Electrophilic substitution — Friedel–Crafts acylation
Carbonyl & aromatic chemistry · ethanoyl chloride + AlCl₃ (catalyst) · heat under reflux, anhydrous
Reagents: ethanoyl chloride + AlCl₃ (catalyst) · Conditions: heat under reflux, anhydrous
Step 1 of 2
- 1.Two electrons from the delocalised π ring attack the positively charged carbon of the acylium ion, forming a new C–C bond.
AlCl₃ removes a chloride from ethanoyl chloride: CH₃COCl + AlCl₃ → CH₃CO⁺ + AlCl₄⁻. The acylium ion CH₃CO⁺ is the electrophile.
The ring bonds to the acylium carbon, breaking aromaticity: the horseshoe (Wheland) intermediate.
Step 2 of 2
- 1.The C–H bonding pair moves back into the ring, restoring aromaticity and releasing H⁺.
The H⁺ lost from the ring reacts with AlCl₄⁻: H⁺ + AlCl₄⁻ → AlCl₃ + HCl, regenerating the catalyst.
Aromaticity is restored and H⁺ is lost (regenerating AlCl₃): phenylethanone forms.
Product: phenylethanone
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