Predict the products of the following Claisen condensations.
(d)

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Step 1: Identify the reactants involved in the Claisen condensation. The reaction involves cyclohexanone (a ketone) and methyl acetoacetate (an ester) in the presence of sodium methoxide (NaOCH3) as the base and methanol (CH3OH) as the solvent.

Step 2: Understand the mechanism of Claisen condensation. The base (NaOCH3) deprotonates the alpha-hydrogen of the ester (methyl acetoacetate), forming an enolate ion. This enolate ion is nucleophilic and will attack the electrophilic carbonyl carbon of the ketone (cyclohexanone).

Step 3: Write the nucleophilic attack step. The enolate ion formed from methyl acetoacetate attacks the carbonyl carbon of cyclohexanone, leading to the formation of a tetrahedral intermediate. This intermediate will rearrange to form a new carbon-carbon bond.

Step 4: Eliminate the leaving group. The tetrahedral intermediate collapses, expelling the methoxide ion (CH3O⁻) as the leaving group. This results in the formation of a β-keto ester product.

Step 5: Analyze the final product. The product of the reaction is a β-keto ester, where the new carbon-carbon bond connects the alpha-carbon of methyl acetoacetate to the carbonyl carbon of cyclohexanone. The structure of the product can be deduced by combining the fragments formed during the reaction.

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Key Concepts

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

Claisen Condensation

Claisen condensation is a reaction between two esters or an ester and a carbonyl compound in the presence of a strong base, typically an alkoxide. This reaction results in the formation of a β-keto ester or a β-diketone. The mechanism involves the deprotonation of an alpha hydrogen, followed by nucleophilic attack on the carbonyl carbon of another ester, leading to the formation of a new carbon-carbon bond.

Enolate Ion Formation

In Claisen condensation, the formation of an enolate ion is a crucial step. An enolate ion is generated when a strong base abstracts an alpha hydrogen from an ester, creating a resonance-stabilized anion. This enolate ion acts as a nucleophile, attacking the carbonyl carbon of another ester, which is essential for the condensation process to occur.

Product Prediction

Predicting the products of a Claisen condensation involves understanding the structure of the reactants and the regioselectivity of the reaction. The final product typically features a β-keto ester or β-diketone, depending on the starting materials. Additionally, the reaction conditions, such as the choice of base and solvent, can influence the outcome, including the possibility of side reactions or further condensation.

Predict the products of the following Claisen condensations. (d)