Question

Assertion (A): Phenol is less acidic than 4-methylphenol. Reason (R): The presence of an electron releasing group in phenol makes it less acidic.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Electron-releasing groups decrease acidity of phenols; electron-withdrawing groups increase acidity.

Answer 1

The Correct Option is D

Concept:
Acidity of phenols depends on the stability of the phenoxide ion formed after loss of proton. Electron-withdrawing groups increase acidity by stabilising phenoxide ion. Electron-releasing groups decrease acidity by destabilising phenoxide ion. The methyl group \((-CH_3)\) is electron releasing.

Step 1: Compare phenol and 4-methylphenol.
Phenol forms phenoxide ion: \[ C_6H_5OH \rightarrow C_6H_5O^-+H^+ \] 4-methylphenol has a methyl group at para position. \[ CH_3-\text{group} \Rightarrow \text{electron releasing group} \] The methyl group increases electron density on the ring and destabilises the phenoxide ion. So 4-methylphenol is less acidic than phenol. Phenol is more acidic than 4-methylphenol Therefore, the Assertion is false.

Step 2: Check the Reason.
The reason says that electron releasing group makes phenol less acidic. The principle is correct: electron releasing groups reduce acidity of phenol derivatives. So Reason is considered true in concept.

Step 3: Final conclusion.
Assertion is false, but Reason is true. Hence: \[ \boxed{\text{(D)}} \]