Spectroscopic Characterization and Photochemistry of the Atmospherically Relevant Methanesulfenic Acid.

Methanesulfenic acid, CHSOH, is a fleeting intermediate in the ·OH-initiated oxidation reactions of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) in the atmosphere. Herein, we report the characterization and photochemistry of CHSOH in Ar- and N-matrices at 10 K. The characterization of CHSOH with matrix-isolation IR and UV-vis spectroscopy is supported by D and C isotope labeling experiments and quantum chemical calculations. In line with the observed absorption at 260 nm for CHSOH, its photolysis at 254 nm leads to dissociation by yielding the novel water complex HCS···HO, which exhibits a five-membered ring structure with intermolecular S···HO and CH···O hydrogen bonding interactions. Upon further irradiation at 193 nm, the HCS···HO complex undergoes dehydrogenation to form CS···HO, which can further convert to HC(O)SH under irradiation at 254 nm. When the photolysis of CHSOH was performed in an O-doped Ar-matrix, methanesulfonic acid (MSA, CHSOH) was obtained as the oxidation product.