256 results on '"Theo Kurtén"'
Search Results
2. Molecular rearrangement of bicyclic peroxy radicals is a key route to aerosol from aromatics
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Siddharth Iyer, Avinash Kumar, Anni Savolainen, Shawon Barua, Christopher Daub, Lukas Pichelstorfer, Pontus Roldin, Olga Garmash, Prasenjit Seal, Theo Kurtén, and Matti Rissanen
- Subjects
Science - Abstract
Abstract The oxidation of aromatics contributes significantly to the formation of atmospheric aerosol. Using toluene as an example, we demonstrate the existence of a molecular rearrangement channel in the oxidation mechanism. Based on both flow reactor experiments and quantum chemical calculations, we show that the bicyclic peroxy radicals (BPRs) formed in OH-initiated aromatic oxidation are much less stable than previously thought, and in the case of the toluene derived ipso-BPRs, lead to aerosol-forming low-volatility products with up to 9 oxygen atoms on sub-second timescales. Similar results are predicted for ipso-BPRs formed from many other aromatic compounds. This reaction class is likely a key route for atmospheric aerosol formation, and including the molecular rearrangement of BPRs may be vital for accurate chemical modeling of the atmosphere.
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- 2023
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3. Atomic structures, conformers and thermodynamic properties of 32k atmospheric molecules
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Vitus Besel, Milica Todorović, Theo Kurtén, Patrick Rinke, and Hanna Vehkamäki
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Science - Abstract
Abstract Low-volatile organic compounds (LVOCs) drive key atmospheric processes, such as new particle formation (NPF) and growth. Machine learning tools can accelerate studies of these phenomena, but extensive and versatile LVOC datasets relevant for the atmospheric research community are lacking. We present the GeckoQ dataset with atomic structures of 31,637 atmospherically relevant molecules resulting from the oxidation of α-pinene, toluene and decane. For each molecule, we performed comprehensive conformer sampling with the COSMOconf program and calculated thermodynamic properties with density functional theory (DFT) using the Conductor-like Screening Model (COSMO). Our dataset contains the geometries of the 7 Mio. conformers we found and their corresponding structural and thermodynamic properties, including saturation vapor pressures (p Sat ), chemical potentials and free energies. The p Sat were compared to values calculated with the group contribution method SIMPOL. To validate the dataset, we explored the relationship between structural and thermodynamic properties, and then demonstrated a first machine-learning application with Gaussian process regression.
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- 2023
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4. Positive feedback mechanism between biogenic volatile organic compounds and the methane lifetime in future climates
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Michael Boy, Putian Zhou, Theo Kurtén, Dean Chen, Carlton Xavier, Petri Clusius, Pontus Roldin, Metin Baykara, Lukas Pichelstorfer, Benjamin Foreback, Jaana Bäck, Tuukka Petäjä, Risto Makkonen, Veli-Matti Kerminen, Mari Pihlatie, Juho Aalto, and Markku Kulmala
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Environmental sciences ,GE1-350 ,Meteorology. Climatology ,QC851-999 - Abstract
Abstract A multitude of biogeochemical feedback mechanisms govern the climate sensitivity of Earth in response to radiation balance perturbations. One feedback mechanism, which remained missing from most current Earth System Models applied to predict future climate change in IPCC AR6, is the impact of higher temperatures on the emissions of biogenic volatile organic compounds (BVOCs), and their subsequent effects on the hydroxyl radical (OH) concentrations. OH, in turn, is the main sink term for many gaseous compounds including methane, which is the second most important human-influenced greenhouse gas in terms of climate forcing. In this study, we investigate the impact of this feedback mechanism by applying two models, a one-dimensional chemistry-transport model, and a global chemistry-transport model. The results indicate that in a 6 K temperature increase scenario, the BVOC-OH-CH4 feedback increases the lifetime of methane by 11.4% locally over the boreal region when the temperature rise only affects chemical reaction rates, and not both, chemistry and BVOC emissions. This would lead to a local increase in radiative forcing through methane (ΔRFCH4) of approximately 0.013 Wm−2 per year, which is 2.1% of the current ΔRFCH4. In the whole Northern hemisphere, we predict an increase in the concentration of methane by 0.024% per year comparing simulations with temperature increase only in the chemistry or temperature increase in chemistry and BVOC emissions. This equals approximately 7% of the annual growth rate of methane during the years 2008–2017 (6.6 ± 0.3 ppb yr−1) and leads to an ΔRFCH4 of 1.9 mWm−2 per year.
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- 2022
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5. Author Correction: Molecular rearrangement of bicyclic peroxy radicals is a key route to aerosol from aromatics
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Siddharth Iyer, Avinash Kumar, Anni Savolainen, Shawon Barua, Christopher Daub, Lukas Pichelstorfer, Pontus Roldin, Olga Garmash, Prasenjit Seal, Theo Kurtén, and Matti Rissanen
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Science - Published
- 2023
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6. Molecular mechanism for rapid autoxidation in α-pinene ozonolysis
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Siddharth Iyer, Matti P. Rissanen, Rashid Valiev, Shawon Barua, Jordan E. Krechmer, Joel Thornton, Mikael Ehn, and Theo Kurtén
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Science - Abstract
Oxidation of volatile organic compounds leads to aerosol formation in the atmosphere, but the mechanism of some fast reactions is still unclear. The authors, using quantum chemical modelling and experiments, reveal that in key monoterpenes the cyclobutyl ring that would hinder the reactivity is broken in the early exothermic steps of the reaction.
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- 2021
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7. The role of highly oxygenated organic molecules in the Boreal aerosol-cloud-climate system
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Pontus Roldin, Mikael Ehn, Theo Kurtén, Tinja Olenius, Matti P. Rissanen, Nina Sarnela, Jonas Elm, Pekka Rantala, Liqing Hao, Noora Hyttinen, Liine Heikkinen, Douglas R. Worsnop, Lukas Pichelstorfer, Carlton Xavier, Petri Clusius, Emilie Öström, Tuukka Petäjä, Markku Kulmala, Hanna Vehkamäki, Annele Virtanen, Ilona Riipinen, and Michael Boy
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Science - Abstract
Forests emit compounds into the atmosphere that are oxidized into highly oxygenated molecules that serve as precursors for cloud condensation nuclei–a process that impacts the climate, but is poorly represented in models. Here the authors create a new model that accurately depicts highly oxygenated molecule and climate dynamics over Boreal forests.
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- 2019
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8. Hydroxyl radical-induced formation of highly oxidized organic compounds
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Torsten Berndt, Stefanie Richters, Tuija Jokinen, Noora Hyttinen, Theo Kurtén, Rasmus V. Otkjær, Henrik G. Kjaergaard, Frank Stratmann, Hartmut Herrmann, Mikko Sipilä, Markku Kulmala, and Mikael Ehn
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Science - Abstract
Secondary organic aerosols are important contributors to the Earth’s radiation budget, however questions remain about their formation from highly-oxidized precursors. Here the authors show that the daytime reaction of hydroxyl radicals with α- and β-pinene is a greater source of highly-oxidized products than previously assumed.
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- 2016
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9. Temporal and Spatial Variation in Scots Pine Resin Pressure and Composition
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Kaisa Rissanen, Teemu Hölttä, Luís F. M. Barreira, Noora Hyttinen, Theo Kurtén, and Jaana Bäck
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scots pine ,resin pressure ,resin composition ,tree water potential ,monoterpene emissions ,Forestry ,SD1-669.5 ,Environmental sciences ,GE1-350 - Abstract
Resin is a first-line defense in pine trees, but important questions regarding its temporal and spatial variation remain unsolved. Resin pressure varies according to water potential in dry conditions, but in moist conditions, it follows temperature dynamics for a yet unknown reason. Relations between resin composition, resin pressure, and shoot monoterpene emissions are also unquantified. To gain mechanistic understanding on the resin dynamics in a boreal forest, we measured temperature and water potential dependency of Scots pine resin pressure. We attempted to quantify the temperature dependency of resin pressure in terms of three contributions: (1) saturation vapor pressure, (2) thermal expansion, and (3) N2, O2, and CO2 solubility. We also analyzed monoterpene composition in the resin and the shoot emissions of 16 pines with gas chromatography mass spectrometry to study their interrelations. We show that in moist conditions, resin pressure is driven by temperature at a diurnal scale, but also affected by soil water potential at a day-to-day scale. Diurnal temperature dependency was explained by thermal expansion of resin and changes in bubble volume due to changes in gas solubility in resin with temperature. Resin pressures correlated also with total monoterpene and α-pinene content in resin and with total monoterpene and Δ3-carene and terpinolene emissions from shoots.
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- 2019
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10. A Comment on Nadytko et al., 'Amines in the Earth’s Atmosphere: A Density Functional Theory Study of the Thermochemistry of Pre-Nucleation Clusters'. Entropy 2011, 13, 554–569
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Theo Kurtén
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nucleation ,amines ,ammonia ,sulfuric acid ,thermochemistry ,Science ,Astrophysics ,QB460-466 ,Physics ,QC1-999 - Abstract
Nadykto, Yu, Jakovleva, Herb and Xu have recently reported a DFT study on the structure and formation thermodynamics of sulfuric acid-base-water clusters, with ammonia and a handful of amines as bases [1]. This study partially overlaps with our previous work [2], and a significant part of the discussion in their manuscript concerns differences between their results and ours. This comment is intended to address some issues related to that discussion. Specifically, it is shown that the errors related to basis-set effects in our calculations are very likely much smaller than claimed by Nadykto et al. [1]. Composite calculations including e.g., higher-level electron correlation also agree better with our results.
