Solvation of ions. XXVI. Free energies of transfer of ions to multi-site solvents and solvent mixtures

Abstract

The free energies of solvent transfer of Ag⁺, K⁺, Cl^-, Br^-, I^- and ClO₄^- from acetonitrile to glycolonitrile, 3-hydroxypropionitrile and mixtures of 2,2,2-trifluoroethanol or water with acetonitrile are reported.    

The anion-solvating properties of a series of hydroxylic solvents decrease by 24 kJ mol^-1 in the order CF₃CH₂OH > CNCH₂OH > CNCH₂CH₂OH > CH₃OH > CH₃CH₂OH; Ag⁺-solvating properties decrease by 70 kJ mol^-1 in the order CH₃CN > HOCH₂CH₂CN > HOCH₂CN > CH₃CH₂OH > CF₃CH₂OH; and the K⁺- solvating properties decrease by 27 kJ mol^-1 in the order CH₃CN > HOCH₂CH₂CN ≈ CH₃OH ≈ HOCH₂CN ≈ CH₃CH₂OH > CF₃CH₂OH.

It is not possible to make more than qualitative generalizations as to the ion-solvating properties of solvent mixtures if only the solvating properties of the pure components are known. Multi-site solvents like CNCH₂OH are compared with related equimolar mixtures, like CH₃CN/HOH, in their ability to solvate ions.