1
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Paul D, Sun BJ, He C, Yang Z, Goettl SJ, Yang T, Zhang BY, Chang AHH, Kaiser RI. Competing Si 2CH 4-H 2 and SiCH 2-SiH 4 Channels in the Bimolecular Reaction of Ground-State Atomic Carbon (C( 3P j)) with Disilane (Si 2H 6, X 1A 1g) under Single Collision Conditions. J Phys Chem A 2023; 127:1901-1908. [PMID: 36790335 DOI: 10.1021/acs.jpca.2c08417] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Abstract
The bimolecular gas-phase reaction of ground-state atomic carbon (C(3Pj)) with disilane (Si2H6, X1A1g) was explored under single-collision conditions in a crossed molecular beam machine at a collision energy of 36.6 ± 4.5 kJ mol-1. Two channels were observed: a molecular hydrogen elimination plus Si2CH4 (reaction 1) pathway and a silane loss channel along with the formation of SiCH2 (reaction 2), with branching ratios of 20 ± 3 and 80 ± 4%, respectively. Both channels involved indirect scattering dynamics via long-lived Si2CH6 reaction intermediate(s); the latter eject molecular hydrogen and silane in "molecular" elimination channels within the rotational plane of the fragmenting intermediate nearly perpendicularly to the total angular momentum vector. These molecular elimination channels are associated with tight exit transition states as reflected in a significant electron rearrangement as visible from the chemical bonding in the light reaction products molecular hydrogen and silane. Once these hydrogenated silicon-carbide clusters are formed within the inner envelope of carbon stars such as of IRC + 10216, the stellar wind can drive both Si2CH4 and SiCH2 to the outside sections of the envelope, where they can be photolyzed. This is of particular importance to unravel potential formation pathways to disilicon monocarbide (Si2C) observed recently in the circumstellar shell of IRC + 10216.
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Affiliation(s)
- Dababrata Paul
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Bing-Jian Sun
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Chao He
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Zhenghai Yang
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Shane J Goettl
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Tao Yang
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Bo-Yu Zhang
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Agnes H H Chang
- Department of Chemistry, National Dong Hwa University, Shoufeng, Hualien 974, Taiwan
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
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2
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Galimova GR, Mebel AM, Goettl SJ, Yang Z, Kaiser RI. A crossed molecular beams and computational study on the unusual reactivity of banana bonds of cyclopropane (c-C 3H 6; ) through insertion by ground state carbon atoms (C( 3P j)). Phys Chem Chem Phys 2022; 24:22453-22463. [PMID: 36102937 DOI: 10.1039/d2cp03293g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The mechanism and chemical dynamics of the reaction of ground electronic state atomic carbon C(3Pj) with cyclopropane c-C3H6 have been explored by combining crossed molecular beams experiments with electronic structure calculations of the pertinent triplet C4H6 potential energy surface and statistical computations of product branching ratios under single-collision conditions. The experimental findings suggest that the reaction proceeds via indirect scattering dynamics through triplet C4H6 reaction intermediate(s) leading to C4H5 product(s) plus atomic hydrogen via a tight exit transition state, with the overall reaction exoergicity evaluated as 231 ± 52 kJ mol-1. The calculations indicate that C(3Pj) can easily insert into one of the three equivalent C-C 'banana' bonds of cyclopropane overcoming a low barrier of only 2 kJ mol-1 following the formation of a van der Waals reactant complex stabilized by 15 kJ mol-1. The carbon atom insertion into one of the six C-H bonds is also feasible via a slightly higher barrier of 5 kJ mol-1. These results highlight an unusual reactivity of cyclopropane's banana C-C bonds, which behave more like unsaturated C-C bonds with a π-character than saturated σ C-C bonds, which are known to be generally unreactive toward the ground electronic state atomic carbon such as in ethane (C2H6). The statistical theory predicts the overall product branching ratios at the experimental collision energy as 50% for 1-butyn-4-yl, 33% for 1,3-butadien-2-yl, i-C4H5, and 11% for 1,3-butadien-1-yl, n-C4H5, with i-C4H5 (230 kJ mol-1 below the reactants) favored by the C-C insertion providing the best match with the experimentally observed reaction exoergicity. The C(3Pj) + c-C3H6 reaction is predicted to be a source of C4H5 radicals under the conditions where its low entrance barriers can be overcome, such as in planetary atmospheres or in circumstellar envelopes but not in cold molecular clouds. Both i- and n-C4H5 can further react with acetylene eventually producing the first aromatic ring and hence, the reaction of the atomic carbon with c-C3H6 can be considered as an initial step toward the formation of benzene.
