Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

In this article, the experimental data of excess molar enthalpies HE m and excess molar volumes V E m are presented for a set of 20 binary mixtures comprised of the first four butyl alkanoates (methanoate to butanoate) and five a,x-dichloroalkanes (1,2-dichloroethane to 1,6- dichlorohexane), obtained at atmospheric pressure and at a temperature of 298.15 K. The results indicate the existence of specific interactions between both kinds of compounds resulting in exothermic processes for most mixtures, except for those containing butyl methanoate which give rise to net endo/exothermic effects. The V E m are positive for mixtures of (butyl esters + 1,2-dichloroethane or 1,3-dichloropropane) and negative for the remaining ones. The change in HE m with the dichloroethane chain length for a same ester is regular although the V E m presents an irregular variation. It can, therefore, be deuced from this that the mixing process involves both effects, exothermic/endothermic and expansion/contraction, simultaneously. The behaviour of the mixtures is interpreted on the basis of the results observed and attributed to different effects taking place among the molecules studied. To improve application of the UNIFAC model using the version of Dang and Tassios, average values were recalculated again for parameters of the ester/chloride interaction, distinguishing, during its application, the functional group of the acid part of the ester. In spite of this, the model does not adequately reproduce the systems? behaviour.