Mechanism of the Reaction of Nitriles with Alkaline Hydrogen Peroxide. Reactivity of Peroxycarboximidic Acid and Application to Superoxide Ion Reaction

Formation of peroxycarboximidic acid (1) is not rate-determining in the reaction of nitrile with alkaline hydrogen peroxide to form amide and oxygen; the yield of amide based on H2O2 varies from 20 to 60%. When dimethyl sulfoxide (DMSO), a reactive substrate, is added, the rate is independent of [DMSO] and governed in turn by a rate-determining addition of HOO− to nitrile. This reaction gives a reliable α-value of kHOO−/kHO−, which is 10000 for benzonitrile. A facile conversion of nitrile to amide may be achieved by the reaction in the presence of DMSO, unaccompanied by side reactions such as the epoxyamide formation from α,β-unsaturated nitrile. Kinetics and product analysis suggest that a predominant reaction is not a non-radical oxidation of H2O2 with 1 but a radical decomposition of H2O2 which is induced by the homolysis of anion of 1 (1A). No singlet oxygen could be trapped chemically. The reaction of superoxide ion, O2\ewdot, with acetonitrile is shown to be analogous to that of HOO−; the decomposition of O2\ewdot is fast in the presence of MeCN and DMSO in benzene, affording acetamide and dimethyl sulfone.