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Affiliation(s)
- Galiya R Galimova
- 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.
| | - Shane J Goettl
- 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.
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Mānoa, Honolulu, HI 96822, USA.
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3
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Yang Z, He C, Goettl S, Kaiser RI. Reaction Dynamics Study of the Molecular Hydrogen Loss Channel in the Elementary Reactions of Ground-State Silicon Atoms (Si( 3P)) With 1- and 2-Methyl-1,3-Butadiene (C 5H 8). J Phys Chem A 2021; 125:5040-5047. [PMID: 34096290 DOI: 10.1021/acs.jpca.1c03023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The bimolecular gas-phase reactions involving ground-state atomic silicon (Si; 3P) and 1- and 2-methyl-1,3-butadiene were studied via crossed molecular beam experiments. Our data revealed indirect scattering dynamics through long-lived SiC5H8 collision complex(es) along with molecular hydrogen loss pathways, leading to facile formation of SiC5H6 isomer(s). We propose that the reactions of silicon with 1- and 2-methyl-1,3-butadiene possess reaction dynamics in an analogy to the silicon-1,3-butadiene system. This leads to cyclic methyl-substituted 2-methylene-1-silacyclobutene isomers via nonadiabatic reaction dynamics through intersystem crossing (ISC) from the triplet to the singlet surface in overall exoergic reactions through tight exit transition states and molecular hydrogen loss. Our study also suggests that the methyl group-although a spectator from the chemical viewpoint-can influence the disposal of the angular momentum into the rotational excitation of the final product.
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Affiliation(s)
- Zhenghai Yang
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Chao He
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Shane Goettl
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, United States
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4
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Goettl SJ, Doddipatla S, Yang Z, He C, Kaiser RI, Silva MX, Galvão BRL, Millar TJ. Chemical dynamics study on the gas-phase reaction of the D1-silylidyne radical (SiD; X 2Π) with deuterium sulfide (D 2S) and hydrogen sulfide (H 2S). Phys Chem Chem Phys 2021; 23:13647-13661. [PMID: 34120159 DOI: 10.1039/d1cp01629f] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reactions of the D1-silylidyne radical (SiD; X2Π) with deuterium sulfide (D2S; X1A1) and hydrogen sulfide (H2S; X1A1) were conducted utilizing a crossed molecular beams machine under single collision conditions. The experimental work was carried out in conjunction with electronic structure calculations. The elementary reaction commences with a barrierless addition of the D1-silylidyne radical to one of the non-bonding electron pairs of the sulfur atom of hydrogen (deuterium) sulfide followed by possible bond rotation isomerization and multiple atomic hydrogen (deuterium) migrations. Unimolecular decomposition of the reaction intermediates lead eventually to the D1-thiosilaformyl radical (DSiS) (p1) and D2-silanethione (D2SiS) (p3) via molecular and atomic deuterium loss channels (SiD-D2S system) along with the D1-thiosilaformyl radical (DSiS) (p1) and D1-silanethione (HDSiS) (p3) through molecular and atomic hydrogen ejection (SiD-H2S system) via indirect scattering dynamics in barrierless and overall exoergic reactions. Our study provides a look into the complex dynamics of the silicon and sulfur chemistries involving multiple deuterium/hydrogen shifts and tight exit transition states, as well as insight into silicon- and sulfur-containing molecule formation pathways in deep space. Although neither of the non-deuterated species - the thiosilaformyl radical (HSiS) and silanethione (H2SiS) - have been observed in the interstellar medium (ISM) thus far, astrochemical models presented here predict relative abundances in the Orion Kleinmann-Low nebula to be sufficiently high enough for detection.
