Gas-phase oxidation of CH2 = C(CH3 )CH2 Cl initiated by OH radicals and Cl atoms: kinetics and fate of the alcoxy radical formed (original) (raw)
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Rate coefficients for the reactions of hydroxyl radicals and chlorine atoms with methyl crotonate and ethyl crotonate have been determined at 298 K and atmospheric pressure. The decay of the organics was monitored using gas chromatography with flame ionization detection (GC-FID), and the rate constants were determined using the relative rate method with different reference compounds. Room temperature rate coeficcients were found to be (in cm 3 molecule −1 s −1 ): k 1 (OH + CH 3 CHCHC(O)OCH 3 ) = (4.65 ± 0.65) × 10 −11 , k 2 (Cl + CH 3 CH CHC(O)OCH 3 ) = (2.20 ± 0.55) × 10 −10 , k 3 (OH + CH 3 CH CHC(O)OCH 2 CH 3 ) = (4.96 ± 0.61) × 10 −11 , and k 4 (Cl + CH 3 CH CHC(O)OCH 2 CH 3 ) = (2.52 ± 0.62) × 10 −10 with uncertainties representing ±2σ. This is the first determination of k 1 , k 3 , and k 4 under atmospheric pressure. The rate coefficients are compared with previous determinations for other unsaturated and oxygenated VOCs and reactivity trends are presented. In addition, a comparison between the experimentally determined k OH with k OH predicted from k vs E HOMO relationships is presented. On the other hand, product identification under atmospheric conditions has been performed for the first time for these unsaturated esters by the GC−MS technique in NO x -free conditions. 2-Hydroxypropanal, acetaldehyde, formaldehyde, and formic acid were positively observed as degradation products in agreement with the addition of OH to C2 and C3 of the double bond, followed by decomposition of the 2,3-or 3,2-hydroxyalkoxy radicals formed. Atmospheric lifetimes, based on of the homogeneous sinks of the unsaturated esters studied, are estimated from the kinetic data obtained in the present work.
Journal of Physical Chemistry A, 2007
Relative rate techniques were used to study the kinetics of the reactions of Cl atoms and OH radicals with ethylene glycol diacetate, CH 3 C(O)O(CH 2) 2 OC(O)CH 3 , in 700 Torr of N 2 /O 2 diluent at 296 K. The rate constants measured were k(Cl + CH 3 C(O)O(CH 2) 2 OC(O)CH 3)) (5.7 (1.1) × 10-12 and k(OH + CH 3 C(O)O(CH 2) 2 OC(O)CH 3)) (2.36 (0.34) × 10-12 cm 3 molecule-1 s-1. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the absence of NO in 700 Torr of O 2 /N 2 diluent at 296 K show the primary products to be CH 3 C(O)OC(O)CH 2 OC(O)CH 3 , CH 3 C(O)OC(O)H, and CH 3 C(O)OH. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the presence of NO in 700 Torr of O 2 /N 2 diluent at 296 K show the primary products to be CH 3 C(O)OC(O)H and CH 3 C(O)OH. The CH 3 C-(O)OCH 2 O• radical is formed during the Cl atom initiated oxidation of ethylene glycol diacetate, and two loss mechanisms were identified: reaction with O 2 to give CH 3 C(O)OC(O)H and R-ester rearrangement to give CH 3 C(O)OH and HC(O) radicals. The reaction of CH 3 C(O)OCH 2 O 2 • with NO gives chemically activated CH 3 C(O)OCH 2 O• radicals which are more likely to undergo decomposition via the R-ester rearrangement than CH 3 C(O)OCH 2 O• radicals produced in the peroxy radical self-reaction.
