Description of thermodynamic behavior of the systems formed by alkyl ethanoates with 1-chloroalkanes using the COSMO-RS methodology contributing with new experimental information

Abstract

For this work, V E and H E have been measured at a temperature of 298.15 K and at atmospheric pressure for a set of binary mixtures composed of seven alkyl ethanoates (from methyl to octyl, except heptyl) and six 1-chloroalkanes (C-4 to C-9). Of the 42 binary mixtures, measurements have only been made for systems for which the excess quantities have not been published previously. Except for the octyl ethanoate +1-chlorobutane E E system, with V-m(E) < 0, and hexyl ethanoate+1-chlorobutane, with V-m(E)approximate to 0, the mixtures present expansive effects. In the case of the enthalpies, methyl ethanoate+1-chloroalkane mixtures are all endothermic and evolve toward H-m(E) < 0 as the alkanolic part of the ethanoate increases, and mixtures of octyl ethanoate+1-m chloroalkane are all totally exothermic. The COSMO-RS model, based on quantum chemical calculations, has been used to explain the behavior of these mixtures, which estimate the enthalpic effects as a result of the inter/intramolecular interactions of the two types of ester/chloroalkane molecules. The results obtained with the COSMO-RS give a good qualitative prediction with an explanation of the different effects that determine the behavior of these mixtures, especially the influence, in both the pure substance and the mixture, of the increased chain length in both types of compound. Application of two different versions of the UNIFAC method gives acceptable results, although with the original version of Dang and Tassios(10) it was necessary to determine new parameters using the experimental database of this work.