated sulphuric acid and 
shaking up with the benzene. If thiophene is present, a blue 
colour is produced (indophenin reaction). 

Fractional Distillation. It is often possible to separate 
almost completely by a single distillation, two liquids occurring 
together in a mixture when their boiling points lie widely apart. 
The more volatile liquid first passes over, the temperature 
suddenly rises, and the higher boiling liquid distils. 

It is otherwise-when a liquid consists of a mixture of sub- 
stances boiling at temperatures not very far removed from one 



BENZENE 



137 



another, especially in the case of homologous compounds, such 
as occur in petroleum and coal-tar naphtha. One distillation 
suffices only to produce very partial separation of the different 
substances, a portion of the less volatile liquid being carried 
over in the first distillate, together with the more volatile body, 




FIG. 76 represents a series of simple and efficient fractionating columns or still- 
heads. A is that of Vigreux, in which the constrictions are formed by in- 
denting the tube itself ; B is Hempel's column and consists of a long wide tube 
filled with glass beads ; c, D, and E are columns devised by Young and Thomas, 
the last being useful when large quantities of liquid have to be distilled, c con- 
tains a series of glass discs fused on to a rod, which can be removed from the 
tube ; p has a series of pear-shaped bulbs blown on the stem, and K is a wide 
tube with a series of constrictions in each of which a small bent glass dripping 
tube is suspended in a gauze cup. 

the temperature gradually rising throughout the distillation. In 
order to effect separation of the several substances, recourse is 
had to the method of fractional distillation. 

The liquid is distilled in a round flask over wire-gauze or, 
better, in a fusible metal bath, a bit of porous pot or a coil of 



138 PRACTICAL ORGANIC CHEMISTRY 

platinum-wire being placed in the flask to prevent bumping. 
The flask is surmounted with a fractionating column, in which 
the thermometer is fixed. Various forms of fractionating columns 
are used (see Fig. 76). 

The effect of the column may be explained as follows : the 
vapour given off from a mixture of liquids contains a larger pro- 
portion of the more volatile constituent than the liquid. If this 
vapour is condensed in its ascent, the vapour above this con- 
densed liquid will be still richer in the more volatile constituent. 
If, by a series of constrictions or diaphragms, the condensed 
liquid is obstructed in its return flow, a momentary equilibrium 
between liquid and vapour is established at each diaphragm, and 
the longer the column the greater will be the amount of more 
volatile constituent in the last portion of vapour to undergo con- 
densation. This passes off by the condenser and is collected 
in the receiver. The apparatus (Fig. 76, E) can be made out 
of a piece of wide tubing. This is constricted in the blow-pipe 
flame, near one end, and a piece of copper wire-gauze with a 
circular hole, carrying the little bent tube, is placed on the con- 
striction. A second constriction is made and another gauze 
diaphragm introduced. The number of diaphragms may vary 
from 10 to 20, according to the degree of separation required. 1 

Commercial 50 per cent, and 90 per cent. Benzene 
are mixtures of benzene and larger or smaller quantities of its 
higher boiling homologues, viz., toluene (b. p, I ro) and the 
xylenes (b. p. 137 143). The constituents may be separated by 
fractional distillation. 

Fit up an apparatus with fractionating column and distil 
200 c.c. 50 per cent, or 90 per cent, benzene, at a regular speed, 
so that the drops falling from the end of the condenser may be 
readily counted. Collect the distillate between every five degrees 
in separate flasks. Redistil each of these fractions in order, 
adding the next to the residne of the previous one in the 
distilling-flask. Collect portions boiling below 85 and above 
105, between every two or three degrees. It will be found that 
by a repetition of the process the liquid is gradually separated 
into two large fractions, consisting chiefly of benzene and toluene, 
and a number of smaller intermediate fractions. The following 
table gives the volume in c.c., and the- boiling points of the 

1 Trans. Chem. Sac., 1899, 76, 700. 



fractions obtained by this method from 200 c.c., 50 per cent, 
benzene, each table denoting a complete series of fractionations, 
using a simple column with two bulbs. 



A. 
71-5-85 


B. 

85-90 


C. 

90-95" 


D 

95-100 


E. 

100-105 


F. 
105-110 

17 c.c. 


G. 

110-115 


Residue. 


in c.c. 


53 c.c. 


26 c.c. 


15 c.c. 


13 c.c. 


21 C.C. 


33 c.c. 



II. 





A' 

below 

79- 


B'. 

79-81 


C'. 

81-85 


D'. 

85-105 


E'. ' 

105-108 


F'. 
108-110' 


Residue. 


A. 
















Added 
B. 

Added 
C. 




42 c.c. 


'lOC.C.*) 

(9 c c ) 


. - 


... 


... 




Added 
D. E. 
















Added 
F. 


... 














Added 
G. 
















*Refrac- 
tionated 
C'. 
















E'. 










6 uc 
























5 c.c. 


54 c.c. 


7 c.c. 


50 c.c. 


6 c.c. 


27 c.c. 


42 c.c. 



The fraction 79 8r is further purified in the manner already 
described. 



140 PRACTICAL ORGANIC CHEMISTRY 

PREPARATION 46. 
Bromobenzene (Phenyl bromide), C G H 6 Br. 

Cohen and Dakin, Trans. Chem. Soc., 1899, 76, 894; Cross 
and Cohen, Proc. Chem. Soc., 1908. 

50 grms. benzene. 
120 (40 c.c.) bromine. 
5 pyridine. 

The apparatus is similar to that shown in Fig. 63, p. 89, but the 
flask should be placed in a water-bath, in which it can be heated, 
and the tap-funnel may be dispensed with. The benzene, bro- 
mine, and pyridine .are placed in the flask and heated to 2 5 30, 
when a vigorous and steady evolution of hydrogen bromide 
takes place, the gas being absorbed by the water in the beaker. 
When the action slackens (about i hour) the temperature of the 
water-bath is gradually raised to 65 70, and the process 
stopped when most of the bromine has disappeared and the 
evolution of hydrogen bromide has nearly ceased. The con- 
tents of the flask are cooled and poured into dilute caustic soda 
solution contained in a separating funnel and shaken. Suffi- 
cient alkali must be present to give an alkaline reaction after 
shaking. The lower layer is drawn off and dehydrated over 
calcium chloride. When perfectly clear the bromobenzene is 
filtered or decanted into a distilling flask (200 c.c.) provided 
with a thermometer and distilled over wire-gauze. Unchanged 
benzene first passes over ; the temperature then rises rapidly 
and the portion boiling at 140 170 is collected separately. It 
is redistilled and collected at 150 160. Yield 60 grams. 



The pyridine acts as "halogen carrier," probably by forming 
the additive compound C 5 H 5 NBr 2 , which gives up its bromine to 
the benzene. 

Properties. Colourless liquid ; b. p. 154 155 ; sp. gr. 1*496 
at 1 6. 

Hydrobromic Acid. The weak solution of hydrobromic 
acid which collects in the beaker in the course of the above re- 



ETHYL BENZENE 141 

action may be concentrated by fractional distillation, as in the 
case of hydriodic acid (p. 113), and used in the preparation of 
bromotoluene (p. 167). It boils at 126 at the normal pressure, 
has a sp. gr. of 1*49, and contains about 47 per cent, of HBr. 
See Appendix, p. 271. 

PREPARATION 47. 

Ethyl Benzene, C 6 H 5 .C 2 H 5 

Fittig, Annalen, 1864, 131, 303. 

60 grms. bromobenzene. 

52 ethyl bromide (see p. 54). 

26'5 sodium. 

A quantity of ether, which has been freed from alcohol by 
distilling over caustic potash, and dried over calcium chloride 
and sodium (see p. 61), is poured into a round flask (i litre). 
The amount of ether should be about twice the volume of the 
mixed phenyl and ethyl bromides. The sodium, cut into thin 
slices with the sodium knife, or squeezed into fine wire, is added 
to the ether, and when all evolution of hydrogen has ceased, 
the flask is attached to an upright condenser and immersed in 
a vessel of ice-water. The mixture of bromobenzene and ethyl 
bromide, lx>th carefully dehydrated, is poured into the flask. 
The reaction is allowed to commence spontaneously, the fact 
being indicated by the appearance of the sodium, which be- 
comes darker in colour and r.inks to the bottom of the vessel. 
Although the flask is allowed to remain in the outer vessel, and 
is cooled by water and ice, the heat evolved often causes the 
ether to boil. The flask is therefore not removed until the re- 
action is over. It is convenient to leave it over night. The 
liquid is then decanted from the sodium bromide, which has a 
blue colour, into a distilling flask, and rinsed out once or twice 
with ether. The ether is removed on the water-bath, a bit of 
porous pot being added, and the residue is fractionated with a 
fractionating column. The portion boiling at 132 135 is 
collected separately. Yield 20 25 grams. 

C R H 5 Br + CoH 5 Br + 2Na = C 6 H 5 .C,H 5 + 2 NaBr. 

Properties. Colourless liquid; b. p. 134; sp. gr. O'8664 at 
22 P 5. See Appendix, p. 273. 



142 PRACTICAL ORGANIC CHEMISTRY 



PREPARATION 48. 

Nitrobenzene, C 6 H 5 NO 2 
Mitscherlich, Annalen, 1834, 12, 305. 

50 grms. benzene. 

80 (60 c.c.) cone, nitric acid, sp. gr. 1*4. 
120 (60 c.c.) cone, sulphuric acid. 

The two acids are mixed and well cooled, and then slowly 
added from a tap-funnel to the benzene, which is contained in a 
flask ( litre). The contents of the flask are well shaken after 
each fresh addition. Nitrous fumes are evolved, and a consider- 
able amount of heat developed. Care must, however, be taken 
that the temperature does not exceed 50 60 by immersing the 
flask, if necessary, in cold water. The nitrobenzene separates 
out as a brown, oily Iryer on the surface of the acid liquid. 
When the acid has all been added, an operation which lasts 
about half an hour, the mixture is heated for about twenty 
minutes on the water-bath, and again well shaken. The con- 
tents of the flask, on cooling, are poured into a stoppered sepa- 
rating -funnel, the lower layer of acid removed, and the nitro- 
benzene washed free from acid by shaking once with water 
(50 c.c.), then with dilute carbonate of soda solution, and again 
with water, the oil being each time withdrawn from the bottom 
of the vessel. The nitrobenzene, separated as carefully as pos- 
sible from water, is allowed to stand over a few pieces of fused 
calcium chloride, and shaken occasionally until the liquid is 
clear. The yellow liquid is decanted, or filtered from the 
calcium chloride, and distilled in a distilling-flask, with con- 
denser tube only. At first a little benzene passes over ; the 
temperature then rises, and the nitrobenzene distils at 204- 
207', and is separately collected. The brown residue con^is 
of dinitrobenzene, the quantity depending upon whether the 
temperature during nitration has been allowed to rise too high. 
Yield about 60 grams. 

C 6 H 6 + HO.NO 2 = C 6 H 5 NO, + H 2 O. 

The function of the sulphuric acid is that of a dehydrating 
agent taking up the water formed in the reaction. 

Properties. Light yellow liquid, with a smell of bitter 



AZOXYBEXZEXE 143 



'almonds ; b. p. 206 207, sp. gr. I'loS at 15 ; m. p. 3; in- 
soluble in water, soluble in alcohol ether, and benzene. 

Reaction. Pour a drop of nitre benzene into a test-tube with 
I c.c. water and i c.c. glacial acet'c acid. Add a little zinc-dust 
on the point of a penknife, and warm for a minute. Dilute 
with a few c.c. of water, and add caustic soda solution until 
alkaline, and pour a few drops into a test-tube half filled with 
sodium hypochlorite solution. A violet colouration, which 
gradually fades, is produced, due io the presence of aniline 
(see p. 1 50). See Appendix, p. 274. 

PREPARATION 49. 
Azoxybenzene, C 6 H 5 'N -- N.C 3 H 6 



Klinger, Ber., 1882, 15, 865. 

200 grms. methyl alcohol. 
20 sodium. 
30 nitrobenzene. 

Attach an upright condenser to a round flask (J litre). Pour 
in the methyl alcohol and add the sodium in small pieces, 
2 3 grams at a time. A good stream of water should pass 
through the condenser, but otherwise the flask need not be 
cooled. When the sodium has dissolved, the nitrobenzene is 
introduced, and the mixture boiled on a water-bath three to 
four hours. The methyl alcohol is then distilled off in the 
water-bath. As the liquid is liable to bump, owing to the 
separation of solid matter, it is advisable to add a few bits of 
pot. When no more alcohol distils, the residue is poured into a 
beaker of water and rinsed out. A dark-coloured oil is deposited, 
which soon solidifies, and is then washed by decantation, and 
pressed on a porous plate. Yield about 23 grams. It is re- 
crystallised, when dry, from ligroin, in which it is rather soluble. 

2C 6 H 5 N - N.C H 5 + 3 HCO.ONa 



Properties. Ydlow needles ; m. p. 36. See Appendix, 
p. 274. 



144 



PRACTICAL ORGANIC CHEMISTRY 



Azoxybenzene from Nitrobenzene by Electro- 
lysis. Nitrobenzene can be conveniently converted intoazoxy- 
benzene by electrolytic reduction. The apparatus required is 
shown in Fig. 77. 

It consists of a porous cell which forms the cathode chamber 
and contains 20 grams nitrobenzene and 160 grams 2*5 per 
cent, caustic soda solution. The two are kept well mixed 
throughout the operation by a rapidly revolving stirrer. The 
cathode is a cylinder of nickel gauze (12 cms. x 8'5 cms. = 100 sq. 
cms.). The anode chamber is the outer glass vessel or beaker, 




FIG. 77. 

which contains a solution of sodium sulphate acidified with 
sulphuric acid ; a cylinder of sheet lead serves as the anode. 
An ordinary ammeter (A) and resistance (/?) are connected in 
series with the battery and electrodes, and it is also useful, 
though not essential, to insert a voltameter ( V) between the 
two electrodes. A current density of i to 5 amperes per too sq. 
cms. is used and 15 20 ampere hours will complete the 
reduction. 1 

The oily liquid which separates in the cathode chamber, and 

1 The current may be obtained from a number of secondary batteries or from a 
direct electric light circuit with a suitable resistance. 



AZOBENZENE 145 



consists of azoxybenzene mixed with aniline and a little un- 
changed nitrobenzene, is distilled in steam, which removes the 
impurities. The residue then solidifies on cooling, and is filtered, 
dried, and recrystallised. Yield 1 1 grams (60 70 per cent, of 
the theory) (Elbs, Electrolytic Preparations, trans, by R. S. 
Hutton, p. 76). 

PREPARATION 50. 

Azobenzene, C C H 5 N:N.C 6 H 5 

Mitscherlich, Annalen, 1834, 12, 311. 

5 grms. azoxybenzene. 
15 iron filings. 

The azoxybenzene and iron filings, both of which must be 
carefully dried on the water-bath, are powdered together and 
distilled from a small retort, which is conveniently made by 
blowing a large bulb on the end of a piece of rather wide 
tubing li cm. inside diameter, and then allowing the bulb 
whilst hot to bend over. The mixture is carefully heated, the 
burner being moved about until the contents are thoroughly 
hot, and then the mixture is more strongly heated until nothing 
further distils. The distillate, which forms a solid, dark-red 
mass, is washed with a little dilute hydrochloric acid and water, 
and then pressed on a porous plate. It is crystallised from 
ligroin, in which it is very soluble. 

C G H 5 N N.C C H 5 + Fe = C 6 H S N : N.C H 5 + FeO. 

^O/ 

Properties. Red plates; m. p. 68"; b. p. 295. See Appendix^ 
p. 274. 

Azobenzene from Nitrobenzene by Electrolysis. A 
good yield of azobenzene can be obtained by the electrolytic 
reduction of nitrobenzene in alcoholic solution. The apparatus 
is similar to that shown in Fig. 77, p. 144, but in the present 
case the cathode chamber is the outer vessel, which should be a 
deep, narrow glass cylinder or beaker. The cathode liquid is 
a solution of 20 grams nitrobenzene and 5 grams sodium acetate 
crystals in 200 c.c. 70 per cent, spirit. The cathode is a cylinder 
of nickel gauze. A large porous cell forms the anode chamber, 

COHEN'S ADV. p. o. c. i. 



145 PRACTICAL ORGANIC CHEMISTRY 

and contains a cold saturated solution of sodium carbonate. 
The anode is a wide strip of sheet lead. A current density of 
6 to 9 amperes per 100 sq.. cms. is passed for 17^4 ampere hours, 
and then a lower current density for a further i 2 ampere hours. 
During the reduction the cathode liquid becomes very hot and 
the alcohol which evaporates must be replaced. The cathode 
liquid at the end of the process contains, in addition to azoben- 
zene, azoxybenzene and hydrazobenzene. It is poured into a 
flask and the hydrazobenzene is oxidised to azobenzene by 
aspirating a current of air through the solution for half an 
hour. The greater part of the azobenzene separates and can be 
filtered ; the remainder, which is less pure, is precipitated from 
the filtrate by the addition of water. It is recrystallised from 
ligroin. Yield 90 per cent, of the theory. 

(Elbs, Electrolytic Preparations, trans, by R. S. Hutton, 
P- 78.) 

PREPARATION 51. 
Hydrazobenzene (Diphenylhydrazine)C 6 H 5 NH.NHC 6 H 5 

Alexejew, Zeitschr.f. Chem., 1867, 33 ; 1868, 497 ; E. Fischer, 
Anleitung zur Darstellung org. Praparate, p. 23. 

50 grms (42 c.c.) nitrobenzene. 
54 caustic soda (in 200 c.c. water). 
50 c.c. alcohol. 
100 125 grms. zinc dust. 

The apparatus is shown in Fig. 78. It consists of a large, 
round, wide-necked flask (\\ litre) furnished with a cork perfor- 
ated with three holes. Through one hole a stirrer, moved by a 
water-turbine or electric motor, passes in the manner shown in 
Fig. 78. To the stem of the stirrer a short, wide glass tube is 
attached which revolves in the annular space formed at the end 
of an adapter by fusing to it an outer concentric piece of wider 
tubing. When this space is filled with water it serves as a 
water seal. Through a second hole a wide glass tube is inserted 
by which the zinc dust is introduced, and is fitted with 
a cork. The third hole is furnished with an adapter to which 
a condenser is attached. The nitrobenzene, caustic soda solu- 
tion, and the alcohol are poured into the flask and the stirrer set 



HYDRAZOBENZENE 



in rapid motion so that the contents are kept thoroughly agitated. 

The thorough mixing of the materials is essential to the success 

of the process. The zinc dust is added in quantities of 3 4 

grams at a time through the wide glass tube, which is closed by 

a cork after each addition. The mixture soon becomes warm 

and eventually boils. To prevent the liquid boiling over the 

frothing is allowed to subside before fresh zinc dust is added. 

The operation is usually completed in f hour, when the liquid, 

which has first a deep 

red colour (azobenzene), 

becomes pale yellow. To 

examine the colour a 

sample should be with- 

drawn with a pipette 

and filtered. The stir- 

ring is continued for 

another J hour. A litre 

of cold water is added 

which precipitates the 

hydrazobenzene. The 

mixture of hydrazoben- 

zene and zinc residues 

is filtered at the pump 

and washed free from 

alkali with water. The 

precipitate is then pressed down and extracted with 750 c.c. 

of spirit on the water-bath with reflux condenser and filtered. 

On cooling in a freezing mixture, the hydrazobenzene crystal- 

lises in colourless plates, which are filtered and washed with a 

little spirit. The mother liquor is used for a second extraction 

of the zinc residues, and from the filtrate a further quantity 

of hydrazobenzene is precipitated with water. If the second 

crop of crystals have a yellow colour crystallisation from alcohol 

will remove it. Yield 30 35 grams. 




FIG. 78. 



C 6 H 5 NO. 2 



} 6NaOH = C 6 H 5 NH.NHC 6 H 5 + 3Zn(OH) . 



Properties. Colourless plates ; m. p. 125. 

Reactions. r. Heat a small quantity in a dry test-tube. 
Notice the colour. On cooling add a little water and pour a few 
drops into a solution of sodium hypochlorite. A violet coloura- 

L 2 



148 PRACTICAL ORGANIC CHEMISTRY 

tion indicates aniline. 2C H 6 NH.NH.C H 6 =C a H 6 N:NC 6 H 6 = 
2 C 6 H 6 NH 2 . 

2. Heat a small quantity with Fehling's solution and observe 
the formation of cuprous oxide. The hydrazobenzene is oxidised 
to azobenzene. 

Benzidine. Five grams of powdered hydrazobenzene are 
shaken with 125 c.c. hydrochloric acid (3 per cent.) at 20 30. In 
a quarter to half an hour the substance will have completely dis- 
solved. Finally, the mixture is heated to 45 50, a little water 
added to redissolve any benzidine hydrochloride, and filtered 
warm. The benzidine is precipitated from the solution of the 
hydrochloride by adding to the cold solution an excess of caustic 
soda solution. It is filtered and washed free from alkali, and 
recrystallised from boiling water or dilute alcohol. It crystallises 
in plates with nacreous lustre, m. p. 127. 

C 6 H 5 NH.NHC 6 H 5 = NH 2 C 6 H 4 .C 6 H 4 NH 2 . 
See Appendix, p. 275. 

PREPARATION 52. 
Phenylhydroxylamine, C 6 H 5 .NH.OH 

Bamberger, er., 1894, 27, 1548; Wohl, Ber., 1894,2?, 1432; 
Friedlander, 7 ~ heerfarbenfabrikation, IV.. 48. 

6 grms. ammonium chloride (in 200 c.c. water). 
12 nitrobenzene. 
1 8 ,, zinc dust. 

Mix the nitrobenzene and ammonium chloride solution in a 
flask (| litre). The zinc dust is added in portions of about a gram 
at a time with constant shaking or stirring by turbine, the tem- 
perature being maintained below 1 5, by cooling if necessary in ice 
water. The addition of the zinc dust should take about an hour. 
The shaking is continued for another quarter of an hour, when 
the smell of nitrobenzene will have disappeared. The contents 
of the flask are filtered and washed with 100 c.c. water, so that 
the water trickles slowly through the filter. The filtrate is 
saturated with clean salt (80 grams) and cooled to o. Colour- 
less crystals of phenylhydroxylamine fill the liquid. They are 
filtered at the pump, dried on a porous plate, and recrystallised 
if necessary from benzene. Yield 6 8 grams. 



ANILINE 149 

Properties. Colourless needles ; m. p. 81. 

Reactions. Add to a solution of phenylhydroxylamine Feh- 
ling's solution and warm. Cuprous oxide is precipitated. To 
another portion add ammoniacal silver nitrate and warm. Silver 
is deposited. See Appendix, p. 276. 

Nitrosobenzene. Dissolve 4 grams of phenylhydroxyl- 
amine in the equivalent quantity of ice cold 6 per cent, sulphuric 
acid (4 c.c. in 66 c.c. water), and add a well-cooled solution of 4 
grams potassium bichromate in 200 c.c. water. Yellow crystals of 
nitrosobenzene are deposited which distil in the vapour of steam 
with an emerald-green colour ; m. p. 67-68. 

C 6 H 5 .NHOH + O = C 6 H 5 NO + H 2 O. 

p-Aminophenol. Add gradually i gram of phenylhydroxyl- 
amine to 10 c.c. cone, sulphuric acid and 15 grams of ice, dilute 
with 100 c.c. of water and boil. Test a small sample with bi- 
chromate solution in order to see if the smell is that of nitro- 
benzene or quinone. In the latter case conversion is complete. 
The acid liquid is neutralised with sodium bicarbonate, saturated 
with common salt and extracted with ether. On distilling off 
the ether, w-amidophenol crystallises ; m. p. 186. 

C H 5 .NH.OH -OH.C 6 H 4 .NH 2 . 



PREPARATION 53. 

Aniline (Aminobenzene ; Phenylamine), C 6 H 5 NH 2 
Zinin, Annalen, 1842, 44, 283. 

50 grms. nitrobenzene. 
90 granulated tin. 
170 c.c. cone, hydrochloric acid (sp. gr. ri6). 

Introduce the tin and nitrobenzene into a round flask (i 
litre), and fit it with a straight upright tube about 2 feet long 
(air-condenser). Heat the mixture for a few minutes on the 
water-bath. Then remove the flask and add the concentrated 
hydrochloric acid in quantities of 5 10 c.c. at a time, and shake 
repeatedly. The liquid should become hot and boil quietly ; 
but, if the action becomes too violent it must be moderated by 



PRACTICAL ORGANIC CHEMISTRY 



cooling the flask in cold water. In the course of i f hour all 
the acid should have been added ; the flask is then replaced on 
the water-bath without the air-condenser, and heated for an 
hour or more until the reduction is complete. This is ascer- 
tained by the absence of any smell of nitrobenzene. The 
contents of the flask, on cooling, solidify to a crystalline mass 
(a double salt of stannic chloride and aniline hydrochloride) 
Whilst still warm, water (100 c.c.) and strong caustic soda 
solution (140 grams in 200 c.c. water) are added until the 
stannic oxide, which is first precipitated, nearly redissolves 
and the liquid has a stongly alkaline reaction. If the mixture 
begins to boil during the addition of the caustic soda solution 
it must be cooled. The aniline, which separates out as a dark- 
coloured oil, is distilled in steam. The apparatus is shown in 
Fig. 68, p. 107. The flask containing the aniline is gently 
heated on the sand-bath, and steam is passed in from the tin 
bottle. It is advisable to heat the aniline mixture on the 
water-bath before steam is admitted, as otherwise a large 
quantity of water condenses in the flask. On distillation, 
aniline and water collect in the receiver, the former as a colour- 
less oil. When the distillate, as it comes over, appears clear 
instead of milky, the distillation is stopped. The oil is now 
extracted from the distillate by shaking up the liquid in a 
separating-funnel three times with small quantities (30 c.c.) or 
chloroform. The chloroform solution, separated as far as possible 
from water, is further dehydrated by adding a little solid potas- 
sium carbonate. The clear liquid is decanted into a distilling- 
flask, the flask rinsed with a little chloroform, and the 
chloroform removed by distillation until the temperature 
reaches 100, when the receiver is changed. Aniline distils at 
182 183, and has usually a faint amber colour. Yield, about 
30 grams. 

2C C H 5 NO 2 + 3Sn + I2HC1 = 2C H 5 NH 2 + 3SnCl 4 + 4H 2 O 

Properties. Colourless, highly refractive liquid, which soon 
darkens in colour ; b. p. 183 ; sp. gr. 1-0265 at 15. 

Reactions. i. Add a drop of the oil to a solution of bleach- 
ing powder or sodium hypochlorite. An intense violet coloura- 
tion is produced, which gradually fades. 

2. Heat a drop of the oil with a few drops of chloroform, and 



ACETANILIDE 



about i c.c. of alcoholic potash, in the fume-cupboard. Phenyl 
carbamine is formed, which possesses an intolerable smell. 
(Hofmann's reaction for primary amines.) 

3. Add to a drop of aniline in a basin a few drops of con- 
centrated sulphuric acid, and stir with a glass rod. Then add 
a few drops of potassium bichromate solution. An intense 
blue colour is obtained. 

4. Dissolve a few drops of aniline in 5 c.c. dilute hydrochloric 
acid, cool under the tap and add a few drops of a solution of 
sodium nitrite. Then pour some of the solution into about 
half a gram of phenol dissolved in a few c.c. of caustic soda 
solution. An orange solution of sodium hydroxyazobenzene is 
formed (see Reaction 6, p. 163). 



= C 6 H 5 .N 2 C H 4 ONa 
+ NaOH 4-NaCl + H.j 

See Appendix, p. 277. 



PREPARATION 54. 

Acetanilide (Phenylacetamide), C 6 H V NH.CO.CH 3 
G. Williams, Trans. Chevi. Soc., 1864, 2, 106. 

25 grms. aniline (freshly distilled). 
30 c.c. glacial acetic acid. 

Boil the mixture gently in a flask (250 c.c.), fitted with an air- 
condenser, for a day (7 8 hours). As the liquid solidifies on 
cooling, it is at once poured out, while hot, into a basin of cold 
water (500 c.c.). It is filtered and washed with cold water. 
Acetanilide crystallises best from hot water, in which, however, 
it is not very soluble. Place the moist acetanilide in a large 
basin, and add gradually about a litre of boiling water. If the 
substance does not dissolve completely on boiling, a small quan- 
tity of spirit will bring it into solution. Filter through a large 
fluted filter or hot-water funnel (p. 53) and set the solution aside 
to crystallise. If the product is dark coloured it is redissolved 



152 PRACTICAL ORGANIC CHEMISTRY 

as before, and heated with a little animal charcoal (5 10 grams) 
for half hour and then filtered. Yield, 30 35 grams. 

C 6 H 5 NH 2 +CH 3 .COOH = C 6 H 5 NH.CO.CH3+H 2 O 

Properties. Rhombic plates ; m.p. II2 3 ; b.p. 295. 

Reaction. Introduce about o'5 gram of the substance into a 
test-tube, and 1 add 3 c.c. concentrated hydrochloric acid. Boil 
for a minute. On diluting with water, a clear solution is ob- 
tained. 



See Appendix, p. 278. 

PREPARATION 55. 

p-Bromacetanilide, C 6 H 4 <^g 2 3 
Remmers, Her., 1874, 7, 346. 



5 grms. acetanilide. 

25 c.c. glacial acetic acid. 

6 grms. bromine. 



Dissolve the acetanilide in the acetic acid in a flask (\ litre), 
and add gradually the bromine, dissolved in about twice its 
volume of glacial acetic acid, and shake well. When the 
bromine has been added, let the mixture stand \ hour and 
then pour into 200 c.c. water and rinse out with water. 
Filter the crystalline precipitate at the pump and wash three or 
four times with water. Press it well down and let it drain. 
Dissolve the moist substance in spirit (about 60 c.c.) and 
pour into a beaker to crystallise. Filter the crystals, wash 
with a little dilute spirit, and dry on filter paper. Yield 6 7 
grams. 

C 6 H 5 NH.C 2 H 3 O + Br 2 = C c H 4 Br.NH.C 2 H 3 O + HBr 

Properties. Colourless needles ; m.p. 165 166. On hy- 
drolysis with concentrated hydrochloric acid, /-bromaniline is 
formed (see above reaction for acetanilide). 



p-NITRANILINE 153 



PREPARATION 56. 
p-Nitraniline. 

Bender and Erdmann, Chemische Praparatenkunde, vol. ii., 
p. 438. 

25 grms. acetanilide. 

25 c.c. acetic acid (glacial). 

50 cone, sulphuric acid. 

10 fuming nitric acid (sp. gr. i'5). 

The acetanilide, acetic acid, and sulphuric acid are mixed by 
means of a mechanical stirrer and cooled in a freezing mixture. 
The fuming nitric acid is then gradually added from a tap- 
funnel at such a speed that the temperature does not exceed 
20. After the acid has been added, the mixture is stirred for 
an hour and poured on to ice. The product is then diluted 
with water, left to stand for a time, filtered, washed, and dried 
on a porous plate. It maybe recrystallised from dilute alcohol, 
but is usually pure enough for further treatment. Yield is 
80 per cent, of the theory ; the remaining 20 per cent, is ortho- 
compound and remains in solution ; m. p. 207. 

C 6 H 5 .NH.COCH 3 + HN0 3 =N0 2 .C 6 H 4 .NH.COCH 3 +H 2 O 

The /-nitracetanilide is either boiled with 7.\ times its weight of 
concentrated hydrochloric acid, or heated on the water-bath 
with twice its weight of equal volumes of sulphuric acid and 
water until the liquid remains clear, on diluting with water. 
The/>-nitraniline which is now present in the liquid as the hydro- 
chloride or sulphate, is diluted with water and precipitated by 
the addition of an excess of caustic soda or ammonia. When 
cold, the yellow crystalline precipitate is filtered, washed and 
re-crystallised from boiling water. Yield, 25 grams. 

NO 2 .C 6 H 4 .NHCOCH 3 + H 2 O + HC1 = NO 2 .C 6 H 4 .NH,,.HC1 
+ CH 3 COOH 

Properties. Yellow needles ; m. p. 147 ; soluble in hot 
water ; very soluble in alcohol. 



154 PRACTICAL ORGANIC CHEMISTRY 



PREPARATION 57. 
m-Dinitrobenzene. C 6 H 4 < 



Deville, Ann. Chim. Phys., 1841 (3), 3, 187 ; Hofmann, 
Muspratt, Annalen, 1846, 57, 214. 

30 grms. nitrobenzene. 

35 (24 c.c.) fuming nitric acid ; sp. gr. 1*5. 

35 (20 c.c.) cone, sulphuric acid. 

The acids are mixed in a flask (500 c.c.), and the nitrobenzene 
added in portions of 5 10 c.c. at a time. Heat is evolved, and 
the mass becomes somewhat deeper in colour. When the nitro- 
benzene has been added, the flask is heated for a short time on 
the water-bath. A few drops are then poured into a test-tube of 
water. The dinitrobenzene should, if the reaction is complete, 
separate out as a hard pale yellow cake If it is semi- 
solid, the heating must be continued. The contents of the flask 
are then poured, whilst warm, into a large quantity of water. 
The dinitrobenzene, which separates out, is filtered at the pump 
and well washed with water. It is then dried. The yield is 
nearly theoretical. A few grams should be recrystallised from 
spirit. The remainder may be used for the next preparation 
without further purification. 

C H 5 .N0 2 + HN0 3 =C C H 4 (N0 2 ) 2 + H 2 

Properties. Colourless long needles; m. p. 90 ; b. p. 297. 
See Appendix, p. 279. 

PREPARATION 58. 
m-Nitraniline. C B : 



Hofmann, Muspratt, Annalen, 1846, 57, 217. 

25 grms. ;;/-dinitrobenzene. 

75 (95 c.c.) spirit. 

12 (13 c.c.) cone, ammonia. 

The powdered dinitrobenzene, spirit and ammonia, are 
mixed together in a flask (\ litre). Hydrogen sulphide, 



m-NITRANILINE 155 



washed through water, is passed into the dark red pasty mass, 
which is occasionally shaken.* The dinitrobenzene slowly 
dissolves, whilst, at the same time, flakes of crystallised sulphur 
are deposited. When the gas has been passing for an hour the 
flask is removed and heated on the water-bath fora few minutes. 
After cooling, the liquid is again saturated with hydrogen 
sulphide and then heated on the water-bath as before. When 
the gas has been passing in a steady stream for fully two hours 
the process is complete. Water is no\y added to the liquid until 
nothing further is precipitated. The mixture is filtered at the 
pump and washed with a little water. The solid residue is 
transferred to a flask and shaken up with successive small 
quantities of hot dilute hydrochloric acid and the liquid 
decanted through the original filter. The nitraniline dissolves, 
leaving the sulphur. When no more nitraniline is extracted 
(this may be ascertained by adding ammonia in excess to 
a portion of the acid solution, when no precipitate is formed), 
the acid solution is somewhat concentrated, cooled, and con- 
centrated ammonia added. The w-nitraniline is precipitated, 
filtered when cold, and purified by recrystallisation from 
boiling water. The filtrate from the nitraniline may be concen- 
trated on the water-bath and a further small quantity obtained. 
Yield, about 15 grams. 



Properties. Yellow needles ; m. p. 114; b. p. 285. With 
tin and hydrochloric acid it is reduced to ;-phenylenediamine, 
C 6 H 4 (NH 2 ) 2 . 

m-Phenylenediamine. Dissolve 30 grams stannous chloride 
(SnCl 2 + 2H 2 O)in 5oc.c. cone, hydrochloric acid in a round flask 
( litre) and gradually add 5 grams ;;/-nitraniline. The mixture 
is heated on the water-bath until no precipitate is formed on 
adding water (\ hour). The liquid is diluted with $00 c.c. 
water, heated nearly to boiling and a current of hydrogen 
sulphide passed in until all the tin is precipitated as sulphide 
(4 | hour). With this object a small quantity should be 
filtered and tested from time to time by passing in hydrogen 
sulphide. The precipitate is left overnight to subside, the clear 
liquid decanted and the residue filtered at the pump through a 



156 PRACTICAL ORGANIC CHEMISTRY 

double-filter. The clear filtrate is concentrated on the water- 
bath until crystallisation commences and allowed to cool. 
The crystals of the hydrochloride of phenylenediamine separate 
and are filtered. A further quantity may be obtained by con- 
centrating the mother-liquors. Yield 6'5 grams. 



+ 2H 2 O. 

Reaction. Dissolve a "few crystals in water, acidify with 
dilute hydrochloric acid, and add a drop of sodium nitrite solu- 
tion. A deep brown solution (Bismarck brown) is obtained. 
See Appendix, p. 279. 



PREPARATION 59. 

Dimethylaniline, C 6 H 5 N(CH 3 ) 2 

Poirrier, Chappat, Jahresb., 1866, p. 903. 

20 grms. aniline hydrochloride. 

15 aniline. 

22 methyl alcohol. 

The aniline hydrochloride is prepared by gradually adding 
cone, hydrochloric acid to aniline (20 grams in a beaker) 
until a drop brought on to a piece of filter paper, stained with 
methyl violet, turns it green. The liquid is quickly cooled and 
stirred so as to produce small crystals. It is then filtered, well 
pressed and dried on a porous plate. The dry hydrochloride is 
brought into a thick-walled tube closed at one end, and the 
mixture of aniline and methyl alcohol added. The tube is then 
sealed in the ordinary way and heated in the tube furnace 
gradually to 150 during two hours, and then to 180 200 for 
six hours more. The contents of the tube divide into two 
layers, the lower one consisting of the hydrochloride of the 
base and water, and the upper one of the free bases. The whole 
of the contents are poured out into a large separating funnel, 
and caustic soda added in excess. The addition of a little ether 
causes the bases to separate out more readily. The top layer 
is removed, and the lower aqueous portion is shaken up twice 



p-NITROSODIMETHYLANILINE 157 

with small quantities of ether. The ethereal solution is de- 
hydrated over solid caustic potash, the liquid filtered and the 
ether removed on the water-bath. The residue is now boiled 
with 25 grams acetic anhydride, using an upright condenser, for 
an hour in the same flask, the side limb of which is stoppered. 
The contents are then distilled. Unchanged acetic anhydride 
passes over at 130 150 ; the thermometer then rises, and the 
portion boiling at 190 200 is collected separately. When the 
higher temperature is reached, it is advisable to keep only the 
lower half of the condenser filled with water. The distillate 
has a bright amber colour. Yield, 20 grams. The residue in 
the flask consists of acetanilide and methylacetanilide and 
solidifies on cooling. 



Properties. Colourless liquid ; b. p. 192 ; sp.gr 0*957 at 20. 
Reaction. Warm, with an equal volume of methyl iodide ; the 
crystalline quaternary ammonium iodide will be formed, 

C 6 H 5 N(CH 3 ) 2 +CH I = C 6 H 5 N(CH 3 ) 2 .CH 3 I. 
See Appendix, p. 279. 

PREPARATION 60. 
p-Nitrosodimethylaniline, 

N (CH 3 ) 3 , CH , 

/f \ / r >^3/ ) 2 1 

Baeyer, Caro, Bet:, 1874, 7, 810 and 963 ; Meldola, Trans. 
Chem. Soc., 1881, 39, 37. 

20 grms. dimethylaniline. 

52 (45 c.c.) cone, hydrochloric acid diluted with 

loo c.c. of water. 
12 sodium nitrite (in 20 c.c. of water.) 

The dimethylaniline is dissolved in the dilute hydrochloric 
acid in a beaker and cooled in a freezing mixture. The sodium 



158 PRACTICAL ORGANIC CHEMISTRY 

nitrite, dissolved in a small quantity of water, is then slowly 
added with frequent stirring. The separation of the hydro- 
chloride of nitrosodimethylaniline in the form of small yellow 
needles soon begins, and the liquid is gradually filled with a 
thick crystalline deposit. When, after standing for a short time 
(half an hour), no further increa3e in the quantity of crystals is 
observed, the mass is filtered at the purnp and washed with 
spirit, to which one or two c.c. of concentrated hydrochloric 
acid has been added. It is then washed once or twice with 
spirit, drained and pressed on a porous plate. Yield, nearly 
theoretical. It may be recrystallised by adding small quantities 
of hot water, until the salt is just dissolved, and then setting 
aside to cool. If the free base is to be prepared, recrystallisa- 
tion is unnecessary. Ten grams of the hydrochloride are mixed 
into a paste with water in a flask, and caustic soda solution added 
in the cold until alkaline. The yellow colour of the salt changes 
to green of the free base. Sufficient ether is added to dissolve 
the green precipitate. The ethereal solution is carefully 
separated by means of a separating-funnel and most of the ether 
is then removed by distillation. The remaining liquid is poured 
out into a beaker and set aside to crystallise. The base remains 
on evaporation of the ether in the form of brilliant green foliated 
crystals. 

C 6 H 5 N(CH 3 ) 2 HC1+HNO 2 = (NO)C 6 H 4 N(CH 3 )2.HC1 + H 2 O 

Properties. Large green foliated crystals ; m. p. 85. 

Reactions. I. Dissolve a few crystals in dilute hydrochloric 
acid and add a little zinc dust. The solution is decolourised 
through the formation of dimethyl /-phenylenediamine, 
(CH 3 ) 2 N.C 6 H 4 NH 2 . 

2. Warm a few of the crystals with yellow ammonium sulphide 
solution for a few minutes, acidify with hydrochloric acid, and 
finally add a little ferric chloride. A deep blue colouration is 
produced, due to the formation of methylene blue. 

3. Dissolve 6 grams of caustic soda in 250 c.c. of water and 
heat to boiling. Add 5 grams of the hydrochloride of nitroso- 
dimethylaniline gradually. The free base, which separates out in 
oily drops, is allowed to dissolve before each fresh addition. The 
boiling is continued until the dark green colour of the liquid 



THIOCARBANILIDE 159 

changes to reddish-yellow. Dimethylamine is evolved and is 
easily recognised by its smell. After cooling, acidify the liquid 
in the flask and extract with ether. On distilling off the ether, 
nitrosophenol (quinoneoxime) remains in the form of dark- 
coloured crystals, which are difficult to purify. 



The presence of a nitroso-compound may be detected as 
follows : Melt together a minute quantity of nitrosophenol and a 
few crystals of phenol. Add about 2 c.c. concentrated sulphuric 
acid and warm very gently. A blue solution is obtained, which 
changes to red on dilution with water, and back to blue on 
adding alkali (Liebermann's "nitroso" reaction ; see Reaction, 
p. 1 80). See Appendix, p. 280. 

PREPARATION 61. 
Thiocarbanilide (Diphenylthiourea), CS/ fi 



Hofmann, Annalen, 1849, 70, 142. 

30 grms. aniline. 

30 carbon bisulphide. 

30 absolute alcohol. 

The aniline, carbon bisulphide, 1 and alcohol are poured into a 
round flask (i litre), and heated for a day (8 hours) on the water- 
bath with upright condenser. As hydrogen sulphide is evolved 
the operation must either be conducted in the fume cupboard or 
an exit tube must be attached to the top of the condenser tube 
dipping into soda-lime. The contents of the flask solidify after 
a time. When the reaction is complete, the condenser is reversed. 
and excess of carbon bisulphide and alcohol distilled off on the. 
water-bath. The residue is washed on to a filter with very dilute 
hydrochloric acid, to remove any unchanged aniline, and then 
with water. The crystals are dried on a porous plate, and a por- 
tion crystallised from spirit. Yield 30 35 grams. 

2 = CS(NHC (i H 5 ),+ H 2 S 



1 Carbon bisulphide being very volatile and exceedingly inflammable, great care 
must be taken when using it in the neighbourhood of a flame. 



160 PRACTICAL ORGANIC CHEMISTRY 

Properties. Colourless rhombic plates ; m.p. 151 ; scarcely 
soluble in water, easily soluble in alcohol or ether. 

Phenyl Thiocarbimide (Phenyl Mustard Oil), C 6 H 5 N:CS 

The thiocarbanilide is boiled with two to three times the 
weight of concentrated hydrochloric acid in a flask with an 
upright condenser for half an hour. It is decomposed into 
triphenylguanidine, which remains as the hydrochloride in solu- 
tion (it is subsequently separated) and phenyl mustard oil, which 
separates out as a brown oil. On distilling the product in 
steam, the phenyl mustard oil is carried over into the receiver. 
It is separated by shaking out with ether, and removing the 
ethereal layer with a tap-funnel. It is dehydrated over 
calcium chloride, and decanted into a small distilling flask. 
The ether is removed on the water-bath and the mustard oil 
distilled, with the thermometer, using a short condenser tube. 
Yield, 9 10 grams. 

Properties. Colourless oil with a peculiar smell ; b. p. 220 ; 
sp. gr. r 1 35 at 15. 

Reactions. i. Heat gently for a few minutes o'5 c.c. phenyl 
mustard oil, o'5 c.c. alcohol and \\ c.c. concentrated ammonia. 
On cooling, thiocarbanilamide, NH 2 .CS.NH.C 6 H 6 , crystallises in 
needles. 

2. Heat gently o'5 c.c. phenyl mustard oil, and 0*5 c.c. aniline ; 
on cooling and rubbing with a glass rod, thiocarbanilide 
crystallises. 

3. Heat on the water-bath in a small flask with upright con- 
denser 3 grams of phenyl mustard oil and 10 c.c. absolute alcohol 
for 3 hours, and pour into cold water. Phenylthiourethane, 
C 6 M 5 NH.CS.OC 2 H 5 , separates out and may be recrystallised 
from alcohol. Yield, 2^ grams ; m. p. 67. 

4. Heat a few drops of the mustard oil with yellow mercuric 
oxide and notice the irritating smell of phenyl carbimide. 

C 6 H 5 N:CS + HgO = C 6 H 5 N:CO + HgS 

Triphenylguanidine. In order to separate the triphenyl- 
guanidine remaining in the flask as hydrochloride after distilling 
off the phenyl mustard oil, the hot solution must be somewhat 
concentrated. The colourless salt, which crystallises out on cool- 



DIAZOBENZENE SULPHATE 161 

ing, Is filtered and washed with a little water. It is then warmed 
gently for a few minutes with dilute caustic soda solution. The 
base is liberated, filtered, washed with water and recrystallised 
from spirit. 

.NHC H 5 

2CS(NHC H 5 ) 2 + HC1 = CSNC C H 5 + C.NHC 6 H 6 .HC1 + H 2 S 

:NC 6 H 5 

Thiocarbanilide. Phenyl Mustard Triphenylguanidine 

Oil. Hydrochloride. 

Properties. Colourless needles ; m. p. 143. 
Reaction. Boil for a short time with moderately strong 
caustic soda solution. Aniline is formed. 



See Appendix, p. 281. 



PREPARATION 62. 
Diazobenzene Sulphate, C C H 5 :N.SO 4 H 

N 

Griess, Annalen, 1866, 137, 76; Knoevenagel, Ber., 1895,28, 
2049. 

15 grms. aniline. 

140 (175 c.c.) absolute alcohol. 1 
30 (16 c.c.) cone, sulphuric acid. 
20 amyl nitrite. 

Mix the aniline and alcohol and add the concentrated 
sulphuric acid in a slow stream with constant shaking. The 
precipitate of aniline sulphate, which first appears, redissolves. 
Cool the mixture to 30' and keep at 30 35 (thermometer in 
the liquid) and out of direct sunlight whilst the amyl nitrite is 
dropped in from a tap-funnel. Then cool in ice water and 
leave for half an hour. The diazobenzene sulphate separates as 
a colourless or pale green mass of needle-shaped crystals. It 
is filtered at the pump and washed with a little alcohol. 
Although diazobenzene sulphate is much more stable than the 

1 Neither methylated spirit noi methyl alcohol can be substituted. 

COHEN'S ADV. p. o. c. M 



1 62 PRACTICAL ORGANIC CHEMISTRY 

nitrate, it is undesirable to let the precipitate become quite dry. 
The various reactions described below are carried out with 
the slightly moist and well pressed precipitate. 



+ 2C 5 H U OH + 2H 2 O. 

Properties. Colourless needles ; soluble in water and 
methyl alcohol ; slightly soluble in ethyl alcohol. 

Reactions. The following reactions are performed in test- 
tubes with about a gram of the substance. 

1. Warm the substance with a few c.c. of ethyl alcohol. 
Vigorous effervescence occurs and the liquid turns red. When 
effervescence ceases, add water. An cil separates out on the 
surface consisting of benzene mixed with a little phenetol. 

C 6 H 5 N 2 SO 4 H + C 2 H 6 O = C 6 H 6 + N 2 + C 2 H 4 O + H,SO 4 
C 6 H 5 N 2 SO 4 H + C 2 H 6 O = C 6 H 5 OC 2 H 5 + N 2 + H 2 SO 4 . 

2. Dissolve about a gram of the substance in a little water, 
cool in ice and make alkaline with caustic soda. Make an 
alkaline solution of stannous hydrate by dissolving 3 4 grams 
of stannous chloride in twice its weight of water and adding 
strong caustic soda solution until the precipitate redissolves. 
Cool the diazo solution and add the alkaline stannous hydrate. 
Effervescence occurs, nitrogen is liberated and benzene separates 
on the surface of the liquid and can be detected by its smell. 

C 6 H 5 N 2 . ONa + Sn(ONa) 2 + H 2 O - C 6 H 6 + N 2 + Na.jSnO 3 + NaOH. 

3. Dissolve the substance in a few c.c. of cold water and add 
a solution of bromine in potassium bromide until no further 
turbidity is produced. A black oil collects at the bottom of the 
test-tube. Pour off the top layer as far as possible, and let the 
oil stand in cold water. It solidifies. This is the perbromide of 
diazobenzene. 

C 6 H 5 N 2 S0 4 H + KBr + Br 2 = C 6 H 6 NBrNBr 2 + KHSO 4 . 

Decant any liquid a_nd warm the perbromide with a little alcohol. 
Nitrogen and bromine are given off and bromobenzene is 
formed. 

C 6 H 5 NBrNBr 2 =C 6 H 5 Br + N 2 + Br 2 . 

4. Dissolve the substance in a little cold water and add 



TOLUENE FROM p-TOLUIDINE 163 

potassium iodide solution. Effervescence occurs and a dark 
coloured liquid separates out. This is iodobenzerte. 

C 8 H 5 N 2 SO 4 H + KI = C C H 5 I + N 2 + KHSO 4 . 

5. Dissolve the substance in water and warm gently. Effer- 
vescence occurs and a dark coloured oil separates, which has the 
smell of phenol. When effervescence ceases, cool and shake 
up with a little ether. Decant the ether into a dry test-tube. 
Evaporate the ether and test the residue for phenol, see p. 179. 

C H 5 N 2 SO 4 H + H 2 O = C 6 H 5 OH + H 2 SO 4 + N 2 . 

6. Dissolve the substance in cold water and add it to a 
solution of phenol in caustic soda, drop by drop. An orange 
crystalline precipitate of hydroxyazobenzene is formed. Repeat, 
using 0-naphthol in place of phenol. A scarlet precipitate is 
obtained. 

C C H 5 N 2 SO 4 H + C H 6 ONa = C 6 H 5 N:N.C 6 H 4 ONa + Na 2 SO 4 
+ 2NaOH + 2H 2 O. 

7. Dissolve in cold water and add a few drops of aniline, 
and shake up. Diazoaminobenzene separates out as a yellow 
crystalline precipitate. 

C H 5 N 2 SO 4 H + C G H 5 NH 2 = C G H 5 N:N.NHC G H 5 + H 2 SO 4 . 

8. Heat 0*5 gram of the dry substance on an iron tray. It 
decomposes with slight explosion. 

Any of the diazo-compound which remains over should be 
dissolved in water and poured away. See Appendix, p. 282. 

PREPARATION 63. 

Toluene from p-Toluidine, C H 5 .CH3. 
Friedliinder, Ber., 1889, 22, 587. 

10 grms. /-toluidine. 

30 c.c. cone, hydrochloric acid (in 60 c.c. water). 

7' 5 sodium nitrite (in powder). 

15 of caustic soda (in 50 c.c. water). 

30 stannous chloride (in 75 c.c. water). 

The ^-toluidine, which is placed in a beaker, is dissolved in 
the hydrochloric acid by warming and is then cooled under the 

M 2 



1 64 PRACTICAL ORGANIC CHEMISTRY 

tap, so as to obtain small crystals of the hydrochloride. The 
beaker is placed in a freezing mixture and the contents cooled 
below 10. The sodium nitrite is added in small portions at a 
time with stirring, the temperature being kept below 10. The 
hydrochloride gradually dissolves in the form of the soluble 
diazonium salt. Towards the end of the operation a drop of the 
solution is occasionally tested with potassium iodide and starch 
paper when an excess of nitrite is indicated by a blue stain. 
The solution is poured very slowly into the solution of caustic 
soda previously cooled in ice, so that the temperature does not 
rise above 10. 

CH 3 .C 6 H 4 N 2 C1 + 2NaOH = CH 3 .C 6 H 4 N 2 ONa + NaCl + H 2 O. 

Meantime the stannous chloride solution is converted into sodium 
stannite by adding a 50 per cent, solution of caustic soda until 
the precipitate of the hydrate nearly redissolves (about 30 grams 
of caustic soda). The liquid is placed in a round flask (500 c.c.) 
attached to a condenser and cooled in ice. The alkaline diazo 
solution is poured through the top of the condenser in small 
quantities at a time. After each addition there is a vigorous 
effervescence and evolution of nitrogen,and a brown oil separates 
which consists of impure toluene. 

CH 3 C 6 H 4 N 2 ONa + Sn(ONa) 2 + H 2 O = CH 3 .C 6 H 5 + N 2 + Na 2 SrO 3 
+ NaOH. 

When the solution has all been added the toluene is distilled off 
in steam, separated from the water, and dehydrated over calcium 
chloride. It distils at 110. Yields 6 grams. See Appendix, 
p. 284. 

PREPARATION 64. 

p-Cresol, C 6 ' 

Griess, Annalen, 1866, 137, 39; Ihle, /. prakt. Chem.^ 1876, 
14,451- 

25 grms. ^-toluidine. 

25 cone, sulphuric acid (in 750 c.c. water). 

20 sodium nitrite (in 40 c.c. water). 

?,lix the dilute sulphuric acid and toluidine in a large round 
flask (\\ litre) and cool to the ordinary temperature. The nitrite 



p-CIILOROTOLUENE 165 

solution 5s gradually added. The clear solution is then gently 
warmed on the water-bath until the evolution of nitrogen ceases. 
The solution, which has become very dark coloured, is distilled 
in steam until the distillate produces only a slight precipitate 
with bromine water (500 c.c.). A small quantity of tarry residue 
remains. The distillate is then extracted three times with small 
quantities (50 c.c.) of ether. The ethereal solution is dehydrated 
over anhydrous sodium sulphate, filtered, and the ether removed 
on the water-bath. The/-cresol is then distilled over the flame 
with a condenser tube, and collected at 195 200. The distil- 
late, which has a yellow colour, solidifies on cooling. Yield 10 
15 grams. 

(CH 3 .C 6 H 4 NH 2 ) 2 H 2 SO 4 + 2NaNO 2 ==2CH 3 .C 6 H 4 .OH 



Properties. Colourless crystals ; m. p. 36 ; b. p. 202. 

Reactions. Make a solution of /-cresol by shaking up a 
few drops with 5 c.c. of water. To one portion add a few drops 
of bromine water. A white precipitate of tetrabromocresol 
is formed. To another portion add a drop of ferric chloride. 
A blue colouration is produced. See Appendix, p. 284. 

PREPARATION 65. 
p-Chlorotoluene, C C 

Sandmeyer, Ber., 1884, 17, 2651 ; Wynne, Trans. Chem. Soc., 
1892, 61,1072. 

50 grms. /-toluidine. 

