Alcohols, Phenols and Ethers - Acidic nature of phenol

Phenol ($C_6H_5OH$) is more acidic than alcohols but less acidic than carboxylic acids. Its acidic nature is demonstrated by its reaction with active metals (like $Na$) and aqueous $NaOH$ to form phenoxide salts.

The acidity of phenol is due to the formation of a stable phenoxide ion ($C_6H_5O^-$) after losing a proton. The negative charge on the oxygen atom is delocalized over the benzene ring through resonance, which stabilizes the ion.

In contrast, alcohols ($R-OH$) form alkoxide ions ($R-O^-$) upon losing a proton. Alkoxide ions are not resonance-stabilized, and the $+I$ effect of the alkyl group increases electron density on the oxygen, making the ion less stable.

The presence of Electron Withdrawing Groups (EWG) like $-NO_2$, $-CN$, or $-Cl$ at ortho and para positions increases the acidity of phenol by stabilizing the phenoxide ion through $-M$ and $-I$ effects.

The presence of Electron Donating Groups (EDG) like $-CH_3$ or $-OCH_3$ decreases the acidity of phenol because they increase the electron density on the oxygen atom, destabilizing the phenoxide ion through $+I$ and $+M$ effects.

Phenols do not react with sodium bicarbonate ($NaHCO_3$), unlike carboxylic acids, because they are weaker acids than carbonic acid ($H_2CO_3$).