title: A clock reaction based on molybdenum blue.
abstract: Clock reactions are rare kinetic phenomena, so far limited mostly to systems with ionic oxoacids and oxoanions in water. We report a new clock reaction in cyclohexanol that forms molybdenum blue from a noncharged, yellow molybdenum complex as precursor, in the presence of hydrogen peroxide. Interestingly, the concomitant color change is reversible, enabling multiple clock cycles to be executed consecutively. The kinetics of the clock reaction were experimentally characterized, and by adding insights from quantum chemical calculations, a plausible reaction mechanism was postulated. Key elementary reaction steps comprise sigmatropic rearrangements with five-membered or bicyclo[3.1.0] transition states. Importantly, numerical kinetic modeling demonstrated the mechanism's ability to reproduce the experimental findings. It also revealed that clock behavior is intimately connected to the sudden exhaustion of hydrogen peroxide. Due to the stoichiometric coproduction of ketone, the reaction bears potential for application in alcohol oxidation catalysis.
authors: Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.
authors: Ulrich
authors: U
authors: Neuenschwander
authors: Arnaldo
authors: A
authors: Negron
authors: Klavs F
authors: KF
authors: Jensen
mesh_terms: D003511:Cyclohexanols / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry*; D010084:Oxidation-Reduction
chemical_list: D003511:Cyclohexanols; C017541:molybdenum blue; D008982:Molybdenum