Determination of a High Potential Barrier Hindering Internal Rotation from the Microwave Ground State Spectrum The Methylbarrier of Antiperiplanar and Synclinal Normal Propyl Fluoride

Abstract

The microwave ground state spectra of antiperiplanar and synclinal normal propyl fluoride have been measured by microwave Fourier transform spectroscopy and analysed for methyl torsion fine structure. Additionally, the spectrum of the synclinal form in the first excited state of the methyl group has been investigated due to methyl torsion. The difference of the values determined for the barrier heights in the ground and first excited state of the synclinal form is discussed by an approximate treatment of the coupling of CH3 and C - C torsional motions. As high J transitions were measured a centrifugal distortion analysis was necessary.