Electrophilic substitution reaction

Electrphilic substitution reaction occurs on the aromatic ring as in this substitution reaction an electrophile (Electron loving species) gets substituted. Electrophile would join on the carbon atom which is having heigher electron density and on the aromatic ring due to delocalization of pi electrons the electron density is hegher. Thus SE reaction occurs on aromatic ring.

The general mechanism of SE reactions is as follows

The important electrophile reaction that are occuring on the benzene ring are 

1)  CHLORINATION REACTION (Halogenation): Chlorinium ion (Cl +) is the active reagent formed by reaction

      of Chlorine gas and a halogrn carrier ferric chloride or anhydrous Aluminum Chloride. The resonating

      forms world be same as above.

2)   NITRATION REACTION: Nitronium ion (NO2 +) is the active reagent formed by reaction of nitrating

      mixture (Conc. Nitric Acid + Conc. Sulohuric Acid). The resonating forms world be same as above.

3)  SULPHONATION REACTION : Sulphonium ion (SO3H +) is tha active reagent wich is formed by the

     dissociation of conc. sulphuric acid. The resonating forms world be same as above.