1
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Thøgersen J, Madzharova F, Weidner T, Jensen F. Aqueous pyruvate partly dissociates under deep ultraviolet irradiation but is resilient to near ultraviolet excitation. Nat Commun 2024; 15:1978. [PMID: 38438353 PMCID: PMC10912111 DOI: 10.1038/s41467-024-46309-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2023] [Accepted: 02/14/2024] [Indexed: 03/06/2024] Open
Abstract
The deep ultraviolet photochemistry of aqueous pyruvate is believed to have been essential to the origin of life, and near ultraviolet excitation of pyruvate in aqueous aerosols is assumed to contribute significantly to the photochemistry of the Earth's atmosphere. However, the primary photochemistry of aqueous pyruvate is unknown. Here we study the susceptibility of aqueous pyruvate to photodissociation by deep ultraviolet and near ultraviolet irradiation with femtosecond spectroscopy supported by density functional theory calculations. The primary photo-dynamics of the aqueous pyruvate show that upon deep-UV excitation at 200 nm, about one in five excited pyruvate anions have dissociated by decarboxylation 100 ps after the excitation, while the rest of the pyruvate anions return to the ground state. Upon near-UV photoexcitation at a wavelength of 340 nm, the dissociation yield of aqueous pyruvate 200 ps after the excitation is insignificant and no products are observed. The experimental results are explained by our calculations, which show that aqueous pyruvate anions excited at 200 nm have sufficient excess energy for decarboxylation, whereas excitation at 340 nm provides the aqueous pyruvate anions with insufficient energy to overcome the decarboxylation barrier.
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Affiliation(s)
- Jan Thøgersen
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000, Aarhus C, Denmark
| | - Fani Madzharova
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000, Aarhus C, Denmark
| | - Tobias Weidner
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000, Aarhus C, Denmark
| | - Frank Jensen
- Department of Chemistry, Aarhus University, Langelandsgade 140, DK-8000, Aarhus C, Denmark.
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2
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Sader M, Prieto-Grosso M, Suhr M, Choël M, Visez N, Moreau M, Billon G, Gómez-Castaño JA, Tobón YA. Direct photodegradation of internally mixed sodium chloride and malonic acid single aerosols: Impact of the photoproducts on the hygroscopic properties of the particles. CHEMOSPHERE 2024; 349:140795. [PMID: 38016525 DOI: 10.1016/j.chemosphere.2023.140795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 10/26/2023] [Accepted: 11/22/2023] [Indexed: 11/30/2023]
Abstract
Sea-salt aerosols (SSA) are one of the key natural aerosols in our atmosphere, consisting predominantly of sodium chloride (NaCl). Throughout their atmospheric transport, these aerosols undergo complex internal mixing, giving rise to a rich variety of inorganic and organic species, including dicarboxylic acids. This study investigates firstly the composition and deliquescence properties of coarse particles containing pure malonic acid (MA2, CH2(COOH)2) and internally mixed NaCl and MA2, by means of an acoustic levitation system coupled with a Raman microspectrometer. Secondly, we report here the first experimental observation and characterization of the products arising from photochemical reactions under UV-Visible irradiation (338 ≤ λ ≤ 414 nm) in the absence of an oxidant under acoustic levitation conditions in MA2 and NaCl/MA2 aerosols. Furthermore, the impact of photodegradation on the hygroscopic properties of these particles is examined. We confirmed the irreversible formation of monosodium malonate (NaMA, HOOCCH2COONa), which coexists with NaCl or MA2 on non-irradiated particles. We also demonstrated the formation of oxalic acid (OA2, HOOC-COOH) within irradiated MA2 droplets and the appearance of glyoxylic acid (GlyA, HCOCOOH) in NaCl containing droplets. The photolysis process exerts a marked effect on the hygroscopic properties of the particles, resulting in a shift in deliquescence transitions toward higher relative humidity (RH) values. This study contributes to the understanding of the intricate physicochemical processes involved in SSA during their atmospheric transport. Likewise, this work sheds light on the impacts of these types of aerosols on cloud formation and climate change.
