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-β-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 ρ constant (0.34) was compared with analogue values for structurally similar acids.

Određene su pKa vrednosti za seriju od osam p-supstituisanih trans-2,3-epoksi-4-okso-4-fenilbutanskih kiselina (p-supstituisanih trans-β-aroilepoksiakrilnih kiselina). Vrednosti su određene potenciometrijski u vodenoj sredini na 25 °C i jonskoj sili 0.1 mol/dm3 (NaCl). Proučavan je prenos polarnih efekata sa supstituenata na fenil jezgru ka karboksilnoj grupi kroz bočni niz koji sadrži karbonilnu grupu i epoksidni prsten. pKa vrednosti su korelisane sa strukturom primenom Hammett-ovog, Taft-ovog i Yukawa-Tsuno-ovog pristupa. Hammett-ova ρ konstanta (0,34) je upoređena sa analognim vrednostima za strukturno slične kiseline.