Nitrogen dioxide nitrate radical reaction

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... 

Chemical radicals—such as hydroxyl, peroxyhydroxyl, and various alkyl and aryl species—have either been observed in laboratory studies or have been postulated as photochemical reaction intermediates. Atmospheric photochemical reactions also result in the formation of finely divided suspended particles (secondary aerosols), which create atmospheric haze. Their chemical content is enriched with sulfates (from sulfur dioxide), nitrates (from nitrogen dioxide, nitric oxide, and peroxyacylnitrates), ammonium (from ammonia), chloride (from sea salt), water, and oxygenated, sulfiirated, and nitrated organic compounds (from chemical combination of ozone and oxygen with hydrocarbon, sulfur oxide, and nitrogen oxide fragments). ... 

These fragments either combine intramolecularly to form the ortho and para nitro compounds or dissociate completely and then undergo an intermolecular reaction to form the same products. The theory was not developed to include a detailed transition state and no mention was made of how the para isomer was formed. Reduction of the cation-radical could give the amine (which was observed experimentally76), but one would expect the concurrent formation of nitrogen dioxide and hence nitrite and nitrate ions however, the latter has never been... 

The sulfate and nitrate content of atmospheric particles comes primarily from the conversion of sulfur dioxide and nitrogen dioxide. Photochemi-cally initiated atmospheric reactions and transient free radicals are... 

Photolytic. Methyl vinyl ketone and methacrolein were reported as major photooxidation products for the reaction of 2-methyl-l,3-butadiene with OH radicals. Formaldehyde, nitrogen dioxide, nitric oxide, and HO2 were reported as minor products (Lloyd et al, 1983). Synthetic air containing gaseous nitrous acid and exposed to artificial sunlight (X = 300-450 nm) photo-oxidized 2-methyl-1,3-butadiene into formaldehyde, methyl nitrate, peroxyacetal nitrate, and a compound tentatively identified as methyl vinyl ketone (Cox et al, 1980). 

Nitropyrene was the sole product formed from the gas-phase reaction of pyrene with OH radicals in a NOx atmosphere (Arey et al, 1986). Pyrene adsorbed on glass fiber filters reacted rapidly with N2O5 to form 1-nitropyrene. When pyrene was exposed to nitrogen dioxide, no reaction occurred. However, in the presence of nitric acid, nitrated compounds were produced (Yokley et al, 1985). Ozonation of water containing pyrene (10-200 pg/L) yielded short-chain aliphatic compounds as the major products (Corless et al, 1990). A monochlorinated pyrene was the major product formed during the chlorination of pyrene in aqueous solutions. At pH 4, the reported half-lives at chlorine concentrations of 0.6 and 10 mg/L were 8.8 and <0.2 h, respectively (Mori et al, 1991). 

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 ... 

One of the most important of these reactions occurs between a peroxyl radical and nitrogen dioxide to produce compounds known as peroxyalkyl and peroxyacyl nitrates ... 

Much experimental evidence established that the reaction occurs by a free-radical mechanism164 173 similar to that suggested above [Eqs. (10.26)—(10.28)] for liquid-phase nitration. The nitrous acid produced during the transformation is unstable under the reaction conditions and decomposes to yield nitric oxide, which also participates in nitration, although less effectively. It was found that nitric acid and nitrogen dioxide yield identical products but that the former gives better yields and higher rates.172... 

The use of nitrogen dioxide for the selective oxidation of polysaccharides to polyuronic acids was introduced by Kenyon and his coworkers13,63 in 1941. By this means extensive oxidation of the primary alcohol groups in cellulose was obtained, through the mechanism of preferential nitration followed by decomposition of the nitric acid ester with carboxyl forma-tion.68(0< > Apparently some undissociated nitration products also were formed, since infrared absorption studies54 indicated the presence of nitrate radicals in the polyuronic acid. Side reactions produced carboxyl,... 

The ozone-mediated reaction of bicumene and some derivatives (11) with nitrogen dioxide in dichloromethane (kyodai nitration) at low temperatures results in the cleavage of the central C—C bond to yield the benzyl nitrate and products therefrom, in contrast to the behaviour of bibenzyl.36 This result is interpreted in terms of electron transfer from the substrate to NO3- to give a radical cation species which fragments to form tertiary benzylic species in the former cases. 

Nitration of fluoroolefins can be achieved by several methods. Widely studied thermal reaction of N204 with fluoroolefins has a radical mechanism, although the low temperature reaction of nitrogen dioxide with polyfluorinated vinyl ethers proceeds as electrophilic addition of nitrosonium nitrate NO+ N02 across the C=C bond [6] ... 

As Barr et al. (2003) pointed out, the importance of such emissions is determined mainly by their impact on the three processes taking place in the atmosphere. The first consists in that such NMHCs as isoprene form in the course of carboxylization in plants and contribute much thereby to the formation of biospheric carbon cycle. The second process is connected with NMHCs exhibiting high chemical activity with respect to such main oxidants as hydroxyl radicals (OH), ozone (03), and nitrate radicals (N03). Reactions with the participation of such components result in the formation of radicals of alkylperoxides (R02), which favor efficient transformation of nitrogen monoxide (NO) into nitrogen dioxide (N02), which favors an increase of ozone concentration in the ABL. Finally, NMHC oxidation leads to the formation of such carbonyl compounds as formaldehyde (HCHO), which stimulates the processes of 03 formation. Finally, the oxidation of monoterpenes and sesquiterpenes results in the intensive formation of fine carbon aerosol with a particle diameter of <0.4 pm... 

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