Rotational Spectra of 2, 3, 6-Trifluoropyridine: Effect of Fluorination on Ring Geometry

The ground state rotational spectrum of 2,3,6-trifluoropyridine has been investigated in the 2.0-20.0 GHz region by pulsed jet Fourier transform microwave spectroscopy. The experimental rotational constants are A=3134.4479(2) MHz, B=1346.79372(7) MHz, and C=941.99495(6) MHz. The transitions are so intense that rotational transitions of all mono-C-13 and N-15 isotopologues are measured in natural abundance. The semi-experimental equilibrium rotational constants of the 7 isotopologues were derived by taking account of the anharmonic vibrational corrections, which allowed a semi-experimental determination of the equilibrium structure of 2,3,6-trifluoropyridine.