Nitrogen dioxide formation

Checkel, M. D. et al., J. Loss Prevention, 1995, 8(4), 215 Flammability limits of mixtures of nitric oxide and ammonia were studied. The limits are 15-70% ammonia tenfold pressure rise and explosion are possible. Introduction of oxygen into flammable compositions will produce autoignition, via nitrogen dioxide formation, contamination with air might. 

AltshuUer, A. P., and I. R. Cohen. Structural effects on the rate of nitrogen dioxide formation in the photo zidation of organic compound-nitric oxide mixtures in air. Int. J. Air Water Pollut. 7 787-797. 1%3. 

Undet physiological conditions. Reaction 22 is neglectable, because of the slow rate of nitrogen dioxide formation in vivo. Nitrogen dioxide is more likely... 

Freiling, Johnston, and Ogg155 studied the kinetics of the latter reaction by following nitrogen dioxide formation absorptiometrically over the temperature range 274-344°K. They found the reaction to be homogeneous and first order with respect to each reactant. The second-order rate constant was found to be log k19 = 8.92 — 6.9/6. 

Table I. Relative Rates of Nitrogen Dioxide Formation in the Steel Chamber...

Table I presents the relative values for the maximum rate of nitrogen dioxide formation, Table II gives the maximum rates for hydrocarbon disappearance, and Table III presents the relative oxidant maxima. For comparison, we have included the values for a,a,a-trifluorotoluene, a particularly unreactive aromatic hydrocarbon propylene, one of the principal hydrocarbons in automobile exhaust (13) and 2-methyl-2-butene, an especially volatile and reactive olefin that is often present in small amounts in gasoline (12).

Lead nitrate [10099-74-8] Pb(N02)2, mol wt 331.23, sp gr 4.53, forms cubic or monoclinic colorless crystals. Above 205°C, oxygen and nitrogen dioxide are driven off, and basic lead nitrates are formed. Above 470°C, lead nitrate is decomposed to lead monoxide and Pb O. Lead nitrate is highly soluble in water (56.5 g/100 mL at 20°C 127 g/100 mL at 100°C), soluble in alkalies and ammonia, and fairly soluble in alcohol (8.77 g/100 mL of 43% aqueous ethanol at 22°C). Lead nitrate is readily obtained by dissolving metallic lead, lead monoxide, or lead carbonate in dilute nitric acid. Excess acid prevents the formation of basic nitrates, and the desired lead nitrate can be crystallized by evaporation. 

Low temperatures strongly favor the formation of nitrogen dioxide. Below 150°C equiUbrium is almost totally in favor of NO2 formation. This is a slow reaction, but the rate constant for NO2 formation rapidly increases with reductions in temperature. Process temperatures are typically low enough to neglect the reverse reaction and determine changes in NO partial pressure by the rate expression (40—42) (eq. 13). The rate of reaction, and therefore the... 

Nitrogen dioxide rapidly forms an equiUbtium mixture with its dimer, dinitrogen tetroxide (AH g = —28.6 kJ/mol of NO2 consumed). The formation of tetroxide is favored by low temperature and high pressure. 

At room temperature, Htde reaction occurs between carbon dioxide and sodium, but burning sodium reacts vigorously. Under controUed conditions, sodium formate or oxalate may be obtained (8,16). On impact, sodium is reported to react explosively with soHd carbon dioxide. In addition to the carbide-forrning reaction, carbon monoxide reacts with sodium at 250—340°C to yield sodium carbonyl, (NaCO) (39,40). Above 1100°C, the temperature of the DeviHe process, carbon monoxide and sodium do not react. Sodium reacts with nitrous oxide to form sodium oxide and bums in nitric oxide to form a mixture of nitrite and hyponitrite. At low temperature, Hquid nitrogen pentoxide reacts with sodium to produce nitrogen dioxide and sodium nitrate. 

The carbon dioxide removed in synthesis gas preparation can be reacted with ammonia, to lonn urea CO(NH2)2- This is an excellent fertilizer, highly concentrated in nitrogen (46.6%) and also useful as an additive in animal feed to provide the nitrogen for formation of meat protein. Urea is also an important source of resins and plastics by reacting it with formaldehyde from methanol. 

In contrast to carbon monoxide, small hydrocarbon molecules and soot that result from incomplete conversion of the hydrocarbon fuels, nitric oxide and nitrogen dioxide, are noxious emissions that result from the oxidizer—air. However, fuel components that contain nitrogen may also contribute, in a lesser way, to the formation of the oxides of nitrogen. 

Investigation into the effect has been mainly devoted to reactions with red fuming nitric acid . It seems that in red fuming nitric acid a preliminary reaction results in the formation of a surface deposit of finely divided metallic titanium ignition or pyrophoricity can then be initiated by any slight impact or friction. The tendency to pyrophoricity increases as the nitrogen dioxide content of the nitric acid rises from zero to maximum solubility at about 20%, but decreases as the water content rises, the effect being nearly completely stifled at about 2% water. 

A number of NMP processes have been reported where the nitroxide is formed in situ. Nitrones 1 and nitroso-compounds128 have been used as nitroxide precursors. Control of methacrylate polymerization by mixtures of nitric oxide and nitrogen dioxide has also been attributed to in situ formation of a nitroxide. 130... 

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)... 

Ponzio Reaction. The formation of phenyl-dinit romethane from benzaldoxime by oxidation with nitrogen dioxide in eth (Refs 1 2) CH=NOH CH(N02)2... 

The reaction with nitrite proceeds smoothly and with relatively high yields of the corresponding nitroarene (see Sec. 10.6). Obviously a major part of the driving force of this reaction is the formation of a stable, i. e., an energetically favorable, radical, nitrogen dioxide. With the hydroxide ion — a much stronger nucleophile than the nitrite ion — the reaction is expected to produce very unstable radicals, the hydroxy radical OH and the oxygen radical anion O, from the diazohydroxide (Ar - N2 — OH) and the diazoate (Ar-N20 ) respectively. Consequently, dediazoniation in alkaline aqueous solution does not follow the simple Scheme 8-41 with Yn = OH, but instead involves diazoanhydrides (Ar — N2 —O —N2 —Ar) as intermediates (see Sec. 8.8). 

The formation of aryl radicals from benzenediazonium ions, initiated by electron transfer from a nitrite ion, has already been discussed in Section 8.6. It is an excellent example of a dediazoniation assisted by a donor species that is capable of forming a relatively stable species on release of an electron, in this case a nitrogen dioxide radical NO2 (Opgenorth and Rtichardt, 1974). 

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... 

Nitrogen dioxide in the atmosphere undergoes the same reaction and contributes to the formation of acid rain. It also initiates a complex sequence of smog-forming photochemical reactions. 

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