Chloramine 336963 221282237 2008-06-23T21:05:51Z 134.84.206.60 {{Chembox new | Name = Chloramine | ImageFile = Chloramine-2D.png | ImageSize = 140px | ImageName = Chloramine | ImageFile1 = Chloramine-3D-vdW.png | ImageSize1 = 140px | ImageName1 = Chloramine | OtherNames = Monochloramine<br />Chloramide | Section1 = {{Chembox Identifiers | CASNo = [10599-90-3] }} | Section2 = {{Chembox Properties | Formula = NH<sub>2</sub>Cl | MolarMass = 51.48 g/mol | Appearance = colorless | Solvent = other solvents | SolubleOther = Soluble | MeltingPt = −66 °C | BoilingPt = °C }} | Section8 = {{Chembox Related | OtherCpds = [[Dichloramine]]<br />[[Nitrogen trichloride]]}} }} '''Chloramine''' (monochloramine) is a [[chemical compound]] with the [[chemical formula|formula]] NH<sub>2</sub>Cl. It is usually used as a dilute solution where it is used as a [[disinfectant]]. The term chloramine also refers to a family of [[organic compound]]s with the formulas R<sub>2</sub>NCl and RNCl<sub>2</sub> (R is an organic group). [[Dichloramine]], NHCl<sub>2</sub>, and [[nitrogen trichloride]], NCl<sub>3</sub>, are also well known. ==Synthesis and chemical reactions== NH<sub>2</sub>Cl is a highly unstable compound in concentrated form, much less as a pure liquid. Pure NH<sub>2</sub>Cl decomposes violently above &minus;40 °C.<ref>Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.</ref> NH<sub>2</sub>Cl is, however, quite stable in dilute solution, and this considerable stability is the basis of its applications. NH<sub>2</sub>Cl is prepared by the [[chemical reaction]] between [[ammonia]] and [[hypochlorous acid]]<ref name=ref29>Fair, G. M., J. C. Morris, S. L. Chang, I. Weil, and R. P. Burden. 1948. The behavior of chlorine as a water disinfectant. J. Am. Water Works Assoc. 40:1051-1061.</ref> under mildly alkaline conditions: :NH<sub>3</sub> + HOCl &rarr; NH<sub>2</sub>Cl + H<sub>2</sub>O The synthesis is conducted in dilute solution. In this reaction HOCl undergoes attack by the [[nucleophile]] NH<sub>3</sub>. At lower pH's, further chlorination occurs. The above syntheses are useful but do not deliver NH<sub>2</sub>Cl in pure form. The pure compound can be prepared by contacting [[fluoroamine]] with [[calcium chloride]]: :NH<sub>2</sub>F + CaCl<sub>2</sub> &rarr; NH<sub>2</sub>Cl + CaClF NH<sub>2</sub>Cl is a key intermediate in the traditional synthesis of [[hydrazine]]. Monochloramine oxidizes sulfhydryls and disulfides in the same manner as HClO,<ref name=ref46>Jacangelo, J. G., V. P. Olivieri, and K. Kawata. 1987. Oxidation of sulfhydryl groups by monochloramine. Water Res. 21:1339-1344.</ref> but only possesses 0.4% of the biocidal effect of HClO.<ref name=ref64>Morris, J. C. 1966. Future of chlorination. J. Am. Water Works Assoc. 58:1475-1482.</ref> ==Uses in water treatment== NH<sub>2</sub>Cl is commonly used in low [[concentration]]s as a [[disinfectant]] in [[municipal water system]]s as an alternative to [[chlorination]]. This application is increasing. [[Chlorine]] (sometimes referred to as '''Free Chlorine''') is being displaced by chloramine, which is much more stable and does not dissipate from the [[water]] before it reaches consumers. NH<sub>2</sub>Cl also exhibits less tendency to convert organic materials into [[chlorocarbon]]s such as [[chloroform]] and [[carbon tetrachloride]]. Such compounds have been identified as [[carcinogen]]s and in 1979 the U.S. [[EPA]] began regulating their levels in U.S. drinking water. Furthermore, water treated with chloramine lacks the distinct chlorine odour of the gaseous treatment and so has improved taste. Chloramine in tap water gives a greenish cast to the water in bulk, versus the normally bluish cast to pure water or water containing only free chlorine disinfectant. This greenish color may be observed by filling a white polyethylene bucket with chloraminated tap water and comparing it to chloramine-free water such as distilled water or a sample from a swimming pool. [[Image:Rkinch chloramine