Role of Hyperconjugation in Determining Carbon−Oxygen Bond Dissociation Enthalpies in Alkylperoxyl Radicals

<UFIGR ID="ol027094xn00002">Theoretical calculations of carbon−oxygen bond dissociation enthalpies in substituted methylperoxyl radicals (YCH<INF>2</INF>OO^•) reveal that bond strengths are not governed solely by the stability of YCH2^• radicals but are largely affected by hyperconjugation when Y is electron-donating or conjugating. In many cases, this hyperconjugative effect is greater than stabilization of the methyl radical by Y. All electron-withdrawing Y exert small destabilizing effects via inductive withdrawal of electrons from the polarized C−OO^• bond.