在离子S(N) 2反应中,固体和溶解效应
Xin Chen1, Colleen K Regan, Stephen L Craig
1Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA.
Journal of the American Chemical Society
|October 22, 2009
概括
对S(N) 2反应的溶解效应显示最小的尺寸依赖. 在基尼特中,固体阻碍在气体和溶液阶段是相似的,这表明了补偿溶解效应.
科学领域:
- 有机化学 有机化学
- 物理化学 物理化学
- 计算化学的计算化学
背景情况:
- 绝缘效应显著影响有机化学中的反应速率.
- 了解溶解在S(N) 2反应中的作用对于预测反应性至关重要.
研究的目的:
- 为了研究溶解对S(N) 2反应中的固态效应的贡献.
- 为了比较气体和溶液阶段的固态效应,使用基尼特作为模型系统.
主要方法:
- 化物离子反应与基尼特利尔的实验动力学研究.
- 理论研究,包括偏振连续模型和QM/MM模拟.
主要成果:
- 在β-碳中增加的替代始终降低了反应性,表明了固态阻碍.
- 在气相和溶液相中,固态阻碍的幅度相似.
- 过渡状态的溶解能量显示对替代物大小的依赖性很弱.
结论:
- 溶解不会显著改变这些S(N) 2反应中的固体效应.
- 较弱的尺寸依赖性是由于直接屏蔽和间接溶解效应之间的补偿.
- 这些发现与其他离子系统形成鲜明对比,其中溶解强烈取决于大小.
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