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Electron ionization mass spectra of 8‐aryl‐3,4‐dioxo‐2 H ,8 H ‐6,7‐dihydroimidazo[2,1‐ c ][1,2,4]triazines. Do they exhibit tautomerism in the gas phase?
Author(s) -
Martiskainen Olli,
Sztanke Krzysztof,
Matosiuk Dariusz,
Pihlaja Kalevi
Publication year - 2006
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.2628
Subject(s) - chemistry , tautomer , enol , electron ionization , ion , mass spectrum , aryl , ionization , medicinal chemistry , stereochemistry , organic chemistry , catalysis , alkyl
The electron ionization mass spectra of the title compounds (1: a R = H, b 2‐CH 3 , c 4‐CH 3 , d 2,3‐diMe, e 2‐OCH 3 , f 4‐OCH 3 , g 2‐Cl, h 3‐Cl, i 4‐Cl, j 3,4‐diCl) were recorded at 70 eV to determine the effects of substituents and the possible keto‐enol tautomerism. The compounds showed several common fragment ions but also fragment ions which divided them into three classes, namely 1a–1d (parent compound and Me‐substituted derivatives), 1e and 1f (MeO‐substituted derivatives), and 1g–1j (Cl‐substituted derivatives). The presence of the HOCN + . ion as well as the exponential dependence of its total ion current in the case of p ‐ and also 3‐Cl‐substituted compounds (1a, c, f, h–j) on the Hammett σ constants and the loss of CHO or one or two HOCN moieties can be somewhat easier explained by the presence of the enol form but as a whole the results support the predominance of the keto form, in parallel to the situation in solution. Copyright © 2006 John Wiley & Sons, Ltd.