Gibbs energies, entropies and enthalpies of transfer for monovalent cations from acetonitrile to several solvents

Abstract

Polarographic half-wave potentials and their temperature dependences have been measured for the cations Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, Ag⁺, Tl⁺ and Cu⁺ in up to 22 solvents. Gibbs energies of transfer were derived from reversible polarographic half-wave potentials via the bis(biphenyl)chromium assumption, entropies of transfer were calculated from temperature coefficients on the basis of a negligible thermal diffusion potential and enthalpies of transfer from the equation Δ_tH°=Δ_tG°+TΔ_tS°. Single-ion transfer properties from acetonitrile into the solvents water, methanol, ethanol, trifluoroethanol, propan-1-ol, butan-1-ol, hexan-1-ol, ethane-1,2-diol, phenylethanol, benzaldehyde, formic acid, acetic acid, propylene carbonate, trimethylphosphate, formamide, N-methylformamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoric triamide, nitrobenzene, dimethyl sulfoxide, acetonitrile, propanenitrile, butanenitrile, benzonitrile, pyridine, pyrrole, aniline, mercaptoethanol, thiophenol, N,N-dimethylthioformamide and N-methyl-2-thiopyrrolidone are reported.

The entropies of transfer as well as the TΔ_tS° values of these cations were found to be linearly dependent on each other with slopes close to unity. An ordering of the solvents with respect to the entropies of transfer based on average values for the cations investigated is proposed, since no correlations between the TΔ_tS° values for these cations and solvent parameters reflecting either physical, macroscopic or microscopic solvent properties were found.