单片氧的反应的机制. 一个两步的无中间机制
Daniel A Singleton1, Chao Hang, Michael J Szymanski
1Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842, USA. singleton@mail.chem.tamu.edu
Journal of the American Chemical Society
|January 30, 2003
概括
使用同位素效应研究单片氧与的反应机制,揭示了标准理论计算的局限性. 高级计算方法准确地预测了实验数据,显示了两个没有中间体的过渡状态.
科学领域:
- 物理有机化学 有机化学
- 计算化学计算化学
- 反应机制研究 反应机制研究
背景情况:
- 反应是一种基本的有机转化,涉及单片氧和.
- 了解反应机制对于预测反应性和设计合成策略至关重要.
- 以前的理论研究已经提供了洞察力,但往往难以准确地复制实验观测.
研究的目的:
- 阐明单片氧和简单基之间的反应的详细机制.
- 评估各种理论计算方法在预测实验同位素效应方面的准确性.
- 开发一个可靠的计算模型来描述一个反应路径.
主要方法:
- 试验确定分子间和分子内碳-13 ((13) C) 和 ((2) H) 动态同位素效应.
- 使用各种方法进行理论计算,包括RHF,CASSCF和B3LYP.
- 高级合集群单双与扰动三倍 (CCSD(T)) 单点能量计算在B3LYP优化几何上.
主要成果:
- 对2,4-二甲基-3-异-2-的实验性 (13) C同位素效应很小,对烯酸碳的效应几乎相同.
- 标准理论方法 (RHF,CASSCF,B3LYP) 无法准确预测实验中的同位素效应.
- 通过CCSDT//B3LYP计算方法,成功地重现了实验中的 (13) C和 (2) H同位素效应和反应屏障.
结论:
- 一种新的计算策略,将高级单点能量计算与DFT几何相结合,提供了准确的机械洞察力.
- 经过验证的计算模型揭示了一个能量表面,有两个相邻的过渡状态,没有中间状态.
- 这项研究提供了第一个实验支持的这样一个反应表面的例子,其中包括一个山谷 - 丘陵的拐点.
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