PREFERENTIAL SOLVATION OF A DIPOLAR SOLUTE IN MIXED BINARY SOLVENT - A STUDY BY UV-VISIBLE SPECTROSCOPY

The preferential solvation in mixed binary solvent, e.g., ethanol + acetonitrile, ethanol + propionitrile, and ethanol + butyronitrile, has been studied by monitoring the solvatochromic charge-transfer band of N-alkylpyridinium iodide. It appears that alcohols are preferred over the nitriles. A model for describing the preferential solvation of a dipolar solute in binary solvent mixture has been developed and discussed in relation to other existing approaches. The role of (a) solvent-solvent interaction and (b) difference in size of the component solvent molecules in determining the preferential solvation has also been discussed.