Nitrogen dioxide reaction mechanisms

Pryor, W.A. and Lightsey, J.W. 1981. Mechanisms of nitrogen dioxide reactions Initiation of lipid peroxidation and the production of nitrous acid. Science 214 435 -37. 

Pryor, W. A., and J. W. Lightsey, Mechanisms of Nitrogen Dioxide Reactions Initiation of Lipid Peroxidation and the Production of Nitrous Acid, Science, 214, 435-437 (1981). 

Data have been presented on the kinetics of nitration of acetanilide in mixtures of nitric and sulfuric acids.29 A review discusses the several mechanisms operative in the nitration of phenol including /> / -sclective nitrosation-oxidation and mechanisms involving phenoxy radical-nitrogen dioxide reaction yielding a 55 45 ortho para nitration ratio.30 The kinetics of mononitration of biphenyl-2-carboxylic acid have been investigated in several solvents. The maximum ortho para product ratio of 8.4 is observed in tetrachloromethane.31 Nitration products were not formed in the presence of dioxane.31,32 Quantum-chemical AMI calculations were performed and the predominant formation of the ortho-nitro product is accounted for by stabilization of the cr-complex by the carboxyl group.33... 

At lower temperatures the reaction between carbon monoxide and nitrogen dioxide takes place by a quite different mechanism. Two steps are involved ... 

N,4-DinitrO N-methylaniline, bright yellow needles from benz, mp 142.5° (Ref 2) CA Registry No 16698-03-6. It is prepu by the alkylation of N,p-dinitroaniline with methyl iodide in alk soln (Refs 8 9). It is one compd isolated from aged NC propints stabilized with N-methyl-p-nitroaniline. Hollingsworth at ERDE examined the reaction of nitrogen dioxide with this stabilizer in order to elucidate the mechanism of the formation of the compds isolated. He found that after 7 days at 35°,. a good yield of N,4-dinitro-N-methylaniline was obtd and postulated that it arose from the oxidn of N-nitroso-4-nitroaniline (Ref 16)... 

Goheen and Bennett9 showed that regular nitric acid could be used, in about two molar excess, for the oxidation of dimethyl sulphoxide to dimethyl sulphone in 86% yield. The reaction temperature was 120-150°C with a reaction time of about 4 hours. The mechanism for this reaction was postulated to involve initially a protonated sulphoxide species (which has been shown to be present in other strongly acidic systems101 ) followed by nucleophilic attack by nitrate, and the loss of nitrogen dioxide as shown in equations (4) and (5). 

It is believed that SCR by hydrocarbons is an important way for elimination of nitrogen oxide emissions from diesel and lean-burn engines. Gerlach etal. [115] studied by infrared in batch condition the mechanism of the reaction between nitrogen dioxide and propene over acidic mordenites. The aim of their work was to elucidate the relevance of adsorbed N-containing species for the F>cNOx reaction to propose a mechanism. Infrared experiments showed that nitrosonium ions (NO+) are formed upon reaction between NO, NOz and the Brpnsted acid sites of H—MOR and that this species is highly reactive towards propene, forming propenal oxime at 120°C. At temperatures above 170°C, the propenal oxime is dehydrated to acrylonitrile. A mechanism is proposed to explain the acrylonitrile formation. The nitrile can further be hydrolysed to yield... 

Gerlach, T., Schutze, F.-W. and Baerns, M. (1999) An FTIR study on the mechanism of the reaction between nitrogen dioxide and propene over acidic mordenites, J. Catal., 185, 131. 

The mechanisms of explosions in solidified gas mixtures at low temperatures containing unsaturated hydrocarbons and oxides of nitrogen is discussed. Fast radical addition of nitrogen dioxide to double bonds is involved, and with dienes it is a fast reaction of very low energy of activation. Possibilities of preventing explosions are discussed. 

Nitric oxide is the primary nitrogen oxide emitted from most combustion sources. The role of nitrogen dioxide in photochemical smog has already been discussed. Stringent emission regulations have made it necessary to examine all possible sources of NO. The presence of N20 under certain circumstances could, as mentioned, lead to the formation of NO. In the following subsections the reaction mechanisms of the three nitrogen oxides of concern are examined. 

Although the above reactions generate a few fi radicals, most of the oxidation of nitric oxide to nitrogen dioxide is carried out by the alkyl-peroxy, RO, and hydroperoxy radicals that are formed in later reactions involving reactive hydrocarbons, aldehydes, or even carbon monoxide. One such example is shown in Figure 2-7. There is still considerable uncertainty as to the mechanism of these secondary reactions. The modeling studies should be consulted for details. ... 

Once the kinetics of a reaction have been worked out, it is possible to propose a mechanism for the reaction. Consider, for example, the reaction between nitrogen dioxide and fluorine. The stoichiometric equation for the reaction is 2NO2 + 2NO2F... 

An attempt to combine electrochemical and micellar-catalytic methods is interesting from the point of view of the mechanism of anode nitration of 1,4-dimethoxybenzene with sodinm nitrite (Laurent et al. 1984). The reaction was performed in a mixture of water in the presence of 2% surface-active compounds of cationic, anionic, or neutral nature. It was established that 1,4-dimethoxy-2-nitrobenzene (the product) was formed only in the region of potentials corresponding to simultaneous electrooxidation of the substrate to the cation-radical and the nitrite ion to the nitrogen dioxide radical (1.5 V versus saturated calomel electrode). At potentials of oxidation of the sole nitrite ion (0.8 V), no nitration was observed. Consequently, radical substitution in the neutral substrate does not take place. Two feasible mechanisms remain for addition to the cation-radical form, as follows ... 

Clearly, the short half-life of nitric oxide is an important determinant for its biological function, but the chemical basis for this short half-life is still unknown. It cannot be due to the most commonly accepted mechanism reaction with oxygen to form nitrogen dioxide. 

At low acid concentrations, nitric oxide tends to form. This evidently may attack nitrosophenol to form diazonium compounds directly. The diazonium salts, in turn, may couple with unreacted phenol to give colored products. Nitrous acid may also produce nitrophenols from phenols. The mechanism of this reaction may involve oxidation of initially formed nitrosophenols, homolytic attack by nitrogen dioxide, or nucleophilic attack by nitrite ions [1]. 

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