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Computational Study of the Reaction Mechanism of the Methylperoxy Self-Reaction

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journal contribution
posted on 24.11.2011, 00:00 by Yan-Ni Liang, Jun Li, Quan-De Wang, Fan Wang, Xiang-Yuan Li
To provide insight on the reaction mechanism of the methyperoxy (CH3O2•) self-reaction, stationary points on both the spin-singlet and the spin-triplet potential energy surfaces of 2(CH3O2•) have been searched at the B3LYP/6-311++G(2df,2p) level. The relative energies, enthalpies, and free energies of these stationary points are calculated using CCSD(T)/cc-pVTZ. Our theoretical results indicate that reactions on a spin-triplet potential energy surface are kinetically unfavorable due to high free energy barriers, while they are more complicated on the spin-singlet surface. CH3OOCH3 + O21 can be produced directly from 2(CH3O2•), while in other channels, three spin-singlet chain-structure intermediates are first formed and subsequently dissociated to produce different products. Besides the dominant channels producing 2CH3O• + O2 and CH3OH + CH2O + O2 as determined before, the channels leading to CH3OOOH + CH2O and CH3O• + CH2O + HO2• are also energetically favorable in the self-reaction of CH3O2• especially at low temperature according to our results.