1 20 c.c. cone, hydrochloric acid (in 80 c.c. water). 
40 grms. sodium nitrite (coarsely powdered). 
30 copper carbonate to be dissolved in 300 c.c. cone. 

hydrochloric acid 

Dissolve the ^-toluidine in the hydrochloric acid and then 
cool quickly in a beaker, and stir so as to obtain small crystals. 
Place the beaker in ice and salt and, whilst it is cooling, 
prepare a solution of cuprous chloride. Dissolve the copper 
carbonate in the hydrochloric acid, and boil with excess of 
copper turnings until a nearly colourless solution is obtained. 
The solution is decanted into a large round flask (2 litres) 



166 PRACTICAL ORGANIC CHEMISTRY 

which is loosely corked, and placed in ice. Whilst this 
solution is cooling to o the diazotoluene chloride is prepared 
by adding the powdered sodium nitrite gradually to the p- 
toluidine hydrochloride and stirring. The temperature should 
not rise above 10. When three-quarters of the nitrite has been 
added, test occasionally with potassium iodide-starch paper until 
a drop gives an immediate deep blue or dark brown colouration. 
Add this solution gradually in portions of about 20 c.c. at a time 
to the cold solution of the cuprous chloride, and shake up well 
after each addition. A thick crystalline mass of orange coloured 
needles, consisting probably of the diazo-copper salt separates, 
and, on standing, decomposes slowly, forming a dark-coloured 
liquid. After standing a short time, the liquid is distilled in steam. 
The distillate is shaken up with a little caustic soda to remove 
cresol, and the chlorotoluene, which sinks to the bottom, is 
separated. The liquid is further shaken out with a little chloro- 
form, which is then added to the chlorotoluene, and the whole 
dehydrated with calcium chloride. The liquid is decanted, the 
chloroform distilled off and the residue collected at 115 165. 
Yield, about 45 grams. 

CH 3 C 6 H 4 NH 2 HCl + NaNO 2 + HCl = CH 3 C 6 H 4 N 2 Cl + 

NaCl + 2H 2 O. 
CH 3 C 6 H 4 N 2 C1 = CH 3 C,H 4 C1 + Nj. 

Properties. Colourless liquid ; o. p. 162 ; m. p. 7^4 

Reactions. Chlorobenzoic Acid. Boil 10 grams /-chloro- 
toluene with 20 grams permanganate dissolved in 500 c.c. of water 
in a brine or calcium chloride bath, with upright condenser, for a 
day. The bath should keep the contents of the flask boiling 
briskly whilst the permanganate is gradually added. The oily 
drops of chlorotoluene will gradually cease to drip from the con- 
denser and the permanganate will be nearly decolourised. 

The precipitated manganese dioxide is now dissolved as sul- 
phate by passing in sulphur dioxide gas until the last trace of 
brown precipitate has disappeared. The colourless chloro- 
benzoic acid comes down in the acid solution on cooling, and 
is filtered, washed with water, and recrystallised from spirit ; 
m. p. 236. The yield is theoretical. 

CH 3 .C 6 H 4 CH-O 3 = COOH.C 6 H 4 C1 + H.,O. 

See Appendix, p. 284. 



p-BROMOTOLUENE 167 

PREPARATION 66. 

/CH 3 : 
p-Bromotoluene, C 6 H 4 <^ 

x Br 4 

Sandmeyer, er., 1884,17,2651 ; Gattermann, ffer., 1890, 23, 
1218. 

50 grms. ^-toluidine. 

100 c.c. cone, hydrochloric acid (in 60 c.c. water). 

35 grms. sodium nitrite (in powder). 

90 crystallised copper sulphate (in 300 c.c. water). 

45 potassium bromide (in 100 c.c. water). 

150 c.c. hydrobromic acid (sp.gr. i'49 = 47 per cent. HBr). 

The ^-toluidine is diazotised as described in the previous experi- 
ment (Prep. 65) by forming the hydrochloride, cooling and 
gradually adding the sodium nitrite. The solution of the 
diazonium chloride is then poured into cuprous bromide dis- 
solved in hydrobromic acid. The cuprous bromide is prepared 
by adding the potassium bromide solution to the copper sulphate 
solution and passing in sulphur dioxide until no more precipitate 
forms. The white cuprous bromide (about 35 grams) is filtered, 
washed, and well pressed on the funnel and introduced into a 
round flask (i\ litre). It is dissolved in 150 c.c. hydrobromic acid 
and well cooled in ice. The diazonium chloride is now added 
slowly with constant shaking. A thick pasty mass separates and 
nitrogen is evolved. When the evolution of gas has slackened 
the flask is heated on the water-bath until effervescence ceases 
and the bromotoluene is then distilled in steam. The heavy 
yellow liquid is extracted with chloroform, shaken with caustic 
soda solution to remove traces of cresol, dehydrated over calcium 
chloride, and distilled. The distillate is collected at 180 190 
On cooling, it solidifies to a pale yellow mass, m. p. 28 ; b. p. 
185. Yield, 35 grams. 

CH 3 .C 6 H 4 N 2 Cl + CuBr=CH 3 .C 6 H 4 Br+CuCl + N 2 . 

Gattermann's Method. According to this method the 
diazonium bromide is first prepared and then decomposed by 
finely divided metallic copper. The 50 grams ^-toluidine is 
dissolved in 200 c.c. hydrobromic acid previously diluted with 
ico c.c. water and diazotised in the usual way. To this solution 



i6S PRACTICAL ORGANIC CHEMISTRY 

the copper powder is gradually added. It is prepared by dis- 
solving 100 grams crystallised copper sulphate in 300 c.c. water 
and dusting in through a fine muslin bag 25 grams zinc dust with 
constant stirring. It is left until the blue colour of the copper 
salt has nearly disappeared. The precipitated powder is washed 
by decantation two or three times with cold water and then with 
very dilute hydrochloric acid to remove metallic zinc and 
finally filtered and washed at the pump. The pasty mass is not 
allowed to dry, but is added at once in small quantities to the 
diazonium solution with constant stirring. After the evolution 
of nitrogen has ceased the bromotoluene is distilled in steam 
and purified as described above. See Appendix, p. 284. 

PREPARATION 67. 
p-Iodotoluene. 
Griess, Annalen, 1866, 137, 76. 

25 grms. ^J-toluidine. 

50 (27 c.c.) cone, sulphuric acid (in 250 c.c. water). 

20 sodium nitrite (in 40 c.c. water). 

60 potassium iodide (in 100 c.c. water). 

Mix the dilute sulphuric acid and ^-toluidine in a large 
beaker (f litre) and cool to o in a freezing mixture. Stir, 
whilst cooling, to produce small crystals of the sulphate. Add 
the solution of sodium nitrite slowly, and if the temperature 
rises above 10', add a few lumps of ice. When three-quarters 
of the nitrite solution has been added, test occasionally with 
potassium iodide-starch paper until a blue or brown stain is 
produced. Now add the solution of potassium iodide gradually, 
and, after well stirring, leave the mixture at the ordinary temper- 
ature for an hour, and then warm cautiously on the water-bath 
until effervescence ceases. The liquid is dark coloured, and a 
black oil settles to the bottom of the vessel, which when cold 
solidifies. The oil consists of iodotoluene, and the dark colour of 
the solution is due to free iodine, which may be removed by the 
addition of a gram or two of sodium bisulphite. The mixture 
is now distilled in steam, using a beaker as receiver. Care must 
be taken to prevent the condenser tube becoming blocked by the 
iodotoluene, which is solid at the ordinary temperature. This is 



p-TOLYLCYANIDE 169 



effected by running the water very slowly through the condenser 
so that the upper part remains warm. The iodotoluene solidifies 
in the receiver. It has a yellow tint, which may be removed by 
recrystallisation from spirit. Yield, 45 50 grains. 
CH 3 .C 6 H 4 NH 2 + NaNO 2 + 2H 2 SO 4 = CH 3 .C H 4 N,.O 4 H + 

NaHS0 4 + H 2 0. 

CH 3 .C C H 4 N 2 .SO 4 H + KI = CH 3 .C H 4 I + N, + KHSO 4 . 
Properties. Colourless plates ; m. p. 35 ; b. p. 211 212. 

1. Tolyliodochloride. Dissolve 10 grams iodotoluene in 
five times its weight of chloroform, cool in ice, and pass in dry 
chlorine until saturated. If a chlorine cylinder is not available, 
the chlorine is conveniently made by dropping concentrated 
hydrochloric acid from a tap-funnel on to powdered potassium 
bichromate or permanganate in a round flask, heated on the 
water-bath. The chlorine is dried through concentrated 
sulphuric acid. When chlorine is no longer absorbed, the 
yellow needle-shaped crystals of the iodochloride are filtered, 
washed with a little chloroform, and dried on a porous plate. 

CH 3 .C C H 4 I + C1 2 = CH 3 .C 6 H 4 IC1,. 

2. lodosotoluene. Dissolve 2'5 grams taustic soda in 20 
c.c. water, and grind with 5 grams of iodochloride in a mortar. 
Leave overnight and then filter and wash with water. The 
colourless crystals of the iodoso-compound are dried on a porous 
plate. 

CH 3 .C G H 4 ICl 2 + 2NaOH = CH 3 .C 6 H 4 IO + 2NaCl + H 2 O. 
See Appendix, p. 285. 

PREPARATION 68. 

/CH 3 i 
p-Tolylcyanide, C 6 H 4 ^ 

X CN 4 

Sandmeyer, Ber., 1884, 17, 2653. 

20 grms. ^-toluidine. 

45 c.c. cone, hydrochloric acid (in 150 c.c. water). 

1 6 grms. sodium nitrite (in 40 c.c. water). 

50 copper sulphate (in 200 c.c. water). 

55 potassium cyanide (in 100 c.c. water). 

The copper sulphate is dissolved in 200 c.c. water on the 
water-bath in a round flask (2 litres). Pure potassium cyanide 



170 PRACTICAL ORGANIC CHEMISTRY 

is gradually added to the warm solution.* The cuprous cyanide 
dissolves in excess of the potassium cyanide and cyanogen gas 
is liberated. 2CuSO 4 + 4KCN = 2CuCN + 2K 2 SO 4 + (CN) 2 . 
The solution is left, whilst the ^-toluidine is diazotised. 
The base is dissolved in the dilute hydrochloric acid, cooled in 
ice, and well stirred. The mixture is kept cold whilst the sodium 
nitrite solution is gradually added, until it gives an immediate 
colouration with potassium iodide-starch paper. The diazo- 
solution is then added in portions of about 10 c.c. at a 
time to the warm cuprous cyanide solution, with frequent 
shaking. A rapid effervescence occurs, nitrogen and some 
hydrocyanic acid being evolved. When, in the course of about 
fifteen minutes, the diazo-solution has been added, it is left 
on the water-bath until effervescence ceases (J hour). The 
liquid turns a dark colour, and a black tarry deposit is 
formed. The product is distilled in steam. This should be 
carried out in the fume cupboard, as not only is hydrocyanic 
acid liberated, but a small quantity of isocyanide, which is formed 
inthe reaction, and produces an intolerable smell. The distillation 
is continued until no more yellow oil passes over. The tolyl 
cyanide solidifies in the receiver on cooling as a yellow crystal- 
line mass, which is filtered, dried on a porous plate, and may be 
purified by distillation ; but for the preparation of toluic acid 
this is unnecessary. Yield about 1 5 grams. 

CH 3 .C 6 H 4 NH 2 .HC1 + NaNO 2 + HC1 = CH 3 .C G H 4 N 2 C1 + 
NaCl + 2H 2 O. 

CH 3 .CH 4 N 2 C1 + CuCN = CH 3 .C 6 H 4 .CN + N 2 + CuCl 

Properties. Colourless crystals ; m. p. 29 ; b. p. 218. 

Reaction. p-Toluic Acid. Boil up 10 grams tolylcyanide 
with a mixture of 30 c.c. cone, sulphuric acid and 20 c.c. water, in a 
round flask with upright condenser until colourless crystals of 
toluic acid appear in the condenser tube (about half an hour). On 
cooling, the acid crystallises out, and is separated by filtration, 
washed with water, and recrystallised from hot water ; m. p. 179. 

CH 3 .C 6 H 4 .CN + 2H 2 O + H 2 SO 4 = CH 3 .C 6 H 4 .CO.OH 
+ NH 4 .H.SO 4 . 

The yield is nearly theoretical. 



DIAZOAMINOBENZENE 171 

Terephthalic Acid. Dissolve 5 grams/-toluic acid in dilute 
caustic soda solution and boil with reflux condenser, adding 12 
grams of permanganate in 250 c.c. water gradually from a tap 
funnel inserted through the top of the condenser. When the red 
colour of the permanganate persists after continued boiling the 
solution is treated with sulphur dioxide (see p. 1 66), which dissolves 
the manganese dioxide and precipitates the terephthalic acid as 
a white amorphous powder. The latter is filtered, washed, and 
dried. It sublimes without melting at 300' and is insoluble in 
water and alcohol. The yield is nearly theoretical. 

CH 3 .C 8 H 4 .COONa + NaOH + 2KMnO 4 = 

NaOOC.C H 4 .COONa+ 2KOH + MnO 2 + 2H 2 O. 

PREPARATION 69. 
Diazoaminobenzene, C 6 H 5 N:N.NH.C 6 H 5 . 

Griess, Annalen, 1866, 137, 58 ; Staedel, Bauer, Ber., 1886, 19, 

1952. 

20 grms. aniline. 

6 cone, sulphuric acid. 
600 water. 
7*4 sodium nitrite. 

The acid is poured into the water contained in a large beaker 
(i litre) and the aniline then added. About half the aniline 
dissolves as sulphate. The liquid is warmed in the water-bath to 
27 and the sodium nitrite, dissolved in a small quantity of water, 
is slowly added and the whole well stirred. The temperature 
is maintained at 27 30 for a quarter of an hour. As soon as 
the sodium nitrite is added the liquid turns yellow and rapidly 
becomes turbid from the formation of diazoaminobenzene, 
which separates out in yellowish brown crystalline crusts. The 
solution is now allowed to stand at the ordinary temperature 
for half an hour, when nearly the whole of the diazoamino- 
benzene crystallises our. It is filtered, washed with cold water, 
pressed well on the filter, and dried on a porous plate or a pad 
of filter paper. It forms a brown sandy powder and may be 
purified by recrystallisation from benzene or alcohol. In 
crystallising, it is necessary to bring the substance into solution 
as quickly as possible. Boiling spirit (about three times the 



172 PRACTICAL ORGANIC CHEMISTRY 

weight of substance) should be added and the liquid heated for 
a moment until a clear solution is obtained and then allowed to 
cool. On prolonged boiling it decomposes. For the preparation 
of aminoazobenzene the dry powder is sufficiently oure. Yield, 
nearly theoretical. 

(C 6 H 5 NH 2 ) 2 H 2 SO 4 + 2NaNO 2 + 2H,SO 4 = 

2C G H 5 N 2 .SO 4 H + Na 2 SO 4 + 4H 2 O. 
C C H 5 N 2 .S0 4 H + C 6 H 5 NH 2 = C H 5 N:N.NHC G H 5 + H 2 SO 4 . 

N.B. The sulphuric acid, set free in the second phase of the reaction, 
acts upon the sodium nitrite, so that one molecule only is required. 

Properties. Golden yellow plates (from alcohol) m. p. 98 ; 
insoluble in water ; it explodes when heated above its melting 
point. 

Reaction. Dissolve a little of the substance in alcohol and 
add a drop or two of an alcoholic solution of silver nitrate. A 
red crystalline precipitate of C<jH 5 N:N.NAg.C H 5 is deposited. 
See Appendix, p. 285. 

PREPARATION 70. 
Aminoazobenzene (Aniline yellow), C G H 5 N:NC G H 4 NHo. 

Mene, /a/mv$., 1861, 496 ; Kekule, Zeitsch.f. Ch., 1866, 2, 689 ; 
Staedel, Bauer, Ber., 1886, 19, 1953. 

10 grms. diazoaminobenzene. 
25 aniline. 
5 ,, aniline hydrochloride. 

The finely powdered diazoaminobenzene, aniline hydro- 
chloride (see p. 156), and aniline are mixed together and heated 
to 40 for an hour. The mixture forms a clear, deep red solution. 
After standing for 24 hours at the ordinary temperature, the 
diazoaminobenzene is converted into aminoazobenzene. A 
slight excess of moderately strong hydrochloric acid is added, 
care being taken that no great evolution of heat occurs. On 
cooling, the aminoazobenzene separates out together with 
aniline hydrochloride. It is filtered and washed with cold, very 
dilute hydrochloric acid, when small violet crystals of aminoazo- 
benzene hydrochloride remain on the filter. In order to obtain 
the free base, the hydrochloride is warmed with dilute ammonia. 



PHENYLHYDRAZINE 173 

The base, which has a brown colour, is filtered and dissolved 
in hot spirit, with the addition of a few drops of concentrated 
ammonia. Yield, about 8 grams. 

C C H 5 N:N.NHC H 6 + H.C G H 4 NH 2 .HC1 = 

C 6 H 5 N:N.C 6 H 4 .NH 2 + C 6 H 5 NH 2 .HC1. 

Properties. Orange prisms ; m. p. 127. 

Reaction. Make a solution of 4 grams stannous chloride in 
10 c.c. cone, hydrochloric acid, add 2 grams aminoazobenzene, 
and boil for a few minutes. On cooling crystals of the hydro- 
chlorides of aniline and /-phenylenediamine separate out. 
The liquid is filtered and washed with a little cone, hydro- 
chloric acid to remove the tin salts. If the precipitate is 
dissolved in water and made alkaline with caustic soda, a 
mixture of liquid aniline and solid /-phenylenediamine is pre- 
cipitated, from which the former may be removed by filtering, 
washing, and draining on a porous plate. 

C 6 H 5 N:N.C 6 H 4 NH, + 2SnCl 2 + 4HC1 = 

C 6 H 6 NH 2 + H 2 N.C C H 4 .NH 2 + 2SnCl 4 . 

/-Phenylenediamine, when warmed with dilute sulphuric acid 
and potassium bichromate or lead peroxide, gives the odour of 
quinone (p. 192). After warming and cooling, extract with ether. 
The ethereal solution has a yellow colour. Decant the ether 
extract on to a watch-glass and leave it to evaporate in the air. 
A deposit of microscopic yellow crystals remains. See Appen- 
dix, p. 286. 

PREPARATION 71. 
Phenylhydrazine, C H 5 NH.NH 2 

E. Fischer, Annalen, 1878, 190, 167 ; Meyer, Lecco, Ber., 
1883, 16, 2976 ; Meyer and Jacobson, Lehrbuch, 2, 505. 

20 grms. aniline. 
200 (170 c.c.) cone, hydrochloric acid. 

20 sodium nitrite (in 100 c.c. water). 
1 20 crystallised stannous chloride (in 100 c.c. 
cone, hydrochloric acid). 

The aniline is dissolved in the concentrated hydrochloric 
acid and cooled to o in a freezing mixture. The solution of 



174 PRACTICAL ORGANIC CHEMISTRY 

sodium nitrite is gradually added, the temperature being kept 
below 10, until a drop of the mixture, diluted with water, turns 
potassium iodide-starch paper blue. To the mixture, still cooled 
in ice, 120 grams stannous chloride, dissolved in about an 
equal weight of cone, hydrochloric acid, is added. A thick 
white crystalline precipitate of phenylhydrazine hydrochloride 
separates. It is allowed to stand for half an hour and filtered at 
the pump ; it is then separated as far as possible from the mother 
liquor, and transferred to a flask. The free base is obtained by 
decomposing the hydrochloride with caustic soda. An excess 
of caustic soda is added, and the mixture well shaken. The 
free base, which separates as a reddish coloured oil, is extracted 
with ether, and the ethereal solution dehydrated over solid 
potassium carbonate. The ether is then removed on the water- 
bath, and the residual oil either used without further purification 
or distilled in vacua. Yield, 1 5 20 grams. 



NaCl + 2H 2 O. 



Properties. Nearly colourless oil when freshly distilled ; 
b. p. 241242 ; m. p. 17-5 ; sp. gr. 1-097 at 23. 

Reactions. I. Add a few drops of phenylhydrazine to 2 c.c. 
of water, then a drop or two of copper sulphate solution and 
excess of caustic soda. Cuprous oxide is precipitated with 
effervescence and benzene separates, C G H 5 NH.NH 2 -r2CuO- 
C 6 H 6 + N 2 +Cu 2 O + H 3 O. The same reaction takes place if 
the phenylhydrazine is dissolved in dilute acetic acid and copper 
sulphate solution added and warmed. 

2. Add 2 grams of phenylhydrazine to 4 c.c. water in a boiling 
tube, warm until dissolved, and then add about 3 c.c. of a warm 
saturated solution of cupric hydrate dissolved in cone, ammonia. 
Nitrogen is evolved and cuprous hydroxide dissolves. Add a 10 
per cent, caustic potash solution until there is a slight permanent 
precipitate of cuprous hydroxide and heat the liquid in the 
water-bath. A copper mirror is deposited on the surface of the 
glass (Chattaway). 

3. Add to a few drops of phenylhydrazine an equal quantity 
of glacial acetic acid, dilute with a little water, and add a 



SULPHANILIC ACID 175 

drop of benzaldehyde. In a short time the phenylhydrazone of 
benzaldehyde will crystallise out. 

4. Phenylmethylpyrazolone. Mix together lograms dry 
phenylhydrazine hydrochloride and 9 grams acetoacetic ester in a 
flask (200 c.c.), add 3 or 4 drops cone, hydrochloric acid and 
warm for 10 15 minutes. A clear reddish solution is obtained, 
which is poured into water and carefully neutralised with caustic 
soda. The precipitated oil solidifies almost immediately and 
can be recrystallised from alcohol ; m. p. 127. Yield 8 grams. 



CH,.C 0" CH,.CX)f6C.H 5 i CH..C CH,.CO 



+ NiH 2 NiH !C 6 H 5 Si lt.C 6 H 5 

flip + C 2 H 5 OH. 

See also the Reactions on pp. 70, and 135, and Appendix, 
p. 287. 

PREPARATION 72. 

/NH 2 i 
Sulphanilic Acid, C 6 H 4 / 

X SO 3 H 4 

Gerhardt, Annalen, 1846, 60, 312 ; Buckton, Hofmann, 
Annalen, 1856, 100, 163. 

25 grms. aniline. 

80 cone, sulphuric acid. 

The aniline and sulphuric acid are cautiously mixed in a 
round flask (250 c.c.) and heated to 180 190 in an oil or metal 
bath for four to five hours until a sample dissolved in water 
remains clear on the addition of caustic soda in excess and no 
aniline separates. The product is poured into cold water, which 
precipitates the Sulphanilic acid as a grey crystalline mass. It 
is filtered, washed with a little cold water, recrystallised from 
hot water with the addition of a little animal charcoal, and dried 
in the air. Yield, 2530 grams. 

C 6 H 5 NH 2 + H 2 SO 4 = NH 2 .C 6 H 4 .SO 3 H + H 2 O. 

Properties. Colourless rhombic plates, containing 2 mols. ot 
water of crystallisation, which they lose slowly in the air, and 
the crystals fall to powder. See Appendix, p. 289. 



176 PRACTICAL ORGANIC CHEMISTRY 

PREPARATION 73. 
Methyl Orange (Heliamhin), SO 3 Na.C G H 4 N:N.C H 4 N(CH 3 ) 2 

10 grms. sulphanilic acid. 

2'5 anhydrous sodium carbonate (in 100 c.c. water). 
3'5 sodium nitrite (in 20 c.c. water). 
6 cone, hydrochloric acid (in 10 c.c. water). 
6 dimethylaniline (in 6 c.c. cone. HC1 and 20 c.c. 
water). 

The sulphanilic acid is dissolved in the sodium carbonate 
{& mol.) solution and the sodium nitrite (i mol.) solution added. 
The mixture is cooled in ice, and the solution of hydrochloric 
acid (i mol.) gradually added. The solution of dimethylaniline 
(i mol.) is now poured in, and the liquid made alkaline with 
caustic soda. The separation of methyl orange at once begins, 
and is assisted by the addition of a little common salt (20 grams). 
The precipitate is filtered at the pump, and crystallised from 
hot water. Yield, nearly theoretical. 

SO 3 Na.C 6 H 4 NH 2 4- NaNO 2 + 2HC1 = SO 3 Na.C H 4 N,.Cl + 

NaCl + 2H*O. 

SO 3 Na.C fi H 4 N2.Cl + C 6 H 5 N(CH 3 ) 2 HC1 = 
SO 3 H.C 6 H 4 .N 2 .C 6 H 4 N(CH 3 ) 2 + NaCl + HC1. 

SO 8 H.C 6 H 4 N:N.C 6 H 4 N(CH s )s + NaOH = 
SO 3 Na.C 6 H 4 N:N.C H 4 N(CH 3 ) 2 + H 2 O. 

Properties. Methyl orange is the sodium salt of the sul- 
phonic acid, and dissolves in water with a yellow colour. The 
free acid is red, and its action as an indicator depends upon 
this change on the addition of mineral acid. 

Reaction. Methyl orange is decomposed, like the majority of 
azo-compounds, by stannous chloride in hydrochloric acid into 
two molecules, produced by the addition of hydrogen to the 
double-linked nitrogen atoms (see p. 173). 

HS0 3 .C 6 H 4 N:N.C G H 4 N(CH 3 ) 2 + 2SnCl, + 4HC1 = 
HS0 3 .C H 4 NH 2 + H 8 NC 6 H 4 N(CH s ) a + 2 SnCl 4 . 



POTASSIUM BENZENE SULPHONATE 177 

Make a solution of 4 grams stannous chloride in 10 c.c. cone, 
hydrochloric acid, add I gram of methyl orange dissolved in a 
few drops of hot water, and boil for a few minutes until the red 
colour disappears. On cooling a crystalline precipitate consist- 
ing of sulphanilic acid and dimethyl ^-phenylenediamine is 
deposited. In order to separate the base, dilute with water, add 
caustic soda solution until the precipitate of stannous* hydrate 
redissolves, shake out the cold solution with ether, and de- 
hydrate over potassium carbonate. On distilling off the ether, 
the dimethyl j^-phenylenediamine remains as a crystalline 
solid ; m. p. 41. On wanning with dilute sulphuric acid and 
lead peroxide the odour of quinone is readily perceived 
(seep. 192). It also gives the ' methylene blue' reaction, like 
nitrosodimethylainline (see p. 158). See Appendix, p. 289. 



PREPARATION 74. 
Potassium Benzenesulphonate, QH^SOgK + |H 2 O 

Mitscherlich, Pogg. Ann., 1834, 31, 283 and 364 ; Michael, 
Adair, Ber., 1877, 10, 585. 

60 c.c. benzene. 

60 cone, sulphuric acid. 

The benzene and sulphuric acid are heated together on a 
sand-bath in a round flask ( litre) with upright condenser. 
The mixture is kept at a gentle boil with frequent shaking (an 
apparatus like that shown in Fig. 78, p. 147, with mechanical 
stirrer is preferable) until the top layer of benzene has been 
nearly absorbed by the sulphuric acid (six to eight hours). On 
cooling, the dark-coloured liquid is poured into cold water 
(i litre) contained in a large basin, boiled up and neutralised 
with powdered chalk or thick milk of lime. The mass is 
filtered hot through a porcelain funnel or cloth from the pre- 
cipitate of calcium sulphate, washed with hot water and 
somewhat concentrated. The solution, which contains the 
calcium salt of benzene sulphonic acid, is treated with just 
sufficient potassium carbonate solution to precipitate the calciuia 
as carbonate and convert the sulphonic acid into the potassium 

COHEN'S ADV. p. o. c. N 



i;8 PRACTICAL ORGANIC CHEMISTRY 

salt. This is ascertained by filtering small samples and testing 
the filtrate with potassium carbonate. The liquid is again 
filtered through cloth or through a porcelain funnel and concen- 
trated first over a ring burner, and finally on the water-bath, 
until a sample crystallises on cooling. The potassium salt is 
drained at the pump and dried on porous plate. Yield, about 
80 grams. 

C H + H 2 S0 4 = C 6 H 6 S0 3 H + H 2 O. 

2C 6 H 5 SO 3 H + CaCO 3 = (C 6 H 5 SO 3 ) 2 Ca + CO 2 + H 2 O. 
2 CO 3 =2C 6 H SO 3 



Properties. Colourless pearly plates, which slowly effloresce 
in the air and which melt above 300 with slight decomposition \ 
very soluble in water. See Appendix, p. 292. 



PREPARATION 75. 

Benzenesulphonic Chloride, C G H 6 SO 2 Ci 
Gerhardt, Chiozza, Annalen, 1853, 87, 299. 

15 grms. potassium benzene sulphonate, 
25 phosphorous pentachloride. 

The potassium benzenesulphonate is carefully dried on the 
water-bath, powdered, and mixed with the phosphorus penta- 
chloride in a flask.* A vigorous reaction sets in. When it has 
abated, the flask is heated on the water-bath for one hour,* 
and the mass occasionally stirred with a glass rod. The pro- 
duct is poured into a flask containing 200 c.c. cold water and 
allowed to stand an hour. The sulphonic chloride, which 
separates as an oil, is then extracted with ether, dehydrated 
over calcium chloride, decanted, and the ether removed on the 
water-bath. Yield, 10 grams of a light brown oil. 

C H 5 SO 3 K + PC1 3 = C H 5 SO S C1 + POC1 3 + KC1. 

Properties. Colourless oil when pure ; b. p. 246 247 with 
decomposition ; m. p. 14 ; distils undecomposed in -vacuo. 



PHENOL. 179 

Reaction. I. Grind up in a mortar I c.c. of sulphonic chloride 
with 5 grams powdered ammonium carbonate, and leave on the 
water-bath until the smell of the sulphonic chloride has gone. 
Add water, filter, and wash, and crystallise the residue of 
benzene sulphonamide from spirit, C H 5 SO 2 Cl + 2NH 4 HCO 3 = 



2. Add I c.c. of the sulphonic chloride co 2 c.c. aniline, stir 
up well, add water, and acidify with a few drops of concentrated 
HC1 (methyl violet paper). Filter, wash, and crystallise the 
benzenesulphonanilide from spirit, C c H 3 SO 2 Cl + NH.>C (i H 5 = 
C C H 6 SO 2 NHC H 5 + HC1. 

3. Add 2 c.c. absolute alcohol to I c.c. sulphonic chloride and 
excess of caustic soda until alkaline ; warm gently for five 
minutes and add more caustic soda if necessary. Cool, and 
extract with ether. The residual liquid consists of benzene ethyl 
sulphonate, C 6 H 5 SO 2 C1 + HOC 2 H 5 = C 6 H 5 SO 2 OC 2 H 5 + HC1. 

4. Repeat 3, using phenol in place of alcohol. See Appendix^ 
p. 293. 

PREPARATION 76. 
Phenol (Carbolic acid, Hydroxybenzene), C 6 H 5 .OH 

Kekule, Wurtz, Dusart, Zeitschr. f. Ch. N. F., 1867, 3, 
299-301 ; Degener, /. prakt. Chim. 1878, (2), 17, 394. 

20 grms. potassium benzenesulphonate. 
35 caustic potash. 

The caustic potash is dissolved in the smallest quantity of 
water (5 c.c.) by heating in a silver or nickel basin or crucible, 
and the powdered potassium benzenesulphonate added. The 
temperature of the melt, which during the process is kept con- 
stantly stirred, must not exceed 250. It is convenient to use 
the thermometer as stirrer, the bulb and part of the stem being 
encased in a glass tube closed at one end. When the requisite 
temperature has been reached, a small flame is sufficient to 
maintain it. The mass is first thick and pasty, but soon be- 
comes semi-fluid and remains in this condition, gradually 
changing in colour from yellow to brown. Towards the end of 
the operation (one hour) it regains somewhat its original con- 
sistency. On cooling, the melt is dissolved in a little water 

N 2 



i8o PRACTICAL ORGANIC CHEMISTRY 

and the alkaline reddish-brown liquid (potassium phenate and 
excess of alkali) acidified with concentrated hydrochloric acid in 
the cold. Phenol separates out as a light yellow oil, which is 
extracted three times with ether. The ethereal solution de- 
hydrated over anhydrous sodium sulphate is distilled, first on 
the water-bath until the ether is removed, and then over the 
flame. The portion boiling at 175 185 is nearly pure phenol. 
It distils as a colourless liquid and solidifies at once on cooling. 
Yield, 6 7 grams. 

C H 6 SO 3 K + KOH = C G H 5 OK + KHSO 3 . 
C 6 H 5 OK+HC1 = C 6 H 5 OH + KC1. 

Properties. Colourless needles, with a characteristic smell ; 
m. p. 42 43 ; b. p. 182 ; easily soluble in alcohol and ether ; 
and in about 1 5 parts of water at the ordinary temperature ; 
produces blisters on the skin. 

Reactions. i. Make a solution of phenol in water, and to one 
portion add a drop of ferric chloride. A violet colouration is 
produced. 

2. Add to another portion a drop of bromine water. A white 
crystalline precipitate of tribromophenol is formed. 

3. To a third portion add an equal volume of dilute ammonia 
and a few drops of sodium hypochlorite and warm gently. A 
copper-sulphate-blue colour is produced. 

4. Add a small fragment of solid sodium nitrite to 5 c.c. concen- 
trated sulphuric acid and warm very gently until dissolved. On 
adding about o - 5 gram of phenol, a brown solution is obtained, 
which rapidly changes to deep blue. If the blue solution is 
poured into water, a cherry red colouration is produced, which 
changes to blue on the addition of an alkali (Liebermann's 
' nitroso ' reaction, see p. 1 59). 

5. Mix I gram of phenol with i c.c. of dimethyl sulphate l 
and add 4 c.c. of a 10 per cent, solution of caustic soda. 
Warm and shake. The odour of phenol is replaced by that of 
anisole, which can be extracted from the liquid by ether 
^Ullmann's reaction). See Appendix, p. 294. 



I The vapour of dimethyl sulphate is very poisonous, and care should be taken 
not to breathe it. 



ANISOLE 181 

PREPARATION 77. 

Anisole (Methyl phenate, Phenyl methyl ether), C H 5 .O.CH 3 
Cahours, Annalen, 1851, 78, 226. 

5 grms. sodium. 

100 c.c. methyl alcohol. 

20 grms. phenol. 

40 methyl iodide. 

The methyl alcohol is poured into a round flask (250 c.c.) 
connected with an upright condenser. The sodium, cut into 
small pieces, is then added, the flask being detached from the 
condenser for a moment and replaced. When the sodium has 
dissolved, the phenol and methyl iodide are added. The mixture 
is heated on the water-bath until the solution has no longer an 
alkaline reaction (two to three hours). As much as possible of 
the methyl alcohol is distilled off on the water-bath and water 
added to the amber-coloured residue. A colourless oil separates 
out, which is extracted with ether. The ethereal solution is 
dehydrated over calcium chloride and distilled, first on the 
water-bath until the ether has been driven off, and then over 
the flame. Almost the whole of the residue distils at 150 155. 
Yield, nearly theoretical. 



Properties. Colourless liquid, possessing an agreeable smell , 
b. p. 154 ; sp. gr. 0-991 at 15. See Appendix, p. 294. 



PREPARATION 78. 

Hexahydrophenol (Cyclohexanol), C H n .OH 

Sabatier and Senderens, Compt. rend., 1901, 132, 2ic. 

50 grms. phenol. 

The phenol is reduced with hydrogen in presence of finely 
divided metallic nickel ; which acts as a catalyst. The 
apparatus is shown in Fig. 79. 



1 82 



PRACTICAL ORGANIC CHEMISTRY 



It consists of an oblong Lothar-Meyer air-bath about 5o cms. 
(24 ins.) long and 15 cms. ( 6 ins.) wide. It is heated on each side 
by a series of small gas jets made by perforating an iron pipe 
which runs below the air-bath. The hot air passes up the 
space between the outside metal casing and an inner rectangular 
metal box, and then down and into the interior of the air-bath 
through a number of round holes at the bottom of a central 




"9 =r 



< 60 cm.- -> 

FIG. 79. 

rectangular chamber, and finally escapes through a series of 
holes in top of the outer cover. The air-bath is perforated 
at both ends so as to admit a piece of wide glass tubing. This 
tubing (1*5 2 cms. diam.) is of such a length that it projects 
about 2 3 cms. at one end and 5-6 cms. at the other, the latter 
being bent and connected to a receiver. The shorter end is 
attached by a cork to a small distilling flask through which a 
current of dry hydrogen is passed from a Kipp by a delivery 
tube, which reaches to the bottom of the flask. 



o- AND p-NITROPHENOL 183 

Small pieces of pumice impregnated with a paste of nickel 
oxide (NiO) and water is dried on the water-bath and packed into 
the wide tube, which is then loosely plugged at each end with 
asbestos. The phenol is melted and poured into the distilling flask. 
The air-bath is slightly tilted so that any liquid which may collect 
in the tube can run down into the receiver. The process is 
conducted as follows : the delivery tube from the Kipp is first 
raised above the surface of the phenol and a slow current of 
pure dry hydrogen passed through the apparatus, the tempera- 
ture of which is maintained at 300 for 20 minutes. The nickel 
oxide is thereby reduced and changes from black to pale yellow. 
After reduction, the temperature is lowered to 160-170 and 
kept at this point. The phenol in the flask is now melted and 
heated just below its boiling-point, whilst a fairly rapid current 
of hydrogen is passed through the delivery tube, which is 
thrust well into the liquid. The hexahydrophenol slowly distils 
and condenses in the receiver. Care must be taken that the 
phenol does not condense in the tube, but that only the vapour 
passes ov'er. When sufficient liquid has collected, it is shaken 
with caustic soda solution, extracted with ether, dehydrated over 
potassium carbonate and distilled. 

C 6 H 6 OH + 6H =C 6 H U OH. 

Properties. Colourless liquid ; b. p. 170 ; pleasant aromatic 
smell distinct from phenol ; insoluble in water and solutions of 
caustic alkalis. See Appendix, p. 295. 



PREPARATION 79. 
o- and p-Nitrophenol, C 6 H 4 



2 4 



Hofmann, Annalen, 1857, 103, 347 ; Fritsche, Annalen, 1859, 
110, 150 ; Kekule, Lehrbuch d. org. chem., 3, 40. 

40 grms. phenol. 

70 (50 c.c.) cone, nitric acid (in 170 c.c. water). 

The phenol, melted in a basin on the water-bath, is slowly 
added in small quantities to the nitric acid and water contained 



184 PRACTICAL ORGANIC CHEMISTRY 

in a large round flask (i litre), and the contents of the flask 
well shaken or stirred mechanically. The temperature should 
be maintained below 30 by cooling with water. On the 
addition of the phenol, the liquid immediately changes to 
a deep brown or black colour, and a heavy dark-brown 
oil separates out. When the phenol has been added, the 
mixture is allowed to stand for 12 hours. The oil has by 
that time collected at the bottom of the vessel, and may 
be freed from acid by repeatedly decanting and pouring in 
fresh w^.ter (three or four times). The contents of the flask 
consist of nearly equal quantities of para- and ortho-nitrophenol 
mixed with resinous products. In order to separate the two 
isomers, the product is distilled in a current of steam (see Fig. 
68, p. 107) until the distillate is almost colourless. The ortho- 
compound distils in the form of a yellow oil, which may solidify 
in the condenser, in which event the water is temporarily run 
out of the condenser. The solid in the receiver is separated by 
filtration and dissolved in spirit at 40, to which water is then 
added, drop by drop, until a turbidity is produced. Yield, 15 
grams. The solid residue contains the para-compound mixed 
with black, resinous substances, from which it is separated by 
repeatedly extracting with boiling water. The united portions 
of the aqueous extract are boiled with animal charcoal for 
half an hour in a large basin, and filtered through a fluted filter 
moistened with water. The filtrate is made alkaline with 
caustic soda solution, and concentrated to a small bulk (100 
c.c.). If tarry matter separates, it must be filtered through a wet 
filter. To obtain the free para-compound, the concentrated 
aqueous solution of the sodium salt is cooled, and the separated 
sodium salt filtered. The crystals are dissolved and acidified 
with concentrated hydrochloric acid, and the nitrophenol, which 
separates, is filtered and recrystallised from hot water. Yield, 
10 grams. 

C 6 H 5 OH + HONO 2 = OHC 6 H 4 NO 2 + H 2 O. 

Properties. Q-Nitrophenol, sulphur-yellow needles, pos- 
sessing a peculiar smell ; m. p. 45 ; b. p. 214 ; distillable with 
steam ; soluble in alcohol, ether, and hot water ; less soluble in 
cold water. 

p-Nitrophenol, colourless needles ; m. p. 114 ; easily soluble 



PICRIC ACID 



in alcohol and hot water ; slightly soluble in cold water. See 
Appendix, p. 295. 

PREPARATION 80. 

/NO, 2 

Picric Acid (Trinitrophenol),C 6 H,(OH)(-NO2 4 

X NO 2 6 

Woulfe, 1771 ; Schmidt, Glutz, Ber., 1869, 2, 52. 
25 grms. phenol. 

125 (68 c.c.) cone, sulphuric acid. 
100 ,. (70 c.c.) cone, nitric acid, sp. gr. 1'4. 

The phenol and concentrated sulphuric acid are heated 
together in a porcelain basin for half an hour on the water-bath, 
until a clear solution of phenol sulphonic acid is obtained. It is 
diluted with 100 c.c. of water, well cooled, poured into a flask 
(i litre), and then 50 c.c. nitric acid slowly added, in small 
quantities at a time, from a tap-funnel, and well shaken.* The 
liquid assumes a deep red colour, a considerable rise of tempera- 
ture occurs, and red fumes are evolved. When the nitric 
acid has been added, the flask is placed on the water-bath 
and heated, with the addition of the remaining 20 c.c. of 
nitric acid, for i 2 hours.* On cooling, picric acid separates 
out as a yellow, crystalline mass. It is diluted with water, 
filtered at the pump, and washed free from the mother liquor 
with cold water. It is then purified by recrystallisation from a 
large quantity of hot water acidified with a few drops of 
sulphuric acid. Yield, about 30 grams. 

C H 5 (OH) + H,SO 4 = C 6 H 4 (OH).SO 3 H + H 2 O. 
C 6 H 4 (OH)SO 3 H + 3HONO,= 

C C H.,(OH)(N0 2 ) 3 + 3 H 2 +H 2 S0 4 . 

Properties. Yellow, prismatic crystals; m. p. I2r5; sub- 
limes on gently heating ; explodes on detonation ; easily soluble 
in alcohol and ether ; with difficulty in cold, more readily in 
hot water ; the solution has a bitter taste. 

Reactions. i. To an aqueous solution of picric acid add a 
little potassium cyanide solution, and warm. A brown crystal- 
line precipitate of isopurpuric acid separates. 

2. Add picric acid and a few drops of caustic soda to a dilute 
solution of grape sugar and warm. The liquid turns deep brown 



186 PRACTICAL ORGANIC CHEMISTRY 

3. Dissolve naphthalene in a little spirit, and add an 
equal quantity of a solution of picric acid in spirit. On 
cooling, yellow needles of naphthalene picrate separate, 
C 10 H 8 .C 6 H 2 OH(NO.,) 3 . Benzene forms colourless crystals, 
anthracene, scarlet needles, having a similar composition. See 
Appendix, p. 295. 

PREPARATION Si. 

.(C 6 H 4 OH) 2 
Phenolphthalein, of 



\ X C H 4 CO.O 

' V. / 



Baeyer, Ber., 1876, 9, 1230, and Annalcn, 1880, 202, 68. 
10 grms. phthalic anhydride. 
20 phenol. 
8 cone, sulphuric acid. 

The phthalic anhydride, phenol, and concentrated sulphuric 
acid are heated together to 1 15 120 in the oil-bath 8 9 hours. 
The mass becomes semi-fluid and of a dark red colour. It is 
poured, whilst hot, into a basin of water (500 c.c.) and boiled 
until the smell of phenol has disappeared, the water being 
renewed as it evaporates. The undissolved yellow granular 
precipitate, on cooling, is separated from the liquid by filtration, 
and washed with water. It is then dissolved in dilute caustic 
soda solution, filtered from the undissolved residue, and the 
filtrate acidified with acetic acid and a few drops of hydro- 
chloric acid. The phthalein separates out, after standing for 
some hours, as a light yellow, sandy powder, which is filtered 
and dried. It is purified by dissolving in absolute alcohol with 
the addition of animal charcoal (i part phenolphthalein, 6 parts 
alcohol, and ^ part charcoal) and boiling the solution on the 
water-bath for an hour. The mass is filtered hot, washed with 
2 parts boiling alcohol, and the filtrate evaporated down to 
two-thirds its bulk on the water-bath. On adding 8 times the 
quantity of cold water to the cooled solution, the latter becomes 
turbid. The liquid is well stirred, and, after standing a few 
seconds, filtered through cloth from the resinous oil which 
separates. On heating the filtrate on the water-bath to expel 



FLUORESCEIN AND EOSIN 187 

excess of alcohol, phenolphthalein crystallises out in the form 
of a white powder: Yield, 5 grams. 



/COv . 

2C 6 H 6 (OH) + C 6 H/ >0 - - C C H 4 < >0 + H 2 O. 

X C(X X CO 

Properties. White, granular, crystalline powder ; m. p. 
250 253 ; very slightly soluble in water, readily soluble in hot 
alcohol ; soluble in alkalis with a crimson colour. See Appendix, 
p. 296. 

PREPARATION 82. 
Fluorescein and Hosin, 

X C 6 H,OH /C 6 HBn,OH 

r ' >O r ' >O 

U \C 6 HoOH ^\C c HBr 2 OH 

QI^CO.O I X C 6 H 4 CO.O 

v _ j \ _ / 

Baeyer, Annalcn, 1876, 183, 3. 

10 grms. phthalic anhydride. 
1 5 resorcinol. 
7 zinc chloride (fused and powdered). 

The phthalic anhydride and resorcinol are ground together 
and heated in a deep tin dish or cylinder to 180. To the 
fused mass the zinc chloride is added with continual stirring in 
the course of ten minutes. The temperature is now raised to 
210 and the heating continued until the mass is quite hard 
(about 2 hours). On cooling, the melt is chipped out, pulverised, 
and boiled for ten minutes with 150 c.c. water and 10 c.c. cone. 
hydrochloric acid. The fluorescein is filtered off, washed, and 
boiled with a small quantity of absolute alcohol to dissolve 
impurities. The residue is then dried on the water-bath. Yield 
20 grams. 

Eosin. Fifteen grams of the fluorescein are mixed in a flask 
with 80 c.c. spirit and 1 1 c.c. bromine are dropped in from a 
burette in the course of quarter of an hour. Heat is developed 
and the fluorescein gradually dissolves until, when half the 
bromine has been added, a clear solution is obtained. Further 
addition of bromine precipitates the tetrabromo-compound 



188 PRACTICAL ORGANIC CHEMISTRY 

(eosin). After standing two hours the precipitate is filtered, 
washed with spirit, and dried at 110 to expel alcohol of crystalli- 
sation. Yield 30 grams. 

In order to obtain the sodium compound, 6 grams of the 
product are ground in a mortar with I gram of sodium carbonate, 
placed in a beaker, and moistened with alcohol. Five c.c. of 
water are added and the mixture boiled until the evolution of 
carbon dioxide ceases. To the sodium salt 25 c.c. spirit are 
added and the mixture boiled and filtered. On standing for 
a day or two, the sodium salt crystallises in brown needles. 



/\ /** 

/CO. / I X C 6 H 3 < 

C 6 H 4 < >0 + 2C 6 H 4 (OH) 2 > C 6 H 4 < O X OH 

X CO X \ | 

X CO 

/OH /OH 

/C 6 H/ /CeHBr/ 

C' ^O C- O 



O OH + 8Br >CH O OH 



See Appendix, p. 296. 

PREPARATION 83. 

Salicylaldehyde (0-Hydroxybenzaldehyde) 
p-Hydroxybenzaldehyde, 

Reimer, Tiemann, Ber., 1876, 9, 824. 

r H /OH i i 
^ H 4\CO.H 2 4' 

50 grms. phenol. 

100 ,, caustic soda. 

1 60 water. 

75 chloroform. 

The phenol, caustic soda and water are mixed together in a 
round flask (i litre) attached to an upright condenser and 
heated to 50 60. The chloroform is then added gradually 



SALICYLALDEHYDE 189 

through the top of the condenser and, after each addition, the 
flask is well shaken. A gentle reaction sets in, and the temper- 
ature rises. At the same time the surface of the brownish 
yellow solution takes a violet tint, which rapidly fades, the 
liquid finally assuming a deep red colour. When all the chloro- 
form has been added, the contents of the flask are boiled for half 
.an hour. A yellow semi-solid mass separates out of the solution. 
The unattacked chloroform is now distilled off on the water- 
bath, the liquid diluted with water and strongly acidified with 
dilute hydrochloric or sulphuric acid. A thick red oil separates 
out on the surface and is subjected to distillation in steam. An 
oil, having a faintly yellow colour, distils over with the water, and 
settles to the bottom of the receiver. When drops of oil cease 
to condense, the distillation is stopped. The distillate, which con- 
tains salicylaldehyde and phenol, is extracted with ether, and the 
ethereal solution well shaken with a saturated solution of sodium 
bisulphite (see Reaction 2, p. 67). The bisulphite compound 
of salicylaldehyde separates out in colourless needles, which are 
filtered, washed free from traces of phenol with alcohol and then 
decomposed by heating with dilute sulphuric acid. The aldehyde 
which separates is taken up with ether, dehydrated over calcium 
chloride, the ether driven off and the aldehyde distilled. 
Yield, 10 grams. In the distilling flask from which the salicyl- 
aldehyde has in the first instance been removed with steam, 
there remains a brownish liquid and a dark red substance, which 
sinks to the bottom of the vessel, and forms a brittle resin on 
cooling. The aqueous portion is filtered hot through a moistened 
filter, which retains the resin, and the filtrate, containing'^-hydr- 
oxybenzaldehyde, is extracted when cold with ether. On distilling 
off the solvent, the aldehyde remains in the form of a yellow 
mass of stellar-shaped needles, which may be purified by 
crystallisation from hot water. Yield, about 2 grams. 

C 6 H 6 ONa + 3 NaOH + CHC1 3 = C 6 
3NaCl + 2H 2 O. 

Properties. Salicylaldehyde. Colourless fragrant oil, b. p. 
I96'S 3 ; sp.gr. ri73 at I3'5 ; solidifies at 20, forming large 
crystals. Volatile in steam ; soluble in water ; miscible in all 
proportions with alcohol and ether. 



190 PRACTICAL ORGANIC CHEMISTRY 



Reaction. Add a drop of ferric chloride to the aqueous 
solution of the aldehyde. A deep violet colouration is produced 

p-Hydroxybenzaldchyde. Colourless needles, m. p. 1 1 5 1 16; 
scarcely soluble in cold water, readily in hot water, alcohol and 
ether. Non-volatile in steam. The bisulphite of sodium 
compound dissolves readily in water. 

Reaction. The same as above ; but the colouration is less 
intense. See Appendix, p. 297. 



PREPARATION 84. 

Salicylic Acid (0-Hydroxybenzoic Acid), C e H 4 <^pQ 
t. Chent., 1874, (2), 10, 95. 



10 grms. caustic soda. 
23 phenol. 

This preparation should be commenced first thing in the 
morning. Dissolve the caustic soda in about 10 c.c. of water in 
a small porcelain basin and add the phenol. Heat the basin on 
wire-gauze over a very small flame, and, whilst holding it firmly 
with a small clamp (tongs are too insecure), keep constantly 
stirring with a glass rod. After a short time the mass becomes 
stiff and balls together. The basin should now be removed 
from the gauze, and the mass stirred and broken up as it cools. 
When still warm, it is sufficiently hard to powder in a mortar. 
It is quickly powdered and transferred to a small retort (200 c.c.) 
heated in an oil or paraffin bath to 130 140, and dried by 
passing over it a fairly rapid current of dry hydrogen from a 
Kipp. In about an hour all the moisture is removed, and the 
body of the retort appears dry. The light coloured mass in the 
retort is allowed to cool whilst the hydrogen is passing through, 
then broken up and shaken into a mortar, when it is quickly 
powdered and replaced. The object of the above operation is 
to obtain perfectly dry, uncharred and well-powdered sodium 
phenate, upon which the success of the preparation entirely 
depends. A moderate stream of carbon dioxide, dried through 
concentrated sulphuric acid, is now passed over the surface of 



SALICYLIC ACID 191 



the sodium phenate by means of a bent tube fixed through the 
tubulus of the retort, and terminating just above the substance. 
The temperature of the oil-bath is gradually raised from 140 to 
180 190", whilst fresh surfaces are exposed by occasionally 
stirring with a glass rod inserted for a moment through the 
tubulus. At the end of four hours the temperature is raised to 190- 
200 for another hour, and the process stopped. During the 
heating a considerable quantity of phenol distils, and solidifies in- 
the neck of the retort, whilst the contents become dark coloured. 
The mass is shaken out into a basin without disturbing the phenol 
in the neck, and the residue dissolved by filling the retort two- 
thirds full of water. This is poured into the basin containing 
the other portion, which soon dissolves. The solution is acidi- 
fied with concentrated hydrochloric acid, which throws down 
impure salicylic acid in the form of a dark brown pre- 
cipitate. When cold, the precipitate is filtered at the pump r 
and washed with a little cold water. A further quantity 
may be obtained by evaporating the filtrate to a small bulk. It 
is purified by dissolving in water, boiling with a little animal 
charcoal and filtering. The filtrate deposits the acid, on cooling,. 
in colourless needles. Yield about 6 grams. 

I. C 6 H 5 ONa + CO 2 = C G H 5 O.CO.ONa 

Sodium phenyl carbonate. 



2. C 6 H 5 O.CO.ONa + C H 3 ONa =C 

Disodium salicylate. 

Properties. Colourless needles; m. p. 155 156; soluble in 
alcohol and hot water. 100 parts water dissolve '0*225 P art at 
15 and 7^925 parts at 100. 

Reactions. i. Dissolve a little of the acid in water and add 
a drop of ferric chloride. A violet colouration is obtained. 

2. Grind up some of the acid with soda-lime and cover with a 
shallow layer of the same substance. On heating strongly the 
smell of phenol is perceived. 

C 6 H 4 (OH)CO.OH + CaO = C H 6 OH + CaCO 3 . 
See Appendix, p. 297. 



192 PRACTICAL ORGANIC CHEMISTRY 

PREPARATION 85. 
Quinone and Quinol (Hydroquinone), 

C H ^ and C H / OH x 
^ H a C H4 



Woskresensky, Annalen, 1838, 27, 268 ; Nietzki, Ber., 1886, 
19, 1467 ; Meyer and Jacobson, Lehrbuch, vol. ii., 421. 

25 grms. aniline. 

200 (no c.c.) cone, sulphuric acid. 
750 c.c. water. 

80 grms. potassium bichromate. 1 

The water and aniline are mixed together in a large glass jar 
{\\ litres) and the sulphuric acid added. The mixture is cooled 
in ice and stirred with a turbine (see Fig. 64, p. 91). The finely- 
powdered bichromate is added every few minutes in small quan- 
tities on the end of a small spatula, until about one-third has 
been added, care being taken that the temperature does not 
exceed 10. The mixture is then left to stand over night, and 
the remaining two-thirds of the bichromate introduced as before. 
Aniline black separates out in the first part of the operation, 
and in the second part of the process gradually dissolves, 
giving a deep brown solution. The liquid, after standing for 
four to five hours more, is divided into two about equal portions. 
One half is shaken up, not too vigorously, with a large quantity 
(200 c.c.) of ether three times. The same ether may be distilled 
and used again. Vigorous shaking produces an emulsion, which 
very slowly separates. On distilling off the ether, the quinone 
remains in the form of yellow needle-shaped crystals, which may 
be purified by sublimation. The substance is placed in a flask 
attached to a condenser, and a rapid current of steam blown 
through. The quinone sublimes and collects in the receiver, 
and is separated from the water by filtration, and dried. Yield 
about 10 grams. 

