Atmospheric Oxidation Mechanism of 1,2-Dibromoethane†

2009 ◽  
Vol 113 (26) ◽  
pp. 7189-7204 ◽  
Author(s):  
Carrie J. Christiansen ◽  
Joseph S. Francisco
Keyword(s):  
Oxidation Mechanism ◽  
Atmospheric Oxidation

Atmospheric oxidation mechanism of polyfluorinated sulfonamides — A quantum chemical and kinetic study

2013 ◽  
Vol 91 (6) ◽  
pp. 472-478 ◽  
Author(s):  
Xiaoyan Sun ◽  
Lei Ding ◽  
Qingzhu Zhang ◽  
Wenxing Wang
Keyword(s):  
Rate Constants ◽  
Density Functional ◽  
Single Point ◽  
Oxidation Mechanism ◽  
Basis Set ◽  
Atmospheric Oxidation ◽  
Oh Radicals ◽  
Oh Radical ◽  
Orbital Theory ◽  
Point Energy

Polyfluorinated sulfonamides (FSAs, F(CF2)nSO2NR1R2) are present in the atmosphere and may serve as the source of perfluorocarboxylates (PFCAs, CF3(CF2)nCOO–) in remote locations through long-range atmospheric transport and oxidation. Density functional theory (DFT) molecular orbital theory calculations were carried out to investigate OH radical-initiated atmospheric oxidation of a series of sulfonamides, F(CF2)nSO2NR1R2 (n = 4, 6, 8). Geometry optimizations of the reactants as well as the intermediates, transition states, and products were performed at the MPWB1K level with the 6-31G+(d,p) basis set. Single-point energy calculations were carried out at the MPWB1K/6-311+G(3df,2p) level of theory. The OH radical-initiated reaction mechanism is given and confirms that the OH addition to the sulfone double bond producing perfluoroalkanesulfonic acid directly cannot occur in the general atmosphere. Canonical variational transition-state (CVT) theory with small curvature tunneling (SCT) contribution was used to predict the rate constants. The overall rate constants were determined, k(T) (N-EtFBSA + OH) = (3.21 × 10−12) exp(–584.19/T), k(T) (N-EtFHxSA + OH) = (3.21 × 10−12) exp(–543.24/T), and k(T) (N-EtFOSA + OH) = (2.17 × 10−12) exp(–504.96/T) cm3 molecule−1 s−1, over the possible atmospheric temperature range of 180–370 K, indicating that the length of the F(CF2)n group has no large effect on the reactivity of FSAs. Results show that the atmospheric lifetime of FSAs determined by OH radicals will be 20–40 days, which agrees well with the experimental values (20–50 days), 20 thus they may contribute to the burden of perfluorinated pollution in remote regions.

Atmospheric Oxidation Mechanism of Methyl Acetate

2000 ◽  
Vol 104 (2) ◽  
pp. 345-351 ◽  
Author(s):  
L. K. Christensen ◽  
J. C. Ball ◽  
T. J. Wallington
Keyword(s):  
Methyl Acetate ◽  
Oxidation Mechanism ◽  
Atmospheric Oxidation

scholarly journals A new model mechanism for atmospheric oxidation of isoprene: global effects on oxidants, nitrogen oxides, organic products, and secondary organic aerosol

2019 ◽  
Author(s):  
Kelvin H. Bates ◽  
Daniel J. Jacob
Keyword(s):  
Secondary Organic Aerosol ◽  
Transport Model ◽  
Oxidation Mechanism ◽  
Organic Aerosol ◽  
Atmospheric Oxidation ◽  
Peroxy Radicals ◽  
Chemical Transport Model ◽  
Total Size ◽  
Hydrogen Shift ◽  
Isomer Distribution

