Peroxonitrites

Peroxonitrite is beHeved to be present in the crystals of nitric acid trihydrate that form in the stratosphere and in Martian soil (see Extraterrestrial materials). Peroxonitrous acid may be present in mammalian blood and other biochemical systems. However, peroxonitric acid, HNO, is not known. Before the chemistry of peroxonitrous acid was understood, these two acids were sometimes confused. 

Edwards, John O. and Plumb, Robert C., The Chemistry of Peroxonitrites... 41 599... 

Peroxomonosulfuric acid, 18 404—405 Peroxonitrite ion, 18 402 Peroxonitrous acid/salts, 18 402 Peroxophosphoric acids/salts, 18 402-404 Peroxopolyoxometallates, 18 415-416 Peroxosilicates, 18 402 Peroxosulfuric acids/salts, 18 404-405 Peroxotin compounds, 18 402 Peroxyacetic acid, 1 148 14 66, 67 Peroxyacetyl nitrate (PAN), 1 789, 795 Peroxyacids, 18 462 466... 

Kinetic and mechanistic studies of hexacyanoferrate(II) reductions include those of hypochlorite, of peroxodisulfate (for which activation volumes were determined), and of trart5-[Co(salen)(H20)2] (salen = A,A -ethylenebis(salicylideneaminate), (37)). Peroxonitrite oxidation of hexacyanoferrate(II) is first-order in peroxonitrite, zeroth-order in hexacyanoferra-te(II). The inference that the rate-limiting step in this reaction is decomposition of the oxidant is supported by activation volume data - the value of A for oxidation of hexacyanoferrate(II), -fllcm moU lies within the range established for peroxonitrite decomposition but is very different from the value of AF, -7cm moU ... 

Blough, N. V., and Zafiriou, O. C. (1985). Reaction of superoxide with nitric oxide to form peroxonitrite in alkaline aqueous solution. Inorg. Chem. 24, 3504-3505. 

Hughes, M. N., and Nicklin, H. G. (1970). The chemistry of peroxonitrites. Part 11. Copper (11)-catalysed reaction between hydroxylamine and peroxonitrite in alkali. T Chem. Soc. (A), 925-928. 

The decomposition rate increases with increasing pH. In the presence of oxygen, for example, in air, pure hydroxylamine or its aqueous solution decompose rapidly, especially at slightly elevated temperatures. At temperatures above 373 K, hydroxylamine decomposes explosively. Autoxidation takes place in basic solutions in the presence of transition metals and dioxygen. Hydroxylamine is oxidized to nitrite via nitrosyl and peroxonitrite ions. 

Reaction of the nitroxyl anion NO with dioxygen O2 forms peroxonitrite, which isomerizes in acidic solution to nitrate. 

The peroxonitrite ion has a partial double bond between nitrogen and the first peroxide oxygen. As shown in... 

Peroxonitrous acid is an acid of medium strength (p/fa = 6.8), which rapidly decomposes in neutral conditions (ti/2 = Is at pH = 7.4). Peroxonitrite can isomerize to nitrate or decompose to nitrite and dioxygen. Isomerization to nitrate is a major pathway in acidic media. The mechanism for the decomposition is still in doubt, but it is believed that HOONO homolyzes to give the NO2/OH radical pair. Peroxonitrites are stable in basic solution. Peroxonitrous acid is formed as a yellow intermediate in the reaction of nitrite solutions with hydrogen peroxide that leads to nitrates. 

Tetramethylammonium cw-peroxonitrite, which decomposes at 383 K, is prepared by reacting tetramethylammonium superoxide with nitric oxide in liquid ammonia at 195... 

Decomposition occurs to the same extent for pathways (272) and (273), whereas path (273) is of very minor importance. No peroxonitrite is formed in a cage-recombination reaction of the products of (271). The oxygen anion of (271) reacts further with water to form hydroxyl radicals that can oxidize nitrite anions back to NO2. 

Reaction of the peroxonitrite ONOO anion with OH- radicals from (274) forms the peroxonitrite radical ONOO-, that decomposes to dioxygen and NO, the major source for the formation of nitrite ions N02 in the system. 

The peroxonitrite anion, ONOO, has been identified [56] as a primary product of UV-irradiation of solid nitrates at 254 run. This has been identified as a principal path for nitrate breakdown. 

The cis form (85) is predicted to be more stable than the transform (86) by 12 -17kjmol by quantum chemical calculations. Tetramethylammonium peroxonitrite crystallizes inthecisform (85) (d(0=N) 116pm,d(N-O) 135pm,d(N-0) 141 pm) and is nearly flat with a torsion angle of 22°. In a solid argon matrix, both conformers show a reversible photoisomerism. 

Earley, Joseph E., Nonbridging Ligands in Electron-Tranter Reactions. Edwards, John O. and Plumb, Robert C., The Chemistry of Peroxonitrites. . . Edwards, John O., see Chaffee, Eleanor... 

Superoxide dismutase, SOD (54), contains copper and zinc in one subunit. The superoxide anion, 02 , is produced by the reduction of oxygen during respiration in all living species and photosynthesis reactions in plants. This radical anion is toxic probably via the formation of peroxonitrite (54) and hydrogen peroxide (54). Superoxide dismutase functions as an antioxidant via a catalytic reaction (reaction (38)) ... 

Copper ions catalyze a variety of inorganic redox reactions. The kinetics and mechanisms of some of these reactions were analyzed in detail. Thus, the reduction of V(IV) by Sn(II) and Ge(II) is catalyzed by Cu ions in the presence of high concentrations of Cl. The mechanism involves the reduction of Cu(II) by Sn(II) or by Ge(II) followed by the reduction of V(IV) by Cu(I) (134). These reactions proceed via the inner-sphere mechanism (134). Also the copper-catalyzed reduction of peroxonitrite by sulfite (135), the copper-catalyzed reduction of a Ni(IV) complex by thiols (136), and the reduction of superoxide boimd to binuclear cobalt(III) complexes by thiols (137) and by ascorbate (138) follow analogous inner-sphere mechanisms. Copper ions also catalyze the reduction of peroxide-boimd Cr(IV) by ascorbate(i39). 

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