A Clock Reaction Based on Molybdenum Blue
Author(s)Neuenschwander, Ulrich; Negron, Arnaldo; Jensen, Klavs F.
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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.
DepartmentMassachusetts Institute of Technology. Department of Chemical Engineering
The Journal of Physical Chemistry A
American Chemical Society (ACS)
Neuenschwander, Ulrich, Arnaldo Negron, and Klavs F. Jensen. “A Clock Reaction Based on Molybdenum Blue.” The Journal of Physical Chemistry A 117, no. 21 (May 30, 2013): 4343–4351.
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