Dissociation and Ion-Molecule Reactions of Alkane Radical Cations. Time-Resolved FDMR
Alkane and olefin radical cations, fundamental reaction intermediates in organic chemistry and in the radiation chemistry of hydrocarbons, have been characterized by time-resolved Fluorescence Detected Magnetic Resonance (FDMR) in pulse radiolysis of alkane liquids and solids from 30K to room temperature. Studies of olefin cations in neat and mixed alkane liquids have elucidated the mechanism for conversion of alkane cations into olefin cations by loss of H2. Alkane cations are extremely short-lived in neat alkane liquids, and their detection and characterization in pure hydrocarbon systems by magnetic resonance techniques have been elusive. Stabilization of alkane cations can result from (1) lowered temperature and/or (2) isolation of the cation from neutral parent molecules (as in alkane mixtures). Our observations suggest that alkane cations rapidly undergo proton transfer to neutral alkane molecules, in competition with geminate recombination.