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Destabilized carbenium ions: α‐imidoyl carbenium ions and the electron impact mass spectra of α‐haloaldimines and α‐haloketimines
Author(s) -
Sürig Thomas,
Grützmacher HansFriedrich,
de Kimpe Norbert
Publication year - 1991
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210261014
Subject(s) - chemistry , ion , carbenium ion , fragmentation (computing) , mass spectrum , substituent , mass spectrometry , electron ionization , polyatomic ion , kinetic energy , medicinal chemistry , organic chemistry , physics , chromatography , quantum mechanics , computer science , ionization , operating system
A series of α‐chloro‐ and α‐bromoketimines compounds (1‐9) with different substituents at the α‐position and at the imino group has been investigated by electron impact mass spectrometry as possible precursors of the correspondingly substituted α‐imidoyl carbenium ion, an important class of destabilized carbenium ions. The main fragmentation of the molecular ions of compounds, 1‐9 in the ion source corresponds to an α‐cleavage at the imino group; however, fragment ions are also formed by loss of the α‐halo substituent. These fragment ions correspond at least formally to α‐imidoyl carbenium ions. Their further reactions in dependence on the type of substituents at the imino group and at the α‐C atom, were studied by mass‐analysed ion kinetic energy and collisional activation mass spectrometry. The results agree with the initial formation of destabilized α‐imidoyl carbenium ions but indicate an easy rearrangement of these ions in the presence of suitable alkyl substituents by 1,2‐ and 1,4‐hydrogen shifts to more stable isomers.