Next Article in Journal
Physical and Statistical Links between Errors at the Surface, in the Boundary Layer, and in the Free Atmosphere in Medium-Range Numerical Weather Predictions
Previous Article in Journal
Comparative Analysis of Two Tornado Processes in Southern Jiangsu
Previous Article in Special Issue
Quantifying Urban Daily Nitrogen Oxide Emissions from Satellite Observations
 
 
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Oxidation of Aminoacetaldehyde Initiated by the OH Radical: A Theoretical Mechanistic and Kinetic Study

Department of Chemical Engineering, The University of Melbourne, Parkville 3010, Australia
*
Author to whom correspondence should be addressed.
Atmosphere 2024, 15(8), 1011; https://doi.org/10.3390/atmos15081011
Submission received: 13 July 2024 / Revised: 8 August 2024 / Accepted: 18 August 2024 / Published: 21 August 2024
(This article belongs to the Special Issue Reactive Nitrogen and Halogen in the Atmosphere)

Abstract

:
Aminoacetaldehyde (glycinal, NH2CH2CHO) is a first-generation oxidation product of monoethanolamine (MEA, NH2CH2CH2OH), a solvent widely used for CO2 gas separation, which is proposed as the basis for a range of carbon capture technologies. A complete oxidation mechanism for MEA is required to understand the atmospheric transformation of carbon capture plant emissions, as well as the degradation of this solvent during its use and the oxidative destruction of waste solvent. In this study, we have investigated the OH radical-initiated oxidation chemistry of aminoacetaldehyde using quantum chemical calculations and RRKM theory/master equation kinetic modeling. This work predicts that aminoacetaldehyde has a tropospheric lifetime of around 6 h and that the reaction predominantly produces the NH2CH2CO radical intermediate at room temperature, along with minor contributions from NH2CHCHO and NHCH2CHO. The dominant radical intermediate NH2CH2CO is predicted to promptly dissociate to NH2CH2 and CO, where NH2CH2 is known to react with O2 under tropospheric conditions to form the imine NH = CH2 + HO2. The NH2CHCHO radical experiences captodative stabilization and is found to form a weakly bound peroxyl radical upon reaction with O2. Instead, the major oxidation product of NH2CHCHO and the aminyl radical NHCH2CHO is the imine NH = CHCHO (+HO2). In the atmosphere, the dominant fate of imine compounds is thought to be hydrolysis, where NH = CH2 will form ammonia and formaldehyde, and NH = CHCHO will produce ammonia and glyoxal. Efficient conversion of the dominant first-generation oxidation products of MEA to ammonia is consistent with field observations and supports the important role of imine intermediates in MEA oxidation.

1. Introduction

Amine-based carbon capture and storage (CCS) is a proposed technology to handle CO2 pollution from fossil fuel-fired power plants and other industries [1,2,3,4], where CO2 is absorbed from flue gas into a reactive amine solvent, then thermally stripped to produce a concentrated CO2 stream. Monoethanolamine (MEA, or 2-aminoethanol) is the benchmark solvent for CO2 gas separation, including carbon capture technology [5,6,7,8]. A serious concern with solvent-based CCS operations is their potential to release volatile amines like MEA into the atmosphere, where they can contribute to secondary aerosol formation and the generation of toxic oxidized nitrogen compounds [4,9,10,11]. Moreover, aqueous amine solvents are known to degrade over time as they are exposed to high temperatures and reactive flue gases. This produces large quantities of waste solvents that must be disposed of. Various thermal and oxidative process technologies exist to dispose of waste amines, such as incineration, co-firing, and supercritical water oxidation (SCWO). There is, therefore, a great need to understand the oxidation chemistry of MEA and related amines in diverse environments, including in the atmosphere, during CO2 absorption and stripping, in combustion, and during SCWO.
The presently accepted mechanism for the atmospheric degradation of MEA is shown in Scheme 1. Recent investigations of MEA oxidation [12,13,14,15,16] demonstrate that the process is primarily initiated by OH radical attack via H-abstraction from the two unique C—H sites and, to a lesser extent, from the N—H and O—H sites, to produce four isomeric radicals. This reaction proceeds with a relatively large rate coefficient of 7.27 × 10−11 cm3 molecule−1 s−1 at 298 K. Based on several experimental and theoretical investigations, the α-aminoalkyl (NH2CHCH2OH) and α-hydroxyalkyl (NH2CH2CHOH) radicals are expected as the dominant initial products of the MEA + OH reaction, and their subsequent reactions will, therefore, determine the primary initial products of MEA oxidation [12,14,15].
A recent analysis of MEA atmospheric chemistry shows that the NH2CHCH2OH radical reacts with O2 to directly produce 2-iminoethanol (NH = CHCH2OH) and HO2 radical via the chemically activated α-aminoalkylperoxyl mechanism [16]. Similarly, the NH2CH2CHOH radical reacts with O2 to produce aminoacetaldehyde (NH2CH2CHO) and HO2 via the α-hydroxyalkylperoxyl mechanism [12,17]. The C2H5NO isomers 2-iminoethanol and aminoacetaldehyde are, thus, the key first-generation oxidation products of MEA.
In the atmosphere, 2-iminoethanol is expected to undergo hydrolysis to produce ammonia and glycolaldehyde (CH2OHCHO) [16,18]. The atmospheric fate of aminoacetaldehyde, however, is all but unknown despite this compound being detected in atmospheric MEA oxidation experiments [4] and in the stack gases of industrial MEA absorbers [19]. Aminoacetaldehyde has also been implicated as a product of redox reactions [20] and flame-induced aqueous oxidation [21,22] of MEA. Past chemical transport modeling of the atmospheric impact of MEA emissions has assumed that the aminoacetaldehyde intermediate predominantly reacts to give formamide (NH2CHO), with smaller yields of 2-oxoacetamide (NH2C(O)CHO) [23], but there is little experimental or theoretical support for these mechanisms.
This study attempts to address the gaps in our understanding of the atmospheric fate of aminoacetaldehyde through a theoretical investigation of the aminoacetaldeyhde + OH reaction. A theoretical approach is warranted here because α-amino aldehydes are reactive, challenging to synthesize, and prone to assembly in the condensed phase (which may help explain the absence of direct experimental studies) [24]. Rate coefficients and branching fractions are presented for the aminoacetaldeyhde + OH reaction as a function of temperature, followed by an investigation of the oxidation reactions of the radicals that are formed. In addition to its role in atmospheric chemistry, aminoacetaldehyde has been proposed as an important species in interstellar and prebiotic chemistry, where it can serve as a precursor to the amino acid glycine (note that within this context, aminoacetaldehyde is usually referred to as glycinal) [25,26,27,28]. The present investigation of aminoacetaldehyde and its free radicals may, therefore, also be of relevance to understanding its astrochemical significance.

