Solvent Effects on the Kinetics of Amide Bond Cleavage in p-Chloro and p-Bromo Oxazolinones in Acetonitrile–Water Mixtures

Abstract

The kinetics of amide bond cleavage in p-chloro and p-bromo oxazolinone have been studied using triethylamine as a base catalyst under pseudo-first order conditions, in the temperature range (303.15–333.15 K). The reaction rate was measured spectrophotometrically over a range of acetonitrile–water mixed solvent (30–70 %, v/v) compositions. The reaction rate was found to be faster for p-Cl than for p-Br oxazolinone. The thermodynamic parameters of activation were calculated: ∆G* increased gradually as the mole fraction of the cosolvent increased due to quasi-mirror image compensation of ∆H* and ∆S* (entropy–enthalpy compensation). The isokinetic temperature indicates that the reaction is enthalpy controlled. The reactivity was analyzed in the light of various simple and multiple regression equations using the Kamlet–Taft solvatochromic parameters.