Predict the major products of the following reactions.
(b) benzamide (PhCONH₂) + Na (liquid NH₃, CH₃CH₂OH)

Verified step by step guidance

Step 1: Analyze the reaction conditions. Sodium (Na) in liquid ammonia (NH₃) is a strong reducing agent, often used in Birch reduction reactions. Ethanol (CH₃CH₂OH) is added in the second step, likely to quench the reaction.

Step 2: Identify the functional groups in the starting material. The molecule contains a benzene ring and an ester group (O=C-OCH₃). The benzene ring is susceptible to reduction under Birch conditions.

Step 3: Predict the effect of the Birch reduction on the benzene ring. Birch reduction typically reduces aromatic rings to 1,4-cyclohexadienes. The electron-donating ester group directs the reduction to occur at positions meta to the ester group.

Step 4: Consider the second step with ethanol. Ethanol serves to quench the reaction by protonating any remaining reactive intermediates, stabilizing the final product.

Step 5: Combine the insights to predict the major product. The benzene ring will be reduced to a 1,4-cyclohexadiene structure, with the ester group intact. Ensure the positions of the double bonds are consistent with the directing effects of the ester group.

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Key Concepts

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

Birch Reduction

The Birch reduction is a chemical reaction that involves the reduction of aromatic compounds using sodium (Na) in liquid ammonia (NH3) and an alcohol, typically ethanol or isopropanol. This reaction results in the formation of 1,4-cyclohexadienes from aromatic rings, effectively breaking the aromaticity and introducing double bonds in a specific pattern.

Aromatic Compounds

Aromatic compounds are a class of cyclic compounds characterized by their stable ring structure and delocalized π-electrons, which confer unique chemical properties. Benzamide, the compound in the question, is an aromatic amide that contains a benzene ring attached to a carbonyl group and an amine, making it a suitable substrate for reactions like the Birch reduction.

Electrophilic and Nucleophilic Reactions

In organic chemistry, electrophilic reactions involve species that seek electrons (electrophiles), while nucleophilic reactions involve species that donate electrons (nucleophiles). The Birch reduction mechanism involves the nucleophilic attack of the sodium metal on the aromatic ring, leading to the formation of radical anions, which are crucial for the subsequent steps of the reaction.

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