Question

Which of the following does not give iodoform test?

• A. Ethanol
• B. Ethanal
• C. Propan-2-ol
• D. Butan-1-ol

Hint:

$1^\circ$ alcohols (except Ethanol) do not give a positive Iodoform test.

Answer 1

The Correct Option is D

Step 1: Concept
The Iodoform test requires the presence of a methyl keto group ($CH_3-CO-$) or a secondary alcohol that can be oxidized to it ($CH_3-CH(OH)-$).
Step 2: Analysis

• Ethanol ($CH_3CH_2OH$) and Ethanal ($CH_3CHO$) both possess the required structure.
• Propan-2-ol ($CH_3CH(OH)CH_3$) is a $2^\circ$ alcohol with a terminal methyl, so it gives a positive test.
• Butan-1-ol ($CH_3CH_2CH_2CH_2OH$) is a $1^\circ$ alcohol with no methyl attached to the carbinol carbon.

Step 3: Conclusion
Hence, Butan-1-ol does not give the iodoform test.
Final Answer:(D)