title: Dissociation mechanism of acetic acid in water.
abstract: The reaction mechanism for acetic acid dissociation in aqueous solution has been investigated by combining the metadynamics method with transition path sampling (TPS). By using collective variables that describe not only the deprotonation of the acid but also the solvation state of the hydronium ion and its distance from the acetate, a reactive trajectory in which stable separated ions were produced was obtained. More transition trajectories were sampled by using the TPS technique, taking the metadynamics trajectory as the initial trajectory. Two different dissociation reaction pathways were determined, one driven by the breaking of an H-bond formed by the water molecule in contact with the hydroxyl and involving the formation of a metastable contact ion pair and the other characterized by a direct transfer of the proton to the solution through an unstable Zundel-ion-like intermediate.
authors.affiliation: Computational Science and Department of Chemistry and Applied Biosciences, ETH Zurich, USI Campus, Via Giuseppe Buffi 13, CH-6900 Lugano, Switzerland. jpark@comas.frsc.tsukuba.ac.jp
authors.forename: Jung Mee
authors.initials: JM
authors.lastname: Park
authors.forename: Alessandro
authors.initials: A
authors.lastname: Laio
authors.forename: Marcella
authors.initials: M
authors.lastname: Iannuzzi
authors.forename: Michele
authors.initials: M
authors.lastname: Parrinello
mesh_terms: D019342:Acetic Acid / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D012995:Solubility; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D019342:Acetic Acid