Preferential Solvation of a Dipolar Solute in Mixed Binary Solvent. A Study by UV-Visible Spectroscopy

Abstract

Solvation characteristics of p-nitroaniline have been studied in completely miscible binary solvent mixtures, namely, ethanol + dichloromethane (I), ethanol + hexane (II) and butanol + dioxane (III), by monitoring the solvatochromic absorption band. The maximum energy of absorption (E) of the solute in a binary solvent mixture differs significantly from the mole fraction average of the E values in the component solvents. The results have been explained in terms of preferential solvation using a two phase model of solvation. In I and II negative deviation is observed while in III both positive and negative deviation is observed. The local mole fraction of the component solvents has been calculated explained in terms of specific solute-solvent and solvent-solvent interaction.