Atmospheric oxidation of carbon disulfide (CS₂)

This contribution investigates primary steps governing the OH-initiated atmospheric oxidation of CS₂. Our approach comprises high-level density functional theory calculation of energies and optimisation of molecular structures as well as RRKM-ME analysis for estimating pressure-dependent reaction rate constants. We find the overall reaction OH + CS₂→ OCS + SH too slow to account for the formation of the reported experimental products. The initial reaction of OH with CS₂proceeds to produce an S-adduct, SCS(OH). Species-formation history for the system OH + CS₂indicates that, the S-adduct represents the most plausible product with a barrier-less addition process and a stability amounting to 48.5 kJ/mol, in reference to the separated reactants. This adduct then undergoes a bimolecular reaction with atmospheric O₂yielding OCS and HOSO, rather than dissociating back into its separated reactants. We also find that further atmospheric oxidation of the C-adduct (if formed) yields two of the major experimental products namely OCS and SO₂. The kinetic analysis provided in this study explains the atmospheric fate of reduced sulfur species, an important S-bearing group in the global cycle of sulfur.