Low-Temperature Kinetic Isotope Effects in CH3OH+H -> CH2OH+H2 Shed Light on the Deuteration of Methanol in Space

Abstract

We calculated reaction rate constants including atom tunneling for the hydrogen abstraction reaction CH3OH+H -> CH2OH+H2 with the instanton method. The potential energy was fitted by a neural network, that was trained to UCCSD(T)-F12/VTZ-F12 data. Bimolecular gas-phase rate constants were calculated using microcanonic instanton theory. All H/D isotope patterns on the CH3 group and the incoming H atom are studied. Unimolecular reaction rate constants, representing the reaction on a surface, down to 30 K, are presented for all isotope patterns. At 30 K they range from 4100 for the replacement of the abstracted H by D to ~ 8 for the replacement of the abstracting H to about 2--6 for secondary KIEs. The ${}^{\text{12}}$C/${}^{\text{13}}$C kinetic isotope effect is 1.08 at 30 K, while the ${}^{\text{16}}$O/${}^{\text{18}}$O kinetic isotope effect is vanishingly small. A simple kinetic surface model using these data predicts high abundances of the deuterated forms of methanol.

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Cited by in corpus (3)

• Methoxymethanol Formation Starting from CO-Hydrogenation
• Isotopomer-Specific Carbon Isotope Ratio of Complex Organic Molecules in Star-Forming Cores
• Chemistry of Dark Molecular Clouds