Activity coefficients at infinite dilution (gamma(infinity)), vapor-liquid equilibria (VLE) and excess enthalpies (H-E) for different alkanes and alkenes with the ionic liquids 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM]+[OTF](-), 1-hexyl-3-methylimidazolium trifluoromethanesulfonate[HMIM](+)[OTF](-) and 1-octyl-3-methylimidazolium trifluoromethanesulfonate[OMIM](+)[OTF](-) have been measured. The new data were used to revise and extend the group interaction parameter matrix of modified UNIFAC (Dortmund). (C) 2010 Elsevier B.V. All rights reserved.