GASEOUS ION-MOLECULE REACTIONS OF F-, CF3-, C2F5-, CF3+, AND C2F5+ WITH HEXAFLUOROPROPENE OXIDE

The gas-phase reactions of F-, CF3-, C2F5-, CF3+ and C2F5+ with hexafl uoropropene oxide (HFPO, C3F6O) have been studied using a selected ion flow tube (SIFT) instrument at 300 K. Reactions of C4F9- and C3F7+ wi th HFPO have also been studied as secondary reactions. Reaction rate c onstants and product branching fractions were measured. The F-, CF3- a nd C2F5- ions react rapidly with HFPO. The major reaction process is t he formation of CF2O and the corresponding negative product ions. A mi nor pathway is the production of the ion CF3O-. Another reaction chann el of F- and CF3- with HFPO is the formation of C2F4 and the correspon ding ions. C4F9- ion reacts with HFPO by F- transfer to produce C3F7O- . The C3F7+ ion is the only product observed for the reaction of CF3with HFPO. The C2F5+ ion reacts rapidly with HFPO, The major product i s C3F7+ which, in turn, reacts with HFPO to regenerate C2F5+,forming a cationic catalytic cycle for the formation of the inferred neutrals C 2F4O and C4F8O from HFPO. Both C2F5+ and C3F7+ react with HFPO to prod uce neutral C3F8 and the corresponding positive ions. A rather rapid a ssociation reaction was observed between C3F7+ and HFPO, forming the a dduct C6F13O+. A systematic estimation for the enthalpies of formation for a series of perfluorinated neutrals and ionic species is also pre sented.