The molecular ion peak is usually observable, and will be a good indication of the presence of an amide (nitrogen rule).
An important fragmentation pattern involves a-cleavage (breaking either bond to the carbonyl carbon) as shown in figure 50.
Figure 50. a-cleavage.
McLafferty rearrangement can take place for amides in the alkyl portion (see figure 51).
Figure 51. McLafferty rearrangement of an amide.
The complete mass spectrum for propanamide is given in figure 52, which illustrates most of these points.
Figure 52. Mass spectrum for propanamide.
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