Oleg Gadzhiev - Quantum Chemical Study of Trimolecular Reaction Mechanism between Nitric Oxide and Oxygen in the Gas Phase J. Phys. Chem. A, 2009, 113 (32), pp 9092-;

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  Publication Details (including relevant citation   information): Quantum Chemical Study of Trimolecular   Reaction Mechanism between Nitric Oxide and Oxygen in the Gas   Phase J. Phys. Chem. A, 2009, 113 (32), pp 9092-;9101 Publication   Date (Web): July 17, 2009 Singlet and triplet potential energy   surfaces of the reaction between molecular oxygen and two nitric   oxide(II) molecules were studied by quantum chemical methods   (coupled cluster, CASSCF, and density functional theory: B3LYP,   TPSS, VSXC, BP86, PBE, B2-PLYP, B2K-PLYP). Elementary steps   involving various N2O4 isomers (cyclic, cis-cis-, cis-trans-,   trans-trans-ONOONO, cis- and trans-ONONO2, O2NNO2) were   considered, as well as weakly bound molecular clusters preceding   formation of O2NNO2, and Coupe-type quasi-aromatic hexagonal ring   intermediate NO2O2N. We found that activation energy strongly   depends on the conformation of ONOONO peroxide, which is formed   barrierlessly. The best agreements with experimental values were   achieved by the B3LYP functional with aug-pc3 basis set. The   lowest transition state (TS) energies correspond to the following   reaction channel: 2NO + O2 (0 kJ/mol) cis-cis-ONOONO (-45 kJ/mol)   TS1 NO2O2N (-90 kJ/mol) TS2 cis-ONONO2 (-133 kJ/mol) TS3   trans-ONONO2 (-144 kJ/mol) TS4 O2NNO2 (-193 kJ/mol). A valley   ridge inflection (VRI) point is located on the minimum energy   path (MEP) connecting NO2O2N and cis-ONONO2. The energy landscape   between NO2O2N and CC-TS2 can be classified as a downhill   valley-pitchfork VRI bifurcation according to a recent   classification of bifurcation events [Quapp, W. J. Mol. Struct.   2004, 95, 695-696]. The first and second transition states   correspond to barrier heights of 10.6 and 37.0 kJ/mol,   respectively. These values lead to the negative temperature   dependence of the rate constant. The apparent activation enthalpy   of the overall reaction was calculated to be rH(0) = -4.5 kJ/mol,   in perfect agreement with the experimental value.

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  Address (URL): http://pubs.acs.org/doi/pdf/10.1021/jp900484s