32.2.5—Phenol nitration and bromination conditions

The –OH group donates electron density into the ring, activating phenol towards electrophilic substitution. Therefore phenol brominates readily with bromine water and nitrates under milder conditions than benzene.

Activation changes both rate and product distribution. It does not mean the ring has lost aromaticity; the substitution mechanism still restores it.

Phenol reacts with bromine water at room temperature to give 2,4,6-tribromophenol, whereas benzene normally requires a Lewis-acid catalyst for bromination.

Do not apply benzene’s catalyst and temperature requirements automatically to phenol; the hydroxyl substituent changes the ring’s electron density.