Introducing an acyl group
During Friedel–Crafts acylation, benzene undergoes electrophilic substitution and gains an acyl substituent in place of a ring hydrogen. For the acyl chlorides considered here, this substituent contains a carbonyl group bonded to an alkyl group.
Benzene reacts with an acyl chloride, , using anhydrous aluminium chloride, . Changing the alkyl group in the acyl chloride changes the acyl group introduced onto the aromatic ring.
| Feature | Friedel–Crafts acylation |
|---|---|
| Organic reagent | Acyl chloride, |
| Catalyst | Anhydrous |
| Conditions | Heat under reflux, about |
| Electrophile | Acylium ion, |
| Reaction type | Electrophilic substitution |
Example: ethanoylation of benzene
With ethanoyl chloride as the acyl chloride, one ring hydrogen is replaced by an ethanoyl group. The products are phenylethanone and hydrogen chloride.
Ethanoyl chloride
Phenylethanone
The product contains a carbonyl-containing side group on the aromatic ring. This makes Friedel–Crafts acylation an important way of building molecules during organic synthesis.