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Medvedkov IA, Nikolayev AA, Yang Z, Goettl SJ, Mebel AM, Kaiser RI. Elucidating the chemical dynamics of the elementary reactions of the 1-propynyl radical (CH 3CC; X 2A 1) with 2-methylpropene ((CH 3) 2CCH 2; X 1A 1). Phys Chem Chem Phys 2024; 26:6448-6457. [PMID: 38319693 DOI: 10.1039/d3cp05872g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Exploiting the crossed molecular beam technique, we studied the reaction of the 1-propynyl radical (CH3CC; X2A1) with 2-methylpropene (isobutylene; (CH3)2CCH2; X1A1) at a collision energy of 38 ± 3 kJ mol-1. The experimental results along with ab initio and statistical calculations revealed that the reaction has no entrance barrier and proceeds via indirect scattering dynamics involving C7H11 intermediates with lifetimes longer than their rotation period(s). The reaction is initiated by the addition of the 1-propynyl radical with its radical center to the π-electron density at the C1 and/or C2 position in 2-methylpropene. Further, the C7H11 intermediate formed from the C1 addition either emits atomic hydrogen or undergoes isomerization via [1,2-H] shift from the CH3 or CH2 group prior to atomic hydrogen loss preferentially leading to 1,2,4-trimethylvinylacetylene (2-methylhex-2-en-4-yne) as the dominant product. The molecular structures of the collisional complexes promote hydrogen atom loss channels. RRKM results show that hydrogen elimination channels dominate in this reaction, with a branching ratio exceeding 70%. Since the reaction of the 1-propynyl radical with 2-methylpropene has no entrance barrier, is exoergic, and all transition states involved are located below the energy of the separated reactants, bimolecular collisions are feasible to form trimethylsubstituted 1,3-enyne (p1) via a single collision event even at temperatures as low as 10 K prevailing in cold molecular clouds such as G+0.693. The formation of trimethylsubstituted vinylacetylene could serve as the starting point of fundamental molecular mass growth processes leading to di- and trimethylsubstituted naphthalenes via the HAVA mechanism.
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Affiliation(s)
- Iakov A Medvedkov
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, HI 96822, USA.
| | | | - Zhenghai Yang
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, HI 96822, USA.
| | - Shane J Goettl
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, HI 96822, USA.
| | - Alexander M Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, USA.
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, HI 96822, USA.
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2
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He C, Yang Z, Doddipatla S, Thomas AM, Kaiser RI, Galimova GR, Mebel AM, Fujioka K, Sun R. Directed gas phase preparation of ethynylallene (H 2CCCHCCH; X 1A′) via the crossed molecular beam reaction of the methylidyne radical (CH; X 2Π) with vinylacetylene (H 2CCHCCH; X 1A′). Phys Chem Chem Phys 2022; 24:26499-26510. [DOI: 10.1039/d2cp04081f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The elementary reaction of the methylidyne radical with vinylacetylene leading to the predominant formation of ethynylallene and atomic hydrogen via indirect scattering dynamics.
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Affiliation(s)
- Chao He
- Department of Chemistry, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
| | - Zhenghai Yang
- Department of Chemistry, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
| | - Srinivas Doddipatla
- Department of Chemistry, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
| | - Aaron M. Thomas
- Department of Chemistry, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
| | - Ralf I. Kaiser
- Department of Chemistry, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
| | - Galiya R. Galimova
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, USA
| | - Alexander M. Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, USA
| | - Kazuumi Fujioka
- Department of Chemistry, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
| | - Rui Sun
- Department of Chemistry, University of Hawai‘i at Mānoa, Honolulu, HI 96822, USA
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3
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Levey ZD, Laws BA, Sundar SP, Nauta K, Kable SH, da Silva G, Stanton JF, Schmidt TW. PAH Growth in Flames and Space: Formation of the Phenalenyl Radical. J Phys Chem A 2021; 126:101-108. [PMID: 34936357 DOI: 10.1021/acs.jpca.1c08310] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are intermediates in the formation of soot particles and interstellar grains. However, their formation mechanisms in combustion and interstellar environments are not fully understood. The production of tricyclic PAHs and, in particular, the conversion of a PAH containing a five-membered ring to one with a six-membered ring are of interest to explain PAH abundances in combustion processes. In the present work, resonant ionization mass spectrometry in conjunction with isotopic labeling is used to investigate the formation of the phenalenyl radical from acenaphthylene and methane in an electrical discharge. We show that in this environment the CH cycloaddition mechanism converts a five-membered ring to a six-membered ring. This mechanism can occur in tandem with other PAH formation mechanisms such as hydrogen abstraction/acetylene addition (HACA) to produce larger PAHs in flames and the interstellar medium.
