Theoretical studies on the oxetane⋯HCl and thietane⋯HCl complexes

The oxetane⋯HCl and thietane⋯HCl complexes have recently been studied by rotational spectroscopy in a supersonic jet. In this Letter we report on stability, axial, and equatorial HCl arrangement in the complexes studied by means of MP2 calculations. The shape of the potential functions was studied for the ring-puckering and HCl inversion motions. For the oxetane complex, the barrier of the ring-puckering is small enough to be overcome by the ring-puckering vibration. For the thietane complex, the analogous barrier is higher than the vibration energy. Therefore, one oxetane and two thietane complex conformations were observed in the experiment.