Unconventional Pathways in Nitrogen-Centered S<sub>N</sub>2 Reactions: From Roundabout to Hydride Transfer
The mechanisms and dynamics of bimolecular nucleophilic substitution (S<sub>N</sub>2) reactions are complex and influenced by the nature of the central atom. In this study, we explore S<sub>N</sub>2 at a nitrogen center (S<sub>N</sub>2@N) by investigating the reac...
محفوظ في:
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| منشور في: |
2024
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| الملخص: | The mechanisms and dynamics of bimolecular nucleophilic substitution (S<sub>N</sub>2) reactions are complex and influenced by the nature of the central atom. In this study, we explore S<sub>N</sub>2 at a nitrogen center (S<sub>N</sub>2@N) by investigating the reaction of chloramine (NH<sub>2</sub>Cl) with methoxide ion (CH<sub>3</sub>O<sup>–</sup>) using ab initio classical trajectory simulations at the MP2(fc)/aug-cc-pVDZ level of theory. We observe that, in addition to the expected S<sub>N</sub>2 product formation (CH<sub>3</sub>ONH<sub>2</sub> + Cl<sup>–</sup>), a high-energy proton-transfer pathway leading to CH<sub>3</sub>OH and NHCl<sup>–</sup> dominates, with near-quantitative agreement between simulations and experimental data. Notably, we identify a novel hydride-transfer pathway yielding NH<sub>3</sub>, H<sub>2</sub>CO, and Cl<sup>–</sup>, revealing alternative reactivity channels previously uncharacterized in nitrogen-centered S<sub>N</sub>2 reactions. Mechanistic analysis uncovers unconventional roaming-mediated and roundabout pathways alongside the traditional direct rebound and indirect mechanisms. Additionally, an umbrella inversion of the NH<sub>2</sub> group resulting in retention of configuration in the CH<sub>3</sub>ONH<sub>2</sub> product was observed in a fraction of trajectories. |
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