Mass spectra of tetrahydroquinolines

Abstract

The mass spectra of 1,2,3,4-tetrahydroquinoline and 5,6,7,8-tetrahydroquinoline have been recorded. The spectra of the 1-d1, 2,2-d2, 3,3-d2, and 4,4-d2 analogues of 1,2,3,4-tetrahydroquinoline, and the spectra of the 5-d1, 6,6-d2, and 8,8-d2 analogues of 5,6,7,8-tetrahydroquinoline have aided in the interpretation of the fragmentation mechanisms. The spectra of both isomers are characterized by fragment ions at M–1, M–15, and M–16 while the 5,6,7,8-isomer has an additional peak at M–28. The spectra of 2-, 3-, 4-, and 6-methyl-1,2,3,4-tetrahydroquinolines have also been examined. Substitution of a hydrogen by a methyl group in the 2- and 4-positions results in an intense M–15 peak, and substitution in the 3-position results in a peak at M–29. The main features of these spectra can be predicted from the proposed fragmentation pathways of the parent tetrahydroquinoline.