Cavallotti Carlo, Mancarella Silvia, Rota Renato, Carrà Sergio
Dip. Chimica, Materiali e Ingegneria Chimica "G. Natta"/CIIRCO, Politecnico di Milano, Via Mancinelli 7, 20131 Milano, Italy.
J Phys Chem A. 2007 May 17;111(19):3959-69. doi: 10.1021/jp067117f. Epub 2007 Feb 14.
We have recently proposed that the addition of C2H2 to the cyclopentadienyl radical can lead to the rapid formation of the cycloheptatrienyl radical and, in succession, of the indenyl radical. These reactions represent an interesting and unexplored route for the enlargement of gas-phase cyclic species. In this work we report ab initio calculations we performed with the aim of investigating in detail the gas-phase reactivity of cycloheptatrienyl and indenyl radicals. We found that the reaction of the cycloheptatrienyl radical with atomic hydrogen can lead to its fast conversion into the more stable benzyl radical. This reaction pathway involves the intermediate formation of heptatriene, norcaradiene, and toluene. Successively we investigated whether this reaction mechanism can be extended to polycyclic aromatic hydrocarbons (PAHs). For this purpose we studied the reaction of C2H2 with the indenyl radical, which can be considered as a superior homologue of the cyclopentadienyl radical. This reaction proceeds through a pathway similar to that proposed for C5H5 but with a reaction rate about an order of magnitude smaller. The present calculations extend thus the previously proposed C5-C7-C9 mechanism to bicyclic PAH and suggest a fast route for the conversion of C5 into C6 cyclic radicals, mediated by the formation of C7 cyclic species.
我们最近提出，将乙炔添加到环戊二烯基自由基中可导致迅速形成环庚三烯基自由基，进而形成茚基自由基。这些反应代表了气相环状物种扩大的一条有趣且未被探索的途径。在这项工作中，我们报告了为详细研究环庚三烯基和茚基自由基的气相反应性而进行的从头算计算。我们发现环庚三烯基自由基与氢原子的反应可导致其快速转化为更稳定的苄基自由基。该反应途径涉及庚三烯、降蒈二烯和甲苯的中间形成。接着，我们研究了这种反应机制是否可以扩展到多环芳烃（PAHs）。为此，我们研究了乙炔与茚基自由基的反应，茚基自由基可被视为环戊二烯基自由基的高级同系物。该反应通过与为C5H5提出的途径相似的途径进行，但反应速率约小一个数量级。因此，目前的计算将先前提出的C5-C7-C9机制扩展到双环PAH，并提出了一条由C7环状物种的形成介导的将C5转化为C6环状自由基快速途径。
