Question

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R :
Assertion A : Aryl halides cannot be prepared by replacement of hydroxyl group of phenol by halogen atom.
Reason R : Phenols react with halogen acids violently. In the light of the above statements.
Choose the most appropriate from the options given below:

• A. Both A and R are true but R is NOT the correct explanation of A
• B. A is false but R is true
• C. A is true but R is false
• D. Both A and R are true and R is the correct explanation of A

Answer 1

The Correct Option is C

To determine the correct option, let's analyze both the assertion (A) and the reason (R) given in the question. 

1. Assertion (A): "Aryl halides cannot be prepared by replacement of hydroxyl group of phenol by halogen atom."
   • Phenols have a hydroxyl group (\(-OH\)) attached to an aromatic benzene ring.
   • In phenols, the oxygen of the hydroxyl group forms a resonance-stabilized bond with the benzene ring, making the bond quite strong and stable.
   • This stabilizing effect makes it difficult to directly replace the \(-OH\) group with a halogen atom.
   • Hence, the assertion is true.
2. Reason (R): "Phenols react with halogen acids violently."
   • Phenols do not react violently with halogen acids like HCl, HBr, or HI.
   • The halogen acids might not react significantly with phenols under normal conditions because phenol itself doesn't readily undergo substitution reactions by simply heating with HX acids.
   • This suggests that the reason is false.

From the above analysis:

• The assertion (A) is true as the direct replacement of the hydroxyl group in phenols by a halogen atom is not feasible due to the resonance stabilization.
• The reason (R) is false; phenols do not react violently with halogen acids such as HCl or HBr.

Therefore, the most appropriate option given the statements is: A is true but R is false.

Answer 2

Assertion (A): The given statement is correct because in phenol, the hydroxyl group cannot be replaced by a halogen atom through a simple halogen acid reaction. This is due to the resonance stabilization of the hydroxyl group in phenol, which prevents such a substitution.
Phenol (C₆H₅OH) + HX → No Reaction
Reason (R): The statement that phenols react violently with halogen acids is incorrect in this context, as this does not relate to the inability to form aryl halides by replacing the hydroxyl group.

Thus, Assertion (A) is correct but Reason (R) is false.

So, the correct answer is : Option (3).