Aromatic chemistry

This chapter explores aromatic chemistry. It begins by looking at electrophilic aromatic substitution (SEAr), where a functional group on an aromatic ring, usually a proton, is replaced by an electrophile. In order to undergo reaction with the electrophile, the aromatic ring must be electron-rich. This is because the mechanism requires the cloud of electrons on the benzene ring to attack the electrophile; if the ring were electron-deficient, it would not be able to do this as readily. The mechanism proceeds via a carbocation intermediate, also known as the Wheland intermediate. The chapter then considers nucleophilic aromatic substitution (SNAr), where a group on an aromatic ring is replaced by a nucleophile. It also discusses azo coupling, which is when an aromatic diazonium-containing compound is joined to another aromatic compound.