2. Methods

Ab initio calculations reported here are all with the composite G3X-K method [29], which uses M06-2X/6-31G(2df,p)-optimized structures and vibrational frequencies in a series of single-point wave function theory energy evaluations at up to the CCSD(T) level of theory. Reported energies are 0 K enthalpies (i.e., zero point energy corrected electronic energies). Relaxed internal rotor scans were performed to identify the lowest energy conformation for each stationary point. Intrinsic reaction coordinate (IRC) scans were used to confirm the connectivity of each transition state. All electronic structure theory calculations were performed in the Gaussian 16 program [30].
Statistical reaction rate theory calculations were performed using the MultiWell 2016 [31] program suite. Sums and densities of states are from M06-2X/6-31G(2df,p)-optimized structures calculated according to the rigid rotor-harmonic oscillator model. Microscopic rate coefficients k(E) are from RRKM theory, with structures treated as symmetric tops with an active 1-dimensional and an inactive 2-dimensional rotor. Hydrogen abstraction reactions are corrected for quantum mechanical tunneling from Eckart’s theory. The barrierless association of NH2CH2CHO with OH was treated with the restricted Gorin model [32], following an approach described in further detail previously [33,34]. In the master equation calculations, bath gas collisions are treated using a Lennard-Jones model. The Lennard-Jones parameters for all C2H6NO2 wells were estimated as σ = 4.94 Å and ε = 555.6 K using the Joback method for boiling point estimation along with additivity procedures [35]. Stochastic master equation simulations feature 106 trials of up to 100 collisions at 1 atm pressure for the temperature range of 300–2000 K. Calculated rate coefficients are fit to Arrhenius expressions for use in chemical kinetic modeling. Based upon the choice of theoretical method, we estimate that our rate coefficient calculations have an uncertainty of less than 1 kcal/mol in activation energies Ea and a factor of two in pre-exponential factors A.

