Reaction Mechanisms of a Photo-Induced [1,3] Sigmatropic Rearrangement via a Nonadiabatic Pathway

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• 作者：Weiqiang Wu ; Kunhui Liu ; Chunfan Yang ; Hongmei Zhao ; Huan Wang ; Youqing Yu ; Hongmei Su
• 刊名：Journal of Physical Chemistry A
• 出版年：2009
• 出版时间：December 17, 2009
• 年：2009
• 卷：113
• 期：50
• 页码：13892-13900
• 全文大小：356K
• 年卷期：v.113,no.50(December 17, 2009)
• ISSN：1520-5215

文摘

Time-resolved Fourier transform infrared absorption spectroscopy measurements and B3LYP/cc-pVDZ calculations have been conducted to characterize the reaction dynamics of a remarkable photoinduced 1,3-Cl sigmatropic rearrangement reaction upon 193 or 266 nm excitation of the model systems acryloyl chloride (CH₂CHCOCl) and crotonyl chloride (CH₃CHCHCOCl) in solution. The reaction is elucidated to follow nonadiabatic pathways via two rapid ISC processes, S₁ → T₁ and T₁ → S₀, and the S₁/T₁ and T₁/S₀ surface intersections are found to play significant roles leading to the nonadiabatic pathways. The S₁ → T₁ → S₀ reaction pathway involving the key participation of the T₁ state is the most favorable, corresponding to the lowest energy path. It is also suggested that the photoinduced 1,3-Cl migration reaction of RCHCHCOCl (R = H, CH₃) proceeds through a stepwise mechanism involving radical dissociation−recombination, which is quite different from the generally assumed one-step concerted process for pericyclic reactions.