TY - JOUR
T1 - Atmospheric oxidation of CH3Br
T2 - Chemistry of the CH2BrO radical
AU - Orlando, John J.
AU - Tyndall, Geoffrey S.
AU - Wallington, Timothy J.
PY - 1996/4/25
Y1 - 1996/4/25
N2 - The Cl-atom-initiated photooxidation mechanism of CH3Br has been investigated in chamber experiments conducted under conditions applicable to the lower atmosphere. Major carbon-containing products obtained in the presence of O2 and NO, as determined by FTIR absorption spectroscopy, are CH2O and CO. In addition, HC(O)Br is observed in the absence of NO. At low temperature, in the presence of NO, CH2BrO2NO2 was also identified as a reaction product. The results are used to determine the fate of the alkoxy radical, CH2-BrO. It is found that unimolecular decomposition of CH2BrO to CH2O + Br is the dominant process in 1 atm of O2 at all temperatures studied (between 228 and 298 K), while reaction with O2, CH2BrO + O2-HC(O)Br + HO2, and the three-centered elimination of HBr, CH2BrO → HCO + HBr, are found to be minor pathways under these conditions (less than 5% each). Assumption of a rate constant of 6 × 10-14 cm3 molecule-1 s-1 for the reaction of CH2BrO with O2 (DeMore, W. B., et al. NASA JPL Publ. 1994, No. 94-26) provides a lower limit to the rate of Br-atom elimination of 3 × 107 s-1 at 228 K, 1 atm of pressure.
AB - The Cl-atom-initiated photooxidation mechanism of CH3Br has been investigated in chamber experiments conducted under conditions applicable to the lower atmosphere. Major carbon-containing products obtained in the presence of O2 and NO, as determined by FTIR absorption spectroscopy, are CH2O and CO. In addition, HC(O)Br is observed in the absence of NO. At low temperature, in the presence of NO, CH2BrO2NO2 was also identified as a reaction product. The results are used to determine the fate of the alkoxy radical, CH2-BrO. It is found that unimolecular decomposition of CH2BrO to CH2O + Br is the dominant process in 1 atm of O2 at all temperatures studied (between 228 and 298 K), while reaction with O2, CH2BrO + O2-HC(O)Br + HO2, and the three-centered elimination of HBr, CH2BrO → HCO + HBr, are found to be minor pathways under these conditions (less than 5% each). Assumption of a rate constant of 6 × 10-14 cm3 molecule-1 s-1 for the reaction of CH2BrO with O2 (DeMore, W. B., et al. NASA JPL Publ. 1994, No. 94-26) provides a lower limit to the rate of Br-atom elimination of 3 × 107 s-1 at 228 K, 1 atm of pressure.
UR - https://www.scopus.com/pages/publications/0000048535
U2 - 10.1021/jp951813q
DO - 10.1021/jp951813q
M3 - Article
AN - SCOPUS:0000048535
SN - 0022-3654
VL - 100
SP - 7026
EP - 7033
JO - Journal of Physical Chemistry
JF - Journal of Physical Chemistry
IS - 17
ER -