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Affiliation(s)
- Mikel Sader
- Univ. Lille, CNRS, UMR 8516 - LASIRE - LAboratoire de Spectroscopie pour Les Interactions, La Réactivité et L'Environnement, F-59000, Lille, France
| | - Manuel Prieto-Grosso
- Univ. Lille, CNRS, UMR 8516 - LASIRE - LAboratoire de Spectroscopie pour Les Interactions, La Réactivité et L'Environnement, F-59000, Lille, France; Grupo Química-Física Molecular y Modelamiento Computacional (QUIMOL), Escuela de Ciencias Químicas, Universidad Pedagógica y Tecnológica de Colombia (UPTC), Sede Tunja, Avenida Central Del Norte, 150003, Boyacá, Colombia
| | - Madeleine Suhr
- Univ. Lille, CNRS, UMR 8516 - LASIRE - LAboratoire de Spectroscopie pour Les Interactions, La Réactivité et L'Environnement, F-59000, Lille, France
| | - Marie Choël
- Univ. Lille, CNRS, UMR 8516 - LASIRE - LAboratoire de Spectroscopie pour Les Interactions, La Réactivité et L'Environnement, F-59000, Lille, France
| | - Nicolas Visez
- Univ. Lille, CNRS, UMR 8516 - LASIRE - LAboratoire de Spectroscopie pour Les Interactions, La Réactivité et L'Environnement, F-59000, Lille, France
| | - Myriam Moreau
- Univ. Lille, CNRS, UMR 8516 - LASIRE - LAboratoire de Spectroscopie pour Les Interactions, La Réactivité et L'Environnement, F-59000, Lille, France
| | - Gabriel Billon
- Univ. Lille, CNRS, UMR 8516 - LASIRE - LAboratoire de Spectroscopie pour Les Interactions, La Réactivité et L'Environnement, F-59000, Lille, France
| | - Jovanny A Gómez-Castaño
- Univ. Lille, CNRS, UMR 8516 - LASIRE - LAboratoire de Spectroscopie pour Les Interactions, La Réactivité et L'Environnement, F-59000, Lille, France; Grupo Química-Física Molecular y Modelamiento Computacional (QUIMOL), Escuela de Ciencias Químicas, Universidad Pedagógica y Tecnológica de Colombia (UPTC), Sede Tunja, Avenida Central Del Norte, 150003, Boyacá, Colombia
| | - Yeny A Tobón
- Univ. Lille, CNRS, UMR 8516 - LASIRE - LAboratoire de Spectroscopie pour Les Interactions, La Réactivité et L'Environnement, F-59000, Lille, France.
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3
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Li M, Boothby C, Continetti RE, Grassian VH. Size-Dependent Sigmoidal Reaction Kinetics for Pyruvic Acid Condensation at the Air-Water Interface in Aqueous Microdroplets. J Am Chem Soc 2023; 145:22317-22321. [PMID: 37787586 PMCID: PMC10591466 DOI: 10.1021/jacs.3c08249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Indexed: 10/04/2023]
Abstract
The chemistry of pyruvic acid (PA) under thermal dark conditions is limited in bulk solutions, but in microdroplets it is shown to readily occur. Utilizing in situ micro-Raman spectroscopy as a probe, we investigated the chemistry of PA within aqueous microdroplets in a relative humidity- and temperature-controlled environmental cell. We found that PA undergoes a condensation reaction to yield mostly zymonic acid. Interestingly, the reaction follows a size-dependent sigmoidal kinetic profile, i.e., an induction period followed by reaction and then completion. The induction time is linearly proportional to the surface area (R2), and the maximum apparent reaction rate is proportional to the surface-to-volume ratio (1/R), showing that both the induction and reaction occur at the air-water interface. Furthermore, the droplet size is shown to be dynamic due to changes in droplet composition and re-equilibration with the relative humidity within the environmental cell as the reaction proceeds. Overall, the size-dependent sigmoidal kinetics, shown for the first time in microdroplets, demonstrates the complexity of the reaction mechanism and the importance of the air-water interface in the pyruvic acid condensation reaction.
