ION-MOLECULE REACTIONS IN GASEOUS CF4 CO MIXTURES - FORMATION AND REACTIVITY OF CF3CO+ IONS/

The reactivity of CF3CO+ ions, formed via two different routes, has be en studied in the gas phase by the joint use of mass spectrometric and radiolytic techniques, spanning a pressure range from 10(-8) Torr to ca. 1 atm. The 23 kcal mol(-1) exothermic addition of CF3+ to CO provi des a route to CF3CO+ requiring third-body stabilization of the adduct ion. In the 10(-8) Torr pressure regime of Fourier transform ion cycl otron resonance (FT-ICR) spectrometry, CF3CO+ ions from electron ioniz ation (EI) induced fragmentation of trifluoroacetic anhydride yield Nu CF(3)(+) products from oxygen-centered nucleophiles (Nu) and XC(6)H(4) CO(+) ions from aromatics (C(6)H(5)X) At ca. 1 atm trifluoroacetylated products are efficiently formed even with strongly deactivated aromat ics, showing distinct intra- and intermolecular selectivity features p ertaining to the reactant CF3CO+ ions. The reactivity pattern is inter preted according to a kinetic interplay of collisional and chemical ev ents depending on the activation of C(6)H(5)X toward electrophilic att ack.