An energy-resolved study of the fragmentation of protonated polyfluoro- and polychloro-benzenes

Abstract

The collision-induced dissociation mass spectra of protonated polyfluoro- and polychloro-benzenes have been studied as a function of collision energy over the energy range 5–100 eV (laboratory frame) using a hybrid tandem BEqQ mass spectrometer. For the protonated fluorobenzenes, elimination of HF dominates the breakdown graph for lower members of the series but elimination of CF 2 increases in importance with increasing fluorine content and becomes the dominant fragmentation reaction for protonated pentafluorobenzene. It is suggested that the elimination of CF 2 involves rearrangement through the intermediacy of a bridged fluoronium ion. For the protonated chlorobenzenes, elimination of HCl is the dominant fragmentation reaction for lower members of the series but elimination of Cl increases in importance with increasing collision energy and increasing chlorine content.