Question

Given below are two statements:
Statement I: Bromination of phenol in a solvent with low polarity such as CHCl\(_3\) or CS\(_2\) requires a Lewis acid catalyst.
Statement II: The Lewis acid catalyst polarizes the bromine to generate \( \text{Br}^+ \).
In light of the above statements, choose the correct answer from the options given below:

• A. Statement I is true but Statement II is false.
• B. Both Statement I and Statement II are true
• C. Both Statement I and Statement II are false.
• D. Statement I is false but Statement II is true.

Answer 1

The Correct Option is D

Phenol is a highly activated compound and can undergo bromination directly with bromine without any Lewis acid. However, the Lewis acid catalyst indeed polarises the bromine to generate Br⁺, making Statement II true.
Thus the correct answer is Option 4.

Answer 2

Step 1: Recall the general concept of phenol bromination
Phenol is highly reactive toward electrophilic aromatic substitution due to the activating effect of its –OH group. In aqueous or highly polar solvents, phenol readily reacts with bromine water even without a catalyst to give 2,4,6-tribromophenol. However, when phenol is brominated in nonpolar solvents like CCl₄, CHCl₃, or CS₂, the reaction rate decreases because bromine is not sufficiently polarized to generate electrophilic Br⁺ ions on its own.

Step 2: Examine Statement I
Statement I: “Bromination of phenol in a solvent with low polarity such as CHCl₃ or CS₂ requires a Lewis acid catalyst.”
This statement claims that a Lewis acid catalyst is required. Actually, this is false because phenol is itself strongly activating and can polarize bromine even in low-polarity solvents due to the lone pair donation from oxygen into the ring (resonance). Thus, bromination of phenol can proceed without an external Lewis acid, though the extent of substitution depends on the medium polarity.

Step 3: Examine Statement II
Statement II: “The Lewis acid catalyst polarizes the bromine to generate Br⁺.”
This statement is true in general for electrophilic aromatic substitution reactions using bromine in the presence of Lewis acids (like FeBr₃ or AlBr₃). The Lewis acid interacts with Br₂ to produce an electrophile (Br⁺), which attacks the aromatic ring:
\[ Br_2 + FeBr_3 \rightarrow Br^+ + FeBr_4^- \] This mechanism explains how bromine becomes reactive enough to substitute aromatic rings in less activated systems such as benzene.

Step 4: Logical conclusion
Therefore:
• Statement I is false because phenol itself is sufficiently reactive and does not necessarily require a Lewis acid in low-polarity solvents.
• Statement II is true because a Lewis acid indeed helps polarize bromine into Br⁺ in general aromatic bromination reactions.

Final answer

Statement I is false but Statement II is true.