Ab initio MRD CI ground and excited state potential curves for addition of O to H2CCH2 and oxirane formation and decomposition

Roszak, Szczepan; Buenker, Robert J.; Hariharan, P. C.; Kaufman, Joyce J.

doi:10.1016/0301-0104(90)85016-p

Cited by 7 publications

(3 citation statements)

References 12 publications

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“…1 In particular, they play a very important role in our understanding of combustion processes and oxidation mechanisms of hydrocarbon. [2][3][4][5] The reaction of O( 3 P) with isobutene has recently attracted much experimental attentions.…”

Section: Introductionmentioning

confidence: 99%

“…The reactions of O( 3 P) with alkenes are important in a wide variety of areas ranging from atmospheric chemistry to metabolic activation of hydrocarbon carcinogens . In particular, they play a very important role in our understanding of combustion processes and oxidation mechanisms of hydrocarbon. − The reaction of O( 3 P) with isobutene has recently attracted much experimental attentions. − …”

Section: Introductionmentioning

confidence: 99%

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A Theoretical Study of the Reaction of O(³P) with Isobutene

2006

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The reaction of O((3)P) with isobutene ((CH(3))(2)C=CH(2)) is investigated using the unrestricted second-order Møller-Plesset perturbation (UMP2) and complete basis set CBS-4M level methods. The minimum energy crossing point (MECP) between the singlet and triplet potential energy surfaces is located using the Newton-Lagrange method, and it is shown that the MECP plays a key role. The calculational results indicate that the site selectivity of the addition of O((3)P) to either carbon atom of the double bond of isobutene is weak, and the major product channels are CH(2)C(O)CH(3) + CH(3,) cis-/trans-CH(3)CHCHO + CH(3), (CH(3))(2)CCO + H(2), and CH(3)C(CH(2))(2) + OH, among which (CH(3))(2)CCO + H(2) is predicted to be the energetically most favorable one. The complex multichannel reaction mechanisms are revealed, and the observations in several recent experiments could be rationalized on the basis of the present calculations. The formation mechanisms of butenols are also discussed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Theoretical Study of the Reaction of O(³P) with Isobutene

2006

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“…Despite these uncertainties, it is generally accepted that the isomerization of c -C 2 H 4 O to form CH 3 CHO proceeds through C−O rupture to form the • CH 2 CH 2 O • biradical, followed by 1,2-H shift in the biradical to form CH 3 CHO. − The singlet and triplet states of • CH 2 CH 2 O • are expected to be very close, with differences attributable almost entirely to the O−C−C−H dihedral angle, as illustrated in Figure . Because the two electrons that form the biradical are separated in space and with little electronic coupling, the spin pairing energy is small and the singlet and triplet states are close in energy.…”

Section: Introductionmentioning

confidence: 99%

Thermal Decomposition of Ethylene Oxide: Potential Energy Surface, Master Equation Analysis, and Detailed Kinetic Modeling

et al. 2005

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The unimolecular decomposition of ethylene oxide (oxirane) and the oxiranyl radial is examined by molecular orbital calculations, Rice-Ramsperger-Kassel-Marcus (RRKM)/Master Equation analysis, and detailed kinetic modeling of ethylene oxide pyrolysis in a single-pulse shock tube. It was found that the largest energy barrier to the decomposition of ethylene oxide lies in its initial isomerization to form acetaldehyde, and in agreement with previous studies, the isomerization was found to proceed through the *CH2CH2O* biradical. Because of the biradical nature of the transition states and intermediate, the energy barriers for the initial C-O rupture in ethylene oxide and the subsequent 1,2-H shift remain highly uncertain. An overall isomerization energy barrier of 59 +/- 2 kcal/mol was found to satisfactorily explain the available single pulse shock tube data. This barrier height is in line with the estimates made from an approximate spin-corrected procedure at the MP4/6-31+G(d) and QCISD(T)/6-31G(d) levels of theory. The dominant channel for the unimolecular decomposition of ethylene oxide was found to form CH3 + HCO at around the ambient pressure. It accounts for >90% of the total rate constant for T > 800 K. The high-pressure limit rate constant for the unimolecular decomposition of ethylene oxide was calculated as k(1,infinity)(s(-1)) = (3.74 x 10(10))T(1.298)e(-29990/T) for 600 < T < 2000 K.

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