Measurement And Estimation Of The Vaporization Enthalpy For Threonine Ionic Liquids [C_nmim][thr](n=2,4)

This article mainly based on the two kinds of ionic liquids?ILs?,1-alkyl-3-methylimidazolium threonine salt[C_nmim][thr]?n=2,4?.They were synthesized by the method of two step neutralization.In order to confirm the structures of them,we conducted experiments,such as ¹H NMR and ¹³C NMR spectroscopy and Element analysis.All experimental results show that these ILs are the substance which we need.Firstly,we obtained the initial decomposition temperature and the molar vaporization enthalpy,?_l^gH_m^o(T_av),at the average temperature,T_av=438.15 K,by using the conventional TGA and the isothermogravimetrical analysis.On the base of statistical thermodynamics,the difference of heat capacities between the liquid phase and the gaseous phase,?_l^gC^o_pm,for[C_nmim][thr]?n=2,4?were obtained by using the Verevkin's method.And then,with the help of?_l^gC^o_pm,the values of?_l^gH_m^o(T_av)were turned into?_l^gH_m^o?298?.Secondly,dielectric constant can't accurately describe the polarity of ILs.Therefore,we creatively put forward a new scale of ILs'polarity,?_???_?² is the contribution of the dipole moment to the cohesive energy?,with the use of the theory of Hildebrand solubility parameter and the value of?_l^gH_m^o?298?.And then,the value of?_?can be estimated.According to the ionic liquids'new concept,the rule of the polarity for[C_nmim][thr]?n=2,4?was predicted,that is,the polarity decreases with the increasing of methylene.Finally,in order to precisely predict ILs'molar vaporization enthalpy,a new model of vaporization enthalpy of aprotic ILs was proposed and used to study the relationship between surface tension and molar vaporization enthalpy of protic ionic liquids and predict the vaporization enthalpy of[C_nmim][thr]?n=3,5,6?.