Solubility and Excess Molar Properties of 1,3-Dimethylimidazolium Methylsulfate, or 1-Butyl-3-Methylimidazolium Methylsulfate, or 1-Butyl-3-Methylimidazolium Octylsulfate Ionic Liquids with n-Alkanes and Alcohols: Analysis in Terms of the PFP and FBT Models1

The solubility of 1-butyl-3-methylimidazolium octylsulfate, [BMIM][OcSO4], has been determined in hydrocarbon (n-hexane, n-heptane, n-octane or n-decane) solutions and alcohol (methanol, 1-butanol, 1-hexanol, 1-octanol or 1-decanol) solutions. Densities and excess molar volumes, VEm, have been determined for 1-methyl-3-methylimidazolium methylsulfate, [MMIM][CH3SO4], solutions with an alcohol (methanol, ethanol or 1-butanol) and with water; for 1-butyl-3-methylimidazolium methylsulfate, [BMIM][CH3SO4], with an alcohol (methanol, ethanol, 1-butanol, 1-hexanol, 1-octanol or 1-decanol) and with water; and for 1-butyl-3-methylimidazolium octylsulfate, [BMIM][OcSO4], with an alcohol (methanol, 1-butanol, 1-hexanol, 1-octanol or 1-decanol) at 298.15 K and atmospheric pressure. The systems exhibit very negative or positive molar excess volumes, VEm, and negative or positive excess molar enthalpies, HEm, as predicted by the Flory–Benson–Treszczanowicz (FBT) model. Our experimental VEm data were used for the description of HEm for solutions of [MMIM][CH3SO4] with the alcohols under study. The simple Prigogine–Flory–Paterson (PFP) model, without including the association of the alcohol, gave slightly worse results. Negative molar excess volumes, VEm, are attributed to hydrogen bonding between the short chain alcohols and ionic liquid and to efficient packing effects. The FBT model overestimates self-association of the alcohol in the solutions under study and shifts the calculated curves to higher alcohol mole fractions. The thermophysical characteristics of [BMIM][OcSO4] were also examined by differential scanning calorimetry (DSC).