The importance of non-minimum energy reactant conformations in the norrish type II reaction

Abstract

The Norrish type II γ-hydrogen atom abstraction rate constants in solution for the ketone homologous series (1)–(4) do not correlate with the abstraction geometries as determined by X-ray crystallography, but follow instead the well established bimolecular free radical hydrogen abstraction reactivity pattern cycloheptane > cyclopentane ∼cyclohexane > cyclobutane; this is interpreted as being due to rapid hydrogen atom abstraction from non-minimum energy reactant conformations.