酸氧化基. 基的氧化. 替代剂和溶剂的影响. 在MP2计算方面遇到困难
Kenneth B Wiberg1, Yi-gui Wang, Stepan Sklenak
1Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, USA.
Journal of the American Chemical Society
|August 31, 2006
概括
对基的酸氧化进行了计算和实验研究. 计算揭示了一个影响激活能量的中间复合体,在高介电介质中减少,与实验结果保持一致.
科学领域:
- 物理化学 物理化学
- 有机化学 有机化学
- 计算化学计算化学
背景情况:
- 酸氧化是有机合成中的一个关键反应.
- 了解反应机制,包括过渡状态和替代剂效应,对于控制反应性至关重要.
研究的目的:
- 通过计算来研究基的甲酸氧化过渡状态结构.
- 将理论计算与实验数据进行比较,并阐明差异.
- 为了确定溶剂介电常数对反应能量的影响.
主要方法:
- 在B3LYP/6-311++G**级别进行密度函数理论 (DFT) 计算.
- 反应场计算以模拟溶剂效应.
- 第二阶MøllerPlesset扰动理论 (MP2) 和合集群 (CCSD) 的计算进行比较.
- 试验确定反应速率和产品分析.
主要成果:
- DFT计算预测了一个影响激活能量的中间电荷双极复合体.
- 反应场的计算表明,这种复合物在高介电介质中解离,从而缩小了激活能量范围.
- CCSD计算为和酸盐离子提供了准确的结果,表明乙烯氧化早期过渡状态.
- 发现反应具有高度的外热性 (-69 kcal/mol),通过热量计证实了这一点.
- 对醇和烯酸的实验研究显示了类似的反应性.
结论:
- 这项研究阐明了介质复合物在甲酸烯氧化中的作用.
- 计算方法,特别是CCSD,可以准确地建模这些反应.
- 溶剂的影响显著影响反应路径和能量.
- 实验验证证证实了外热性质,并为特定基质提供了动力数据.
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