Complete resolution of the reaction Rates of flavylium Networks. The role played by 2-phenyl-2H-chromen-4-ol and the hydroxyl attack to the quinoidal Base

Complete analytical resolution of the network of chemical reactions involving the flavylium compounds was achieved by means of the Laplace transform, general partial fraction theorem and Vieta's formulae. The kinetic model includes basic and acid catalysis of the hydration and tautomerization reactions. The formation of phenyl-2H-chromen-4-ol (B-4) and the role it plays in the kinetics in the case of compounds lacking of the hydroxyl substituents was also accounted for. In all cases four kinetic steps could be individualized and the pH dependent mole fraction distribution of the several species monitored as a function of time, the last one leading to the equilibrium. It is worth of note the role of B-4 in the network, which like the quinoidal base is a kinetic product that retards the formation of Ct. The evolution of B-4 is also dependent on the existence or not of the cis-trans isomerisation barrier. Application of the model to the data of flavylium networks previously reported in literature, predicts with great accuracy the respective behavior.