Acyl halide

Acyl halides have R–CO–X. Learn how to name acyl chlorides, understand their reactivity, and distinguish them from esters and anhydrides.

Functional group

R–CO–X (X = Cl, Br)

How to name it with IUPAC

Name the acyl group derived from the acid, then add “chloride” or “bromide”. CH₃COCl is ethanoyl chloride (acetyl chloride).

Properties and applications

The polar carbonyl and halide leaving group make acyl halides highly reactive. They are activated derivatives and must be handled with attention to moisture and corrosivity.

Characteristic reaction

They undergo nucleophilic acyl substitution: water gives a carboxylic acid, an alcohol gives an ester, and an amine gives an amide. HX is released, so a base is often used.

Examples

Methanoyl chloride (HCOCl) · Ethanoyl chloride (CH₃COCl) · Benzoyl chloride (C₆H₅COCl)

Do not confuse

Acyl halides have R–CO–X; simple organic halides have R–X without a carbonyl. The carbonyl defines the class and its high reactivity.

Visual connectivity example

R represents the rest of the chain; the highlighted group defines the function.

Build an acyl halide in the simulator →