Impact of upwardly revised ΔHf0 of primary, secondary, and tertiary radicals on mechanistic constructs in thermal reorganizations

Impetus for upward revision in the heats of formation of the ethyl (primary), isopropyl (secondary), and t -butyl (tertiary) free radicals has gained sufficient momentum in the last 6 yr to prompt an illustrative assessment of the far-ranging implications for interpretation of thermal reorganizations. Previous obstacles to consideration of diradicals as transition states in rearrangements of cyclopropanes and cyclobutanes are removed. The energetic relation of cyclohexa-1,4-diyl as an intermediate diradical in the Cope rearrangement to the transition state of a concerted mechanism is clarified. diradicals cyclopropane cyclobutane Cope rearrangement