Synthesis of new ionic liquid 1-ethyl-1-methylpyrrolidinium lactate (racemate), [EMPYR][Lac] was performed. The characterization of the new compound by NMR spectra, elementary analysis, water content, and TG/DTA is presented. The activity coefficients at infinite dilution, gamma(infinity)(13), for 54 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, ethers, ketones, acetonitrile, pyridine, 1-nitropropane, thiophene, and esters in the [EMPYR][Lac] were determined by gas-liquid chromatography for most of the solutes at eight temperatures within the range of (308.15 to 378.15) K and for alcohols and water at higher temperatures in a range of (358.15 to 408.15) K. The partial molar excess Gibbs energy, Delta G(1)(E,infinity), enthalpy Delta H-1(E,infinity), and entropy term T-ref Delta S-1(E,infinity) at infinite dilution were calculated from the experimental gamma(infinity)(13) values obtained over the temperature range. The values of selectivity for few separation problems as hexane/hex-1-ene, cyclohexane/cyclohexene and hexane/benzene were calculated from gamma(infinity)(13) and compared to literature values for pyrrolidinium-based ionic liquids (ILs) on the same separation problems. In comparison with the former measured ILs, the [EMPYR][Lac] presents quite high selectivity for the separation of alkenes from aliphatic hydrocarbons, an average capacity for alkenes. The data presented here shows that [EMPYR][Lac] may be proposed as an alternative solvent for the separation of alkenes from the aliphatic hydrocarbons. (C) 2015 Elsevier Ltd. All rights reserved.