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Merino P, Martínez L, Santoro G, Martínez JI, Lauwaet K, Accolla M, Ruiz Del Arbol N, Sánchez-Sánchez C, Martín-Jimenez A, Otero R, Piantek M, Serrate D, Lebrón-Aguilar R, Quintanilla-López JE, Mendez J, De Andres PL, Martín-Gago JA. n-Alkanes formed by methyl-methylene addition as a source of meteoritic aliphatics. Commun Chem 2024; 7:165. [PMID: 39080475 PMCID: PMC11289383 DOI: 10.1038/s42004-024-01248-6] [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: 12/19/2023] [Accepted: 07/18/2024] [Indexed: 08/02/2024] Open
Abstract
Aliphatics prevail in asteroids, comets, meteorites and other bodies in our solar system. They are also found in the interstellar and circumstellar media both in gas-phase and in dust grains. Among aliphatics, linear alkanes (n-CnH2n+2) are known to survive in carbonaceous chondrites in hundreds to thousands of parts per billion, encompassing sequences from CH4 to n-C31H64. Despite being systematically detected, the mechanism responsible for their formation in meteorites has yet to be identified. Based on advanced laboratory astrochemistry simulations, we propose a gas-phase synthesis mechanism for n-alkanes starting from carbon and hydrogen under conditions of temperature and pressure that mimic those found in carbon-rich circumstellar envelopes. We characterize the analogs generated in a customized sputter gas aggregation source using a combination of atomically precise scanning tunneling microscopy, non-contact atomic force microscopy and ex-situ gas chromatography-mass spectrometry. Within the formed carbon nanostructures, we identify the presence of n-alkanes with sizes ranging from n-C8H18 to n-C32H66. Ab-initio calculations of formation free energies, kinetic barriers, and kinetic chemical network modelling lead us to propose a gas-phase growth mechanism for the formation of large n-alkanes based on methyl-methylene addition (MMA). In this process, methylene serves as both a reagent and a catalyst for carbon chain growth. Our study provides evidence of an aliphatic gas-phase synthesis mechanism around evolved stars and provides a potential explanation for its presence in interstellar dust and meteorites.
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Affiliation(s)
- P Merino
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain.
| | - L Martínez
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - G Santoro
- Instituto de Estructura de la Materia (IEM), CSIC, Serrano 121, 28006, Madrid, Spain
| | - J I Martínez
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - K Lauwaet
- Instituto Madrileño de Estudios Avanzados IMDEA Nanociencia, Madrid, Spain
| | - M Accolla
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
- INAF-Osservatorio Astrofisico di Catania, Via Santa Sofia 78, 95123, Catania, Italy
| | - N Ruiz Del Arbol
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - C Sánchez-Sánchez
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - A Martín-Jimenez
- Instituto Madrileño de Estudios Avanzados IMDEA Nanociencia, Madrid, Spain
| | - R Otero
- Instituto Madrileño de Estudios Avanzados IMDEA Nanociencia, Madrid, Spain
- Dep. De Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049, Madrid, Spain
- IFIMAC, Universidad Autónoma de Madrid, 28049, Madrid, Spain
| | - M Piantek
- Laboratorio de Microscopias Avanzadas, Universidad de Zaragoza, 50018, Zaragoza, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50018, Zaragoza, Spain
| | - D Serrate
- Laboratorio de Microscopias Avanzadas, Universidad de Zaragoza, 50018, Zaragoza, Spain
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50018, Zaragoza, Spain
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-UNIZAR, 50009, Zaragoza, Spain
| | - R Lebrón-Aguilar
- Instituto de Química-Física "Blas Cabrera" (IQF), CSIC, Serrano, 119, 28006, Madrid, Spain
| | - J E Quintanilla-López
- Instituto de Química-Física "Blas Cabrera" (IQF), CSIC, Serrano, 119, 28006, Madrid, Spain
| | - J Mendez
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - P L De Andres
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
| | - J A Martín-Gago
- Instituto de Ciencia de Materiales de Madrid (ICMM), CSIC, Sor Juana Inés de la Cruz 3, 28049, Madrid, Spain
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Job N, Chandrasekaran V, Thimmakondu VS, Thirumoorthy K. Theoretical Studies on the Isomerization Kinetics of Low-Lying Isomers of the SiC 4H 2 System. J Phys Chem A 2024; 128:73-80. [PMID: 38116994 PMCID: PMC10979431 DOI: 10.1021/acs.jpca.3c05658] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 12/08/2023] [Accepted: 12/08/2023] [Indexed: 12/21/2023]
Abstract
