The microwave spectrum and structure of pentafluoroethane (R125)

The rotational spectra of three isotopic species of pentafluoroethane (R125) (CF3CHF2, 13CF3CHF2 and CF313CHF2) were observed in the region from 4.5 to 18 GHz using a molecular beam Fourier transform microwave spectrometer (MB-FTMW). The rotational and centrifugal distortion constant were determined. The rs (C-C) bond length of the molecule was determined to be 1.517(5) Å. On the inspection of the C-C bond length of seven fluorine substituted ethane (CH3CHnF3-n, CF3CHnF3-nn=0-3), the C-C length has a minimum value for the molecule CH3CF3 among these molecules. The variation of the C-C bond length coincides with the length calculated by the ab initio calculation of the MP2/6-31G(d,p) level. Several c-type transitions have many complex components presumably due to the spin-spin splitting due to fluorine, however the splitting patterns was not analyzed at this time.