3. Results

A potential energy surface for the NH2CH2CHO + OH reaction is shown in Figure 1. The optimized wells and transition state structures are presented in Figure 2 and Figure 3.
Figure 1 reveals the reaction of aminoacetaldehyde with OH to proceed through the formation of the pre-reactive complexes W1, W2, and W3 (see Figure 2), with each sitting at around 4 to 5 kcal mol−1 below the energy of the reactants. In each of these complexes, the OH radical is coordinated with—and acting as a hydrogen bond acceptor for—the H atom, which it abstracts, via TS1 (−1.4 kcal mol−1), TS2 (−0.6 kcal mol−1), and TS3 (−0.7 kcal mol−1), respectively. These three channels produce the N-centered radical NHCH2CHO (TS1) and the two C-centered radicals, NH2CHCHO (TS2) and NH2CH2CO (TS3), along with H2O. Moreover, the pre-reaction complexes can interconvert via TSW1-2 and TSW1-3, with barriers around 2–3 kcal mol−1 below the reactants.
A statistical reaction rate model of the NH2CH2CHO + OH reaction has been developed on the basis of the potential energy surface shown in Figure 1. In this model, barrierless formation of the NH2CH2CHO∙∙∙OH adducts (W1W3) is treated using the restricted Gorin approach, based on Morse potential fits. The parameters used to fit the Morse potential, external 2D rotor, and restricted internal rotational constants are listed in Table 1 for the formation of W1 at 300–2000 K. Similar parameters for the formation of W2 and W3 are provided in the Supporting Information. The transition state 2D moment of inertia decreases from around 300 to 150 amu Å2 as temperature increases from 300 to 2000 K, indicating a tightening of the hypothetical rate-determining structures.
Master equation simulations were carried out to predict the overall rate coefficient and branching fractions for the NH2CH2CHO + OH reaction from 300 to 2000 K in 1 atm of N2. The calculated rate coefficients are depicted in Figure 4, with branching fractions shown in Figure 5. Figure 4 reveals that the reaction is relatively rapid at 300 K, with a total rate coefficient of 2.3 × 10−11 cm3 molecule−1 s−1, compared to a capture rate of 7.8 × 10−11 cm3 molecule−1 s−1. For a typical daytime tropospheric OH concentration of 2 × 106 molecule/cm3, we predict that the lifetime of aminoacetaldehyde is ca. 6 h, indicating that it will experience limited transport beyond the planetary boundary layer.
At 300 K, the reaction of aminoacetaldehyde with OH is dominated by formyl group OC—H abstraction to NH2CH2CO (46.5%), with smaller yields of the NHCH2CHO (28.3%) and NH2CHCHO (25.2%) radicals. As temperature increases from 300 K, the NH2CH2CHO + OH reaction exhibits classical negative activation energy behavior, as the activated pre-reaction complexes demonstrate increased probability to re-dissociate. This effect is particularly pronounced for formyl abstraction, with the rate coefficient dropping from ca. 5 × 10−11 cm3 molecule−1 s−1 to 1 × 10−11 cm3 molecule−1 s−1 across the investigated temperature range.
Our calculations indicate that NH2CH2CO will be the dominant intermediate radical in the OH radical-initiated oxidation of aminoacetaldehyde, along with non-negligible yields of NHCH2CHO and NH2CHCO. The NH2CH2CO radical is relatively fragile and can dissociate to CH2NH2 + CO with a barrier of less than 9 kcal/mol, as shown in Figure 6. This barrier is sufficiently low to be rapid at room temperature. Moreover, because of the exothermicity of the reaction NH2CH2CHO + OH → NH2CH2CO + H2O (>30 kcal/mol), the nascent NH2CH2CO radical will carry sufficient excess vibrational energy to undergo prompt dissociation before it is able to participate in collisions with surrounding O2 molecules, thus precluding the formation of a peroxyl radical intermediate. In the air, the NH2CH2 radical will react with O2 to produce NH = CH2 + HO2 [36,37,38]. Assuming that NH = CH2 reacts with water to produce ammonia and formaldehyde, formyl abstraction from aminoacetaldehyde in the air, therefore, results in the following net outcome:
NH2CH2CHO + OH + O2 + H2O → NH3 + HCHO + CO + H2O + HO2
Importantly, the above process illustrates that a cascade of reactions following OH radical initiation can rapidly convert aminoacetaldehyde into ammonia and oxygenated single-carbon species. This is consistent with the experimental observation of high ammonia concentrations both in the stack emissions of CO2 absorbers operating on MEA [19] and in atmospheric chamber studies of MEA photooxidation [4].
Potential energy surfaces for reactions of the minor NH2CHCHO and NHCH2CHO radicals with O2 have been developed and are shown in Figure 7 and Figure 8, respectively (structures of the key wells and transition states are illustrated in the Supporting Information). By analogy with the α-aminoalkyl radical oxidation mechanism [37], the NH2CHCHO radical associates with O2 to form a peroxyl radical intermediate that can eliminate HO2 to form an imine, without the participation of a hydroperoxide intermediate. However, as Figure 7 reveals, O2 addition to NH2CHCHO releases surprisingly little energy (11 kcal/mol). We attribute this to the captodative effect, where resonance stabilization between the NH2CH—CH = O and NH2—CH = CH—O radical forms is further enhanced by electron donation from the nitrogen lone pair to create zwitterionic resonance structures such as ●+NH2—CH = CH—O [39]. This is demonstrated in the spin density plot for NH2CH2CO (Figure 8), which reveals contributions from all three of the above-mentioned resonance structures. The consequence of captodative stabilization of NH2CHCHO is evident in Figure 1, where this radical is stabilized by over 20 and 30 kcal/mol relative to the respective NH2CH2CO and NHCH2CHO isomers. This is consistent with previous calculations on this free radical, which predict a radical stabilization energy of 22 kcal/mol, of which around 10 kcal/mol is attributed to the captodative effect [39]. Although the peroxyl radical intermediate (W2-1) can still eliminate HO2 with a relatively low barrier (ca. 19 kcal/mol), comparable to that in other α-aminoalkylperoxyl radicals [36,37], the low exothermicity of O2 addition makes this an overall endothermic process.
Canonical transition state theory calculations have been used to estimate rate coefficients for direct H abstraction by O2 from NH2CHCHO via the transition state depicted in Figure 7. This assumes that the reaction bypasses the weak peroxyl radical intermediate and likely represents an upper limit to the true rate coefficient. At room temperature, this gives k = 1.3 × 10−15 cm3 molecule−1 s−1. Although relatively slow, for a tropospheric O2 concentration of 5.2 × 1018 molecule cm−3, this corresponds to a pseudo-first-order reaction rate of 6760 s−1 or a lifetime of 150 μs. We, therefore, predict that the NH2CHCHO radical product of the aminoaceteldehyde + OH reaction will react with O2 to form the imine NH = CHCH = O (+ HO2) in the atmosphere. Stabilization of the peroxyl radical intermediate NH2CH(O2)CHO is not expected to be significant under atmospheric conditions due to the binding energy of only 11 kcal/mol. However, if this species forms, we expect it will react with NO to give the alkoxyl radical NH2CH(O)CHO. Calculations at the G3X-K level of theory predict that this compound dissociates to the formyl radical (HCO) and formamide (NH2CHO) with a barrier of less than 1 kcal/mol. Production of formamide in even small yields may be significant given the rapid atmospheric conversion of amides to highly toxic isocyanic acid [40,41,42]. The relatively slow reaction of O2 with the captodative stabilized radical NH2CHCHO means that it may also be available to associate with NO and NO2 in the atmosphere, forming the NH2CH(NO)CHO and NH2CH(NO2)CHO radicals, respectively.
From the potential energy surface for the NHCH2CHO radical + O2 reaction (Figure 9), we see that this reaction proceeds via the process described by Alam et al. [43] for the NHCH3 + O2 radical. Here, a weak amino-peroxyl radical intermediate (W3-1) first forms, from which HO2 can be eliminated via TS3-1, which sits at 1.8 kcal/mol above the reactants. Following a similar approach to the NH2CHCHO + O2 reaction above, we predict a tropospheric lifetime of 447 μs, providing it with little opportunity to react with NOx to form nitrosamines and other harmful substances [44,45,46,47].
This study has developed a photochemical oxidation mechanism of aminoacetaldehyde, as summarized in Scheme 2, with calculated rate coefficient expression parameters listed in Table 2. Irrespective of the initial abstraction site, a sequence of oxidation and hydrolysis reactions efficiently converts the reduced nitrogen in aminoacetaldehyde into ammonia alongside oxidized C1 and C2 VOCs. The dominant reaction channel proceeds via the fragile NH2CH2CO radical, which ultimately fragments, oxidizes, and hydrolyses to CO + HCHO + NH3, thus cleaving the C—N and both C—C bonds in the initial reactant.

