Nucleophilic Substitution in Solution: Activation Strain Analysis of Weak and Strong Solvent Effects.,Chemistry - A European Journal

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Nucleophilic Substitution in Solution: Activation Strain Analysis of Weak and Strong Solvent Effects.
Chemistry - A European Journal ( IF 3.9 ) Pub Date : 2018-03-24 , DOI: 10.1002/chem.201706075
Trevor A Hamlin ₁ , Bas van Beek ₁ , Lando P Wolters ₁ , F Matthias Bickelhaupt _{1,

2}

Affiliation

We have quantum chemically studied the effect of various polar and apolar solvents on the shape of the potential energy surface (PES) of a diverse collection of archetypal nucleophilic substitution reactions at carbon, silicon, phosphorus, and arsenic by using density functional theory at the OLYP/TZ2P level. In the gas phase, all our model SN 2 reactions have single-well PESs, except for the nucleophilic substitution reaction at carbon (SN 2@C), which has a double-well energy profile. The presence of the solvent can have a significant effect on the shape of the PES and, thus, on the nature of the SN 2 process. Solvation energies, charges on the nucleophile or leaving group, and structural features are compared for the various SN 2 reactions in a spectrum of solvents. We demonstrate how solvation can change the shape of the PES, depending not only on the polarity of the solvent, but also on how the charge is distributed over the interacting molecular moieties during different stages of the reaction. In the case of a nucleophilic substitution at three-coordinate phosphorus, the reaction can be made to proceed through a single-well [no transition state (TS)], bimodal barrier (two TSs), and then through a unimodal transition state (one TS) simply by increasing the polarity of the solvent.

中文翻译：

溶液中的亲核取代：弱溶剂效应和强溶剂效应的活化应变分析。

我们利用 OLYP 的密度泛函理论，在量子化学上研究了各种极性和非极性溶剂对碳、硅、磷和砷的各种典型亲核取代反应的势能面 (PES) 形状的影响/TZ2P级别。在气相中，我们的所有模型 SN 2 反应都具有单井 PES，除了碳上的亲核取代反应 (SN 2@C) 具有双井能量分布。溶剂的存在会对 PES 的形状产生显着影响，从而对 SN 2 过程的性质产生显着影响。比较了一系列溶剂中各种 SN 2 反应的溶剂化能、亲核试剂或离去基团上的电荷以及结构特征。我们展示了溶剂化如何改变 PES 的形状，这不仅取决于溶剂的极性，还取决于在反应的不同阶段电荷如何分布在相互作用的分子部分上。在三配位磷发生亲核取代的情况下，反应可以通过单孔[无过渡态（TS）]、双峰势垒（两个TS）进行，然后通过单峰过渡态（一个过渡态）进行。 TS）只需增加溶剂的极性即可。

更新日期：2018-03-24

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