Decomposition of carboxylate anions

The mechanism below may be formulated for a number of acids that undergo decarboxylation via their anion S is solvent. Two requirements must be satisfied 

ACTIVATION ENERGIES FOR THE DECARBOXYLATION OF STRONG ACIDS IN WATER  

The anion (R ), which is generated in reaction (12), may be a carbanion or an enolate anion. It was found that dibromomalonate monoanion decarboxylation obeys a first-order rate law and that in the presence of bromine, the rate of decarboxylation equals the rate of bromine uptake . This indicates the formation of an enolate anion in the rate-determining step (12). 

As was indicated earlier, acid catalyzed decompositions are omitted. However, it should be mentioned that some anionic decompositions are subject to acid catalysis. The mechanism for these decompositions involves protonation of the TT-system of the carboxylate anion followed by a rate-determining loss of carbon dioxide . Caution should then be used in assigning the above mechanism, reactions (11)-(13), to acids with jr-systems in the R-group. 

---