Mass spectrometry of heterocyclic compounds—II: Electron‐impact induced fragmentation of 3,5‐diphenyl‐1,2,4‐oxadiazole

Abstract

Abstract The electron‐impact induced fragmentation of 3,5‐diphenyl‐1,2,4‐oxadiazole has been investigated by labelling experiments, defocused metastable ion detections and high resolution mass measurements. The main fragmentation process suggests heterocyclic cleavage at the 1 to 5 and 3 to 4 bonds confirming our previous interpretation. The structure of the major fragment ion [C 7 H 5 NO] + · has been interpreted as being represented by the isomeric benzonitrile oxide and phenylisocyanate structures, the latter isomerising irreversibly from the former. The benzonitrile oxide structure is consistent with [C 7 H 5 NO] + · formation by cleavage of the 1 to 5 and 3 to 4 bonds.