4. Conclusions

The photochemical oxidation mechanism and reaction kinetics of aminoacetaldehyde are determined in this study through the application of a high-level composite theoretical method and transition state theory calculations. This study reveals that formyl H-abstraction to produce the NH2CH2CO radical dominates, with appreciable contriubutions from abstraction at the other two unique sites. The NH2CH2CO radical subsequently decomposes to NH2CH2 and CO, and the reactions of NH2CH2, NH2CHCHO, and NHCH2CHO with O2 to produce imine products are shown to be important processes. Interestingly, captodative stabilization in NH2CHCHO substantially limits its reactivity toward O2.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/atmos15081011/s1, Figure S1: Optimized structures for intermediate well and transition state in the NH2CHCHO + O2 reaction, at the M06-2X/6-31G(2df,p) level; Figure S2: Optimized structures for intermediate well and transition state in the NHCH2CHO + O2 reaction, at the M06-2X/6-31G(2df,p) level; Table S1: Parameters used to Fit Morse Potential and Restricted Gorin Transition States to the NH2CH2CHO +OH Reaction, As a Function of Temperature (300−2000 K); Table S2: Parameters used to Fit Morse Potential and Restricted Gorin Transition States to the NH2CH2CHO +OH Reaction, As a Function of Temperature (300−2000 K).

