抽象与素交换的障碍:电荷转移结合的实验表现
Philippe C Hiberty1, Claire Megret, Lingchun Song
1Laboratoire de Chimie Physique, Groupe de Chimie Théorique, Université de Paris-Sud, 91405 Orsay Cédex, France. philippe.hiberty@lcp.u-psud.fr
Journal of the American Chemical Society
|March 2, 2006
概括
交换和抽象反应的反应障碍的差异量化了X-H键中的共价离子共振能量. 这凸显了电荷转移键在化学反应中的重要作用,特别是化 (H-F).
科学领域:
- 化学动力学 化学动力学
- 量子化学 是一个量子化学.
- 理论化学 理论化学
背景情况:
- 了解化学键的性质,特别是共价离子共振,对于预测反应动态至关重要.
- 交换 (H + XH) 和抽象 (X + HX) 反应为研究这些键特性提供了一个框架.
研究的目的:
- 研究反应障碍与H-X键 (X = F,Cl,Br) 中的共价离子共振能之间的关系.
- 用价值键分析阐明共价和离子结构对反应障碍的贡献.
主要方法:
- 结合集群的单元和双元激发和扰动三倍校正 (CCSD(T)) 计算.
- 呼吸轨道价值键 (BOVB) 方法用于价值键 (VB) 分析.
主要成果:
- 对共价结构的障碍在两个反应序列中都是相同的;在素交换中,较高的障碍是由于离子结构的混合效率较低而产生的.
- HXH和XHX反应序列之间的屏障差异与共价离子共振能量相关,从F下降到I.
- F键表现出最大的共价离子共振能量 (87 kcal/mol),导致最大的屏障差异 (22 kcal/mol).
结论:
- 屏障差异在实验中测量了共价离子共振能量.
- 交换反应中的高屏障是H-F键中电荷转移结合的实验指标.
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