Identification of Alcohol Conformers by Raman Spectra in the C-H Stretching Region
Identification of Alcohol Conformers by Raman Spectra in the C-H Stretching Region
复制标题
C-H 拉伸区域拉曼光谱鉴定酒精构象异构体
DOI：
10.1021/jp513027r
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发表时间：
2015-04-02
影响因子：
2.9
通讯作者：
Luo, Yi
中科院分区：
文献类型：
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作者：
Chen, Lin;Zhu, Weiduo;Luo, Yi
在C-H伸缩区记录了正、氘代醇（C-2-C-5）的自发偏振拉曼光谱。在各向同性的拉曼光谱中，所有醇在低于2900 cm（-1）和高于2950 cm（-1）处都有一个-C α H伸缩振动的双峰。通过比较各种氘代醇的实验和计算光谱，双峰归因于不同构象的-C α H伸缩振动。对于乙醇，在2970 cm（-1）处观察到的谱带被指定为在gauche构象异构体的C-alpha-O-H平面中的-C alpha H的伸缩振动，而在2895 cm（-1）处的谱带由反式构象异构体的-C alpha H2对称伸缩振动和gauche构象异构体的C-alpha-O-H平面外的-C alpha H伸缩振动贡献。估计液体乙醇中的gauche构象异构体的数量为54%。对于较大的醇，同样的分配的双峰，和gauche构象与平面碳骨架的人口被发现略大于乙醇，这是一致的分子动力学模拟的结果。
The spontaneous polarized Raman spectra of normal and deuterated alcohols (C-2-C-5) have been recorded in the C-H stretching region. In the isotropic Raman spectra, a doublet of -C alpha H stretching vibration is found for all alcohols at below 2900 cm(-1) and above 2950 cm(-1). By comparing the experimental and calculated spectra of various deuterated alcohols, the doublets are attributed to the -C alpha H stretching vibration of different conformers. For ethanol, the band observed at 2970 cm(-1) is assigned as the stretching vibration of -C alpha H in the C-alpha-O-H plane of the gauche-conformer, while the band at 2895 cm(-1) is contributed from both the -C alpha H2 symmetrical stretching vibration of the trans-conformer and the -C alpha H stretching vibration out of the C-alpha-O-H plane of the gauche-conformer. The population of gauche-conformer is estimated to be 54% in liquid ethanol. For the larger alcohols, the same assignments for the doublet are obtained, and the populations of gauche-conformers with plane carbon skeleton are found to be slightly larger than that of ethanol, which is consistent with results from molecular dynamics simulations.