Question

Show what esters would undergo Claisen condensation to give the following β-keto esters. (b)

Accepted Answer

Step 1: Identify the β-keto ester structure in the given compound. The β-keto ester contains a ketone group (C=O) at the β-position relative to the ester group (COOR). In this case, the compound has a phenyl group (Ph) attached to the α-carbon and another phenyl group attached to the β-carbon. Step 2: Recall the Claisen condensation mechanism. This reaction involves two ester molecules reacting in the presence of a strong base (such as alkoxide) to form a β-keto ester. One ester acts as the nucleophile, and the other acts as the electrophile. Step 3: Analyze the structure of the product to deduce the starting esters. The product has two distinct ester groups: one with a methyl group (OCH₃) and the other with a phenyl group (Ph-CH₂). This suggests that the starting esters are methyl benzoate (Ph-CH₂-COOCH₃) and methyl phenylacetate (Ph-CH₂-COOCH₃). Step 4: Write the reaction setup. In the Claisen condensation, the enolate ion formed from one ester (via deprotonation at the α-carbon) attacks the carbonyl carbon of the second ester. This leads to the formation of the β-keto ester after elimination of the alkoxide group. Step 5: Verify the compatibility of the starting esters with the product. Ensure that the phenyl groups and methyl groups in the product match the substituents in the starting esters. The reaction conditions typically involve a base like sodium ethoxide (NaOEt) in ethanol (EtOH) to facilitate the condensation.

Show what esters would undergo Claisen condensation to give the following β-keto esters.
(b)

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Key Concepts

Claisen Condensation

Enolate Ion Formation

β-Keto Esters