Kinetics and mechanisms for the reaction of hydroxyl radicals with trifluoroacetic acid under atmospheric conditions

The rate constant for the gas-phase reaction of the hydroxyl radical with trifluoroacetic acid has been determined over the temperature range 283–323 K using a relative rate technique. The results provide a value of k(OH+CF3C(O)(OH) = 2.0 × 10−13 exp (−146±500/T) cm3 molecule−1 s−1 based on k(OH+C2H6)=7.8×10−12 exp(−1020±100/T) cm3 moleculet−1 s−1 for the rate constant of the reference reaction. The OH-radical initiated oxidation of CF3C(O)OH was investigated at 298 K in oxygen at 1 atm total pressure using Fourier-transform infrared spectroscopy. The major carbon-containing products were C(O)F2, CF3O3CF3 and CO2, suggesting that the dominant reaction channel for loss of the CF3C(O)O radical, formed by hydrogen atom abstraction, is carboncarbon bond cleavage. The results indicate that the gas-phase reaction of OH radicals with trifluoroacetic acid may provide a sink for this compound in the troposphere that cannot be neglected.