The activity coefficients at infinite dilution, gamma(infinity)(13) for 35 solutes: alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, 1 thiophene, ethers, acetone and water in the ionic liquids 1-hexyloxymethyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)-imide [C6H13OCH2MIM][NTf2] and 1,3-dihexyloxymethyl-imidazolium bis(trifluoromethylsulfonyl)-imide [(C6H13OCH2)(2)IM][NTf2] were determined by gas-liquid chromatography over a wide range of temperature from (298.15-368.15) K. The values of the partial molar excess enthalpies at infinite dilution, Delta H-1(E,infinity), were calculated from the experimental gamma(infinity)(13) values obtained in the temperature range investigated. The selectivity for the separation of n-hexane/benzene, cyclohexane/benzene, n-hexane/thiophene, hex-1-ene/n-hexane and hex-1-ene/benzene by the extractive distillation or solvent extraction processes were calculated from the gamma(infinity)(13), values and were compared to the literature values for other ionic liquids, and popular entrainers as NMP and sulfolane at temperature T = 298.15 K. (C) 2009 Elsevier B.V. All rights reserved.