| In this paper,two kinds of amino acid ionic liquids were synthesized,which were 1-alkeyl-3-methylimidazolyl threonine salt[Cnmim][Thr]?n=3,6?.In this paper,a multi-step synthesis method was used to obtain functional ionic liquids,which were characterized by 1H NMR and 13C NMR spectroscopy and thermogravimetric analysis.The product was analyzed by these means to determine that the synthesized product was the target product.Firstly,the relationship between the mass loss amount of two different amino acid ionic liquids and temperature was determined by constant temperature thermogravimetry.Secondly,the evaporation constant of the reference substance benzoic acid was calculated by Langmuir equation,and then the vapor pressure of1-alkeyl-3-methylimidazolyl threonine salt[Cnmim][thr]?n=3,6?was calculated.The vapor pressure?p?and vaporization enthalpy and temperature?T?can be contacted by the Clausius-Clapeyron equation to find the value of the vaporization enthalpy of the two ionic liquids at an average temperature Tav=438.15 K.The vaporization enthalpy at an average temperature Tav=438.15 K was converted to a vaporization enthalpy at298.15 K by the method of Verevkin.In this paper,the new semi-empirical equation is used to calculate the vaporization enthalpy of[Cnmim][Thr]?n=3,6?.It was found that the average contribution of each methylene group?-CH2-?to vaporization enthalpy is 3.7 kJ·mol-1,it is similar to?35?lgHmo?-CH2-?=3.89 kJ·mol-1of the contribution of methylene to vaporization enthalpy proposed by Zaitsau et al.,indicating rationality of these data and the new model.Finally,we can make use of the literature values of vaporized hydrazine[Cnmim][Thr]?n=4,5?.This also undoubtedly illustrates the vaporization enthalpy of the amino acid ionic liquid[Cnmim][Thr]?n=3,4,5,6?can be greatly affected by the length of the side chain of the imidazole ring... |
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