Abstract. Atmospheric oxidation of isoprene, the most abundantly emitted non-methane hydrocarbon, affects the abundances of ozone, the hydroxyl radical (OH), nitrogen oxide radicals (NOx), carbon monoxide (CO), oxygenated and nitrated organic compounds, and secondary organic aerosol (SOA). We analyze these effects in box models and in the global GEOS-Chem chemical transport model using the new Reduced Caltech Isoprene Mechanism (RCIM) condensed from a recently developed explicit isoprene oxidation mechanism. We find many similarities with previous global models of isoprene chemistry along with a number of important differences. Proper accounting of the isomer distribution of peroxy radicals following the addition of OH and O2 to isoprene influences the subsequent distribution of products, decreasing in particular the yield of methacrolein, and increasing the capacity of intramolecular hydrogen shifts to promptly regenerate OH. Hydrogen shift reactions throughout the mechanism lead to increased OH recycling, resulting in less depletion of OH under low-NO conditions than in previous mechanisms. Higher organonitrate yields and faster tertiary nitrate hydrolysis lead to more efficient NOx removal by isoprene and conversion to inorganic nitrate. Only 20 % of isoprene-derived organonitrates (excluding peroxyacyl nitrates) are chemically recycled to NOx. The global yield of formaldehyde from isoprene is 22 % per carbon and less sensitive to NO than in previous mechanisms. The global molar yield of glyoxal is 2 %, much lower than in previous mechanisms because of deposition and aerosol uptake of glyoxal precursors. Global production of isoprene SOA is about one third each from isoprene epoxydiols (IEPOX), organonitrates, and tetrafunctional compounds. We find a SOA yield from isoprene of 13 % per carbon, much higher than commonly assumed in models, and likely offset by SOA chemical loss. We use the results of our simulations to further condense RCIM into a Mini-Caltech Isoprene Mechanism (Mini-CIM) for less expensive implementation in atmospheric models, with a total size (108 species, 345 reactions) comparable to currently used mechanisms.

scholarly journals A new model mechanism for atmospheric oxidation of isoprene: global effects on oxidants, nitrogen oxides, organic products, and secondary organic aerosol

2019 ◽  
Vol 19 (14) ◽  
pp. 9613-9640 ◽  
Author(s):  
Kelvin H. Bates ◽  
Daniel J. Jacob
Keyword(s):  
Secondary Organic Aerosol ◽  
Transport Model ◽  
Oxidation Mechanism ◽  
Organic Aerosol ◽  
Atmospheric Oxidation ◽  
Peroxy Radicals ◽  
Chemical Transport Model ◽  
Total Size ◽  
Hydrogen Shift ◽  
Isomer Distribution

Abstract. Atmospheric oxidation of isoprene, the most abundantly emitted non-methane hydrocarbon, affects the abundances of ozone (O3), the hydroxyl radical (OH), nitrogen oxide radicals (NOx), carbon monoxide (CO), oxygenated and nitrated organic compounds, and secondary organic aerosol (SOA). We analyze these effects in box models and in the global GEOS-Chem chemical transport model using the new reduced Caltech isoprene mechanism (RCIM) condensed from a recently developed explicit isoprene oxidation mechanism. We find many similarities with previous global models of isoprene chemistry along with a number of important differences. Proper accounting of the isomer distribution of peroxy radicals following the addition of OH and O2 to isoprene influences the subsequent distribution of products, decreasing in particular the yield of methacrolein and increasing the capacity of intramolecular hydrogen shifts to promptly regenerate OH. Hydrogen shift reactions throughout the mechanism lead to increased OH recycling, resulting in less depletion of OH under low-NO conditions than in previous mechanisms. Higher organonitrate yields and faster tertiary nitrate hydrolysis lead to more efficient NOx removal by isoprene and conversion to inorganic nitrate. Only 20 % of isoprene-derived organonitrates (excluding peroxyacyl nitrates) are chemically recycled to NOx. The global yield of formaldehyde from isoprene is 22 % per carbon and less sensitive to NO than in previous mechanisms. The global molar yield of glyoxal is 2 %, much lower than in previous mechanisms because of deposition and aerosol uptake of glyoxal precursors. Global production of isoprene SOA is about one-third from each of the following: isoprene epoxydiols (IEPOX), organonitrates, and tetrafunctional compounds. We find a SOA yield from isoprene of 13 % per carbon, much higher than commonly assumed in models and likely offset by SOA chemical loss. We use the results of our simulations to further condense RCIM into a mini Caltech isoprene mechanism (Mini-CIM) for less expensive implementation in atmospheric models, with a total size (108 species, 345 reactions) comparable to currently used mechanisms.

Sign in / Sign up

Export Citation Format

Share Document