Nonadiabatic reaction mechanisms of the O(3P) with cyclopentene

• The complex nonadiabatic reaction pathways are newly revealed.
• The most probable reaction mechanism is described, which can rationalize the experimentally observed product distributions logically.
• New product channels are predicted, which involves the formation of cyclopentenol, one kind of enols believed to be the key reaction intermediate in the flame of hydrocarbons.

The reaction mechanism of the ground state oxygen atom O(3P) with cyclopentene is investigated theoretically. The triplet and singlet potential energy surfaces are calculated at the CCSD(T)//MP2/6-311G(d,p) level and the minimum energy crossing points (MECPs) between the two surfaces are located by means of the Newton–Lagrange method, from which the complex nonadiabatic reaction pathways are revealed. Based on the theoretical results, the most probable reaction mechanism of O(3P) with c-C5H8 is described, which agrees with the experimental results nicely, including the condensed phase experiment. At the same time, the newly revealed reaction mechanism clarifies the previous controversial product distribution, and predicts the possible existence of the new enol product, cyclopentenol.

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