Friedel–Crafts Alkylation: Installing Alkyl Groups on Aromatic Rings

Learn Friedel–Crafts alkylation step-by-step: electrophile activation, sigma complex, and deprotonation. Master rearrangements, polyalkylation, and why it fails on deactivated rings.

• Electrophile generation: R–Cl + AlCl3 → stronger electrophile (carbocation-like)
• Core mechanism: EAS sigma complex formation → deprotonation
• Major pitfalls: Carbocation rearrangements; polyalkylation; fails on strongly deactivated rings
• Comparison: Acylation avoids rearrangement and polyalkylation (usually)
• Exam type: Predict the major product
• Exam type: Failure modes / distractors
• Exam type: Choose conditions