Reactions of nitrogen-containing compounds with ozone: kinetics and mechanisms

Nitrogen-containing moieties are widespread in natural waters in dissolved organic nitrogen and micropollu-tants. They are often susceptible to an electrophilic attack of ozone because of the electron-rich nature of the neutral form of nitrogen in organic compounds. This indicates that reactions of nitrogen-containing compounds with ozone inevitably occur in water and wastewater treatment where ozonation is applied for disinfection or oxidation. Despite the relevance to ozone chemistry, the knowledge on reactions of ozone with some principal nitrogen-containing functional groups is limited. The aim of this thesis was to elucidate reaction mechanisms of nitrogen-containing compounds with ozone for common nitrogen-containing functional groups: aliphatic amines and azoles. The primary objectives were (1) to determine the second-order rate constants for the reactions of nitrogen-containing compounds with ozone (kO3), (2) to identify/quantify transformation products and reactive oxygen species, (3) to perform kinetic simulations and quantum chemical computations to supplement or corroborate empirical evidences. Reaction mechanisms were proposed by compiling the results from all aspects, providing a better understanding of nitrogen-ozone chemistry. The investigation of triethylamine, diethylamine, and ethylamine yielded kO3 of the neutral form of amines ranging from 9.310^4 M-1 s-1 to 2.210^6 M-1 s-1. The apparent kO3 at pH 7 for potential or identified transformation products were 6.810^5 M-1 s-1 for N,N-diethylhydroxylamine, ~10^5 M-1 s-1 for N-ethylhydroxylamine, 1.910^3 M-1 s-1 for N-ethylethanimine oxide, and 3.4 M-1 s-1 for nitroethane. All amines predominantly underwent oxygen-transfer pathways to form major transformation products containing nitrogen-oxygen bonds: triethylamine N-oxide (88% per abated triethylamine) and nitroethane (69% per abated diethylamine and 100% per abate ethylamine). N,N-diethylhydroxylamine was a potential primary transformation product during the diethylamine-ozone reaction. Its formation was not confirmed due to its high ozone reactivity, but supported by measurements of reactive oxygen species, kinetic simulations, and quantum chemical computations. Pyrrole and imidazole reacted fast (kO3 > 10^3 M-1 s-1 at pH 1 â 12), whereas pyrazole reacted moderately fast with ozone (kO3 = 56 M-1 s-1 at pH 7). All studied azoles underwent an addition of ozone to the C-C double bond in the ring. Subsequent pathways after the initial ozone addition varied considerably among the azoles. Pyrrole reacted with ozone via a Criegee-type and an oxygen-addition mechanism. The major identified products (yield per abated pyrrole) were maleimide (34%), formamide (14%) and formate (54%). Imidazole predominantly reacted via a Criegee-type mechanism with ring cleavage and formation of the three fragments, formamide, cyanate, and formate (~100 % yields, respectively), completely closing the mass balance. For pyrazole, only carbonous products were identified (126% formate and 34% glyoxal per abated pyrazole). Products containing hydroxypyrazole and hydrazide moieties were postulated, possibly formed via an oxygen addition and a Criegee-type mechanism, respectively. The nitrogenous transformation products identified during this study may have different environmental implications. Some of them (e.g., nitroalkanes, N-formyl compounds) require further efforts to understand their impact on the aquatic environment and human health.

