Question

Br\(_2\)/CS\(_2\) 

Hint:

The presence of the hydroxyl group makes phenol highly reactive to electrophilic substitution, resulting in tribromination in the ortho and para positions.

Answer 1

Bromination of Phenol 

When phenol reacts with bromine in carbon disulfide (CS₂), an electrophilic substitution reaction occurs. The hydroxyl group (-OH) on the phenol ring activates the ring towards substitution at the ortho and para positions relative to the hydroxyl group.

Reaction:

The reaction between phenol and bromine in CS₂ can be represented as: \[ \text{C}_6\text{H}_5\text{OH} + 3\text{Br}_2 \xrightarrow{\text{CS}_2} \text{C}_6\text{H}_2\text{Br}_3\text{OH} \] In this reaction, bromine atoms are added to the ortho and para positions relative to the hydroxyl group on the benzene ring.

Mechanism:

The hydroxyl group (-OH) is an electron-donating group, which activates the benzene ring by increasing the electron density at the ortho and para positions. This makes the ring more reactive toward electrophilic substitution, specifically towards bromine (Br₂), which acts as the electrophile.

Major Product:

The major product of this reaction is **2,4,6-Tribromophenol**, where three bromine atoms are substituted at the ortho and para positions relative to the hydroxyl group.

Conclusion:

The bromination of phenol in the presence of bromine and carbon disulfide (CS₂) leads to the formation of **2,4,6-Tribromophenol** as the major product. The reaction occurs due to the activating effect of the hydroxyl group, which makes the ring more reactive to electrophilic substitution.