- When mono substituted benzene undergoes an electrophilic substitution reaction, the rate of the reaction and the site of attack of the incoming electrophile depends on the functional group already attached to it.
- Some groups increases the reactivity of benzene ring and are known as activating groups.
- Some groups decreases the reactivity of benzene ring and are known as de-activating groups.
- Example:
Activating groups: – NH2 – OH. – CH3 etc.
Deactivating groups: – NO3 . CN, – CHO etc,