ACS Earth and Space Chemistry最新文献

{"title":"Mechanistic Insights into the Silica-Mediated Synthesis of Glyceraldehyde from Glycolaldehyde and Hydroxymethylene","authors":"Gianluca Rinaldi,&nbsp;Zoi Salta and Nicola Tasinato*,&nbsp;","doi":"10.1021/acsearthspacechem.4c0030210.1021/acsearthspacechem.4c00302","DOIUrl":"https://doi.org/10.1021/acsearthspacechem.4c00302https://doi.org/10.1021/acsearthspacechem.4c00302","url":null,"abstract":"<p >Minerals are crucial ingredients in prebiotic chemistry as they could have promoted the evolution of simple organic molecules toward proto-biomolecules that are on the route of the emergence of self-replicating information-rich macromolecules. In this respect, the formose reaction, involving the sequential autocatalytic condensation of formaldehyde, is the generally accepted pathway for sugar synthesis. Although obtained under controlled laboratory conditions with enhanced sugar yields promoted by the presence of silicate in the reaction medium, it presents a number of limitations, and the underlying reaction mechanism remains an unsolved riddle. In this work, the focus is on the second step of the formose reaction, namely, the synthesis of glyceraldehyde, which is accomplished by considering the reaction between glycolaldehyde and hydroxymethylene taking place on the edingtonite mineral. The reaction mechanism is explored by quantum chemical simulations performed at various degrees of sophistication to shed light on the thermochemical and kinetic feasibility of the reaction. The same pathway is also investigated in the gas phase in order to disentangle the role played by the zeolitic mineral. The obtained results show that the exothermic reaction between glycolaldehyde and hydroxymethylene yields glyceraldehyde by a submerged reaction path, both in the gas phase and on the edingtonite surface. The mineral substrate provides further stabilization, by about 20 kcal mol^–1, of all the species involved in the reaction pathway and acts as a scaffold favoring the interaction of the two reactants.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"9 1","pages":"146–157 146–157"},"PeriodicalIF":2.9,"publicationDate":"2024-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143086087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring the Mechanism of Hydrogen Cyanide Formation on Metal Surfaces in the Interstellar Medium: A Computational Perspective","authors":"Arun Ramamurthy,&nbsp;Yuvaraj Ravi and Gopi Ragupathy*,&nbsp;","doi":"10.1021/acsearthspacechem.4c0023210.1021/acsearthspacechem.4c00232","DOIUrl":"https://doi.org/10.1021/acsearthspacechem.4c00232https://doi.org/10.1021/acsearthspacechem.4c00232","url":null,"abstract":"<p >By utilizing quantum chemical calculations, we inspect four various reaction pathways for the formation of hydrogen cyanide (HCN) on interstellar medium in two interstellar conditions, i.e., gas phase and metal surface, respectively. We found their reactivity and feasibility of a chemical reaction under both conditions. Additionally, we probe how HCN interacts with metal surfaces to determine the thermodynamic parameters and reactive energetic barriers of the chemical reactions in cosmic environments. The alternative pathways created by the metal considerably lowered the reactive potential barriers, resulting in a notable increase in the reaction rate. From this theoretical research, it is revealed that the catalytic potential of metal surfaces in ISM significantly enhances the feasibility of chemical reactions and becomes the most favorable route for the formation of HCN.