Claveau Emily E, Heller Eric R, Richardson Jeremy O, Miliordos Evangelos
Department of Chemistry and Biochemistry, Auburn University, Auburn, Alabama 36849, United States.
Department of Chemistry and Applied Biosciences, ETH Zürich, 8093 Zürich, Switzerland.
J Phys Chem Lett. 2023 Oct 5;14(39):8749-8754. doi: 10.1021/acs.jpclett.3c02274. Epub 2023 Sep 22.
The selective partial oxidation of methane to methanol has been a major chemistry challenge over the past several decades. The reason for this is that the weaker C-H bond of the desired product (methanol) is readily activated by the same catalyst used to activate the stronger C-H bond of methane. Quantum chemical calculations reveal how hydrogen-bonding interactions with the catalyst as well as other electronic and geometric effects slow the unwanted methanol oxidation reaction. Thus, the oxidation of methane (the tortoise in Aesop's fable) becomes faster than methanol (Aesop's hare), increasing the selectivity toward the desired product. Activation barriers are calculated for two different mechanisms (2+2 and radical), and reaction rates for the oxidation of the two molecules are obtained using semiclassical instanton theory to include tunneling effects for the proton transfers. The tunneling effects are shown to accelerate all reactions substantially but do not dramatically affect the selectivity.
