Question

The products P, Q, R and S formed in the following reactions are 

• A. A
• B. B
• C. C
• D. D

Hint:

Primary or secondary alcohols can be converted to nitriles via HBr + CuCN, which upon hydrolysis yield carboxylic acids. Major product = acid, minor = unhydrolyzed nitrile.

Answer 1

The Correct Option is D

Step 1: Reaction sequence overview.
The reaction proceeds through three main steps:
1. Conversion of alcohol to alkyl bromide by HBr.
2. Substitution of Br by –CN using CuCN (Rosenmund–von Braun reaction) forming nitrile.
3. Acidic hydrolysis of nitrile to carboxylic acid.
Step 2: For 1-butanol.
\[ \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{OH} \xrightarrow{\text{HBr}} \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{Br} \xrightarrow{\text{CuCN}} \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{CN} \xrightarrow[\text{H$_2$O}]{\text{Conc. HCl}} \text{CH}_3\text{CH}_2\text{CH}_2\text{COOH} \] Thus, P = butanoic acid (major), Q = butyronitrile (minor).
Step 3: For 2-butanol.
\[ \text{CH}_3\text{CH(OH)CH}_2\text{CH}_3 \xrightarrow{\text{HBr}} \text{CH}_3\text{CHBrCH}_2\text{CH}_3 \xrightarrow{\text{CuCN}} \text{CH}_3\text{CH(CN)CH}_2\text{CH}_3 \xrightarrow[\text{H$_2$O}]{\text{Conc. HCl}} \text{CH}_3\text{CH(COOH)CH}_2\text{CH}_3 \] Thus, R = 2-methylbutanoic acid (major), S = corresponding nitrile (minor).
Step 4: Conclusion.
Hence, both reactions form nitriles via CuCN, which upon hydrolysis give carboxylic acids as major products.
So, P = R = carboxylic acids and Q = S = nitriles.
Therefore, the correct answer is (D).