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Reactions within and between adjacent dimethylamino groups: Collision‐induced dissociation tandem mass spectrometric study of the 1,9‐bis(dimethylamino)phenalenium cation
Author(s) -
Rentzea Marina,
Hofmeister Jörg,
Staab Heinz A.
Publication year - 1993
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.1210280524
Subject(s) - chemistry , fragmentation (computing) , dissociation (chemistry) , mass spectrum , collision induced dissociation , ion , tandem mass spectrometry , steric effects , electron ionization , mass spectrometry , substructure , ionization , computational chemistry , photochemistry , medicinal chemistry , stereochemistry , organic chemistry , chromatography , structural engineering , computer science , engineering , operating system
The electron impact (EI) ionization‐induced fragmentation pathways of the new 1,9‐bis(dimethylamino) phenalenium cation [1] + were investigated. The peri ‐dimethylamino substituents of [1] + are incorporated in a trimethine cyanine substructure and show strong steric interactions. A mechanism is proposed for the unusual elimination of CH 3 NCH 2 , HN(CH 3 ) 2 and (CH 3 ) 3 N from [1] + and for the accompanying cyclizations to heterocyclic ions: prior to fragmentation, the intact cation [1] + rearranges, by reciprocal CH 3 and H transfers, to new isomeric cations which decompose subsequently in a characteristic way. A wealth of consistent information on dissociation pathways and fragment structures is provided by collision‐induced dissociation tandem mass spectra, collision‐induced dissociation mass‐analysed ion kinetic energy spectra and exact mass measurements of the salt cation and of its primary fragment ions. The liquid secondary ion mass spectrum of [1] + is very similar to its EI mass spectrum.