在 [12]annulene 中的 Möbius 芳香度:通过扭曲合键转移转移的 cis-trans 异构化
Claire Castro1, William L Karney, Miguel A Valencia
1Department of Chemistry, University of San Francisco, California 94117, USA. castroc@usfca.edu
Journal of the American Chemical Society
|July 7, 2005
概括
在 [12]annulene 中,容易发生的热配置变化是通过扭曲合键移位机制发生的. 这个过程涉及到一种具有Möbius拓的高度芳香的过渡状态,与典型的annulene机制不同.
科学领域:
- 有机化学 有机化学
- 理论化学 理论化学
- 计算化学的计算化学
背景情况:
- 无烯是循环碳化合物,具有交替的单键和双键.
- 了解annulenes中的动态过程和构造变化对于预测它们的反应性和特性至关重要.
- 之前的研究经常假设平面键转移机制对无效的配置变化.
研究的目的:
- 为了阐明易于改变 [12]annulene 的热配置的机制.
- 为了研究参与 [12]annulene异构化中的过渡状态的性质.
- 要将拟议的机制与在非循环聚烯和其他无效烯中观察到的机制进行对比.
主要方法:
- 密度函数理论 (DFT) 的计算.
- 结合集群 (CC) 的计算,特别是CCSD) /cc-pVDZ//BH&HLYP/6-311+G**.
- 对异构化途径的过渡状态的识别和表征.
主要成果:
- 对于 [12]annulene.的热配置变化,已经确定了一个扭曲合的键位转移机制.
- 这个过程的过渡状态表现出高芳香度和Möbius拓.
- 对于三转 [12] 烯与其二转异构体的计算异构化障碍为 18.0 kcal/mol,与实验数据非常一致.
- 对于其他 [12]annulene conformers,还发现了两个额外的芳香的 Möbius 键转移过渡状态.
结论:
- 中性 [4n] 烯中的动态过程涉及中性莫比乌斯芳香烯.
- 鉴定出来的机制挑战了长期以来关于 annulenes 中平面键移动的假设.
- 这项研究提供了Möbius芳香度在annulenes的结构动态中的重要作用的证据.
相关概念视频
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