Aromatic units from the macromolecular material in meteorites: Molecular probes of cosmic environments

Sephton, Mark A.

doi:10.1016/j.gca.2012.12.042

Cited by 9 publications

(11 citation statements)

References 46 publications

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“…A process akin to this may have been responsible for the free PAHs found in CMs, as well as differences between CMs and CIs (Sephton et al. ; Sephton ).…”

Section: Discussionmentioning

confidence: 99%

Elemental, isotopic, and structural changes in Tagish Lake insoluble organic matter produced by parent body processes

Alexander

Cody

Kebukawa

et al. 2014

Meteorit & Planetary Scien

109

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Abstract-Here, we present the results of a multitechnique study of the bulk properties of insoluble organic material (IOM) from the Tagish Lake meteorite, including four lithologies that have undergone different degrees of aqueous alteration. The IOM C contents of all four lithologies are very uniform and comprise about half the bulk C and N contents of the lithologies. However, the bulk IOM elemental and isotopic compositions vary significantly. In particular, there is a correlated decrease in bulk IOM H/C ratios and dD values with increasing degree of alteration-the IOM in the least altered lithology is intermediate between CM and CR IOM, while that in the more altered lithologies resembles the very aromatic IOM in mildly metamorphosed CV and CO chondrites, and heated CMs. Nuclear magnetic resonance (NMR) spectroscopy, C X-ray absorption near-edge (XANES), and Fourier transform infrared (FTIR) spectroscopy confirm and quantitate this transformation from CR-like, relatively aliphatic IOM functional group chemistry to a highly aromatic one. The transformation is almost certainly thermally driven, and probably occurred under hydrothermal conditions. The lack of a paramagnetic shift in 13 C NMR spectra and 1s-r* exciton in the C-XANES spectra, both typically seen in metamorphosed chondrites, shows that the temperatures were lower and/or the timescales were shorter than experienced by even the least metamorphosed type 3 chondrites. Two endmember models were considered to quantitatively account for the changes in IOM functional group chemistry, but the one in which the transformations involved quantitative conversion of aliphatic material to aromatic material was the more successful. It seems likely that similar processes were involved in producing the diversity of IOM compositions and functional group chemistries among CR, CM, and CI chondrites. If correct, CRs experienced the lowest temperatures, while CM and CI chondrites experienced similar more elevated temperatures. This ordering is inconsistent with alteration temperatures based on mineralogy and O isotopes.

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“…A process akin to this may have been responsible for the free PAHs found in CMs, as well as differences between CMs and CIs (Sephton et al. ; Sephton ).…”

Section: Discussionmentioning

confidence: 99%

Elemental, isotopic, and structural changes in Tagish Lake insoluble organic matter produced by parent body processes

Alexander

Cody

Kebukawa

et al. 2014

Meteorit & Planetary Scien

109

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“…Pyrolysis‐GC‐MS is commonly used to study macromolecular OM in terrestrial samples like kerogens and coals but also in extraterrestrial samples such as meteorites (Murae ; Komiya and Shimoyama ; Remusat et al. ; Okumura and Mimura ; Sephton ) and tholins (Khare et al. ; McGuigan et al.…”

Section: Resultsmentioning

confidence: 99%

“…Pyrolysis-GC-MS is commonly used to study macromolecular OM in terrestrial samples like kerogens and coals but also in extraterrestrial samples such as meteorites (Murae 1995;Komiya and Shimoyama 1996;Remusat et al 2005a;Okumura and Mimura 2011;Sephton 2013) and tholins (Khare et al 1981;McGuigan et al 2006;Szopa et al 2006). The IOM synthesized in this study was therefore analyzed using Curie point pyrolysis.…”

Section: Pyrolysis-gc-ms Analysis Of the Iommentioning

confidence: 99%

“…; Sephton et al. ; Sephton , ; Remusat et al. , ), along with high‐resolution transmission electron microscopy (Derenne et al.…”

