Ammonium aerobic oxidation

When organics containing reduced nitrogen are degraded, they usually produce ammonium, which is in equilibrium with ammonia. As the pK for NH3 NH4" is 9.3, the ammonium ion is the primary form present in virtually all biological treatment systems, as they operate at pH < 8.5 and usually in the pH range of 6.5-7.5. In aerobic reactions, ammonium is oxidized by nitrifying bacteria (nitrosomonas) to nitrite... 

Hydroxylamine is a powerful reducant, particularly when anhydrous, and if exposed to air on a fibrous extended surface (filter paper) it rapidly heats by aerobic oxidation. It explodes in contact with air above 70°C [1]. Barium peroxide will ignite aqueous hydroxylamine, while the solid ignites in dry contact with barium oxide, barium peroxide, lead dioxide and potassium permanganate, but with chlorates, bromates and perchlorates only when moistened with sulfuric acid. Contact of the anhydrous base with potassium dichromate or sodium dichromate is violently explosive, but less so with ammonium dichromate or chromium trioxide. Ignition occurs in gaseous chlorine, and vigorous oxidation occurs with hypochlorites. 

L — maltolate the coordination environment of the vanadium in K[V02(malt)2] H2O is approximately octahedral, the two 0x0 ligands being in cis positions. [K(H20)e] units link adjacent vanadium(V) complex anions to give a chain structure 166). The main products of aerobic oxidation of [V O(dmpp)2l in aqueous solution are [V02(dmpp)] and [VOo(dmpp)2]. High pH favors these V products, whereas at low pH V species predominate 171). Vanadium(V) also forms a VO(OR)(malt)2 series, readily prepared from ammonium vanadate, maltol, and the appropriate alcohol in a water-alcohol-dichloromethane medium 172), and 3-hydroxy-4-pyridinonate analogues V0(0R)L2 on oxidation of their oxovanadium(IV) precursors in solution in the appropriate alcohol ROH 168). 

In another example, RuCl2(PPh3)3 in [BMIMjCl was shown to be a much less active catalyst than this complex in the ionic liquids [R4N]C1 or [R4N]OH for the aerobic oxidation of alcohol (199). The weaker association of the bulky tetraalkyl-ammonium cation than the planar [BMIM] cation with the anion appears to be the principal reason for the difference. 

Oxidation of alcohols. The pernithenate salt is an excellent catalyst for aerobic oxidation of alcohols to aldehydes and ketones in the presence of 4A molecular sieves. The use of a polymer-supported ammonium perruthenat is perhaps an improvement, with good discrimination in the oxidation in favor of primary alcohols. Another versioif specifies a system containing CuCl and 2-aminopyridine also. 

A novel methodology, including the aerobic oxidation of alcohols to their corresponding carbonyl compounds in the presence of several ruthenium catalysts in various ammonium salts, as ionic liquids, was proposed by Wolfson et al. (Scheme 14.39) [41]. 

Scheme 14.39 Ruthenium and ammonium salts used in the aerobic oxidation of alcohols...

N2O is a reduced gas which is produced in the ocean primarily by microbial nitrification and denitrification. N2O is released during ammonium (NH4) oxidation to nitrite (NO2) (Figure 1), although the exact mechanism has yet to be confirmed. N2O may be an intermediate of nitrification, or a byproduct of the decomposition of other intermediates, such as nitrite or hydroxylamine. Nitrification is an aerobic process, and the N2O yield under oxic conditions is low. However, as the nitrification rate decreases under low oxygen, the relative yield of N2O to nitrate production increases and reaches a maximum at 10-20 (imol dm oxygen (pmol = 1 x 10 mol). Conversely, denitrification is an anaerobic process in which soluble oxidized nitrogen... 

Nitrification in wetlands is restricted to aerobic zones of soil and water column or under drained soils conditions, where ammonium is oxidized to nitrate. Nitrification reaction supports denitrification by supplying heterotrophs with nitrate as their electron acceptor. In a broader sense, nitrification is defined as the conversion of organic or inorganic compounds from reduced state to a more oxidized state. Three groups of microorganisms are capable of oxidizing ammonium under aerobic conditions ... 

Ammonium N has been shown to be a competitive inhibitor of methane oxidation, suggesting that ammonia and ammonium are oxidized by the methane monooxygenase system. There are striking similarities between ammonium oxidation by Nitrosomonas and methane oxidation by methanotrophs. The methanotrophic bacteria are obligate aerobes and closely associated with the... 

Phenyl mercuric nitrate, iodoacetate, thiourea, and ammonium sulfate stimulated arsenite-oxidizing activity, whereas cupric ion, and p-chloromercuriben-zoate inhibited it significantly. Legge (8) showed that cytochromes associated with the solid fraction from broken cells of P. arsenoxydans-quinque played a role in aerobic oxidation of arsenite. 

