6.11 Fragmentation of Ketones and Aldehydes
Both ketones and aldehydes give prominent molecular ion peaks though the [M+] peak is more prominent in ketones. The majority of compounds in these categories undergo an important rearrangement, the McLafferty rearrangement.
This rearrangement is mediated by the p systems of the carbonyl group but can occur in other p systems such as in nitriles (Section 6.17). The only ketones and aldehydes that do not undergo this rearrangement are those which lack a side chain that can donate a hydrogen atom to the p system.
©Dunnivant & Ginsbach, 2008