Explain how does -OH group attached to a carbon of benzene ring Activates it towards electrophilic substitution .

Explanation

Phenol can be regarded as a resonance hybride of the following structures .

Due to + R effect of the -OH group the electron density in the benzene ring increases This facilitates the attack of electrophilie on the ring . In other words ,presence of - OH group , attached to carbon of benzene ring activates the benzene ring towards electrophilic substitutions . Further since the electron density is relatively higher at the two o and p and one p- position , therefore electrophilic substitution occur mainly at o and p positions .