Question

Which of the following reagent is suitable for the preparation of the product in the above reaction ? (reaction of ketone to alkane)

• A. NaBH4
• B. NH2-NH2/C2H5ONa
• C. Ni/H2
• D. Red P + Cl2

Hint:

Wolff-Kishner is best for base-stable molecules; Clemmensen is best for acid-stable molecules. Both achieve the same result: $>C=O \to >CH_2$.

Answer 1

The Correct Option is B

To determine which reagent is suitable for the conversion of a ketone to an alkane, we need to consider the reaction mechanisms involved.

1. The reaction in question involves converting a ketone to an alkane. This transformation is typically achieved through the Wolff-Kishner  reduction.
2. The Wolff-Kishner reduction uses hydrazine (\(NH_2-NH_2\)) in the presence of a base, usually sodium ethoxide (\(C_2H_5ONa\)), to convert the carbonyl group in ketones and aldehydes to a methylene group.
3. In this reaction mechanism, hydrazine reacts with the ketone to form a hydrazone, which is then decomposed in a strongly basic solution to give the corresponding alkane.
4. Let's rule out the other options:
   • NaBH₄: This is a mild reducing agent and is effective for reducing aldehydes and ketones to alcohols, not alkanes.
   • Ni/H₂: This catalyst system is used for hydrogenation reactions and may reduce carbon-carbon double bonds, not specifically converting ketones to alkanes.
   • Red P + Cl₂: This combination is not applicable for reducing ketones to alkanes. It is generally used in other types of reactions like chlorination.
5. Therefore, the suitable reagent for converting a ketone to an alkane in this scenario is \(NH_2-NH_2/C_2H_5ONa\).

Conclusion: The correct reagent for this transformation is NH₂-NH₂/C₂H₅ONa, as it facilitates the Wolff-Kishner reduction.