Question

Aldehydes that do not undergo aldol condensation are (1) propanal (2) trichloroethanal (3) methanal (4) ethanal (5) benzaldehyde

• A. $3$ and $4$ only
• B. $3$ and $5$ only
• C. $1, 2$ and $3$ only
• D. $2, 3$ and $5$ only

Answer 1

Answer: (D)

$2, 3$ and $5$ only

Answer 2

The carbonyl compounds must contain an $\alpha -$ hydrogen atom to undergo aldol condensation. Thus, propanal and ethanal are the aldehydes that can undergo aldol condensation. However, methanol though does not contain $\alpha -$ hydrogen atom yet undergoes cross aldol condensation in the presence of limewater. Thus, aldehydes that do not undergo aldol condensation are trichloroethanal, benzaldehyde and methanal.