Novel CFCs-Substitutes Recommended by EPA (Hydrofluorocarbon-245fa and Hydrofluoroether-7100): Ion Chemistry in Air Plasma and Reactions with Atmospheric Ions

The ion chemistry of the title compounds, a nonafluorobutyl methyl ether and a hydrofluoropropane, is elucidated by a combination of studies using atmospheric pressure ionization mass spectrometry and triple quadrupole mass spectrometry. In the positive ion mode, the hydrofluoroether readily forms an [M − F]+ ion, attributable to hydronium ion induced dehydrofluorination, the product of which can be further hydrated to give a protonated hydrofluoroester. By contrast, the hydrofluoropropane does not react with the hydronium ion but rather gives hydrofluoroalkenylium cations via H atom and F atom abstraction by the dioxygen radical cation. In the negative ion mode, the fluorobutyl methyl ether undergoes dissociative electron capture with O2−·, O2−·(H2O), O3−·, and NO2− to generate the fluorobutoxy anion, which can dissociate by CF2O loss to give the perfluorocarbanion when the precursor ions are internally excited. The hydrofluoropropane reacts readily with common atmospheric anions to form molecular complexes with F−, O2−·, and O3−· and the strongly H-bonded species, O2−·(HF) and F−(HF). Interestingly, isomeric pentafluoropropanes form in the reaction with O2−·, either O2−·(HF) or F−(HF), depending on the specific pattern of the fluoro substitution.