Question

Which of the following compounds does not undergo Cannizzaro reaction?

• A. Formaldehyde
• B. 2,2-Dimethylbutanal
• C. Benzaldehyde
• D. Acetaldehyde

Hint:

Aldehydes having at least one \(\alpha\)-hydrogen generally undergo aldol condensation, whereas aldehydes lacking \(\alpha\)-hydrogen undergo Cannizzaro reaction.

Answer 1

The Correct Option is D

Step 1: Check formaldehyde.
Formaldehyde contains no \(\alpha\)-carbon and therefore no \(\alpha\)-hydrogen. Hence it undergoes Cannizzaro reaction. \[ {\text{Undergoes Cannizzaro reaction}} \]

Step 2: Check 2,2-dimethylbutanal.
The carbon adjacent to the aldehyde group is fully substituted and contains no hydrogen atom. Therefore no \(\alpha\)-hydrogen is present. Hence it undergoes Cannizzaro reaction. \[ {\text{Undergoes Cannizzaro reaction}} \]

Step 3: Check benzaldehyde.
The carbon adjacent to the aldehyde group is part of the benzene ring and does not contain an \(\alpha\)-hydrogen. Thus benzaldehyde undergoes Cannizzaro reaction. \[ {\text{Undergoes Cannizzaro reaction}} \]

Step 4: Check acetaldehyde.
Acetaldehyde possesses \(\alpha\)-hydrogen atoms. \[ CH_3CHO \] Therefore it undergoes aldol condensation rather than Cannizzaro reaction. \[ {\text{Does not undergo Cannizzaro reaction}} \]

Step 5: Final answer.
\[ {\text{Acetaldehyde}} \]