Solute‐solvent and solvent‐solvent interactions in binary solvent mixtures. 2. Effect of temperature on the ET(30) polarity parameter of dipolar hydrogen bond acceptor‐hydrogen bond donor mixtures

The effect of temperature on the Dimroth-Reichardt ET(30) parameter of binary mixtures of dimethyl sulfoxide, acetonitrile and nitromethane with alcohols and water was studied. The ET(30) polarity parameter of many of these binary mixtures exhibits a strong synergism. Dimethyl sulfoxide, acetonitrile and nitromethane form hydrogen-bonded complexes with the alcohols more polar than themselves. The ET(30) values of the mixtures were fitted according to an earlier model, based on solvent exchange equilibria, that allows calculation of the ET(30) values of the hydrogen-bonded complexes. The variation of the ET(30) values of the pure solvents and the hydrogen-bonded complexed solvents with temperature shows that the synergism decreases as the temperature increases.