FUNDAMENTAL PROCESSES OF

DYE CHEMISTRY

By HANS EDUARD FIERZ-DAVIDand Louis BLANGEY

Eidgenossische Technische Hochschule, Zurich

Translated from the Fifth Austrian EditionBy PAUL W. VITTUM

Eastman Kodak Company, Rochester, New York

Published and distributed in the public interest with theconsent of the Attorney-General under License No. A-1360

1949

INTERSCIENCE PUBLISHERS, INC., NEW YORKINTERSCIENCE PUBLISHERS LTD., LONDON

43G39

Translated from Grundlegende Operationen der Farbenchemie,Siebente Unveranderte Auflage, Springer-Verlag, Wien, 1947.The sixth (1946) and seventh (1947) Austrian editions are

unchanged reprints of the fifth (1943) Austrian edition.Preface to the Fifth Austrian Edition

Copyright, 1922, Springer-Verlag OHG., Berlin. Copyright,1938, 1943, Springer-Verlag OHG., Vienna. Copyright vest-ed in the Alien Property Custodian, 1944, pursuantto law. Copyright, 1949, Interscience Publishers, Inc.

ALL RIGHTS RESERVED

This translation or any part thereof must notbe reproduced without permission of the pub-lishers in writing. This applies specificallyto photostatic and microfilm reproductions.

I N T E R S C I E N C E PUBLISHERS, INC.215 Fourth Avenue, New York 3, N. Y.

For Great Britain and Northern Ireland:I N T E R S C I E N C E PUBLISHERS LTD.2a Southampton Row, London, W. C. 1

This fifth edition of Grundlegende Operationen der Farbenchemieconstitutes an expansion of the fourth edition. Since the appearance ofthe first edition in 1920, so many new processes of dye chemistry havebeen discovered that it appeared necessary to rework or enlarge varioussections. In particular, the preparation of several important intermedi-ates has been resurveyed.

The book is intended principally to introduce to the beginner themethods of dye chemistry, and not merely to present a collection ofrecipes. To this end, the chapter on the practical work in the organicindustrial laboratory has been reworked and enlarged in order to clarifyall the important points. The chapter on analysis of dyes has been re-vised so that the student may gain some insight into this difficult field.Also, the section on the determination of light fastness has been re-written, and we are grateful to Dr. Ris (Basel) for his contributions tothis subject. These additions have increased the scope of the book. Wehope that they have also increased its usefulness.

H. E. Fierz-DavidLouis Blangey

Zurich, November 3, 1942Chem.-Techn. Laboratorium der

Eidgenossischen TechnischenHochschule

PRINTED IN THE UNITED STATES OF AMERICAOFFSET BY NEW YORK LITHOGRAPHING CORP., NEW YORKCOMPOSED BY GRAPHIC PRODUCTION CORP., NEW YORK

Preface to the Translation

Twenty-eight years have elapsed since the publication of the firstedition of Grundlegende Operationen der Farbenchemie. In the mean-time the technology of dyestuff intermediates and the dyes obtainedfrom them has developed widely, and the processes described in 1920are very well known today.

Editions subsequent to the first (up to the seventh edition, publishedin Vienna in 1947) were expanded considerably in collaboration withL. Blangey. The main aim was always to explain the fundamental prin-ciples of dye chemistry to the student; and, since it was the endeavorof the authors to write a laboratory book and not an encyclopedia, ingeneral only simple examples were given in this work. The preface tothe first edition indicated that the processes described were perhapsnot the best, but that by following the instructions exactly the resultsstated would be obtained. In dye chemistry, as is well known, manyroads lead to the same goal.

The present edition is not intended to compete with more compre-hensive books such as that of P. H. Groggins, Unit Processes in OrganicSynthesis (1947). The latter is a textbook, while Grundlegende Opera-tionen der Farbencherhie, like Gattermann's book Praxis des Organ-ischen Chemikers, is primarily a laboratory manual. The reprinting ofthe fifth Austrian edition in the United States without the consent ofthe authors indicated recognition of the need for such a volume.

It seems apropriate, however, to publish a new, American edition inwhich several reactions are described that have not appeared in pre-vious editions and which corrects minor errors discovered in the Aus-trian edition on which the translation is based. These are the onlychanges considered necessary.

After the present translation had been printed, the allied reportson German and Japanese industry were made public. The authors notedto their satisfaction that the processes they described correspondedclosely in many cases with those of the German dye factories. Certainlarge-scale industrial reactions can be reproduced only with difficultyin the laboratory with the small amounts of material at the chemist'sdisposal. In our opinion, for example, it is practically impossible in the

via PREFACE TO THE TRANSLATION

laboratory to fractionate and crystallize out at low temperatures themixtures of chlorotoluenes as described in BIOS Final Report No. 1145.On the other hand, we would like to point out here that 1-naphthyl-amine-3-sulfonic acid can be separated easily from the mixture of the1,6-, 1,7-, and 1,8- acids by precipitating carefully with acid, accordingto FIAT Final Report No. 1016. The other processes correspond soclosely with those we present that there is no need for further amend-ments.

We want to thank Dr. Paul W. Vittum for a translation that corre-sponds so well with the sense of the original German. We hope that thisAmerican edition will fulfill its purpose and be cordially received.

H. E. Fierz-DavidLouis Blangey

Zurich, December 1, 1948Swiss Federal Institute of Technology

CONTENTS

Preface to the Austrian edition vPreface to the translation viiIndex of reactions , xixList of figures xxviiList of tables xxix

The foundations of the dye industry 1

I. INTERMEDIATESGeneral discussion 3The various operations of intermediate chemistry 6

Sulfonation 6Nitration 6Reduction 7Introduction of the hydroxyl group 7Introduction of amino and alkoxy groups 8Oxidation methods 8Introduction of halogen 9

Practical work in the industrial organic laboratory 10General 10Proportions and weighing 13Laboratory journals and reports 14Apparatus 14Stirring apparatus 15Filtration 18Distillation 21

Distillation under ordinary pressure 21Vacuum distillation 25Steam distillation 25

Separation of reaction products 27Basic substances 27Acidic substances 30

Purification of products 34Testing the product for purity 40Orientation rules 50

Orientation in the benzene series 50Orientation in the naphthalene series 53Orientation in the anthraquinone series 56Orientation in the carbazole series 60

X CON-TCNTS

A. Compounds of the benzene series 62Chlorobenzene 62

Halogenation in general 65Nitrobenzene 68

Nitration in general 69The Lunge nitrometer 72

Aniline from nitrobenzene 75Reduction in general 77

Benzenesulfonic acid 80Sulfonation in general 82

Phenol 86Alkali fusion in general 88

Derivatives of chlorobenzene 90o- and p-Nitrochlorobenzene 90p- and 0-Nitroaniline from p- and o-nitrochlorobenzene 92p-Nitrophenyloxamic acid and p-aminophenyloxamic

acid 93p-Nitrophenylhydrazine 95o-Nitroanisole from o-nitrochlorobenzene 97p-Nitrochlorobenzene-o-sulfonic acid and p-nitroaniline-

o-sulfonic acid from p-nitrochlorobenzene 99Diaminodiphenylaminesulfonic acid 99Aminodiphenylaminesulfonic acid (III), and

aminophenyltolylaminesulfonic acid 1002,4-Dinitrochlorobenzene from chlorobenzene 101m-Phenylenediaminesulfonic acid from 2,4-dinitro-

chlorobenzene 103Aniline-2,5-disulfonic acid from chlorobenzene 104

2-Nitrochlorobenzene-4-sulfonic acidfrom chlorobenzene 104

Nitrobenzene-2,5-disulfonic acid 106Anilme-2,5-disulfonic acid 106

4-Chloro-2-aminophenol from p-dichlorobenzene . . . . 108Nitro-p-dichlorobenzene from p-dichlorobenzene . . . 1084-Chloro-2-nitrophenol from nitro-p-dichlorobenzene 1094-Chloro-2-aminophenol from 4-chloro-2-nitrophenol 110

Derivatives of nitrobenzene Illm-Dinitrobenzene from nitrobenzene Illm-Nitroaniline from m-dinitrobenzene 113

Partial reductions in general 114m-Phenylenediamine from m-dinitrobenzene 115m-Chloronitrobenzene from nitrobenzene 1162-Chloro-4-dimethylaminobenzaldehyde 118

p-Tolyhydroxylaminesulfonic acid 1182-Chloro-4-dimethylaminobenzaldehyde 119

m-Nitrobenzenesulfonic acid and metanilic acidfrom nitrobenzene 120

2,2'-Benzidinedisulfonic acid from nitrobenzene 123Benzidine from nitrobenzene 124

CONTENTS XI

Derivatives of aniline 126Sulfanilic acid from aniline (baking process) 126

The baking process in general 1271- (p-Sulfophenyl) -3-methyl-5-pyrazolone from

sulfanilic acid 128Phenylhydrazine-p-sulfonic acid 128p-Sulfophenyl-3-methyl-5-pyrazolone 129

p-Aminoacetanilide from aniline 129Acetanilide from aniline 130p-Nitroacetanilide from acetanilide 131p-Aminoacetanilide from p-nitroacetanilide 132

Dimethylaniline (diethyl- and ethylbenzylanilines) . . . 133Ethylbenzylanilinesulfonic acid 136Tetramethyl-p,p'-diaminodiphenylmethane from

dimethylaniline and formaldehyde 137Tetramethyl-p,p'-diaminobenzohydrol (Michler hydrol) 138Tetramethyl-p,p'-diaminobenzophenone

(Michler ketone) 139Diphenylamine from aniline and aniline salt 140Acetoacetanilide 142

Derivatives of benzenesulfonic acid 143Benzene-m-disulfonic acid 143Resorcinol 144

Derivatives of phenol 145o- and p-Chlorophenol from phenol 145Chloranil 146o- and p-Nitrophenols and their ethers 147

Alkylation of nitrophenols 148Trinitrophenol (picric acid) 150Picramic acid 1522-Aminophenol-4,6-disulfonic acid from phenol 153Salicylic acid from phenol 154p-Aminosalicylic acid 156

Preparation of the azo dye 156Reduction 157

Derivatives of toluene 158Benzal chloride and benzaldehyde from toluene . . . . 158

Benzal chloride 158Benzaldehyde 158

2,6-Dichlorobenzaldehyde from o-nitrotoluene 160Chloronitrotoluene from o-nitrotoluene 1602,6-Chlorotoluidine 1612,6-Dichlorotoluene 1612,6-Dichlorobenzal chloride 1622,6-Dichlorobenzaldehyde 162

Benzidine-3,3'-dicarboxylic acid from o-nitrobenzoic acid 16.42-Nitro-4-aminotoluene from p-toluidine 165Dinitrostilbenedisulfonic acid and diaminostilbenedisul-

fonic acid from p-nitrotoluene (simultaneous oxida-tion of two molecules) 167

xii CONTENTS

Dinitrostilbenedisulfonic acid 167Reduction to diaminostilbenedisulfonic acid 168

