Halogenated ether
Encyclopedia
A halogenated ether is a subcategory of a larger group of chemicals known as ether
s. 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 trichloroethane
. 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 trichloroethane.
All inhalation anesthetics in current clinical use are halogenated ethers, except for halothane
(which is a halogenated hydrocarbon or haloalkane), nitrous oxide, and xenon.
Halogenated ethers have the advantages of being non-flammable as well as less toxic than earlier general anesthetics. Halogenated ethers differ from other ethers because they contain at least one halogen
atom in each molecule. Examples of halogenated ethers include the general anesthetics isoflurane
, desflurane
, and sevoflurane
. However, not all halogenated ethers have anesthetic effects, and some compounds such as flurothyl
do the opposite and have stimulant and convulsant
effects.
Inhalation anesthetics are vaporized and mixed with other gases prior to their inhalation by the patient before or during surgery. These other gases always include oxygen or air, but may also include other gases such as nitrous oxide or helium.
In most surgical situations, other drugs such as opiates are used for pain and skeletal muscle relaxants are used to cause temporary paralysis. Additional drugs such as midazolam
may be used to produce amnesia during surgery.
Newer intravenous anesthetics (such as propofol
) have increased the options of anesthesiologists, but halogenated ethers remain a mainstay of general anesthesia.
Ether
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
s. An ether is an organic chemical that contains an ether group — an oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
connected to two (substituted) alkyl groups. A good example of an ether is the solvent diethyl ether
Diethyl ether
Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
.
What differentiates a halogenated ether from other types of ethers is the substitution (halogenation
Halogenation
Halogenation is a chemical reaction that incorporates a halogen atom into a molecule in substitution of hydrogen atom. Halogenation takes place in the gas phase. There are four types of halogenation: fluorination, chlorination, bromination, and iodination...
) of one or more hydrogen atoms with a halogen
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...
atom. Halogen atoms include fluorine
Fluorine
Fluorine is the chemical element with atomic number 9, represented by the symbol F. It is the lightest element of the halogen column of the periodic table and has a single stable isotope, fluorine-19. At standard pressure and temperature, fluorine is a pale yellow gas composed of diatomic...
, chlorine
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
, bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
, and iodine
Iodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
.
Perhaps the most common use of halogenated ethers has been in anesthesiology. The first widely used inhalation anesthetic was diethyl ether
Diethyl ether
Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...
, 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
Chloroform
Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous...
and trichloroethane
Trichloroethane
Trichloroethane can refer to either of two isomeric chemical compounds:* 1,1,1-Trichloroethane * 1,1,2-Trichloroethane...
. Halothane
Halothane
Halothane is an inhalational general anesthetic. Its IUPAC name is 2-bromo-2-chloro-1,1,1-trifluoroethane. It is the only inhalational anesthetic agent containing a bromine atom; there are several other halogenated anesthesia agents which lack the bromine atom and do contain the fluorine and...
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 trichloroethane.
All inhalation anesthetics in current clinical use are halogenated ethers, except for halothane
Halothane
Halothane is an inhalational general anesthetic. Its IUPAC name is 2-bromo-2-chloro-1,1,1-trifluoroethane. It is the only inhalational anesthetic agent containing a bromine atom; there are several other halogenated anesthesia agents which lack the bromine atom and do contain the fluorine and...
(which is a halogenated hydrocarbon or haloalkane), nitrous oxide, and xenon.
Halogenated ethers have the advantages of being non-flammable as well as less toxic than earlier general anesthetics. Halogenated ethers differ from other ethers because they contain at least one halogen
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...
atom in each molecule. Examples of halogenated ethers include the general anesthetics isoflurane
Isoflurane
Isoflurane is a halogenated ether used for inhalational anesthesia. Together with enflurane and halothane, it replaced the flammable ethers used in the pioneer days of surgery. Its name comes from being a structural isomer of enflurane, hence they have the same empirical formula...
, desflurane
Desflurane
Desflurane is a highly fluorinated methyl ethyl ether used for maintenance of general anesthesia. Like halothane, enflurane and isoflurane, it is a racemic mixture of and optical isomers...
, and sevoflurane
Sevoflurane
Sevoflurane , also called fluoromethyl hexafluoroisopropyl ether, is a sweet-smelling, nonflammable, highly fluorinated methyl isopropyl ether used for induction and maintenance of general anesthesia. Together with desflurane, it is replacing isoflurane and halothane in modern anesthesiology...
. However, not all halogenated ethers have anesthetic effects, and some compounds such as flurothyl
Flurothyl
Flurothyl is a volatile liquid drug from the halogenated ether family, related to inhaled anaesthetic agents such as diethyl ether, but having the opposite effects, acting as a stimulant and convulsant...
do the opposite and have stimulant and convulsant
Convulsant
A convulsant is a drug which induces convulsions and/or epileptic seizures, the opposite of an anticonvulsant. These drugs generally act as stimulants at low doses, but are not used for this purpose due to the risk of convulsions and consequent excitotoxicity...
effects.
Inhalation anesthetics are vaporized and mixed with other gases prior to their inhalation by the patient before or during surgery. These other gases always include oxygen or air, but may also include other gases such as nitrous oxide or helium.
In most surgical situations, other drugs such as opiates are used for pain and skeletal muscle relaxants are used to cause temporary paralysis. Additional drugs such as midazolam
Midazolam
Midazolam is a short-acting drug in the benzodiazepine class developed by Hoffmann-La Roche in the 1970s. The drug is used for treatment of acute seizures, moderate to severe insomnia, and for inducing sedation and amnesia before medical procedures. It possesses profoundly potent anxiolytic,...
may be used to produce amnesia during surgery.
Newer intravenous anesthetics (such as propofol
Propofol
Propofol is a short-acting, intravenously administered hypnotic agent. Its uses include the induction and maintenance of general anesthesia, sedation for mechanically ventilated adults, and procedural sedation. Propofol is also commonly used in veterinary medicine...
) have increased the options of anesthesiologists, but halogenated ethers remain a mainstay of general anesthesia.
See also
- AnesthesiaAnesthesiaAnesthesia, or anaesthesia , traditionally meant the condition of having sensation blocked or temporarily taken away...
- EtherEtherEthers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
- HalogenHalogenThe halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...
- HalogenationHalogenationHalogenation is a chemical reaction that incorporates a halogen atom into a molecule in substitution of hydrogen atom. Halogenation takes place in the gas phase. There are four types of halogenation: fluorination, chlorination, bromination, and iodination...
- HydrocarbonHydrocarbonIn organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....