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Title: Gas-Phase Formation of 1-Methylcyclopropene and 3-Methylcyclopropene via the Reaction of the Methylidyne Radical (CH; X 2 Π) with Propylene (CH 3 CHCH 2 ; X 1 A')

Abstract

The crossed molecular beam reactions of the methylidyne radical (CH; X2Π) with propylene (CH3CHCH2; X1A') along with (partially) substituted reactants were conducted at collision energies of 19.3 kJ mol–1. Combining our experimental data with ab initio electronic structure and statistical calculations, the methylidyne radical is revealed to add barrierlessly to the carbon–carbon double bond of propylene reactant resulting in a cyclic doublet C4H7 intermediate with a lifetime longer than its rotation period. These adducts undergo a nonstatistical unimolecular decomposition via atomic hydrogen loss through tight exit transition states forming the cyclic products 1-methylcyclopropene and 3-methylcyclopropene with overall reaction exoergicities of 168 ± 25 kJ mol–1. These C4H6 isomers are predicted to exist even in low-temperature environments such as cold molecular clouds like TMC-1, since the reaction is barrierless and exoergic, all transition states are below the energy of the separated reactants, and both the methylidyne radical (CH; X2Π) and propylene reactant were detected in cold molecular clouds such as TMC-1.

Authors:
 [1]; ORCiD logo [1];  [2]; ORCiD logo [3]; ORCiD logo [1]
  1. Univ. of Hawaii at Manoa, Honolulu, HI (United States)
  2. Florida International Univ., Miami, FL (United States); Samara National Research Univ., Samara (Russian Federation)
  3. Florida International Univ., Miami, FL (United States)
Publication Date:
Research Org.:
Univ. of Hawaii at Manoa, Honolulu, HI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1603231
Grant/Contract Number:  
FG02-03ER15411
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
Additional Journal Information:
Journal Volume: 123; Journal Issue: 49; Journal ID: ISSN 1089-5639
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

He, Chao, Thomas, Aaron M., Galimova, Galiya R., Mebel, Alexander M., and Kaiser, Ralf I.. Gas-Phase Formation of 1-Methylcyclopropene and 3-Methylcyclopropene via the Reaction of the Methylidyne Radical (CH; X 2 Π) with Propylene (CH 3 CHCH 2 ; X 1 A'). United States: N. p., 2019. Web. https://doi.org/10.1021/acs.jpca.9b09815.
He, Chao, Thomas, Aaron M., Galimova, Galiya R., Mebel, Alexander M., & Kaiser, Ralf I.. Gas-Phase Formation of 1-Methylcyclopropene and 3-Methylcyclopropene via the Reaction of the Methylidyne Radical (CH; X 2 Π) with Propylene (CH 3 CHCH 2 ; X 1 A'). United States. https://doi.org/10.1021/acs.jpca.9b09815
He, Chao, Thomas, Aaron M., Galimova, Galiya R., Mebel, Alexander M., and Kaiser, Ralf I.. Wed . "Gas-Phase Formation of 1-Methylcyclopropene and 3-Methylcyclopropene via the Reaction of the Methylidyne Radical (CH; X 2 Π) with Propylene (CH 3 CHCH 2 ; X 1 A')". United States. https://doi.org/10.1021/acs.jpca.9b09815. https://www.osti.gov/servlets/purl/1603231.
@article{osti_1603231,
title = {Gas-Phase Formation of 1-Methylcyclopropene and 3-Methylcyclopropene via the Reaction of the Methylidyne Radical (CH; X 2 Π) with Propylene (CH 3 CHCH 2 ; X 1 A')},
author = {He, Chao and Thomas, Aaron M. and Galimova, Galiya R. and Mebel, Alexander M. and Kaiser, Ralf I.},
abstractNote = {The crossed molecular beam reactions of the methylidyne radical (CH; X2Π) with propylene (CH3CHCH2; X1A') along with (partially) substituted reactants were conducted at collision energies of 19.3 kJ mol–1. Combining our experimental data with ab initio electronic structure and statistical calculations, the methylidyne radical is revealed to add barrierlessly to the carbon–carbon double bond of propylene reactant resulting in a cyclic doublet C4H7 intermediate with a lifetime longer than its rotation period. These adducts undergo a nonstatistical unimolecular decomposition via atomic hydrogen loss through tight exit transition states forming the cyclic products 1-methylcyclopropene and 3-methylcyclopropene with overall reaction exoergicities of 168 ± 25 kJ mol–1. These C4H6 isomers are predicted to exist even in low-temperature environments such as cold molecular clouds like TMC-1, since the reaction is barrierless and exoergic, all transition states are below the energy of the separated reactants, and both the methylidyne radical (CH; X2Π) and propylene reactant were detected in cold molecular clouds such as TMC-1.},
doi = {10.1021/acs.jpca.9b09815},
journal = {Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory},
number = 49,
volume = 123,
place = {United States},
year = {2019},
month = {11}
}

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