1-(2-Hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid ([hemim][NTf2]) was synthesized as a new functionalized ionic liquid to study the effect of addition of the hydroxyl group to the imidazolium cation on aliphatic/aromatic separations. For this purpose, liquid liquid equilibrium (LLE) data for {heptane + toluene or benzene + 1-(2-hydroxyethyl)-3-methylimidazolium bis (trifluoromethylsulfonyl)imide ([hemim][NTf2])} systems were measured at 313.2 K and atmospheric pressure. The measured LLE data were correlated,using three basically distinct thermodynamic models; that is, nonrandom two-liquid (NRTL), Othmer-Tobias, and Hand correlations. Results show that there is good agreement between correlated and experimental data. Our experimental results indicate that the addition of the hydroxyl group to imidazolium cation significantly enhances the performance of the ionic liquid in terms of selectivity.