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"9 1","pages":"106–118 106–118"},"PeriodicalIF":2.9,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143084798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Measuring the Stable Isotope Composition of Water in Brine from Halite Fluid Inclusions and Borehole Brine Seeps Using Cavity Ring-Down Spectroscopy","authors":"Daniel L. Eldridge*,&nbsp;Melissa M. Mills,&nbsp;Hayden B. D. Miller,&nbsp;Shawn Otto,&nbsp;Jon E. Davis,&nbsp;Eric J. Guiltinan,&nbsp;Thom Rahn,&nbsp;Kristopher L. Kuhlman and Philip H. Stauffer,&nbsp;","doi":"10.1021/acsearthspacechem.4c0010710.1021/acsearthspacechem.4c00107","DOIUrl":"https://doi.org/10.1021/acsearthspacechem.4c00107https://doi.org/10.1021/acsearthspacechem.4c00107","url":null,"abstract":"<p >Naturally occurring bedded salt deposits are considered robust for the permanent disposal of heat-generating nuclear waste due to their unique physical and geological properties. The Brine Availability Test in Salt (BATS) is a US-DOE Office of Nuclear Energy funded project that uses heated borehole experiments underground (∼655 meters depth) at the Waste Isolation Pilot Plant (WIPP) in the bedded salt deposits of the Salado Formation to investigate the capacity for safe disposal of high-level, heat generating nuclear waste in salt. Uncertainties associated with brine mobility near heat-generating waste motivates the need to characterize the processes and sources of brine in salt deposits. Intragranular halite fluid inclusions are a potential source of brine that can migrate under temperature gradients toward heat sources. We developed a methodology to measure the stable isotopic compositions of water (δ<i>D</i>_VSMOW, δ¹⁸<i>O</i>_VSMOW) in brine from halite fluid inclusions using Cavity Ring-Down Spectroscopy that accounts for memory effects using a unique reference-sample-reference bracketing approach and that minimizes sample size requirements. We applied this approach to halite samples obtained from WIPP and compare these data to seeped brines collected from horizontal boreholes at WIPP after drilling at ambient conditions. The stable isotope compositions that we obtain for halite fluid inclusions (δ¹⁸<i>O</i>_VSMOW = +3.24 ± 0.53‰, δ<i>D</i>_VSMOW = −25.3 ± 5.1‰, ±1σ, <i>n</i> = 5) generally agree with previous measurements and likely reflect a combination of syn-depositional and/or postdepositional processes. The seep brines are isotopically distinct (δ¹⁸<i>O</i>_VSMOW = +3.46 ± 0.84‰, δ<i>D</i>_VSMOW = +7.3 ± 3.5‰, ±1σ, <i>n</i> = 35) and instead resemble evaporated seawater. We discuss our results in the context of prior WIPP-proximal waters and lay the groundwork for using stable isotopes of water in brine as a tool to assess the heat-induced mobilization of halite fluid inclusions in ongoing heating experiments that comprise the Brine Availability Test in Salt.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"9 1","pages":"16–30 16–30"},"PeriodicalIF":2.9,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143084766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Measuring the Stable Isotope Composition of Water in Brine from Halite Fluid Inclusions and Borehole Brine Seeps Using Cavity Ring-Down Spectroscopy.","authors":"Daniel L Eldridge, Melissa M Mills, Hayden B D Miller, Shawn Otto, Jon E Davis, Eric J Guiltinan, Thom Rahn, Kristopher L Kuhlman, Philip H Stauffer","doi":"10.1021/acsearthspacechem.4c00107","DOIUrl":"10.1021/acsearthspacechem.4c00107","url":null,"abstract":"<p><p>Naturally occurring bedded salt deposits are considered robust for the permanent disposal of heat-generating nuclear waste due to their unique physical and geological properties. The Brine Availability Test in Salt (BATS) is a US-DOE Office of Nuclear Energy funded project that uses heated borehole experiments underground (∼655 meters depth) at the Waste Isolation Pilot Plant (WIPP) in the bedded salt deposits of the Salado Formation to investigate the capacity for safe disposal of high-level, heat generating nuclear waste in salt. Uncertainties associated with brine mobility near heat-generating waste motivates the need to characterize the processes and sources of brine