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Affiliation(s)
- Shane J Goettl
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, USA.
| | - Srinivas Doddipatla
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, USA.
| | - Zhenghai Yang
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, USA.
| | - Chao He
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, USA.
| | - Ralf I Kaiser
- Department of Chemistry, University of Hawai'i at Manoa, Honolulu, Hawaii 96822, USA.
| | - Mateus X Silva
- Centro Federal de Educação Tecnológica de Minas Gerais, CEFET-MG, Av. Amazonas 5253, 30421-169 Belo Horizonte, Minas Gerais, Brazil.
| | - Breno R L Galvão
- Centro Federal de Educação Tecnológica de Minas Gerais, CEFET-MG, Av. Amazonas 5253, 30421-169 Belo Horizonte, Minas Gerais, Brazil.
| | - Tom J Millar
- School of Maths and Physics, Queen's University Belfast, University Road, Belfast BT7 1NN, Northern Ireland, UK.
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5
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Hickson KM, Loison JC, Wakelam V. Temperature dependent product yields for the spin forbidden singlet channel of the C(3P) + C2H2 reaction. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.07.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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6
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Mebel AM, Kaiser RI. Formation of resonantly stabilised free radicals via the reactions of atomic carbon, dicarbon, and tricarbon with unsaturated hydrocarbons: theory and crossed molecular beams experiments. INT REV PHYS CHEM 2015. [DOI: 10.1080/0144235x.2015.1075280] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Alexander M. Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Ralf I. Kaiser
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, HI 96822, USA
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7
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McKee ML, Reisenauer HP, Schreiner PR. Combined ab Initio Molecular Dynamics and Experimental Studies of Carbon Atom Addition to Benzene. J Phys Chem A 2014; 118:2801-9. [DOI: 10.1021/jp501107b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Hans Peter Reisenauer
- Institute
of Organic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392 Giessen, Germany
| | - Peter R. Schreiner
- Institute
of Organic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392 Giessen, Germany
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8
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Kaiser RI, Gu X, Zhang F, Maksyutenko P. Crossed beam reactions of methylidyne [CH(X2Π)] with D2-acetylene [C2D2(X1Σg+)] and of D1-methylidyne [CD(X2Π)] with acetylene [C2H2(X1Σg+)]. Phys Chem Chem Phys 2012; 14:575-88. [DOI: 10.1039/c1cp22635e] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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9
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Misochko EY, Akimov AV, Korchagin DV, Masitov AA, Shavrin KN. Matrix isolation ESR spectroscopy and quantum chemical calculations on 5-methylhexa-1,2,4-triene-1,3-diyl, a highly delocalized triplet “hybrid” carbene. Phys Chem Chem Phys 2012; 14:2032-9. [DOI: 10.1039/c2cp22853j] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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10
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Balucani N, Casavecchia P. Crossed molecular beam studies of astronomically relevant bimolecular reactions. RENDICONTI LINCEI 2011. [DOI: 10.1007/s12210-011-0128-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Parker DSN, Zhang F, Kim YS, Kaiser RI, Mebel AM. On the formation of resonantly stabilized C5H3 radicals--a crossed beam and ab initio study of the reaction of ground state carbon atoms with vinylacetylene. J Phys Chem A 2011; 115:593-601. [PMID: 21194192 DOI: 10.1021/jp109800h] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The formation of polycyclic aromatic hydrocarbons in combustion environments is linked to resonance stabilized free radicals. Here, we investigated the reaction dynamics of ground state carbon atoms, C((3)P(j)), with vinylacetylene at two collision energies of 18.8 kJ mol(-1) and 26.4 kJ mol(-1) employing the crossed molecular beam technique leading to two resonantly stabilized free radicals. The reaction was found to be governed by indirect scattering dynamics and to proceed without an entrance barrier through a long-lived collision complex to reach the products, n- and i-C(5)H(3) isomers via tight exit transition states. The reaction pathway taken is dependent on whether the carbon atom attacks the π electron density of the double or triple bond, both routes have been compared to the reactions of atomic carbon with ethylene and acetylene. Electronic structure/statistical theory calculations determined the product branching ratio to be 2:3 between the n- and i-C(5)H(3) isomers.
