Fragmentation Pattern
The characteristic set of smaller ions produced when a molecular ion breaks apart in a mass spectrometer.
Unit
Da
In depth
Bonds break preferentially where the resulting cation is most stable, so the pattern is reproducible and diagnostic. Characteristic mass losses — 15 for a methyl group, 18 for water, 29 for an ethyl or formyl group — identify structural features directly.
Examples in the real world
A McLafferty rearrangement in ketones giving a distinctive even-mass fragment.