OUTER-SPHERE AND INNER-SPHERE PROCESSES IN ORGANIC-CHEMISTRY - REACTION OF TRIFLUOROMETHYL BROMIDE WITH ELECTROCHEMICALLY GENERATED AROMATIC ANION RADICALS AND SULFUR-DIOXIDE ANION RADICALS

The reduction of CF3Br by electrochemically generated aromatic anion radicals gives rise to purely catalytic currents. An activation-driving force relationship characterizing outer-sphere electron donors can thus be established. Electrochemically generated sulfur dioxide anion radicals do not give rise to catalytic currents upon reaction with CF3Br but rather produce trifluoromethyl sulfinate according to an overall two electron per molecule stoichiometry. The rate constant of the rate-determining step of the the reaction is at least 4 orders of magnitude larger than that of an aromatic anion radical of the same standard potential, unambiguously showing that SO2*- does not react as an outer-sphere;electron donor. Among the various possible inner-sphere processes, bromine atom abstraction appears as the most likely. © 1990, American Chemical Society. All rights reserved.