Thermodynamic study of (alkyl esters plus alpha,omega-alkyl dihalides) VII. H-m(E) and V-m(E) for 20 binary mixtures {xC(u-1)H(2u-1)CO(2)C(3)H(7) + (1-x)alpha,omega-ClCH2(CH2)(v-2)CH2Cl}, where u=1 to 4, alpha=1 and v = omega=2 to 6. An analysis of behavior using the COSMO-RS methodology

Abstract

Excess enthalpies H-m(E) and excess volumes V-m(E) obtained at a temperature of 298.15 K and atmospheric pressure are presented for a set of 20 binary mixtures comprised of the first four propyl esters, Cu-1H2u-1COOC3H7 (u = 1 to 4), and five alpha,omega-dichloroalkanes, ClCH2(CH2)(v-2)CH2Cl (v = 2 to 6). All the mixtures are exothermic except for those corresponding to propyl methanoate with v >= 4. The V-m(E) are positive in most mixtures except for those where v = 4, 5, 6, for V-m(E) < 0. There is a regular rise in H-m(E) with v, while the increase in u produces a greater exothermicity in the mixing process, which becomes inverted for propyl butanoate. The variation in V-m(E) with the chain length of the compounds of the mixtures studied is not regular since both the enthalpic and the volumetric effects are due to interactions of different nature, positive and negative. Interpretation of the behavior was assisted by applying the quantum-chemistry method COSMO-RS. This method describes qualitatively and quantitatively the contribution of the different types of interactions, electrostatic, van der Waals, and those due to the (Cl,Cl) bond in the dihalide, and the influence of the ester and dichloroalkane chains. This information was also useful to adequately modify the application of the UNIFAC group contribution model, proposing parameters for the Cl, Cl/carboxylate interaction that vary with the chain length of the compounds involved. With this modification, the results estimated by UNIFAC model can be considered good. (c) 2008 Published by Elsevier Ltd.