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24.5 The Claisen Condensation

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  • Because esters can contain α hydrogens they can undergo a condensation reaction similar to the aldol reaction called a Claisen Condensation. In a fashion similar to the aldol, one ester acts as a nucleophile while a second ester acts as the electrophile. During the reaction a new carbon-carbon bond is formed. The product is a β-keto ester. A major difference with the aldol reaction is the fact that hydroxide cannot be used as a base because it could possibly react with the ester. Instead, an alkoxide version of the alcohol used to synthesize the ester is used to prevent transesterification side products.

    Claisen Condensation

    Basic reaction

    Going from reactants to products simply

    Example 1: Claisen Condensation

    Claisen Condensation Mechanism

    1) Enolate formation

    2) Nucleophilic attack

    3) Removal of leaving group


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