The correct answer is: (b) C6H5COOC2H5
Claisen self-condensation is a reaction where an ester reacts with another molecule of the same ester to form a β-ketoester. This reaction involves the deprotonation of the ester by a strong base, followed by nucleophilic attack and subsequent elimination.
In the case of option (b) C6H5COOC2H5, the ester is ethyl benzoate, and it contains a phenyl (C6H5) group attached to the carbonyl group. The presence of an aromatic ring (phenyl group) significantly hinders the deprotonation step and the subsequent nucleophilic attack required for Claisen self-condensation. This is due to the resonance stabilization of the phenyl group, which makes the acidic hydrogen on the alpha carbon less acidic and less prone to deprotonation.
Therefore, ethyl benzoate (C6H5COOC2H5) cannot easily undergo Claisen self-condensation compared to the other options.
