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

Bromopentafluoropropane (C3H2BrF5) has Come under consideration as a potent ial replacement compound for ozone-depleting chlorofluorocarbons and Halons . No rate constants for the reaction of the isomers of C3H2BrF5 with hydrox yl radical in the atmosphere have yet been measured. The existing ozone dep letion potential recommendations, which are based on estimated reaction rat e constants for the C3H2BrF5 isomers, are not in agreement. In this study, we seek to clarify the ozone depletion potential of the C3H2BrF5 isomers. F irst, 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 pred ict hydroxyl reaction rate constants using that estimation method for the C 3H2BrF5 isomers and calculate both atmospheric lifetimes and ozone depletio n potentials through semiempirical methods. This study obtains C3H2BrF5 atm ospheric lifetimes ranging from 1.4 to 59 years and ozone depletion potenti als ranging from 0.30 to 12, which reflects the strong dependence of hydrox yl reactivity on the isomeric structure of the potential replacement compou nd.