Carbon, hydrogen, and nitrogen isotope fractionation associated with oxidative transformation of substituted aromatic N-alkyl amines.
We investigated the mechanisms and isotope effects associated with the N-dealkylation and N-atom oxidation of substituted N-methyl- and N,N-dimethylanilines to identify isotope fractionation trends for the assessment of oxidations of aromatic N-alkyl moieties by compound-specific isotope analysis (CSIA). In laboratory batch model systems, we determined the C, H, and N isotope enrichment factors for the oxidation by MnO(2) and horseradish peroxidase (HRP), derived apparent (13)C-, (2)H-, and (15)N-kinetic isotope effects (AKIEs), and characterized reaction products. The N-atom oxidation pathway leading to radical coupling products typically exhibited inverse (15)N-AKIEs (up to 0.991) and only minor (13)C- and (2)H-AKIEs. Oxidative N-dealkylation, in contrast, was subject to large normal (13)C- and (2)H-AKIEs (up to 1.019 and 3.1, respectively) and small (15)N-AKIEs. Subtle changes of the compound's electronic properties due to different types of aromatic and/or N-alkyl substituents resulted in changes of reaction mechanisms, rate-limiting step(s), and thus isotope fractionation trends. The complex sequence of electron and proton transfers during the oxidative transformation of substituted aromatic N-alkyl amines suggests highly compound- and mechanism-dependent isotope effects precluding extrapolations to other organic micropollutants reacting along the same degradation pathways.
Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland.
Marita
M
Skarpeli-Liati
Sarah G
SG
Pati
Jakov
J
Bolotin
Soren N
SN
Eustis
Thomas B
TB
Hofstetter
D000814:Aniline Compounds / Q000737:chemistry* / Q000378:metabolism; D031215:Armoracia / Q000201:enzymology; D002244:Carbon / Q000032:analysis*; D006735:Horseradish Peroxidase / Q000378:metabolism; D006841:Hydrocarbons, Aromatic / Q000737:chemistry* / Q000378:metabolism; D006859:Hydrogen / Q000032:analysis*; D007554:Isotopes / Q000032:analysis; D017895:Manganese Compounds / Q000737:chemistry; D009584:Nitrogen / Q000032:analysis*; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry
D000814:Aniline Compounds; D006841:Hydrocarbons, Aromatic; D007554:Isotopes; D017895:Manganese Compounds; D010087:Oxides; C015157:N,N-dimethylaniline; D002244:Carbon; D006859:Hydrogen; D006735:Horseradish Peroxidase; D009584:Nitrogen; C016552:manganese dioxide