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Affiliation(s)
- Meng Li
- Department of Chemistry and
Biochemistry, University of California San
Diego, La Jolla, California 92093, United States
| | - Christian Boothby
- Department of Chemistry and
Biochemistry, University of California San
Diego, La Jolla, California 92093, United States
| | - Robert E. Continetti
- Department of Chemistry and
Biochemistry, University of California San
Diego, La Jolla, California 92093, United States
| | - Vicki H. Grassian
- Department of Chemistry and
Biochemistry, University of California San
Diego, La Jolla, California 92093, United States
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4
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Pollet R, Chin W. In silico Investigation of the Thermochemistry and Photoactivity of Pyruvic Acid in an Aqueous Solution of NaCl. Chemistry 2023; 29:e202302225. [PMID: 37539648 DOI: 10.1002/chem.202302225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 08/03/2023] [Accepted: 08/04/2023] [Indexed: 08/05/2023]
Abstract
The photochemistry of oxocarboxylic acids contributes significantly to the complex chemistry occurring in the atmosphere. In this regard, pyruvic acid undergoes photoreactions that lead to many diverse products. The presence of sodium cation near pyruvic acid in an aqueous solution, or its conjugate base in non-acidic conditions, influences the hydration equilibrium and the photosensitivity to UV-visible light of the oxocarboxylic acid. We performed an ab initio metadynamics simulation which serves two purposes: first, it unveils the mechanisms of the reversible hydration reaction between the keto and the diol forms, with a free-energy difference of only 2 kJ/mol at 300 K, which shows the influence of sodium on the keto/diol ratio; second, it provides solvent-shared ion pairing (SSIP) and contact ion pairing (CIP) structures, including Na+ coordinated to carbonyl, for the calculations of the electronic transition energies to an antibonding π* orbital, which sheds light on the photoactivity of these two forms in the actinic region.
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Affiliation(s)
- Rodolphe Pollet
- Université Paris-Saclay, CEA, CNRS, NIMBE, 91191, Gif-sur-Yvette, France
| | - Wutharath Chin
- Université Paris-Saclay, CNRS, Institut des Sciences Moléculaires d'Orsay, 91405, Orsay, France
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Ricker H, Leonardi A, Navea JG. Reduction and Photoreduction of NO 2 in Humic Acid Films as a Source of HONO, ClNO, N 2O, NO X , and Organic Nitrogen. ACS EARTH & SPACE CHEMISTRY 2022; 6:3066-3077. [PMID: 36561196 PMCID: PMC9762234 DOI: 10.1021/acsearthspacechem.2c00282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 11/18/2022] [Accepted: 11/21/2022] [Indexed: 06/17/2023]
Abstract
Atmospheric nitrous acid (HONO), a trace atmospheric gas, is often underestimated in global atmospheric models due to the poor understanding of its daytime sources and sinks. HONO is known to accumulate during nighttime and undergo rapid photodissociation during the day to form NO and highly reactive OH radical, making it important to have accurate atmospheric HONO estimations. Despite its rapid photolysis, recent field observations have found quasi-steady-state concentrations of HONO at midday, suggesting photolytic HONO formation pathways to replenish daytime atmospheric HONO. Recent studies suggest that the presence of complex organic photosensitizers in atmospheric aerosols converts atmospheric NO2 into HONO. To better understand the effect of environmental photosensitizers in daytime mechanisms of HONO formation, we present here laboratory studies on the heterogeneous photolytic reduction of NO2 by humic acid films, a proxy for organic chromophoric compounds. The effect of pH and Cl- in the photosensitized formation of HONO and other nitrogen-containing gases is also investigated. A dual Fourier transform infrared (FTIR) system is utilized to simultaneously perform in situ analysis of condensed-phase reactants and gas-phase products. We find that the rate of HONO formation is faster at lower pHs. Nitrogen incorporation in the complex organic chromophore is observed, suggesting a competing pathway that results in suppressed daytime formation of nitrogenous gases. Significantly, the presence of chloride ions also leads to the organic-mediated photolytic formation of nitrosyl chloride (ClNO), a known precursor of HONO. Overall, this work shows that organic acid photosensitizers can reduce adsorbed NO2 to form HONO, ClNO, and NO while simultaneously incorporating nitrogen into the organic chromophores present in aerosol.
