双碳醇水溶液的~1H NMR实验与理论分析（英文）

发布时间：2018-11-04 08:38

【摘要】：采用核磁共振氢谱(~1H NMR)和量子化学(QC)方法研究不同温度下乙醇水溶液和乙二醇水溶液中醇与水之间的相互作用。观察实验结果发现两种醇水溶液中水质子的化学位移呈现两种不同的变化趋势。随着含水量的增加,乙醇(ET)水溶液中水质子化学位移急剧降低,而乙二醇(EG)水溶液中水质子的化学位移缓慢增加。两种醇水溶液中的羟基质子随着浓度的增加,其共振峰移向低场。不同温度下随着浓度的增加两种醇水溶液的烷基质子共振峰单调的移向低场。几何结构优化结果表明醇羟基质子与水质子之间氢键的形成弱化了醇中O—H键,从而导致其键长增加。值得注意的是在相同的极化作用和扩散作用下采用密度泛函理论(DFT)(B3LYP)计算得到的ET和EG的C-H键,C-C键和O-H键的键长值大于采用HF理论计算得到的结果。与此相反的是采用HF理论得到的ET和EG的O-H…O键强度大于采用DFT(B3LYP)理论得到的结果。几何构型优化结果与实验结果相吻合。在NMR化学位移的计算中,就文中所提到的理论水平而言,DFT要优于HF。而对于同一理论,其基组越大,计算值越接近实验值。
[Abstract]:The interaction between alcohols and water in ethanol aqueous solution and ethylene glycol aqueous solution at different temperatures was studied by 1H NMR and quantum chemical (QC) method. The experimental results show that the chemical shifts of water in two kinds of alcohol aqueous solutions show two different trends. With the increase of water content, the chemical shift of water in ethanol (ET) aqueous solution decreases sharply, while that in ethylene glycol (EG) aqueous solution increases slowly. With the increase of concentration, the resonance peak of hydroxy proton in two kinds of alcohol aqueous solution shifts to low field. At different temperatures, the alkyl proton resonance peaks of two kinds of alcohol aqueous solutions move monotonously to the low field with the increase of the concentration. The results of geometric structure optimization show that the formation of hydrogen bond between hydroxy proton and water ions weakens the O-H bond in alcohol, which leads to the increase of bond length. It is worth noting that the C-H bond of ET and EG is calculated by using density functional theory (DFT) (B3LYP) under the same polarization and diffusion. The bond length of C-C bond and O-H bond is larger than that calculated by HF theory. In contrast, ET and EG's O-H are obtained by using HF theory. The O bond strength is higher than that obtained by DFT (B3LYP) theory. The results of geometric configuration optimization are in agreement with the experimental results. In the calculation of NMR chemical shifts, DFT is superior to HF. in terms of the theoretical level mentioned in this paper. For the same theory, the larger the base set, the closer the calculated value is to the experimental value.
【作者单位】：合肥工业大学汽车与交通工程学院;合肥工业大学电气与自动化工程学院;
【分类号】：O645.11

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