Vibrational Spectra and Molecular Conformations of Dialkyl Disulfides

The infrared and Raman spectra of several dialkyl disulfides were measured and their conformations were discussed in relation with the characteristic S–S and C–S stretching vibrations. The infrared spectra in the solid state and the temperature dependence of Raman spectra were measured for ethyl methyl disulfide and diethyl disulfide. For ethyl methyl disulfide, the gauche-gauche isomer was more stable than the trans-gauche isomer by about 0.9 kcal/mol while for diethyl disulfide the gauche-gauche-gauche isomer was more stable than the trans-gauche-gauche isomer by about 0.6 kcal/mol in the liquid state. Only the gauche-gauche form for ethyl methyl disulfide and only the gauche-gauche-gauche form for diethyl disulfide were observed in the solid state.