Ab initio quantum chemical study of the formation, decomposition and isomerization of the formaldiminoxy radical (CH2NO): comparison of the Gaussian-2 and CASPT2 techniques in the calculation of potential energy surfaces |
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Authors: | Warwick A Shapley George B Bacskay |
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Institution: | (1) School of Chemistry, University of Sydney, NSW 2006, Australia, AU |
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Abstract: | The reaction between triplet methylene and nitric oxide, producing the formaldiminoxy (CH2NO) radical, and the subsequent decomposition and isomerization reactions of CH2NO have been studied using ab␣initio quantum chemical techniques that include the Gaussian-2 (G2), CASSCF and CASPT2 methods.
Stationary points on the potential energy surfaces were located at MP2/6-31G(d) and CASSCF/cc-pVDZ levels of theory, while the electronic energies were determined using G2, G2(MP2), QCISD(T)/cc-pVTZ,
RCCSD(T)/cc-pVTZ and CASPT2/cc-pVTZ approaches. G2 is believed to be reliable at equilibrium geometries, but the determination
of certain transition state geometries and energies requires a MCSCF-based approach. The calculations suggest that CH2NO (2A′) forms in a barrierless reaction and could readily decompose to H+HCNO. A subsequent abstraction reaction then results in
H2+CNO. No molecular elimination channel was found. An alternative pathway is the formation of CH2ON, which readily isomerizes to CH2NO.
Received: 8 May 1998 / Accepted: 11 August / Published online: 9 October 1998 |
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Keywords: | : Combustion reactions Potential energy surfaces CASPT2 Gaussian-2 |
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