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研究了某些长链碳氢化合物和甾体化合物的C—H伸缩振动谱带的光谱行为差异 .结果发现 ,在低温下 ,甾体化合物的C—H伸缩振动谱带存在复杂的精细结构 ,而长链碳氢化合物的谱带结构却相当简单 .MM 3分子力学计算表明 ,长链碳氢化合物的C—H基团以大规模偶合方式振动 ,其中少数几种振动模式由于采取同步同相振动 ,使其偶极矩变化得到同向加强 ,强度大大增加 ,因而在光谱上掩盖了其他模式的振动 ,造成谱带结构的简单化 .在甾体化合物中 ,C—H基团以局部偶合的方式振动 ,由于不存在同相加强效应 ,不同谱带之间强度差异不大 ,使得谱带存在复杂的精细结构 .造成上述光谱行为差异的一个主要原因是长链碳氢化合物的C—H基团所处的微环境大致相同 ,而甾体化合物的不同C—H基团所处的微环境差异较大 .
The spectral behavior of some C-H stretching vibration bands of some long-chain hydrocarbons and steroids was studied. The results showed that the C-H stretching vibration band of the steroid compound had complex fine structure at low temperature, However, the band structure of long-chain hydrocarbons is rather simple.MM 3 Molecular mechanics calculations show that the C-H groups of long-chain hydrocarbons vibrate in a large-scale coupling mode, and a few of the vibration modes adopt synchronous in-phase vibration , So that the dipole moment changes to be strengthened in the same direction, the intensity is greatly increased, thus spectrally masking the vibration of other modes, resulting in the simplification of the band structure.In the steroidal compounds, C-H groups to the local coupling Mode vibration, because there is no in-phase enhancement effect, the intensity difference between different bands is not large, making the band there is a complex fine structure.Small spectral differences caused by one of the main reasons for the long-chain hydrocarbon C-H group The microenvironment in which they are located is roughly the same, but the microenvironment in which the different C-H groups of the steroid compound are located is quite different.