Hydroxylamine nitrite formation

Amarger, N., and Alexander, M. (1968). Nitrite formation from hydroxylamine and oximes by Pseudomonas aeruginosa. ]. Bacteriol. 95, 1651-1657. 

Thus, copper and platinum give similar results the nitrite formation is greater with iron, nickel, and cobalt, and the nitrate formation less. The gases were mainly nitrous oxide and nitrogen with a small proportion of oxygen. N. D. Zelinsky and S. G. Krapiwin showed that the decomposition of hydroxylamine into acid and base does not occur in soln. with methyl alcohol as solvent. J. Tafel showed that an aq. soln. of hydroxylamine sulphate in presence of 20-50 per cent, of sulphuric acid is not reduced at a copper cathode. O. Flaschner observed some reduction in dil. sulphuric acid soln. J. Tafel and H. Hahl found that reduction always takes place when the sulphuric acid cone, in the layer of electrolyte in contact with the cathode is reduced beyond a certain point, and when there is no excess of acid in other words, when hydroxylamine sulphate itself is electrolyzed, the reduction is quantitative. These results are most readily accounted for on the view that only free hydroxylamine (produced in this case by partial hydrolysis of the sulphate), but not the hydroxylammonium ion, NH3OH, is reduced at a copper... 

Fig. 3.6. A schematic presentation of nitrite formation from hydroxylamine in the cell of Alcaligenes faecalis. Circled numbers 1, ammonia monooxygenase 2, pyruvic oxime...

The autoxidation of hydroxylamine to nitrite also involves a radical chain process (Kono, 1978), and the reaction is carried out at high pH. The assay was originally utilized by Elstner and Heupel (1976) who initiated the autoxidation by O2 generated by the xanthine/xanthine oxidase reaction. Nitrite formation was determined colorimetrically at 530 nm by diazo coupling with a-naphthylamine and superoxide dismutase was found to inhibit end product formation. Kono (1978) developed the assay further by utilizing nitroblue tetrazolium as the... 

Figure 7. Nitrite formation from hydroxylamine. Reaction mixture contained in 3 mL 50 mM phosphate buffer pH 7.8 1 fjjnol of NH OH chloroplasts with 75 /xg of chlorophyll and where indicated 6.6 /aM paraquat 50 units SOD. Illuminated at 275 Wm at 22°C. Key control, plus paraquat. A plus SOD, and plus paraquat and SOD, A (72).

This chapter covers more specifically the copper-catalyzed C(aryl)-N bond formation via the coupling of aryl halides with nitrogen nucleophiles such as N-heterocycles, amines, anilines, amides, ammonia, azides, hydroxylamines, nitrite salts or phosphonic amides. The C(aryl)-N bond formation as a result of the coupling between these nucleophiles and arylboronic acids (the Chan-Lam reaction) will be also presented. It is worth noting that this chapter mainly focuses on the most significant results and important breakthroughs in this field. 

The reduction of NOJ to NH3 is an 8-electron process, which probably involves the intermediate formation of nitrite and hydroxylamine ... 

Coin-cyclam322-324 and Nin-cyclam322 catalyze the electroreduction of nitrate in aqueous electrolytes with good current efficiencies and turnover numbers, giving mixtures of ammonia, nitrite, and hydroxylamine at a variety of electrode materials. Mechanistic investigations suggested the adsorption of electroreduced Co1- and Ni1 cyclam onto the electrode surface,322 and the formation of an oxo-metal bond via reduction of coordinated nitrate.323... 

Given that hydroxylamine reacts rapidly with heme proteins and other oxidants to produce NO [53], the hydrolysis of hydroxyurea to hydroxylamine also provides an alternative mechanism of NO formation from hydroxyurea, potentially compatible with the observed clinical increases in NO metabolites during hydroxyurea therapy. Incubation of hydroxyurea with human blood in the presence of urease results in the formation of HbNO [122]. This reaction also produces metHb and the NO metabolites nitrite and nitrate and time course studies show that the HbNO forms quickly and reaches a peak after 15 min [122]. Consistent with earlier reports, the incubation ofhy-droxyurea (10 mM) and blood in the absence of urease or with heat-denatured urease fails to produce HbNO over 2 h and suggests that HbNO formation occurs through the reactions of hemoglobin and hydroxylamine, formed by the urease-mediated hydrolysis of hydroxyurea [122]. Significantly, these results confirm that the kinetics of HbNO formation from the direct reactions of hydroxyurea with any blood component occur too slowly to account for the observed in vivo increase in HbNO and focus future work on the hydrolytic metabolism of hydroxyurea. 

S-Nitrososulphinates can be made by treating sulphinic acids with N2O4 at about —20 °C in ether (equation 32)76. Use of nitrous acid on alkyl nitrites leads to the formation of the corresponding hydroxylamines (equation 33) in a reaction where it is believed that the first formed nitrososulphinate nitrosates another molecule of the reactant sulphinic acid77. 

Similar complexes can be prepared using other thiol-containing reagents and/ or by starting with hydroxylamine or with nitrite and a reductant such as sodium dithionite. Formation of the complex is favorable enough so that it can be quantitatively prepared. The reaction may be used as an assay for free iron (Salerno et al., (1976). 

Green plants, algae, fungi, cyanobacteria and bacteria that assimilate nitrate also produce assimilatory nitrite reductases, which catalyze the six-electron reduction of nitrite to ammonia (equation 89). The formation of heme-nitrosyl intermediates has been detected in several cases,1515 while hydroxylamine is commonly thought to be an intermediate. Added hydroxylamine is rapidly reduced to ammonia. However, no intermediates are released, and ammonia is the only product... 

It is now well established that hydroxylamine is an intermediate, the oxygen atom being derived from dioxygen (equation 93).1539 The formation of hydroxylamine and its subsequent oxidation to nitrite are affected differently by various inhibitors, while certain inhibitors cause an accumulation of hydroxylamine. This suggests that the two processes are independent. The presence of dioxygen is essential for hydroxylamine to be oxidized to nitrite, otherwise N20 and NO are formed. 

The pure, anhydrous nitrite is not hygroscopic, but as usually prepared the substance is a very deliquescent, crystalline solid, its aqueous solution having a slight alkaline reaction. At 15-5° C. the solubility is 300 grams per 100 grams of water.11 The heat of formation in aqueous solution from the elements is 88-9 Cal.12 The products of electrolytic reduction are hyponitrite, ammonia, and hydroxylamine. 

That hydroxylamine might not be an obligatory intermediate, or occur as a free intermediate, in the reduction of nitrite to ammonia is suggested by the properties of nitrite reductases of Azotobacter chroococcum and Escherichia coli. The former is an adaptive enzyme, the formation of which requires nitrate or nitrite in the culture (31,2). It is FAD-depen-dent and presumably contains metals and p-mercuribenzoate inhibitable... 

N-Nitrosation of oximes by nitrosyl halides or nitrite esters often results in the formation of N-nitrimines, R R C=NN02, these compounds being formed by rearrangement of the initial adducts. N-Amination of oximes by chloramine or by hydroxylamine-O-sulfonic acid can result in the formation of diazo compounds (Scheme 28). The reaction, known as the Forster reaction, has been used for the preparation of aryldiazoalkanes, although better methods are usually available. Diazo ketones of the general formula (49) have also been prepared by this method from the oximes. "... 

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