Application of a new theoretical procedure for calculating Kirkwood correlation factors in alkanol + hexane and alkanol + pentane mixtures

Abstract

A recently developed statistical mechanical model for calculating Kirkwood correlation factors g_K in self associating liquids and liquid mixtures has been applied for the simultaneous description of g_K, the molar enthalpy of mixing H^E_m and the infrared absorption of monomer alcoholic species as function of the composition in alkanol + hexane and alkanol + pentane mixtures (alkanol: butan-1-ol, pentan-1-ol, hexan-1-ol, heptan-1-ol, sec-butanol, tert-butanol).The majority of parameters involved into the theory are obtained by independent quantum mechanical ab initio calculations of molecular clusters consisting of up to four alcohol molecules. As a consequence only two parameters have to be adjusted freely to each binary system, a third parameter responsible for the non specific intermolecular dispersion interaction has been adjusted within a limited range of possible values given by physical arguments. Excellent agreement between theory and experimental data of g_K, H^E_m and IR absorbance is obtained covering the whole range of concentration including the temperature dependence of these properties without adjusting further parameters. The Kirkwood correlation factor g_K turns out to be a sensitive response to peculiarities of the molecular structure of hydrogen bonded systems in the condensed liquid state. The successful application of the theoretical model opens a new way of a deeper and more reliable understanding of such liquid structures.