Identification of derivatives of 2H-chromenes and their acyclic tautomeric forms in the gas phase by mass spectrometry

It was established that mass spectrometry makes it possible to identify in the gas phase molecular ions with both the 2H-chromene structure and their acyclic tautomers from the characteristic (M-OH)⁺ and (M-ArNH)⁺ fragment ions, respectively. The fragmentation scheme was confirmed by methods involving dissociation of ions activated by collision and deuterium labeling. Measurement of the ionization energies of the investigated compounds makes it possible to exclude the possibility of the existence in the gas phase of a tautomeric form with an o-quinoid structure.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 746–750, June, 1988.