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 iodoform test
A. CH3OH
B. CH3CH2OH
C. CH3CH(OH)CH3
D. CH3CH2CH2OH
Choose the correct option
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → B and C only
The iodoform test (\( \ce{I2} \) + NaOH, i.e. sodium hypoiodite) is given by compounds with a CH3CO– group, or a CH3CH(OH)– group which the hypoiodite oxidises to \( \ce{CH3CO} \)–. The \( \ce{CH3} \) group ends up as yellow \( \ce{CHI3} \).
A. \( \ce{CH3OH} \) — Does not undergo the test. It has no \( \ce{CH3CH(OH)} \)– group.
B. \( \ce{CH3CH2OH} \) — Undergoes the test. It is oxidised to \( \ce{CH3CHO} \), which then gives iodoform:
\( \displaystyle \ce{CH3CH2OH + 4I2 + 6NaOH -> CHI3 v + HCOONa + 5NaI + 5H2O} \)
C. \( \ce{CH3CH(OH)CH3} \) — Undergoes the test. Propan-2-ol is oxidised to acetone:
\( \displaystyle \ce{(CH3)2CHOH + 4I2 + 6NaOH -> CHI3 v + CH3COONa + 5NaI + 5H2O} \)
D. \( \ce{CH3CH2CH2OH} \) — Does not undergo the test. The OH is on the end carbon; it gives propanal, which has no \( \ce{CH3CO} \)– group.
NCERT (2026-27 edition):
Oxidation of Methyl Ketones by Haloform Reaction – …
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| – | – | – | 20-06 S3 09-06 S3 | – |