Microwave spectrum, barrier to internal rotation, structure, and dipole moment of methane selenol

The microwave spectra of the ground state and excited torsional states of several isotopic species of methane selenol have been observed. The barrier hindering internal torsion has been determined to be 1001±50 cal/mole. The structural parameters are C–Se= 1.959 Å, Se–H= 1.473 Å, C–H= 1.088 Å, ∠C–Se–H= 95.45°, ∠H–C–H= 110.00°, with the symmetry axis of the methyl group tilted 1.5° away from the C–Se internuclear line. The dipole moment components are μA=1.253 D, μB=0.314 D, μtotal=1.291 D. The implications of this barrier height determination for theories on the orgin of the barrier are discussed.