Section: Introductionmentioning

confidence: 99%

“…The analysis of the chemical composition of the meteoritic organic matter has been mainly focused on the Murchison meteorite over the last three decades. The chemical structure of the IOM was recently investigated using a combination of analytical approaches including various spectroscopic methods (Cronin et al 1987;Gardinier et al 2000;Binet et al 2002Binet et al , 2004Cody et al 2002;Cody and Alexander 2005;Orthous-Daunay et al 2010), thermal and chemical degradations followed by gas chromatography coupled with mass spectrometry (GC-MS) (Studier et al 1972;Levy et al 1973;De Vries et al 1993;Sephton et al 1998;Sephton 2004Sephton , 2013Remusat et al 2005aRemusat et al , 2005b, along with high-resolution transmission electron microscopy Le Guillou et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Toward an experimental synthesis of the chondritic insoluble organic matter

Biron

Derenne

Robert

et al. 2015

Meteorit & Planetary Scien

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International audienceBased on the statistical model proposed for the molecular structure of the insoluble organic matter (IOM) isolated from the Murchison meteorite, it was recently proposed that, in the solar T-Tauri disk regions where (photo)dissociation of gaseous molecules takes place, aromatics result from the cyclization/aromatization of short aliphatics. This hypothesis is tested in this study, with n-alkanes being submitted to high-frequency discharge at low pressure. The contamination issue was eliminated using deuterated precursor. IOM was formed and studied using solid-state nuclear magnetic resonance, pyrolysis coupled to gas chromatography and mass spectrometry, RuO4 oxidation, and high-resolution transmission electron microscopy. It exhibits numerous similarities at the molecular level with the hydrocarbon backbone of the natural IOM, reinforcing the idea that the initial precursors of the IOM were originally chains in the gas. Moreover, a fine comparison between the chemical structure of several meteorite IOM suggests either that (i) the meteorite IOMs share a common precursor standing for the synthetic IOM or that (ii) the slight differences between the meteorite IOMs reflect differences in their environment at the time of their formation i.e., related to plasma temperature that, in turn, dictates the dissociation–recombination rates of organic fragments

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One Collision—Two Substituents: Gas‐Phase Preparation of Xylenes under Single‐Collision Conditions

Medvedkov,

Nikolayev,

et al. 2023

Angewandte Chemie

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The fundamental reaction pathways to the simplest dialkylsubstituted aromatics—xylenes (C6H4(CH3)2)—in high‐temperature combustion flames and in low‐temperature extraterrestrial environments are still unknown, but critical to understand the chemistry and molecular mass growth processes in these extreme environments. Exploiting crossed molecular beam experiments augmented by state‐of‐the‐art electronic structure and statistical calculations, this study uncovers a previously elusive, facile gas‐phase synthesis of xylenes through an isomer‐selective reaction of 1‐propynyl (methylethynyl, CH3CC) with 2‐methyl‐1,3‐butadiene (isoprene, C5H8). The reaction dynamics are driven by a barrierless addition of the radical to the diene moiety of 2‐methyl‐1,3‐butadiene followed by extensive isomerization (hydrogen shifts, cyclization) prior to unimolecular decomposition accompanied by aromatization via atomic hydrogen loss. This overall exoergic reaction affords a preparation of xylenes not only in high‐temperature environments such as in combustion flames and around circumstellar envelopes of carbon‐rich Asymptotic Giant Branch (AGB) stars, but also in low‐temperature cold molecular clouds (10 K) and in hydrocarbon‐rich atmospheres of planets and their moons such as Triton and Titan. Our study established a hitherto unknown gas‐phase route to xylenes and potentially more complex, disubstituted benzenes via a single collision event highlighting the significance of an alkyl‐substituted ethynyl‐mediated preparation of aromatic molecules in our Universe.

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Aromatic units from the macromolecular material in meteorites: Molecular probes of cosmic environments

Cited by 9 publications

References 46 publications

Elemental, isotopic, and structural changes in Tagish Lake insoluble organic matter produced by parent body processes

Elemental, isotopic, and structural changes in Tagish Lake insoluble organic matter produced by parent body processes

Toward an experimental synthesis of the chondritic insoluble organic matter

One Collision—Two Substituents: Gas‐Phase Preparation of Xylenes under Single‐Collision Conditions

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