Energy-Resolved Electrospray Mass Spectrometry of Diexo -Norbornane and Norbornene Derivatives Containing a Fused,Phenyl-Substituted,1,3-oxazinE Ring: Competitive Retro-Diels—Alder Fragmentation Processes

The fragmentation behaviour of an organic ion depends on both the amount and the distribution of internal energy resulting from the ionisation process. Thus, investigations of the fragmentation pathways of complex ions can gain some advantage from energy-resolved mass spectrometry (ERMS) techniques. These methods are able to establish a relationship between the internal energy level of a precursor ion of interest and the nature and extent of the generated fragment ions. In the present study, the competitive retro-Diels–Alder fragmentation processes from norbornane and norbornene ions linked to 1,3-oxazine moieties were examined by ERMS, using an electrospray ionisation source and in-source collisional activation.