Dyestuff

Phosgene has been commonly employed as an intermediate for the dyestuffs industry [577,718a,l(X 3], and the treatment of aminoazo dyes with phosgene in aqueous solution, to give symmetrical urea azo dyes, has been practiced since the end of the last century [99a,99b]. 

When phosgene is combined with A ,iV-dimethyianiiine in the presence of aluminium(III) chloride, Michler s ketone, 4,4 -bis(dimethylamino)benzophenone, is produced (see Section 10.2.1.1), which undergoes further reaction with lV,N-dimethylaniline (also in the presence of aluminium(ni) chloride or POCij) to give the colouring material crystal violet , used in the production of methyl violet indicator paper. When Michler s ketone is warmed with Ai-phenyl-1-naphthylamine in the presence of POCI3, Victoria blue (4.13) is formed, which is used as a dye for natural fibres [718a]. 

Treatment of V-phenylaniline with COClj in the presence of aluminium(III) chloride gives diphenylamine blue, (4.14) [577]. Similarly, triphenylamine reacts with phosgene to form 

The commercially important Direct Yellow 50 (4.16 C.I. No. 29025) is obtained by treatment of two molar equivalents of the aminoazo compound (4.17) with phosgene [992a]  

Disazo and trisazo dyes (containing two and three azo groups, respectively) can be treated with COClj to give mostly red or brown shades. For example. Direct Red 80 (4.18 C.I. No. 35780) is prepared by treating (4.19) with phosgene [992a]  

The synthetic dye manufacturing industry was founded in 1857 by Perkin Sons, who set up a chemical works near London for the manufacture of an artificial dye, mauveine (C.I. 50245) by the following route  

The process was discovered and patented in 1856 by William Henry Perkin, at a time when the wool and cotton industries were enjoying a trade boom and the demand for colorants threatened to outstrip the supplies of natural dyes, mostly vegetable, then available. Crude benzol from the well-established coal-gas and coal-tar distillation industries was commercially available, as were mineral acids, alkalis, bichromates, saltpetre and other materials. Mauveine followed by other synthetic dyes from Perkin Sons, soon became a success. Other, rival pioneers built factories in the UK and Europe and introduced new dyes, the result of their own research work. 

After 1857 synthetic dyestuffs research, both academic and industrial, had three main objectives  

Abbreviations A/Q, anthraquinone CA, secondary cellulose acetate C.I., colour index CT, cellulose triacetate CuPc, copper phthalocyanine PA, polyamide PAC, polyacrylonitrile PES, polyester. 

Names of firms Acna, Aziende Color Nazionali Affini BASF, Badische Anilin- und Soda-Fabrik A.G. CGY, Ciba-Geigy Ltd CIBA, CIBA Ltd DH, Durand Huguenin S.A., Basle FBy, Farbenfabriken Bayer A.G. FH, Farbwerke Hoechst A.G. Fran, Compagnie Francaise des Matieres Colorantes S.A. Gy, J.R. Geigy A.G. ICI, Imperial Chemical Industries Ltd S, Sandoz A.G. YCL, Yorkshire Chemicals Ltd. 

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Mordant acid dyes combine simultaneously with the mordanting agent (generally Cr(OH)j) and the fibre the dyestuff generally contains ortho OH -azo or OH-OH groups. 

It is an important dyestuffs intermediate. It condenses with chloroethanoic acid to give phenylglycine-o-carboxylic acid for the synthesis of indigo. It can be diazotized and used as a first component in azo-dyes it condenses also with chloroanthraquinones to give intermediates for anthraquinone dyes. 

Anlhraquinone-2-su phonic acid. The sodium salt, commonly called silver salt , is used for the preparation of alizarin and 2-aminoanthraquinone and to prepare Fieser s solution. Aminoanthraquinone derivatives are the basis of many dyestuffs. 

Its chief importance is as a source of cinnamic acid by condensation with sodium ethan-oate and ethanoic anhydride and as a source of triphenylmethane dyestuffs by condensation with pyrogallol, dimethylaniline, etc. It is also used in the manufacture of perfumes. 

It is a valuable dyestuffs intermediate. When fused with KOH, two molecules of benz-anthrone combine at the positions marked above to give a dibenzanthrone which is in itself a vat dye. Also used as an intermediate for the preparation of the valuable Caledon Jade Green. 

A potent carcinogen, it is now little used for dyestuffs for cotton. Still used for blood detection. 

Much of the benzoic acid produced is converted to sodium benzoate, which is used as a food preservative (as is the acid) and a corrosion inhibi tor. Other important uses of the acid are in the manufacture of alkyd resins, plasticizers, caprolactam, dyestuffs and pharmaceuticals. 

Bismarck brown, Basic Brown 1 Basic azo-dyestuff, dyes wool (reddish brown), used for cotton with tannin as mordant. Used as hair dye. 

The most important reaction of the diazonium salts is the condensation with phenols or aromatic amines to form the intensely coloured azo compounds. The phenol or amine is called the secondary component, and the process of coupling with a diazonium salt is the basis of manufacture of all the azo dyestuffs. The entering azo group goes into the p-position of the benzene ring if this is free, otherwise it takes up the o-position, e.g. diazotized aniline coupled with phenol gives benzeneazophenol. When only half a molecular proportion of nitrous acid is used in the diazotization of an aromatic amine a diazo-amino compound is formed. 

Other 3-(alkylamino)phenols are commonly used, and are prepared by analogous methods. They are used as intermediates in the preparation of dyestuffs. 

Gallic acid has a limited use as a dyestuffs intermediate and as a source of medicinals. 

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