Author Contributions

Conceptualization, A.A. and G.d.S.; methodology, A.A. and G.d.S.; software, A.A. and G.d.S.; validation, A.A. and G.d.S.; formal analysis, A.A. and G.d.S.; investigation, A.A. and G.d.S.; resources, A.A. and G.d.S.; data curation, A.A. and G.d.S.; writing—original draft preparation, A.A.; writing—review and editing, G.d.S.; visualization, A.A. and G.d.S.; supervision, G.d.S.; project administration, G.d.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data is contained within the article or Supplementary Material.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Veawab, A.; Tontiwachwuthikul, P.; Chakma, A. Corrosion behavior of carbon steel in the CO2 absorption process using aqueous amine solutions. Ind. Eng. Chem. Res. 1999, 38, 3917–3924. [Google Scholar]
  2. Puxty, G.; Rowland, R.; Allport, A.; Yang, Q.; Bown, M.; Burns, R.; Maeder, M.; Attalla, M. Carbon dioxide postcombustion capture: A novel screening study of the carbon dioxide absorption performance of 76 amines. Environ. Sci. Technol. 2009, 43, 6427–6433. [Google Scholar]
  3. Rubin, E.S.; Mantripragada, H.; Marks, A.; Versteeg, P.; Kitchin, J. The outlook for improved carbon capture technology. Prog. Energy Combust. Sci. 2012, 38, 630–671. [Google Scholar]
  4. Nielsen, C.J.; D’Anna, B.; Dye, C.; Graus, M.; Karl, M.; King, S.; Maguto, M.M.; Müller, M.; Schmidbauer, N.; Stenstrøm, Y. Atmospheric chemistry of 2-aminoethanol (MEA). Energy Procedia 2011, 4, 2245–2252. [Google Scholar]
  5. Veltman, K.; Singh, B.; Hertwich, E.G. Human and environmental impact assessment of postcombustion CO2 capture focusing on emissions from amine-based scrubbing solvents to air. Environ. Sci. Technol. 2010, 44, 1496–1502. [Google Scholar] [PubMed]
  6. Karl, M.; Wright, R.F.; Berglen, T.F.; Denby, B. Worst case scenario study to assess the environmental impact of amine emissions from a CO2 capture plant. Int. J. Greenh. Gas Control 2011, 5, 439–447. [Google Scholar]
  7. Reynolds, A.J.; Verheyen, T.V.; Adeloju, S.B.; Meuleman, E.; Feron, P. Towards commercial scale postcombustion capture of CO2 with monoethanolamine solvent: Key considerations for solvent management and environmental impacts. Environ. Sci. Technol. 2012, 46, 3643–3654. [Google Scholar] [PubMed]
  8. Rochelle, G.T. Amine scrubbing for CO2 capture. Science 2009, 325, 1652–1654. [Google Scholar]
  9. Luis, P. Use of monoethanolamine (MEA) for CO2 capture in a global scenario: Consequences and alternatives. Desalination 2016, 380, 93–99. [Google Scholar]
  10. Sharma, S.D.; Azzi, M. A critical review of existing strategies for emission control in the monoethanolamine-based carbon capture process and some recommendations for improved strategies. Fuel 2014, 121, 178–188. [Google Scholar]
  11. Pitts, J.N., Jr.; Grosjean, D.; Van Cauwenberghe, K.; Schmid, J.P.; Fitz, D.R. Photooxidation of aliphatic amines under simulated atmospheric conditions: Formation of nitrosamines, nitramines, amides, and photochemical oxidant. Environ. Sci. Technol. 1978, 12, 946–953. [Google Scholar]
  12. Xie, H.-B.; Li, C.; He, N.; Wang, C.; Zhang, S.; Chen, J. Atmospheric chemical reactions of monoethanolamine initiated by OH radical: Mechanistic and kinetic study. Environ. Sci. Technol. 2014, 48, 1700–1706. [Google Scholar] [PubMed]
  13. Borduas, N.; Abbatt, J.P.; Murphy, J.G. Gas phase oxidation of monoethanolamine (MEA) with OH radical and ozone: Kinetics, products, and particles. Environ. Sci. Technol. 2013, 47, 6377–6383. [Google Scholar] [PubMed]
  14. Onel, L.; Blitz, M.; Seakins, P. Direct Determination of the Rate Coefficient for the Reaction of OH Radicals with Monoethanol Amine (MEA) from 296 to 510 K. J. Phys. Chem. Lett. 2012, 3, 853–856. [Google Scholar]
  15. Karl, M.; Dye, C.; Schmidbauer, N.; Wisthaler, A.; Mikoviny, T.; d’Anna, B.; Müller, M.; Borrás, E.; Clemente, E.; Muñoz, A. Study of OH-initiated degradation of 2-aminoethanol. Atmos. Chem. Phys. 2012, 12, 1881–1901. [Google Scholar]
  16. da Silva, G. Atmospheric chemistry of 2-aminoethanol (MEA): Reaction of the NH2CHCH2OH radical with O2. J. Phys. Chem. A 2012, 116, 10980–10986. [Google Scholar] [PubMed]
