Theoretical study on the mechanism and kinetics for the self-reaction of C2H5O2 radicals.
Theoretical study on the mechanism and kinetics for the self-reaction of C2H5O2 radicals.
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DOI：
10.1021/jp301308u
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发表时间：
2012-04
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影响因子：
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通讯作者：
Pei Zhang;Wenliang Wang;Tianlei Zhang;Long Chen;Yongmei Du;Chunying Li;J. Lü
中科院分区：
文献类型：
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作者：
Pei Zhang;Wenliang Wang;Tianlei Zhang;Long Chen;Yongmei Du;Chunying Li;J. Lü
在CCSD（T）/cc-pVDZ//B3 LYP/6- 311 G（2d，2 p）水平上研究了C（2）H（5）O（2）自由基单重态和三重态自反应的氧-氧偶联、直接夺氢和氧-α-碳亲核取代过程，探讨了反应机理、可能产物和速率常数.计算结果表明，该反应主要通过单线态氧-氧偶联机理进行，生成了四氧化物中间体，主要产物为通道R5中生成的C（2）H（5）O + HO（2）+ CH（3）CHO（P5）.从P5（C（2）H（5）O，HO（2））和反应物（C（2）H（5）O（2））的自由基产物出发，共发生了5个次级反应HO（2）+ HO（2）（a），HO（2）+ C（2）H（5）O（B），C（2）H（5）O + C（2）H（5）O（c），HO（2）+ C（2）H（5）O（2）（d），C（2）H（5）O + C（2）H（5）O（2）（e）主要在三重态势能面上进行。在这些反应中，（a）、（B）和（d）由于较低的势垒高度而在动力学上是有利的。在200 ~ 295 K范围内，R5通道的速率常数几乎与温度无关，与实验结果一致。在最终产物分布上，CH（3）CHO、C（2）H（5）OH、C（2）H（5）OOH、H（2）O（2）和（3）O（2）是主要的，而C（2）H（5）OOC（2）H（5）应该是次要的。
Oxygen-to-oxygen coupling, direct H-abstraction and oxygen-to-(α)carbon nucleophilic substitution processes have been investigated for both the singlet and triplet self-reaction of C(2)H(5)O(2) radicals at the CCSD(T)/cc-pVDZ//B3LYP/6-311G(2d,2p) level to evaluate the reaction mechanisms, possible products and rate constants. The calculated results show that the title reaction mainly occurs through the singlet oxygen-to-oxygen coupling mechanism with the formation of entrance tetroxide intermediates, and the most dominant product is C(2)H(5)O + HO(2) + CH(3)CHO (P5) generated in channel R5. Beginning from the radical products of P5 (C(2)H(5)O, HO(2)) and reactant (C(2)H(5)O(2)), five secondary reactions HO(2) + HO(2) (a), HO(2) + C(2)H(5)O (b), C(2)H(5)O + C(2)H(5)O (c), HO(2) + C(2)H(5)O(2) (d), and C(2)H(5)O + C(2)H(5)O(2) (e) mainly proceed on the triplet potential energy surface. Among these reactions, (a), (b), and (d) are kinetically favorable because of lower barrier heights. The calculated rate constants of channel R5 between 200 and 295 K are almost independent of the temperature, which is in agreement with the experimental report. With regard to the final products distribution, CH(3)CHO, C(2)H(5)OH, C(2)H(5)OOH, H(2)O(2), and (3)O(2) are predicted to be major, whereas C(2)H(5)OOC(2)H(5) should be in minor amount.