Reductions by hyponitrite

Hyponitrites, salts of the weak acid HO-N=N-OH, hyponitrous acid, react, in aqueous solution (pH 4-8), with an array of inorganic oxidants. With the h igh potential reagents Br-2 and [Fe(bipy)(3)](3+) in excess, conversion is mainly to nitrate, whereas with I-2 and [IrCl6](2-), the product is nitrite . Kinetic acidity patterns indicate that nearly all oxidations proceed larg ely through the conjugate base, HN2O2-. With I-2, I-3(-), and Br-2 there is also evidence also for a doubly deprotonated route, possibly involving a h alogen-N2O22- complex. The 1e(-) metal oxidants [Fe(bipy)(3)](3+) and [IrCl 6](2-) probably operate through a series of outer-sphere 1e(-) steps in whi ch the initial transfer is rate-determining, whereas with I-2 and Br-2, rea ction via a halogen bridge, resulting in net transfer of X+ (a 2e(-) change ) is more likely. None of the reaction profiles exhibits irregularities att ributable to the intervention of an intermediate formed or destroyed on a t ime scale commensurate with the initial reaction.