1 Or an equivalent quantity of sodium bichromate (75 grams), which may be 
dissolved in 3 4 times its weight of water and delivered from a tap-funnel 



QUINONE AND QUINOL 193 

The reaction 'consists in the oxidation and elimination of the amino- 
group and simultaneous replacement of two hydrogen atoms in the 
benzene nucleus by oxygen, and cannot well be expressed in the 
form of equation. 

Properties. Golden-yellow, needle-shaped crystals ; m. p. 
1 16 ; with difficulty soluble in water, readily soluble in alcohol 
and ether ; sublimes on heating ; its vapour has a penetrating 
smell and attacks the eyes. 

Reaction. Dissolve a few crystals in water and add a solution 
of sulphur dioxide. The solution first darkens from the forma- 
tion of quinhydrone, C 6 H 4 .O 2 .C 6 H 4 (OH) 2 , and then becomes 
colourless and contains quinol. 

Quinol. The other half of the product is treated with a 
current of sulphur dioxide until, after standing for a time, it 
retains the smell of the gas.* The sulphur dioxide is most 
conveniently obtained from a bottle of liquid, or it may be pre- 
pared by dropping concentrated sulphuric acid from a tap- 
funnel on to sodium sulphite. The liquid, after standing one to 
two hours, is extracted with ether until no more quinol is 
removed. The ether is distilled off, and the dark coloured 
residue recrystallised from water with the addition of sulphur 
dioxide and a little animal charcoal. Yield about 10 grams. 

C 6 H 4 O 2 + SO 2 + 2H 2 O = C G H 4 (OH) 2 + H 2 SO 4 . 

Properties. Colourless prisms ; m.p. 169 ; sublimes at a 
gentle heat ; easily soluble in alcohol, ether, and hot water. 

Reactions. i. To a solution of quinol in water, add a few 
drops of ferric chloride. The solution turns brown and ether 
now extracts quinone. 

C a H 4 (OH) 2 + 2FeCl 3 = C 6 H 4 O 2 + 2FeCl 2 + 2HC1. 

2. Add to the solution of quinol in water, a drop of copper 
sulphate, and caustic soda, and warm. Cuprous oxide is pre- 
cipitated. 

C 6 H 4 (OH) 2 + 2CuO = C 6 H 4 O 2 + Cu 2 Q + H 2 O. 
See Appendix, p. 297. 

COHEN'S ADV. p. o. c. o 



194 



PRACTICAL ORGANIC CHEMISTRY 



PREPARATION 86. 

Benzyl Chloride, C 6 H 5 CH 2 C1 

Cannizzaro, Annalen, 1853, 88, 129. 

100 grms. toluene, 
i phosphorous trichloride. 

The apparatus consists of vessels for evolving and drying chlo- 
rine (see Fig. 62, p. 88) and a weighed retort (300 c.c.) standing 
on wire-gauze, into which the toluene is brought. (Fig. 80.) The 
chlorine enters through an inlet tube, fixed through the tubulus 
of the retort, the neck being fixed to a reflux condenser. The 




FIG. 80. 



dry chlorine is conducted into the toluene, which is kept boiling 
gently until it has gained about 37 grams in weight.* The liquid 
turns yellow, and hydrochloric acid fumes are evolved at the 
upper end of the condenser. When the reaction is complete the 
contents of the retort are distilled.* At first .unchanged toluene 
distils ; the fraction boiling at 165 185 contains nearly the 
whole of the benzyl chloride, and forms the greater part of 
the product. The liquid, which passes over above 185, is a 
mixture of higher chlorinated compounds, and consists chiefly 
of benzal chloride, C 6 H 5 CHC1 2 , and benzotrichloride, C 6 H 5 CC1 3 . 



BENZYL ALCOHOL 195 

The portion containing the benzyl chloride is repeatedly frac- 
tionated until a liquid is obtained, boiling at 176 180, which 
is nearly pure benzyl chloride. Yield 80- 90 grams. 

C G H 5 CH 3 + C1 2 = C H 5 CH 2 C1 + HC1. 

Properties. Colourless liquid with an irritating smell ; b. p. 
176' ; sp. gr. rio7 at 14. .See Appendix, p. 299. 



PREPARATION 87. 

Benzyl Alcohol, C G H 6 CH 2 OH 

Soderbaum, Widman, Ber., 1892, 25, 3290. 

20 grms. benzyl chloride. 

1 6 potassium carbonate (in 200 c.c. water). 

In a round flask ( litre) attached to a reflux condenser, 
boil the mixture of benzyl chloride and potassium carbonate 
solution over wire-gauze with the addition of a few bits of porous 
pot. The boiling must be continued until the smell of benzyl 
chloride has disappeared (6 8 hours). Extract the liquid with 
ether, dehydrate over potassium carbonate, decant through a 
filter and distil off the ether on the water-bath. Continue the 
distillation over wire-gauze, run the water out of the condenser 
and collect at 200210. Yield 12 15 grams. 

2C 6 H 5 CH 2 C1 + H 2 O + K 2 CO 3 == 2C 6 H 5 CH 2 OH + 2KC1 + CO 2 . 

Properties, Colourless liquid with a faint aromatic smell ; 
b, p. 206' 5 ; sp. gr. ix>5 at I5'4 ; moderately soluble in water. 

Reactions. i. Boil 2 or 3 drops with 2 3 c.c. dilute nitric 
acid (iHNO 3 ,4H 2 O) ; benzaldehyde isfirst formed and is detected 
by the smell. On continued boiling, benzoic acid is formed and 
separates on cooling in crystals. 

2. Warm i c.c. of the alcohol with i c.c. concentrated hydro- 
chloric acid. The clear solution becomes turbid and benzyi 
chloride separates out. 

C 6 H 5 CH,OH + HC1 = C 6 H 5 CH 2 C1 +H 2 O. 

See Appendix, p. 300. 

O 2 



190 PRACTICAL ORGANIC CHEMISTRY 

PREPARATION 88. 
Benzaldehyde (Bitter Almond Oil), C C H 5 .CO.H 

Liebig, Wohler, Annalen, 1837, 22, i ; Lauth, Grimaux, Ann- 
alen, 1867, 143, 186. 

50 grms. benzyl chloride. 
40 copper nitrate. 
500 c.c. water. 

The mixture of benzyl chloride, copper nitrate and water is 
heated to boiling in a round flask (\\ litre) with upright 
condenser on the sand-bath for a day (8 9 hours). A slow 
current of carbon dioxide is at the same time passed through 
the liquid to prevent oxidation of the benzaldehyde by absorp- 
tion of oxygen from the air. During the process nitrous fumes 
are slowly evolved. When the reaction is complete, the contents 
of the flask are extracted with ether, and the yellow oil remaining, 
after distilling off the ether, is well shaken with a satu- 
rated solution of sodium bisulphite l and allowed to stand for 
a time. The colourless crystalline mass which separates 
out is filtered, washed with a little alcohol and ether, and then 
drained on a porcelain filter. The aldehyde is regained by 
adding dilute sulphuric acid in excess and distilling in steam. 
The distillate is extracted with ether, dehydrated over calcium 
chloride, decanted, and the ether distilled off". Yield, about 15 
grams. 

2C 6 H 6 CH 2 C1 + Cu(NO 3 ) 2 = 2C 6 H 6 COH + CuCl 2 + 2HNO 2 . 

Properties. Colourless liquid, with a pleasant smell ; b. p. 
179 ; sp. gr. TO5O4 at 15 ; it quickly oxidises in the air, forming 
benzoic acid. 

Reactions. I. Leave a drop of benzaldehyde on a watch- 
glass. It solidifies by becoming oxidised to benzoic acid. 

2. Add 5 c.c. concentrated ammonia to i c.c. benzaldehyde, 
cork up and leave two days. Crystals of hydrobenzamide, 

1 The solution is prepared either by dissolving solid sodium bisulphide in water or 
by passing sulphur dioxide into powdered sodium carbonate covered with a shallow 
rave.' of water. The carbonate dissolves with effervescence, forming a heavy apple- 
green liquid smelling strongly of sulphur dioxide 



a- AAb 0-HKNZALDOXIMES 197 

(C G H 5 CH) 3 N2, separate out, which may be recrystallised from 
spirit. 

3 C 6 H 5 COH + 2NH 3 = (C 6 H 5 CH) 3 N 2 + 3 H 2 O. 

3. Heat on the water-bath 2 c.c. benzaldehyde and 2 c.c. 
aniline for an hour. Crystals of benzalaniline are formed 
on cooling, C G H 5 COH + C 6 H 5 NH 2 = C 6 H 5 CH:N.C 6 H 5 + H 2 O, 
which may be filtered and crystallised from spirit ; m. p. 42. 

4. Shake up together 10 grams of benzaldehyde with 9 grams 
caustic potash in 6 c.c. of water until a permanent emulsion is 
formed and let stand 3 4 hours. Dissolve the solid product in 
a little water and shake out with ether twice. On acidifying 
the aqueous portion with hydrochloric acid, benzoic acid is 
precipitated. Filter and wash with a little cold water and dry. 
Distil the ether from the ethereal solution. The residue 
is benzyl alcohol (Cannizzaro)* 

2C C H 5 COH + KOH = C C H,COOK + C H 5 CH 2 OH. 
See also Reactions on p.- 135 and p. 174, and Appendix, p. 30x3. 

PREPARATION 89. 

a- and -Benzaldoximes, C 6 H 5 CH:NOH 
Beckmann, Bcr., 1890, 23, 1684. 

21 grms. benzaldehyde. 

15 hydroxylamine hydrochloride. 

14 caustic soda (in 40 c.c. water). 

The solution of caustic soda and benzaldehyde are mixed and 
the hydroxylamine hydrochloride gradually added with constant 
shaking. The liquid becomes slightly warm and the oil even- 
tually dissolves, forming a yellow solution which has lost the 
smell of benzaldehyde. On cooling, a crystalline mass of the 
hydrochloride of benzaldoxime separates. Sufficient water is 
added to form a clear solution, through which a current of 
carbon dioxide is passed. A colourless emulsion of the a- or 
a//-aldoxime separates on the surface and is extracted with 
ether, dehydrated over anhydrous sodium sulphate and the 
ether removed on the water-bath. Impure benzaw&'aldoxime 
remains and is purified as follows. It is poured into a 
saturated solution of sodium ethoxide in alcohol (prepared by 
dissolving 5 grams sodium in 60 c.c. alcohol), when the aldoxime 



PRACTICAL ORGANIC CHEMISTRY 



separates as the sodium compound in the form of a semi-solid 
mass. It is filtered and washed with a saturated solution of sodium 
ethoxide in alcohol to dissolve out the /3-oxime. The product 
is dissolved in water, saturated with carbon dioxide and 
extracted with ether as before. Dry air is then drawn through 
the liquid to remove the last traces of ether when, if pure, 
the oxirne, on cooling to o, solidifies. If not, it should be 
distilled in vacua. At 12 mm. it boils at 122124 : at lomm. 
at 118 119. 
Yield, 10 grams. 

+ 3H0 2 . 
C 6 H B .CHO + NHjOH.HCl + 2NaOH = C 6 H 5 CH:NONa + NaCl 

C 6 H 5 CH:NONa + CO 2 + H 2 O = C 6 H 5 CH:NOH + NaHCO 3 . 

Properties of a.-Benzaldoxime. Colourless needles, m. p. 

34-35- 

Reaction. Dissolve a small quantity of the a-oxime in a few 
drops of acetic anhydride, warm if necessary, and cool quickly 
by adding a little ice. Add to the clear solution solid sodium 
carbonate and a little caustic soda solution. The solution 
becomes clear on shaking or warming. 

/3-Benzaldoxime. The various steps in the preparation 
of the /3-oxime must be carried out continuously, and it is 
therefore necessary to be provided beforehand with about 
300 c.c. of pure anhydrous ether. 

The a-compound is dissolved in 50 c.c. pure dry ether, and 
dry hydrogen chloride is passed in with constant shaking to 
prevent the delivery tube from becoming blocked. Colour- 
less crystals of the hydrochloride of the /3-oxime separate 
and are filtered and washed with dry ether and then placed 
in a separating funnel and covered with a layer of ether. 
A concentrated solution of sodium carbonate is gradually added 
with constant shaking until no further effervescence is observed. 
Sodium chloride is precipitated and the /3-oxime dissolves in 
the ether. The ether extract is separated, dehydrated over 
sodium sulphate, and the ether removed as rapidly as possible 
at the ordinary temperature by evaporation in -uacuo. The 
residue crystallises, and when pressed on a porous plate leaves 
a mass of small silky needles, m. p. 126 130. It may be re- 



BENZOIC ACID 199 

crystallised by dissolving it in the smallest quantity of ether and 
then adding petroleum ether. 
The yield is theoretical. 

C 6 H 5 CH HCl C 6 H 5 CH Na 2 C0 3 C 6 H 5|j H 

HO.N N. OH. HCl N.OH 

a- or anfi-oxlme. ft- or syn-oxlme. 

Properties of the $-Benzaldoxime. Colourless needles, m. p. 

130". 

Reaction. Repeat the reaction for n-benzaldoxime. In this 
case benzonitrile is formed, which separates in oily drops having 
a characteristic smell. See Appendix, p. 301. 



PREPARATION 90. 
Benzole Acid, C H 6 CO.OH 

5 grms. benzyl chloride. 

4 anhydrous sodium carbonate (in 50 c.c. water). 
8*5 potassium permanganate (in 150 c.c. water). 

The benzyl chloride" and sodium carbonate solution are mixed 
in a round flask ( litre) attached to a reflux condenser, and 
boiled gently over wire-gauze, whilst the permanganate solution 
is gradually dropped in from a tap-funnel pushed through the 
top of the condenser. In the course of 2 3 hours the pink 
colour of the permanganate will have vanished and been replaced 
by a mass of dark brown precipitate of manganese dioxide. 
When the liquid is cold, a stream of sulphur dioxide is passed in 
until the manganese dioxide is dissolved (see p. 166). The 
liquid is allowed to cool and the benzoic acid, which separates, 
is filtered at the pump, washed with a little cold water and 
recrystallised from hot water ; m. p. 121. The yield is 
theoretical. The reaction probably occurs in two steps. 

1. 2C 6 H 5 CH 2 C1 + Na 2 CO 3 + H,O = 

2C 6 H 5 CH 2 OH + 2NaCl + CO 2 . 

2. 3C 6 H 5 CH 2 OH f 4KMnO 4 = 

3C 6 H 5 COOK + 4MnO 2 + KOH + 4H 2 O. 



PRACTICAL ORGANIC CHEMISTRY 



Properties. Crystallises in needles; m. p. 121; on heating 
it melts and sublimes ; soluble in hot water, alcohol and ether. 
It distils in steam. 

Reactions, i. Make a neutral solution of ammonium benzoate 
by adding excess of ammonia to benzoic acid and boiling until 
neutral. To different portions add solutions of calcium chloride, 
ferric chloride, silver nitrate and lead acetate and note the 
results. 

2. Grind up 0*5 gram of the acid with four times the weight of 
soda-lime and heat gently at first and then more strongly. 
Vapours of benzene will be given off, which may be detected by 
the smell. C 6 H 5 CO.OH + CaO = C 6 H 6 + CaCO 3 . 

See Appendix, p. 302. 



PREPARATION 91. 
m-Nitro, m-Amino- and m-Hydroxybenzoic Acids, 

/N0 2 r H /NH, r /OH i 

3 



40 grms. benzoic acid. 
80 potassium nitrate. 
100 c.c. cone, sulphuric acid. 

The benzoic acid and potassium nitrate are mixed and care- 
fully powdered. The sulphuric acid is warmed to 70 and 
stirred mechanically, whilst the mixture of benzoic acid and 
nitrate is added slowly, so that the temperature does not exceed 
80. When all is added the temperature is raised to 90, and 
kept at this temperature until the nitrated acid separates as an 
oily layer on the surface. On cooling, the layer solidifies and 
can be separated. It is then distilled in steam to remove 
benzoic acid. The residue containing the nitrobenzoic acid is 
heated to boiling and made slightly alkaline with baryta. Two 
litres of water are added and the liquid raised to the boiling 
point by passing in steam and then filtered. On cooling, the 
barium salt crystallises and is filtered off and decomposed with 
hot dilute hydrochloric acid. The precipitated acid is re- 
crystallised from water ; m. p. 141. Yield, 28 grams. 



m-BROMOBENZOIC ACID 201 

m-Aminobenzoic Acid 
20 grms. nitrobenzoic acid. 
40 granulated tin. 
1 20 c.c. cone, hydrochloric acid. 

The nitrobenzoic acid, tin, and hydrochloric acid are mixed 
in a litre flask and warmed until the reaction begins. When 
the first vigorous action is over, the mixture is heated on the 
water-bath until the tin is dissolved. The liquid is poured 
into a basin and evaporated on the water-bath to expel the 
excess of hydrochloric acid. The tin is then precipitated by 
passing into the hot, dilute solution a current of hydrogen 
sulphide. The sulphide is filtered and washed with hot water, 
and the filtrate evaporated to dryness. To obtain the free acid, 
a small portion of the residue is dissolved in very little water 
made alkaline with ammonia, and acidified with acetic acid. 
It is recrystallised from water, and melts at 174. 

m-Hydroxybenzoic Acid, 

15 grms. ?-aminobenzoic acid hydrochloride (in 200 c.c. water). 
6*5 sodium nitrite (in 15 c.c. water). 

The nitrite solution is slowly added to the solution of the 
hydrochloride dissolved in water. The liquid is heated on 
the water-bath until the evolution of nitrogen ceases, and then 
filtered and concentrated. The hydroxybenzoic acid separates 
on cooling as a brown mass, which may be purified by dissolving 
in water and boiling with animal charcoal. It separates in 
colourless crystals, m. p. 200. Yield, 7 grams. See Appendix, 
P- 33- 

PREPARATION 92. 

m-Bromobenzoic Acid, C C 



Hiibner, Petermann, Annalen, 1869, 149, 131. 

5 grms. benzoic acid. 
7 bromine. 
30 c.c. water. 

The mixture is brought into a thick-walled tube, closed at one 
end and sealed in the usual way. The tube is heated in the 



PRACTICAL ORGANIC CHEMISTRY 



tube furnace to 140 150 for eight to nine hours. After cooling, 
the capillary is opened and the tube removed from the furnace. 
The bromine will have completely disappeared, and colourless 
crystals of bromobenzoic acid now fill the tube. The contents 
are removed, filtered, and boiled with water (100 c.c.) in a 
ba= ; n to drive off unchanged benzoic acid. The liquid is 
cooled, filtered, and the bromobenzoic acid crystallised from 
hot water. Yield, 5 grams. 

C 6 H 5 CO.OH + Br 2 = C 6 H 4 Br.CO.OH + HBr. 
Properties. Colourless needles ; m. p. 155. 



PREPARATION 93. 

C 6 H 5 .CHOH 
Benzoin, 

C H 5 .CO 

Liebig, Wohler, Annalen, 1832, 3, 276 ; Zinin, Annalen^ 1840, 
34, 1 86. 

25 grms. benzaldehyde. 
5 potassium cyanide (in 20 c.c. water). 
50 c.c. absolute alcohol. 

The mixture of benzaldehyde, potassium cyanide and alcohol 
is heated on the water-bath with an upright condenser for 
about half an hour. On cooling the liquid, the benzoin separates 
out as a mass of small colourless crystals, which are filtered and 
washed with a little alcohol. Yield, about 20 grams. A portion 
of the substance may be purified by recrystallisation from spirit. 

2C 6 H 5 COH = C 6 H 5 CO.CH(OH).C C H 5 . 

Properties. Colourless prisms; m. p. 137 ; slightly soluble 
in water ; soluble in alcohol and ether. 

Reaction. Add Fehling's solution to benzoin dissolved in 
alcohol. Benzil is formed and cuprous oxide precipitated. 
Benzil is also formed on oxidation with nitric acid. 



BENZILIC ACID 203 



Benzil, C 6 H 5 CO.CO.C 6 H 5 
15 grms. benzoin. 
35 cone, nitric acid, sp. gr. i'4. 

The benzoin and nitric acid are heated on the water-bath with 
an air condenser, the flask being occasionally shaken. Nitrous 
fumes arc evolved, and the crystals of benzoin are converted 
into a yellow oil, which, after two hours' heating, is free from un- 
changed benzoin. The contents of the flask are now poured 
into water, and the yellow crystalline deposit separated by 
nitration, washed with water, and recrystallised from alcohol. 
Yield, 10 12 grams. 

Properties. Yellow prisms ; m. p. 95 ; insoluble in water ; 
soluble in hot alcohol. 

Reaction. I. Dissolve a small quantity of benzil in a little 
alcohol, add a fragment of caustic potash and boil. A violet 
solution is obtained. 

Benzilic Acid, (C 6 H 5 ) 2 C(OH).CO 2 H 
10 grms. benzil. 
50 caustic potash. 

The caustic potash is melted with a small quantity of water in a 
silver or nickel crucible. The temperature of the mass is brought 
to 1 50, and the finely powdered benzil added. The benzil melts, 
and the mixture shortly changes to a solid mass of potassium 
.benzilate. The cooled melt is dissolved in water, and the 
alkaline solution acidified with hydrochloric acid, which precipi- 
tates the benzilic acid. The- crystalline mass, which contains 
small quantities of benzoic acid, is separated from the mother- 
liquor and washed with cold water. It is then transferred to a 
porcelain basin, dissolved in hot water, and the solution boiled 
until the smell of benzoic acid has gone. On cooling, benzilic 
acid crystallises out, and is purified by a second crystallisation 
from hot water. 

C 6 H 5 .CO.CO.C 6 H 5 + KOH = (C H 5 ) 2 C.(OH).COOK. 
' Properties. Colourless needles ; m. p. 150 ; scarcely soluble 
in cold, readily in hot water and alcohol. 

Reaction. Add a little concentrated sulphuric acid to benzilic 
acid. It dissolves with an intense red colour. See Appendix, 
P- 303- 



204 PRACTICAL ORGANIC CHEMISTRY 

PREPARATION 94. 

Cinnamic Acid (Phenylacrylic Acid), 
C 6 H 5 .CH:CH.CO 2 H 

Bertagnini, Annalcn, 1856, 100, 126 ; Perkin, Trans. Chem, 
Soc., 1868, 21, 53 ; Fittig, Ber., 1881, 14, 1826. 

20 grms. benzaldehyde. 

10 sodium acetate (fused). 

30 acetic anhydride. 

The mixture of benzaldehyde, sodium acetate, and acetic an- 
hydride is heated to 180 in a small round flask with upright 
condenser in an oil-bath for about eight hours. The mass is 
poured out whilst hot into a large round flask (i litre), sodium 
carbonate added until alkaline, and any unchanged benzaldehyde 
distilled off with steam. After filtering from undissolved resin- 
ous by-products, hydrochloric acid is added, which precipitates 
the free cinnamic acid in white crystalline flakes. It may 
be purified by recrystallisation from hot water. Yield, 15 20 
grams. 

1. C 6 H 5 CO.H + CH 3 .CO.ONa = C 6 H 5 CH:CH.CO.ONa + H 2 O. 

2. C c H 5 .CH:CH.CO.ONa+H 2 O + (CH 3 .CO) 2 O=: 
C 6 H 5 .CH :CH.COOH + CH 3 CO.~ONa+ CH 3 .COOH. 

Properties. Colourless prisms; m. p. 133; b. p. 300 304. 
See Appendix, p. 304. 

PREPARATION 95. 

Hydrocinnamic Acid (Phenylpropionic Acid), 
C 6 H 6 CH,.CH,.CO 2 H 

Erlenmeyer, Alexejeff, Annalen, 1862, 121, 375, and 1866, 
137, 237. 

10 grms. cinnamic acid, 
loo water. 
170 sodium amalgam (2^ per cent). 

The sodium amalgam is prepared by warming 200 grams of 
mercury in a porcelain basin for a few minutes. The mercury 



MANDELIC ACID 205 



is poured out into a mortar which is placed in the fume cup- 
board, the window of which is drawn down so as to protect the 
face. Five grams of sodium are introduced in small pieces, the 
size of a pea, and pressed with a pestle under the surface of the 
mercury. Each piece dissolves with a bright flash. The 
amalgam is poured out whilst semi-fluid on to an iron tray, 
broken up, and kept in a wide-necked stoppered bottle. 1 

The cinnamic acid and water are introduced into a strong 
beaker or bottle (300 c.c.), and the liquid made slightly alkaline 
with caustic soda, which dissolves the acid forming the sodium 
salt. The sodium amalgam is added in small pieces from time 
to time and the liquid thoroughly agitated. The solution, which 
remains clear, becomes slightly warm, and the amalgam soon 
liquefies, but no hydrogen is evolved until towards the end of 
the operation. When the whole of the amalgam has been 
added, and bubbles of gas cease to be given off, the solution is 
decanted from the mercury, which is rinsed with water. On 
acidifying the solution with hydrochloric acid, hydrocinnamic 
acid is precipitated as a colourless oil, which solidifies on stand- 
ing. It may be recrystallised from a large quantity of warm 
water. Yield, 8 9 grams. 



Properties. Long colourless needles; m. p. 47; b. p. 280; 
soluble in water and alcohol ; volatile in steam. See Appendix, 
p. 306- 

PREPARATION 96. 

Mandelic Acid, C G H 5 .CH(OH).COOH 
Friedlander, Theerfarbenfabrikation IV, 160. 

15 grms. benzaldehyde. 

50 c.c. cone, sodium bisulphite solution. 

12 grms. potassium cyanide (in 20 c.c. water). 

The benzaldehyde and sodium bisulphite are mixed together 
and stirred. The mixture forms a semi-solid mass of the 

1 If larger quantities of amalgam are required, the mercury is heated in a small 
enamelled pan, or crucible, the sodium added in one lot, and the vessel immediately 
closed with a lid, which is held down with long crucible tongs until the reaction is 
over, and then poured out whilst fluid. 



206 PRACTICAL ORGANIC CHEMISTRY 

bisulphite compound, which after standing for half an hour is 
filtered and pressed at the pump and washed with a little water 
and spirit. The mass is then ground to a thick paste with water 
and the solution of potassium cyanide added. After a short 
time mandelic nitrile separates as a reddish oil and is removed 
by means of a tap-funnel with the addition of a little ether. 



C 6 H 6 CH(OH)SO 3 Na + KCN = C 8 H 6 CH(OH).CN + (K)(Na)SO 3 

The ether is allowed to evaporate on the water-bath and the 
nitrile is then hydrolysed by continuing to heat it on the water- 
bath with the addition of 4 5 times its volume of cone. 
hydrochloric acid until crystals appear on the surface. Water 
is added and the hot liquid decanted and filtered from any oil. 
On cooling, the crystals are filtered, washed with a little cold 
water and dried. A further quantity can be extracted from the 
filtrate with ether. It may be recrystallised from benzene. 
Yield, 10 15 grms. 

C 6 H 5 CH(OH)CN + HC1 + 2H,O 

= C 6 H 5 CH(OH).COOH + NH 4 C1. 

Properties. Colourless needles, m. p. 118-119; dissolves 
readily in hot water and in 6 parts of water at 20. The acid is 
racemic ; the active components exhibit a rotation of [a]g= 
157 in aqueous solution. See Appendix^ p. 306. 



PREPARATION 97. 
Phenyl Methyl Carbinol, C 6 H 5 CH(OH).CH 3 

Grignard, Compt. rend. 1900, 130, 1322; Klages and Ullen- 
dorf, Her., 1898, 31, 1003. 

36 grms. methyl iodide. 
1 50 c.c. ether (purified and carefully dried over sodium). 

6 grms. magnesium ribbon or powder. 
26 benzaldehyde. 

The magnesium methyl iodide is first prepared and is 
formed by. the action of methyl iodide on the metal. The 
magnesium ribbon or powder is placed in a dry, round flask 



PHENYL METHYL CARBINOL . 



207 



(i litre), connected with a long condenser and dropping funnel 
as shown in Fig. 81. 

The methyl iodide and 50 c.c. of dry ether are mixed in a 
separate vessel and 20 c.c. 
of this mixture poured on 
to the magnesium. In a few 
seconds a vigorous action 
usually sets in or if it is de- 
layed may be started by 
adding a crystal of iodine. 
When the first reaction has 
subsided, 70 c.c. of dry ether 
are added, and the remainder 
of the alkyl iodide and ether 
mixture run in drop by drop 
from the tap-funnel. The FIG. 81. 

contents of the flask are 

then boiled on the water-bath for half an hour when (if there 
has been no loss of alkyl iodide) the magnesium completely dis- 
solves. 




The flask is now disconnected and whilst it is kept cool in ice- 
water the benzaldehyde mixed with an equal volume of dry ether 
is dropped in from a tap-funnel with constant shaking. The 
white solid magnesium compound separates and is left over- 
night. 



The contents of the flask are cooled under the tap whilst water 
and just sufficient hydrochloric acid to dissolve the magnesia 
are added, the acid being cautiously dropped in from a tap- 
funnel. The aqueous layer is removed in a separating funnel 
and the ether washed first with sodium bicarbonate solution, 
then with sodium bisulphite (to remove free iodine) and again 
with sodium bicarbonate. 



208 PRACTICAL ORGANIC CHEMISTRY 

The ether extract is then dried over potassium carbonate and 
the ether removed by distillation on the water-bath. The 
phenyl methyl carbinol which remains is distilled under reduced 
pressure; b. p. 100 at 15 mm. ; 110-111 at 28 mm. ; 118 at 
40 mm. Yield, 20 grams. 

The same method may be used without modification for pre- 
paring phenyl ethyl carbinol using a corresponding quantity of 
ethyl iodide. See Appendix, p. 307. 



PREPARATION 98. 
Benzoyl Chloride, C 6 H 5 CO.C1 

Wohler, Annalen, 1832, 3, 262 ; Cahours, Annalen, 1846, 60, 

255- 

28 grms. benzoic acid. 

50 phosphorous pentachloride. 

A round flask (250 c.c.) is fitted with an air-condenser. The 
phosphorous pentachloride is introduced from the bottle and 
weighed by difference. The operation must be conducted in 
the fume-cupboard. The benzoic acid is then added, and the 
air-condenser attached to the flask.* The action begins almost 
immediately, and clouds of hydrochloric fumes are evolved. 
The whole contents become liquid and consist of benzoyl 
chloride (b. p. 200), phosphorous oxychloride (b. p. 107), and 
unchanged pentachloride. Most of the oxychloride may be 
removed by distilling in -vacua on the water-bath. The re- 
mainder is fractionated at the ordinary pressure and collected at 
190-200. Yield, 20 25 grams. 

C C H 6 COOH + PC1 5 = C 6 H 5 CO.C1 + POC1 3 + HC1. 

Properties. Colourless liquid, which fumes in the air and 
possesses a pungent smell ; b. p. I98'5 ; sp. gr. i'2i4 at 19. 

Reactions. i. Add a few drops of benzoyl chloride to i c.c. of 
water ; the benzoyl chloride does not decompose at once, and 
requires warming for some time before it is completely dissolved 
(compare acetyl chloride, p. 74). 

2. Add 2 c.c. ethyl alcohol to i c.c. benzoyl chloride and 
caustic soda solution until alkaline, and warm gently. After a 
time the smell of benzoyl chloride disappears, and ethyl benzoate 



ETHYL BENZOATE 



remains as an oily liquid with a fragrant smell. C C H 5 COC1 + 
C. 2 H 5 OH + NaOH = C H 5 COOC,H 5 + NaCl + H,O. Repeat the 
same reaction with phenol and separate the solid phenyl 
benzoate. (Schotten-Baumann reaction.) 

3. Add 5 grams benzoyl chloride to 10 grams ammonium 
carbonate in a mortar* and grind up well. The reaction pro- 
ceeds quietly. If after ten minutes the smell of benzoyl chloride 
still remains, add a few drops of concentrated ammonia. Add 
cold water and filter. Benzamide remains on the filter in the 
form of a white crystalline powder, and may be recrystallised 
from hot water; m. p. 128. QH 5 COC1 + 2NH 4 HCO 3 = 
C 6 H 5 CONH i! -fNH 4 Cl + 2CO 2 + 2H 2 O. See Appendix, p. 308. 



PREPARATION 99, 

Ethyl Benzoate (Ethyl Benzoic Ester), C C H 5 CO.OC 2 H,. 
E. Fischer and Speier, Ser., 1895, 28, 1150. 

. 25 grms. benzoic acid. 
75 (9 C - C absolute alcohol. 

Pass dry hydrochloric acid gas (see p. 93) through the alcohol, 
cooled in water until it has increased about 3 grams in weight. 
Add the benzoic acid and boil the mixture with upright con- 
denser over wire-gauze for two hours. On pouring a small 
quantity of the product into water, only the ester, which is a 
heavy oil, should separate, but no solid benzoic acid. The 
excess of alcohol is now distilled off on the water-bath and the 
residue poured into water. Any free hydrochloric or benzoic 
acid is removed by shaking with a dilute solution of sodium 
carbonate. On adding ether and shaking, the ester dissolves in 
the top layer of ether, which is separated and dehydrated over 
calcium chloride. The ether is removed on the water-bath, and 
the ethyl benzoate is then distilled over wire-gauze, a few bits of 
porcelain being added to prevent bumping. The distillate is 
collected between 205 and 212. Yield, about 22 grams. 

H=CHCOOC,H + H,O. 



Properties. Colourless, sweet-smelling oil ; b. p. 211 ; sp. gr, 
I '05 at 1 5. 
COHEN'S ADV. p. o. c. p 



PRACTICAL ORGANIC CHEMISTRY 




/f 



Quantitative Hydrolysis of Ethyl Benzoate.The 
quantitative estimation of an ester by hydrolysis is conducted as 
follows : a standard half-normal solution of alcoholic potash is 
prepared by dissolving 7 grams of caustic potash in about an 
equal weight of water and diluting to 250 c.c. with absolute 
alcohol. The liquid is allowed to stand overnight in a stoppered 
flask and filtered through asbestos 
into a clean dry bottle closed with a 
cork through which a 25 c.c. pipette 
is inserted. The solution is first 
standardised by titration against half- 
normal sulphuric acid, using phenol- 
phthalein as indicator. About i gram 
of ethyl benzoate is carefully weighed 
by difference by means of the ap- 
paratus shown in Fig. 82. 

A volume corresponding to about 
I gram is delivered into a round 
flask (200 c.c.) by attaching a piece of rubber tubing to the wide 
end of the apparatus and blowing until the liquid descends to 
the required graduation on the wide limb. Twenty-five c.c. of the 
standard alcoholic potash solution is added, and the mixture 
boiled on the water-bath with reflux condenser for twenty 
minutes. 

C 6 H 5 COOC 2 H 5 + KOH = C 6 H 6 COOK + C 2 H 5 OH. 

The amount of free alkali is estimated by titration with 
standard sulphuric acid and the quantity of ester calculated. 
Example. 1'355 grams required 15'! c. c. N/2H 2 SO 4 
15*1 x 0^150 x IOQ 

2x1-1355 
See Appendix^ p. 308. 



FIG. 82. 



= 997 per cent. 



PREPARATION 100. 

Acetophenone (Phenylmethylketone, Hypnone), 
C 6 H 5 .CO.CH 3 

Friedel, Crafts, Ann. Chim. Phys., 1884, 1, 507 ; 14, 455- 
30 grms. benzene. 

50 aluminium chloride (anhydrous). 
35 acetyl chloride. 



ACETOPHENONE 



The various reactions, known as the Friedel-Crafts reactions, 
are effected by means of anhydrous aluminium chloride. The 
aluminium chloride, being very hygroscopic, cannot be kept 
long, even in a stoppered bottle, without undergoing gradual 
decomposition. As the success of the reaction, depends entirely 
on the quality of the chloride, it should be either freshly pro- 
cured from a reliable firm or resublimed from a retort. It may 
also be prepared on a small scale by passing dry hydrochloric 
acid over heated aluminium foil or filings, but the operation is 
troublesome and scarcely repays the time spent. Attach a 
round flask (500 c.c.) to an upright condenser, and bring into it 
the aluminium chloride, which should be well powdered, and 
immediately cover it with the benzene. Place the flask in ice- 
water, and add the acetyl chloride drop by drop from a tap-funnel, 
which is pushed into the top of the condenser.* A vigorous 
effervescence occurs, and hydrochloric acid is evolved. The 
contents of the flask are converted into a brown, viscid mass, 
which, after standing an hour, is stirred up and shaken into a 
beaker containing ice and water (250 c.c.). The mass decom- 
poses with evolution of heat, and a dark oil separates on the 
surface. The liquid is poured into a separat ing-funnel and a 
little benzene added. The aqueous portion is drawn off, and 
the benzene layer shaken up with dilute caustic soda and then 
with water. The benzene solution is finally separated, de- 
hydrated over calcium chloride, filtered, and distilled. The 
benzene first passes over. The thermometer then rises quickly 
to 195* The receiver is now changed, the water run out of the 
condenser, and the distillate, which boils at 195 200", collected 
separately. It forms a pale yellow oil with a characteristic 
sweet smell, and solidifies completely on standing. Yie\d, 
20 25 grams. 

C 6 H 6 + CH 3 COC1 = C G H 5 .CO.CH 3 + HC1. 

Properties. Colourless piates ; m. p. 20 ; b. p. 202 ; insoluble 
in water. 

Reactions. i. Acetophenoneoxime. Mix together 5 
grams of hydroxylamine hydrochloride dissolved in 10 c.c. of 
water, 8 grams of acetophenone, and 3 grams of caustic soda 
dissolved in a very little water. Add spirit until, on warming, the 
solution becomes clear, and boil it on the water-bath 2 3 hours. 

P 2 



PRACTICAL ORGANIC CHEMISTRY 



Pour into 100 c.c. water, and extract with ether. Distil off the 
ether and crystallise the solid residue from petroleum spirit, 
Yield, 8 grams ; m. p. 5860". C H 5 .CO.CH 3 + NH,OH.HC1 + 
NaOH = C H 5 C(NOH).CH 3 + NaCl + 2H,O. 

2. Acetophenonesemicarbazone. Mix i gram of semi- 
carbazide hydrochloride with r, grams of crystallised sodium 
acetate, and dissolve in the smallest quantity of warm water. 
Add I gram of acetophenone and sufficient spirit to produce a 
clear solution when hot. Continue to heat for a few minutes. On 
cooling, the semicarbazone deposits as a yellow, crystalline 
mass. C H 5 .CO.CH 3 + NH 2 .NH.CO.NH. 2 .HC1 + NaC.,H 3 O, 
= C 6 H 5 C(N.NH.CONH 2 )CH 3 + NaCl + C 2 H 4 O,. Theoretical 
yield ; in. p. 185 188. 

3. Beckmann's Reaction. Dissolve i gram of aceto- 
phenoneoxime in 30 c.c. anhydrous ether, and add gradually 
i '5 grams of powdered phosphorus pentachloride. Distil off the 
ether, and add a little water to the residue. On cooling, crystals 
of acetanilide separate. Recrystallise from water, and determine 
the melting point. 

1. C 6 H 5 .C(NOH).CH 3 + PC1 5 

' = C 6 H 5 .C(NC1).CH 3 + POC1 3 + HC1. 

2. C 6 H 5 C(NC1)CH 3 + H,O - C 6 H 5 NH.CO.CH 3 + HC1. 

4. Benzoylacetone (Claiseris Reaction). Six grams of dry, 
powdered sodium ethoxide are added to 20 grams of dry ethyl 
acetate, and cooled in water. The sodium ethoxide is prepared 
by dissolving 4 grams of sodium in 40 c.c. absolute alcohol, and 
distilling off the excess of alcohol, first from the water-bath, and 
then from the metal-bath, in a current of dry hydrogen, the 
temperature of the bath being raised gradually to 200, until 
nothing more passes over. The white cake is detached rapidly 
powdered, and the requisite quantity quickly weighed out and 
added to the ethyl acetate. After standing a quarter of an 
liour, 10 grams of acetophenone are added, when sodium benzoyl 
acetone begins to separate. A little ether is added, and, after 
standing for a few hours, the sodium compound is filtered and 
washed with ether. The sodium compound is then dried in 
tie air, dissolved in cold water, and acidified with acetic acid. 
Benzoylacetone separates out. Yield, 9 lograms; m.p. 60 6i D . 



DIPHENYLMETHANE 213 

It behaves towards ferric chloride and copper acetate like ethyl 
acetoacetate (see Reactions, p. 84). 

/ONa 
I. CH 3 .Cf-OC,H 6 + CH 3 .CO.C H 5 

X OC.;H, 

= CH 3 .C(ONa):CH.CO'.C H 5 + 2C 2 H 5 OH 

CH 3 .C(ONa):CH.COC G H 5 + C,H 4 O, 
= CH 3 .CO.CH 2 .CO.C C H 5 + NaCjHsOa. 

See Appendix, p. 309. 

PREPARATION 101. 

Diphenylmethane, C ( ,H 5 .CH2.C H 5 

Cohen, Hirst, Trans. Chem. Soc., 1895, 67, 826. 

60 grms. benzene. 
30 benzyl chloride, 
i aluminium-mercury couple. 

The benzene is placed in a flask attached to an upright con- 
denser.* The aluminium-mercury couple is then added. It is 
prepared by pouring a saturated solution of mercuric chloride 
on to aluminium foil, which is cut into strips or formed into rolls. 
After about a minute, the surface of the aluminium is coated 
with a film of metallic mercury. The solution is poured off, the 
foil well washed with water, then with alcohol, and finally 
.with a ^ttle benzene. This must be done quickly and the 
pieces of couple dropped into the benzene. The benzyl 
chloride is added slowly from a tap-funnel inserted through 
the top of the condenser. A brisk effervescence occurs, accom- 
panied by a considerable rise of temperature, and fumes of 
hydrochloric acid are evolved. When, in the course of an hour, 
the benzyl chloride has been added, the flask is heated on the 
water-bath for ten to fifteen minutes. The contents of the flask 
ar now shaken up with water containing a little caustic soda, 
and the benzene solution separated in a tap-funnel. The 
aqueous portion is again extracted with benzene, and the whole of 
the benzene solution is dehydrated over calcium chloride. The 
benzene is then distilled off, and when the thermometer reaches 
iot> the distillation is continued in vacno. At 80 mm. diphenyl- 
methane boils at 174 176. This fraction solidifies completely 



2U PRACTICAL ORGANIC CHEMISTRY 

on cooling, and is pure diphenylmethane ; m. p. 25 26. 
Yield, 14 grams. 

C 6 H 5 CH 2 C1 + C 6 H G = C H 5 CH,C 6 H 5 + HC1. 

Properties. Colourless needles ; m. p. 26 27 ; b. p. 262 3 . 
On boiling with potassium dichromate and sulphuric acid it is 
oxidised to benzophenone, C 6 H 5 CH 2 C 6 H 5 + O 2 = C 6 H 5 .CO.C H 5 
+ H 2 O. See Appendix, p. 312. 

PREPARATION 102. 
Triphenylmethane, CH(C 6 H 5 ) 3 

Friedel, Crafts, Compt. rend., 1877, 1450 ; E. and O. Fischer, 
Annalen, 1878, 197, 252 ; Biltz, Ber., 1893, 26, 1961. 

200 grms. (230 c.c.) benzene. 
40 (26 c.c.) chloroform. 
30 aluminium chloride. 

The benzene and chloroform are mixed together and 
dehydrated over calcium chloride overnight before use. The 
liquid is then decanted into a retort connected with an upright 
condenser,* and the powdered aluminium chloride added in 
portions of about 5 grams at a time at intervals of five minutes 
and well shaken. On the addition of the chloride the reaction 
sets in spontaneously, and the liquid begins to boil with evolu- 
tion of hydrochloric acid. The aluminium chloride g^dually 
dissolves, forming a dark-brown liquid. The reaction is com- 
pleted by boiling for half an hour on the sand-bath. When 
cold, the contents of the retort are poured into an equal volume 
of cold water, which decomposes the aluminium compound with 
evolution of heat, and the free hydrocarbon dissolves in the 
excess of benzene with a reddish-brown colour. The upper layer 
of benzene is separated from the aqueous portion, and the former 
dehydrated over calcium chloride. The excess of benzene is 
distilled off on the water-bath, and the dark-coloured residue 
fractionated up to 200. It is then distilled in vacua from a 
retort without condenser. At first an oil distils, which consists 
of impure diphenylmethane. When most of the diphenyl 
compound has passed over, the distillation suddenly slackens. 
The receiver is. now changed, and the retort more strongly 



BENZALDEHYDE GREEN 215 

heated. An orange-coloured oil passes over, which crystallises 
in the receiver. The distillation is continued until the distillate 
no longer solidifies on cooling. A black, resinous mass remains 
in the retort. The crude triphenylmethane in the receiver is 
recrystallised from hot benzene, with which it forms a crystal- 
line compound of the formula C ]9 H 16 .C 6 H e . This is again 
crystallised. By heating the substance on the water-bath it 
loses benzene, and the hydrocarbon is finally crystallised from 
hot alcohol. Yield, 25 30 grams. 

CHC1 3 + 3 C 6 H 6 = CH(C 6 H 6 ) 3 + 3 HC1. 

Properties. Colourless plates ; m. p. 92 ; b. p. 360. 

Reactions. Synthesis of Pararosaniline. Dissolve a 
gram of the hydrocarbon in about 5 c.c. cold fuming nitric acid, 
pour into water, filter, wash, dry on porous plate, and dissolve in 
5 c.c. glacial acetic acid. Add a gram of zinc dust on the point 
of a knife gradually, and shake up. The colour changes to brown, 
and the leuco-base of pararosaniline is formed. It is diluted 
with water and precipitated by ammonia. It is then filtered and 
dried. On gently warming the dry precipitate with a few drops 
of concentrated hydrochloric acid in a porcelain basin and then 
diluting with water, a. magenta colouration is produced from the 
formation of pararosaniline" hydrochloride (E. and O. Fischer). 
See Appendix, p. 312. 

PREPARATION 103. 
Benzaldehyde Green (Malachite Green) 

(Tetramethyldiaminotriphenylmethane), 

/C 6 H 5 

C^C H 4 .N(CH 3 ) 2 
^C 6 H 4 :N(CH 3 ) 2 C1 

O. Fischer, Annalen, 1883, 217, 250, 262. 

50 grms. dimethylaniline. 

20 benzaldehyde. 

40 zinc chloride (fused and powdered). 

A mixture of the above is heated on the water-bath in a 
porcelain basin until the srnell of benzaldehyde has disappeared 



216 PRACTICAL ORGANIC CHEMISTRY 

(4 hours). The viscous mass is melted in boiling water, trans- 
ferred to a round flask (i litre) and distilled in steam until no 
more dimethylaniline passes over. On cooling, the base adheres 
to the flask and is washed by decantation. It is recrystallised 
from absolute alcohol and is colourless. The yield is nearly 
theoretical. This is the leuco-base, and is formed according to 
the following equation : 

/C C H 4 N(CH 3 ) 2 
C C H 5 CHO + 2C H 5 N(CH 3 ), = C G H 3 CH<; +H 2 O. 

\C 6 H 4 N(CH 3 ) 2 

It is converted into the colouring matter by oxidation. Ten 
grams of the base are dissolved by slightly warming with dilute 
hydrochloric acid containing exactly 27 grams of hydrogen 
chloride (made by diluting cone, hydrochloric acid with twice its 
volume of water and then determining the specific gravity or 
titrating with standard caustic soda). The liquid is diluted with 
800 c.c. water, and 10 grams of a 40 per cent, acetic acid solution 
added. The mixture is cooled with a few lumps of ice, and a 
thin paste of freshly precipitated lead peroxide containing exactly 
7'5 grams PbO 2 (estimated by drying a small weighed sample on 
the water-bath) is added in the course of five minutes with 
frequent shaking. The product is left 5 minutes, and then a 
solution of 10 grams sodium sulphate in 50 c.c. water is run in 
and the solution filtered from lead sulphate. To the filtrate a solu- 
tion of 8 grams zinc chloride in a little water is added, and then a 
saturated solution of common salt until no more of the dye is 
thrown down. It is filtered, and recrystallised by dissolving in 
water and adding salt solution. Yield, 80 per cent, of the theory 
of zinc salt. 

X C 6 II 4 N(CH 3 ) 2 /C B H 5 

C 6 H 5 CII( +O + HC1= C/C 8 H 4 N(CH 3 ), +H 2 O. 

X -C 6 H 4 N(CH 3 ) 2 \C 6 H 4 :N(CH 3 ) 2 C1 

See Appendix, p. 313. 



Naphthalene, C 10 U S 

Naphthalene is obtained from the " middle oil " in the distil- 
lation of coal-tar. It crystallises in colourless, glistening plates, 
which have a characteristic smell. 

Properties. -M. p. 80; b. p. 218; sp. gr. 1-145 at 4- It 



PHTHALIC ACID 217 



sublimes readily, arid can be distilled in steam. It is soluble in 
most of the common organic solvents. 

Reaction. Make strong solutions of about equivalent quanti- 
ties of naphthalene and picric acid in acetic acid, or alcohol, and 
pour them together. On cooling, yellow, needle-shaped crystals 
of naphthalene picrate separate : C 10 H g + C 6 H 2 (NO,)3OH ; m. p. 
149. 

PREPARATION 104. 



Phthalic Acid, C 04 

Friedlander. Thecrfarbenfabrikation, iv, 164. 

15 grms. naphthalene. 
1 20 c.c. cone, sulphuric acid. 
7' 5 grms. mercuric sulphate. 

The mixture of naphthalene, sulphuric acid, and mercuric 
sulphate is placed in a retort (300 c.c.). The retort is clamped 
with the neck sloping upwards, and heated gently over wire- 
gauze with occasional shaking until the liquid surface layer 
of naphthalene dissolves.* The retort is now placed in the 
ordinary position, with the neck sloping down, to which a con- 
denser tube is attached by means of a roll of asbestos paper, or 
a lute of plaster of Paris. The end of the condenser tube is 
provided with a receiver containing water (100 c.c.), and cooled 
in cold water. 

The retort is now heated (at first cautiously and then strongly) 
over the bare flame, and the contents distilled. The liquid 
rapidly darkens in colour. At about 250 oxidation begins, with 
evolution of sulphur dioxide, which becomes very vigorous as the 
temperature of the liquid rises to the boiling-point. A little 
naphthalene first distils, and after a time crystals of phthalic 
anhydride appear in the condenser tube, whilst phthalic acid 
collects in the receiver. The distillation is continued until the 
residue becomes viscid or even dry. The contents of the 
receiver, when cold, are filtered and washed, and then dissolved 
in caustic soda. Any undissolved naphthalene is removed by 
filtration, and the acid reprecipated by hydrochloric acid. The 



218 PRACTICAL ORGANIC CHEMISTRY 

acid may be recrystallised from water or dilute alcohol. Yield, 
about 7 grams. 



Properties. Crystallises in plates with no definite melting- 
point, as the acid passes into the anhydride on heating. Soluble 
in alcohol and in hot water, slightly soluble in cold water. 

Reactions. Sublime a little of the acid in a test-tube or in a 
clock glass covered with a filter paper and funnel. Phthalic 
anhydride sublimes in long needles, in. p. 1 28. 

,CO 
C 6 H 4 (COOH) 2 = C 6 H 4 / ^O + H 2 O. 

\;o 

Heat about 0*25 gram of the anhydride with 0*5 gram of 
resorcinol in a test-tube over a small flame for a few minutes, 
so that the temperature remains at about 200. Cool, dissolve 
in dilute caustic soda solution, and pour into water. A green 
fluorescence is produced, due to the formation of fluorescein 
(p. 187). See Appendix, 314. 

PREPARATION 105. 

/3-Naphthalenesulphonate of Sodium, C 10 H 7 SO 3 Na 
Merz, Weith, Ber., 1870, 3, 196. 

50 grms. naphthalene. 

60 cone, sulphuric acid. 

The mixture is heated in a round flask (250 c.c.) in the metal- 
bath to 160 170' for four or five hours. . The liquid is then 
poured into a basin of water (i litre), which is heated up and 
neutralised with chalk or slaked lime in the form of a thick 
cream. The hot liquid is filtered through cloth, squeezed out, 
and washed with hot water. The filtrate is evaporated on a 
ring-burner until a sample crystallises on cooling. The crys- 
talline mass of the calcium salt of naphthalene sulphonic acid 
is filtered and well pressed. It is redissolved in hot water, and 
a solution of sodium carbonate added, until the calcium is 
just precipitated. The liquid is again filtered through cloth, or 
at the pump, washed and well pressed. The filtrate is evaporated 



0-NAPHTHOL 219 



to crystallisation as before. The sodium naphthalene sulphonate 
is separated by filtration, and dried in a basin on the water-bath. 
The mother-liquor, on evaporation, yields a further quantity of 
the salt. Yield, about 60 grams. 



C 10 H 8 + H 2 SO 4 =C 10 H 7 SO 3 

2C 10 H 7 SO 3 H + CaO = (C 10 H 7 SO 3 ) 2 Ca+ H 2 O. 



3. 10r 

Properties. Foliated crystals ; soluble in water. See 
Appendix, p. 315. 

PREPARATION 106. 
/3-Naphthol, C 10 H 7 .OH 

Eller, Annalen, 1869, 152, 275 ; E. Fischer, Anleitung z. d. 
org. Prdparate. 

30 grms. ^-naphthalene sulphonate of sodium. 
90 caustic soda. 
3 c.c. water. 

The caustic soda and water are heated in a nickel or silver 
crucible, and stirred with a thermometer, protected as described 
under the preparation of phenol (p. 179). When the temperature 
reaches 280, the powdered naphthalene sulphonate is added a 
little at a time. When all has been added, the temperature is 
raised. At about 300 the mass froths up and becomes light 
yellow in colour, which indicates the commencement of the 
reaction. The temperature is maintained at 310 320 for a 
few minutes, and the end of the process is indicated by the 
yellow mass becoming thinner and also darker in colour, and 
separating into two layers. The stirring is now stopped and 
the flame withdrawn. The product, when cold, is dissolved in 
a little water, and acidified with a mixture of equal volumes of 
concentrated hydrochloric acid and water.* 

The naphthol is filtered off when cold, and is recrystallised 
from water. Yield, 15 grams. 

C 10 H 7 SO 3 Na + NaOH = C 10 H 7 ONa +NaHSO 3 . 
Properties. Colourless leaflets ; m. p. 122 ; b. p. 286. 



PRACTICAL ORGANIC CHEMISTRY 



Reactions. Add to a solution of the naphthol in water a few 
drops of ferric chloride. A green colouration is produced, and 
after a time a flocculent precipitate of dinaphthol, C-2oH 14 O 2 . 

See also Reaction 6, p. 163. 

/3-Naphthyl methyl ether. Dissolve 3'6grams /3-naphthol 
in I2'5 c.c. 10 per cent, caustic soda solution, add 3 c.c. methyl 
sulphate, warm the liquid gently and shake vigorously. In a 
short time the naphthyl methyl ether separates as a solid mass. 
The product is heated for ten minutes on the water-bath, a little 
water is added, and the naphthyl ether filtered and washed with 
water. It is. crystallised from alcohol and deposits in lustrous 
plates ; m. p. 70 72. The yield is theoretical. It may be 
used for analysis by Zeisel's method. 

Zeisel's Method. The method consists in estimating 
methoxyl or ethoxyl groups by decomposing the substance with 
strong hydriodic acid and eliminating the alkyl group as alkyl 
iodide. The alkyl iodide is passed through an alcoholic solution 
of silver nitrate, which decomposes the alkyl iodide and the 
silver iodide is weighed. 

