GB694929A - Improvements in the preparation of derivatives of 1:4-diamino-benzene-n-sulphonic acid - Google Patents

Abstract

A process for preparing water-soluble salts of the 1 : 4 - diaminobenzene - N4 - sulphonic acids which have the amino group in the 1-position of benzene nucleus substituted with an aryl radical comprises heating in the presence of water an alkali metal bisulphite and a substance to elevate the pH of the mixture with a 4-nitroaminobenzene, the amino group of which is substituted with an aryl radical. The substance to raise the pH of the mixture may be selected from the caustic alkalies, alkali metal carbonates and alkali metal sulphites. A solvent such as alcohol, miscible with water, may be present. In the example N-(4-nitrophenyl)-amino benzene, sodium bisulphite, sodium sulphite, water and alcohol are heated in a closed apparatus. The alcohol is distilled off after adding sodium carbonate and water and the product, sodium N1-phenyl-1 : 4-diamino-benzene-N4-sulphonate crystallizes out after filtration and cooling. The products can be used in the dyestuffs, dyeing and printing industries. Known processes for preparing alkali metal salts of primary arylamines, the amino groups of which are substituted with a sulphonic group by reacting a mixture of sodium sulphite and sodium bisulphite with the corresponding aromatic nitro derivatives and for reacting the corresponding nitro derivatives which carry an amino group either unsubstituted or substituted by a hydrocarbon residue with bisulphite alone are referred to.