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6
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Chen J, Miao XN, An T. Detection of excited triplet species from photolysis of carbonyls: Direct evidence for single oxygen formation in atmospheric environment. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 837:155464. [PMID: 35508234 DOI: 10.1016/j.scitotenv.2022.155464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Revised: 04/08/2022] [Accepted: 04/19/2022] [Indexed: 06/14/2023]
Abstract
Excited triplet species play an important role in the photolytic formation of 1O2 from carbonyls, but the related mechanism is still uncertain, due to lack of direct evidence. In this study, steady-state and transient photolysis of eleven carbonyls to produce 1O2 was investigated. Dicarbonyl displayed greater 1O2 production ability than monocarbonyl, while dicarbonyl containing both ketone and carboxyl groups connected by CC bond (i.e., pyruvic acid (PA)) showed the highest 1O2 steady-state concentration ([1O2]SS). For the first time, the production of 3PA* from PA with narrow energy gap was confirmed by laser flash photolysis technique and the second-order decay rate constant of 3PA* was 2.78 × 107 M-1 s-1. Quenching results verified the dominant contribution of 3PA* to 1O2 production from PA. Addition of inorganic salt or increase in solution pH showed negligible effect on 3PA*, but significantly decreased the [1O2]SS of PA by up to two orders of magnitude, due to reduction of hydrate content. Photolysis of methylglyoxal and dimethylamine mixture led to higher content of excited triplet species at pH ≈ 11 and remarkably enhanced [1O2]SS, which was 2.3 times of that from PA and dimethylamine mixture. These findings provide direct evidence for the contribution of transient species from carbonyls or their product to 1O2 formation in atmospheric environment.
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Affiliation(s)
- Jiangyao Chen
- Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangdong Technology Research Center for Photocatalytic Technology Integration and Equipment Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, China; Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China.
| | - Xu-Nuo Miao
- Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangdong Technology Research Center for Photocatalytic Technology Integration and Equipment Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, China
| | - Taicheng An
- Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangdong Technology Research Center for Photocatalytic Technology Integration and Equipment Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou 510006, China; Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China
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7
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Hammami F, Issaoui N. A DFT Study of the Hydrogen Bonded Structures of Pyruvic Acid–Water Complexes. FRONTIERS IN PHYSICS 2022. [DOI: 10.3389/fphy.2022.901736] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The molecular geometries of the possible conformations of pyruvic acid–water complexes (PA-(H2O)n = 1–4) have been fully optimized at DFT/B3LYP/6-311G++ (d, p) levels of calculation. Among several optimized molecular clusters, we present here the most stable molecular arrangements obtained when one, two, three, and four water molecules are hydrogen-bonded to a central pyruvic acid molecule. Appropriate topological and geometrical parameters are considered primary indicators of H-bond strength. Atoms in molecules analysis shows that pyruvic acid can form a ring structure with water, and the molecular structures are stabilized by both strong O–H⋅⋅⋅O and C–H⋅⋅⋅O hydrogen bonds. In large clusters, classical O–H⋅⋅⋅O hydrogen bonds still exist between water molecules, and a cage-like structure is built around some parts of the central molecule of pyruvic acid.
