THE KINETIC AND THERMODYNAMIC INFLUENCE OF FLUORINE VERSUS METHYL SUBSTITUENTS IN METHYLENECYCLOPROPANE REARRANGEMENTS

A comprehensive review of the kinetic and thermodynamic influences of methyl and fluorine substituents on the methylenecyclopropane rearrang ement is presented. In spite of a superficial similarity of the overal l influence of these two substituents, methyl's effect derives largely from the incremental nature of its radical- and alkene-stabilizing, a nd steric impact, while fluorine's effect derives from its large and n on-incremental influence on the strain of cyclopropane coupled with it s similarly variable effect on the stability of alkenes and free radic als.