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The far-infrared spectra of ON 35 Cl and ON 37 Cl were recorded from 20 to 100 cm −1 at a resolution of 0.004 cm −1 . Thirteen pure rotational Q branches were assigned for each molecule in the ground vibrational state from which the rotational constants A and the distortion constants φ K and φ K were obtained utilizing previously reported values of the constants B and C from microwave studies. Rotational Q branches were also observed for both molecules in two vibrationally excited states. Ab initio calculations up to those using fourth-order perturbation (MP4) with configuration interaction utilizing the 6-31G* basis set were carried out. Optimized geometries obtained at this level are compared with those obtained with smaller basis sets without configuration interaction and with the experimentally determined values. Force constants were calculated which are compared with the values previously reported. The potential energy distributions and quartic distortion constants were obtained at all levels of ab initio calculations up to MP2/6-31G*.

The infrared spectrum at a resolution of 0.06 cm−1 has been recorded for vinylsilane. Vibrational-rotational analysis has been carried out on ν6, ν13, ν15, and the strongly coupled pair of ν12 and ν19. The rotational constants and some of the distortion constants have been determined for ν6, ν13, and ν15, whereas higher resolution of 0.004 cm−1 was required to obtain similar data from the coupled pair of ν12 and ν19. These data are compared to the ground state constants previously obtained from the microwave spectrum.

The Raman and IR spectra of diallyl sulfide and diallyl disulfide in the liquid and solid state are reported and examined in order to determine their most stable conformations. In both the liquid and solid state, the allyl moieties in both molecules are in a “gauche” conformation in which the sulfur atoms and the terminal vinyl carbons probably form a dihedral angle of between 105° and 120°. In the liquid state, there are two possible S-S rotational conformers of diallyl disulfide. The “gauche” conformer with a C-S-S-C dihedral angle of approximately 70° is 242±24 cal mol−1 more stable than the “near-cis” conformer which probably has a C-S-S-C dihedral angle of approximately 25°. Only the “gauche” S-S rotational conformer of diallyl disulfide exists in the solid state. Additionally, in the liquid state, there are two C-S rotational conformers for each molecule. The “gauche” conformer corresponds to a C-C-S-C (diallyl sulfide) or C-C-S-S (diallyl disulfide) dihedral angle of 70° and the “trans” conformer corresponds to a C-C-S-C or C-C-S-S dihedral angle of 180°. For diallyl sulfide the “trans” C-S conformer is 260±26 cal mol−1 more stable than the “gauche” C-S conformer while for diallyl disulfide the “gauche” C-S conformer is 358±20 cal mol−1 more stable than the “trans” C-S conformer. In the solid state, both C-S conformers exist for diallyl sulfide but only the “gauche” C-S conformer exists for diallyl disulfide.