Using nitrogen isotope fractionation to assess the oxidation of substituted anilines by manganese oxide
| Autor: | William A. Arnold, Martin Jiskra, Aurora Turgeon, Marita Skarpeli-Liati, Ashley N. Garr, René P. Schwarzenbach, Christopher J. Cramer, Thomas B. Hofstetter |
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| Rok vydání: | 2011 |
| Předmět: |
Imine
Inorganic chemistry Chemical Fractionation Gas Chromatography-Mass Spectrometry chemistry.chemical_compound Isotope fractionation Deprotonation Kinetic isotope effect Environmental Chemistry Aniline Compounds Molecular Structure Nitrogen Isotopes Bond strength Cationic polymerization Oxides General Chemistry Hydrogen atom Hydrogen-Ion Concentration chemistry Manganese Compounds Linear Models Density functional theory Environmental Pollutants Oxidation-Reduction Chromatography Liquid Environmental Monitoring |
| Zdroj: | Environmental sciencetechnology. 45(13) |
| ISSN: | 1520-5851 |
| Popis: | We explored the N isotope fractionation associated with the oxidation of substituted primary aromatic amines, which are often the position of initial attack in transformation processes of environmental contaminants. Apparent (15)N-kinetic isotope effects, AKIE(N), were determined for the oxidation of various substituted anilines in suspensions of manganese oxide (MnO(2)) and compared to reference experiments in homogeneous solutions and at electrode surfaces, as well as to density functional theory calculations of intrinsic KIE(N)for electron and hydrogen atom transfer reactions. Owing to the partial aromatic imine formation after one-electron oxidation and corresponding increase in C-N bond strength, AKIE(N)-values were inverse, substituent-dependent, and confined to the range between 0.992 and 0.999 in agreement with theory. However, AKIE(N)-values became normal once the fraction of cationic species prevailed owing to (15)N-equilibrium isotope effects, EIE(N), of 1.02 associated with N atom deprotonation. The observable AKIE(N)-values are substantially modulated by the acid/base pre-equilibria of the substituted anilines and isotope fractionation may even vanish under conditions where normal EIE(N) and inverse AKIE(N) cancel each other out. The pH-dependent trends of the AKIE(N)-values provide a new line of evidence for the identification of contaminant degradation processes via oxidation of primary aromatic amino groups. |
| Databáze: | OpenAIRE |
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