The kinetics and mechanism, and the equilibrium position as a function of pH, of the isomerisation of naringin and the 4′-rhamnoglucoside of 2′,4,4′,6′-tetrahydroxychalcone

Abstract

The pH–rate profile for the title reaction has been determined and accounted for in terms of contributions from the various ionised species. The effect of ionisation of a chalcone 4-OH group on rate of cyclisation is quantitatively accommodated for the first time. The rate data have been used to calculate the position of the equilibrium and its rate of attainment as a function of pH, and this information should be of general value for optimising conditions for synthesis of 2′,4,6′-trihydroxychalcones by ring-opening 4′,5-dihydroxyflavanones.