REACTIVITY OF SOME FLAVYLIUM CATIONS AND CORRESPONDING ANHYDROBASES

The indices of superdelocalizability were calculated for the nucleophilic attack in positions C-2 and C-4 of the cationic and anhydrobase forms of 10 synthetic flavylium salts. Compounds 1-5 have no substituent at position C-4, while compounds 6-10 are methylated at this position. The inductive model was shown to be the most appropriate for treating the methyl group. The obtained results indicate that decolorization of weakly acidic solutions of flavylium salts was caused by hydration reactions taking place at the C-2 position of the anhydrobase form of flavylium chromophore. UV-vis spectra of compounds 2 and 5 confirm the obtained results. © 1990 American Chemical Society.