Reaction Energetics for the Abstraction Process C2H3 + H2 → C2H4 + H

Abstract

The fundamentally important combustion reaction of vinyl radical with hydrogen has been studied in the laboratory by at least five experimental groups. Herein, the reaction C2H3 + H2 → C2H4 + H has been examined using focal-point analysis. Molecular energies were determined from extrapolations to the complete basis-set limit using correlation-consistent basis sets (cc-pVTZ, cc-pVQZ, and cc-pV5Z) and coupled-cluster theory with single and double excitations (CCSD), perturbative triples [CCSD(T)], full triples [CCSDT], and perturbative quadruples [CCSDT(Q)]. Reference geometries were optimized at the all-electron CCSD(T)/cc-pCVQZ level. Computed energies were also corrected for relativistic effects and the Born–Oppenheimer approximation. The activation energy for hydrogen abstraction is predicted to be 9.65 kcal mol–1, and the overall reaction is predicted to be exothermic by 5.65 kcal mol–1. Natural resonance theory (NRT) analysis was performed to verify the reaction pathway and describe bond-breaking and ...