Nitrogen dioxide formation, rates

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).

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... 

Peroxynitrite reacts with heme proteins such as prostacycline synthase (PGI2), microperoxidase, and the heme thiolate protein P450 to form a ferryl nitrogen dioxide complex as an intermediate [120]. Peroxynitrite also reacts with acetaldehyde with the rate constant of 680 1 mol 1 s" 1 forming a hypothetical adduct, which is decomposed into acetate, formate, and methyl radicals [121]. The oxidation of NADH and NADPH by peroxynitrite most certainly occurs by free radical mechanism [122,123], Kirsch and de Groot [122] concluded that peroxynitrite oxidized NADH by a one-electron transfer mechanism to form NAD and superoxide ... 

It is necessary to take into consideration the fact that the decomposition of nitric esters has an autocatalytic character water and nitrogen dioxide formed during the decomposition lead to the formation of nitric and nitrous acids which accelerate the reaction of decomposition of the nitric ester. The influence of nitric acid on the rate of decomposition of nitroglycerine was studied by Roginskii [79] and is described below. 

The standard free energy of formation of a substance measures its thermodynamic stability with respect to its constituent elements. Substances that have a negative value of AG°f, such as carbon dioxide and water, are stable and do not decompose to their constituent elements under standard-state conditions. Substances that have a positive value of AG°f, such as ethylene and nitrogen dioxide, are thermodynamically unstable with respect to their constituent elements. Once prepared, though, such substances can exist for long periods of time if the rate of their decomposition is slow. 

Pokholok T. V., Pariiskii G. B. Formation of spin-labeled maeromoleeules in reactions of elastomers with nitrogen dioxide. Polymer Science, Ser A 1997 39 (7) 765-71. Giamalva D. H., Kenion G. B., Chureh D. F., Pryor W. A. Rates and mechanisms of reactionof nitrogen dioxide with alkenes in solution. J. Am. Chem. Soc. 1987 (109) 7059-63. 

They then studied the reaction between isotopically labeled nitrogen dioxide and ordinary SO2. The formation of labeled SO2 was taken as evidence for reaction ( — 14), and therefore for the mechanism consisting of (14) and (15). From the rate of isotopic substitution, Jaffe and Klein were able to calculate and -14-1 15 Their results were... 

Huorothene vessel. Other methods include the decomposition of various nitrosyl adducts. In the present method, nitrogen dioxide is allowed to react at room temperature with an excess of potassium fluoride to produce nitrosyl fluoride, in nearly quantitative yields, as the only volatile product. The rate of formation of nitrosyl fluoride may be dramatically increased by first forming a potassium fluoride-hexafluoroacetone adduct which is subsequently thermally decomposed to yield potassium fluoride having a high surface area. 

Previously it has been reported that biacetyl, bibutyryl, pyruvic acid, and butyl nitrite produce ozone upon irradiation without the addition of nitrogen dioxide. In the absence of nitrogen dioxide, ozone formation can be established by irradiation of biacetyl at a concentration of 40 p.p.m. in its presence the rate of formation is still pronounced in the 1-p.p.m. range, and equals that of 2-butene. Butyl nitrite without the addition of nitrogen dioxide is even more active than 2-butene. After 94 hours the total crack depth of the rubber pieces corresponds to the production of 80 p.p.m. of ozone, demonstrating again a chain mechanism in its formation. 

The oxidation rate of nitric oxide (by oxygen) in these concentrations is slow. But under the conditions of these experiments, using irradiated 50-liter flasks and mixtures containing 1 to 10 p.p.m. of hydrocarbons and 0.1 to 1.0 p.p.m. of nitric oxide, a rapid oxidation to nitrogen dioxide appeared to take place, accompanied by the formation of some ozone. 

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