Abstract

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. It is experimentally shown that these peroxy 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, followed by O₂ addition, 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.