R.OCH 3 +HI = R.OH + CH 3 I. 

The apparatus devised by W. H. Perkin, senior, is shown in 
Fig. 83 (Proc. Cheat. Soc., 1903, 19, 1370). 

It consists of a distilling flask (100 c.c.) with a long neck ; the 
distance between the bulb and side tube is about 20 cms. (8 ins.). 
It is provided with an inlet tube which terminates above the 
surface of the liquid and is attached at the other end with a 
carbon dioxide Kipp and wash-bottle containing silver nitrate 
solution to remove traces of hydrochloric acid or hydrogen sul- 
phide. The side tube of the distilling flask is attached to two 
small 100 c.c. Erlenmeyer flasks, provided with double-bored 
rubber corks. The first bent tube which is attached to the side 
tube of the distilling flask is cut off below the cork, the second 
terminates just above the surface of the liquid in the first flask 
and dips below the liquid in the second. The third or outlet 
tube is bent at right angles and is cut off below the cork. 

Thedistillingflaskisheated in a basin containingglycerol. The 
first Erlenmeyer flask is charged with 20 c.c. alcoholic silver 
nitrate, and the second with 15 c.c. of the same solution which 
is prepared by dissolving 2 grams of fused silver nitrate in 5 



0-NAPHTHOL 



c.c. water and adding 45 c.c. absolute alcohol. An accurately 
weighed quantity (0*3 o - 6 gram) of substance is introduced in a 
small weighing tube into the distilling flask and 15 c.c. of strong 
hydriodic acid (acid of sp. gr. 17 for Zeisel's estimations can be 
purchased). When the apparatus has been carefully fixed 
together the glycerol bath is heated to 130 140 and a slow 
current of carbon dioxide (two bubbles a second) is passed 
through the apparatus. The temperature of the glycerol bath 
is slowly raised until the hydriodic acid begins to boil gently. A 
white deposit (a compound of silver iodide and nitrate) begins to 




FIG. 83. 

form on the surface of the first flask and gradually settles to 
the bottom, but usually only a trace appears in the second vessel. 
The operation is generally completed in one hour ; but before 
stopping the process it is advisable to test the vapour passing 
through by removing the flasks and attaching the small bent 
tl-tube (shown in the Fig. and containing a little alcoholic silver 
nitrate solution) to the end of the side tube. If in the course of 
ten minutes no turbidity appears, the operation may be con- 
sidered at an end, otherwise it is necessary to connect up the 
flask and continue the heating for another twenty minutes. 
About 50 c.c. of water are heated to boiling in a beaker (250 



PRACTICAL ORGANIC CHEMISTRY 



c.c.) and the contents of both flasks gradually added and well 
washed out with hot water. The white precipitate changes to f*he 
yellow iodide and the alcohol is driven off. 

When the top liquid is no longer opalescent but clear, the 
precipitate is collected in a Gooch crucible and dried and 
weighed as described on p. 26. 

For volatile substances like anisole this method cannot be em- 
ployed. 

Example. 0*3150 gram naphthyl ether gave 0*468 gram Agl: 
31 xo'468 x 100 
235x0-3150 = '9'6 per cent. 

Calculated for Ci H 7 OCH 3 :CH 3 O = i9.6 per cent. 

^-Naphthyl Acetate. Boil gently 5 grams /3-naphthol and 
10 grams acetic anhydride for j hour with air condenser and 
pour the product into water. Crystallise from dilute alcohol ; 
m. p. 70^. 

A. G. Perkin's Acetyl method. (Proc. Chem. Soc., 1904, 
20, 171). The method consists in hydrolysing the acetyl 
derivative in presence of alcohol and distilling off the ethyl 
acetate and then estimating the quantity by hydrolysis. 

R.O.COCH 3 + C 2 H 5 OH = R.OH + CH 3 .COOC 2 H 5 . 

The apparatus is shown in Fig. 84. It consists of a small 
distilling flask (200 c.c.) with bent side-tube which is fitted to a 




FIG. 84. 

long condenser A tap-funnel is inserted into the neck and the 
flask is heated over wire-gauze. About 0*5 gram of naphthyl 
acetate is accurately weighed out of a small sample tube by 



NAPHTHOL 223 



difference and any dust adhering to the neck of the flask washed 
down with 5 c.c. pure cone, sulphuric acid and 30 c.c. 
pure alcohol, which are slowly run in with shaking. A small 
fragment of porous pot is also added. Twenty c.c. half-normal 
alcoholic potash (see p. 210) are introduced into the round flask 
(200 c.c.) which serves as receiver and 20 c.c. pure alcohol are 
poured into the tap-funnel. The liquid in the flask is slowly distilled 
whilst the alcohol is delivered drop by drop from the tap-funnel 
at about the same rate as the liquid distils. The distillation is 
continued until about half the bulk of liquid originally present 
in the flask remains. This residue should be quite colourless. 
The receiver is now attached to a reflux condenser and boiled 
on the water-bath for ^ hour and finally titrated with half-normal 
sulphuric acid, using phenolphthalein as indicator. 

The method does not give good results with acetamido- 
compounds like acetanilide, &c. 

Example. o'66$ gram naphthyl acetate required 7-5 c.c. 
N/2 KOH. 

loo 

= 23-6 per cent. 



-- 

2x0-633 

Calculated for C 10 H 7 .O.COCH 3 ; C 2 H 3 O=.23'i per cent. 

Tschugaeff' s Hydroxyl Method. This method rests 
upon the action of hydroxyl compounds on magnesium methyl 
iodide by which methane is evolved. 



R.OH + Mg 3 = R.Mgl + CH 4 . 

The apparatus is an ordinary Lunge nitrometer filled with 
mercury, which together with the attached Erlenmeyer flask 
is kept at constant temperature by a flow of water through 
an outer jacket. The three-way cock is connected with the 
Erlenmeyer flask (150 c.c.) by stout rubber tubing. A stock 
solution of magnesium methyl iodide is first prepared by 
mixing together in a flask connected with a reflux con- 
denser zoo grams amyl ether distilled over sodium, 9*6 
grams clean magnesium ribbon and 35-5 grams dry methyl iodide 
and a few iodine crystals. After the first reaction is over the mix- 
ture is heated for i 2 hours on the water-bath with condenser to 
expel unchanged methyl iodide, and preserved in a vaselined 
stoppered vessel. About o'i o'i 5 gram /3-naphthol is accurately 



224 PRACTICAL ORGANIC CHEMISTRY 

weighed in a tube which is of such a length that it rests against 
the side of the nitrometer flask. About 10 c.c. of the reagent are 
poured into the flask ; the tube containing the substance, which is 
dissolved in a little amyl ether, is slipped in ; the flask is attached 
to the side tube of the nitrometer and is then cut off from the 
nitrometer tube by turning the tap. A little moisture and 
oxygen in the flask are absorbed by the reagent and the pressure 
falls. After standing for j hour the nitrometer tube is nearly filled 
up with mercury, the tap is withdrawn for a moment to readjust 
pressure and the tube then completely filled with mercury. The 
tap is now turned so as to establish communication between the 
flask and nitrometer tube and the mercury reservoir lowered. 
The tube containing the solution of the naphthol is inverted 
and shaken. Evolution of methane rapidly occurs and in a 
short time the volume remains constant. The volume, tempera- 
ture and pressure are read off and the percentage of hydroxyl 
calculated. 

Example. 0*120 gram /8-naphthol gave 20 c.c. methane at 
N.T.P. 

20 x 17 x loo _ ., 

224OO X O'I2O 

Calculated for C 10 H 7 OH ; OH = I rS per cent. 

(Tschugaeff, Ber., 1902, 35, 3912 ; Hibbert and Sudborough, 
Proc. Chem. Soc., 1903, 19, 285 ; Zerewitinoff, Ber., 1907, 40, 
2023.) See Appendix, p. 315. 

PREPARATION 107. 

O 
/\ 

^NO, 




Naphthol Yellow, 

\/\. 

NO, 

Friedlander, Thcerfarbenfabrikation, I, 322, II., 215 ; Cain 
and Thorpe, The Synthetic Dye stuffs, p. 226. 

20 grms. a-naphthol. 

80 (45 c.c.) cone, sulphuric acid. 

40 (30 c.c.) cone, nitric acid (sp. gr. 1*4). 

The mixture of a-naphthol and sulphuric acid is heated for 
2 hours to I2O 3 and then dissolved in 120 c.c. water. The solu- 



ANTHRAQUINONE 225 



tion is cooled to 20 and stirred mechanically whilst the nitric 
acid is run in drop by drop. As the temperature should not 
rise above 40 it will be found necessary at the beginning to 
cool the vessel in a freezing mixture. After the nitric acid has 
been added the stirring is continued for another hour and the 
product is then left overnight. The naphthol yellow crystallises 
out and is filtered and washed with small quantities of a cold, 
saturated solution of salt. The precipitate is then dissolved in a 
large basin of hot water and potassium carbonate solution added 
until the liquid gives an alkaline reaction. On cooling, the 
potassium salt separates in small orange needles, and is filtered 
and dried on a porous plate. Yield, 20 25 grams. 

C 10 H 7 OH + 3 H 2 S0 4 = C 10 H 4 (OH)(S0 3 H)3. 

C 10 H 4 (OH)(S0 3 H) 3 + 2HN0 3 = C 10 H 4 (OH)(NO 2 ) 2 SO 3 H 

+ 2H 2 SO 4 . 

2C 10 H 4 (OHXN0 2 ) 2 S0 3 H + K,C0 3 = 2C 10 H 4 (OH)(NO 2 ) 2 SO 3 K 

+ CO 2 + H 2 O. 
See Appendix, p. 315. 

PREPARATION 108. 
Anthraquinone, C 6 H 4 ^ ^Q /C 6 H 4 

Graebe, Liebermann, Annalen, Spl., 1869, 7, 28', 

10 grms. anthracene (pure). 
1 20 c.c. glacial acetic acid. 

20 grms. chromium trioxide dissolved in 15 c.c. water, and 
then 75 c.c. glacial acetic acid added. 

The anthracene is dissolved in the acetic acid by boiling them 
together in a round flask (| litre) with upright condenser over 
wire-gauze. The solution of chromium trioxide is then dropped 
in from a tap-funnel pushed into the top end of the condenser 
whilst the liquid is kept boiling. The operation should last about 
an hour. The solution becomes a deep green. It is allowed to 
cool and poured into water (500 c.c.), which precipitates the 
anthraquinone in the form of a brown powder. After standing an 
hour, it is filtered through a large fluted filter, washed with a little 

COHEN'S ADV. p. o. c. o 



226 PRACTICAL ORGANIC CHEMISTRY 

hot water, then with warm dilute caustic soda and water again. 
Yield, 10 12 grams. 

Sublimation. A portion of the dry substance may be 
purified by sublimation. It is placed (2 3 grams) on a large 
watch-glass, which is heated on the sand-bath over a very small 
flame. The watch-glass is covered with a sheet of filter paper, 
which is kept flat by a funnel placed above. After five minutes 
or so pale yellcw, needle-shaped crystals of anthraquinone will 
have sublimed on to the filter paper. 

CH /CO, 

4 2 = C 6 H 4 <; >C G H 4 + 



H 2 O-r-Cr 2 (C 2 H 3 O 2 ) 6 . 

Properties. Yellow needles : m. p. 277 ; sublimes at 250 ; 
b. p. 382 ; insoluble in water, soluble in acetic acid, less soluble 
in benzene and other organic solvents. 

Reaction. Add a little dilute caustic soda to a small quantity 
of anthraquinone, and then a little zinc dust. On heating to 
boiling, an intense red colouration is produced, which disappears 

/CO ___ \ 

on shaking. Sodium oxanthranolate, C 6 H 4 ^ (-u/Qxr \/C 6 H 4 , 

formed, which oxidises in the air to anthraquinone. See 
Appendix ; p. 316. 

PREPARATION 109. 
Anthraquinone /3-monosulphonate of Sodium, 



Graebe, Liebermann, Annalen, 1871, 160, 131 ; A. G. Perkin. 
Private communication. 

30 grms. anthraquinone. 

30 fuming sulphuric acid (40 per cent. SOs). 1 

The 40 per cent, fuming sulphuric acid is removed from the 
bottle by cautiously melting it in a sand-bath, and it is then 
weighed out in a flask (j litre). The anthraquinone is added, 
and the flask attached by a cork to an air-condenser. The 

1 As fuming sulphuric acid k difficult to keep in an ordinary stoppered bottle 
without absorbing moisture, it is advisable to coat the stopper with a layer of 
paraffin wax, and a substantial covering of plaster of Paris above this. 



ALIZARIN 227 

mixture is heated in ~. paraffin or metal-bath to 150 160 for 
8 hours. The dark coloured mass is poured whilst hot into a 
large basin containing about a litre of cold water, and boiled 
for an hour. The unattacked anthraquinone, which does not 
dissolve, is removed by filtration at the pump. The precipitate 
is then replaced in the basin and boiled up again with about 
^ litre of water, filtered and finally washed once or twice with 
boiling water. The combined filtrate and washings, which have 
a deep brown colour, are evaporated with the addition of 0*2 gram 
of potassium chlorate until about litre of liquid remains. It 
is now nearly neutralised with sodium carbonate solution (about 
1 20 grams soda crystals) but not completely, as the sodium salt 
of the monosulphonic acid is less soluble in presence of acid. 
It is therefore convenient to pour out half a test-tube of the 
acid liquid, and proceed to neutralise the remainder. The small 
quantity of acid liquid is then replaced. The liquid is evapo- 
rated on the water-bath until a scum covers the surface, and it 
is then left to cool. The sodium salt of the sulphonic acid 
crystallises in pale yellow, silky crystals, and is separated at the 
pump. After being washed three or four times with a very little 
slightly acid water, it is dried on a porous plate. Yield, 20 25 
grams. A further quantity of the salt may be obtained by 
evaporating the mother-liquor, but it is liable to contain sodium 
sulphate. 

C 14 H 8 O 2 + H 2 SO 4 = Ci 4 H 7 O 2 .SO 3 H + H 2 O. 

Properties. The sodium salt of the sulphonic acid crystal- 
lises, when pure, in colourless leaflets, slightly soluble in cold 
water, insoluble in alcohol. 

PREPARATION no. 
Alizarin, C 6 



Graebe, Liebermann, Annalen, Spl., 1869, 300; Perkin, 
Patent, 1869, No. 1948 ; A. G. Perkin. Private communi- 
cation. 

20 grms. anthraquinone monosulphonate of sodium. 
90 caustic soda. 
5 potassium chlorate. 

Q 2 



228 



PRACTICAL ORGANIC CHEMISTRY 





The caustic soda is dissolved in about half its weight of water, 
and is added hot to the anthraquinone sulphonate of sodium, 
previously mixed into a paste with the potassium chlorate 
dissolved in about 50 c.c. of water. The mixture, which forms 
a stiff paste, is transferred at once to a small metal pressure tube 
of steel or phosphor-bronze of the shape and dimensions shown 
g . SeM in Fig. 85. 1 The mixture fills it 

about two-thirds full. A sheet 
of asbestos cardboard is inserted 
between the body and the top- 
of the vessel, and the metal top 
is then screwed firmly on. The 
pressure tube is heated for three 
hours in a paraffin or oil-bath, 
so that the thermometer in- 
serted into the inner tube, which 
contains a little paraffin, regis- 
ters 190 200. The dark violet 

coloured mass, after cooling, is scraped out and digested with 
boiling water for an hour. Milk of lime is added until the 
violet calcium alizarate is all precipitated. This can be ascer- 
tained in a small filtered sample by adding a little milk of lime, 
when no violet precipitate should be formed. The precipitate is 
filtered at the pump and washed with boiling water until the 
filtrate is no longer red. The red filtrate contains a little mono- 
hydroxyanthraquinone, which may be precipitated . by hydro- 
chloric acid. The calcium alizarate on the filter is sus- 
pended in a large quantity of hot water, and decomposed by 
adding hydrochloric acid. The alizarin, which separates as an 
orange, flocculent precipitate, is filtered cold, washed about eight 
times with cold water, and finally dried and crystallised from 
alcohol or preferably cumene. Yield, 10 15 grams. 



The thickness of the metal is i cm. 
FIG. 85. 



Properties. Orange needles ; m. p. 289 290 ; sublimes 
completely at 140 without decomposition ; soluble in alkalis 
with a deep purple colour (sodium alizarate). It is reduced to 
anthracene on heating with dry zinc dust. 

1 The apparatus was made for us by West's Gas Improvement Co., Miles Platting, 
Manchester. 



ISATIN 229 

Reaction. Make a small quantity of solution of alizarin in 
caustic soda, and pour into a beaker containing a strong solution 
of alum. The insoluble aluminium alizarate is precipitated as a 
red lake. See Appendix, p. 316. 

PREPARATION in. 

/ C0 \ 
Isatin from Indigo, C 6 H 4 <( J)C(OH) 

^ N " 

Erdmann /. prakt. Chem., 1841, 24, 11 ; Knop, Jahresb. 
1865, 580. 

loo grms. indigo (in fine powder). 
50 c.c. cone, nitric acid diluted with 10 c.c. water. 

Mix up the indigo into a paste with 300 c.c. of boiling water 
in a large basin. Heat to boiling and remove the flame. Then 
add the nitric acid to the hot liquid from a tap-funnel at the rate 
of a drop or two a second, so that it is all added in the course 
of twenty minutes, and stir well all the time. The mass, which 
is at first pasty, froths up, and towards the end becomes thinner. 
Boil up for about two minutes, as soon as the acid has all been 
added, and then pour out about half the liquid into a second 
large basin and add a litre of boiling water to each. Boil up 
for five minutes, and decant from the floating lumps of tarry 
matter through a large fluted filter paper previously moistened 
with water. Add another litre of hot water to each basin, boil up, 
and filter. Evaporate the combined red coloured filtrates to 
about \\ litre, and filter again, if necessary, from a further deposit 
of tar. On cooling, a quantity of red crystals discoloured with 
tar will separate. Filter and concentrate the filtrate. Re- 
dissolve the crystals in the smallest quantity of boiling water, 
and let the liquid cool somewhat, so that some of the tarry 
matter may separate ; filter and evaporate the filtrate, until 
crystals of i satin nearly cover the surface ; then cool and filter 
off the red crystalline deposit. A further quantity of crystals 
may be obtained by evaporating the mother-liquors, which 
must be frequently filtered from tarry deposit. The crystals 
obtained in this way may be purified by dissolving them in 
caustic potash solution, and adding concentrated hydrochloric 
acid to the clear liquid so long as a black precipitate is 



230 PRACTICAL ORGANIC CHEMISTRY 

formed. The liquid is then filtered, and the purified isatin 
completely thrown down in the filtrate with more acid. The 
substance is then filtered and recrystallised from water. Yield, 
about 10 grams. 

C 16 H 10 N 2 2 + 2 = 2C 8 H 5 N 2 . 

Properties. Red monoclinic prisms; m. p. 201; soluble in 
hot water and alcohol. 

Reaction. Dissolve a few crystals in concentrated sulphuric 
acid in the cold and shake up with a little coal-tar benzene. A 
blue colour due to thiophene is produced. See Appendix, p. 318. 

PREPARATION 112, 
CH CH 



Quinoline, 

HC^ 

CH N 

Skra.up,Monats/i., 1880, 1, 316 ; 1881,2. 141; Ktinigs, ^r., 1880, 

13, 911. 

24 grms. nitrobenzene. 

38 ,, aniline. 
120 glycerol. 
100 cone, sulphuric acid. 

A large round flask (i 2 litres) is attached to an upright 
condenser. The mixture of nitrobenzene, aniline, glycerol, and 
sulphuric acid is poured in and heated on the sand-bath until 
the reaction sets in (ten to fifteen minutes), i.e. until white vapours 
rise from the liquid. The flask is now raised from the sand- 
bath or the burner extinguished, and when the first reaction is 
over the contents are gently boiled for two to three hours. The 
dark coloured product is diluted with water, and unchanged 
nitrobenzene driven over with steam. The residue is made 
strongly alkaline with caustic soda, and the oily layer (quinoline 
and aniline) distilled off with steam. In order to remove the 
aniline present, the distillate is acidified with sulphuric acid, and 
sodium nitrite added, until a sample of the liquid ceases to 
give the aniline reaction with sodium hypochlorite. It is then 
boiled, whereby the aniline is converted into phenol. The 



QUININE SULPHATE 231 

liquid is again made alkaline with caustic soda, and submitted 
to a third distillation with steam. The distillate is extracted 
with ether, dehydrated over solid caustic potash, and, after 
decanting and driving off the ether, the residue is distilled. 
Yield, 40 grams of a pale yellow oil. 



Properties. Colourless liquid; b. p. 237; sp. gr. rio8 at 
o c ; insoluble in water ; soluble in alcohol and ether. 

Reactions. i. Dissolve a few drops of quinoline in a little 
hydrochloric acid and add platinic chloride. Orange crystals of 
the chloroplatinate are deposited (C 9 H 7 N) 2 H 2 PlCl(j+H.2O. 

2. Add to a solution of quinoline in acid, potassium chromate 
solution ; the dichromate, (C 9 H 7 N) 2 H 2 Cr 2 O r , is precipitated. 

3. Add to I c.c. of quinoline I c.c. of methyl iodide and 
warm. A reaction sets in, and on cooling, the quaternary 
ammonium iodide, C 9 H 7 N.CH 3 I, crystallises in yellow crystals. 

4. To a few drops of quinoline add a solution of bromine in 
chloroform. A crystalline compound, C 9 H 7 N.Br 2 , is formed. 
See Appendix, p. 318. 

PREPARATION 113. 
Quinine Sulphate from Cinchona Bark, 

C 20 H 24 N 2 O 2 .SO 4 H 2 + 8H,O 
Pelletier, "Caventou, Ann. Chim. Phys., 1820, (2), 15, 291. 

100 grms. cinchona bark (ground in a coffee mill). 
20 quicklime. 

Slake the quicklime, and mix it into a thin cream with 200 c.c. 
water. Pour the liquid into a basin containing the powdered 
bark and stir up the mass well. Dry the mixture thoroughly 
on the water-bath, taking care to powder up the lumps that 
ball together. When cold place the powder in a flask, pour 
over it 200 c.c. chloroform, and let the mixture stand over- 
night. Filter through a porcelain funnel and wash with a 
/urther 200 c.c. chloroform. The chloroform solution, which 
has now a faint yellow colour, is shaken up well with 50 c.c. 
and again with 25 c.c. dilute sulphuric acid, and then with water 
until the aqueous solution has no longer a blue fluorescence. 
The combined acid and aqueous extracts are carefully neutralised 



232 PRACTICAL ORGANIC CHEMISTRY 

with ammonia and the liquid concentrated on the water-bath 
until crystals of quinine sulphate begin to form on the surface. 
The liquid is allowed to cool and filtered. A further quantity of 
crystals may be obtained from the mother-liquor by evaporation, 
but the product is not so pure. The crystals are purified by 
recrystallisation from water. Yield, I to 2 grams, or more, 
according to the quality of the bark. 

Properties. The free base, which is precipitated with sodium 
carbonate from a solution of its salts, crystallises with 3H 2 O. 
The anhydrous base melts at 277 ; soluble in alcohol and ether. 

Reactions. Use a solution of the hydrochloride prepared by 
adding a few drops of hydrochloric acid to the sulphate mixed 
with water. 

1. Add to a little of the solution a few drops of iodine solu- 
tion ; a brown amorphous precipitate is formed. This reaction 
is given by many of the alkaloids. 

2. Add chlorine water and then ammonia in excess. An 
emerald green colouration is produced. 

3. Add sodium carbonate solution and then shake with ether. 
The free base is precipitated and dissolves in the ether. Decant 
the ether on to a watch-glass and let it evaporate. Crystals of 
the base remain. 

4. Dissolve in a few drops of acetic acid and add a large 
volume of water. A blue fluorescent liquid is obtained. See 
Appendix,^. 319. 

PREPARATION 114. 

/N 
Diazobenzolimide, C 6 H 5 N< i; 

X N 

Phenylmethyltriazole carboxylic Acid, 
N.CH, 



N ( \ C.CH 3 

C.COOH 



Dimroth, Ber., 1902, 35, 1,029. 

30 grms. phenylhydrazine. 

45 c.c. cone, hydrochloric acid (in 400 c.c. water). 

24 grms. sodium nitrite (in 50 c.c. water). 



PHENYLMETHYLTRIAZOLE CARBOXYLIC ACID 233 

The phenylhydrazine and hydrochloric acid are mixed 
together, stirred mechanically and cooled with a few lumps of 
ice whilst the nitrite solution is added, until the test with starch- 
iodide paper shows that an excess is present. The hydro- 
chloride dissolves, and diazobenzolimide separates out as an 
oil. 

/ N 
C 6 H 5 NH.NH 9 +HNO 2 = C 6 H 5 N< || +2H,O. 

\N 

Part of the water is removed by a syphon and the oil is 
extracted with ether ; after removing the ether, the diazobenzol- 
imide is purified by distillation in steam. It is again extracted 
and separated with ether as before. Yield, about 25 grams. 

4 grms. sodium. 
68 c.c. absolute alcohol. 
22 grms. acetoacetic ester. 
20 diazobenzolimide. 

The sodium is dissolved in the alcohol, and to the cold solu- 
tion a mixture of the acetoacetic ester and diazobenzolimide 
is added, and then warmed to boiling with reflux condenser. 
As soon as this occurs, the flask is removed and cooled, if the 
action becomes too violent. After the reaction is over, the 
mixture is heated for an hour on the water-bath with reflux con- 
denser, when the contents of the flask become almost solid. The 
mass is dissolved in the smallest quantity of hot water, and the 
liquid, if neutral, made strongly alkaline and boiled again for an 
hour. About 350 c.c. hot water are added, and sufficient hydro- 
chloric acid to precipitate the triazole carboxylic acid. It is 
filtered and washed with a little water, and is then nearly pure ; 
m. p. 155. Yield, about 27 grams. 

N.C 6 H 5 N.C 6 H 5 



N / + + C H ON = N C.CH 3 + 2C 2 H 5 OH. 

|l/ CO.CHg "25 l| II 

N ! N C.COONa 

CH 2 .COOC 2 H 5 

See Appendix, p. 320. 



APPENDIX 

NOTES ON THE PREPARATIONS 
PREPARATION i. 

Ethyl Potassium Sulphate. The combination betw&en 
alcohol and sulphuric acid is not complete, a condition of 
equilibrium being reached before either constituent is com- 
pletely converted. The reaction is known as a reversible one 
and may be represented thus : 

C 2 H 5 OH + H 2 SO 4 ;r C 2 H 5 HSO 4 + H 2 O, 

which implies that the alkyl sulphate reacts with water, re- 
generating alcohol and sulphuric acid. The free alkyl acid 
sulphates are, as a rule, viscid liquids, which cannot be dis- 
tilled without yielding the olefine. On boiling with water, 
the alcohol is regenerated. The salts are used for preparing 
various alkyl derivatives, such as mercaptans, thio-ethers and 
cyanides. 

KHS = 



Ethyl mercaptan. 

2S 2\OK HS + K 2 S = (C 2 H 5 ) 2 S + 2 K 2 S0 4 

Ethyl thio-ether. 

5 + KCN = C.jH 5 CN + K,SO 4 
Ethyl cyanide. 

Compare the action of sulphuric acid on phenol (see Prep. 
74, P- 177)- 

PREPARATION 2. 

Ethyl Bromide. The replacement of the hydrogen by 
halogen (Cl, Br) may be effected by the direct action of the 
halogen on the paraffin. 

C Q H 6 + Cl.j = C 2 H 6 C1 + HC1. 



APPENDIX 235 



A simpler method is to replace the alcohol hydroxyl by halo- 
gen by the action of hydracid (HC1, HBr, HI), 

C 2 H 5 OH + HC1 = C 2 H 5 C1 + H 2 O. 

Or by that of the phosphorus compound (PC1 3 , PBr 3 , PI 3 ), 
3 C 2 H 5 OH + PC1 3 = 3C 2 H 6 C1 + P(OH),. 

The preparation of ethyl bromide may be taken as an ex- 
ample of the first method, in which the hydracid is liberated by 
the reaction, 

KBr + H 2 SO 4 = HBr + KHSO 4 . 

A further example is that of isopropyl iodide : see Prep. 31, 
p. 1 10, in which the hydricdic acid is obtained by the action of 
water on phosphorus iodide, 

PI 8 + 3H 2 O = 3HI + P(OH) 3 . 

The action of HC1 is much more sluggish than that of HBr 
or HI, and in the preparation of ethyl chloride a dehydrating 
agent (ZnCl 2 ) is usually added to the alcohol, which is kept 
boiling whilst the HC1 gas is passed in. In the case of poly- 
hydric alcohols, all the hydroxyl groups cannot be replaced by 
Cl by the action of HC1. Glycol gives ethylene chlorhydrin and 
glycerol yields the dichlorhydrin (see Prep. 32, p. in). The use 
of PBr 3 , PI 3 does not necessitate the previous preparation of 
these substances. Amorphous phosphorus is mixed with the 
alcohol, and bromine or iodine added as in the preparation of 
methyl iodide (see Prep. 6, p. 68). PC1 5 or PC1 3 will always 
replace OH by chlorine in all hydroxy-compounds, including 
phenols, on which HC1 does not act. 

The alkyl halides are utilised in a variety of reactions, 
examples of which are given, ethyl iodide being taken as the 
type. 

i. Aqueous potash or water with metallic oxide (Ag 2 O, PbO) 
yields the alcohol (see Prep, 87, p. 195), 

C 2 H 5 I + KOH = C 2 H 6 OH + KI. 
2. Alcoholic potash gives an olefine, 

C 2 H 5 I + KOH = C 2 H 4 + KJ + H ? O, 
3. Sodium alcoholate gives an ether, 

C 3 H 5 I + NaOC 2 H 5 = C 2 H B OC 2 II 5 + NaL 



236 PRACTICAL ORGANIC CHEMISTRY 

4. Alcoholic ammonia forms a mixture of primary, secondary 
and tertiary amines, 

C 2 H 5 I + NH 3 = C,H 5 NH 2 + HI 
2C 2 H 5 I + NH 3 = (C 2 H 5 ),NH + 2 HI 
3C 2 H 5 I + NH 3 = C 2 H 5 ) 3 N + 3 HI. 

The tertiary amines unite with the alkyl iodide to form the 
quaternary ammonium iodide, which is produced at the same 
time as the other products. 

(C 2 H 5 ) 3 N + C 2 H 5 I = (C 2 H 5 ) 4 NI. 

5. Potassium cyanide forms alkyl cyanide, 

C 2 H 5 I + KCN = C 2 H 5 CN + KI. 

6. Potassium hydrosulphide gives the mercaptan, 

C 2 H 5 I + KSH = C 2 H 5 SH + KI. 

7. Potassium sulphide forms the thio-ether, 

2C 2 H S I + K-,8 = (C 2 H 5 ) 2 S + 2KI 

8. Silver nitrite gives the nitro-paraffin, 

C 2 H 5 I + AgN0 2 = C 2 H 5 N0 2 + Agl. 

9. Silver salts of organic or inorganic acids yield the alkyl 
esters, 

2C 2 H 5 I +A g2 S0 4 = (C 2 H 5 ) 2 S0 4 + 2AgI. 
C 2 H 5 I + CH 3 .COOAg = CH 3 .COOC 2 H 5 . + Agl. 

PREPARATION 3. 

Ethyl Ether. This reaction is of a general character. By 
using a different alcohol in the reservoir from that in the flask, 
a mixed ether may be obtained. Thus, ethyl alcohol and amyl 
alcohol may be combined to form ethyl amyl ether, 

C 2 H 5 OH + H 2 SO 4 = C.,H 5 SO 4 H + H.O. 
C,H 5 HSO 4 + C 5 H U OH = C 2 H 5 OC 5 H n + H 2 SO 4 . 

That the sulphuric acid acts in the above manner and not 
merely as a dehydrating agent appears not only from the 
formation of mixed ethers, but also from the fact that the 
sulphuric acid may be replaced by phosphoric, arsenic and 
benzene sulphonic acids. 



APPENDIX 237 



The ethers are also formed by the action of sodium alcoholate 
on the alkyl iodide (Williamson), 

C 2 II 5 ONa + C 2 H 5 I^ C 2 H 5 .O.C 2 H 5 + Nal, 
and by this method mixed ethers may also be prepared. 

The inertness of the ethers arises probably from the fact 
that the whole of the hydrogen present is united to carbon. 
Note the action of sodium and PC1 5 on alcohol and on ether. 
The ethers are not decomposed with PC1 5 except on heating, 
when they give the alkyl chlorides, 

(C 2 H 5 ) 2 O + PC1 5 = 2C 2 H 5 C1 + POC! 3 . 
Hydracids, especially HI, have a similar action 

(C 2 H 5 ) 2 O + 2HI = 2C 2 H 5 I + H 2 O. 

Hot, strong sulphuric acid breaks up ether into ethyl sulphuric 
acid and water, 

(C 2 H 5 ) 2 O + 2H 2 SG 4 = 2C 2 H 5 .SO 4 H + H 2 O. 
Compare the action of caustic alkalis on ethers, esters and 
anhydrides. 

/C 2 H 5 /CoHs /CO.CH 3 

000 
\C 2 H 5 \TO.CH 3 \:O.CH 3 

Diethyl ether. Ethyl acetate. Acetic anhydride. 

PREPARATION 4. 

Ethylene Bromide. The formation of defines by the 
action of cone. H 2 SO 4 and other dehydrating agents on the 
alcohols is a very general reaction. Among the higher alcohols 
the action of heat alone suffices ; cetyl alcohol, C 10 H 34 O, gives 
cetylene, Ci C ,H 32 , on heating. The olefines are also obtained by 
the action of alcoholic potash on the alkyl bromides and 

iodides, 

C 2 H 8 Br + KOH = C. 2 H 4 + KBr + H 2 O, 

and by the electrolysis of the dibasic salts ; potassium succinate 
gives ethylene, 

C 2 H 4 (COOK) 2 = C 2 H 4 + 2CO, + K 2 (H 2 ). 

The olefines combine with : 

(i) Hydrogen in presence of platinum black, or finely divided 
nickel (see Prep. 78, p. 181). 

CH 2 : CH 2 + H 2 = CH 3 .CH 3 . 

Ethylene. Ethane. 



PRACTICAL ORGANIC CHEMISTRY 



(2) The hydracids (HC1, HBr, HI), in which case the halogen 
attaches itself to the carbon with the least number of hydrogen 
atoms, 

CH 3 .CH:CH 2 + HI = CH 3 .CHI.CH 3 . 

Propylene. Isopopyl iod-de. 

(3) The halogens (Cl, Br, I), 

CH 2 :CH 2 + C1 2 = CH 2 C1.CH 2 C1. 

Ethylene. Ethylene chloride. 

(4) Cone, sulphuric acid, 

/OH /OCH 2 .CH 3 

CH 2 : CH 2 + O-jS^ = OoS/ 

Ethyl hydrogen sulphate. 

(5) Hypochlorous acid, 

CII 2 :CH 2 + HOC1 = CH 2 OH.CH 2 C1. 

Ethylene chlorhydrin. 

Potassium permanganate oxides the define, forming in the 
first stage the corresponding glycol. By further oxidation the 
molecule is decomposed by the parting of the carbon atoms at 
the original double link, 

CH :! .CH : CH 2 + H 2 O + O = CH<.CHOH.CH 2 OH. 
Propylene. Propylene glycol. 

CH 3 .CHOH.CH 2 OH + 2O 2 = CH 3 .COOH + CO 2 + 2H 2 O. 

Acetic acid. 

Alkylene chlorides and bromides with both halogen atoms 
attached to the same carbon are obtained by the action of 
PC1 5 and PBr 5 on aldehydes and ketones. 

CH 3 .CO.CH 3 + PC1 5 = CH 3 .CC1 2 .CH 3 + POC1 3 . 

/8j3-Dichloropropane. 

PREPARATION 5. 

Acetaldehyde. The formation of aldehyde from alcohol 
probably occurs by the addition of oxygen and subsequent 
elimination of water, 

CH 3 CH 2 OH + O = CH 3 .CH(OH) 2 = CH 3 .CO.H + H 2 O. 

The aldehydes may also be obtained by the reduction of acid 
chlorides and of anhydrides in some cases, but the method is 
rarely adopted. Aldehydes can only be obtained directly from 



APPENDIX 239 



the fatty acids by distilling the calcium salt with calcium form- 
ate ; but in no case by direct reduction, unless in the form of 
lactones, 

(CH 3 .COO) 2 Ca + (HCOO) 2 Ca = 2CH 3 .CO.H + 2CaCO 3 . 

The aldehydes are readily reduced to the alcohols. Charac- 
teristic properties of the aldehydes are the formation of aldehyde 
ammonias, SchifPs reaction, the reduction of metallic salts and 
the production of acetals by the action of alcohol in presence of 
hydrochloric acid gas (E. Fischer). 

CH 3 .CO.H + 2C 2 H 5 OH = CH 3 .CH(OC 2 H 5 ) 2 + H 2 O. 

Acetal. 

They also polymerise readily. These reactions should be com- 
pared with those of benzaldehyde (Prep. 88, p. 196). There are 
many reactions which are common to both aldehydes and 
ketones, i.e., to all substances which contain a ketone CO group 
Such, for example, are : (i) The formation of an additive com- 
pound with sodium bisulphite. 

> CO + NaHS 3=><S0 3 Na 

(2) The action of PC1 5 , which replaces oxygen by chlorine, 

\CO + PC1 5 =\CC1 2 + POC1 3 . 

(3) The formation of a cyanhydrin with hydrocyanic acid, 

^>CO + HCN = 

which on hydrolysis yields a hydroxy-acid. 

(4) The formation of an oxime with hydroxylamine (see Preps. 
9, p. 71, and 89, p. 197). 

\CO + H 2 NOH =\C:NOH + H 2 O. 

(5) The formation of a phenylhydrazone with phenylhydr- 
azine. 



CO + H 2 N.NH.C 6 H 5 =>C:N.NHCH 5 -!- H 2 O. 



240 PRACTICAL ORGANIC CHEMISTRY 

(6) The formation of a semicarbazone with semicarbazide 
(see Prep. 100, p, 212). 

O + H 2 N.NH.CO.NH 2 = \C:N.NH.CONH 2 + H 2 O. 

Both aldehydes and ketones readily undergo condensation, 
and a great variety of syntheses have been effected in this way 
(see Preps. 94, p. 204, and 103, p. 215). 

The aldehydes unite with zinc alkyl (Wagner) and mag- 
nesium alkyl halide (Grignard, see p. 206) to form additive com- 
pounds, which decompose with water, yielding secondary 
alcohols. 

/OZnCH 3 
CH 3 .CO.H + Zn(CH 3 ), = CH 3 .CH< 

X CH 3 
,OZnCH s 
CH 3 .CH/ + 2H 2 O = CH 3 .CHOH.CH 3 + Zn(OH) 2 + CH 4 . 

CH 3 Isopropyl alcohol. 

/OMgl 
CH 3 CO.H + MgCH 3 I = CH 3 .CHc; 

X CH, 
/OMgl 

CH 3 .CH( + H,O = CH 3 .CHOH.CH 3 + Zn(OH) 2 + CH 4 . 

\CH 3 

Acetaldehyde, in presence of HC1, polymerises, forming 
aldol. With zinc chloride the reaction goes a step further and 
crotonaldehyde is formed, 

CH 3 .COH + CH 3 .COH = CH 2 .CH(OH).CH 2 .COH. 

Aldol. 

CH 3 .CHOH.CH 2 .COH = CII 3 .CH:CH.COH + H 2 O. 

Crotonaldehyde. 

PREPARATION 6. 
Methyl Iodide. Read notes on Prep. 2, p. 234. 

PREPARATION 7. 

Amyl Nitrite. The nitrites of the general formula 
R'.O.NO are isomeric with the nitre-paraffins R'NO 2 . Whereas 
the nitrites are hydrolysed with KOH like other esters into the 
alcohol and the acid, 

C 2 H 5 ONO + KOH = C 2 H 5 OH + KNO 2 , 
and are decomposed by reducing agents into the alcohol and 



APPENDIX 24I 



ammonia (and in some cases hydroxylamine), the primary nitro- 
paraffins are not hydrolysed by potash, but dissolve, forming 
the soluble potassium salt, and on reduction give the primary 
amine, 

C 2 H 5 NO., + sH 2 = C 2 H 5 NH 2 + 2H 2 O. 

Amyl nitrite is used in the preparation of diazo-salts (see Prep. 
62, p. 161). 

PREPARATION 10. 

Acetyl Chloride. Either PC1 3 or PC1 5 are almost in- 
variably used in the preparation of acid chlorides. In the case 
of PC1 5 only a portion of the chlorine of the reagent is utilised 
(see Prep. 98, p. 208), POC1 3 being produced in the reaction, 
The use of one or other reagent is determined by the nature of 
the product. If the latter has a low boiling-point the trichloride 
is preferred, if a high boiling-point, the pentachloride may be 
used and the oxychloride expelled by distilling in vacua from a 
water-bath (see Prep. 16, p. 85). The pentachloride is more 
frequently used m the preparation of aromatic acid chlorides, 
but there are occasions, which experience can only determine, 
when the trichloride is preferable. 

Phosphorus oxychloride and the sodium salt of the acid can 
also be used. 

2CH 3 .COONa + POCL, = 2CH 3 .COC1 + NaPO 3 + NaCl. 

Also thionyl chloride, SOC1 2 , may often be used with advan- 
tage in place of the chlorides of phosphorus, 

CH 3 .COOH + SOC1 2 = CH 3 .COC1 + HC1 + SO 2 . 

Acid chlorides react with alcohols and phenols, and in general 
with substances containing a "hydroxyl " (OH) group. Acid 
anhydrides have a similar behaviour, and both substances may 
be used in determining the number of such groups in a 
compound. Thus glycerol forms a triacetyl derivative, whilst 
glucose yields a pentacetyl compound. By hydrolysing the 
acetyl derivative with alkali, and then estimating the amount of 
alkali neutralised by titration, the number of acetyl groups can 
be estimated (see p. 222). 

The presence of the "amino" (NH 2 ) group is determined by 
a similar reaction. 

The synthesis of aromatic ketones may be effected with the 

COHEN'S ADV. p. o. c R 



242 PRACTICAL ORGANIC CHEMISTRY 

acid chlorides, using the Friedel-Crafts' reaction (see Prep. 100, 
p. 210), also of aliphatic ketones and tertiary alcohols with zinc 
methyl and ethyl, &c. (Butlerow) or magnesium alkyl halide 
(Grignard). 

/OZnCH 3 

(1) CH 3 .COC1 + Zn(CH 3 ) 2 = CH 3 .C Cl 

\CH 3 

/OZnCH 3 ,C1 

CH 3 .C^-C1 + H 2 O = CH 3 .CO.CII 3 + Zn< + CH 4 . 

X CH 3 Acetone. X OH 

/OZnCH, /CH, 

(2) CH 3 .COC1 + 2Zn(CH 3 ) 2 = CH 3 .C^CH 3 + Zn< 

\CH 3 X C1 

/OZnCH 3 

CH 3 .C^-CH 3 + 2Hp = CH 3 .C(OH)(CH 3 ) 2 + Zn(OH) 2 + CH 4 
^CH 3 Tertiary butyl alcohol. 

An additive compound with zinc methyl is formed, in the 
first reaction with one molecule, in the second with two mole- 
cules, and the product in each case is then decomposed with 
water. The reaction with magnesium methyl iodide is 
similar. 

PREPARATION n. 

Acetic Anhydride. The anhydrides may be regarded as 
oxides of the acid radicals, just as ethers are the oxides of the 
alcohol radicals, and, like the ethers, both simple and mixed 
anhydrides may be prepared. The latter, however, on distilla- 
tion decompose, giving a mixture of the simple anhydrides. 

C 2 H 3 0\ Q _ C 2 H 3 0\ C 5 H 9 0\ Q 
2 C 5 H 9 0/ U - C 2 H 3 0/ U + C 5 H 9 0/ U 

Anhydrides may also be prepared by the action of POC1 3 en 
the potassium salt of the acid in presence of excess of the 
latter, the reaction occurring in two phases : 

2CH 3 .COOK + POCL, = 2CH 3 .COC1 + KPO 3 +KC1. 
CH 3 .COOK + C 2 H 3 OC1 = (C 2 H 3 O) 2 O + KC1. 

In addition to the reactions described under the Preparation, 
the anhydrides undergo the following changes : 

I. With HC1, HBr, and HI they give, on heating, the acid 
chloride and free acid, 

(CH 3 CO) 2 O + HC1 = CH 3 COC1 + CH 3 .COUH. 



APPENDIX 243 



2. With Cl they form acid chloride and chlorinated acid, 

(CH 3 CO). 2 O + CU = CH 3 COC1 + CH 2 C1.COOH. 

3. With Na amalgam they are reduced to aldehydes. 

PREPARATION 12. 

Acetamide. The acid amides, or simply amides, corre- 
spond to the amines, being ammonia in which hydrogen is 
replaced by acid radicals, and, like the amines, exist in the form 
of primary secondary and tertiary amides. The following 
methods are used for obtaining the amides, in addition to that 
described under the preparation : 

1. The action of ammonia on the acid chlorides or anhy- 
drides (see Prep. 98, p. 209). 

CH 3 .CO.C1 + 2NH 3 = CH 3 .CO.NH 2 + NH 4 C1. 
CH 3 CO/ + 2NHs = CH 3-CO.NII 2 + CH 3 .COONH 4 . 

2. The action of ammonia on the esters (see Prep. 26, p. 102). 

CII 3 .COOC. 2 H 5 + NH 3 . = CH 3 .CONH 2 + C 2 H 5 OII. 

3. Partial hydrolysis of the cyanides by cone, hydrochloric 
or sulphuric acid, 

CH 3 CN + H 2 O = CH 3 .COXH 2 . 

The alkyl amides or substituted ammonias, with both acid 
and alkyl radicals, also exist, and are formed by the first two 
of the above redactions and by heating the salt of the amine 
(see Prep. 54, p. 151). 

CH 3 .CO.C1 + NIToQHs = CH 3 .CO.NHC,H 5 + HCI. 

Aceteth y lam id e. 

CH 3 .COOH.NH. 2 C 6 H 5 = CH 3 .CONH.C 6 H 5 + H 2 O. 

Aniline acetate. Acetanilide. 

With the exception of formamide, which is a viscid liquid, the 
majority of these compounds are crystalline solids. The lower 
members are soluble in water, and they all dissolve in alcohol 
or ether. Many of them distil without decomposition. They 
are neutral substances uniting with both mineral acids and 
a few of them with caustic alkalis and alkaline alcoholates 
to form compounds which are rapidly decomposed by water. 

The hydrogen of the amido-group is also replaceable by 

R 2 



244 PRACTICAL ORGANIC CHEMISTRY 

metals, and derivatives of acetamide of the following formulae 
are known : 

CH 3 CONHNa, CH 3 .CONHAg, (CH 3 .CO.NH) 2 Hg. 

They are converted by nitrous acid into the organic acid, 
and in the case of substituted amides into nitrosainides, 

CH 3 CONH 2 + HNO 2 = CH..CO.OH + N 2 + H 2 O. 

CH 3 .CO.NHC 6 H 5 + HNO., = CH 3 .CO.N(NO).C 6 H 5 +" H 2 O. 

Acetanilide. Nitrosoacetanilide. 

With the latter class of substituted amides, PC1 5 forms the 
jmidochlorides, a reaction which is usually formulated in two 
steps, 

CH 3 .CO.NHC 6 H 5 + PC1 5 = CH 3 .CC1 2 .NHC B H 5 + .POC1 3 . 
CH 3 .CC1. 2 .NHC 6 H 5 = CH 3 CC1 : NC 6 H 5 + HC1. 

The substituted amides give both imidochloride and the 
cyanide with PC1 5 , 

CH 3 .CONH 2 + PC1 5 = CH,,.C/ H + POC1 3 + HC1. 



= CH 3 .CN + HC1. 



PREPARATION 13 

Acetonitrile. The various reactions by which the nitriles 
or alkyl cyanides are obtained have already been mentioned 
in one or other of the previous notes, but they may be 
recapitulated. 

I. By the action of KCN on the alkyl iodide or alkyl 
potassium sulphate, 

C 2 H 5 I + KCN = C 2 H 5 CN + KI. 

3 + KCN = C 2 H s CN + K 2 S0. 



i. By the action of PC1 5 (as well as P 2 O 5 ) on the amide, 

CH 3 .CONH 2 + PC1. 5 = CH 3 CN + POC1 3 + aHCl. 
3. By heating the aldoxime with acetic anhydride, 

CH 3 .CH : NOH + (CH 3 CO) 2 O = CH 3 CN + 2CH 3 .COOH. 

They are compounds which are, for the most part, insoluble 
in water, possess an ethereal smell, have a neutral reaction, and 
may be distilled. 



APPENDIX 24<5 



The fact that they are eminently unsaturated compounds is 
evidenced by their general behaviour towards a great variety 
of reagents. 

1. On reduction they give the primary amine (Mendius), 

CH 3 CN + 2H 2 = CH 3 CH 2 NH 2 . 

2. With HC1, HBr,and HI they form imidohalides (Wallach), 

CH 3 CN + HC1 = CH 3 .C 

3. With alcohol and HC1 they form the' hydrochloride of the 
imidoethers, from which caustic alkali liberates the base 
(Pinner), 



CH 3 CN + C 2 H 5 OH + HC1 = CH 3 . 

Cl + NaOH = CH.C + NaCI + H,O. 



These imidoethers unite with ammonia and amines and form 
the amidines, 

CH 3 .C^g*? H5 + NH 3 = CH 8 .C^Jg a + C 2 H 5 OH. 

Acetamidine. 

4. The latter are also formed by the direct action of ammonia 
on the cyanide, 

CH 3 .CN + NH 3 = CH 



5. Hydroxylamine unites with the cyanides, forming amid- 
oximes, 

CH.CN + NHoOH = CH 



6. With H.jS the thiamides are formed, 

CH 3 .CN + H 2 S = CH 3 .CS.NH 2 . 

PREPARATION 14 

Mebhylamine Hydrochloride. This reaction, which 
yields the primary amine, is applicable, not only to the aliphatic, 
but also to the aromatic amides. The formation of anthranilicacid 
from phthalimide is a process of technical importance. By the 



/CONHo 


.CONHBr 


C 6 H 4 < ' + Br 2 
\COOH 


4 \COOH 


xCONHBr 


/NCO 


%rob& 


= C 6 H 4 < + 
V COOH 


/NCO 


xNH 2 


C 6 H 4 ( + H 2 


= Q H 4\ + 



246 PRACTICAL ORGANIC CHEMISTRY 

action of bromine and caustic potash, phthalaminic acid is first 
formed, which then yields the amino-acid, 

/CC\ ,CONH q 

C 6 H/ >NH + H 2 = C 6 H 4 < 

XXX \COOH 



HBr. 



HBr. 



C0 2 
COOH COOH 

The primary amines may also be obtained by the following 
reactions : 

1. Action of alcoholic ammonia on the alkyl iodides and 
nitrates, 

C 2 H 5 I + NH 3 = C 2 H 5 NH 2 + HI. (Hofmann.) 

Secondary and tertiary amines are also formed (see p. 156), 
C 2 H 5 ONO 2 + NH 3 = C 2 H 5 NH 2 + HNO 3 . (Wallach.) 

2. Reduction of the following chisses of compounds : 

nitro-com pounds 
cyanides 
oximes 
phenylhydrazones 

C 2 H 5 N0 2 + 3H 2 = C 2 H 5 NH, + 2H 2 O. (V. Meyer.) 
C 2 H 5 CN + 2lI 2 = C 2 H 5 CH 2 NH 2 . (Mendius.) 
CH 3 .CH:NOH + 2H 2 = CHg.CH.^NHa + H 2 O. (Goldschmidt.) 
CH 3 .CH:N.NHC 6 H 3 + 2H 2 = CH 3 .CH 2 .NH 2 + C 6 H 5 .NH 2 . (Tafel.) 

3. Hydrolysis of the isocyanides with cone. HC1, which occurs 
m two steps : 

C,H,NC + H O = C 2 H B NH.COH 
C 2 H 5 NH.COH + H 2 O = C 2 H 5 NH 2 + HCO.OH. 

The three classes of aliphatic amines (primary, secondary, and 
tertiary) may be distinguished by their behaviour with nitrous 



APPENDIX 247 



acid and alkyl iodide. The primary amine is decomposed with 
HNO 2 , forming the alcohol, and nitrogen is evolved, 

C 2 H 5 NH 2 + HNO 2 = C 2 H 5 OH + N 2 + H O. 

The secondary amine forms the nitrosamine, insoluble in water 
(CaHg^NH + HNO 2 = (C 2 H 5 ) 2 N.NO +H 2 O. 

Diethylnitrosamine. 

The tertiary amine is unacted on by nitrous acid, but, unlike 
the other two, unites with an alkyl iodide and forms the 
quaternary ammonium iodide (Hofmann), 

(C 2 H 5 ) 3 N + CH,I = (C,H,) ;! NCH 3 I. 

Triethylmethylammonium iodide. 

The behaviour of nitrous acid with the aromatic amines is 
somewhat different (See Preps. 60, p. 157, and 62, p. 161). 

The primary amines may also be distinguished from second- 
ary and tertiary amines by the isocyanide reaction (p. 150), which 
consists in heating the amine with a Itttle chloroform and alco- 
holic potash solution. An intolerable odour of isocyanide is 
emitted, 

CgHjNHa + CHC1 3 + sKOH = C 2 H 5 NC + sKCl + 3H 2 O. 



PREPARATION 15. 

Ethyl Acetate. Esters may be obtained by the direct action 
of the alcohol on the acid as in the case of methyl oxalate. 
(Prep 26, p. 101). A certain quantity of ethyl acetate is also 
obtained from ethyl alcohol and acetic acid,-but the action, which 
is a m>erstble one, stops when a certain proportion of the con- 
stituents have combined (p. 234). It is represented thus : 

C 2 H 3 OH + CH 3 .COOH^CH 3 .COOC 2 H K + H 2 O, 

which signifies that the ester and water react and regenerate 
alcohol and acid, whilst the reverse process is in operation. By 
removing the water as it is formed by means of sulphuric acid 
or by distillation, this condition of equilibrium is disturbed and 
the reaction is completed. This does not, however, explain the 
fact, first discovered by Scheele and afterwards investigated by 
Fischer and Speier (see Prep. 99, p. 209), that a very limited 
quantity of cone. 1 sulphuric or hydrochloric acid wiii produce 



248 PRACTICAL ORGANIC CHEMISTRY 

the same result. According to Henry the reaction with HC1 
takes place in several steps, 

CH 3 .COOH + C 2 H 5 OH = CH 3 C(OH) 2 OC 2 H 5 . 
CH 3 .C(OH) 2 OC 2 H 5 + HC1 = CH 3 C(OH)C1OC 2 H 5 + H 2 O. 
CH 3 .C(OH)C10C 2 H 5 - CH 3 .COOC 2 H S + HC1. 

Other methods for the preparation of esters are by the action of 
alcohol on the acid chloride or anhydride (see Reactions, p. 75), 
or by boiling up the dry powdered silver salt of the acid with the 
alkyl iodide, 

CH 3 .COOAg + C 2 H 5 i = CH 3 .COOC 2 H 5 + Agl. 

The esters are, for the most part, colourless liquids or solids of 
low m. p., with a fruity smell and insoluble in water. They are 
hydrolysed by potash (most readily with alcoholic potash) and 
give amides with ammonia, 

CH 3 .COOC 2 H 5 + NH, = CH 3 .CONH 2 + C 2 H 5 OH. 

