STERIC EFFECT AS A MECHANISTIC TOOL IN MASS SPECTRAL DECOMPOSITIONS . COMMENTS ON ACTIVATED COMPLEX FOR LOSS OF NO FROM SUBSTITUTED NITROBENZENES

The effect of ortho substituents in nitrobenzence radical cation decompositions are discussed for non‐interacting halogen substituents. These effects are distinct from those of the same substituents in the meta and para positions, and support previous indications that ring position identity is retained in nitrobenzene molecular ions. More importantly, the steric effect of the halo substituents may be gauged from these data; it indicates that several previously suggested mechanisms for the loss of NO must be reconsidered. The existence of steric effect in very well defined systems may be used as a structural tool in organic mass spectrometry. Copyright © 1969 John Wiley & Sons, Ltd.