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Affiliation(s)
- Dorian S N Parker
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii, USA
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12
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Maksyutenko P, Zhang F, Gu X, Kaiser RI. A crossed molecular beam study on the reaction of methylidyne radicals [CH(X2Π)] with acetylene [C2H2(X1Σg+)]—competing C3H2+ H and C3H + H2channels. Phys Chem Chem Phys 2011; 13:240-52. [DOI: 10.1039/c0cp01529f] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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13
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Zhang F, Jones B, Maksyutenko P, Kaiser RI, Chin C, Kislov VV, Mebel AM. Formation of the Phenyl Radical [C6H5(X2A1)] under Single Collision Conditions: A Crossed Molecular Beam and ab Initio Study. J Am Chem Soc 2010; 132:2672-83. [DOI: 10.1021/ja908559v] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Fangtong Zhang
- Department of Chemistry, University of Hawai’i, Honolulu, Hawaii 96822, and Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
| | - Brant Jones
- Department of Chemistry, University of Hawai’i, Honolulu, Hawaii 96822, and Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
| | - Pavlo Maksyutenko
- Department of Chemistry, University of Hawai’i, Honolulu, Hawaii 96822, and Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
| | - Ralf I. Kaiser
- Department of Chemistry, University of Hawai’i, Honolulu, Hawaii 96822, and Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
| | - Christine Chin
- Department of Chemistry, University of Hawai’i, Honolulu, Hawaii 96822, and Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
| | - Vadim V. Kislov
- Department of Chemistry, University of Hawai’i, Honolulu, Hawaii 96822, and Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
| | - Alexander M. Mebel
- Department of Chemistry, University of Hawai’i, Honolulu, Hawaii 96822, and Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199
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14
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Wu Q, Cheng Q, Yamaguchi Y, Li Q, Schaefer HF. Triplet states of cyclopropenylidene and its isomers. J Chem Phys 2010; 132:044308. [PMID: 20113034 DOI: 10.1063/1.3273321] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The unique importance of the cyclopropenylidene molecule conveys significance to its low-lying isomers. Eleven low-lying electronic triplet stationary points as well as the two lowest singlet structures of C(3)H(2) have been systematically investigated. This research used coupled cluster (CC) methods with single and double excitations and perturbative triple excitations [CCSD(T)] and Dunning's correlation-consistent polarized valence cc-pVXZ (where X=D, T, and Q) basis sets. Geometries, dipole moments, vibrational frequencies, and associated infrared intensities of the targeted molecules have been predicted. The electronic ground state of cyclopropenylidene (3S, the global minimum) is the X (1)A(1) state with C(2v) point group symmetry. Among the 11 triplet stationary points, 7 structures are found to be minima, 2 structures to be transition states, and 2 structures to be higher-order saddle points. For the six lowest-lying triplet structures and singlet propadienylidene (2S), relative energies (zero-point vibrational energy corrected values in parentheses) with respect to the global minimum [ X (1)A(1) (3S)] at the cc-pVQZ-UCCSD(T) level of theory are predicted to be propynylidene (3)B(1aT)15.5(11.3)<propadienylidene[(1)A(1)(2S)]14.2(13.3)<propadienylidene[(3)B(1)(2T)]45.0(43.8)<cyclopropenylidene[(3)A(3aT)]53.8(52.5)<cyclopropyne[(3)B(2)(4aT)]70.0(70.6)<cyclopropenylidene [(3)B(1)(3cT)]71.2(69.9)<trans-propenediylidene [(3)A(")(5T)]73.6(70.7) kcal mol(-1). The combined energy for the [C((3)P)+C(2)H(2)(X (1)Sigma(g) (+))] system with respect to the global minimum (3S) is determined to be 107.4(103.8) kcal mol(-1). Therefore, these six triplet equilibrium structures are all energetically well below the dissociation limit to [C((3)P)+C(2)H(2)(X (1)Sigma(g) (+))].
