Gas-Phase Reactivity of Copper Cations with Ketones

Abstract

Gas-phase ion–molecule reactions between copper ions and ketones were investigated. Organometallic adducts were prepared using a chemical ionisation/fast-atom bombardment source. Abundant pseudo-molecular ion adducts were observed in the Cu+-chemical ionisation mass spectra and their unimolecular decompositions were studied by tandem mass spectrometry. Mass-analysed ion kinetic energy spectroscopy revealed diagnostic fragmentation patterns. Losses of alkenes, losses of alkanes and dehydrogenation and dehydration reactions were observed, as well as eliminations of CuR (R = C nH2 n + 1). The rich reaction chemistry of the cationised ketones enabled differentiation of the majority of the linear and branched ketone isomers studied. Isotope-labelled derivatives were employed to elucidate fragmentation mechanisms.