A STUDY ON THE SOLVATION OF Na IN BINARY MIXTURE OF SOLVENTS BY Na-23 NMR

Na-23(+) chemical shift of NaClO4 in mixed solvents of water-acetone, water acetonitrile, and water-ethanol and of NaBPh4 in methanol-DMF, methanol-benzene, and methanol-dioxane were measured. By means of iso-solvation point the solvating abilities were compared as water>aentone >= acetonitile >= ethanol and DMF>methanol. The preferential salvation tree energies of Na+ for the pairs solvenst, methanol-DMF and water-acetone,were evaluated as -2.7 kJ mol(-1) for DMF to methanol and 4.6kJ mol(-1) for acetone to water. Na-23(+) chmical shift in methanol-benzene is independent of the content of benzene. It verified the simple solvation modle for ion in methanol inert solvent mixture. However the chemical shift of Na-23(+) in methanol dioxane mixture varies with the composition of solvent. The linewidth of Na-23 resonance peak increases dramtically with the increasing of dioxane. It seems that the dioxane molecules disturb the primary solvation shell of Na+ in methanol and result a unsymmetrical immediate surrounding for Na+ cation,