COSMO-RS analysis on mixing properties obtained for the systems 1-butyl-X-methylpyridinium tetrafluoroborate [X = 2,3,4] and 1,ω-dibromoalkanes [ω = 1–6]

Abstract

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.

Description of the Behavior of Dichloroalkanes-Containing Solutions with Three [bXmpy][BF4] Isomers, Using the Experimental Information of Thermodynamic Properties, 1H NMR Spectral and the COSMO-RS-Methodology

“…When the analysis of the results was based on the different position of the methyl group −CH 3 in the IL (X = 2, 3, and 4), the theoretical model did not detect any differences in two of the three contributions for the three of the ILs isomers, except for those due to the van der Waals forces. This behavior of the properties is to be expected, owing to the nature of the halogen, for a same dihalide chain length, thus confirming the results of a previous work with 1,ωdibromoalkanes, 8 which have quantitatively higher properties. Bromine derivatives are less polar than the corresponding chlorinated compounds, due to a lower electronegativity of the bromine atoms and are also less soluble in the [bXmpy][BF 4 ] compounds.…”

“…Electrical calibration of the apparatus was checked at two working temperatures with the mixture propan-1-ol+benzene, 33 with an uncertainty of 1% for h E . In this work, for mixtures with isomers of [bXmpy][BF 4 ], a special cell was used equipped with a gentle stirring mechanism, described previously, 8 that maintained a constant stirring action during the entire process. The net interaction energy is obtained from the difference between the thermogram of the process and that corresponding to the stirring, previously estimated in a pilot experience using IL.…”

Thermodynamic Behavior of the Binaries 1-Butylpyridinium Tetrafluoroborate with Water and Alkanols: Their Interpretation Using 1H NMR Spectroscopy and Quantum-Chemistry Calculations

“…For the alkanols, values of the parameters practically coincide with those reported in previous papers. 2,3 The densities of the pure compounds are recorded in Table S3 4 ] the densities were lower than those shown in the literature by Mokhtarami et al, 12 of, respectively, 1213.4 and 1199.8 kg 3 m À3 probably due to a slightly higher water content in the IL used by these authors compared to that recorded by us, see Table 1. The exponential of the densities gives us a mean value for the thermal expansion coefficients in the temperature interval considered, and the obtained values are in agreement with those reported in the literature.…”

“…The first, equipped with a cylindrical minishaker, has been described in a previous paper. 1 A set of measurements were made with another cell, but only in the composition interval 0.2 e x IL e 1 for purposes of verification, which presents slight modifications of other measurements described previously, 4 and the scheme is shown in Figure 1. In this interval, the values obtained for H m E with both procedures were almost identical.…”

“…As can be observed in Figure 10, the calculations indicate that both ILs are completely dissociated in the mixture with all the solvents studied, in accordance with experimental evidence. 15 This suggests that a molecular model of independent ions (C + + A À ) may be more appropriate to simulate the mixtures [ 4 ] as a function of the solvent, using the CA ion-pair model, Figure 11a, and the independent ions C + + A À , Figure 11b. As can be observed, the quantum-chemistry observations 1 The Journal of Physical Chemistry B ARTICLE theoretical and experimental data for the tendencies of the 1 H NMR signals as a function of the solvent of the mixture.…”