Ionic solvation in water–Co-solvent mixtures. Part 21.—Free energies of transfer of single ions from water into water–2-ethoxyethanol mixtures

Abstract

The free energy of transfer of the proton between water and water-rich mixtures of water and 2-ethoxyethanol has been determined experimentally by investigating spectrophotometrically the competition of 4-nitroaniline for two solvated protonated species, one containing water molecules alone and the other containing, in addition, a molecule of 2-ethoxyethanol. Using these values of ΔG⁰_t(H⁺), ΔG⁰_t(Cl^–) has been calculated from ΔG⁰_t(HCl). pK values for organic acids in water–2-ethoxyethanol have been combined with the ΔG⁰_t(H⁺) values to produce free energies of transfer of the charge alone on these organic molecules for both positive and negative ions. All these free energies of transfer are compared with values obtained in mixtures of other co-solvents with water. To aid this, the relative partial molar volumes of water and of 2-ethoxyethanol in their mixtures have been calculated from the variation of density with solvent composition.