R. Atkinson

Evaluation of Kinetic and Mechanistic Data for Modeling of Photochemical Smog

This review is a critical evaluation of the rate constants, mechanisms, and products of selected atmospheric reactions of hydrocarbons, nitrogen oxides, and sulfur oxides in air. The evaluation considers eight hydrocarbons (n‐butane, 2,3‐dimethylbutane, ethene, propene, 1‐butene, trans‐2‐butene, toluene, and m‐xylene) for which smog chamber irradiations have been carried out under carefully controlled conditions and which have been the subject of computer modeling studies by more than one research group. The reactions involved are treated in the following categories: inorganic reactions in organic‐NOx‐air irradiations; organic reactions of the formaldehyde‐NOx‐air system; organic reactions of the acetaldehyde‐NOx‐air system; organic reactions of the alkene‐NOx‐air systems; organic reactions of the alkane‐NOx‐air systems; organic reactions of selected carbonyl‐NOx‐air systems; organic reactions of the aromatic‐NOx‐air systems; combination reactions of peroxy radicals, and homogeneous gas phase SO2 reaction...

Rate constants for the reaction of OH radicals with CHF2Cl, CF2Cl2, CFCl3, and H2 over the temperature range 297–434 °K

Rate constants for the reaction of OH radicals with CHF2Cl, CF2Cl2, CFCl3, and H2 have been determined over the temperature range 297–434u2009°K using a flash photolysis–resonance fluorescence technique. The following Arrhenius expressions were obtained: k1(CHF2Cl) =1.21×10−12e−(3250±300)/RT cm3 molecule−1u2009sec−1, k1(CF2Cl2) <1×10−15 cm3 molecule−1u2009sec−1 (T=297–424u2009°K), k1(CFCl3) <1×10−15 cm3 molecule−1u2009sec−1 (T=297–424u2009°K), k1(H2) =5.9×10−12 e−(3990±300)/RT cm3 molecule−1u2009sec−1. The rate constants for the reaction of OH radicals with H2, which were used to check the experimental system, are in good agreement with literature values. The atmospheric significance of the reaction of OH radicals with CHF2Cl is briefly discussed.

Rate constants for the reactions of the OH radical with NO2 (M=Ar and N2) and SO2 (M=Ar)

Absolute rate constants for the reactions OH+NO2+M→HNO3+M (M=Ar, N2) OH+SO2+M→HSO3+M (M=Ar) have been determined at 298°K, using a flash photolysis–resonance fluorescence technique. Rate constants k1 and k2 were determined over the pressure range 25–648 torr for M=Ar, while a rate constant for the first reaction was also obtained for M=N2 at 25 torr total pressure. The low pressure third order rate constants were determined to be k1(M=Ar) = (1.02±0.10) ×10−30 cm6 molecule−2⋅sec−1 and k2(M=Ar) = (1.64±0.33) ×10−31 cm6 molecule−2⋅sec−1, in reasonable agreement with the literature values. The bimolecular rate constants at 760 torr total pressure were determined to be kbi1= (5.9±0.7) ×10−12 cm3 molecule−1⋅sec−1 (M=Ar), kbi1= (6.4±1.0) ×10−12 cm3 molecule−1⋅sec−1 (M=N2), and kbi2= (6.7±0.7) ×10−13 cm3 molecule−1⋅sec−1 (M=Ar). Extrapolation of the data led to limiting high pressure second order constants of k∞1?8.5×10−12 cm3 molecule−1⋅sec−1 and k∞2?8.3×10−13 cm3 molecule−1⋅sec−1.

