Amphielectronic ionization of a π-radical, a basis for correlating radical with nucleophilic and/or electrophilic reactivities

Abstract

The stable free radical 9-[fluorenylidene(phenyl)methyl]fluorenyl ionizes to the corresponding cation in acidic media, whereas in basic solvents it is converted into the relevant carbanion, by accepting single electrons from various anions and from aliphatic amines. This transformation provides, in part another example of the thermodynamic cycle recently used by Breslow and Mazur in order to correlate pK_a with pK_R⁺ values of related carbanions and carbocations. The reality of this transformation suggested a successful attempt to inter-relate kinetic and thermodynamic parameters of radicals, carbocations, and carbanions. These correlations may be thought of as corollaries of the combined Breslow–Mazur and Brønsted equations.