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A theoretical-experimental study for a set of 18 binary systems comprised of [bXmpy][BF(4)] (X=2-4) + 1,ω-Br(CH(2))(v)Br (v =ω=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(E)(m) and V(E)(m). These properties are then determined for those systems that present a miscibility zone. Binary systems containing 1,ω-dibromoalkanes with ω=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(E)(m) <0, whereas H(E)(m) >0 for the other binary systems. Sigmoidal curves were observed for the V(E)(m) describing expansion and contraction processes for all the systems, except for the mixtures of [b2mpy][BF(4)] 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.

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Thermodynamic study of (alkyl esters + a,x-alkyl dihalides) II:H E m and V E m for 25 binary mixtures {xC u À 1 H 2u À 1 CO 2 C 2 H 5 + (1 À x)a,x-BrCH 2 (CH 2 ) v À 2 CH 2 Br}, where u = 1 to 5, a = 1 and v = x = 2 to 6 Abstract Excess molar enthalpies H E m , and excess molar volumes V E m , have been determined experimentally at constant conditions of atmospheric pressure and a temperature of T = 298.15 K, for a set of 25 binary mixtures, composed of ethyl alkanoate (methanoate to pentanoate) with each of the a,x-dibromoalkanes (1,2-dibromoethane to 1,6-dibromohexane), presenting the values of excess quantities Y E m as a function of the ester composition x. Most of the mixtures presented V E m > 0, except those formed by 1,5-dibromopentane and 1,6-dibromohexane with propanoate, butanoate and ethyl pentanoate, for which V E m < 0. The five mixtures of (ethyl methanoate + a,x-dibromoalkanes) are all endothermic, although, in the other systems this endothermicity decreases slightly with the increase in the ester acid chain length, producing sigmoidal curves that reflect exo/endothermic effects in the mixing process. The results are explained on the basis of a structural model that considers the existence of several effects, some positive and some negative, which produce the previously mentioned variations in excess quantities.In all cases, the experimental values are correlated with a suitable polynomial equation. Finally, predictions of H E m are made using two versions of the UNIFAC group contribution model. The version proposed by Dang and Tassios produces unacceptable estimations, while the version of Gmehling et al. produces results closer to experimentals.