Electron ionization mass spectrometry as a tool for the investigation of the ortho effect in fragmentation of some Schiff bases derived from amphetamine analogs

The electron ionization‐induced fragmentation patterns of three forensically relevant Schiff bases, originating from the condensation between 2‐, 3‐ and 4‐methoxyamphetamine and the corresponding ketones, were studied. The proposed fragmentation routes and ion structures are supported by high‐resolution data and B/E linked‐scan and mass‐analyzed ion kinetic energy spectra. The rationalization of the ortho effect, which is responsible for the formation of the [M − OCH3] fragment in the case of the imine bearing ortho‐substituted methoxy group, is given. Copyright © 2004 John Wiley & Sons, Ltd.