Knowledge Bank

Recent interest in $SH(D)$ derivatives of $BCl3$ prompted a vibrational study of $BCl2SH$ and $BCl2SD$. Raman spectra of the liquid and gas phases were recorded from 100 to 2700 $cm-1$. Infrared spectra of the vapors were recorded from 200 to 2700 $cm-1$. All nine fundamentals were observed and assigned for both molecules. The observation of 7 polarized and 2 depolarized Raman bands confirm the planar configuration. The infrared vapor spectra showed the fundamental and three ``hot” bands of the SH(D) torsional vibration. A comparison of our spectral results with an earlier study is presented. The structure of the infrared torsional band allowed calculation of the barrier toward internal rotation. Barrier values of 11.8 and 12.4 Kcal/mol $(1Kcal/mol=4.184kJ/mol)$ were calculated for the protonated and deuterated molecules, respectively, utilising the $V=(V2/2)(1-cos2\phi )$ potential. Potential barrier values of 10.2 and 9.9 $Kcal/mol$ were obtained with the quartic potential, $V=A(z4+Bz2)$. The potential barrier calculations, utilizing two different potential functions, afforded an evaluation of the choice of potentials for double minimum systems with high barriers. A barrier of about $12\pm 1$ Kcal/mol is estimated for this species. Thermodynamic functions were also calculated.