Nitrogen dioxide production rate

The first-order decomposition rates of alkyl peroxycarbamates are strongly influenced by stmcture, eg, electron-donating substituents on nitrogen increase the rate of decomposition, and some substituents increase sensitivity to induced decomposition (20). Alkyl peroxycarbamates have been used to initiate vinyl monomer polymerizations and to cure mbbers (244). They Hberate iodine quantitatively from hydriodic acid solutions. Decomposition products include carbon dioxide, hydrazo and azo compounds, amines, imines, and O-alkyUiydroxylarnines. Many peroxycarbamates are stable at ca 20°C but decompose rapidly and sometimes violently above 80°C (20,44). 

Irradiation of gaseous formaldehyde containing an excess of nitrogen dioxide over chlorine yielded ozone, carbon monoxide, nitrogen pentoxide, nitryl chloride, nitric and hydrochloric acids. Peroxynitric acid was the major photolysis product when chlorine concentration exceeded the nitrogen dioxide concentration (Hanst and Gay, 1977). Formaldehyde also reacts with NO3 in the atmosphere at a rate of 3.2 x 10 cmVmolecule-sec (Atkinson and Lloyd, 1984). 

Tuazon et al. (1984a) investigated the atmospheric reactions of TV-nitrosodimethylamine and dimethylnitramine in an environmental chamber utilizing in situ long-path Fourier transform infared spectroscopy. They irradiated an ozone-rich atmosphere containing A-nitrosodimethyl-amine. Photolysis products identified include dimethylnitramine, nitromethane, formaldehyde, carbon monoxide, nitrogen dioxide, nitrogen pentoxide, and nitric acid. The rate constants for the reaction of fV-nitrosodimethylamine with OH radicals and ozone relative to methyl ether were 3.0 X 10 and <1 x 10 ° cmVmolecule-sec, respectively. The estimated atmospheric half-life of A-nitrosodimethylamine in the troposphere is approximately 5 min. 

Photolytic. Glyoxal, methylglyoxal, and biacetyl were produced from the photooxidation of 1,2,3-trimethylbenzene by OH radicals in air at 25 °C (Tuazon et al., 1986a). The rate constant for the reaction of 1,2,3-trimethylbenzene and OH radicals at room temperature was 1.53 x 10 " cmVmolecule-sec (Hansen et al., 1975). A rate constant of 1.49 x 10 L/molecule-sec was reported for the reaction of 1,2,3-trimethylbenzene with OH radicals in the gas phase (Darnall et al., 1976). Similarly, a room temperature rate constant of 3.16 x 10 " cm /molecule-sec was reported for the vapor-phase reaction of 1,2,3-trimethylbenzene with OH radicals (Atkinson, 1985). At 25 °C, a rate constant of 2.69 x lO " cm /molecule-sec was reported for the same reaction (Ohta and Ohyama, 1985). 2,3-Butanedione was the only products identified from the OH radical-initiated reaction of 1,2,4-trimethylbenzene in the presence of nitrogen dioxide. The amount of 2,3-butanedione formed decreased with increased concentration of nitrogen dioxide (Bethel et al., 2000). 

Photolytic. Irradiation of vinyl chloride in the presence of nitrogen dioxide for 160 min produced formic acid, HCl, carbon monoxide, formaldehyde, ozone, and trace amounts of formyl chloride and nitric acid. In the presence of ozone, however, vinyl chloride photooxidized to carbon monoxide, formaldehyde, formic acid, and small amounts of HCl (Gay et al, 1976). Reported photooxidation products in the troposphere include hydrogen chloride and/or formyl chloride (U.S. EPA, 1985). In the presence of moisture, formyl chloride will decompose to carbon monoxide and HCl (Morrison and Boyd, 1971). Vinyl chloride reacts rapidly with OH radicals in the atmosphere. Based on a reaction rate of 6.6 x lO" cmVmolecule-sec, the estimated half-life for this reaction at 299 K is 1.5 d (Perry et al., 1977). Vinyl chloride reacts also with ozone and NO3 in the gas-phase. Sanhueza et al. (1976) reported a rate constant of 6.5 x 10 cmVmolecule-sec for the reaction with OH radicals in air at 295 K. Atkinson et al. (1988) reported a rate constant of 4.45 X 10cmVmolecule-sec for the reaction with NO3 radicals in air at 298 K. 

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... 

At temperatures above 30°C, the rate increased slightly with temperature in a cylindrical reaction vessel but decreased slightly in a spherical vessel. A sharp increase in rate was noted as the temperature was decreased from 30°C. In the absence of water vapor or nitrogen dioxide a distinct induction period was observed, during which products were formed very slowly. The apparent rate increased slowly, and reached a maximum one-fourth to one-third of the way to reaction completion. The results quoted below were obtained near the start of the reaction but after the apparent induction period. The autocatalytic effect of nitrogen dioxide had been observed earlier in aqueous solutions. The reaction was found to obey the following rate law reasonably well. 

Nitrogen dioxide is about 20 to 50% of the total nitrogen oxides NO, (NO, NOz, HN03, N2Os), while CIO represents about 10 to 15% of the total chlorine species CIO, (Cl, CIO, HCI) at 25 to 30 km. Hence, the rate of ozone removal by CIO, is about equal to that by NO, if the amounts of NO, are equal to those of CIO,. According to a calculation by Turco and Whitten (981), the reduction of ozone in the stratosphere in the year 2022 with a continuous use of chlorofluoromethanes at present levels would be 7%. Rowland and Molina (843) conclude that the ozone depletion level at present is about 1%, but it would increase up to 15 to 20% ifthechlorofluoromethane injection were to continue indefinitely at the present rates. Even if release of chlorofluorocarbons were stopped after a large reduction of ozone were found, it would take 100 or more years for full recovery, since diffusion of chlorofluorocarbons to the stratosphere from the troposphere is a slow process. The only loss mechanism of chlorofluorocarbons is the photolysis in the stratosphere, production of HCI, diffusion back to the troposphere, and rainout. 

For the reaction between nitrogen dioxide and carbon monoxide, the mechanism is thought to involve the steps shown in Fig. 15.8, where k1 and k2 are the rate constants of the individual reactions. In this mechanism gaseous N03 is an intermediate, a species that is neither a reactant nor a product but that is formed and consumed during the reaction sequence (see Fig. 15.8). 

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. 

Nitrosyl chloride can be obtained by direct combination of chlorine with nitric oxide, by the reaction of NOHSO4 or NaNOj with HCl, or as a by-product in the preparation of KNOs from KCl and NO2, in which KCl is moistened with 2.4% water. Nitrosyl bromide is usually prepared by direct combination of bromine nuth nitric oxide. Nitrosyl chloride and nitrosyl bromide can be prepared by reacting the appropriate potassium halide with nitrogen dioxide at room temperature. The reaction rate increases with increased size of the halide, and NOCl and NOBr can be obtained in a reasonable length of time by powdering the halide salt before adding NO. ... 

The stoichiometry is more complicated here because 2 mol of dinitrogen pentoxide produce 4 mol of nitrogen dioxide and 1 mol of oxygen. So, it is no longer true that the rate of decrease of the reactant concentration equals the rates of increase of the product concentrations. However, this difficulty can be overcome if, in order to define the reaction rate, we divide by the coefficients from the balanced equation. For this reaction, we get the following. 

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