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Affiliation(s)
- Zachariah D Levey
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Benjamin A Laws
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Srivathsan P Sundar
- Department of Chemical Engineering, The University of Melbourne, Parkville 3010, Australia
| | - Klaas Nauta
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Scott H Kable
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Gabriel da Silva
- Department of Chemical Engineering, The University of Melbourne, Parkville 3010, Australia
| | - John F Stanton
- Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
| | - Timothy W Schmidt
- Centre of Excellence in Exciton Science, University of New South Wales, Sydney, NSW 2052, Australia
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Role of the Interchangeable Cations on the Sorption of Fumaric and Succinic Acids on Montmorillonite and its Relevance in Prebiotic Chemistry. ORIGINS LIFE EVOL B 2021; 51:87-116. [PMID: 34251577 DOI: 10.1007/s11084-021-09609-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 04/21/2021] [Indexed: 10/20/2022]
Abstract
It has been proposed that clays could have served as key factors in promoting the increase in complexity of organic matter in primitive terrestrial and extraterrestrial environments. The aim of this work is to study the adsorption-desorption of two dicarboxylic acids, fumaric and succinic acids, onto clay minerals (sodium and iron montmorillonite). These two acids may have played a role in prebiotic chemistry, and in extant biochemistry, they constitute an important redox couple (e.g. in Krebs cycle) in extant biochemistry. Smectite clays might have played a key role in the origins of life. The effect of pH on sorption has been tested; the analysis was performed by UV-vis and FTIR-ATR spectroscopy, X-ray diffraction and X-ray fluorescence. The results show that chemisorption is the main responsible of the adsorption processes among the dicarboxylic acids and clays. The role of the ion, present in the clay, is fundamental in the adsorption processes of dicarboxylic acids. These ions (sodium and iron) were selected due to their relevance on the geochemical environments that possibly existed into the primitive Earth. Different mechanisms are proposed to explain the sorption of dicarboxylic acids in the clay. In this work, we propose the formation of complexes among metal cations in the clays and dicarboxylic acids. The organic complexes were probably formed in the prebiotic environments enabling chemical processes, prior to the appearance of life. Thus, the data presented here are relevant to the origin of life studies.
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5
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He C, Zhao L, Thomas AM, Galimova GR, Mebel AM, Kaiser RI. A combined experimental and computational study on the reaction dynamics of the 1-propynyl radical (CH 3CC; X 2A 1) with ethylene (H 2CCH 2; X 1A 1g) and the formation of 1-penten-3-yne (CH 2CHCCCH 3; X 1A'). Phys Chem Chem Phys 2019; 21:22308-22319. [PMID: 31576858 DOI: 10.1039/c9cp04073k] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The crossed molecular beam reactions of the 1-propynyl radical (CH3CC; X2A1) with ethylene (H2CCH2; X1A1g) and ethylene-d4 (D2CCD2; X1A1g) were performed at collision energies of 31 kJ mol-1 under single collision conditions. Combining our laboratory data with ab initio electronic structure and statistical Rice-Ramsperger-Kassel-Marcus (RRKM) calculations, we reveal that the reaction is initiated by the barrierless addition of the 1-propynyl radical to the π-electron density of the unsaturated hydrocarbon of ethylene leading to a doublet C5H7 intermediate(s) with a life time(s) longer than the rotation period(s). The reaction eventually produces 1-penten-3-yne (p1) plus a hydrogen atom with an overall reaction exoergicity of 111 ± 16 kJ mol-1. About 35% of p1 originates from the initial collision complex followed by C-H bond rupture via a tight exit transition state located 22 kJ mol-1 above the separated products. The collision complex (i1) can also undergo a [1,2] hydrogen atom shift to the CH3CHCCCH3 intermediate (i2) prior to a hydrogen atom release; RRKM calculations suggest that this pathway contributes to about 65% of p1. In higher density environments such as in combustion flames and circumstellar envelopes of carbon stars close to the central star, 1-penten-3-yne (p1) may eventually form the cyclopentadiene (c-C5H6) isomer via hydrogen atom assisted isomerization followed by hydrogen abstraction to the cyclopentadienyl radical (c-C5H5) as an important pathway to key precursors to polycyclic aromatic hydrocarbons (PAHs) and to carbonaceous nanoparticles.