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8
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Karimova NV, Luo M, Sit I, Grassian VH, Gerber RB. Absorption Spectra and the Electronic Structure of Gallic Acid in Water at Different pH: Experimental Data and Theoretical Cluster Models. J Phys Chem A 2022; 126:190-197. [PMID: 34990547 DOI: 10.1021/acs.jpca.1c07333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Gallic acid (GA) has been characterized in terms of its optical properties in aqueous solutions at varying pH in experiments and in theoretical calculations by analyzing the protonated and deprotonated forms of GA. This work is part of a series of studies of the optical properties of different carboxylic acids in aqueous media. The experimental electronic spectra of GA exhibit two strong well-separated absorption peaks (B- and C-bands), which agree with previous studies. However, in the current study, an additional well-defined low-energy shoulder band (A-band) in the optical spectra of GA was identified. It is likely that the A-band occurs for other carboxylic acids in solution, but because it can overlap with the B-band, it is difficult to discern. The theoretical calculations based on density functional theory were used to simulate the optical absorption spectra of GA in water at different pH to prove the existence of this newly found shoulder band and to describe and characterize the full experimental optical spectra of GA. Different cluster models were tested: (i) all water molecules are coordinated near the carboxy-group and (ii) additional water molecules near the hydroxy-groups of the phenyl ring were included. In this study, we found that both the polarizable continuum model (dielectric property of a medium) and neighboring water molecules (hydrogen-bonding) play significant roles in the optical spectrum. The results showed that only an extended cluster model with water molecules near carboxy- and hydroxy-groups together with the polarizable continuum model allowed us to fully reproduce the experimental data and capture all three absorption bands (A, B, and C). The oscillator strengths of the absorption bands were obtained from the experimental data and compared with theoretical results. Additionally, our work provides a detailed interpretation of the pH effects observed in the experimental absorption spectra.
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Affiliation(s)
- Natalia V Karimova
- Department of Chemistry, University of California Irvine, Irvine, California 92697, United States
| | - Man Luo
- Department of Chemistry and Biochemistry, University of California San Diego, San Diego, California 92093, United States
| | - Izaac Sit
- Department of Nanoengineering, University of California San Diego, San Diego, California 92093, United States
| | - Vicki H Grassian
- Department of Chemistry and Biochemistry, University of California San Diego, San Diego, California 92093, United States
| | - R Benny Gerber
- Department of Chemistry, University of California Irvine, Irvine, California 92697, United States.,Institute of Chemistry and Fritz Haber Research Center, Hebrew University of Jerusalem, Jerusalem 91904, Israel
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9
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Barquilla MDP, Mayes ML. Role of hydrogen bonding in bulk aqueous phase decomposition, complexation, and covalent hydration of pyruvic acid. Phys Chem Chem Phys 2022; 24:25151-25170. [DOI: 10.1039/d2cp03579k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The behavior of hydrogen bonding changes between the gas and aqueous phase, altering the mechanisms of various pyruvic acid processes and consequently affecting the aerosol formation in different environments.
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Affiliation(s)
- Michael Dave P. Barquilla
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, USA
| | - Maricris L. Mayes
- Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, North Dartmouth, MA 02747, USA
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10
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Aqueous Photochemistry of 2-Oxocarboxylic Acids: Evidence, Mechanisms, and Atmospheric Impact. Molecules 2021; 26:molecules26175278. [PMID: 34500711 PMCID: PMC8433822 DOI: 10.3390/molecules26175278] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 08/27/2021] [Accepted: 08/29/2021] [Indexed: 11/17/2022] Open
Abstract
Atmospheric organic aerosols play a major role in climate, demanding a better understanding of their formation mechanisms by contributing multiphase chemical reactions with the participation of water. The sunlight driven aqueous photochemistry of small 2-oxocarboxylic acids is a potential major source of organic aerosol, which prompted the investigations into the mechanisms of glyoxylic acid and pyruvic acid photochemistry reviewed here. While 2-oxocarboxylic acids can be contained or directly created in the particles, the majorities of these abundant and available molecules are in the gas phase and must first undergo the surface uptake process to react in, and on the surface, of aqueous particles. Thus, the work also reviews the acid-base reaction that occurs when gaseous pyruvic acid meets the interface of aqueous microdroplets, which is contrasted with the same process for acetic acid. This work classifies relevant information needed to understand the photochemistry of aqueous pyruvic acid and glyoxylic acid and motivates future studies based on reports that use novel strategies and methodologies to advance this field.
