Partitioning of entropy of solvation : single-ion entropy of solvation in aqueous and non-aqueous solvents and the correlation of electrostatic entropy of solvation with electrostriction viscosity B and nmr B′ coefficients

Abstract

Entropies of hydration of alkali-metal halides have been partitioned on the basis of a correspondence plot with the ionic B coefficient obtained by a method recentiy developed. Single-ion values in six non-aqueous solvents have been obtained from the combination of ionic entropies of hydration with the corresponding entropies of transfer from water to the respective solvent. The values thus obtained agree closely with those obtained by recent workers. Entropies of solvation for different concentric layers surrounding ions have been calculated using the two-layer-model equation developed by Abraham and co-workers based on a continuum model and have been correlated with the electrostriction viscosity B and NMR B′ coefficients. The present study shows that the information obtained from the NMR B′ coefficient is confined to the first concentric layer, whereas the viscosity B coefficient covers all the layers of solvation around the ions. Different energies of activation obtained from these two coefficients in different solvents have been discussed as additional proof for this information. The presence of a highly disordered second layer makes the magnitude of the B and B′ coefficients closer in water and ethylene glycol, but the absence of the second layer makes them different in non-aqueous solvents.