2-Chloro-5-aminobenzoic acid 169Gallamide and gallic acid from tannin 170Benzene derivatives from naphthalene 171

Phthalic anhydride from naphthalene bycatalytic oxidation 171

Preparation of the catalyst 171Performing the reaction. Apparatus 172

Phthalimide from phthalic anhydride 173Anthranilic acid from phthalimide 174

B. Compounds of the naphthalene series 175a-Nitronaphthalene and a-naphthylamine 175

Phenyl-a-naphthylamine 179o-Naphthol from a-naphthylamine 180Naphthionic acid from a-naphthylamine 180

Preparation of the acid sulfate 180Baking process 181

l-Naphthol-4-sulfonic acid (Nevile-Winther acid) fromnaphthionic acid (Bucherer reaction) 182

The sulfonic acids of naphthalene 1831,6- and 1,7-Naphthylaminesulfonic acids (Cleve acids) 184Naphthalene-/3-sulfonic acid and -naphthol 187Sulfonation of /3-naphthol 1912-Naphthol-6-sulfonic acid (Schaeffer acid)

(R acid and G acid) 1942-Naphthol-6,8-disulfonic acid (G acid) and

2-naphthol-3,6-disulfonic acid (R acid) 1972-Naphthylamine-l-sulfonic acid (Tobias acid)

from /3-naphthol 1982-Naphthol-l-sulfonic acid from j3-naphthol 1992-Naphthylamine-l-sulfonic acid from

2-naphthol-l-suJfonic acid 200l-Amino-2-naphthol-4-sulfonic acid from j8-naphthol

Preparation of an aminonaphtholsulfonic acid fromthe hydroxynitroso compound (quinonemon-oxime) 201

/3-Naphthylamine from /3-naphthol 2032,8,6- and 2,5,7-Aminonaphtholsulfonic acids (Gamma

and J acids) from -naphthylamine 2042,6,8- and 2,5,7-Naphthylaminedisulfonic acids from

/3-Naphthylamine. 2052-Amino-8-naphthol-6-sulfonicacfd (Gamma acid) . . 2072-Amino-5-naphthol-7-sulfonic acid (J acid, iso-

Gamma acid) 207From 2-naphthol-6,8-disulfonic acid 208From G acid and 2,8-dihydroxynaphthalene-6-

sulfonic acid 208Phenyl-gamma acid 209

CONTENTS xiii

l-Naphthylamine-3,6-disulfonic acid (Freund acid) 209l-Amino-8-naphthol-3,6-disulfonic acid (H acid) 211

l-Naphthylamine-3,6,8-trisulfonic acid (Koch acid) 211l-Amino-8-naphthol-3,6-disulfonic acid (H acid) . . 213

l-Naphthylamine-5- and -8-sulfonic acids 214l-Aminonaphthalene-4,8-disulfonic acid, 2-aminonaphthalene-

4,8-disulfonic acid, and l-aminonaphthalene-3,8-disul-fonic acid 219

Naphthalene-l,4,5,8-tetracarboxylic acid from pyrene 221Tetrachloropyrene 221Naphthalenetetracarboxylic acid 222

C. Compounds of the anthraquinone series 224Anthraquinone 224

Method 1: oxidation of anthracene 224Method 2: from phthalic anhydride and benzene 225

o-Benzoylbenzoic acid 225Anthraquinone 226

l-Amine>-2-methylanthraquinone 2272-Methylanthraquinone 227l-Nitro-2-methylanthraquinone 227l-Amino-2-methylanthraquinone 228

2-Aminoanthraquinone . 228Sodium anthraquinone-2-sulfonate ("silver salt") . . . 2282-Amin9anthraquinone 229

1-Aminoanthraquinone and 1,4-diaminoanthraquinone 230Anthraquinone-1 -sulfonic acid 2301-Aminoanthraquinone 2311-Anthraquinonyloxamic acid 2314-Nitro-l-anthraquinonyloxamic acid 2321,4-Diaminoanthraquinone 232

1,5- and 1,8-Dihydroxyanthraquinone, and 1,5-dichloro-anthraquinone 234

Anthraquinone-1,5- and -1,8-sulfonic acid 2341,5- and 1,8-Dihydroxy anthraquinone 2361,5-Dichloroanthraquinone 236

1,5-Dinitroanthraquinone and 1,5-diaminoanthraquinone . . . 2361,5-Dinitroanthraquinone 237Reduction to 1,5-diaminoanthraquinone 237

Quinizarin from p-chlorophenol 237

II. DYESD. Azo dyes 239

Laboratory preparation of azo dyes 239Fundamental considerations 239Diazotization 241

Examples 243

xiv CONTENTS

Coupling 249Theoretical . . . . 249Practical 252

Isolation of dyes 257Dyes without sulfo or carboxyl groups 257Dyes with sulfo or carboxyl groups 258

Technical diazotization procedures 259Aniline 259p-Nitroaniline 260a-Naphthylamine 260Sulfanilic acid 261Benzidine 261

Coupling reactions 262Single coupling reactions with hydroxy compounds . . . . 262

Acid orange A*or orange II 262Acetyl-H acid and amidonaphthol red G 263Fast light yellow G (Bayer) 265Hansa yellow G 266Permanent red 2G 267Helio Bordeaux BL 268

Preparation of the sodium salt 268Preparation of the calcium lake 269

Single coupling reactions with amines 270p-Aminoazobenzene from aniline 270Tropaeoline or orange IV and azo yellow from sulfanilic

acid and diphenylamine 273Tropaeoline or orange IV 274Azo yellow (Indian yellow, helianthine, etc.) . . . . 275

Secondary disazo and polyazo dyes 277Naphthylamine black D 277Benzo light blue 2 GL or sirius light blue G 279

Aniline-2,5-disulfonic acid. a-Naphthylamine 279Aniline-2,5-disulfonic acid. a-Naphthylamine.

l-Naphthylamine-7-sulfonic acid 280Preparation of the trisazo dye 281

Disazo and polyazo dyes from diamines 282Bismarck brown G and R 282

Bismarck brown R (Vesuvine R, etc.) 282Chrysophenine G 283

Benzidine dyes 285The intermediate from benzidine and salicylic acid

(or from o-tolidine and o-cresotinic acid) 285Dianil brown 3 GN 286Diamine green B 288Direct deep black EW 29]Congo red 293Acid anthracene red G and chromocitronine R 294

Special methods 295Eriochrome flavine A 295Sun yellow G from p-nitrotoluene 296

CONTENTS XV

E. Di- and triphenylmethane dyes 298Auramine OO 298Malachite green 299

Leuco malachite green 299Oxidation of the leuco base to the dye 300

Xylene blue VS 301Toluenedisulfonic acid 302Benzaldehydedisulfonic acid 303Condensation to the leuco dye 303Oxidation to the dye 304

Wool blue 5B 305Victoria blue B 306Wool green S 307

F. Oxazine and thiazine dyes 308Gallamine blue from gallamide 308

Nitrosodimethylaniline 308Gallamine blue 309

Methylene blue from dimethylaniline 311p-Aminodimethylaniline 311Thiosulfonic acid of Bindschadler green 312

C. Anthraquinone dyes 314Mordant dyes 314

Alizarin 314Acid dyes 317

Quinizarin green or alizarin cyanine green G 317Alizarin saphirol B and SE 319

Sulfonation and nitration 319Reduction 320Splitting out of one sulfo group : . . . 320

Vat dyes 321Indanthrene blue RS from /9-aminoanthraquinone . . . . 321Indanthrene yellow GK 322

H. Indigoid dyes 323Indigo 323

Heumann synthesis 323Phenylglycine-o-carboxylic acid 323Indoxylcarboxylic acid 324Indigo 324

Traugott Sandmeyer synthesis 324Thiocarbanilide 326Hydrocyanocarbodiphenylimide 326"Thioamide" 327a-Isatinanilide

t 327a-Thioisatin and indigo '. 329

Thioindigo 330o-Carboxyphenylthioglycolic acid (O acid) 3303-Hydroxythionaphthene 331

XVI CONTENTS

I. Sulfur fusions 332Primuline 332

Chloramine yellow FF (naphthamine yellow NNand thiazole yellow 332

Separation of the melt 334Naphthamine yellow NN (also FF)

and thiazole yellow 335Naphthamine yellow NN 335Thiazole yellow or Clayton yellow 336

Sulfur black T from dinitrochlorobenzene 337J. Phthalocyanines 338

Monastral fast blue BS, heliogen blue B . . . 338

III. TECHNICAL DETAILSK. Vacuum distillation in the laboratory and plant 341L. The filter press 348M. The construction and use of autoclaves 350

General rules on the use of pressure vessels 361N. Construction materials for dye chemistry 362

Metals 362Nonmetals 365Materials of organic origin 367

O. Technical details of factory management 369Charges 372Steam consumption 372Compressed air and vacuum 373Function of the plant chemist 373Manufacturing 373Sample dyeing 375Grinding 377

P. Calculation of costs for a simple dye 378Orange II or acid orange A 378

0-Naphthol 378Sodium ]3-naphthalenesulfonate 378Fusion of the sodium salt 379

Sulfanilic acid 380Nitrobenzene ". 380Reduction of nitrobenzene 380Sulfonation of aniline 380

Preparation of the dye from sulfanilic acid and 0-naphthol 381

IV. ANALYTICAL SECTIONPreparation of standard titrimetric substances 384

Preparation of pure sulfanilic acid 384Preparation of 1 N sodium nitrite solution 385Preparation of 0.1 N phenyldiazonium solution 385

CONTENTS xvii

Determination of amines 386Direct determination 386Indirect determination 387

Determination of naphthols 387/3-Naphthol 387a-Naphthol 388Dihydroxynaphthalenes (molecular weight 160) 388

Determination of aminosulfonic acids 388Determination of aminonaphtholsulfonic acids 389

H acid. l-Amino-8-naphthol-3,6-disulfonic acids 389Determination of naphtholmono- and -disulfonic acids

and dihydroxynaphthalenemono- and -disulfonic acids 390Example: Nevile-Winther acid (l-naphthol-4-sulfonic

acid) (molecular weight 224) 390Determination of 2-naphthylamine-5,7-disulfonic acid in the

presence of 2-naphthylamine-6,8-disulfonic acid . . . . 391Volumetric determination of dyes by the Edmund Knecht

reduction method 392Principle of the Knecht method 392Preparation of the titanium trichloride solution 393Titration of methylene blue 393Azo dyes 394Triphenylmethane dyes 394

The common test papers 395Solution for spot tests on filter paper 396Evaluation of zinc dust , . . . . 396Evaluation of lead peroxide paste 397

V. THE ANALYSIS OF COMMERCIAL DYESPolar brilliant red 3B and B 404Polar brilliant red 3B 404Benzo light grey BL 407Brilliant sulfo flavine (I.G.) 409Literature on analysis of dyes 410

