Color reactions of homovanillic acid related compounds with nitrosonaphthols

Abstract

Color reactions of 36 homovanillic acid related compounds were examined using threekinds of nitrosonaphthols, 1-nitroso-2-naphthol, 2-nitroso-1-naphthol and 2-nitroso-1-naphthol-4-sulfonic acid. Reaction specificity is discussed. Guaiacols, phenols with an electron donating group para to the hydroxyl and 5-hydroxyindoles gave generally positive reaction, while compounds having strongly electron-withdrawing groups resulted in no coloration. Catechol derivatives also gave no coloration. Differences were observed in color intensity of some compounds when acetic acid and ethanol were used as the solvent. However, the three reagents resulted in slight variations.