Thermodynamic study of (alkyl esters + α,ω-alkyl dihalides) VI. H_m~E and V_m~E for 20 binary mixtures {xC_(u-1)H_(2u-1)CO _2(CH_2)_3CH_3 + (1 - x)α,ω-BrCH_2(CH_2)_(v-2)CH_2Br} to 6

摘要

This work shows the experimental values obtained for H_m~E and V_m~E at the temperature of 298.15 K and atmospheric pressure, for a set of 20 binary mixtures comprised of the first four butyl esters (methanoate to butanoate) with five α,ω-dibromoalkanes (1,2-dibromoethane to 1,6-dibromohexane). The H_m~E are endothermic for mixtures with butyl methanoate, while for the other esters the H_m~E adopt a sigmoidal shape. The V_m~E are positive for mixtures with low molecular weight dibromoalkanes, becoming negative with contractive effects in the final mixture, as the dihalide chain increases. The results indicate that the mixtures present specific interactions, with simultaneous expansion/contraction and exothermic/endothermic effects, and an explanation is given for the different types of interaction taking place. Experimental data are correlated with a polynomial equation used in previous works with satisfactory results. Modelling of the experimental results of the mixtures is carried out on the H_m~E values, giving rise to an adequate definition of the different interactions taking place. Two versions of the UNIFAC method were used, and for Dang and Tassios' version different possibilities were considered for the interaction parameters of the ester (G)/dibromide (G′). The best estimations were obtained when the pair of interaction parameters, type a_(G / G′), depended on the number of carbon atoms in the compounds constituting the mixture.