Vibrational spectra and rotational isomerism of ethanethiol and ethanethiol-D1

Abstract

The infrared spectra of gaseous, liquid, and solid C2H5SD, and the Raman spectrum of the liquid compound are analyzed and the corresponding spectra of C2H5SH were reinvestigated under improved conditions. In the deuterated compound the CH2 rocking vibration does not interact with the SD bending vibration and therefore does not split into vibrations of the conformers. The measurements suggest for gaseous and liquid C2H5SH and C2H5SD the simultaneous presence of the trans and gauche conformers, appearing at room temperature in the ratio of the order of 1:3. In analogy to solid C2H5SH, the exclusive presence of the gauche conformers can be inferred for solid C2H5SD. The spectra reported in the literature for the C2H5SH molecules embedded in matrices at low temperatures permit a similar interpretation. The doublet structure observed for the vibrational bands, not only of pure solid C2H5SH and C2H5SD but also of their solid mixtures, may be due to non-equivalent sites of the unit cell.