A conformational and vibrational study of CF(3)COSCH(2)CH(3).

The molecular structure and conformational properties of S-ethyl trifluorothioacetate, CF(3)COSCH(2)CH(3), were determined in the gas phase by electron diffraction and vibrational spectroscopy (IR and Raman). The experimental investigations were supplemented by ab initio (Moller Plesset of second order) and density functional theory quantum chemical calculations at different levels of theory. Both experimental and theoretical methods reveal two structures with C(s) (anti, anti) and C(1) (anti, gauche) symmetries, although there are disagreements about which is more stable. The electron diffraction intensities are best interpreted with a mixture of 51(3)% anti, anti and 49(3)% anti, gauche conformers. This conformational preference was studied using the total energy scheme and the natural bond orbital scheme. In addition, the infrared spectra of CF(3)COSCH(2)CH(3) are reported for the gas, liquid and solid phases as well as the Raman spectrum of the liquid. Using calculated frequencies as a guide, evidence for both C(s) and C(1) structures is obtained in the IR spectra. Harmonic vibrational frequencies and scaled force fields have been calculated for both conformers.

Molecular structure and vibrational spectra of iodotrimethylgermane (GeIMe3) by theory and experiment.

The geometry of iodotrimethylgermane has been determined by experimental and computational methods. Fourier transform infrared spectra have been recorded over a range of temperatures along with the Raman spectrum to obtain comprehensive vibrational data for the fundamental modes. The stretching, rocking, and deformation bands of the methyl groups have been resolved into their components with the aid of low-temperature infrared spectroscopy using Fourier self-deconvolution and curve-fitting methods. The optimized geometries and vibrational harmonic frequencies were calculated by density functional theory methods employing Pople-type basis sets, as well as those with descriptions for an effective core potential describing both germanium and iodine atoms. A scaled quantum mechanical analysis was carried out to yield the best set of harmonic force constants and obtain a transferable set of scale factors that can be applied to the (CH3)(3-)GeX (X = H, Cl, Br, I) series.