THE MICROWAVE SPECTRUM OF TOLUENE$\bullet SO_{2}$: A LOW BARRIER INTERNAL ROTOR

Author Institution: Department of Chemistry, University of MichiganThe microwave spectrum of toluene $\bullet SO_{2}$ has been observed using the FTMW technique. The spectrum displays a-, b- and c-type transitions. The transitions occur as doublets arising from the internal rotation of the methyl group. The transitions were fit using the Principal Axis Method (PAM) internal rotation Hamiltonian with a 3-fold symmetry potential barrier. The barrier height, $V_{3}$, is 85 $cm^{-1}$. The internal rotation spectra of toluene-$CD_{3}\bullet SO_{2}$ and toluene-$d_{8}\bullet SO_{2}$ were also assigned. For structural purposes the m = 0 transitions of toluene$\bullet S^{18}O_{2}$ and toluene$\bullet S^{16}O^{18}O$ were measured. Toluene$\bullet SO_{2}$ has no plane plane of symmetry in its equilibrium geometry. The toluene and $SO_{2}$ planes are approximately parallel; the distance, $R_{cm}$, joining their centers of mass is 3.37 {\AA}. The dipole moment of the complex is 1.87 D