Acetamide. 



PREPARATION 16. 

Ethyl Acetoacetate. The explanation of the manner in 
which this substance is produced has been given in the account 
of the preparation. The result was arrived at, not by the isola- 
tion of the intermediate compound formed by the union of 
ethyl acetate with sodium ethylate, but by analogy with the 
behaviour of benzoic methyl ester with sodium benzylate, which 
gave the same additive product as that obtained by combining 
benzoic benzyl ester with sodium methylate, showing that such 
combinations could occur, 

/ONa 
C 6 H 5 CfOCH 3 

\OCH 2 .C 6 H 5 

Also by the fact that sodium only attacks ethyl acetate in 
presence of ethyl alcohol, although the quantity of the latter 
may be very minute. Similar reactions have been effected 
with either metallic sodium or sodium ethylate by Claisen, 



APPENDIX 249 



\V. Wislicenus and others, of which the following examples 
must suffice ; 

C 6 H 5 COOC 2 H 5 + CH 3 .COOC 2 H 5 = C 6 H 5 CO.CH. 2 .COOC 2 H 5 

Benzoic ester. Acetic ester. Benzoylbenzoic ester. + C 2 H 5 OH. 

HCOOC 2 H 5 + CH 3 .COOC 2 H 5 = H.CO.CH 2 .COOC 2 H 5 

Formic ester. Acetic ester. Formylacetic ester. + C 2 H 5 OH. 

C 2 H 5 OCO.COOC 2 H, = CoH 5 OCO.CO.CHo.COOC 2 H 5 

Oxalic ester. + CH 3 .CpOC 2 II 5 Oxalylacetic ester. + C 2 H 5 OH. 

Acetic ester. 

From this it would appear that condensation might always bo 
effected between an ester on the one hand and a compound 
containing the group CH 2 .CO on the other. This seems very 
generally to be the case, and Claisen has succeeded in pro- 
ducing condensation products between esters and ketones or 
aldehydes containing this group. (See Prep. 100, p. 212.) 

The formula for ethyl acetoacetate would imply the properties 
of a ketone, a view which is borne out by its reduction to a 
hydroxy-acid, 

CH 3 .CHOH.CH 2 .COOC 2 H 5 , 

/3-Hydroxybutyric ester. 

and by its behaviour with phenylhydrazine and hydroxylamine. 
The latter reactions give rise to the formation of the usual 
phenylhydrazone and oxiine, whilst a molecule of alcohol is also 
removed resulting in a closed chain, in the former case phenyl- 
methylpyrazolone, and in the latter methylisoxazolone being 
formed, 

CH 3 .C.CH 2 .CO CH 3 .C.CH 2 .CO 

N N.C 6 H 5 N O 

Phenylmethylpyrazolone. Methylisoxazolone. 

The "methylene" group (CH 2 ) standing between two CO 
groups, such as occurs in acetoacetic ester, is characterised by 
certain properties, which are shared by all compounds of similar 
structure, viz., by their behaviour towards nitrous acid, diazo- 
benzene salts, and metallic sodium or sodium alcoholate. 

The first reaction leads to the formation of isonitrosoacetone, 

CH 3 .CO.CII 2 .COOC 2 H B + HN0 2 = CH 3 .CO.CH:NOII + CO 2 

+ C 2 H 5 OH. 



250 PRACTICAL ORGANIC CHEMISTRY 

The second yields, in acetic acid solution, for mazy I derivatives, 

CH 3 .CO.CH 2 .COOC 2 H 3 + C 6 H 5 N,C1 = CHj.CO.CHiN.NH.QH,; 
+ H 2 O + CO 2 + C 2 H 5 OH + HC1. 

CH 3 .CO.CH:N.NHC 6 H 5 + C 6 H 5 N 2 C1 



Acetyl diphenyl formazyl. 

The third is capable of the utmost variety, since the sodium 
in the sodium compound may be removed by the action of : 

1. Iodine, which leads to the formation of acetosuccinic 
ester, 

CH 3 . CO. CHNa. COOC 2 H 5 CH 3 . CO. CH. COOC 2 H 5 

+ I a = + 2NaI. 

CH 3 .CO.CHNa.COOC 2 H 5 CH 3 .CO.CH.COOC 2 H 5 

Acetosuccinic ester. 

2. Alkyl iodide, whereby two atoms of hydrogen may be 
successively replaced by the same or different radicals, 

CH 3 .CO.CHNa.COOC. 2 H 5 + CH 3 I = CH 3 .CO.CH(CH 3 )COOC 2 H 5 

+ Nal. 

CH 3 .CO.CNa(CH 3 ).COOC2H 5 + CH 3 I =CH 3 .CO.C(CH 3 ) 2 .COOC2H S 

+ Nal. 

3. Acid chloride, which is of similar character to the fore- 
going process, but gives rise in some cases to the simultaneous 
formation of two isomeric compounds, a fact which at one time 
threw considerable doubt on the ketonic character of aceto- 
acetic ester. Thus chloroformic ester and sodium acetoacetic 
ester produce the following two derivatives, of which the second 
predominates : 

CH 3 .CO.CH(C0 2 C 2 H 5 ) 2 . CH 3 . C(OCO 2 G 2 H 5 ):CH.CO 2 C 2 II 5 . 

Acetylmalonic esier. (3-Carboxethylacetoacetic ester. 

The synthetic capabilities of this compound are not yet 
'exhausted. Acetoacetic ester and its alkyl derivatives undergo 
decomposition in two ways, according to whether dilute 
alkalis and acids or, on the other hand, strong alkalis are 
employed. 



APPENDIX 



1. With dilute aqueous or alcoholic caustic alkalis, or baryta, 
or sulphuric acid, a ketone is formed (ketonic decomposition), 

CH 3 .CO.CH 2 .COOC 2 H 5 + H 2 O = CH 3 .CO.CH 3 + CO 2 + C 2 H 5 OH. 

2. Concentrated alcoholic potash decomposes the ester into 
two molecules of acid (acid decomposition), 

CH 3 .CO.CH 2 .COOC 2 H 5 + 2H 2 O = CH 3 .COOH + CH 3 .COOH 

+ C 2 H 5 OH. 

If the alkyl derivatives of the ester are employed, it is 
possible to effect the synthesis of a series of ketones and 
saturated aliphatic acids, according to whether the one or other 
reaction is used. 

Of the other synthetic processes which have been studied in 
connection with this substance, the following may be mentioned : 

I. The monoalkyl derivatives yield with nitrous acid the 
isonitroso-derivative, from which the ortho-diketone may be 
obtained (v. Pechmann), 

CH 3 .CO.CH(CH 3 ).COOC 2 H B + HNO. = CH 3 .CO.C:(NOH).CH 3 

+ C 2 H 5 OH + C0 2 



CH 3 .CO.C:(NOH).CH 3 



H 2 O = CH 3 .CO.CO.CH 3 

Diacetyl. 



NH 2 OH. 



These compounds readily condense, forming derivatives of 
quinone, 



CH 3 .C 


.CO 


CH H 2 CH 3 .C.CO.CH 

_ I! || 


HC 

2. Aldehyde 
derivatives (H 


H 2 .CO 


. C O .CH 3 CH.CO.C.CH 3 

Dimethyl quinone. - 

is and acetoacetic ester yield pyridine 
: NH 

L /\ 

CH 3 .C C.CH 3 . 

;l - || |; 
:C.CO.OC 2 H 5 C 2 H 5 O.CO.C C.CO.OC 2 H 5 


ammoni 

intzsch), 


1 H 
CH a .C| 

C 2 H 6 OCO.C| H 


Nil H 


HH H 




O 


\/ 
CH 


._. 

CH, 


CH 3 

Dihydrocollidinedicarboxylic ester. 



252 PRACTICAL ORGANIC CHEMISTRY 

3. Orthoformic ester and acetoacetic ester in presence of 
acetic anhydride form a hydroxymethylene ester (Claisen), 

CH 3 CH 3 

I I 

CO CO 

I I 

CIL, + HC(OC,H 5 ), = C:CH.OCoH 5 + 2C 2 H 5 OH. 
I I 

COOC 2 H 5 COOC 2 H 5 

4. The derivatives of acetosuccinic ester are very numerous 
the compound lending itself readily to the formation of hetero- 
cyclic compounds (pyrrole, furfurane, thiophene, pyridine, c., 
derivatives). 

The impartial way in which acetoacetic ester was found to 
behave, sometimes playing the part of a hydroxy-compound, 
sometimes that of a ketone, has led to much discussion on the 
merits of the formulae proposed by Geuther and Frankland, 

CH 3 .C(OH):CH.COOC 2 H S . CH 3 .CO.CH 2 .COOC 2 H 5 . 

Geuther's formula. Frankland's formula. 

From its physical properties and from its close analogy with 
compounds which are known in both desmotropic forms, there 
is now little doubt that the liquid is a mixture of both com- 
pounds, the proportion of each being determined by tempera- 
ture and other conditions. It is a typical example of tautomer- 
isw. 1 

PREPARATIONS 17 18. 

Moncchloracetic Acid and Monobromacetic Acid. 
The action of chlorine on the aliphatic acids takes place in 
presence of sunlight, also on the addition of small quantities of 
the "halogen-carriers," iodine, sulphur, and red phosphorus. By 
the action of iodine, IC1 is formed, which decomposes more readily 
than the molecule of chlorine, and hydriodic acid is liberated, 

CII 3 .COOH + IC1 = CH 3 C1.COOH + HI. 

The hydriodic acid is then decomposed by chlorine, and IC1 
regenerated. Phosphorus acts by forming the chloride of 
phosphorus from which the acid chloride is produced, which is 
more readily attacked by chlorine than the acid. Sulphur 
behaves in a similar fashion, sulphur chloride converting the 

1 For a full discussion of the subject of tautomerism, see the author's Organic 
Chemistry for Advanced Students, E. Arnold, London. 



APPENDIX 253 



acid into the acid chloride. Bromine in presence of phosphorus 
forms in the same way, first, the acid bromide, and in the 
second stage of the reaction, the bromine substitution product. 
The bromine in all cases attaches itself to the a-carbon (i.e., 
next the carboxyl). Where no free hydrogen exists in this 
position, as in trimethylacetic acid, no substitution occurs. 
Iodine can be introduced by the action of KI on the bromine 
derivative, 

CH 2 Br.COOH + KI = CH 2 I.COOH + KBr. 

Monohalogen derivatives may also be obtained from the 
unsaturated acids by the action of the hydracids (HC1, HBr, 
HI). In this case the halogen attaches itself to the carbon 
farthest from the carboxyl. Thus acrylic acid gives with HBr 
the -bromopropionic acid, 

CH 2 :CH.CO.OH + HBr = CH 2 Br.CH 2 .COOH. 

The action of the hydracids, PC1 5 andPBr 5 , on the hydroxy- 
acids also yields the halogen derivatives, 

CH 3 .CH(OH).COOH + HBr. = CH 3 .CHBr.COOH + H 2 O. 

CH 3 .CH(OH).COOH + 2PC1 5 = CH 3 .CHC1.COC1 + 2POC1 3 

+ 2HC1. 

In the latter case the acid chloride must be subsequently 
decomposed by water to obtain the acid. 

The increase in the number of halogen atoms in the acid 
raises the boiling point as well as the strength of the acid as 
determined by its dissociation constant K. 

B.P. K. 

Acetic acid 118 '0018 

Monochloracetic acid . . . 185 '155 

Dichloracetic acid 190 5-14 

Trichloracetic acid .... 195 121 

Some of the transformations of monohalogen acids are 
illustrated by the following equations : 

CH 2 C1.COOH + H 2 O = CHoOH.COOH + HCU 
CHoCl.COOH + KCN = CH^CN.COOH + KC1 ^ 
CII 2 C1.COOH + 2NH 3 = CH 2 NH 2 .COOH + NH 4 C1. 

CHo.COOH 
2CH 2 Br.COOH + Ag 2 = + 2AgBr 

CH 2 .COOH 
CH a I.CH Q COOH -f KOH = CH 2 :CH.COOH + KI + K 2 G. 



254 



PREPARATIONS 19 20. 

Glycocoll. By the action of primary and secondary amines, 
corresponding amino-acids are formed. Chloracetic acid and 
methylamine yield sarcosine, 

xCl /NHCHj 

CH 2 + NH 2 CH 3 = CH 2 + HC1. 

\COOH SCOOH 

The amino-acids are further obtained by the reduction 
(Zn and HC1) of nitro-, oximino- and cyano-acids, thus : 
CH 2 (NO 2 ).COOH + 3H 2 = CH 2 (NH 2 )COOH + 2H 2 O, 
CH 3 .C(NOH).COOH + 2lI 2 = CH 3 .CH(NH 2 ).COOH + H.,O, 
CN.COOH + 2H 2 = CH 2 (NH 2 ).COOH, 

and by the action of NH 3 on the cyanhydrin of aldehydes and 
ketones, or simply of ammonium cyanide. The product is then 
hydrolysed with HC1, 

HCN / CN NH 3 / CN H,0 

CH 3 .COH -> CII 3 .CH -> CII 3 .CH -> CH 3 .CH 



The amino-acids are crystalline compounds usually of a sweet 
taste and soluble in water. They are neutral compounds, from 
which it may be assumed that an inner ammonium salt is 
formed 



CH . 

x 2 \ 

x coo 

By the action of an acid chloride on the ami no-acid, the hydro- 
gen of the amino-group may be replaced by an acid radical. 
Hippuric acid has been synthesised in this way. 
sNH 2 /NH.CO.C 6 H 5 

CH 2 + C 6 H 5 COC1 = CH 2 + HC1 . 

\TOOH ^COOH 

The amino-acids are not acted on by a hot solution of caustic 
alkali, but on fusion with caustic soda or potash, yield the 

amine and CO.,, 

/NH 2 

CH 3 .CH = CH 3 .CH 2 .NH 2 + CO 2 . 



APPENDIX 



With nitrous acid the hydroxy-acid is formed, 
/NH 2 /OH 

CH 2 + HNO, = CH 2 + N 2 + H 2 O. 

\:OOH \IOOH 

PREPARATION 21. 

Diazoacetic Ester. The primary amines of the aliphatic 
series differ from those of the aromatic group in the fact that the 
former yield no diazo-compounds with nitrous acid. It is other- 
wise with the amino-esters, the ester group probably furnish- 
ing the acid character (represented by the nucleus in the aromatic 
series) necessary to give stability to the compound. It should 
be pointed out that the two classes of compounds have not an 
identical structure. The formation of diazoacetic ester from 
pyruvic ester and hydrazine and subsequent oxidation with mer- 
curic oxide indicates that both nitrogen atoms are attached to 
carbon, 

CH 3X CH 3X /NH 

>CO + NH 2 .NH 2 -> >C< | -> 

CH 3 O.CO/ CH 3 O.CO/ \NH 

,N 



CHgCXCCK 

In addition to the reactions described in the preparation 
diazoacetic ester unites with unsaturated acids and forms cyclic 
compounds. Fumaric ester, for example, combines in the 
following way : 

,N N 

^ H \& + ( ji H - COOR -> RO.OC.HC/'V -> 

COOR CH.COOR RO.OC.HCL J C H.COOR 

RO.CO.CH 

+ N 2 . 
RO.CO.CH CH.COOR 

When bisdiazoacetic ester is heated with water or dilute acid 
it breaks up into hydrazine and oxalic acid, 

/N=Nv COOH 

HOOC.CH< >CH.COOH + 4H 2 O = 2 | + 2NH 2 .NH,. 

N N=N/ COOH 



*5& PRACTICAL ORGANIC CHEMISTRY 

PREPARATION 22 23. 

Ethylmalonic Acid. Like acetoacetic ester (see p. 83), 
diethylmalonate contains the group CO.CH 2 .CO. By the 
action of sodium or sodium alcoholate, the hydrogen atoms of 
the methylene group are successively replaceable by sodium. 
The sodium atoms are in turn replaceable by alkyl or acyl 
groups. Thus, in the present preparation, ethyl malonic ester 
is obtained by the action of ethyl iodide on the monosodium 
compound. If this substance be treated with a second mole- 
cule of sodium alcoholate and a second molecule of alkyl iodide, 
a second radical would be introduced, and a compound formed 
of the general formula 

X \ 
r /C(CO 2 C 2 H 5 ) 2 , 

in which X and Y denote the same or different radicals. 

These compounds yield, on hydrolysis, the free acids, which, 
like all acids containing two carboxyl groups attached to the 
same carbon atom, lose CO 2 on heating. Thus, ethyl malonic 
acid yields butyric acid. In this way the synthesis of mono- 
basic acids may be readily effected. Malonic ester, moreover, 
may be used in the preparation of cyclic compounds as well as 
of tetrabasic and also dibasic acids of the malonic acid series 
(Perkin). To give one illustration : malonic ester, and ethylene 
bromide in presence of sodium alcoholate, yield trimethylene 
dicarboxylic ester and tetramethylene tetracarboxylic ester. The 
first reaction takes place in two steps, 
CHNa(COOC 2 H 5 ). 2 + C 2 H 4 Br 2 = CH 2 Br.CH 2 .CH(COOC 2 H 5 ) 2 + NaBr. 

CHNa(COOC 2 H,) 2 + CH 2 BrCH 2 CH(COOC 2 H 5 ) 
CH 2 , 

>C(COOC 2 H 5 ), + NaBr + CH 2 (COOC 2 H 5 ) 2 . 
CH/ 

In the second step a second molecule of sodium malonic ester- 
exchanges its sodium with the substituted malonic ester and a 
second molecule of NaBr is then removed. 

The formation of the tetracarboxylic ester occurs simultane- 
ously, 

2CHNa(COOC H,)o + G>H 4 Br 

= (COOC 2 H 5 ). i CH.CH 2 .CH 2 .CH(COOC. ! H 5 ). 2 + 2NaBr 



APPENDIX 257 



The free acid derived from the ester by hydrolysis loses two 
molecules of CO 2 on heating, and gives adipic acid, 

(COOH) 2 CH.CH 2 .CH2.CH(COOH) 2 

= COOH.CH 2 .CH 2 .CH2.CH 2 .COOH + 2CO 2 . 

Cyanacetic ester has similar properties to malonic ester, inas- 
much as the methylene hydrogen is replaceable by sodium and 
thus by alkyl groups. 

CN CN CN 

CH, -> CHNa > CHX 

I I I 

COOC 2 H 5 COOC 2 H 5 COOC 2 H 6 

PREPARATION 24. 

Trichloracetic Acid. This acid may also be obtained by 
direct substitution of acetic acid by chlorine (Dumas) (see Prep. 
17, p. 87). The oxidation of the corresponding aldehyde is, 
however, the more convenient method. Trichloracetic acid 
decomposes with alkalis on heating into carbon dioxide and 
chloroform, 

CC1 3 .COOH = CHC1 3 + COa. 

The reaction resembles the formation of methane from sodium 
acetate when heated with soda-lime. 

On reduction with sodium or potassium amalgam, trichlor- 
acetic acid is converted into acetic acid (Melsens), 

CC1 3 .COOH + 3H 2 = CH 3 .COOH + slid. 

Dichloracetic acid may also be obtained from chloral by the 
action of potassium cyanide and water, 

CC1 3 COH + H 2 O + KCN = CHC1 2 .COOH + KC1 + HCN. 
Whereas mono- and tri-chloracetic acid are solid, dichloracetic 
acid is a liquid at the ordinary temperature. 

PREPARATION 25. 

Oxalic Acid. The preparation of oxalic acid by the action 
of nitric acid on sugar was introduced by Scheele, and was used 
for some time as a technical process. Thfe vanadium pent- 
oxide acts as carrier of oxygen, being alternately reduced to 
tetroxide and re-oxidised. The present commercial method is 
to heat sawdust with a mixture of caustic potash and soda on 

COHEN'S ADV. p. o. c. 



258 PRACTICAL ORGANIC CHEMISTRY 

iron plates to 200 220, and to lixiviate the product with water. 
The acid is precipitated as the calcium salt, which is then decom- 
posed with sulphuric acid. 

PREPARATION 27. 

Glyoxylic and Glycollic Acids. The process of electro- 
lytic reduction has been applied successfully to a large number 
of organic compounds, and has not only been found to have 
definite practical advantages in many cases over other methods, 
but, on account of the ease with which it may be controlled, has 
elucidated the various stages in the mechanism of some of the 
more complex changes. The reduction of nitro-compounds is 
illustrated in Preps. 49 and 50. The reduction of organic acids, 
ketones and carbonyl compounds generally has been developed 
by Tafel and others, and in these cases it is found advantageous 
to use a mercury or lead electrode. An essential feature of the 
process is a clean metallic surface at the cathode and the absence 
of foreign metallic impurities. The reduction of the carbonyl 
group proceeds in three steps : 

>CO + 2H = C(OH) - C(OH) 
>CO + 2H = >CHOH 
>CO + 4 H= >CH 2 + H,0. 

PREPARATION 28. 

Palmitic Acid. This acid, together with stearicand oleic 
acids, in the form of the glycerides, are the chief constituents of 
fats. Palmitin (glyceride of palmitic acid) is also found in 
certain vegetable oils like palm and olive oil. The acid occurs 
also as the cetyl ester in spermaceti and as the myricyl ester 
in bees-wax. It may be obtained from oleic acid by fusion 
with potash, 

Cis H 342 + 5 + 5 K OH = C 16 H 31 O 2 K + 2K 2 CO 3 + 4H 2 O. 
In the analysis of oils and fats, where the quantity of fatty acid 
is the chief object of the determination, it is customary to 
hydrolyse the substance with a standard solution of alcoholic 
potash in place of aqueous potash, and to estimate the excess 



APPENDIX 259 



of free alkali with standard acid, using phenolphthalein as 
indicator. The difference gives the amount of alkali neutralised 
by the fatty acid (see p. 210). 

PREPARATION 29. 

Formic Acid. In addition to the method described, the 
acid is formed in the decomposition of chloral (see p. 9), 
chloroform (see Prep. 8, p. 71), by the action of cone. HC1 on 
the isocyanides, 

C 2 H 5 NC + 2H 2 O = C 2 H 5 NH 2 + HCO.OH, 

by the decomposition of aqueous hydrocyanic acid, which yields 
the ammonium salt, 

HCN + 2H 2 O = HCOONH 4 , 

and by the oxidation of methyl alcohol with potassium bichrom- 
ate and sulphuric acid. It is present in the sting of ants and 
nettles, and is also occasionally found among the products of 
bacterial fermentation of polyhydric alcohols and carbohydrates. 
The commercial method is to act on solid NaOH with CO 
under pressure and at a temperature of about 100 : 

CO + NaOH = HCOONa. 

The calcium salt is used in the preparation of aldehydes by 
heating it with the calcium salt of a higher aliphatic acid, 

(HCOO) 2 Ca + (CH 3 .COO) 2 Ca = 2CH 3 CO.H + 2CaCO 3 . 

The reducing action of formic acid and formates on metallic 
salts may be ascribed to the presence of the aldehyde group 
(OH)CH:O in the acid. 

PREPARATION 30. 

Allyi Alcohol. Note the difference produced by the 
change in the relative quantities of glycerol and oxalic acid, 
and the temperature at which the reaction is brought about. 
In the case of formic acid, it is the oxalic acid alone which 
undergoes decomposition, and theoretically a small quantity of 
glycerol will effect the decomposition of an unlimited amount 
of oxalic acid. But at the higher temperature it is the glycerol 
which yields the main product. Allyl alcohol being an un- 

S 2 



2bo PRACTICAL ORGANIC CHEMISTRY 

saturated compound, forms additive compounds with halogens 
and halogen acids. With permanganate solution it may be 
converted into glycerol, 

CH 2 :CH.CH 2 OH + H- 2 O + O = CH 2 OH.CHOH.CH 2 OH. 

On oxidation with silver oxide it yields the corresponding alde- 
hyde (acrolein) and the acid (acrylic acid). 

PREPARATION 31 

Isopropyl Iodide. The replacement of hydroxyl by iodine 
in the action of phosphorus and iodine on alcohols has already 
been described (see Prep. 6, p. 68), but here the presence of an 
excess of hydriodic acid, which is due to the action of water on 
the phosphorus iodide, 

PI, + 3H 2 = P(OH) 3 + 3HI, 

exerts in addition a reducing action on certain of the hydroxyl 
groups. By diminishing the proportion of phosphorus and 
iodine to glycerol, the reaction may be interrupted at an earlier 
stage, when allyl iodide is formed. This is probably due to the 
splitting off of iodine from propenyl tri-iodide, 

CH 2 I.CHI.CH 2 I = CH 2 :CH.CH 2 I + I 2 . 

On the other hand a larger proportion of phosphorus and iodine 
or cone, hydriodic acid will reduce allyl iodide to propylene, 

CH 2 :CH.CH 2 I + HI = CH 2 :CH.CH 3 + I 2 . 

The action of hydriodic acid on glycerol is typical of the 
polyhydric alcohols. Hydriodic acid converts erythritol into 
secondary butyl iodide, and mannitol into secondary hexyl 
iodide. The normal iodides are never formed. 

PREPARATION 32. 

Epichlorhydrin. It is a noteworthy fact that although 
hydrochloric acid can replace hydroxyl by chlorine in the case 
of the monohydric alcohols, the number of hydroxyl groups which 
are substituted in the case of polyhydric alcohols is strictly 
limited. Like glycerol, ethylene glycol gives a chlorhydrin, 
CH 2 OH.CH 2 OH + HC1 = CH 2 OH.CH 2 C1 + H 2 O. 



APPENDIX 261 



The remaining hydroxyls can always be replaced by chlorine 
by the action of PC1 5 . The chlorhydrins may also be obtained 
by the action of HOC1 on the olefines. It is a general property 
of these compounds to form the oxide when heated with caustic 
alkalis. Ethylene chlorhydrin gives ethylene oxide in this way, 

CH 2 C1.CH 2 OH + NaOH = CH 2 .CH 2 + NaCl + H 2 O. 

O 

Compounds like ethylene oxide and epichlorhydrin may be 
regarded as inner ethers, 

/CH 2 CH 3 

X CH 2 \CH 3 

Ethylene oxide. Dimethyl ether. 

These oxides are easily decomposed. With water, ethylene oxide 
forms glycol; with hydrochloric acid, the chlorhydrin; with hydro- 
cyanic acid, the cyanhydrin. Epichlorhydrin behaves similarly. 



PREPARATION 33. 

Succinic Acid. Tartaric acid, like malic acid, is converted 
into succinic acid on reduction with HI, and the relationship of 
these three acids is thereby established. The constitution of 
succinic acid itself has been determined by its synthesis from 
ethylene (Maxwell Simpson). Ethylene unites with bromine, 
forming ethylene bromide, which yields ethylene cyanide with 
potassium cyanide. The latter is then hydrolysed. 

CH 2 CH 2 Br CH 2 CN CH 2 .COOH 

CH 2 CH 2 Br CH-jCN CH 2 .COOH 

It is an interesting fact, not yet fully explained, that the 
alkyl succinic acids give anhydrides more readily than succinic 
acid, and the greater the number of alkyl groups, the more 
readily is the anhydride produced. Thus the anhydride of 
tetramethyl succinic acid is so stable that it is not decomposed 
by water. 

The symmetrical dialkyl succinic acids exist in two foVms, 
each yielding a separate anhydride. From their similarity to 



PRACTICAL ORGANIC CHEMISTRY 



the anhydrides of hexahydrophthalic acid, they are distinguished 
as cis- and trans-compounds (see Notes on Prep. 37, p. 265). 

CH 3 CH 2 

H 2 C CII.CO 



CH.CO 
\ 

/ 
CK.CO 



CH 3 

Dimethylsuccinic 
anhydride. 



\ 



O 



H 2 C CH.CO 



CH 2 

Hexahydrophthalic 
anhydride. 



PREPARATION 34. 

Ethyl Tartrate. The speculations of Pasteur (1860) on the 
cause of the optical activity and hemihedry of tartaric acid and 
its salts, and of Wislicenus (1873) on the existence of three 
lactic acids, have developed in the hands of Van't Hoff and 
Le Bel (1874) into the present theory of stereo-chemistry or 
atomic space arrangement. Optical activity is found to be in- 
variably associated with the presence in the substance of an 
asymmetric carbon atom, i.e. one linked to four different groups. 
Now every asymmetric (unsymmetrical) object like a hand or 
foot has its fellow ; but the two do not precisely overlap, and 
every substance containing an asymmetric carbon atom, round 
which the four groups are distributed, not, as usually repre- 
sented, in one plane, but in space of three dimensions, is 
capable of existing in two forms, which correspond to a left and 
right hand, or to an object and its reflected image. 

This is represented by making the carbon atom the centre of 
a tetrahedron and attaching the four different groups to the 





B 



B 



four solid angles. The two forms will then appear as in the 
Fig., in which ABCD represent four different groups. When 



APPENDIX 263 



using actual models, it will be found that they cannot be turned 
so as to coincide until two of the groups in one model have been 
interchanged. 

The main difference between two such substances lies in their 
action on polarised light, the one turning it to the right (dextro- 
rotatory) and the other to the left (laevo-rotatory), when in the 
liquid or dissolved state. Although every optically active sub- 
stance contains at least one asymmetric carbon atom like amyl 
alcohol and malic acid, or two like tartaric acid (the asymmetric 
carbon is represented in heavy type), 

H 
CH 3 CH^COOH | 

IIO C COOH 
C.H 5 C H HO C H 

HO c coon 

CH 2 OH COOH 

H 

Active amyl alcohol. Malic acid. Tartaric acid. 

the converse does not always hold ; for there are many com- 
pounds which possess an asymmetric carbon atom and show no 
rotation. The cause of this may be, either that the substance is 
a mixture of equal quantities of the two forms, which by having 
opposite rotations neutralise each other's effect as in the case of 
racemic acid, which consists of equal quantities of dextro- and 
laevo-tartaric acid and produces what is termed " external com- 
pensation," or the two similar asymmetric carbon atoms exist 
within the same molecule and neutralise each other's effect by 
" internal compensation," as in the case of mesotartaric acid. 
External compensation is generally exhibited by artificially 
prepared compounds as distinguished from natural products. 
Thus, glyceric acid from glycerol is inactive, though it contains 
an asymmetric carbon atom, 

CH 2 OH * 

H C OH , 
COOH 

because it consists of a mixture of dextro- and laevo-glyceric 
acid in equal quantities, whereas tartaric acid, which occurs in 
grapes, malic acid, which is obtained from mountain ash berries, 
and also the sugars, terpenes, alkaloids, and a number of other 



264 



natural products are all active. One of the great achievements 
of Pasteur in this line of research was the separation of inactive 
''externally compensated" compounds into their active com- 
ponents or " optical antipodes " or " enantiomorphs." One 
method of separation is described in Prep. 35. For details of 
other methods a book on stereo-chemistry must be consulted. 

On the formation of ethyl tartrate, see notes on Prep. 15, p 247. 
Ethyl tartrate may also be obtained by the method described 
in Prep. 99, which rather curtails the operation and does not 
necessitate the use of more than half the quantity of ethyl 
alcohol required by the earlier process. 

PREPARATION 35. 

Racemic and Mesotartaric Acids. These two acids 
represent two inactive types of compounds containing asymmetric 
carbon atoms (see above). Apart from certain well-marked 
differences in physical properties they also differ in one 
important feature ; racemic acid can be resolved into its optical 
enantiomorphs, whereas mesotartaric acid cannot. The latter 
belongs to. what is termed the inactive indivisible type. If we 
examine the structural formula of tartaric acid it will be seen 
that it possesses two asymmetric carbon atoms, denoted in the 
formula by thick type. 

H 

HO C COOH 
HO C COOH 
H 

Each asymmetric carbon atom is attached to similar groups. 
Let us suppose that each asymmetric carbon with its associated 
groups produces a certain rotation in a given direction. We 
mayimagine the following combinations of two similarasymmetric 
groups. Both produce dextro-rotation, or both produce laevo-ro- 
tation. They will represent the dextro and laevoenantiomorphs, and 
the mixture of the two will produce inactive racemic acid. Racemic 
acid is said to be inactive by external compensation. Suppose, 
finally, that the two asymmetric groups produce rotation in 
opposite directions. They will neutralise one another. The 



APPENDIX 265 



resulting compound will be inactive by internal compensation. 
Such a compound cannot be resolved by any process into its 
active components. The above compounds may be represented 
by the following projection formulae, in which the groups must 
be assumed to occupy three-dimensional space (the asymmetric 
carbon atoms being denoted by cross-lines), 

COOH COOH COOH 



OH 


H 


H 


OH 


H 


OH - 


OH 


H 


COOH 

d. Tartaric acid. 


COOH 

/. Tartaric acid. 

^ 



II- 

H 



O 
OH 



COOH 



Racemic acid. Mesotartaric acid. 

The conversion of active tartaric acid into the inactive forms 
is known as racemisation, and according to Winther is effected 
by the interchange of the groups round each asymmetric carbon 
atom successively so that part of the active acid is first con- 
verted into mesotartaric acid, which then passes into the laevo 
variety. 

PREPARATION 37. 

Citraconic and Mesaconic Acid. The theory of Le Bel 
and Van't Hoff has been extended to unsaturated compounds 
like fumaric and maleic and the above two acids, which form 
isomeric pairs. These two pairs of acids bear a close resemblance. 
It has already been observed in the course of the preparation 
that citraconic is readily converted into mesaconic acid. More- 
over, they both yield pyrotartaric acid, on reduction, but only one, 
citraconic acid, forms an anhydride. Maleic acid in the same 
way is easily converted into fumaric acid by bromine, both 
maleic and fumaric acid yield succinic acid on reduction, but 
only maleic acid forms an anhydride. The explanation is as 
follows : in each pair of compounds there exists two carbon 
atoms linked to one another by a double bond and each attached 
to two different groups. Van't Hoff refers the isomerism of each 
pair to a space arrangement, which may be represented by 
supposing two tetrahedra to be joined by a common edge. 
As the centre of each tetrahedron is occupied by a carbon atom, 



266 



PRACTICAL ORGANIC CHEMISTRY 



and the four bonds are directed towards the four corners of 
the tetrahedron, this space arrangement will correspond to a 
doubly-linked carbon. If the two spare corners of each tetra- 
hedron are now occupied by different groups, it is possible to 





B 



produce two forms by transposing one pair of groups. Suppos- 
ing A and B to represent two different groups, the above forms 
will result. 

The two pairs of acids will be represented as follows : 



HO-CO 



CO-OH HO-CO 





H CO-OH 

Fumaric acid. 



H CO-OH 

Maleic acid. 




CH, 



CO-OH 



H CO-OH 

Mesaconic acid. 




H CO-OH 

Citraconic acid. 



Isomerism in this case is not characterised by optical activity, 
as the groups lie in one plane and no structural asymmetry is 
possible ; but is exhibited by such physical differences as solu- 
bility, melting-point, electrical conductivity, and by the fact that 
in the case of dibasic acids only one of the pair yields an anhy- 
dride. Maleic and citraconic acid form anhydrides, but fumaric 
and mesaconic acid do not. In the case of the acids which form 
anhydrides, the carboxyl groups are supposed to be nearer 
together, i.e. on the same side (cis) of the molecule, in the other 
case on opposite sides (trans) of the molecule. Maleic and 
citraconic are " cis " acids, fumaric and mesaconic are " trans " 



APPENDIX 267 



acids. The following table gives the various physical proper- 
ties, solubility, melting-point, and dissociation constant K of the 
two pairs of acids. 



Maleic . ... 


s. 
very soluble. 


M.P. 

130 


K. 
I-I7 


Fumaric .... 
Citraconic . . . 
Mesaconic . . . 


much less soluble, 
very soluble, 
much less soluble. 


sublimes at 200 
80 
202 


093 
340 
079 



PREPARATION 38. 

Urea. In addition to the method described in the prepara- 
tion, urea may be obtained by the oxidation of anhydrous 
potassium ferrocyanide with potassium bichromate (Williams), 
or manganese dioxide at a red heat, or by the action of per- 
manganate on a cold solution of potassium cyanide (Volhard). 
It has been synthesised by the action of ammonia on (i) phos- 
gene, (2) urethane, (3) chloroformic ester, and (4) ethyl carbonate. 

I. COC1 2 + 4NH 3 = NH 2 .CO.NH 2 + 2NH 4 C1. 

1 2. NH 2 .COOC 2 H 5 + NH 3 = NH 2 .CO.NH 2 + C 2 H 6 OH. 

3. C1COOC 2 H 5 + 3NH 8 = NH 2 .CO.NH 2 + C 2 H S OH + NH 4 C1. 

4. CO(OC 8 H 5 ) 2 + 2NH 3 = NH 2 .CO.NH 2 + 2C 2 H S OH. 

also (5) by the action of dilute acid on cyanamide, and (6) by 
heating guanidine with dilute sulphuric acid or baryta. 

5. CNNH 2 + H 2 O = NH 2 .CO.NH 2 . 

' 6. ~ NH : C(NH 8 ) 2 + H 2 O = NH 2 .CO.NH 2 + NH 3 . 

The synthesis of urea by Wohler in 1828 is usually regarded 
as a turning-point in the history of organic chemistry, when 
organic compounds ceased to be merely products of a vital force, 
associated with living animals and plants. They new assumed 
for the first time an independent role as substances capable of 
synthesis by ordinary chemical means. In point of fact this is 
not strictly true, for Scheele had prepared oxalic acid, only 
previously known in wood sorrel and other plants, from cane 
sugar, and Dobereiner had obtained the formic acid of ants by 
the oxidation of tartaric acid. The formation of urea offers an 
interesting example of intramolecular change of which many 
cases are now known. See the formation of benzidine from 



268 PRACTICAL ORGANIC CHEMISTRY 

hydrazobenzene (Prep. 51, p. 148) and aminoazobenzene from 
diazoaminobenzene (Prep. 70, p. 172). 

PREPARATION 39. 

Thiocarbamide. This is an example of a reversible 
reaction, in which either ammonium-thiocyanate or thiourea 
when heated yields the same equilibrium mixture. It may be 
shown by melting a little thiourea for a minute, when the 
presence of thiocyanate is indicated by the addition of FeCl 3 . 

PREPARATION 41. 

Alloxan. The decomposition of uric acid into alloxan and 
area renders the constitution of alloxan of value in elucidating 
the structure of uric acid. The constitution is derived from the 
following facts : Alloxan is decomposed with caustic soda or 
potash into mesoxalic acid and urea, and with hydroxylamine it 
combines to form violuric acid, which points to the presence of 
a ketone group (Baeyer). Barbituric acid and nitrous acid 
also give violuric acid, and seeing that barbituric acid has 
been synthesised from malonic acid and urea by the action of 
phosphorus oxychloride (Grimaux), it is unquestionably malonyl 
urea. The relationship of these substances must therefore be 
represented as follows : 

NH CO NH CO NH CO 

II I II 

CO CO CO C:NOH CO CH 2 

II II II 

NH CO NH CO NH CO 

Alloxan. Violuric acid. Barbituric acid. 

A renewed interest attaches to alloxan since E. Fischer's dis- 
covery of the new synthesis of uric acid. The steps in the 
synthesis are briefly the following. Alloxan and ammonium 
sulphite form thionuric acid, which is decomposed by hydro- 
chloric or sulphuric acid into uramil. 

NH CO NH CO NH CO 

I I I /NH 2 

tO CO -> CO C< > CO CH.NH a 

I I I X S0 3 H | 

NH CO NH CO NH CO 

Alloxan. Thionuric acid Uramil. 



APPENDIX 269 



Uramil and potassium cyanate unite to form potassium pseudo- 
urate, 

NH CO NH CO 

II I I 

CO CHNH 2 + OC.NK = CO CH.NH.CO.NHK. 

II II 

NH CO NH CO 

Potassium pseudourate. 

When free pseudouric acid is heated with 20 per cent, hydro- 
chloric acid it yields uric acid, 

NH-CO NH CO 

II II 

CO CH.NH.CO.NH 2 = CO C NH\ 

|| | || >CO + H 2 0. 

NH CO NH C NH/ 

Pseudouric acid. Uric acid. 

Other synthetic methods are also known for which a book of 
reference must be consulted. 

PREPARATION 42. 

Caffeine. The close relationship existing between uric acid 
and caffeine has long suggested the possibility of converting uric 
acid, a comparatively plentiful material, into caffeine, an important 
and costly drug, occurring only in small quantities in tea and 
coffee. The problem has been solved by E. Fischer, who has 
succeeded in synthesizing caffeine in a variety of ways. Fischer 
found that by using the same series of processes as described 
above in the synthesis of uric acid, but substituting dimethyl- 
alloxan for alloxan, and methylamine^ sulphite for ammonium 
sulphite, trimethyl uric acid is formed, and is identical with 
hydroxycaffeine, 

CH 3 N CO 

I I 

CO C N(CH 3 ) 

\CO 



CH 3 N C Nil 

Trimethyl uric acid (Hydroxycaffeine). 



Hydroxycaffeine is converted into caffeine by acting upon it 
with a mixture of phosphorus pentachloride and oxychloride. 



270 



PRACTICAL ORGANIC CHEMISTRY 



This forms chlorocaffeine, which is then reduced with hydriodic 
acid to caffeine, 



CH 3 N - CO 

i I I 

CO C-N(CH 3 ) 



-/ 

CH 3 N - C N 

Chlorocaffeine. 



CH 3 N - CO 

CO C N(CH 3 ) 



CH 3 N - C N 

Caffeine. 



The same result may be obtained in a simpler way by 
nethylating uric acid, and converting it into trimethyluric acid 
and then into caffeine ; or by preparing the mono- and di-methyl 
derivatives of uric acid, reducing these to the corresponding 
mono- and di-methylxanthines and introducing additional 
methyl groups into the product. 



PREPARATION 44. 

Tyrosine, Leucine. It has long been known that mineral 
acids and alkalis possess the property of breaking up albuminoid 
substances and resolving them into the simpler amino-acids. 
The recent introduction by Fischer of a method of separating 
the amino-acids by converting them into volatile esters followed 
by fractional distillation in vacua has led to the recognition of the 
wide distribution of such acids as alanine, serine, and phenyl- 
alanine, and to the discovery of two cyclic acids, pyrrolidine- 
carboxylic acid and hydroxypyrrolidine carboxylic acid. The 
following is a list of amino-acids from albuminoid substances 
which have been separated by fractional distillation of their 
esters under reduced pressure : 



Ethyl ester. 


b. p. 


Pressure in mm. 


Glycocoll 


si'i 52'!; 


IO 


Alanine 
Aminoisovaleric acid . . 
Leucine 
Aspartic acid 
Glutamic acid 
Phenvlalanine . 


48-5 
63-5 
83-5 
126-5 
139140 
uV 


10 
8 
12 
II 
10 

M 



APPENDIX 271 

PREPARATION 45. 

Grape-sugar. Although grape-sugar yields neither a bi- 
sulphite compound nor gives SchifPs reaction under ordinary 
conditions, its properties are for the most part those of an 
aldehyde. In addition to its reducing action on copper and 
silver salts, and its combination with phenylhydrazine, it forms 
an oxime with hydroxylamine and a cyanhydrin with hydro- 
cyanic acid. On reduction it gives the hexahydric alcohol 
sorbitol, and, on oxidation, the corresponding monobasic acid, 
gluconic acid, and the dibasic acid, saccharic acid, 

CH 2 OH(CHOH) 4 COOH. COOH(CHOH) 4 COOH. 

Gluconic acid. Saccharic acid. 

The presence of five hydroxyl groups in glucose is determined 
by the existence of a pentacetyl derivative. These and other 
facts, which cannot be discussed in detail, have led to the adop- 
tion of the present formula. The discovery of the optical 
antipode >f grape-sugar (which is dextro-rotatory) has deter- 
mined the present name of dextro-glucose to distinguish it from 
laevo-glucose, which is laevo-rotatory. For the synthesis of 
these two sugars and the other mono-saccharoses, a text-book 
must be consulted. 

The other common sugars, which reduce alkaline copper 
sulphate, are fructose (laevulose), galactose, maltose and milk- 
sugar, the two latter being disaccharoses. They are most 
readily identified by the microscopic appearance and melting- 
point of their phenylosazones. Cane-sugar is readily dis- 
tinguished from the majority of the common sugars by its 
indifference towards alkaline copper sulphate, until previously 
boiled with a few drops of dilute sulphuric acid. It is then 
inverted and gives the reactions for glucose and fructose. 

PREPARATION 46. 

Bromobenzene. -The replacement of hydrogen by the 
halogens Cl and Br, in the nucleus of aromatic hydrocarbons, is 
assisted by the presence of a " halogen carrier," the action of 
which has been referred to in the Note on the preparations of 
chlor- and brom-acetic acids, p. 252. Iodine, iron, iron and 
aluminium chlorides and bromides, the aluminium-mercury 



272 



couple, and pyridine all behave in this way. The action of 
iodine has already been explained on p. 252. Iron and its salts 
are supposed to act by alternately passing from the ferrous to 
the ferric state, the ferric salt delivering up its halogen in the 
nascent state, 

2FeBr 2 + Br 2 = 2FeBr 3 . 
FeBr 3 = FeBr 2 + Br. 

The action of aluminium and its compounds is not fully under- 
stood. Pyridine probably acts by the intermediate formation of 
the perbromide, as explained. 

Unless a large excess of the hydrocarbon is present, the 
action of the halogen will effect the substitution of a second 
atom of hyrogen. By increasing the proportion of halogen, 
all the hydrogen may be ultimately replaced by chlorine or 
bromine. The second halogen atom enters the ortho- and para- 
positions, never the meta. Another kind of compound is 
obtained if the halogen is allowed to act in presence of sun- 
light. In the case of benzene, the additive compounds, benzene 
hexachloride and hexabromide, are then formed. They are very 
unstable compounds, and readily give off hydrochloric and 
hydrobromic acid. If boiled with alcoholic potash they are de- 
composed, forming trichloro- and tribromo-benzene, 

C 6 H 6 C1 6 + 3KOH = C 6 H 3 C1 3 + 3 KC1 + 3 H,O. 

If chlorine and bromine are allowed to act upon an aromatic 
hydrocarbon like toluene, which has a side-chain, substitution 
may occur in the nucleus or the side-chain, according to the 
conditions. Generally speaking, in the cold and in presence of 
a " halogen carrier," nuclear substitution occurs, but at a high 
temperature the halogen passes into the side-chain (see Prep. 
86, p. 194). 

The halogen derivatives of the aromatic hydrocarbons, like 
those of the aliphatic series, are colourless liquids or solids, 
denser than water, and possessing an agreeable smell, unless 
the side-chain is substituted. The latter substances can often 
be distinguished by their irritating action on the eyes and mucous 
membrane of the nose (see Prep. 86, p. 194). 

The halogen in the aromatic nucleus is much more firmly 
fixed than in the case of the aliphatic compounds, e.g. bromo- 
benzene is quite unaffected by most of the reagents which act 



APPENDIX 273 



upon ethyl bromide. The presence of //r<?-groups, however, 
disturbs this stability, and the halogen in a substance like 
dinitrochlorobenzene is readily replaced by hydroxyl with 
potash, or by NH 2 with ammonia. When the halogen is in the 
side-chain, the substance behaves like an aliphatic compound. 



PREPARATION 47. 

Ethyl Benzene. "Fittig's reaction," so-called from its 
discoverer, is analogous to the synthetical method employed by 
Wurtz for the preparation of the aliphatic hydrocarbons, as in 
the formation of butane from ethyl bromide, 

2C 2 H 5 Br + aNa = C 4 H 10 + 2NaBr. 

In the case of the aromatic hydrocarbons, a second side- 
chain may be introduced from a< dibromo-derivative either 
simultaneously with the first, or subsequently by a repetition of 
the process. Both dibromobenzene and monobromotoluene 
may be converted into xylene. 

C 6 H 4 Br 2 + 2CH 3 I + 4Na = C 6 H 4 (CH 3 ) 2 + 2NaBr + 2NaI. 
C 6 H 4 BrCH 3 + CH 3 I + 2Na = C 6 H 4 (CH 3 ) 2 + Nal + NaBr. 

The action also takes place between aromatic hydrocarbons 
substituted either in the nucleus or side-chain. Bromobenzene 
yields diphenyl, whereas benzyl bromide yields dibenzyl, 

2C 6 H 5 Br + 2Na = C 6 H 6 .C 6 H 5 + 2NaBr. 
2C 6 H B CH 2 Br + 2Na = C 6 H 5 .CH 2 .CH 2 .C 6 H 5 +-2NaBr. 

This reaction does not, however, occur with the same readiness 
in all cases, nor does it always yield exclusively the anticipated 
product. Para-bromotoluene and sodium give tolyl phenyl 
methane and dibenzyl as well as ditolyl (Weiler). Again, p- 
bromotoluene gives a good yield of ^-xylene, the ortho-compound 
reacts sluggishly, whilst the meta-derivative gives no xylene. 
Occasionally the action is vigorous, and has to be moderated by 
dilution with an indifferent solvent. At other times it is sluggish 
and has to be promoted by raising the temperature. Often the 
addition of a little ethyl acetate will start the decomposition. 
For the synthesis of some of the aromatic hydrocarbons, it is 
preferable to use the Friedel-Crafts' reaction (see Prep. 102, 
p. 214). 
COHEN'S ADV. p. o. c. T 



274 PRACTICAL ORGANIC CHEMISTRY 

PREPARATION 48 

Nitrobenzene. The formation of nitro-compounds, by the 
action of strong nitric acid on the hydrocarbon, is a distinctive 
property of aromatic compounds, although recent researches 
have shown that dilute nitric acid under pressure will convert 
some of the paraffins, especially the tertiary hydrocarbons, into 
mono- and di-nitro-derivatives. The production of nitro-com- 
pounds is usually effected by strong or fuming nitric acid, or 
solid potassium nitrate, in presence of cone, sulphuric acid. 
Where the action is vigorous, as in the case of the phenols, it 
is necessary to use moderately dilute acid. The number of 
hydrogen atoms replaceable by the nitro-group(NO 2 ) is limited. 
In benzene the first nitro-group is introduced with great ease, 
the second less readily, and the third with some difficulty. The 
position taken up by the nitro-groups may be briefly stated as 
follows : When a negative group (nitro, carboxyl, cyanogen, 
aldehyde) is already present, the nitro-group enters the meta- 
pcfeition to the first group. In the presence of other groups 
(alkyl, hydroxyl, halogen, amino), the nitro-group attaches itself 
to both ortho- and para-positions. Benzoic acid and benz- 
aldehyde give, on nitration, mainly meta-compounds, whereas 
toluene, phenol, and aniline form simultaneously ortho- and 
para-derivatives. 

Nitro-compounds have often a yellow or red colour, are with 
difficulty or not at all volatile, possess a much higher boiling- 
point than the corresponding halogen derivatives, and are 
denser than water, and insoluble in that liquid. 

PREPARATIONS 4951. 

Azoxybenzene, Azobenzene, Hydrazobenzene. 

Nitro-compounds yield a series of reduction products accordingto 
the nature of the reducing agent. Alkaline reducing agents : 
sodium methylate, zinc dust and caustic soda, stannous chloride 
and caustic soda, produce azoxy, azo- and hydrazo-compounds. 

C 6 H 5 N0 4 C 6 H S N C 6 H 5 N C 6 II 5 NII 

I. >0 || I 

C 6 H S N0 2 C 6 H 5 N/ C 6 H 5 N C 6 H 5 NH 

Nitrobenzene. Azoxybenzene. Azobenzene. Hydrazobenzene. 

The sodium methylate acts as a reducing agent by taking up 
oxygen and forming sodium formate. 



APPENDIX 275 



In the preparations, the nitrobenzene is converted by suc- 
cessive steps into azoxy-, azo- and hydrazo-benzene ; but, by 
suitably modifying the conditions, the intermediate steps may 
be omitted. Thus, nitrobenzene may be converted with alcoholic 
caustic soda and zinc dust directly into hydrazobenzene. 

If the reduction of nitrobenzene takes place in neutral 
solution with zinc dust and water in presence of a little calcium 
or ammonium chloride, or with aluminium-mercury couple and 
water, /3-phenylhydroxylamine is formed (see Prep. 52, p. 148). 

C 6 H 5 NO 2 + 2H 2 = C 6 H 5 NIIOH + H 2 O. 

Reduction in acid solution produces an amine (see Prep. 53, 
p. 149). The mechanism of the change, although giving rise to 
such different products when carried out in alkaline, neutral, or 
acid solution, is not essentially different in the three cases. The 
first reduction product is nitrosobenzene, C 6 H 5 NO, followed by 
that of ^-phenylhydroxylamine. In alkaline solution the two 
compounds unite with elimination of water to form azoxybenzene, 
which may undergo further reduction in a normal fashion giving 
rise to azo- and hydrazo-benzene. In acid solution, on the 
other hand, phenylhydroxylamine does not combine with nitroso- 
benzene and can then undergo further reduction. The reduction 
of nitrobenzene in alkaline and neutral solution is also effected, 
as already described, by electrolysing the liquid in contact with 
the negative electrode. If the process is conducted in presence 
of concentrated sulphuric acid ^-aminophenol is obtained 
(Gattermann). The latter is produced by intramolecular change 
from phenylhydroxylamine, which is first formed, 

C 6 H S NHOH = 



Azobenzene, though not a colouring matter, may be regarded 
as the mother substance of the large family of azo-colours, 
which are, however, prepared by a totally distinct method, viz., 
by the action of a diazo-salt on a phenol or base (see Prep. 62, 
p. 163). The intramolecular change from hydrazobenzene to 
benzidine is one of great technical importance. The change 
occurs by the transfer of the link between the two nitrogen 
atoms to the two carbon atoms in the/d 

/ \NH Nil/ \ = H 9 N 




276 PRACTICAL ORGANIC CHEMISTRY 

If one of the nuclei of hydrazobenzene is already substituted 
in the ^tens-position, the reaction may give rise to diphenylamine 
derivatives, which are known > as ortho- or para-semidines 
(Jacobson), 





NH 

Ortho-semidine. 

Benzidine and its homologues are used in the manufacture of 
valuable azo-colours, congo-red, benzopurpurin, &c. (see p. 291). 

PREPARATION 52. 

Phenylhydroxylamine. The necessity for conducting 
the reduction of nitrobenzene in neutral solution has been 
explained in the previous note. In addition to the reagent 
named in the preparation, the aluminium -mercury couple in 
presence of water or ammonium sulphide in alcoholic solution 
may be also used. The conversion of nitrobenzene into 
/>-aminophenol on electrolysis in acid solution will also be 
evident from the fact that phenylhydroxylamine readily under- 
goes isomeric change. Phenylhydroxylamine reacts with 
nitrous acid, forming a nitroso-derivative, 

C 6 H 5 NHOH + HNO 2 = C 6 H 5 N(NO)OH +H 2 O. 
It also condenses with aldehydes in the following way : 

C 6 H 5 NHOH + C 6 H 6 CHO = C 6 H 5 N CH.C 6 H S + H 2 O. 



O 

Nitrosobenzene, which shares the general character of nitroso- 
compounds in giving rise to a green vapour or solution, is 
readily reduced to phenylhydroxylamine and aniline. It 
condenses with amino-compounds, yielding azo- or diazo- 
derivatives. 

C 6 H 5 NO + H 2 N.C 6 H 5 = C 6 H 5 N = N.C 6 II 5 + H 2 O. 
+ H 2 N.OH = C 6 H 6 N = N.OH + H 2 O. 



APPENDIX 277 



PREPARATION 53. 

