Question

Identify the product formed when phenol reacts with bromine water.

• A. Bromobenzene
• B. \(o\)-Bromophenol
• C. \(2,4,6\)-Tribromophenol
• D. Chlorobenzene

Hint:

Phenol reacts with bromine water without any catalyst due to the strongly activating \(-OH\) group. The reaction gives \(2,4,6\)-tribromophenol as a white precipitate and is often used as a test for phenol.

Answer 1

The Correct Option is C

Concept: Phenol contains a hydroxyl group \((-OH)\) attached to a benzene ring. The \(-OH\) group is a strongly activating and ortho/para directing group. It increases the electron density in the benzene ring through resonance. Because of this increased electron density, electrophilic substitution reactions occur very easily in phenol.

Step 1: Understand the effect of the hydroxyl group. The \(-OH\) group directs incoming electrophiles to the:
• Ortho position
• Para position Thus bromination tends to occur at the \(2\), \(4\), and \(6\) positions of the benzene ring.

Step 2: Reaction with bromine water. When phenol reacts with bromine water, bromine atoms substitute the hydrogen atoms at the ortho and para positions. The reaction is: \[ \text{Phenol} + 3Br_2 \rightarrow 2,4,6\text{-Tribromophenol} + 3HBr \]

Step 3: Observation of the reaction. During this reaction:
• Bromine water gets decolourised.
• A white precipitate of \(2,4,6\)-tribromophenol is formed. Thus the product formed is \[ \boxed{2,4,6\text{-Tribromophenol}} \]