The Experts below are selected from a list of 39 Experts worldwide ranked by ideXlab platform
Milan Remko - One of the best experts on this subject based on the ideXlab platform.
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gas phase binding of li na and mg2 to formaldehyde acetaldehyde and their silicon and sulfur analogs a theoretical study by means of ab initio molecular orbital methods at the g2 level of theory
Chemical Physics Letters, 1997Co-Authors: Milan RemkoAbstract:Abstract Ab initio molecular orbital methods at the G2 level of theory have been used to study the structure and gas-phase bonding of Li + , Na + and Mg 2+ to formaldehyde, acetaldehyde, silanone, methylsilanone, thioformaldehyde and Thioacetaldehyde. Calculated interaction energies vary as Mg 2+ > Li + > Na + . Absolute values of gas-phase interaction energies computed by the G2, G2(MP2) and G1 methods were comparable in accuracy. The binding energies evaluated by these three methods are in good agreement with experimental data.
łukasz Albrecht - One of the best experts on this subject based on the ideXlab platform.
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enantioselective synthesis of spirocyclic tetrahydrothiophene derivatives bearing a benzofuran 3 2h one scaffold unusual supramolecular crystal structure with high z
Tetrahedron Letters, 2016Co-Authors: Dorota Kowalczyk, Jakub Wojciechowski, łukasz AlbrechtAbstract:Abstract Herein, we report our studies on the enantioselective synthesis of spirocyclic tetrahydrothiophene derivatives bearing a benzofuran-3(2 H )-one scaffold. The developed method utilizes 2-arylidenebenzofuran-3(2 H )-ones and 2-Thioacetaldehyde, generated in situ from 1,4-dithiane-2,5-diol, as starting materials and proceeds in a cascade manner involving a thio-Michael-aldol reaction sequence. The absolute configuration of the obtained tetrahydrothiophenes was assigned by single crystal X-ray analysis. Unusually high Z′ crystal packing was found in the crystal.
Margulès L. - One of the best experts on this subject based on the ideXlab platform.
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SUBMILLIMETER WAVE SPECTRUM OF Thioacetaldehyde AND ITS SEARCH IN SgrB2
'International Symposium on Molecular Spectroscopy', 2017Co-Authors: Margulès L.Abstract:Sulfur chemistry in the interstellar medium is clearly misunderstood, the tenth most abundant element in the Galaxy, it is depleted in molecular clouds by a factor of 1000 footnote{A. Tieftrunk; {em et al.}, 1994, {em A&A}~{bf289}, 579}. This suggests that sulfur chemistry is important on icy grain mantles, and that sulfur-bearing molecules may be not detected yet due to the lack of laboratory data. The present study is about Thioacetaldehyde (CH$_3$CHS), the analog of acetaldehyde._x000d_ Previously, the rotational spectra were recorded up to 40 GHz footnote{H. Kroto; {em et al.}, 1974, {em Chem. Phys. Lett.}~{bf29}, 265},footnote{H. Kroto; {em et al.}, 1976, {em J. Mol. Spectrosc.}~{bf62}, 346}. New spectra were recorded from 150 to 660 GHz using the Lille solid-state based spectrometer. The new fast version of the spectrometer using DDS component is particulary suitable for reactive species like Thioacetaldehyde. Thioacetaldehyde was produced in-situ by pyrolisis at 750$^{circ} {rm C}$ and introduced in a 1m long pyrex cell in a flow mode. _x000d_ Analysis of the spectra is not obvious, like in acetaldehyde, as this molecule exhibits internal rotation of the methyl group. The internal rotation barrier is higher in Thioacetaldehyde, 542 cm-1, than in acetaldehyde, 408 cm-1. However, the coupling between the internal rotation and the overall rotation in Thioacetaldehyde is strong, the coupling parameter $rho$ value is 0.261 just slightly smaller than the acetaldehyde value of 0.329. The spectroscopic results and its searches in SgrB2 will be presented.\_x000d_ em{This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI. This work was also done under ANR-13-BS05-0008-02 IMOLABS
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THZ SPECTROSCOPY OF SULFUR DERIVATIVES OF ASTROPHYSICAL INTEREST
International Symposium on Molecular Spectroscopy, 2026Co-Authors: Margulès L.Abstract:About 200 molecules have thus far been detected in the interstellar medium. Twenty-two are sulfur-bearing chemical compounds (and analogues of oxygenated species), making sulfur the tenth most abundant element in the galaxy. We report here the sub-THz spectroscopic observations of two reactive species: Thioacetaldehyde (\chem{CH_3CHS}) and \chem{NS^+}.\footnote{Cernicharo J.; {\em et al.}, 2018, {\em ApJL}~{\bf L22}, 852} The latter new cation has been firmly detected for the first time towards many interstellar sources (cold molecular clouds, pre-stellar cores and shocks) using the IRAM-30m radiotelescope. Although a recent study of the chemistry of sulfur in cold dense clouds has been carried out \footnote{Fuente A.; {\em et al.} {\em A\&A}~{\bf 593}, (2016) A94} the formation pathways of the sulfur species are still misunderstood. \\ The rotational spectrum of \chem{CH_3CHS} was previously recorded up to 40~GHz.\footnote{H. Kroto; {\em et al.}, 1976, {\em J. Mol. Spectrosc.}~{\bf 62}, 346} New measurements performed up to 660~GHz represent a significant extension in terms of frequency range and analysis. The final spectroscopic analysis, including the internal rotation treatment, and searches for it towards SgrB2 and other sources will be presented. \\ \\ \footnotesize{Acknowledgements: These results were supported by the Programme National PCMI of CNRS/INSU, the French National Research Agency (ANR-13-BS05-0008 ”IMOLABS”), the CaPPA project (ANR-11-LABX-0005-01), the spanish MINECO (grants AYA2012-32032, AYA2016- 75066-C2-1-P, CSD2009-00038 and RyC-2014-16277) and the European Research Council (grant ERC- 2013-SyG 610256, NANOCOSMOS). Kharkov group acknowledge support of the Volkswagen foundation and assistance of the Science and Technology Center in Ukraine (STCU partner project P686).
