The fragmentation of 5-phenyl-1,4-benzodiazepin-2-ones. Mechanism for the formation of [M ? H]+

The fragmentations under electron impact of 5-phenyl-1,4-benzodiazepin-2-ones are investigated with the aid of high resolution, metastable decompositions and deuterium labeling. Based on our data a mechanism for the formation of the M – H]⁺ ion is proposed. It is shown that the M – CHO]⁺ ion is probably formed by two different pathways. Data on two minor fragment ions give support to the structure proposed for the M – CHO]⁺ ion.