The microwave spectrum of trans-2,3-dimethyloxirane (CH 3 CHOCHCH 3 ) in the excited torsional states u 17 = 1 and v i3 -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 /. g 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 t was found to be -0.2600(12) kJ/mol. The value of the parameter V[ 2 describing the top-top coupling in the potential function (via V[ 2 sin3r! sin3i 2 ), was determined to -0.4240(6) kJ/mol.
Pulsed-beam Fourier transform microwave spectroscopy was used to study ethanethial S-oxide, an unstable species generated in a (Z)/(E) ratio of 97/3 by pyrolysis of 2-methyl-2-propylvinyl sulfoxide at 350°C in Ar or Ne/He gas flows. Rotational transitions of the (Z) normal isotopomer exhibited A-E state splittings due to internal rotation of the methyl group. A global fit of the observed A and E state lines of the (Z) isomer to an internal rotor Hamiltonian gave rotational constants and centrifugal distortion constants of A ) 14237.0861 (5) MHz, B ) 4678.4488 (3) MHz, C ) 3594.8008 (2) MHz, ∆ JK ) -9.43 (55) kHz, ∆ J ) 3.48 (11) kHz, and δ J ) 1.11 (2) kHz and a 3-fold internal rotor barrier of 285.6 (3) cm -1 . No internal rotation splitting was observed for the (E) isomer and a pseudorigid rotor fit of the observed transitions of the normal isotopomer gave A ) 31 128 (27) MHz, B ) 3475.8521 (16) MHz, C ) 3188.4429 (23) MHz, and ∆ J ) 0.49 (12) kHz.Microwave spectra of eight (Z) isotopomers were assigned, and a partial substitution structure was derived: r(CdS) ) 1.618 (3) Å, r(SsO) ) 1.477 (4) Å, r(CsC) ) 1.493 (3) Å, θ(CSO) ) 113.9 (2)°, and θ(CCS) ) 125.4 (2)°. The electric dipole moment components of the (Z) isomer along the a and b principal axes were measured to be µ a ) 2.714 (5) D and µ b ) 1.869 (35)D, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.