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 an d the distribution of internal energy resulting from the ionisation process . Thus, investigations of the fragmentation pathways of complex ions can ga in some advantage from energy-resolved mass spectrometry (ERMS) techniques. These methods are able to establish a relationship between the internal en ergy 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 ionisati on source and in-source collisional activation.