Dihalogen

Dihalogen is a general chemistry term used to describe any molecule that contains two halogen atoms. The halogens ordinarily considered are fluorine, chlorine, bromine, and iodine. The phrase covers both simple diatomic halogen species, in which the two halogen atoms form a molecule of their own (X2, such as F2, Cl2, Br2, I2), and more complex molecules in which two halogen atoms are present within the structure, for example as two substituents on a carbon atom or on adjacent atoms.

Diatomic halogens are the elemental forms of the halogens and are typically nonpolar molecules with a single halogen–halogen bond. Bond strength and reactivity vary down the group: F2 is highly reactive, Cl2 is a strong oxidizer and widely used in chemistry and disinfection, Br2 is reactive but less so than Cl2, and I2 is comparatively less reactive. In addition to these, many dihalogen derivatives exist as part of larger compounds.

Dihalogenated compounds are molecules in which two halogen atoms are incorporated into an otherwise nonhalogenated scaffold. Examples include dichloromethane (CH2Cl2), difluoromethane (CH2F2), and 1,2-dichloroethane (C2H4Cl2). The presence of two halogens can significantly influence reactivity, polarity, volatility, and toxicity, making such compounds common as solvents, intermediates in organic synthesis, refrigerants, and precursors to polymers.

Nomenclature generally distinguishes between elemental dihalogens (X2) and dihalogenated compounds or dihalides, with terminology such as dihalogenated hydrocarbon or dihalide used to describe the latter. In summary, dihalogen describes any molecule containing two halogen atoms, whether as an elemental diatomic or as part of a larger chemical framework.