pool.jpg|thumb|New swimming pool initially filled with chloramine-treated tap water, showing greenish color of chloramine in bulk water. The color is less apparent in smaller volumes, but is noticeable in a white 5-gallon bucket, or even faintly detectable in a glass tumbler on careful inspection.]] Chloramine can be removed from tap water by treatment with superchlorination (10 ppm or more of free chlorine, such as from a dose of sodium hypochlorite bleach or pool sanitizer) while maintaining a pH of about 7 (such as from a dose of hydrochloric acid). Hypochlorous acid from the free chlorine strips the ammonia from the chloramine, and the ammonia outgasses from the surface of the bulk water. This process takes about 24 hours for normal tap water concentrations of a few ppm of chloramine. Residual free chlorine can then be removed by exposure to bright sunlight for about 4 hours. ==Situations where NH<sub>2</sub>Cl should be removed== [[Aquarium]] owners must remove the chloramine from their [[tap water]] because it is [[toxic]] to [[fish]]. Aging the [[water]] for a few days removes [[chlorine]] but not the more stable chloramine, which can be neutralised using products available at pet stores. Many animals are sensitive to chloramine and it must be removed from water given to many animals in zoos. Chloramine must also be removed from the water prior to use in [[kidney dialysis]] machines, as it would come in contact with the bloodstream across a permeable membrane. However, since chloramine is neutralized by the digestive process, kidney dialysis patients can still safely drink chloramine-treated water. [[Homebrewing|Home brewers]] use reducing agents such as [[sodium metabisulfite]] or [[potassium metabisulfite]] to remove chloramine from brewing liquor as it, unlike [[chlorine]], cannot be removed by boiling (A.J. DeLange). Residual sodium can cause off flavors in beer (See Brewing, Michael Lewis) so potassium metabisulfite is preferred. In swimming pools, chloramines are formed by the reaction of free chlorine with organic substances. Chloramines, compared to free chlorine, are both less effective as a sanitizer and more irritating to the eyes of swimmers. When swimmers complain of eye irritation from "too much chlorine" in a pool, the problem is typically a high level of chloramines, caused by too ''little'' chlorine in relation to the amount of organic matter. Pool test kits designed for use by homeowners are sensitive to both free chlorine and chloramines, which can be misleading. ==Organic chloramines== A variety of organic chloramines are known and proven useful in [[organic synthesis]]. One example is ''N''-chloromorpholine ClN(CH<sub>2</sub>CH<sub>2</sub>)<sub>2</sub>O, ''N''-chloro[[piperidine]], and ''N''-chloro[[quinuclidine|quinuclidinium]] chloride.<ref>Lindsay Smith, J. R.; McKeer, L. C.; Taylor, J. M. "4-Chlorination of Electron-Rich Benzenoid Compounds: 2,4-Dichloromethoxybenzene" Organic Syntheses, CollectedVolume 8, p.167 (1993)..http://www.orgsyn.org/orgsyn/pdfs/CV8P0167.pdf describes several N-chloramines</ref> ==Safety== NH<sub>2</sub>Cl is toxic in large quantities. US EPA regulations limit chloramine concentration to 4 parts per million (ppm). A typical target level in US public water supplies is 3 ppm. ==References== <references/> ==External links== *[http://www.skepticalaquarist.com/docs/water/chlorine.shtml Chlorine and chloramines in the freshwater aquarium] *[http://sfwater.org/mto_main.cfm/MC_ID/13/MSC_ID/166/MTO_ID/399 Chloramine FAQ from the San Francisco Public Utilities Commission] *[http://www-cie.iarc.fr/htdocs/monographs/vol52/01-water.htm "Chlorinated drinking water", IARC Monograph (1991)] *[http://www.epa.gov/safewater/mcl.html#mcls EPA Maximum Contaminant Levels] [[Category:Nitrogen compounds]] [[Category:Chlorides]] [[Category:Nonmetal halides]] [[Category:Water treatment]] [[ca:Cloramina]] [[de:Chloramine]] [[it:Clorammine]] [[ja:クロラミン]] [[pl:Chloroamina]] [[pt:Cloramina]] [[sr:Хлороамин]]