Theoretical Investigation of the Radical–Radical Reaction of O(³P) + C₂H₃ and Comparison with Gas-Phase Crossed-Beam Experiments

Abstract

Herein, we present an ab initio study of the prototypal radical-radical reactions of ground-state atomic oxygen [O((3)P)] with the vinyl (C2H3) radical using density functional theory and a complete basis set model. Two distinctive pathways on the lowest doublet potential energy surfaces (PESs) were predicted to be in competition: addition and abstraction. The barrierless addition of O((3)P) to the hydrocarbon radicals leads to energy-rich intermediate formation followed by subsequent isomerization and decomposition to yield various products: CH2CO (ketene) + H, CO + CH3, C2HOH (acetylenol) + H, (3,1)CCHOH + H, H2O + C2H, (3,1)CH2 + HCO, H2CO (formaldehyde) + CH, C2H2 (acetylene) + OH, and (3,1)CCH2 + OH. The competing but minor H-atom abstraction mechanisms produce C2H2 + OH and (1,3)CCH2 + OH. The optimized structures of the reactants, products, intermediates, and transition states and the reaction mechanisms were obtained on the lowest doublet PESs. The major pathway was predicted to be the formation of CH2CO + H through the low-barrier, single-step cleavages of the addition intermediates. The Levine-Bernstein prior method, statistical surprisal approach, and microcanonical Rice-Ramsperger-Kassel-Marcus theory were applied to deduce the energy distributions of H atoms and OH products and quantitative rate constants. On the basis of the statistical theory and the population analysis, the predicted energy distributions were compared to the kinetic energy release of H and the preferential population of the Π(A') component of OH products reported in recent gas-phase crossed-beam investigations (Park, M. J.; Jang, S. C.; Choi, J. H. J. Chem. Phys. 2012, 137, 204311), and their kinetic and dynamic characteristics were discussed.

Syntone chemistry and prebiotic stage in life evolution 1. Aziridinone, a key compound in formation of the first proteinogenic amino acids and polypeptides

“…2012; Jung et al . 2015). We believe these reactions can occur at low temperature, under 0 °C and the resulting intermediates can be stable until the contact with some components of the primordial atmosphere (water, carbon dioxide, ammonia, hydrogen sulphide and methane) when in favourable thermodynamic conditions they will form simultaneously proteinogenic amino acids and the corresponding polypeptides.…”

KMC Study on Byproduct Formation in the Process of Acetylene to Vinyl Acetate

“…The 38 Se-Hee indicates the possibility of CH 2 COH formed by CHC and H 2 O. CH 2 COH generates two different products CH 3 CO and CH 2 CHO through the isomerization reaction. 39 In the process of dissociation of acetaldehyde, Han found that CH 3 CO and CH 2 CHO can generate acetaldehyde through hydrogenation. 40 In addition, the possibility that acetaldehyde can be formed by a combination of vinyl and water is also speculated.…”

Syntone Chemistry. Theoretical Study on the Formation of Cysteine, Aspartic Acid, Asparagine and Threonine

“…We must note that in this study we calculated the enthalpies of formation and Gibbs free energies only for reactions apparently without transition state [14][15][16][17], which result at low temperatures. For the reactions occurring at contact with atmospheric primary components that may require activations too, reactions which occur at higher temperatures, we have mentioned only the reaction enthalpies.…”

“…It was considered that all reactions after which the derivative precursors of aziridinone would get, at low temperatures, would form only by reactions resulting after the photochemical reactions model [13], it means that in their way from initial states to final states we would have to do only with a decreasing in energies of involved reaction systems [14][15][16][17]. In more drastically thermodynamic conditions, reactions between precursors and primary atmospheric components would be produced.…”