Nitrogen oxides dimer

Nitrogen dioxide, N02 (oxidation number -t-4), is a choking, poisonous, brown gas that contributes to the color and odor of smog. The molecule has an odd number of electrons, and in the gas phase it exists in equilibrium with its colorless dimer N204. Only the dimer exists in the solid, and so the brown gas condenses to a colorless solid. When it dissolves in water, NOz disproportionates into nitric acid (oxidation number +5) and nitrogen oxide (oxidation number +2) ... 

Volatile decomposition products may include HC1, HBr, HI, nitrogen oxides (NO ), and toxic dimerization products. 

The hydroxymethyl group in a position a to the heterocyclic nitrogen is sensitive to further oxidation and tends to form an oxidative dimer product [Eq. (45)]. 

Nitrogen dioxide readily converts to other forms of nitrogen oxides. It coexists in equilibrium with its dimeric form, N2O4. The latter is more stable at ordinary temperatures. 

In another example of oxidation without fission, the major product obtained from the reaction of methyl 2-pyridylacetate with ethyl a-bromopropionate was not the expected indolizine (63) but its oxidation product (64). This was shown by a repetition of the reaction under nitrogen leading to (63), which subsequently could be oxidized to (64) by potassium ferricyanide (70JCS(C)1434). An oxidative dimerization at the 3-position of 1,2-dimethylin-dolizine was achieved with potassium ferricyanide (71TL1273) or palladium on charcoal in boiling xylene (81BCJ2833). 

The biomedical research on nitrogen oxides has nearly exclusively involved NO and its oxidative metabolites. Reduced species, such as nitroxyl (HNO) and hydroxylamine (NH2OH), have been largely unexplored in mammalian systems until recently. The initial interest in the biochemistry of HNO arose following observation of nitrous oxide (N20) during bacterial reduction of nitrite to NH3. Dehydrative dimerization of HNO to form N20 (77, 78) was well documented in the gas phase,... 

Acyl and perfluoroalkyl diazomethanes react with nitrogen oxides, and a-diazosulfones with nitrosyl chloride or dinitrogen trioxide, to give furoxans. The process is believed to involve nitrosation, followed by loss of nitrogen to form the nitrile oxide which subsequently dimerizes. Nitrosation of dimethylphenacylsulfonium bromide with nitric acid/sodium nitrite gives dibenzoylfuroxan. 

Among the products of the irradiation of FNO are found all of the nitrogen oxides, the various known polyoxygen fluorides, nitrogen, oxygen, and possibly FNO3, as well as the proposed dimers and trimers. The evidence for polymeric (FNO) was obtained from the product distillate at 223° K. where the mass spectrometric data shown in Table IX were obtained. 

Oxidative Radical Generation via Nitrogen Dioxide Dimer Conversions Induced by Amide Groups of Macromolecules... 

Oxidative Radical Generation via Nitrogen Dioxide Dimer Conversions. 

The nitrogen oxide gas is then cooled down and, if necessary, compressed. Here the nitrogen oxide is partly oxidized by the dioxygen in air to NO2 (293) (AH = — 113.6kJmol ), which dimerizes to N2O4 (294) (AH = -58.08 kJmor ) ... 

Another class of nitrogen-bridged expanded porphyrins was first reported in 1993 by Dolphin and coworkers. Referred to as porphocyanines, the first of these tetrapyrrolic expanded porphyrins to be reported was system 9.110. It was prepared via the oxidative dimerization (with loss of ammonia) of the bis(amino-methyl)dipyrrylmethane derivative 9.109, a precursor derived, in turn, from the bis(-cyano)-substituted dipyrrylmethane 9.108 (Scheme 9.2.2). ... 

No detailed mechanistic study of these reactions has been made, and there is little evidence to support the intermediacy of nitrosyl or dinitrogen oxide complexes. Since this report, much interest has been shown in the efficient synthesis of oxide-bridged clusters and dimers of IIIA-VIA metals using nitrogen oxides as the oxidizing agents. The following reactions provide t5q)ical examples (205 207) ... 

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