Complex reactions ammonia oxidation

Half-reaction (i) means that Co(II) in aqueous solution cannot be oxidised to Co(III) by adding ammonia to obtain the complexes in (ii), oxidation is readily achieved by, for example, air. Similarly, by adding cyanide, the hexacyanocobaltate(II) complex becomes a sufficiently strong reducing agent to produce hydrogen from water ... 

MAA and MMA may also be prepared via the ammoxidation of isobutylene to give meth acrylonitrile as the key intermediate. A mixture of isobutjiene, ammonia, and air are passed over a complex mixed metal oxide catalyst at elevated temperatures to give a 70—80% yield of methacrylonitrile. Suitable catalysts often include mixtures of molybdenum, bismuth, iron, and antimony, in addition to a noble metal (131—133). The meth acrylonitrile formed may then be hydrolyzed to methacrjiamide by treatment with one equivalent of sulfuric acid. The methacrjiamide can be esterified to MMA or hydrolyzed to MAA under conditions similar to those employed in the ACH process. The relatively modest yields obtainable in the ammoxidation reaction and the generation of a considerable acid waste stream combine to make this process economically less desirable than the ACH or C-4 oxidation to methacrolein processes. 

Another copper catalyst, prepared by treating a NaY zeolite with copper nitrate, for ammonia oxidation (160—185°C) has been studied by Williamson et al. [349], The reaction is first order in NH3 and zero order in oxygen. The mechanism here is based on a Cu(II)(NH3)4+ complex formed in the large cavities of the zeolite. The rate-determining step is the reduction of Cu(II) by ammonia. 

Figure 18-19 The ammonia oxidation system of the bacterium Nitrosomonas. Oxidation of ammonium ion (as free NH3) according to Eq. 18-17 is catalyzed hy two enzymes. The location of ammonia monooxygenase (step a) is uncertain but hydroxylamine oxidoreductase (step b) is periplas-mic. The membrane components resemble complexes I, III, and IV of the mitochondrial respiratory chain (Fig. 18-5) and are assumed to have similar proton pumps. Solid green lines trace the flow of electrons in the energy-producing reactions. This includes flow of electrons to the ammonia monoxygenase. Complexes HI and IV pump protons out but complex I catalyzes reverse electron transport for a fraction of the electrons from hydroxylamine oxidoreductase to NAD+. Modified from Blaut and Gottschalk.315...

Dioiganotin dihalides are moderately strong Lewis acids and form stable complexes with ammonia and amines. The commercially important diorganotin compounds are most frequently the oxides, carboxylates, and mercaptocarboxylic acid esters. The oxides are amorphous or polycrystalline, highly polymeric, infusible, and insoluble solids. They are moderately strong bases and react readily with a wide variety of strongly and weakly acidic compounds. Their insolubility in all nonreactive solvents makes the choice of proper reaction conditions for such a neutralization reaction an important consideration for optimum yields. 

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