Dynamics effects on an E2/E1cb borderline mechanism: unimolecular elimination of 2-aryl-3-chloro-2-R-propanols.
Dynamics effects on an E2/E1cb borderline mechanism: unimolecular elimination of 2-aryl-3-chloro-2-R-propanols.
复制标题
动力学对 E2/E1cb 边界机制的影响：2-芳基-3-氯-2-R-丙醇的单分子消除。
作者：
Shuhei Itoh;H. Yamataka
在HF、M05-2X和MP2理论水平上，对碱促进的2-芳基-3-氯-2-R-丙醇消除反应的协同E2和分步E1 cb之间的机理二分法进行了计算研究。过渡态（TS）和反应中间体的优化以及内禀反应坐标（IRC）计算表明，每种底物都有一条单一的反应路线，通过引入吸电子取代基使碳负离子中间体更稳定，反应机理可以从E2转变为E1 cb.分子动力学模拟表明，轨迹开始于一个单一的TS直接导致两个产品区域;碳负离子中间区域在E1 cb机制，和烯烃产品区域在E2机制，通过路径分叉后的TS。本系统是闭壳层分子反应中分支的一个新例子。整体反应机制动态变化，从E2到E1 cb的E2和E1 cb轨迹的比例逐渐变化，而不是在并发途径的路径切换。
The mechanistic dichotomy between concerted E2 and stepwise E1cb of the base-promoted elimination of 2-aryl-3-chloro-2-R-propanols was examined computationally at the HF, M05-2X, and MP2 levels of theory. Optimizations of transition states (TSs) and reaction intermediates, and intrinsic reaction coordinates (IRC) calculations showed that there was a single reaction route for each substrate, and that the mechanism could be changed from E2 to E1cb by making a carbanion intermediate more stable through the introduction of electron-withdrawing substituents. Molecular dynamics simulations revealed that trajectories started at a single TS led directly to two product regions; the carbanion intermediate region in the E1cb mechanism, and the alkene product region in the E2 mechanism, through path bifurcation after the TS. The present system is a new example of bifurcation in reactions of closed-shell molecules. The overall reaction mechanism changes dynamically from E2 to E1cb by a gradual change in the ratio of E2 and E1cb trajectories, rather than a path switch in concurrent pathways.
影响因子：
15
作者：
Thomas, Jacqueline B.;Waas, Jack R.;Harmata, Michael;Singleton, Daniel A.
通讯作者：
Singleton, Daniel A.
影响因子：
3.6
作者：
Celebi-Oelcuem, Nihan;Ess, Daniel H.;Houk, K. N.
通讯作者：
Houk, K. N.
影响因子：
15
作者：
Bekele, T;Christian, CF;Singleton, DA
通讯作者：
Singleton, DA