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Question: which is more acidic onitrophenol meta or para...

which is more acidic onitrophenol meta or para

A

o-nitrophenol

B

m-nitrophenol

C

p-nitrophenol

Answer

Para-nitrophenol

Explanation

Solution

The acidity of nitrophenols is determined by the stability of their conjugate base (phenoxide ion). The nitro group (-NO₂) is a strong electron-withdrawing group (-M and -I effects).

  1. Para-nitrophenol: Strong -M effect at the para position effectively delocalizes the negative charge on the phenoxide oxygen, leading to significant stabilization and highest acidity.

  2. Ortho-nitrophenol: While it has strong -M and -I effects, intramolecular hydrogen bonding stabilizes the neutral molecule, making proton removal harder and reducing its acidity compared to para.

  3. Meta-nitrophenol: Only the -I effect is significant at the meta position; the -M effect does not directly stabilize the phenoxide charge. This results in the least stabilization among the three isomers.

Thus, the order of acidity is Para-nitrophenol > Ortho-nitrophenol > Meta-nitrophenol.