Oleg G. Tereshin

Mixtures of halogenated hydrocarbons-organic solvent: molecular interactions, structure and physicochemical properties

Abstract The results on the modelling of molecular interactions, supramolecular organization and physicochemical properties of halogenated hydrocarbon mixtures with organic solvents are presented. The mixtures both with negative deviation from ideality, such as propanone–trichloromethane, dimethylsulfoxide (DMSO)–trichloromethane and positive one (tetrachloromethane–methanol, trichloromethane–methanol, trichloromethane–ethanol) has been studied. The models of the aggregation of mixtures investigated due to specific intermolecular interactions are proposed. The thermodynamic characteristics of aggregation (constants of equilibrium, Gibbs energy, enthalpy and entropy) and structural parameters of aggregates have been determined. The manifestations of the supramolecular ordering on the physicochemical properties of the mixture are discussed.

Modeling of Supramolecular Structure and Physicochemical Properties of the Propanone–Methanol Mixture

The results on modeling of the supramolecular organization and physicochemical properties of the propanone-methanol mixture are presented. An analysis of the excess thermodynamic functions (Gibbs energy, enthalpy, and entropy) and the permittivity of mixtures have been performed in the whole range of compositions and temperatures. It has been demonstrated that the model of supramolecular structure, taking into account the chain and cyclic association of methanol molecules and complexation of alcohol aggregates with propanone, describes the properties of the mixture. It established that both specific and universal interactions contribute to the positive deviations from the thermodynamic ideal solution behavior. Positive deviation of the dipole correlation factor from unity is due to a predominantly parallel orientation of the dipoles of the molecules in methanol aggregates and their complexes with propanone. The thermodynamic parameters of aggregation and structural parameters of aggregates have been determined. The cooperativity of H bonding was established. Distribution functions of the aggregate, according to size and structure, are presented. The manifestations of the supramolecular ordering on the physicochemical properties of the mixture are discussed.

Modeling of supramolecular structure and dielectric properties of butanols from melting point to supercritical state.

The supramolecular structure and dielectric properties of pure fluid butanols have been modeled in the temperature range from the melting point to the vicinity of the critical point using the quasichemical model of nonideal associated solution (QCNAS). The model of supramolecular structure takes into account both chain-like and cyclic aggregates. Dielectric permittivity and dipole correlation factor of n-, sec-, and tert-butanol are calculated in the temperature intervals 191-553, 166-533, and 298-503 K, respectively, using parameters obtained earlier for ambient conditions. The thermodynamic and structural parameters of supramolecular aggregation are reported. Size and structure distribution functions of aggregates are evaluated in the entire temperature range. Mean degree of aggregation of n-butanol decreases from hundreds at low temperatures to about 1.3 around critical point. The structure of n-butanol and s-butanol is characterized mainly by chain-like aggregation. tert-Butanols degree of aggregation is about 4 at ambient conditions and falls to 1.4 approaching the critical point. The fractions of molecules in chain-like and cyclic aggregates are comparable for tert-butanol. This conclusion refutes the frequently expressed opinion that tert-butanol consists mostly of cyclic species.