Mass spectrometry of nitroazoles: 2—the mass spectra of methyl substituted nitroimidazoles

Abstract

The mass spectra of six isomers of methylnitrobidazoles are reported and discussed. AM compounds exhiiit strong molecular ions, along with the characteristic fragmentations of aromatic nitro compounds. In some cases ortho effects-losses of OH', HzO, CHO', CHzO-are observed, due to interactions of adjacent substituents.

Decomposition of nitroimidazole ions: experiment and theory

“…The successive loss of NO and CO has been proposed by Luijten et al in the study of the methylated nitroimidazoles. 32 The decay peak of C 2 H 3 N 2 + has a Gaussian peak shape indicating a rather small KER. Indeed, the calculation of the KER using eqn (1) leads to a value of about 200 meV.…”

“…6 shows the MIKE spectrum of metastable M + of 4(5)nitroimidazole (Fig. 6a) and high-energy CID spectra of M + and 32 The decay peak of C 2 H 3 N 2 + has a Gaussian peak shape indicating a rather small KER. Indeed, the calculation of the KER using eqn (1) leads to a value of about 200 meV.…”

Synthesis and mass spectra of labelled 4(5)‐nitro‐1H‐imidazole‐5(4)‐carbonitriles

“…In standard mass spectra, recorded at 70 eV for compounds 13 C-and 15 N-labelled in the cyano group, molecular peaks and almost all fragmentation peaks of m=z higher than 37 corresponded to similar, but 1 unit smaller, peaks in the mass spectra recorded for non-labelled compounds. The only exceptions were peaks of m=z ¼ 69 present in the spectra of all 4(5)-nitro-5(4)-imidazolecarbonitriles and peaks of m=z ¼ 83 or 42 (CH 3 CNH + ) present in the spectra of all 2-methyl-4(5)-nitro-5(4)-imidazolecarbonitriles (Tables 1 and 2 The appearance of peaks of m=z=M-114 and M-87 in the spectra of 2-methyl-4(5)-nitro-5(4)-imidazolecarbonitriles corresponding to peaks of m=z=M-100 and M-73 in the spectra of 4(5)-nitro-5(4)-imidazolecarbonitriles can be easily explained considering other data concerning behaviour of nitroimidazoles in mass spectrometer [3][4][5] and a reasonable assumption (confirmed by us by semi-empirical AM1 and PM3 calculations) that in the gas phase a fast equilibrium exists between 4-nitroimidazole-5-carbonitriles and 5-nitroimidazole-4-carbonitriles.…”

Mass spectrometry of nitroazoles: 4—ortho effects: The loss of CHO˙ and CH2O from methyl substituted nitrodiazoles

“…Samples were introduced through an all-glass heated inlet system at temperatures of 160-200 "C; compound 1 was introduced at a temperature of 90 "C, to avoid thermal rearrangement. 7 Elemental compositions of all ions were determined at resolving powers above 15 000; high resolution measurements of deuterium labelled compounds were performed at a resolving power of 25 000. Fragmentation schemes were derived from accelerating voltage scans at a trap current of 500pA, using an energy resolving variable monitor slit, set at 80% transmission to obtain symmetrical peak shapes and consequently improved mass determinations.…”