The Abiotic Nitrite Oxidation by Ligand-Bound Manganese (III): The Chemical Mechanism
Abstract Given their environmental abundances, it has been long hypothesized that geochemical interactions between reactive forms of manganese and nitrogen may play important roles in the cycling of these elements. Indeed, recent studies have begun shedding light on the possible role...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Springer Netherlands
2021
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| Online Access: | https://hdl.handle.net/1721.1/136887 |
| _version_ | 1811092241163223040 |
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| author | Luther III, George W. Karolewski, Jennifer S. Sutherland, Kevin M. Hansel, Colleen M. Wankel, Scott D. |
| author_facet | Luther III, George W. Karolewski, Jennifer S. Sutherland, Kevin M. Hansel, Colleen M. Wankel, Scott D. |
| author_sort | Luther III, George W. |
| collection | MIT |
| description | Abstract
Given their environmental abundances, it has been long hypothesized that geochemical interactions between reactive forms of manganese and nitrogen may play important roles in the cycling of these elements. Indeed, recent studies have begun shedding light on the possible role of soluble, ligand-bound Mn(III) in promoting abiotic transformations under environmentally relevant conditions. Here, using the kinetic data of Karolewski et al. (Geochim Cosmochim Acta 293:365–378, 2021), we provide the chemical mechanism for the abiotic oxidation of nitrite (NO2−) by Mn(III)-pyrophosphate, MnIIIPP, to form nitrate (NO3−). Nitrous acid (HNO2), not NO2−, is the reductant in the reaction, based on thermodynamic and kinetic considerations. As soluble Mn(III) complexes react in a one-electron transfer reaction, two one-electron transfer steps must occur. In step one, HNO2 is first oxidized to nitrogen dioxide, ·NO2, a free radical via a hydrogen atom transfer (HAT) reaction. We show that this inner sphere reaction process is the rate-limiting step in the reaction sequence. In step two, ·NO2 reacts with a second MnIIIPP complex to form the nitronium ion (NO2+), which is isoelectronic with CO2. Unlike the poor electron-accepting capability of CO2, NO2+ is an excellent electron acceptor for both OH− and H2O, so NO2+ reacts quickly with water to form the end-product NO3− (step 3 in the reaction sequence). Thus, water provides the O atom in this nitrification reaction in accordance with the O-isotope data. This work provides mechanistic perspective on a potentially important interaction between Mn and nitrogen species, thereby offering a framework in which to interpret kinetic and isotopic data and to further investigate the relevance of this reaction under environmental conditions. |
| first_indexed | 2024-09-23T15:15:19Z |
| format | Article |
| id | mit-1721.1/136887 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T15:15:19Z |
| publishDate | 2021 |
| publisher | Springer Netherlands |
| record_format | dspace |
| spelling | mit-1721.1/1368872021-11-02T03:07:47Z The Abiotic Nitrite Oxidation by Ligand-Bound Manganese (III): The Chemical Mechanism Luther III, George W. Karolewski, Jennifer S. Sutherland, Kevin M. Hansel, Colleen M. Wankel, Scott D. Abstract Given their environmental abundances, it has been long hypothesized that geochemical interactions between reactive forms of manganese and nitrogen may play important roles in the cycling of these elements. Indeed, recent studies have begun shedding light on the possible role of soluble, ligand-bound Mn(III) in promoting abiotic transformations under environmentally relevant conditions. Here, using the kinetic data of Karolewski et al. (Geochim Cosmochim Acta 293:365–378, 2021), we provide the chemical mechanism for the abiotic oxidation of nitrite (NO2−) by Mn(III)-pyrophosphate, MnIIIPP, to form nitrate (NO3−). Nitrous acid (HNO2), not NO2−, is the reductant in the reaction, based on thermodynamic and kinetic considerations. As soluble Mn(III) complexes react in a one-electron transfer reaction, two one-electron transfer steps must occur. In step one, HNO2 is first oxidized to nitrogen dioxide, ·NO2, a free radical via a hydrogen atom transfer (HAT) reaction. We show that this inner sphere reaction process is the rate-limiting step in the reaction sequence. In step two, ·NO2 reacts with a second MnIIIPP complex to form the nitronium ion (NO2+), which is isoelectronic with CO2. Unlike the poor electron-accepting capability of CO2, NO2+ is an excellent electron acceptor for both OH− and H2O, so NO2+ reacts quickly with water to form the end-product NO3− (step 3 in the reaction sequence). Thus, water provides the O atom in this nitrification reaction in accordance with the O-isotope data. This work provides mechanistic perspective on a potentially important interaction between Mn and nitrogen species, thereby offering a framework in which to interpret kinetic and isotopic data and to further investigate the relevance of this reaction under environmental conditions. 2021-11-01T14:34:00Z 2021-11-01T14:34:00Z 2021-05-31 2021-08-12T03:52:05Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/136887 en https://doi.org/10.1007/s10498-021-09396-0 Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. The Author(s), under exclusive licence to Springer Nature B.V. application/pdf Springer Netherlands Springer Netherlands |
| spellingShingle | Luther III, George W. Karolewski, Jennifer S. Sutherland, Kevin M. Hansel, Colleen M. Wankel, Scott D. The Abiotic Nitrite Oxidation by Ligand-Bound Manganese (III): The Chemical Mechanism |
| title | The Abiotic Nitrite Oxidation by Ligand-Bound Manganese (III): The Chemical Mechanism |
| title_full | The Abiotic Nitrite Oxidation by Ligand-Bound Manganese (III): The Chemical Mechanism |
| title_fullStr | The Abiotic Nitrite Oxidation by Ligand-Bound Manganese (III): The Chemical Mechanism |
| title_full_unstemmed | The Abiotic Nitrite Oxidation by Ligand-Bound Manganese (III): The Chemical Mechanism |
| title_short | The Abiotic Nitrite Oxidation by Ligand-Bound Manganese (III): The Chemical Mechanism |
| title_sort | abiotic nitrite oxidation by ligand bound manganese iii the chemical mechanism |
| url | https://hdl.handle.net/1721.1/136887 |
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