Examples of Carbocation Formation =>

Formation of Alkyl Benzene => + -

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. =>

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. =>

Mechanism of Acylation =>

Clemmensen Reduction Acylbenzenes can be converted to alkylbenzenes by treatment with aqueous HCl and amalgamated zinc. =>

Gatterman-Koch Formylation Formyl chloride is unstable. Use a high pressure mixture of CO, HCl, and catalyst. Product is benzaldehyde. =>

Nucleophilic Aromatic Substitution A nucleophile replaces a leaving group on the aromatic ring. Electron-withdrawing substituents activate the ring for nucleophilic substitution. =>

Examples of Nucleophilic Substitution =>

Addition-Elimination Mechanism =>