The elimination of small neutral molecules and fragments in mass spectra—II: 2-substituted 8-hydroxyquinolines

The mass spectra of a series of 2-substituted 8-hydroxyquinolines and related compounds are reported. Fragmentation pathways based upon interpretation of spectra and metastable transitions for 8-quinolinol; 2-methyl-8-quinolinol; 4-methyl-8quinolinol; 2-hydroxymethyl-8-quinolinol; 2-aminomethyl-8-quinolinol; 8-quinolinol-2-carboxaldehyde; 8-quinolinol-2-carb-oxaldehyde oxime; and 8-quinolinol-2-carboxaldehyde tert-butylimine are discussed, as are dissociations in the related compounds 2-hydroxymethyl quinoline and quinoline-2-carboxaldehyde oxime. It is suggested that the molecular ions of 2-substituted-8-quinolinols undergo rearrangement to a substituted azatropylium ion prior to dissociation. An ion of m/e 89 has been observed in these spectra and is considered to be characteristic of the quinoline nucleus bearing an X-substituent in any position, where X ? OR, SR, NH₂ etc. (R ? H, CH₃, etc).