Question

Assertion (A): p-nitrophenol is less acidic than phenol.
Reason (R): Nitro group is an electron-withdrawing group, which stabilises the phenoxide ion.

• 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:

Electron Withdrawing Groups (EWGs) like $-NO_2$ INCREASE acidity. Electron Donating Groups (EDGs) like $-CH_3$ DECREASE acidity.

Answer 1

The Correct Option is D

Step 1: Evaluate the reason first.
The nitro group ($-NO_2$) is indeed a strong electron-withdrawing group, exerting both $-I$ (inductive) and $-M$ (mesomeric) effects. At the para position it efficiently withdraws electron density from the oxygen of the phenoxide ion through the ring, dispersing the negative charge and stabilising it. The reason is true.
Step 2: Determine the effect on acidity.
A more stable conjugate base (p-nitrophenoxide ion) means the equilibrium for proton donation lies further to the right. Therefore, p-nitrophenol is a stronger acid than phenol, not a weaker one.
Step 3: Evaluate the assertion.
The assertion claims p-nitrophenol is less acidic than phenol. Since p-nitrophenol is actually more acidic (its $K_a$ is larger), the assertion is false.
Step 4: Conclusion.
Assertion is false; Reason is true and correctly explains the stabilisation of the phenoxide ion.
\[ \boxed{\text{A is false, R is true}} \]