N,N‐Coupled heterobicycles from cyclic hydrazine derivatives. Part 6. Electron ionization mass spectrometry of some substituted 1‐thiocarbamoyl and 1‐carbamoylpyrazolidines

Abstract

AbstractThe electron ionization mass spectra of six substituted 1‐thiocarbamoyl and four substituted 1‐carbamoyl‐pyrazolidines were measured and carefully analyzed. The fragmentation pathways were elucidated by metastable ion analysis and exact mass measurement. The principal fragmentations were the same for all the compounds studied. The related importance of different decomposition channels, however, varied according to the structure of the compounds. Some substituents also prompted fragmentations unique to them. The most important reaction was the loss of the thiocarbamoyl or carbamoyl substituent with simultaneous hydrogen atom migration from the (thio)carbamoyl nitrogen to the ring nitrogen giving rise to ionized pyrazolidine at m/z 72. In this process for 1‐(N‐arylthiocarbamoyl)pyrazolidines the charge tended to remain with the substituent part of the molecule. Moreover for all the compounds studied [M‐2H]+. ion peaks formed by dehydrogenization of the original compounds were observed.