Polyhalogenated

Polyhalogenated is a chemical descriptor for compounds that contain two or more halogen atoms in the same molecule. Halogens include fluorine, chlorine, bromine, and iodine. The term covers a broad range of substances, from small inorganic salts and halogenated gases to large organic molecules and polymers in which multiple X atoms are substituted on carbon or other backbones.

Properties of polyhalogenated compounds depend on the halogen type and arrangement. They often exhibit high electronegativity and strong C–X or X–X bonds, which can confer chemical stability, low reactivity, and, in many cases, lipophilicity. Many are persistent in the environment and can bioaccumulate in living organisms. Fluorinated, chlorinated, and brominated members show different degradation pathways and toxicities.

Industrial and consumer applications include solvents (chlorinated solvents like carbon tetrachloride and chloroform), refrigerants, flame retardants (brominated compounds such as PBDEs), polymers (chlorinated polymers like polyvinyl chloride), and historically, pesticides (e.g., lindane, DDT). Some polyhalogenated compounds are used for specialty coatings, surfactants, and electronic materials.

Environmental and health considerations have led to regulatory controls in many regions. Many polyhalogenated substances are classified as persistent organic pollutants due to persistence, bioaccumulation, and toxicity. International and national frameworks regulate production, handling, use, and disposal, with phased reductions or bans on several chlorinated and brominated compounds.