EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

New pathways of the reaction of OH radicals with dimethyl sulfide based on CH3SCH2O2 isomerization

Torsten Berndt1, Wiebke Scholz2,3, Bernhard Mentler2, Lukas Fischer2, Erik Hans Hoffmann1, Andreas Tilgner1, Noora Hyttinen4, Nonne Prisle4, Armin Hansel2,3, and Hartmut Herrmann1
Torsten Berndt et al.
  • 1Atmospheric Chemistry Dept. (ACD), Leibniz Institute for Tropospheric Research (TROPOS), 04318 Leipzig, Germany (
  • 2Institute for Ion Physics and Applied Physics, University of Innsbruck, 6020 Innsbruck, Austria
  • 3IONICON Analytik GmbH, 6020 Innsbruck, Austria
  • 4Nano and Molecular Systems Research Unit, University of Oulu, 90014 Oulu, Finland

Dimethyl sulfide (DMS), produced by marine organisms, represents the most abundant, biogenic sulfur emission into the Earth´s atmosphere. The gas-phase degradation of DMS is mainly initiated by the reaction with the OH radical forming first CH3SCH2O2 radicals from the dominant H-abstraction channel. A fast CH3SCH2O2 isomerization process was proposed as a result of quantum chemical calculations. In the present study, experimental investigations on the product formation from OH + DMS have been conducted in a free-jet flow system at 295 ± 2 K and 1 bar air. Very efficient detection of CH3SCH2O2 isomerization products has been achieved by iodide-CI-APi-TOF measurements allowing to run the reaction for close to atmospheric conditions. It is experimentally shown that the CH3SCH2O2 radicals undergo a two-step isomerization process finally forming a product consistent with the formula HOOCH2SCHO. The isomerization process is accompanied by OH recycling. The rate-limiting first isomerization step, CH3SCH2O2 → CH2SCH2OOH proceeds with k = (0.23 ± 0.12) s-1 at 295 ± 2 K. Competing bimolecular CH3SCH2O2 reactions with NO, HO2 or RO2 radicals are less important for trace-gas conditions over the oceans.  Results of atmospheric chemistry simulations demonstrate the predominance (≥95%) of CH3SCH2O2 isomerization. The rapid peroxy radical isomerization, not yet considered in models, substantially changes the understanding of DMS´s degradation processes in the atmosphere.

How to cite: Berndt, T., Scholz, W., Mentler, B., Fischer, L., Hoffmann, E. H., Tilgner, A., Hyttinen, N., Prisle, N., Hansel, A., and Herrmann, H.: New pathways of the reaction of OH radicals with dimethyl sulfide based on CH3SCH2O2 isomerization, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10345,, 2020


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