VI. THE DETERMINATION OF LIGHT FASTNESS

TablesItoXXI 417-465Subject Index

467

INDEX OF REACTIONS

1. HalogenationGeneral 9, 65Direct chlorination:

With chlorine:Chlorobenzene and dichlorobenzene from benzene 62m-Chloronitrobenzene from nitrobenzene 116Trichlorophenol from phenol 145Benzal chloride from toluene 1582-Nitro-6-chlorotoluene from o-nitrotoluene 1602,6-Dichlorobenzaldehyde from 2,6-dichlorotoluene 162Tetrachloropyrene from pyrene 221

With sulfuryl chloride:o- and p-Chlorophenol from phenol 145

Indirect introduction of chlorine:Replacement of SO3H by Cl:

1,5-Dichloroanthraquinone from anthraquinone-l,5-disulfonic acid 236Replacement of NH2 by Cl (Sandmeyer reaction):

2,6-Dichlorotoluene from 2-amino-6-chlorotoluene 161Oxidative chlorination with aqua regia:

Chloranil from trichlorophenol 146Bromination:

2,4-Dibromo-l-aminoanthraquinone from 1-aminoanthraquinone . . 2332. Nitration

General 6, 69Nitrobenzene 68m-Dinitrobenzene from nitrobenzene Illo- and p-Nitrochlorobenzene 902,4-Dinitrochlorobenzene from chlorobenzene 101Nitro-p- dichlorobenzene 1082-Nitrochlorobenzene-4-sulfonic acid 104p-Nitroacetanilide 131o- and p-Nitrophenol 147Picric acid from phenol 1502-Nitrophenol-4,6-disulfonic acid 1532-Nitro-4-aminotoluene 1653-Nitro-6-chlorobenzoic acid 169Azo yellow G from tropaeoline 276a-Nitronaphthalene 175l-Nitronaphthalene-5- and 8-sulfonic acid 215l-Nitronaphthalene-6- and 7-sulfonic acid 184l-Nitronaphthalene-3,6-disulfonic acid 209l-Nitronaphthalene-3,8- and 4.8-disulfonic acid, and

2-nitronaphthalene-4,8-disulfonic acid 219

KX INDEX OF REACTIONS

l-Nitronaphthalene-3,6,8-trisiilfonic acid 2111,5-Dinitroanthraquinone from anthraquinone 237l-Nitro-2-methylanthraquinone 2274-Nitro-l-anthraquinonyloxamic acid 2324,8-Dinitro-l,5-dihydroxyanthraquinone-2,6-disulfonic acid 319Methylene green from methylene blue 313

3. Nitrosationp-Nitrosodimethylaniline from dimethylaniline 308l-Nitroso-2-naphthol from /3-naphthol 201Nitrosotropaeoline from tropaeoline 275

4. ReductionGeneral 7, 77NO2 to NH2:

Reduction of all the nitro groups present:Aniline (Fe) 75m-Phenylenediamine from nitrobenzene (Fe) 115Metanilic acid (Fe) 121Aniline-2,5-disulfonic acid (Fe) 106m-Phenylenediaminesulfonic acid (Fe) 103p-Aminoacetanilide (Fe) 132p-Aminophenyloxamic acid (Fe) 944-Chloro-2-aminophenol (Fe) 1102-Aminophenol-4,6-disulfonic acid (Na2S) 1546-Chloro-2-aminotoluene (Fe) 161p,p'-Diaminostilbenedisulfonic acid (Fe) 1686-Chloro-3-aminobenzoic acid (Zn) 169a-Naphthylamine (Fe) 1761.5- and 1,8-Naphthylaminesulfonic acid (Fe) 2151.6- and 1,7-Naphthylaminesulfonic acid (Fe) 186l-Naphthylamine-3,6-disulfonic acid 210l-Naphthylamine-3,8- and 4,8-disulfonic acid and

2-naphthylamine-4,8-disulfonic acid (Fe) 219l-Naphthylamine-3,6,8-trisulfonic acid (Fe + H2SO4) 212l-Amino-2-methylanthraquinone (Na2S) 2281,4-Diaminoanthraquinone (Na2S) 2321,5-Diaminoanthraquinone (Na2S) 237Alizarin saphirol B (NaSH) -. 320

Reduction of only one of several nitro groups (partial reduction):General 114m-Nitroaniline from m-dinitrobenzene (NaSH) 113Picramic acid from picric acid (Na2S) 152

_NO2 to NHOH:p-Tolylhydroxylamine-o-sulfonic acid (Zn) 118

NO2 to NHNH, followed by benzidine rearrangement:Benzidine from nitrobenzene (Zn) 124Benzidine-2,2/-disulfonic acid (Zn) 123Benzidine-3,3'-dicarboxylic acid (Zn) 164

NO to NH2:p-Aminodimethylaniline (Zn) 311l-Amino-2-naphthol-4-sulfonic acid (simultaneous

sulfonation, with SO2) 201N=N to NH2:

p-Aminosalicylic acid (Na2S2O4) 157Reductive splitting of polar brilliant red 3B (Na2S2O4) 404Reductive splitting of polar brilliant red 3B (SnCl2) 404Reductive splitting of benzo light grey BL (SnCl2) 407

INDEX OF REACTIONS xxi

N=N+C1- to NHNH2:- and o-Nitrophenylhydrazine from p- and o-nitroaniline

(Na2S03 + NaHSOa) 95Phenylhydrazinesulfonic acid^ (Na2SOa) 128

Other reductions:Thiosalicylic acid from dithiosalicylic acid (Fe) 331Leuco quinizarin from quinizarin (SnCl2) 318Modem violet from galfamine blue (Na2S) 310o-Thioisatin from isatinanilide (NaSH) 329

5. OxidationGeneral 8Phthalic anhydride from naphthalene (air) 171Benzaldehyde-2,4-disulfonic acid from toluenedisulfonic acid (MnO2) 303v p'-Dinitrostilbenedisulfonic acid from p-nitrotoluene-o-sulfonic acid

(NaOCl) 167Naphthalene-1,4,5,8-tetracarboxylic acid from tetrachloropyrene (HNOa) 222Anthraquinone from anthracene (CrOa) 224Tetramethyldiaminobenzhydrol (Michler hydrol) from

tetramethyldiaminodiphenylmethane (PbO2) 138Malachite green from the leuco base (PbO2) 300Xylene blue VS from the leuco compound (PbO2) 304Wool green S from the leuco compound (CrOa) 308Bindscbedler green-thiosulfonic acid from dimethylaniline,

p-aminodimethylaniline, and thiosulfate (CrOa) 312Indigo from indoxylcarboxylic acid (air) 324Thioindigo from 3-hydroxythionaphthene (S) 332Naphthamine yellow NN from dehydrothiotoluidinesulfonic acid

(NaOCl) 335Alizarin from anthraquinone-j8-sulfonic acid (NaOCl in alkali fusion;

simultaneous replacement of SOaH by OH) 3146. Sulfonation

General 6, 82Direct sulfonation:

Benzenesulfonic acid (oleum) 80Benzene-m-disulfonic acid (oleum) 143Toluene-2,4-disulfonic acid (oleum) 302p-Chlorobenzenesulfonic acid (oleum) 104m-Nitrobenzenesulfonic acid (oleum) 120p-Nitrochlorobenzene-o-sulfonic acid (oleum) 99p-Nitrotoluene-o-sulfonic acid (oleum) 167, 296Sulfanilic acid (baking process) 126

The baking process in general 127Ethylbenzylanilinesulfonic acid (oleum) 136p-Aminoazobenzenedisulfonic acid (fast yellow) (oleum) 271Azo flavine FF (100$ H2SO4) 272Phenol-2,4-disulfonic acid (oleum) 150, 153Naphthalenesulfonic acids, general 183Naphthalene-a-sulfonic acid (100% H2SO4) 215Naphthalene-/3-sulfonic acid (H2SO4, 66 Be) 184, 187Naphthalene-1,5- and 1,6-disulfonic acid (oleum) 219Naphthalene-2,7-disulfonic acid (100% H2SO4) 209Naphthalene-1,3,6-trisulfonic acid (oleum) 211/3-Naphtholsulfonic acids, general 1912-Naphthol-l-sulfonic acid (C1SO8H) 1992-Naphthol-6-sulfonic. acid (H2SO4, 66'Be) 1942-Naphthol-3,6- and 6,8-disulfonic acid (H2SO4, 66 Be;

oleum) : 194, 197l-Naphthylamine-4-sulfonic acid (baking) 181

xxii INDEX OF REACTIONS

103

320

2-Naphthylamine-5,7- and 6.8-disulfonic acid (oleum) 205Anthraquinone-1-sulfonic acid (oleum -f Hg) 230Anthraquinone-2-sulfonic acid (oleum) 228Anthraquinone-1,5- and 1,8-disulfonic acid (oleum + Hg) 234l,5-Dihydroxyanthraquinone-2,6-disulfonic acid (oleum) 319Alizarin pure blue B from the dye base (oleum) 233Quinizarin green from the dye base (oleum) 318Dehydrothiotoluidinesulfonic acid (oleum) 334Primuline from primuline base (oleum) 334

Indirect, replacement of Cl by SOaH:2,4-Dinitrobenzenesulfonic acid from 2,4-dinitrochlorobenzene . . .Nitrobenzene-2,5-disulfonic acid from 2-nitrochlorobenzene-

4-sulfonic acid . . . . . * 106Simultaneous reduction and sulfonation by SC>2:

l-Ammo-2-naphthol-4-sulfonic acid from nitroso-j3-naphthol . . . . 2017. Splitting out of sulfo groups

Alizarin saphirol SE from alizarin saphirol B

8. Introduction of hydroxyl groupsGeneral 7, 88Replacement of SOaH by OH:

Phenol 86Resorcinol 144/3-Naphthol 1882-Amino-8-naphthol-6-sulfonic acid 2072-Amino-5-naphthol-7-sulfonic acid 207l-Amino-8-naphthol-3,6-disulfonic acid 2131,5- and 1,8-Dihydroxyanthraquinone 236Alizarin from anthraquinone-/3-sulfonic acid 314

Replacement of Cl by OH:4-Chloro-2-nitrophenol from nitro-p-dichlorobenzene 1092,4-Dinitrophenol from 2,4-dinitrochlorobenzene 337Azosalicylic acid (eriochrome flavine A) from

chloroaminobenzoic acid-azo-salicylic acid 295Replacement of NH2 by OH:

a-Naphthol from a-naphthylamine 180l-Naphthol-4-sulfonic acid from naphthionic acid

x. . . 182The Bucherer reaction in general \ . . 182

Direct introduction of OH by oxidationAlizarin from anthraquinone-/3-sulfonic acid 314

9. Introduction of alkoxyl groupsGeneral 8Replacement of Cl by -o-alkyl:

o-Nitroanisole from o-nitrochlorobenzene 97Alkylation of phenols (see 14)

