Mass spectrometric investigation of isomeric 1,2,3,4-tetrahydro-4-oxoquinazolines

Six isomeric methylphenyl-1,2,3,4-tetrahydro-4-oxoquinazolines have been prepared and their fragmentation patterns upon electron impact studied. Deuterium labelling and high-resolution measurements were performed in order to facilitate the interpretation of the spectra. The dissociation of the molecular ion follows two main routes, the fragmentation being governed by the position of the phenyl group.