Microvawe spectra and ring puckering vibrations in dihydrothiophenes

A re-investigation of the microwave spectra of 2,5- and 2,3-di-hydrothiophene was performed. For the 2,5 isomer lines up to J = 40 were measured for the ground and first five vibrationally excited states of the ring-puckering mode. The centrifugal distortion constants in the ground and excited states show the expected behaviour for a single mininum potential function. For 2,3-dihydrothiophene evidence was found for a Coriolis interaction between the ground vibrational state and the first excited state of the ring-puckering vibration. A preliminary analysis of this effect places the vibrational energy separation ?E01 at 348 ± 4 MHz.