The –OH group
attached to the benzene ring activates it towards electrophilic
substitution Also, it directs the incoming group to ortho and para
positions in the ring as these positions become electron rich due to
the resonance effect caused by –OH group The resonance structures
are shown under acidity of phenols Common electrophilic aromatic substitution reactions taking place
in phenol are as follows:
(i) Nitration: With dilute nitric acid at low temperature (298 K),
phenol yields a mixture of ortho and para nitrophenols