Studies on thermodynamic dissociation constants of 2,2 '-bipyridine, or 1,10-phenanthroline in acetone plus water mixtures and Gibbs energy of transfer of the hydrogen ion from water to acetone plus water mixtures

The thermodynamic dissociation constants for isoelectric reaction of the ty pe LH+ = L + H+ (where L = 2,2'-bipyridine or 1,10-phenanthroline) have bee n determined pH-metrically at 298 K in acetone + water mixtures (0-90% of a cetone). 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 Gi bbs energies of transfer of the H+ ion from water to acetone + water mixtur es 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 propertie s of acetone + water mixtures from a comparative study of DeltaG(t)(0)(H+) profiles, excess relative permittivity epsilon (E)(r)(X) and excess Gibbs e nergy 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.