title: DFT Study of the Reaction Mechanisms of Carbon Dioxide and its Isoelectronic Molecules CS2 and OCS Dissolved in Pyrrolidinium and Imidazolium Acetate Ionic Liquids.
abstract: The reaction mechanisms of CO2 and its isoelectronic molecules OCS and CS2 dissolved in N-butyl-N-methylpyrrolidinium acetate and in 1-butyl-3-methylimidazolium acetate were investigated by DFT calculations in "gas phase". The analysis of predicted multistep pathways allowed calculating energies of reaction and energy barriers of the processes. The major role played by the acetate anion in the degradation of the solutes CS2 and OCS as well as in the capture of OCS and CO2 by the imidazolium ring is highlighted. In both ionic liquids, this anion governs the conversion of CS2 into OCS and of OCS into CO2 through interatomic S-O exchanges between the anion and the solutes with formation of thioacetate anions. In imidazolium acetate, the selective capture of CS2 and OCS by the imidazolium ring competes with the S-O exchanges. From the calculated values of the energy barriers a basicity scale of the anions is proposed. The (13)C NMR chemical shifts of the predicted adducts were calculated and agree well with the experimental observations. It is argued that the scenario issued from the calculated pathways is shown qualitatively to be independent from the functionals and basis set used, constitute a valuable tool in the understanding of chemical reactions taking place in liquid phase.
authors.affiliation: Institut des Sciences Moléculaires, CNRS (UMR 5255), Université Bordeaux , 351 Cours de la Libération 33405 Talence Cedex, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Danten
authors.affiliation: Centro de Física Atómica, Universidade de Lisboa , Avenida Professor Gama Pinto 2, 1694-003 Lisboa Codex, Portugal.|Departamento de Física, Instituto Superior Técnico , UTL, Avenida Rovisco Pais 1049-001 Lisboa, Portugal.
authors.forename: M I
authors.initials: MI
authors.lastname: Cabaço
authors.affiliation: CICECO, Departamento de Química, Universidade de Aveiro 3810-193 Aveiro, Portugal.
authors.forename: J A P
authors.initials: JA
authors.lastname: Coutinho
authors.affiliation: Institut des Sciences Moléculaires, CNRS (UMR 5255), Université Bordeaux , 351 Cours de la Libération 33405 Talence Cedex, France.
authors.forename: Noël
authors.initials: N
authors.lastname: Pinaud
authors.affiliation: Institut des Sciences Moléculaires, CNRS (UMR 5255), Université Bordeaux , 351 Cours de la Libération 33405 Talence Cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: Besnard