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- 2011
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11. Computational Investigation of Substituent Effects on the Alcohol + Carbonyl Channel of Peroxy Radical Self- and Cross-Reactions
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Galib Hasan, Vili-Taneli Salo, Thomas Golin Almeida, Rashid R. Valiev, and Theo Kurtén
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Physical and Theoretical Chemistry - Published
- 2023
12. An Experimental and Master Equation Investigation of Kinetics of the CH2OO + RCN Reactions (R = H, CH3, C2H5) and Their Atmospheric Relevance
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Lauri Franzon, Jari Peltola, Rashid Valiev, Niko Vuorio, Theo Kurtén, Arkke Eskola, Department of Chemistry, INAR Physical Chemistry, Department of Physics, Doctoral Programme in Atmospheric Sciences, Doctoral Programme in Chemistry and Molecular Sciences, Doctoral Programme in Materials Research and Nanosciences, and Molecular Science
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Chemistry ,Ozonolysis ,Criegee intermediate ch2oo ,Gas ,116 Chemical sciences ,Physical and Theoretical Chemistry ,Absorption cross-sections ,Hcn - Abstract
We have performed direct kinetic measurements of the CH2OO + RCN reactions (R = H, CH3, C2H5) in the temperature range 233-360 K and pressure range 10-250 Torr using time-resolved UV-absorption spectroscopy. We have utilized a new photolytic precursor, chloroiodomethane (CH2ICl), whose photolysis at 193 nm in the presence of O2 produces CH2OO. Observed bimolecular rate coefficients for CH2OO + HCN, CH2OO + CH3CN, and CH2OO + C2H5CN reactions at 296 K are (2.22 +/- 0.65) x 10-14 cm3 molecule-1 s-1, (1.02 +/- 0.10) x 10-14 cm3 molecule-1 s-1, and (2.55 +/- 0.13) x 10-14 cm3 molecule-1 s-1, respectively, suggesting that reaction with CH2OO is a potential atmospheric degradation pathway for nitriles. All the reactions have negligible temperature and pressure dependence in the studied regions. Quantum chemical calculations (omega B97X-D/aug-cc-pVTZ optimization with CCSD(T)-F12a/VDZ-F12 electronic energy correction) of the CH2OO + RCN reactions indicate that the barrierless lowest-energy reaction path leads to a ring closure, resulting in the formation of a 1,2,4-dioxazole compound. Master equation modeling results suggest that following the ring closure, chemical activation in the case of CH2OO + HCN and CH2OO + CH3CN reactions leads to a rapid decomposition of 1,2,4-dioxazole into a CH2O + RNCO pair, or by a rearrangement, into a formyl amide (RC(O)NHC(O)H), followed by decomposition into CO and an imidic acid (RC(NH)OH). The 1,2,4-dioxazole, the CH2O + RNCO pair, and the CO + RC(NH)OH pair are atmospherically significant end products to varying degrees.
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- 2023
13. Ring-opening yields and auto-oxidation rates of the resulting peroxy radicals from OH-oxidation of α-pinene and β-pinene
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Ben H. Lee, Siddharth Iyer, Theo Kurtén, Jonathan G. Varelas, Jingyi Luo, Regan J. Thomson, and Joel A. Thornton
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Chemistry (miscellaneous) ,Environmental Chemistry ,Pollution ,Analytical Chemistry - Abstract
Atmospheric oxidation of monoterpenes (C10H16) contributes to ambient particle number and mass concentrations due, in part, to the resulting peroxy radicals undergoing auto-oxidation to low-volatility highly oxygenated molecules (HOMs).
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- 2023
14. Atmospheric Oxidation of Imine Derivative of Piperazine Initiated by OH Radical
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Thomas Golin Almeida and Theo Kurtén
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Atmospheric Science ,Space and Planetary Science ,Geochemistry and Petrology - Published
- 2022
15. Critical Role of Iodous Acid in Neutral Iodine Oxoacid Nucleation
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Rongjie Zhang, Hong-Bin Xie, Fangfang Ma, Jingwen Chen, Siddharth Iyer, Mario Simon, Martin Heinritzi, Jiali Shen, Yee Jun Tham, Theo Kurtén, Douglas R. Worsnop, Jasper Kirkby, Joachim Curtius, Mikko Sipilä, Markku Kulmala, Xu-Cheng He, Tampere University, Physics, Institute for Atmospheric and Earth System Research (INAR), Polar and arctic atmospheric research (PANDA), INAR Physical Chemistry, Department of Chemistry, and Department of Physics
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MECHANISM ,Health Physics and Radiation Effects ,particle formation ,iodic acid ,iodous acid ,116 Chemical sciences ,AMINES ,General Chemistry ,OXIDATION ,114 Physical sciences ,atmospheric cluster dynamics simulation ,SULFURIC-ACID ,ATMOSPHERIC PARTICLES ,METHANESULFONIC-ACID ,GROWTH ,WATER ,Environmental Chemistry ,AEROSOL FORMATION ,iodine oxoacid nucleation ,quantum chemical calculation ,Chemical Physics and Chemistry - Abstract
Nucleation of neutral iodine particles has recently been found to involve both iodic acid (HIO3) and iodous acid (HIO2). However, the precise role of HIO2in iodine oxoacid nucleation remains unclear. Herein, we probe such a role by investigating the cluster formation mechanisms and kinetics of (HIO3)m(HIO2)n(m = 0-4, n = 0-4) clusters with quantum chemical calculations and atmospheric cluster dynamics modeling. When compared with HIO3, we find that HIO2binds more strongly with HIO3and also more strongly with HIO2. After accounting for ambient vapor concentrations, the fastest nucleation rate is predicted for mixed HIO3-HIO2clusters rather than for pure HIO3or HIO2ones. Our calculations reveal that the strong binding results from HIO2exhibiting a base behavior (accepting a proton from HIO3) and forming stronger halogen bonds. Moreover, the binding energies of (HIO3)m(HIO2)nclusters show a far more tolerant choice of growth paths when compared with the strict stoichiometry required for sulfuric acid-base nucleation. Our predicted cluster formation rates and dimer concentrations are acceptably consistent with those measured by the Cosmic Leaving Outdoor Droplets (CLOUD) experiment. This study suggests that HIO2could facilitate the nucleation of other acids beyond HIO3in regions where base vapors such as ammonia or amines are scarce. publishedVersion
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- 2022
16. Curation of High-level Molecular Atmospheric Data for Machine Learning Purposes
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Vitus Besel, Milica Todorović, Theo Kurtén, Patrick Rinke, and Hanna Vehkamäki
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As cloud and aerosol interactions remain large uncertainties in current climate models (IPCC) they are of special interest for atmospheric science. It is estimated that more than 70% of all cloud condensation nuclei origin from so-called New Particle Formation, which is the process of gaseous precursors clustering together in the atmosphere and subsequent growth into particles and aerosols. After initial clustering this growth is driven strongly by condensation of low volatile organic compounds (LVOC), that is molecules with saturation vapor pressures (pSat) below 10-6 mbar [1]. These origin from organic molecules emitted by vegetation that are subsequently rapidly oxidized in the air, so-called Biogenic LVOC (BLVOC). We have created a big data set of BLVOC using high-throughput computing and Density Functional Theory (DFT), and use it to train Machine Learning models to predict pSat of previously unseen BLVOC. Figure 1 illustrates some sample molecules form the data. Figure 1: Sample molecules, for small, medium large sizes. Figure 2: Histogram of the calculated saturation vapor pressures. Initially the chemical mechanism GECKO-A provides possible BLVOC molecules in the form of SMILES strings. In a first step the COSMOconf program finds and optimizes structures of possible conformers and provides their energies for the liquid phase on a DFT level of theory. After an additional calculation of the gas phase energies with Turbomole, COSMOtherm calculates thermodynamical properties, such as the pSat, using the COSMO-RS [1] model. We compressed all these computations together in a highly parallelised high-throughput workflow to calculate 32k BLVOC, that include over 7 Mio. molecular conformers. See a histogram of the calculated pSat in Figure 2. We use the calculated pSat to train a Gaussian Process Regression (GPR) machine learning model with the Topological Fingerprint as descriptor for molecular structures. The GPR incorporates noise and outputs uncertainties for predictions on the pSat. These uncertainties and data cluster techniques allow for the active choosing of molecules to include in the training data, so-called Active Learning. Further, we explore using SLISEMAP [2] explainable AI methods to correlate Machine Learning predictions, the high-dimensional descriptors and human-readable properties, such as functional groups. [1] Metzger, A. et al. Evidence for the role of organics in aerosol particle formation under atmospheric conditions. Proc. Natl. Acad. Sci. 107, 6646–6651, 10.1073/pnas.0911330107 (2010)[2] Klamt, A. & Schüürmann, G. Cosmo: a new approach to dielectric screening in solvents with explicit expressions for the screening energy and its gradient. J. Chem. Soc., Perkin Trans. 2 799–805, 10.1039/P29930000799 (1993).[3] Björklund, A., Mäkelä, J. & Puolamäki, K. SLISEMAP: supervised dimensionality reduction through local explanations. Mach Learn (2022). https://doi.org/10.1007/s10994-022-06261-1
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- 2023
17. Collision-sticking rates of acid-base clusters in the gas phase determined from atomistic simulation and a novel analytical interacting hard-sphere model
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Huan Yang, Ivo Neefjes, Valtteri Tikkanen, Jakub Kubečka, Theo Kurtén, Hanna Vehkamäki, Bernhard Reischl, Institute for Atmospheric and Earth System Research (INAR), INAR Physical Chemistry, Department of Chemistry, and Department of Physics
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116 Chemical sciences ,114 Physical sciences ,1172 Environmental sciences - Abstract
Kinetics of collision-sticking processes between vapor molecules and clusters of low-volatility compounds govern the initial steps of atmospheric new particle formation. Conventional non-interacting hard-sphere models underestimate the collision rate by neglecting long-range attractive forces, and the commonly adopted assumption that every collision leads to the formation of a stable cluster (unit mass accommodation coefficient) is questionable for small clusters, especially at elevated temperatures. Here, we present a generally applicable analytical interacting hard-sphere model for evaluating collision rates between molecules and clusters, accounting for long-range attractive forces. In the model, the collision cross section is calculated based on an effective molecule–cluster potential, derived using Hamaker's approach. Applied to collisions of sulfuric acid or dimethylamine with neutral bisulfate–dimethylammonium clusters composed of 1–32 dimers, our new model predicts collision rates 2–3 times higher than the non-interacting model for small clusters, while decaying asymptotically to the non-interacting limit as cluster size increases, in excellent agreement with a collision-rate-theory atomistic molecular dynamics simulation approach. Additionally, we calculated sticking rates and mass accommodation coefficients (MACs) using atomistic molecular dynamics collision simulations. For sulfuric acid, a MAC ≈1 is observed for collisions with all cluster sizes at temperatures between 200 and 400 K. For dimethylamine, we find that MACs decrease with increasing temperature and decreasing cluster size. At low temperatures, the MAC ≈1 assumption is generally valid, but at elevated temperatures MACs can drop below 0.2 for small clusters.
