Experimental and Theoretical Study of the OH-Initiated Degradation of Piperazine under Simulated Atmospheric Conditions

Tan, Wen; Zhu, Liang; Mikoviny, Tomáš; Nielsen, Claus J.; Wisthaler, Armin; D’Anna, Barbara; Antonsen, Simen Gjelseth; Stenstrøm, Yngve; Farren, Naomi J.; Hamilton, Jacqueline F.; Boustead, Graham A.; Brennan, Alexander; Ingham, T.; Heard, D. E.

doi:10.1021/acs.jpca.0c10223

Cited by 12 publications

(16 citation statements)

References 49 publications

(86 reference statements)

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“…In addition, the activation energy for the H abstraction from the -NH-group in the q Cl + indole reaction is much lower than the corresponding q OH + indole reaction. This is consistent with previously reported reactions of other amines with q OH and q Cl (F. F. Ma et al, 2018aMa et al, , 2021bXie et al, 2014Xie et al, , 2015Xie et al, , 2017Tan et al, 2021;Ren and Da Silva, 2019;Borduas et al, 2015).…”

Section: Initial Reactions Of Indolesupporting

confidence: 93%

“…It was found that the spin density distribution was mainly centered at the C atoms (C4 (0.662), C6 (0.261), C8 (0.178)) and N atom (0.256), indicating that the C 8 H 6 N radical is delocalized. This is in contrast to previously studied N-centered radicals formed from alkylamine oxidation, which is highly localized (Xie et al, 2015(Xie et al, , 2014Ma et al, 2018a;Tan et al, 2021;Borduas et al, 2015). Therefore, O 2 addition to the C4, C6, C8 and N1 sites (including attack from both sides) is considered for the reaction of the C 8 H 6 N radicals with O 2 .…”

Section: Subsequent Reactions Of C 8 H 6 N Radicals From the H-abstra...mentioning

confidence: 95%

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Atmospheric oxidation mechanism and kinetics of indole initiated by ●OH and ●Cl: a computational study

Xue

Elm

et al. 2022

Atmos. Chem. Phys.

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Abstract. The atmospheric chemistry of organic nitrogen compounds (ONCs) is of great importance for understanding the formation of carcinogenic nitrosamines, and ONC oxidation products might influence atmospheric aerosol particle formation and growth. Indole is a polyfunctional heterocyclic secondary amine with a global emission quantity almost equivalent to that of trimethylamine, the amine with the highest atmospheric emission. However, the atmospheric chemistry of indole remains unclear. Herein, the reactions of indole with ⚫OH and ⚫Cl, and subsequent reactions of resulting indole radicals with O2 under 200 ppt NO and 50 ppt HO2⚫ conditions, were investigated by a combination of quantum chemical calculations and kinetics modeling. The results indicate that ⚫OH addition is the dominant pathway for the reaction of ⚫OH with indole. However, both ⚫Cl addition and H abstraction are feasible for the corresponding reaction with ⚫Cl. All favorably formed indole radicals further react with O2 to produce peroxy radicals, which mainly react with NO and HO2⚫ to form organonitrates, alkoxy radicals and hydroperoxide products. Therefore, the oxidation mechanism of indole is distinct from that of previously reported amines, which primarily form highly oxidized multifunctional compounds, imines or carcinogenic nitrosamines. In addition, the peroxy radicals from the ⚫OH reaction can form N-(2-formylphenyl)formamide (C8H7NO2), for the first time providing evidence for the chemical identity of the C8H7NO2 mass peak observed in the ⚫OH + indole experiments. More importantly, this study is the first to demonstrate that despite forming radicals by abstracting an H atom at the N site, carcinogenic nitrosamines were not produced in the indole oxidation reaction.

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Section: Initial Reactions Of Indolesupporting

confidence: 93%

Section: Subsequent Reactions Of C 8 H 6 N Radicals From the H-abstra...mentioning

confidence: 95%

Atmospheric oxidation mechanism and kinetics of indole initiated by ●OH and ●Cl: a computational study

Xue

Elm

et al. 2022

Atmos. Chem. Phys.

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“…Imines have been detected as major products in the atmospheric gas phase photo-oxidation of amines, − with N -methylmethanimine (CH 3 NCH 2 , MMI) accounting for around 70% of the products formed in dimethylamine and 50% in trimethylamine photo-oxidation . Amines are normally found in the low ppbv-range in the natural atmosphere, with methylamine, dimethylamine, and trimethylamine being among the most abundant .…”

