Examples of Carbocation Formation

1. => Examples ofCarbocation Formation

2. - + => Formation of Alkyl Benzene

3. Limitations ofFriedel-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-CraftsAcylation 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

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

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

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

9. Examples ofNucleophilic Substitution =>

10. => Addition-EliminationMechanism