Ab initio molecular orbital study of potential energy surface for the reaction of C 2H 3 with H 2 and related reactions

Alexander M. Mebel*, Keiji Morokuma, Ming-Chang Lin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The potential energy surface of the reaction C 2H 3+H 2→C 2H 4+H→C 2H 5 has been investigated using various theoretical methods including QCISD(T), CCSD(T), RCCSD(T), Gaussian-2 (G2), and the density-functional B3LYP approach. The reaction of the vinyl radical with molecular hydrogen is shown to take place through the hydrogen atom abstraction channel leading to the formation of C 2H 4+H with the activation energy of 10.4 kcal/mol at all the G2, QCISD(T)/ 6-311+G(3df,2p), and CCSD(T)/6-311+G(3df/,2p) levels. The rate constant, calculated using the variational transition state theory with tunneling correction, k=3.68·10 -20·T 2.48·exp(-3587/T) cm 3 molecule -1 s -1, is in good agreement with the experimental estimates. C 2H 5 cannot be formed directly by inserting C 2H 3 to H 2, but can only be produced by addition of H to C 2H 4, with a barrier of 4.5-4.7 kcal/mol calculated at high levels of theory. In order to match the experimental rate constant, the activation energy needs to be adjusted to 2.8 kcal/mol. Generally, the B3LYP method is found to predict well the geometries and vibrational frequencies of various species. However, it is less reliable for energy calculations than the QCISD(T) and CCSD(T) methods.

Original languageEnglish
Pages (from-to)3440-3449
Number of pages10
JournalThe Journal of chemical physics
Volume103
Issue number9
DOIs
StatePublished - Sep 1995

Fingerprint

Dive into the research topics of 'Ab initio molecular orbital study of potential energy surface for the reaction of C 2H 3 with H 2 and related reactions'. Together they form a unique fingerprint.

Cite this