Target Exam

CUET

Subject

Chemistry

Chapter

Organic: Aldehydes, Ketones and Carboxylic Acids

Question:

Which of the following compounds will undergo Cannizzaro reaction

Options:

Benzaldehyde

Acetophenone

Benzophenone

Propionaldehyde

Correct Answer:

Benzaldehyde

Explanation:

The correct answer is Option (1) → Benzaldehyde

Reason:

Cannizzaro reaction is shown only by those aldehydes that do not have α-hydrogen (i.e., no hydrogen attached to the carbon next to the carbonyl group).

Compound

Formula

Has α-hydrogen?

Undergoes Cannizzaro?

Benzaldehyde

C₆H₅CHO

No

Yes

Acetophenone

C₆H₅COCH₃

Yes (on CH₃)

No (it's a ketone)

Benzophenone

(C₆H₅)₂CO

No

No (it's a ketone)

Propionaldehyde

CH₃CH₂CHO

Yes (on CHâ‚‚)

No

Key Points:

  • Only aldehydes without α-hydrogen undergo Cannizzaro reaction.
  • Ketones never undergo Cannizzaro reaction (even if they lack α-H, e.g., benzophenone).
  • Benzaldehyde → undergoes Cannizzaro to give benzyl alcohol + benzoic acid.

Final Answer: Benzaldehyde