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

Abstract

Abstract The microwave spectrum of trans-2,3-dimethyloxirane (CH 3 CHOCHCH 3 ) in the excited tor-sional states υ 17 = 1 and υ 33 = 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 V 3 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 V 6 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 τ 1 sin 3 τ 2 ), was determined to -0.4240(6) kJ/mol.