On the mechanisms of electron‐impact‐induced sulfur dioxide elimination from the molecular ions of 4‐nitro‐ and 6‐nitro‐2,1‐benzisothiazoline 2,2‐dioxide derivatives

Abstract

AbstractIt is shown that metastably decomposing molecular ions of the title compounds eliminate sulfur dioxide via two reaction pathways provided that an α‐hydrogen atom adjacent to the heterocyclic ring nitrogen atom is present. One of the channels leads to the initial formation of an o‐azaxylylene ionic species and is associated with the narrow component of the accompanying composite metastable peak. The other channel involvel a multistep pathway which eventually leads to the formation of an aldimine ionic species and which is associated with the broad component of the accompanying composite metastable peak. Collision‐induced dissociation and deuterium‐labelling experiments have provided evidence that the initially generated o‐azaxylylene ionic species, both as long‐lived and as decomposing ions, have rearranged to the aldimine ionic species via a 1,5‐shift of the α‐hydrogen atom adjacent to the heterocyclic ring nitrogen atom.