Gaseous ion-molecule reactions of F(-), CF3(-), C2F5(-), CF3(+) and C2F5(+) with hexafluoropropene oxide

Article abstract of DOI:10.1016/0022-1139(95)03266-G

The gas-phase reactions of F(1-), CF3(1-), C2F5(1-), CF3(1+) and C2F5(1+) with hexafluoropropene oxide (HFPO, C3F6O) have been studied using a selected ion flow tube (SIFT) instrument at 300 K.Reactions of C4F9(1-) and C3F7(1+) with HFPO have also been studied as secondary reactions.Reaction rate constants and product branching fractions were measured.The F(1-), CF3(1-) and C2F5(1-) ions react rapidly with HFPO.The major reaction process is the formation of CF2O and the corresponding negative products ions.A minor pathway is the production of the ion CF3O(1-).Another reaction channel of F(1-) and CF3(1-) with HFPO is the formation of C2F4 and the corresponding ions.C4F9(1-) ion reacts with HFPO by F(1-) transfer to produce C3F7O(1-).The C3F7(1+) ion is the only product observed for the reaction of CF3(1+) with HFPO.The C2F5(1+) ion reacts rapidly with HFPO.The major product is C3F7(1+) which, in turn, reacts with HFPO to regenerate C2F5(1+), forming a cationic catalytic cycle for the formation of the inferred neutrals C2F4O and C4F8O from HFPO.Both C2F5(1+) and C3F7(1+) react with HFPO to produce neutral C3F8 and the corresponding positive ions.A rather rapid association reaction was observed between C3F7(1+) and HFPO, forming the adduct C6F13O(1+).A systematic estimation for the enthalpies of formation for a series of perfluorinated neutrals and ionic species is also presented. - Keywords: Ion-molecule reactions; Hexafluoropropene oxide; Fluorine ion; Trifluoromethyl ion; F-ethyl ion; Reaction kinetics