title: Atmospheric formation of the NO3 radical from gas-phase reaction of HNO3 acid with the NH2 radical: proton-coupled electron-transfer versus hydrogen atom transfer mechanisms.
abstract: The gas-phase reaction of nitric acid with the amidogen radical under atmospheric conditions has been investigated using quantum mechanical (QCISD and CCSD(T)) and DFT (B3LYP, BH&HLYP, M05, M05-2X, and M06-2X) calculations with the 6-311+G(2df,2p), aug-cc-pVTZ, aug-cc-pVQZ and extrapolation to the CBS basis sets. The reaction begins with the barrierless formation of a hydrogen-bonded complex, which can undergo two different reaction pathways, in addition to the decomposition back to the reactants. The lowest energy barrier pathway involves a proton-coupled electron-transfer mechanism, whereas the highest energy barrier pathway takes place through a hydrogen atom transfer mechanism. The performance of the different DFT functionals in predicting both the geometries and relative energies of the stationary points investigated has been analyzed.
authors.affiliation: Departament de Química Biològica i Modelització Molecular, (IQAC - CSIC), Jordi Girona, 18-26, E-08034 Barcelona, Catalonia, Spain. anglada@iqac.csic.es.
authors.forename: Josep M
authors.initials: JM
authors.lastname: Anglada
authors.forename: Santiago
authors.initials: S
authors.lastname: Olivella
authors.forename: Albert
authors.initials: A
authors.lastname: Solé
mesh_terms: D001272:Atmosphere / Q000737:chemistry*; D004583:Electrons; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D005740:Gases / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry*; D009566:Nitrates / Q000138:chemical synthesis* / Q000737:chemistry; D017942:Nitric Acid / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory
chemical_list: D005609:Free Radicals; D005740:Gases; D009566:Nitrates; D011522:Protons; D017942:Nitric Acid; D006859:Hydrogen