title: Chemical Equilibria and Kinetics in Aqueous Solutions of Zymonic Acid.
abstract: The chemistry of pyruvic acid is of great interest due to its essential role in metabolism for all life and its role in atmospheric chemistry. Pyruvic acid under a wide range of conditions, including normal storage conditions, will spontaneously dimerize to form zymonic acid. We isolated zymonic acid and, using a variety of 1D and 2D NMR techniques, identified it as a single structure as a solid or dissolved in DMSO. When in aqueous solution, however, we identified a mixture of five different tautomers and hydrates in equilibrium with each other with no single dominant form. The kinetics of this conversion were studied in situ via NMR. The reactivity of the tautomers and hydrates in aqueous solution is investigated and discussed in terms of aqueous reaction mechanisms. There is strong evidence for a direct, reversible conversion from an enol to a geminal diol without passing through a ketone intermediate, which implies the reversible addition of water across a double bond under ambient conditions. Additionally, there is evidence for a base catalyzed lactone ring formation, which is in essence a base catalyzed esterification reaction. The equilibrium between pyruvic acid and its oligomers in aqueous solution is of consequence in the natural environment.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado at Boulder , UCB 215, Boulder, Colorado 80309, United States.|Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder , UCB 215, Boulder, Colorado 80309, United States.
authors.forename: Russell J
authors.identifier: http://orcid.org/0000-0002-2351-2362
authors.initials: RJ
authors.lastname: Perkins
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado at Boulder , UCB 215, Boulder, Colorado 80309, United States.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Shoemaker
authors.affiliation: School of Chemistry and the Physical Organic Chemistry Centre, Cardiff University , Cardiff CF10 3AT, United Kingdom.
authors.forename: Barry K
authors.initials: BK
authors.lastname: Carpenter
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado at Boulder , UCB 215, Boulder, Colorado 80309, United States.|Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder , UCB 215, Boulder, Colorado 80309, United States.
authors.forename: Veronica
authors.identifier: http://orcid.org/0000-0001-5863-8056
authors.initials: V
authors.lastname: Vaida
mesh_terms: D007700:Kinetics; D015394:Molecular Structure; D019289:Pyruvic Acid / Q000737:chemistry*; D012996:Solutions; D014867:Water / Q000737:chemistry
chemical_list: D012996:Solutions; D014867:Water; D019289:Pyruvic Acid