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Chapter 12: Reactions of Arenes. Electrophilic Aromatic Substitution



Summary | Overview | Nitration | Sulfonation | Halogenation | Friedel-Crafts Alkylation | Friedel-Crafts Acylation | Substituent Effects | Making Polysubstituted Benzenes | Polyaromatics | Heterocycles | Self Assessment | Quiz |


Halogenation

Chapter 12 : Reactions of Arenes. Electrophilic Aromatic Substitution

 

Halogenation of Benzene

halogenation of arenes
Reaction type: Electrophilic Aromatic Substitution

Summary.

MECHANISM FOR HALOGENATION OF BENZENE
Step 1:
The bromine reacts with the Lewis acid to form a complex that makes the bromine more electrophilic.
bromination of benzene
Step 2:
The p electrons of the aromatic C=C act as a nucleophile, attacking the electrophilic Br, and displacing iron tetrabromide. This step destroys the aromaticity giving the cyclohexadienyl cation intermediate.
Step 3:
Removal of the proton from the sp3 C bearing the bromo- group reforms the C=C and the aromatic system, generating HBr and regenerating the active catalyst.


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