Position-dependent fragmentation mechanism for radical anions of fluorinated benzoates

Abstract

Abstract DFT calculations were used to study the potential energy surfaces (PESes) of a full series of fluorinated benzoate radical anions (RAs). The sections of PESes along the C–F bond cleavage coordinates in polar media were built, and the transition states for RA fragmentation with fluoride anion elimination were located. The estimated reaction barrier heights let us interpret the experimental regularities of the RA decay including the process regioselectivity. The fragmentation mechanism was shown to depend on the position of the leaving fluorine atom. When defluorination occurs at an ortho - or meta - position to the CO 2 − group, the reaction coordinate involves pseudorotation as a way for odd electron density transfer to the breaking C–F bond. Additional gas phase calculations were performed to confirm the pseudorotational architecture of the PESes of polyfluorinated benzoate RAs. The results obtained clearly demonstrated that the multihole PES structure gives rise to the multichannel mechanism of RA cleavage.