Studies on Thermodynamic Dissociation Constants of 2,2’-Bipyridine, or 1,10-Phenanthroline in Acetone + Water Mixtures and Gibbs Energy of Transfer of the Hydrogen Ion from Water to Acetone + Water Mixtures

Abstract

Abstract The thermodyamic dissociation constants for isoelectric reaction of the type LH+ ⇔ L + H+ (where L = 2,2’-bipyridine or 1,10-phenanthroline) have been determined pH-metrically at 298 K in acetone + water mixtures (0-90% of acetone). The pK-values were found to pass through a minimum at about 64-74 Wt% of acetone and then increase. The data are utilized to calculate the Gibbs energies of transfer of the H+ ion from water to acetone + water mixtures from which inferences have been made regarding structural variations and solvent basicity of aquo-organic mixtures. Attempts have been made to understand the basicity and structural properties of acetone + water mixtures from a comparative study of ΔG0 t(H+) profiles, excess relative permittivity εE r(X) and excess Gibbs energy profiles. Acetone has been found to structure forming over the whole composition range and structure formation is maximum in the region 60-70 Wt% of acetone.