Reactions of Halogenated Acetic and Propionic Acids with Fluorine Atoms

Halogenated acids are of anthropogenic and natural origin and play an important role in atmospheric processes. The global distribution and high stability of halogenated acids is concerning because they are toxic, accumulate in surface waters, and pose a threat to humans and the ecosystem. Knowledge of the reaction mechanism of halogenated acids in the gas phase makes it possible to explain and control many important processes occurring in the atmosphere and during combustion. In this paper, we experimentally study the reactions of atomic fluorine with monochloroacetic, dichloroacetic, trichloroacetic, trifluoroacetic, and pentafluoropropionic acids at a pressure of 1 Torr. The experiments are carried out using a flow reactor connected to a mass spectrometer with a modulated beam. The rate constants of these reactions at room temperature are determined by the method of competing reactions (MCR) using the available published data. It is shown that in this series the fastest reaction is F + CH 2 ClCOOH. In addition, the temperature dependences of the rate constants are obtained for F + CF 3 COOH and F + C 2 F 5 COOH reactions in the ranges of 258–343 and 262–343 K, respectively.