Electrophilic Aromatic Substitution

This chapter is organized based on the nature of the electrophile and then subdivided by the type of products obtained from the substitution. It covers reaction of nitrogen electrophiles, sulfur electrophiles, halogenation, and carbon electrophiles. A feature of nitrogen electrophilic reaction is that it directly functionalizes an arene C-H bond, and the reagent used, nitric acid, is inexpensive. Another advantage of the nitration reaction is that the active nitrating species, the nitronium ion, is very reactive, and the reaction typically stops after a single nitration due to the deactivating effect of a nitro substituent. While the sulfonation reaction is not utilized as often as the chlorosulfonation, this transformation allows for the direct formation of a sulfonic acid. Sulfonation is conducted in fuming sulfuric acid, a highly corrosive reagent. Electrophilic fluorination of arenes is not a very common reaction. Several of the reagents used for electrophilic fluorination are not practical or present safety concerns for scaling.