Reaction of Atmospheric Ions with Selected Hydrofluorocarbons

Article abstract of DOI:10.1021/j100016a040

Selected atmospheric ions have been studied for reactivity with the hydrofluorocarbons (HFC's) CF3CH2F, CF3CHFCF3, and CF3CHFCHF2 and with CHBrF2; the reactant ions chosen for study are O⁺, O2⁺, O^-, O2^-, H3O⁺, H3O⁺*H2O, H3O⁺*(H2O)2, NO3^-, and NO3^-*HNO3.Rate constants and product branching fractions for these ion-molecule reactions were measured using a selected ion flow tube (SIFT) instrument operated at 300 K.The ions O⁺ and O^- reacted at the collisional rates, forming a number of ionic products in most cases.Most of the other reactions studied were found to be inefficient.The ions H3O⁺ and NO3^- reacted inefficiently by association in all cases.The solvated ions H3O⁺*H2O, H3O⁺*(H2O)2, and NO3^-*HNO3, which are representative of the abundant ionic species in the lower atmosphere, were unreactive with the compounds investigated; we conclude from this that atmospheric ion chemistry is not a significant sink for these HFC's.The observation of proton transfer from CF3CHFCF3 and CF3CHFCHF2 to O^- allows a lower bound to the gas-phase acidities of these HFC's to be assigned: ΔH_acid(CF3CHFCF3) and ΔH_acid(CF3CHFCHF2) < 1599 kJ mol^-1.