[C]+· and [CH]+ from doubly charged ions formed from malononitrile

The metastable ions [M]2+, [M – H]2+· and [M – H2]2+ from malononitrile fragment by loss of [CH]+, [C]+· and [C]+·, respectively. The reaction of the molecular ion involves the methylene and nitrile carbon atoms in the statistical probability ratio, while that of [M – H]2+· involves exclusively the nitrile carbon and that of [M  H2]2+ involves an approximately equal contribution, from both sources. It is suggested that the metastable molecular ion fragments through a bipyrimidal intermediate.