10. Introduction of amino groupsGeneral 8Replacement of SO3H by NH2:

o-Aminoanthraquinone 231/3-Aminoanthraquinone ' 229

Replacement of Cl by NH2:p- and o-Nitroaniline 92p-Nitroaniline-o-sulfonic acid 99

INDEX OF REACTIONS

Replacement of OH by NH2:0-Naphthylamine from 0-naphthol 2032-Naphthylamine-l-sulfonic acid 200

Replacement of CONH2 by NH2 (Hoffmann degradation):Anthranilic acid from phthalimide 174

Reduction of NO2, NO, or N=N (see 4)11. Introduction of arylamino groups

Replacement of halogen by arylamino:4-Nitrodiphenylamine-2-sulfonic acid from

p-nitrochlorobenzene-o-sulfonic acid and p-phenylenediamine 1004-Nitro-4/-aminodiphenylamine-2-sulfonic acid from p-nitrochloro-

benzene-o-sulfonic acid and p-aminoazobenzene 99Dinitrophenylaminoazobenzene from 2,4-dinitrochlorobenzene

and p-aminoazobenzene 2724-p-Toluidine-2-bromo- 1-aminoanthraquinone from

2,4-dibromo-l-aminoanthraquinone and p-toluidine 233Replacement of OH by NH aryl:

Quinizarin green base from leuco quinizarin and p-toluidine . . . . 31712. Introduction of aldehyde groups

2-Chloro-4-dimethylaminobenzaldehyde from m-chlorodimethylaniline,p-tolylhydroxylaminesulfonic acid and formaldehyde (see also 17) ... 119

13. Introduction of carboxyl groups (Kolbe-Schmidt synthesis)Salicylic acid from phenol 154

14. AlkylationOf amines:

Dimethylaniline 133Diethylaniline 134Ethylbenzylaniline 134

Of phenols:o- and p-Nitroanisole and -phenetole 148Chrysophenine from brilliant yellow 284

15. PhenylationDiphenylamine 140Phenyl-a-naphthylamine 1792-Phenylamino-8-naphthol-6-sulfonic acid (phenyl-Gamma acid) . . . . 209

16. AcylationAcetylation

Acetanilide 130l-Acetamino-8-naphthol-3,6-disulfonic acid (acetyl-H acid) 263

Oxalylation:p-Nitrophenyloxamic acid 93Anthraquinonyl-1-oxamic acid 231

Benzoylation:Indanthrene yellow GK 322

17. HydrolysisP-Nitroaniline from p-nitroacetanilide 132p-Phenylenediamine from p-aminoacetanilide 133Benzaldehyde from benzal chloride 1592,6-DichlorobenzaIdehyde from 2,6-dichlorobenzal chloride 162

xxiv INDEX OF REACTIONS

2-Chloro-4-dimethylaminobenzaldehyde from chlorodimethylamino-benzal-p-toluidinesulfonic acid 119

Isatin from isatin-o-anilide 328

18. DiazotizationGeneralAniline 156, 243, 259,p-Chloroaniline ,2,5-Dichloroanilineo-Nitroaniline 97,p-Nitroaniline 95, 246,2,4-Dinitroaniline2-Nitro-4-chloroaniline3-Nitro-4-toluidinep-Aminoacetanilidep-Aminodiphenylaminep-AminoazobenzeneSulfanilic acid 128, 248, 261, 262,Aniline-2,5-disulfonic acidBenzidineBenzidine-2,2'-disulfonic acidp,p'^Diaminostilbenedisulfonic acidAnthranilic acid6-Chloro-3-aminobenzoic acida-Naphthylamine 245,l-Naphthylamine-3,6-disulfonic acidl-Amino-2-naphthol-4-sulfonic acidDehydrothiotoluidinesulfonic acid

241270244244246260247247246245249245273279261294283330295260277248336

19. CouplingGeneral 249Aniline -f aniline '. . . . 270Aniline + salicylic acid 156Aniline + acetyl-H acid 264Aniline 4- p-sulfophenylmethylpyrazolone 265p-Nitroaniline + H acid 2882,4-Dinitroaniline + /3-naphthol 2673-Nitro-4-toluidine -f acetoacetanilide 266Sulfanilic acid -f wi-phenylenediamine 287Sulfanilic acid -f- diphenylamine 274Sulfanilic acid 4- /3-naphthol 262Aniline-2,5-disulfonic acid -J- a-naphthylamine 2796-Chloro-3-aminobenzoic acid + salicylic acid 295l-Naphthylamine-3,6-disulfonic acid + a-naphthylamine 277Dehydrothiotoluidinesulfonic acid -f- dehydrothiotoluidinesulfonic acid 336m-Toluylenediamine -f- 2 m-toluylenediamine 282Benzidine + salicylic acid 285Benzidine -f 2 naphthionic acid 293Benzidine -f H acid 291Benzidine-2.2'-disulfonic acid -f 2 /3-naphthol 294Benzidine-2.2'-disulfonic acid 4- 2 salicylic acid 295Diaminostilbenedisulfonic acid -f- 2 phenol 283

(See also Table of Contents, under Azo Dyes)20. Condensation

Acetoacetanilide from aniline and acetoacetic .ester 142Phenylglycine-o-carboxylic acid from anthranilic acid

and chloroacetic acid 323Phenylthioglycolic acid-o-carboxylic acid from

thiosalicylic acid and chloroacetic acid 330

INDEX OF REACTIONS

Thiocarbanilide from aniline and carbon disulfide 326Tetramethyldiaminodiphenylmethane from dimethylaniline

and formaldehyde 137Tetramethyldiaminobenzophenone (Michler ketone)

from dimethylaniline and phosgene 139p-Sulfophenylmethylpyrazolone from phenylhydrazinesulfonic acid

and acetoacetic ester 1293-Hydroxythionaphthene from phenylthioglycolic acid-o-carboxylic acid 331Indoxylcarboxylic acid from phenylglycine-o-carboxylic acid 324a-Isatinanilide from thiooxamidodiphenylamidine 327Indigo from o-thioisatin 329o-Benzoylbenzoic acid and anthraquinone from phthalic anhydride

and toluene 225Quinizarin from phthalic anhydride and p-chlorophenol 237Sun yellow from p-nitrotoluene-o-sulfonic acid 297Leuco malachite green from benzaldehyde and dimethylaniline 299Leuco xylene blue VS from benzaldehydedisulfonic acid

and diethylaniline 303Leuco wool green S from tetramethyldiaminobenzhydrol and R s a l t . . . . 307Leuco wool blue 5B from o-chloro-p-dimethylaminobenzaldehyde and

ethylbenzylanilinesulfonic acid 305Victoria blue B from Michler ketone and phenyl-a-naphthylamine . . . . 306Gallamine blue from nitrosodimethylaniline and gallamide 309Methylene blue from Bindschedler green-thiosulfonic acid 312Indanthrene blue RS from /3-aminoanthraquinone 321

21. Introduction of sulfurDithiosalicylic acid from o-diazobenzoic acid 330Thiooxamidodiphenylamidine from hydrocyanocarbodiphenylimide . . . 327Dehydrothiotoluidine and primuline base from p-toluidine 332Sulfur black T from 2,4-dinitrophenol 337

22. MiscellaneousPhthalimide from phthalic anhydride 173Auramine from tetramethyldiaminodiphenylmethane 298Hydrocyanocarbodiphenylimide from thiocarbanilide 326o-Thioisatin from a-isatinanilide 329Gallic acid and gallamide from tannin 170

FIGURES

1. Porcelain stirrers for attaching to a bent glass rod 172. Melting point apparatus 443. Thiele melting point apparatus 444. Iseli melting point apparatus 455. Laboratory chlorination apparatus 636a. Three-necked flask fitted with thermometer, filling funnel,

and propeller stirrer with gas-tight seal 686b. Three-necked flask fitted with reflux condenser, dropping funnel,

and paddle stirrer with gas-tight seal 687. Distillation apparatus for high-boiling liquids 718. Nitration kettle with auger-type stirrer, equipped for

external and internal cooling 719. Separating funnel and extraction apparatus with propeller

stirrer and transparent window 7110. The Lunge nitrometer 7311. Closed, coppered reduction vessel fitted with stirrer,

dropping funnel, and reflux condenser 7712. Hydraulic press with automatic cut-out on pump 7913. Laboratory suction filter 8114a. Fusion kettle for alkali fusions 8714b. Fusion kettle with central thermometer tube 8715. Temperature-pressure curves for aqueous sodium

hydroxide solutions 8916. Temperature-pressure curves for aqueous ammonia 9217. Apparatus with propeller stirrer for Bechamp-Brimmeyr

reductions 9418. Reduction kettle with auger-type stirrer 9619. Sulfonation and nitration vessel 10120. Autogenously welded sulfonation vessel, especially for use

with oleum 10521. Screw press with wrought iron frame 10722. Curve for determination of p-tolylhydroxylaminesulfonic acid . . . 12123a. Laboratory apparatus for distilling with superheated steam . . . . 14123b. Laboratory distillation vessel for distilling with superheated steam 141

xxvii

xxviii

24.25a.25b.26.27.28.

29.30.31.32.33.34.35.36.

37.38a-38c.39.40.

41.42.43.44.45.46.47.48.49.50.51.52.53.54.55.56.57.

