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.
Uses
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. The so-called g acid is an important component in azo dyes; coupling can be carried out under acid or alkaline conditions. The oamino azo configuration obtained under acid conditions leads to high lightfastness of special importance in monoazo acid red dyes for wool and polyamide, such as C.I. Acid Reds 37, 57, and 266.
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
