Thermodynamics of mixtures containing linear monocarboxylic acids II. Binary systems showing cross-association between components: DISQUAC characterization of linear monocarboxylic acid + 1-alkanol, or + linear monocarboxylic acid mixtures

Abstract

Binary mixtures containing compounds which show cross-association between them are investigated in terms of DISQUAC: namely, systems with two linear monocarboxylic acids, or with one acid and one 1-alkanol. In the former, the interactions between the COOH groups of the acids are represented by dispersive parameters only. Binary systems involving two 1-alkanols behave similarly. In the linear monocarboxylic acids + 1-alkanol mixtures, the COOH/OH interactions are represented by structure-dependent dispersive and quasichemical parameters. It is shown that those solutions with methanol and ethanol do not fit into the general scheme followed by the higher members of each homologous series considered here. A similar behaviour is found when mixtures containing methanol and benzene or CCl 4 are compared with those involving higher alkanols in the frameworks of DISQUAC or of the Barker's theory. Vapor-liquid equilibria, VLE, and excess enthalpy, H E, data are consistently described by DISQUAC. Discrepancies are analysed. The UNIQUAC association model or an equation of state (Carnahan-Starling) with the association built in have been applied in the literature as pure correlations of the experimental data for acids + 1-alkanols systems. Their results are compared with those reported in this work by DISQUAC.