Ortho effect of the nitro group in the fragmentation of 1-phenyl-3-nitrophenyl-2-pyrazolines

Electron impact mass spectra and mass-analysed ion kinatic energy spectra of the title compounds are discussed. The characteristic fragment ions of the ortho isomer are shown by high resolution and kinetic energy release measurements to involve the transfer of hydrogen to the nitro group and oxygen from the nitro group to the pyrazoline carbon.