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

(N/A) The acidity of phenols is determined by the stability of the corresponding phenoxide ion. The nitro group $(-NO_2)$ is a strong electron-withdrawing group ($-I$ and $-M$ effect). In ortho and para nitrophenols,the negative charge on the oxygen atom of the phenoxide ion is delocalized into the benzene ring and further stabilized by the electron-withdrawing nitro group at the ortho or para positions. This additional resonance stabilization makes the ortho and para nitrophenoxide ions significantly more stable than the phenoxide ion,thereby increasing the acidity of the parent phenols.