在溶液中寻找对称的C-F-C离子:动态同位素效应,合成标记和计算,溶剂和速率研究
Mark D Struble1, Maxwell Gargiulo Holl1, Michael T Scerba1
1Department of Chemistry, Johns Hopkins University , 3400 North Charles Street, Baltimore, Maryland 21218, United States.
Journal of the American Chemical Society
|August 16, 2015
概括
这项研究提供了对称离子中间体溶液的全面证据. 这一发现得到了动态同位素效应实验和DFT计算的支持,揭示了可调节的SN1反应机制.
科学领域:
- 有机化学
- 反应机制
- 计算化学
背景情况:
- 根据有限的同位素标记,先前的研究表明来自前体的对称离子 ([C-F-C](+).
- 一个强有力的科学主张需要广泛而多样化的支持证据.
研究的目的:
- 为了全面验证对称离子中间体的存在.
- 通过详细的实验和计算研究阐明反应机制.
- 研究影响反应途径和中间稳定的因素.
主要方法:
- 广泛的同位素标记研究.
- 动态同位素效应 (KIE) 测量 (二次和远程测量).
- 密度函数理论 (DFT) 的计算.
- 包括对照基质在内的合成研究.
- 在不同的溶剂和添加剂条件下进行测量.
主要成果:
- 二次KIE实验和远程同位素效应证实了在过渡状态中的参与.
- DFT计算和KIE数据显示了对称离子中间体的捕获.
- 一个表皮原体的水解也会捕获离子,这表明参与的前沿SNi机制.
- 通过溶剂和添加剂调节SN1反应的速率决定步骤.
- 合成了一种非化对照基质,以比较无化辅助剂.
结论:
- 反应系统完全通过"可调节"的SN1机制进行,其中涉及离子中间体.
- 即使在强迫条件下,也没有观察到像SN2这样的替代反应途径.
- 这些发现为对称离子及其在反应中的作用提供了强有力的证据.
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