Electron-impact studies—LX Negative-ion mass spectrometry of functional groups skeletal-rearrangements in aryl nitro compounds

The molecular anions of nitrobenzenes containing an electron-withdrawing substituent eliminate NO· via a skeletal rearrangement process in the order ortho > para > meta. An ortho substituted nitrobenzene may eliminate a neutral molecule after the loss of NO· Hydrogen-rearrange-ment processes, hydrogen-scrambling processes, and unusual concerted eliminations are noted in certain spectra. Isomeric nitrobenzenes are generally more readily differentiated by negative-ion than positive-ion mass spectrometry.