Question

Benzyl alcohol is obtained from benzaldehyde by –

• A. Aldol condensation
• B. Cannizzaro’s reaction
• C. Gattermann-Koch reaction
• D. Clemmensen reduction

Hint:

In Cannizzaro’s reaction, aldehydes without $\alpha$-hydrogens undergo disproportionation to form alcohol and carboxylate salt.

Answer 1

The Correct Option is B

Step 1: Recall Cannizzaro’s reaction.
Aldehydes without $\alpha$-hydrogens undergo Cannizzaro’s reaction in the presence of strong base. In this reaction, one molecule of aldehyde is reduced to alcohol and another molecule is oxidized to carboxylic acid.

Step 2: Apply to benzaldehyde.
Benzaldehyde has no $\alpha$-hydrogen. So, it undergoes Cannizzaro’s reaction: \[ 2C_6H_5CHO \xrightarrow{NaOH} C_6H_5CH_2OH + C_6H_5COONa \] Here, one molecule forms benzyl alcohol (C$_6$H$_5$CH$_2$OH), and the other forms sodium benzoate.

Step 3: Analyze options.
- (A) Aldol condensation: Requires $\alpha$-hydrogen, not possible in benzaldehyde.
- (B) Cannizzaro’s reaction: Correct, gives benzyl alcohol.
- (C) Gattermann-Koch reaction: Used for formylation of benzene, not applicable here.
- (D) Clemmensen reduction: Reduces carbonyl group to methylene, not giving benzyl alcohol.

Step 4: Conclusion.
Thus, benzyl alcohol is obtained from benzaldehyde by Cannizzaro’s reaction.

Final Answer: \[ \boxed{\text{(B) Cannizzaro’s reaction}} \]