Hydroxy Mercapto Methylene: The Missing H2CSO Isomer

Markus Schauermann and Peter R. Schreiner
J. Phys. Chem. Lett.2022, 13, 3138–3142. DOI: 10.1021/acs.jpclett.2c00344.

We report the isolation of hydroxy mercapto methylene (HO–C̈–SH) under cryogenic conditions via pyrolysis of 2-ethoxy-2-thioxo-acetic acid. The two most stable carbene rotamers form via extrusion of ethylene and CO₂ from this precursor. This donor-stabilized carbene represents a hitherto uncharacterized CH₂SO species and the first spectroscopically characterized free mercapto carbene. CCSD(T)/cc-pVTZ computations support our findings.