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Affiliation(s)
- Chao He
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, USA.
| | - Long Zhao
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, USA.
| | - Aaron M Thomas
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, USA.
| | - Galiya R Galimova
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, USA. and Samara National Research University, Samara 443086, Russia
| | - Alexander M Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, USA. and Samara National Research University, Samara 443086, Russia
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, USA.
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Giri G, Pati YA, Ramasesha S. Correlated Electronic States of a Few Polycyclic Aromatic Hydrocarbons: A Computational Study. J Phys Chem A 2019; 123:5257-5265. [PMID: 31058503 DOI: 10.1021/acs.jpca.9b02196] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In recent years, polycyclic aromatic hydrocarbons (PAHs) have been studied for their electronic properties as they are viewed as nanodots of graphene. They have also been of interest as functional molecules for applications such as light-emitting diodes and solar cells. Since the last few years, varying structural and chemical properties corresponding to the size and geometry of these molecules have been studied both theoretically and experimentally. Here, we carry out a systematic study of the electronic states of several PAHs using the Pariser-Parr-Pople model, which incorporates long-range electron correlations. In all of the molecules studied by us, we find that the 2A state is below the 1B state and hence none of them will be fluorescent in the gaseous phase. The singlet-triplet gap is more than half of the singlet-singlet gap in all cases, and hence, none of these PAHs can be candidates for improved solar cell efficiencies in a singlet fission. We discuss in detail the properties of the electronic states, which include bond orders and spin densities (in triplets) of these systems.
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Affiliation(s)
- Geetanjali Giri
- Solid State and Structural Chemistry Unit , Indian Institute of Science , Bangalore 560012 , India
| | - Y Anusooya Pati
- Solid State and Structural Chemistry Unit , Indian Institute of Science , Bangalore 560012 , India
| | - S Ramasesha
- Solid State and Structural Chemistry Unit , Indian Institute of Science , Bangalore 560012 , India
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Kaminský J, Chalupský J, Štěpánek P, Kříž J, Bouř P. Vibrational Structure in Magnetic Circular Dichroism Spectra of Polycyclic Aromatic Hydrocarbons. J Phys Chem A 2017; 121:9064-9073. [PMID: 29112435 DOI: 10.1021/acs.jpca.7b10120] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Absorption and magnetic circular dichroism (MCD) spectroscopies are powerful and simple methods to discriminate among various compounds. Polycyclic aromatic hydrocarbons provide particularly strong signal, which, for example, facilitates their detection in the environment. However, interpretation of the spectra is often based on quantum-chemical simulations, providing a limited precision only. In the present work, we use time-dependent density functional theory and complete active space second-order perturbation theories to understand spectral features observed in a series of naphthalene, anthracene, phenanthrene, and three larger compounds. The electronic computations provided reasonable agreement with the experiment for the smaller molecules, while a large error persisted for the bigger ones. However, many discrepancies could be explained by vibrational splitting of the electronic transitions across the entire spectral range. Compared to plain absorption, MCD spectral bands and their vibrational splitting were more specific for each aromatic molecule. The computational tools allowing simulations of detailed vibrational features in the electronic spectra thus promise to open a qualitatively new chapter in the spectroscopy of aromatic compounds.
