dehalogenated

Dehalogenated refers to a molecule from which halogen atoms have been removed. The halogens commonly involved are fluorine, chlorine, bromine, and iodine. Removal of halogens reduces the degree of halogenation and often leaves hydrogen in the substituted positions; additional functionalization may occur depending on the system.

Dehalogenation can occur by chemical, biological, or photochemical means. In synthesis, reductive dehalogenation or hydrodehalogenation employs catalysts and hydrogen donors to replace halogens with hydrogen, using metals like palladium, nickel, zinc, or iron under suitable conditions. In environmental contexts, organohalide-respiring microorganisms (such as Dehalococcoides species) can use halogenated compounds as electron acceptors, releasing halide ions and yielding dehalogenated products. Abiotic processes include reductive dehalogenation by reduced minerals and photochemical pathways.

Applications and implications include its use to tailor properties or remove toxic halogen substituents in organic synthesis, and to remediate halogenated pollutants. However, dehalogenation can generate intermediate products that may be hazardous (for example vinyl chloride from certain chlorinated alkenes), so product outcomes and safety must be considered. The term is used across chemistry, environmental science, and related fields to describe the state or result of halogen removal in a molecule or process.