Question

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

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

Answer 1

The correct option is B $2$ and $5$ only

Aldehyde having no $\alpha$ hydrogen cannot undergo aldol condensation. By the shown figure there is no $\alpha -H$ present in trichloroethanal and benzaldehyde.