Gas‐phase fragmentations of <i>N</i>‐methylimidazolidin‐4‐one organocatalysts

N ‐methylimidazolidin‐4‐one organocatalysts were studied in the gas phase. Protonated and sodium‐cationized (sodiated) molecules are conveniently accessible by electrospray mass spectrometry. Protonation enables three different closed‐shell paths of ring cleavage leading to iminium ions. The fragmentation pattern is largely unaffected by exocyclic substituents and thus is valuable to characterize the substance type as N ‐methylimidazolidin‐4‐ones. Sodiated species show a distinctly different fragmentation that is less useful for characterization purposes: apart from signal loss due to dissociation of Na + , the observation of benzyl radical loss is by far predominant. Only in absence of a benzyl substituent, an analogue of the third ring cleavage (loss of [C 2 H 5 NO]) is observed. Copyright © 2017 John Wiley &amp; Sons, Ltd.