RAMAN FREQUENCIES OF NORMAL-PARAFFIN MOLECULES
RAMAN FREQUENCIES OF NORMAL-PARAFFIN MOLECULES
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DOI：
10.1021/ja01172a050
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发表时间：
1949-01-01
影响因子：
15
通讯作者：
SIMANOUTI, T
中科院分区：
文献类型：
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作者：
MIZUSHIMA, SI;SIMANOUTI, T
本实验室Mizu-shima、Morino、Watanabe、Simanouti等人对二卤化乙烯的拉曼效应、红外吸收、偶极矩和电子衍射的实验结果1表明，在以碳单键为轴的一次完整旋转中存在三个潜在的极小值（图1）。这三个潜在的最小值对应于一个反式(T)，其中两个卤素原子相距最远，从反式内旋±120度可以得到两个间扭式（G和G'）（见图2）。反式和间扭式最小值之间的能量差为1千卡/摩尔（二氯乙烯为1.2千卡，二溴乙烯为1.3千卡），由此可以很容易地计算出气态的平衡同分异构体比，但由于分子间效应，该比在液态中自然地变得不同。在固态中，分子间力（即晶体力）起着如此重要的作用，以至于只使转变稳定，这从凝固时分配给间扭式的拉曼线的消失中最清楚地看到。2
I. Intramolecular Rotation The experimental results of Raman effect, infra-red absorption, dipole moment and electron diffraction made for ethylene dihalides by Mizu-shima, Morino, Watanabe, Simanouti, andothers in our Laboratory1 has shown that there are three potential minima in one complete rotation about a carbon single bond as axis (Fig. 1). These three potential minima corre-spond to one trans form (T) in which two halogen atoms are at the farthest distance apart andtwo gauche forms (G and G') obtainable from the trans formby internal rotation of±120 (see Fig. 2). The energy difference between the trans and the gauche minima amounts to 1 kcal./mole (1.2 kcal. for ethylene dichloride and 1.3 kcal. for ethylene dibromide), from which the equi-librium isomeric ratio in the gaseous state can readily be calculated, but this ratio becomes naturally differ-ent in the liquid state owing to the intermolecular effect. In the solid state the intermolecular force (i. e., crystal force) plays such a predominant role as to make only the trans form stable, which is most clearly seen from the disappearance of Raman lines assigned to gauche form on solidification. 2