The role of steric effects on hydrogen atom transfer reactions

TL;DR

This study investigates how steric effects impact hydrogen atom transfer reactions, revealing that bulky substituents on radicals significantly influence activation barriers and reaction enthalpies, with quantum chemical computations supporting these findings.

Contribution

It provides new insights into the role of steric and dispersion effects on HAT reaction mechanisms through quantum chemical analysis.

Findings

Steric effects on radicals significantly alter activation barriers.

Activation barriers correlate with reaction enthalpies via Evans-Polanyi.

Dispersion effects can stabilize transition states in certain cases.

Abstract

We explored how steric effects influence the rate of hydrogen atom transfer (HAT) reactions between oxyradicals and alkanes. Quantum chemical computations of transition states show that activation barriers and reaction enthalpies are both influenced by bulky substituents on the radical, but less so by substituents on the alkane. The activation barriers correlate with reaction enthalpies via the Evans-Polanyi relationship, even when steric effects are important. Dispersion effects can additionally stabilize transition states in some cases.