Question

What is meant by activating or deactivating a benzene ring?

Answer 1

Increasing the electron density in benzene ring is called as ring activation.

If you substitute the H by Electron Donating Group (EDG) (eg. -OH) in the benzene ring then the ring will activated.

Here “activation” means, activation of benzene ring towards the attack of electrophiles.

Rate of electrophilic aromatic substitution will be fast on activated ring(benzene ring).

Similarly, deactivation means decreasing electron density in benzene ring. Deactivated ring will be less reactive towards attack of electrophiles. If you substitute H atom by Electron Withdrawing Group(EWG)( eg. -NO2) the ring will be deactivated.