A milestone in the aerobic oxidation of alcohols was the report of Kaneda and CO workers describing the use of palladium supported on hydroxyapatite as a highly active and reusable soUd catalyst for the atmospheric-pressure aerobic oxidation of alcohols [98]. Hydroxyapatite is a synthetic calcium phosphate phase obtained reproducibly by precipitation starting from soluble calcium nitrate and ammonium hydrogenophosphate salts. The hydroxyapatite-supported palladium was water insensitive and exhibited unprecedentedly high turnover numbers for alcohol oxidation, particularly high for 1-phenylethanoL The catalyst showed a general activity for primary, secondary, ahphatic and aromatic alcohols. 

Tetrahydrofolic acid is also an enzymic acceptor of a formimino group from formiminoglycine or from formiminoglutamic acid. The product, 5-formimino-5,6,7,8-tetrahydrofolic acid, is converted in acidic solution to anhydrofolinic acid and ammonium ion and has a half-Ufe of about i h at 37° over a pH range i of 5-9. Aerobic oxidation of tetrahydrofolic acid produces />-aminobenzoy lutamic acid and a number of pteridines, including xanthopterin . ... 

In the same year, Jiao and coworkers developed a Cu-catalyzed synthesis of pyridines from acetaldehydes and nitrogen source [63]. 3,5-Diarylpyridines were produced in good cascade Chichibabin-type cycli-zation, C-(sp )-C(sp ) cleavage, and aerobic oxidation (Scheme 3.28). Azide and ceric ammonium nitrate (CAN) were found as efficient nitrogen donors and with O2 as the oxidant. 

It is interesting to develop a novel route to the CL precursor, PDHA, which was hitherto prepared by hydrogen peroxide oxidation of cyclohexanone (3) followed by treatment with ammonia [126,130]. Because ofthe ease of transformation of PDHA to a 1 1 mixture of CL and 3 under the influence of an appropriate catalyst such as lithium halides, the CL production via PDHA is considered to be a superior candidate for a next-generation waste-free process for CL. The NHPI-catalyzed aerobic oxidation of KA oil was applied to the synthesis of PDHA without formation of any ammonium sulfate waste. The strategy is outlined in Scheme 6.10. The NHPI-catalyzed oxidation of KA oil (a mixture of 3 and 2) with O2 produces 1,1 -dihydroxydicyclohexyl peroxide, which seems to exist in equilibrium with cyclohexanone and H2O2 (path 1). Subsequent treatment of the resulting reaction mixture... 

We have found that quaternary ammonium bromides accelerate the NHPl-catalyzed aerobic oxidation even in the absence of any metal catalyst Matsunaka,... 

Polystyrene-based immobilized ruthenium catalysts can be used in oxidation of alcohols with NMO, TEMPO/O2, or O2 [94]. Catalytic oxidative cleavage of vicinal diols to aldehydes with dioxygen was reported with RuCl2(PPh3)3 on active carbon [95]. Ionic liquids such as tetramethyl ammonium hydroxide and Aliquat 336 can be used as the solvent for the RuCl2(PPh3)3-catalyzed aerobic oxidation of alcohols [96]. 

Ammonium salts are another class of alternatives for hydrazoic acid that make the handling of reactions more convenient. For example, ammonium acetate could be used under aerobic oxidative transformation of aromafic aldehydes to nitriles. Notably, hydroxylammonium chloride has been a widely used nitrogen source for the ammoxidation of aldehydes since a long time ago. In 1935, veratronitrile was synthesized via veratraldoxime intermediate from the reaction of veratraldehyde with the warm solution of hydroxylammonium chloride (Scheme 4.4) [41]. The aldoxime was then placed with acetic anhydride to give the corresponding nitrile in 70-76 % yield based upon the aldehyde. Therefore, hydroxylammonium chloride mediated reactions involve Beckmann rearrangement with the loss of water [42—44]. This class of anunoxidation is also applicable to aliphatic aldehydes. 

Yadav DKT, Bhanage BM (2013) Copper-catalyzed synthesis of nitriles by aerobic oxidative reaction of alcohols and ammonium formate. Eur J Org Chem 23 5106-5110... 

Jiao et al. developed copper-catalyzed diverse constructions of 3,5-diarylpyridines and 2-(lTf)-pyridones through tandem Chichibabin-type cyclization, C(sp )-C(sp ) bond cleavage, and aerobic oxidation with high selectivity. Azide, ceric ammonium nitrate (CAN), and 2-aminopyridine are efficient nitrogen donors in this Cu catalytic system for the selective synthesis of pyridines and pyridones [151] (Scheme 8.81). 

---