When phenol is heated with a solution of mixture of KBr and KBrO₃. The major product formed is

WHen KBr is added to KBrO₃ , Br₂ is formed by a red ox reaction. 

$5 {\mathrm{Br}}^{=}+\hspace{0.17em}{\mathrm{BrO}}_3^{-}+\hspace{0.17em}6{\mathrm{H}}^{+}\stackrel{ }{\to }3{\mathrm{Br}}_2+3{\mathrm{H}}_2\mathrm{O}$

In the reaction mixture Br₂/H₂O reacts with phenol to form tribromophenol.