Chloramine
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| Chloramine | |
|---|---|
| Image:Chloramine-2D.png | |
| Image:Chloramine-3D-vdW.png | |
| Other names | Monochloramine Chloramide |
| Identifiers | |
| CAS number | |
| Properties | |
| Molecular formula | NH2Cl |
| Molar mass | 51.48 g/mol |
| Appearance | colorless |
| Melting point |
−66 °C |
| Boiling point |
°C |
| Solubility in other solvents | Soluble |
| Related Compounds | |
| Related compounds | Dichloramine Nitrogen trichloride |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references | |
Chloramine (monochloramine) is a chemical compound with the formula NH2Cl. 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 compounds with the formulas R2NCl and RNCl2 (R is an organic group). Dichloramine, NHCl2, and nitrogen trichloride, NCl3, are also well known.
Contents |
Synthesis and chemical reactions
NH2Cl is a highly unstable compound in concentrated form, much less as a pure liquid. Pure NH2Cl decomposes violently above −40 °C.[1] NH2Cl is, however, quite stable in dilute solution, and this considerable stability is the basis of its applications.
NH2Cl is prepared by the chemical reaction between ammonia and hypochlorous acid[1] under mildly alkaline conditions:
- NH3 + HOCl → NH2Cl + H2O
The synthesis is conducted in dilute solution. In this reaction HOCl undergoes attack by the nucleophile NH3. At lower pH's, further chlorination occurs.
The above syntheses are useful but do not deliver NH2Cl in pure form. The pure compound can be prepared by contacting fluoroamine with calcium chloride:
- NH2F + CaCl2 → NH2Cl + CaClF
NH2Cl is a key intermediate in the traditional synthesis of hydrazine.
Monochloramine oxidizes sulfhydrals and disulfides in the same manner as HClO,[1] but only possesses 0.4% of the biocidal effect of HClO.[1]
Uses in water treatment
NH2Cl is commonly used in low concentrations as a disinfectant in municipal water systems 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. NH2Cl also exhibits less tendency to convert organic materials into chlorocarbons such as chloroform and carbon tetrachloride. Such compounds have been identified as carcinogens 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.
Situations where NH2Cl 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.
Home brewers use reducing agents such as sodium metabisulfite to remove chloramine from brewing liquor as it, unlike chlorine, cannot be removed by boiling.
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 toolittle 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(CH2CH2)2O, N-chloropiperidine, and N-chloroquinuclidinium chloride.[1]
Safety
NH2Cl 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
External links
- Chlorine and chloramines in the freshwater aquarium
- Chloramine FAQ from the San Francisco Public Utilities Commission
- "Chlorinated drinking water", IARC Monograph (1991)
- EPA Maximum Contaminant Levelsde:Chloramine
it:Clorammine ja:クロラミンsr:Хлороамин
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
