Electron‐impact studies—L: Skeletal‐rearrangement fragments in the mass spectra of diphenylpyrazoles and ‐isoxazoles

The mass spectra of all diphenylpyrazoles and ‐isoxazoles contain rearrangement peaks at m / e 165 [C 13 H 9 ] + . In addition, the spectra of 3,5‐diphenylisoxazoles contain peaks at m / e 180 [C 13 H 10 N] + , which are produced by specific phenyl migrations. The mechanisms of both rearrangement processes have been studied by deuterium labelling.