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Affiliation(s)
- Jakub Kaminský
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences , Flemingovo náměstí 2, 16610 Prague, Czech Republic
| | - Jakub Chalupský
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences , Flemingovo náměstí 2, 16610 Prague, Czech Republic
| | - Petr Štěpánek
- NMR Research Unit, Faculty of Science, University of Oulu , P.O. Box 3000, 90014 Oulu, Finland
| | - Jan Kříž
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences , Flemingovo náměstí 2, 16610 Prague, Czech Republic
| | - Petr Bouř
- Institute of Organic Chemistry and Biochemistry, Academy of Sciences , Flemingovo náměstí 2, 16610 Prague, Czech Republic
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Temperature-induced oligomerization of polycyclic aromatic hydrocarbons at ambient and high pressures. Sci Rep 2017; 7:7889. [PMID: 28801612 PMCID: PMC5554131 DOI: 10.1038/s41598-017-08529-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 07/10/2017] [Indexed: 11/09/2022] Open
Abstract
Temperature-induced oligomerization of polycyclic aromatic hydrocarbons (PAHs) was found at 500–773 K and ambient and high (3.5 GPa) pressures. The most intensive oligomerization at 1 bar and 3.5 GPa occurs at 740–823 K. PAH carbonization at high pressure is the final stage of oligomerization and occurs as a result of sequential oligomerization and polymerization of the starting material, caused by overlapping of π-orbitals, a decrease of intermolecular distances, and finally the dehydrogenation and polycondensation of benzene rings. Being important for building blocks of life, PAHs and their oligomers can be formed in the interior of the terrestrial planets with radii less than 2270 km.
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Thomas AM, Lucas M, Yang T, Kaiser RI, Fuentes L, Belisario‐Lara D, Mebel AM. A Free‐Radical Pathway to Hydrogenated Phenanthrene in Molecular Clouds—Low Temperature Growth of Polycyclic Aromatic Hydrocarbons. Chemphyschem 2017; 18:1971-1976. [DOI: 10.1002/cphc.201700515] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Indexed: 11/11/2022]
Affiliation(s)
- Aaron M. Thomas
- Department of Chemistry University of Hawaii at Manoa Honolulu HI 96822 USA
| | - Michael Lucas
- Department of Chemistry University of Hawaii at Manoa Honolulu HI 96822 USA
| | - Tao Yang
- Department of Chemistry University of Hawaii at Manoa Honolulu HI 96822 USA
| | - Ralf I. Kaiser
- Department of Chemistry University of Hawaii at Manoa Honolulu HI 96822 USA
| | - Luis Fuentes
- Department of Chemistry and Biochemistry Florida International University Miami FL 33199 USA
| | - Daniel Belisario‐Lara
- Department of Chemistry and Biochemistry Florida International University Miami FL 33199 USA
| | - Alexander M. Mebel
- Department of Chemistry and Biochemistry Florida International University Miami FL 33199 USA
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Yang T, Kaiser RI, Troy TP, Xu B, Kostko O, Ahmed M, Mebel AM, Zagidullin MV, Azyazov VN. HACA's Heritage: A Free‐Radical Pathway to Phenanthrene in Circumstellar Envelopes of Asymptotic Giant Branch Stars. Angew Chem Int Ed Engl 2017; 56:4515-4519. [DOI: 10.1002/anie.201701259] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2017] [Indexed: 11/10/2022]
Affiliation(s)
- Tao Yang
- Department of Chemistry University of Hawai'i at Manoa Honolulu HI 96822 USA
| | - Ralf I. Kaiser
- Department of Chemistry University of Hawai'i at Manoa Honolulu HI 96822 USA
| | - Tyler P. Troy
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
| | - Bo Xu
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
| | - Oleg Kostko
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
| | - Musahid Ahmed
- Chemical Sciences Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA
| | - Alexander M. Mebel
- Department of Chemistry and Biochemistry Florida International University Miami FL 33199 USA
| | - Marsel V. Zagidullin
- Department of Physics Samara National Research University Samara 443086 Russian Federation
| | - Valeriy N. Azyazov
- Department of Physics Samara National Research University Samara 443086 Russian Federation
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HACA's Heritage: A Free‐Radical Pathway to Phenanthrene in Circumstellar Envelopes of Asymptotic Giant Branch Stars. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201701259] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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12
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Kaiser RI, Parker DS, Mebel AM. Reaction Dynamics in Astrochemistry: Low-Temperature Pathways to Polycyclic Aromatic Hydrocarbons in the Interstellar Medium. Annu Rev Phys Chem 2015; 66:43-67. [DOI: 10.1146/annurev-physchem-040214-121502] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Ralf I. Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822;
| | - Dorian S.N. Parker
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822;
| | - Alexander M. Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
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Low temperature formation of naphthalene and its role in the synthesis of PAHs (polycyclic aromatic hydrocarbons) in the interstellar medium. Proc Natl Acad Sci U S A 2011; 109:53-8. [PMID: 22198769 DOI: 10.1073/pnas.1113827108] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are regarded as key molecules in the astrochemical evolution of the interstellar medium, but the formation mechanism of even their simplest prototype-naphthalene (C(10)H(8))-has remained an open question. Here, we show in a combined crossed beam and theoretical study that naphthalene can be formed in the gas phase via a barrierless and exoergic reaction between the phenyl radical (C(6)H(5)) and vinylacetylene (CH(2) = CH-C ≡ CH) involving a van-der-Waals complex and submerged barrier in the entrance channel. Our finding challenges conventional wisdom that PAH-formation only occurs at high temperatures such as in combustion systems and implies that low temperature chemistry can initiate the synthesis of the very first PAH in the interstellar medium. In cold molecular clouds, barrierless phenyl-type radical reactions could propagate the vinylacetylene-mediated formation of PAHs leading to more complex structures like phenanthrene and anthracene at temperatures down to 10 K.
