The acidity of phenols is due to its ability to lose hydrogen ion to form phenoxide ions. In a phenol molecule, the sp2hybridised carbon atom of benzene ring attached directly to the hydroxyl group acts as an electron withdrawing group. This sp2 hybridized carbon atom of benzene ring attached directly to the hydroxyl group has higher electronegativity in comparison to hydroxyl group. Due to the higher electronegativity of this carbon atom in comparison to the hydroxyl group attached, electron density decreases on oxygen atom. The decrease in electron density increases the polarity of O-H bond and results in the increase in ionization of phenols. Thus, the phenoxide ion is formed. The phenoxide ion formed is stabilized by the delocalization of negative charge due to the resonance in benzene ring. Phenoxide ion has greater stability than phenols, as in case of phenol charge separation takes place during resonance.The resonance structures of phenoxide ions explain the delocalization of negative charge. In case of substituted phenols, acidity of phenols increases in the presence of electron withdrawing group. This is due to the stability of the phenoxide ion generated. The acidity of phenols further increases if these groups are attached at ortho and para positions. This is due to the fact that the negative charge in phenoxide ion is mainly delocalized at ortho and para positions of the attached benzene ring. On the other hand, the acidity of phenols decreases in presence of electron donating groups as they prohibit the formation of phenoxide ion.

Resonance stabilization of phenol ions

The acidity of phenols is primarily due to the resonance stabilization of its ions. Let's break down this concept further:

Definition of phenols
- Phenols are a class of organic compounds that contain a hydroxyl group (-OH) attached to an aromatic ring.

Acidity of phenols
- Phenols are acidic in nature due to the presence of the hydroxyl group, which can donate a proton (H+) to form a phenoxide ion (phenolate ion).

Resonance stabilization
- The phenoxide ion formed after the donation of a proton can undergo resonance stabilization. This means that the negative charge on the oxygen atom can delocalize over the aromatic ring through resonance, leading to stability of the ion.

Effect on acidity
- The resonance stabilization of the phenoxide ion makes it more stable compared to other ionized forms of alcohols. This stability enhances the acidity of phenols as the removal of a proton is favored due to the stabilization provided by resonance.

Comparison with alcohols
- In alcohols, the negative charge on the oxygen atom after donating a proton is localized on the oxygen atom itself, leading to less stability compared to the delocalized charge in phenols.

In conclusion, the acidity of phenols is primarily attributed to the resonance stabilization of its ions, which enhances the stability of the phenoxide ion and promotes the donation of a proton, making phenols more acidic than alcohols.