Estimates of atmospheric lifetimes and ozone depletion potentials for the bromopentafluoropropane isomers

Bromopentafluoropropane (C3H2BrF5) has come under consideration as a potential replacement compound for ozone-depleting chlorofluorocarbons and Halons. No rate constants for the reaction of the isomers of C3H2BrF5 with hydroxyl radical in the atmosphere have yet been measured. The existing ozone depletion potential recommendations, which are based on estimated reaction rate constants for the C3H2BrF5 isomers, are not in agreement. In this study, we seek to clarify the ozone depletion potential of the C3H2BrF5 isomers. First, we apply two hydroxyl reaction rate constant estimation methods to a series of bromofluorocarbons likely to have similar reactivity to C3H2BrF5 in order to select one estimation method to apply to C3H2BrF5. We then predict hydroxyl reaction rate constants using that estimation method for the C3H2BrF5 isomers and calculate both atmospheric lifetimes and ozone depletion potentials through semiempirical methods. This study obtains C3H2BrF5 atmospheric lifetimes ranging from 1.4 to 59 years and ozone depletion potentials ranging from 0.30 to 12, which reflects the strong dependence of hydroxyl reactivity on the isomeric structure of the potential replacement compound.