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11
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Karimova NV, Alves MR, Luo M, Grassian VH, Gerber RB. Toward a microscopic model of light absorbing dissolved organic compounds in aqueous environments: theoretical and experimental study. Phys Chem Chem Phys 2021; 23:10487-10497. [PMID: 33899856 DOI: 10.1039/d0cp06554d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Water systems often contain complex macromolecular systems that absorb light. In marine environments, these light absorbing components are often at the air-water interface and can participate in the chemistry of the atmosphere in ways that are poorly understood. Understanding the photochemistry and photophysics of these systems represents a major challenge since their composition and structures are not unique. In this study, we present a successful microscopic model of this light absorbing macromolecular species termed "marine derived chromophoric dissolved organic matter" or "m-CDOM" in water. The approach taken involves molecular dynamics simulations in the ground state using on the fly Density Functional Tight-Binding (DFTB) electronic structure theory; Time Dependent DFTB (TD-DFTB) calculations of excited states, and experimental measurements of the optical absorption spectra in aqueous solution. The theoretical hydrated model shows key features seen in the experimental data for a collected m-CDOM sample. As will be discussed, insights from the model are: (i) the low-energy A-band (at 410 nm) is due to the carbon chains combined with the diol- and the oxy-groups present in the structure; (ii) the weak B-band (at 320-360 nm) appears due to the contribution of the ionized speciated form of m-CDOM; and (iii) the higher-energy C-band (at 280 nm) is due to the two fused ring system. Thus, this is a two-speciated formed model. Although a relatively simple system, these calculations represent an important step in understanding light absorbing compounds found in nature and the search for other microscopic models of related materials remains of major interest.
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Affiliation(s)
- Natalia V Karimova
- Department of Chemistry, University of California, Irvine, CA 92697, USA.
| | - Michael R Alves
- Department of Chemistry and Biochemistry, University of California, San Diego, CA 92093, USA.
| | - Man Luo
- Department of Chemistry and Biochemistry, University of California, San Diego, CA 92093, USA.
| | - Vicki H Grassian
- Department of Chemistry and Biochemistry, University of California, San Diego, CA 92093, USA. and Department of Nanoengineering and Scripps Institution of Oceanography, University of California, San Diego, CA 92093, USA
| | - R Benny Gerber
- Department of Chemistry, University of California, Irvine, CA 92697, USA. and Institute of Chemistry and Fritz Haber Research Center, Hebrew University of Jerusalem, Jerusalem 91904, Israel
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12
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Pollet R, Chin W. Reversible Hydration of α-Dicarbonyl Compounds from Ab Initio Metadynamics Simulations: Comparison between Pyruvic and Glyoxylic Acids in Aqueous Solutions. J Phys Chem B 2021; 125:2942-2951. [PMID: 33725456 DOI: 10.1021/acs.jpcb.0c09748] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Glyoxylic and pyruvic oxoacids are widely available in the atmosphere as gas-phase clusters and particles or in wet aerosols. In aqueous conditions, they undergo interconversion between the unhydrated oxo and gem-diol forms, where two hydroxyl groups replace the carbonyl group. We here examine the hydration equilibrium of glyoxylic and pyruvic acids with first-principles simulations in water at ambient conditions using ab initio metadynamics to reconstruct the corresponding free-energy landscapes. The main results are as follows: (i) our simulations reveal the high conformational diversity of these species in aqueous solutions. (ii) We show that gem-diol is strongly favored in water compared to its oxo counterpart by 29 and 16 kJ/mol for glyoxylic and pyruvic acids, respectively. (iii) From our atomic-scale simulations, we present new insights into the reaction mechanisms with a special focus on hydrogen-bond arrangements and the electronic structure of the transition state.
