Competing oxygen migrations inortho nitro aromatic thioamides on electron impact

Mass spectral fragmentation patterns of some 2-methyl-3-furancarboxanilides and 2-methyl-3-furancarbothioanilides. II

The electron impact mass spectra of some 2-methyl-3-furancarboxanilides and 2-methyl-3-furancarbothioanilides are discussed. Dominant peaks are formed by simple cleavage of a C-N bond in the anilides as well as in the thioanilides. Thioanilides show some additional fragmentation pathways recently reported which are not seen in the anilides. (T. Jagodzinski and M. Stobiecki, Org. Mass Spectrom., Vol. 25, p. 333 (1990)).

Sequential ortho effects: characterization of novel [M - 35](+) fragment ions in the mass spectra of 2-alkyl-4, 6-dinitrophenols

High-resolution mass spectrometry (HRMS), hybrid tandem mass spectrometry (MS/MS) (EBqQ), and photoelectron-photoion coincidence (PEPICO) experiments were conducted to examine a possible ortho-ortho effect resulting in a novel [M - 35](+) fragment ion in 2-alkyl-4, 6-dinitrophenols. For compounds having ethyl or larger alkyl substituents, [M35](+) was observed only when [M - 18](+) ions were present, with the ortho nitro group being involved in the reaction to [M- 35](+). For [M - 18](+) and [M - 35](+), HRMS results were consistent with losses of H2O and H2O + OH, respectively, whereas MS/MS results indicated a sequential reaction due to metastable dissociations. The appearance energy determined by PEPICO for [M - 35](+) was found to be greater than the appearance energy for [M - 18](+), thus supporting a sequential reaction. 69-75).