Aniline. The reduction of a nitro-compound in an acid 
solution is a very general method for preparing primary amines. 
For laboratory purposes it is customary to use tin and hydro- 
chloric or a solution of stannous chloride crystals (SnCl. 2 + 2H i! O) 
in cone, hydrochloric acid or zinc dust and acetic acid. The 
manufacture of aniline on the industrial scale is effected by 
means of iron borings and hydrochloric acid ; but of the latter 
only a fraction of the theoretical quantity, required by the 
equation Fe + 2HC1 = FeCl 2 + H 2 , is employed. The main 
reaction is probably represented by the following equation, 

C 6 H 5 NO, + 2Fe + 4 H 2 = C 6 H 5 NH 2 + Fe 2 (OH) 6 . 

When the base is volatile in steam, as in the present case, 
the simplest method of separation is to add an excess of alkali 
and to distil in steam. Otherwise the base may be separated 
by shaking out with ether, or the tin may be precipitated in the 
warm solution by H 2 S and the filtrate evaporated to dryness. 
If the compound contains more than one nitro-group, the 
reduction is carried out with one of the above reducing agents 
in the manner described, but if it is necessary to reduce only 
one of the nitro-groups, it is effected by the action of H 2 S in 
presence of ammonia (see Prep. 58, p. 1 54). Another method, 
which may also be used for determining the number of 
nitro-groups, is to prepare an alcoholic solution of the nitro- 
compound, and to add an alcoholic solution of the calculated 
quantity of stannous chloride. In this way the reduction of the 
groups may be carried out in succession and estimated. 

The aromatic amines are colourless liquids or solids, which 
may be distilled without decomposition. Although they form 
salts with acids, they are much weaker bases than the aliphatic 
amines owing to the negative character of the phenyl group, 
The salts have an acid reaction to litmus, whilst the free bases 
are neutral. The neutralisation of an aromatic base by acid is 
usually determined by the use of methyl violet, magenta, Or 
congo-red paper. The first is turned green, the second colour- 
less, and the third blue by free acid. 

Aromatic amines, containing the amino-group in the side- 
chain, have the basic character and properties of aliphatic 
amines. 



278 PRACTICAL ORGANIC CHEMISTRY 

PREPARATIONS 54 55. 

Acetanilide, Bromacetanilide. Primary and second- 
ary bases form acetyl derivatives with acetic acid, acetyl 
chloride, or acetic anhydride (see Reactions, pp. 76, 77). 
Tertiary bases are unacted on in this way. As the acetyl 
derivatives are much less volatile than the original bases, the 
method is frequently used for separating a tertiary base from 
mixtures containing the other two (see Prep. 59, p. 1 56). The 
anilides are very stable compounds ; they can be distilled, as a 
rule, without decomposition, and may be directly brominated, 
chlorinated and nitrated. In these reactions, either the ortho- 
or para- or both derivatives are formed. The remaining 
hydrogen atom of the amino- group may be replaced by (i) a 
second acid radical, by the action of acetic anhydride, (2) 
sodium, by the action of the metal, (3) a nitroso-group, with 
nitrous acid, and (4) chlorine or bromine, by the action of hypo- 
chlorous or hypobromous acid. 

C 6 H 5 N(CO.CH 3 ) 2 Diacetanilide. 

C 6 H 5 NNa.CO.CH 3 Sodium acetanilide. 

C 6 H 5 N(NO)CO.CH 3 Nitrosoacetanilide. 

C 6 H 8 NC1. CO. CH 3 Acetchloranilide. 

The mechanism of the change effected in producing substitu- 
tion products by halogens appears to occur in two steps, the first 
being the addition of a molecule of halogen, probably to the 
nitrogen, the second being an isomeric change accompanied (if 
water is present) by the elimination of halogen acid. 
C 6 H 5 .NH.C 2 H 3 O + Br 2 = C 6 H 5 NH.C 2 H 3 O 



Br Br 

C 6 H 5 NHBr 2 .C 2 H 3 O = C 6 II 4 BrNH.C 2 H 3 O.HBr. 
All the anilides are hydrolysed by strong mineral acids or 
alkalis and the acid radical removed (see also Beckmann's 
reaction, Prep. 100, p. 212). 

Formanilide is a tautomeric compound, i.e., it reacts as though 
it possessed the alternative formulae, 

C 6 H 5 N:CH(OH) C 6 H 5 NH.CO.H, 

for it yields two isomeric ethers, the one, by the action of 
methyl iodide on the silver salt, and the other by the action of 
methyl iodide on the sodium compound (Comstock). Acet- 



APPENDIX 279 



anilide is known in pharmacy as antifebrin, and is used as an 
antipyretic. 

PREPARATIONS 5758. 

m-Dinitrobenzene. In the Notes on Prep. 48, p. 274, 
it is mentioned that the second nitro-group enters the meta- 
position to the first. This is usually the case where two 
acid groups are successively introduced into the hydrocarbon. 
Thus, benzenedisulphonic acid, obtained by heating benzene 
sulphonic acid (see Prep. 74, p. 177) with fuming sulphuric acid, 
is a meta-compound. 

m-Nitraniline. The reduction product of ;-dinitrobenz- 
ene is naturally #z-nitraniline. The o- and /-nitranilines can 
be obtained by acting upon aniline or, preferably, acetanilide, 
with fuming nitric acid. 

Whereas the first nitro-group of a tri- or di-nitro derivatives is 
rapidly and completely reduced by ammonium sulphide, the 
second is very slowly attacked. The rate of change appears to 
be determined mainly by the acidic nature of the molecule as a 
whole, the halogens and carboxyl playing a similar role to that of 
the nitro-group. In all these cases hydroxylamine compounds 
are produced as intermediate products. 

PREPARATION 59. 

Dimethylaniline. It is a well-known fact that the alkyl 
halides convert the primary amines into secondary and tertiary 
bases (Hofmann). The formation of dimethylaniline is prob- 
ably due to the action of CH 3 C1, which is formed, as an 
intermediate product, by the action of hydrochloric acid on the 
methyl alcohol. There is always a small quantity of mono- 
methylaniline, C 6 H 5 NHCH 3 , produced at the same time. The 
three bases cannot well be separated by fractional distillation, 
as their boiling points lie too near together, 

Aniline 180. 

Methylaniline 192. 

Dimethylaniline 192. 

It is for this reason that the action of acetic anhydride is 
utilised, which only unites with the primary and secondary base. 
Dimethylaniline is a weak base, which, like aniline, is neutral 



a8o PRACTICAL ORGANIC CHEMISTRY 

to litmus, but gives no stable salts. It is used in the prepara- 
tion of malachite green (benzaldehyde green) by heating 
together dimethylaniline, benzaldehyde, and solid zinc chloride. 
The product (leuco-malachite green) is then oxidised with lead 
peroxide and hydrochloric acid (see p. 216), 

HC/ /C 6 H 5 

! X> H |C 6 H 4 N(CH 3 ) 2 -> HC^C 6 H 4 N(CH 3 ) 2 
H iC 6 H 4 N(CH 3 ) 2 C 6 H 4 N(CH 3 ) 2 

Leuco-malachite green. 

/C 6 H 5 

-> HOC^-C 6 H 4 N(CH 3 ) 2 
\C 6 H 4 N(CH 3 ) 2 
Base of malachite green. 

The latter, in presence of the hydrochloric acid, is converted 
into the hydrochloride, 



/6s- 

HOCr-C 6 H 4 N(CH 3 ) 2 + HC1 = C^-C 6 H 4 N(CH 3 ) 2 + H. 2 O. 
\C 6 H 4 N(CH 3 ) 2 V 6 H 4 :N(CH 3 ) 2 C1 

Hydrochloride of 
malachite green. 

Dimethylaniline is also used for the preparation of tetra- 
methyldiaminobenzophenone (Michler's compound), which forms 
the basis of many colouring matters, and is obtained by acting 
upon dimethylaniline with phosgene (see p. 314), 

/C 6 H 4 N(CH 3 ) 2 

COCL, + 2C 6 H 5 N(CH 3 ) 2 = OC< + 2HC1. 

\C 6 H 4 N(CH 3 ) 2 

Michler's compound. 

PREPARATION 60. 

Nitrosodimethylaniline. It is a peculiarity of the 
tertiary aromatic amines, which distinguish them from the 
corresponding aliphatic compounds, that they are capable of 
reacting with nitrous acid. Here the nitroso-group replaces 
hydrogen in the para-position to the dimethylami no-group. 

The substances, thus formed, are bases, and form salts with 
acids, which dissolve in water with a yellow colour. The solu- 
bility of the hydrochloride of the nitroso-bases in water dis- 
tinguishes them from the nitrosamines of the secondary bases, 
which are insoluble. 



APPENDIX 281 



Nitrosodimethylaniline is readily oxidised ,to nitrodimethyl- 
aniline. 

It is an interesting fact that the nitrosamines of the 
secondary bases undergo molecular change when acted on 
with alcoholic hydrochloric acid. The nitroso-group is thereby 
transferred to the para-position in the nucleus (O. Fischer), 

C 6 H 5 N(NO)CH 3 = NO.C 6 H 4 .NHCH 3 . 

The para-nitroso derivatives of both secondary and tertiary 
amines are decomposed with caustic soda into nitrosophenol 
and alkylamine. 

The formation of methylene blue may be explained as 
follows : By the action of ammonium sulphide on nitroso- 
dimethylaniline, the nitroso-group is reduced to an amino- 
group. Two molecules of/-aminodimethylaniline then combine 
with the elimination of ammonia to form a diphenylamine 
derivative, 

(CH 3 ) 2 NC 6 H 4 ! NH,""H" : HNC 6 H 4 N(CH 3 ) 2 

= (CH 3 ) 2 NC 6 H 4 .NH.C 6 H 4 N(CH 3 )2. 

The sulphur of the hydrogen sulphide then enters the mole- 
cule under the oxidising influence of the ferric chloride, forming 
a thiodiphenylamine derivative, 

H H 

(CH 3 ) 2 NC 6 H 3 N C 6 H 3 .N(CH 3 ) 2 C1 
H H 

H S H 
O O 

= (CH 3 ) 2 NC 6 H 3 .N:C 6 H 3 :N(CH 3 ) 2 C1. 

Methylene blue 

PREPARATION 61. 

Thiocarbanilide, Thiocarbimide, Triphenylguan- 
idine. Whereas carbon bisulphide reacts with aromatic ammo- 
compounds yielding a thiocarbanilide, with primary aliphatic 
amines the reaction takes a different course and thiocarbamates 
are produced, 

.SH.NHj.CjH, 
CS 2 + 2C 2 H 5 NH 2 = SOT 

\VH r w. 



282 PRACTICAL ORGANIC CHEMISTRY 

.The product can, however, be converted into the mustard oil 
by treatment with a metallic salt which removes hydrogen 
sulphide. 



/-a-a,, 

SC< = H 2 S -F NH .C 2 H 5 + SC:NC 2 H S . 

\NH.C 2 H 5 

Among the reactions appended to this preparation, the for- 
mation of phenylcarbimide from phenyl mustard oil is described. 
It should be noted that phenyl carbimide, like the thiocarbimide, 
unites with ammonia, amines, and more especially with alcohols 
and phenols. The bases yield urea derivatives ; the alcohols 
and phenols form urethanes. 

C 6 H 5 N:CO + NH 3 = C 6 H 5 NH.CO.NH 2 Phenyl urea. 
C 6 H S N:CO + NH 2 CH 3 = C 6 H S NH.CO.NHCH 3 Methyl phenyl urea. 
C 6 H S N:CO + C 2 H 5 OH = C 6 H 8 NH.CO.OC 2 H 6 Phenyl urethane 
C 6 H 5 N:CO + CgHjOH = C 6 II 5 NH.CO.OC 6 H 5 Phenyl carbamic 

phenyl ester. 

The latter two reactions are frequently used for detecting 
the presence of a hydroxyl group (Goldschmidt). 

PREPARATION 62. 

Diazobenzene Sulphate. Whereas nitrous acid imme- 
diately decomposes the primary alip"hatic amines with evolution 
of nitrogen, 

CH 3 NH 2 + HNO 2 = CH 3 OH + N 2 + H 2 O, 

no nitrogen is evolved if nitrous acid is allowed to act upon a 
salt of a primary aromatic amine in the cold. The solution then 
contains a diazo-salt, which is readily soluble in water. It may 
already have been observed that in the salts of diazobenz- 
ene, the radical, diazobenzene, C 6 H 5 N 2 , plays the part of am- 
monium, NH 4 , in the ammonium salts. Diazobenzene chloride, 
nitrate, sulphate, &c., correspond to ammonium chloride, nitrate, 

and sulphate. 

C 6 H 5 N,.C1 NH 4 .C1. 

C 6 H 5 N 2 .N0 3 NH 4 .N0 3 . 

C 6 H 5 N 2 .SO 4 H NH 4 .SO 4 H. 

The hydrate of diazobenzene, C 6 H 5 N 2 .OH, which would be 
analogous to NH 4 OH, is also known as an unstable oil. Con- 



APPENDIX 283 



siderations of this kind have suggested the alternative 
formula, 

C.HJ.NEEN 

X 

in which X stands for the acid radical (Blomstrand). The 
nitrogen which combines with the acid radical is thereby quin- 
quivalent, as in the ammonium salts. On the other hand, di- 
azobenzene hydrate forms two isomeric potassium salts, one of 
which is obtained by adding caustic potash to diazobenzene 
chloride. This compound is unstable, and unites in the ordi- 
nary way with phenols to form hydroxyazobenzene derivatives 
(see Reaction 6, p. 163;. The second one, which is obtained by 
heating the first to 130 with caustic potash, is very stable, and 
does not combine directly with phenols (Schraubeand Schmidt). 
Other derivatives of diazobenzene exist in two forms, such as 
the cyanide and sulphite. The difference has been explained 
in two ways. According to one theory, the two potassium com- 
pounds represent two different space configurations similar to 
that of citraconic and mesaconic acid (see p. 266) and the 
oximes (see p. 301), and are distinguished by the terms 'syn 
and ' anti ' (Hantzsch). 

C 6 H 5 N % C 6 H 6 N 

KO.N N.OK 

Syn-benzene diazotate of potassium. Anti-benzene diazotate of potassium. 

The second theory ascribes the difference to structural 
arrangement, and the compounds are termed diazo- and iso- 
diazo-compounds (Bamberger). 

C 6 H 5 N:NOK. C 6 H ? NK.NO. 

Benzene diazotate of potassium. Benzene isodiazotate of potassium. 

It is now generally admitted that the diazo-salts of the 
stronger acids, which have only one representative, are most 
satisfactorily represented by the "diazonium," or Blomstrand 
formula, and the salts are known as diazonium salts. 

A few of the numerous changes which the diazonium salts 
undergo are illustrated in the series of reactions which follow 
the preparation, and are among the most important in organic 
chemistry. Some of these reactions are carried out on a larger 



284 PRACTICAL ORGANIC CHEMISTRY 

scale in Preps. 63 69. It will there be noticed that it is 
unnecessary, as a rule, to isolate the diazonium salt, but that 
the substance is prepared in solution, and is decomposed by 
the specific reagent. 

With few exceptions, all aromatic compounds which contain 
a nuclear amino-group may be diazotised. At the same time 
there are notable differences in the ease with which the process 
is effected. 

PREPARATION 63. 

Toluene from Toluidine. It is often desirable to obtain 
the hydrocarbon from the base. The process of diazotisation 
offers the only convenient method. The diazonium salt may be 
reduced by alcohol (Reaction i, p. 162) or, as in the present in- 
stance, by sodium stannite. Less direct methods are the con- 
version of the diazonium compound into (i) the hydrazine (see 
p. 174), (2) the acid and distillation with lime (p. 200), (3) the 
halogen derivative and reduction with sodium amalgam, or, 
finally (4) the phenol and distillation with zinc dust. 

PREPARATION 64. 

^-Cresol. This reaction resembles that of nitrous acid on 
an aliphatic primary amine ; but the liquid requires to be 
warmed. 

PREPARATIONS 65 66. 

p-Chlorotoluene, p-Bromotoluene. The action of cu- 
prous chloride, bromide, and cyanide on diazonium chlorides was 
discovered by Sandmeyer, and is known as ' Sandmeyer's re- 
action. 5 

C 6 H 5 N 2 .C1 = C 6 H 5 C1 + N 2 . 

C 6 H 5 N 2 .Br = C 6 H 5 Br + N 2 . 

C 6 H 5 N 2 .CN = C 6 H 5 CN + N 2 . 

Some of the cuprous chloride compounds of the diazonium 
salts have been isolated and analysed, and correspond to the 
formula C 6 H 5 N 2 Cl.Cu 2 Cl 2 (Hantzsch). The formation of a 
crystalline copper compound is rendered very evident in the 
present preparation. A modification of Sandmeyer's reaction 
is the introduction of precipitated metallic copper in place of 
the cuprous salt (Gattermann). 



APPENDIX 285 



The preparation of potassium iodide-starch paper is made 
by dipping strips of filter paper into a thin solution of starch 
paste to which a little potassium iodide has been added, and 
drying the paper. 

The oxidation of a side-chain by means of permanganate 
solution is one which is commonly employed where the acid is 
required. The monohalogen derivatives are readily oxidised in 
this way, but greater difficulty is experienced if two halogen 
atoms or other acid groups are present. The dichlorotoluenes, 
for example, are only slowly attacked. 

PREPARATION 67. 

lodosotoluene. The most interesting of the compounds 
belonging to this group, which were carefully investigated by 
V. Meyer, is the substance prepared by shaking a mixture of 
iodosobenzene and iodoxybenzene (obtained by the oxidation of 
the iqdoso-compound) with moist silver oxide. Diphenyl- 
iodonium oxide is thus produced, which in basic properties 
resembles ammonium hydrate, 

C 6 H 5 IO + C 6 H 5 I0. 2 + AgOH = (C 6 H 5 ) 2 I.OH + AglOg. 
With hydriodic acid it forms the iodide, (C 6 H 6 ) 2 I.I. 

PREPARATION 69. 

Diazoaminobenzene. Diazoamino-compounds are also 
formed by the action of diazonium salts on primary and 
secondary amines of both the aliphatic and aromatic series. 
The method given in the preparation must then be modified. 
The diazonium salt is first prepared, and the amine stirred in 
with the addition of sodium acetate. The sodium combines 
with the mineral acid, liberating the weaker acetic acid, which 
thereby assists the separation of the diazoamino-compound. 
Compounds of the following formulas have been prepared in 
this way. 

C 6 H 5 N:N.NHC 6 H 4 .CH 3 Diazobenzene-aminotoluene. 

C 6 H 5 N :N. N HC 2 H 5 Diazobenzene-ethylamine. 

C S H S N:N.N(CH 3 ) !! Diazobenzene-dimethylamine. 

C 6 H 5 N:N.NC S H 10 Diazobenzene-piperidine. 



286 PRACTICAL ORGANIC CHEMISTRY 

The last compound has been utilised for the preparation of 
fluorobenzene, and its congeners by the action of cone, hydro- 
fluoric acid, 

C 6 H 8 N:N.C S H 10 + 2HF = C 6 H 5 F + N 2 + C 5 H 10 NH.HF. 

Diazoaminobenzene undergoes the following reactions : 

1. The hydrogen of the imino-group may be replaced by acid 
and alkyl radicals. In the latter case the sodium compound is 
treated with an alkyl iodide. 

2. Phenyl carbimide forms a urea derivative, 

C 6 H 5 N:N.NHC 6 H 6 + C 6 H 5 N.CO = C 6 H 5 N:N.NC 6 H 8 

yco. 

C 6 H 5 NH/ 

3. With strong hydrochloric acid, decomposition into diazo- 
nium salt and amine takes place, 

C 6 H 5 N:N.NHC 6 H 5 + HC1 = C 6 H 5 N 2 .C1 + C 6 H 5 NH 2 . 

If nitrous acid is added, the second molecule of base is also 
converted into diazobenzene chloride. In presence of cuprous 
chloride, chlorobenzene is formed. 

4. On boiling with water, diazoaminobenzene decomposes 
into phenol and base, 

C 6 H 5 N:N.NH.C 6 H 5 + H a O = C G H 5 OH + C 6 H 5 NH 2 + N 2 . 

5. On reduction, it splits up into phenylhydrazine and aniline,. 

C 6 H 5 N:N.NHC 6 H 5 + 2H 2 = C 6 H 5 NH.NH 2 + C 6 H 5 NH 2 . 



PREPARATION 70. 

Aminoazobenzene. The conversion of diazoaminobenz- 
ene into aminoazobenzene resembles the formation of benzidine 
from hydrazobenzene (see p. 148). The diazo-nitrogen seizes 
on the carbon of the nucleus in the para-position to the amino>- 
group, 

/ \ N:N.NH/ \ = / ~y~ N:N { ^NHa 



APPENDIX 287 



If the para-position is already occupied, the nitrogen ^akes 
the ortho-position to the amino-group, 

NiN.NH/ 



NH 2 . 

but the reaction only takes place readily where the para-position is 
free. The manner in which the change is brought about has not 
been satisfactorily explained, although from the fact that/-diazo- 
aminotoluene yields, on warming with aniline hydrochloride, 
/-toluene azoaminobenzene and/-toluidine, 



N:N.NH< >CH 3 + < >NH, 



= CH, 



it would appear as if the hydrochloride of the base were the 
chief factor in the decomposition, and that the change was 
rather inter- than z/r<2-molecular. Aminoazobenzene, under 
the name of aniline yellow, has been used as a colouring matter. 
Its chief technical application at present is in the manufacture 
of a class of dark blue colours, known as indulines. On reduc- 
tion with tin and hydrochloric acid, it decomposes into two 
molecules of base, aniline and ^>-phenylenediamine, a reaction 
which is shared by most of the azo-compounds (see p. 176), 

C 6 H 6 N:N.C 6 H 4 NH 2 = C G H 5 NH 2 + NH 2 C 6 H 4 NHj5. 



PREPARATION 71. 

Phenylhydrazine, Phenylmethylpyrazolone. The 
use of phenylhydrazine or, in some cases /-bromo- or ^-nitro- 
phenylhydrazine, as a reagent for the detection of aldehydes and 
ketones, has been illustrated in the reactions on p. 70. 
One of its most important technical uses is in the prepara- 
tion of antipyrine, in which the product, obtained by the action 



PRACTICAL ORGANIC CHEMISTRY 



of phenylhydrazine on ethyl acetoacetate, is acted upon with 
methyl iodide. The two reactions are represented as follows : 

CH 3 .CO.CH 2 .COOC,H 5 CH 3 .C CH 2 .CO 

| + H 2 + C 2 H 5 OH. 

+ NH 2 .NH.C 6 H 5 N -- N.C 6 H 3 

Pherylmethylpyrazolone. 

CH 3 .C CH 2 .CO CH 3 .C=CH.CO 

II I + CH 3 I = | | +HI 

N -- N.C 6 H 5 CH 3 .N - -N.C 6 H 5 

Phenyldimethylpyrazolone 
(antipyrine). 

The variety of syntheses into which phenylhydrazine enters 
cannot be described here ; but reference must be made to the 
text-book. 

It should be noted that the action of phenylhydrazine on 
the ketone group, and of diazobenzene salts on the methylene 
group situated between two CO groups, are analogous to that 
of hydroxylamine and nitrous acid upon these two groups, of 
which the following are examples : 

COOC n H 5 
I 

+ NH 2 .NHC 6 H 5 = C:N.NH.C 6 H, -f- H 2 O 
CO.OC 2 H 5 # 
| COOC 2 H 5 

1. CO 

I COOC 2 H 5 

CO.OC 2 H 5 xx 
Mesoxalic ' + NH 2 OH = C:NOH + II 2 O 

ester. 

COOC 2 H 5 

COOC,H 5 

I 

^ + C1N:N.C 6 H 4 = C:N.NH.C 6 H 5 + HC1. 
COOC 2 H 5 * | 

| COOC 2 H 5 

2. CH 2 

| COOC,H 5 



Sucdnic 

', ; ester. 

COOC 2 H 5 

Phenylhydrazine has been used in the synthesis of indole 
derivatives. The hydrazones of aldehydes and ketones contain- 



APPENDIX 289 



ing a methyl group are decomposed on heating with zinc chloride, 
indoles being formed with elimination of ammonia. (E. Fischer.) 

CH 3 
CH, I 



CH 
CH 3 

Acetone-phenylhj'drazone. Methyl indole. 

PREPARATION 72. 

Sulphanilic Acid. The acid characters of this substance, 
which is both base and acid, are more prominently developed 
than the basic character. Nevertheless it reacts with nitrous 
acid like a primary amine, and forms a diazonium salt, which 
has the following constitution (see Prep. 62, p. 161) : 

N : K 



S0. 2 .0 

Diazobenzene sulphonic acid. 

The formation of suphanilic acid is probably preceded by the 
sulphonation of the amino-group, 

C 6 H 5 NH.SO 3 H. 

A compound of this character has been obtained which 
decomposes with acids into o- and /-aminosulphonic acid by 
a process of intramolecular change (Bamberger). The fact of 
the para-compound being exclusively formed at the higher 
temperature may account for the production of this substance 
in the present preparation. 

PREPARATION 66. 

Methyl Orange. The first point to notice in this reaction 
is that the diazonium salt forms no diazoamino-compound with 
the dimethylaniline, but at once produces an azo-compound, 
This is always the case with tertiary amines, some secondary 
amines like diphenylamine and the phenols. The reaction may 
be regarded as typical .of the formation of all azo-colouring 
matters. At least two substances are requisite in this process ; 
on the one hand an aromatic compound containing an amino- 
group in the nucleus, and, on the other, a base or phenol 

COHEN'S ADV. p. o. c. u 



290 PRACTICAL ORGANIC CHEMISTRY 

The first is diazotised and combined or coupled with the second. 
The coupling takes place, in the case of amines, in a faintly 
acid or neutral solution, in the case of phenols, in an alkaline 
solution (see Reaction 6, p. 163). In all cases the diazo-group 
seizes upon the^carbon in the para-position to the amino- or 
hydroxyl group of the coupled nucleus. When the para-position 
is already appropriated, the ortho-position serves as a link, but 
no coupling ever occurs in the meta-position. The sulphonic 
acid derivatives of the base or phenol are frequently preferable 
to the unsubstituted compound. The dyes formed have in 
consequence of the presence of the SO 3 H group an acid character, 
which renders them capable of forming soluble sodium salts, 
and adapts them better for dyeing purposes. When an azo-com- 
pound is formed by coupling the diazo-compound with a primary 
amine, the new product is capable of being diazotised and 
coupled a second time. Thus a tetrazo-compound is formed 
containing a double diazo-group -N:N-. Aminoazobenzene, 
when diazotised, forms diazo-azobenzene with nitrous acid, which, 
like a simple diazo-compound, reacts with the phenols, 

C 6 H 5 N:N.C 6 H 4 NH 2 HC1 + HNO 2 = C 6 H 5 N:N.C 6 H 4 N2.C1 + 2H 2 O. 

5 ONa 
= C 6 H 5 N:N.C 6 II 4 N:N.C 6 H 4 OH + NaCl. 

If aminoazobenzene is sulphonated with fuming sulphuric acid, 
and the product again diazotised and coupled with /3-naphthol, 
Biebrich scarlet is formed, 

/SO,H 

C 6 H/ /S0 3 H 

\N:N.C 6 H 3 < 

\N:N.C 10 H 6 OH. 
Biebrich scarlet. 

If in the last phase the different sulphonic acids of -naphthol 
are employed, various shades of red, known as Croceins, are pro- 
duced. Thus it appears that the colour deepens from orange to 
red with the introduction of a second azo-group. 

This is not the only method of forming tetrazo-compounds. 
Each amino-group of a diamine may be diazotised and coupled. 
Benzidine and its homologues, which have been utilised in this 
way, have a special value for the cotton dyer, as the shades pro- 
duced are not only very brilliant, but, unlike the majority of 






APPENDIX 291 



colouring matters, are substantive colours, i.e., possess the pro- 
perty of attaching themselves to the cotton fibre without the aid 
of a mordant. Congo reds and benzopurpurins are combina- 
tions of benzidine and its homologues with the sulphonic acids 
of naphthol and naphthylamine. The following is the constitu- 
tion of Congo red, the simplest of these compounds, which is 
used in the form of its sodium salt : 

/NH a 
N:N.C 10 H/ 
/\ \SO,Na 



N:N.C 10 H< 

\SO 3 Na 

Attention should be drawn to the fact that azobenzene, 
although a brightly coloured substance, is without dyeing pro- 
perties, i.e., it is not a colouring matter, whereas aminoazobenz- 
ene and methyl orange are true dyes. They all three contain 
the azo-group (-N:N-), called by Witt a chromophore, united 
to two aromatic nuclei ; but in the case of aminoazobenzene 
and methyl orange, one of these nuclei contains a basic group, 
NH 2 or N(CH 3 ) 2 . It will also have been observed that the 
combinations with phenols likewise result in the production of 
colouring matters. It would appear, therefore, as if there were 
at least two essentials to a dye, a fundamental or mother sub- 
stance like azobenzene, termed a chromogenic compound, and 
an amino- or hydroxyl group, called an auxochrome. The same 
thing has been observed in the case of other colouring matters 
(see Note on Prep. 103, p. 313). 

Most of the azo-colours split at the double link, on reduction 
with stannous chloride and hydrochloric acid, forming two 
molecules of base. Methyl orange yields sulphanilic acid and 
dimethyl /-phenylenediamine, 

S0 3 H.C 6 H 4 N:N.C 6 H 4 N(CH 3 ) 2 + aH 2 

= S0 3 H.C 6 H 4 NH 2 + NH 2 C 6 H 4 N(CH 3 ).,j. 



U -2. 



292 PRACTICAL ORGANIC CHEMISTRY 

PREPARATION 74. 

Potassium Benzenesulphonate. The formation of sul- 
phonic acids by the action of sulphuric acid, &c., on the aromatic 
hydrocarbon is a special property of aromatic hydrocarbons, 
although, in a few cases, paraffins have been found to react in a 
similar manner. The process is called " sulphonation." In 
place of cone, sulphuric acid, fuming sulphuric acid, i.e., an acid 
containing varying proportions of sulphur trioxide (see Prep. 109, 
p. 226), and, occasionally, chlorosulphonic acid, C1SO 2 OH, are 
used. In the two latter cases sulphones are sometimes formed 
as a by-product, 

2C 6 H 6 + S0 3 = (C 6 H 6 ) 2 S0 2 + H 2 0. 
2C 6 H 6 + C1S0 2 OH = (C 6 H 5 ) 2 S0 2 + HC1 + H 2 O. 

The sulphonic acids are also obtained by the oxidation of 
thiophenols, a reaction which, at the same time, indicates their 
constitution, 

C 6 H 5 SH + 3 = C 6 H 5 S0 3 H. 

The majority of aromatic sulphonic acids are very soluble in 
water, and are difficult to obtain in the crystalline form. On 
the other hand, the sodium or potassium salts generally crystal- 
lise well, and it is customary to prepare them by pouring the 
sulphonic acid directly after sulphonation into a strong solution 
of sodium or potassium chloride (Gattermann). 

The sulphonic acids decompose on heating into the hydro- 
carbon and SO 3 . This reaction is greatly facilitated by heating 
with cone, hydrochloric acid to 150 180 (Jacobsen), or by 
passing superheated steam into the sulphonic acid mixed 
with moderately strong sulphuric acid (Armstrong). 

This method is sometimes used for separating hydrocarbons, 
one of which is more easily sulphonated than another. The 
sulphonic acid is separated from the unchanged hydrocarbon, 
and the hydrocarbon is then regenerated from the sulphonic 
acid. 

The salts of the sulphonic acids undergo the following re- 
actions : 

i. By fusion with caustic alkalis, phenols are prepared (see 
Preps. 106 and 219), 

C e H 5 SO ;i Na + N?OH = C B H 5 OH + Na. 2 SO 3 . 



APPENDIX 293 



2. By distillation with potassium cyanide, the nitriles are 
obtained, 

C 6 H 5 S0 3 K + KCN = C 6 H 5 CN + 



3. By fusion with sodium formate, the sulphonic group is 
replaced by carboxyl, 

C 6 H 5 SO 3 Na + HCOONa = C 6 H 5 COONa + NaHSO 3 . 

4 By the action of phosphorus pentachloride the sulphonic 
chloride is obtained, 

C 6 H 5 SO S K + PC1 5 = C 6 H 5 S0 2 C1 + POC1 3 + KC1. 

PREPARATION 75. 

Benzenesulphonic Chloride. The sulphonic chlorides 
differ from the carboxylic chlorides in being very slowly decom- 
posed by water. They react, however, in an analogous fashion 
with alcohols, phenols, and amines in presence of caustic soda. 

The behaviour of primary, secondary, and tertiary amines 
has been suggested as a basis of separation of these three classes 
of compounds. The primary amines usually form compounds 
with the sulphonic chloride, which dissolve in caustic soda ; the 
derivatives of the secondary amine are insoluble, whereas the 
tertiary amines do not react with the sulphonic chloride (Hins- 
berg). The method cannot always be employed. 

On reduction of the sulphonic chloride with zinc dust and 
water, the zinc salt of the sulphinic acid is formed, 

2C 6 H 5 SO 2 C1 + 2Zn = (CgHjSO^-jZn + ZnCl 2 . 

The acid is separated from the zinc salt by boiling with 
sodium carbonate, filtering from zinc carbonate, and decom- 
posing the soluble sodium salt with sulphuric acid, which pre- 
cipitates the sulphinic acid. 

The sulphinic acids are unstable compounds. They are readily 
oxidised to sulphonic acids ; on fusion with alkalis they are con- 
verted into the hydrocarbon and alkaline sulphite, 

CH.SO 2 Na + NaOH = 



on reduction they form thiophenols, 

C 6 II 5 .SO 2 H + 2H 2 = C 6 H 5 SH + 2H 2 O. 



294 PRACTICAL ORGANIC CHEMISTRY 



PREPARATION 76. 

Phenol. Fusion of the alkali salt of the sulphonic acid 
with caustic soda or potash is a common method for preparing 
phenols (see Prep. 106, p. 219). Phenols correspond in consti- 
tution to the tertiary alcohols of the aliphatic series, but differ 
in their more negative character. The phenols dissolve in 
caustic alkalis, forming alkaline phenates, which are, however, 
decomposed by carbon dioxide. In this way a phenol may be 
separated from an acid. The solution in caustic soda is satu- 
rated with carbon dioxide, and the phenol is then extracted 
with ether or filtered off. The entrance of nitro-groups into- 
the nucleus converts phenols into strong acids (see Preps. 79 
and 80). 

The various reactions which the phenols undergo are illus- 
trated in Preps. 79 84. 

The technical method for obtaining phenol is by shaking out 
with caustic soda the " middle oil" of the coal-tar distillate, after 
some of the naphthalene has crystallised out. The phenol dis- 
solves in the alkali, and is then removed from insoluble oils. 
The alkaline liquid is acidified, the phenol separated, distilled, 
and finally purified by freezing. 

PREPARATION 77. 

Anisole. The preparation of anisole from phenol is analo- 
gous to Williamson's synthesis of the ethers (see p. 236), but the 
others of phenol cannot be obtained by the action of the alcohol 
on the phenol in presence of sulphuric acid. This reaction can, 
Liowever, be effected in the case of the naphthols (see p. 316). 
Another method of replacing hydrogen by methyl, in addition 
to the use of alkyl halide and alkyl sulphate, is by the action of 
diazomethane on the phenol : 

Nv 

C 6 H 6 OH + 1 1 >CH 2 = C 6 H 5 OCH 3 + N* 

W 

The methyl group in anisole can be split off, and the phenol 
regenerated by heating with HC1 or HI, 

C 6 H 5 OCH 3 + HI = CH 3 I + C 6 H 5 OH. 
The latter reaction has been made the basis of a quantitative 





APPENDIX 295, 



method for determining the number of methoxyl groups (OCH 3 ) 
present in a compound (Zeisel, see p. 220). 

PREPARATION 78. 

Hexahydrophenol. The method of Sabatier and Sen- 
derens for the reduction of organic compounds is very generally 
applicable. It consists in passing the vapour of the organic 
compound mixed with hydrogen over finely divided metals, 
especially nickel, as in the example given. Aldehydes and 
ketones are reduced to alcohols, olefines to paraffins, and, in 
the aromatic series, hydrogen is taken up in the nucleus and 
hydrocyclic compounds result. The hydrocarbons form cyclo- 
paraffins ; the phenols, cyclic alcohols ; the bases, cyclic 
amines, &c. 

PREPARATION 79. 

o- and p-Nitrophenol. The action of nitric acid on 
phenol is much more energetic than it is in the case of 
benzene. To obtain the mono-derivatives, the acid has, in 
consequence, to be diluted. 

The entrance of the nitro-group renders the phenol more 
strongly acid, so that the nitrophenols, unlike the phenols, form 
stable salts with alkaline carbonates. It should be noted that 
the nitro-group enters the ortho- and para-position, but not the 
meta-position to the OH group, according to the general rule 
explained on p. 274. Moreover, the ortho-compound is more 
volatile than the para-compound. Compare o- and ^>-hydr- 
oxybenzaldehyde (Prep. 83, p. 188). 

PREPARATION 80. 

Picric Acid. The presence of three nitro-groups converts 
the phenol into a strong acid. Picryl chloride, which is formed 
by the action of PC1 6 on the acid, behaves like an acid chloride, 
is decomposed by water and alkalis and forms picramide or 
trinitraniline with ammonia, 

C 6 H 2 (NO 2 ) 3 C1 + NH 3 = C 6 H 2 (NO 2 ) 3 NH 2 + HC1. 

Note that the three nitro-groups occupy meta-positions in 
regard to one another ; ortho- or para-positions in reference 
to the hydroxyl group. 



296 PRACTICAL ORGANIC CHEMISTRY 



PREPARATIONS 81 82. 

Phenolphthalein. The action of phthalic anhydride on 
phenol takes place in two ways. When equal molecules of the 
substance react in presence of cone, sulphifric acid, hydroxyan- 
thraquinone is formed (Baeyer), 



/ C0 
C 6 H 4 / 



C0 \ / C0 

\0 + C 6 H 5 OH = C 6 H 4 / C 6 H 3 OH + H 2 O. 



It is by a similar process that alizarin has been synthesised 
with the object of ascertaining its constitution (see Notes on 
Prep. 1 10, p. 316). When two molecules of phenol and one mole- 
cule of phthalic anhydride are heated together with cone, sul- 
phuric acid, then phenolphthalein is formed (Baeyer). Its 
constitution has been determined by its synthesis from phthalyl 
chloride and benzene by means of the " Friedel-Crafts' reaction " 
{see Notes on Prep. 100, p. 309). Phthalyl chloride and benzene 
yield in presence of A1C1 3 phthalophenone, 

C 6 H 5 




CO 

Phthalophenone. 

Phthalophenone is then converted successively into dinitro-, 
diamino-, and, finally, by the action of nitrous acid, into dihydr- 
oxyphthalophenone or phenolphthalein, 

C H,- C H 4 NO C H NH 

C < r^ U C<f. TT XTO C<p TT VTU 

/x v_/gn. 4 i> v_/ 2 x\ ^6 4 2 

C 6 H 4 \/ C -> C 6 H 4 \/ C 

Diaminophthalophenone. 



CO 

Phthalophenone. 


CO 

Dinitrophthalophenone. 

r C 6 H 4 OH 
X C 6 H 4 OH 
C 6 H/>0 



CO 

Phenolphthalein. 

An important group of colouring matters, known as the 
" rhodamines," is obtained from phthalic anhydride and m- 
aminophenol and its derivatives. They have a constitution similar 



APPENDIX 297 

to that of fluorescein. The simplest of these compounds is 
represented by the following formula : 

C 6 H,NH 2 

/ C \ / 
CeH/ O C <> H ' NH * 

N:o 

Rhodamine. 

PREPARATION 83. 

Salicylaldehyde, p-Hydroxybenzaldehyde. "Reimer's 
reaction " for the preparation of hydroxyaldehydes from phenols 
is applicable to a very large number of monohydric and poly- 
hydric phenols. The substitution of two H atoms by two alde- 
hyde groups sometimes occurs, as in the case of resorcinol. An 
analogous reaction is that of caustic potash and carbon tetra- 
chloride on phenol, which yields chiefly /-hydroxybenzoic acid, 

/OH 

C 6 H 5 OH + CC1 4 + 5KOH = C 6 H 4 < + 4 KC1 + 3H 2 O. 

X COOK 

PREPARATION 84. 

Salicylic Acid. The reaction was discovered by Kolbe, 
and is known as " Kolbe's synthesis." It will have been ob- 
served that it takes place in two steps. Sodium phenylcarbonate 
is first formed, which then undergoes intramolecular change 
with the production of sodium salicylate (Schmidt). The tech- 
nical process is carried out in autoclaves, in which carbon 
dioxide is passed into the sodium phenate under pressure at 
120 130. It is a curious fact that the use of potassium phenate 
yields, especially at a high temperature (220), almost exclusively 
the /-hydroxybenzoate of potassium. 

The above reaction may be applied in the case of other 
phenols. 

PREPARATION 85. 

Quinone and Quinol. Quinone, which was originally 
obtained by the oxidation of quinic acid (the acid associated 



298 PRACTICAL ORGANIC CHEMISTRY 

with quinine in cinchona bark), is now prepared from aniline. 
The aniline, in process of oxidation to quinone, appears to pass 
through the following intermediate stages, 



66 . 64 ->C 6 H 4 .O a . 

The aniline is first oxidised to phenylammonium oxide, which 
changes into phenylhydroxylamine. The latter also under- 
goes intramolecular change, being converted into /-amino- 
phenol, which is finally oxidised to quinone (Bamberger). 
It may also be obtained by the oxidation of para-derivatives of 
aniline, such as /-phenylenediamine, sulphanilic acid, p- 
aminophenol, &c. Other amino-compounds and phenols yield 
corresponding quinones, and it can even be prepared from an 
arnino-compound or phenol, if an alkyl group occupies the para- 
position, as in the case of mesidine, which loses a methyl group 
and yields w-xyloquinone. Quinone is sometimes regarded as a 
superoxide (Graebe), sometimes as a para-diketone (Fittig). 

C CO 

/|\ A 

HC/ o V:H HC/ NCH 

O JcH HcJ JCH 

C CO 

Superoxide formula. Diketone formula. 

The facts in favour of the first are that quinone, like a peroxide, 
has a strong oxidising action, that on reduction it yields, not a 
glycol, but a dihydroxybenzene ; moreover, with PC1 5 instead 
of a tetra-chloro-derivative, a dichlorobenzene is formed. In 
favour of the ketone structure is the formation of a mono- and 
di-oxime (Goldschmidt), 

CO C:NOH 

HC/\CH HC/\CH 



HC' "H HCl ^ 

C:NOH C:NOH. 



APPENDIX 299 



Phenylhydrazones^ are not formed, as phenylhydrazine acts as a 
reducing agent and produces quinol. 

The constitution of quinhydrone, the intermediate product 
formed by the reduction of quinone or oxidation of quinol, is 
represented by the formula, 

C(OH) 




\ HCx 

C(OH). 
For the formation of dimethylquinone, see p. 251. 

PREPARATION 86. 

Benzyl Chloride. The action of chlorine on boiling 
toluene is quite distinct from the action which occurs in the 
cold or in presence of a "halogen carrier " (see pp. 252, 271). 
In "the present instance substitution takes place in the side- 
chain. It is a curious fact, however, that chlorine produced by 
electrolysis in presence of boiling toluene mainly enters the 
nucleus. 

By prolonged action all three hydrogen atoms of the side-chain 
may be replaced, and the following compounds obtained: 

C 6 H 5 CH 2 C1 Benzyl Chloride. 

C 6 H 5 CHC1 2 Benzal Chloride. 

C 6 H 8 CC1 3 Benzotrichloride. 

Hydrocarbons containing the halogen in the side-chain may- 
be generally, though not invariably distinguished, by their 
irritating action on the eyes and mucous membrane of the nose, 
from those in which the halogen is present in the nucleus. 
Moreover, the halogen in the side-chain is much more readily 
substituted or removed than when it occurs in the nucleus. In 
this respect the above compounds resemble the members of the 
aliphatic series (alkyl and alkylene halides). Benzyl chloride is 
decomposed by water, ammonia, and potassium cyanide, forming; 
benzyl alcohol, benzyl cyanide, and benzylamine. 

C 6 H 5 CH 2 C1 + H 2 = C 6 H B CH 2 OH + HC1. 

Benzyl alcohol. 

C 6 H 5 CH 2 C1 + KCN = C 6 H S CH 2 CN + KC1. 

Benzyl cyanide. 

C 6 H 5 CH 2 C1 + 2NH 3 = C 6 H 5 CH 2 NH 2 + NH 4 C1. 

Benzylamine. 



300 PRACTICAL ORGANIC CHEMISTRY 

It is also much more easily oxidised than toluene to benzoic 
acid, 

C 6 H 5 CH 2 C1 + O 2 = C 6 H S COOH + HCL 

Benzal chloride and benzotrichloride are also decomposed by 
water, the former in presence of calcium carbonate, and the 
latter at a high temperature, yielding, in the one case, benzalde- 
hyde, and in the other, benzoic acid, 

C 6 H 5 CHC1 2 + H 2 O = C 6 H 5 COH + aHCl. 

Benzaldehyde. 

C 6 H 5 CC1 3 + 2H 2 = CeHsCO.011 + 3HC1. 

Benzoic acid. 

PREPARATION 87. 

Benzyl alcohol may be also obtained by the action of caustic 
potash on benzaldehyde (see Reaction 4, p. 197). This reaction 
is specially characteristic of cyclic-compounds containing an 
aldehyde-group in the nucleus, although some of the higher 
aliphatic aldehydes behave in a similar fashion (Cannizzaro), 

2 C 6 H 5 COH + KOH = C 6 H 5 CH 2 OH + C 6 H 5 COOK. 

Benzyl alcohol. Potassium benzoate. 

Benzyl alcohol has the properties of an aliphatic alcohol, and 
not those of a phenol. On oxidation, it gives benzaldehyde 
and benzoic acid, and it forms benzyl esters with acids or acid 

chlorides, 

C 6 H,CO.OCH 2 .C 6 H 5 . 

Benzyl benzoate. 

PREPARATION 88. 

Benzaldehyde. The aldehydes of the aromatic series 
may also be obtained by the oxidation of a methyl side-chain 
with chromium oxychloride. The solid brown product, 
C 6 H 5 CH 3 (CrO 2 Cl2)2, formed by adding CrO 2 Cl 2 to toluene, 
dissolved in carbon bisulphide, is decomposed with water, and 
benzaldehyde separates out (Etard). Other methods for pre- 
paring aromatic aldehydes are (i) the Friedel-Crafts reaction, in 
which a mixture of carbon monoxide and hydrogen chloride are 
passed into the hydrocarbon in presence of aluminium chloride 

and a little cuprous chloride, 

/CH 3 

C 6 H,.CH 3 + HCL CO = C 6 H 4 < + HC1 ; 

\CHO 



APPENDIX 301 



(2) also by passing a mixture of hydrogen cyanide and hydrogen 
chloride into a phenol ether in presence of A1C1 3 , 

/OCH 3 
C 6 H S OCH 3 + HCN.HC1 = C 6 H 4 < + HC1. 



/ 

C 6 H 4 < 
X 



The product is then hydrolysed with hydrochloric acid 
(Gattermann), 

OCH 3 /OCH 3 

+ H 2 = C 6 H 4 < + NH,. 

CH:NH \CIIO 

(3) GngnarcTs reaction can also be used for preparing aromatic 
aldehydes (p. 308). 

The numerous reactions which benzaldehyde undergoes are 
described in this preparation, and in some of the subsequent 
ones (see Preps. 93-97). 

On reduction, benzaldehyde yields, in addition to benzyl 
alcohol, a pinacone known as hydrobenzoin, 

C 6 H 5 COH C 6 H 6 CHOH 

+ H 2 = | 

C 6 H 5 COH C 6 H 5 CHOH 

Hydrobenzoin. 

PREPARATION 89. 

a- and /3-Benzaldoximes. The existence of two isomeric 
benzaldoximes was first observed by Beckmann in 1889, who 
explained their relation by a difference in structure. 
C 6 H 5 CH:NOH C 6 H 5 CH.NH 

O 

a-Benzaldoxime. (3-Benzaldoxime. 

In the following year Hantzsch and Werner published their 
theory, by which the greater number of isomeric oximes both of 
aldehydes and ketones have found a satisfactory explanation. 

These compounds were not structurally but stereo-isomeric, the 
relation being similar to that which exists between fumaric, maleic 
or mesaconic and citraconic acids (p. 265), or again between the 
two diazotates of potassium (p. 283), and which may be 
represented as follows : 

C 6 H 5 .C.H C 6 H 5 . C. H 

HO.N N.OH 

o-Benzaldoxime. /3-Benzaldoxime. 



302 PRACTICAL ORGANIC CHEMISTRY 

It will be easily understood from these formula why the ^-com- 
pound should yield benzonitrile with acetic anhydride whilst the a- 
compound does not. The proximity of hydrogen and hydroxyl in 
the former case facilitates the formation and elimination of water. 
In this way the configuration of most of the aldoximes may be 
ascertained. 

PREPARATION 90. 

Benzole Acid. The oxidation of the side-chains in aromatic 
hydrocarbons is a matter of considerable interest, as illustrating 
the difference of stability of the side-chain and nucleus, and also 
the influence which the relative positions of the side-chains, 
where more than one is present, exert in presence of oxidising 
agents. 

The oxidation of the side-chain of an aromatic hydrocarbon, 
when more than one is present, takes place in successive steps. 
Thus, mesitylene is converted into the following compounds on 
oxidation . 

^ C 6 H 3 (CH 3 ) 2 CO.OH Mesitylenic acid. 

Mesitylene, C 6 H 3 (CH 3 ) 3 > C 6 H 3 CH 3 (CO.OH) 2 Uvitic acid. 

X 

* C 6 H 3 (CO.OH) 3 Trimesic acid. 

The reagents usually employed are (i) chromic acid or 
potassium bichromate and sulphuric acid, (2) dilute nitric acid 
and (3) potassium permanganate in alkaline or neutral solution. 
The action of these upon the side-chain, when more than one 
side-chain is present, depends upon their relative position. 
Thus, for example, potassium bichromate and sulphuric acid 
either does not act, or completely destroys the compound when 
the side-chains occupy the ortho-position (Fittig), whereas the 
para- and meta-compounds yield the corresponding carboxylic 
acids. This is true also of substituted hydrocarbons with one 
side-chain ; thus with nitric acid m- and ^-nitrotoluene give 
m- and ^-nitrobenzoic acid, whilst the ortho-compound is either 
unattacked or destroyed. If, however, the substituent is a 
halogen and the oxidising agent nitric acid, the m eta-compound 
is least, and the para-compound most acted on. Dilute nitric 
acid or alkaline permanganate are most serviceable for oxidising 



APPENDIX 303 



side -chains where only one side-chain is to be converted into 
carboxyl on account of their less energetic action. 

The oxidation of a halogen-substituted side-chain by the usual 
oxidising agents is much more readily accomplished than that 
of a simple alkyl group. A similar case is that of naphthalene 
tetrachloride, C 10 H 8 C1 4 , which, though an additive compound, is 
much more readily converted into phthalic acid than naphthalene 
itself. 

PREPARATION 91. 

m-Nitro-, m-Amino-, m-Hydroxy-benzoic Acids. 

This series of compounds merely furnishes an exercise in the 
processes previously described and illustrates the application of 
the same reactions in the case of a substituted benzene derivative 
containing a nitro-group. It also illustrates the manner in which 
meta-compounds of benzoic acid may be indirectly prepared 
where a direct method is inapplicable. 



Benzoin. As a small quantity of potassium cyanide is 
capable of converting a large quantity of benzaldehyde into 
benzoin, the action of the cyanide has been explained as follows : 
The potassium cyanide first reacts with the aldehyde and 
forms a cyanhydrin, which then condenses with another molecule 
of aldehyde, hydrogen cyanide being finally eliminated 
(Lapworth), 

/OH /OH 

C 6 H 6 CH < + C 6 H 5 CHO = C 6 H 6 .C^ CH(OH)C 6 H 5 . 

\CN \CN 

= C 6 H S .CO.CH(OH).C 6 H S + HCN. 

The same reaction occurs with other aromatic aldehydes 
(anisaldehyde, cuminol, furfurol, &c.). 

Benzoin yields hydrobenzoin on reduction with sodium 
amalgam, and desoxybenzoin, C 6 H 5 CO.CH 2 .C 6 H 5 , when reduced 
with zinc and hydrochloric acid. 

The latter, which contains the group CO.CH 2 .C 6 H 5 , behaves 
like malonic ester, the hydrogen of the methylene group being 
replaceable by sodium, and hence by alkyl groups. 



304 PRACTICAL ORGANIC CHEMISTRY 

PREPARATION 94. 

Cinnamic Acid. The reaction, which takes place when an 
aldehyde (aliphatic or aromatic) acts on the sodium salt of an 
aliphatic acid in presence of the anhydride, is known as 
" Perkin's reaction," and has a very wide application. Accord- 
ing to the result of Fittig's researches on the properties of the 
unsaturated acids described below, the reaction occurs in two 
steps. The aldehyde forms first an additive compound with 
the acid, the aldehyde carbon attaching itself to the a-carbon 
(i.e., next the carboxyl) of the acid. A saturated hydroxy-acid is 
formed, which is stable, if the a-carbon is attached to only one 
atom of hydrogen, as in the case of isobutyric acid, 

CH 3 
CH 3X 

C 6 H 5 CHO + >CH.COOH = C 6 H 5 CH(OH).C.COOH. 
CH/ | 

CH 3 

If, as in acetic and propionic acids, the group CH 2 is present 
in the a-position, water is simultaneously split off, and an 
unsaturated acid results, 

CH 3 

C 6 H 5 CHO + CH 3 .CH 2 .COOH = C 6 H 5 CH:C.COOH + H 2 O. 

a-Methylcinnamic acid. 

That a-methylcinnamic acid is formed and not phenyliso- 
crotonic acid according to the equation, 

C 6 H B CHO + CH 3 .CH 2 .COOH = C 6 H 5 CH:CH.CH 2 .COOH + H 2 O, 

Phenylisocrotonic acid. 

follows from Fittig's researches, and depends upon the marked 
difference exhibited by the two principal groups of unsaturated 
acids, viz., the a)3 acids, which have the double link between 
the first and second carbon from the carboxyl, and /3y acids, in 
which the double link lies between the second and third 
carbons. Methylcinnamic acid belongs to the first group, 
whereas phenylcrotonic acid belongs to the second group. 

It may be noted in passing that this reaction bears a close 
resemblance to that studied by Claisen, which occurs in 
presence of caustic soda solution between aldehydes or ketones 
on the one hand, and compounds containing the group 



APPENDIX 305 



CH 2 .CO. Benzaldehyde and acetone combine under these 
conditions to form benzylidene- and dibenzylidene-acetone, 

C 6 H 5 COH + CH 3 .CO.CH 3 = C 6 H 5 CH:CH.CO.CH 3 . 

Benzylidene acetone. 

2C 6 H 5 COH + CH 3 .CO.CH 3 = C 6 H 6 CH:CH.CO.CH:CH.C 6 H 5 . 

Dibenzylidene acetone. 

All the unsaturated acids have the following properties in 
common. They form additive compounds with nascent 
hydrogen, halogen acids, and the halogens. On oxidation with 
alkaline permanganate in the cold, they take up two hydroxyl 
groups to form a dihydroxy-derivative, and, on further oxidation, 
ultimately divide at the double link. Cinnamic acid may be 
taken by way of illustration. On reduction it forms phenyl- 
propionic acid, with hydrobromic acid, /3-bromophenylpropionic 
acid (the bromine attaching itself to the ^-carbon, see p. 253), 
with bromine a-dibromophenylpropionic acid, on oxidation with 
permanganate, phenylglyceric acid and then benzaldehyde and 
benzoic acid, 
C 6 H 5 CH:CH.CO.OH + H 2 = C 6 H 5 CH 2 .CH 2 .CO.OH. 

