Reactions in Fluorinated Acetic Acid Esters Triggered by Slow Electrons: Bond Cleavages, Hydrogen Transfer Reactions and Loss of Halocarbons

Abstract

Abstract Low energy electron induced reactions in the four fluorinated acetic acid esters CF3COOCH3, CF3COOC2H5, CF3COOCH2CF3 and CH3COOCH2CF3 are studied by means of a crossed electron-molecular beam experiment and mass spectrometric detection of the anions. All target molecules exhibit a prominent resonance located near 1 eV which is subjected to a variety of unimolecular reactions. The observation of the carboxylate anion CF3COO–/CH3COO– indicates rupture of the O−R ester bond, which in turn demonstrates that the prominent cleavage of the O−H bond recently observed in trifluoroacetic acid and acetic acid is not blocked when O−H is replaced by O−R (R=−CH3, −C2H5, −CH2CF3). In CF3COOCH3 and CF3COOC2H5 an ion of the form CF2COO– is generated which is identified to arise from a complex reaction involving multiple bond cleavages and substantial rearrangement in the transitory negative ion ultimately generating CH3F and C2H5F, respectively, as neutral counterpart. A fragment ion of the type (M-H)– (M: target molecule), i.e. loss of a neutral hydrogen atom, is only observed in CH3COOCH2CF3 which directly demonstrates that dehydrogenation selectively occurs at the CH3 site.