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The microwave spectrum of (CH3)3SiCl and its isotopic species (CH3)3Si37Cl, (CH3)329SiCl, (CH3)330SiCl, and (13CH3)(CH3)2SiCl has been studied in the frequency range of 3 to 40 GHz. The barrier to internal rotation, the chlorine quadrupole coupling, and the structure were determined. Ab initio calculation were compared with the experimental results. [Copyright &y& Elsevier]

The rotational spectrum of 1-chloro-2-methylpropene has been measured with very high resolution using pulsed molecular-beam Fourier transform microwave (MB-FTMW) spectrometers in the range from 3 to 40 GHz. The analysis yielded accurate rotational constants, centrifugal distortion constants, the complete (35)Cl and (37)Cl quadrupole coupling tensors, and the V(3) hindering barriers of both methyl rotors. These results supplement and improve previous observations made with waveguide microwave and infrared spectroscopy under considerably lower resolution. Moreover, a potential surface depending on the two angles of internal rotation was calculated using ab initio methods. This enabled us to compare theoretical and experimental potential barriers and to obtain information on higher potential terms and top-top interaction constants, which were not available from the experimental data alone. Copyright 2000 Academic Press.

The rotational spectrum of aniline-methanol was investigated in the frequency region 3-19 GHz using a pulsed molecular beam Fourier transform microwave spectrometer. Sixty-three measured a- and b-type transitions show a fine structure due to internal rotation of the methyl group. The resulting A and E lines are additionally split into hyperfine components arising from quadrupole coupling of the (14)N nucleus. The torsional motion of the methyl group is hindered by an effective barrier V(3) of nearly 215 cm(-1), which is almost one-half of the methanol barrier height. The structure of the complex was calculated assuming a common symmetry plane for the monomers. These form a linear N vertical ellipsis H-O hydrogen bond. Its distance was found to be 3.03 Å, which is identical with that of aniline-water. Copyright 1999 Academic Press.

The ground state rotational spectra of SiH3CN and its 29Si, 30Si, 13C, 15N, d1, d2, and d3 isotopic species have been measured by Fourier transform microwave spectroscopy and by millimeterwave spectroscopy. Accurate rotational, centrifugal distortion, and 14N and D nuclear quadrupole coupling constants have been derived. The dipole moment of the parent species has also been measured, µ = 3.4400(42) D. The structure, force field, dipole moment, and nuclear quadrupole coupling constants have been calculated ab initio at the SCF, MP2, and B3LYP levels using triple zeta polarized basis sets. The experimental ro, rs, and rz structures have been determined. An approximate equilibrium structure has been obtained by combining the experimental results and the ab initio calculations: re(C&tbond;N) = 1.159 Å, re(Si&sbond;C) = 1.848 Å, re(Si&sbond;H) = 1.470 Å, and angle(HSiC) = 107.4 degrees. Copyright 1998 Academic Press.

The rotational spectra of aniline-water and its 18O isotopomer have been studied in the microwave region between 3 and 26.5 GHz using a pulsed molecular beam FT microwave spectrometer. The spectra were described in terms of a centrifugally distorted asymmetric rotor. Assuming a linear hydrogen NellipsisH-O bond and that the water molecule was located in the symmetry plane of aniline, two structures turned out to be possible. In structure (I) the free water proton is directed toward the aniline ring. In structure (II) the proton is bent away from it. Ab initio calculations indicate that only structure (I) is supported by the experimental results. Copyright 1998 Academic Press.