(a) When the reaction is carried out in solvents of low polarity
such as CHCl3 or CS2 and at low temperature,
monobromophenols are formed The usual halogenation of benzene takes place in the
presence of a Lewis acid, such as FeBr3 (Unit 6, Class XII),
which polarises the halogen molecule In case of phenol, the
polarisation of bromine molecule takes place even in the
absence of Lewis acid It is due to the highly activating
effect of –OH group attached to the benzene ring