Phenylpropionic acid. 

C 6 H 5 CH:CH.CO.OH + HBr = C 6 H 5 CHBr.CH 2 .CO.OH. 

Phenyl /3-bromopropionic acid. 

C 8 H 5 CH:CH.CO.OH + Br 2 = C 6 H 5 CHBr.CHBr.CO.OH. 

Phenyl a/3-dibromopropionic acid. 

C 6 H 5 CH:CH.CO.OH + H 2 O + O = C 6 H 5 CHOH.CHOH.CO.OH. 

Phenylglyceric acid. 

C 6 H 5 CH:CH.CO.OH + 2O 2 = C 6 II 5 COH + 2CO 2 + H 2 O. 

Benzaldehyde. 

The chief difference between the two groups of a/3 and /3y 
unsaturated acids lies in the behaviour of the additive compounds 
which they form with hydrobromic acid and bromine. 

In the case of the a/3 acids, the hydrobromide of the acid, on 
boiling with water, yields the corresponding /3 hydroxy-acid, 
and, on boiling with alkalis, a mixture of the original acid and 
the unsaturated hydrocarbon, formed by the elimination of 
carbon dioxide and hydrobromic acid, 



/3-Oxyphenyl-propionic acid. 

2. C 6 H 5 CHBr.CH 2 .COOH + NaOH = C 6 H,CH:CH.COOH + NaBr 

Cinnamic acid. -f H 2 O. 

3. C 6 H 5 CHBr.CH 2 .COOH + NaOH = C 6 H 6 CH:CH 2 + CO 2 +NaBr 

Styrene. + H 2 O. 

COHEN'S ADV. p. o. c. x 



306 PRACTICAL ORGANIC CHEMISTRY 

The hydrobromides of /3y unsaturated acids like 0-phenyl- 
crotonic acid behave quite differently. On boiling with water, 
lactonqs:are formed, /.<?., inner anhydrides of oxy-acids, 

H 5 CHBf.CH2.CH 2 .COOH = C 6 II 5 CH.CH 2 .CII 2 + HBr. 

O O 

Phenylbutyrolactone. 

The readiest method for distinguishing a /3y-acid, especially 
of the aliphatic series, is to heat the acid with a mixture of 
equal volumes of cone, sulphuric acid and water to about 140. 
The lactone is formed if a /3y-acid is present, whereas an a/3-acid 
remains unchanged. By diluting, neutralising with sodium 
carbonate, and extracting with ether, the lactone is separated, 
the a/3-acid remaining in solution. 

An interesting relation exists between the two groups of acids. 
It has been found that, on heating /3y-acids with caustic soda 
solution, a shifting of the double link on the a/3-position takes 
place, 

C 6 H S CH:CH.CH 2 .COOH = C 6 H 5 CH 2 .CH:CH.COOH. 

y /3 a j3 a 

PREPARATION 95. 

Hydrocinnamic Acid. The preparation illustrates the use 
of sodium amalgam as a reducing agent. It should be noted 
that hydrocinnamic acid may be also obtained from malonic 
ester by acting upon the sodium compound with benzyl chloride, 
then hydrolysing and removing carbon dioxide, 

C 6 H 5 CH 2 C1 + NaCH(COOC,H 5 ) 2 -> C 6 H 5 CHo.CH(COOC,H 5 )o 
-> C 6 H 5 CH2.CH(COOH) 2 + C 6 H 5 CH 2 .CH,COOH. 



PREPARATION 96. 

Mandelic Acid. The reaction furnishes a simple and 
general method for obtaining hydroxy-acids from aldehydes or 
ketones by the aid of the cyanhydrin. The formation of the 
cyanhydrin may be effected in the manner described or by the 
action of hydrochloric, acid on a mixture of the aldehyde or 
ketone with potassium cyanide, or, as in the case of the sugars, 
by the use of liquid hydrocyanic acid and a little ammonia. 



APPENDIX 307 



Mandelic acid was originally derived from bitter almonds, and 
can be obtained by the action of baryta on amygdalin, the 
glucoside of bitter almonds, which breaks up into glucose and 
mandelic acid. Mandelic acid contains an asymmetric carbon 
atom, and is capable, therefore, of being resolved into optical 
enantiomorphs (p. 262). This has been effected by fractional 
crystallisation of the cinchonine salt, from a solution of which 
the dextro-rotatory component first separates. Another method, 
known as the biochemical method, is to cultivate certain low 
organisms in a solution of a salt of the acid when one of the 
components is destroyed or assimilated. Thus ordinary green 
mould (penidllhuii) assimilates and removes the Irevo component, 
leaving a dextro-rotatory solution. These two methods, together 
with the separation of the enantiomorphous crystalline forms 
described on p. 123, comprise the three classical methods devised 
by Pasteur for resolving inactive substances into their active 
components. Mandelic acid may also be resolved by partial 
hydrolysis of its esters by the ferment "lipase" (Dakin) and 
also by the partial esterification of the acid with an active alcohol 
such as menthol (Marckvvald). 



PREPARATION 97. 

Phenylmethylcarbinol. The method of Grignard, of 
which this preparation serves as an illustration, has received a 
very wide application. The following is a brief and incomplete 
list of these reactions, in which the organic radical (R) represents 
within certain wide limits both an alkyl and aryl group : 

Hydrocarbons. The magnesium compound is decomposed 
by water, 

RMgl -t H 2 O = R.H + Mgl(OH). 

Alcohols may be obtained from aldehydes, ketones, esters, 
acid chlorides, and anhydrides, 

R x R\ /OMgl R v /OH 

>CO + RMgl -* >C<; -> >C< 

R/ R/ \R IV NR 

/O /OMgl /OMgl /OH 

R.Cf + 'RMgI-R.C^-OCgH 5 -R.c-R ' -R.C-R 

X OC 2 H 5 \R \R \R. 

X 2 



308 PRACTICAL ORGANIC CHEMISTRY 

Aldehydes can be prepared from dimethylformamide, 

HCO.NRR + RMgl -> HCR(OMgI)NRR ->- RCHO + NHRR + 

Mg(OH}I, 
and from formic and orthoformic ester, 



+ RMgI-=>RCHO + MgI.OC 2 H 5 . 
Ketones may be obtained from cyanogen, cyanides, or amides, 

/NMgl 

RCN + RMgl -> R.C< -> R.CO.R + NH 3 + Mg(OH)I. 

\R 

Acids are produced by passing carbon dioxide into the ether 
solution of the magnesium alkyl compound, 

/OMgl /OH 

RMgl + CO 2 -> R.C/ -> R.C/ + Mgl(OH). 

In addition to the above, Grignard's reagent has been utilised 
in preparing olefines, ethers, ketonic esters, hydroxy-acids, 
quinols, amides, hydroxylamines, &c., for details of which books 
of reference must be consulted. 1 

PREPARATION 98. 

Benzoyl Chloride. The formation of esters by the action 
of benzoyl chloride or other acid chloride on an alcohol or phenol 
in presence of caustic soda is known as the " Schotten-Baumann 
reaction." The reaction may also be employed in the prepara- 
tion of derivatives of the aromatic amines containing an acid 
radical, like benzanilide, C 6 H 6 NH.CO.C 6 H 6 , 



C 6 H 5 COCl + NH 2 .C 6 H 5 + NaOH = C 6 II 5 CO.NHC 6 H 8 + NaCl + H 2 O. 



PREPARATION 99. 

Ethyl Benzoate. The method of Fischer and Speier for 
the preparation of esters, by boiling together the acid with the 
aUohol containing about 3 per cent, of either hydrochloric acid 

1 Schmidt, Ahrens' Vortrage, 1905, 10, 68. 



APPENDIX 309 



or cone, sulphuric acid, can be adopted in the majority of cases 
with good results, and has many advantages over the old 
method of passing hydrochloric acid gas into a mixture of the 
alcohol and acid until saturated. Read Notes on Prep. 15, 
P- 247- 

PREPARATION 100. 

Acetophenone. The " Friedel-Crafts' reaction," of which 
this preparation is a type, consists in the use of anhydrous 
aluminium chloride for effecting combination between an 
aromatic hydrocarbon or its derivative on the one hand, and a 
halogen (Cl or Br) compound on the other. The reaction is 
always accompanied by the evolution of hydrochloric or hydro- 
bromic acid, and the product is a compound with A1C1 3 , which 
decomposes and yields the new substance on the addition of 
water. This reaction has been utilised, as in the present case, 
(i) for the preparation of ketones, in which an acid chloride 
(aliphatic or aromatic) is employed, 

C 6 H 6 + Cl.CO.CHs = C 6 H 5 .CO.CH 3 + HC1. 

Acetophenone. 

C 6 H 6 + C1.CO.C 6 H 5 = C 6 H 6 .CO.C 6 H 6 + HC1. 

Benzophenone. 

If a substituted aromatic hydrocarbon is used, the ketone 
group then enters the para-position, or, if this is occupied, the 
ortho-position. Substituted aromatic acid chlorides may also 
be used, and if the acid is dibasic and has two carboxyl chloride 
groups, two molecules of the aromatic hydrocarbon may be 
attached. If phosgene is used with two molecules of benzene, 
benzophenone is obtained, 

2C 6 H 6 + C1 2 CO = C 8 H 5 .CO.C 6 H 8 + 2HC1. 

Benzophenone. 

(2) This reaction may be modified by decreasing the propor- 
tion of the hydrocarbon, and an acid chloride is then formed, 

C 6 H 6 + C1COC1 = C 6 H S .COC1 + HC1. 

Benzoyl chloride. 



PRACTICAL ORGANIC CHEMISTRY 



(3) With an aromatic hydrocarbon and a halogen derivative 
of an aliphatic hydrocarbon or aromatic hydrocarbon substi' 
tuted in the side-chain, new hydrocarbons may be built up (see 
Prep. 1 02, p. 214), 



CH 



C 2 H 5 Br = C 6 H 5 .C 2 H 5 + HBr. 

Ethylbenzene. 



C 6 H 6 + C1CH 2 .C 6 H 5 = C 6 H 5 .CH 2 .C fi H 5 + HC1. 

Diphenylmethane. 

3C 6 H 6 + CHC1 3 = CH(C 6 H 5 ) 3 + 3 HC1. 

Triphenylmethane. 

Anthracene has been synthesised from tetrabromethane and 
benzene by this method, 



C 6 H 4 



Br 


CH 


Br 


H ? 


1 


H, 


Br 


CH 


Br 



/ CH \ 

C 6 H 4 = C 6 H/ | >QH 4 + 4 HBr. 

NCH/ 

Anthracene. 

(4) Amides may be prepared by the use of chloroformamide, 
C 6 H 6 + C1CONH 2 = C 6 H 5 .CO.NH 2 + HC1. 

The chloroformami'de is obtained by passing HC1 gas over 
heated cyanuric acid (Gattermann), 

HOCN + HC1 = Cl.CONHa- 

(5)'Hydroxyaldehydes have been obtained indirectly by the 
use of the crystalline compound HC1.HCN (which hydrochloric 
acid forms with hydrocyanic acid) acting upon a phenol ether, 



C 6 H 5 OCH 3 + HC1.HCN = C 6 H 4 < 



,OCH. 



The aldime is subsequently hydrolysed with dilute sulphuric 
acid (Gattermann), 



,OCH, 



X>CH a 



C 6 H 4 < " + H 2 = C 6 H 4 < 

X C:NH \COH 



NH. 



In addition to the Friedel-Crafts' reaction, the aromatic 
ketones may be obtained by distilling the calcium salt of the 



APPENDIX 311 



aromatic acid or a mixture of the salts of an aromatic and 
aliphatic acid. The reaction is precisely analogous to the 
process used for the preparation of aliphatic ketones, 

2C 6 H 5 COOca' = C G H 5 CO.C e H 5 + CaCO 3 . 

Benzophenone. 

C 6 H 5 COOca' + CH 3 COOca' = C 6 H 5 .CO.CH 3 + CaCO 3 . 

Acetophenone. 

They possess the usual properties of ketones of the aliphatic 
series (see p. 69), which are illustrated by the various reactions 
described at the end of this preparation. 

A special interest attaches to the oximes of those ketones 
which contain two different radicals linked to the CO 
group. Many of these substances exist in two isomeric 
forms, which are readily converted into one another. Phenyl- 
tolylketoxime exists in two forms and benzildioxime in three 
forms, which cannot be explained by structural differences 
of constitution. They must therefore represent different 
space configurations of a type analogous to that of citra- 
conic and mesaconic acid (Hantzseh, see p. 265). They 
are distinguished by the terms " syn "and " anti," corresponding' 
to "cis"and " trans " among the unsaturated acids. "Anti" 
signifies away from the group, the name of which follows ; 
" syn " signifies the position near that group (see pp. 283 and 
301), 

QHj. C. C C H 4 . CH 3 C 6 H 5 . C. C a H 4 . CI I 3 

HO.N / N.OH 

Syn-Phenyltolylketoxime. ^^/-Phenyltolylketoxime. 

! ' 

Benzil forms three dioximes which are distinguished by the 
names "syn," "anti," and "amphi." 

C 6 H 5 C.C.C 6 H 5 CH 5 .C C.C 6 H 5 C 6 H 5 .C C.C 6 H 5 

HO.N N.OH HO.N HO.N N.OH HO.N 

anti. amphi. syn. 

The action of PC1 5 on these substances, known as Beckmann s 
reaction, is of great importance in distinguishing the different 



312 PRACTICAL ORGANIC CHEMISTRY 

forms of ketoximes. The two isomeric phenyltolylketoximes 
yield two different amides, 

C 6 H 5 .C.C 6 H 4 .CH, C 6 H 5 .C.C 6 H 4 CH 3 OC.C 6 H 4 CH 3 



HON 


C1.N 


C 6 H 5 HN 
Toluic anilide. 


C 6 H 5 . C. C 6 H 4 CH 3 


CgHg. C. CgH 4 . CrI 3 


C 6 H 5 CO 


II ~> 


II ~> 


I 


NOH 


N.C1 


NHC 6 H 4 CH 3 

Benzoic toluide. 



Toluic anilide, on hydrolysis, forms toluic acid and aniline, 
whereas benzoic toluide yields benzoic acid and toluidine. It 
follows therefore that, in the original compound, the first con- 
tains the hydroxyl nearer the phenyl group and the second 
nearer the tolyl group. 

For further details on the stereoisomerism of nitrogen com- 
pounds, the text-book must be consulted. 

PREPARATION 101. 

Diphenylmethane. This reaction is analogous to that of 
aluminium chloride on a mixture of benzene and benzyl chloride 
referred to in the notes on Prep. 100, p. 310. The reaction is 
also effected by the use of zinc dust or finely-divided copper 

(Zincke). 

PREPARATION 102. 

Triphenylmethane. This is another example of the 
" Friedel-Crafts'" reaction, which has already been referred to 
in the notes on Prep. 100, p. 309, 

The synthesis of pararosaniline from triphenylmethane is one 
which has gone far to solve the problem of the constitution of 
the important class of triphenylmethane colouring matters. 

Rosaniline or magenta was originally obtained by oxidising 
with arsenic acid a mixture of aniline with o- and p- 
toluidine. The product was then lixiviated and treated with 
common salt, which converted the arsenate into the hydro- 
chloride of rosaniline. Pararosaniline was prepared in a similar 
way from a mixture of aniline and /-toluidine. The series 



APPENDIX 



313 



of reactions by which triphenylmethane is converted into para- 
rosaniline may be represented as follows : 

/C 6 H 5 /C 6 H 4 N0 2 /C H H 4 NH 2 /C 6 H 4 NH 2 

HC^QH 5 -> HC(-C 6 H 4 NO 2 -> HCf-C 6 H 4 NH 2 (HO)C^-C 6 H 4 NH 2 

\C 6 H 5 \C 6 H 4 N0 2 \C 6 H 4 NH 2 \C 6 H 4 NH 2 

Triphenylmethane. TrIn ^S enyl - Paraleucaniline. Para = iline 

By the action of hydrochloric acid on the base, the hydro- 
chloride of pararosaniline is formed, which is the soluble 
colouring matter, 

HO.C(C S H 4 NH 2 ) 3 + HC1 = C(C 6 H 4 NH 2 ) 3 C1 + H 2 O. 

The constitution of the hydrochloride is doubtful ; but the 
so-called quinonoid structure, by which the substance is repre- 
sented as a derivative of quinone, is generally accepted, 

C(C 6 H 4 NH 2 ) 2 



HC 
H 



\ 



CH 
CH 



C 



NH.HC1. 

Pararosaniline hydrochloride. 

The formation of rosaniline from a mixture of aniline, o- and 
/-toluidine is represented by assuming that the methyl-group 
of ^>-toluidine acts as the link which connects the nuclei of 
aniline and <?-toluidine. 



HC 



II H 
H H 



C 6 H 4 NH 2 
/NH 



CH ; 



\CH 3 



30 = 



C H / NH 2 
Rosaniline base. 



2 H 3 O 



PREPARATION 103. 

Benzaldehyde Green. The formation of malachite 
green (benzaldehyde green) by the action of benzaldehyde 



PRACTICAL ORGANIC CHEMISTRY 



upon dimethylaniline in presence of zinc chloride, and subse- 
quent oxidation of the product, may be interpreted on similiar 
lines, and has already been referred to. (See notes on Prep. 59, p. 

279)- 

/C 6 H 5 



HC.,-'Hj QH 4 N(CH 3 ) 2 
:: --?. H;C 6 H 4 N(CH 3 ) 2 



/C 6 H 5 

HC^C 6 H 4 N(CH 3 ) 2 
\C 6 H 4 N(CH 3 ) 2 

Leukobase of 
malachite green. 



.HC^CgH 4 i N(CH 3 )..'+ O = HO.C^-CeH 4 N(CH 3 ) 2 
\C 6 H 4 N(CH 3 ) 2 \C 6 H 4 N(CH 3 ) 2 

Base of malachite 
green. 

The preparation of " crystal violet " from Michler's compound 
and dimethylaniline in presence of POC1 3 may be explained in a 
similar fashion, 

or /C 6 H 4 N(CH 3 ) 2 /C 6 H 4 N(CH 3 ) 2 

UC \C 6 H 4 N(CH,) 2 = HO.C^-C 6 H 4 N(CH 3 ) 2 

+ HC 6 H 4 N(CH 3 ) 2 \C 6 H 4 N(CH 3 ) 2 

Base of crystal 

violet. 

The constitution of the hydrochlorides of malachite green and 
crystal violet will appear as follows : 



r /C 6 H 5 
V\C 6 II 4 N(CH 3 ) 2 



r /C 6 H 4 N(CH 3 ) 2 
C \C 6 H 4 N(CH 3 ) 2 



CH 

IIC; ,CH 

\/ 
C 

N(CH 3 ) 2 
Cl 

Malachite green. 




N(CH 3 ) 2 



Cl 

Crystal violet. 



PREPARATION 104. 

Phthalic Acid. In the formation of phthalic acid by the 
oxidation of naphthalene with sulphuric acid,. the mercuric sul- 



APPENDIX 315 



phate acts as a catalyst. The latter reagent has been used success- 
fully in other oxidising processes, although the manner of its 
action is not yet explained. The formation of phthalic acid from 
naphthalene represents the initial stage in the manufacture of 
artificial indigo from coal-tar. The subsequent processes consist 
in converting the acid into the anhydride by sublimation, the 
anhydride into phthalimide by the action of ammonia gas, and the 
phthalimide into anthranilic acid by the action of sodium hypo- 
bromite (Hofmann's reaction, see p. 80). 

CO. CO CONHBr 

C 6 H 4 



4 - 6 6 

X CCK XXK \COOH 



X COOH. 

The anthranilic acid is then converted into indigo by 
combining it with chloracetic acid and fusing the product with 
caustic alkali, which gives indoxyl and finally indigo by oxida- 
tion, 

\VTJT "\TtH"*T4 /T^/~*T4 

yi\ ilg / ilv^rl^i \^\J\Jil 

C 6 H 4 < + C1CH 2 .COOH = C 6 H 4 < 

X COOH X COOH 

,NHCH 2 .COOH /NH X 

C 6 H 4 / -> C 6 H 4 < >CH 2 

\COOH X CO/ 

Indoxyl. 

C 6 H 4 <^ /C = C\ ^>C 6 H 4 . 

\CQ / ^CO ' 

l Indigo. 

PREPARATIONS 105 and 106. 

Naphthalenesulphonate of Sodium. /3-Naphthol. 

The formation of the sulphonic acid of naphthalene and the 
corresponding phenol by fusion with caustic soda is analogous 
to that of benzene sulphonic acid and phenol (see Prep. 74, 
p. 177, and 76, p. 179. It should be noted that naphthalene 
forms two series of mono-derivatives distinguished as a and ft 
compounds. By the action of sulphuric acid on naphthalene, 
both a and (3 sulphonic acids are formed. At a lower tempera- 
ture (100) the product consists mainly of the a compound ; at a 



316 PRACTICAL ORGANIC CHEMISTRY 

higher temperature (170) of the /3 compound. /3-Naphthol and 
its derivatives are used for the preparation of azo-colours (see 
Reaction 6, p. 163), and for that of /3-naphthylamine. The latter 
is obtained by the action of ammonia under pressure on j3- 
naphthol, 

C 10 H 7 OH + NH 3 = C 10 H 7 NH 2 + H 2 O. 

This reaction is resorted to for the reason that naphthalene 
forms only the a-nitro-compound with nitric acid. The method, 
similar to that used for preparing aniline from nitrobenzene, 
cannot, therefore, be employed for the production of /3-naphthyl- 
amine. a-Naphthol is mainly used for the manufacture of 
yellow and orange colours (Martius and naphthol yellow) by 
the action of nitric acid, and are similar in constitution to picric 
acid (see Prep. 107). 

The naphthols differ from the phenols of the benzene series 
in forming ethers after the manner of aliphatic alcohols, viz., by 
the action of sulphuric acid on a mixture of the naphthol and the 
alcohol, which the other phenols do not, 

C 10 H 7 OH + CH 3 OH = C 10 H 7 OCH 3 + H 2 O 

Naphthyl methyl ether. 

PREPARATION 108. 

Anthraquinone. The constitution of anthraquinone is 
derived from various syntheses, such as the action of zinc dust 
on a mixture of phthalyl chloride and benzene, or by heating 
benzoyl benzoic acid with P 2 O 5 , 

/COC1 /CO X 

C 6 H 4 < + C 8 H 6 = C 6 H 4 < >C 6 H 4 + 2HC1 

X COC1 XXK 

/CO. Cg H 6 / CO\ 

V.H 4 + HA 



Unlike benzoquinone, it is not reduced by sulphur dioxide 
(see Prep. 85, p. 193). Heated with HI or zinc dust it is con- 
verted into anthracene. 

PREPARATION no. 

Alizarin. The first synthesis of alizarin is due to Graebe 
and Liebermann (1868). The present method was discovered 
simultaneously by these chemists and by Perkin. By the action 



APPENDIX 



317 



of fuming sulphuric acid on anthraquinone, the main product is 
/3-anthraquinone monosulphonic acid, 




By fusion of the sodium salt with caustic soda and potassium 
chlorate, the hydroxyl groups enter the a and /3 position. The 
constitution of alizarin is therefore 



OH 



\/\ 



OH 



ox ^ 

Alizarin. 

The constitution has been determined by its synthesis from 
phthalic anhydride and catechol in presence of concentrated 
sulphuric acid (Baeyer), 



C 6 H 4 



xCO v 
/ 

xx 



+ C.H 



OH 



X O 



H 



co 



\, 



OH 
OH 



Other colouring matters have been obtained by the oxidation of 
alizarin (purpurin), and by fusion of the disulphonic acids of 
anthraquinone with caustic soda (anthrapurpurin and flavo- 
purpurin). It is an interesting fact that, among the numerous di- 
and poly-hydroxyanthraquinones, only those which have the two 
hydroxyls in the aft position are colouring matters (Liebermann 
and Kostanecki), 

OH OH 




OH 



\/\rn/\ 



Purpurin. 



Flavopurpurin. 



PRACTICAL ORGANIC CHEMISTRY 



PREPARATION in. 

Isatin. The formation of isatin from indigo may be 
represented as follows : 



co 



O 



CO v /CO 



,\^V\ /\S\J \ /\^\J V 

C 6 H 4 <^ ^>C = C<^ ^>C 6 H 4 = 2C 6 H 4 <^ ^CO. 



O Pseudo-isatin. 



Indigo. 

This compound represents the unstable pseudo- or lactam- 
form, and passes into the stable or lactim-form (Baeyer), 

/CO X 
C 6 H 4 / ^C(OH). 

Isatin (stable form). 

There exists, however, some uncertainty as to which formula 
represents the stable form. Derivatives of both forms are 
known, and the compound offers an example of tautomerism 
(see Notes on Preps. 16, p. 252), or, as it has been also termed, 
psetidomerism. 

The constitution of isatin has been determined by its synthesis 
from 0-nitrophenylglyoxylic acid, 

/CO.COOH /CO.COOH /CO, 

\f 



C 6 H 4 ^C 6 H 4 ^C 6 H 4 C(OH), 

\N0 2 \NH 2 \ N " 

which passes on reduction into the amino-compound, the latter 
forming the anhydride or isatin (Claisen). 



PREPARATION 112. 

Quinoline. The formation of quinoline by " Skraup's 
reaction " may be explained as follows : The sulphuric acid 
converts the glycerol into acrolein, which then combines with 
the aniline to form acrolein-aniline. The latter on oxidation 
Avith nitrobenzene yields quinoline. 



APPENDIX 



319 



CHoOH.CHOH.CHoOH = CH 2 : CH.COH + 2H 2 O 

Acrolein. 



C 6 H 5 NH 2 



OCH.CH : CH 2 = C 6 H 5 N : CH.CH : CH 2 

Acrolein aniline. 



HO 



O j 
H ;CH 

/\ H |\H 



CH 



H.,0. 



\ir/ 



N 
Quinoline. 



The reaction is a very general one, and most of the primary 
aromatic amines and their derivatives can be converted into 
quinoline derivatives, provided that one ortho-position to the 
amino-group is free. 0-Aminophenol, for example, yields 
<?-hydroxyquinoline in the same way, 



0-Aminophenol. 



OH N 
0-Hydroxyquinoline. 



PREPARATION 113. 

Quinine Sulphate. Quinine belongs to the group of 
" vegetable bases " or alkaloids. These substances are widely 
distributed among different orders of plants, and are usually 
colourless, odourless, and crystalline solids. A few, however, 
are liquids (conine and nicotine), and possess an unpleasant 
smell. There is no general method by which the alkaloids can 
be isolated from the plants in which they are found. They 
usually exist in combination with acids, such as malic, lactic, 
and other common vegetable acids. Frequently the acid present 
is peculiar to the plant in which it occurs. Quinine and the 
other cinchona alkaloids are found in combination with quinic 
acid, morphine with meconic acid, aconitine with aconitic 
acid, &c. A common method for separating the alkaloid is to 
add an alkali. If the base is volatile in steam, like conine, it 
is distilled with water ; if, as generally happens, the substance 
is non-volatile, it is extracted by means of a suitable volatile 



320 



PRACTICAL ORGANIC CHEMISTRY 



solvent, such as ether, chloroform, alcohol, amyl alcohol, &c. 
The solvent is then distilled off, and the alkaloid, which remains, 
is either crystallised or converted into a crystalline salt. 

The alkaloids are strong bases, which turn red litmus blue, and 
are very slightly soluble in water. They form soluble salts and 
double salts with platinic and auric chlorides. The principal 
general reagents for the alkaloids are : 

1. A solution of iodine in potassium iodide, which forms a 
reddish-brown precipitate of the periodides. 

2. A solution of phosphomolybdic acid in nitric acid, which 
gives yellow precipitates of different shades. 

3. A solution of potassium mercuric iodide, which forms white 
or yellowish-white precipitates. 

The constitution of quinine is not yet elucidated. Its relation- 
ship to quinoline has long been known, since it gives this 
substance on distillation with caustic potash (Gerhardt). 

PREPARATION 114. 

Phenylmethyltriazole Carboxylic Acid. The mother 
substance of this compound is a triazole, viz., pyrro-a/3-diazole, 
which is one of four isomeric compounds : 

NH NH Nil NH 



N 



/\ 



HC CH 



N 



N CH 



N 



/\ 



CH 



TO 



HC 



N N 



CH 



Pyrro-oa'-diazole. Pyrro-ojS-diazole. Pyrro-a/y-diazole. Pyrro-/3j3'-diazole. 

Pyrro-er/3-diazole was first obtained by the oxidation of azimido- 
toluene, which in turn was prepared by the action of nitrous 
acid on <?-toluylenediamine, 



CH 





NH 
HOOCC/^N 



Azimidotoluene. 



HO.OC\/ 



Azimidobenzoic acid. 
HC/\N 



HOOC.C 



N 



Triazoledicarboxylic acid 



LN 

Pyrro-o/S-diazole. 



APPENDIX 321 



It is a colourless oil, b. p. 280', with the properties of a weak 
secondary base, dissolving in acids, and forming easily hydro- 
lysable salts. 

The reaction described in this preparation is of a general 
character, and furnishes a useful method for preparing members 
of this series of heterocyclic compounds. Diazobenzolimide 
condenses in a similar fashion with ketones (acetophenone) and 
dibasic esters (malonic ester) as well as with ketonic esters, as in 
the present case. These substances possess the usual properties of 
cyclic compounds ; carboxyl may be removed as CO 2 , and alkyl 
side-chains oxidised to carboxyl ; they may be sulphonated and 
nitrated, and the nitro-group reduced to an amino-group ; the 
phenyl group attached to the nitrogen may also be removed by 
oxidation. Thus, phenylmethyltriazole carboxylic acid, loses 
CO 2 on heating, and on oxidation the methyl group becomes 
carboxyl and can also be removed in the same way. The 
resulting product is phenyl triazole. The properties of the 
individual triazoles are influenced, like other cyclic compounds, 
by the groups attached to the nucleus, and to some extent also by 
the basic character of the mother substance. 



COHEN'S ADV. p. o. c. 



322 



PRACTICAL ORGANIC CHEMISTRY 



HINTS ON THE INVESTIGATION OF ORGANIC 
SUBSTANCES 

Provide yourself with a good book of reference, or chemist's 

pocket book which contains tables of physical constants. 

Homogeneity. Determine if the substance is homogeneous. 

A Liquid. If it is a liquid, distil a few c.c. from a miniature 

distilling flask with a long side-tube, but no condenser, or with 

the apparatus shown in 
Fig. 86, in which the con- 
densing surface is sup- 
plied by an inner tube 
through which water per- 
colates. 1 

Use a thermometer and 
collect the distillate in a 
test-tube. Note the boil- 
ing-point, and observe if 
it fluctuates or remains 
constant and if any solid 
residue remains. A low 
boiling-point generally 
denotes a low molecular 
weight. A portion dis- 
tilling in the neighbour- 
hood of joo may indicate 
the presence of water. 

It is useful to shake a 
known volume (5 c.c.) of 
the liquid with an equal 
volume of water and tc 
note if the substance dissolves, or if any marked change in the 
volume of the liquid occurs. A convenient apparatus for this 

1 This apparatus can ako be used as reflux condenser or for collecting evolved gas 
if the side piece is furnished with a delivery tube dipping under water or mercury. 




FIG. 86. 



APPENDIX 



323 



purpose is shown in Fig. 87, which is merely a small and narrow, 
graduated cylinder holding 10 c.c. 1 The solubility of a portion 
of the liquid is an indication of the presence of a 
mixture. Furthermore, the specific gravity of the in- 
solubie portion (its floating or sinking in the water) 
will be roughly indicated and should be noted. 

A Solid. If the substance is a solid, examine a 
few particles on a slide under the microscope, or, 
better still, recrystallise a little if possible and notice 
if the crystals appear similar in shape. If it is a 
mixture, try to separate the constituents by making a 
few trials with different solvents, water, alcohol, ether, 
benzene, petroleum spirit, ethyl acetate, acetic acid, etc. 
If it appears homogeneous, determine the melting- 
point, the sharpness of which will be a further con- 
firmation. If it turns out to be a mixture, it must 
be further treated in the manner described under 
" mixtures " (p. 343). 

The Action of Heat. We will assume in the first FIG. s 7 . 
place that the substance is homogeneous and consists 
of a single individual. Heat a portion on platinum foil and 
notice if it volatilises, chars, or burns with a clear, luminous, 
non-luminous (aliphatic), or smoky (aromatic) flame. Determine 
the nature of the residue, if any, when the carbon has burnt 
away. 

Metal or metallic oxide or carbonate may indicate the presence 
of an organic acid, phenate, or double salt of a base. 

Sulphate, sulphite, or sulphide may indicate a sulphate, 
sulphonate, mercaptan, or bisulphite compound of an aldehyde 
or ketone. 

Cyanide may indicate a cyanide or ferrocyanide, etc. 

Heat a little of the substance in a small, hard-glass tube and 
observe whether the substance melts, chars, explodes, sublimes, 
or volatilises ; whether an inflammable gas, water, etc., is evolved ; 
also notice the smell. 

Carbohydrates, polyhydric alcohols, higher organic acids (e.g.. 
stearic), dibasic and hydroxy-acias (^.g., tartaric), certain amides 
(e.g., oxamide), alkaloids, and azo and other organic colours char 

1 Both pieces of apparatus (Figs. 86 and 87) can be obtained from Mr. O. Baum- 
bach, 10, Lime Grove, Oxford Street, Manchester. 

Y 2 



324 PRACTICAL ORGANIC CHEMISTRY 

and give off water or (if nitrogen is present) ammonia or basic 
constituents. But a great number of common organic com- 
pounds are volatile without decomposition. 

The Elements. Test for nitrogen, 1 sulphur, and halogens. If 
none of these are found, carbon and hydrogen are present and, if 
the substance has given off water or is soluble in water, it may 
be assumed that oxygen is present as well. The action of sodium 
on the substance, if liquid, or on its solution in benzene orligroin, 
if solid, should be tried in the apparatus, Fig. 86, and the gas 
evolved tested for hydrogen, which if present, may indicate 
hydroxyl, ketone, or ester groups. 

The presence of nitrogen may indicate an ammonium salt, 
organic base (amine or alkaloid), amino-acid, amide, cyanide, 
\socyanide, oxime, nitroso- or nitro-compound, azo-compound, etc. 

The presence of sulphur may indicate a sulphate of an organic 
base, alkyl sulphate, sulphite, stilphide, mercaptan, sulphonic add, 
bistdphite compound of aldehyde or ketone. 

The presence of a halogen may indicate a haloid salt of a 
base, alkyl, alkylene, or aryl halide, acid halide, haloid derivative 
of an aldehyde or acid. Some substances, like mustard oils, 
amino-sulphonic acids and thioamides, contain both nitrogen 
and sulphur. 

Solubility. Try if the substance dissolves in hot or cold 
water. Apart from the salts of organic bases and acids, many of 
which are very soluble in water, the solubility of simple organic 
substances is generally determined by the presence of the OH 
group (including CO.OH and SO. 2 .OH groups) and to some 
extent by the NH 2 group. The greater the proportion of OH 
groups to carbon, the greater, as a rule, is the solubility in water. 
The lower alcohols, methyl, ethyl and propyl alcohols, are 
miscible with water ; normal butyl and zVobutyl alcohols (fermenta- 
tion) dissolve in about 10 parts of water at the ordinary tempera- 
ture ; amyl alcohol (fermentation) in about 40 parts of water. The 
first two may be separated from solution by the addition of solid 
potassium carbonate. The addition of common salt is sufficient to 

1 It is sometimes difficult to detect nitrogen by tjhe sodium test. The result should 
not be regarded as conclusive, especially if the substance is volatile, unless it has 
been dropped in small quantities at a time into the melted metal, which should be 
heated in a hard glass tube clamped in a retort-stand. Special care must be used with 
nitro-compounds, which may explode and shatter the tube. 



APPENDIX 325 



separate the last three (propyl, butyl, and amyl). The poly- 
pi ydricalcohols,glycol, glycerol,and mannitol, and also substances 
like the sugars are extremely soluble, for the proportion of OH 
groups to carbon is high. Ordinary phenol requires for solution 
1 5 parts of water, whereas the di- and tri-hydric phenols readily 
dissolve. The same applies to acids. The lower monobasic 
aliphatic acids (formic, acetic, propionic, and normal butyric) 
are easily soluble in water, whereas zsobutync requires 3 parts 
and valeric about 30 parts of water. The last three separate 
from water on the addition of salt. The dibasic and hydroxy- 
acids, where the proportion of carbon is small (succinic, tartaric, 
and citric), are naturally more soluble than the monobasic 
acids having the same number of carbon atoms. 

The majority of aromatic acids are not very soluble in water 
at the ordinary temperature, for the proportion of carbon to 
carboxyl is high ; the hydroxy- and polybasic and also amino- 
acids are more soluble than the unsubstituted monobasic acids 
(or, if substituted, where the substituents are halogens or nitro- 
groups, which diminish, as a rule, the solubility). One thousand 
parts of water dissolve about 2^ parts of benzoic, 2^ parts of 
salicylic, 8 parts of phthalic, and 159 parts of mandelic acid. 
Acids such as gallic and tannic acids are readily soluble in water. 

The sulphonic acids and also many of their salts are very 
soluble. 

The lower aliphatic amines and amides are soluble in water, 
but not the higher members, nor the simple aromatic amines ; 
but some diamines, amino-phenols and amino-acids are moder- 
ately soluble. Many of these soluble compounds may be 
extracted with ether after salting-out (adding common salt to 
saturation). If the substance is soluble in water, it maybe one 
of the above-named compounds, or a lower aldehyde or ketone, 
or a bisulphite compound of these substances, or the salt of a 
base or acid. 

The following is a list of the more soluble organic compounds 
their boiling-points, melting-points and solubilities, which are 
roughly indicated by the letters s. (soluble in cold water) h.s. 
(soluble in hot water). 



326 



PRACTICAL ORGANIC CHEMISTRY 



SOLUBLE LIQUIDS AND SOLIDS. 





Soluble. 


Melting- 
point. 


Boiling- 
point. 


A Icohols 
Methyl (p. 67) .... 


s. 

s. 

h.s. 
s. 

h.'s. 


decomp. 

57 
78 

decomp. 

62 

5* 

5 
236 
66 

10 

80 

98 
132 

112 

180 

IOO 

169 

'54 
80 

122 
137 
ISO 


66 
78 
97 
85 
117 
io3 

97 
207 

'97 
290 

- 21 
21 

9 6 

, 97 
decomp. 

52 

56 

81 

IOO 

119 
140 
163 

155 
1 86 
190 
195 
208 

140 
decomp. 

deromp. 
165 

decomp. 

I forms \ 
1 anhyd. / 
decomp. 

anhyd. 


Ethyl (p. 49) 










Allyl (p. log) 




Glycol 


Glycerol (p. 106) 


A Idehydes 






Chloral 




Butyl chloral hydrate 




Ketones 




Bisulphite compounds of aldehydes and ketones 
Acids 
















Bromacetic (p. 89) 




























p. X ^ k * * 


P't r fn T c^ 


R / \ 











APPENDIX 



327 



SOLUBLE LIQUIDS AND SOLIDS (continued). 





Soluble. 


Melting- 
point 


Boiling- 
point. 


Acids 
0-Hydroxybenzoic (Salicylic) (p. iro; .... 


h.s. 


155 


anhyd. 


p. M 


M 






<?-Aminobenzoic (Anthranilic) ... .... 





144 





p. n 


** 


187 










_ 


















Gallic . . . . 




















118 






h.s. 
















" 






Phthalic (p. 217) 
























0- (p. 218) 




ifc 












6.8. disulphonic G 
3.6. R 


h's. 

















h.s. 


126 




Phenols 


h.s. 




181 




8. 










118 








160 


subl 




'* 


s6 






" 








11 








" 




U1 




h.s. 


184 












B- . (D. 210) . 


** 






Carbohydrate 




146 








167 
















1 60 






1 








11 








J * 








b.'s. 






Glucosides 










h.s. 


187 














1 












( 



3 2S 



PRACTICAL ORGANIC CHEMISTRY 



SOLUBLE LIQUIDS AND SOLIDS (continued). 





Soluble. 


Melting- 
point. 


Boiling- 
point. 


Bases 


















* f 




M 


Kihylamine 


" 






Diethylamine 


*' 








" 




180 




" 




18^ 




h.s. 






?//- ,, (p. 155) .... . . 




63 




/- ,, (p. 173) 










" 


1 3d 






V 




116 










A ) 'tn'ties and Cyanides 
Formamide 












82 






M 








h.s 






Succinimide 




126 




Benzamide(p. 209) 


h.s. 


128 








46 






M 












82 


Salts of bases and acids. 

Acid anhydrides and chlorides dissolve gradually 
on warming and yield the acid. 









The above preliminary investigation will determine the further 
course of investigation, but the following rough plan may serve 
as a guide. 

I. SINGLE SUBSTANCE SOLUBLE IN WATER : 
i. Contains only Carbon, Hydrogen and Oxygen. 

The number of such substances, as seen from the above table, is 
comparatively small. It may be an alcohol, aldehyde or ketone 
of low molecular weight, acid, phenol, carbohydrate or glucoside. 
Acids. Make a solution (if not already dissolved) and test 
with litmus. If the liquid is acid, a free arid\?> probably present. 
If the liquid is neutral and a metal has been found, a metallic 
salt is probably present. If the liquid is alkaline, it may be the 
alkaline salt of a phenol or an alkaline cyanide, both of which 
are hydrolysed in solution. The separation and identification of 
the acid is not a very simple matter. If the acid is an aromatic 



APPENDIX 329 



or an aliphatic acid of high molecular weight, in short, any acid 
which either does not appear in the table or is marked as only 
soluble in hot water, a few drops of cone, hydrochloric acid will 
usually precipitate it, and it may then be filtered, or removed 
with ether, and its melting-point determined. If no precipitate is 
formed, but the solution turns brown on the addition of an alkali, 
tannic or gallic acid may be present. If the acid is volatile 
and has a distinctive smell (formic, acetic, butyric, etc.), the 
solution should be acidified with sulphuric acid and distilled. 
The distillate will contain the free acid, which will probably 
have a distinctive smell. Individual tests may then be directly 
applied, but it is preferable to neutralise the distillate with 
caustic soda and evaporate to dryness on the water-bath, so 
as to obtain the sodium salt before testing. The free acid may 
be soluble and non-volatile, like oxalic, tartaric, succinic, citric, 
etc., and then special tests must be applied (see tests for these 
acids). 

Phenols. If it is a free phenol, ether will extract it from its 
aqueous solution. If it is present in alkaline solution^the solution 
should first be saturated with carbon dioxide. (N.B. The alkaline 
solutions of catechol, quinol and pyrogallol darken rapidly in 
the air.) The following tests should then be applied. 

Ferric chloride reaction. Dissolve a drop of the free phenol 
in water and add a drop of neutral ferric chloride. A green 
(catechol), blue (orcinol, pyrogallol) or purple (phenol, 
resorcinol) colouration is produced, which is often destroyed by 
acid or alkali. Quinol is oxidised to quinone, and turns brown 
(p. 193). The naphthols give precipitates of dinaphthol (p. 220). 

Schotten-Baumann reaction (p. 209). This may be applied to 
the pure phenol in order to obtain the benzoyl derivative, and the 
melting-point determined, or the acetyl derivative may be pre- 
pared by boiling for a minute with acetic anhydride with the 
same object. 

The action of bromine water (p. 180), Liebermann's nitroso- 
reaction (p. 1 80) and the phenolphthalein reaction (p. 186), using 
cone, sulphuric acid or zinc chloride, may also be applied. 

Alcohols. It may be a liquid alcohol (methyl, ethyl, 
propyl, etc., glycerol, benzyl) or a solution of it fn water. In the 
former case its boiling-point will have already been determined. 
It may be further identified (i) by converting it into the benzoic 



330 PRACTICAL ORGANIC CHEMISTRY 

ester by the Schotten-Baumann reaction, and determining the 
boiling-point or melting-point ; (2) by oxidation with excess of 
bichromate mixture (10 grams of K 2 Cr 2 O 7 in 100 c.c. dilute 
sulphuric acid, i 13 by volume). The alcohols are boiled for some 
time with reflux condenser, and the product distilled, neutralised 
with alkali and evaporated on the water-bath and the sodium 
salts tested. Glycerol will be identified by its viscid character 
and reactions (p. 106). If the alcohol is in aqueous solution, it 
should first be fractionated and potassium carbonate added to 
the distillate, when the alcohol will separate. Glycerol or glycol 
in aqueous solution may be separated by evaporation on the 
water-bath. 

Aldehydes and Ketones are detected in the first instance 
by: (i) Shaking with a cold saturated solution of sodium 
bisulphite (see Reaction 2, p. 67). (2) Adding to the aqueous 
solution /-bromo- or /-nitro-phenylhydrazine acetate solution 
(see Reaction 2, p. 70). 

The aldehyde may be distinguished from the ketone by its 
reducing action on alkaline copper sulphate, ammonia-silver 
nitrate and by Schiffs test (see Reactions, p. 67). 

Carbohydrates will char on heating, and give off water and emit 
a smell of burnt sugar. The substance is tested with alkaline 
copper sulphate, ammonia-silver nitrate, phenylhydrazine acetate 
or Molisch's test (see p. 136). Cane-sugar will not respond to 
these reactions until it has been boiled for a few minutes with a 
few drops of dilute sulphuric acid and inverted (see Prep, and 
Notes). Special tests may then be applied to identify the 
particular sugar. A few glucosides are soluble in water, and give 
the sugar reactions after boiling with dilute acid. 

2. Contains Nitrogen. First test the original solid or 
liquid by heating in a hard-glass tube with soda-lime (p. 2), and 
notice if the smell is that of ammonia (ammonia salt, amide or 
cyanide), an amine (amine or amino-acid) or a pyridine base 
(alkaloid). 

Dissolve the substance in water, add caustic soda solution and 
warm. 

Ammonium or amine salts, if present, emit the smell of 
ammonia or amine ; if the salt of an insoluble organic base is 
present (amine, alkaloid), it may be precipitated as a liquid or 
solid. Salts of aliphatic bases and bases such as benzylamine 



APPENDIX 331 



and piperidine are neutral ; salts of aromntic bases (amino- 
group in the nucleus) are acid. A soluble organic base (lower 
amine, benzylamine, pyridine) will be detected by its smell. Most 
aromatic amino-compounds and alkaloids are insoluble in water. 
Some aromatic diamines and aminophenols are moderately 
soluble. The nature of the amine, whether primary, secondary, 
or tertiary, should then be investigated as described under II. 

2. 

Amino-acids of both the aliphatic and aromatic series will also 
come under this head. Substances like glycocoll, alanine, etc., are 
very soluble in water, giving neutral solutions, and may be 
identified by means of the copper salt (see p. 91). Amino-acids 
of the aliphatic series also evolve nitrogen when treated with 
sodium nitrite and hydrochloric acid, and give off amines when 
heated with soda-lime. Amino-acids of the aromatic series 
may be diazotised and coupled with phenols, like aromatic 
amines (see p. 151). 

Amides and Cyanides. Many amides and a few cyanides are 
soluble in water. They are decomposed by hot concentrated 
aqueous or alcoholic caustic soda solutions, by concentrated 
hydrochloric acid or sulphuric acid (equal vols. of acid and water) 
on long reflux boiling. In the first case, ammonia is evolved ; in 
the latter two cases, salts of ammonia are formed, which yield 
ammonia on heating with excess of caustic soda. Anilides 
behave similarly, but aniline in place of ammonia is liberated and 
must be looked for. Some amides are difficult to hydrolyse with 
any of these reagents. In such cases, gently heating with 
a mixture of one volume of cone, sulphuric acid and two 
volumes of ethyl alcohol will yield the ester of the acid and 
ammonium sulphate. The ester can then be separated by 
adding a little water and extracting with ether, and can be hydro- 
lysed and the organic acid identified (see p. 333), whilst the 
aqueous solution, after driving off dissolved ether, will give the 
smell of ammonia on warming with excess of alkali. 

3. Contains Halogen. It may be a halogen add (e.g., 
chloracetic acid) or its salt, or the hydrochloride of a base or 
amino-acid, or a substituted aldehyde (chloral, butyl chloral). 
If it is a free halogen acid, the solution will have an acid reaction, 
and the solution will remain clear on adding caustic soda. If it 
is the hydrochloride of a base, it will give a precipitate with 



332 PRACTICAL ORGANIC CHEMISTRY 

AgNO 3 , and the addition of caustic soda will cause the base to 
separate (if insoluble) as solid or liquid, or, if the base is volatile, 
will produce a strong ammoniacal smell. The further examination 
of the base is the same as that described under I, 2. Acid 
chlorides are usually insoluble in water, but rapidly decompose, 
and may pass into solution as the free acid, giving at the same 
time free hydrochloric acid. 

4. Contains Sulphur. It may be the sulphate of a base, 
in which case the solution will give a precipitate with barium 
chloride, and the process of examination is that described under 
I, 2. Heat with dilute hydrochloric acid. The bisulphite 
compound of an aldehyde or ketone will be decomposed and 
sulphur dioxide evolved. An alkyl acid sulphate will also be 
decomposed, and free sulphuric acid will be found in solution 
(see Reaction, p. 54). Distil with dilute sulphuric acid, and 
test the distillate for volatile aldehyde or ketone. /.-Bromo- and 
/-nitro-phenylhydrazine are useful reagents (see I, i). An 
acid er>ter of sulphuric or sulphurous acid will also be decomposed 
by dilute sulphuric acid, and the distillate may be tested for an 
alcohol. If it is an aromatic sulphonic acid, it may be distilled 
in steam with the addition of cone, sulphuric acid, when 
the hydrocarbon will distil (p. 292), or fused with caustic potash, 
when the phenol will be obtained (p. 179). Thiourea will also 
appear under this head, and should be looked for. Heat a little 
of the substance to the melting-point for a minute, and test for 
thiocyanate with HC1 and FeCl 3 . 

II. SINGLE SUBSTANCES, INSOLUBLE OR 
SLIGHTLY SOLUBLE IN HOT OR COLD WATER. This 
category includes the majority of organic compounds. 

i. Contains only Carbon and Hydrogen, or Carbon, 
Hydrogen, and Oxygen. 

Liquids. It may be a hydrocarbon (paraffin,olefine,aromatic) 
higher alcohol (e.g., amyl alcohol), aldehyde (e.g., benzaldehyde) 
ketone (e.g., acetophenone) acid (e.g., valeric acid), ether, ester, 
phenol (e.g., carvacrol) phenol ether (e.g., anisole). 

Hydrocarbons. The action of sodium when testing for the 
elements will already have indicated the hydrocarbon by its 
inertness. The immediate decolourisation of bromine water will 
identify it as an unsaturated hydrocarbon. A paraffin may be 
distinguished from an aromatic hydrocarbon by treating the 



APPENDIX 333 



liquid with a mixture of concentrated sulphuric and nitric acids, 
(p. 142). The product is then poured into water. If the product 
sinks as a yellow liquid or solid it is probably a nitro-compound 
and the original hydrocarbon is aromatic. If it floats unchanged 
on the surface of the water, it is probably a paraffin. An 
aromatic hydrocarbon also dissolves in fuming sulphuric acid on 
warming and shaking and does not separate on pouring the 
solution into water. A paraffin is unacted on and separates on 
the surface. There is also a marked difference in the smell of 
the two classes of hydrocarbons. 

Higher Alcohols and Phenol. The substance will react 
with metallic sodium yielding hydrogen, with phosphorus 
pentachloride giving HC1. It can be identified by its 
boiling point and by the b.p. or m.p. of the benzoic ester (p. 208). 
In the case of a phenol it will possess a phenolic smell and may 
give a distinctive colour reaction with FeCl 3 (p. 180). 

Aldehydes and Ke tones. The usual tests are applied 

(P- 33)- 

Adds. The number of liquid, insoluble acids is very limited 
and is confined to the aliphatic series. They possess distinctive 
b.p.'s and smells and dissolve readily in a solution of sodium 
carbonate. 

Ethers and Phenol Ethers have usually a pleasant odour 
and if the methyl or ethyl ether is present are decomposed on 
heating with strong hydriodic acid. The evolved gas passed into 
alcoholic silver nitrate will give a precipitate as in Zeisel's method 
(p. 220). 

Esters possess a fruity smell and usually distil without 
decomposition. Boil with reflux for 5 minutes on the water-bath 
a few c.c. of the liquid with 3 to 4 volumes of a ten per cent, solu- 
tion of caustic potash in methyl alcohol and pour into water. 
Notice if the liquid dissolves and has lost the odour of the ester. 
An ester will be completely hydrolysed, and if the alcohol is 
soluble in water a clear solution will be obtained. If the alco- 
hol is volatile and the solution neutralised with sulphuric acid 
and evaporated on the water-bath, the alkali salt of the organic 
acid mixed with potassium sulphate will be left and the acid 
may be investigated as described under 1. If it is required to 
ascertain the nature of the alcohol in the ester, hydrolysis must 
be effected with a strong aqueous solution of caustic potash 



PRACTICAL ORGANIC CHEMISTRY 



(iKOH,3H 2 O). Then distil the liquid, using a thermometer. 
The alcohol, if volatile, will pass into the receiver, whilst the 
acid remains as the potassium salt in the vessel. The boiling 
point will give some indication of the former. The distillate 
should be fractionated and dehydrated with solid potassium 
carbonate. Its boiling-point and that of the benzoic ester is 
then determined. 

Glycerides. If the substance is a liquid fat or oil (/.<?. non- 
volatile, which decomposes on heating, turning brown and 
evolving the smell of acrolein) then the hydrolysis is effected 
with methyl-alcoholic potash as described. After hydrolysis, the 
alcohol is driven off on the water-bath, the residue dissolved in 
water, and the organic acid set free with hydrochloric acid. The 
acid if solid is filtered, if liquid extracted with ether, or if soluble 
and volatile (butyric acid) distilled and the remaining liquid 
neutralised and evaporated to dryness. The glycerol is then 
extracted with alcohol and the alcoholic solution evaporated on 
the water-bath. The tests for glycerol may then be applied 
(p. 106). The following is a table of common insoluble liquids 
with their boiling-points and specific gravities. Where the 
temperature is not indicated the specific gravity has been deter- 
mined at o. 

ORGANIC LIQUIDS, INSOLUBLE IN WATER. 
(Containing C and H or C, H, and O.) 



1 


Boiling- 
point. 


Sp. gr. 


t. 


Hydroca rbans 








-Pentane "I f 


39 


0*626 


17 


' H " I Pre9ent in Petro ' .Petrol- I 
f eum, Ether, and Ligroin | 
- Heptane 1 


3 
72 

97 


0-638 
0-660 
0*712 


14 
20 

16 


?/-Octane J \ 


124 


0-708 


12 






/ 0-803 


Amer. 






\ 0-822 
o"68o 


Russ. 




80 


o"88o 




Toluene (p. 163) 


no 


0-865 


20 




136 


0-867 


20 




142 


0-865 


20 






o'863 




p. ... 


138 


0-869 




Cumene (Isopropyl benzer.e) 


152 


o'88o 






1 66 


o'86i 









0*855 


20 


1 









APPENDIX 



335 



ORGANIC LIQUIDS, INSOLUBLE IN WATER (continued}. 





Boiling- 
point. 


Sp. gr. 


/. 


