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NEET CHEMISTRYMedium

Given below are two statements: 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.

In the light of the above statements, choose the most appropriate answer from the options given below:

A

Statement I is incorrect but Statement II is correct.

B

Both Statement I and Statement II are correct.

C

Both Statement I and Statement II are incorrect.

D

Statement I is correct but Statement II is incorrect.

Step-by-Step Solution

  1. Statement I is Correct: The nitro group (−NO2-NO_2) is an electron-withdrawing group (EWG) exhibiting both −I-I (inductive) and −R-R (resonance) effects. When present on the phenol ring, it withdraws electron density, thereby stabilizing the phenoxide ion formed after the loss of a proton. Consequently, all monosubstituted nitrophenols are stronger acids than unsubstituted phenol.
  2. Statement II is Incorrect: The acidic strength depends heavily on the position of the substituent. The resonance effect (−R-R) of the nitro group allows for the effective delocalization of the negative charge on the phenoxide ion only when the group is at the ortho or para position. At the meta position, only the weaker inductive effect (−I-I) operates. Therefore, the acidic strength varies in the order: pp-nitrophenol > oo-nitrophenol > mm-nitrophenol. They do not have the same acidic strength.
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