Environmental Science and Pollution Research, 2009
Background, aim, and scope Unsaturated esters are emitted to the atmosphere from biogenic and anthropogenic sources, including those from the polymer industry. Little information exists concerning the atmospheric degradation of unsaturated esters, which are mainly initiated by OH radicals. Limited information is available on the degradation of alkenes by Cl atoms and almost no data exists for the reactions of unsaturated esters with Cl atoms. This data is necessary to assess the impact of such reactions in maritime environments where, under circumstances, OH radical-and Cl atom-initiated oxidation of the compounds can be important. Rate coefficients for the reactions of chlorine atoms with vinyl acetate, allyl acetate, and n-butyl acrylate have been determined at 298±3 K and atmospheric pressure. The kinetic data have been used in combination with that for structurally similar compounds to infer the kinetic contributions from the possible reaction channels to the overall reaction rate.
The Journal of Physical Chemistry A, 2007
Relative rate techniques were used to study the kinetics of the reactions of Cl atoms and OH radicals with ethylene glycol diacetate, CH 3 C(O)O(CH 2) 2 OC(O)CH 3 , in 700 Torr of N 2 /O 2 diluent at 296 K. The rate constants measured were k(Cl + CH 3 C(O)O(CH 2) 2 OC(O)CH 3)) (5.7 (1.1) × 10-12 and k(OH + CH 3 C(O)O(CH 2) 2 OC(O)CH 3)) (2.36 (0.34) × 10-12 cm 3 molecule-1 s-1. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the absence of NO in 700 Torr of O 2 /N 2 diluent at 296 K show the primary products to be CH 3 C(O)OC(O)CH 2 OC(O)CH 3 , CH 3 C(O)OC(O)H, and CH 3 C(O)OH. Product studies of the Cl atom initiated oxidation of ethylene glycol diacetate in the presence of NO in 700 Torr of O 2 /N 2 diluent at 296 K show the primary products to be CH 3 C(O)OC(O)H and CH 3 C(O)OH. The CH 3 C-(O)OCH 2 O• radical is formed during the Cl atom initiated oxidation of ethylene glycol diacetate, and two loss mechanisms were identified: reaction with O 2 to give CH 3 C(O)OC(O)H and R-ester rearrangement to give CH 3 C(O)OH and HC(O) radicals. The reaction of CH 3 C(O)OCH 2 O 2 • with NO gives chemically activated CH 3 C(O)OCH 2 O• radicals which are more likely to undergo decomposition via the R-ester rearrangement than CH 3 C(O)OCH 2 O• radicals produced in the peroxy radical self-reaction.
Kinetics and mechanism for the oxidation of 1,1,1-trichloroethane
International Journal of Chemical Kinetics, 1990
The reaction mechanisms for oxidation of CH,CCI, and CC13CH2 radicals, formed in the atmospheric degradation of CH3CC1, have been elucidated. The primary oxidation products from these radicals are CH,CClO and CCl,CHO, respectively. Absolute rate constants for the reaction of hydroxyl radicals with CH3CC13 have been measured in 1 atm of Argon at 359, 376, and 402 K using pulse radiolysis combined with UV kinetic spectroscopy giving k(OH + CH,CC13) = (5.4 ? 3) lo-'' exp(-3570 5 890/RT) cm3 molecule-' s-'. A value of this rate constant of 1.3 x cm3 molecule-' s-' at 298 K was calculated using this Arrhenius expression. A relative rate technique was utilized to provide rate data for the OH + CH3CC13 reaction as well as the reaction of OH with the primary oxidation products. Values of the relative rate constants a t 298 K are: k(OH + CH3CC13) = (1.09 ? 0.35) x k(OH + CH,CClO) = (0.91 ? 0.32) x k(OH + CC1,CHO) = (178 ? 31) x k(OH + CC1,O) < 0.1 x all in units of cm3 molecule-' s-'. The effect of chlorine substitution on the reactivity of organic compounds towards OH radicals is discussed.
