正壬烷构象的振动光谱研究

Vibrational study of the chain conformations of n-Nonane

对于含有一个gauche构象的正壬烷,包括全反式构象在内主要有四种稳定构象。为了得到各种构象与特征频率之间的对应关系,运用从头计算方法分别计算出了这四种构象的红外振动频率以及相应强度。根据其振动强度以及振动特征,特别是振动发生在gauche位置的振动模式,得到了各种构象在整个范围内的红外光谱特征峰以及相同振动模式随构象变化的规律。这不但弥补了正壬烷链构象实验研究的不足,而且还起到一定的理论指导作用。

Ab initio calculations have been used to compute normal mode frequencies and intensities of four stable conformations of n-nonane, including the all-trans form and the three conformations with one gauche arrangement. By analysis of the intensities and other characteristics of the normal modes, particularly those associated with the gauche arrangement, the correlation between IR frequency and conformation was established over the full spectral range. The results obtained provide a mean of resolving ambiguities in the.interpretation of the experimental vibrational spectrum of n-nonane and are also of fundamental interest.