title: Influence of Solvation and Dynamics on the Mechanism and Kinetics of Nucleophilic Aromatic Substitution Reactions in Liquid Ammonia.
abstract: The role of the solvent and the influence of dynamics on the kinetics and mechanism of the SNAr reaction of several halonitrobenzenes in liquid ammonia, using both static calculations and dynamic ab initio molecular dynamics simulations, are investigated. A combination of metadynamics and committor analysis methods reveals how this reaction can change from a concerted, one-step mechanism in gas phase to a stepwise pathway, involving a metastable Meisenheimer complex, in liquid ammonia. This clearly establishes, among others, the important role of the solvent and highlights the fact that accurately treating solvation is of crucial importance to correctly unravel the reaction mechanism. It is indeed shown that H-bond formation of the reacting NH3 with the solvent drastically reduces the barrier of NH3 addition. The halide elimination step, however, is greatly facilitated by proton transfer from the reacting NH3 to the solvent. Furthermore, the free energy surface strongly depends on the halide substituent and the number of electron-withdrawing nitro substituents.
authors.affiliation: Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB) , Pleinlaan 2, 1050 Elsene, Brussels, Belgium.
authors.forename: Samuel L C
authors.initials: SL
authors.lastname: Moors
authors.affiliation: Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB) , Pleinlaan 2, 1050 Elsene, Brussels, Belgium.
authors.forename: Ben
authors.initials: B
authors.lastname: Brigou
authors.affiliation: Center for Molecular Modeling (CMM), Ghent University , Technologiepark 903, 9052 Zwijnaarde, Belgium.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Hertsen
authors.affiliation: Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB) , Pleinlaan 2, 1050 Elsene, Brussels, Belgium.
authors.forename: Balazs
authors.initials: B
authors.lastname: Pinter
authors.affiliation: Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB) , Pleinlaan 2, 1050 Elsene, Brussels, Belgium.
authors.forename: Paul
authors.initials: P
authors.lastname: Geerlings
authors.affiliation: Center for Molecular Modeling (CMM), Ghent University , Technologiepark 903, 9052 Zwijnaarde, Belgium.
authors.forename: Veronique
authors.initials: V
authors.lastname: Van Speybroeck
authors.affiliation: Department of Chemistry, Bogazici University , Bebek 34342, Istanbul, Turkey.
authors.forename: Saron
authors.initials: S
authors.lastname: Catak
authors.affiliation: Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB) , Pleinlaan 2, 1050 Elsene, Brussels, Belgium.
authors.forename: Frank
authors.initials: F
authors.lastname: De Proft