Supramolecular structure and physicochemical properties of the trichloromethane–ethanol mixtures

Abstract

The excess thermodynamic functions (Gibbs energy, enthalpy, and entropy) and the dielectric permittivity of the trichloromethane–ethanol solutions have been analyzed in the entire range of compositions and in a wide temperature range in the framework of the quasichemical model of nonideal associated solution (QCNAS). The model of supramolecular structure, taking into account the chain-like and cyclic association of alcohol molecules and complexation of alcohol aggregates with trichloromethane, is able to reproduce the physicochemical properties of the mixtures with good accuracy. The equilibrium constants, enthalpies and entropies of aggregation, and structural parameters of supramolecular aggregates have been determined. Distribution functions of aggregates over size and structure have been calculated. Supramolecular ethanol aggregates with long-range molecular correlations, which extend beyond the nearest coordination shells have been revealed. Specific interactions are shown to give the main contribution to the positive deviations from the ideal solution behavior. Positive deviation of the dipole correlation factor from unity is due to predominantly parallel orientation of the dipoles in the ethanol aggregates and in the complexes with trichloromethane. The influence of ethanol association (linear and cyclic) as well as solvation on the physicochemical properties of the mixtures is discussed.