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题名: Simulation studies of the Cl- + CH3I S(N)2 nucleophilic substitution reaction: Comparison with ion imaging experiments
作者: Zhang, Jiaxu1;  Lourderaj, Upakarasamy2;  Sun, Rui2;  Mikosch, Jochen3;  Wester, Roland4;  Hase, William L.2
刊名: JOURNAL OF CHEMICAL PHYSICS
发表日期: 2013-03-21
DOI: 10.1063/1.4795495
卷: 138, 期:11
收录类别: SCI
文章类型: Article
WOS标题词: Science & Technology ;  Physical Sciences
类目[WOS]: Physics, Atomic, Molecular & Chemical
研究领域[WOS]: Physics
英文摘要: In the previous work of Mikosch et al. [Science 319, 183 (2008)], ion imaging experiments were used to study the Cl- + CH3I -> ClCH3 + 1(-) reaction at collision energies E-rel of 0.39, 0.76, 1.07, and 1.9 eV. For the work reported here MP2(fc)/ECP/d direct dynamics simulations were performed to obtain an atomistic understanding of the experiments. There is good agreement with the experimental product energy and scattering angle distributions for the highest three E-rel, and at these energies 80% or more of the reaction is direct, primarily occurring by a rebound mechanism with backward scattering. At 0.76 eV there is a small indirect component, with isotropic scattering, involving formation of the pre- and post-reaction complexes. All of the reaction is direct at 1.07 eV. Increasing E-rel to 1.9 eV opens up a new indirect pathway, the roundabout mechanism. The product energy is primarily partitioned into relative translation for the direct reactions, but to CH3Cl internal energy for the indirect reactions. The roundabout mechanism transfers substantial energy to CH3Cl rotation. At E-rel = 0.39 eV both the experimental product energy partitioning and scattering are statistical, suggesting the reaction is primarily indirect with formation of the pre-and post-reaction complexes. However, neither MP2 nor BhandH/ECP/d simulations agree with experiment and, instead, give reaction dominated by direct processes as found for the higher collision energies. Decreasing the simulation Erel to 0.20 eV results in product energy partitioning and scattering which agree with the 0.39 eV experiment. The sharp transition from a dominant direct to indirect reaction as Erel is lowered from 0.39 to 0.20 eV is striking. The lack of agreement between the simulations and experiment for Erel = 0.39 eV may result from a distribution of collision energies in the experiment and/or a shortcoming in both the MP2 and BhandH simulations. Increasing the reactant rotational temperature from 75 to 300 K for the 1.9 eV collisions, results in more rotational energy in the CH3Cl product and a larger fraction of roundabout trajectories. Even though a ClCH3-I(-)post-reaction complex is not formed and the mechanistic dynamics are not statistical, the roundabout mechanism gives product energy partitioning in approximate agreement with phase space theory. (C) 2013 American Institute of Physics.[http://dx.doi.org/10.1063/1.4795495]
关键词[WOS]: S(N)2 NUCLEOPHILIC-SUBSTITUTION ;  GAS-PHASE S(N)2 ;  CLASSICAL TRAJECTORY SIMULATIONS ;  GRADIENT APPROXIMATIONS GGAS ;  DENSITY-FUNCTIONAL THEORY ;  VIBRATIONAL-EXCITATION ;  AB-INITIO ;  DISPLACEMENT-REACTIONS ;  MOLECULAR CALCULATIONS ;  ENERGY-DISTRIBUTIONS
语种: 英语
WOS记录号: WOS:000316544500023
Citation statistics: 
内容类型: 期刊论文
URI标识: http://cas-ir.dicp.ac.cn/handle/321008/137969
Appears in Collections:中国科学院大连化学物理研究所_期刊论文

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作者单位: 1.Chinese Acad Sci, Inst Chem, Beijing Natl Lab Mol Sci, State Key Lab Mol React Dynam, Beijing 100190, Peoples R China
2.Texas Tech Univ, Dept Chem & Biochem, Lubbock, TX 79409 USA
3.Natl Res Council Canada, Steacie Inst Mol Sci, Ottawa, ON K1AOR6, Canada
4.Univ Innsbruck, Inst Ionenphys & Angew Phys, A-6020 Innsbruck, Austria

Recommended Citation:
Zhang, Jiaxu,Lourderaj, Upakarasamy,Sun, Rui,et al. Simulation studies of the Cl- + CH3I S(N)2 nucleophilic substitution reaction: Comparison with ion imaging experiments[J]. JOURNAL OF CHEMICAL PHYSICS,2013,138(11).
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