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Affiliation(s)
- Qunyan Wu
- Institute of Chemical Physics, Beijing Institute of Technology, Beijing 100081, People's Republic of China
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15
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Costes M, Naulin C. Integral and differential cross sections of reactions relevant to astrochemistry. Phys Chem Chem Phys 2010; 12:9154-64. [DOI: 10.1039/c003656k] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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16
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Seburg R, Hodges J, McMahon R. Propynal Equivalents and Diazopropyne: Synthesis of All Mono-13C Isotopomers. Helv Chim Acta 2009. [DOI: 10.1002/hlca.200800446] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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17
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Seburg RA, Patterson EV, McMahon RJ. Structure of Triplet Propynylidene (HCCCH) as Probed by IR, UV/vis, and EPR Spectroscopy of Isotopomers. J Am Chem Soc 2009; 131:9442-55. [DOI: 10.1021/ja901606a] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Randal A. Seburg
- Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, and Department of Chemistry, Truman State University, Kirksville, Missouri 63501
| | - Eric V. Patterson
- Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, and Department of Chemistry, Truman State University, Kirksville, Missouri 63501
| | - Robert J. McMahon
- Department of Chemistry, University of Wisconsin, 1101 University Avenue, Madison, Wisconsin 53706, and Department of Chemistry, Truman State University, Kirksville, Missouri 63501
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18
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Balucani N. Elementary reactions and their role in gas-phase prebiotic chemistry. Int J Mol Sci 2009; 10:2304-2335. [PMID: 19564951 PMCID: PMC2695279 DOI: 10.3390/ijms10052304] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2009] [Revised: 05/13/2009] [Accepted: 05/15/2009] [Indexed: 11/23/2022] Open
Abstract
The formation of complex organic molecules in a reactor filled with gaseous mixtures possibly reproducing the primitive terrestrial atmosphere and ocean demonstrated more than 50 years ago that inorganic synthesis of prebiotic molecules is possible, provided that some form of energy is provided to the system. After that groundbreaking experiment, gas-phase prebiotic molecules have been observed in a wide variety of extraterrestrial objects (including interstellar clouds, comets and planetary atmospheres) where the physical conditions vary widely. A thorough characterization of the chemical evolution of those objects relies on a multi-disciplinary approach: 1) observations allow us to identify the molecules and their number densities as they are nowadays; 2) the chemistry which lies behind their formation starting from atoms and simple molecules is accounted for by complex reaction networks; 3) for a realistic modeling of such networks, a number of experimental parameters are needed and, therefore, the relevant molecular processes should be fully characterized in laboratory experiments. A survey of the available literature reveals, however, that much information is still lacking if it is true that only a small percentage of the elementary reactions considered in the models have been characterized in laboratory experiments. New experimental approaches to characterize the relevant elementary reactions in laboratory are presented and the implications of the results are discussed.
