Oxidation of Substituted Hydrazines by Superoxide Ion: The Initiation Step for the Autoxidation of 1,2-Diphenylhydrazine

Article abstract of DOI:10.1021/ja00329a007

Superoxide ion (O2^-.) in aprotic media and in the gas phase reacts with 1,2-disubstituted hydrazines to produce the anion radical of the 1,2-disubstituted azo compound.The latter species, upon exposure to molecular oxygen, is rapidly and cleanly oxidized to the pure azo compound.This combination of reactions represents a superoxide-catalyzed autoxidation; for 10 mM 1,2-diphenylhydrazine and O2 at 1 atm in dimethyl sulfoxide catalytic turnover numbers in excess of 200 are observed.The reaction cycle parallels the xanthine oxidase catalyzed autoxidation of reduced flavin/xanthine, which produces H2O2 and fractional quantities of O2^-..Monosubstituted hydrazines (e.g., PhNHNH2) are oxidized by O2^-. with a one-to-two stoichiometry; PhNHNH2 + 2O2^-. -> PhH + N2 + 2H2O2^-.Mechanisms are proposed for the O2^-./hydrazine oxidation processes and for the O2^-. induced autoxidation of 1,2-disubstituted hydrazines.