Abstract
Preferential solvation of the Na + ion was studied by determining the 23Na chemical shifts for sodium tetraphenylborate solutions in all possible binary solvent mixtures of nitromethane, acetonitrile, hexamethylphosphoramide, dimethylsulfoxide, pyridine and tetramethylurea. Generally, these studies reflected the relative donicity of each solvent in a given solvent pair where the solvent of higher donicity was preferentially contained in the inner solvation shell of the Na + ion. The enhanced donicity of tetramethylurea and dimethylsulfoxide in binary mixtures was rationalized in terms of strong solvent—solvent dipole interactions which disrupt the structure of these solvents. Finally, the results are treated quantitatively to yield a geometric equilibrium constant, K 1/ n the free energy of preferential salvation, Δ G p.s./ n, as outlined by Covington.
Published Version
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