Mass spectrometric analysis of N‐substituted cyclohexene‐1,2‐dicarboximides

Both low and high resolution mass spectra of cis ‐4‐cyclohexene‐1,2‐dicarboximide, its N‐methyl, N‐ethyl, N‐ n ‐propyl and N‐ n ‐butyl derivatives, and cyclohexane‐1,2‐dicarboximide were obtained at 70 eV. Each of the spectra exhibited characteristic nominal ions at masses 151, 136, 123 and a group of ions at masses 77, 78, 79, 80 and 81 of which m / e 80 was always the base peak except for the unsubstituted cyclohexane compound. The m / e 77 to 81 fragments are composed of carbon and hydrogen and derived from the cyclohexene ring. The ions possessing higher masses are heterocyclic and certain of them show doublets and triplets. Evidence for a 1,3 hydrogen migration was supplied by studies with the N‐(ethyl‐2‐d 3 ) derivative and evidence for a 1,4 migration by the N‐( n ‐propyl‐3‐d 3 ) derivative.