Explain the resistance to bromination of benzene in comparison to phenol.
In phenol, one of the lone pairs of electrons in a p-orbital of the oxygen atom in the -OH group overlaps with the delocalised ring of electrons in the ring. This lone pair is partially delocalised into the pi-system in the benzene ring. This increases electron density of the ring, meaning it is able to induce a dipole in Br2 and so can undergo electrophilic substitution. In benzene, the electrons are delocalised which means the negative charge is spread out through the ring causing benzene to have a lower electron density and so can't induce a dipole in Br2.
