Illustrated Glossary of Organic Chemistry

Halogen-metal exchange: A reaction or reaction mechanism step in which a bond between a halogen atom and another atom (often a carbon) is changed into a bond between a metal atom and another atom.

Generalized halogen-metal exchange. X is a halogen atom (Cl, Br, or I; rarely F).

-butyl magnesium bromide, a Grignard reagent, can be prepared by halogen-metal exchange. When Mg is added to tert-butyl bromide, the carbon-bromine bond is exchanged for a carbon-magnesium bond.

Phenyllithium can be prepared by a halogen-metal exchange reaction starting with tert-butyllithium and iodobenzene.