Hydrocarbons (continued) 




o'8s3 




Turpentine oil (Pinene) 


155 1 60 


1 0-865 






160 -165 


i 0'858 




Alcohols 




l-c.86i 
0*812 




Octyl 


IGO 




16 


Linalol ; 


198 


0*868 






286 






A Idchydes- - 








Citral 


229 


0*897 






















248 














Salicylaldehyde (p. 188) 


106 






Ketones 








^ cetophenone (p. 210) (m.p. 20") 


202 


1*032 




Acids 


176 














A n hydrides 


138 


i '08 




Phenols 
Phenol (p. 179) (m.p. 43) 


182 


1*070 


20 










/- (p. 164) 




















0*985 






248 




18 




260 


1*08 


16 


Ethers and Phenol Ethers 








Amyl , . . 


176 


0*800 




Methylal 












o 831 








0*988 




Phenetole ... 
























Esters 








,, acetate 

















336 



PRACTICAL ORGANIC CHEMISTRY 



ORGANIC LIQUIDS, INSOLUBLE IN WATER (continued']. 





Boiling- 
poi'it. 


Sp. gr 


j 


Esters (continued) 












0*896 














1 08 








280 






benzoate 




i '086 








1*182 




Ethyl formate 
















acetoacetate (p. 83) 


181 










0*896 




z-valerate 




0*889 






1 86 


o'866 






108 


1*080 








1*076 
























i '184 






81 










0*882 








0*88 ; 
















o'8o7 






















nfi 










0*866 






136 


0*887 
























0*880 








0*856 






160 


0*887 






178 


0*882 






























2=18 




























16 


,, benzoate (m. p. 20) 


3 2 3 


i-ii 4 





Solids. It may be a hydrocarbon (e.g., paraffin wax, 
naphthalene) higher alcohol (e.g., cetyl alcohol) ; aldehyde (e.g., 
^-hydroxybenzaldehyde) ketone and quinone (e.g., benzo- 
phenone, camphor) acid (higher fatty, e.g., palmitic acid or 
aromatic acid) ester (of glycerol, phenols or aromatic alcohols) 
phenol (e.g., thymol). 

The process of investigation is similar to that described in the 
preceding section. 



APPENDIX 



337- 



Acids. A free acid may be at once identified by its solubility 
in a solution of sodium carbonate and by being reprecipitated 
by concentrated hydrochloric acid. If a metal has been dis- 
covered in the preliminary examination, a careful examination 
must be made for an organic acid. As the substance is insoluble 
in water the metal will probably not be an alkali metal. Boil 
the substance with sodium carbonate solution, The sodium 
salt of the acid passes into solution and the metallic carbonate 
is precipitated. Filter ; boil the filtrate with a slight excess of 
nitric acid, add excess of ammonia and boil until neutral, tests 
may then be applied in order to identify one of the common 
acids and the m.p. determined ; but beyond this it is impossible 
to carry the investigation in a limited time. 

INSOLUBLE SOLIDS. 
(Containing C and H, or C, H, and O.) 





Melting- 
point. 




Melting- 
point. 


Hydroca rbons 


4560 
80 
217 
99 
"5 

5 
42 

81 
37 

48 
95 
137 
i?5 

116 
125 
115120 
decomp. 

285 
205 

62 
6q 

122 
155 
200 
2IO 


A cids (con tin ued) 


184 

102 
110 
179 

70 
213 

subl. 

42 

128 

31 
36 
44 
95 

122 

54 
53 
0265 
62 

7i 
69 

43 

21 


Naphthalene (p. 216) . . 
Anthracene (p. 225) . . 
Phenanthrene 






/- (P- 17) 
Phenvl acetic 
o-Phthalic (p. 217) . . . 
tit- (isophthalic . 
p- (terephthalic) 
(P- '7') 

A nhydrides 
Benzoic 


Alcohols 
Cetyl Alcohol .... 




Aldehydes 
Vanillin 




Phthalic (p. 218) .... 
Phenols 


Ketones 
Benzophenone .... 


P- (p. 164) .... 
Thymol . 


Benzoin (p. 203) . . . 


a-Naphlhol 


Qitinones * 
Benzoquinone (p. 192) . 
o-Naphthaquinone . . . 
0- 

Anthraquinone (p. 225) . 
Phenanthraquinone . . 

Acids 
Palmitic (p. 104) .... 


0- (p. 219) . . 

Esters 
Methyl oxalate (p. 101) . 
Cetyl palmitate (Sper- 
macrti) 
Myricyl palmitate (Bees 


Glyceryl tripalmitate 
(Palmitin) (p. 104) . 
Glyceryl tristearate 


Benzoic (p. 199) .... 
0-Hydroxybenzoic(p. 190) 
m- ,, (p. 201) 
/- .- 


Phenyl benzoate .... 
,, salicylate . . 
Benzyl benzoate .... 
salicylate .... 



COHEN'S ADV. P. O. C. 



PRACTICAL ORGANIC CHEMISTRY 



2. Contains Nitrogen. 

Organic base. If it is a base or amine, amino-phenol or 
amino-acid, it will probably dissolve in dilute hydrochloric acid 
and yield a chloroplatinate with platinic chloride. Some 
aromatic bases like diphenylamine are not veiy soluble in dilute 
acids. Amino-phenols and acids may be extracted with ether 
from an acid solution to which ammonia has been added till 
faintly acid and then sodium acetate. Many amines and 
amino-phenols give quinones on oxidation with potassium 
bichromate and sulphuric acid having a characteristic smell 
(p. 192). Many of the common alkaloids when dissolved in 
hydrochloric acid (avoid excess) give a brown amorphous 
precipitate with iodine solution and respond to other general 
reactions for the alkaloids (see p. 320). To identify the 
individual alkaloid, special tests must be applied. 

Primary, secondary, and tertiary amines may be distinguished 
as follows : To a solution of the base in dilute hydrochloric acid 
add a few drops of sodium nitrite solution. In the case of 
primary aliphatic amines, a rapid evolution of nitrogen will at 
once occur ; a primary aromatic amine at first gives a clear 
solution of the diazonium-salt, which evolves nitrogen and turns 
darker on warming. The effervescence, due to the liberation of 
nitrous fumes, is easily distinguished from that of nitrogen, 
which goes on uninterruptedly, even when the liquid is removed 
from the flame. 

After the solution of the diazonium salt has been decomposed 
by warming, the phenol which has been produced may be 
extracted with ether, the ether evaporated, and the phenol 
identified by special tests. A solution of the diazonium salt, 
when poured into a solution of /3-naphthol in caustic soda, will 
usually give a red azo-colour. The original amine, if liquid, may 
sometimes be identified by warming with a little acetyl chloride 
and converting' it into the solid acetyl derivative, which is 
recrystallised and the melting-point determined (see Reaction 3, 
P- ?6). 

In the case of a secondary base, the above treatment with 
hydrochloric acid and sodium nitrite will give an insoluble 
nitrosamine (liquid or solid), which is frequently yellow. It may 
be separated by ether and, after removing the ether, tested by 
Liebermann's nitroso-reaction (see Reaction 3, p. 159). Nitrous 
.acid has no action on tertiary aliphatic amines, but forms nitroso- 



APPENDIX 339 



bases with tertiary aromatic amines (see p. 157), which dissolve 
in water in presence of hydrochloric acid, with which they form 
soluble hydrochlorides. Tertiary amines also combine with 
methyl iodide on warming (see Reaction, p. 157), but not with 
acetyl chloride. Primary amines give the carbamine reaction 
(p. 1 50), and unite with carbon bisulphide (p. 1 59). 

Oximes. It should be remembered that oximes act as bases 
as well as acids, and dissolve in both caustic alkalis and acids. 
On reduction in acid solution (with tin or zinc) they yield 
amines. 

Cyanides and Amides are hydrolysed by caustic potash 
(aqueous or, better, alcoholic), cone, hydrochloric or sulphuric 
acid as mentioned previously under I, 2. It should be mentioned 
that some amides are attacked only with difficulty, and must then 
be treated as described under I, 2. 

Nitro-compounds are frequently yellow or orange in 
colour. Heated with stannous chloride in cone. HC1 or zinc 
dust and glacial acetic acid they dissolve and remain in solution 
on the addition of water. The base which is thus formed maybe 
separated by adding an excess of caustic soda until the metallic 
oxide dissolves and then shaking out with ether. When the 
ether is removed, the base remains. If liquid, the base should 
be converted into the acetyl derivative by warming with acetyl 
chloride for a few minutes and pouring into water. The free 
base or solid acetyl derivative, as the case may be, should be 
recrystallised and the melting-point determined. It can also be 
diazotised and coupled with /3-naphthol. 

Alkyl Nitrates are hydrolysed like other esters, and yield 
alcohol and nitric acid (p. 82). 

Nitro-phenols and Nitro-acids dissolve in caustic alkalis 
as a rule with a deep yellow or orange colour. On re- 
duction with stannous chloride or zinc dust, as described 
above, they yield the amino-derivatives. In the case of the 
amino-phenol, the solution is made alkaline with caustic soda, 
saturated with CO 2 , salt added and extracted with ether. In 
the case of the amino-acid, the method used is that described 
under Prep. 91 (p. 201). 

Azo- and Azoxy-compounds. Both classes of compounds 
are usually highly coloured and are rapidly decolorised by 
warming with a solution of stannous chloride and hydrochloric 
acid, forming amino-compounds (see Reactions, pp. 173, 177). 

Z 2 



340 



PRACTICAL ORGANIC CHEMISTRY 



INSOLUBLE SUBSTANCES. 
(Containing C, H, and N or C, H, O, and N. ) 





Melting- 
point. 


Boiling- 
point. > 




Melting- 
point. 


Boiling 
point. 


Bases (primary) 
Aniline (p. 149) . . 
<7-Nitramline . . . 
m- (p. 154) 
/- ,, (P- 'S3) 
o-Chloraniline . . . 
t- ,, ... 
P- ... 
0-Bromaniline . . . 
in- ... 
P- ,. (P- 152) 
e-Toluidine .... 
m- ,, .... 
/- . . . . 
i-3-4-Xylidine . . . 
i-2-4-5-Cuinidine 
/-Hydroxyaniline(/- 
aminophenol) . 


7i 

114 

147 

70 

3i 
18 
63 

45 
63 
184 

5 

1 12 
122 
128 
102 

63 
M7 

4 1 
23 

33 

54 

108 
"3 


182 

207 
230 
230 
251 
251 

iQ7 
199 
198 
215 
234 

226 
228 

241 

191 
206 
298 

292 

105 
166 

192 
213 
183 
208 
129 
239 


A minophenols 
/-Aminophenol (p. 


,84 

87 
80 
decomp. 

10 
60 

35 
'30 
Co 

29 
decomp. 

128 

no 
142 
46 

112 
J02 
92 
l6 3 
245 
I 10 

'53 
235 

143 

J59 
132 

187 
decomp. 
144 

90 


decomp. 

decomp. 
191 

218 

210 


0-MethyIamino- 
phenol (Metol) . 
/-Methylamino- 
phenol (Ortol) . 
2-4-Diaminophenol 
(.Amidol) .... 

Cyanhydrins and 
Oxintes 
Benzaldehyde cyan- 
hydrin (p. 206) . 
Acetoxime (p. 71) 
a-Benzaldoxime (p. 


/3-Benzaldoxime (p. 


Phenetidine . . . 
a-Naphthylamine . 

ft- 
Benzidine (p. 148) . 
0-Tolidine .... 
o-Phenylenediamine 
m- 
(p. 155) . . . . 
/>-Pnenylenediamine 
(p. 173) .... 
/-Dimethylphenyl- 
enediamine (p. 
177) 


Acetophenoneoxime 
(p. 211) .... 

Cyanides and 
Amides 
Succinamide . . . 
Phenyl cyanide . . 
^-Tolyl cyanide (p. 
169) 


Oxamide (p. 102) . 
Benzamide (p. 209) 
Hydrobenzamide (p. 


Phenylhydrazine (p. 
173) 


Salicylamide . . . 
Formanilide .... 
Acetanilide (p. 151) 
Methylacetanilide 
Propionanilide . . 
Benzanilide .... 


Bases (secondary) 
Methylaniline . . . 
Ethylaniline . . . 
Benzylaniline . . . 
Diphenylamine . . 
Methyldiphenyl- 
amine . ... 
, Phenyl /3-naphthyl- 


oAcetotoluide . . 
P- 
Diphenylurea . . 
Tnphenyl guanidine 
(p. 160) . . . . 
a-Acetnaphthal:de . 
/ 

Amino-acids 
Hippuric acid . . . 
Uric acid 
Anthranilic acid . . 

Nitre-compounds- 
N itrobenzene (p. 1 42) 
?-Dinitrobenzene 


Piperidine .... 


Bases (tertiary) 
Dimethylaniline (p. 
156) 


Dieth\ laniline . . 
Dimethyl 0-toluidine 

a-Picoline 
Quinoline (p. 230) 
Antipyrine .... 
1 he alkaloids . . 





APPENDIX 



341 



INSOLUBLE SUBSTANCES (continued). 





Melting- 
point. 


Boiling- 
point. 




Melting- 
point. 


Boiling- 
point. 


Nitro-compounds (con- 
tinued). 
Trinitrobenzene . . 
oNitrotoluene . . 


122 


223 


Nitroso-conipounds 
/-Nitrosodimethyl- 
aniline (p. 157) . 
/Nitrosodiethyl- 


85 

84 


- 


1-2-4-Dinitrotoluene 
o-Nitronaphthalene 
0-Nitracetanilide . 
P- ,. (P- 'S3) 

Nitro-phenols, Alde- 
hydes and Acids 
<?-Nitrophenol(p. 183) 
>- ,, . . 
/ (p.i8 3 ) 
Trinitrophenol (p. 
185) 


54 
7i 
61 
?8 
207 

45 
96 
"4 


238 


Nitroso-B-naphthol 

A Ikyl Nitrites and 
Nitrates 
Ethyl nitrite" . . . 
nitrate . . . 
Amyl nitrite (p. 69) 
,, nitrate . . . 


job 


16 
86 
95 
H7 


Nitroanisole . . . 
w-Nitrobenzalde- 


58 


~ 


Azo- and Azoxy-com- 
pounds 
Azoxybenzene (p. 








118 






36 




nt- ,, 
(p. 200) .... 
/-Nitrobenzoic acid 
i-z-4-Dinitro benzole 


141 

338 


- 


Azobenzene (p. 145) 
Hydrazobenzene (p. 
146) .... 
Diazoaminobenzene 
(p. 171) . . 


68 
125 
98 


- 


1-3'5-Dinitrobenzoic 






Aminoazobenzene 



















3. Contains Halogen. Halogen compounds may \>zalkyl, 
alkylene, aryl or acid halides or halogen acids (e.g., ethyl bromide, 
ethylene bromide, bromobenzene, benzoyl chloride, or chloro- 
benzoic acid). 

Alkyl, Alkylene and Aryl Halides are usually liquids or 
solids specifically heavier than water and with a sweet penetrating 
smell, or if aromatic compound's substituted in the side-chain, 
they have a sharp penetrating smell and attack the eyes. They 
are for the most part colourless, but the bromine and iodine 
compounds usually acquire a brown colour on standing. lodo- 
form is naturally yellow. In the case of alkyl and alkylene 
halides and aromatic compounds substituted in the side- chain, 
alcoholic silver nitrate will, on warming, yield silver halide. 
Strong methyl-alcoholic potash will, with the same compounds, 
produce olefines and acetylenes (p. 64). The experiment should 
be tried with the apparatus Fig. 86, and the gas collected 



342 



PRACTICAL ORGANIC CHEMISTRY 



and tested. Aromatic compounds substituted in the nucleus 
are not, as a rule, acted on by these reagents unless nitro-groups 
are also present ; many of these react with magnesium in 
presence of dry ether (p. 206). 

INSOLUBLE SUBSTANCES. 
(Containing C, H and halogens or C, H, O and halogens.) 





Melting- 
point. 


Boiling- 
point. 




Melting- 
point. 


Boiling- 
point. 


A Iky I, Alkylene, and 






A Iky I, Alkylene, and 






Aryl ffalides 






A ryl ffalides 






Methyl iodide (p. 






(continued) 






68) .. 





40 


0-Dibromobenzene . 





225 


Ethyl bromide (p. 




T j 


/*-Dibromoben^ene . 


89 


218 


54) ... 





38 


0-Chlorotoluene . . 




157 


Ethyl iodide . . . 





72 


>- ,, . . 





I* 


-Propyl chloride . 





44 


P- ,. (P- 165) 





160 


,, bromide . 





7 1 


<?-Bromotoluene 





182 


,, iodide . . 





IO2 


>n- . . 





184 


i- chloride . 





36 


/> , r (p. 167) 


28 


185 


,, bromide . 





60 


a-Chloronaphtha- 






,, iodide . . 





89 


lene 





263 


H-Butyl chloride . . 





77 


/3-Chloronaphtha- 






,, bromide 





IOO 


lene 


56 


265 


,, iodide . . 





130 


a-Bromonaphtha- 






z- chloride 





68 


lene 





279 


,, bromide 





92 


/3-Bromonaphtha- 






. , iodide . . 





1 20 


lene 


59 


282 


z'-Amyl chloride . . 





IOO 








,, bromide . . 





1 20 


Phenols 






iodide . . . 





148 


Trichlorophenol 


68 





Allyl bromide . . . 





71 


Tribromophenol . . 


95 





,, iodide . . . 





101 








Methylene chloride 





41 


Acid Chlorides 






bromide 





58 


Acetyl chloride(p.74) 





55 


Ethylene chloride . 





84 


Benzoyl ,, (p. 208) 





I9 8 


Ethylidene 





58 








Ethylene bromide 






Acids 






(p. 62) 





J 3i 


0-Chlorobenzoic . . 


r 37 





Ethylidene bromide 





103 


m- ,, . . 


'53 





Chloroform (p 70) . 





6r 


P- (p. 166) 


236 





Bromoform .... 





'Si 


0-Bromobenzoic 


147 





lodoform 


119 




m- ,, (p. 201) 


'55 


- 


Carbon tetrachloride 




76 


P- 


251 





Benzyl chloride (p. 

















176 


Esters 






Benzal ,, 





204 


Methyl chloroform- 






Benzotrichloride 





21 1 


ate ... 





7 1 


Chlorobenzene . . 





L J 

I3 2 


Methyl chloracetate 





130 


Bromobenzene(p. 140) 





155 


,, bromacetate 





144 


lodobenzene . . 





188 


Ethyl chloroformate 





94 


c-Dichlorobenzene . 





179 


,, chlorncetate 





M3 


P- 


53 


173 


bromacetate 


~ 


159 



Acid Chlorides and Bromides are also specifically heavier 
tnan water, but reveal th^ir presence by fuming in moist 



APPENDIX 



343 



air. They are decomposed by water more or less rapidly, 
and give the corresponding acid and hydrochloric acid, which 
may be tested for. They are also acted on rapidly by strong 
ammonia, and give the amide, the melting-point of which may 
be ascertained (p. 209). 

Halogen Acids and Esters. Most of the insoluble halogen 
acids belong to the aromatic series, and have a distinctive 
melting-point. For further confirmation, they may be converted 
into the acid chloride and amide. Insoluble esters containing 
halogens may belong to both series, and the acid and alcohol 
must then be separated and separately investigated. 

4. The following among the more common organic substances 
contain sulphur or sulphur and nitrogen in addition to carbon, 
hydrogen and oxygen. 

INSOLUBLE SUBSTANCES. 
(Containing C, H, and S or C, H, O, S, and N.) 





Melting- 
point. 


Boiling- 
point. 




Melting- 
point. 


Boiling- 
point. 


Sulphides 












Allyl sulphide . . 





140 


Thiocyanates 






Benzyl ,, 


49 




Allyl thiocyanate . 





151 


Sulfhonic Acids 
Sulphobenzoic acid 


decomp. 




Phenyl 
(p. 160) . . . . 





222 


Sulphanilic acid (p. 
175) . 






Thioamides 






Naphthionic acid . 








Thiocarbamide (p. 
128) 


175 




/3-Naphthylamine 
sulphonic acid 


(J 


_ 


Thiocarbanilide (p. 


151 




/3-Naphthylamine 












disulphonic acid . 
R acid . . 


,, 





Sul/>hona.mides 
Benzenesulphon- 






G 







amide (p. 179) 


15 





Sulphates 






Benzenesulphonani- 






Methyl sulphate 





187 


lide (p. 179) . . 


no 





Ethyl 


~ 


208 









Mixtures. A preliminary investigation carried out as 
described on p. 322 will determine roughly if the substance is a 
mixture. Before proceeding to identify the substances present, 
it is essential that they should first be separated. This may be 
a long and difficult operation, but the following methods may 
lead to the desired result. 

If the substance cannot be satisfactorily separated by fractional 



344 PRACTICAL ORGANIC CHEMISTRY 

distillation (if a liquid) or by crystallisation (if a solid), shake 
with caustic soda solution. This will dissolve the acid or phenol, 
and the insoluble constituent may be removed mechanically or, 
if volatile, by distillation in steam, by extraction with ether or, if 
solid, by filtration. 

A rid and Phenol, if present together, may be separated by 
adding sodium bicarbonate in excess and extracting with ether, 
or by dissolving in caustic soda solution, saturating with carbon 
dioxide and then extracting with ether. The ether extracts the 
phenol, which is insoluble in sodium carbonate, leaving the acid. 

Ester and Hydrocarbon may be separated by hydrolysis, which 
decomposes (he ester, but not the hydrocarbon. 

Paraffin and Aromatic Hydrocarbon may be separated by the 
action of fuming sulphuric acid, which forms the sulphonic acid 
with the aromatic hydrocarbon. The product is poured into 
water. The sulphonic acid dissolves readily in water, whereas 
the paraffin is insoluble. 

Amine or Base may be separated from the majority of 
insoluble organic substances by shaking it with dilute hydro- 
chloric acid, with which it forms the soluble hydrochloride. 

Aldehyde or Ketone may be separated from the other 
constituents by shaking the liquid, which should be free from 
water, with a saturated solution of sodium bisulphite, and de- 
canting or filtering the liquid residue. If the liquid is soluble 
in water, like ethyl alcohol, it may precipitate the bisulphite of 
sodium. This is prevented by adding a little ether before 
introducing the bisulphite into the liquid. 

In separating two liquids in a test-tube, for example, an 
ethereal from an aqueous solution, either the ether may be 
decanted or it may be desirable to withdraw the lower aqueous 
layer. This is done by sucking the liquid into a small pipette 
furnished with a mouth-piece of rubber tubing, which may be 
nipped when the requisite quantity is removed. The pipette is 
then withdrawn, keeping the rubber tube tightly closed, and the 
liquid transferred to another test-tube. It is often advisable to 
adopt this method previous to decanting the top layer, which 
is much more effectively separated from a small than from a 
large quantity of the aqueous layer, 



APPENDIX 



345 



I. TABLE OF THE ATOMIC WEIGHTS OF THE ELEMENTS. 
O = 16. 



Element. 


Symbol. 


A'omic 
Weight. 


Element. 


Symbol. 


Atomic 
Weight. 


Almminium . . . 
Antimony .... 


Al. 
Sb. 
Ar. 
As. 
Ba. 
Be. 
Bi. 
B. 
Br. 
Cd. 
Cs. 
Ca. 
C. 
Ce. 
Cl. 
Cr. 
Co. 
Cu. 
F. 
G. 
Ge. 
Au. 
He. 
H. 
In. 
I. 
Ir. 
Ke. 
La. 
Pb. 
Kr. 
I.i. 
Mg. 
Mn. 
Hg. 
Mo. 


27-1 

I20'2 

39 '9 
75 
1 37 '4 
9' 1 
208 
ii 
79-96 
112-4 

133 
40-1 

12 
I40-25 

35-45 
52-1 
59 
63-6 

*9 
70 
72-5 
197-2 
4'o 
i '008 
"S 
126-97 

193 

55 '9 
138-9 
206-9 
81-8 
7'3 
24 '36 
55 
200 
96 




Ne. 
Ni. 
Nb. 
N. 
Os. 
O. 
Pd. 
P. 
Pt. 
K. 
Ra. 
Rh. 
Rb. 
Ru. 
Sc. 
Se. 
Si. 
Ag. 
Na. 
Sr. 
S. 
Ta. 
Te. 
Tl. 
Th. 
Sn. 
Ti. 
W. 
U. 
V. 
X. 
Yb. 
Y. 
Zn. 
Zr. 


20 
587 
94' 
14*01 
I 9 , 

16 
106-5 
31 
194-8 

39''5 
22; 
103 
85-5 
101-7 

44"i 
79-2 
28-4 
10791 
23'05 
87-6 

T.2 "06 

181 

I27'6 

204 "I 

232-5 
119 

48-1 
184 
238-5 
51-2 
128 

'73 
89 
654 
90 "6 


Nickel . . . 


Niobium .... 
Nitrogen .... 
Osmium 
Oxygen .... 




Barium 
Beryllium .... 
Bismuth .... 


Palladium .... 
Phosphorus . . . 
Platinum ... 




Cadmium .... 


Potassium .... 
Radium 
Rhodium . . . . 
Rubidium .... 
Ruthenium .... 
Scandium .... 
Selenium .... 
Silicon ... 










Chromium .... 
Cobalt 




Silver ..... . 
Sodium 


Fluorine ..... 
Gallium .... 
Germanium . . . 
Gold 


Strontium .... 


Tantalum .... 
Tellurium .... 
Thallium 




Hydrogen .... 


Thorium 




Tin . . 








Tungsten .... 
Uranium .... 
Vanadium .... 


Lanthanum . . . 
Lead 


Krypton .... 


Ytterbium .... 
Yttrium 


Magnesium . . . 
Manganese .... 




Zirconium .... 


Molybdenum . . . 



346 



PRACTICAL ORGANIC CHEMISTRY 



VAPOUR TENSION OF WATER FROM 5 TO 20. 



t 


Tension. 


t 


Tension. 


t 


Tension. 


t 


Tension. 


S*o 


6-507 


9-0 


8-548 


I3'o 


11-137 


17-0 


J 4'395 


'i 


'552 


'I 


606 


'i 


'2IO 


'i 


486 


'2 


'597 


'2 


664 


'2 


'283 


'2 


578 


'3 


'643 


'3 


722 


'3 


356 


'3 


'670 


'4 


689 


'4 


781 


'4 


4^0 


'4 


763 


'5 


736 


'5 


840 


'5 


'5"S 


'j 


3 5 6 


6 


782 


6 


899 


6 


580 


6 


950 


'7 


829 


'7 


'959 


'7 


655 


'7 


1 5 '044 


8 


876 


8 


9-019 


8 


'731 


8 


139 


'9 


924 


'9 


079 


'9 


'807 


'9 


234 


6'o 


971 


zo'o 


140 


14-0 


'884 


i8'o 


'330 


'i 


7 '020 


'i 


'201 


'i 


'960 


'i 


427 


'2 


068 


'2 


'262 


'2 


1 2 '038 


'2 


'524 


'3 


117 


'3 


324 


'3 


116 


"3 


'621 


'4 


166 


4 


386 


4 


194 


'4 


'7 r 9 


'5 


215 


'5 


'449 


'5 


' 2 73 


'5 


818 


6 


265 


6 


512 


6 


352 


6 


V7 


'7 


'314 


'7 


'575 


7 


432 


'7 


i6'oi7 


8 


365 


8 


'639 


8 


'512 


8 


117 


'9 


'4'5 


'9 


'70S 


"9 


'593 


'9 


218 


7' 


466 


n'o 


767 


15' 


674 


ig'o 


319 


'i 


'Si7 


'i 


832 


i 


'755 


'i 


421 


'2 


568 


'2 


897 


"2 


837 


'2 


'523 


'3 


"620 


'3 


962 


'3 


920 


'3 


626 


'4 


672 


'4 


IO'O28 


'4 


1 3 '3 


'4 


'73 


'5 


725 


'5 


095 


'5 


086 


'5 


"834 


6 


'777 


6 


161 


6 


170 


6 


'939 


'7 


830 


'7 


228 


'7 


'254 


'7 


17-044 


8 


883 


8 


'296 


8 


'339 


8 


'150 


'9 


'937 


'9 


364 


'9 


424 


'9 


256 


8-0 


'99 i 


I2'0 


'432 


i6'o 


'5 10 


20 '0 


'363 


i 


8045 


'I 


501 


*i 


596 


'I 


'471 


'2 


'100 


'2 


'57 


'2 


683 ' 


'2 


'579 


'3 


-I 55 


'3 


'639 


3 


!Z5 


'3 


688 


'4 


'210 


'4 


709 


4 


858 


'4 


'797 


'5 


266 


'5 


780 


'5 


946 


5 


907 


6 


321 


6 


850 


6 


1 4 '35 


6 


i8'oi8 


'7 


378 


"7 


921 


'7 


124 


'7 


"129 


8 


'434 


8 


"993 


8 


214 


3 


241 


'9 


491 


'9 


1 1 '065 


'9 


'34 


'9 


353 



APPENDIX 



347 



VAPOUR TENSION OF CAUSTIC POTASH SOLUTIONS FROM 10 20. 



t 


3 oKOH. 
ioo H^O. 


4 oKOH. 
iooH a O. 


49KOH. 
iooH 2 O. 


I0'0 


7'3* 


6'so 


1'62 


K>'S 


7-56 


6'72 


5-81 


i I'D 


7-82 


6-95 


6'oi 


11-7 


8-19 


7-28 


6'29 


I2'I 


8- 4l 


7 '47 


6-46 


12-5 


8-63 


7-67 


6-63 


13' 


8-92 


7 '93 


6-86 


I3'5 


9'22 


8-19 


7-00 


1 3 '95 


9'49 


8-44 


7'3 


H'S 


9-83 


8-74 


7-56 


i5 - i5 


0-25 


9-11 


7-88 


1 5 '3 


'35 


9'20 


7-96 


i6'o 


0-82 


9 '62 


8-33 


16-35 


1-07 


9-85 


8'53 


17-0 


i '54 


O'26 


8-88 


i7'5 


1-91 


'59 


9'i7 


i8'o 


2 '29 


0-93 


Q'47 


i8'5 


2'6g 


i '29 


9-78 


19*0 


3'9 


1-65 


lo'og 


19-4 


3'4i 


''93 


i'33 


20 o 


3 '93 


2-40 


10-75 


2O'25 


4'i5 


2'59 


lo'gi 



PRACTICAL ORGANIC CHEMISTRY 



II. TABLE OF SPECIFIC GRAVITY AND PERCENTAGE OF SULPHURIC ACID 
IN AQUEOUS SOLUTION. (Kolbe.) 

i"/. gr. at 15 compared with water at o" = i. 



Degrees 
Beaum. 


Sp. gr. 
d-=. 15/0. 


TOO parts by 
weight contain 
H 2 SO 4 . 


Degrees 
Beaume. 


Sp. gr. 
d 15/0. 


TOO parts by 
weight contain 
H 2 S0 4 . 


i 


007 


i '9 


34 


'308 


40'2 


2 


014 


2'8 


35 


320 


41-6 


3 


'022 


38 


36 


'332 


43 


4 


'029 


4'8 


37 


'345 


44 '4 


5 


037 


5*8 


38 


'357 


45'6 


6 


045 


6'8 


39 


'370 


46-9 


7 


'052 


7-8 


40 


'383 


48'3 


8 


060 


8-8 


41 


'397 


49'8 


9 


067 


9'8 


42 


'410 


51-2 


10 


'075 


j.o'8 


43 


424 


52'6 


ii 


083 


11-9 


44 


438 


54' 


12 


'091 


13 


45 


'453 


55.4 


'3 


'100 


14-1 


46 


468 




'4 


108 


I5'2 


47 


'483 


j8'3 


15 


116 


l6'2 


48 


498 


59'6 


16 


'125 


I7|3 


49 


'5M 


61 


17 


''34 




5 


'53 


62 '5 


18 


142 


19*6 


51 


'54 


64 


'9 


''52 


20'8 


52 


'563 


65'5 


20 


'162 


22'I 


53 


580 


67 


21 


''7 1 


23'3 


54 


'597 


68-6 


22 


180 


24'5 


55 


'615 


7 


23 


190 


25-8 


56 


'634 


71-6 


24 


'200 


27-1 


57 


652 


73'2 


25 


'210 


28-4 


58 


'671 


74'7 


26 


'220 


29*6 


59 


'691 


76'4 


27 


'231 


3'9 


60 


711 


78-1 


28 


'241 


3 2 '2 


61 


'732 


79'9 


29 


'252 


33 '4 


62 


'753 


8r 7 


3 


'263 


34'7 


63 


'774 


84-1 


3 1 


'274 


36 


64 


796 


86-5 


32 


'285 


37 '4 


65 


81 


89-7 


33 


297 


38 8 


66 


842 


100 



APPENDIX 



349 



II. TABLE OF SPECIFIC GRAVITY AND PEKCENTAGE OF H2SO4 IN 
CONCENTRATED SULPHURIC ACID. (Lunge and Naef.) 

SJ. gr. at 15 compared with water at 4 = i. 



Per cent. 


Sp. gr. 


Per cent. 


Sp. gr. 


HvSO^. 


^=15/4. 


H 2 S0 4 . 


^=15/4 


90 


3i8 S 


96 


8406 


9 1 


8241 


97 


8410 


92 


8294 


98 


8412 


93 


8339 


99 


8403 


94 


'8372 


IOO 


8384 


95 


8390 







IV. TABLE OF SPECIFIC GRAVITY AND PERCENTAGE OF NITRIC ACID 
IN AQUEOUS SOLUTION. (Kolbe.) 

Sp. gr. at 15 compared with water at o = i. 





V 




V 




V 




H 




M . 




be . 




bO . 




u . 


l " 


a n 


*- ' 


/*? 


t" * 


rt c^ 


K o " 




d.*-> 


tl 


O.W 


& 


D. *- 


2 


Q.4-* 


' 


in i 


S 


O> rt 


J* 


CO rt 


feS 


C/3 


s w 




a, 









A 




0, 


i '530 


ioo 


'451 


77-6 


363 


58 


237 


37 '95 


1*529 


99'5 


'445 


76 


358 


57 


'225 


36 


''523 


97 '9 


442 


75 


'353 


5 6-I 


-2l8 


35 


1-516 


96 


438 


74 


346 


55 


'211 


33'8 


i'5i4- 


95 '2 


'435 


73 


'34i 


54 


'198 


32 


i '59 


94 


'432 


72-4 


'339 


53'8 


"102 




1-506 


93 


429 


71-2 


'335 


53 


'185 


3 


i '53 


92 


423 


69-9 


'331 


5 2 '3 


-179 


29 


1-499 


9 1 


419 


69-2 


'323 


51 


172 


28 


I- 495 


90 


414 


68 


317 


49'9 


166 


27 


1-494 




410 


67 


312 


49 


'157 


25'7 


1-488 


88 


'45 


66 


'34 


48 


'138 


23 


1-486 


87-4 


"400 


6s 


298 


47' 1 


"I2O 


20 


1-482 


86-1 


'395 


64 


'-95 


46-6 


'IO5 


I7'4 


1-478 


85 


'393 


63-6 


284 


45 


'089 


15 


i '474 


84 


386 


62 


274 


43'5 


077 


13 


1-470 


83 


'381 


6l'2 


264 


42 


-06 7 


11-4 


1-467 


82 


'374 


60 


'257 


4' 


'045 


7-2 


l'463 


80-9 


'372 


59' 6 


'251 


40 


'022 


4 


1*460 


80 


368 


58-8 


'244 


39 


"OIO 


2 


1*456 


79 















35 



PRACTICAL ORGANIC CHEMISTRY 



V. TABLE OF SPECIFIC GRAVITY AND PERCENTAGE OF HYDROCHLORIC ACID 
IN AQUEOUS SOLUTION. 





u 




to 




CO 




to 


^ . 


rt 


&' 


rt 


H . 


a 


>- ' 




en 


u 


10 
&H 


P 


C/2 rt 


V 


C/> rt 


is 




0, 




A 








fL, 


007 


i 5 


'"55 


II'O 


i'n6 


23-1 


''75 


34 '7 


*OIO 


2"2 


"060 


12 


I"I25 


24-8 


180 


35'7 


014 


2'9 


"067 


13-4 


i''34 


26-6 


185 


36-8 


'019 




75 


'5 


i"i43 


28-4 


190 


37 '9 


O22 


4 - S 


083 




1*150 


29-7 


194 


38-6 


'029 




"091 


18-1 


1*152 


30-2 


199 


39'8 


'031 


6'2 


094 


18.6 


i''59 


31-5 


*2O2 


40-5 


'036 


7'? 


"too 


19-9 


ii6i 


3 2 


"2O5 


41-2 


044 


3- 9 


105 


20-9 


1-166 


33 


"2IO 


42*4 


052 


io'4 


108 


21-5 


1-171 


33'9 


"212 


43 



VI. TABLE OF SPECIFIC GRAVITY AND PERCENTAGE OF CAUSTIC POTASH IN 
AQUEOUS SOLUTION. 





V 




i> 




V 




u 




ffni 




|s 


c 




U o ' 


|s 


bo "^ 


cO 


tem 




bV> 


cO 


bo "o 




M 


S^ 


O.I! 


S^ 


d.^ 


S* 


d 


^s 


rt 


i_ 


co 3 


fll *- 


c a 


s<~ 


en rt 


V- 




&J 




fe 




& 




ol 


'009 


i 


1-166 


19 


'374 


37 


i '590 


54 


-017 


2 


1-177 


20 


387 


38 


i '604 


55 


-025 


3 


1-188 


21 


400 


39 


1-618 


56 


'033 


4 


198 


22 


412 


40 


1*630 


57 


'041 


5 


209 


23 


'425 


41 


1*642 


58 


'049 


6 


"220 


24 


438 


42 


1*655 


59 


058 


7 


230 


25 


'45 


43 


1*667 


60 


-06 S 


8 


241 


26 


462 


44 


1*68 1 


61 


'074 


9 


252 


27 


'475 


45 


i '695 


62 


083 


10 


264 


28 


488 


46 


i '75 


63 


'(,92 


ii 


"276 


29 


'499 


47 


1*718 


64 


'131 


12 


288 


3 


"5" 


48 


1-729 


65 


"no 


13 


300 


31 


525 


49 


1-740 


66 


119 


'4 


! 3 " 


32 


'539 


5 


i'754 


67 


128 


15 




33 


552 


51 


1-768 


68 


'137 


16 


336 


34 


565 


52 


1-780 


60 


"146 


17 


349 


35 


578 


53 


1-790 


70 


155 


18 


-361 


36 











APPENDIX 



VII. -TABLE OF SPECIFIC GRAVITY AND PERCENTAGE OF CAUSTIC SODA IN 
AQUEOUS SOLUTION. 



fr 


tg 


Co' 


cO 


-' 


IQ 


ft 


fg 












v <* 




Z ft 


d 
C/3 


u* 2 " 


<n a 


V* 


nS 


Efc 


tflrt 


v* 




ft.'o 




ft.'o 




"0 




a> 


012 


I 


213 


19 


'f5 


37 


'580 


54 


023 


2 


225 


20 


"415 


38 


'59' 


55 


'035 


3 


'236 


21 


426 


39 


601 


56 


048 


4 


247 


22 


'437 


40 


611 


57 


058 


5 


258 


23 


'447 




'622 


58 


'070 


6 


269 


24 


'457 


42 


'633 


59 


08 1 


7 


279 


25 


468 


43 


'643 


60 


'092 


8 


'290 


26 


'478 


44 


654 


61 


'103 


9 


300 


27 


488 


45 


666 


62 


'"5 


10 


310 


28 


'499 


46 


674 


63 


ia6 


ii 


321 


29 


|59 


47 


684 


64 


137 


12 


'332 


3 




48 


'695 


65 


148 


13 


'343 


3 1 


'529 


49 


'705 


66 


'159 


14 


'353 


32 


'540 


5 


'715 


67 


170 


IS 


363 


33 


'550 


51 


726 


68 


181 


l6 


"374 


34 


'560 


52 


'737 


69 


'192 


17 


"384 


35 


'57 


53 


748 


70 


"202 


18 


'395 


36 











VIII. TABLE OF SPECIFIC GRAVITY AND PERCENTAGE OF AMMONIA IN 
AQUEOUS SOLUTION. 

Sp. gr. at 14 compared -with water at 14 = i. 





U I! 


V 









V 




W) ^ 








be . 




tc . 






, 












M 


HE 


B 


| 


M 


~i 


tio 


iw 


d. 


oZ 


Q. 




d. 


K 


a. 




VI 


o3 u- 


m 


S'o 






09 


flj **" 




* 




ft, 




&, 




ft, 


884 


36 


'95 


27 


'931 


18 


'963 


9 


886 


35 


907 


26 


'934 


17 


967 


8 


888 


34 


910 


25 


938 


16 


970 


7 


890 


33 


'9' 3 


24 


'941 


15 


'974 


6 


892 


32 


916 


23 


'944 


14 


'979 


5 


895 


3' 


919 


22 


948 


13 


983 


4 


897 


3 


922 


21 


952 


12 


'987 


3 


900 


29 


925 


20 


'955 


II 


991 


2 


902 


28 


928 


19 


'959 


10 


'995 


I 



INDEX 



ACETALDEHYDE, 64, 238 a-Beiizaldoxime, 197, 301 

Acetamide, 77, 243 /3-Benzaldoxime, 197, 301 

Acetanilide. 151, 278 Benzam.de, 209 

Acetic acid, 74 Benzene, 13^, 162 

Acetic anhydride, 76, 242 Benzene ethyl sulphonate, 173 

Acetic ether, 8 1 Benzene phenyl sulphonate, 179 

Acetmonobromamide, 81 Benzene sulphonau.ide, 179 

Acetoacetic ester, 83 Benzene sulphonanilide, 179 

Acetone. 69 Benzene sulp'ionic acid, 177 

Acetonitri e, 79, 244 Benzene sulphonic chloride, 178, 293 

Acetophenone. 210, 309 Benzidine, 148 

Acetophenoneoxime, 211 Benzil, 203 

Acetophenonesemicarbazone, 212 Benzilic acid, 203 

Acetoxime. 71 Benzoic acid, 199, 302 

Acetyl chloride, 74, 241 Benzoic ester, 109 

Acetylene, 64 Benzoin, 20 1, 303 

Acetyl method (Perkin) 222 Benzoyl chloride, 208, 308 

Acrplein, 106 Benzoylacetone, 212 

Action of heat, the, 323 Benzyl alcohol, 195 197,300 

Alcohol. 49 Benzyl chloride, 1^4, 299 

Aldehyde-ammonia, 66 nisdia/oacetale, 96 

Alizarin, 2"27. 316 Bitter almond oil, 196 

Alloxan. 130, 268 Biuret, 127 

Alloxantin, 129 Boiling-point method, 37 

Ally! alcohol, 109, 259 determination of, & 

Aluminium-mercury couple, 213 correction for, 59 

Aminoacetic acid, 90 /-Viromacetanilide, 152,278 

Aminoazobenzene, 172, 286 Bromacetic acid, 90 

w-Aminobenz ic acid, 201, 303 Bromacetyl bromide, 90 

/-Aminophenol. 149 Bromobenzene, 140, 271 

Ammon ; a, table of specific gravity, &c., w-Bromobenzoic acid, 201 

of, 351 /-bromotnluene, 167, 284 

Ammoniacal cuprous chloride, 64 Butyric acid, 99 
Amyl alcohol, 69 
Amy 1 nitrite. 69. 240 

Aniline, 149, 177 CAFKEINE, 131, 269 

Anisole, 181, 2^4 C'arbamide, 126 

Anschut/ thermometer. 60 Carbamine reaction, 71 

Anthraqumone 225, 316 Carbolic acid, 179 
A'.ithiaquinone j3- mono ulphonate of Carbon, qualitative analysis, i 

sodium, 226 quantitative analysis, 4 

Appendix. 234 Can'tis' meihod, 22, 23 

Atomic weights, table of, 345 Caustic potash, table of specific gravity, 
Azobenzene, 145, 274 &c-, of, 350 

Azoxybenzene 143,274 Can tic soda, table of specific gravity, &c., 

of, 351 

Chatttiivavs reaction, 174 
Chloracetic acid, t>7 

Beckmann freezing-point apparatus, 33 Chloral, 99 

boiling-point apparatus, 38 Chloral hydrate, 99 

thermometer. 34 Chlorhvdrin, in 

Becknianns reaction, 212 Chlorobenzoic acid, 166 

Benzalaniline, 197 Chloroform, 70 , 

Benzaldehyde, 196, 300 ^-Chlorotoluene, 165, 284 

Benzaldehyde green, 215, 313 Cinnamic acid, 204, 304 

COHEN'S ADV. p.o.c. 353 A A 



354 INDEX 



Citraconic acid, 125, 265 Ethyl benzene, ui, 273 

Citric acid, 124 Ethyl benzoate, 209, 308 

Ciaisen flask, 85 Ethyl bromide, ^4, 234 

Claisen's reaction, 212 Kthylene bromide, 62, zyj 

Combustion furnace, 4 Ethyl ether, 59, 236 

Combustion, 4 Ethyl malonate, 97 

carbon and hydrogen, 4 Ethyl malonic acid, 97, 256 

nitrogen compounds, 13 Ethyl potassium sulphate, 50, 734 

substances containing halogens and Ethyl tartrate. in, 262 
sulphur, 13 relation of, 120, 263 

substances containing nitrogen, 12 Eykman depressimeter, 36 

volatile and hygroscopic substances, 

ii 

Coirection for boiling-point, 59 FILTER-PUMP, 43 

Creatine, 132 Filtration through cloth, 131 
/>-Cresol, 164, 284 under reduced pressure, 43 

Cryoscopic method, 32 with fluted filter, 53 

Crystallisation, 52 Fischer's ester method, 133 

Cuprous chloride, 166 Fluorescein, 187 

Cyclohexanol, 181 Fluted filter, 53 

Formic acid, 106, 259 
Fractional distillation, 136 

DEPRESSIMETER, 37 Fractionating columns, 137 

Determination of boiling-point, 58 Freezing-point method, 32 

freezing-point, 33 Friedel-C tofts' reaction, 211 

melting-po nt, 72 Furnace, combustion, 4 

rotatory power, 116 tube, 23 

specific gravity, 56 Fusel oil, 69 
Dextrose, 135 
Diazoacetic ester, 94, 255 

Diazoaminobenzene, 171, 285 GATTERM ANN'S furnace, 23 
Diazobenzene perbromide, 162 diazo-reaction, 167 

Diazobenz^ne sulphate, 161, 282 Gelatine, hydrolysis of, 93 

Diazobenzoljmide, 232 Glucose, 135 

Dichlorhydrin, in Glycerin, 106 

Diethyl malonate, 96 Glycerol, too 

Dihydroxysuccinic acid, 114 Glycme, 90 

Dimethylaniline, 156, 279 Glycocoll, 90, 254 
Dimethyl /-phenylenediamine, 177 ester hydrochloride, 92 

Dinaphthol, 2^0 Glycollic acid, 102, 258 

/-Dinitrobenzene, 154, 279 Glyoxylic acid, 102, 258 

Diphenylhyd'azine, 146 Grape-sugar, 135, 271 
Diphenylmethane, 213, 312 
Diphenylthiourea, 159 

Distillation in steam, 107 HgSO^, table of specific gravity of, in 

in vacuo, 84, 94 concentrated sulphuric acid, 349 

Drying apparatus, 4 Halogens, qualitative determination, 3 

quantitative ,, 22, 32 

Heat, the action of, 323 

EBULLIOSCOPIC method, 37 Heating under pressure, 78 

Electrolytic reduction, oxalic acid, 102 Hexahydrophenol, 181,295 

nitrobenzene. 144, 145 Helianthin, 176 

Elements, the, 324 Hempel fractionating column, 137 

Eosin, 187 Holtnann's bottles, 30 

Epichlorhydrip, i'i, 260 Homogeneity, 322 

Estimation of oaibon and hydrogen, 4 Hot-water funnel, 53 

halogens, 22 Hydrazobenzen", 146, 274 

nitrogen, 13, 20 Hydriodic acid, 113 

sulphur, 28 Hydrobenzamide, 196 

Ether, 50 Hydrobromic acid, 140 

commercial, 61 Hydrochloric acid gas, 93 
Ethyl acetate, 81, 247 table of specific gravity, &c., of, 350 

Ethyl acetoacetate, 83, 248 Hydrocinnamic acid, 204, 306 

Ethyl alcohol, 49 Hydrogen, qualitative determination, i 



INDEX 



355 



Hydrogen, quantitative determination, 4 
Hydrolysis of ethyl acetate, 82 
Hydroquinone, 192 
0-Hydroxybenzaldehyde, 788 
p. ,, 188, 297 

Hydroxybenzene, 179 
0-Hydroxybenzoic acid, 190 
in- 200, 303 

Hydroxyl method (Tsckngafff), 223 
Hypnone, 210 



lODOBENZENE, 163 

lodoform reaction, 50 
lodosotolueiie, 169, 285 
/-lodotoluene, 168 
Insoluble solids, 337 

substances, 340 et seq. 
Isatin, 229, 318 
Isopropyl iodide, no, 260 



Kjeldahts method, 20 



NAPHTHALENE, 216 

Naphthalene picrate, 217 

Naphthalene sulphonate of sodium, 218, 

3i5 

/3-Naphthol, 219, 315 
Naphthol yellow, 224 
/3-Naphthyl acetate, 222 
p-Naphthyl methyl ether, 220 
/>-Nitracetanilule, 153 
-Nilraniline, 154, 279 
/-NitraniIine, 153 
Nitric acid (fuming), 22 

table of specific gravity, &c., of, 

349 

Nitrobenzene, 142, 274 
//'Nitrobenzoic acid, 200. 301 
Nitrogen, qualitative estimation, 2 

quantitative estimation, 13 
o-Nitrophenol, 183, 295 
/-Nitrophenol, 183 

Nitrosobenzene, 149 

/-Nitrosodimethylaniline, 157, 280 
Nitrosophenol, 159 



Laurent's polarimeter, 1 16 
Leucine, 133, 270 

I.ieberniaitHS nitroso reaction, 159 
Liquid, a, 322 



MALACHITE green, 215 

Malic acid, 112 

Malonic ester, 96 

Mandelic acid, 205. 306 

Melting-point determination, 72 

Mesacomc acid. 125, 265 

M esotj-.rtaric acid, 122, 264 

Methoxyl method (Ziisel), 220 

Methyl acetate, ?i 

Methyl alcohol, 67 

Methyl alcoholic potash, 64 

Methylamine hydrochloride, 80, 245 

Methylated spirit, purification of, 48 

Methyl cyanide, 79 

Methyleneamino-acetonitrile, 92 

Methyl 1 iodide, -68, 240 

JSIethy! orange, 176, 289 

Methyl oxalate, 101 

Methyl phjuate, 181 

Methyl poKssium sulphate,' 50 . 

Mixtures, 343 

Molecular rotation, 119 

Molecular weight- 
vapour density, 29 
freezing-point, 33 
boiling-point, 38 
organic acids, 43 
organic bases, 46 

Malisctis reaction, 136 

Monobromacetic acid, 89, 252 

Monochloracetic acid, 87, 252 

Monochlorhydrin, 112 

Murexide, 129 



ORGANIC analysis, i 

Organic liquids insoluble in water, 334-6 

Oxalic acid, ico, 257 

Oxamide, 102 

Oxanthranolate of sodium, 226 



PALMITIC acid, 104, 258 

Palm oil, 104 

Paraldehyde, 67 

Pararosaniline, 215 

Per/tin* acetyl method, 222 

Perkins pyknometer, 57 

Phenol, 179, 294 

Phenolphthalem, 186, 296 

Phenylacetamide, 151 

Phenylacrylic acid, 204 

Phenyl bromide, 140 

/w-Phenylenediamine, 155 

/-Phenylenediamine, 173 

Phenylhydrazine, 173, 287 

Phenylhydroxylamine, 148, 276 

Phenyl methyl carbinol, 206, 307 

Phenyl methyl ether, 181 

Phenyl methyl ketone, 210 

Phenyl methyl pyrazolone, 175, 287 

Phenyl methyl triazolecarboxylic acid, 

232, 320 

Phenyl mustard oil, 160 
Phenylpropionic acid, 204 
Phenylthiocarbimide, 160 
Phenylthiourethane, 160 
Phosphorus, qualitative analysis, 3 
Phthalic acid, 217, 314 
Picric acid, 185, 295 
Piria & Schijff ' s method, 27 
Polarimeter, 116 
Potash apparatus, 4 



356 INDEX 

Potassium benzene sulphonate, 177, 292 TABLE of atomic weights, 345 

Potassium ethyl sulphate, 50 Table of specific gravity and percentage 

Potassium methyl sulphate, 50 of 

Preparations, general remarks, 47 ammonia in aqueous solution, 351 

Pressure tube, glass, 24, 78 caustic potas i ,, 350 

furnace, 24 cau-ticsoda ,, 351 

metal, 227 H^Sp4 in concentrated sulphuric 

Purification of ether, 60 acid, 349 

methylated spirit, 48 hydrochloric acid in aqueous solution, 

Pyknometer, 57 350 

Pyruvic acid, 124 nitric acid in aqueous solulion. 340 

sulphuric acid ,, 348 

Tartaric acid, 114 

QUANTITATIVE estimation of carbon and Terephthalic acid, 171 
hydrogen, 4 Tetrabromocresol, 165 

halogens, 22 Thiocarbamide, 128, 268 

nitrogen, 13 '1 hiocarbanilamiue, 160 

sulphur, 28 Thiocarbanilide, 159, 281 

Quinine sulphate, 231, 319 Thiocarbimide, 281 

Quinol, 193, 297 Thiourea, 128 

Quinoline, 230, 318 Toluene from /-toluidine, 163, 284 

Quinone, 192, 297 ^-Toluic acid, 170 

Quinoneo.xime, 159 Toluidine toluene, from 281, 284 

/-Tolyl cyanide, 169 
Tolyliodochloride, 169 
RACEMIC acid, 122, 264 Tribromophenol, 180 

resolution of, 123 Trichloracetic acid, 99, 257 

Ring-burner, 108 Tr methyl xanthine, 131 

Rotation of ethyl tartrate, 120 Trinitrophenol, 185 

tartaric acid, 120 Triphenylguanidine, 160, 281 

Triphenylmethane, 214, 312 
'1'schugatffs hydroxyl method, 223 

SALICYLAI.DEHVDE, 188, 207 Tube furnace, 23 

Salicylic acid, 190, 297 Tyiosine, 133, 270 

Sandmeyers reaction, 16-,, 167 
Saponification of eihyl acetate, 82 



Schotten-Baitmantis reaction, 209 cia ' I2c 

Sealed tube furnace, 23 

Sealed tubes, 24 

Single substances soluble in water, 328 VACUUM desiccator, 45 

insoluble in water, 332 Vacuum disiillation, 84, 94 

Sodium bisulphite, 67 Vapour density method, 29 

knife, 61 Vapour tension of water, 346 

press, 61 of caustic potash solutions, 347 

Solid, a, 323 Victor Meyer apparatus, 29 

Solids, 336 I'igreux's fractionating column, 137 

insoluble, 337 
Solubility, 324 

Soluble liquids and solids, 326-8 

Specific gr.tvity determination, 56 WATER-JET aspirator, 44 

Specific rotation, 119 Water turbine, 9 x 

Sp ; rits of w : ne, purification of, 48 
Sfirengel's pyknometer, 57 

Substances, insoluble, 340 et seq. Yt>nng and Thomas fractionating column, 

Succinic acid, 113, 261 ^ 

Sulphanilic acid, 175, 289 
Sulphur, estimation of, 28 
Sulphuric acid, percentage of, in aqueous 

solution, 348 Zeiscl's method, 220 

PRINTED IN GREAT BRITAIN BY R. CLAY AND SON8, LTD., 
BRUNSWICK STREET, STAMFORD STREKT, 8.E I, AND BUNOAY, SUFFOLK. 




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