• 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Chemistry: A European journal >The Mechanism of the Photochemical Hydrogen Migration in 1,3,5-Cycloheptatriene: A Theoretical Study
【24h】

The Mechanism of the Photochemical Hydrogen Migration in 1,3,5-Cycloheptatriene: A Theoretical Study

机译：1,3,5-环庚三烯中光化学氢迁移的机理：理论研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Based on CASSCF calculations for the reaction profile of the photochemical [1,7]-sigmatropic hydrogen shift in 1,3,5-cycloheptatriene (CHT), the detailed mechanism of the excited-state reaction is discussed. The results are in agreemetn with the obsered ultrafast rates for passage from the initially-excited 1 A” state by way of the dark 2 A' state to the ground-state (1 A') potential-energy surface. The kinetics and the selectivity of the reaction are characterized by a small energy barrier on teh dark 2A' state that separates the excited-state minimum from a contical intersectio at pericyclic geometries. This intersection is responsible for efficient, excited-state deactivatio. At the CASSCF level the barrier height is calculated to be 7.3 kcal mol~(-1). If dynamci correlatin effects are taken into account with the CASPT2 method, the barrier is reduced to 3.8 kcal mol~(-1). The existence of an excited-state barrier as the decisive mechanistic feature of the hydrogen migration was verified by considering 1-substituted CHT. The barriers calcualted for sigmatropic shifts away form and toward the substituent differ considerably. In agreement with experimental observatin, the smaller barrier is found for migration away from an acceptor and toward a donor substituent. The differences in barrier height are in excellent agreement with the experimentally observed product distriubtion.
机译：基于CASSCF计算的1,3,5-环庚三烯（CHT）中光化学[1,7]-σ向氢位移的反应谱，讨论了激发态反应的详细机理。结果与从初始激发的1 A“状态通过暗2 A'状态到基态（1 A'）势能表面的超快速率相一致。反应的动力学和选择性的特征是在暗2A'态上有一个小的能垒，该能垒将激发态的最小值与圆锥形相交处的周界几何形状分开。该交点负责有效的激发态失活。在CASSCF水平上，势垒高度经计算为7.3 kcal mol〜（-1）。如果用CASPT2方法考虑动力相关性效应，则屏障可降至3.8 kcal mol〜（-1）。通过考虑1-取代的CHT验证了作为氢迁移的决定性机理的激发态势垒的存在。计算出的σ迁移势垒从形式上向取代基移动很大。与实验观察到的观点一致，发现较小的壁垒可从受体迁移到供体取代基。阻挡层高度的差异与实验观察到的产物分布高度吻合。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号