Knowledge Bank

The infrared and Raman spectra of $CH3NCS$, $CH3SCN$, $CH3CH2NCS$ and $CH3CH2SCN$, as well as $CD3NCS$ and $CD3CD2NCS$, have been recorded for all three phases. The vibrational spectrum of methylisothiocyanate has been interpreted in terms of a ``pseudo"" symmetric top molecule and assigned according to $C3v$ symmetry, whereas the methyl torsion for methylthiocyanate, assigned according to $C3$ symmetry, has been observed and the barrier has been calculated. The vibrational spectra of the ethylthiocyanate and ethylisothiocyanate molecules, which can exist as a mixture of conformers, have been assigned; however, only the vibrational spectrum of the $CH3CH2SCN$ molecule shows evidence of a second conformer. A variable temperature study of the Ramanspectrum of liquid $CH3CH2SCN$ has been carried out in the region of the C-S-C symmetric stretch, and the $\Delta$H has been obtained. Normal coordinate calculations have been carried out on all of these molecules. The force fields will compared among these compounds, as well as among other thiocyanate molecules.