Activity coefficients at infinite dilution gamma(infinity)(i) of alkanes, alkenes, and alkylbenzenes as well as of the linear and branched C-1-C-6 alcohols, esters, and aldehydes in the ionic liquids 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide have been determined by gas chromatography using the ionic liquids as stationary phase. The measurements were carried out at different temperatures between 301 K and 396 K. From the temperature dependence of the limiting activity coefficients, partial molar excess enthalpies at infinite dilution H-i(E,infinity) of the solutes in the ionic liquids have been derived.