Question

A in the above reaction is:

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is B

The given reaction is an intramolecular Claisen condensation, also known as a Dieckmann condensation.

 In this reaction, a 1,6-diketone reacts with a strong base (OEt-) and heat to form a cyclic β-diketone. Explanation: 

1. Reactant Structure: The reactant is a 1,6-diketone with the structure Me-C(=O)-(CH2)4-C(=O)-CH3.

 2. Base-Catalyzed Enolate Formation: The ethoxide base (OEt-) will deprotonate an α-hydrogen (hydrogen adjacent to a carbonyl group). This creates an enolate.

 3. Intramolecular Nucleophilic Attack: The enolate, being a nucleophile, will then attack the other carbonyl group in the same molecule. This forms a six-membered ring intermediate. 

4. Elimination and Product Formation: Through a series of proton transfers and elimination steps, the final product formed is a cyclic β-diketone. Determining the Product: To determine the product, we need to consider the ring size that will be formed. In this case, a six-membered ring will be formed. The two carbonyl carbons will become part of the ring. The carbon chain between the two carbonyl carbons will form the rest of the ring. The methyl group (Me) and the CH3 group attached to the carbonyl groups will remain as substituents on the ring. The correct product is option (3): The product is a six-membered ring with a methyl group (Me) and a CH3 group attached to the ring. The ring also contains two carbonyl groups (C=O) in a 1,3-relationship (β-diketone). Therefore, the answer is (3).