Gallegos Miguel, Costales Aurora, Pendás Ángel Martín
Department of Analytical and Physical Chemistry, University of Oviedo, E-33006, Oviedo, Spain.
Chemphyschem. 2021 Apr 19;22(8):775-787. doi: 10.1002/cphc.202000975. Epub 2021 Mar 18.
Steric hindrance (SH) plays a central role in the modern chemical narrative, lying at the core of chemical intuition. As it however happens with many successful chemical concepts, SH lacks an underlying physically sound root, and multiple mutually inconsistent approximations have been devised to relate this fuzzy concept to computationally derivable descriptors. We here argue that being SH related to spatial as well as energetic features of interacting systems, SH can be properly handled if we chose a real space energetic stance like the Interacting Quantum Atoms (IQA) approach. Drawing on previous work by Popelier and coworkers (ChemistryOpen 8, 560, 2019) we build an energetic estimator of SH, referred to as E . We show that the rise in the self-energy of a fragment that accompanies steric congestion is a faithful proxy for the chemist's SH concept if we remove the effect of charge transfer. This can be done rigorously, and the E here defined provides correct sterics even for hydrogen atoms, where the plain use of deformation energies leads to non-chemical results. The applicability of E is validated in several chemical scenarios, going from atomic compressions to archetypal S reactions. E is shown to be a robust steric hindrance descriptor.
空间位阻（SH）在现代化学理论中起着核心作用，是化学直觉的核心所在。然而，与许多成功的化学概念一样，SH缺乏坚实的物理基础，人们设计了多种相互矛盾的近似方法，将这个模糊的概念与可通过计算得出的描述符联系起来。我们在此认为，由于SH与相互作用体系的空间和能量特征相关，如果我们选择一种实空间能量视角，比如相互作用量子原子（IQA）方法，就能恰当地处理SH。借鉴Popelier及其同事之前的工作（《化学开放》8, 560, 2019），我们构建了一个SH的能量估计器，称为E 。我们表明，如果去除电荷转移的影响，伴随空间拥挤的片段自能增加是化学家的SH概念的可靠代表。这可以严格地做到，并且这里定义的E即使对于氢原子也能提供正确的空间效应，而单纯使用变形能会得出不符合化学实际的结果。E的适用性在从原子压缩到典型S反应的几种化学情形中得到了验证。结果表明E是一个稳健的空间位阻描述符。
