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 x 10(-13)exp(-146+/-500/T) cm3 molecule-1 s-1 based on k(OH + C2H6)=7.8 x 10(-12)exp(-1020+/-100/T) cm3 molecule-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.