The molar enthalpy of vaporization, Delta H-g(l)m(o) (T-av), at the average temperature, T-av = 438.15 K, for the ionic liquids (ILs), 1-alkyl-3-methylimidazolium threonine salt [C(n)min][Thr](n = 2, 4) were determined by using the isothermogravimetrical analysis. With the use of Verevkin's method, the difference of heat capacities between the gaseous phase and the liquid phase, Delta H-g(l)m(o), for [C(n)min][Thr](n = 2, 4) were calculated based on the statistical thermodynamics. Therefore, with the use of Delta H-g(l)m(o), the values of Delta H-g(l)m(o)(T-av) were transformed into Delta H-g(l)m(o) (298). According to the new scale of polarity for ILs, the order of the polarity of [C(n)min][Thr](n = 2, 4) was predicted, that is, the polarity reduces with the increasing of methylene. In addition, a new model about the enthalpy of vaporization for aprotic ILs was proposed and used to predict the vaporization enthalpy for [C(n)min][Thr](n = 3, 5, 6), but these predicted values also need to be verified in our future experiments. (C) 2017 Elsevier Ltd.