Solute–solvent and solvent–solvent interactions in binary solvent mixtures. Part 1. A comparison of several preferential solvation models for describing E T (30) polarity of bipolar hydrogen bond acceptor-cosolvent mixtures

The influence of solute–solvent and solvent–solvent interactions on the preferential solvation of solvatochromic indicators in binary solvent mixtures of Bipolar hydrogen bond acceptors has been studied. Several equations based on solvent exchange models that relate the transition energy of the Dimroth–Reichardt ET(30) indicator with the solvent composition are derived and compared. The models tested assume that the two solvents mixed interact to form a common structure with an ET(30) value not always intermediate between those of the solvents mixed. The solvatochromic indicator can be preferentially solvated by any of the solvents mixed or by the mixed solvent obtained. The parameters obtained explain the strong synergism observed for some of the mixtures with strong hydrogen bond donors (alcohols and chloroform).