in salt deposits. Intragranular halite fluid inclusions are a potential source of brine that can migrate under temperature gradients toward heat sources. We developed a methodology to measure the stable isotopic compositions of water (δ<i>D</i> _VSMOW, δ¹⁸ <i>O</i> _VSMOW) in brine from halite fluid inclusions using Cavity Ring-Down Spectroscopy that accounts for memory effects using a unique reference-sample-reference bracketing approach and that minimizes sample size requirements. We applied this approach to halite samples obtained from WIPP and compare these data to seeped brines collected from horizontal boreholes at WIPP after drilling at ambient conditions. The stable isotope compositions that we obtain for halite fluid inclusions (δ¹⁸ <i>O</i> _VSMOW = +3.24 ± 0.53‰, δ<i>D</i> _VSMOW = -25.3 ± 5.1‰, ±1σ, <i>n</i> = 5) generally agree with previous measurements and likely reflect a combination of syn-depositional and/or postdepositional processes. The seep brines are isotopically distinct (δ¹⁸ <i>O</i> _VSMOW = +3.46 ± 0.84‰, δ<i>D</i> _VSMOW = +7.3 ± 3.5‰, ±1σ, <i>n</i> = 35) and instead resemble evaporated seawater. We discuss our results in the context of prior WIPP-proximal waters and lay the groundwork for using stable isotopes of water in brine as a tool to assess the heat-induced mobilization of halite fluid inclusions in ongoing heating experiments that comprise the Brine Availability Test in Salt.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"9 1","pages":"16-30"},"PeriodicalIF":2.9,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11745166/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vibrational and Electronic Spectroscopy of 2-Cyanoindene Cations","authors":"Thomas E. Douglas-Walker,&nbsp;Eleanor K. Ashworth,&nbsp;Mark H. Stockett,&nbsp;Francis C. Daly,&nbsp;Isabelle Chambrier,&nbsp;Vincent J. Esposito,&nbsp;Marius Gerlach,&nbsp;Angel Zheng,&nbsp;Julianna Palotás,&nbsp;Andrew N. Cammidge,&nbsp;Ewen K. Campbell,&nbsp;Sandra Brünken and James N. Bull*,&nbsp;","doi":"10.1021/acsearthspacechem.4c0027010.1021/acsearthspacechem.4c00270","DOIUrl":"https://doi.org/10.1021/acsearthspacechem.4c00270https://doi.org/10.1021/acsearthspacechem.4c00270","url":null,"abstract":"<p >2-Cyanoindene is one of the few specific aromatic or polycyclic aromatic hydrocarbon (PAH) molecules positively identified in Taurus molecular cloud-1 (TMC-1), a cold, dense molecular cloud that is considered the nearest star-forming region to Earth. We report cryogenic mid-infrared (550–3200 cm^–1) and visible (16,500–20,000 cm^–1, over the <i>D</i>₂ ← <i>D</i>₀ electronic transition) spectra of 2-cyanoindene radical cations (2CNI⁺), measured using messenger tagging (He and Ne) photodissociation spectroscopy. The infrared spectra reveal the prominence of anharmonic couplings, particularly over the fingerprint region. There is a strong CN-stretching mode at 2177 ± 1 cm^–1 (4.593 μm), which may contribute to a broad plateau of CN-stretching modes across astronomical aromatic infrared band spectra. However, the activity of this mode is suppressed in the dehydrogenated (closed shell) cation, [2CNI-H]⁺. The IR spectral frequencies are modeled by anharmonic calculations at the B3LYP/N07D level of theory that include resonance polyad matrices, demonstrating that the CN-stretch mode remains challenging to describe with theory. The <i>D</i>₂ ← <i>D</i>₀ electronic transition of 2CNI⁺, which is origin dominated, occurs at 16,549 ± 5 cm^–1 in vacuum (6041.8 Å in air). There are no correspondences with reported diffuse interstellar bands.