A halogenated ether is a subcategory of a larger group of chemicals known as ethers. An ether is an organic chemical that contains an ether group — an oxygen atom connected to two (substituted) alkyl groups. A good example of an ether is the solvent diethyl ether.
What differentiates a halogenated ether from other types of ethers is the substitution (halogenation) of one or more hydrogen atoms with a halogen atom. Halogen atoms include fluorine, chlorine, bromine, and iodine.
Perhaps the most common use of halogenated ethers has been in anesthesiology. The first widely used inhalation anesthetic was diethyl ether, which is a non-substituted (non-halogenated) ether. This drug enabled surgeons to perform otherwise painful operations on patients after rendering them unconscious.
Diethyl ether has the unfortunate disadvantage of being extremely flammable, especially in the presence of enriched oxygen mixtures. This property has resulted in many instances of fires and even explosions in operating rooms during surgery. This is among the most important reasons that diethyl ether has fallen out of favor as a general anesthetic. Diethyl ether is still commonly used as a solvent and reagent in organic chemistry laboratories, though with caution.
Diethyl ether was initially replaced by non-flammable (but more toxic) halogenated hydrocarbons such as chloroform and trichloroethylene. Halothane is another halogenated hydrocarbon anesthetic agent which was introduced into clinical practice in 1956. Due to its ease of use and improved safety profile with respect to organ toxicity, halothane quickly replaced chloroform and trichloroethylene.