2-Aminonaphthalene-1,5-disulfonic acid [117-62-4]. 5-sulfo-Tobias acid, C10H9NO6S2, Mr 303.32, is purified by crystallization of the dipotassium salt from water. Alkali fusion results in formation of 2-amino-5-hydroxynaphthalene-1-sulfonic acid. Sulfonation (40 % oleum, 100℃) gives 2-aminonaphthalene-1,5,7-trisulfonic acid. Heating with aqueous sulfuric acid produces 2-aminonaphthalene-5- sulfonic acid. The diazo compound is converted to 2-diazo-1-hydroxynaphthalene-5-sulfonic acid on treatment with alkaline hypochlorite.
?As a diazo component in orange and red azo reactive dyes, 2-Amino-1,5-naphthalenedisulfonic acid gives more bathochromic shades than Tobias acid.
Sulfonation of Tobias acid to produce 2-aminonaphthalene-5-sulfonic acid proceeds via 2-Aminonaphthalene-1,5-disulfonic acid, which is isolated from the quenched reaction mixture with careful avoidance of desulfonation.
