Aminopyrine and antipyrine free radical-cations: pulse radiolysis studies of one-electron transfer reactions
Abstract
Absolute rate constants for the reaction of a variety of electrophilic free radicals with the pyrazoline derivatives aminopyrine and antipyrine have been measured by pulse radiolysis. In the case of aminopyrine the resulting radical cation is a particularly stable species (ε325 5.35 × 103 dm3 mol–1 cm–1). Both compounds are readily oxidised to their respective radical-cations with the one-electron oxidation potential of antipyrine (E° 1.1–1.6 V) being higher than that of aminopyrine (E° 0.26–0.5 V). Studies of the reaction of the radical-cations with reducing agents suggest that aminopyrine in particular may prove to be a useful reference compound in studies of free radical one-electron oxidations.