Excited-State Chemistry of Hydroperoxymethyl Thioformate in the Troposphere

Dimethyl sulfide (DMS; CH₃SCH₃) is a gas produced by phytoplankton in the ocean and emitted into the atmosphere. DMS emission is the largest source of atmospheric sulfur. Hydroperoxymethyl thioformate (HPMTF) is an oxidation product of DMS in the marine atmosphere. While the formation pathways of HPMTF are well established, the atmospheric removal processes have yet to be fully characterized. Here, we study the photochemistry of HPMTF using computational methods. Our results indicate that HPMTF photolysis is efficient (high quantum yield, ϕ = 0.67), primarily proceeding via S–C bond cleavage in the thioformate (−SCHO) group. However, it is limited by the weak absorption of UV–vis solar radiation, resulting in a long photolytic lifetime (τ ≈ 30 h). Therefore, photolysis is expected to represent a minor sink for atmospheric HPMTF.