Investigating the Effect of Aqueous Ethylene Glycol on the Kinetics and Mechanism of Alkaline Hydrolysis of Ethyl Pyruvate

The alkaline hydrolysis of ethyl pyruvate, a biologically relevant α-keto ester, was investigated in aqueous ethylene glycol media over solvent composition from 10-50% (v/v) and temperatures 20-50°C. The reaction kinetics were followed by conductometric measurements, and the corresponding specific rate constants were evaluated from the conductivity data. A systematic decrease in the specific rate constant was observed with increasing ethylene glycol content in the reaction medium. This behaviour is attributed to changes in the solvent environment, including solvation, hydrogen-bonding interactions and solvent polarity. Thermodynamic activation parameters were subsequently evaluated to obtain information about the energetic changes associated with formation of the activated state. The iso-composition activation energy decreases from 46.50 kJmol-1 to 34.73 kJmol-1 with increasing ethylene glycol concentration from 10 to 50% (v/v). The variation of the kinetic and activation parameters with solvent composition provides insight into the influence of ethylene glycol–water interactions on hydroxide-ion reactivity and transition-state stabilization. The study demonstrates that changing the composition of an aqueous ethylene glycol medium can significantly modify the kinetic characteristics of alkaline ester hydrolysis.

Ethyl pyruvate; alkaline hydrolysis; ethylene glycol; solvation; thermodynamic activation parameters.

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