 Chloroacetyl chloride

Chloroacetyl chloride is $\mathrm{ClC}{\mathrm{H}}_2\mathrm{COCl}$, an acyl chloride bearing an additional chlorine on the adjacent carbon. The two chlorine atoms occupy chemically different sites.

Nucleophiles can replace the acyl chloride leaving group to form chloroacetyl derivatives. The retained carbon-bound chlorine can then provide a separate site for substitution, illustrating functional-group differentiation within one molecule.