Tasi Domonkos A, Czakó Gábor
MTA-SZTE Lendület Computational Reaction Dynamics Research Group, Interdisciplinary Excellence Centre and Department of Physical Chemistry and Materials Science, Institute of Chemistry, University of Szeged, Rerrich Béla tér 1, Szeged H-6720, Hungary.
J Chem Phys. 2024 Jan 28;160(4). doi: 10.1063/5.0189561.
We report a comprehensive characterization of the vibrational mode-specific dynamics of the OH- + CH3I reaction. Quasi-classical trajectory simulations are performed at four different collision energies on our previously-developed full-dimensional high-level ab initio potential energy surface in order to examine the impact of four different normal-mode excitations in the reactants. Considering the 11 possible pathways of OH- + CH3I, pronounced mode-specificity is observed in reactivity: In general, the excitations of the OH- stretching and CH stretching exert the greatest influence on the channels. For the SN2 and proton-abstraction products, the reactant initial attack angle and the product scattering angle distributions do not show major mode-specific features, except for SN2 at higher collision energies, where forward scattering is promoted by the CI stretching and CH stretching excitations. The post-reaction energy flow is also examined for SN2 and proton abstraction, and it is unveiled that the excess vibrational excitation energies rather transfer into the product vibrational energy because the translational and rotational energy distributions of the products do not represent significant mode-specificity. Moreover, in the course of proton abstraction, the surplus vibrational energy in the OH- reactant mostly remains in the H2O product owing to the prevailing dominance of the direct stripping mechanism.
我们报告了OH⁻ + CH₃I反应中特定振动模式动力学的全面表征。在我们先前开发的全维高水平从头算势能面上，于四种不同碰撞能量下进行了准经典轨迹模拟，以研究反应物中四种不同简正模式激发的影响。考虑到OH⁻ + CH₃I的11种可能反应途径，在反应活性中观察到了明显的模式特异性：一般来说，OH⁻伸缩振动和CH伸缩振动的激发对反应通道的影响最大。对于SN2和质子抽取产物，反应物初始攻击角和产物散射角分布除了在较高碰撞能量下的SN2反应外，没有显示出主要的模式特异性特征，在较高碰撞能量下的SN2反应中，CI伸缩振动和CH伸缩振动激发促进了前向散射。还对SN2和质子抽取反应后的能量流动进行了研究，结果表明，由于产物的平动和转动能量分布没有显著的模式特异性，过量的振动激发能更多地转移到产物的振动能量中。此外，在质子抽取过程中，由于直接剥离机制占主导地位，OH⁻反应物中的多余振动能量大多保留在H₂O产物中。
