Dimerization and continuous association including formation of cyclic dimers

Abstract

New aspects of the theory of ideal associated mixtures related to a differentiation between formed cyclic and linear dimers are discussed. A mathematical analysis is presented for the dimerization model, A + B + A2, the continuous association (Mecke–Kempter) model, [Formula: see text], both coupled with the cyclic dimmer → linear dimer transformation and for the unsymmetrical (mixed) dimer formation model, A + B + A2 + B2 + AB. Introduction of the standard reaction enthalpies and volumes associated with transformations of dimers leads to a considerable change in behavior and symmetry properties of the excess thermodynamic functions. In terms of the modified Mecke–Kempter model, a consistent representation of the excess Gibbs energy of mixing GE, heat of mixing HE, and excess molar volume VE is reported for the acetic acid – water system at 298.15 K. Key words: association, dimerization, linear dimers, cyclic dimers, hydrogen bonding, carboxylic acids, alcohols, aqueous solutions.