The retroaldol reaction of chalcone

Abstract

All four rate constants required to describe the hydration and aldolization/dealdolization reactions of chalcone (1,3-diphenyl-2-propen-1-one) have been determined in aqueous sodium hydroxide solutions. Kinetics were studied starting with chalcone, with its hydrate, 1,3-diphenyl-3-hydroxy-1-propanone, and with benzaldehyde in the presence of excess acetophenone. The rate constants for hydroxide catalyzed reactions, defined in terms of eq. [1] are: k12 = 10.5 ± 0.5 × 10−4 M−1 s−1; k21 = 0.026 ± 0.002 M−1 s−1; k23 = 0.194 ± 0.017 M−1 s−1; and k32 = 0.84 ± 0.12 M−2 s−1 (all at ionic strength 0.1). The corresponding equilibrium constants for aldol adduct formation and dehydration are 4.3 M−1 and 25.