乙和甲稳定化物的两性反应性
Peter A Byrne1, Konstantin Karaghiosoff1, Herbert Mayr1
1Department Chemie, Ludwig-Maximilians-Universität München , Butenandtstraße 5-13, 81377 München, Germany.
Journal of the American Chemical Society
|August 9, 2016
概括
这项研究研究了稳定型化物与离子的反应,揭示氧攻击通常比碳攻击更快. 维蒂格反应通过协同循环加法进行,挑战传统的选择性预测.
科学领域:
- 有机化学
- 反应动力学
- 光谱学
背景情况:
- 稳定的化物作为两性核友,能够在氧和α-碳上反应.
- 基离子是与核友反应的电友,其区域选择性受易斯酸度等因素的影响.
- 了解核友攻击机制对于预测反应结果和设计合成策略至关重要.
研究的目的:
- 研究甲基和乙基稳定化物与酸离子之间的动力学和反应机制.
- 确定O攻击与C攻击的速率常数,并推导出核友特异性参数 (N和sn).
- 合理化这些反应的区域选择性,并与已确定的化学原理比较,如HSAB.
主要方法:
- 使用紫外线和核磁共振光谱来监测反应进展并确定中间体.
- 对O和C攻击途径确定了二次速率常数.
- 核友特异性参数 (N和sN) 使用相关性lgk (20°C) =sN(E+N进行计算.
主要成果:
- 基离子对化物的氧攻击通常比碳攻击更快.
- 最初形成的O攻击产物 (基基离子) 只能与高度酸性的基离子观察到;否则,它们会重新排列为C攻击产物.
- 乙稳定型化物与化物的维蒂格反应明显快于预测的C-或O-攻击率,这表明一个协调的 [2+2] 循环添加机制.
结论:
- 这项研究提供了动力学数据和机械学见解,以了解稳定化物与酸离子的双重反应性.
- 传统的选择性模型如HSAB和电荷/轨道控制被发现不足以预测这些反应的区域选择性.
- 维蒂格反应机制被证实是协调的 [2+2] 循环添加,与简单的核友攻击途径不同.
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