Comparison of low-energy CAD spectra of sulphonium,ammonium and phosphonium cations,propene elimination from allyl-substituted oniums |
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Authors: | Hlne Mestdagh Nicole Morin Christian Rolando |
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Institution: | Hélène Mestdagh,Nicole Morin,Christian Rolando |
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Abstract: | The low-energy collision-activated dissociation of symmetrical n-butyl-substituted and of allyl-substituted onium cations has been recorded using fast atom bombardment ionization and a tandem mass spectrometry quadrupole mass spectrometer. Structure of the fragments and decomposition pathways have been ascertained using a multi-quadrupole MS/MS/MS triple analyser instrument. Whereas most sulphonium cations exhibit only heterolytic cleavages, fragmentation of ammonium and phosphonium is mainly homolytic. Allylic sulphonium, and to a lesser extent allylic ammonium, easily undergo propene elimination. This reaction, which does not occur in 1-propenyl oniums, might involve a McLafferty type rearrangement. |
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