Kinetics of the Methyl–Vinyl Radical + O2 Reactions Associated with Propene Oxidation
Journal of Physical Chemistry A, 2019
The bimolecular rate coefficients of reactions CH 3 CCH 2 + O 2 (1) and cis/trans-CH 3 CHCH + O 2 (2a/3a) have been measured using a tubular laminar flow reactor coupled with a photoionization mass spectrometer (PIMS). These reactions are relevant in the combustion of propene. Pulsed excimer laser photolysis of a ketone or a bromide precursor molecule at 193 or 248 nm wavelength was used to produce radicals of interest homogeneously along the reactor. Timeresolved experiments were performed under pseudo-first-order conditions at low pressure (0.3−1.5 Torr) over the temperature range 220−660 K. The measured bimolecular rate coefficients were found to be independent of bath gas concentration. The bimolecular rate coefficients possess negative temperature dependence at low temperatures (T < 420 K) and appear to be independent of temperature at high temperatures (T > 420 K). Observed products of the reaction CH 3 CCH 2 + O 2 were CH 3 and H 2 CO, while for the reaction cis/trans-CH 3 CHCH + O 2 , observed products were CH 3 CHO and HCO. Current results indicate that the reaction mechanism of both reactions is analogous to that of C 2 H 3 + O 2. Methyl substitution of the vinyl radical changes its reactivity toward O 2 upward by ca. 50% if it involves the α-position and downward by ca. 30% if the methyl group takes either of the β-positions, respectively.
Journal of Physical Chemistry A, 2009
Kinetics of the reactions of OH radicals and Cl atoms with four saturated esters have been investigated. Rate coefficients for the gas-phase reactions of OH radicals with ethyl propanoate (k 1), n-propyl propanoate (k 2), methyl 2-methylpropanoate (k 3), and ethyl n-butanoate (k 4) were measured using a conventional relative rate method and the pulsed laser photolysis-laser induced fluorescence technique. At (296 (2) K, the rate coefficients obtained by the two methods were in good agreement. Significant curvatures in the Arrhenius plots have been observed in the temperature range 243-372 K for k 1 , k 3 , and k 4. The rate coefficients for the reactions of the four esters with Cl atoms were determined using the relative rate method at (296 (2) K and atmospheric pressure. The values obtained are presented, compared with the literature values when they exist, and discussed. Reactivity trends and atmospheric implications for these esters are also presented.
2019
The quantum mechanical calculations of the decomposition pathways of 1, 2-hydroxy alkoxy radical i.e., CH2(OH)C(O)(CH3)CH2Cl radical have been performed. This radical species has been formed from the successive reactions with O2 molecule and NOx or HO2 radicals with the most stable primary oxidation product of 3-chloro-2-methyl-1propene and OH radical reaction. Geometry optimization and frequency calculations of all the stable species including transition states in the three possible C-C bond scission pathways (i.e., C-CH3, C-CH2Cl and C-CH2OH) of CH2(OH)C(O)(CH3)CH2Cl radical have been performed at M06-2X/6-31+G(d,p) level of theory. Single point energy calculations of all the optimized species at the higher level of CCSD(T) method along with cc-pVTZ triple-zeta basis set have been performed. The rate constants for the various decomposition reactions have been evaluated using Canonical Transition State Theory (CTST) within the temperature range of 250–400 K. Rate constants for C–C ...
Atmospheric Environment, 2010
Relative kinetic studies have been performed on the reactions of Cl atoms with a series of methyl alkyl esters in a 405-liter borosilicate glass chamber at (298 AE 3) K and one atmosphere of synthetic air using in situ FTIR spectroscopy to monitor the reactants. Rate coefficients (in units of cm 3 molecule À1 s À1 ) were determined for the following compounds: methyl acetate (2.48 AE 0.58) Â 10 À12 ; methyl propanoate (1.68 AE 0.36) Â 10 À11 ; methyl butanoate (4.77 AE 0.87) Â 10 À11 ; methyl pentanoate (7.84 AE 1.15) Â 10 À11 ; methyl hexanoate (1.09 AE 0.31) Â 10 À10 ; methyl heptanoate (1.56 AE 0.37) Â 10 À10 ; methyl cyclohexane carboxylate (3.32 AE 0.76) Â 10 À10 ; methyl-2-methyl butanoate (9.41 AE 1.39) Â 10 À11 .