The Microwave Spectrum of trans-2,3-Dimethyloxirane in Torsional Excited States

Abstract

Abstract The microwave spectrum of trans-2,3-dimethyloxirane (CH3CHOCHCH3) in the excited tor-sional states υ17 = 1 and υ33 = 1 has been measured in the range from 8 to 26 GHz and assigned. An analysis of internal rotation splittings of the observed rotational transitions was performed using the internal axis method (or "combined axis method") with a newly developed program accounting for the top-top coupling. The threefold hindering potential V3 and the direction cosines λ g,i of the internal rotation axes i with respect to the principal inertia axes g are in a good agreement with the ground state values. Additionally, the sixfold hindering parameter V6 was found to be - 0.2600(12) kJ/mol. The value of the parameter V′12 describing the top-top coupling in the potential function (via V′12 sin 3 τ1 sin 3 τ2), was determined to -0.4240(6) kJ/mol.