Iwamoto Reikichi, Nara Akishi, Matsuda Toshihiko
KRI Inc., Chudojiminamimachi 134, Shimogyoku, Kyoto, 600-8813 Japan.
Appl Spectrosc. 2006 Apr;60(4):450-8. doi: 10.1366/000370206776593627.
We characterized near-infrared spectra of the CH2 sequence in CH2X2 (X=halogen), CH2ClCHCl2, and CH3(CH2)5CH3. Each near-infrared absorption in the region from 3500 to 10,000 cm-1 is consistently assigned to one of the five different combination or overtone groups, in the order of increasing frequency, of the {[v(CH)]+[delta(CH)]} (A), {[v(CH)]+[2delta(CH)]} (B), [2v(CH)] (C), {[2v(CH)]+[delta(CH)]} (D), and [3v(CH)] (E) types, where v(CH) and delta(CH) denote the CH stretching and CH deformation normal modes, respectively. Each group has its own characteristic frequency zone. The bands of B, D, and E, which are second-order combinations or overtones, are weaker by 1/10-1/50 than those of A and C, which are first-order combinations or overtones. The near-infrared spectra of the CH2 sequence show "window zones" of very weak or no absorptions. This suggests that we can perceive the characteristic near-infrared bands of a functional group through the window zones, and we give an example to demonstrate this. The first-order combination bands of type A only of CH2X2 are reasonably assigned to a pair of the normal modes of v(CH) and delta(CH). From this we predict that the first-order combination bands should give structural information on the CH2 chain, similar to the infrared fundamental bands.
我们对CH2X2（X = 卤素）、CH2ClCHCl2和CH3(CH2)5CH3中CH2序列的近红外光谱进行了表征。在3500至10,000 cm-1区域内的每个近红外吸收均被一致地归属为五个不同的组合或泛音组之一，按照频率递增的顺序，分别为{[v(CH)] + [δ(CH)]} （A）、{[v(CH)] + [2δ(CH)]} （B）、[2v(CH)] （C）、{[2v(CH)] + [δ(CH)]} （D）和[3v(CH)] （E）类型，其中v(CH)和δ(CH)分别表示CH伸缩振动和CH变形的简正模式。每个组都有其自己的特征频率区域。B、D和E带是二级组合或泛音带，比一级组合或泛音带A和C弱1/10 - 1/50。CH2序列的近红外光谱显示出非常弱或无吸收的“窗口区域”。这表明我们可以通过窗口区域感知官能团特征近红外带，并且我们给出一个例子来证明这一点。仅CH2X2中A类型的一级组合带被合理地归属为v(CH)和δ(CH)的一对简正模式。由此我们预测一级组合带应给出与红外基频带类似的关于CH2链的结构信息。
