Which is the most suitable reagent for following conversion? $CH_{3}-CH=CH-CH_{2}-C(=O)-CH_3 \rightarrow CH_{3}-CH=CH-CH_{2}-C(=O)-ONa$

Question

Accepted Answer

The conversion in question involves transforming a ketone group into a sodium enolate. The most suitable reagent for this conversion is Option 3: $I_{2}$ and NaOH solution. Here's why this option is correct and why the others are not:

1. **Explanation for Option 3 ($I_{2}$ and NaOH solution):**
   - The reaction described is a classic example of the haloform reaction. In this reaction, methyl ketones (or alcohols that can be oxidized to methyl ketones) react with halogens in the presence of a base to form carboxylate salts. Here, the methyl ketone group ($C(=O)-CH_3$) reacts with iodine ($I_{2}$) in the presence of a base (NaOH) to form the sodium enolate ($C(=O)-ONa$). The iodine acts as the halogen, and the NaOH provides the necessary basic conditions for the reaction to proceed. This process results in the cleavage of the methyl group and the formation of the sodium enolate, which matches the desired conversion.

2. **Why Option 1 (Tollen's reagent) is incorrect:**
   - Tollen's reagent is typically used to test for aldehydes, as it oxidizes aldehydes to carboxylic acids while reducing silver ions to metallic silver. It is not suitable for the conversion of a ketone to a sodium enolate, as it does not provide the necessary conditions or reactants for the haloform reaction.

3. **Why Option 2 (Benzoyl peroxide) is incorrect:**
   - Benzoyl peroxide is an organic peroxide commonly used as a radical initiator in polymerization reactions. It does not have the capability to convert a ketone to a sodium enolate. It lacks the halogen component and the basic conditions required for the haloform reaction.

4. **Why Option 4 (Sn and NaOH solution) is incorrect:**
   - Tin (Sn) in the presence of NaOH is not a suitable reagent for the haloform reaction. Tin is typically used in reductions, such as reducing nitro groups to amines, and does not facilitate the conversion of a ketone to a sodium enolate. The absence of a halogen source in this option makes it unsuitable for the desired transformation.

In conclusion, Option 3 ($I_{2}$ and NaOH solution) is the correct choice because it provides the necessary halogen and basic conditions to carry out the haloform reaction, resulting in the conversion of the methyl ketone to the sodium enolate.