halide

A compound containing one of the halogens [fluorine (F), chlorine (Cl), bromine (Br), iodine (I)] and another element or organic group. Halides have the general formula M_xX_y, where M is a metal or organic group and X is a halogen. Halides are composed of almost every element in the periodic table, and they are referred to as fluorides, chlorides, bromides, or iodides. See also Halogen elements; Periodic table.

The halides are divided into classes that reflect the nature of bonding between the halogen and metal or organic species. The bonding of halides ranges from purely ionic to essentially covalent. The classes include ionic halides, molecular halides, halides and halogens that behave as ligands in coordination complexes, and organic halides.

Ionic halides such as sodium chloride (NaCl) and potassium chloride (KCl) are prepared from the vigorous reaction of the alkali and alkaline-earth metals with the halogens. These compounds possess high melting and boiling points and are soluble in very polar solvents. Ionic halides are extremely important to the chemical industry, where they are used to produce commodity chemicals such as sodium hydroxide (NaOH), hydrochloric acid (HCl, a hydrogen halide), and potassium nitrate (KNO₃).

The organic halides are divided into the alkyl halides (haloalkanes) and the aryl halides. The alkyl halides have the general formula RX, where R is any alkyl group and X is one of the halogens; for example, 1-chlorobutane (CH₃CH₂CH₂CH₂Cl). Halides are good leaving groups in nucleophilic substitution reactions and are good nucleophiles. The aryl halides are compounds where the halogen is attached directly to an aromatic ring and have the general formula ArX, where Ar is an aromatic group. See also Coordination chemistry; Coordination complexes; Electrophilic and nucleophilic reagents; Halogenated hydrocarbon; Halogenation.

A compound of a halogen with an element or radical.

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