Mass spectral fragmentation pathways in aminonitrobenzenes. A mass spectrometry/mass spectrometry collision‐induced dissociation study

A collision‐induced dissociation (CID) study of a series of aminonitrobenzenes was carried out using a tandem BB mass spectrometer. Fragmentation pathways were determined in the electron impact mode. Loss of NO · was found to be a major decomposition process. Peaks formed by this process were ‘dished’ in compounds having a nitro group para or ortho to an amino group and Gaussian peaks for compounds having a nitro group meta to an amino group. This loss of NO · with formation of dished peaks occurred for both unimolecular and collision‐induced dissociation pointing to a similar process for both modes of dissociation involving large kinetic energy release. Loss of OH · , due to an ortho effect, was a major decomposition route only in a compound having two nitro groups ortho to the amino group, whilst in other compounds where a nitro group was ortho to an amine this process was smaller because of competitive decomposition processes. Loss of NO 2 · was a major decomposition route in most compounds and it preceded the cleavage of the aromatic ring.