172177181191

FIGURES

Apparatus for large-scale distillation with superheated steam . . . 142Method of introducing alky! chloride into a laboratory autoclave 149Auxiliary cylinder (gas pipe) for handling alkyl chlorides . . . . 149Stone filter funnel for strongly acid precipitates 150Portable filter for coarsely crystalline precipitates 151Apparatus for preparation of phthalic anhydride by

catalytic oxidationCast iron reaction kettle with stirrer for use at pressures up to 2 atm.Vacuum baking apparatusSulfonation and nitration kettle with steam jacket (double wall) . .Graduated vessel for coupling reactions 263Centrifuge with bottom discharge 315Kettle heated with steam or hot water (Frederking) 316Reaction kettle (Samesreuther) 316Iron fusion kettle with copper oil bath for use in primuline,

indigo, and alkali fusions, etc 333Fractionating column with partial condenser 342

-b. Kubierschky columns 343Raschig column 343Rotary compressor and vacuum pump 345Vacuum distillation equipment for substances which solidify easily

(naphthols, phenylenediamine, etc.) 346Laboratory vacuum distillation set-up 347Filter press 349Cast steel works autoclave 352Cast iron works autoclave with steam heating 353Cross section through an autoclave 355Cast steel laboratory autoclave with stirrer 357Cross section through the laboratory autoclave shown in Figure 46 358Vertical cast steel autoclave 358Rotating wrought iron autoclave with worm gear drive 359Cross section through the rotating autoclave 360Detail of the rotating autoclave 361Vacuum drying oven for dyes 373Sketch of the "Perplex" disintegrator 374Disintegrator for dyes 374Dye mixing machine with automatic filling and discharge . . . . 375Manufacturing area of a dye plant 376Step exposure 415

I

TABLES

I. Derivatives of o~ and p-dichlorobenzene 418II. Derivatives of chlorobenzene-p-sulfonic acid 420

III. Derivatives of o-nitrochlorobenzene 422IV. Derivatives of p-nitrochlorobenzene 424V. Derivatives of 2,4-dinitrochlorobenzene 426

VI. Derivatives of nitrobenzene 428VII (a and b). Derivatives of aniline 430

VIII. Derivatives of benzenesulfonic acid and of phenol . . . . 434IX (aandb). Derivatives of toluene 436X. Derivatives of a-nitronaphthalene 440

XI. Derivatives of naphthalene-a- and -yft-sulfonic acids . . . . 442XII. Derivatives of /?-naphthol 446

XIII (a and b). Derivatives of 2-amino-5-naphthol-7-sulfonic acid (J acid) 448

XIV. Derivatives of 2-naphthylamine-5,7-disulfonic acid 451XV. Other derivatives of naphthalene 452

XVI. Derivatives of anthraquinone 454XVII. Derivatives of anthraquinone-/?-sulfonic acid 456

XVIII. Derivatives of anthraquinone-orsulfonic acid 458XIX. Derivatives of a-aminoanthraquinone 460XX. Derivatives of alizarin 462

XXI. Derivatives of ^-methylanthraquinone 464

xxix

The Foundations of the Dye Industry

The modern dye industry is built upon the coal tar industry as itssource of material, and upon the Kekule benzene theory as its scientificbasis. Without these foundations, the dye industry could not have beendeveloped.

The last thirty years have seen a very large increase in the numberof raw materials for the dye industry, obtained by the dry distillationof coal tar. To the hydrocarbons known for a long time, such as benzene,toluene, xylene, naphthalene, and anthracene, have now been addedmany new compounds which previously were known only in scientificcircles. These compounds could not be considered for industrial appli-cation until they had been obtained in large quantity and at low costby coal tar distillation. Some of these newer raw materials are, for ex-ample, carbazole, quinoline, pyridine, acenaphthene, pyrene, chrysene,indene, and other coal tar constituents which are now used in large quan-tities for the preparation of valuable dyes. Various other hydrocarbonsand nitrogen-containing compounds have been placed on the market buthave found no industrial application as yet, although some of these mayprove to be useful in the future. No uses have been found for phenan-threne, for example, although it is available in almost unlimited amounts.The homologs of benzene which are present in coal tar in only relativelysmall quantities have also been synthesized, in recent years, from ali-phatic hydrocarbons.

With the increasing demands of the dye plants, the purity df theraw materials has steadily improved, and today many of these productsmay be called chemically pure. Modern methods have permitted thedirect manufacture of pure compounds by fractional distillation andfractional crystallization. These improved techniques of the tar industryhave resulted from extensive work and they constitute one of the foun-dations for the manufacture of intermediates for the dye industry.

Generally, the supply of the necessary raw materials satisfies thedemand. It is interesting to note, however, that in recent years there hasbeen an increase in the price of naphthalene, which previously wasusually available in excess. This situation has arisen because changes in

FOUNDATIONS OF THE DYE INDUSTRY

gas manufacture by chamber distillation have resulted in the pyrolytiedecomposition ("cracking") of the greater part of the naphthalenepresent in the tar. This situation has naturally had an eflFect on dye inter-mediates derived from naphthalene (phthalic anhydride, anthraqui-none, H acid, naphthols, etc.).

I. Intermediates

General DiscussionThe term intermediates refers to those compounds which are pre-

pared from the original coal tar constituents by various chemical pro-cedures and which, in turn, can be converted into commercial dyes byrelatively simple further transformations. A typical example is aniline,which is prepared from benzene in various ways, and which can be con-verted into numerous dyes.

The reactions used in the preparation of intermediates are, for themost part, simple operations. Frequently, they proceed quantitativelyaccording to the rules of stoichiometry. In other cases, side reactionsare encountered which complicate the reaction and greatly reduce theyield. It is one of the important tasks of the dye chemist to study theseundesirable side reactions sufficiently to understand their nature andthen, if possible, to select the reaction conditions which will favor onlythe main reaction leading to the desired intermediate. This end is notalways attained, because often the set of conditions which will elimin-ate the side reactions is not known, but the chemist must always bearin mind the possibility of achieving these conditions by further study.The preparation of l,8-aminonaphthol-3,6-disulfonic acid (H acid) illus-trates this point. This compound has been known for nearly fifty yearsand is still being studied extensively in many laboratories, yet to this dayhas not been prepared in satisfactory yield.

In many cases, so-called quantitative yields are obtained but theproduct is not a pure compound. Thus, the reaction yields the cal-culated quantity of product, but this is a mixture of isomeric oranalogous compounds which must be separated by some type ofphysical method. The isomeric nitrotoluenes (ortho, meta, and para),

4 INTERMEDIATES

for example, are always obtained in mixture, and special methods havehad to be evolved to separate the pure individuals economically. Some-times a circuitous route can be followed to arrive at an uncontaminatedintermediate. For example, a substituent (usually a sulfo group) maybe introduced and split out later (e.g., the preparation of o-chloro-toluene, page 163. In other cases, the reactions are selected so as toprevent the formation of undesirable isomers as in the preparationof "Tobias acid" (2-naphthylamine-l-sulfonic acid). This intermediatecannot be obtained directly from /2-naphthylamine, but can be preparedunder the proper conditions from /2-naphthol (see page 198).

As already mentioned, the basic operations of dye chemistry utilizesimple chemical reactions. An intermediate can frequently be preparedin several entirely different ways and, in these cases, careful calcula-tions must be made to determine which procedure is most advantageous.The least expensive process is often not necessarily the best when otherfactors are taken into account. For example, the question of apparatusmay enter, and calculations may show that it is uneconomical topurchase an expensive apparatus for the process if a small quantityof the material is to be produced. Furthermore, consideration must begiven to the usability of the side products formed. These often cannotbe used at all (e.g., primuline), but may be valuable or even indispen-sable in another process (e.g,, chromium sulfate in the production ofanthraquinone).

In evaluating a manufacturing procedure, the apparatus in whichthe operations are carried out must always be considered. Unlikepreparations done in the laboratory, those in the plant cannot be carriedout in glass equipment except in unusual cases. Furthermore, it mustbe remembered that the chemicals often attack the apparatus, so itsamortizement is an important consideration.

Most of the intermediates entering into the preparation of com-mercial organic dyes are members of the aromatic series. The sub-stituents most frequently present are methyl, halogen (usually chlorine),nitro, amino, hydroxyl, alkoxyl, sulfo, carboxy, and (in some cases)aldehyde and ketone groups the latter also in the form of quinonegroups. These substituents, and other less common ones, may be intro-duced into the molecule either singly or in combination, and theirintroduction may be made in various sequences and in different manners,so that the number of possibilities is practically unlimited. Obviously,however, practice is governed by general principles, and the chemistwho knows the fundamentals and has a command of the methods caneasily determine the simplest method for preparing a desired compound.

GENERAL DISCUSSION O

Stoichiometric quantities of reactants are almost always used, and only. the most unusual cases is it necessary to use more or less of a reactantthan the quantity demanded by the chemical equation. On the otherhand, diluents must often be used in order to have the correct mixtureduring the reaction. It should also be emphasized that intensive mixing(stirring) is usually necessary for the satisfactory progress of the reac-tion. Also, the reaction temperature often plays an important role, forexample, in preventing the formation of undesirable isomers.

In view of the factors cited, it is frequently quite unnecessary togive an exact "recipe" for the preparation of a product. Instead, thechemist is given an indication of the general principles involved andhe, on the basis of his own experience, is immediately in a position toset up his own satisfactory procedure.

Accordingly, in this book the compounds in the tables are arrangedin a genetic system, the derivatives being listed under their parentsubstances. This form of presentation has the advantage of giving thebeginner a clear picture of the similarities in the reactions and, at thesame time, giving information to the expert as to the preparation ofthe compound he desires. In order to increase the usefulness of thesetables, there are included references, either to a procedure given in thisbook or to a literature source such as patents, scientific publications,etc., which describe the type of preparation for most of the compounds.Obviously, since it has not been possible to consider all possibilities in arelatively small laboratory book, the tables are necessarily incompleteand give only a general outline. The book Is designed principally forthe beginner, and it is hoped that it will serve for teaching purposesin the industrial chemical laboratory. The expert, however, may alsofind some use for the tables, particularly those relating to fields whichare not his special provinces.

The subject material for the text of the book has also been arrangedgenetically. It covers, first, the most important operations: chlorination,nitration and reduction, sulfonation and alkali fusion, starting with thesimplest basic structure, benzene. From the intermediates thus obtained,more complicated derivatives are built up by reaction series serving asillustrative examples. Following this, the derivatives of benzene homo-logs are treated in a similar manner, then the derivatives of naphthalene,and finally those of anthraquinone. Such an arrangement simplifies thestudy since not only is each intermediate traced from its parent structurebut also its possible further transformations into more complicated inter-mediates are shown. In this way the beginner is taught to consider eachoperation both by itself and in connection with the total synthesis.

INTERMEDIATES

The Various Operations of Intermediate ChemistryIn this section some of the most important operations are described

in general terms, intentionally avoiding specific comments about indi-vidual compounds. All the variations cannot be mentioned because thiswould lead to too great detail.

1. SulfonationBy sulfonation is meant the introduction of an SO3H group into

a molecule. The operation results in a product which is usually verysoluble in water, either in the form of the free sulfonic acid, as isoften the case, or in the form of its salts. Of the salts, the inexpensivesodium salt is usually encountered.

Sulfonation is effected: (1) with ordinary concentrated sulfuric acid(66Be); (2) with 100 per cent sulfuric acid; (3) with fuming sulfuricacid (oleum), with the concentration of SO3 varying from 5 to 70 percent; (4) with chlorosulfonic acid, with or without diluent; or (5) by"baking" (dry heating) the acid sulfate of an amine, often in vacuum.

Less frequently the sulfonic acid group is introduced indirectly:(6) by replacing a halogen atom with the sulfonic acid group by meansof sodium sulfite; (7) by the action of bisulfite on a nitro compoundor on a quinone or quinoneoxime (nitrosophenol); (8) by oxidation ofa sulfinic acid, a mercaptan, or a disulfide; and (9) by the introductionof the CH2SO3H group by means of formaldehyde-bisulfite.

2. Nitration

Nitration means the introduction of the nitro group, NO2, intoa molecule. It is accomplished: (1) with dilute or concentrated nitricacid; (2) with mixed acid, i.e., a mixture of nitric and sulfuric acid,sometimes containing some water; (3) by first sulfonating the compoundand then nitrating the sulfonic acid, thereby splitting out the sulfogroup and replacing it by the nitro group (picric acid, see page 150);(4) by oxidizing with dilute nitric acid a previously formed nitroso com-pound (tropaeoline, see page 275); and (5) by treatment of a diazoniumcompound with hot, dilute nitric acid, introducing simultaneously ahydroxyl group and a nitro group (e.g., nitrocresol from p-toluidine).

