Mass spectrometry of 8-hydroxyquinoline derivatives

In contrast to the fragmentation of the corresponding alkyl aryl ethers, characteristic M-H]⁺ and M-H, -CO]⁺ fragments were observed in the fragmentation of 5-nitro(halo)-substituted 8-alkoxyquinolines. It was found by means of deuterium labeling that a hydrogen atom is split out primarily from the alkoxy group. It was demonstrated that an M-H, -CO]⁺ fragment was formed from the M-H]⁺ ion, which has a three-ring structure and a quaternary nitrogen atom. The formation of an M-CO]⁺ fragment is characteristic for the fragmentation of 5(7)-nitro(halo)-substituted 8-hydroxyquinolines. The interrelationship between the intensities of the M-H]⁺, M-H, -CO]⁺, and M-CO]⁺ ion peaks and the protonation constants (pK_a) of the investigated compounds is discussed.Communication 4 from the series Mass spectrometry of biologically active substances, See 1] for communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 786–791, June, 1984.