Reducibility of the carbon-fluorine bond in the trifluoromethyl group

Trifluoromethylarenes can be reduced in liquid ammonia via an irreversible stepwise mechanism. The number of electrons involved in the first reduction wave observed by cyclic voltammetry is always higher than two, i.e. more than one carbon-fluorine bond is reduced at the reduction potential of the trifluoromethylarene. The cleavage rate constant of the transient anion-radical decreases when the standard reduction potential of the trifluoromethylarene increases. The electrochemical reduction of a trifluoromethoxyarene such as 4-trifluoromethoxybenzonitrile occurs via a bielectronic stepwise mechanism in which the trifluoromethoxyl group behaves as a leaving group.