: 210
The -OH group activates the benzene ring through +M effect (resonance donation > -I withdrawal), directing electrophiles to ortho and para positions.
Bromination: Phenol + Br2(aq) -> 2,4,6-tribromophenol (white precipitate, no catalyst needed). For monosubstitution, use Br2/CS2 at low temperature -> p-bromophenol. Nitration: dilute HNO3 gives o- and p-nitrophenol mixture; concentrated HNO3/H2SO4 gives picric acid (2,4,6-trinitrophenol). Friedel-Crafts fails directly on phenol (-OH coordinates to AlCl3).
Anisole (C6H5OCH3) has similar activating +M effect but FC reactions work because -OCH3 doesn't complex strongly with AlCl3. FC acylation gives mainly p-methoxyacetophenone. This phenol-vs-anisole FC reactivity difference is a classic JEE comparison question.
For electrophilic substitution reactivity: phenol > anisole > toluene > benzene > chlorobenzene > nitrobenzene. Phenol is the most activated because -OH is a stronger +M group than -OCH3.