Electron‐ionization‐Induced fragmentation of N‐monosubstituted 2‐phenylacetamides

Abstract

Electron‐ionization‐induced mass spectra of N‐monosubstituted 2‐phenylacetamides were recorded and their fragmentation patterns were studied by metastable‐ion analyses. Representative deuterated analogues of these compounds have also been synthesized and their mass spectra compared with those of the unlabelled parent compounds. The most typical fragmentation for N‐alkyl‐, N‐isoalkyl‐ and N‐cycloalkyl‐2‐phenylacetamides is cleavage of the bond β to the carbonyl function, resulting in an ion fragment of m/z 92, following the transfer of hydrogen and elimination of a corresponding ketene. The primary fragmentation process for N‐aryl substituted 2‐phenylacetamides is the loss of an aromatic hydrogen atom from the molecular ion. The other principal fragmentation processes observed with these compounds are discussed.