Secondary Deuterium Kinetic Isotope Effects in the Rotations of Alkenes and Allyl Radicals: Theory and Experiment
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- 作者：Leif P. Olson ; Satomi Niwayama ; Hi-Young Yoo ; K. N. Houk ; Nathan J. Harris ; and Joseph J. Gajewski
- 刊名：Journal of the American Chemical Society
- 出版年：1996
- 出版时间：January 31, 1996
- 年：1996
- 卷：118
- 期：4
- 页码：886 - 892
- 全文大小：178K
- 年卷期：v.118,no.4(January 31, 1996)
- ISSN：1520-5126
文摘
Secondary deuterium kinetic isotope effects (KIEs) associated withrestricted rotation about the C-Cbonds of ethylene, propene, and allyl radical substituted by H or Dwere calculated. Geometries and force constantsof ground states and transition states were obtained by abinitio MCSCF calculations with the 6-31G* and/or6-311G**basis sets. The KIEs were then calculated from the partitionfunctions for the Bigeleisen equation. The"rotational"KIEs are predicted to be larger than typical secondary KIEs. Forsimple alkenes, predictedkH/kD values rangefrom1.32-1.46 at 25 
C to 1.15-1.25 at 275 C. Predictedvalues are compared with existing experimental results.Asa test of our prediction that high-temperature alkene isomerizationsshould display large KIEs, samples of cis-stilbene and 
,'-dideuterio-cis-stilbene were pyrolyzed;the measured KIE was a remarkablekH/kD2 = 1.47 ±0.13(
n) at 287 C.
C to 1.15-1.25 at 275 C. Predictedvalues are compared with existing experimental results.Asa test of our prediction that high-temperature alkene isomerizationsshould display large KIEs, samples of cis-stilbene and ,'-dideuterio-cis-stilbene were pyrolyzed;the measured KIE was a remarkablekH/kD2 = 1.47 ±0.13(n) at 287 C.