Question

Ortho and para nitrophenols are more acidic than phenol. Draw the resonance structures of the corresponding phenoxide ions.

Answer 1

    Resonance structures of o-nitrophenoxide ion

    Resonance structures of p-nitrophenoxide ion

    Resonance structures of phenoxide ion

In substituted phenols, electron withdrawing groups such as nitro group increase the acidic strength of phenol. This effect becomes more potent when such groups are present at ortho and para positions. This is because of the effective delocalisation of the anion of the phenoxide ion. Hence, o- and p-nitrophenols are more acidic than phenol.