Question

Which one of the following compounds would not undergo Aldol condensation?

• A. Phenyl ethanal
• B. 1-Phenyl propanone
• C. 2,2-Dimethyl butanal
• D. 2-Methyl pentanal

Hint:

Aldol condensation only occurs in compounds with \(\alpha\)-hydrogens, i.e., hydrogens attached to the carbon adjacent to the carbonyl group.

Answer 1

The Correct Option is C

Aldol condensation requires the presence of an \(\alpha\)-hydrogen (a hydrogen attached to the carbon adjacent to the carbonyl group). If a compound does not have this \(\alpha\)-hydrogen, it cannot undergo the reaction. Let's analyze each option:
(A) Phenyl ethanal (C\(_6\)H\(_5\)CH\(_2\)CHO):
Phenyl ethanal is an aldehyde with an \(\alpha\)-hydrogen. It can undergo Aldol condensation.
(B) 1-Phenyl propanone (C\(_6\)H\(_5\)COCH\(_2\)CH\(_3\)):
1-Phenyl propanone is a ketone with an \(\alpha\)-hydrogen. It can undergo Aldol condensation.
(C) 2,2-Dimethyl butanal (C\(_6\)H\(_12\)O):
2,2-Dimethyl butanal is an aldehyde, but it does not have any \(\alpha\)-hydrogens. The carbon adjacent to the carbonyl group is attached to two methyl groups, which means there are no hydrogens available for abstraction by a base. Hence, it will not undergo Aldol condensation.
(D) 2-Methyl pentanal (C\(_6\)H\(_12\)O):
2-Methyl pentanal is an aldehyde with \(\alpha\)-hydrogens, so it can undergo Aldol condensation.
Conclusion:
The compound that will not undergo Aldol condensation is 2,2-Dimethyl butanal.