Relation of the Gibbs free energy of transfer of ions from water to polar solvents to the properties of the solvents and the ions

Abstract

A statistical treatment of data for the standard molar Gibbs free energies of transfer of monovalent ions from water to polar solvents has been made in terms of properties of the solvents and the ions. A common multiple regression equation with seven fitting constants, for almost 200 data points, has been found to describe the data in terms of four solvent properties: their electron donor and acceptor abilities, dielectric constant, and cohesive energy density, and three ionic properties: charge, size, and softness. For the ions Na+, K+, Rb+, Cs+, Tl+, (Ph)4As+, Cl−, Br− and N3− the predictions of the equation are within acceptable error limits of the data, and encourage its application to solvents beyond the thirteen used for the data base. For other ions, e.g. H+, Ag+, and the larger anions, further interactions must be taken into account.