Solvation in nitration of benzene and the valence electronic structure of the Wheland intermediate
Solvation in nitration of benzene and the valence electronic structure of the Wheland intermediate
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苯硝化中的溶剂化和 Wheland 中间体的价电子结构
DOI：
10.1039/d2cp01699k
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发表时间：
2022
影响因子：
3.3
通讯作者：
Sato Hirofumi
中科院分区：
文献类型：
--
作者：
Nakatani Kaho;Teshigawara Sho;Tanahashi Yuta;Kasahara Kento;Higashi Masahiro;Sato Hirofumi
苯的硝化反应是一个典型的芳香取代反应，与σ-络合物（arenium离子或“Wheland”中间体）概念有关。该反应通常在混合酸溶液中进行以产生硝鎓离子，并且溶剂分子如何在反应中发挥作用一直是人们非常感兴趣的。在这里，我们将揭示新的光的反应，即电子结构和溶剂化的微观见解，这已经很少讨论到目前为止。我们采用参考相互作用位模型-空间电子密度分布约束自洽场（RISM-SCF-cSED）方法，以硫酸和水分子为溶剂，研究了这一过程。该方法基于分子液体的量子化学和统计力学，自洽地确定溶质的电子结构和溶剂化结构。验证了溶液中的溶剂化自由能面和溶剂化结构。在苯与硝鎓离子成键过程中，硫酸分子的溶剂化结构发生了剧烈的变化，溶剂化作用对自由能的影响很大。通过对价电子结构的分析，揭示了σ-配合物在气相和溶液中π电子体系中的共振结构。
Nitration of benzene is a representative aromatic substitution reaction related to the σ-complex (arenium ion or “Wheland” intermediate) concept. This reaction is typically carried out in a mixed acid solution to generate nitronium ions, and how solvent molecules play roles in the reaction has been of great interest. Here we will shed new light on the reaction, namely the electronic structure and the microscopic insights of the solvation, which have been rarely discussed so far. We studied this process using the reference interaction site model-self consistent field with constrained spatial electron density distribution (RISM-SCF-cSED) method, considering sulfuric acid or water molecules as a solvent. In this method, the electronic structure of the solute and the solvation structure are self-consistently determined based on quantum chemistry and statistical mechanics of molecular liquids. The solvation free energy surfaces in solution and solvation structures were verified. In the bond formation process of benzene and nitronium ions, the solvation structure by sulfuric acid molecules drastically changes and the solvation effect on the free energy is quite large. We revealed largely contributing resonance structures in the π-electron system of the σ-complex in gas and solution phases by analysing the valence electronic structures.