Aromatic compounds tend to undergo electrophilic aromatic substitutions rather than addition reactions. Substitution of a new group for a hydrogen atom takes place via a resonance-stabilized carbocation. As the benzene ring is quite electron-rich, it almost always behaves as a nucleophile in a reaction which means the substitution on benzene occurs by the addition of an electrophile. Substituted benzenes tend to react at predictable positions. Alkyl groups and other electron-donating substituents enhance substitution and direct it toward the ortho and para positions. Electron-withdrawing substituents slow the substitution and direct it toward the meta positions.
Aromatic compounds also undergo …show more content…
The second step in the formation of 4-bromoaniline, involved reacting the acetanilide with bromine in acidic conditions to produce N-(4-bromophenyl) ethanamide or p-bromoactetanilie. Acetanilide is a para-directing group and so an incoming electrophilic attack on the para position will yield p-bromoacetanilide. The reaction occurred via the following electrophilic substitution mechanism: An electron pair from the benzene ring attacks the Br2 forming a new C-Br bond and leaving a non-aromatic carbocation intermediate. The carbocation intermediate loses H+, and the neutral substitution product forms as two electrons from the C-H