Modeling of supramolecular ordering and dielectric properties: Hexane or cyclohexane — n-alkanol mixtures

Abstract

The QuasiChemical Nonideal Associated Solution (QCNAS) model was used to analyze the dielectric permittivity and thermodynamic mixing functions of binary mixtures hydrocarbon (cyclohexane, hexane) — n-alkanol (pentan-1-ol, hexan-1-ol and heptan-1-ol) in the entire range of compositions at 298 K. The new model of supramolecular organization was substantiated, taking into account both chain and cyclic aggregation of alcohol with the formation of chain aggregates of arbitrary size with two possible states of H-bonds in the alcohol aggregates. This model describes a set of physicochemical properties of these mixtures with complicated behavior of both dielectrics and thermodynamics. Equilibrium constants, thermodynamic parameters of H-bonding with cooperative character, integral and differential characteristics of aggregation, and the structural parameters of aggregates were determined. It was established that the role of non-polar cyclic structures becomes more important with decreasing alcohol concentration. The proposed model describes the permittivity of the solutions in the entire range of compositions and reproduces the minimum of the dipolar correlation factor in the range of dilute alcohol solutions. The new data obtained on the supramolecular ordering characterized by the long-range molecular correlations due to H-bonding are discussed in detail.