Measurement of vaporization enthalpy by isothermogravimetrical method and prediction of the polarity for 1-alkyl-3-methylimidazolium acetate {[C(n)mim][OAc] (n=4, 6)} ionic liquids
Measurement of vaporization enthalpy by isothermogravimetrical method and prediction of the polarity for 1-alkyl-3-methylimidazolium acetate {[C(n)mim][OAc] (n=4, 6)} ionic liquids
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1-烷基-3-甲基咪唑鎓醋酸盐{[C(n)mim][OAc] (n=4, 6)}离子液体的等温重法测量汽化焓及极性预测
作者：
Wei Jie;Bu Xiaoxue;Guan Wei;Xing Nannan;Fang Dawei;Wu Yang
采用中和法制备了离子液体乙酸1-丁基-3-甲基咪唑鎓[C4mim][OAc]和乙酸1-己基-3-甲基咪唑鎓[C6mim][OAc]，并通过1H NMR谱和差示扫描量热法（DSC）进行了验证。使用等温重量分析，确定 [Cnmim][OAc] (n = 4, 6) 在平均温度 Tav 下的汽化焓 ΔglH°m(Tav)。使用所建立的方法，根据统计热力学计算[Cnmim][OAc] (n = 4, 6) 的气相和液相之间的热容差ΔglC°pm。因此，可以利用ΔglC°pm将ΔglH°m(Tav)的值转化为ΔglH°m(298)。通过分子动力学（MD）模拟进一步测试了汽化焓，结果与相应的实验值吻合良好。就 IL 的新极性尺度而言，[Cnmim][OAc] (n = 4, 6) 的极性顺序也被预测，并且与我们的经验非常一致。
Ionic liquids 1-butyl-3-methylimidazolium acetate [C4mim][OAc] and 1-hexyl-3-methylimidazolium acetate [C6mim][OAc] were prepared by the neutralization method and confirmed by 1H NMR spectroscopy and differential scanning calorimetry (DSC). Using isothermogravimetrical analysis, the enthalpy of vaporization, ΔglH°m(Tav), at the average temperature, Tav, for [Cnmim][OAc] (n = 4, 6) were determined. Using the established method, the difference of heat capacities between the vapor phase and the liquid phase, ΔglC°pm, for [Cnmim][OAc] (n = 4, 6) were calculated based on the statistical thermodynamics. Therefore, the value of ΔglH°m(Tav) can be transformed into ΔglH°m(298) by using ΔglC°pm. The vaporization enthalpies were also further tested by molecular dynamic (MD) simulations, and the results were in good agreement with the corresponding experimental values. In terms of the new scale of polarity for ILs, the order of the polarity of [Cnmim][OAc] (n = 4, 6) was also predicted and good agreement with our experiences.