Tags

Type your tag names separated by a space and hit enter

Elucidating the Chemical Dynamics of the Elementary Reactions of the 1-Propynyl Radical (CH3CC; X2A1) with Methylacetylene (H3CCCH; X1A1) and Allene (H2CCCH2; X1A1).
J Phys Chem A 2019; 123(26):5446-5462JP

Abstract

The reactions of the 1-propynyl radical (CH3CC; X2A1) with two C3H4 isomers, methylacetylene (H3CCCH; X1A1) and allene (H2CCCH2; X1A1), along with their (partially) deuterated counterparts were explored at collision energies of 37 kJ mol-1, exploiting crossed molecular beams to unravel the chemical reaction dynamics to synthesize distinct C6H6 isomers under single collision conditions. The forward convolution fitting of the laboratory data along with ab initio and statistical calculations revealed that both reactions have no entrance barrier, proceed via indirect (complex-forming) reaction dynamics involving C6H7 intermediates with life times longer than their rotation period(s), and are initiated by the addition of the 1-propynyl radical with its radical center to the π-electron density of the unsaturated hydrocarbon at the terminal carbon atoms of methylacetylene (C1) and allene (C1/C3). In the methylacetylene system, the initial collision complexes undergo unimolecular decomposition via tight exit transition states by atomic hydrogen loss, forming dimethyldiacetylene (CH3CCCCCH3) and 1-propynylallene (H3CCCHCCCH2) in overall exoergic reactions (123 and 98 kJ mol-1) with a branching ratio of 9.4 ± 0.1; the methyl group of the 1-propynyl reactant acts solely as a spectator. On the other hand, in the allene system, our experimental data exhibit the formation of the fulvene (c-C5H4CH2) isomer via a six-step reaction sequence with two higher energy isomers-hexa-1,2-dien-4-yne (H2CCCHCCCH3) and hexa-1,4-diyne (HCCCH2CCCH3)-also predicted to be formed based on our statistical calculations. The pathway to fulvene advocates that, in the allene-1-propynyl system, the methyl group of the 1-propynyl reactant is actively engaged in the reaction mechanism to form fulvene. Because both reactions are barrierless and exoergic and all transition states are located below the energy of the separated reactants, the hydrogen-deficient C6H6 isomers identified in our investigation are predicted to be synthesized in low-temperature environments, such as in hydrocarbon-rich atmospheres of planets and their moons such as Titan along with cold molecular clouds such as Taurus Molecular Cloud-1.

Authors+Show Affiliations

Department of Chemistry , University of Hawai'i at Manoa , Honolulu , Hawaii 96822 , United States.Department of Chemistry , University of Hawai'i at Manoa , Honolulu , Hawaii 96822 , United States.Department of Chemistry , University of Hawai'i at Manoa , Honolulu , Hawaii 96822 , United States.Department of Chemistry and Biochemistry , Florida International University , Miami , Florida 33199 , United States.Department of Chemistry and Biochemistry , Florida International University , Miami , Florida 33199 , United States.Department of Chemistry , University of Hawai'i at Manoa , Honolulu , Hawaii 96822 , United States.

Pub Type(s)

