Transition-State Geometry Measurements from 13C Isotope Effects. The Experimental Transition State for the Epoxidation of Alkenes with Oxaziridines
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- 作者：Jennifer S. Hirschi ; Tetsuya Takeya ; Chao Hang ; Daniel A. Singleton
- 刊名：Journal of the American Chemical Society
- 出版年：2009
- 出版时间：February 18, 2009
- 年：2009
- 卷：131
- 期：6
- 页码：2397-2403
- 全文大小：216K
- 年卷期：v.131,no.6(February 18, 2009)
- ISSN：1520-5126
文摘
We here suggest and evaluate a methodology for the measurement of specific interatomic distances from a combination of theoretical calculations and experimentally measured 13C kinetic isotope effects. This process takes advantage of a broad diversity of transition structures available for the epoxidation of 2-methyl-2-butene with oxaziridines. From the isotope effects calculated for these transition structures, a theory-independent relationship between the C−O bond distances of the newly forming bonds and the isotope effects is established. Within the precision of the measurement, this relationship in combination with the experimental isotope effects provides a highly accurate picture of the C−O bonds forming at the transition state. The diversity of transition structures also allows an evaluation of the Schramm process for defining transition-state geometries on the basis of calculations at nonstationary points, and the methodology is found to be reasonably accurate.