P. Merino, L. Martínez, G. Santoro, J. I. Martínez, K. Lauwaet, M. Accolla, N. Ruiz del Arbol, C. Sánchez-Sánchez, A. Martín-Jimenez, R. Otero, M. Piantek, D. Serrate, R. Lebrón-Aguilar, J. E. Quintanilla-López, J. Mendez, P. L. De Andres, J. A. Martín-Gago
{"title":"n-Alkanes formed by methyl-methylene addition as a source of meteoritic aliphatics","authors":"P. Merino, L. Martínez, G. Santoro, J. I. Martínez, K. Lauwaet, M. Accolla, N. Ruiz del Arbol, C. Sánchez-Sánchez, A. Martín-Jimenez, R. Otero, M. Piantek, D. Serrate, R. Lebrón-Aguilar, J. E. Quintanilla-López, J. Mendez, P. L. De Andres, J. A. Martín-Gago","doi":"10.1038/s42004-024-01248-6","DOIUrl":null,"url":null,"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. Extraterrestrial organic matter found in meteorites may hold a unique record of its synthesis, and chemical and thermal alterations in the parent body, however, the origin of such aliphatics remains enigmatic. Here, the authors propose sequential gas-phase methyl-methylene addition growth of n-C8H18 to n-C32H66 alkanes based on a series of sputter gas aggregation source experiments and DFT calculations.","PeriodicalId":10529,"journal":{"name":"Communications Chemistry","volume":null,"pages":null},"PeriodicalIF":5.9000,"publicationDate":"2024-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11289383/pdf/","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Communications Chemistry","FirstCategoryId":"92","ListUrlMain":"https://www.nature.com/articles/s42004-024-01248-6","RegionNum":2,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
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. Extraterrestrial organic matter found in meteorites may hold a unique record of its synthesis, and chemical and thermal alterations in the parent body, however, the origin of such aliphatics remains enigmatic. Here, the authors propose sequential gas-phase methyl-methylene addition growth of n-C8H18 to n-C32H66 alkanes based on a series of sputter gas aggregation source experiments and DFT calculations.
期刊介绍:
Communications Chemistry is an open access journal from Nature Research publishing high-quality research, reviews and commentary in all areas of the chemical sciences. Research papers published by the journal represent significant advances bringing new chemical insight to a specialized area of research. We also aim to provide a community forum for issues of importance to all chemists, regardless of sub-discipline.