Kinetic study of the OH-initiated photo-oxidation of four unsaturated (allyl and vinyl) ethers under simulated atmospheric conditions (original) (raw)
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Kinetic study of the OH reaction with some hydrochloroethers under simulated atmospheric conditions
Atmospheric Environment, 2010
Using the relative rate technique, rate constants for the gas-phase reactions of hydroxyl radicals with 2-chloroethyl methyl ether (k 1), 2-chloroethyl ethyl ether (k 2) and bis(2-chloroethyl) ether (k 3) have been measured. Experiments were carried out at (298 AE 2) K and atmospheric pressure using synthetic air as bath gas. Using n-pentane and n-heptane as reference compounds, the following rate constants were derived: k 1 ¼ (5.2 AE 1.2) Â 10 À12 , k 2 ¼ (8.3 AE 1.9) Â 10 À12 and k 3 ¼ (7.6 AE 1.9) Â 10 À12 , in units of cm 3 molecule À1 s À1. This is the first experimental determination of k 2 and k 3 under atmospheric pressure. The rate constants obtained are compared with previous literature data and the observed trends in the relative rates of reaction of hydroxyl radicals with the ethers studied are discussed. The atmospheric implications of the results are considered in terms of lifetimes and fates of the hydrochloroethers studied.
Chemical Physics Letters, 1976
Relative rate constants have been obtained for the reaction of the hydroxyl radical (OH) with isopropyl alcohol nnd diethyl and din -propyl ether in environmental chamber photooxidation studies employing hydrocarbon-NO_r mixtures in air at 1 atmosphere and 305 f 2 K. These results were obtained from measurements of the relative rates of disappearance of these compounds on the previously validated basis that OH radica!s are dominantly responsible for their disappearance in the initial stqcs of reaction under the experimental conditions employed. Absolute rate constants, obtained by using the published rate constant for 011 + isobutcne of 3.05 X lOlo Q mole-' s-' are (k X low9 P mole-' s-l): isopropyl alcohol, 4.3 + 1.3; diethyl ether, 5.6 i 1.1; and din -propyl ether, 10.4 + 2.1. No previous determinations of these rate constants have been reported.
Atmospheric photodegradation of ethyl vinyl ketone and vinyl propionate initiated by OH radicals
Chemical Physics Letters, 2011
Rate coefficients for the reactions of hydroxyl radicals with ethyl vinyl ketone and vinyl propionate were determined at 298 K and atmospheric pressure. A collapsible chamber with gas chromatography was used to perform relative kinetic determinations. The room temperature rate coefficients (in cm 3 molecule À1 s À1 ) were: k 1 (OH + CH 2 @CHC(O)CH 2 CH 3 ) = (2.90 ± 0.79) Â 10 À11 and k 2 (OH + CH 2 @ CHOC(O)CH 2 CH 3 ) = (2.46 ± 0.28) Â 10 À11 . This is the first kinetic study of title reactions under atmospheric conditions. The kinetic data were compared with previous literature values, used to calculate atmospheric lifetimes and correlated with the ionization potential of the unsaturated compounds.
Product Study of the OH, NO3, and O3 Initiated Atmospheric Photooxidation of Propyl Vinyl Ether
Environmental …, 2006
A product study is reported on the gas-phase reactions of OH and NO 3 radicals and ozone with propyl vinyl ether (PVE). The experiments were performed in a 405 L borosilicate glass chamber in synthetic air at 298 ( 3 K using long path in situ FTIR spectroscopy for the analysis of the reactants and products. In the presence of NO x (NO + NO 2 ) the main products for the OH-radical initiated oxidation of PVE were propylformate and formaldehyde with molar formation yields of 78.6 ( 8.8% and 75.9 ( 8.4%, respectively. In the absence of NO x propylformate and formaldehyde were formed with molar formation yields of 63.0 ( 9.0% and 61.3 ( 6.3%, respectively. In the reaction of NO 3 radicals with PVE propylformate 52.7 ( 5.9% and formaldehyde 55.0 ( 6.3% were again observed as major products. The ozonolysis of PVE led to the production of propylformate, formaldehyde, hydroxyperoxymethyl formate (HPMF; HC(O)OCH 2 OOH), and CO with molar formation yields of 89.0 ( 11.4%, 12.9 ( 4.0%, 13.0 ( 3.4%, and 10.9 ( 2.6%, respectively. The formation yield of OH radicals in the ozonolysis of PVE was estimated to be 17 ( 9%. Simple atmospheric degradation mechanisms are postulated to explain the formation of the observed products.