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"9 1","pages":"134–145 134–145"},"PeriodicalIF":2.9,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acsearthspacechem.4c00270","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143084609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vibrational and Electronic Spectroscopy of 2-Cyanoindene Cations.","authors":"Thomas E Douglas-Walker, Eleanor K Ashworth, Mark H Stockett, Francis C Daly, Isabelle Chambrier, Vincent J Esposito, Marius Gerlach, Angel Zheng, Julianna Palotás, Andrew N Cammidge, Ewen K Campbell, Sandra Brünken, James N Bull","doi":"10.1021/acsearthspacechem.4c00270","DOIUrl":"10.1021/acsearthspacechem.4c00270","url":null,"abstract":"<p><p>2-Cyanoindene is one of the few specific aromatic or polycyclic aromatic hydrocarbon (PAH) molecules positively identified in Taurus molecular cloud-1 (TMC-1), a cold, dense molecular cloud that is considered the nearest star-forming region to Earth. We report cryogenic mid-infrared (550-3200 cm^-1) and visible (16,500-20,000 cm^-1, over the <i>D</i> ₂ ← <i>D</i> ₀ electronic transition) spectra of 2-cyanoindene radical cations (2CNI⁺), measured using messenger tagging (He and Ne) photodissociation spectroscopy. The infrared spectra reveal the prominence of anharmonic couplings, particularly over the fingerprint region. There is a strong CN-stretching mode at 2177 ± 1 cm^-1 (4.593 μm), which may contribute to a broad plateau of CN-stretching modes across astronomical aromatic infrared band spectra. However, the activity of this mode is suppressed in the dehydrogenated (closed shell) cation, [2CNI-H]⁺. The IR spectral frequencies are modeled by anharmonic calculations at the B3LYP/N07D level of theory that include resonance polyad matrices, demonstrating that the CN-stretch mode remains challenging to describe with theory. The <i>D</i> ₂ ← <i>D</i> ₀ electronic transition of 2CNI⁺, which is origin dominated, occurs at 16,549 ± 5 cm^-1 in vacuum (6041.8 Å in air). There are no correspondences with reported diffuse interstellar bands.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"9 1","pages":"134-145"},"PeriodicalIF":2.9,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11744931/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142996045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetics and Oligomer Products of the Multiphase Reactions of Hydroxyacetone with Atmospheric Amines, Ammonium Sulfate, and Cloud Processing","authors":"David O. De Haan*,&nbsp;Lelia Nahid Hawkins,&nbsp;Elyse A. Pennington,&nbsp;Hannah G. Welsh,&nbsp;Alyssa A. Rodriguez,&nbsp;Michael A. Symons,&nbsp;Alyssa D. Andretta,&nbsp;Michael A. Rafla,&nbsp;Chen Le,&nbsp;Audrey C. De Haan,&nbsp;Tianqu Cui,&nbsp;Jason D. Surratt,&nbsp;Mathieu Cazaunau,&nbsp;Edouard Pangui and Jean-François Doussin,&nbsp;","doi":"10.1021/acsearthspacechem.4c0023710.1021/acsearthspacechem.4c00237","DOIUrl":"https://doi.org/10.1021/acsearthspacechem.4c00237https://doi.org/10.1021/acsearthspacechem.4c00237","url":null,"abstract":"<p >Hydroxyacetone (HA) is an atmospheric oxidation product of isoprene and other organic precursors that can form brown carbon (BrC). Measured bulk aqueous-phase reaction rates of HA with ammonium sulfate, methylamine, and glycine suggest that these reactions cannot compete with aqueous-phase hydroxyl radical oxidation. In cloud chamber photooxidation experiments with either gaseous or particulate HA in the presence of the same N-containing species, BrC formation was minor, with similar mass absorption coefficients at 365 nm (&lt;0.05 m² g^–1). However, rapid changes observed in aerosol volume and gas-phase species concentrations suggest that the lack of BrC was not due to slow reactivity. Filter-based UHPLC/(+)ESI-HR-QTOFMS analysis revealed that the SOA became heavily oligomerized, with average molecular masses of ∼400 amu in all cases. Oligomers contained, on average, 3.9 HA, 1.5 ammonia, and 1.6 other small aldehydes, including, in descending order of abundance, acetaldehyde, glycolaldehyde, glyoxal, and methylglyoxal. PTR-ToF-MS confirmed the production of these aldehydes. We identify C₁₇H₂₆O₅, C₁₀H₂₂O₉, C₁₅H₂₇NO₇, C₁₇H₂₃NO₅, and C₁₈H₃₂N₂O₉ as potential tracer ions for HA oligomers. We hypothesize that efficient oligomerization without substantial BrC production is due to negligible N-heterocycle (e.g., imidazoles/pyrazines) formation. While HA photooxidation is unlikely a significant atmospheric BrC source, it may contribute significantly to aqueous SOA formation.