Question:
Which of the following compounds dose NOT respond positively to the iodoform test ?
Which of the following compounds dose NOT respond positively to the iodoform test ?
Show Hint
Iodoform test needs a CH3CO- group or a CH3CH(OH)- group.
Updated On: Oct 1, 2026
- Acetaldehyde
- Propan-2-ol
- Propanone
- Pentan-3-one
Show Solution
Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
The iodoform test is positive for compounds having a \(\text{CH}_3\text{CO-}\) group or a \(\text{CH}_3\text{CH(OH)-}\) group, which is oxidised to the former by \(\text{I}_2/\text{NaOH}\).
Step 2: Check each:
A: Acetaldehyde, \(\text{CH}_3\text{CHO}\), has \(\text{CH}_3\text{CO-}\). Positive.
B: Propan-2-ol, \(\text{CH}_3\text{CH(OH)CH}_3\), has \(\text{CH}_3\text{CH(OH)-}\). Positive.
C: Propanone, \(\text{CH}_3\text{COCH}_3\), has \(\text{CH}_3\text{CO-}\). Positive.
D: Pentan-3-one, \(\text{CH}_3\text{CH}_2\text{COCH}_2\text{CH}_3\), has a carbonyl flanked by two \(\text{CH}_2\) groups and no \(\text{CH}_3\text{CO-}\) unit. Negative.
Final Answer:
Pentan-3-one does not respond to the iodoform test, option (D). \[ \boxed{\text{Pentan-3-one}} \]
The iodoform test is positive for compounds having a \(\text{CH}_3\text{CO-}\) group or a \(\text{CH}_3\text{CH(OH)-}\) group, which is oxidised to the former by \(\text{I}_2/\text{NaOH}\).
Step 2: Check each:
A: Acetaldehyde, \(\text{CH}_3\text{CHO}\), has \(\text{CH}_3\text{CO-}\). Positive.
B: Propan-2-ol, \(\text{CH}_3\text{CH(OH)CH}_3\), has \(\text{CH}_3\text{CH(OH)-}\). Positive.
C: Propanone, \(\text{CH}_3\text{COCH}_3\), has \(\text{CH}_3\text{CO-}\). Positive.
D: Pentan-3-one, \(\text{CH}_3\text{CH}_2\text{COCH}_2\text{CH}_3\), has a carbonyl flanked by two \(\text{CH}_2\) groups and no \(\text{CH}_3\text{CO-}\) unit. Negative.
Final Answer:
Pentan-3-one does not respond to the iodoform test, option (D). \[ \boxed{\text{Pentan-3-one}} \]
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