1. Examples of Carbocation Formation
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2. Formation of Alkyl Benzene
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3. Limitations of Friedel-Crafts
Reaction fails if benzene has a substituent that is more deactivating than halogen.
Carbocations rearrange. Reaction of benzene with n-propyl chloride and AlCl3 produces isopropylbenzene.
The alkylbenzene product is more reactive than benzene, so polyalkylation occurs =>

4. Friedel-Crafts Acylation
Acyl chloride is used in place of alkyl chloride.
The acylium ion intermediate is resonance stabilized and does not rearrange like a carbocation.
The product is a phenyl ketone that is less reactive than benzene =>

5. Mechanism of Acylation
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6. Clemmensen Reduction
Acylbenzenes can be converted to alkylbenzenes by treatment with aqueous HCl and amalgamated zinc.
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7. Gatterman-Koch Formylation
Formyl chloride is unstable. Use a high pressure mixture of CO, HCl, and catalyst.
Product is benzaldehyde.
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8. Nucleophilic Aromatic Substitution
A nucleophile replaces a leaving group on the aromatic ring.
Electron-withdrawing substituents activate the ring for nucleophilic substitution =>

9. Examples of Nucleophilic Substitution
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10. Addition-Elimination Mechanism
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