Section: Introductionmentioning

confidence: 99%

Atmospheric Chemistry of N-Methylmethanimine (CH₃N═CH₂): A Theoretical and Experimental Study

et al. 2022

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The OH-initiated photo-oxidation of N -methylmethanimine, CH 3 N=CH 2 , was investigated in the 200 m 3 EUPHORE atmospheric simulation chamber and in a 240 L stainless steel photochemical reactor employing time-resolved online FTIR and high-resolution PTR-ToF-MS instrumentation and in theoretical calculations based on quantum chemistry results and master equation modeling of the pivotal reaction steps. The quantum chemistry calculations forecast the OH reaction to primarily proceed via H-abstraction from the =CH 2 group and π-system C-addition, whereas H-abstraction from the −CH 3 group is a minor route and forecast that N-addition can be disregarded under atmospheric conditions. Theoretical studies of CH 3 N=CH 2 photolysis and the CH 3 N=CH 2 + O 3 reaction show that these removal processes are too slow to be important in the troposphere. A detailed mechanism for OH-initiated atmospheric degradation of CH 3 N=CH 2 was obtained as part of the theoretical study. The photo-oxidation experiments, obstructed in part by the CH 3 N=CH 2 monomer–trimer equilibrium, surface reactions, and particle formation, find CH 2 =NCHO and CH 3 N=CHOH/CH 2 =NCH 2 OH as the major primary products in a ratio 18:82 ± 3 (3σ-limit). Alignment of the theoretical results to the experimental product distribution results in a rate coefficient, showing a minor pressure dependency under tropospheric conditions and that can be parametrized k ( T ) = 5.70 × 10 –14 × ( T /298 K) 3.18 × exp(1245 K/ T ) cm 3 molecule –1 s –1 with k 298 = 3.7 × 10 –12 cm 3 molecule –1 s –1 . The atmospheric fate of CH 3 N=CH 2 is discussed, and it is concluded that, on a global scale, hydrolysis in the atmospheric aqueous phase to give CH 3 NH 2 + CH 2 O will constitute a dominant loss process. N 2 O will not be formed in the atmospheric gas phase degradation, and there are no indications of nitrosamines and nitramines formed as primary products.

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“…Piperazine is an efficient and widely employed CCS amine solvent, whose initial oxidation by OH radical has so far been reported to have a low potential for generating nitrosamines and nitramines. , Its major channel of oxidation is formation of its imine derivative 1,2,3,6-tetrahydropyrazine (THPyz) as shown in Scheme , with branching ratio values of 0.2–0.6 and 0.9 found by computational and experimental studies. − The atmospheric fate of this imine product however has received no attention. In fact, just a few studies have focused on the atmospheric chemistry of imines in general, − despite consistently appearing as major products of amine oxidation. − …”

Section: Introductionmentioning

confidence: 99%

Atmospheric Oxidation of Imine Derivative of Piperazine Initiated by OH Radical

Almeida

Kurtén

2022

ACS Earth Space Chem.

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The cyclic imine 1,2,3,6-tetrahydropyrazine (THPyz) has been observed to be the major atmospheric photo-oxidation product of piperazine, a widely used solvent in carbon-capture technology, yet little is known about its own fate. Very few studies have focused on the atmospheric chemistry of imines in general, despite consistently appearing as major products of amine oxidation. In this work, we explore the reaction mechanism of THPyz oxidation initiated by OH radicals, as well as the fate of the first-generation C-centered (alkyl) and N-centered (aminyl) radical products, with quantum chemistry and theoretical kinetics methods. We predict that the major initial reaction steps involve H-abstraction from a carbon adjacent to the amine nitrogen, leading to subsequent formation of a second imine function via the O 2 -addition/HO 2 -elimination pathway. Calculated yields of potentially hazardous products are low but non-negligible. Typically carcinogenic compounds, nitrosamines and nitramines, are expected to have a maximum yield of ∼7% and ∼11%, respectively, under high NO x regimes, considering the uncertainties in the obtained rates. Low yield (1−14%) of an isocyanate is also predicted, formed in a channel following initial H-abstraction from the imine carbon. The aminyl radical formed from OH radical addition to the imine carbon undergoes fast C−C bond scission, leading to an imidic acid. These pathways are minor for OH radical oxidation of THPyz but could be more competitive for other Schiff bases.

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Experimental and Theoretical Study of the OH-Initiated Degradation of Piperazine under Simulated Atmospheric Conditions

Cited by 12 publications

References 49 publications

Atmospheric oxidation mechanism and kinetics of indole initiated by ●OH and ●Cl: a computational study

Atmospheric oxidation mechanism and kinetics of indole initiated by ●OH and ●Cl: a computational study

Atmospheric Chemistry of N-Methylmethanimine (CH₃N═CH₂): A Theoretical and Experimental Study

Atmospheric Oxidation of Imine Derivative of Piperazine Initiated by OH Radical

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Experimental and Theoretical Study of the OH-Initiated Degradation of Piperazine under Simulated Atmospheric Conditions

Cited by 12 publications

References 49 publications

Atmospheric oxidation mechanism and kinetics of indole initiated by ●OH and ●Cl: a computational study

Atmospheric oxidation mechanism and kinetics of indole initiated by ●OH and ●Cl: a computational study

Atmospheric Chemistry of N-Methylmethanimine (CH3N═CH2): A Theoretical and Experimental Study

Atmospheric Oxidation of Imine Derivative of Piperazine Initiated by OH Radical

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Atmospheric Chemistry of N-Methylmethanimine (CH₃N═CH₂): A Theoretical and Experimental Study