Photodimerization of 1-Phenylcyclohexene. A Novel Transient-Transient Component
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- 作者：David J. Unett ; Richard A. Caldwell ; and Duane C. Hrncir
- 刊名：Journal of the American Chemical Society
- 出版年：1996
- 出版时间：February 21, 1996
- 年：1996
- 卷：118
- 期：7
- 页码：1682 - 1689
- 全文大小：367K
- 年卷期：v.118,no.7(February 21, 1996)
- ISSN：1520-5126
文摘
Low-temperature irradiations of 1-phenylcyclohexene (PC6) yieldtwo singlet state 2 + 2 photodimersand two 4 + 2 cycloadducts. The 4 + 2 adducts are not observedin low intensity lamp irradiations at room temperaturebut are produced in significant quantities when PC6 solutions aresubjected to higher intensity laser irradiation. Theresults indicate a reaction mechanism involving twotrans-PC6 molecules. The findings are consistent withearlierkinetic observations that the decay of trans-PC6 adopts asignificant second-order component at lower temperatures.The transient-transient reaction also occurs undertriplet-sensitized low-temperature/low-intensity or roomtemperature/high-intensity irradiation conditions. Triplet-sensitizedirradiations also yield significant amounts of the 2 + 2photodimers produced by attack of the PC6 triplet on its ground state.Quantum yield studies reveal that the rate ofaddition of 3PC6* to its ground state is in the range0.28 to 4.0 × 105 L mol-1 s-1consistent with the 1,2-biradicalmodel for alkene triplet reactivity.