Preferential solvation in mixed binary solvent

Abstract

A model of preferential solvation is presented in terms of solute–solvent and solvent–solvent interactions and relative size of the solvent molecules and is compared with other models. The interrelation between various model parameters is discussed. When the component solvent molecules are the same size, the stepwise solvent exchange model and the quasi-lattice quasi-chemical model give identical results. The models have been applied to extract the parameters characterising preferential solvation of the Dimroth–Reichardt betaine dye in binary mixed solvents from the UV–VIS spectroscopic data. The possibility of incorporating the effect of molecular size in the existing models has also been investigated. For the simple case of solvent ideality solvents with a smaller size are preferred by the solute.