Manufacture of diazotizable azo-dyestuffs and intermediate products therefor


266,533. Chemical Works formerly Sandoz, and B÷niger, M. Feb. 19, 1926. Addition to 252,957. Pyrazolones. - 3<1>-nitro-4<1>-methyl-5<1>-sulpho-1- phenyl-3-methyl (or carboxy)-5-pyrazolones are obtained by condensing 2-nitro-4-tolylhydrazine- 6-sulphonic acid (prepared in the usual manner from 4-amino-2-nitrotoluene-6-sulphonic acid, which is formed on partial reduction of 2 : 4- dinitrotoluene, the latter body being obtained by sulphonating 4-nitrotoluene and nitrating the product) with ethyl acetoacetate or ethyl oxaloacetate and hydrolyzing the products. The corresponding amino bodies are obtained on reducing with iron borings in acid solution. Disazo dyes are obtained by combining one molecule of the tetrazo-compound of a. p-diamine of the diaryl series with two molecules of one of the above aminopyrazolones, or with one molecule of one of the aminopyrazolones and one molecule of another component, e.g. an aminonaphthalene sulphonic acid or an aryl-o-oxycarboxylic acid. The same dyestuffs may be obtained by using the nitropyrazolones as components and reducing the nitro group in the products. The products dye cotton directly in various shades which can be diazotized and developed on the fibre. In examples, (1) tetrazotized dianisidine is coupled with two molecules of the aminopyrazolone carboxylic acid; the product dyes unmordanted cotton in heliotrope shades, which become very fast to washing without material change in tone when diazotized and developed with #-naphthol, (2) tetrazotized benzidine is coupled with one molecule of salicylic acid and with one molecule of the above aminomethylpyrazolone; the product dyes cotton directly in orange shades, which become more reddish when diazotized on the fibre and developed with #-naphthol, and (3) tetrazotized tolidine is coupled with one molecule of the nitromethylpyrazolone and with one molecule of 1 : 6 or 1 : 7 naphthylamine sulphonic acid and the nitro dye formed is reduced with sodium sulphide ; the product dyes cotton directly in redbrown shades which change to chestnut-brown when diazotized and developed with #-naphthol.




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