Stability constants and free energies of complexation of metal-ion cryptates in nitromethane. Derived parameters for the extraction of cations by cryptand 222 from water to pure nitromethane

Abstract

Stability constants have been measured and free energies of complexation of alkali-metal and silver cations in nitromethane at 298 K have been derived. The results obtained in this solvent are compared with corresponding data in different reaction media. Free energies of transfer of metal-ion cryptates from water to nitromethane are derived. Among the dipolar aprotic solvents the free energies of transfer of cryptand 222 and metal-ion cryptates are in most cases close to 0 kcal mol–1. Ion-pair formation constants and ion-size parameters of cryptate salts in nitromethane as obtained from conductance measurements are reported. The implications of these results on the extraction of cations by cryptand 222 in the water + nitromethane solvent systems are discussed.