Sulphonation of the benzene in organic chemistry is one of the best examples of the electrophilic substitution reaction. In the process of the sulphonation what happens is that we will add the sulphur trioxide to the benzene ring, here the sulphur trioxide is the electrophile which will further bring about the electrophilic substitution reaction. Then the sulphur trioxide gets added to the benzene ring and will lead to the substitution and further the formation of the product called  the benzene sulphonic acid.