Rate constants for the reaction of the OH radical with H2 and NO (M=Ar and N2)

Absolute rate constants for the reaction of OH radicals with H2 and NO (M=Ar, N2) have been determined at 298±1u2009°K using a flash photolysis–resonance fluorescence technique. The rate constant for the reaction OH+H2 was determined to be (6.97±0.70) ×10−15 cm3u2009 molecule−1u2009sec−1 in good agreement with recent literature values. Rate constants for the reaction OH + NO + M (M = Ar) were obtained over the pressure region 25–655 torr, while a rate constant for M = N2 was obtained at 25 torr total pressure. The low pressure third order rate constants for this reaction were determined to be (4.25±0.43) ×10−31 cm6 molecule−2u2009sec−1 (M=Ar) and (6.1±0.7) ×10−31 cm6u2009 molecule−2u2009sec−1 (M = N2), in good agreement with the available literature values. The bimolecular rate constants at 760 torr total pressure were determined to be (5.2±0.8) ×10−12 cm3u2009 molecule−1u2009sec−1 for M = Ar and (6.1±1.0) ×10−12 cm3u2009molecule−1u2009sec−1 for M = N2. A value of 8×10−12 cm3u2009molecule−1u2009sec−1 was obtained as a probable lower limit for the limit...

Absolute rate constants for the reaction of OH radicals with allene, 1,3‐butadiene, and 3‐methyl‐1‐butene over the temperature range 299–424 °K

Absolute rate constants for the reaction of OH radicals with allene, 1,3‐butadiene, and 3‐methyl‐l‐butene have been determined over the temperature range 299–424u2009°K, using a flash photolysis–resonance fluorescence technique. The Arrhenius expressions obtained were k (allene) =5.59×10−12u2009e(305±300)/RT cm3u2009molecule−1u2009sec−1, k (1,3‐butadiene) =1.45×10−11u2009e(930±300)/RT cm3u2009molecule−1u2009sec−1, k (3‐methyl‐1‐butene) =5.23×10−12u2009e(1060±300)/RT cm3u2009molecule−1u2009secu2009−1, with rate constants at room temperature of (9.30±0.93) ×10−12, (6.85±0.69) ×10−11, and (3.10±0.31) ×10−11 cm3u2009molecule−1u2009sec−1 for allene, 1,3‐butadiene, and 3‐methyl‐l‐butene, respectively.

A study of the atmospheric reactions of 1,3-dichloropropene and other selected organochlorine compounds

Thecis- andtrans-1,3-dichloropropene isomers are widely used as an insecticide fumigant in a variety of commercial formulations such as D-D,® Vidden D,® Telone,® Telone II,® and Telone C17.® In order to investigate their atmospheric lifetimes and reaction mechanisms, kinetic and product data have been obtained at room temperature for the gas phase reactions of part-per-million (ppm) concentrations ofcis- andtrans-1,3-dichloropropene with O3 and with OH radicals in Teflon chambers. In addition, rate constants for OH radical and O3 reactions with 1,2-dichloropropane and 3-chloro-2-chloromethyl-1-propene have been determined. The products observed by FT-IR analyses from the reaction of O3 with the two 1,3-dichloropropene isomers were formyl chloride and chloroacetaldehyde, together with chloroacetic acid, HCl, CO, CO2, and formic acid. The products observed from the reaction of OH radicals with the 1,3-dichloropropene isomers were formyl chloride and chloroacetaldehyde, with unit yields. The kinetic data allow atmospheric lifetimes to be estimated for the four halogenated organic chemicals studied and, together with literature data, permit the estimation of atmospheric lifetimes for other halogenated organic compounds for which no experimental data are available. The reaction pathways and atmospheric lifetimes of these widely employed chemicals are discussed.

Rate constants for the reaction of OH radicals with CHFCl2 and CH3Cl over the temperature range 298–423 °K, and with CH2Cl2 at 298 °K

Rate constants for the reaction of OH radicals with CHFCl2 and CH3Cl have been determined over the temperature range 298–423u2009°K using a flash photolysis–resonance fluorescence technique. The Arrhenius expressions obtained were k1(CHFCl2) =1.75×10−12e−(2490±300)/RT cm 3 molecule−1 sec−1, k1(CH3Cl) =4.1×10−12 e−(2700±300)/RT cm3 molecule−1 sec−1. In addition, the rate constant for the reaction of OH radicals with CH2Cl2 was determined to be k1(CH2Cl2) = (1.45±0.20) ×10−13 cm3 molecule−1 sec−1 at 298.5u2009°K. These rate constants are in good agreement with literature values.

