氧负离子与乙烯自由基反应的理论研究

在G3MP2B3理论水平下研究了氧负离子与乙烯自由基的反应机理. 反应入口势能面的刚性扫描显示: 对于不同的初始反应取向, 体系存在3种不同的反应机理, 分别对应直接脱水、插入反应和直接键合成中间体通道. 其中, 通过插入反应形成的富能中间体CH2＝C—OH]－及键合中间体CH2＝CHO]－都可以进一步经异构化和解离生成其它各种可能产物, 如C2H－＋H2O, OH－＋CH2C和 ＋CO产物通道. 基于计算得到的反应势垒的相对高度, 直接脱水反应显然是该反应体系最主要的产物通道, 同时我们还结合Mulliken电荷布居分析研究了其中涉及的电子交换过程. 由此, 计算结果证实了以往OH－与C2H2反应的实验研究结果. 此外, 还对比了该反应体系、氧原子与乙烯自由基、氧负离子与乙烯分子三个反应的不同机理.

Theoretical Investigation of the Reaction between Atomic Oxygen Radical Anion and Vinyl Radical

The reaction mechanism of atomic oxygen radical anion with vinyl radical has been investigated at the G3MP2B3 level of theory. The entrance potential energy surface for the title reaction has been scanned with a rigid scan method. Three different reaction mechanisms were observed as a direct dehydration channel, an insertion reaction and a direct bonding process, corresponding to the different initial spatial collision directions respectively. The energy-rich intermediate anions, eg. CH2＝C—OH]－ as the initial product of the insertion reaction and CH2＝CHO]－ as the direct bonding product, are able to isomerize and decompose to various final products, such as C2H－＋H2O, CH2C＋OH－ and CH3－＋CO. Based on the calculated relative potential barrier heights of various product pathways, the initial direct dehydration reaction was thought as the most favorable product channel for the title reaction system. Additionally, the electron transfers involved in these processes have been discussed by using the Mulliken charge population analysis. The present investigation is consistent with the previous experimental studies of the OH－＋C2H2 reaction. Moreover, the different reaction mechanisms of the O＋•C2H3, O－＋C2H4 and the present reaction were compared as well.