Chemical Properties
?1-Aminonaphthalene-5-sulfonic acid [84- 89-9]. (5-aminonaphthalene-1-sulfonic acid), Laurent’s acid, L acid, Purpurin acid, C10H9NO3S, Mr 223.24, crystallizes from hot water as needles of the monohydrate. The alkalimetal salts are all readily soluble in water. Bromination yields the 2,4-dibromo derivative, vigorous nitration gives 2,4-dinitro-1- hydroxynaphthalene, and sulfonation results in 1-aminonaphthalene-2,5,7-trisulfonic acid. 1- Hydroxynaphthalene-5-sulfonic acid is obtained by heating 104 with aqueous bisulfite (reverseBucherer reaction) or via the diazo compound. Caustic fusion produces 5-amino-1-hydroxynaphthalene. Coupling with diazo compounds takes place in the 2-position.
