Interactions of Ionic Liquids and Acetone: Thermodynamic Properties, Quantum-Chemical Calculations, and NMR Analysis

Abstract

The interactions between ionic liquids (ILs) and acetone have been studied to obtain a further understanding of the behavior of their mixtures, which generally give place to an exothermic process, mutual miscibility, and negative deviation of Raoult's law. COSMO-RS was used as a suitable computational method to systematically analyze the excess enthalpy of IL-acetone systems (>300), in terms of the intermolecular interactions contributing to the mixture behavior. Spectroscopic and COSMO-RS results indicated that acetone, as a polar compound with strong hydrogen bond acceptor character, in most cases, establishes favorable hydrogen bonding with ILs. This interaction is strengthened by the presence of an acidic cation and an anion with dispersed charge and non-HB acceptor character in the IL. COSMO-RS predictions indicated that gas-liquid and vapor-liquid equilibrium data for IL-acetone systems can be finely tuned by the IL selection, that is, acting on the intermolecular interactions between the molecular and ionic species in the liquid phase. NMR measurements for IL-acetone mixtures at different concentrations were also carried out. Quantum-chemical calculations by using molecular clusters of acetone and IL species were finally performed. These results provided additional evidence of the main role played by hydrogen bonding in the behavior of systems containing ILs and HB acceptor compounds, such as acetone.

Indirect assessment of the fusion properties of choline chloride from solid-liquid equilibria data

“…The activity coefficients at 300, 400 and 500 K of the [Ch]Cl(1)þIC(2) systems were estimated by COSMO-RS and this information used to assess the ideality of the solutions. Before the estimations, all the IC structures were optimized [29]. The ions of each compound were optimized simultaneously as an ion pair.…”

“…The ions of each compound were optimized simultaneously as an ion pair. On a second step, the COSMO file of each structure was generated by Gaussian, computing the ideal screening charges on the molecular surface at the BVP86/TZVP/DGA level [29].…”

Distribution of N-Methylimidazole in Ionic Liquids/Organic Solvents Systems

“…Regarding 1-alkyl-3-methyimidazolium-based ILs, there are three main binding sites in the imidazolium ion capable of participating as hydrogen bond donors, and these are at positions H-( 4 C), H-( 5 C), and H-( 2 C). Indeed, it was shown that the IL anion prefers to bind to the proton at the ( 2 C) position, the latter being the most acidic amongst the others [45][46][47], and that the introduction of a solute/solvent to the IL leads to a competition for the active sites of both ions, the outcome of which strongly depends on the differences between the acidic/basic properties of the participants [44][45][46][47][48][49][50][51][52]. In other words, solutes with pronounced acidic properties will compete with the imidazolium ion to form H-bonds with Cl − , whereas those with basic properties will compete with the chloride anion for the acidic sites of the cation.…”

Extractive distillation with the mixture of ionic liquid and solid inorganic salt as entrainers

“…To obtain the binding energy between water (or ethanol) and the entrainers, all optimized geometries were obtained by using the Gaussian 03 software package 50 at the M05-2X/ 6-31111G(d,p) level with the keyword "int 5 ultrafine," which has been previously used for studying the interactions between ILs and polar organic molecules. 51,52 The M05-2X functional is one of the newest DFT methods and is assumed to correctly reproduce weak interactions. 53 To obtain the most favorable clusters (composed of IL ions, KAc, water, and ethanol), harmonic frequency analysis calculations were performed to verify the optimized geometries to obtain the lowest energy points (no imaginary frequency) rather than local minima.…”