Question

Phenol upon treatment with bromine in the presence of carbondisulphide at 0 °C yields:

• A. 4‐Bromophenol
• B. 2‐Bromophenol
• C. 2,4‐Dibromophenol
• D. 2,4,6‐Triibromophenol

Answer 1

The Correct Option is A

The reaction of phenol with bromine in the presence of carbon disulfide (CS₂) at 0°C is a type of electrophilic aromatic substitution reaction. In this reaction, we need to understand the orientation and reactivity of the substituents on the aromatic ring, particularly with phenol as the starting compound.

1. Phenol (C₆H₅OH), due to the electron-donating effect of the hydroxyl (-OH) group, activates the benzene ring and directs incoming electrophiles to the ortho (position 2) and para (position 4) positions.
2. Without a solvent like water or other polar solvents that facilitate multiple substitutions, using an inert solvent such as carbon disulfide at low temperatures (0°C) typically results in selective mono-bromination.
3. At 0°C and in CS₂, bromine preferentially adds to the para position due to lesser steric hindrance compared to the ortho position, resulting in 4-bromophenol as the major product.

Let's evaluate each option:

• 4-Bromophenol: This is the expected major product under the described conditions. The para position is favored due to minimal steric hindrance and high reactivity resulting from the electron-donating effect of the hydroxyl group.
• 2-Bromophenol: This could also be formed to a minor extent because the ortho position is also activated. However, steric hindrance generally makes para substitution more favorable.
• 2,4-Dibromophenol: Formation of dibrominated products occurs more readily at higher temperatures or in the presence of excess bromine. Given the conditions (0°C and CS₂), this is not likely to be a major product.
• 2,4,6-Tribromophenol: Forming a tri-substituted product requires even harsher conditions (often solvent-free or at elevated temperatures), making this option incorrect under the given conditions.

Conclusion: Under the reaction conditions provided, phenol with bromine in carbon disulfide at 0°C yields 4-bromophenol as the major product. Hence, the correct answer is 4-Bromophenol.