Rotational Spectra, Molecular Structure, and Electric Dipole Moment of Propanethial S-Oxide

Abstract

Pulsed-beam Fourier transform microwave spectroscopy was used to study propanethial S-oxide (1), an unstable species generated in a (Z)/(E) ratio of 98/2 by pyrolysis of 2-methyl-2-propyl-1′-propenyl vinyl sulfoxide at 350°C in Ar or Ne/He gas flows. A fit of 25 transition frequencies to a Watson "A" reduced Hamiltonian gave the following rotational constants and centrifugal distortion constants for the normal isotopomer of (Z)-1a: A ) 10 182.2558 (3) MHz, B ) 2209.5000(9) MHz, C ) 1997.1734(8) MHz, ∆ JK ) -62.69(2) kHz, ∆ J ) 4.165(3) kHz, δ J ) 0.3336(3) kHz and δ K ) -31.7(4) kHz. Twelve transitions were fit in the same manner for (E)-1b to give A ) 16231(86) MHz, B ) 1823.6154(7) MHz, C ) 1785.7215 (7) MHz, ∆ JK ) -12.5(5) kHz, ∆ J ) 0.48(1) kHz, δ J ) -0.060(8) kHz. Microwave spectra of six (Z) isotopomers were assigned and a partial substitution structure was derived: r(CdS) ) 1.585(6) Å, r(SsO) ) 1.473(2) Å, r(dCHsCH 2 ) ) 1.513(7) Å, r(CH 3 sCH 2 ) ) 1.536(3) Å, θ(CSO) ) 113.8(2)°, θ(CCS) ) 126.7(3)°, and φ(CCCS) ) 118.4°. The electric dipole moment components of the (Z) isomer along the a, b, and c principal axes were measured to be µ a ) 2.59(2) D, µ b ) 2.11(2) D, and µ c ) 0.33(6) D, respectively, which gives a total electric dipole moment of 3.35(2) D.

Blue‐shifted H‐bond in aromatic sulfines: An ab initio calculation

“…For each of the Z and E isomers, Table I presents the relative energies. As shown in Table I, in all compounds, Z isomers (as the major product) are more stable than E ones, in good agreement with the experimental results 9–11. The obtained results in Table I show that the conformer 2(Z) is more stable than its rotated form 2(Z)′.…”

“…The stability and Z/E interconversion of some of the aromatic and aliphatic thioaldehyde S ‐oxides have been investigated experimentally by NMR technique 9. Gillies et al have studied rotational spectra, molecular structure, and electric dipole moment of propanethial and ethanethial S ‐oxides by pulsed‐beam Fourier transform microwave spectroscopy 10, 11. The experimental and theoretical studies have identified that the Z isomer of thial S ‐oxides is more stable than the E one 1, 9–12.…”

More reliable partial atomic charges when using diffuse basis sets

“…Our data set of experimental dipole moments has been assembled from several different sources and compilations. [60][61][62][63][64][65][66][67][68] For molecules where an experimental dipole moment is used, except for molecules containing Li and P, mPW1PW91 69 / MIDI! 70,71 geometries were used.…”

Computational determination of the enthalpy of formation of alkylthial S-oxides and alkylthione S-oxides: a study of (Z)-propanethial-S-oxide, the lachrymatory factor of the onion (Allium cepa)

“…5 Very few thermochemical properties are known for the higher members in the series 3 and even the geometrical structure of propanethial S-oxide (1) was determined experimentally only in recent times. 6 Very recently, Shen and Parkin 7 developed a system that allows the generation of pure thiosulfinates and propanethial S-oxide, 1, thus ensuring that this family of compounds will receive much more attention in the next few years. Our purpose in this connection will be the determination of thermochemical properties which may help in the follow up of the complicated chemical reactions observed in freshly prepared Allium extracts.…”

“…None of these reactions is directly useful however, because the necessary experimental data for propanethial (3), ethanethial S-oxide (6), or propanethione (9) are not available. Therefore, we need a general scheme to calculate the missing data, at the same time that we get an estimation of the error involved.…”