Question

Name the reagent used in the bromination of phenol to form 2,4,6-Tribromophenol.

Hint:

In electrophilic aromatic substitution reactions such as bromination and formylation, electron-rich aromatic rings are more reactive. The presence of activating groups like hydroxyl (–OH) increases the reactivity of phenol.

Answer 1

The reagent used in the bromination of phenol to form 2,4,6-Tribromophenol is Bromine water (Br\(_2\) in water). ### Detailed Explanation:
1. Electrophilic Aromatic Substitution: - The bromination of phenol is an example of electrophilic aromatic substitution, where the phenol acts as an electron-rich aromatic compound due to the presence of the hydroxyl group (-OH). The hydroxyl group is an activating group and directs incoming electrophiles to the ortho- and para- positions of the aromatic ring. 2. Action of Bromine:
- Bromine water (a solution of Br\(_2\) in water) acts as the electrophile in this reaction. The bromine molecule (Br\(_2\)) is polarized by the electron-rich benzene ring, and one of the bromine atoms becomes highly electrophilic, attacking the ortho- and para- positions relative to the hydroxyl group on the benzene ring. 3. Result:
- The reaction results in the formation of 2,4,6-Tribromophenol, where the three bromine atoms are attached to the ortho- and para- positions of the phenol ring, as shown below: \[ \text{C}_6\text{H}_5\text{OH} + 3\text{Br}_2 \xrightarrow{\text{H}_2\text{O}} \text{C}_6\text{H}_2(\text{Br})_3\text{OH} \] - The bromine atoms occupy the 2, 4, and 6 positions (relative to the hydroxyl group), making the product 2,4,6-Tribromophenol. Thus, the reagent used is Bromine water.