对氧,和基的利离子的易斯酸度尺度
Robert J Mayer1, Armin R Ofial1, Herbert Mayr1
1Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstrasse 5-13, 81377 München, Germany.
Journal of the American Chemical Society
|March 4, 2020
概括
这项研究量化了离子的易斯酸度和各种的易斯度,揭示了线性自由能量关系. 发现突出了解决方案
科学领域:
- 超分子化学
- 物理有机化学
- 热力学
背景情况:
- 二盐 (Ar2I+X-) 是有机合成中的多功能试剂.
- 了解它们与易斯基的相互作用对于预测反应性至关重要.
- 之前的研究已经探讨了易斯酸相互作用,但缺乏对离子的综合尺度.
研究的目的:
- 系统地研究17种利盐与11种不同的易斯基的平衡常数.
- 建立一个线性自由能量关系 (LFER),描述离子的易斯酸度和各种核友的易斯度.
- 阐明影响离子形成的热力学和动力学因素.
主要方法:
- 在20°C时使用定位方法 (光度计,导电计) 和异热定位热量计 (ITC) 确定平衡常数 (KI).
- 应用了线性自由能量关系 (lg KI = s I LAI + LBI) 来量化易斯酸度 (LAI) 和易斯度 (LBI).
- 进行了温度依赖的平衡测量和动力学研究 (酸盐转移),以分析热力学贡献和反应机制.
主要成果:
- 平衡常数跨越六个数量级,使得一个强大的LFER能够发展.
- 成功确定了17个离子的易斯酸度参数 (LAI) 和10个易斯基的易斯度参数 (LBI) 和易感度 (sI).
- 观察到对吉布斯反应能量的显著值贡献,归因于溶解效应. 酸转移动力学遵循通过SN1型机制的第一阶段速率定律.
结论:
- 已建立的LFER为了解离子与易斯酸相互作用提供了定量框架.
- 对离子的易斯基本值不同于对离子的易斯基本值,表明不同的热力学控制因子.
- 溶解效应在形成的热力学中起着至关重要的作用,而离子转移的动力学是机械定义的.
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