Spectroscopic Characterization and Photochemistry of the Atmospherically Relevant Methanesulfenic Acid.

Methanesulfenic acid, CH 3 SOH, 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 CH 3 SOH in Ar- and N 2 -matrices at 10 K. The characterization of CH 3 SOH with matrix-isolation IR and UV-vis spectroscopy is supported by D and 13 C isotope labeling experiments and quantum chemical calculations. In line with the observed absorption at 260 nm for CH 3 SOH, its photolysis at 254 nm leads to dissociation by yielding the novel water complex H 2 CS···H 2 O, which exhibits a five-membered ring structure with intermolecular S···HO and CH···O hydrogen bonding interactions. Upon further irradiation at 193 nm, the H 2 CS···H 2 O complex undergoes dehydrogenation to form CS···H 2 O, which can further convert to HC(O)SH under irradiation at 254 nm. When the photolysis of CH 3 SOH was performed in an O 2 -doped Ar-matrix, methanesulfonic acid (MSA, CH 3 SO 3 H) was obtained as the oxidation product.