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Affiliation(s)
- Nadia Balucani
- Dipartimento di Chimica, Università degli Studi di Perugia, 06123 Perugia, Italy; E-Mail:
; Tel. +39-075-585-5513; Fax: +39-075-585-5606
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19
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Zhang F, Kim YS, Zhou L, Chang AHH, Kaiser RI. A crossed molecular beam study on the synthesis of the interstellar 2,4-pentadiynylidyne radical (HCCCCC). J Chem Phys 2009; 129:134313. [PMID: 19045096 DOI: 10.1063/1.2987366] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Crossed molecular beam experiments are performed to elucidate the synthesis of the 2,4-penta-diynylidyne [HCCCCC(X (2)Pi)] radical under single collision conditions--a crucial reaction intermediate to form polycyclic aromatic hydrocarbons and carbonaceous nanostructures in the interstellar medium and in combustion flames. The experiments demonstrate that the chemical dynamics of ground state carbon reacting with diacetylene [HCCCCH(X (1)Sigma(g)(+))] are indirect and proceed via addition of the electrophilic carbon atom to the pi electron density of the diacetylene molecule yielding ultimately the carbenelike HCCCCCH(X (3)Sigma(g)(-)) molecule. This intermediate fragments via hydrogen atom emission to yield the 2,4-pentadiynylidyne [HCCCCC(X (2)Pi)] radical. The chemical dynamics elucidated also allows us to predict that reaction of carbon atoms with polyynes of the generic formula H(C[triple bond]C)(n)H leads to the formation of hydrogen-terminated carbon clusters of the generic form HC(2n+1) in extreme environments. The acetylene-related reactivity and electronic structure of the diacetylene molecule also allow us to project that reactions of the diacetylene molecule with cyano and ethynyl radicals result in a stepwise extension of the carbon skeleton forming cyanodiacetylene (HCCCCCN) and triacetylene (HCCCCCCH) plus atomic hydrogen. These predictions open the door to extensive laboratory studies involving hitherto poorly understood reactions of the diacetylene molecule under single collision conditions.
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Affiliation(s)
- Fangtong Zhang
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA
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Casavecchia P, Leonori F, Balucani N, Petrucci R, Capozza G, Segoloni E. Probing the dynamics of polyatomic multichannel elementary reactions by crossed molecular beam experiments with soft electron-ionization mass spectrometric detection. Phys Chem Chem Phys 2008; 11:46-65. [PMID: 19081908 DOI: 10.1039/b814709d] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this Perspective we highlight developments in the field of chemical reaction dynamics. Focus is on the advances recently made in the investigation of the dynamics of elementary multichannel radical-molecule and radical-radical reactions, as they have become possible using an improved crossed molecular beam scattering apparatus with universal electron-ionization mass spectrometric detection and time-of-flight analysis. These improvements consist in the implementation of (a) soft ionization detection by tunable low-energy electrons which has permitted us to reduce interfering signals originating from dissociative ionization processes, usually representing a major complication, (b) different beam crossing-angle set-ups which have permitted us to extend the range of collision energies over which a reaction can be studied, from very low (a few kJ mol(-1), as of interest in astrochemistry or planetary atmospheric chemistry) to quite high energies (several tens of kJ mol(-1), as of interest in high temperature combustion systems), and (c) continuous supersonic sources for producing a wide variety of atomic and molecular radical reactant beams. Exploiting these new features it has become possible to tackle the dynamics of a variety of polyatomic multichannel reactions, such as those occurring in many environments ranging from combustion and plasmas to terrestrial/planetary atmospheres and interstellar clouds. By measuring product angular and velocity distributions, after having suppressed or mitigated, when needed, the problem of dissociative ionization of interfering species (reactants, products, background gases) by soft ionization detection, essentially all primary reaction products can be identified, the dynamics of each reaction channel characterized, and the branching ratios determined as a function of collision energy. In general this information, besides being of fundamental relevance, is required for a predictive description of the chemistry of these environments via computer models. Examples are taken from recent on-going work (partly published) on the reactions of atomic oxygen with acetylene, ethylene and allyl radical, of great importance in combustion. A reaction of relevance in interstellar chemistry, as that of atomic carbon with acetylene, is also discussed briefly. Comparison with theoretical results is made wherever possible, both at the level of electronic structure calculations of the potential energy surfaces and dynamical computations. Recent complementary CMB work as well as kinetic work exploiting soft photo-ionization with synchrotron radiation are noted. The examples illustrated in this article demonstrate that the type of dynamical results now obtainable on polyatomic multichannel radical-molecule and radical-radical reactions might well complement reaction kinetics experiments and hence contribute to bridging the gap between microscopic reaction dynamics and thermal reaction kinetics, enhancing significantly our basic knowledge of chemical reactivity and understanding of the elementary reactions which occur in real-world environments.
