C-beta-H stretching vibration as a new probe for conformation of n-propanol in gaseous and liquid states
C-beta-H stretching vibration as a new probe for conformation of n-propanol in gaseous and liquid states
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C-β-H伸缩振动作为气态和液态正丙醇构象的新探针
DOI：
10.1039/c6cp00244g
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发表时间：
2016
影响因子：
3.3
通讯作者：
Liu Shilin
中科院分区：
文献类型：
--
作者：
Yu Yuanqin;Wang Yuxi;Hu Naiyin;Lin Ke;Zhou Xiaoguo;Liu Shilin
在有机化学和生物化学中，开发潜在的探针来鉴定分子构象是必不可少的。在这项工作中，我们研究了特定的C-H伸缩振动作为构象探针的模型化合物，1，1，3，3，3-氘代正丙醇（CD3CH2CD2OH），使用受激光声拉曼光谱在气相和传统的自发拉曼光谱在液体状态。沿着量子化学计算，实验结果表明，CH 2在β-碳位的对称伸缩模对正丙醇的构象结构非常敏感，可以作为正丙醇所有5种构象的新探针。与正丙醇的构象传感器O-H伸缩振动相比，本文提出的C β-H伸缩振动在液态下具有更好的构象分辨能力。利用该探针研究了正丙醇在纯液体和稀水溶液中的构象选择性。结果表明，在纯液体中，正丙醇分子更倾向于反式-OH构象，而在稀水溶液中，这种倾向性增强，说明水分子对反式-OH正丙醇构象起着进一步稳定的作用.这导致构象演变，即具有gauche-OH结构的正丙醇分子在用水稀释后转移到反式-OH结构。这些结果不仅为正丙醇在不同环境中的结构提供了重要的信息，而且也表明了C-H伸缩振动作为构象分析的一种新工具的潜力.当考虑到烃链是有机和生物分子中的结构单元时，这一点尤其重要。
The development of potential probes to identify molecular conformation is essential in organic and biological chemistry. In this work, we investigated a site-specific C–H stretching vibration as a conformational probe for a model compound, 1,1,3,3,3-deuterated n-propanol (CD3CH2CD2OH), using stimulated photoacoustic Raman spectroscopy in the gas phase and conventional spontaneous Raman spectroscopy in the liquid state. Along with quantum chemistry calculations, the experiment shows that the CH2 symmetric stretching mode at the β-carbon position is very sensitive to the conformational structure of n-propanol and can serve as a new probe for all five of its conformers. Compared with the O–H stretching vibration, a well-established conformational sensor for n-propanol, the Cβ–H stretching vibration presented here shows better conformational resolution in the liquid state. Furthermore, using this probe, we investigated the conformational preference of n-propanol in pure liquid and in dilute water solution. It is revealed that in pure liquid, n-propanol molecules prefer the trans-OH conformation, and in dilute water solution, this preference is enhanced, indicating that the water molecules play a role of further stabilizing the trans-OH n-propanol conformers. This leads to conformational evolution that n-propanol molecules with gauche-OH structure are transferred to the trans-OH structure upon diluting with water. These results not only provide important information on structures of n-propanol in different environments, but also demonstrate the potential of the C–H stretching vibration as a new tool for conformational analysis. This is especially important when considering that hydrocarbon chains are structural units in organic and biological molecules.