Trihalomethane 1482837 214086761 2008-05-22T01:12:25Z Razorflame 5792322 Reverted edits by [[Special:Contributions/24.225.86.66|24.225.86.66]] ([[User talk:24.225.86.66|talk]]) to last version by Edgar181 '''Trihalomethanes''' ('''THM'''s) are [[chemical compound]]s in which three of the four hydrogen atoms of [[methane]] (CH<sub>4</sub>) are replaced by [[halogen]] atoms. Many trihalomethanes find uses in industry as [[solvent]]s or [[refrigerant]]s. THMs are also environmental pollutants, and many are considered [[carcinogen|carcinogenic]]. Trihalomethanes with all the same halogen atoms are called '''haloforms'''. ==Table of common trihalomethanes== {| border="1" cellpadding="5" cellspacing="0" align="center" |+'''Common trihalomethanes''' (ordered by [[molecular mass|molecular weight]]) |- !Molecular formula ![[IUPAC]] name !Common name !Other names !Molecule |- |CHF<sub>3</sub> |trifluoromethane |[[fluoroform]] |[[Freon]] 23, R-23, HFC-23 |align="center"|[[Image:Fluoroform-3D-vdW.png|50px|Fluoroform]] |- |CHClF<sub>2</sub> |[[chlorodifluoromethane]] |align="center"| - |R-22, HCFC-22 |align="center"|[[Image:Chlorodifluoromethane-3D-vdW.png|50px|Chlorodifluoromethane]] |- |CHCl<sub>3</sub> |trichloromethane |[[chloroform]] |methyl trichloride |align="center"|[[Image:Chloroform-3D-vdW.png|50px|Chloroform]] |- |CHBrCl<sub>2</sub> |bromodichloromethane |align="center"| - |align="center"| - |align="center"|[[Image:Bromodichloromethane-3D-vdW.png|50px|Bromodichloromethane]] |- |CHBr<sub>2</sub>Cl |dibromochloromethane |align="center"| - |align="center"| - |align="center"|[[Image:Dibromochloromethane-3D-vdW.png|50px|Dibromochloromethane]] |- |CHBr<sub>3</sub> |tribromomethane |[[bromoform]] |methyl tribromide |align="center"|[[Image:Bromoform-3D-vdW.png|50px|Bromoform]] |- |CHI<sub>3</sub> |triiodomethane |[[iodoform]] |methyl triiodide |align="center"|[[Image:Iodoform-3D-vdW.png|50px|Iodoform]] |} ==Industrial uses== ===Refrigerants=== Trifluoromethane and chlorodifluoromethane are both used as [[refrigerant]]s in some applications. Trihalomethanes released to the environment break down faster than [[CFC|chlorofluorocarbons]] (CFCs), thereby doing much less damage to the [[ozone layer]] (if they contain chlorine). Chlorodifluoromethane is a refrigerant [[HCFC]], or hydrochlorofluorocarbon, while fluoroform is an HFC, or [[hydrofluorocarbon]]. Fluoroform is not ozone depleting. Unfortunately, the breakdown of trihalomethane HCFCs does still result in the creation of some free chlorine radicals in the upper atmosphere and subsequent ozone destruction. Ideally, HCFCs will be phased out entirely in favour of entirely nonchlorinated refrigerants. ===Solvents=== Chloroform is a very common [[solvent]] used in organic chemistry. It is a significantly less [[dipole|polar]] solvent than water, well-suited to dissolving many [[organic compound]]s. Although still toxic and potentially carcinogenic, chloroform is significantly less harmful than [[carbon tetrachloride]]. Because of the health and regulatory issues associated with the use of carbon tetrachloride, in modern chemistry laboratories chloroform is used as a cheaper, cleaner alternative wherever possible. ==Water pollutants== Trihalomethanes are formed as a by-product when [[chlorine]] or [[bromine]] are used to disinfect water for drinking (commonly known as [[Disinfection by-product|disinfection by-products]]). They result from the reaction of chlorine and/or bromine with organic matter in the water being treated. The THMs produced may have adverse health effects at high concentrations, and many governments set limits on the amount permissible in drinking water. In the [[United States]], the [[United States Environmental Protection Agency|EPA]] limits the total concentration of chloroform, bromoform, bromodichloromethane, and dibromochloromethane to 80 parts per billion in treated water. This number is called "total trihalomethanes" (TTHM). [[Chloroform]] is also formed in [[swimming pools]] which are disinfected with [[chlorine]] or [[hypochlorite]] in the [[haloform reaction]] with organic substances ([[urine]], [[sweat]] and [[skin]] particles). The reaction to [[phosgene]] under the influence of UV is also possible. Some of the THMs are quite volatile and may easily vaporize into the air. This makes it possible to inhale while showering, for example. The EPA, however, has determined that this exposure is minimal compared to that from consumption. ==External links== * [http://www.npi.gov.au/database/substance-info/profiles/23.html National Pollutant Inventory - Chloroform and trichloromethane] * [http://www.biozone.com/trihalomethanes.html How Ozone Technology] * [http://www.caslab.com/News/testing-for-trihalomethanes-in-your-water-tthm.html Testing for Trihalomethanes] * [http://yosemite.epa.gov/water/owrccatalog.nsf/9da204a4b4406ef885256ae0007a79c7/be44ad7c8f83f25a85256b06007255e9!OpenDocument EPA - Trihalomethanes in Drinking Water] [[Category:Halomethanes]] [[Category:Halogenated solvents]] [[Category:Refrigerants]] [[de:Trihalogenmethane]] [[es:Trihalometano]] [[ja:トリハロメタン]] [[pl:Trihalogenometany]]