Isotopic labeling and energy-resolved collision-induced dissociation (CID) experiments show that methyl cation loss from protonated acetaldehyde occurs by at least two different mechanisms, one involving direct cleavage and the second involving rearrangement. A statistical scrambling mechanism is ruled out from the CID appearance curves for the CH3+ and CH2D+ products from CH3C(OD)H+, whereas a possible kinetic isotope effect is ruled out by using the alternately labeled CD3C(OH)H+ acetaldehyde ion. The results show that dissociation of protonated aldehydes is even more complex than is suggested by standard CID spectra.
- Dissociation mechanisms
- Energy-resolved mass spectrometry
- Kinetic isotope effects
- Protonated aldehydes