Mass spectral fragmentations of alkylpyridine N ‐oxides

The behavior of a series of (2‐, 3‐ and 4‐) methyl‐, ethyl‐ and n‐butylpyridine N‐oxides has been investigated at 70 and 14 eV. A loss‐of‐OH fragmentation occurs in all the N‐oxides studied but is most important for 2‐methyl‐ and 2‐ethylpyridine N‐oxides. All isomeric n ‐butylpyridine N ‐oxides show only a very weak loss‐of‐OH fragmentation from the molecular ion and a much stronger loss‐of‐OH fragment ion from the [M – 42] fragment. The loss‐of‐oxygen fragmentation is relatively intense in all cases studied, however. The loss‐of‐alkyl and McLafferty rearrangement fragmentations characteristic of the ethyl‐ and butylpyridines appear in the N ‐oxide mass spectra and are manifest from the molecular [M] and [M – 16] ions.