Ring-Opening Reactions of Aminocyclopropanes and Aminocyclobutanes

Mingming Wang

Nitrogen-containing compounds are an important class of molecules in medicinal chemistry, chemical biology, biochemistry, material sciences or environmental sciences. Organic nitrogen occurs in many forms, ranging from small building blocks such as urea, amino acids, nucleotides, to complex natural products, drug molecules, proteins, nucleic acids, among others. The transformation of easily-accessed nitrogen-containing building blocks into more complex nitrogen-containing structures is therefore important for the synthesis of bioactive compounds or functional materials. Interested in donor-acceptor aminocyclopropanes and aminocyclobutanes, we first developed a Lewis-acid catalyzed formal [4+1] cycloaddition of donor-acceptor aminocyclobutanes with isocyanides, which resulted in the formation of cyclopentene-1,2-diamines. We then attempted to develop a formal [3+2] cycloaddition of donor-acceptor aminocyclopropanes with electron-deficient alkenes, which was mechanistically inspired by the Morita-Baylis-Hillman reaction. Apart from the donor-acceptor system, we were also attracted by simple aminocyclopropanes without electron-withdrawing group at vicinal position. We anticipated that the incorporation of cyclopropylamine into carboxylic-containing compounds followed by ring opening functionalization reactions could be used for the synthesis of more complex products. Therefore, we first disclosed an oxidative ring-opening strategy to transform acyl, sulfonyl or carbamate protected aminocyclopropanes into 1,3-dielectrophilic carbon intermediates bearing a halide atom (Br, I) and a N,O-acetal. Replacing the alkoxy group of the N,O-acetal was achieved under acidic conditions via an elimination-addition pathway, while substitution of the halides by nucleophiles was done under basic conditions via a SN2 pathway, generating a wide range of 1,3-difunctionalized propylamines. Based on the transformation described above, we further discovered an efficient synthesis of 4-amino thiochromans starting from simple aminocyclopropanes and thiophenols through a formal [3+3] annulation reaction. Next, we developed an oxidative ring-opening strategy to transform cyclopropylamides and cyclobutylamides into fluorinated imines. The imines can be isolated in their more stable hemiaminal form, with the fluorine atom installed selectively at the terminal position. Both cheap benzophenone with UV A light or organic and inorganic dyes with blue light could be used as photoredox catalysts to promote this process. Various fluorinated amines were then obtained by nucleophilic attack on the hemiaminals in one pot, giving access to a broad range of useful building blocks for medicinal chemistry. Finally, we turned our attention to the synthesis of diamines, which are essential building blocks for the synthesis of agrochemicals, drugs and organic materials, yet their synthesis remains challenging, as both nitrogen moieties need to be differentiated and diverse substitution patterns (1,2-, 1,3 or 1,4) are required. We described a new strategy giving access to 1,2-, 1,3- and 1,4- amido azides as orthogonally protected diamines based on the nitrogen-directed diazidation of alkenes, cyclopropanes and cyclobutanes.Other unsuccessful efforts over the last four years have also been described, together with some preliminary results of ring-opening cyanation and arylation reactions.

EPFL2022

Elimination of micropollutants in wastewater treatment plants : Ozonation or activated carbon? Conclusions of a one-year pilot project

David Andrew Barry, Luiz Felippe De Alencastro, Anoys Magnet, Jonas Margot, Luca Rossi

Many organic micropollutants present in wastewater, such as pharmaceuticals and pesticides, are poorly removed in conventional wastewater treatment plants (WWTP). To reduce the release of these substances into the aquatic environment, advanced treatments are necessary and may be soon mandatory in Switzerland. Two advanced treatments were tested in pilot systems over more than one year at the municipal WWTP of Lausanne, Switzerland. The first pilot involves the ozonation of the effluent to oxidize organic substances. It is followed by a sand filtration (SF) to remove the readily biodegradable reaction products. The second pilot consists of a powdered activated carbon (PAC) addition into the effluent to sorb micropollutants. It is followed either by a membrane filtration (ultrafiltration) or a sand filtration to separate the PAC from the treated water. A selection of 58 potentially problematic substances (pharmaceuticals, pesticides, endocrine disruptors) were regularly measured at different stages of treatment by ultra performance liquid chromatography coupled to a tandem mass spectrometer, and a large battery of ecotoxicological tests (16 in vitro and 9 in vivo assays with different organisms) were performed to evaluate the toxicity of the effluents. The results showed that most compounds were removed over 80% with an average ozone dose of about 5.5 mgO3/l or a PAC dose between 10 and 20 mg/l. Only some single compounds, such as X-ray contrast media, were only partially eliminated in both cases. A clear reduction in toxicity was also observed after the two treatments in most of the cases. These two processes (ozonation and PAC addition) are therefore effective to reduce the release of micropollutants into surface waters. Ozonation-SF and PAC-SF proved to be feasible in terms of implementation and operation at large-scale in WWTP, for relatively similar investment and operation costs (about 0.1 to 0.15 € per m3 treated based on local costs). Each technique has its advantages and disadvantages. Therefore the method selection should be made case by case for each WWTP depending on the local constraints (e.g. space, security, energy costs, existing treatment processes, sludge disposal process, need for disinfection, etc.), the quality and the quantity of incoming water and the desired output water quality.

