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
• E. $5$ only

Answer 1

Answer: (D)

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.