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Kinetics and mechanism of the reactions of 2,3-butadione with F and Cl atoms, UV absorption spectra of CH 3 C(O)C(O)CH 2 · and CH 3 C(O)C(O)CH 2 O 2 · radicals, and atmospheric fate of CH 3 C(O)C(O)CH 2 O· radicals

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FTIR-smog chamber techniques were used to determine rate constants for the gas-phase reaction of Cl and F atoms with CH 3 C(O)C(O)CH 3 and F atoms with CH 3 C(O)F of (4.0 ± 0.5) x 10 -3 , (4.9 ± 0.7) x 10 -11 , and (3.6 ± 0.4) x 10 -12 cm 3 molecule -1 s -1 , respectively. Two pathways for the reaction of Cl and F atoms with CH 3 C(O)C(O)CH 3 were found: (1a) Cl + CH 3 C(O)C(O)CH 3 → HCl + CH 3 C(O)C(O)CH 2 ·, (1b) Cl + CH 3 C(O)C(O)CH 3 → CH 3 C(O)Cl + CH 3 C(O)·, (2a) F + CH 3 C(O)C(O)CH 3 → HF + CH 3 C(O)C(O)CH 2 ·, (2b) F + CH 3 C(O)C(O)CH 3 → CH 3 C(O)F + CH 3 C(O)·, with branching ratios of k 1b /(k 1b + k 1a ) = 0.23 ± 0.02 and k 2b /(k 2b + k 2a ) = 0.56 ± 0.09. It was determined that the atmospheric fate of CH 3 C(O)C(O)CH 2 O· radicals is decomposition to give HCHO, CO, and CH 3 C(O)· radicals. Pulse radiolysis coupled to UV absorption spectroscopy was used to study the kinetics of the reaction of F atoms with CH 3 C(O)C(O)CH 3 as well as spectra of CH 3 C(O)C(O)CH 2 · and CH 3 C(O)C(O)CH 2 O 2 · radicals over the wavelength range 220-400 nm at 295 K. The rate constant for the reaction of F atoms with CH 3 C(O)C(O)CH 3 was determined to be (4.6 ± 0.8) x 10 -11 cm 3 molecule -1 s -1 . The absorption cross sections of CH 3 C(O)C(O)CH 2 and CH 3 C-(O)C(O)CH 2 O 2 · radicals were (5.4 ± 1.0) x 10 -18 at 250 nm and (2.0 ± 0.5) x 10 -18 cm 2 molecule -1 at 320 nm, respectively. Results are discussed with respect to the available database concerning the reaction of Cl and F atoms with organic compounds.

OriginalsprogEngelsk
TidsskriftJournal of Physical Chemistry A
Vol/bind102
Udgave nummer45
Sider (fra-til)8913-8923
Antal sider11
ISSN1089-5639
StatusUdgivet - 5 nov. 1998

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