Ethylene bromonium and 1-bromoethyl cations and their neutral and anionic counterparts: a tandem mass spectrometry study of dissociations and gas phase redox reactions

The unimolecular chemistry of ethylene bromonium cation (cyclo-CH2CH2Br+, 1+) and 1-bromoethyl cation (CH3CH+Br, 2+) has been probed by metastable ion (MI) characteristics, collisionally activated dissociation (CAD) and neutral fragment reionization (NfR). These isomers undergo many common decompositions but can, nevertheless, be distinguished based on the structurally indicative >˙>CH3vs. CH2 losses. Neutralization–reionization (NR) experiments have further shown that the gas phase reduction of 1+ and 2+ leads to 2-bromoethyl (>˙>CH2CH2Br, 3) and 1-bromoethyl (CH3ĊHBr, 2) radicals, respectively, both of which are stable species. However, from the incipient C2H4Br– anions emerging upon charge reversal of 1+ and 2+, only CH3CH–Br (2–) is found to be a bound anion.

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