Supersonic molecular jet spectroscopy of ethylbenzene, the ethyltoluenes, and the diethylbenzenes
Supersonic molecular jet spectroscopy of ethylbenzene, the ethyltoluenes, and the diethylbenzenes
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DOI：
10.1063/1.453019
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发表时间：
1987-09
影响因子：
4.4
通讯作者：
P. Breen;E. Bernstein;J. I. Seeman
中科院分区：
文献类型：
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作者：
P. Breen;E. Bernstein;J. I. Seeman
给出了喷射冷却1,2‐，1,3‐和1,4‐二乙苯以及2‐，3‐和4‐乙基甲苯的S1←s起源区域的飞行时间质谱。二乙基苯的光谱有两个来源，分别是相对于芳环的乙基的顺构象和反构象。在1,3 -二乙基苯光谱中存在两个原点，而在3 -乙基甲苯光谱中只有一个原点，这强烈表明乙基的稳定取向是乙基的β -碳原子垂直于芳香环的平面。通过将甲基视为一维刚性转子，并将计算的能级与光谱中观测到的特征拟合，得到了环甲基旋转势垒的大小和形状。对异构体B=5.20 cm−1,V6=31.00 cm−1；对间异构体B=5.40 cm−1,V3=78.00 cm−1；对邻异构体B=5.50 cm−1,V3=89.00 cm−1)结果表明，甲基的分子量和分子量均大于0。
Time‐of‐flight mass spectra are presented for the S1←S0 origin region of jet‐cooled 1,2‐, 1,3‐, and 1,4‐diethylbenzene, and 2‐, 3‐, and 4‐ethyltoluene. The spectra for the diethylbenzenes exhibit two origins which are assigned to syn and anti conformations of the ethyl groups relative to the aromatic ring. The existence of two origins in the 1,3‐diethylbenzene spectrum, and only one in the 3‐ethyltoluene spectrum, strongly implies that the stable orientation of the ethyl groups is with the β‐carbon atom of the ethyl group projecting perpendicular to the plane of the aromatic ring. The size and shape of the potential barrier to rotation of the ring methyl group is obtained by treating the methyl group as a one‐dimensional rigid rotor and fitting the calculated energy levels to observed features in the spectra. The results (for the para isomer B=5.20 cm−1, V6=31.00 cm−1; for the meta isomer, B=5.40 cm−1, V3=78.00 cm−1; and for the ortho isomer, B=5.50 cm−1, V3=89.00 cm−1) indicate that the methyl group expe...