Activity coefficients at infinite dilution (γ13 ∞) for organic solutes in deep eutectic solvent (DES) prepared by {1-butyl-2,3-dimethylimidazolium chloride (BDMIM Cl) + ethylene glycol (EG)} at a molar ratio of 1:3 have been measured using the gas–liquid chromatographic method (GLC). The thermal stability of the entrainer was determined by the thermogravimetric analyzer. The measurements were carried out in the temperature range of T = (313.15 to 343.15) K and at atmospheric pressure. The values of the partial molar excess enthalpies at infinite dilution (H 1 E,∞) were derived from the temperature dependence of the γ13 ∞∞ values. The entropies (T ref ΔS 1 E,∞) and Gibbs energies (ΔG 1 E,∞) of organic solutes at a reference temperature T ref = 323.15 K were also calculated from the γ13 ∞ values. These excess thermodynamic functions were calculated to further explain the intermolecular interactions occurring between the volatile organic solvents and the prepared deep eutectic solvent. Important separation parameters such as selectivities (S ij ∞) and capacities (K j ∞) at infinite dilution were computed from the activity coefficients at infinite dilution data at T = 313.15 K. Selectivity and capacity data were calculated for the industrial mixtures such as cyclohexane/benzene, hexane/thiophene, cyclohexane/ethanol. There results were compared to the literature data comprising deep eutectic solvents and ILs with the cation of 1-butyl-3-methylimidazolium. The investigated solvent was found suitable to separate azeotropes formed by alkanes/alcohols.