Electron impact induced formation of ions by skeletal rearrangement of some phenyl substituted cyclic ketones

The base peak at 70 eV for 7-phenylbicyclo 3.1.1] heptan-6-one is due to the ion only. The direct formation of this ion from the molecular ion, as deduced from metastable ion decompositions in the field free regions, involves a rearrangement of 7-phenylbicyclo 3.1.1] heptan-6-one to its 7-phenylbicyclo 3.2.0]-heptan-6-one isomer. Evidence for this rearrangement has been obtained from ¹³C labelling of 7-phenyl-bicyclo 3.1.1] heptan-6-one, from investigation of its independently synthesized bicyclic 3.2.0] isomer and of related compounds, and from measurements of kinetic energy release in fragmentations generating the various ions.