Question

Which of the following compounds will undergo a Cannizzaro reaction:
\( \text{CH}_3\text{CHO},\ \text{C}_6\text{H}_5\text{CHO},\ \text{CH}_3\text{COCH}_3 \)?

• A. \( \text{CH}_3\text{CHO} \)
• B. \( \text{C}_6\text{H}_5\text{CHO} \)
• C. \( \text{CH}_3\text{COCH}_3 \)
• D. Both \( \text{CH}_3\text{CHO} \) and \( \text{C}_6\text{H}_5\text{CHO} \)

Hint:

Aldehydes lacking \(\alpha\)-hydrogen atoms undergo the Cannizzaro reaction in the presence of strong bases such as NaOH or KOH.

Answer 1

The Correct Option is B

Concept: The Cannizzaro reaction occurs in aldehydes that do not contain an \(\alpha\)-hydrogen atom. Such aldehydes undergo disproportionation in the presence of a strong base to give an alcohol and a carboxylate salt.

Step 1: Check for the presence of \(\alpha\)-hydrogen atoms. Cannizzaro reaction occurs only if \(\alpha\)-hydrogen is absent.

Step 2: Analyze each compound. \[ \text{CH}_3\text{CHO} \] Acetaldehyde contains \(\alpha\)-hydrogen atoms, so it does not undergo Cannizzaro reaction. \[ \text{CH}_3\text{COCH}_3 \] This is a ketone and also contains \(\alpha\)-hydrogen atoms, so it does not undergo Cannizzaro reaction. \[ \text{C}_6\text{H}_5\text{CHO} \] Benzaldehyde has no \(\alpha\)-hydrogen, so it undergoes the Cannizzaro reaction.

Step 3: Final result. \[ \boxed{\text{C}_6\text{H}_5\text{CHO}} \]