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Electron impact and chemical ionization mass spectra of bis(methoxycarbonyl) [2.2](2,5)pyridinophanes. Formation of quinolizinium ions under electron impact
Author(s) -
Rentzea Marina,
Hasselbach HansJoachim,
Staab Heinz A.
Publication year - 1986
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.1210210612
Subject(s) - electron ionization , chemistry , fragmentation (computing) , ion , mass spectrum , ionization , chemical ionization , mass spectrometry , spectral line , polyatomic ion , analytical chemistry (journal) , computational chemistry , organic chemistry , physics , chromatography , astronomy , computer science , operating system
For four isomeric bis(methoxycarbonyl)[2.2](2,5)pyridinophanes differing only in the mutual orientation of the two nicotinic ester units, electron impact mass spectra were measured. The fragmentations observed distinguish surprisingly well between the isomers, depending on the transannular substitution pattern. Of special interest is that for one isomer the otherwise unimportant ion at m / z 298 is found as base peak. This ion is formed by expulsion of HCN from the molecular ion, transannular cycloaddition and aromatization to a stable quinolizinium ion. Fragmentation pathways of the isomers are compared, and chemical ionization and negative ion chemical ionization mass spectra are discussed.