Forskning ved Københavns Universitet - Københavns Universitet


Atmospheric chemistry of HFC-236fa: Spectrokinetic investigation of the CF3CHO2CF3 radical, its reaction with NO, and the fate of the CF3CHOCF3 radical

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A pulse radiolysis technique was used to investigate the UV absorption spectrum of CF3CHO2CF3 over the wavelength range 220-290 nm. At 250 nm the absorption cross section for CF3CHO2CF3 was σ = (186 ± 27) × 10-20 cm3 molecule-1. The rate constant for the self-reaction rate of CF3CHO2CF3 was determined to be (5.6 ± 0.7) × 10-12 cm3 molecule-1 s-1. By following the increase in NO2 at 400 nm, the rate constant for the reaction of CF3CHO2CF3 with NO was found to be (1.1 ± 0.3) × 10-11 cm3 molecule-1 s-1. The reaction of CF3CHO2CF3 with NO gives CF3CHOCF3. A Fourier transform infrared technique was used to show that in the atmosphere >99% of CF3CHOCF3 react with O2 to give CF3COCF3. The atmospheric fate of CF3COCF3 is photolysis or incorporation into rain-cloud-sea water followed by rapid hydrolysis. As part of the present work relative rate techniques were used to measure rate constants at 295 ± 2 K for the reactions of Cl and F atoms with CF3CH2CF3 of <8 × 10-17 and (1.8 ± 0.4) × 10-13 cm3 molecule-1 s-1, respectively. In addition, the rate constant for reaction of F atoms with (CF3)2CHOH was determined to be (3.5 ± 1.1) × 10-12 cm3 molecule-1 s-1. All experiments were performed at 296 ± 2 K.

TidsskriftJournal of Physical Chemistry
Udgave nummer15
Sider (fra-til)5373-5378
Antal sider6
StatusUdgivet - 1 dec. 1995

ID: 228191661