The product of the following reaction is : $CH_{3}CH_{2}CH_{2}COOH\xrightarrow[(2)H_{2}O]{(1)Cl_{2}/red P} $

Question

Accepted Answer

The reaction in question involves the conversion of butanoic acid ($CH_{3}CH_{2}CH_{2}COOH$) using chlorine ($Cl_{2}$) in the presence of red phosphorus, followed by hydrolysis with water ($H_{2}O$). This is a classic example of the Hell-Volhard-Zelinsky (HVZ) reaction, which is used to halogenate carboxylic acids at the alpha position.

1. **Explanation for Option 1 (2-Chloro butanoic acid):**
   - The HVZ reaction specifically targets the alpha carbon of a carboxylic acid. In butanoic acid, the alpha carbon is the one directly adjacent to the carboxyl group ($COOH$). 
   - The reaction proceeds by first forming an acyl chloride intermediate with the help of red phosphorus and chlorine. The chlorine then substitutes the hydrogen at the alpha position, resulting in the formation of 2-chlorobutanoic acid.
   - Therefore, the product of this reaction is 2-chloro butanoic acid, which corresponds to Option 1.

2. **Explanation for why other options are incorrect:**
   - **Option 2 (3-Chloro butanoic acid):** This option suggests chlorination at the beta position (third carbon), which is not favored in the HVZ reaction. The reaction specifically targets the alpha position, making this option incorrect.
   - **Option 3 (4-Chloro butanoic acid):** This option implies chlorination at the gamma position (fourth carbon), which is not possible in the HVZ reaction. The reaction does not affect carbons beyond the alpha position, thus making this option incorrect.
   - **Option 4 (Butanoyl chloride):** This option suggests the formation of an acyl chloride without further substitution. While an acyl chloride intermediate is formed during the HVZ reaction, it is not the final product. The final product is the halogenated carboxylic acid, not the acyl chloride, making this option incorrect.

In conclusion, the correct product of the given reaction is 2-chloro butanoic acid, which is accurately represented by Option 1.