The unimolecular dissociation of the glyoxylate, pyruvate, trifluoropyruvate, and α-oxobutyrate anions. Decarboxylation vs. decarbonylation of simple α-ketocarboxylates

- Decarboxylation is found to readily occur for four simple α-oxo carboxylates.
- CO loss also occurs but is only efficient for glyoxylate and trifluoropyruvate.
- Decarbonylation is limited by kinetic factors for pyruvate and 2-oxobutyrate.
- Linear structure vs. energy relationships explain trends in reactivity.

A series of simple α-oxo acids (RCOCOOH, R = H, CH3, CH3CH2, CF3) were deprotonated by negative electrospray ionisation and subjected to collision-induced dissociation and mass spectrometric analysis. Decarboxylation is the major process, observed for all four carboxylates. In addition, glyoxylate (R = H) and trifluoropyruvate (R = CF3) undergo efficient decarbonylation. Pyruvate (R = CH3) and 2-oxobutyrate (R = CH3CH2) also lose CO, but to a minor extent. The mechanistic and kinetic details of these processes have been investigated, supported by quantum chemical and RRKM modelling. The observed reactivity trends are in good agreement with conventional structure/reactivity relationships.

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