Vapor–liquid equilibrium for systems that contain more than one alcohol: comparison of Kretschmer–Wiebe and mobile order models

As part of a continuing study of associated mixtures, we compare the abilities of two solution models to represent vapor–liquid equilibria for binary mixtures of alcohols. Specifically, we compare mobile order theory, in which the degree of association is governed by the fraction of time for which a molecule is free of hydrogen bonding, to the Kretschmer–Wiebe model, in which hydrogen bonding is modelled classically by chemical equilibria. Both models contain parameters which reflect physical interactions, self-association and cross-association and both contain the same number of adjustable parameters. In addition to comparing the abilities of each model to represent VLE data, we examine the temperature dependence of the model parameters.