Assertion (A): p-nitrophenol is less acidic than phenol.
Reason (R): Nitro group is an electron-withdrawing group, which stabilises the phenoxide ion.
Reason (R): Nitro group is an electron-withdrawing group, which stabilises the phenoxide ion.
Show Hint
- Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
- Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
- Assertion (A) is true, but Reason (R) is false.
- Assertion (A) is false, but Reason (R) is true.
The Correct Option is D
Solution and Explanation
The acidity of a phenol derivative depends heavily on the stability of its conjugate base, the phenoxide ion.
Step 2: Meaning
Any substituent that stabilizes the phenoxide ion (by dispersing its negative charge) will increase the acidity of the parent compound.
Step 3: Analysis
The nitro group ($-NO_2$) is a powerful electron-withdrawing group (EWG) due to its -I (inductive) and -R (resonance) effects. When attached at the para position, it efficiently withdraws electron density and highly stabilizes the resulting p-nitrophenoxide ion. Thus, p-nitrophenol is significantly more acidic than phenol.
Step 4: Conclusion
The assertion claims p-nitrophenol is less acidic, which is false. The reason correctly identifies the nitro group as an EWG that stabilizes the phenoxide ion, which is a true statement.
Final Answer: (D)
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