Self-condensation (Claisen) of ethyl acetate under base yields which β-keto ester?

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Multiple Choice

Self-condensation (Claisen) of ethyl acetate under base yields which β-keto ester?

In a Claisen condensation, an ester is deprotonated at the α-position to form an enolate, which then attacks the carbonyl of a second ester molecule. After a tetrahedral intermediate forms and the alkoxide leaves, a β-keto ester is produced. Here, the enolate of ethyl acetate attacks another molecule of ethyl acetate. The result is ethyl acetoacetate (Ethyl 3-oxobutanoate), with the structure CH3-CO-CH2-COOEt. This is a β-keto ester because the ketone (the CH3-CO– fragment) sits adjacent to the ester carbonyl, with a CH2 group in between—the β position relative to the ester. The other options don’t come from this self-condensation: they don’t have the two-carbonyl arrangement in the β-keto ester format produced by this mechanism.

In a Claisen condensation, an ester is deprotonated at the α-position to form an enolate, which then attacks the carbonyl of a second ester molecule. After a tetrahedral intermediate forms and the alkoxide leaves, a β-keto ester is produced.

Here, the enolate of ethyl acetate attacks another molecule of ethyl acetate. The result is ethyl acetoacetate (Ethyl 3-oxobutanoate), with the structure CH3-CO-CH2-COOEt. This is a β-keto ester because the ketone (the CH3-CO– fragment) sits adjacent to the ester carbonyl, with a CH2 group in between—the β position relative to the ester.

The other options don’t come from this self-condensation: they don’t have the two-carbonyl arrangement in the β-keto ester format produced by this mechanism.

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