Supramolecular structure and physicochemical properties of the systems acetone-methanol and acetone-ethanol.

V.A. Durov, O.G. Tereshin, I.Yu. Shilov

Rus.J.Phys.Chem., v. 74 (2), p. 240-245, 2000 (Zh.fiz.khim., v 74 (2), c. 245-250, 2000)

Abstract. Thermodynamic properties (activity coefficients of components, excess Gibbs energy, enthalpy and entropy) and dielectric properties (static dielectric constant, dipole correlation factor) are analyzed and modelled in the framework of unified quasichemical approach in the whole concentration range and the wide temperature interval. The structural model implying formation of chain alcohol aggregates of arbitrary length able to form complexes with ketone molecules gives a satisfactory description of a set of various macroscopic properties. A number of thermodynamic and structural parameters of association and complex formation is obtained. . The enthalpy of H-bonding O-H...O-H between alcohol molecules and H-bonding O-H...O= between alcohol and ketone molecules have been obtained. The distribution function of aggregates on size and composition as well as the mean degrees af affrefation have been derived. The possibility is shown for the unified description of mixing functions, dielectric constant and quantitative analysis of association equilibria and intermolecular interactions in the mixtures ketone-alcohol in the framework of quasichemical models The specific interactions (hydrogen bonding) make the main contribution to the excess thermodynamic functions, positive deviation from ideal solution behavior being due to chain-like association of alcohol molecules. Positive deviations of dipole correlation factor from unity are connected with mostly parallel orientation of dipole moments of molecules in methanol aggregates and their complexes with acetone. The physicochemical properties of the systems acetone-methanol and acetone-ethanol are similar, quantitative difference being due to different degrees of association of pure alcohols and solutions.

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