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"8 12","pages":"2574–2586 2574–2586"},"PeriodicalIF":2.9,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acsearthspacechem.4c00237","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142842045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kinetics and Oligomer Products of the Multiphase Reactions of Hydroxyacetone with Atmospheric Amines, Ammonium Sulfate, and Cloud Processing.","authors":"David O De Haan, Lelia Nahid Hawkins, Elyse A Pennington, Hannah G Welsh, Alyssa A Rodriguez, Michael A Symons, Alyssa D Andretta, Michael A Rafla, Chen Le, Audrey C De Haan, Tianqu Cui, Jason D Surratt, Mathieu Cazaunau, Edouard Pangui, Jean-François Doussin","doi":"10.1021/acsearthspacechem.4c00237","DOIUrl":"10.1021/acsearthspacechem.4c00237","url":null,"abstract":"<p><p>Hydroxyacetone (HA) is an atmospheric oxidation product of isoprene and other organic precursors that can form brown carbon (BrC). Measured bulk aqueous-phase reaction rates of HA with ammonium sulfate, methylamine, and glycine suggest that these reactions cannot compete with aqueous-phase hydroxyl radical oxidation. In cloud chamber photooxidation experiments with either gaseous or particulate HA in the presence of the same N-containing species, BrC formation was minor, with similar mass absorption coefficients at 365 nm (<0.05 m² g^-1). However, rapid changes observed in aerosol volume and gas-phase species concentrations suggest that the lack of BrC was not due to slow reactivity. Filter-based UHPLC/(+)ESI-HR-QTOFMS analysis revealed that the SOA became heavily oligomerized, with average molecular masses of ∼400 amu in all cases. Oligomers contained, on average, 3.9 HA, 1.5 ammonia, and 1.6 other small aldehydes, including, in descending order of abundance, acetaldehyde, glycolaldehyde, glyoxal, and methylglyoxal. PTR-ToF-MS confirmed the production of these aldehydes. We identify C₁₇H₂₆O₅, C₁₀H₂₂O₉, C₁₅H₂₇NO₇, C₁₇H₂₃NO₅, and C₁₈H₃₂N₂O₉ as potential tracer ions for HA oligomers. We hypothesize that efficient oligomerization without substantial BrC production is due to negligible N-heterocycle (e.g., imidazoles/pyrazines) formation. While HA photooxidation is unlikely a significant atmospheric BrC source, it may contribute significantly to aqueous SOA formation.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"8 12","pages":"2574-2586"},"PeriodicalIF":2.9,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11664653/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laboratory Studies on the Influence of Hydrogen on Titan-like Photochemistry.","authors":"Melissa S Ugelow, Scott T Wieman, Madeline C R Schwarz, Victoria Da Poian, Jennifer C Stern, Melissa G Trainer","doi":"10.1021/acsearthspacechem.4c00102","DOIUrl":"10.1021/acsearthspacechem.4c00102","url":null,"abstract":"<p><p>Laboratory investigations of photochemical reactions in simulated Titan-like atmospheric systems provide insight into the formation of gas and aerosol products and the influence of different environmental parameters on the types of organic molecules generated. Studying the gas-phase products as a function of reaction time provides further insight into the reaction pathways that lead to organic production. The stable isotopes in the reactants and products serve as tracers and help to disentangle these reaction pathways. We report a time study on the chemical composition and relative abundance of the evolved gas-phase products formed by far-ultraviolet reactions between 5% CH₄ and N₂ in a closed system. Two experimental setups are