Peroxynitrous acid 0-0 bond homolysis

The second proposal is a bit more imaginative and arises from the above arguments that 0—0 bond homolysis is much too slow to be involved in oxidations by peroxynitrate. Pryor and coworkers invoked the intermediacy of a metastable form of peroxynitrous acid (HO—ONO ) in equilibrium with its ground state. This so-called excited state of peroxynitrous acid has, to date, eluded detection or characterization by the experimental community. However, recent high-level theoretical calculations by Bach and his collaborators have presented plausible evidence for the intermediacy of such a shortlived species with a highly elongated 0—0 bond and have confirmed its involvement in the oxidation of hydrocarbons (see below). The discovery of this novel series of biologically important oxidants has fostered a new area of research in both the experimental and theoretical communities. In this chapter we will describe many of the more pertinent theoretical studies on both the physical properties and chemical reactivity of peroxynitrous acid. 

The oxidation of thiophene (Th) by peroxynitrous acid (HOONO), generated in the H2O2-HNO2 system, proceeds simultaneously in both the gaseous and the liquid phases of the reactor. The conclusion that the active oxidant in both cases is the HO radical, formed by HO-ONO bond homolysis, is based on the equality of the rate constants of the reaction in the two phases. ... 

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