Explain Benzene ring effect. Also give common substituent groups and their effect on EAS, Electrophilic Aromatic Substitution.

Substituent groups on a benzene ring affect electrophilic aromatic substitution reactions in two ways:

Reactivity

•      activate  (faster than benzene)

•      or deactivate (slower than benzene)

Orientation

•     ortho- + para- direction

•     or meta- direction
  
  -CH₃

•     activates the benzene ring towards EAS
•     directs substitution to the ortho- & para- positions

             -NO₂

•     deactivates the benzene ring towards EAS
•     directs substitution to the meta- position

Common substituent groups and their effect on EAS: