COSMO-RS analysis on mixing properties obtained for the systems 1-butyl-X-methylpyridinium tetrafluoroborate [X=2,3,4] and 1,omega-dibromoalkanes [omega=1-6]

Abstract

A theoretical-experimental study for a set of 18 binary systems comprised of [bXmpy][BF4] (X = 2-4) + 1,omega-Br(CH2)(nu)Br (nu = omega = 1-6) at a temperature of 298.15 K is presented. The solubility curves are determined for each binary system, establishing the intervals of measurement for the excess properties, H-m(E) and V-m(E). These properties are then determined for those systems that present a miscibility zone. Binary systems containing 1,omega-dibromoalkanes with omega = 5,6 present reduced solubility intervals at the temperature of 298.15 K. However, the mixtures with 1,1-dibromomethane were totally miscible with the three isomers of 1-butyl-X-methylpyridinium tetrafluoroborate. Mixtures with dibromomethane present H-m(E) < 0, whereas H-m(E) > 0 for the other binary systems. Sigmoidal curves were observed for the V-m(E) describing expansion and contraction processes for all the systems, except for the mixtures of [b2mpy][BF4] with the smaller dibromoalkanes, which present contraction effects. The COSMO-RS methodology was used to estimate the solubilities and the intermolecular interaction energies, giving an acceptable explanation of the behavioral structure of pure compounds and solutions.