$1$. પ્રોપેનાલ
$2$. ટ્રાયક્લોરોઇથેનાલ
$3$. મિથેનાલ
$4$. ઇથેનાલ
$5$. બેંઝાલ્ડિહાઈડ
$\underset{propanal}{\mathop{C{{H}_{3}}C{{H}_{2}}CHO}}\,$ $\underset {trichloroethanal}{\mathop {Cl_3CCHO}}$
$\underset {methanal} {\mathop {HCHO}}$ $\underset {ethanal} {\mathop CH_3CHO}$
$\underset {benzaldehyde} {\mathop {C_7H_6O}}$
Trichloroethanal, methanal and benzaldehyde do not undergo aldol condensation. Aldol condensation is not given by aldehydes and ketones which do not contain $\alpha $ - hydrogen atom $(s)$.