Mass spectra of 2,4-dinitroimidazole and its isotopomers using simultaneous thermogravimetric modulated beam mass spectrometry

Abstract

The EI mass spectrum of 2,4-dinitroimidazole (2,4-DNI) was studied at 20 and 70 eV ionizing energy using simultaneous thermogravimetric modulated beam mass spectrometry. Product ion formulas and their origin from within the 2,4-DNI molecule were identified from the evaluation of perdeuterated and various 15 N-labeled 2,4-DNI mass spectra. The molecular ion (M +. ; m/z 158) is present in all the spectra and the NO + ion (m/z 30) is the major primary product ion. The base peak is formed by the M .+ ion at 20 eV and by the NO + ion at 70 eV. Other primary product ions are NO 2 + (m/z 46), CH 2 N + (m/z 28) and CHN 2 O 2 + (m/z 73). Fragmentation pathways are postulated based on the identity and relative abundance of the product ions, and on the change in relative abundance of the ions as a function of ionizing energy. Comparisons of the 70 eV mass spectra of 2,4-DNI, 4,5-dinitroimidazole (4,5-DNI) and 1,4-dinitroimidazole (1,4-DNI) show that the fragment product ions have the same m/z values in the three spectra but differ in their relative abundance and in the ion that forms the base peak. The base peak for 2,4-DNI and 4,5-DNI is formed by the ion at m/z 30 (NO + ) and for 1,4-DNI, the ion at m/z 46 (NO 2 + ). This difference is probably due to the nitramine functionality of 1,4-DNI