Naphthionic acid

Химические свойства

?slightly greyish to beige powder and granules. 1-Aminonaphthalene- 4 -sulfonic acid [84- 86-6]. (4-aminonaphthalene-1-sulfonic acid), naphthionic acid, Piria’s acid, C10H9NO3S, Mr 223.24, is sparingly soluble in water (0.25 % at 100℃), but the sodium, potassium, calcium, and barium salts are all readily soluble. Chlorination of 1-Aminonaphthalene- 4 -sulfonic acid with copper(II) chloride produces 4-chloro-1-aminonaphthalene, whereas the action of chlorine on an aqueous sulfuric acid solution gives 2,3-dichloro-1,4-naphthoquinone. High-temperature bromination gives 2,4- dibromo-1-aminonaphthalene, whereas vigorous nitration yields 2,4-dinitro-1-hydroxynaphthalene. Sulfonation with 25 % oleum gives 1-aminonaphthalene-4,6- and 4,7-disulfonic acids, whereas prolonged heating with sulfuric acid at 130℃ leads to 1-aminonaphthalene-5- and 6- sulfonic acids. Hydrolysis of the 1-amino group to give 1-hydroxynaphthalene-4-sulfonic acid is best achieved by a reverse-Bucherer reaction but also results from prolonged heating with 50 % sodium hydroxide.

Использование

Intermediate for azo dyes, e.g., Congo red. Naphthionic acid is used as an intermediate in the production of 1-hydroxynaphthalene-4-sulfonic acid, 1-aminonaphthalene-2-sulfonic acid, and 1-aminonaphthalene-4,6- and 4,7-disulfonic acids. Use as a diazo component has been previously described, e.g., C.I. Food Red 3, C.I. Food Red 7, C.I. Food Red 9, and C.I. Acid Red 25.

Общее описание

4-Amino-1-naphthalenesulfonic acid is a diazo compound. It is also known as Piria′s acid.

Методы очистки

It crystallises from H2O as needles of the 0.5 hydrate. Salt solutions fluoresce strongly blue. The S-benzylisothiuronium salt has m 195o (from aqueous EtOH). [Beilstein 14 IV 2793.]