On nitration to produce a dinitro compound, the two nitro groupsenter into positions meta to each other, but the reaction product isnever uncontaminated (see, e.g., m-dinitrobenzene, page 111).

VARIOUS OPERATIONS OF INTERMEDIATE CHEMISTRY 7

3. Reduction

The reduction most frequently encountered by the dye chemist isthe transformation of a nitro compound into an amine, but numerousother reductions play an important role in dye chemistry. The followingmethods are employed.

( 1 ) Reduction with iron and water, with the addition of small amounts ofacid (hydrochloric, sulfuric, or acetic acid, and occasionally mixtures of these). This"neutral" reduction method of Bechamp-Brimmeyr can be carried out only withcertain kinds of iron, notably gray-iron casting, which must always be tested pre-viously to establish its usability. In general, other kinds of iron are not usable (manyexamples have been given).

(2) Reduction with iron and enough acid so that all of the iron used in thereduction goes into solution as the ferrous salt. For this purpose, any kind of ironcan be used but it is desirable to use a variety low in carbon, for example, iron nails,iron plate, steel, etc., so that no contaminating graphite particles are formed (seeH acid, page 212).

(3) Reduction with hydrogen sulfide or its salts (many examples are given inthis book).

(4) Reduction with zinc dust and acid or alkali (rarely with tin).(5) Reduction with hydrosulfite (e.g., p-aminosalicylie acid from phenylazo-

salicylic acid, page 157).(6) Electrolytic reduction, as in the preparation of hydrazobenzene from

nitrobenzene, or of p-aminophenol from nitrobenzene. The latter reduction involvesa simultaneous rearrangement of the intermediate phenylhydroxylamine.

(7) Reduction with ferrous hydroxide, Fe (OH) 2, now seldom used.(8) Reduction with aluminum powder, for example, in the preparation of

benzanthrone, or of quinizarin from purpurin (seldom used).(9) Catalytic reduction with hydrogen.

(10) Reduction with sulfur dioxide, often giving simultaneous sulfonation.

4. Introduction of the Hydroxyl GroupThe hydroxyl group can be introduced into a molecule in various

ways.(1) Fusion of a sulfonic acid with sodium hydroxide. This method is often

referred to as "potash fusion," a term applied when potassium hydroxide was usedalmost exclusively. The cheaper sodium hydroxide is now almost always used. Diluteor concentrated hydroxide is employed, depending on the conditions. In using dilutesodium hydroxide (30 to 60 per cent), it is necessary to work in an autoclave if thereaction temperature is higher than the boiling point. The pressure makes no directcontribution to the reaction, but is necessary, unfortunately, to maintain the reactiontemperature. Some variations of the procedure follow, (a) Alkali fusion in thepresence of an oxidizing agent, whereby, in addition to the replacement of thesulfonic acid group by hydroxyl, a second hydroxyl group is introduced (see alizarin,page 314). (b) Alkali fusion in the presence of an alkaline-earth hydroxide, whichprecipitates the sulfite formed in the reaction as the insoluble alkaline-earth sulfite,and thus prevents reduction of. the final product (anthraquinone series, see 2-ammoanthraquinone, page 229).

(2) Replacement of a labile halogen by the hydroxyl group, e.g., dinitrophenolfrom dinitrochlorobenzene, and many other similar preparations (see sulfur black TPage 337). / r r

8 INTERMEDIATES

() Heating a diazonium salt, sometimes in the presence of copper salts (hydro-quinone from p-aminophenol, or guaiacol from o-anisidine).

(4) Treatment of an amine with bisulfite, and hydrolysis of the intermediatecompound (Bucherer's method, page 182).

(5) Heating as amine with acid or alkali under pressure.(6) Frequently, by treatment with weak alkali, an ortho sulfo or nitro group,

or a chlorine atom, in a diazonium salt is smoothly replaced by the hydroxyl group.

5. Introduction of Amino and Alkoxy GroupsThe introduction of amino and alkoxy groups into aromatic mole-

cules is frequently accomplished by methods analogous to those usedfor introducing the hydroxyl group. Thus, for example, nitrochloro-benzene and anthraquinone derivatives in many cases can be trans-formed into amino or alkoxy compounds. The sulfonic acid group canbe replaced by an amino group, as can also the hydroxyl group, thelatter by heating with ammonia, or, better, by the Bucherer method ofheating with ammonium bisulfite.

Aminoanthraquinone affords an example of the replacement of asulfonic acid group by amino. More recently, however, it has beenfound better to prepare 2-aminoanthraquinone from 2-chloroanthra-quinone, since this leads to a purer product, o- and p-Nitroanilines areprepared today almost exclusively from the corresponding nitrochloro-benzenes (page 92).

The alkyl ethers of phenols, naphthols and hydroxyanthraquinonescan be prepared, in many cases, by treatment of "the halogen compoundswith alcoholates at high temperature under pressure (e.g., anisole,page 97). Of course, the phenols themselves can be etherified (cf., page148), and the cheaper method is used in each case. The dialkyl sulfatesserve as active alkylating reagents in certain instances, as in the prepara-tion of Caledon jade green (dimethoxydibenzanthrone).

6. Oxidation Methods

Many methods have been evolved for oxidizing organic compounds.Oxidation may be brought about by:

(1) Air, often in the presence of a catalyst. Examples of this methodare the preparation of phthalic anhydride from naphthalene by air andvanadium oxide (WohFs method, page 171), and the analogous oxida-tion of anthracene to anthraquinone. In the latter case, anthracenewhich is not entirely pure can be used.

(2) Chromic acid. This method is very important in the preparationof many heterocyclic dyes, such as methylene blue. The reaction isfrequently carried out in the presence of oxalic acid.

VARIOUS OPERATIONS OF INTERMEDIATE CHEMISTRY 9

(3) Manganese dioxide (MnO2), or the so-called "Weldon mud"which is a manganous-manganic oxide (xylene blue V, page 303).

(4) Sodium hypochlorite (see dinitrostilbenedisulfonic acid, page,167).

(5) Nitric acid (seldom used).(6) Lead peroxide, for triphenylmethane dyes.(7) Nitrosylsulfuric acid (aurin dyes by Sandmeyer's method).(8) Ferric chloride (with certain triphenylmethane dyes, e.g., Hel-

vetia blue).(9) Chlorination of a side chain (in toluene and xylene) followed

by hydrolysis of the chlorinated product. Examples of the procedureare:

(o) toluene - benzyl chloride - benzyl alcohol, or(b) toluene - benzal chloride -> benzaldehyde.

(10) An excess of one of the dye-forming reactants (examples arevery numerous, e.g., gallamine blue, Meldola's blue, etc.).

7. Introduction of HalogenHalogen atoms, usually chlorine or bromine (rarely iodine or

fluorine1) are generally introduced by the action of the elementaryhalogen on the compound to be substituted. It is often necessary to usea catalyst; otherwise chlorine adds instead of substitutes (replacinghydrogen), The catalyst most commonly employed is iron (ferricchloride), sometimes iron with a trace of iodine and, less frequently,antimony, sulfur, or phosphorous compounds.

In place of elementary chlorine (bromine), sodium hypochlorite inthe presence of mineral acid is used in certain cases (e.g., chlorinationof acet-o-toluidide). The nascent chlorine reacts very energetically andundesirable side reactions do not occur.

If for any reason the direct introduction of chlorine is not possible,or the chlorine does not enter the desired position in the molecule,recourse may be had (but rarely!) to the Sandmeyer reaction (seeexample on page 161). In some cases, the Sandmeyer reaction can beavoided (it is rather bothersome and expensive) by the use of a trickreaction, such as in the preparation of o-chlorotoluene from p-toluene-sulfonic acid2 (page 163).

Other methods may be used for halogenating phenols. Thus, phenol-

/ i n j Hoffa and Miiller (LG ') Gen Pat 551,882 (1932) [Frdl, 19,(1934); C.A., 26, 4959 (1932)]; and Osswald, Muller, and SteinhaW( I.G. ) , Ger. Pat. 575,593 ( 1933 ) [Frdl., 20, 475 ( 1935 ) ; C.A., 27, 4813 ( 1933 ) ].Badische A. und S.F., Ger. Pat. 294,638 (1916) [Frdl., 12, 908 (1914-1916)-C-A., 11, 2582 (1917)]. "

10 INTERMEDIATES

ate and hypochlorite react to produce chiefly the o-chlorophenol (75to 80 per cent), while the reaction of free phenol and sulfuryl chlorideyields p-chlorophenol as the chief product (about 78 per cent)3 (seepage 145).

In special cases, chlorination is brought about by replacement ofa sulfonic group by chlorine. This reaction is particularly importantwith anthraquinone compounds, but it is also known in the benzeneseries (see page 236).

These reactions do not by any means cover the whole field, butrepresent only the more important portions of it Later in this book,other less important reactions are mentioned, such as alkylation ofamines, introduction of the aldehyde group by the Sandmeyer method,and phenylation. Although some of these reactions are carried out on alarge scale, especially in the preparation of alkyl- and benzylanilinesand toluidines, they are in terms of quantity of considerably less im-portance than the operations discussed above.

In all industrial operations, the chemist must always strive to achievethe greatest yield at the smallest cost. The methods which are suitablefor scientific research frequently are not successful in industry. It mustalso be remembered that the intermediates should be as pure as possiblebecause small variations in purity often lead to disproportionately largelosses in the manufacture of the dye. For this reason, many of the com-mercially available intermediates are chemically pure, and the require-ments in recent years have become even more exacting.

Practical Work in the Industrial Organic LaboratoryGeneral

It cannot be overemphasized to the beginner in organic industrialwork that absolute cleanliness of work is the first requirement forsuccess, not only in analytical and research laboratories, but also inthe industrial laboratory. This applies both to the apparatus and con-tainers and to the materials employed. Keeping the apparatus clean isoften more difficult than it is in the analytical laboratory because theindustrial work involves materials which are more strongly colored and,not infrequently, tarry. Also, non-transparent containers are usuallyemployed and the cleanliness of these is not so easily determined. Underthese conditions, special attention is given to cleaning each vesselthoroughly, immediately after emptying it. Immediate cleaning is to*Frdl, 7, 90 (1902-1904) (Note).

PRACTICAL WORK IN THE INDUSTRIAL ORGANIC LABORATORY 11

be recommended also because it may often be effected satisfactorilywith hot water, either alone or with small quantities of acid or alkali,whereas a residue, once dried and crusted, may be much more difficultto remove, requiring powerful solvents such as sulfuric and chromicacids. In many cases, ordinary household cleaning powders are veryuseful in removing oily and tarry residues.

