title: Kinetics of the reactions of CH2I, CH2Br, and CHBrCl radicals with NO2 in the temperature range 220-360 K.
abstract: The kinetics of the CH2I + NO2, CH2Br + NO2, and CHBrCl + NO2 reactions have been studied at temperatures between 220 and 360 K using laser photolysis/photoionization mass spectrometry. Decays of radical concentrations have been monitored in time-resolved measurements to obtain reaction rate coefficients under pseudo-first-order conditions. The bimolecular rate coefficients of all three reactions are independent of the bath gas (He or N2) and pressure within the experimental range (2-6 Torr) and are found to depend on temperature as follows: k(CH2I + NO2) = (2.18 +/- 0.07) x 10(-11) (T / 300 K)(-1.45) (+/- 0.22) cm3 molecule(-1) s(-1) (220-363 K), k(CH2Br + NO2) = (1.76 +/- 0.03) x 10(-11) (T/300 K)(-0.86) (+/- 0.09) cm3 molecule(-1) s(-1) (221-363 K), and k(CHBrCl + NO2) = (8.81 +/- 0.28) x 10(-12) (T/300 K)(-1.55) (+/- 0.34) cm3 molecule(-1) s(-1) (267-363 K), with the uncertainties given as one-standard deviations. Estimated overall uncertainties in the measured bimolecular reaction rate coefficients are about +/-25%. In the CH2I + NO2 and CH2Br + NO2 reactions, the observed product is formaldehyde. For the CHBrCl + NO2 reaction, the product observed is CHClO. In addition, I atom and iodonitromethane (CH2INO2) or iodomethyl nitrite (CH2IONO) formations have been detected for the CH2I + NO2 reaction.
authors.affiliation: Laboratory of Physical Chemistry, PO Box 55 (A.I. Virtasen aukio 1), FIN-00014 University of Helsinki, Finland.
authors.forename: Arkke J
authors.initials: AJ
authors.lastname: Eskola
authors.forename: Dorota
authors.initials: D
authors.lastname: Wojcik-Pastuszka
authors.forename: Emil
authors.initials: E
authors.lastname: Ratajczak
authors.forename: Raimo S
authors.initials: RS
authors.lastname: Timonen