College of Chemistry, Sichuan University, Chengdu, People's Republic of China.
J Phys Chem A. 2011 Nov 24;115(46):13534-41. doi: 10.1021/jp2048508. Epub 2011 Oct 26.
To provide insight on the reaction mechanism of the methyperoxy (CH(3)O(2)•) self-reaction, stationary points on both the spin-singlet and the spin-triplet potential energy surfaces of 2(CH(3)O(2)•) 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. CH(3)OOCH(3) + O(2)(1) can be produced directly from 2(CH(3)O(2)•), 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 2CH(3)O• + O(2) and CH(3)OH + CH(2)O + O(2) as determined before, the channels leading to CH(3)OOOH + CH(2)O and CH(3)O• + CH(2)O + HO(2)• are also energetically favorable in the self-reaction of CH(3)O(2)• especially at low temperature according to our results.
为了深入了解甲氧基过氧自由基（CH(3)O(2)•）自反应的反应机理，在 B3LYP/6-311++G(2df,2p)水平上对双自由基（2CH(3)O(2)•）的自旋单重态和自旋三重态势能面上的所有驻点进行了搜索。使用 CCSD(T)/cc-pVTZ 计算了这些驻点的相对能量、焓和自由能。我们的理论结果表明，由于自由能垒较高，自旋三重态势能面上的反应在动力学上是不利的，而在自旋单重态表面上的反应则更为复杂。CH(3)OOCH(3) + O(2)(1) 可以直接由 2(CH(3)O(2)•)生成，而在其他通道中，首先形成三种自旋单重态链状结构中间体，然后它们解离产生不同的产物。除了之前确定的主导通道 2CH(3)O• + O(2)和 CH(3)OH + CH(2)O + O(2)之外，根据我们的结果，在 CH(3)O(2)•的自反应中，导致 CH(3)OOOH + CH(2)O 和 CH(3)O• + CH(2)O + HO(2)•的通道在低温下也是能量有利的。
