Reaction equation for 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

Reagents

Reagents involved in Friedel-Crafts acylation: benzene + acetyl chloride → acetophenone, grouped by role.
Reagent	Role	Equiv	MW	ρ
71-43-2 71-43-2 · C6H6 Benzene — slight excess; suppresses polyacylation (already kinetically disfavoured by ring deactivation, but excess locks this in). Carcinogen — strict hood discipline.	reactant	1.05	78.11	0.880
Acetyl Chloride 75-36-5 · C2H3ClO Acetyl chloride — limiting reagent. Moisture-sensitive (hydrolyses to acetic acid + HCl); transfer by syringe under N2. Stench is characteristic — work in a hood.	reactant	1.0	78.50	1.110
Aluminium Chloride 7446-70-0 · AlCl3 Aluminum chloride (anhydrous) — Lewis acid. Listed at 1.1 equiv rather than catalytic because the ketone product complexes the AlCl3 1:1; stoichiometric load is needed to keep free AlCl3 available for the next turnover. Aqueous workup decomposes the complex.	catalyst	1.1	133.34	2.480
Dichloromethane 75-09-2 · CH2Cl2 Dichloromethane — anhydrous. Chlorobenzene (108-90-7) and carbon disulfide (also classic) are alternatives but DCM is the modern bench standard. Excludes water — AlCl3 reacts violently with H2O.	solvent	—	84.93	1.330
Acetophenone 98-86-2 · C8H8O Acetophenone — colourless liquid, bp 202 °C; sweet almond/hawthorn-like odour. Used industrially as a fragrance ingredient and pharmaceutical intermediate (e.g. ephedrine synthesis).	product	1.0	120.15	1.030

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