The bromination mechanism of 1-aminoanthraquinone-2,4-disulfonic acid in sulfuric acid

1-Amino-4-bromoanthraquinone-2-sulfonic acid (bromoamine acid) is an important intermediate for dyes. 1-Aminoanthraquinone-2,4-disulfonic acid is the major impurity when 1-aminoanthraquinone is sulfonated in oleum to synthesize bromoamine acid. The mechanism of bromination of 1-aminoanthraquinone-2,4-disulfonic acid in sulfuric acid has been studied. It is proved that 1-aminoanthraquinone-2,4-disulfonic acid undergoes de-sulfonation first to form 1-aminoanthraquinone-2-sulfonic acid, and then bromination to form bromoamine acid. Based on this mechanism, a new optimal process for the synthesis of bromoamine acid is developed. In this way, bromoamine acid is afforded in high yield and good quality.