Gas-Phase Study of the Elementary Reaction of the D1-Ethynyl Radical (C₂D; X²Σ⁺) with Propylene (C₃H₆; X¹A′) under Single-Collision Conditions

Abstract

The bimolecular gas-phase reactions of the D1-ethynyl radical (C 2 D; X 2 Σ + ) with propylene (C 3 H 6 ; X 1 A′) and partially substituted D3− 3,3,3-propylene (C 2 H 3 CD 3 ; X 1 A′) were studied under single collision conditions utilizing the crossed molecular beams technique. Combining our laboratory data with electronic structure and statistical calculations, the D1ethynyl radical is found to add without barrier to the C1 and C2 carbons of the propylene reactant, resulting in doublet C 5 H 6 D intermediate(s) with lifetime(s) longer than their rotational period(s). These intermediates undergo isomerization and unimolecular decomposition via atomic hydrogen loss through tight exit transition states forming predominantly cis/trans-3penten-1-yne ((HCC)CHCH(CH 3 )) and, to a minor amount, 3-methyl-3buten-1-yne ((HCC)C(CH 3 )CH 2 ) via overall exoergic reactions. Although the title reaction does not lead to the cyclopentadiene molecule (c-C 5 H 6 , X 1 A 1 ), high-temperature environments can convert the identified acyclic C 5 H 6 isomers through hydrogen atom assisted isomerization to cyclopentadiene (c-C 5 H 6 , X 1 A 1 ). Since both the ethynyl radical and propylene reactants have been observed in cold interstellar environments such as TMC-1 and the reaction is exoergic and all barriers lie below the energy of the separated reactants, these C 5 H 6 product isomers are predicted to form in those low-temperature regions.

Spiers Memorial Lecture: New directions in molecular scattering

“…In general, the application of theory in combination with crossed-molecularbeams experiments has led to fundamental understanding of quite complex reactions. [234][235][236][237][238][239][240][241][242][243][244][245][246][247][248][249][250][251] The impact of modern scattering on real systems can be exem-plied in the studies of O( 3 P) + C 6 H 6 (benzene). Here, a theoretical statistical approach could be validated by comparison to the crossed-molecular-beam results and subsequently used to compute channel-specic rate constants as a function of temperature and pressure.…”

A crossed molecular beams and computational study on the unusual reactivity of banana bonds of cyclopropane (c-C3H6; ) through insertion by ground state carbon atoms (C(3Pj))

“…Unsaturated and hydrogen-deficient resonance stabilized hydrocarbon free radicals (RSFRs) play an important role in the growth of polycyclic aromatic hydrocarbons (PAH), which in turn serve as precursors of soot and carbonaceous particles in various environments spanning from high-temperature combustion flames [1][2][3][4][5][6][7][8][9] and circumstellar envelopes to low-temperature planetary atmospheres and the interstellar medium (ISM). [10][11][12][13][14][15][16][17][18] The first stage of the PAH growth process is the formation of the first aromatic ring (benzene, C 6 H 6 ; phenyl, C 6 H 5 ) or two fused aromatic rings such as naphthalene (C 10 H 8 ) from nonaromatic hydrocarbons, which is followed by their further enlargement through addition of extra six-or five-membered rings.…”

10 Years of the ACS PHYS Astrochemistry Subdivision

“…In this virtual special issue, N 2 O is reacted with C( 3 P), producing rate coefficients for such chemical processes, 21 and a similar study on fluoromethane and calcium atomic cations is also reported. 22 Additionally, the deuterated ethynyl radical is reacted with propylene producing a wealth of hydrocarbons, 23 NO + the propargyl radical generates branching ratios for eight common astrochemical products, 24 furan + H 2 reactions generate various c-C 4 H x O (x = 4−8) species, 25 myriad nitrous oxides are synthesized in H 2 O−N 2 O/N 2 ice mixtures, 26,27 dinitriles are shown to be produced from gas-phase reactions of cyano radicals and cyanoethane, 28 and porous amorphous solid water appears to catalyze interstellar organic chemistry. 29 From theory, the earliest molecule in the universe (HeH + ) is most efficiently rotationally excited by collisions with H 2 , 30 H 2 CCS and HCCSH are likely not detected since they are destroyed through barrierless reactions with atomic hydrogen, 31 and MgNC reacts with water clusters to produce the known HMgNC molecule along with other Mg-containing species.…”