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- 2023
18. Atmospheric oxidation of imine derivative of piperazine by OH radical
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Thomas Golin Almeida and Theo Kurtén
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Amines are emitted to the Earth's atmosphere by several biogenic and anthropogenic sources. One such source, expected to increase in importance in the coming decades, is Carbon-Capture (CC), which often employs amine solvents as CO2 filters. Given that atmospheric oxidation of amines have the potential to produce nitrosamines (R1R2NNO) and nitramines (R1R2NNO2), known carcinogenic compounds, several chemical kinetics studies have investigated these reactions aiming to assess the impact on air quality from CC emissions. Piperazine is a widely employed CC amine solvent whose reaction with OH radical, the main atmospheric oxidant, has been the target of previous works, revealing a low yield of hazardous products. However, almost nothing is known about the fate of the major oxidation product, the cyclic imine 1,2,3,6-tetrahydropyrazine (THP). In fact, only a few studies focused on the atmospheric chemistry of imines in general, despite consistently appearing as major products of amine oxidation. In this work, we employed quantum chemistry and theoretical kinetics methods to investigate the mechanism and kinetics of reaction between THP and OH radical. Our findings predict that this reaction has a low, but not negligible potential to produce nitrosamines and nitramines, with a maximum yield of ~18% under high NOx conditions. The major reaction channels involve the formation of a second imine functional group, leading to the diimines 2,3-dihydropyrazine and 2,5-dihydropyrazine. Our calculations also revealed two new oxidation pathways, both involving fast C-C bond scissions. One of these pathways produce an isocyanate (RN=C=O), which is also potentially toxic. While this channel is minor for THP + OH radical (maximum yield of 14%), we argue that it could be more important during the OH radical-initiated oxidation of other imines relevant to the atmosphere.
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- 2023
19. Molecular rearrangement of bicyclic peroxy radicals: key route to aerosol from aromatics
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Siddharth Iyer, Avinash Kumar, Anni Savolainen, Shawon Barua, Christopher Daub, Lukas Pichelstorfer, Pontus Roldin, Olga Garmash, Prasenjit Seal, Theo Kurtén, and Matti Rissanen
- Abstract
The oxidation of aromatics contributes significantly to the formation of atmospheric aerosol. Using toluene as an example, we demonstrate the existence of a novel molecular rearrangement channel in the oxidation mechanism. Based on both flow reactor experiments and quantum chemical calculations, we show that the bicyclic peroxy radicals (BPRs) formed in OH-initiated aromatic oxidation are much less stable than previously thought, and in the case of the toluene derived ipso-BPRs, lead to aerosol-forming low-volatility products with up to 9 oxygen atoms on sub-second timescales. Similar results are predicted for ipso-BPRs formed from many other aromatic compounds. This new reaction class is likely a key route for atmospheric aerosol formation, and including the molecular rearrangement of BPRs may be vital for accurate chemical modeling of the atmosphere.
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- 2023
20. Selective deuteration as a tool for resolving autoxidation mechanisms in α-pinene ozonolysis
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Melissa Meder, Otso Peräkylä, Jonathan G. Varelas, Jingyi Luo, Runlong Cai, Yanjun Zhang, Theo Kurtén, Matthieu Riva, Matti Rissanen, Franz M. Geiger, Regan J. Thomson, Mikael Ehn, Institute for Atmospheric and Earth System Research (INAR), Department of Chemistry, Department of Physics, and INAR Physical Chemistry
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Atmospheric Science ,Volatile organic-compounds ,116 Chemical sciences ,Products ,Molecules ,Multifunctional compounds - Abstract
Highly oxygenated organic molecules (HOMs) from α-pinene ozonolysis have been shown to be significant contributors to secondary organic aerosol (SOA), yet our mechanistic understanding of how the peroxy-radical-driven autoxidation leads to their formation in this system is still limited. The involved isomerisation reactions such as H-atom abstractions followed by O2 additions can take place on sub-second timescales in short-lived intermediates, making the process challenging to study. Similarly, while the end-products and sometimes radical intermediates can be observed using mass spectrometry, their structures remain elusive. Therefore, we propose a method utilising selective deuterations for unveiling the mechanisms of autoxidation, where the HOM products can be used to infer which C atoms have taken part in the isomerisation reactions. This relies on the fact that if a C−D bond is broken due to an abstraction by a peroxy group forming a −OOD hydroperoxide, the D atom will become labile and able to be exchanged with a hydrogen atom in water vapour (H2O), effectively leading to loss of the D atom from the molecule. In this study, we test the applicability of this method using three differently deuterated versions of α-pinene with the newly developed chemical ionisation Orbitrap (CI-Orbitrap) mass spectrometer to inspect the oxidation products. The high mass-resolving power of the Orbitrap is critical, as it allows the unambiguous separation of molecules with a D atom (mD=2.0141) from those with two H atoms (mH2=2.0157). We found that the method worked well, and we could deduce that two of the three tested compounds had lost D atoms during oxidation, suggesting that those deuterated positions were actively involved in the autoxidation process. Surprisingly, the deuterations were not observed to decrease HOM molar yields, as would have been expected due to kinetic isotope effects. This may be an indication that the relevant H (or D) abstractions were fast enough that no competing pathways were of relevance despite slower abstraction rates of the D atom. We show that selective deuteration can be a very useful method for studying autoxidation on a molecular level and likely is not limited to the system of α-pinene ozonolysis tested here.
- Published
- 2023
21. Supplementary material to 'Collision-sticking rates of acid–base clusters in the gas phase determined from atomistic simulation and a novel analytical interacting hard-sphere model'
- Author
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Huan Yang, Ivo Neefjes, Valtteri Tikkanen, Jakub Kubečka, Theo Kurtén, Hanna Vehkamäki, and Bernhard Reischl
- Published
- 2023
22. Pathways to Highly Oxidized Products in the Δ3-Carene + OH System
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Emma L. D’Ambro, Noora Hyttinen, Kristian H. Møller, Siddharth Iyer, Rasmus V. Otkjær, David M. Bell, Jiumeng Liu, Felipe D. Lopez-Hilfiker, Siegfried Schobesberger, John E. Shilling, Alla Zelenyuk, Henrik G. Kjaergaard, Joel A. Thornton, Theo Kurtén, Department of Chemistry, Institute for Atmospheric and Earth System Research (INAR), INAR Physics, Department of Physics, and INAR Physical Chemistry
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Aerosols ,atmospheric chemistry ,GAS-PHASE REACTIONS ,OH OXIDATION ,ONLINE ANALYSIS ,monoterpene oxidation ,INITIATED OXIDATION ,116 Chemical sciences ,highly oxidized organic molecules (HOMs) ,General Chemistry ,MOLECULES ,autoxidation ,RATE CONSTANTS ,ALPHA-PINENE OZONOLYSIS ,SECONDARY ORGANIC AEROSOL ,ISOPRENE ,RADICALS ,Monoterpenes ,Environmental Chemistry ,secondary organic aerosol (SOA) ,Oxidation-Reduction ,Bicyclic Monoterpenes - Abstract
Oxidation of the monoterpene Δ3-carene (C10H16) is a potentially important and understudied source of atmospheric secondary organic aerosol (SOA). We present chamber-based measurements of speciated gas and particle phases during photochemical oxidation of Δ3-carene. We find evidence of highly oxidized organic molecules (HOMs) in the gas phase and relatively low-volatility SOA dominated by C7-C10 species. We then use computational methods to develop the first stages of a Δ3-carene photochemical oxidation mechanism and explain some of our measured compositions. We find that alkoxy bond scission of the cyclohexyl ring likely leads to efficient HOM formation, in line with previous studies. We also find a surprising role for the abstraction of primary hydrogens from methyl groups, which has been calculated to be rapid in the α-pinene system, and suggest more research is required to determine if this is more general to other systems and a feature of autoxidation. This work develops a more comprehensive view of Δ3-carene photochemical oxidation products via measurements and lays out a suggested mechanism of oxidation via computationally derived rate coefficients.
- Published
- 2022
23. Energy transfer, pre-reactive complex formation and recombination reactions during the collision of peroxy radicals
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Christopher David Daub, Itai Zakai, Rashid Valiev, Vili-Taneli Salo, R. Benny Gerber, Theo Kurtén, Department of Chemistry, and INAR Physical Chemistry
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Recombination, Genetic ,116 Chemical sciences ,Molecular Conformation ,General Physics and Astronomy ,VAN-DER-WAALS ,SIMULATIONS ,Kinetics ,Energy Transfer ,FORCE-FIELD ,IMPLEMENTATION ,PROGRAM ,HYDROCARBONS ,Physics::Chemical Physics ,Physical and Theoretical Chemistry - Abstract
In this paper we study collisions between polyatomic radicals - an important process in fields ranging from biology to combustion. Energy transfer, formation of intermediate complexes and recombination reactions are treated, with applications to peroxy radicals in atmospheric chemistry. Multi-reference perturbation theory, supplemented by coupled-cluster calculations, describes the potential energy surfaces with high accuracy, including the interaction of singlet and triplet spin states during radical recombination. Our multi-reference molecular dynamics (MD) trajectories on methyl peroxy radicals confirm the reaction mechanism postulated in earlier studies. Specifically, they show that if suitable pre-reactive complexes are formed, they will rapidly lead to the formation and subsequent decomposition of tetroxide intermediates. However, generating multi-reference MD trajectories is exceedingly computationally demanding, and we cannot adequately sample the whole conformational space. To answer this challenge, we promote the use of a novel simplified semi-empirical MD methodology. It assumes the collision is governed by two states, a singlet (S-0) and a triplet (T-1) state. The method predicts differences between collisions on S-0 and T-1 surfaces, and qualitatively includes not only pre-reactive complex formation, but also recombination processes such as tetroxide formation. Finally, classical MD simulations using force-fields for non-reactive collisions are employed to generate thousands of collision trajectories, to verify that the semi-empirical method is sampling collisions adequately, and to carry out preliminary investigations of larger systems. For systems with low activation energies, the experimental rate coefficient is surprisingly well reproduced by simply multiplying the gas-kinetic collision rate by the simulated probability for long-lived complex formation.
