Dual mechanisms for the fragmentation of 1-benzoylbenzotriazole upon electron impact

The electron impact induced fragmentation of 1-benzoylbenzotriazole has been studied by ¹³C labelling experiments. It has been found that the loss of CO from the [M ? N₂]⁺˙ ions proceeds by two routes; about 78% of the ions decompose via the molecular ions of the corresponding thermal fragmentation product, 2-phenylbenzoxazole, and 22% via those of the corresponding photochemical fragmentation product, 6-phenanthridone.