Question

mechanism of perkin reaction

Answer 1

Perkin reaction. The Perkin reaction is an organic reaction developed by English chemist William Henry Perkin that is used to make cinnamic acids. It gives an α,β-unsaturated aromatic acid by the aldol condensation of an aromatic aldehyde and an acid anhydride, in the presence of an alkali salt of the acid.
Mechanism

The generally accepted mechanism of the Perkin reaction is represented by the following steps:

1. The first step involves the abstraction of proton by the carboxylate ion to form the resonance stabilized carbanion, which is a species containing carbon with a negative charge.

2. The second step involves the nucleophilic addition of the carbanion to the carbonyl carbon atom of the aldehyde to form a tetrahedral intermediate.

3. The tetrahedral intermediate is protonated (addition of H+) by the acetic acid formed in the process.

4. Elimination of water molecule from the hydroxy derivative.

5. Hydrolysis (addition of water) of the unsaturated compound to the unsaturated acid.

Answer 2

The above mechanism is not universally accepted, as several other versions exist, including decarboxylation without acetic group transfer.[7]


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