Predict the products formed when cyclohexanone reacts with the following reagents.
(h) sodium acetylide, then mild H₃O⁺

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Identify the functional group in cyclohexanone. Cyclohexanone is a cyclic ketone, which contains a carbonyl group (C=O) as its functional group.

Understand the reactivity of sodium acetylide (NaC≡CH). Sodium acetylide is a strong nucleophile due to the negatively charged carbon in the acetylide ion (C≡C⁻). It can attack electrophilic centers, such as the carbonyl carbon in cyclohexanone.

Propose the nucleophilic addition mechanism. The acetylide ion will attack the electrophilic carbonyl carbon of cyclohexanone, breaking the π bond of the carbonyl group and forming a tetrahedral alkoxide intermediate.

Account for the role of mild H3O⁺. The alkoxide intermediate formed in the previous step will be protonated by the mild acid (H3O⁺), resulting in the formation of a hydroxy group (-OH) at the former carbonyl carbon.

Predict the final product. The reaction will yield a compound where the acetylide group (C≡CH) is attached to the former carbonyl carbon, and the oxygen atom is converted into a hydroxyl group (-OH), forming a propargylic alcohol.

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Key Concepts

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

Nucleophilic Addition

Nucleophilic addition is a fundamental reaction mechanism in organic chemistry where a nucleophile attacks an electrophilic carbon atom, typically in a carbonyl group. In the case of cyclohexanone, the carbonyl carbon is susceptible to attack by nucleophiles like sodium acetylide, leading to the formation of an alkoxide intermediate.

Acetylide Ion

The acetylide ion is a strong nucleophile derived from terminal alkynes, formed by deprotonating an alkyne with a strong base like sodium amide or sodium hydride. In this reaction, sodium acetylide acts as a nucleophile that adds to the carbonyl carbon of cyclohexanone, resulting in a new carbon-carbon bond.

Hydrolysis

Hydrolysis is a chemical reaction involving the addition of water to a compound, often leading to the breakdown of that compound. After the nucleophilic addition of sodium acetylide to cyclohexanone, mild H3O+ (acidic water) is used to protonate the alkoxide intermediate, resulting in the formation of an alcohol product.

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