The oxidation of catechol in the presence of two aliphatic and aromatic amines has been investigated. In aqueous solutions of pH 7•0 and 11•7, the substitution pattern of the adduct was dependent on the type of amine used. Aromatic amines produced 4, 5-disubstituted o-quinones, whereas aliphatic amines gave either 2, 4, 5-trisubstituted or 2, 4-disubstituted o-quinone adducts. A rationale based upon the stability of vinylogous amides is presented to account for the observed substitution pattern. © 1989 ASEG.