Synthesis of benzene derivatives via electrophilic aromatic substitution

This section is on the general mechanism of how an electrophilic atom becomes a part of a benzene ring through the substitution of a hydrogen. Common reactions that proceed by electrophilic aromatic substitution include the nitration and sulfonation of benzene, hydration of benzene, Friedel-Crafts acylation and Friedel-Crafts alkylation.  The catalysts and co-reagents serve to generate the strong electrophilic species needed to effect the initial step of the substitution. The specific electrophile (E or E⁺) believed to function in each type of reaction is listed in the right hand column.