The isomeric .+ Hydrogen-Bridged Radical Cations .+, .+, and .+: Theory and Experiment

Article abstract of DOI:10.1021/ja00258a012

From combination of mass spectrometry based experiments and high-level molecular orbital theory calculations, three new, thermodinamically stable isomers of ionized ethylene glycol, ^.+ (1), have been identified.These are the hydrogen-bridged radical cations ^.+ (2), ^.+ (3), and ^.+ (4); a fifth isomer, also H-bridged, ^.+, has been previously reported.The ion ^.+ (3) was experimentally identified (via a double collision experiment) as the stable ion formed by loss of CO from ionized methyl glycolate, whereas 2 was proposed to be a long-lived, rearranged form of ionized glycol, 1.The common unimolecular dissociations of 2 and 3 into CH3OH2⁺ and HCO⁰ were associated with energy barriers attributed to their rearrangement into (energy-rich) ions of structure 4, from which the dissociation proceeds by direct bond cleavage.This study underlines the important role that -H-O- hydrogen-bridged radical cations can play in the gas-phase ion chemistry of oxigencontaining compounds and is another example of the succesful combination of theory and experiment in gas-phase ion chemistry.