Facultad de Ciencias, Departamento de Química Módulo 13, Universidad Autónoma de Madrid, Madrid, Spain.
J Mol Model. 2012 Jun;18(6):2813-21. doi: 10.1007/s00894-011-1283-1. Epub 2011 Nov 27.
Oxygenation mechanisms of phenylhalocarbenes in vacuum are investigated through the use of density functional theory and CASSCF-PT2 approaches. Reactions with both substituted and unsubstituted phenylhalocarbenes are strongly exothermic. The reactions with nitrosubstituted halocarbenes are predicted to be spin allowed due to the practical degeneracy of the singlet and triplet carbene states. Conversely, for the unsubstituted compounds, the equilibrium between the triplet carbene and (3)O(2) requires a previous singlet-triplet state crossing. The large spin-orbit coupling at this crossing suggests a rather efficient tunneling rate. This would help to explain why the rate constant in solution in these cases is only one order of magnitude smaller than those involving a spin-allowed process. Moreover, the action of the solvent as a third body appears to play a fundamental role in prompting relatively smooth rates.
通过使用密度泛函理论和 CASSCF-PT2 方法，研究了真空条件下芳基卤卡宾的氧化机制。与取代和未取代的芳基卤卡宾的反应都是强放热的。由于单重态和三重态卡宾态的实际简并，预测与亚硝酰取代的卤卡宾的反应是自旋允许的。相反，对于未取代的化合物，三重态卡宾和（3）O（2）之间的平衡需要先经过单重态-三重态交叉。在这个交叉点处的大自旋-轨道耦合表明存在相当有效的隧穿速率。这有助于解释为什么在这些情况下，溶液中的速率常数仅比涉及自旋允许过程的速率常数小一个数量级。此外，溶剂作为第三体的作用似乎在促使相对平滑的速率方面起着至关重要的作用。
