BIOL373L Lecture Notes - Lecture 8: Electrophilic Aromatic Substitution, Aromaticity, Electrophile
12 Mar 2021
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Reactions of aromatic compounds 1: reactions of aromatic compounds. Textbook chapter: 21. 1 to 21. 5, 21. 8 and 21. 9. All pictures reproduced with the permission of top hat. Because benzene is resonance stabilized it is not as reactive as other alkenes. In electrophilic aromatic substitution an electrophile is substituted for one of the hydrogen atoms on the aromatic ring. The key step is the generation of a very reactive electrophile. The mechanism of all eas reactions are addition reactions to produce an intermediate followed by elimination. A lewis acid catalyst (febr3) is needed to enhance the electrophilicity of a br atom in its reaction with benzene. The lewis acid catalyst and br2 form a complex, which serves as the electrophilic agent. Chlorination can also be achieved by the use of cl2 and a suitable lewis acid catalyst to form chlorobenzene. Fluorination is extremely violent and is difficult to control. Iodination is a rather slow process and occurs with relatively poor yields.
