Microwave spectrum of toluene - SO*: Structure, barrier to internal rotation, and dipole moment
نویسندگان
چکیده
The microwave spectrum of toluene * SO2 was observed with a pulsed beam Fouriertransform 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 V,=83.236(2) cm-‘. The torsionalrotational spectra of toluene-CD, * SO2 and toluene-ds * SO, 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 SOZ with respect to the aromatic plane. The moment of inertia data show that the two monomer units are separated by R,,=3.370( 1) A, with the SOZ located above the aromatic ring. The projection of the C, axis of SO2 on the aromatic plane makes an angle of 7=47.0( 1)” with the C, axis of toluene. The dipole moment of the complex is pur= 1.869(27) D.
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