Electrophilic subsitution is the process of introducing a group to an electron dense benzene ring. In a nitration reaction, the electrophile NO2+ is being attracted to the electron dense benzene ring which substitutes hydrogen atom(s) bonded the carbons on benzene.
This reaction allows us to synthesise a nitrobenzene from benene which could be useful for explosives or to further synthesis phenylamines by reduction.
Friedal Crafts acylation is the electrophilic substitution of an acyl group onto a benzene ring. The electrophile required must be generated with the reaction of an acyl chloride with an aluminium chloride catalyst.