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Atmospheric chemistry of 1,1,1-trichloroethane: UV absorption spectra and self-reaction kinetics of CCl3CH2 and CCl3CH2O2 radicals, kinetics of the reactions of the CCl3CH2O2 radical with NO and NO2, and the fate of the alkoxy radical CCl3CH2O

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A pulse radiolysis technique was used to measure the UV absorption spectra of CCl3CH2 and CCl3CH2O2 radicals over the range 220-300 nm. At 220 nm, σ(CCl3CH2) = (9.4 ± 1.1) × 10-18 cm2 molecule-1; at 250 nm, σ(CCl3CH2O2) = (2.9 ± 0.3) × 10-18 cm2 molecule-1. The observed self-reaction rate constants, defined as -d[CCl3CH2]/dt = 2k4[CCl3CH2] and -d[CCl3CH2O2]/dt = 2k5obs[CCl3CH2O2]2, were k4 = (9.1 ± 1.1) × 10-12 and k5obs = (4.7 ± 1.6) × 10-12 cm3 molecule-1 s-1. The reaction of CCl3CH2O2 radicals with NO gives CCl2CH2O radicals. In the atmosphere, >96% of the CCl3CH2O radicals react with O2 to give CCl3CHO. The rate constants for the reactions of CCl3CH2O2 radicals with NO and NO2 were determined to be k6 ≥ 6.1 × 10-12 cm3 molecule-1 s-1 and k7 = (6.5 ± 0.4) × 10-12 cm3 molecule-1 s-1, respectively. As a part of this work, the rate constant for the reaction between F atoms and CCl3CH3 was determined to be k3 = (6.8 ± 1.5) × 10-12 cm3 molecule-1 s-1. A relative rate technique was used to measure rate constants for the reactions of Cl atoms with: CCl3CH3, (9.9 ± 2.0) × 10-15; CCl3CHO, (6.0 ± 1.3) × 10-12; and CCl3CH2OH (3.0 ± 0.6) × 10-12 (units of cm3 molecule-1 s-1) at 296 K. Results are discussed in the context of the atmospheric chemistry of 1,1,1-trichloroethane.

OriginalsprogEngelsk
TidsskriftJournal of Physical Chemistry
Vol/bind99
Udgave nummer17
Sider (fra-til)6570-6579
Antal sider10
ISSN0022-3654
StatusUdgivet - 1 dec. 1995

ID: 228192171