Autoprotolysis constants of ethylene glycol in isodielectric mixtures of ethylene glycol and N, N-dimethyl formamide at 298.15 K and the related Gibbs energies of transfer

Abstract

Autoprotolysis constants (Ks) of ethylene glycol (EgOH) have been determined in the isodielectric mixtures of protic ethylene glycol and dipolar aprotic N,N-dimethyl formamide (20, 40 and 60 wt% DMF) at 298.15 K from emf measurements of cells comprising glass GE (H⁺) and Ag-AgCl electrodes. Transfer Gibbs energies of glycoxide ion (EgO-), ΔG⁰t (EgO-) have been evaluated therefrom using literature values of transfer Gibbs energies of H⁺, ΔG⁰t (H⁺) based on TATB assumption. These are explained in the light of ion-solvent interactions as guided by physicochemical properties of the solvents. The results show that while the acidity of EgOH + DMF mixed solvents decreases with co-solvent due to the increased aproticity and anionophobicity of the cosolvent molecules, the basicity decreases due to the amalgamated effects of increased aproticity as well as increased protophilicity of DMF.