Chemistry Aldehydes & Ketones MDCAT 2012
PMDC Verified Question 90 of 94
Iodoform test will NOT be positive with:
A
\( CH_3-CH_2-CO-CH_2-CH_3 \)
B
\( C_2H_5OH \)
C
\( CH_3-CH_2-CO-CH_3 \)
D
\( CH_3-CHO \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \( CH_3-CH_2-CO-CH_2-CH_3 \)
Concept:

The Iodoform test is highly specific. It is strictly positive for compounds containing a methyl ketone group (\( CH_3-CO- \)) or alcohols that can be oxidized to a methyl ketone group (\( CH_3-CH(OH)- \)).

Solution:

  • Option A (3-pentanone or diethyl ketone) has the structure \( CH_3-CH_2-CO-CH_2-CH_3 \). It lacks the terminal \( CH_3-CO- \) required for the haloform reaction. Thus, it will not give a positive test.


Why other options are incorrect:

Ethanol (Option B) oxidizes to acetaldehyde, giving a positive test. 2-butanone (Option C) contains a methyl ketone group. Acetaldehyde (Option D) is the only aldehyde that gives a positive iodoform test.

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