Microwave spectrum of perfluoropentanoic acid

The pure rotational spectrum of perfluoropentanoic acid, CF₃CF₂CF₂CF₂COOH, has been measured using a pulsed beam Fourier transform Flygare-Balle type microwave spectrometer in the frequency range of 4-7 GHz. A total of 34 transitions, including a-type and b-type transitions were observed and analyzed. The three rotational constants and two quartic centrifugal distortion constants were determined for the first time. The rotational constants are A = 1063.0518(5) MHz, B = 374.8849(1) MHz, and C = 359.2965(1) MHz. Theoretical predictions from ab initio calculations using MP2/6-311G++(2d, p) and MP2/cc-pVTZ were performed and the results are in reasonably good agreement with experimental values.