Ionic solvation in water–cosolvent mixtures. Part 13.—Free energies of transfer of single ions from water into water–tetrahydrofuran mixtures

Abstract

The free energy of transfer of the proton between water and water-rich mixtures of water and tetrahydrofuran (THF), ΔG^°_t(H⁺), has been found by examining spectrophotometrically the redistribution of solvent molecules around the aqua-proton after the latter charged sphere has been transferred into the mixture. Values for ΔG^°_t(HX) calculated from electrochemical data are combined with the new ΔG^°_t(H⁺) to produce ΔG^°_t(X^–) for the transfer of halide ions and of OH^– from water into water–THF mixtures. These ΔG^°_t(X^–) are then used with values for ΔG^°_t(MX) derived from electrochemical and vapour-pressure measurements to give values for ΔG^°_t(M⁺) for alkali-metal ions and for Buⁿ₄N⁺ ions. pK values for two carboxylic acids and for a range of anilinium cations in water–THF mixtures are combined with ΔG^°_t(M⁺) to produce ΔG^°_t(i)_e the free energy of transfer from water into water–THF of the charge on the carboxylate anion or the anilinium cation with the effect of transferring the molecular bulk of the ion removed.