What are the factors that affect the acidity of phenols?

Acidity in phenols occurs because of their ability to lose hydrogen ions to generate phenoxide ions. The acidity of phenols increases based on several factors. One factor is the presence of the electron-withdrawing group, which increases the acidity of phenols. This happens because of the stability of the phenoxide ion created. The sp2 hybridized carbon atom of the benzene ring of phenol attaches directly to the hydroxyl group, acting as an electron withdrawing group. Because of higher electronegativity of the carbon atom compared to the hydroxyl group, electron density decreases on the oxygen molecule. The decrease in electron density increases polarity of O-H bonds and thus causes an increase in ionization of phenols. Acidity of phenols can increase even more if the groups are attached at para and ortho sites. This is because the negative charge in the phenoxide ion is primarily delocalized at the para and ortho sites of the benzene ring. In contrast, the acidity of phenols decreases when electron-donating groups are present as they inhibit the generation of phenoxide ions.