Chemistry Alcohols & Phenols MDCAT 2013
PMDC Verified Question 91 of 95
Aqueous phenol decolorizes bromine water to form a white precipitate. What is the structure of the white precipitate formed?
A
2,4,6-Tribromophenol
B
2-Bromophenol
C
4-Bromophenol
D
2,4-Dibromophenol
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: 2,4,6-Tribromophenol
Concept:

The hydroxyl group (-OH) on a benzene ring is highly activating. In the presence of aqueous bromine (a polar solvent), phenol rapidly undergoes polyhalogenation.

Formula:

$$ \text{C}_6\text{H}_5\text{OH} + 3\text{Br}_2 \xrightarrow{\text{H}_2\text{O}} \text{C}_6\text{H}_2\text{Br}_3\text{OH} + 3\text{HBr} $$

Solution:

  • Bromine is directed to all available ortho (2,6) and para (4) positions simultaneously.


  • The resulting product is 2,4,6-tribromophenol, which appears as a characteristic white precipitate.


Why other options are incorrect:

Mono-bromination (options B and C) requires a non-polar solvent like \(\text{CS}_2\) or \(\text{CCl}_4\) at low temperatures to decrease the electrophilicity of the bromine.

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