Computational Study of Competition between Direct Abstraction and Addition鈥揈limination in the Reaction of Cl Atoms with Propene

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• 作者：Bal谩zs Hornung ; Thomas J. Preston ; Shubhrangshu Pandit ; Jeremy N. Harvey ; Andrew J. Orr-Ewing
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：September 10, 2015
• 年：2015
• 卷：119
• 期：36
• 页码：9452-9464
• 全文大小：672K
• ISSN：1520-5215

文摘

Quasi-classical trajectory calculations on a newly constructed and full-dimensionality potential energy surface (PES) examine the dynamics of the reaction of Cl atoms with propene. The PES is an empirical valence bond (EVB) fit to high-level ab initio energies and incorporates deep potential energy wells for the 1-chloropropyl and 2-chloropropyl radicals, a direct H atom abstraction route to HCl + allyl radical (CH₂CHCH₂^{鈥?/sup>) products (螖_rH_298K鈯?/sup> = 鈭?3.1 kJ mol鈥?), and a pathway connecting these regions. In total, 94鈥?00 successful reactive trajectories were used to compute distributions of angular scattering and HCl vibrational and rotational level populations. These measures of the reaction dynamics agree satisfactorily with available experimental data. The dominant reaction pathway is direct abstraction of a hydrogen atom from the methyl group of propene occurring in under 500 fs. Less than 10% of trajectories follow an addition鈥揺limination route via the two isomeric chloropropyl radicals. Large amplitude motions of the Cl about the propene molecular framework couple the addition intermediates to the direct abstraction pathway. The EVB method provides a good description of the complicated PES for the Cl + propene reaction despite fitting to a limited number of ab initio points, with the further advantage that dynamics specific to certain mechanisms can be studied in isolation by switching off coupling terms in the EVB matrix connecting different regions of the PES.}