Predict the products of self-condensation of the following esters.
(d)

Verified step by step guidance

Step 1: Recognize that the reaction involves self-condensation of esters, which typically occurs via the Claisen condensation mechanism. This reaction requires a base (NaOEt) and an ester with an α-hydrogen.

Step 2: Identify the α-hydrogen in the ester molecule. The α-hydrogen is located on the carbon adjacent to the carbonyl group. In this case, the ester has α-hydrogens available for deprotonation.

Step 3: The base (NaOEt) deprotonates the α-hydrogen, forming an enolate ion. The enolate ion is nucleophilic and can attack the carbonyl carbon of another ester molecule.

Step 4: The nucleophilic enolate ion attacks the carbonyl carbon of another ester molecule, leading to the formation of a tetrahedral intermediate. This intermediate then collapses, expelling the ethoxide ion (EtO⁻) as a leaving group.

Step 5: The final product of the self-condensation reaction is a β-keto ester. The structure of the β-keto ester will include the original ester group and a ketone group separated by one carbon atom.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Self-Condensation of Esters

Self-condensation of esters involves the reaction of an ester with itself in the presence of a base, leading to the formation of β-keto esters or other products. This reaction typically occurs through the formation of an enolate ion, which then attacks another ester molecule, resulting in a new carbon-carbon bond. Understanding this mechanism is crucial for predicting the products of the reaction.

Enolate Ion Formation

Enolate ions are formed when a base abstracts a proton from the α-carbon of an ester, creating a resonance-stabilized anion. This ion is highly nucleophilic and can attack electrophiles, such as another ester molecule. The stability of the enolate ion is influenced by the structure of the ester and the strength of the base used, which is essential for predicting the outcome of the self-condensation reaction.

Synthesis of β-Keto Esters

The synthesis of β-keto esters is a common outcome of ester self-condensation reactions. In this process, the nucleophilic enolate ion attacks the carbonyl carbon of another ester, leading to the formation of a β-keto ester. This compound features a carbonyl group at the β-position relative to the original ester, and understanding its formation is key to predicting the products of the given reaction.

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Related Practice

Textbook Question

Esters with only one α hydrogen generally give poor yields in the Claisen condensation. Propose a mechanism for the Claisen condensation of ethyl isobutyrate, and explain why a poor yield is obtained.

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Textbook Question

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

(a)

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Textbook Question

Propose a mechanism for the self-condensation of methyl 3-phenylpropionate promoted by sodium methoxide.

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Textbook Question

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

(b)

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