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Friedel-Crafts acylation: benzene + acetyl chloride → acetophenone
PhH + CH3–C(=O)–Cl → Ph–C(=O)–CH3 + HCl
Textbook electrophilic aromatic substitution via the AlCl3-generated acylium ion. The product ketone (acetophenone) deactivates the ring toward further acylation, so unlike F-C alkylation, monoacylation is clean — no polyacylation problem. AlCl3 is used at 1.1 equiv (not catalytic) because it complexes the product 1:1; aqueous acidic workup decomposes the complex to free the ketone.
Conditions: Suspend AlCl3 (1.1 equiv) in dry CH2Cl2 (~3 mL per mmol acetyl chloride) under N2. Cool to 0 °C; add acetyl chloride (1.0 equiv, slowly via syringe — exotherm!). The mixture turns yellow-brown as the AlCl3-AcCl complex forms. Add benzene (1.05 equiv, slight excess) dropwise over 10 min keeping T < 5 °C. Warm to RT; stir 1–4 h until HCl evolution ceases. Workup — Cautiously pour onto crushed ice; separate organic; wash with sat. NaHCO3 (decomposes residual AlCl3 complex), water, brine; dry MgSO4; concentrate. Distil at reduced pressure (bp 202 °C at 760 mmHg, or ~80 °C at 10 mmHg). Pure acetophenone is a colourless liquid with a sweet almond-like odour.
- Expected yield
- 72–88 %
- Expected duration
- 1–4 h at RT after 0 °C addition; HCl evolution is the endpoint signal
Computed quantities
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