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- 2022
24. Supplementary material to 'Selective deuteration as a tool for resolving autoxidation mechanisms in α-pinene ozonolysis'
- Author
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Melissa J. A. Meder, Otso Peräkylä, Jonathan G. Varelas, Jenny Luo, Runlong Cai, Yanjun Zhang, Theo Kurtén, Matthieu Riva, Matti P. Rissanen, Franz M. Geiger, Regan James Thomson, and Mikael Ehn
- Published
- 2022
25. Computed Pre-reactive Complex Association Lifetimes Explain Trends in Experimental Reaction Rates for Peroxy Radical Recombinations
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Christopher David Daub, Rashid Valiev, Vili-Taneli Salo, Itai Zakai, R. Benny Gerber, Theo Kurtén, Department of Chemistry, University of Helsinki, INAR Physical Chemistry, and Department of Physics
- Subjects
MECHANISM ,PROTOCOL ,Atmospheric Science ,aerosol ,116 Chemical sciences ,ALPHA-PINENE ,OZONOLYSIS ,SELF-REACTION ,OXIDATION ,TROPOSPHERIC DEGRADATION ,?-pinene ,Space and Planetary Science ,Geochemistry and Petrology ,CRIEGEE INTERMEDIATE CH2OO ,Arrhenius equation ,FORCE-FIELD ,peroxy radicals ,reaction kinetics - Abstract
The lifetimes of pre-reactive complexes, although implicitly part of the equations used to model many gas-phase bimolecular reactions, have seldom been included in quantitative calculations of rate coefficients. Here, we demonstrate the application of empirical molecular dynamics simulations of collisions between peroxy radicals to model association lifetimes. With the exception of the methyl peroxy−acetyl peroxy system, measurements of the lifetimes based on a phenomenological model are shown to correlate well with available experimental data for recombination reactions of peroxy radicals in cases where the rate-limiting transition state lies below the reactants in energy. Further, we predict reaction rates for larger α-pinene-derived peroxy radicals, and we interpret our results in tandem with available experimental data on these systems, which are of great relevance to improve our understanding of atmospheric aerosol formation.
- Published
- 2022
26. Gas-Phase Peroxyl Radical Recombination Reactions : A Computational Study of Formation and Decomposition of Tetroxides
- Author
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Vili-Taneli Salo, Rashid Valiev, Susi Lehtola, Theo Kurtén, Kemian osasto, INAR Physical Chemistry, and Fysiikan osasto
- Subjects
Self-reaction ,Kinetics ,Basis-sets ,Atmospheric chemistry ,Hartree-fock ,Alkylperoxy radicals ,Oxygenated radicals ,116 Kemia ,Physical and Theoretical Chemistry ,Secondary organic aerosol ,Gaussian-type basis ,1172 Ympäristötiede ,Molecular-orbital methods - Abstract
The recombination ("dimerization") of peroxyl radicals (RO2 center dot) is one of the pathways suggested in the literature for the formation of peroxides (ROOR', often referred to as dimers or accretion products in the literature) in the atmosphere. It is generally accepted that these dimers play a major role in the first steps of the formation of submicron aerosol particles. However, the precise reaction pathways and energetics of RO2 center dot + R'O-2 center dot reactions are still unknown. In this work, we have studied the formation of tetroxide intermediates (RO4R'): their formation from two peroxyl radicals and their decomposition to triplet molecular oxygen (O-3(2)) and a triplet pair of alkoxyl radicals (RO center dot). We demonstrate this mechanism for several atmospherically relevant primary and secondary peroxyl radicals. The potential energy surface corresponds to an overall singlet state. The subsequent reaction channels of the alkoxyl radicals include, but are not limited to, their dimerization into ROOR'. Our work considers the multiconfigurational character of the tetroxides and the intermediate phases of the reaction, leading to reliable mechanistic insights for the formation and decomposition of the tetroxides. Despite substantial uncertainties in the computed energetics, our results demonstrate that the barrier heights along the reaction path are invariably small for these systems. This suggests that the reaction mechanism, previously validated at a multireference level only for methyl peroxyl radicals, is a plausible pathway for the formation of aerosol-relevant larger peroxides in the atmosphere.
- Published
- 2022
27. Odd-Number Cyclo[
- Author
-
Glib V, Baryshnikov, Rashid R, Valiev, Lenara I, Valiulina, Alexandr E, Kurtsevich, Theo, Kurtén, Dage, Sundholm, Michael, Pittelkow, Jinglai, Zhang, and Hans, Ågren
- Abstract
Cyclo[
- Published
- 2022
28. Heterogeneous Nucleation of Butanol on NaCl: A Computational Study of Temperature, Humidity, Seed Charge, and Seed Size Effects
- Author
-
Juha Kangasluoma, Hanna Vehkamäki, Jakub Kubečka, Antti Elia Toropainen, Theo Kurtén, Fatemeh Keshavarz, INAR Physics, Department of Physics, Department of Chemistry, and Institute for Atmospheric and Earth System Research (INAR)
- Subjects
HYBRID DENSITY FUNCTIONALS ,Nucleation ,010402 general chemistry ,114 Physical sciences ,01 natural sciences ,GENERAL FORCE-FIELD ,Article ,MOLECULES ,chemistry.chemical_compound ,CHEMISTRY ,0103 physical sciences ,WATER ,Relative humidity ,Physical and Theoretical Chemistry ,SCALE ,BASIS-SETS ,Supersaturation ,010304 chemical physics ,Chemistry ,Butanol ,Condensation ,Humidity ,0104 chemical sciences ,Chemical engineering ,13. Climate action ,GROWTH ,Particle ,AEROSOL FORMATION ,CLUSTERS ,Saturation (chemistry) - Abstract
Using a combination of quantum chemistry and cluster size distribution dynamics, we study the heterogeneous nucleation of n-butanol and water onto sodium chloride (NaCl)(10) seeds at different butanol saturation ratios and relative humidities. We also investigate how the heterogeneous nucleation of butanol is affected by the seed size through comparing (NaCl)(5), (NaCl)(10), and ( NaCl)(25) seeds and by seed electrical charge through comparing (Na10Cl9)(+), (NaCl)(10), and (Na9Cl10)(-) seeds. Butanol is a common working fluid for condensation particle counters used in atmospheric aerosol studies, and NaCl seeds are frequently used for calibration purposes and as model systems, for example, sea spray aerosol. In general, our simulations reproduce the experimentally observed trends for the NaCl-BuOH-H2O system, such as the increase of nucleation rate with relative humidity and with temperature (at constant supersaturation of butanol). Our results also provide molecular-level insights into the vapor-seed interactions driving the first steps of the heterogeneous nucleation process. The main purpose of this work is to show that theoretical studies can provide molecular understanding of initial steps of heterogeneous nucleation and that it is possible to find cost-effective yet accurate-enough combinations of methods for configurational sampling and energy evaluation to successfully model heterogeneous nucleation of multicomponent systems. In the future, we anticipate that such simulations can also be extended to chemically more complex seeds.
- Published
- 2021
29. Fast estimation of the internal conversion rate constant in photophysical applications
- Author
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Rashid R. Valiev, A. E. Kurtsevich, Rinat T. Nasibullin, Dage Sundholm, Victor N. Cherepanov, Theo Kurtén, and Department of Chemistry
- Subjects
Materials science ,116 Chemical sciences ,General Physics and Astronomy ,02 engineering and technology ,010402 general chemistry ,перенос энергии ,7. Clean energy ,01 natural sciences ,Molecular physics ,электронное возбуждение ,chemistry.chemical_compound ,Reaction rate constant ,Molecule ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Azulene ,021001 nanoscience & nanotechnology ,Internal conversion (chemistry) ,электронная волновая функция ,Acceptor ,0104 chemical sciences ,Fluorenone ,chemistry ,Solvent effects ,0210 nano-technology ,Excitation - Abstract
An efficient method for estimating non-adiabatic coupling matrix elements (NACME) and rate constants for internal conversion (k(IC)) is presented. The method, based on Plotnikov's theory, requires only calculations of the electronic wave functions and the corresponding electronic excitation energies. Computationally expensive calculations of the derivatives of the electronic wave function with respect to the nuclear coordinates are avoided. When the main accepting modes of the electronic excitation energy are X-H vibrations, the present method can be used for estimating the efficiency of the energy transfer between donor and acceptor molecules. It can also be used in studies of the influence of hydrogen bonding or solvent effect on fluorescence quenching, in studies of vibronic effects of TADF (thermally activated delayed fluorescence) emitters, and for calculating k(IC). Here, k(IC) and NACME are calculated for free-base porhyrin, magnesium porphyrin, azulene, naphthalene, pyrene and fluorenone interacting with a solvent molecule. Reverse k(IC) and NACME are further calculated for the T-1 -> T-2 transition of dibenzothiophene-S,S-dioxide (PTZ-DBTO2), which is used in TADF applications. Finally, we estimate the efficiency of the energy transfer between two large porphyrinoid dimers.
- Published
- 2021
30. Technical note: Estimating aqueous solubilities and activity coefficients of mono- and α,ω-dicarboxylic acids using COSMOtherm
- Author
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Reyhaneh Heshmatnezhad, Noora Hyttinen, Nønne L. Prisle, Jonas Elm, and Theo Kurtén
- Subjects
Activity coefficient ,chemistry.chemical_classification ,Atmospheric Science ,Aqueous solution ,010504 meteorology & atmospheric sciences ,Carboxylic acid ,Dimer ,Oxalic acid ,Technical note ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,COSMO-RS ,chemistry ,13. Climate action ,Computational chemistry ,Equilibrium constant ,0105 earth and related environmental sciences - Abstract
We have used the COSMOtherm program to estimate activity coefficients and solubilities of mono- and α,ω-dicarboxylic acids and water in binary acid–water systems. The deviation from ideality was found to be larger in the systems containing larger acids than in the systems containing smaller acids. COnductor-like Screening MOdel for Real Solvents (COSMO-RS) underestimates experimental monocarboxylic acid activity coefficients by less than a factor of 2, but experimental water activity coefficients are underestimated more especially at high acid mole fractions. We found a better agreement between COSMOtherm-estimated and experimental activity coefficients of monocarboxylic acids when the water clustering with a carboxylic acid and itself was taken into account using the dimerization, aggregation, and reaction extension (COSMO-RS-DARE) of COSMOtherm. COSMO-RS-DARE is not fully predictive, but fit parameters found here for water–water and acid–water clustering interactions can be used to estimate thermodynamic properties of monocarboxylic acids in other aqueous solvents, such as salt solutions. For the dicarboxylic acids, COSMO-RS is sufficient for predicting aqueous solubility and activity coefficients, and no fitting to experimental values is needed. This is highly beneficial for applications to atmospheric systems, as these data are typically not available for a wide range of mixing states realized in the atmosphere, due to a lack of either feasibility of the experiments or sample availability. Based on effective equilibrium constants of different clustering reactions in the binary solutions, acid dimer formation is more dominant in systems containing larger dicarboxylic acids (C5–C8), while for monocarboxylic acids (C1–C6) and smaller dicarboxylic acids (C2–C4), hydrate formation is more favorable, especially in dilute solutions.
