Microwave Investigation of (Z)- and (E)-Ethanethial S-Oxide

Abstract

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.

Microwave structural studies of organoselenium compounds 1. Microwave spectra, molecular structure, and methyl barrier to internal rotation of dimethyl diselenide

“…The spectra of dimethyl diselenide were recorded with a pulsed-beam Fourier transform microwave spectrometer [31]. Dimethyl diselenide is highly toxic and has an extreme stench.…”

The Rotational Spectra, Structure, Internal Dynamics, and Electric Dipole Moment of the Argon–Ketene van der Waals Complex

“…All spectral data reported in this paper were obtained at Rensselaer with a Fourier transform microwave spectrometer described in the literature (5). Pressurized tanks of 1% ketene in argon were used with pulsed solenoid valves to deliver gas pulses into the cavity of the spectrometer.…”

“…Since the zero point energies of the two forms are different, the higher energy form may not be populated in the cold gas pulse and consequently its spectrum may not be seen. A number of examples of this zero point energy effect are known and have been discussed in the literature for complexes (13) and monomers (5). Internal rotation of ketene in the nonplanar configuration exchanges a hydrogen atom for a deuterium atom, which gives two equivalent but nonsuperimposable frameworks.…”

Reinvestigation of the microwave spectrum of (Z)-Ethanethial S-oxide using the RAM approach

“…[1], rotational transitions of the (Z) isomer exhibiting A-E splittings due to the internal rotation of the methyl group were observed and measured. In this reference, a global fit of the A and E states was reported using the program XIAM developed to analyze internal rotation splitting [3].…”

“…But if both A and E species states are floated simultaneously (see Table 2 of Ref. [1]), the standard deviation of the least-square fits for the normal species (Z)-CH 3 CHSO, the (Z)-CH 3 CH 34 SO, the ðZÞ À CH 13 3 CHSO and for (Z)-13 CH 3 CHSO isotopomers are 20.1 kHz (21 lines), 20.6 kHz (20 lines), 6.9 kHz (13 lines) and 2.8 kHz (14 lines) using 9 parameters.…”