  17. da Silva, G.; Bozzelli, J.W. Role of the a-hydroxyethylperoxy radical in the reactions of acetaldehyde and vinyl alcohol with HO2. Chem. Phys. Lett. 2009, 483, 25–29. [Google Scholar]
  18. Bunkan, A.J.C.; Reijrink, N.G.; Mikoviny, T.; Muller, M.; Nielsen, C.J.; Zhu, L.; Wisthaler, A. Atmospheric chemistry of N-methylmethanimine (CH3N=CH2): A theoretical and experimental study. J. Phys. Chem. A 2022, 126, 3247–3264. [Google Scholar]
  19. Zhu, L.; Schade, G.W.; Nielsen, C.J. Real-time monitoring of emissions from monoethanolamine-based industrial scale carbon capture facilities. Environ. Sci. Technol. 2013, 47, 14306–14314. [Google Scholar]
  20. Venkata Nadh, R.; Syama Sundar, B.; Radhakrishnamurti, P.S. Kinetics of ruthenium(III) catalyzed and uncatalyzed oxidation of monoethanolamine by n-bromosuccinimide. Russ. J. Phys. Chem. A 2016, 90, 1760–1765. [Google Scholar]
  21. Nomoto, S.; Takasaki, M.; Sakata, N.; Harada, K. Flame-induced oxidation reaction of aliphatic amines in an aqueous solution. Tetrahed. Lett. 1983, 24, 3357–3360. [Google Scholar]
  22. Nomoto, S.; Shimoyama, A.; Shiraishi, S.; Sahara, D. Under-flame oxidation of amines and amino acids in an aqueous solution. Biosci. Biotechnol. Biochem. 1996, 60, 1851–1855. [Google Scholar]
  23. Karl, M.; Svendby, T.; Walker, S.-E.; Velken, A.S.; Castell, N.; Solberg, S. Modelling atsmopheric oxidation of 2-aminoethanol (MEA) emitted from post-combustion capture using WRF-Chem. Sci. Total Environ. 2015, 527–528, 185–202. [Google Scholar]
  24. Mestrom, L.; Bracco, P.; Hanefeld, U. Amino aldehydes revisited. Eur. J. Org. Chem. 2017, 7019, 7019–7025. [Google Scholar]
  25. Garrod, R.T. A three-phase chemical model of hot cores: The formation of glycine. Astrophys. J. 2013, 765, 60. [Google Scholar]
  26. Redondo, P.; Sanz-Novo, M.; Largo, A.; Barrientos, C. Amino acetaldehyde conformers: Structure and spectroscopic properties. Mon. Not. R. Astron. Soc. 2020, 492, 1827–1833. [Google Scholar]
  27. Simmie, J.M. C2H5NO isomers: From acetamide to 1,2-oxazetidine and beyond. J. Phys. Chem. A 2022, 126, 924–939. [Google Scholar] [PubMed]
  28. Marks, J.H.; Wang, J.; Kleimeier, N.F.; Turner, A.M.; Eckhardt, A.E.; Kaiser, R.I. Prebiotic synthesis and isomerization in interstellar analog ice: Glycinal, acetamide, and their enol tautomers. Angew. Chem. Int. Ed. 2023, 62, e202218645. [Google Scholar]
  29. da Silva, G. G3X-K theory: A composite theoretical method for thermochemical kinetics. Chem. Phys. Lett. 2013, 558, 109–113. [Google Scholar]
  30. Frisch, M.J.; Trucks, G.W.; Schlegel, H.B.; Scuseria, G.E.; Robb, M.A.; Cheeseman, J.R.; Scalmani, G.; Barone, V.; Petersson, G.A.; Nakatsuji, H.; et al. Gaussian 16; Gaussian, Inc.: Wallingford, CT, USA, 2016. [Google Scholar]
  31. Barker, J.; Nguyen, T.; Stanton, J.; Aieta, C.; Ceotto, M.; Gabas, F.; Kumar, T.; Li, C.; Lohr, L.; Maranzana, A. MultiWell-2016 Software Suite; University of Michigan: Ann Arbor, MI, USA, 2016. [Google Scholar]
  32. Smith, G.; Golden, D. Application of RRKM theory to the reactions OH + NO2 + N2 → HONO2 + N2 (1) and ClO + NO2 + N2 → ClONO2 + N2 (2); a modified gorin model transition state. Int. J. Chem. Kinet. 1978, 10, 489–501. [Google Scholar]
  33. da Silva, G. Reaction of methacrolein with the hydroxyl radical in air: Incorporation of secondary O2 addition into the MACR + OH master equation. J. Phys. Chem. A 2012, 116, 5317–5324. [Google Scholar] [PubMed]
  34. Ren, Z.; da Silva, G. Atmospheric oxidation of piperazine initiated by OH: A theoretical kinetics investigation. ACS Earth Space Chem. 2019, 3, 2510–2516. [Google Scholar]
  35. Sherwood, T.K.; Reid, R.C. The Properties of Gases and Liquids: Their Estimation and Correlation; McGraw-Hill: New York, NY, USA, 1958. [Google Scholar]
  36. Ly, T.; Kirk, B.B.; Hettiarachchi, P.I.; Poad, B.L.J.; Trevitt, A.J.; da Silva, G.; Blanksby, S.J. Reactions of simple and peptidic alpha-carboxylate radical anions with dioxygen in the gas phase. Phys. Chem. Chem. Phys. 2011, 13, 16314–16323. [Google Scholar]
