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Articles you may be interested inStructure and tunneling dynamics in a model system of peptide co-solvents: Rotational spectroscopy of the 2,2,2trifluoroethanolwater complex A comparison of the properties of 2,2,2-trifluoroethanol and 2,2,2-trifluoroethanol/water mixtures using different force fieldsThe microwave spectra of CF 3 CH 2 OH and CF 3 CH 2 OD have been investigated from 5 to 26 GHz with a pulsed-nozzle Fourier-transform microwave spectrometer and from 26 to 42 GHz with an electric resonance optothermal spectrometer. Tunneling of the OH proton between the two isoenergetic gauche conformations splits the observed transitions into two tunneling components. An effective rotation-tunneling Hamiltonian is used to fit the a-and b-type pure rotational and c-type torsional-rotational transitions for both isotopomers to better than 5 and 13 kHz for the OH and OD forms, respectively. The tunneling splittings determined from the fits for the OH and OD isotopomers are 5868.6952͑16͒ and 208.5037͑42͒ MHz, respectively. A structural analysis using the moments of inertia of the OH and OD isotopomers determines that the hydroxyl hydrogen is directed toward the fluorine with a F•••H separation of 2.561͑1͒ Å and a dihedral angle of ͑CCOH͒ϭ68.97͑6͒°. The observed tunneling splittings are fit to a double-minimum potential, giving gauche-gauche tunneling barriers of 763 and 720 cm Ϫ1 and OH torsional fundamental frequencies of 364 and 271 cm Ϫ1 for CF 3 CH 2 OH and CF 3 CH 2 OD, respectively. The uncertainties shown in parentheses throughout the paper are one standard deviation.

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The millimeter-wave spectra of the unstable halofulminates BrCNO and ClCNO were recorded at room temperature in several frequency intervals between 52 and 230 GHz. Besides rotational transitions in the vibrational ground state, transitions in numerous thermally excited states of the XCN bending mode (X ) Br or Cl) could be observed. The irregular sequence of these satellites indicated that in both molecules, the XCN bending mode is highly anharmonic. Indeed, the XCNO molecules exhibit truly quasilinear behavior. From semirigid bender analyses of the rotational data, the effective potential functions and their barriers to linearity were determined. The barrier heights were found to be 130.82 (56) cm -1 for BrCNO and 166.86 (84) cm -1 for ClCNO, resulting in quasilinearity parameters γ 0 of +0.362 and +0.416, respectively.