Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

Excess molar enthalpies HE m and excess molar volumes V E m have been determined experimentally at atmospheric pressure and at a temperature of 298.15 K, for a set of 25 binary mixtures composed of the first five methyl esters (methanoate to pentanoate) with five 1,x-dibromoalkanes (1,2-dibromoethane to 1,6-dibromohexane). Most of the mixtures present positive net mixing effects, endothermic with dilatation, with the exception of those that contain butanoates and pentanoates with the shorter a,x-dibromoalkanes, which present negative HE m values and, by contrast, negative V E m values when x P5, but in both cases at high methyl ester compositions. The experimental data are correlated with a suitable polynomial equation, used previously by our group. Two known versions of the UNIFAC group contribution model are used, the original version by Dang and Tassios and the more recent version of Gmehling et al. The estimations are unacceptable in both cases, so the parameters corresponding to carboxylate/bromine interaction are recalculated for the former version, differentiating the interaction type according to ester acid chain. There is a marked improvement for the methanoate and ethanoate mixtures, although the estimations are not acceptable for the other esters. The second version of UNIFAC, by Gmehling et al., requires other data not available in the literature.