Directive effect in mono substituted benzene derivatives:
The substituent previously present on the benzene ring directs the incoming substituent to inhabit ortho (2 or 6), meta (3 or 5) or para (4) point. This direction relays on the nature of the first substituent and is known as directive or the orientation effect.
The substituent previously available can increase or decrease the rate of additional substitution that is it either deactivates or activates the benzene ring in the direction of further substitution. These effects are termed as activity effects.