Question

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

• 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-withdrawing groups increase phenol acidity. Order: Nitro phenol>Phenol>Alkyl phenol

Answer 1

The Correct Option is A

To determine the correct answer for the given assertion and reason, let's analyze both the assertion (A) and the reason (R) provided:

1. Assertion (A): p-nitrophenol is more acidic than phenol.
   • p-nitrophenol is indeed more acidic than phenol. This is because the presence of the nitro group (-NO₂) at the para position significantly increases the acidity of the phenol.
2. Reason (R): Nitro group is an electron-withdrawing group; it stabilizes phenoxide ion by dispersal of negative charge.
   • The nitro group is a powerful electron-withdrawing group due to its resonance and inductive effects. It draws electron density away from the oxygen in the phenoxide ion.
   • This electron-withdrawing effect increases the stability of the negative charge on the oxygen atom once the hydrogen ion is removed, making the compound more acidic.

Based on the analysis:

• Assertion (A) is true. The presence of the electron-withdrawing nitro group at the para position increases the acidity of p-nitrophenol compared to phenol.
• Reason (R) is true. The nitro group's ability to stabilize the phenoxide ion through dispersal of negative charge is a valid explanation for the increased acidity.
• Reason (R) correctly explains Assertion (A). The increased acidity of p-nitrophenol is directly due to the electron-withdrawing effect of the nitro group, which stabilizes the phenoxide ion.

Therefore, the correct answer is: Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).