Tobias add

Hydroxynaphthalene-l-sulfonic add can be prepared by reaction of 2-naph-thol with chlorosulfonic acid at 0 °C in inert solvents such as o-dichlorobenzene or chloroethane. It is not available in satisfactory yields by the direct sulfonation of 2-naphthol with sulfuric add. Ammonolysis at 150 °C transforms 2-hydroxynaph-thalene-l-sulfonic acid into 2-aminonaphthalene-l-sulfonic acid (Tobias add), which, in quantity terms, is one of the most important derivatives of 2-naphthol. 

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