Project

Discipline

compound-specific isotope analysis; CSIA; kinetic isotope effect; isotope fractionation; redox reactions; groundwater contaminants; organic micropollutants; transformation processes

Lead
Lay summary
Compound-specific stable isotope analysis (CSIA) offers new avenues for assessing transformation pathways of organic micropollutants. Fractionation of stable isotopes in individual compounds is usually indicative for an ongoing (bio)chemical reaction and thus allows one to identify such processes in complex environments as well as studying the mechanisms of degradation. However, a more comprehensive exploitation of stable isotope analysis in contaminant studies is currently hampered as both isotope effects and reaction pathways of many organic pollutants, especially those with N-containing functional groups, are not understood adequately on a mechanistic level. In fact, reactions at N-containing structural moieties (e.g., nitro-, amino-, and azo-compounds, amides, ureas) are often the initial site of attack for transformation processes of contaminants such as pesticides, pharmaceuticals, or explosives. In this project, we will develop approaches to study isotope effects during the oxidation of substituted anilines. Our principal goal is to investigate the multielement isotope fractionation of aromatic N-alkyl amines for a comprehensive application of CSIA to enzyme- and mineral-catalyzed oxidations and addition reactions of this compound class.From the combined evaluation of carbon, hydrogen, and nitrogen isotope fractionation and the corresponding apparent kinetic isotope effects, we will be able to identify the typical bonding changes at the reactive atoms in a set of probe compounds covering substituted aromatic N-methyl and N,N-dimethyl amines as well as N,N-dimethyl di- and triazines. On the basis of the interpretation of multielement isotope effects we will be able to delinate the different, sometimes competing transformation processes of micropollutants containing reactive N-alkyl amine moieties.

Direct link to Lay Summary

Last update: 21.02.2013

Active participation

Self-organised

Title	Year

Number	Title	Start	Funding scheme

Compound-specific stable isotope analysis (CSIA) offers new avenues for assessing transformation pathways of organic micropollutants. Fractionation of stable isotopes in individual compounds is usually indicative for an ongoing (bio)chemical reaction and thus allows one to identify such processes in complex environments as well as studying the mechanisms of degradation. However, a more comprehensive exploitation of stable isotope analysis in contaminant studies is currently hampered as both isotope effects and reaction pathways of many organic pollutants, especially those with N-containing functional groups, are not understood adequately on a mechanistic level. In fact, reactions at N-containing structural moieties (e.g., nitro-, amino-, and azo-compounds, amides, ureas) are often the initial site of attack for transformation processes of contaminants such as pesticides, pharmaceuticals, or explosives. In our current, SNF-funded project (no. 200020-116447/1), we provide the basis for assessing reductions of nitroaromatic compounds at contaminated sites using CSIA and we have developed approaches to study isotope effects during the oxidation of substituted anilines. Here, we propose to investigate the multielement isotope fractionation of aromatic N-alkyl amines to enable a comprehensive application of CSIA to enzyme- and mineral-catalyzed oxidations and addition reactions of this compound class. The requested one-year follow-up project for the termination of a PhD thesis takes full advantage of the model systems set up so far for studying oxidative N-dealkylation processes that are mediated by manganese oxides or peroxidase-enzymes. From the combined evaluation of carbon, hydrogen, and nitrogen isotope fractionation and the corresponding apparent kinetic isotope effects, we will be able to identify the typical bonding changes at the reactive atoms in a set of probe compounds covering substituted aromatic N-methyl and N,N-dimethyl amines as well as N,N-dimethyl di- and triazines. On the basis of the interpretation of multielement isotope effects we will be able to delinate the different, sometimes competing transformation processes of micropollutants containing reactive N-alkyl amine moieties. Finally, the proposed research will also benefit from the international collaboration, which was established during the current project, to obtain theoretical support from density functional theory calculations for the interpretation of observed kinetic and equilibrium isotope effects.