The chloronitramide anion, also known as chloro(nitro)azanide, is a recently identified chemical byproduct of the disinfectant chloramine.[1][2][3] It is present in the tap water of about 113 million people in the United States of America in varying concentrations.[1] Its toxicity has not been determined.[2] The chloronitramide anion was first observed and determined to be a degradation byproduct of chloramine in the early 1980s.[4] Its molecular formula and structure were disclosed in a paper published in November 2024 and an article from the American Chemical Society noted that the researchers identified a potential removal method and that scientific studies are needed to determine its toxicity.[5]
 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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Research
editEarly research
editThe chloronitramide anion was first detected as a UV absorbance interference during monitoring of chloramine and dichloramine in 1981.[4] It was then shown to form during the decomposition of both chemicals.[4] It was shown to likely be an anion in 1990.[6]
Identification of structure
editThe 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][4]
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.[4][7]
Formation
editThe 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.[4][8]
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 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. doi:10.1126/science.adk6749. ISSN 0036-8075. PMID 39571006.
- ^ "Mystery chemical in drinking water identified". Chemical & Engineering News. 2024-11-21. Retrieved 2024-11-21.
- ^ Leung, Solomon W.; Valentine, Richard L. (June 1994). "An unidentified chloramine decomposition product—I. Chemistry and characteristics". Water Research. 28 (6): 1475–1483. doi:10.1016/0043-1354(94)90316-6.
- ^ McCurry, Daniel L. (2024-11-22). "The chloramine dilemma". Science. 386 (6724): 851–852. 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.
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