Journal Article

Language

eng

PubMed ID

31179701

Citation

He, Chao, et al. "Elucidating the Chemical Dynamics of the Elementary Reactions of the 1-Propynyl Radical (CH3CC; X2A1) With Methylacetylene (H3CCCH; X1A1) and Allene (H2CCCH2; X1A1)." The Journal of Physical Chemistry. A, vol. 123, no. 26, 2019, pp. 5446-5462.
He C, Zhao L, Thomas AM, et al. Elucidating the Chemical Dynamics of the Elementary Reactions of the 1-Propynyl Radical (CH3CC; X2A1) with Methylacetylene (H3CCCH; X1A1) and Allene (H2CCCH2; X1A1). J Phys Chem A. 2019;123(26):5446-5462.
He, C., Zhao, L., Thomas, A. M., Morozov, A. N., Mebel, A. M., & Kaiser, R. I. (2019). Elucidating the Chemical Dynamics of the Elementary Reactions of the 1-Propynyl Radical (CH3CC; X2A1) with Methylacetylene (H3CCCH; X1A1) and Allene (H2CCCH2; X1A1). The Journal of Physical Chemistry. A, 123(26), pp. 5446-5462. doi:10.1021/acs.jpca.9b03746.
He C, et al. Elucidating the Chemical Dynamics of the Elementary Reactions of the 1-Propynyl Radical (CH3CC; X2A1) With Methylacetylene (H3CCCH; X1A1) and Allene (H2CCCH2; X1A1). J Phys Chem A. 2019 Jul 5;123(26):5446-5462. PubMed PMID: 31179701.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Elucidating the Chemical Dynamics of the Elementary Reactions of the 1-Propynyl Radical (CH3CC; X2A1) with Methylacetylene (H3CCCH; X1A1) and Allene (H2CCCH2; X1A1). AU - He,Chao, AU - Zhao,Long, AU - Thomas,Aaron M, AU - Morozov,Alexander N, AU - Mebel,Alexander M, AU - Kaiser,Ralf I, Y1 - 2019/06/25/ PY - 2019/6/11/pubmed PY - 2019/6/11/medline PY - 2019/6/11/entrez SP - 5446 EP - 5462 JF - The journal of physical chemistry. A JO - J Phys Chem A VL - 123 IS - 26 N2 - The reactions of the 1-propynyl radical (CH3CC; X2A1) with two C3H4 isomers, methylacetylene (H3CCCH; X1A1) and allene (H2CCCH2; X1A1), along with their (partially) deuterated counterparts were explored at collision energies of 37 kJ mol-1, exploiting crossed molecular beams to unravel the chemical reaction dynamics to synthesize distinct C6H6 isomers under single collision conditions. The forward convolution fitting of the laboratory data along with ab initio and statistical calculations revealed that both reactions have no entrance barrier, proceed via indirect (complex-forming) reaction dynamics involving C6H7 intermediates with life times longer than their rotation period(s), and are initiated by the addition of the 1-propynyl radical with its radical center to the π-electron density of the unsaturated hydrocarbon at the terminal carbon atoms of methylacetylene (C1) and allene (C1/C3). In the methylacetylene system, the initial collision complexes undergo unimolecular decomposition via tight exit transition states by atomic hydrogen loss, forming dimethyldiacetylene (CH3CCCCCH3) and 1-propynylallene (H3CCCHCCCH2) in overall exoergic reactions (123 and 98 kJ mol-1) with a branching ratio of 9.4 ± 0.1; the methyl group of the 1-propynyl reactant acts solely as a spectator. On the other hand, in the allene system, our experimental data exhibit the formation of the fulvene (c-C5H4CH2) isomer via a six-step reaction sequence with two higher energy isomers-hexa-1,2-dien-4-yne (H2CCCHCCCH3) and hexa-1,4-diyne (HCCCH2CCCH3)-also predicted to be formed based on our statistical calculations. The pathway to fulvene advocates that, in the allene-1-propynyl system, the methyl group of the 1-propynyl reactant is actively engaged in the reaction mechanism to form fulvene. Because both reactions are barrierless and exoergic and all transition states are located below the energy of the separated reactants, the hydrogen-deficient C6H6 isomers identified in our investigation are predicted to be synthesized in low-temperature environments, such as in hydrocarbon-rich atmospheres of planets and their moons such as Titan along with cold molecular clouds such as Taurus Molecular Cloud-1. SN - 1520-5215 UR - https://www.unboundmedicine.com/medline/citation/31179701/Elucidating_the_Chemical_Dynamics_of_the_Elementary_Reactions_of_the_1-Propynyl_Radical_(CH3CC L2 - https://dx.doi.org/10.1021/acs.jpca.9b03746 DB - PRIME DP - Unbound Medicine ER -