Nitroxyl species oxygen reactions

Chemical mechanism for reaction of a peracid with a N-hydroxyguanidine to generate the urea product and nitroxyl. This reaction is a chemical model for the second phase of the proposed NOS reaction, which involves nucleophilic attack by an activated oxygen species, C-N bond scission, and incorporation of molecular oxygen. 

This reaction mechanism addresses the product distribution (NO, N2O, and N2) as a function of the degree of oxidation of the catalyst surface. Over an oxidized surface, the selectivity to NO will be very high as the nitroxyl HNO intermediate species will react with lattice oxygen to yield NO, rather than a second-order reaction between two nitroxyl HNO species to N2O. The formation of N2 by step 10 is also a second-order process, fevored at high ammonia partial pressures. A third route for the formation of N2 is through the decomposition of NO, as observed by pulsing NO over the LaCoOg. 

Oxidative reactions of organonitrogen species that do not involve molecular oxygen are rather limited. The only case for which the evidence is at all convincing is the oxidation of arylhydroxylamines to arylnitroso species (Table 2). This reaction resembles the first half of the hydroxylamine oxidoreductase reaction found in nitrifying bacteria. The key difference is that the aryl nitroso compound is stable (although condensation with the arylhydroxy-lamine can occur to produce the azoxy compound, ArN(O)NAr), while the inorganic analog is nitroxyl, HNO, which if released from the enzyme would rapidly dimerize and dehydrate to form N2O. Consequently, HAO does not release the HNO or NO intermediate, but instead oxidizes it to nitrite before any substrate-derived species are released. 

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