2-Naphthylamine-8-sulfonic acid

2-Aminonaphthalene-8-sulfonic acid [86- 60-2]. (7-aminonaphthalene-1-sulfonic acid), Badische acid, C10H9NO3S, Mr 223.24, crystallizes from water as needles or prisms although only 0.5 % soluble at 100 ℃. Alkalimetal salts are quite soluble in water. Caustic fusion yields 7-amino-1-naphthol, sulfonation in the cold with 20 % oleum gives 2-aminonaphthalene-6,8-disulfonic acid, but nitration gives a mixture of products. 2-Aminonaphthalene-8-sulfonic acid reacts with diazo compounds to form diazoamino compounds rather than coupling to give azo derivatives.

Colorless needles, partially soluble in water and alkalies, slightly soluble in alcohol.

Azo dye intermediate.

2-Hydroxynaphthalene-8-sulfonic acid is aminated by a Bucherer reaction under conditions similar to those used for Tobias acid.