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Affiliation(s)
- Rodolphe Pollet
- NIMBE, Université Paris-Saclay, CEA, CNRS, 91191 Gif-sur-Yvette, France
| | - Wutharath Chin
- Institut des Sciences Moléculaires d'Orsay, Université Paris-Saclay, CNRS, 91405 Orsay, France
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13
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Luo M, Wauer NA, Angle KJ, Dommer AC, Song M, Nowak CM, Amaro RE, Grassian VH. Insights into the behavior of nonanoic acid and its conjugate base at the air/water interface through a combined experimental and theoretical approach. Chem Sci 2020; 11:10647-10656. [PMID: 33144932 PMCID: PMC7583472 DOI: 10.1039/d0sc02354j] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Accepted: 06/15/2020] [Indexed: 12/14/2022] Open
Abstract
The partitioning of medium-chain fatty acid surfactants such as nonanoic acid (NA) between the bulk phase and the air/water interface is of interest to a number of fields including marine and atmospheric chemistry. However, questions remain about the behavior of these molecules, the contributions of various relevant chemical equilibria, and the impact of pH, salt and bulk surfactant concentrations. In this study, the surface adsorption of nonanoic acid and its conjugate base is quantitatively investigated at various pH values, surfactant concentrations and the presence of salts. Surface concentrations of protonated and deprotonated species are dictated by surface-bulk equilibria which can be calculated from thermodynamic considerations. Notably we conclude that the surface dissociation constant of soluble surfactants cannot be directly obtained from these experimental measurements, however, we show that molecular dynamics (MD) simulation methods, such as free energy perturbation (FEP), can be used to calculate the surface acid dissociation constant relative to that in the bulk. These simulations show that nonanoic acid is less acidic at the surface compared to in the bulk solution with a pK a shift of 1.1 ± 0.6, yielding a predicted surface pK a of 5.9 ± 0.6. A thermodynamic cycle for nonanoic acid and its conjugate base between the air/water interface and the bulk phase can therefore be established. Furthermore, the effect of salts, namely NaCl, on the surface activity of protonated and deprotonated forms of nonanoic acid is also examined. Interestingly, salts cause both a decrease in the bulk pK a of nonanoic acid and a stabilization of both the protonated and deprotonated forms at the surface. Overall, these results suggest that the deprotonated medium-chain fatty acids under ocean conditions can also be present within the sea surface microlayer (SSML) present at the ocean/atmosphere interface due to the stabilization effect of the salts in the ocean. This allows the transfer of these species into sea spray aerosols (SSAs). More generally, we present a framework with which the behavior of partially soluble species at the air/water interface can be predicted from surface adsorption models and the surface pK a can be predicted from MD simulations.
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Affiliation(s)
- Man Luo
- Department of Chemistry and Biochemistry , University of California , La Jolla , San Diego , CA 92093 , USA . ;
| | - Nicholas A Wauer
- Department of Chemistry and Biochemistry , University of California , La Jolla , San Diego , CA 92093 , USA . ;
| | - Kyle J Angle
- Department of Chemistry and Biochemistry , University of California , La Jolla , San Diego , CA 92093 , USA . ;
| | - Abigail C Dommer
- Department of Chemistry and Biochemistry , University of California , La Jolla , San Diego , CA 92093 , USA . ;
| | - Meishi Song
- Department of Chemistry and Biochemistry , University of California , La Jolla , San Diego , CA 92093 , USA . ;
| | - Christopher M Nowak
- Department of Chemistry and Biochemistry , University of California , La Jolla , San Diego , CA 92093 , USA . ;
| | - Rommie E Amaro
- Department of Chemistry and Biochemistry , University of California , La Jolla , San Diego , CA 92093 , USA . ;
| | - Vicki H Grassian
- Department of Chemistry and Biochemistry , University of California , La Jolla , San Diego , CA 92093 , USA . ;
- Department of Nanoengineering , Scripps Institution of Oceanography , University of California , La Jolla , San Diego , CA 92093 , USA
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Shemesh D, Luo M, Grassian VH, Gerber RB. Absorption spectra of pyruvic acid in water: insights from calculations for small hydrates and comparison to experiment. Phys Chem Chem Phys 2020; 22:12658-12670. [DOI: 10.1039/d0cp01810d] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
This study shows that small hydrate models including the roles of both neutral and deprotonated speciated forms provide a good quantitative description and a microscopic interpretation of the experimental spectrum of pyruvic acid in aqueous solution.
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Affiliation(s)
- Dorit Shemesh
- Institute of Chemistry
- Fritz Haber Research Center
- Hebrew University of Jerusalem
- Jerusalem 91904
- Israel
| | - Man Luo
- Department of Chemistry
- University of California
- San Diego
- USA
| | | | - R. Benny Gerber
- Institute of Chemistry
- Fritz Haber Research Center
- Hebrew University of Jerusalem
- Jerusalem 91904
- Israel
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