The molecular ion peak for aliphatic nitro compounds is seldom observed.
The mass spectrum observed for aliphatic nitro compounds is usually due to the fragmentation of the alkyl portion of the molecule.
However, there are two peaks quite indicative of the nitro group: one peak corresponding to the NO+ ion (m/e = 30), and another corresponding to the NO2+ ion (m/e = 46).
The complete mass spectrum for 1-nitropropane is given in figure 56, which illustrates these points.
Figure 56. Mass spectrum for 1-nitropropane.
The molecular ion peak for aromatic nitro compounds is very intense. The same characteristic peaks (m/e = 30 and 60) are again observed.
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