INFRARED AND RAMAN SPECTRA OF GASEOUS, LIQUID, AND SOLID METHYL AND METHYL-$d_{3}$ VINYL SULFIDE AND THE CONFORMATIONAL STABILITY IN THE GAS PHASE

Author Institution: Department of Chemistry, University of South CarolinaThe Raman spectra $(3500-40 cm^{-1})$ of gaseous, liquid, and solid methyl and methyl-$d_{3}$ vinyl sulfide, $CH_{2}CHSCD_{3}$, have been recorded, and assignments are provided for the observed bands. From a temperature study of the Raman spectrum of the ""light"" compound, the enthalpy difference between the low energy s-cis conformer and the high energy gauche conformer was found to be $750 \pm 68 cm^{-1} (2.14 \pm 0.19 kcal/mol)$. The far infrared spectra of both $CH_{2}CHSCH_{3}$ and $CH_{2}CHSCD_{3}$ have been collected at a resolution of $0.1 cm^{-1}$ for the gases and $1.0 cm^{-1}$ for the solids. The potential function governing the asymmetric torsion in the gas phase has been determined and the s-cis/gauche, gauche/gauche, and gauche/s-cis barriers are 1803 (5.15 kcal/mol), 508 (1.45 kcal/mol), and $1022 cm^{-1} (2.92 kcal/mol)$, respectively. The dihedral angle for the gauche conformer was determined to be $132^{\circ}$. The barriers to internal rotation of the methyl group have been determined for both conformers in both the gas and solid states