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Leonori F, Petrucci R, Segoloni E, Bergeat A, Hickson KM, Balucani N, Casavecchia P. Unraveling the dynamics of the C(3P,1D) + C2H2 reactions by the crossed molecular beam scattering technique. J Phys Chem A 2008; 112:1363-79. [PMID: 18229899 DOI: 10.1021/jp0776208] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A detailed investigation of the dynamics of the reactions of ground- and excited-state carbon atoms, C(3P) and C(1D), with acetylene is reported over a wide collision energy range (3.6-49.1 kJ mol-1) using the crossed molecular beam (CMB) scattering technique with electron ionization mass spectrometric detection and time-of-flight (TOF) analysis. We have exploited the capability of (a) generating continuous intense supersonic beams of C(3P, 1D), (b) crossing the two reactant beams at different intersection angles (45, 90, and 135 degrees ) to attain a wide range of collision energies, and (c) tuning the energy of the ionizing electrons to low values (soft ionization) to suppress interferences from dissociative ionization processes. From angular and TOF distribution measurements of products at m/z=37 and 36, the primary reaction products of the C(3P) and C(1D) reactions with C2H2 have been identified to be cyclic (c)-C3H + H, linear (l)-C3H + H, and C3 + H2. From the data analysis, product angular and translational energy distributions in the center-of-mass (CM) system for both the linear and cyclic C3H isomers as well as the C3 product from C(3P) and for l/c-C3H and C3 from C(1D) have been derived as a function of collision energy from 3.6 to 49.1 kJ mol-1. The cyclic/linear C3H ratio and the C3/(C3 + c/l-C3H) branching ratios for the C(3P) reaction have been determined as a function of collision energy. The present findings have been compared with those from previous CMB studies using pulsed beams; here, a marked contrast is noted in the CM angular distributions for both C3H- and C3-forming channels from C(3P) and their trend with collision energy. Consequently, the interpretation of the reaction dynamics derived in the present work contradicts that previously proposed from the pulsed CMB studies. The results have been discussed in the light of the available theoretical information on the relevant triplet and singlet C3H2 ab initio potential energy surfaces (PESs). In particular, the branching ratios for the C(3P) + C2H2 reaction have been compared with the available theoretical predictions (approximate quantum scattering calculations and quasiclassical trajectory calculations on ab initio triplet PESs and, very recent, statistical calculations on ab initio triplet PESs as well as on ab initio triplet/singlet PESs including nonadiabatic effects, that is, intersystem crossing). While the experimental branching ratios have been corroborated by the statistical predictions, strong disagreement has been found with the results of the dynamical calculations. The astrophysical implications of the present results have been noted.
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Affiliation(s)
- Francesca Leonori
- Dipartimento di Chimica, Università degli Studi di Perugia, 06123 Perugia, Italy
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Mebel AM, Kislov VV, Hayashi M. Prediction of product branching ratios in the C(P3)+C2H2→l-C3H+H∕c-C3H+H∕C3+H2 reaction using ab initio coupled clusters calculations extrapolated to the complete basis set combined with Rice-Ramsperger-Kassel-Marcus and radiationless transition theories. J Chem Phys 2007; 126:204310. [PMID: 17552765 DOI: 10.1063/1.2736683] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Ab initio CCSD(T) calculations of intermediates and transition states on the singlet and triplet C3H2 potential energy surfaces extrapolated to the complete basis set limit are combined with statistical computations of energy-dependent rate constants of the C(3P)+C2H2 reaction under crossed molecular beam conditions. Rice-Ramsperger-Kassel-Marcus theory is applied for isomerization and dissociation steps within the same multiplicity and radiationless transition and nonadiabatic transition state theories are used for singlet-triplet intersystem crossing rates. The calculated rate constants are utilized to predict product branching ratios. The results demonstrate that, in qualitative agreement with available experimental data, c-C3H+H and C3+H2 are the most probable products at low collision energies, whereas l-C3H+H becomes dominant at higher Ec above approximately 25 kJ/mol.
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Affiliation(s)
- A M Mebel
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, USA.
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