Question

Assertion (A) : p-nitrophenol is more acidic than phenol.
Reason (R) : Nitro group is an electron-withdrawing group, it stabilises phenoxide ion by dispersal of negative charge.

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

Hint:

EWG increases acidity; ERG (Electron Releasing Group) decreases acidity in phenols.
The effect of EWG is most pronounced at ortho and para positions due to resonance.
Always look for charge dispersal to determine the stability of the conjugate base.

Answer 1

The Correct Option is A

Step 1: Check the Assertion on its own.
p-Nitrophenol loses a proton more easily than plain phenol because the nitro group at the para position pulls electron density away from the ring and the oxygen. A phenol that loses a proton more easily is the more acidic one, so the Assertion holds.
Step 2: Check the Reason on its own.
The nitro group is electron-withdrawing, and once the phenoxide ion forms, the negative charge on oxygen can spread onto the nitro group through resonance at the para position. Spreading out a negative charge always makes an ion more stable.
Step 3: Test whether the Reason actually explains the Assertion.
A more stable phenoxide ion is exactly what makes deprotonation easier, and easier deprotonation is what more acidic means. So the charge-dispersal explanation in the Reason is the direct cause of the higher acidity stated in the Assertion.
Step 4: State the final match.
Both statements are true, and the Reason correctly explains the Assertion.
\[ \boxed{\text{Both A and R true, R is the correct explanation of A}} \]