A complete study of the structural pH dependent transformations of the synthetic flavylium salt 4',7-dihydroxyflavylium chloride (DHF), occurring in aqueous solutions, including the basic region, is described. The kinetic study of the transformations occurring in acidic media (quinoidal base (A) reversible arrow flavylium cation (AH(+)) reversible arrow hemiacetal (B) reversible arrow cis-chalone (C-cis) reversible arrow trans-chalcone (C-trans)) allowed to conclude that the cis-trans isomerization is faster than the tautomerization and the hydration processes, which is unique in the anthocyanins family. Results obtained with the parent compound 4'7-dimethoxyglavylium chloride (DMF) with relevance to this study are also presented. In equilibrated basic solution the existence of acid-base equilibria involving the trans-Chalcone (C-trans) and its conjugated bases, (C-trans(-) and C-trans(2)), was detected. Freshly prepared solutions at pH >7 show also the presence of a transient species identified as the ionized quinoidal base (A(-)), which is almost completely converted into C-trans(2-) with a pH dependent rate constant.
ISI Document Delivery No.: XH458Times Cited: 14
Cited Reference Count: 18
Pina, F Benedito, L Melo, JM Parola, AJ Lima, JC Macanita, AL
Pina, Fernando/C-8161-2011; Macanita, Antonio/H-9284-2012; Parola, A. Jorge/F-4048-2010; Lima, Joao/F-3658-2010
Macanita, Antonio/0000-0003-0976-6654; Parola, A. Jorge/0000-0002-1333-9076; Lima, Joao/0000-0003-0528-1967
Real soc espan quimica
Madrid