- Published
- 2020
31. Fragmentation inside proton-transfer-reaction-based mass spectrometers limits the detection of ROOR and ROOH peroxides
- Author
-
Haiyan Li, Thomas Golin Almeida, Yuanyuan Luo, Jian Zhao, Brett B. Palm, Christopher D. Daub, Wei Huang, Claudia Mohr, Jordan E. Krechmer, Theo Kurtén, Mikael Ehn, Institute for Atmospheric and Earth System Research (INAR), and Department of Chemistry
- Subjects
Atmospheric Science ,MONOTERPENE ,SULFURIC-ACID ,CHEMISTRY ,CHEMICAL-IONIZATION ,TOF ,116 Chemical sciences ,RO2 RADICALS ,CYCLOHEXENE OZONOLYSIS ,VOC EMISSIONS ,ENERGY-TRANSFER ,PRODUCTS - Abstract
Proton transfer reaction (PTR) is a commonly applied ionization technique for mass spectrometers, in which hydronium ions (H3O+) transfer a proton to analytes with higher proton affinities than the water molecule. This method has most commonly been used to quantify volatile hydrocarbons, but later-generation PTR instruments have been designed for better throughput of less volatile species, allowing detection of more functionalized molecules as well. For example, the recently developed Vocus PTR time-of-flight mass spectrometer (PTR-TOF) has been shown to agree well with an iodide-adduct-based chemical ionization mass spectrometer (CIMS) for products with 3–5 O atoms from oxidation of monoterpenes (C10H16). However, while several different types of CIMS instruments (including those using iodide) detect abundant signals also at “dimeric” species, believed to be primarily ROOR peroxides, no such signals have been observed in the Vocus PTR even though these compounds fulfil the condition of having higher proton affinity than water. More traditional PTR instruments have been limited to volatile molecules as the inlets have not been designed for transmission of easily condensable species. Some newer instruments, like the Vocus PTR, have overcome this limitation but are still not able to detect the full range of functionalized products, suggesting that other limitations need to be considered. One such limitation, well-documented in PTR literature, is the tendency of protonation to lead to fragmentation of some analytes. In this work, we evaluate the potential for PTR to detect dimers and the most oxygenated compounds as these have been shown to be crucial for forming atmospheric aerosol particles. We studied the detection of dimers using a Vocus PTR-TOF in laboratory experiments, as well as through quantum chemical calculations. Only noisy signals of potential dimers were observed during experiments on the ozonolysis of the monoterpene α-pinene, while a few small signals of dimeric compounds were detected during the ozonolysis of cyclohexene. During the latter experiments, we also tested varying the pressures and electric fields in the ionization region of the Vocus PTR-TOF, finding that only small improvements were possible in the relative dimer contributions. Calculations for model ROOR and ROOH systems showed that most of these peroxides should fragment partially following protonation. With the inclusion of additional energy from the ion–molecule collisions driven by the electric fields in the ionization source, computational results suggest substantial or nearly complete fragmentation of dimers. Our study thus suggests that while the improved versions of PTR-based mass spectrometers are very powerful tools for measuring hydrocarbons and their moderately oxidized products, other types of CIMS are likely more suitable for the detection of ROOR and ROOH species.
- Published
- 2022
32. Odd-Number Cyclo[n]Carbons Sustaining Alternating Aromaticity
- Author
-
Glib V. Baryshnikov, Rashid R. Valiev, Lenara I. Valiulina, Alexandr E. Kurtsevich, Theo Kurtén, Dage Sundholm, Michael Pittelkow, Jinglai Zhang, and Hans Ågren
- Subjects
электронная структура ,ароматичность ,CARBON CLUSTERS ,DENSITY FUNCTIONALS ,теория функционала плотности ,THERMOCHEMISTRY ,MOLECULAR-ORBITAL METHODS ,ELECTRONIC-STRUCTURE ,DESIGN ,Teoretisk kemi ,ALL-CARBOATOMIC RING ,Physical and Theoretical Chemistry ,Theoretical Chemistry ,циклоуглероды ,TRANSITION ,BASIS-SETS ,GENERATION - Abstract
Cyclo[n]carbons (n = 5, 7, 9,..., 29) composed from an odd number of carbon atoms are studied computationally at density functional theory (DFT) and ab initio complete active space self-consistent field (CASSCF) levels of theory to get insight into their electronic structure and aromaticity. DFT calculations predict a strongly delocalized carbene structure of the cyclo[n]carbons and an aromatic character for all of them. In contrast, calculations at the CASSCF level yield geometrically bent and electronically localized carbene structures leading to an alternating double aromaticity of the odd-number cyclo[n]carbons. CASSCF calculations yield a singlet electronic ground state for the studied cyclo[n]carbons except for C25, whereas at the DFT level the energy difference between the lowest singlet and triplet states depends on the employed functional. The BHandHLYP functional predicts a triplet ground state of the larger odd-number cyclo[n]carbons starting from n = 13. Current-density calculations at the BHandHLYP level using the CASSCFoptimized molecular structures show that there is a through-space delocalization in the cyclo[n]carbons. The current density avoids the carbene carbon atom, leading to an alternating double aromaticity of the oddnumber cyclo[n]carbons satisfying the antiaromatic [4k+1] and aromatic [4k+3] rules. C11, C15, and C19 are aromatic and can be prioritized in future synthesis. We predict a bond-shift phenomenon for the triplet state of the cyclo[n]carbons leading to resonance structures that have different reactivity toward dimerization. Funding Agencies|Swedish Research Council [2020-04600]; Academy of Finland [325369, 314821]; Danish Council for Independent Research [DFF4181-00206, 9040-00265]; VILLUM FONDEN [40871]; Russian Scientific Foundation [18-19-00268-Pi]
- Published
- 2022
33. Solubility and Activity Coefficients of Atmospheric Surfactants in Aqueous Solution Evaluated Using COSMOtherm
- Author
-
Theo Kurtén, Noora Hyttinen, Georgia Michailoudi, Nønne L. Prisle, Department of Chemistry, and Institute for Atmospheric and Earth System Research (INAR)
- Subjects
Activity coefficient ,ORGANIC FILMS ,DROPLET ACTIVATION ,Inorganic chemistry ,Sodium decanoate ,010402 general chemistry ,114 Physical sciences ,01 natural sciences ,CLOUD CONDENSATION NUCLEI ,chemistry.chemical_compound ,0103 physical sciences ,PARTICLES ,Cloud condensation nuclei ,Physical and Theoretical Chemistry ,Solubility ,Sulfate ,Aqueous solution ,010304 chemical physics ,Chemistry ,AEROSOL ,0104 chemical sciences ,Aerosol ,MODEL ,VAPOR-PRESSURES ,13. Climate action ,SODIUM DECANOATE ,lipids (amino acids, peptides, and proteins) ,FATTY-ACIDS ,SULFATE - Abstract
Fatty acids (CH3(CH2)(n-2)COOH) and their salts are an important class of atmospheric surfactants. Here, we use COSMOtherm to predict solubility and activity coefficients for C-2-C-12 fatty acids with even number of carbon atoms and their sodium salts in binary water solutions and also in ternary water-inorganic salt solutions. COSMOtherm is a continuum solvent model implementation which can calculate properties of complex systems using quantum chemistry and thermodynamics. Calculated solubility values of the organic acids in pure water are in good agreement with reported experimental values. The comparison of the COSMOtherm-derived Setschenow constants for ternary solutions comprising NaCl with the corresponding experimental values from the literature shows that COSMOtherm overpredicts the salting out effect in all cases except for the solutions of acetic acid. The calculated activity and mean activity coefficients of fatty acids and fatty acid sodium salts, respectively, show deviation of the systems from ideal solution. The computed mean activity coefficients of the fatty acid salts in binary systems are in better agreement with experimentally derived values for the organic salts with longer aliphatic chain (C-8-C-10). The deviation of the solutions from ideality could lead to biased estimations of cloud condensation nuclei number concentrations if not considered in Kohler calculations and cloud microphysics.
- Published
- 2019
34. Unexpected quenching effect on new particle formation from the atmospheric reaction of methanol with SO 3
- Author
-
Ling Liu, Xiao Cheng Zeng, Xiuhui Zhang, Theo Kurtén, Lin Du, Joseph S. Francisco, Jie Zhong, Hanna Vehkamäki, Institute for Atmospheric and Earth System Research (INAR), and Department of Chemistry
- Subjects
010504 meteorology & atmospheric sciences ,Abundance (chemistry) ,116 Chemical sciences ,Nucleation ,SO3 ,VOLATILE ORGANIC-COMPOUNDS ,010402 general chemistry ,Photochemistry ,114 Physical sciences ,01 natural sciences ,HYDROGEN SULFATE ,alcohols ,catalytic reactions ,TROPOSPHERE ,Catalysis ,Dimethyl sulfate ,chemistry.chemical_compound ,SULFURIC-ACID ,NANOPARTICLES ,Dimethylamine ,KINETICS ,0105 earth and related environmental sciences ,Multidisciplinary ,Quenching (fluorescence) ,atmospheric aerosol ,Sulfuric acid ,DIMETHYL SULFATE ,0104 chemical sciences ,INTERMEDIATE ,chemistry ,13. Climate action ,Methanol ,CLUSTERS ,nucleation precursors ,NUCLEATION - Abstract
Despite the high abundance in the atmosphere, alcohols in general and methanol in particular are believed to play a small role in atmospheric new particle formation (NPF) largely due to the weak binding abilities of alcohols with the major nucleation precursors, e.g., sulfuric acid (SA) and dimethylamine (DMA). Herein, we identify a catalytic reaction that was previously overlooked, namely, the reaction between methanol and SO3, catalyzed by SA, DMA, or water. We found that alcohols can have unexpected quenching effects on the NPF process, particularly in dry and highly polluted regions with high concentrations of alcohols. Specifically, the catalytic reaction between methanol and SO3 can convert methanol into a less-volatile species-methyl hydrogen sulfate (MHS). The latter was initially thought to be a good nucleation agent for NPF. However, our simulation results suggest that the formation of MHS consumes an appreciable amount of atmospheric SO3, disfavoring further reactions of SO3 with H2O. Indeed, we found that MHS formation can cause a reduction of SA concentration up to 87%, whereas the nucleation ability of MHS toward new particles is not as good as that of SA. Hence, a high abundance of methanol in the atmosphere can lower the particle nucleation rate by as much as two orders of magnitude. Such a quenching effect suggests that the recently identified catalytic reactions between alcohols and SO3 need to be considered in atmospheric modeling in order to predict SA concentration from SO2, while also account for their potentially negative effect on NPF.
