Chemistry Aldehydes & Ketones SET 2019
PMDC Verified Question 53 of 94
Which of the following compounds will produce a yellow precipitate with \( I_2 \) dissolved in \( NaOH_{(aq)} \)?
A
\( HCOOCH_2CH_3 \)
B
\( CH_3CH_2COCH_3 \)
C
\( CH_3OH \)
D
\( CH_3CH_2CHO \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: \( CH_3CH_2COCH_3 \)
Concept:

The reagent mixture of \( I_2 \) and \( NaOH \) is used for the Iodoform Test, which yields a yellow precipitate of \( CHI_3 \) only for methyl ketones or specific secondary alcohols.

Solution:

  • We must look for a compound containing the \( CH_3-CO- \) structural fragment.


  • Option B is 2-butanone (ethyl methyl ketone), with the structure \( CH_3-CH_2-CO-CH_3 \).


  • Because it has a methyl group directly bonded to the carbonyl carbon, it gives a strong positive Iodoform test.


Why other options are incorrect:

Option A is an ester. Option C is methanol, which lacks a methyl adjacent to a \( C-O \) bond. Option D is propanal, an aldehyde that lacks a terminal methyl attached to the carbonyl group.

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