Mass-spectral Fragmentation of 3-(5-Nitro-2-furyl)-1,2,4-triazoles

Abstract

Abstract The mass spectra of 3-(5-nitro-2-furyl)- (I), 5-methyl-3-(5-nitro-2-furyl)- (II), 5-ethyl-3-(5-nitro-2-furyl)-(III), and 5-trideuteriomethyl-3-(5-nitro-2-furyl)-l,2,4-triazole (IV) and their 1-acetyl, 1-trideuterioacetyl, and 1-propionyl derivatives were examined. The mother compounds, I-IV, gave the most prominent molecular ions and showed the same fragmentation pattern. The molecular ions undergo two modes of cleavages; one is the elimination of NO (1) and CO (2), followed by the loss of C2H2 (3), thus giving the M−84 ions which include the 5-substituents of the triazole ring, while the other is the loss of NO2–CO, which directly gives rise to the fragment M−74 ions. The 1-acyl derivatives gave extremely weak molecular ion peaks. In the first step of the fission of the molecular ions, the elimination of an acyl group occurred, with the rearrangement of a hydrogen atom, thus giving rise to prominent ions. These ions correspond to the molecular ions of the mother compounds, I–IV, and are expected to show a similar fragmentation pathway. The fragmentation of these compounds was also considered to occur in view of the existence of meta-stable ion peaks. The meta-stable peaks appearing at the transition of the loss of NO are flat-topped, releasing kinetic energy of 0.78±0.04 eV.