Question

Assertion (A) : The presence of \( -OH \) group in phenols directs the incoming group to ortho and para positions.
Reason (R) : \( -OH \) group in phenols activates the aromatic ring towards electrophilic substitution reaction.

Hint:

Groups that activate the benzene ring by \( +M \) or \( +I \) effects (like \( -OH, -NH_2, -CH_3 \)) are typically ortho-para directors.

Answer 1

Step 1: Understanding the Concept:
Phenol molecules undergo electrophilic aromatic substitution very easily due to the electron-releasing nature of the hydroxyl group. The \( -OH \) group significantly increases the reactivity of the phenol ring, making it more likely to undergo substitution reactions.
Step 2: Detailed Explanation:
The \( -OH \) group contains lone pairs of electrons on the oxygen atom, which are in conjugation with the benzene ring. This interaction leads to the resonance effect (\( +M \) effect), where electron density is increased on the ring, especially at the ortho and para positions.
The increased electron density at these positions makes them more reactive towards electrophiles, facilitating electrophilic substitution reactions. This is why the hydroxyl group is said to activate the ring, making it more prone to substitution. Since the electron density is highest at the ortho and para positions, electrophiles preferentially attack these positions. This explains why the \( -OH \) group is o,p-directing.
Thus, both statements about phenol’s reactivity are correct, and statement R explains why substitution occurs predominantly at the ortho and para positions.
Step 3: Final Answer:
Code (A) is correct.