Advanced Topic 784 of 1102 Organic Chemistry
Friedel-Crafts Reactions
Alkylation or acylation of arenes catalyzed by Lewis acids such as AlCl3.
In-depth explanation of Friedel-Crafts Reactions
Friedel-Crafts reactions attach carbon groups to an aromatic ring using a Lewis acid catalyst such as aluminium chloride. In alkylation, an alkyl halide generates a carbocation that substitutes onto the ring, but the new alkyl group activates the ring, so polyalkylation and carbocation rearrangements can occur. In acylation, an acyl chloride forms a resonance-stabilized acylium ion that does not rearrange, and the ketone product deactivates the ring against a second substitution. The reactions fail on strongly deactivated rings such as those bearing nitro groups.
Going deeper: Friedel-Crafts Reactions
Key ideas: Alkylation (RCl with AlCl3) and acylation (RCOCl with AlCl3). Limitations of alkylation: carbocation rearrangement, polyalkylation because the product is more reactive, and failure on deactivated rings (nitrobenzene) or rings with -NH2. Acylation gives ketones with no rearrangement or overreaction, and the ketone can be reduced by Clemmensen (Zn-Hg and HCl) to the straight-chain alkyl.
Common mistakes and connections: Students predict n-propylbenzene from 1-chloropropane; the product is isopropylbenzene by hydride shift. Another error is expecting acylation to work on deactivated rings. Links to carbocation rearrangement, directing effects and synthesis planning with acylation then reduction.
Visualization of Friedel-Crafts Reactions
AlCl3 generates a carbocation or acylium ion that attacks the benzene ring, attaching an alkyl or acyl group to the aromatic carbon. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Benzene reacts with acetyl chloride in the presence of aluminium chloride to give acetophenone, a ketone.
Frequently asked questions about Friedel-Crafts Reactions
What is Friedel-Crafts Reactions?
Alkylation or acylation of arenes catalyzed by Lewis acids such as AlCl3.
Is Friedel-Crafts Reactions a beginner, intermediate or advanced topic?
Friedel-Crafts Reactions is a advanced topic in Organic Chemistry. It builds on beginner and intermediate topics, so review those first if needed.
What should I learn before Friedel-Crafts Reactions?
Study these earlier topics in Organic Chemistry first: Polymerization of Alkenes, Electrophilic Aromatic Substitution, Nitration of Benzene.
What comes after Friedel-Crafts Reactions?
The next topics in Organic Chemistry are Directing Effects and Haloalkanes.
Can I practise Friedel-Crafts Reactions with quizzes?
Yes. The interactive lesson includes a self-check question on Friedel-Crafts Reactions, and the Organic Chemistry quiz draws on every topic in this area.
Where Friedel-Crafts Reactions fits in Organic Chemistry
Friedel-Crafts Reactions is topic 56 of 148 in Organic Chemistry.