Phenol is heated with a solution of mixture of KBr and KBrO₃(acidic medium). The major product obtained in the reaction is

Br₂ is formed by a redox reaction.
$5{\mathrm{Br}}^{-}+{\mathrm{BrO}}_3^{-}+6{\mathrm{H}}^{+}\to 3{\mathrm{Br}}_2+3{\mathrm{H}}_2\mathrm{O}$
– OH group is the activating group and thus activates the benzene towards electrophilic substitution reaction at o- and p-positions giving yellowish white precipitate of 2, 4, 6-tribromophenol.