Chloronitramide anion
 Structural diagram
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 Spacefill diagram
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| Names | |
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| IUPAC name
Chloro(nitro)azanide
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| Other names
Chloronitramide anion
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| Identifiers | |
3D model (JSmol)
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PubChem CID
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| Properties | |
| ClN2O2− | |
| Molar mass | 95.46 g/mol |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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The chloronitramide anion, also known as chloro(nitro)azanide, is a chemical byproduct of the disinfectant chloramine first identified in 2024.[1][2][3] It is present in the tap water of about 113 million people in the United States in varying concentrations.[1] Its toxicity has not yet been determined,[2] although it may be removable by an activated carbon filter.[4][5] Although its molecular formula and structure were unknown,[4] it was first recorded as a byproduct of chloramine in the early 1980s.[6]
Chloramine is often used as an alternative to chlorine for water disinfection because of chlorine's harmful byproducts, and on the basis that clean water improves health much more than small concentrations of byproducts harm it.[7] Other methods of disinfection exist, including ozone (popular in European countries) and UV light, but these cannot currently be used in the US because the law requires water to have small residual amounts of disinfectant to prevent re-infection.[7]
Research
[edit]Early research
[edit]The chloronitramide anion was first detected as a UV absorbance interference during monitoring of chloramine and dichloramine in 1981.[6] It was then shown to form during the decomposition of both chemicals.[6] It was shown to likely be an anion in 1990.[8] In the 1980s and 1990s methods of producing it in high concentrations were identified, and the molecule was shown through destruction to contain both nitrogen and chlorine.[9] According to Julian Fairey, research on the compound slowed down in the mid-1990s after attempts to identify it were unsuccessful.[9]
Identification of structure
[edit]The structure of the molecule was finally identified in 2024 using a combination of techniques, first identifying the molecular formula, then creating a candidate structure, then confirming it.[1][6]
Ion chromatography, a method of separating ions and ionizable polar molecules, was used to separate the chloronitramide anion from the many salts present in water samples containing it, which otherwise made it difficult to use mass spectrometry; the water salinity was higher than that of saltwater.[1][why?]
Mass spectrometry was sufficient to determine the molecular mass of the ion, but it was too small for structure determination from the fragmentation pattern. The ion was found to have the molecular formula ClN2O2−1 (containing two oxygen atoms, two nitrogen atoms, and one chlorine atom) by electrospray ionisation mass spectrometry. A candidate structure was confirmed by 15N NMR spectroscopy and infrared spectroscopy.[6][10]
Future research
[edit]Research investigating the toxicity of the chloronitramide anion, as well as the reasons for its formation in high or low concentration in different places, is expected.[9]
Formation
[edit]The identifying paper proposes that the chloronitramide anion is formed through the reaction of chloramine (or dichloramine, which forms in chloramine solution) with NO2+, one of its degradation products. The formation of NO2+ begins when dichloramine (NHCl2) is hydrolyzed to form nitroxyl (HNO), which then reacts with dissolved oxygen (O2) to form the unstable peroxynitrite (ONOOH). NO2+ is one of the several reactive nitrogen species formed when peroxynitrite decomposes. The chloronitramide formed in this way then dissociates, losing the hydrogen, to form the corresponding anion.[6][11]
References
[edit]- ^ a b c d Christensen, Jen (2024-11-21). "Solving a 40-year mystery, scientists ID chemical found in millions of Americans' tap water". CNN. Retrieved 2024-11-21.
- ^ a b Achenbach, Joel; Johnson, Carolyn Y. (2024-11-21). "Mysterious chemical byproduct in U.S. tap water finally identified". Washington Post. Retrieved 2024-11-22.
- ^ "Newly identified chemical in drinking water is likely in many homes and could be toxic, study finds". NBC News. 2024-11-21. Retrieved 2024-11-21.
- ^ a b "Mystery chemical in drinking water identified". Chemical & Engineering News. 2024-11-21. Archived from the original on 2024-11-21. Retrieved 2024-11-21.
- ^ "International Research Collaboration Identifies Previously Unknown Chemical Compound in Drinking Water". US EPA. 2024-12-17. Retrieved 2025-01-12.
- ^ a b c d e f Fairey, Julian L.; Laszakovits, Juliana R.; Pham, Huong T.; Do, Thien D.; Hodges, Samuel D.; McNeill, Kristopher; Wahman, David G. (2024-11-22). "Chloronitramide anion is a decomposition product of inorganic chloramines". Science. 386 (6724): 882–887. Bibcode:2024Sci...386..882F. doi:10.1126/science.adk6749. ISSN 0036-8075. PMID 39571006.
- ^ a b Hawking, Tom (2024-11-21). "'Unidentified product' in tap water identified after 40 years". Popular Science. Retrieved 2025-03-21.
- ^ Leung, Solomon W.; Valentine, Richard L. (June 1994). "An unidentified chloramine decomposition product—I. Chemistry and characteristics". Water Research. 28 (6): 1475–1483. Bibcode:1994WatRe..28.1475L. doi:10.1016/0043-1354(94)90316-6.
- ^ a b c Fairey, Julian (20 December 2024). "Engineering Safer Drinking Water" (Interview). Interviewed by Hardin Young. University of Arkansas.
- ^ McCurry, Daniel L. (2024-11-22). "The chloramine dilemma". Science. 386 (6724): 851–852. Bibcode:2024Sci...386..851M. doi:10.1126/science.adt8921. ISSN 0036-8075. PMID 39571038.
- ^ Wogan, Tim. "First detected 40 years ago, a byproduct in chloraminated drinking water has finally been identified". Chemistry World. Retrieved 2024-11-22.