GB381212A - The manufacture of a triaminodiphenyl sulphonic acid and of carbazole compounds therefrom - Google Patents

Abstract

Diphenyl is sulphonated with concentrated sulphuric acid to give diphenyl-4-sulphonic acid by starting the reaction at room temperature and then allowing the temperature to rise to 65 DEG C. The sulphonic acid is then nitrated with nitric acid or mixed acid to give trinitrodiphenyl sulphonic acid and this is reduced by known reducing agents, such as iron and hydrochloric acid to give 2 : 2<1> : 4<1>-triaminodiphenyl-4-sulphonic acid. This compound may then be heated with a dilute mineral acid or acid salt to give 2-aminocarbazole-7-sulphonic acid (by heating from 150 to 170 DEG C.) or 2-aminocarbazole (by heating from 180 to 200 DEG C.). A catalyst which is a metal halogenide for example a heavy metal chloride such as zinc chloride, aluminium chloride or an alkaline earth chloride such as barium chloride may be used. The amino group in the carbazole may be replaced by hydroxyl, chlorine, cyanogen or the like by Sandmeyer's reaction, or the 2-aminocarbazole-7-sulphonic acid may be converted into the corresponding hydroxy derivative by alkali fusion. In examples (1) diphenyl is sulphonated to diphenyl-4-sulphonic acid and this is nitrated with a mixture of sulphuric and nitric acids; the mass is poured into ice water and the trinitrodiphenyl sulphonic acid precipitated by neutralizing the solution; this is reduced by means of iron and acetic or hydrochloric acid to give 2 : 2<1> : 4<1>-triaminodiphenyl-4-sulphonic acid. (2) The triaminodiphenylsulphonic acid is heated to about 160 DEG C. under pressure with dilute hydrochloric or sulphuric acid and the precipitated product is filtered, dissolved in dilute caustic soda, filtered and 2-aminocarbazole-7-sulphonic acid precipitated with hydrochloric acid. (3) By heating triaminodiphenylsulphonic acid as in example (2) to about 200 DEG C. 2-aminocarbazole is obtained.