The low-lying isomers of SiC4H2 are investigated to understand the kinetics of isomerization pathways using density functional theory. In our earlier work, we studied the various possible isomers (J. Phys. Chem. A, 2020, 124, 987-1002) and the chemical bonding of low-lying isomers of SiC4H2 (J. Phys. Chem. A, 2022, 126, 9366-9374). Among them, four isomers, 1-ethynyl-3-silacycloprop-1-en-3-ylidene (1), 3-silapent-1,4-diyn-3-ylidene (2), 1-silapent-1,2,3,4-tetraen-1-ylidene (4), and 1-silapent-2,4-diyn-1-ylidene (5) have already been identified in the laboratory. The previously known theoretical isomer 2-methylene-1-silabicyclo[1.1.0]but-1(3)-en-4-ylidene (3) and the newly identified unknown isomer through the present kinetic studies 5-silabicyclo[2.1.0]pent-1(4),2-dien-5-ylidene (N6) remain elusive in the laboratory to date. The isomerization pathways of the low-lying isomers of SiC4H2 are predicted through the transition state structures. Intrinsic reaction coordinate analysis identifies the minimum energy reaction pathways connecting the transition state from one isomer to another of the investigated system. The present kinetic data reveal the isomerization of global minimum energy isomer 1 to thermodynamically stable low-lying isomers, 2 and 5. Interestingly, isomer 3 interconverts to the experimentally known low-energy isomer 4, the second most thermodynamically stable isomer among them. The thermodynamic and kinetic parameters of the low-lying isomers of SiC4H2 are also documented in this work. The rate coefficient and equilibrium constant for isomerization reactions are calculated using the Rice-Ramsperger-Kassel-Marcus theory. The equilibrium constant delineates the difficulties in forming N6 and 3 through the isomerization pathways. Furthermore, ab initio molecular dynamics studies dictate the stability of low-lying isomers of SiC4H2 within the time scale of the simulation.
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Affiliation(s)
- Nisha Job
- Department
of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore, Tamil Nadu 632 014, India
| | - Vijayanand Chandrasekaran
- Department
of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore, Tamil Nadu 632 014, India
| | - Venkatesan S. Thimmakondu
- Department
of Chemistry and Biochemistry, San Diego
State University, San Diego, California 92182-1030, United States
| | - Krishnan Thirumoorthy
- Department
of Chemistry, School of Advanced Sciences, Vellore Institute of Technology, Vellore, Tamil Nadu 632 014, India
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Bérard R, Makasheva K, Demyk K, Simon A, Reyes DN, Mastrorocco F, Sabbah H, Joblin C. Impact of metals on (star)dust chemistry: a laboratory astrophysics approach. FRONTIERS IN ASTRONOMY AND SPACE SCIENCES 2021; 8:654879. [PMID: 33850840 PMCID: PMC7610582 DOI: 10.3389/fspas.2021.654879] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Laboratory experiments are essential in exploring the mechanisms involved in stardust formation. One key question is how a metal is incorporated into dust for an environment rich in elements involved in stardust formation (C, H, O, Si). To address experimentally this question we have used a radiofrequency cold plasma reactor in which cyclic organosilicon dust formation is observed. Metallic (silver) atoms were injected in the plasma during the dust nucleation phase to study their incorporation in the dust. The experiments show formation of silver nanoparticles (~15 nm) under conditions in which organosilicon dust of size 200 nm or less is grown. The presence of AgSiO bonds, revealed by infrared spectroscopy, suggests the presence of junctions between the metallic nanoparticles and the organosilicon dust. Even after annealing we could not conclude on the formation of silver silicates, emphasizing that most of silver is included in the metallic nanoparticles. The molecular analysis performed by laser mass spectrometry exhibits a complex chemistry leading to a variety of molecules including large hydrocarbons and organometallic species. In order to gain insights into the involved chemical molecular pathways, the reactivity of silver atoms/ions with acetylene was studied in a laser vaporization source. Key organometallic species, Ag n C2H m (n=1-3; m=0-2), were identified and their structures and energetic data computed using density functional theory. This allows us to propose that molecular Ag-C seeds promote the formation of Ag clusters but also catalyze hydrocarbon growth. Throughout the article, we show how the developed methodology can be used to characterize the incorporation of metal atoms both in the molecular and dust phases. The presence of silver species in the plasma was motivated by objectives finding their application in other research fields than astrochemistry. Still, the reported methodology is a demonstration laying down the ground for future studies on metals of astrophysical interest such as iron.
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Affiliation(s)
- Rémi Bérard
- IRAP, Université de Toulouse, CNRS, UPS, CNES, TOULOUSE, France
- LAPLACE, Université de Toulouse, CNRS, UPS, INPT, TOULOUSE, France
| | | | - Karine Demyk
- IRAP, Université de Toulouse, CNRS, UPS, CNES, TOULOUSE, France
| | - Aude Simon
- LCPQ-IRSAMC, Université de Toulouse, UPS, CNRS, TOULOUSE, France
| | | | | | - Hassan Sabbah
- IRAP, Université de Toulouse, CNRS, UPS, CNES, TOULOUSE, France
- LCAR-IRSAMC, Université de Toulouse, UPS, CNRS, TOULOUSE, France
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