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The energy changes in electrophilic aromatic substitution
Higher energy in first step Lower energy in second step
endothermic (slow step) Exothermic (fast step)
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Br
-Most commonly bromination or chlorination. Br2 / FeBr3
-Lewis acid (e.g. FeCl3 or FeBr3) is required
stronger electrophile. to make the halogen a
Mechanism:
Bromonium
Electrophile
• Bromine reacts with ferric bromide to generate a bromonium ion
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