Mass spectra of some deuterium labelled dimethylquinolines

Abstract

The mass spectra of several dimethylquinolines, labelled in the methyl group with deuterium, have been examined. The results are in agreement with the formation of ring-expanded molecular ions prior to fragmentation to the M—H and M—CH3 ions. Two ring-expanded ions may form since there are two methyl groups which can participate in the ring expansion process. Ring expansion through a methyl group located on the benzenoid ring is favored over ring expansion through a methyl group on the pyridine ring.