6-Amino-4-hydroxy-2-naphthalenesulfonic acid

Chemical properties

2-Amino-8-hydroxynaphthalene-6-sulfonic acid [90-51-7]. (6-amino-4-hydroxynaphthalene-2-sulfonic acid), g acid, C10H9NO4S, Mr 239.2, is obtained as white or gray crystals which are only sparingly soluble in water even at 100℃ (0.4%). The sodium salt dissolves readily in water to form solutions that exhibit a blue fluorescence. Coupling with diazo compounds is usually carried out under acid conditions and occurs in the 1-position; coupling in the 7-position can be effected in alkaline solution.

The Uses of 6-Amino-4-hydroxy-2-naphthalenesulfonic acid

6-Amino-?4-?hydroxy-2-naphthalenesulfonic Acid is used in the synthesis of mono-azo dyes for application towards synthetic fibers. Also used in the synthesis of dyes with high technical properties for silk.

Production Methods

2-Aminonaphthalene-6,8-disulfonic acid liquor is added over 16 h to 70 % sodium hydroxide at 190℃, while the water is allowed to evaporate to maintain the temperature. The reaction mixture is then heated for a further 6 h. Completion of the reaction is indicated by a workedup sample giving identical titers for both diazotization and coupling. The batch is diluted with water, acidified, and heated at 75℃ to expel sulfur dioxide. The product is filtered off at 55℃ and washed with warm water; yield is 84 %.
An improved process with 90 % yield is claimed by feeding concentrated 2-aminonaphthalene-6,8-disulfonic acid dipotassium salt liquor and caustic soda liquor simultaneously into the fusion reactor.

Flammability and Explosibility

Not classified