7.3 Hunsdicker Reaction

The usual stability of carbon dioxide result in exothermic decarboxylation of carboxylic acid but reaction is not always easy to carry out because of slow rate of reaction. But some groups present in molecule help decarboxylation to be rapid enough.

Acids having a carbonyl group on $\beta $-carbon atom, called -keto acids, decarboxylate readily when they are heated to 100–150°C.

There are two facts on which case of decarboxylation depends

(i) When the carboxyl ate ion decarboxylate, it forms a resonance stabilized enolate anion.

(ii) When the acid itself decarboxylates it can do so through a six-membered cyclic transition state $\beta $-keto acid on warming alone or in presence of a base undergoes rapid removal of $C{O_2}$ .