Certain Aldehydes, ketone and certain alcohol undergo iodoform test. Certain Aldehydes ketones undergo aldol condensation. While certain aldehydes undergo Cannizzaro’s reaction. Aldehydes respond to Tollens’ reagent and Fehling’s reagent test.
Which amongst the following undergo aldol condensation
A. CH3CHO
B. HCHO
C. CH3COCH3
D. C6H5CHO
Choose the correct option
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A and C only
Aldol condensation needs at least one α-hydrogen (on the carbon next to C=O), which dilute alkali removes to form the enolate.
A. \( \ce{CH3CHO} \) — Undergoes aldol condensation. Three α-H:
\( \displaystyle \ce{2CH3CHO} \xrightarrow{\text{dil. }\ce{NaOH}} \ce{CH3CH(OH)CH2CHO} \)
B. HCHO — Does not undergo aldol condensation. No α-carbon; it gives the Cannizzaro reaction:
\( \displaystyle \ce{2HCHO + NaOH} \xrightarrow[\Delta]{\text{conc.}} \ce{CH3OH + HCOONa} \)
C. \( \ce{CH3COCH3} \) — Undergoes aldol condensation. Six α-H:
\( \displaystyle \ce{2CH3COCH3} \xrightarrow{\ce{Ba(OH)2}} \ce{(CH3)2C(OH)CH2COCH3} \)
D. \( \ce{C6H5CHO} \) — Does not undergo aldol condensation. The CHO is on a ring carbon with no H; it gives the Cannizzaro reaction:
\( \displaystyle \ce{2C6H5CHO} \xrightarrow[\Delta]{\text{conc. }\ce{NaOH}} \ce{C6H5CH2OH + C6H5COONa} \)
NCERT (2026-27 edition):
Aldol Condensation