- Published
- 2019
35. Computational Investigation of the Formation of Peroxide (ROOR) Accretion Products in the OH- and NO3-Initiated Oxidation of alpha-Pinene
- Author
-
Galib Hasan, Rashid R. Valiev, Vili-Taneli Salo, Theo Kurtén, INAR Physical Chemistry, Doctoral Programme in Chemistry and Molecular Sciences, Department of Chemistry, Doctoral Programme in Materials Research and Nanosciences, Doctoral Programme in Atmospheric Sciences, and Department of Physics
- Subjects
MECHANISM ,010504 meteorology & atmospheric sciences ,INITIATED OXIDATION ,116 Chemical sciences ,NOX ,010402 general chemistry ,01 natural sciences ,NITRATES ,0104 chemical sciences ,MODEL ,CHEMISTRY ,SECONDARY ORGANIC AEROSOL ,RADICALS ,Physical and Theoretical Chemistry ,HYDROCARBONS ,0105 earth and related environmental sciences - Abstract
The formation of accretion products ("dimers") from recombination reactions of peroxyl radicals (RO2) is a key 5 3 step in the gas-phase generation of low-volatility vapors, leading to atmospheric aerosol particles. We have recently demonstrated that S 1 this recombination reaction very likely proceeds via an intermediate complex of two alkoxy radicals (RO center dot center dot center dot OR') and that the accretion product pathway involves an intersystem crossing (ISC) of this complex from the triplet to the singlet surface. However, ISC rates have hitherto not been computed for large and chemically complex RO center dot center dot center dot OR' systems actually relevant to atmospheric aerosol formation. Here, we carry out systematic conformational sampling and ISC rate calculations on (3)(RO center dot center dot center dot OR') clusters formed in the recombination reactions of different diastereomers of the first-generation peroxyl radicals originating in both OH- and NO3 -initiated reactions of alpha-pinene, a key biogenic hydrocarbon for atmospheric aerosol formation. While we find large differences between the ISC rates of different diastereomer pairs, all systems have ISC rates of at least 10(6) s(-1), and many have rates exceeding 10(10) s(-1). Especially the latter value demonstrates that accretion product formation via the suggested pathway is a competitive process also for alpha-pinene-derived RO2 and likely explains the experimentally observed gas-phase formation of C-20 compounds in alpha-pinene oxidation.
- Published
- 2021
36. Computational Investigation of the Formation of Peroxide (ROOR) Accretion Products in the OH- and NO
- Author
-
Galib, Hasan, Rashid R, Valiev, Vili-Taneli, Salo, and Theo, Kurtén
- Subjects
Article - Abstract
The formation of accretion products (“dimers”) from recombination reactions of peroxyl radicals (RO2) is a key step in the gas-phase generation of low-volatility vapors, leading to atmospheric aerosol particles. We have recently demonstrated that this recombination reaction very likely proceeds via an intermediate complex of two alkoxy radicals (RO···OR′) and that the accretion product pathway involves an intersystem crossing (ISC) of this complex from the triplet to the singlet surface. However, ISC rates have hitherto not been computed for large and chemically complex RO···OR′ systems actually relevant to atmospheric aerosol formation. Here, we carry out systematic conformational sampling and ISC rate calculations on 3(RO···OR′) clusters formed in the recombination reactions of different diastereomers of the first-generation peroxyl radicals originating in both OH- and NO3-initiated reactions of α-pinene, a key biogenic hydrocarbon for atmospheric aerosol formation. While we find large differences between the ISC rates of different diastereomer pairs, all systems have ISC rates of at least 106 s–1, and many have rates exceeding 1010 s–1. Especially the latter value demonstrates that accretion product formation via the suggested pathway is a competitive process also for α-pinene-derived RO2 and likely explains the experimentally observed gas-phase formation of C20 compounds in α-pinene oxidation.
- Published
- 2021
37. Fragmentation inside PTR-based mass spectrometers limits the detection of ROOR and ROOH peroxides
- Author
-
Haiyan Li, Theo Kurtén, Wei Huang, Thomas Golin Almeida, Jordan E. Krechmer, Mikael Ehn, Brett B. Palm, Christopher D. Daub, Jian Zhao, Claudia Mohr, and Yuanyuan Luo
- Subjects
chemistry.chemical_compound ,Chemical ionization ,Hydronium ,chemistry ,Fragmentation (mass spectrometry) ,Ionization ,Proton affinity ,Protonation ,Photochemistry ,Mass spectrometry ,Ion - Abstract
Proton-transfer-reaction (PTR) is a commonly applied ionization technique for mass spectrometers, where hydronium ions (H3O+) transfer a proton to analytes with higher proton affinities than the water molecule. This method has most commonly been used to quantify volatile hydrocarbons, but later generation PTR-instruments have been designed for better throughput of less volatile species, allowing detection of more functionalized molecules as well. For example, the recently developed Vocus PTR time-of-flight mass spectrometer (PTR-TOF) has been shown to agree well with an iodide adduct based chemical ionization mass spectrometer (CIMS) for products with 3-5 O-atoms from oxidation of monoterpenes (C10H16). However, while several different types of CIMS instruments (including those using iodide) detect abundant signals also at “dimeric” species, believed to be primarily ROOR peroxides, no such signals have been observed in the Vocus PTR, even though these compounds fulfil the condition of having higher proton affinity than water. More traditional PTR instruments have been limited to volatile molecules as the inlets have not been designed for transmission of easily condensable species. Some newer instruments, like the Vocus PTR, have overcome this limitation, but are still not able to detect the full range of functionalized products, suggesting that other limitations need to be considered. One such limitation, well-documented in PTR literature, is the tendency of protonation to lead to fragmentation of some analytes. In this work, we evaluate the potential for PTR to detect dimers and the most oxygenated compounds, as these have been shown to be crucial for forming atmospheric aerosol particles. We studied the detection of dimers using a Vocus PTR-TOF in laboratory experiments as well as through quantum chemical calculations. Only noisy signals of potential dimers were observed during experiments on the ozonolysis of the monoterpene α-pinene, while a few small signals of dimeric compounds were detected during the ozonolysis of cyclohexene. During the latter experiments, we also tested varying the pressures and electric fields in the ionization region of the Vocus PTR-TOF, finding that only small improvements were possible in the relative dimer contributions. Calculations for model ROOR and ROOH systems showed that most of these peroxides should fragment partially following protonation. With inclusion of additional energy from the ion-molecule collisions driven by the electric fields in the ionization source, computational results suggest substantial or nearly complete fragmentation of dimers. Our study thus suggests that while the improved versions of PTR-based mass spectrometers are very powerful tools for measuring hydrocarbons and their moderately oxidized products, other types of CIMS are likely more suitable for the detection of ROOR and ROOH species.
- Published
- 2021
38. Supplementary material to 'Fragmentation inside PTR-based mass spectrometers limits the detection of ROOR and ROOH peroxides'
- Author
-
Haiyan Li, Thomas Golin Almeida, Yuanyuan Luo, Jian Zhao, Brett B. Palm, Christopher D. Daub, Wei Huang, Claudia Mohr, Jordan E. Krechmer, Theo Kurtén, and Mikael Ehn
- Published
- 2021
39. Atmospheric gaseous hydrochloric and hydrobromic acid in urban Beijing, China : detection, source identification and potential atmospheric impacts
- Author
-
Xiaolong Fan, Jing Cai, Chao Yan, Jian Zhao, Yishuo Guo, Chang Li, Kaspar R. Dällenbach, Feixue Zheng, Zhuohui Lin, Biwu Chu, Yonghong Wang, Lubna Dada, Qiaozhi Zha, Wei Du, Jenni Kontkanen, Theo Kurtén, Siddhart Iyer, Joni T. Kujansuu, Tuukka Petäjä, Douglas R. Worsnop, Veli-Matti Kerminen, Yongchun Liu, Federico Bianchi, Yee Jun Tham, Lei Yao, Markku Kulmala, Air quality research group, Institute for Atmospheric and Earth System Research (INAR), INAR Physics, INAR Physical Chemistry, Department of Chemistry, Polar and arctic atmospheric research (PANDA), Global Atmosphere-Earth surface feedbacks, Tampere University, and Physics
- Subjects
NITRYL CHLORIDE ,SUBMICRON AEROSOLS ,HETEROGENEOUS N2O5 UPTAKE ,POWER-PLANT ,FINE PARTICULATE CHLORIDE ,116 Chemical sciences ,SEGREGATED PARTICLE NUMBER ,114 Physical sciences ,BROMINE ,TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES ,13. Climate action ,CHEMISTRY ,CLNO2 ,EMISSIONS - Abstract
Gaseous hydrochloric (HCl) and hydrobromic acid (HBr) are vital halogen species that play essential roles in tropospheric physicochemical processes. Yet, the majority of the current studies on these halogen species were conducted in marine or coastal areas. Detection and source identification of HCl and HBr in inland urban areas remain scarce, thus limiting the full understanding of halogen chemistry and potential atmospheric impacts in the environments with limited influence from the marine sources. Here, both gaseous HCl and HBr were concurrently measured in urban Beijing, China, during winter and early spring of 2019. We observed significant HCl and HBr concentrations ranging from a minimum value at 1 × 108 molecules cm−3 (4 ppt) and 4 × 107 molecules cm−3 (1 ppt) up to 6 × 109 molecules cm−3 (222 ppt) and 1 × 109 molecules cm−3 (37 ppt), respectively. The HCl and HBr concentrations are enhanced along with the increase of atmospheric temperature, UVB and levels of gaseous HNO3. Based on the air mass analysis and high correlations of HCl and HBr with the burning indicators (HCN and HCNO), gaseous HCl and HBr are found to be related to anthropogenic burning aerosols. The gas–particle partitioning may also play a dominant role in the elevated daytime HCl and HBr. During the daytime, the reactions of HCl and HBr with OH radicals lead to significant production of atomic Cl and Br, up to 2 × 104 molecules cm−3 s−1 and 8 × 104 molecules cm−3 s−1, respectively. The production rate of atomic Br (via HBr + OH) is 2–3 times higher than that of atomic Cl (via HCl + OH), highlighting the potential importance of bromine chemistry in the urban area. On polluted days, the production rates of atomic Cl and Br are faster than those on clean days. Furthermore, our observations of elevated HCl and HBr may suggest an important recycling pathway of halogen species in inland megacities and may provide a plausible explanation for the widespread halogen chemistry, which could affect the atmospheric oxidation in China.
