Knowledge Bank

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 slates 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 $MP2/6-311G\ast \ast$ level.