On the origin of the steric effect

Abstract

A quantitative analysis of the steric effect of aliphatic groups was carried out from first principles. An intuitive framework is proposed that allows the separation and straightforward interpretation of two contributors to the steric effect: steric strain and steric shielding (hindrance). When a sterically demanding group is introduced near a reactive center, deformation of its reactive zone will occur. By quantifying this deformation, a convincing correlation was established with Taft's steric parameters for groups of typical size, supporting the intuitive image of steric shielding; bulky groups slow down the reaction by limiting the accessibility of the reactive centre. On the other hand, the strong initial repulsion between the reactant and the substrate by means of the filled-filled orbital interaction results in the deformation of the substrate as well as a less stabilizing reaction zone, which are the manifestations of the steric strain. We thus conclude that both steric strain and steric hindrance can be derived from the Pauli repulsion evolving between the reactants in the course of the reaction.

Microkinetic Modeling of Benzyl Alcohol Oxidation on Carbon‐Supported Palladium Nanoparticles

“…Given the type of kinetic modeling used here, it should be possible to extract the steric factor for the molecule “sticking” to the surface at the beginning of reaction. This will serve as a check to make sure the model has kinetics that are of a physically realistic order of magnitude.…”

Regioselectivity in Electrophilic Aromatic Substitution: Insights from Interaction Energy Decomposition Potentials

“…As this energy term probes the steric repulsion, it gives useful insight into the deformation pressure induced by the approaching electrophile. [36] Based on this, we decided to compute all planes at 2.8 Å. At this distance, the Pauli repulsion is usually low compared to other terms (less than 10 % of the absolute sum of all the energy terms) and deformations are therefore expected to be negligible.…”

Unique bonding pattern and resulting bond stretch isomerism in Be32−

“…Here, DE Pauli represents the repulsive filled-filled orbital interaction, generally noted as the steric interaction, [41] and DE oi corroborates to the interfragment and intrafragment occupied-vacant orbital mixing on the cluster from the predefined fragments. This method combines the extended transition state (ETS) energy decomposition approach [42] with the natural orbitals for chemical valence (NOCV) density analysis method.…”