{"id":36471,"date":"2024-08-01T11:01:58","date_gmt":"2024-08-01T09:01:58","guid":{"rendered":"https:\/\/karmaka.de\/?p=36471"},"modified":"2024-08-01T11:01:59","modified_gmt":"2024-08-01T09:01:59","slug":"n-alkanes-formed-by-methyl-methylene-addition-as-a-source-of-meteoritic-aliphatics","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=36471","title":{"rendered":"n-Alkanes formed by methyl-methylene addition as a source of meteoritic aliphatics<span class=\"badge-status\" style=\"background:#787878\">OPEN ACCESS<\/span>&nbsp;"},"content":{"rendered":"\n<p>P. Merino, L. Mart\u00ednez, G. Santoro, J. I. Mart\u00ednez, K. Lauwaet, M. Accolla, N. Ruiz del Arbol, C. S\u00e1nchez-S\u00e1nchez, A. Mart\u00edn-Jimenez, R. Otero, M. Piantek, D. Serrate, R. Lebr\u00f3n-Aguilar, J. E. Quintanilla-L\u00f3pez, J. Mendez, P. L. De Andres &amp; J. A. Mart\u00edn-Gago<\/p>\n\n\n\n<p>Communications Chemistry, Volume 7, Article number: 165, Published: 30 July 2024<\/p>\n\n\n\n<p><a href=\"https:\/\/www.nature.com\/articles\/s42004-024-01248-6\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>LINK (OPEN ACCESS)<\/strong><\/a><br><a href=\"https:\/\/www.nature.com\/articles\/s42004-024-01248-6.pdf\" target=\"_blank\" rel=\"noreferrer noopener\"><strong>PDF (OPEN ACCESS)<\/strong><\/a><\/p>\n\n\n\n<p class=\"justify-text\">&#8220;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.&#8221;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>P. Merino, L. Mart\u00ednez, G. Santoro, J. I. Mart\u00ednez, K. Lauwaet, M. Accolla, N. Ruiz del Arbol, C. S\u00e1nchez-S\u00e1nchez, A. Mart\u00edn-Jimenez, R. Otero, M. Piantek, D. Serrate, R. Lebr\u00f3n-Aguilar, J. E. Quintanilla-L\u00f3pez, J. Mendez, P&#8230;.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5001,77,2350,9,576,47],"tags":[3872,4965,4911,3991,3273,716,4608,6701,232,1989,304],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/36471"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=36471"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/36471\/revisions"}],"predecessor-version":[{"id":36472,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/36471\/revisions\/36472"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=36471"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=36471"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=36471"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}