- Published
- 2021
40. Measurement of iodine species and sulfuric acid using bromide chemical ionization mass spectrometers
- Author
-
Mingyi Wang, Xu-Cheng He, Henning Finkenzeller, Siddharth Iyer, Dexian Chen, Jiali Shen, Mario Simon, Victoria Hofbauer, Jasper Kirkby, Joachim Curtius, Norbert Maier, Theo Kurtén, Douglas R. Worsnop, Markku Kulmala, Matti Rissanen, Rainer Volkamer, Yee Jun Tham, Neil M. Donahue, Mikko Sipilä, Institute for Atmospheric and Earth System Research (INAR), Polar and arctic atmospheric research (PANDA), Department of Chemistry, INAR Physical Chemistry, Helsinki Institute of Physics, Tampere University, and Physics
- Subjects
ABSORPTION-SPECTROSCOPY ,Astrophysics and Astronomy ,AMMONIA ,TheoryofComputation_MATHEMATICALLOGICANDFORMALLANGUAGES ,ATMOSPHERIC PARTICLES ,13. Climate action ,DENSITY ,IN-SITU MEASUREMENTS ,GROWTH ,114 Physical sciences ,EMISSIONS - Abstract
Iodine species are important in the marine atmosphere for oxidation and new-particle formation. Understanding iodine chemistry and iodine new-particle formation requires high time resolution, high sensitivity, and simultaneous measurements of many iodine species. Here, we describe the application of a bromide chemical ionization mass spectrometer (Br-CIMS) to this task. During the iodine oxidation experiments in the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber, we have measured gas-phase iodine species and sulfuric acid using two Br-CIMS, one coupled to a Multi-scheme chemical IONization inlet (Br-MION-CIMS) and the other to a Filter Inlet for Gasses and AEROsols inlet (Br-FIGAERO-CIMS). From offline calibrations and intercomparisons with other instruments, we have quantified the sensitivities of the Br-MION-CIMS to HOI, I2, and H2SO4 and obtained detection limits of 5.8 × 106, 3.8 × 105, and 2.0 × 105 molec. cm−3, respectively, for a 2 min integration time. From binding energy calculations, we estimate the detection limit for HIO3 to be 1.2 × 105 molec. cm−3, based on an assumption of maximum sensitivity. Detection limits in the Br-FIGAERO-CIMS are around 1 order of magnitude higher than those in the Br-MION-CIMS; for example, the detection limits for HOI and HIO3 are 3.3 × 107 and 5.1 × 106 molec. cm−3, respectively. Our comparisons of the performance of the MION inlet and the FIGAERO inlet show that bromide chemical ionization mass spectrometers using either atmospheric pressure or reduced pressure interfaces are well-matched to measuring iodine species and sulfuric acid in marine environments.
- Published
- 2021
41. New Particle Formation from the Vapor Phase: From Barrier-Controlled Nucleation to the Collisional Limit
- Author
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Kayane K, Dingilian, Martina, Lippe, Jakub, Kubečka, Jan, Krohn, Chenxi, Li, Roope, Halonen, Fatemeh, Keshavarz, Bernhard, Reischl, Theo, Kurtén, Hanna, Vehkamäki, Ruth, Signorell, and Barbara E, Wyslouzil
- Subjects
Letter - Abstract
Studies of vapor phase nucleation have largely been restricted to one of two limiting cases—nucleation controlled by a substantial free energy barrier or the collisional limit where the barrier is negligible. For weakly bound systems, exploring the transition between these regimes has been an experimental challenge, and how nucleation evolves in this transition remains an open question. We overcome these limitations by combining complementary Laval expansion experiments, providing new particle formation data for carbon dioxide over a uniquely broad range of conditions. Our experimental data together with a kinetic model using rate constants from high-level quantum chemical calculations provide a comprehensive picture of new particle formation as nucleation transitions from a barrier-dominated process to the collisional limit.
- Published
- 2021
42. Configurational Sampling of Noncovalent (Atmospheric) Molecular Clusters: Sulfuric Acid and Guanidine
- Author
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Hanna Vehkamäki, Vitus Besel, Jakub Kubečka, Theo Kurtén, Nanna Myllys, INAR Physics, Department of Chemistry, University Management, and Institute for Atmospheric and Earth System Research (INAR)
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010304 chemical physics ,116 Chemical sciences ,Sampling (statistics) ,Sulfuric acid ,010402 general chemistry ,114 Physical sciences ,01 natural sciences ,0104 chemical sciences ,Atmosphere ,chemistry.chemical_compound ,chemistry ,Computational chemistry ,0103 physical sciences ,Physical and Theoretical Chemistry ,Guanidine - Abstract
We studied the configurational sampling of noncovalently bonded molecular clusters relevant to the atmosphere. In this article, we discuss possible approaches to searching for optimal configurations and present one alternative based on systematic configurational sampling, which seems able to overcome the typical problems associated with searching for global minima on multidimensional potential energy surfaces. Since atmospheric molecular clusters are usually held together by intermolecular bonds, we also present a cost-effective strategy for treating hydrogen bonding and proton transferring by using rigid molecules and ions in different protonation states and illustrate its performance on clusters containing guanidine and sulfuric acid.
- Published
- 2019
43. Clustering of H2SO4 with BX3 (X = H, F, Cl, Br, CN, OH) compounds creates strong acids and superacids
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Theo Kurtén, Younes Valadbeigi, Department of Chemistry, and Institute for Atmospheric and Earth System Research (INAR)
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VAPOR-PRESSURE ,116 Chemical sciences ,010402 general chemistry ,DFT ,01 natural sciences ,Biochemistry ,chemistry.chemical_compound ,NEUTRAL ORGANIC SUPERACIDS ,Deprotonation ,Molecular clusters ,0103 physical sciences ,Atom ,Cluster (physics) ,BRONSTED SUPERACIDS ,Physical and Theoretical Chemistry ,GAS-PHASE ACIDITIES ,010304 chemical physics ,AMMONIA-BORANE ,DERIVATIVES ,Chemistry ,Hydrogen bond ,Atoms in molecules ,LEWIS-ACID ,HYDROGEN STORAGE ,Electron deficiency ,HYDRIDE TRANSFER ,Condensed Matter Physics ,Lewis acid ,0104 chemical sciences ,Crystallography ,Boron compounds ,H2SO4 ,Superacid ,Natural bond orbital - Abstract
The interaction of H2SO4 with boron compounds including BH3, BF3, BCl3, BBr3, B(CN)(3) and B(OH)(3) was studied computationally using the omega B97xD density functional. All the BX3 compounds except B(OH)(3) bind to H2SO4 via both SOH center dot center dot center dot X hydrogen bonds, and interactions between the B atoms and the S=O oxygen atoms. B(OH)(3) interacts with H2SO4 solely through hydrogen bonds. B(CN)(3) and BCl3 exhibit the strongest and weakest interactions with H2SO4, respectively. Natural bond orbital (NBO) analysis shows that the relative weakness of the H2SO4- BCl3 interaction may be due to pi-bonding between the B and Cl atoms, and the occupation of the p(z) orbital of the B atom. The strong electron withdrawing groups CN in B(CN)(3) intensify electron deficiency of B atom and promote its tendency to capture electrons of oxygen atom of O=S group. Atoms in molecules (AIM) calculations show bond critical points (BCP) between the X groups of BX3 and the hydrogen atoms of H2SO4 for all cases except X = OH. Enthalpies and Gibbs free energies of deprotonation in the gas phase (Delta H-acid, Delta G(acid)) were calculated for (BX3)H2SO4 and (BX3)(2)H2SO4 complexes. These data revealed that clustering of BX3 with H2SO4 enhances the acidity of H2SO4 by about 9-58 kcal mol(-1). The (B(CN)(3))(2)H2SO4 cluster had Delta H-acid and Delta G(acid) values of 255.0 and 246.7 kcal mol(-1), respectively, and is the strongest Bronsted acids among the (BX3)(2)H2SO4 clusters.
- Published
- 2019
44. Estimating the saturation vapor pressures of isoprene oxidation products C5H12O6 and C5H10O6 using COSMO-RS
- Author
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Noora Hyttinen, Joel A. Thornton, Emma L. D'Ambro, Theo Kurtén, and Nønne L. Prisle
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Atmospheric Science ,010504 meteorology & atmospheric sciences ,Chemistry ,Hydrogen bond ,Vapor pressure ,Thermodynamics ,010501 environmental sciences ,01 natural sciences ,COSMO-RS ,13. Climate action ,Intramolecular force ,Molecule ,Saturation (chemistry) ,Conformational isomerism ,Volatility (chemistry) ,0105 earth and related environmental sciences - Abstract
We have used COSMO-RS (the conductor-like screening model for real solvents), as implemented in the COSMOtherm program, to compute the saturation vapor pressures at 298 K of two photo-oxidation products of isoprene: the dihydroxy dihydroperoxide C5H12O6, and the dihydroperoxy hydroxy aldehyde, C5H10O6. The predicted saturation vapor pressures were significantly higher (by up to a factor of 1000) than recent experimental results, very likely due to the overestimation of the effects of intramolecular hydrogen bonds, which tend to increase saturation vapor pressures by stabilizing molecules in the gas phase relative to the liquid. Modifying the hydrogen bond enthalpy parameter used by COSMOtherm can improve the agreement with experimental results – however the optimal parameter value is likely to be system-specific. Alternatively, vapor pressure predictions can be substantially improved (to within a factor of 5 of the experimental values for the two systems studied here) by selecting only conformers with a minimum number of intramolecular hydrogen bonds. The computed saturation vapor pressures were very sensitive to the details of the conformational sampling approach, with the default scheme implemented in the COSMOconf program proving insufficient for the task, for example by predicting significant differences between enantiomers, which should have identical physical properties. Even after exhaustive conformational sampling, COSMOtherm predicts significant differences in saturation vapor pressures between both structural isomers and diastereomers. For C5H12O6, predicted differences in psat between structural isomers are up to 2 orders of magnitude, and differences between stereoisomers are up to a factor of 20 – though these differences are very likely exaggerated by the overestimation of the effect of intramolecular H-bonds. For C5H10O6, the maximum predicted differences between the three studied structural isomers and their diastereomer pairs are around a factor of 8 and a factor of 2, respectively, when only conformers lacking intramolecular hydrogen bonds are included in the calculations. In future studies of saturation vapor pressures of polyfunctional atmospheric oxidation products using COSMOtherm, we recommend first performing thorough conformational sampling and subsequently selecting conformers with a minimal number of intramolecular H-bonds.
