title: A theoretical study of abiotic methylation reactions of gaseous elemental mercury by halogen-containing molecules.
abstract: Methylation reactions of gaseous elementary mercury by halogen containing molecules such as halogenomethane species CH(3)X (with X = Cl, Br, and I) and the dimethylchlorinium ion CH(3)ClCH(3)(+) were investigated at the density functional level. With CH(3)X, the reaction is predicted to be almost athermic and kinetically demanding for a thermal reaction. The reaction can proceed photochemically in the visible range; therefore sunlight may increase the reaction rate. These results compare well with the experimental data. Consecutive methylation of the CH(3)HgX products (with X = Cl, Br, and I) and subsequent formation of CH(3)HgCH(3) were also studied. These reactions are predicted to be kinetically inaccessible and thermodynamically unfavorable. With CH(3)ClCH(3)(+), the reaction is predicted to be athermic but kinetically easy. This is due to the suitability of the methyl transfer reagent. Geometrical and electronic data were systematically analyzed in order to rationalize the results.
authors.affiliation: Université de Toulouse, INSA, UPS, LPCNO, 135 Avenue de Rangueil, F-31077 Toulouse, France.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Castro
authors.forename: Aurélien
authors.initials: A
authors.lastname: Dommergue
authors.forename: Catherine
authors.initials: C
authors.lastname: Larose
authors.forename: Christophe
authors.initials: C
authors.lastname: Ferrari
authors.forename: Laurent
authors.initials: L
authors.lastname: Maron
mesh_terms: D005740:Gases / Q000737:chemistry*; D006846:Hydrocarbons, Halogenated / Q000737:chemistry*; D007700:Kinetics; D008628:Mercury / Q000737:chemistry*; D008745:Methylation; D008767:Methylmercury Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D008956:Models, Chemical; D013816:Thermodynamics
chemical_list: D005740:Gases; D006846:Hydrocarbons, Halogenated; D008767:Methylmercury Compounds; D008628:Mercury