Question

Which of the following aldehyde does not give Cannizzaro reaction?

• A. HCHO
• B. \( \mathrm{CCl_3CHO} \)
• C. Benzaldehyde
• D. \( \mathrm{CH_3CH_2CHO} \)

Hint:

Cannizzaro reaction is given only by aldehydes without \( \alpha \)-hydrogen. If an aldehyde has \( \alpha \)-hydrogen, think of aldol reaction instead of Cannizzaro reaction.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The Cannizzaro reaction is shown by aldehydes that do not have an $\alpha$-hydrogen atom.
Step 2: Formula Application:
If an aldehyde has an $\alpha$-hydrogen, it undergoes Aldol condensation instead when treated with a base.
Step 3: Explanation:
1. $HCHO$: No $\alpha$-carbon, so no $\alpha$-H. (Gives Cannizzaro) 2. $C_6H_5CHO$: $\alpha$-carbon is part of the ring and has no H. (Gives Cannizzaro) 3. $CCl_3CHO$: $\alpha$-carbon has three Cl atoms, no H. (Gives Cannizzaro) 4. $CH_3CH_2CHO$: The $\alpha$-carbon ($C_2$) has two hydrogen atoms. (Gives Aldol)
Step 4: Final Answer:
Propanal ($CH_3CH_2CHO$) does not give the Cannizzaro reaction.