- Published
- 2018
45. Atmospheric gaseous hydrochloric and hydrobromic acid in urban Beijing, China: detection, source identification and potential atmospheric impacts
- Author
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Lei Yao, Xiaolong Fan, Jing Cai, Chao Yan, Biwu Chu, Kaspar R. Dällenbach, Yonghong Wang, Lubna Dada, Qiaozhi Zha, Jenni Kontkanen, Theo Kurtén, Siddhart Iyer, Joni T Kujansuu, Tuukka Petäjä, Douglas Worsnop, Veli-Matti Kerminen, Yongchun Liu, Federico Bianhi, Yee Jun Tham, and Markku Kulmala
- Abstract
Gaseous hydrochloric (HCl) and hydrobromic acid (HBr) are vital halogen species that play essential roles in tropospheric physicochemical processes. Yet, majority of the current studies on these halogen species were conducted in marine or coastal areas. Detection and source identification of HCl and HBr in inland urban areas (especially megacities) remain scarce, thus, limiting the full understanding of halogen chemistry and potential atmospheric impacts in the environments with limited influence from the marine sources. Here, both gaseous HCl and HBr were concurrently measured by Chemical Ionization-Atmospheric Pressure interface-Long Time Of Flight-Mass Spectrometer (CI-APi-LTOF-MS) in urban Beijing, China at the BUCT station (39.94° N, 116.30° E) during winter and early spring of 2019. We observed significant HCl and HBr concentrations ranged from a minimum value at 1.3×108 cm-3 and 4.3×107 cm-3 up to 5.9×109 cm-3 and 1.2×109 cm-3, respectively. The HCl and HBr concentrations are enhanced along with the increase of atmospheric temperature, UVB, and levels of gaseous HNO3. Based on the air mass analysis and high correlations of HCl and HBr with the burning indicators (HCN and HCNO), the gaseous HCl and HBr are found to be related to anthropogenic burning aerosols. The gas-aerosol partitioning may also play a dominant role in the elevated daytime HCl and HBr. During the daytime, the reaction of HCl and HBr with OH radicals lead to significant production of atomic Cl and Br, up to 1.7×104 cm-3 s-1and 7.9×104 cm-3 s-1, respectively. The production rate of atomic Br (via HBr + OH) are 2-3 times higher than that of atomic Cl (via HCl + OH), highlighting the potential importance of bromine chemistry in the urban area. Furthermore, our observations of elevated HCl and HBr may suggest an important recycling pathway of halogen species in inland megacities, and may provide a plausible explanation for the widespread of halogen chemistry, which could affect the atmospheric oxidation in China.
- Published
- 2021
46. Franck-Condon factors and vibronic patterns of singlet-triplet transitions of 16O3 molecule falling near the dissociation threshold and above
- Author
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O. V. Egorov, Rashid R. Valiev, Vladimir G. Tyuterev, and Theo Kurtén
- Subjects
Physics ,Radiation ,Франка-Кондона факторы ,010304 chemical physics ,Absorption spectroscopy ,порог диссоциации ,Ab initio ,010402 general chemistry ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Dissociation (psychology) ,0104 chemical sciences ,Atomic electron transition ,молекула озона ,Excited state ,триплетное состояние ,0103 physical sciences ,синглет-триплетные переходы ,medicine ,Singlet state ,medicine.symptom ,Atomic physics ,Ground state ,Spectroscopy ,Basis set - Abstract
The Franck-Condon factors were calculated for vertical electronic transitions between the ground singlet (X1 A1 ) and 3 A2 , 3 B2 , and 3 B1 excited triplet states associated with the Wulf band of the ozone molecule (O3 ). The XMCQDPT2 ab initio method including the static and dynamic electronic correlations was used with the aug-cc-pVQZ basis set. Along with the cold bands, a list of the strongest singlet-triplet hot bands falling into the region of the dissociation threshold of O3 is presented. The absorption coefficient simulated for intensities of the electronic-vibrational patterns agrees well with the measured absorbance from literature. In addition, the intensities of the single lines of the electronic-vibrational-rotational transitions were calculated in absolute units for the most pronounced singlet-triplet hot bands located up to the first 3A2 (0 0 0)←X1 A1 (0 0 0) cold band inclusively. The integrated intensity of the 3 A2 (0 0 0)←X1 A1 (0 0 0) band reported in this work agrees well with the available experimental value from literature.
- Published
- 2021
47. Aqueous-phase behavior of glyoxal and methylglyoxal observed with carbon and oxygen K-edge X-ray absorption spectroscopy
- Author
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Georgia Michailoudi, Jack J. Lin, Hayato Yuzawa, Masanari Nagasaka, Marko Huttula, Nobuhiro Kosugi, Theo Kurtén, Minna Patanen, Nønne L. Prisle
- Published
- 2021
- Full Text
- View/download PDF
48. Reaction Mechanisms Underlying Unfunctionalized Alkyl Nitrate Hydrolysis in Aqueous Aerosols
- Author
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Hanna Vehkamäki, Fatemeh Keshavarz, Joel A. Thornton, Theo Kurtén, Institute for Atmospheric and Earth System Research (INAR), Department of Physics, and Department of Chemistry
- Subjects
inorganic chemicals ,Atmospheric Science ,Reaction mechanism ,Ozone ,Radical ,116 Chemical sciences ,010402 general chemistry ,Photochemistry ,basic hydrolysis ,7. Clean energy ,01 natural sciences ,114 Physical sciences ,chemistry.chemical_compound ,Nitrate ,Geochemistry and Petrology ,0103 physical sciences ,acidic hydrolysis ,Nitrogen cycle ,Alkyl ,NOx ,rate coefficient ,chemistry.chemical_classification ,010304 chemical physics ,Chemistry ,respiratory system ,0104 chemical sciences ,13. Climate action ,Space and Planetary Science ,Nitrogen oxide ,reaction kinetics ,alkyl nitrate - Abstract
Alkyl nitrates (ANs) are both sinks and sources of nitrogen oxide radicals (NOx = NO + NO2) in the atmosphere. Their reactions affect both the nitrogen cycle and ozone formation and therefore air quality and climate. ANs can be emitted to the atmosphere or produced in the gas phase. In either case, they can partition into aqueous aerosols, where they might undergo hydrolysis, producing highly soluble nitrate products, and act as a permanent sink for NOx. The kinetics of AN hydrolysis partly determines the extent of AN contribution to the nitrogen cycle. However, kinetics of many ANs in various aerosols is unknown, and there are conflicting arguments about the effect of acidity and basicity on the hydrolysis process. Using computational methods, this study proposes a mechanism for the reactions of methyl, ethyl, propyl, and butyl nitrates with OH- (hydroxyl ion; basic hydrolysis), water (neutral hydrolysis), and H3O+ (hydronium ion; acidic hydrolysis). Using quantum chemical data and transition state theory, we follow the effect of pH on the contribution of the basic, neutral, and acidic hydrolysis channels, and the rate coefficients of AN hydrolysis over a wide range of pH. Our results show that basic hydrolysis (i.e., AN reaction with OH-) is the most kinetically and thermodynamically favorable reaction among our evaluated reaction schemes. Furthermore, comparison of our kinetics results with experimental data suggests that there is an as yet unknown acidic mechanism responsible for acidic catalysis of AN hydrolysis.
- Published
- 2021
- Full Text
- View/download PDF
49. Aromaticity of Even-Number Cyclo[n]carbons (n=6-100)
- Author
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Theo Kurtén, Rashid R. Valiev, Dage Sundholm, Rinat T. Nasibullin, Glib V. Baryshnikov, Hans Ågren, and Department of Chemistry
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CURRENTS ,116 Chemical sciences ,DENSITY FUNCTIONALS ,chemistry.chemical_element ,CARBON RINGS ,Electronic structure ,010402 general chemistry ,Ring (chemistry) ,01 natural sciences ,Physical Chemistry ,114 Physical sciences ,Article ,Delocalized electron ,DESIGN ,0103 physical sciences ,ELEMENTS ,Molecule ,ALL-CARBOATOMIC RING ,Physical and Theoretical Chemistry ,FIELD ,BASIS-SETS ,Fysikalisk kemi ,010304 chemical physics ,Aromaticity ,Triple bond ,0104 chemical sciences ,MOLECULAR-ORBITAL METHODS ,Crystallography ,ELECTRONIC-STRUCTURE ,chemistry ,Carbon ,Antiaromaticity - Abstract
The recently synthesized cyclo[18]carbon molecule has been characterized in a number of studies by calculating electronic, spectroscopic, and mechanical properties. However, cyclo[18] carbon is only one member of the class of cyclo[n]carbons-standalone carbon allotrope representatives. Many of the larger members of this class of molecules have not been thoroughly investigated. In this work, we calculate the magnetically induced current density of cyclo[n]carbons in order to elucidate how electron delocalization and aromatic properties change with the size of the molecular ring (n), where n is an even number between 6 and 100. We find that the Hiickel rules for aromaticity (4k + 2) and antiaromaticity (4k) become degenerate for large C-n rings (n > 50), which can be understood as a transition from a delocalized electronic structure to a nonaromatic structure with localized current density fluxes in the triple bonds. Actually, the calculations suggest that cyclo[n]carbons with n > 50 are nonaromatic cyclic polyalkynes. The influence of the amount of nonlocal exchange and the asymptotic behavior of the exchange-correlation potential of the employed density functionals on the strength of the magnetically induced ring current and the aromatic character of the large cyclo[n]carbons is also discussed.
- Published
- 2020
50. Supplementary material to 'Atmospheric gaseous hydrochloric and hydrobromic acid in urban Beijing, China: detection, source identification and potential atmospheric impacts'
- Author
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Xiaolong Fan, Jing Cai, Chao Yan, Jian Zhao, Yishuo Guo, Chang Li, Kaspar R. Dällenbach, Feixue Zheng, Zhuohui Lin, Biwu Chu, Yonghong Wang, Lubna Dada, Qiaozhi Zha, Wei Du, Jenni Kontkanen, Theo Kurtén, Siddhart Iyer, Joni T. Kujansuu, Tuukka Petäjä, Douglas R. Worsnop, Veli-Matti Kerminen, Yongchun Liu, Federico Bianchi, Yee Jun Tham, Lei Yao, and Markku Kulmala
- Published
- 2020
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