The preparation of 2-aminophenol-4-sulfonic acid from sulfanilic acid

Sulfanilic acid (I) was examined for purity and character. Sodium and potassium salts were acetylated and their isolation and yields were investigated. The salts were nitrated with mixed acids and the reaction mixtures were treated in various ways to ascertain a good method for isolating the desired 2-nitro-sulfanilic acid (II). An attempt was made to characterize the reaction products, and to devise quantitative methods to estimate the yield of 2-nitrosulfanilic acid. A previously unreported by-product of the nitration, 2,4,6-tri-nitroaniline (He), was isolated. Several new salts of 2-nitrosulfanilic acid were prepared, and a possible new derivative was observed from the reaction of phenanthraquinone and the diamine obtained by the reduction of the nitro group in 2-nitrosulfanilic acid. Conversion of the 2-nitrosulfanilic acid (II) to 2-nitrophenol-4-sulfonic acid (III) was accomplished by the replacement of the amino group by hydroxyl with boiling alkali, and the rate was estimated from the ammonia evolved. Reduction of the nitro group with hydrogen gave the desired 2-aminophenol-4-sulfonic acid (IV)