Microwave spectrum of toluene⋅SO2: Structure, barrier to internal rotation, and dipole moment

The microwave spectrum of toluene⋅SO2 was observed with a pulsed beam Fourier-transform microwave spectrometer. The spectrum displays a-, b-, and c-dipole transitions. The transitions occur as doublets arising from the internal rotation of the methyl group. The transitions were assigned using the pr...

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Bibliographic Details
Published in:The Journal of chemical physics 1993-03, Vol.98 (5), p.3627-3636
Main Authors: Taleb-Bendiab, Amine, Hillig, Kurt W., Kuczkowski, Robert L.
Format: Article
Language:English
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Summary:The microwave spectrum of toluene⋅SO2 was observed with a pulsed beam Fourier-transform microwave spectrometer. The spectrum displays a-, b-, and c-dipole transitions. The transitions occur as doublets arising from the internal rotation of the methyl group. The transitions were assigned using the principal-axis method (PAM) internal rotation Hamiltonian with centrifugal distortions. Assuming a threefold symmetry for the internal rotation potential, the barrier height was determined as V3=83.236(2) cm−1. The torsional–rotational spectra of toluene-CD3⋅SO2 and toluene-d8⋅SO2 were also assigned. Additional small splittings of the c-dipole transitions for the normal species and toluene-CD3⋅SO2 suggest a reorientation tunneling motion of SO2 with respect to the aromatic plane. The moment of inertia data show that the two monomer units are separated by Rcm=3.370(1) Å, with the SO2 located above the aromatic ring. The projection of the C2 axis of SO2 on the aromatic plane makes an angle of τ=47.0(1)° with the C3 axis of toluene. The dipole moment of the complex is μT=1.869(27) D.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.465069