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Digitale Medien

Gas phase reactions of alkyl nitrates with hydroxyl radicals under tropospheric conditions in comparison with photolysis (1989)

Becker, K. H. ; Wirtz, K.

Springer

Journal of atmospheric chemistry 9 (1989), S. 419-433

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ISSN: 1573-0662

Schlagwort(e): OH radical ; alkyl nitrates ; photolysis frequency ; lifetime

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Geologie und Paläontologie

Notizen: Abstract Rate constants for the reaction of OH radicals with some branched alkyl nitrates have been measured applying a competitive technique. Methyl nitrite photolysis in synthetic air was used as OH radical source at 295±2 K and 1000 mbar total pressure. Using a rate constant of 2.53×10-12 cm3 s-1 for the reaction of OH radicals with n-butane as reference, the following rate constants were obtained (units: 10-12 cm3 s-1): isopropyl nitrate, 0.59±0.22; isobutyl nitrate, 1.63±0.20; 3-methyl-2-butyl nitrate, 1.95±0.15; 2-methyl-1-butyl nitrate, 2.50±0.15; 3-methyl-1-butyl nitrate, 2.55±0.35. These values have been combined with the literature data to recalculate the substituent factors F(X) for the different nitrate groups which can be used to predict OH rate constants for organic nitrates for which experimental data are not available. Preliminary measurements of the photolysis frequency of isopropyl nitrate have shown that for this nitrate as a model substance, OH reactions and direct photolysis are of equal importance under tropospheric conditions.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00114754

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Digitale Medien

Relative-rate study of the gas-phase reaction of hydroxy radicals with difunctional organic nitrates at 298 K and atmospheric pressure (1991)

Zhu, T. ; Barnes, I. ; Becker, K. H.

Springer

Journal of atmospheric chemistry 13 (1991), S. 301-311

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ISSN: 1573-0662

Schlagwort(e): Organic nitrates ; kinetics ; OH radical ; atmosphere

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Geologie und Paläontologie

Notizen: Abstract Rate coefficients for the reactions of difunctional nitrates with atmospherically important OH radicals are not currently available in the literature. This study represents the first determination of rate coefficients for a number of C(3) and C(4) carbonyl nitrates and dinitrates with OH radicals in a 38 l glass reaction chamber at 1000 mbar total pressure of synthetic air by 298±2 K using a relative kinetic technique. The following rate coefficients (in units of 10-12 cm3 molecule-1 s-1) were obtained: 1,2-propandiol dinitrate, 〈0.31; 1,2-butandiol dinitrate, 1.70±0.32; 2,3-butandiol dinitrate, 1.07±0.26; α-nitrooxyacetone, 〈0.43; 1-nitrooxy-2-butanone, 0.91±0.16; 3-nitrooxy-2-butanone, 1.27±0.14; 1,4-dinitrooxy-2-butene, 15.10±1.45; 3,4-dinitrooxy-1-butene, 10.10±0.50. The possible importance of reaction of OH as an atmospheric sink for the compounds compared to other loss processes is considered.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00058137

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Field study of dimethylsulfide oxibation in the boundary layer: Variations of dimethylsulfide, methanesulfonic acid, sulfur dioxide, non-sea-salt sulfate and aitken nuclei at a coastal site (1992)

Mthalopoulos, N. ; Nguyen, B. C. ; Boissard, C. ; [weitere]

Springer

Journal of atmospheric chemistry 14 (1992), S. 459-477

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ISSN: 1573-0662

Schlagwort(e): Dimethylsulfide ; Methanesulfonie acid ; Sulfur dioxide ; Non-sea-salt sulfate ; Aitken Nuclei ; Coastal area ; Dimethylsulfide Oxidation Mechanisms

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Geologie und Paläontologie

Notizen: Abstract Measurements of atmospheric dimethylsulfide (DMS) and its oxidation products, sulfur dioxide (SO2), methanesulfonic acid (MSA) and non-sea-salt sulfate (nss-SO4 2-) were monitored during the period June 9–26, 1989 at a coastal site in Brittany. As indicated by the radon (Rn-222) activities and the high concentrations of NOx the air masses, for most of the experiment, were continental in origin. The observed concentrations range from 1.9 to 65 nmol/m3 for DMS (n=157), 0.6 to 94.2 nmol/m3 for SO2 (n=50), 0.6 to 11.6 nmol/m3 for MSA (n=44) and 42 to 350 nmol/m3 for nss-SO4 2- (n=44). Aitken nuclei reached values as high as 4.5 × 105 particles/m3. When continental conditions predominated, the measured SO2 concentrations were lower than those expected from a consideration of the observed DMS concentrations and the existence of SO2 background of the continental air masses. Similarly, compared to the MSA/DMS ratio in the marine atmosphere, higher concentrations of MSA were observed than those expected from the measured levels of DMS. The presence of enhanced levels of MSA was also endorsed by the observation that the measured mean MSA/nss-SO4 2- ratio of 6±3% was similar to the mean value of 6.9% observed in the marine atmosphere. These above observations are in line with recent laboratory findings by Barnes et al. (1988), which show an increase of the MSA/DMS yield with a simultaneous decrease of the SO2/DMS yield in the presence of NOx.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00115251

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