The fragmentation of ortho‐methoxyphenyl‐2‐propanone oximes and related compounds–further examples of an ortho‐effect

An [M  31] + ion was a prominent fragment in the mass spectra of three ortho ‐methoxy‐phenyl‐2‐propanone oximes and is shown to be due to the expulsion of a methoxyl radical from the molecular ion as a result of an ortho ‐effect. In contrast, an [M  31] + ion was absent from the spectra of a structurally related ketone and a hydroxylamine, and was not observed in the spectra of meta ‐ and para ‐methoxyphenyl‐2‐propanone oximes.