Question

Which of the following compounds will not undergo aldol condensation?

• A. \(\text{CH}_{3}\text{-CHO}\) (Acetaldehyde)
• B. \(\text{CH}_{3}\text{-CO-CH}_{3}\) (Acetone)
• C. \(\text{C}_{6}\text{H}_{5}\text{-CHO}\) (Benzaldehyde)
• D. \(\text{CH}_{3}\text{-CH}_{2}\text{-CHO}\) (Propionaldehyde)

Hint:

Aldol condensation needs a hydrogen on the carbon next to the carbonyl group. Check which compound has none.

Answer 1

The Correct Option is C

Step 1: Look for alpha-hydrogens
Acetaldehyde, acetone and propionaldehyde each have hydrogens on the carbon next to C=O.

Step 2: Find the exception
Benzaldehyde has no such hydrogen, as its alpha atom is part of the aromatic ring.

Step 3: Conclusion
Without an $\alpha$-hydrogen, benzaldehyde cannot give an aldol.

Final Answer:
Option C, benzaldehyde, is correct. \[ \boxed{\text{(C) }\text{C}_6\text{H}_5\text{-CHO (Benzaldehyde)}} \]