Question

Statement I: The acidic strength of monosubstituted nitrophenol is higher than phenol because of electron withdrawing nitro group.
Statement II: o-nitrophenol, m-nitrophenol and p-nitrophenol will have same acidic strength as they have one nitro group attached to the phenolic ring.
Choose the most appropriate answer from the options given below:

• A. Both Statement I and Statement II are correct.
• B. Both Statement I and Statement II are incorrect.
• C. Statement I is correct but Statement II is incorrect.
• D. Statement I is incorrect but Statement II is correct.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The acidic strength of phenols depends on the stability of the phenoxide ion formed after the release of a proton (\(H^+\)).
Electron Withdrawing Groups (EWG) stabilize the phenoxide ion by dispersing the negative charge, thereby increasing acidity.
Step 2: Detailed Explanation:
Analysis of Statement I:
The nitro group (\(-NO_2\)) is a very strong electron-withdrawing group due to both the inductive effect (\(-I\)) and the resonance effect (\(-R\)).
When a nitro group is attached to the benzene ring of phenol, it pulls electron density away from the phenoxide oxygen, stabilizing the ion.
Thus, any monosubstituted nitrophenol is more acidic than pure phenol. Statement I is correct.

Analysis of Statement II:
While all three have one nitro group, its position (ortho, meta, or para) significantly changes the acidic strength:
1. In para-nitrophenol, the \(-NO_2\) group exerts both \(-I\) and \(-R\) effects strongly, providing maximum stabilization.
2. In ortho-nitrophenol, there is similar stabilization, but intramolecular hydrogen bonding between \(-OH\) and \(-NO_2\) makes it slightly harder to release the proton compared to the para isomer.
3. In meta-nitrophenol, the resonance effect (\(-R\)) does not operate at the meta position. Only the weaker \(-I\) effect acts.
The order of acidity is: para > ortho > meta > phenol.
Since they have different strengths, Statement II is incorrect.
Step 3: Final Answer:
Statement I is correct and Statement II is incorrect.