How does the presence of electron withdrawing group like nitro group on the Ortho and para position in a phenol increases its acidity
Dear Student,
Phenol acidity, is determined by the release of proton from the hydroxyl group of phenol leaving behind the phenoxide ion. The acidity of phenol depends upon the stability of phenoxide ion. As the phenoxide ion is stable, phenol will be more acidic.
The substituents attached to the phenol will account a role player in deciding the acidity of phenol.
As, on the release of proton, phenoxide ion is formed, which is stabilized by the resonance from the benzene ring.
Now if the electron density of this ring is decreased the stability of phenoxide ion increases.
Thus the electron density of benzene ring is decreased by the attached substitutents at ortho and para position.
NO2 , nitro group acts as a electron with drawing group, withdraws the electron density from the phenol ring which stabilizes the phenoxide ion and also decreases the electron density due to -M mesomeric effect of the nitro group.
As stable is the conjugate phenoxide ion is, more acidic will be the nitrosubstituted phenol.
Regards.
Dear Student,
Phenol acidity, is determined by the release of proton from the hydroxyl group of phenol leaving behind the phenoxide ion. The acidity of phenol depends upon the stability of phenoxide ion. As the phenoxide ion is stable, phenol will be more acidic.
The substituents attached to the phenol will account a role player in deciding the acidity of phenol.
As, on the release of proton, phenoxide ion is formed, which is stabilized by the resonance from the benzene ring.
Now if the electron density of this ring is decreased the stability of phenoxide ion increases.
Thus the electron density of benzene ring is decreased by the attached substitutents at ortho and para position.
NO2 , nitro group acts as a electron with drawing group, withdraws the electron density from the phenol ring which stabilizes the phenoxide ion and also decreases the electron density due to -M mesomeric effect of the nitro group.
As stable is the conjugate phenoxide ion is, more acidic will be the nitrosubstituted phenol.
Regards.
