10min:

N. SAKAKIBARA, K. FUCHIGAMI, Y. TATAMITANI, T. OGATA, Department of Chemistry, Faculty of Science, Shizuoka University, Shizuoka, Japan 422-8529.

The rotational spectra of CF₃CF₂CH₃ and trans - and gauche -CF₃CH₂OCH₃, constitute alternative compounds to the CFCs, have been studied by microwave spectroscopy. The spectra were measured using Stark modulation and Fourier-transform microwave spectrometers at Shizuoka University. Both molecules exhibited the spectrum due to many excited states of the CF₃ torsion. Accurate rotational constants and quartic centrifugal distortion constants have been obtained for the ground and torsional excited states up to v = 3. The barrier heights to internal rotation of the CF₃ top have been determined for these molecules. Reasonable molecular structures have been derived from the observed rotational constants and were compared with those of ab~initio calculations of GAUSSIAN MP2/6-311G** level.