Thermodynamics and kinetics of flavylium salts: Malvin revisited

The pH-dependent structural transformations in aqueous solutions of natural and synthetic flavylium salts are re-examined. The procedure uses Malvin as a reference compound and exploits the different timescales of the kinetic process that take place prior to the equilibration. For each process a kinetic expression was deduced allowing calculation of all the equilibrium constants and most of the rate constants of the system. The equilibrium constants were confirmed by comparison with the data obtained by 1H NMR. Clear evidence for the formation of significant amounts of trans-chalcone in Malvin was obtained.