Conformational Equilibria and Molecular Structures of Model Sulfur-Sulfur Bridge Systems: Diisopropyl Disulfide

The conformations and molecular structures of diisopropyl disulfide have been studied by high-resolution microwave spectroscopy and quantum chemical calculations. Three conformers, G'GG', G'GT, and GGG', have been observed in the jet expansion. The global minimum, G'GG', adopts a configuration with the G' orientation of H-C-S-S and S-S-C-H and the G orientation of C-S-S-C showing the C₂ symmetry. The rotational spectra of monosubstituted ¹³C and ³⁴S isotopologues have also been recorded for G'GG', leading to an accurate structural determination of this conformer. Two additional ³⁴S isotopologues have also been measured for G'GT. The relative energies of three observed conformers calculated at the MP2/6-311++(d,p) level of theory are within 2 kJ mol^-1, while the relative intensity measurements suggested their population ratio to be N/N/N ≈ 5:3:2.