Comment on “Isomerization of the methoxy radical revisited: the impact of water dimers” by B. Bandyopadhyay et al., Phys. Chem. Chem. Phys., 2016, 18, 27728 and “Isomerization of methoxy radical in the troposphere: competition between acidic, neutral and basic catalysts” by P. Kumar, B. Bandyopadhyay et al., Phys. Chem. Chem. Phys., 2017, 19, 278

Abstract

In two recent papers Bandyopadhyay and co-workers studied how atmospheric trace gases catalyze the isomerization of methoxy radical (CH₃O˙) to hydroxymethyl radical (˙CH₂OH). Their second paper extensively discussed the altitude dependence of this catalyzed isomerization. Unfortunately, they did not compare their computed isomerization rates with the abundant kinetic data on the long-established fate of CH₃O˙: reaction with O₂. This Comment shows that the fastest rate they compute for catalyzed isomerization is over one million times slower than the O₂ reaction at all altitudes considered in those papers. Furthermore, we argue that, even if the reaction CH₃O˙ → ˙CH₂OH were to occur, it would not have any atmospheric consequence. This is because the near-exclusive atmospheric fate of both ˙CH₂OH and CH₃O˙ is reaction with O₂ to produce CH₂O + HOO.