Nuclear Magnetic Relaxation Studies of Preferential Solvation in Electrolyte Solutions Another Indirect Method Using only Solvent Magnetic Interactions

Abstract

In the mixture ROH/H2O (R = CnD2n+1) an intramolecular proton relaxation contribution due to magnetic dipole interaction only occurs in the water molecule. If the water molecules are preferentially bound to a hydrated cation undergoing relatively slow molecular motions, then only this intramolecular part reflects the slow motion. This principle was used to study preferential solvation of ions in MeOH + H2O mixtures. From the experimental results reported, it is deduced that Mg2+ is preferentially hydrated whereas, in agreement with the theory, for K+ and Rb+ the dynamical effect of preferential solvation is so small that it cannot be detected with the present method.