Dorota Kowalczyk - One of the best experts on this subject based on the ideXlab platform.
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enantioselective synthesis of spirocyclic tetrahydrothiophene derivatives bearing a benzofuran 3 2h one scaffold unusual supramolecular crystal structure with high z
Tetrahedron Letters, 2016Co-Authors: Dorota Kowalczyk, Jakub Wojciechowski, łukasz AlbrechtAbstract:Abstract Herein, we report our studies on the enantioselective synthesis of spirocyclic tetrahydrothiophene derivatives bearing a benzofuran-3(2 H )-one scaffold. The developed method utilizes 2-arylidenebenzofuran-3(2 H )-ones and 2-Thioacetaldehyde, generated in situ from 1,4-dithiane-2,5-diol, as starting materials and proceeds in a cascade manner involving a thio-Michael-aldol reaction sequence. The absolute configuration of the obtained tetrahydrothiophenes was assigned by single crystal X-ray analysis. Unusually high Z′ crystal packing was found in the crystal.
Niño A. - One of the best experts on this subject based on the ideXlab platform.
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Dynamical and spectroscopic studies of nonrigid molecules. Application to the visible spectrum of Thioacetaldehyde
'AIP Publishing', 2020Co-Authors: Smeyers Y. G., Niño A., Moule D. C.Abstract:10 pags., 9 figs., 7 tabs.The methyl torsion and aldehydic hydrogen wagging modes are studied theoretically in Thioacetaldehyde, in both ground and first triplet excited states. For this purpose, the potential energy surfaces were determined by ab initio restricted Hartree Fock and unrestricted Hartree Fock calculations with 4-31 basis set + d orbitals on the sulphur atom. The two electronic states were found to have different preferred conformations. The singlet state exhibits a planar eclipsed conformation, whereas the structure of the triplet state is anti-eclipsed and pyramidal. It was found that a potential function, which was constructed from a symmetry adapted double Fourier expansion of the wagging and torsional coordinates, gave a reasonable fit to the energy points. The two-dimensional Schrödinger equations for the torsion and wagging motions were solved for both singlet and triplet states, taking into account the internal symmetry and the appropriate basis. The relative band locations and the intensities (Franck-Condon factors) were evaluated from the eigenvalues and the eigenvectors. Spectra were calculated for the Thioacetaldehyde CH 3CHS/CH3CDS/CD3CHS/CD3CDS isotopomers. New assignments for the higher bands in the CH3CHS spectrum are proposed. © 1990 American Institute of Physics
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An analysis of the methyl rotation and aldehyde wagging dynamics in the S0 (X̃ 1A′) and T1 (ã3A″) states of Thioacetaldehyde from pyrolysis jet spectra
'AIP Publishing', 2020Co-Authors: Moule D. C., Smeyers Y. G., Bascal H. A., Clouthier D. J., Karolczak J., Niño A.Abstract:9 pags., 7 figs., 5 tabs.Jet-cooled, laser induced phosphorescence (LIP) excitation spectra of Thioacetaldehyde (CH3CHS, CH3CDS, CD3CHS, and CD3CDS) have been observed in the 15 800-17 300 cm-1 region in a continuous pyrolysis jet. The responsible electronic transition, T1 ← S0, ã3A″ ← X̃ 1A′, results from an n → π* electron promotion and gives rise to a pattern of vibronic bands that can be attributed to activity of the methyl torsion and the aldehyde hydrogen out-of-plane wagging modes. Potential and kinetic energy surfaces were mapped out for the aldehyde wagging (α) and the torsional (Θ) internal coordinates by using 6-31G* Hartree-Fock calculations in which the structural parameters were fully relaxed. The potential and kinetic energy data points were fitted to double Fourier expansions in α and Θ and were incorporated into a two-dimensional Hamiltonian operator. The spectrum was simulated from the transition energies and the Franck-Condon factors and was compared to the observed jet cooled LIP spectra. It was concluded that while the RHF procedure gives a good description to the ground state dynamics, the triplet state surface generated by the UHF method is too bumpy and undulating. © 1992 American Institute of Physics.D.C.M. and H. B. would like to thank the Natural Sciences and Engineering Research Council of Canada for financial support of this work. D.l.C. and 1.K. acknowledge the support of the National Science Foundation through Grant No. CHE-8914403. Y. G. S. and A. N. wish to thank the Comision Interministerial de Ciencias y Technologia for economic support through Grant No. PB 90- 0167