Activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate

Infinite dilution activity coefficients γ1∞ and gas–liquid partition coefficients KL of 30 selected hydrocarbons, alcohols, ketones, ethers, esters, haloalkanes, nitrogen- and sulphur-containing compounds in the ionic liquid (IL) 1-ethyl-3-methylimidazolium methanesulfonate [EMIM][MeSO3] were determined by gas–liquid chromatography at five temperatures in the range from 318.15 to 353.15 K. Relative contribution of adsorption at gas–liquid interphase to the overall solute retention, as examined by varying sample size and IL loading in the column, was found negligible. Partial molar excess enthalpies and entropies at infinite dilution were derived from the temperature dependence of the γ1∞ values. The linear free energy relationship (LFER) solvation model was used to correlate successfully the KL values. The LFER correlation parameters and excess thermodynamic functions were analyzed to disclose molecular interactions operating between the IL and the individual solutes. Comparison to [EMIM][NO3] studied previously revealed [MeSO3]− anion to have still greater hydrogen bond basicity than that found for [NO3]−. In addition, similarly to [EMIM][NO3], promising potential of [EMIM][MeSO3] for applications in solvent-aided separation processes was identified, the selectivities of [EMIM][MeSO3] for separation of aromatic hydrocarbons and thiophene from saturated hydrocarbons ranking among the highest ever observed with ILs or molecular solvents.