Chemical Physics Letters, 1976
We have calculated approximate room temperature rate constants for mtramolecular hydrogen shaft rsomerizatrons of alkyd, alkovy and alkylperoxy radrcal mtermediates in photochemical smog and found that alkoxy radicals wrth 6 hydrogcns appear to undergo I,5 hydrogen shifts at ambient conditions Product drstrrbutions observed during irradiations of alkane (n-butane, n-pentane and n-hexant*)-NO,-air systems in two quite different J 6000~liter environmental chambers were found to be consistent with this predictron. For example. in the n-pentane-NO,-air system the observed large yields of f-pentanone reIatrve co 2-pentanone were consistent with room temperature rate constants which we have estimated for the axrespondzng hydrogen shrft rsomrrrzatrons Whrle such rsomerizatrons have been well recognized in studies of free radicals dnr! hrgh temperature hydrocarbon oxidations, they are not taken mto account m current kinetic mechanisms for alkane oxidation under ambient atmospheric condrtrons This has unplications for the construction of computer models of photochemical smog formatron.
International Journal of Chemical Kinetics, 1997
The rate constant for the reaction of CH 3 OCH 2 radicals with O 2 (reaction (1)) and the self reaction of CH 3 OCH 2 radicals (reaction (5)) were measured using pulse radiolysis coupled with time resolved UV absorption spectroscopy. k 1 was studied at 296 K over the pressure range 0.025-1 bar and in the temperature range 296-473 K at 18 bar total pressure. Reaction (1) is known to proceed through the following mechanism: (k prod) (k RO2) where k RO2 is the rate constant for peroxy radical production and k prod is the rate constant for formaldehyde production. The k 1 values obtained at 296 K together with the available literature values for k 1 determined at low pressures were fitted using a modified Lindemann mechanism and the following parameters were obtained: cm 6 cm 3 and cm 3 where k RO2,0 and k RO2,ϱ are the overall termolecular and bimolecular rate constants for formation of CH 3 OCH 2 O 2 rad-s Ϫ1 molecule Ϫ1 k prod,0 ϭ (6.0 Ϯ 0.5) ϫ 10 Ϫ12 s Ϫ1 , molecule Ϫ1 k RO2,ϱ ϭ (1.14 Ϯ 0.04) ϫ 10 Ϫ11 s Ϫ1 , molecule Ϫ2 k RO2,0 ϭ (9.4 Ϯ 4.2) ϫ 10 Ϫ30 k 1 ϭ k RO2 ϩ k prod , CH 3 OCH 2 O 2 # ϩ M 9: CH 3 OCH 2 O 2 ϩ M CH 3 OCH 2 ϩ O 2 ;: CH 3 OCH 2 O 2 # 9: CH 2 OCH 2 O 2 H # 9: 2HCHO ϩ OH CH 3 OCH 2 ϩ O 2 ;: 628 SEHESTED ET AL. icals and k prod,0 represents the bimolecular rate constant for the reaction of CH 3 OCH 2 radicals with O 2 to yield formaldehyde in the limit of low pressure. exp cm 3 was determined at 18 bar total pressure over the temperature range 296-473 K. At 1 bar total pressure and 296 K, cm 3 and at 18 bar total pressure over the temperature range 296-523 K, cm 3 As a part of this study the decay rate of CH 3 OCH 2 radicals was used to study the thermal decomposition of CH 3 OCH 2 radicals in the temperature range 573-666 K at 18 bar total pressure. The observed decay rates of CH 3 OCH 2 radicals were consistent with the literature value of The results are discussed in the context of dimethyl ether as an alternative diesel fuel.
International Journal of Chemical Kinetics, 1998
Some relative rate experiments have been carried out at room temperature and at atmospheric pressure. This concerns the OH-oxidation of some oxygenated volatile organic compounds including methanol (k 1 ), ethanol (k 2 ), MTBE (k 3 ), ethyl acetate (k 4 ), n-propyl acetate (k 5 ), isopropyl acetate (k 6 ), n-butyl acetate (k 7 ), isobutyl acetate (k 8 ), and t-butyl acetate (k 9 ). The experiments were performed in a Teflon-film bag smog chamber. The rate constants obtained are (in ):