Kinetics of the reactions of OH radicals with CO and N2O

Rate constants k1 for the reaction of OH radicals with CO have been determined at 299 ± 1 K over the pressure range 25–654 torr of argon using a flash photolysis-resonance fluorescence technique. The rate constant K1 was observed to be independent of total pressure over the range studied with a value of K1 = (1.54 ± 0.16) × 10−13 cm3 molecule−1 s−1. In addition, upper limits for the rate constants k2 for the reaction of OH radicals with N2O of k2 < 2 × 10−16 cm3 molecule−1 s−1 were obtained at both 298.0 and 442.8 K.

Atmospheric gas phase loss processes for chlorobenzene, benzotrifluoride, and 4-chlorobenzotrifluoride, and generalization of predictive techniques for atmospheric lifetimes of aromatic compounds

The homogeneous gas phase atmospheric loss processes for chlorobenzene (CB), benzotrifluoride (BTF) and 4-chlorobenzotrifluoride (CBTF), compounds chemically and structurally similar to various classes of herbicides and pesticides currently in use, have been experimentally investigated by U.S. Environmental Protection Agency approved protocols. The rate constants, or upper limits thereof, for photolysis (under blacklight irradiation with an NO2 photolysis rate of 0.27 min−1) and reaction with OH radicals and O3 were determined. The rate constants obtained were: k(photolysis) <2.7×10−6 sec−1 for CBTF; k(O3 reaction) <5×10−21 cm3 molecule−1 sec−1 for all three of these aromatic compounds; and k(OH radical reaction)=(8.8±1.1)×10−13 cm3 molecule−1 sec−1 for CB; (4.4±1.1)×10−13 cm3 molecule−1 sec−1 for BTF; and (2.3±0.8)×10−13 cm3 molecule−1 sec−1 for CBTF. Estimated atmospheric lifetimes due to these reactions are calculated and their environmental implications discussed. A predictive technique is presented for estimating the rate constants for addition of OH radicals to aromatic rings.

Structural effects on the chemiluminescence from the reaction of ozone with selected organic compounds

Abstract In order to test experimentally the reaction pathways postulated from previous experimental and theoretical investigations, the following studies were carried out. 1. An investigation into the effect of pressure and O2 on the OH Meinel band emission from the reaction of O3 with simple olefins. 2. An extension of previous studies of chemiluminescence from low pressure gas phase ozone reactions to the following classes of compounds: cyclic olefins (cyclopentene), alkynes (acetylene), diolefins (allene, 1,3-butadiene) and unsaturated aldehydes (acrolein and crotonaldehyde). These compounds provide possibilities for diversion of the normal reaction paths not present in simple olefins. 3. In order to test the mechanisms proposed in the literature to account for chemiluminescent species studies were carried out on the following selected organic compounds to determine whether the chemiluminescence observed was predicted by the mechanistic theories: 3-methyl-1-butene to attempt to determine the mechanistic pathway for the production of glyoxal phosphorescence; 1,1- and 1,2-difluoroethylene, 3,3,3-trifluoropropylene, 1,1-dichloropropylene, cyclopentene, acrolein, trans-3-hexene and trans-4-octene to investigate the pathways for production of formaldehyde fluorescence; a series of deuterated and partially deuterated propylenes for the production of OH Meinel band emission. The data and chemiluminescent spectra obtained are reported, leading to the conclusion that the present theories of ozone—olefin reactions do not entirely predict the chemiluminescing species observed. Furthermore, it appears that the overall mechanism for production of vibrationally excited hydroxyl radicals from ozone—olefin reactions is so complex that a satisfactory mechanism cannot easily be deduced by simply studying the effect of variable reactant concentrations and total pressure.