  37. da Silva, G.; Kirk, B.B.; Lloyd, C.; Trevitt, A.J.; Blanksby, S.J. Concerted HO2 elimination from α-aminoalkylperoxyl free radicals: Experimental and theoretical evidence from the gas-phase NH2CHCO2 + O2 reaction. J. Phys. Chem. Lett. 2012, 3, 805–811. [Google Scholar]
  38. Dash, M.R.; Ali, M.A. Can a single ammonia and water molecule enhance the formation of methanimine under tropospheric conditions? Kinetics of CH2NH2 + O2 (+NH3/H2O). Front. Chem. 2023, 11, 1243235. [Google Scholar] [CrossRef]
  39. Leroy, G.; Dewispelaere, J.-P.; Benkadour, H.; Riffi Temsamani, D.; Wilante, C. Theoretical investigation of some evidences of the captodative effect. Bull. Soc. Chim. Belg. 1994, 103, 367–378. [Google Scholar]
  40. Barnes, I.; Solignac, G.; Mellouki, A.; Becker, K.H. Aspects of the atmospheric chemistry of amides. ChemPhysChem 2010, 11, 3844–3857. [Google Scholar]
  41. Borduas, N.; da Silva, G.; Murphy, J.G.; Abbatt, J.P.D. Experimental and theoretical understanding of the gas phase oxidation of atmospheric amides with OH radicals: Kinetics, products, and mechanisms. J. Phys. Chem. A 2015, 119, 4298–4308. [Google Scholar] [PubMed]
  42. Borduas, N.; Abbatt, J.P.D.; Murphy, J.G.; So, S.; da Silva, G. Gas-phase mechanisms of the reactions of reduced organic nitrogen compounds with OH radicals. Environ. Sci. Technol. 2016, 50, 11723–11734. [Google Scholar]
  43. Alam, M.A.; Ren, Z.; da Silva, G. Nitramine and nitrosamine formation is a minor pathway in the atmospheric oxidation of methylamine: A theoretical kinetic study of the CH3NH + O2 reaction. Int. J. Chem. Kinet. 2019, 51, 723–728. [Google Scholar]
  44. Yizhen, T.; Nielsen, M.; Jorgen, C. Do primary nitrosamines form and exist in the gas phase? A computational study of CH3NHNO and (CH3)2NNO. Phys. Chem. Chem. Phys. 2012, 14, 16365–16370. [Google Scholar]
  45. da Silva, G. Formation of nitrosamines and alkyldiazohydroxides in the gas phase: The CH3NH + NO reaction revisited. Environ. Sci. Technol. 2013, 47, 7766–7772. [Google Scholar] [PubMed]
  46. Liu, C.; Ma, F.; Elm, J.; Fu, Z.; Tang, W.; Chen, J.; Xie, H.-B. Mechanism and predictive model development of reaction rate constants for N-center radicals with O2. Chemosphere 2019, 237, 124411. [Google Scholar] [PubMed]
  47. Nguyen, L.T.; Mai, T.V.-T.; Vien, H.D.; Nguyen, T.T.; Huynh, L.K. Ab initio kinetics of the CH3NH + NO2 reaction: Formation of nitramines and N-alkyl nitroxides. Phys. Chem. Chem. Phys. 2023, 25, 31936–31947. [Google Scholar] [PubMed]
Scheme 1. Key reactions in the atmospheric oxidation of MEA. The further oxidation chemistry of aminoacetaldehyde (shown in red) remains poorly understood.
Scheme 1. Key reactions in the atmospheric oxidation of MEA. The further oxidation chemistry of aminoacetaldehyde (shown in red) remains poorly understood.
Atmosphere 15 01011 sch001
Figure 1. Potential energy surface for the NH2CH2CHO + OH reaction at the G3X-K level of theory (relative 0 K enthalpies in kcal/mol).
Figure 1. Potential energy surface for the NH2CH2CHO + OH reaction at the G3X-K level of theory (relative 0 K enthalpies in kcal/mol).
Atmosphere 15 01011 g001
Figure 2. Optimized structures for intermediate wells in the NH2CH2CHO + OH reaction at the M06-2X/6-31G(2df,p) level of theory.
Figure 2. Optimized structures for intermediate wells in the NH2CH2CHO + OH reaction at the M06-2X/6-31G(2df,p) level of theory.
Atmosphere 15 01011 g002
Figure 3. Optimized structures for transition states in the NH2CH2CHO + OH reaction mechanism at the M06-2X/6-31G(2df,p) level of theory.
Figure 3. Optimized structures for transition states in the NH2CH2CHO + OH reaction mechanism at the M06-2X/6-31G(2df,p) level of theory.
Atmosphere 15 01011 g003
Figure 4. Calculated rate coefficients k(T) for the different product channels in the NH2CH2CHO + OH reaction from 300–2000 K at 1 atm. Dashed black line shows the total rate coefficient.
Figure 4. Calculated rate coefficients k(T) for the different product channels in the NH2CH2CHO + OH reaction from 300–2000 K at 1 atm. Dashed black line shows the total rate coefficient.
Atmosphere 15 01011 g004