used, where one fully removes hydrogen from the experimental system using a palladium membrane (hydrogen-poor experiments) and the other does not remove hydrogen during the experiment (hydrogen-rich experiments). Carbon isotope values (δ¹³C) of CH₄, C₂H₆, and C₃H₈ are also reported and are used, along with the gas-phase composition and relative abundance measurements, to constrain the chemical reactions occurring during our experiments. The gas-phase products C₂H₆, C₃H₈, <i>n</i>-C₄H₁₀, iso-C₄H₁₀, <i>n</i>-C₅H₁₂, iso-C₅H₁₂, C₂H₂, C₂H₄, HCN, and CH₃CN were detected, with some variations between both sets of experiments. The hydrogen-poor experiments highlight the importance of hydrogen in the formation of HCN, <i>n</i>-C₅H₁₂, iso-C₅H₁₂, and CH₃CN. By monitoring the chemical composition and the carbon isotopic ratios of the gas phase during CH₄/N₂ photochemistry, especially under a hydrogen-poor and hydrogen-rich environment, the photochemical reaction pathways and the influence of hydrogen on these pathways in a Titan-like atmosphere can be better understood.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"8 12","pages":"2362-2371"},"PeriodicalIF":2.9,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11664652/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laboratory Studies on the Influence of Hydrogen on Titan-like Photochemistry","authors":"Melissa S. Ugelow*,&nbsp;Scott T. Wieman,&nbsp;Madeline C. R. Schwarz,&nbsp;Victoria Da Poian,&nbsp;Jennifer C. Stern and Melissa G. Trainer,&nbsp;","doi":"10.1021/acsearthspacechem.4c0010210.1021/acsearthspacechem.4c00102","DOIUrl":"https://doi.org/10.1021/acsearthspacechem.4c00102https://doi.org/10.1021/acsearthspacechem.4c00102","url":null,"abstract":"<p >Laboratory investigations of photochemical reactions in simulated Titan-like atmospheric systems provide insight into the formation of gas and aerosol products and the influence of different environmental parameters on the types of organic molecules generated. Studying the gas-phase products as a function of reaction time provides further insight into the reaction pathways that lead to organic production. The stable isotopes in the reactants and products serve as tracers and help to disentangle these reaction pathways. We report a time study on the chemical composition and relative abundance of the evolved gas-phase products formed by far-ultraviolet reactions between 5% CH₄ and N₂ in a closed system. Two experimental setups are used, where one fully removes hydrogen from the experimental system using a palladium membrane (hydrogen-poor experiments) and the other does not remove hydrogen during the experiment (hydrogen-rich experiments). Carbon isotope values (δ¹³C) of CH₄, C₂H₆, and C₃H₈ are also reported and are used, along with the gas-phase composition and relative abundance measurements, to constrain the chemical reactions occurring during our experiments. The gas-phase products C₂H₆, C₃H₈, <i>n</i>-C₄H₁₀, iso-C₄H₁₀, <i>n</i>-C₅H₁₂, iso-C₅H₁₂, C₂H₂, C₂H₄, HCN, and CH₃CN were detected, with some variations between both sets of experiments. The hydrogen-poor experiments highlight the importance of hydrogen in the formation of HCN, <i>n</i>-C₅H₁₂, iso-C₅H₁₂, and CH₃CN. By monitoring the chemical composition and the carbon isotopic ratios of the gas phase during CH₄/N₂ photochemistry, especially under a hydrogen-poor and hydrogen-rich environment, the photochemical reaction pathways and the influence of hydrogen on these pathways in a Titan-like atmosphere can be better understood.</p>","PeriodicalId":15,"journal":{"name":"ACS Earth and Space Chemistry","volume":"8 12","pages":"2362–2371 2362–2371"},"PeriodicalIF":2.9,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.acs.org/doi/epdf/10.1021/acsearthspacechem.4c00102","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142842260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}