Electron ionization mass spectra of 8-aryl-3,4-dioxo-2H,8H-6,7-dihydroimidazo[2,1-c][1,2,4]triazines. Do they exhibit tautomerism in the gas phase?
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 sigma 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.
Martiskainen
Olli
O
Department of Chemistry, University of Turku, FI-20014 Turku, Finland.
Sztanke
Krzysztof
K
Matosiuk
Dariusz
D
Pihlaja
Kalevi
K
D005740:Gases / Q000032:analysis / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D007536:Isomerism; D015394:Molecular Structure; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D014227:Triazines / Q000737:chemistry*
D005740:Gases; D007093:Imidazoles; D014227:Triazines