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Osterrothová K, Jehlička J. Feasibility of Raman microspectroscopic identification of biomarkers through gypsum crystals. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2011; 80:96-101. [PMID: 21397552 DOI: 10.1016/j.saa.2010.12.085] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 12/13/2010] [Accepted: 12/14/2010] [Indexed: 05/30/2023]
Abstract
The miniaturized Raman spectrometer is considered to be a candidate instrument for the Pasteur payload (the ExoMars mission scheduled for 2018). This mission will, for the first time, combine mobility and access to subsurface locations where organic molecules might be well preserved. Evaporitic crystals are among the potential protected habitats that have been postulated. Various concentrations of biomarkers (beta-carotene, glycine and phthalic acid) dispersed in a gypsum matrix were analyzed through transparent mineral (gypsum) plates of different thicknesses. By doing so, conditions were simulated in which biomarkers were trapped within evaporitic crystals. Using a long-working distance objective, all studied concentrations of biomarkers mixed in gypsum powder were detected. The characteristic Raman bands were easily observable for a 10% mixture of all chosen biomarkers not only through a 3.3 mm plate and but even through a 5.2 mm plate. It was possible to detect key Raman bands of 1% phthalic acid/gypsum mixture and 1% beta-carotene/gypsum mixture even through a 5.2 mm gypsum plate. The 1% beta-carotene/gypsum mixture was still clearly distinguishable through an 8.5mm gypsum crystal due to the known resonance Raman effect of the molecule.
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Affiliation(s)
- Kateřina Osterrothová
- Institute of Geochemistry, Mineralogy and Mineral Resources, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
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Ehrenfreund P, Sephton MA. Carbon molecules in space: from astrochemistry to astrobiology. Faraday Discuss 2006; 133:277-88; discussion 347-74, 449-52. [PMID: 17191452 DOI: 10.1039/b517676j] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
How complex carbonaceous molecules in space are, what their abundance is and on what timescales they form are crucial questions within cosmochemistry. Despite the large heterogeneity of galactic and interstellar regions the organic chemistry in the universe seems to follow common pathways. The largest fraction of carbon in the universe is incorporated into aromatic molecules (gaseous polycyclic aromatic hydrocarbon as well as solid macromolecular aromatic structures). Macromolecular carbon constitutes more than half of the interstellar carbon, approximately 80% of the carbon in meteorites, and is likely to be present in comets. Molecules of high astrobiological relevance such as N-heterocycles, amino acids and pre-sugars have all been identified in trace quantities (ppb) in extracts of carbonaceous meteorites. Their presence in inter- and circumstellar regions is either unknown or contentious. In any event such fragile species are easily destroyed by UV radiation, shocks and thermal processing and are unlikely to survive incorporation into Solar System material without some degradation. The more refractory material, in particular macromolecular carbon may retain an interstellar heritage more faithfully. We present laboratory measurements on the photostability of organic compounds and discuss their survival in regions with elevated UV radiation. We also show recent observations of diffuse interstellar bands indicating the presence of fullerenes. We investigate the link between the carbon chemistry in interstellar space and in the Solar System by analyzing the carbonaceous fraction of meteorites and by reviewing stable isotopic data. It also seems evident that both volatile and refractory material from carbonaceous meteoritic has been substantially altered owing to thermal and aqueous processing within the Solar System.
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Affiliation(s)
- Pascale Ehrenfreund
- Leiden Institute of Chemistry, Astrobiology Laboratory, 2300 RA, The Netherlands.
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