Effect of the nature of the solvent on the enthalpy characteristics of solvation of conformationally flexible 1,7-diaza-18-crown-6 molecules

Abstract

Enthalpy changes during dissolution of 1,7-diaza-18-crown-6 (L) in benzene, MeCN, DMSO, methanol, and water have been determined calorimetrically. Standard enthalpies of solution at infinite dilution were calculated and used for analysis of enthalpies of solvation of L in solvents of different natures. The effect of self-association of the solvent, polarization of its molecules, and specific solvation on the concentration dependence of the enthalpies of solution are discussed. Specific interaction of L with methanol and water molecules through H-bonds is established. The concentration dependence of the enthalpies of solution in benzene and acetonitrile are sensitive to conformational equilibria over the range 0–5.10−4 mole/kg.