The Vibrational Assignment and Rotational Isomerism of n-Propyl Mercaptan

The infrared and Raman spectra of n-propyl mercaptan have been measured and vibrational assignments made with relation to the rotational isomerism. The normal vibration calculation has been carried out in a modified Urey-Bradley force field. In the gaseous and liquid states, TT and GT molecular forms have been confirmed to exist. An appreciable energy difference in the isomers has been found even in the liquid state. The TT form has a lower energy than the GT form. The CH2 hydrogen deformation frequencies of CH2CH2 groups in molecules similar to n-propyl mercatpan have been listed and discussed in relation to their molecular forms.