If the chemist does not clean his own apparatus, or have it cleanedunder his direct supervision, he must be very careful not to leave con-tainers with residues which are highly inflammable or explosive orstrongly poisonous (such as ether, alkali metals, sodium amide, dimethylsulfate, phosgene, etc.). The neglect of this rule has resulted in manyaccidents, since the person cleaning the apparatus is not aware of thedanger. Residues of this sort should not be emptied into the laboratorysink, but should be treated so as to make them as harmless as possible.

The work table should always be kept clean and uncluttered. It isthen possible to recover substances which have been spilled and thussave an experiment which otherwise would have to be repeated fromthe beginning. In experiments which require prolonged strong heating,the table top should be protected from the burner by a fire-resistant,insulating cover, such as asbestos or "Transite." Apparatus no longer inuse should not be left in the working space. If space permits, it isdesirable to place larger apparatus outside of the working space proper,and reserve the latter area for test tube experiments, titrations, meltingpoint determinations, and so forth. All necessary equipment for controltests should be readily available, including clean, dry test tubes, glassrod and glass tubing, small filters and funnels, and the most commonreagents and test papers.

The use of pure materials is at least as important as the cleanlinessof the apparatus. In analytical and research laboratories, the use ofchemically pure reagents is understandable, since, as a rule, only smallquantities of materials are used and the cost is of no importance. Inindustrial laboratories, however, cost considerations usually prohibitthe use of chemically pure materials and furthermore one is oftenrestricted to the use of commercially available starting materials in orderto duplicate plant conditions.

It is the general rule, however, in preparing new products and inworking out new procedures to use the purest substances possible with-out regard to their cost and commercial availability. Later it is estab-lished whether the same results can be obtained with technical materials.

In most cases the inorganic chemicals used in industrial organicwork are usable in the form supplied commercially. There are, however,important exceptions. For example, the nitric acid used in the nitration

12 INTERMEDIATES

of free primary amines in sulfuric acid solution must be free from nitricoxide (see page 165). Also, the presence of sulfuric acid in technicalhydrochloric acid may cause difficulties in the diazotization of amineswhich form difficultly soluble sulfates. In still another example, ifchlorate is present in the caustic alkali used for alkali fusion, undesiredoxidation or even an explosion may result. In all such instances, it isessential to use products which are free from the deleterious impurities.It should also be pointed out that certain substances deteriorate onlong standing. This occurs with materials which are strongly hygro-scopic (e.g., oleum and chlorosulfonic acid), easily oxidizable (e.g.,sulfite and bisulfite), or otherwise easily decomposed (e.g., hypochloritesolutions). In these cases, the compounds must be titrated before use.

In the laboratory, distilled water may be used even for technicalwork, in order to avoid cloudiness caused by the separation of calciumsalts. Before a procedure is adapted for large scale operation, however,it must be established that tap water has no harmful effect. Water maybe very injurious when present as an impurity in organic liquids, as inthe chlorination of nitrobenzene (page 117), and in these cases, carefuldrying is necessary. With high-boiling liquids, the drying may beaccomplished by distillation, discarding the forerun.

The presence of impurities in the organic starting material is gener-ally much more injurious than their presence in the inorganic chemicals.Frequently, only very small amounts of a contaminating material mayproduce an appreciable lowering of the yield or a marked decrease inthe purity of the end product. Therefore, the organic chemical industryhas gone to considerable lengths to prepare their intermediates in aspure a form as possible. Considerable progress along this line has beenmade in recent times, so that today many intermediates are available inalmost chemically pure form. This is especially true for those substanceswhich are purified by distillation or vacuum distillation. On the otherhand, all materials which must be isolated by a salting-out processnaturally and unavoidably contain some inorganic salts. This salt isharmless for the great majority of applications, but of course it must betaken into account in determining the quantities to be used. Therefore,it is necessary to determine the purity of all salt-containing startingmaterials. Primary amines can be titrated with nitrite solution, andcompounds which undergo diazo coupling can be analyzed by titrationwith a diazonium compound. With other materials, other suitablemethods are used (see Analytical Section).

The beginner is usually greatly impressed by the strong color ex-hibited by technical products which should be colorless when com-pletely pure. As a rule, this color has no significance for industrial use,

PRACTICAL WORK IN THE INDUSTRIAL ORGANIC LABORATORY 13

unless it is exceptionally strong, indicating decomposition or oxidation,and then purification may be necessary. Still more serious, however, iscontamination by isomers or closely related compounds whose presenceis not so easily discernible, for example, monosulfonic acid in disulfonicacids, or vice versa. Similarly, m-phenylenediamine, which contains onlya few per cent of the ortho and para isomers, gives azo dyes in muchlower yield and purity than the pure meta compound. The impurematerial is also much less stable (see pages 112 and 116). The methodsused for testing the organic starting materials for purity, and for purify-ing them, are the same as those described later for end products (seepage 40 ff.).

Proportions and Weighing

In the organic industrial laboratory the work is almost always donewith molecular quantities. Calculations are thus greatly simplified. One-tenth of a gram molecule, or with large molecules one-twentieth, is thecommonly used unit in the preparation of end products. This quantitygives enough of the product for the first tests of a dye and its dyeingcharacteristics. Using this quantity, it is also possible to determine theyield sufficiently accurately, provided that the weighing is done to0.1 gram, an accuracy possible with an ordinary pan balance. Smalleramounts (0.01 to 0.02 mole) may be used for more qualitative experi-ments. Starting materials or intermediates, which are to be used in anumber of experiments, are usually prepared in quantities of one or twomoles. With these amounts, weighing to one gram is sufficiently ac-curate. The technical chemist should become accustomed from the startto weighing or measuring all substances used, even in neutralizations,etc., instead of simply pouring them out of stock bottles. The quantitiesused should be recorded in his laboratory notebook, because this infor-mation is very necessary if the experiment is to be repeated later.

Many reactions are favored by an excess of one of the reactants,but very often the use of exact stoichiometric quantities is necessary.When a series of experiments is to be carried out, it may be desirable toprepare the required reagents in solutions, containing, for example, onemole in 100, 200, 500, or 1000 cc. In experiments which require specialequipment available only in large size, the quantities taken are, ofcourse, adapted to the capacity of the apparatus.

When hydrated, salt-containing, moist, or otherwise impure startingmaterials are used, their purity must be determined. Some of the usablemethods are described in the Analytical Section. The results of such adetermination may suitably be expressed, not as per cent, but as the

14 INTERMEDIATES

quantity (M) of the raw material containing one mole of the pure sub-stance. Thus, a value of M of 382 for technical H acid means that 382grams of the technical material contains one mole of active H acid. Thenone knows, without any calculation, that 38.2 grams must be used in anexperiment calling for 0.1 mole of H acid, and this quantity is the samewhether the technical sample is the free acid or one of its salts, andwhether the product is a hydrate or not.

Laboratory Journals and ReportsIt is imperative for the technical chemist to keep an accurate record

of all his experiments, and the student should become accustomed torecording all of the work he performs in his laboratory notebook. Heshould not write up the directions he followed, but should describe theprocedure he actually used in sufficient detail so that he later can repeatthe experiment exactly on the basis of his notes, without introducingany new conditions. It is necessary, therefore, to make an accurate recordof quantities used, the temperature maintained, and the reaction time,as well as the nature and size of the apparatus. The notes should alsoinclude observations made during the course of the reaction, such asthe appearance or disappearance of a color or of a precipitate, libera-ation of gas, spontaneous increase in temperature, etc. It should also benoted how the rate of the reaction was controlled, how its completionwas determined, how the purity of the product was established, etc.

When a project has been completed, a report should be written, sum-marizing the results obtained and describing the most successful meth-ods found. The description should be complete enough so that anychemist could use it as a basis for repeating the experiment exactly.

Apparatus

At one time, the school laboratories of industrial chemistry soughtto train students to use the most primitive sorts of apparatus, put to-gether by themselves from the simplest parts. The modern viewpoint isto use not the simplest, but the most suitable, equipment that whichconserves time and effort. To be sure, the simpler of two equally serv-iceable apparatus should be given preference, and unnecessary compli-cations the cost of which is out of proportion to their advantage should be avoided. Nevertheless, it is still desirable for the technicalchemist to be able to operate, in an emergency, with the simplest ma-terials. It is worthwhile, for example, for him to have some proficiencyin glassblowing so that he can prepare simple equipment from glasstubing.

PRACTICAL WORK IN THE INDUSTRIAL ORGANIC LABORATORY

Stirring Apparatus

15

In many reactions involved in industrial organic chemistry, continu-ous, vigorous stirring of the reaction mixture is absolutely essential forgood results. This is especially true if some of the reactants are not insolution in the reaction medium, but are only suspended, in either solidor liquid form. Also, when a precipitate is formed during a reaction,stirring is beneficial because it promotes crystallization and prevents theformation of supersaturated solutions which might solidify all at once.Good stirring is necessary even in homogeneous systems if one of thereactants decomposes slowly. Here the unstable compound must be dis-tributed uniformly throughout the whole mass and high local concentra-tions must be avoided. Stirring is also especially important for stronglyexothermic reactions, such as nitrations, where a local excess of the re-agent may cause a violent reaction or even an explosion.

Since most organic reactions require a long time, stirring by hand,which often suffices in the analytical laboratory, is usually excluded andmechanical stirring devices must be used. In the laboratory, these mech-anical stirrers may be driven by small water turbines, provided that awater pressure of at least two atmospheres is available. An electric motoris used when greater power is needed, as for example, for driving highspeed stirrers in reductions, or for stirrers in autoclaves. Sometimes itmay be advantageous to have a long power shaft so that several appara-tus can be operated simultaneously.

The form of the stirrer itself depends on the nature of the reactionmixture and on the shape and construction of the container in which thestirrer operates.

Naturally, it is most convenient to use open containers, such asbeakers, enamded crocks, open kettles, etc., but these cannot be usedif an appreciable loss of a substance or a solvent is to be expected.Open vessels are unsuitable also for reactions which generate vaporswhich must be absorbed or led to the drain because of their poisonousnature, inflammability, or bad odor. In this connection, it should benoted that many of the intermediates used in the organic industry arestrongly poisonous and may be absorbed into the body not only throughthe stomach, but also through the skin, and, as dust or vapor, throughthe lungs. Examples of some of these compounds are nitrobenzene, ani-line, dinitrobenzene, dinitrochlorobenzene, nitroaniline, and phenol. Ofcourse, open containers cannot be used in cases where air must be ex-cluded because of the deleterious action of oxygen or of the moisture orcarbon dioxide in the air.

