Explain ortho and para directing group influencing in benzene.

Explanation

Ortho and para direacting groups: the groups which direct the incoming groups to ortho and para positions are called ortho and pam directing groups.
Examples: - OH, - OR, -`NH_(2), `- NHR, - `NR_(2)`, - R, - X
Let use discuss the directive influence of - OH group in phenol.
Bacause of resonance effect, electron increases at ortho para positions in the benzene ring. Due to - I effect of the OH group, electron density of benzene ring decreases. However, + R effect is stronger than - I effect which activates the benzene ring for electrophilic substitution. these groups are called activating groups which result in ortho and para substitution products.
in the case of aryl halides, halogens are deactivating because - I effect is stronger than +R effect. Hence, overall electron denstiy of the benzene ring decreases. Hence, in aryl halides, though substitution takes lace in ortho and para positions, the ring is deactivated.