Proton‐Assisted Ethylene Hydration in Aqueous Solution

Abstract

Die spezifische Solvens‐Koordination (siehe Bild) ist entscheidend für die Einleitung reaktiver Schritte in der reversiblen Protonen‐vermittelten Hydratation von Ethylen in wässriger Phase. Eine atomistische Beschreibung der Solvatation der reaktiven Spezies wurde durch diese Ab‐initio‐Moleküldynamikstudie möglich.

Speciation of gold in hydrosulphide-rich ore-forming fluids: Insights from first-principles molecular dynamics simulations

“…In a view of statistical thermodynamics, the dynamical fluctuations of waters form the basis of entropy contribution to the free energy. On the other hand, water also directly participates in the chemical reactions such as the ligand exchange and proton transfer reactions (van Erp and Meijer, 2004;Marx, 2006). However, the previous first principles studies employed the traditional quantum chemistry methods (e.g., geometry optimization), which simplified the effects of solvents by inserting several waters around or with empirical continuum models.…”

Acid dissociation mechanisms of Si(OH)4 and Al(H2O)63+ in aqueous solution

“…Furthermore, in the reactions involving proton transfer, the solvents effects are more significant because the solvent (e.g. water) can directly participate in the reactions as reactant or catalyst (van Erp and Meijer, 2004;Marx, 2006). These factors make it necessary to treat the explicitly solvated systems under a finite temperature and by using full quantum mechanical techniques.…”

Elaborating transition interface sampling methods

“…Some progress has been made by using the coordination number as reaction coordinate [28,29], but this ad hoc approach probably only works for specific systems. For instance, we showed that a proton transfer reaction in water depends very sensitively on the angular orientation of the surrounding water molecules [30]. Similarly, the degrees of freedom in a protein are so large that dynamical folding processes are at best only very qualitatively described by order parameters.…”

“…This lack of ergodicity usually shows up in hysteresis in the free energy curves (see e. g. [30,41]), and gives, besides a low transmission coefficient, rise to an additional error in the rate constant estimate.…”

“…Some hidden order parameters can only be discovered by carefully comparing configurations along reactive and unreactive trajectories that are similar in terms of order parameters which at first sight were considered as being the (only) important ones. For instance, the comparison of reactive and unreactive geometries with an almost identical orientation of the reactants showed that precise tetrahedral ordering of the solvent water molecules was an important factor in the hydration reaction of ketones [30]. Although there is currently no systematic way to extract the reaction coordinates from a path ensemble, once a reaction coordinate is postulated based on physical insight it can be tested using committor distributions [13].…”