2011

Elimination of micropollutants in wastewater treatment plants: Ozonation or activated carbon? Conclusions of a one-year pilot project

David Andrew Barry, Nathalie Chèvre Rossi, Luiz Felippe De Alencastro, Anoys Magnet, Jonas Margot, Luca Rossi

Many organic micropollutants present in wastewater, such as pharmaceuticals and pesticides, are poorly removed in conventional wastewater treatment plants (WWTP). To reduce the release of these substances into the aquatic environment, advanced treatments are necessary. Two advanced treatments were tested in pilot systems over more than one year at the municipal WWTP of Lausanne, Switzerland. The first pilot involves the ozonation of the effluent to oxidize organic substances. It is followed by sand filtration (SF) to remove the readily biodegradable reaction products. The second pilot consists of a powdered activated carbon (PAC) addition into the effluent to sorb micropollutants. It is followed either by a membrane filtration (ultrafiltration) or a sand filtration to separate the PAC from the treated water. A selection of 58 potentially problematic substances (pharmaceuticals, pesticides, endocrine disruptors) were regularly measured at different stages of treatment by ultra performance liquid chromatography coupled to a tandem mass spectrometer, and a large battery of ecotoxicological tests (16 in vitro and 9 in vivo assays with different organisms) were performed to evaluate the toxicity of the effluents. The results showed that most compounds were removed over 80% with an average ozone dose of about 5.5 mgO3/l or a PAC dose between 10 and 20 mg/l. Only some single compounds, such as X-ray contrast media, were only partially eliminated in both cases. A clear reduction in toxicity was also observed after the two treatments in most of the cases. These two processes (ozonation and PAC addition) are therefore effective to reduce the release of micropollutants into surface waters. Ozonation-SF and PAC-SF proved to be feasible in terms of implementation and operation at large-scale in WWTP, for relatively similar investment and operation costs (about 0.1 to 0.15 € per m3 treated based on local costs). Each technique has its advantages and disadvantages. Therefore the method selection should be made case by case for each WWTP depending on the local constraints (e.g. space, security, energy costs, existing treatment processes, sludge disposal process, need for disinfection, etc.), the quality and the quantity of incoming water and the desired output water quality

2011

Ring-Opening Reactions of Aminocyclopropanes and Aminocyclobutanes

Mingming Wang

EPFL2022

Elimination of micropollutants in wastewater treatment plants : Ozonation or activated carbon? Conclusions of a one-year pilot project

David Andrew Barry, Luiz Felippe De Alencastro, Anoys Magnet, Jonas Margot, Luca Rossi

2011

Elimination of micropollutants in wastewater treatment plants: Ozonation or activated carbon? Conclusions of a one-year pilot project

David Andrew Barry, Nathalie Chèvre Rossi, Luiz Felippe De Alencastro, Anoys Magnet, Jonas Margot, Luca Rossi

Many organic micropollutants present in wastewater, such as pharmaceuticals and pesticides, are poorly removed in conventional wastewater treatment plants (WWTP). To reduce the release of these substances into the aquatic environment, advanced treatments are necessary. Two advanced treatments were tested in pilot systems over more than one year at the municipal WWTP of Lausanne, Switzerland. The first pilot involves the ozonation of the effluent to oxidize organic substances. It is followed by sand filtration (SF) to remove the readily biodegradable reaction products. The second pilot consists of a powdered activated carbon (PAC) addition into the effluent to sorb micropollutants. It is followed either by a membrane filtration (ultrafiltration) or a sand filtration to separate the PAC from the treated water. A selection of 58 potentially problematic substances (pharmaceuticals, pesticides, endocrine disruptors) were regularly measured at different stages of treatment by ultra performance liquid chromatography coupled to a tandem mass spectrometer, and a large battery of ecotoxicological tests (16 in vitro and 9 in vivo assays with different organisms) were performed to evaluate the toxicity of the effluents. The results showed that most compounds were removed over 80% with an average ozone dose of about 5.5 mgO3/l or a PAC dose between 10 and 20 mg/l. Only some single compounds, such as X-ray contrast media, were only partially eliminated in both cases. A clear reduction in toxicity was also observed after the two treatments in most of the cases. These two processes (ozonation and PAC addition) are therefore effective to reduce the release of micropollutants into surface waters. Ozonation-SF and PAC-SF proved to be feasible in terms of implementation and operation at large-scale in WWTP, for relatively similar investment and operation costs (about 0.1 to 0.15 € per m3 treated based on local costs). Each technique has its advantages and disadvantages. Therefore the method selection should be made case by case for each WWTP depending on the local constraints (e.g. space, security, energy costs, existing treatment processes, sludge disposal process, need for disinfection, etc.), the quality and the quantity of incoming water and the desired output water quality

2011