When an open vessel cannot be used for any of the above reasons,

16 INTERMEDIATES

recourse is had to a covered kettle or round-bottomed flask often withthree or five necks which is provided with a reflux condenser or an aircondenser, or is connected with an absorption flask to absorb poisonousor irritating vapors. An efficient hood will usually suffice to remove smallamounts of gases generated. Except when work is to be done underpressure, a "closed" apparatus must be provided with an opening forpressure equalization. This opening, if necessary, can be protected witha calcium chloride or soda lime tube to remove moisture or carbondioxide, but it is often sufficient to restrict the entrance of air by meansof a capillary tube or a plug of glass wool.

Regarding container materials, it is to be noted that only metal con-tainers can be used for the Bechamp iron reduction in weakly acid solu-tion, for alkali or polysulfide fusions, or for operations under high pres-sure. Pressure reactions involving very small quantities of materials canbe carried out in sealed tubes, however. Except for these applications,metal is used only for apparatus of more than six- or eight-liter capacity.Glass containers are generally satisfactory for all other uses, especiallysince Pyrex and similar glasses are mechanically strong materials resist-ant to temperature changes and chemical action. Also, they are suitablefor the preparation of three- or five-necked flasks or more complicatedapparatus.

The use of transparent glass apparatus in the laboratory has the greatadvantage that the reaction can be observed throughout its course. Thisis a particularly important factor when a reaction is being run for thefirst time. On the other hand, it is worthwhile for the technical chemistto become accustomed in the laboratory to working with non-transpar-ent apparatus modelled after plant equipment and to controlling thecourse of the reaction by removing test samples, just as it must be doneon a large scale.

In school laboratories, it is customary to use bent glass rods as stirrers,similar to those shown in Figure 19 (page 101) and Figure 20 (page105). These stirrers, which are easily prepared by the individual, arequite suitable for mobile liquids, but are not satisfactory for pasty mix-tures. With the latter, stirrers presenting more flat surface must be used.One form frequently used in open containers in industrial laboratoriesconsists of a rectangular plate of thick, ribbed glass held in position ina forked holder by two setscrews. These stirrers are easy to keep cleanand give a vigorous stirring which can be regulated by changing theangle at which the blade is set. They are, however, quite fragile.

Stirring paddles of porcelain, recently introduced, are less fragileand very satisfactory. They are simply attached to a bent glass rod andare available in various shapes and sizes (Fig. la-c).

PRACTICAL WORK IN THE INDUSTRIAL ORGANIC LABORATORY 17

A propeller-type stirrer is of value for stirring up mixtures containingheavy solids such as iron powder or zinc dust. Such stirrers, an exampleof the container and should be large enough to nearly cover the bottom,of which is shown in Figure 17 (page 94), should reach to the bottom.Anchor- or paddle-type stirrers are also useful under these conditions.

Closed reaction kettles, as a rule, have their stirrers built in, usuallyof the anchor-type which reach nearly to the bottom and sides of thekettle.

(*) (b) (c)Fig. 1. Porcelain stirrers for attaching to a bent glass rod.

It is difficult to get efficient stirring in a glass flask (round-bottomedor three-necked flasks, etc.) because the relatively narrow neck preventsthe introduction of a sufficiently broad stirrer. Special types of stirrershave been devised for this purpose in order to achieve vigorous stirringwith a stirrer of small diameter. Propeller stirrers (Fig. 6a) centrifugalstirrer, and others, belong to this group. All of them give vigorous stir-ring at high speed as long as the mixture being stirred is a homogeneous,mobile liquid, but they fail in viscous or pasty mixtures. With the latter,the best results are usually obtained with a simple glass paddle (Fig.6b) which can be made by pressing out a rolled-up glass spiral.

It should be pointed out that effective stirring is not possible if thecontainer is too full. In open containers of large diameter, such as dishesor flat vessels, the stirrer may set up waves which are thrown over theedge. To prevent this spilling, a "wave-breaker" must be installed,generally consisting of a vertical, thick glass rod near the edge of thecontainer. For the construction and use of autoclaves, see Section M,page 350 ff.

18 INTERMEDIATES

Filtration

The precipitates commonly encountered in the analytical labora-tory are practically insoluble and can be washed with unlimited quan-tities of liquid. Organic products, on the other hand, are usually more orless easily soluble in the solvent employed, and hence it is always neces-sary to use the smallest possible amount of wash liquid which will com-pletely remove the adhering mother liquor. For this reason, gravity filtra-tion is of little value. Instead, filtration methods must be used which pro-vide an appreciable pressure difference above and below the filter. Thispressure difference is obtained by applying pressure above the filter,or suction below it.

The first method is preferred in plant operations, employing thefilter press, in which pressure is supplied by compressed air (see Sec-tion L, page 348 ff.). The filter press is not applicable to operationson a laboratory scale.

On the other hand, the filter centrifuge, in which the pressure issupplied by centrifugal force, is well adapted for use with the quanti-ties usually encountered in industrial laboratory operations. The filtercentrifuge consists of a metal or porcelain "basket," closed at the bot-tom and open at the top, bearing sieve-like perforations around itsperiphery. This basket is mounted in such a way that it can be rotatedat high speed within a surrounding shell serving to collect the liquidthrown out. For filtration purposes, the inside of the basket is linedwith a suitable filter cloth. When the basket is rotated at a sufficientlyhigh speed, the entrained liquid is expelled, and the precipitated ma-terial is obtained in a nearly dry condition. However, the filter centri-fuge is suitable only for the filtration of coarsely granular substances,since a fine precipitate either goes through the filter or packs into adense mass through which the liquid cannot pass. Similar difficultiesare encountered with substances which crystallize in plates. All in all,the number of industrial organic products which can profitably becentrifuged is not large. The most useful application of the centrifugeis in the separation of a mixture of isomers, one of which crystallizesfrom the liquid mixture on cooling (see, e.g., o- and p-nitrochloroben-zenes, page 90).

The filter centrifuge should not be confused with the sedimentation centrifugewidely used in biochemical laboratories. With a sedimentation centrifuge, fine pre-cipitates are not filtered, but are pressed against the walls of the container and thusseparated from the liquid.

The other method of obtaining a pressure difference, namely, suc-tion applied below the filter, can be used in the plant only for well

PRACTICAL WORK IN THE INDUSTRIAL ORGANIC LABORATORY 19

Cl

crystallized, granular precipitates. Here, a fairly deep column of liquidmust be used, and the filtration becomes exceedingly slow if the pre-cipitate is very fine. In laboratory operations, where the layer being fil-tered may not be more than a few centimeters deep, the suction filteris of more general application. Even here, however, failures are en-countered when soft, tarry, or gelatinous products are involved or whenvery finely crystalline materials are filtered. The latter first go throughthe filter and later stop it up. Difficulties are also encountered withplate-like crystalline materials which press down on the filter to forman impermeable mass. Some of these difficulties may be remedied byusing a large filter so that the layer of liquid in it is quite shallow. Itis also of assistance to maintain only a weak suction when the suspen-sion is poured into the filter and to stir the material constantly to keepthe precipitate from settling.

For granular precipitates, filter cloth is used as the filter material,and for finer precipitates, filter paper. If the precipitate is very fine andhas a tendency to go through the filter paper, two or three thicknessesof paper may be used, or, in some cases, hardened filter paper may beemployed. It is recommended that both a filter cloth and a filter paperbe used in the larger suction funnels to prevent tearing the paper andto facilitate the removal of the precipitate from the filter. The cloth andpaper filters should be of exactly the same size as the bottom of thefunnel. If they extend up the side wall of the funnel, wrinkles are formedwhich permit some the precipitate to escape into the filtrate. Wool feltmay be used for filtering strongly acid liquids which attack paper andcotton. Still more suitable, and usable even with concentrated acids,are the sintered glass funnels recently made available commercially ina variety of pore sizes.

In order to achieve efficient washing of the precipitate with the leastpossible amount of liquid, it is important that the mother liquor held inthe filter cake be removed as completely as possible before each addi-tion of wash liquid. After the main bulk of the filtrate has run through,the filter cake is stirred and pressed together with a spatula to packdown the individual particles and produce a cake without cracks. Thenthe cake is pressed down strongly with a pestle or inverted glass stopperuntil no more drops of filtrate are obtained. The vacuum is then inter-rupted and the wash liquid poured onto the filter cake, allowing thesponge-like cake to soak up the liquid. Suction is again applied and thecake is again pressed out. The operations of adding and sucking offsmall portions of the wash liquid are repeated until the impurities havebeen removed to the required extent. The success of the washing de-

20 INTERMEDIATES

pends on the choice of a filter funnel of the correct size. The filtercake should not fill the funnel but enough space should be left aboveit to hold the wash liquid. On the other hand, the use of a funnel whichis too large gives a thin filter cake, and an excessive amount of washliquid is required. Also, the formation of cracks and holes in the filtercake is hard to avoid.

Precipitates, which are so finely crystalline that they go through thesuction filter or clog it, are filtered most satisfactorily through a largefluted filter. In this case, since the precipitate retains a large amount ofliquid, the filter and its contents, after washing, are spread out evenlyon a thick absorbent layer of cheap filter paper, for example. The precip-itate is separated from the filter without difficulty when enough liquidhas been absorbed so that the residue has a pasty consistency, and thelarge amount of mother liquor still retained is removed in the screwpress (Fig. 21). The precipitate is first wrapped in an ordinary filtercloth, then in a thick "press cloth" which can withstand the pressure ofthe press. Pressing is carried out slowly, with only slight pressure atfirst. The liquid must have time to make its way through the precipitateand the filter cloths, otherwise the hydrostatic pressure may becomegreat enough to tear the cloth or force the precipitate through it. Onlytoward the end of the operation, when only a little liquid is present, isfull pressure applied.

Filtration of amorphous, soft, flocculent, or gelatinous precipitatesoffers great difficulty. With these materials, the best results are oftenobtained by the use of a filter cloth, folded in the same manner that afilter paper is formed into a 60-degree cone, and placed in an ordinaryglass funnel. The precipitate can be pressed out right in the filter cloth,carrying out the operation slowly and carefully.

Filtration of warm mixtures always proceeds more rapidly than thefiltration of cold mixtures, because the viscosity is lower at higher tem-peratures. Hence, warm filtration is to be preferred if the stability ofthe material and the solubility relations are favorable.

In general, the filtering properties depend, in large measure, on thephysical properties of the precipitate, and these in turn depend on theprecipitation or crystallization conditions. It is often advantageous tocarry out a precipitation or crystallization at elevated temperature andwith stirring. Frequently, it is beneficial to add salts, or to maintain acertain degree of acidity or alkalinity. In other cases, separation of theprecipitates takes place best in an exactly neutral medium. The condi-tions vary so greatly in individual instances that no general rules canbe set up.

PRACTICAL WORK IN THE INDUSTRIAL ORGANIC LABORATORY 21

Distillation

Distillation, if it is applicable, is the least expensive method for isolat-ing and purifying a reaction product. It is especially useful for: (a)removal of solvents, (b) purification of an already nearly pure reactionproduct (rectification), and, (c) separation of several reaction prod-ucts of different boiling points (fractional distilla