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  • 1995-1999  (3)
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Material
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Year
  • 1
    Electronic Resource
    Electronic Resource
    A quantum chemical investigation of possible intermediates in the reaction of the amidogen and hydroperoxyl radicals (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 8117-8125 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction NH2+HO2→products, a reaction of atmospheric interest, has been studied using ab initio molecular orbital calculations with extended basis sets [6-311++G** and 6-311++G(2df,2pd)], and a variety of methods accounting for electron correlation such as second order Møller–Plesset perturbation theory (MP2) with all electrons, quadratic configuration interaction singles and doubles with triples correction [QCISD(T)], complete active space [CAS(8,8)], and multireference double excitation configuration interaction (MRDCI). Also, the performance of density functional (DFT) calculations has been investigated. In the present study, all stationary points on various potential energy surfaces giving rise to different products, HNO+H2O, NH2O+OH, NH3+O2, H2O2+NH, and HNOO+H2, have been optimized and characterized by their Hessian matrix. Amine oxide and dihydroxyamine have been found to be the precursors for HNO formation. In addition, the paper attempts to explain the experimental finding, nonobservation of OH⋅ during photolysis of ammonia, and it demands new experiments with spectroscopic identification of OH radicals. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472666
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Theoretical investigations on the reactions NH+HO2 and NH2+O2: Electronic structure calculations and kinetic analysis (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 5510-5521 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electronic structure calculations at the MP2, B3LYP-DFT, and quadratic configuration interaction singles and doubles levels of theory, with 6-311++G** and 6-311++G(2df,2pd) basis sets, are reported for the stationary points on the NH+HO2 doublet potential energy surface. Also the transition state on the quartet surface for the direct hydrogen abstraction reaction has been identified. Two minima viz., HNOOH and NH2O2, of almost equal stability and with a very high interconversion barrier have been found. Preferential dissociation of HNOOH to HNO and OH is reported due to its high isomerization barrier. The favorable dissociation channels of the NH2O2 adduct are those leading to NH2+O2 and NH2O+O products. Detailed kinetic analyses have been performed on the calculated DFT-B3LYP potential energy surfaces using quantum statistical Rice–Ramsperger–Kassel theory. The calculated total rate constant for NH+HO2 reaction at 300 K and 1 atm is 1.52×1010 cm3 mol−1 s−1 and the predominant contribution to the disappearance of the HNOOH adduct is the HNO+OH dissociation channel, K31. The NH2+O2 reaction is found to be a slow reaction and the calculated rate coefficient is in good agreement with the upper limit predicted by the experimentalists. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475940
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    An ab initio molecular orbital study of the potential energy surface of the HO2+NO reaction (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 1872-1880 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The potential energy surface of the HO2+NO reaction has been investigated at second order Moller–Plesset perturbation (MP2) and density functional (DFT) methods with the 6-311++G** basis set and at complete active space [CAS(8,8)] self-consistent field level using the 6-31G** basis set. The reaction is shown to give three different groups of products, viz., HO–NO2, NO2+OH, and HNO+O2. The thermodynamically stable HO–NO2 can be formed from the energized ONOOH adduct by the 1,2 migration of the OH group via a loose transition state (referred to as TS2) with a relatively higher barrier height compared to O–O bond fission. The other exothermic product, NO2+OH, arises from a direct O–O dissociation of ONOOH and is expected to be the most favorable process on account of its low barrier height. HNO+O2 can be formed by two different channels: (i) the direct hydrogen abstraction and/or (ii) the barrierless association of the reactants to form the peroxynitrous acid, ONOOH, which then undergoes 1,3 hydrogen migration, giving rise to the HN(O)OO biradical followed by N–O dissociation. Of the two channels, channel (i) has been found to be dominant. Owing to their higher barrier heights, HNO formation is expected only at high temperatures. NOH+O2 and HONO+O are not expected to compete in the kinetics of the HO2+NO system. The energetic of the key reactions, namely HO2+NO→HO–NO2 and HO2+NO→NO2+OH, has also been obtained at the QCISD/6-311++G(2df,2pd)//MP2/6-311++G** level. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.474537
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    Paper (German National Licenses)
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