Kinetic and Mechanistic Investigation of the Alkaline Hydrolysis of Ethyl Isonicotinate in Aqueous Dimethyl Sulfoxide

Abstract

The present study investigates the influence of aqueous dimethyl sulfoxide (DMSO) on the kinetics and thermodynamic activation parameters associated with the alkaline hydrolysis of ethyl isonicotinate. The reaction was investigated conductometrically in aqueous DMSO media containing 10–50% (v/v) DMSO over the temperature range of 20-50. The hydrolysis reaction exhibits second-order kinetics. The specific rate constant decreases progressively with increasing DMSO content, indicating a significant influence of the solvent composition on the reaction rate. The iso-composition activation energy decreases with increasing DMSO concentration, whereas the iso-dielectric activation energy shows a systematic dependence on the dielectric constant of the reaction medium. The thermodynamic activation parameters further indicate changes in the solvation environment of the reacting species and transition state with variation in solvent composition. These observations demonstrate that solvent polarity, dielectric properties, and preferential solvation play important roles in governing the reaction rate and activation process. The study provides useful kinetic and mechanistic insight into the role of aqueous DMSO as a mixed solvent medium for alkaline ester hydrolysis.