Reaction dynamics of the methoxy anion CH3O− with methyl iodide CH3I

IF 3.4 3区化学 Q2 Chemistry

Faraday Discussions Pub Date : 2024-02-16 DOI:10.1039/D3FD00164D

Thomas Gstir, David Sundelin, Tim Michaelsen, Atilay Ayasli, Dasarath Swaraj, Jerin Judy, Fabio Zappa, Wolf Geppert and Roland Wester

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Abstract

Studying larger nucleophiles in bimolecular nucleophilic substitution (S_N2) reactions bridges the gap from simple model systems to those relevant to organic chemistry. Therefore, we investigated the reaction dynamics between the methoxy anion (CH₃O⁻) and iodomethane (CH₃I) in our crossed-beam setup combined with velocity map imaging at the four collision energies 0.4, 0.7, 1.2, and 1.6 eV. We find the two ionic products I⁻ and CH₂I⁻, which can be attributed to the S_N2 and proton transfer channels, respectively. The proton transfer channel progresses in a previously observed fashion from indirect to direct scattering with increasing collision energy. Interestingly, the S_N2 channel exhibits direct dynamics already at low collision energies. Both the direct stripping, leading to forward scattering, and the direct rebound mechanism, leading to backward scattering into high angles, are observed.

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甲氧基阴离子 CH3O- 与甲基碘 CH3I 的反应动力学

在双分子亲核置换（SN 2）反应中研究较大的亲核物，缩小了从简单模型系统到有机化学相关系统的差距。因此，我们在交叉光束装置中结合速度图成像技术，在 0.4、0.7、1.2 和 1.6 eV 四种碰撞能量下研究了甲氧基阴离子 (CH3O-) 和碘甲烷 (CH3I) 之间的反应动力学。我们发现了两种离子产物 I- 和 CH2I-，它们可分别归因于 SN2 和质子转移通道。质子传输通道随着碰撞能量的增加，以先前观察到的间接散射到直接散射的方式进行。有趣的是，SN2 通道在低碰撞能量时就已表现出直接动力学。我们观察到了导致前向散射的直接剥离和导致高角度后向散射的直接反弹机制。

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