Linear solvation energy relationships. Standard molar Gibbs free energies and enthalpies of transfer of ions from water into nonaqueous solvents

Data from the literature on the standard molar Gibbs free energies and enthalpies of transfer of ions from water into nonaqueous solvents have been subjected to multiparameter correlations with solvatochromic and other properties of the solvents and with suitable properties of the ions. Three parameters, π*, α, and β for small univalent or divalent cations and π*, α, and V/100 for anions, are adequate for expressing the dependence of Δ_trG° or Δ_trH° on the properties of the solvents. Four further (normalized) properties, z, 0.1/r, σ, and 100υ, are required for the dependence of the properties of the ions. The first two of these occur only in the combinations z² × 0.1/r and z × 0.1/r for small cations (for the anions z is unimportant, since only univalent ones are considered). For the large, hydrophobic tetraalkylammonium cations only two solvent properties, π* and δ²/1000 (for Δ_trG°) or V/100 (for Δ_trH°), and two ion properties, 1/r and R_D or 100υ, are required. These dependencies are rationalized in terms of the interactions that take place in water and the nonaqueous solvents.