GB887262A - Process for the production of asymmetric azo compounds - Google Patents

Abstract

The preparation of various syn-diazosulphonates, used in the preparation of azo dyes (see Group IV (c)), is described. In an example 2-chloroaniline is diazotised, the diazo-solution added with stirring to a cold aqueous solution of sodium sulphite and sodium carbonate and the syn-diazosulphonate is precipitated by the addition of sodium chloride. Syn-diazosulphonates are similarly prepared from the following amines but not isolated: 4-aminoazobenzene-41-sulphonic acid, 2 - naphthylamine - 8 - sulphonic acid, 2 - amino - 5 - benzenesulphonyl - naphthol - 8-sulphonic acid, 6-nitro-2-naphthylamine-4 : 8-disulphonic acid, 4-aminophenyl, 4-amino-41-(411 - methoxyphenylazo) - stilbene - 1 : 11 - di - sulphonic acid, sulphonilic acid and dehydrothiotoluidine disulphonic acid.ALSO:Asymmetric azo compounds are prepared by reacting a syn-diazosulphonate with a diazo compound of the naphthalene series or with a diazo compound of the benzene series which is preferably substituted by electron-donating substituents, at temperatures between about 0 DEG C. to about 80 DEG C. The corresponding anti-diazosulphonates may be used in the presence of light which converts them to the syn-form. In an example 2-chloroaniline is diazotised, and the diazo solution added with stirring to a cold aqueous solution of sodium sulphite and sodium carbonate and the syn-diazosulphonate is precipitated by the addition of sodium chloride. The syndiazosulphonate is added to a solution of the diazo compound of 1-naphthylamine-4-sulphonic acid and sodium acetate, nitrogen is evolved, the boron precipitate is filtered off and heated in water to 80 DEG C., the solution obtained is cooled and salted out to give 1-(21-chlorophenylazo)-naphthalene-4-sulphonic acid. In further examples the syn-diazosulphonate is not isolated but is reacted in solution. Further syn-diazosulphonates specified are those prepared from 4-aminoazobenzene-41-sulphonic acid, 2-naphthylamine-8-sulphonic acid, 2-amino-5-benzenesulphonyl-naphthol-7-sulphonic acid, 6-nitro-2-naphthylamine-4 : 8-disulphonic acid, 4-aminophenol, 4-amino-41-(411-methoxyphenylazo)-stilbene-1 : 11-disulphonic acid, sulphanilic acid and dehydrothiotoluidine-disulphonic acid. Further diazo compounds specified are those derived from 2-naphthylamine-8-sulphonic acid, 4-aminoazobenzene-41-sulphonic acid, 1- or 2-naphthylamine, 4-aminoacetanilide, 4-amino-1-oxalylaminobenzene-2-sulphonic acid, p-anisidine and 2-acetylamino-6-aminonaphthalene-4 : 8-disulphonic acid.