Oxidation hydroxylamines

Prevents formation of hydroxylamine (oxidizing) metabolite of dapsone... 

See Formaldehyde, above Hydrazine Oxidants Hydroxylamine Oxidants... 

Two general mechanisms exist for NO release from oximes 1. hydrolysis to hydrox-ylamine followed by hydroxylamine oxidation and 2. direct oxidation and decomposition of the oxime. 

Direct oxidation of primary amines with peroxide oxidants does not provide appreciable yield of hydroxylamines. As was mentioned above, oxidation of secondary amines usually proceeds smoothly giving moderate to good yields of iV,iV-disubstituted hydroxylamines. Oxidation of sterically hindered secondary amines such as 125 (equation 88) can also be done with peracids . Further oxidation of the resulting Af,A-disubstituted hydroxylamines 126 with an excess of m-chloroperbenzoic acid is known to end up with the corresponding nitroxyl radicals of type 127 (equation 88) ° although the reaction can be stopped at the hydroxylamine stage. 

Aromatic hydroxylamines, oxidized in the presence of metallic ions, are converted into nitroso compounds. In the absence of such ions, azoxy compounds form. 

Hydroxylamines are commonly postulated as intermediates in diese oxidations, but dey are rarely isolated or detected. Two examples of reactions in which products at the hydroxylamine oxidation level can be isolated bodi involve peroxides. Oxidation of alkylamines (2 R = Bu, Me and niCH2) with arenesul-fonyl peroxides bearing an electron-wididrawing group gave die arenesulfonyloxyamines in good yields (Scheme 6). A similar reaction of primary amines wi dibenzoyl peroxide gave benzoyloxyamines. ... 

HAO catalyzes the four-electron oxidation of hydroxylamine to nitrite. " It is present in autotrophic nitrifying bacteria, like Nitrosomonas, which are obligate chemolithotrophs that use the oxidation of ammonia as their sole energy source. For each cycle of hydroxylamine oxidation, two electrons are returned for the initial step of ammonia oxidation and the other two are either transferred to the terminal oxidase via the components of the respiratory chain, or used to generate NADH by reverse electron transport. 

The overall reaction is energy yielding, and allows sufficient ATP production to support reverse electron transport for CO2 fixation. However, the first step, oxidation of NH3 to hydroxylamine, requires the input of reducing power. The second step, hydroxylamine oxidation, yields four electrons. These join the electron transport chain at the level of ubiquinone, from which two are shunted back to AMO for activation of NH3. The N oxidation and electron transport pathways in Nitrosomonas are linked in the cytoplasmic membrane and periplasmic space detailed information from the N. europaea genome (Chain et al., 2003) is consistent with the previous biochemical characterizations of the system (Whittaker et al., 2000). Depending on conditions (and enhanced at low oxygen concentrations), nitric oxide (NO), nitrous oxide (N2O) and even dinitrogen gas (N2) have been reported as secondary products... 

The anion radical of 2-methyl-2-nitropropane being formed by reduction with alkali metal or electrolysis fragmentates to tert-butyl radicals and nitrite ions. Thus formation of di-tert-butylaminyloxide is initiated85. Treatment of 2-methyl-2-nitro-propane with sodium phenyl gives tert-butyl-phenylaminyloxide the reaction proceeding through an intermediate hydroxylamine oxide salt 65 which is even isolable86. ... 

Alcaligenes faecalis has a hydroxylamine-oxidizing enzyme which differs from the enzyme of other heterotrophic nitrifying bacteria. In this bacterium, hydroxylamine is oxidized through pyruvic oxime (Fig. 3.6). Pyruvic acid derived from lactate, succinate, and other carboxylates reacts nonenzymatically with hydroxylamine formed from ammonia to form pyruvic oxime. This compound is oxidized to nitrite and pyruvic acid by the catalysis of pyruvic oxime dioxygenase (Ono et al., 1996, 1999). 

Numata M (1989) Studies on hydroxylamine oxidation in Nitrosomonas europaea. Dissertation for Masters degree, Tokyo Institute of Technology Numata M, Saito T, Yamazaki T, Fukumori Y, Yamanaka T (1990) Cytochrome P-460 of Nitrosomonas europaea further purification and further characterization. J Biochem 108 1016-... 

Otte S, Schalk J, Kuenen JG, JettenMSM (1999) Hydroxylamine oxidation and subsequent nitrous oxide production by the heterotrophic ammonia oxidizer Alcaligenes faecalis. Appl Microbiol Biotechnol 51 255-261... 

Wehrfritz J-M, Carter JP, Soiro S, Richardson DJ (1997) Hydroxylamine oxidation in heterotro-phic nitrate-reducing soil bacteria and purification of hydroxylamine cytochrome c oxidore-ductase from Pseudomonas species. Arch Microbiol 166 421 —424 Wehrfritz J-M, Reilly A, Spiro S, Richardson DJ (1993) Purification of hydroxylamine oxidase from Thiosphaera pantotropha. Identification of electron acceptors that couple heterotrophic nitrification to aerobic denitrification. FEBS Lett 335 246-250 Wetzstein H-G, Ferguson SJ (1985) Respiration-dependent proton translocation and the mechanism of proton motive force generation in Nitrobacter winogradskyi. FEMS Microbiol Lett 30 87-92... 

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