Internal rotation and barrier height of CCl3 group in trichloromethylbenzene as studied by gas-phase electron diffraction

The molecular structure of gaseous trichloromethylbenzene has been determined from electron diffraction data. An internal rotation of the CCl3 group around the C-C bond was treated as a precession motion. The rotational barrier height of the CCl3 group is 1.3(6) kJ mol(-1), and the minimum of the barrier is at the position such that one of the C-Cl bonds lies on the phenyl plane. The tilt angle of the C-3v symmetry axis is 4.6(14)degrees at the potential minimum position and 3.0(8)degrees at the potential maximum position. The molecular parameters and uncertainties are r(g)(C-C)(ring) = 1.399(1) Angstrom, r(g)(C-H) = 1.096(6) Angstrom, r(g)(C-C) = 1.531(5)Angstrom, r(g)(C-Cl) = 1.784(2) Angstrom, r(g)(C-Cl) = 1.784(2) Angstrom and r(g)(Cl ... Cl) = 2.885(2) Angstrom, where the r(g)(C-C)(ring) is the average value in the ring.