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

Abstract

Here we present experimental data of different properties for a set of binary mixtures composed of water or alkanols (methanol to butanol) with an ionic liquid (IL), butylpyridinium tetrafluoroborate [bpy][BF(4)]. Solubility data (x(IL),T) are presented for each of the mixtures, including water, which is found to have a small interval of compositions in IL, x(IL), with immiscibility. In each case, the upper critical solubility temperature (UCST) is determined and a correlation was observed between the UCST and the nature of the compounds in the mixtures. Miscibility curves establish the composition and temperature intervals where thermodynamic properties of the mixtures, such as enthalpies H(m)(E) and volumes V(m)(E), can be determined. Hence, at 298.15 and 318.15 K these can only be found with the first four alkanols. All mixing properties are correlated with a suitable equation ξ (x(IL),T,Y(m)(E) = 0. An analysis on the influence of the temperature in the properties is shown, likewise a comparison between the results obtained here and those of analogous mixtures, discussing the position of the -CH(3) group in the pyridinic ring. The (1)H NMR spectra are determined to analyze the molecular interactions present, especially those due to hydrogen bonds. Additional information about the molecular interactions and their influence on the mixing properties is obtained by quantum chemistry calculations.

Probing structural patterns of ion association and solvation in mixtures of imidazolium ionic liquids with acetonitrile by means of relative1H and13C NMR chemical shifts

“…14,16,27,38,69 However, from the point of view of interpretation, the most relevant reference concentration is that of the corresponding neat compound, and it is the most frequently used approach. 26,32,40,41,48,[70][71][72][73][74] We combined the two ideas outlined above, e.g., the relative chemical shift and the reference concentration in the concept of 'relative chemical shift variation'. It implies that the initial referencing should be done to one of the studied molecule's signal, terminal CH 3 for Rmim + cation and the most shielded group for a solvent (e.g., CH 3 in AN, MeOH).…”

Optimized ionic liquids for toluene absorption

“…In fact, several publications have demonstrated the general suitability of COSMO‐RS method to predict properties of IL systems, including the solubilities and Henry's law constants of several gases in ILs . Moreover, an important feature is that the different intermolecular interactions between the mixture components can be quantified by COSMO‐RS, contributing to the rational selection of ILs with improved characteristics for specific applications . Indeed, in previous works released by our research group, ILs with optimum characteristics for CO 2 and NH 3 absorption were selected, on the basis of a COSMO‐RS analysis performed for the excess enthalpies of solute‐IL mixtures and the COSMO‐RS description of the intermolecular solute‐IL interactions.…”

Liquid–Liquid Equilibria in Binary Solutions Formed by [Pyridinium-Derived][F4B] Ionic Liquids and Alkanols: New Experimental Data and Validation of a Multiparametric Model for Correlating LLE Data

“…More specifically, some pyridine derivatives (such as those used in this work) have produced good results in certain applications, such as sulfur extracting agents, 1 lubricants, 2 and chemical reactions. 3 Our research group has worked with three isomeric substances having a common nucleus of a pyridine derivative, [butyl-Xmethylpyridinium] (X = 2, 3,4) [tetrafluoroborate], 4À6 and other nonisomeric [butylpyridinium][tetrafluoroborate], 7 using water and several alkanols (methanol to pentanol) as solvents. For some of these mixtures, the miscibility capacities are known; however, these studies are incomplete, because the initial working project included a greater number of alkanols, from methanol to decanol, with the limitations imposed by the variable temperature in experiments carried out at atmospheric pressure.…”