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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Potential Energy Surface for the Chlorine Atom Reaction with Ethylene: A Theoretical Study
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Potential Energy Surface for the Chlorine Atom Reaction with Ethylene: A Theoretical Study

机译：氯原子与乙烯反应的势能面：理论研究

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摘要

The potential energy surface of the reaction between chlorine atom and ethylene was explored at the MP21 6-31G(d,p), Becke3L YP/6-31G(d,p), QCISD/6-3IG(d,p), MP2/6-311+G(d,p), MP2/6-311 ++G(3df,3pd), and MP2/aug-cc-pVDZ levels of theory. Further QCISD(T)/6-31G(d,p) and QCISD(T)/cc-pVDZ optimizations were performed for some structures of special interest. The geometrical parameters computed for the different structures located on the potential energy surface do not differ too much when employing different methods and basis sets with the only exceptions of those structures involving long distance interactions (van der waats structures). The pronounced flatness of the potential energy surface in the regions where these structures appear seems to be the responsible for the observed discrepancies. The full optimized QCISD structures tend to become less stable than those computed at the MP2 level, whereas the opposite is true for the Becke3L yp structures. At the MP2 and QCISD levels, the transition structure associated with a direct shuttle motion in the addition channel is too high in energy to be involved in the dissociation mechanism. The existence of two bridged structures Iadd (minimum) and TSadd (transition structure) on the potential energy surface helps to explain the experimentally detected stereochemical control exercised by the chlorine atom in reactions involving haloethyl radicals. Contrarily, the Becke3L YP calculations suggest a mechanism in which the direct shuttle motion coul.d playa relevant role, although the competing mechanism of rotation around the C-C bond is lower in energy. The MP2 and QCISD abstraction cha~nels also differ considerably from the Becke3L yp one. However, in this case all the different potential energy surfaces seem to be consistent with the reported experimental data on the activation energy and endothermicity for the abstraction reaction. The QCISD(T)I aug-cc-pVDZ//QCISD/6-3IG(d,p) relative energies and barrier heights are consistent with the experimental data available on exo/endothermicities and activation barriers for the addition and abstraction reactions.
机译：在MP21 6-31G（d，p），Becke3L YP / 6-31G（d，p），QCISD / 6-3IG（d，p），MP2处探索了氯原子与乙烯之间反应的势能面/ 6-311 + G（d，p），MP2 / 6-311 ++ G（3df，3pd）和MP2 / aug-cc-pVDZ理论水平。对于某些特殊结构，进一步进行了QCISD（T）/ 6-31G（d，p）和QCISD（T）/ cc-pVDZ优化。当采用不同的方法和基础集时，为位于势能面上的不同结构计算的几何参数不会有太大差异，只有那些涉及长距离相互作用的结构（范德华结构）例外。这些结构出现的区域中势能表面的明显平坦度似乎是造成观察到的差异的原因。完全优化的QCISD结构往往比MP2级别上计算的结构更不稳定，而Becke3L yp结构则相反。在MP2和QCISD级别上，与添加通道中直接穿梭运动相关的过渡结构的能量过高，无法参与解离机制。在势能表面上存在两个桥接结构Iadd（最小）和TSadd（过渡结构）有助于解释氯原子在涉及​​卤乙基自由基的反应中通过实验检测到的立体化学控制。相反，尽管围绕C-C键旋转的竞争机制能量较低，但Becke3L YP计算提出了一种机制，其中直接往复运动coul.d发挥了相关作用。 MP2和QCISD抽象通道也与Becke3L yp通道大不相同。然而，在这种情况下，所有不同的势能面似乎与所报道的关于抽象反应的活化能和吸热性的实验数据一致。 QCISD（T）I aug-cc-pVDZ // QCISD / 6-3IG（d，p）的相对能量和势垒高度与关于外加/吸热和激活势垒的加成和抽象反应的实验数据一致。

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