Determination and structural correlation of the pKa values of p-substituted trans-2,3-epoxy-4-oxo-4-phenylbutanoic acids

Abstract

The pKa values for a series of eight p-substituted trans-2,3-epoxy-4-phenyl butanoic acids (p-substituted trans-b-aroylepoxyacrylic acids) have been determined potentiometrically in aqueous media at 25°C at an ionic strength of 0.1 mol/dm3 (NaCl). The transmission of polar effects from the substituents on the phenyl nucleus to the carboxylic group through the side chain involving a carbonyl group and an epoxide ring was investigated. The pKa values were correlated with structure using the Hammett, Taft and Yukawa-Tsuno approaches. The Hammett r constant (0.34) was compared with analogue values for structurally similar acids