  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.