Figure 5. Calculated branching fractions for the different product channels in the NH2CH2CHO + OH reaction from 300 to 2000 K at 1 atm.
Figure 5. Calculated branching fractions for the different product channels in the NH2CH2CHO + OH reaction from 300 to 2000 K at 1 atm.
Atmosphere 15 01011 g005
Figure 6. Energy diagram for dissociation of NH2CH2CO, at the G3X-K level of theory (relative 0 K enthalpies in kcal mol−1).
Figure 6. Energy diagram for dissociation of NH2CH2CO, at the G3X-K level of theory (relative 0 K enthalpies in kcal mol−1).
Atmosphere 15 01011 g006
Figure 7. Energy diagram for the NH2CHCHO + O2 reaction, at the G3X-K level of theory (relative 0 K enthalpies in kcal/mol).
Figure 7. Energy diagram for the NH2CHCHO + O2 reaction, at the G3X-K level of theory (relative 0 K enthalpies in kcal/mol).
Atmosphere 15 01011 g007
Figure 8. Alpha electron spin density in the NH2CHCHO radical, demonstrating the captodative effect (calculated at the M06-2X/6-31G(2df,p) level of theory).
Figure 8. Alpha electron spin density in the NH2CHCHO radical, demonstrating the captodative effect (calculated at the M06-2X/6-31G(2df,p) level of theory).
Atmosphere 15 01011 g008
Figure 9. Energy diagram for the NHCH2CHO + O2 reaction, at the G3X-K level of theory (relative 0 K enthalpies in kcal mol−1).
Figure 9. Energy diagram for the NHCH2CHO + O2 reaction, at the G3X-K level of theory (relative 0 K enthalpies in kcal mol−1).
Atmosphere 15 01011 g009
Scheme 2. Proposed photochemical oxidation mechanism of aminoacetaldehyde developed in this study.
Scheme 2. Proposed photochemical oxidation mechanism of aminoacetaldehyde developed in this study.
Atmosphere 15 01011 sch002
Table 1. Parameters used to fit restricted Gorin transition states to the NH2CH2CHO + OH → W1 reaction, and resultant hindrance parameter (η) and adiabatic external rotor fits as a function of temperature (300−2000 K).
Table 1. Parameters used to fit restricted Gorin transition states to the NH2CH2CHO + OH → W1 reaction, and resultant hindrance parameter (η) and adiabatic external rotor fits as a function of temperature (300−2000 K).
Morse potential parameters
Vibrational frequency of cleaving bond (cm−1)152.07
Dissociation energy (kcal mol−1) 4.14
Centre of mass distance between fragments (Å)2.5
Capture rate (cm3 molecule−1 s−1)7.81 × 10−11
Fitted Gorin parameters
η0.9964 (300)/0.9971 (600)/0.9973 (800)/0.9974 (1000)
0.9975 (1200)/0.9976 (1500)/0.9976 (2000)
Γ a0.0598 (300)/0.0540 (600)/0.0521 (800)/0.0509 (1000)
0.0501 (1200)/0.0494 (1500)/0.0493 (2000)
Moments of inertia (amu Å2)
adiabatic external rotor [2D] b303.5779 (300)/247.9012 (600)/225.6456 (800)/208.5839 (1000)/194.6673 (1200) 177.445(1500)/154.00 (2000)
a γ = (1 − η)0.5. b from the fitted Morse potential.
Table 2. Calculated rate coefficient expressions k = Aexp(−Ea/RT) for reactions in the aminoacetaldehyde + OH + O2 reaction sequence at 300–2000 K and 1 atm N2.
Table 2. Calculated rate coefficient expressions k = Aexp(−Ea/RT) for reactions in the aminoacetaldehyde + OH + O2 reaction sequence at 300–2000 K and 1 atm N2.
AEa
(cm3 molecule−1 s−1 or s−1)(cal mol−1)
NH2CH2CHO + OH → NHCH2CHO + H2O2.93 × 10−12−252
NH2CH2CHO + OH → NH2CHCHO + H2O1.64 × 10−11848
NH2CH2CHO + OH → NH2CH2CO + H2O4.32 × 10−111060
NHCH2CHO + O2 → NHCHCHO + HO24.46 × 10−143060
NH2CHCHO + O2 → NHCHCHO + HO23.50 × 10−124990
NH2CH2CO → CH2NH2 + CO3.84 × 101611,200
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Alam, A.; da Silva, G. Oxidation of Aminoacetaldehyde Initiated by the OH Radical: A Theoretical Mechanistic and Kinetic Study. Atmosphere 2024, 15, 1011. https://doi.org/10.3390/atmos15081011

AMA Style

Alam A, da Silva G. Oxidation of Aminoacetaldehyde Initiated by the OH Radical: A Theoretical Mechanistic and Kinetic Study. Atmosphere. 2024; 15(8):1011. https://doi.org/10.3390/atmos15081011

Chicago/Turabian Style

Alam, Ashraful, and Gabriel da Silva. 2024. "Oxidation of Aminoacetaldehyde Initiated by the OH Radical: A Theoretical Mechanistic and Kinetic Study" Atmosphere 15, no. 8: 1011. https://doi.org/10.3390/atmos15081011

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop