Solvation of ions. XXII. Solvation of cations by hard N,N-dimethylformamide and soft N,N-dimethylthioformamide

Abstract

The free energies of transfer of some univalent cations from N,N-dimethylformamide to N,N- dimethylthioformamide at 25� are Li+, 64.0; Na+, 50.2; K+, 37.2; Cs+, 23.4; TI+, -4.2 and Ag+, - 87.0 kJ g-ion-1. The values are based on the assumption of negligible liquid junction potential in an electrochemical cell. Certain ones of these values can be interpreted in terms of general interactions of hard and soft cations with hard and soft basic solvents. A linear free energy relationship, ΔGtr(M+) = mΔGtr(K+), is roughly obeyed by many cations for transfer to a variety of solvents. Deviations from this relationship, for example ΔGtr(Ag2+) to acetonitrile, ΔGtr (Ph4As+) to water and ΔGtr (Ag+) to N,N-dimethylthioformamide, allow specific solvation mechanisms to be detected.