Collision-induced dissociations of negative ions. α-Dicarbonyl parent negative ions

α-Dicarbonyl compounds form stable parent negative ions by capture of low-energy electrons. The parent negative ions undergo a variety of collision induced dissociations, the most characteristic being β cleavage to a carbonyl group, i.e. see diagram in paperCyclic α-dicarbonyl parent negative ions may also eliminate molecules of carbon monoxide, for example the fragmentations M- → [M-(R + CO)]- M- →[M - (R-2CO)]- and M- → [M-2CO]- occur in a number of cases.