REACTIVITY OF SUPEROXIDE ION WITH HALOGENONITRILES AND DIHALOCARBONS IN APROTIC MEDIA

The reactivity of superoxide ion (O-2-radical-anion) with halogenated substrates is investigated by cyclic voltammetry and rotated ring-disk electrode method in aprotic solvents. The more positive the reduction potential of the substituted nitrile, the more facile is nucleophilic displacement by O-2-radical-anion. The reaction rates of halogenonitr iles with O-2-radical-anion vary according to the leaving-group propen sity of halide (Br>Cl>F). The relative reaction rates of other substit uted nitriles are in the order of electron-withdrawing propensity of t he substituent group (CN>C(O)NH2>Ph approximate to CH2CN). The reactio n of O-2-radical-anion with dihalocarbons indicates that five-membered rings can be rapidly formed by the cyclization of substrate and O-2-r adical-anion, and the relative rates of cyclization depend on the numb er of methylenic carbons {Br(CH2)(n)Br, [n=1<2<3>4 >5]}. Mechanisms ar e proposed for the reaction of O-2-radical-anion with halogenated subs trates.