Studies of Polarized Ethylenes. Part I. Barriers to Rotation Around the Carbon-Carbon Double Bond in 1,1-Bis-alkylthio-ethylenes.

Sandström, Jan; Wennerbeck, Ingegerd; Engels-Henriksen, Lars; Resser, Dag; Rasmussen, S. E.; Sunde, Erling; Sørensen, Nils Andreas

doi:10.3891/acta.chem.scand.24-1191

Cited by 80 publications

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“…The negative ∆S ≠ values correspond to molecules with more polar ground state. 38 Thus, the calculations are in line with the negative ∆S ≠ value found experimentally 19 for symm triazine 1.…”

Section: Resultssupporting

confidence: 85%

“…Conversely, high positive values of the activation enthalpy are attributed to less polar ground state compared to the transition state. 38 It has been shown above that in compound 1, the high negative activation entropy is in good agreement with the calculated results. The ∆S ≠ value in N methyl 2,4,6 trinitroaniline is also rather high and amounts to 39 J mol -1 K -1 .…”

Section: Resultssupporting

confidence: 82%

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Synthesis, structure, and dynamic behavior in solution of arylamino-1,3,5-triazines

2005

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Ten unsymmetrically substituted arylamino 1,3,5 triazines were synthesized and studied by dynamic NMR spectroscopy. The free energies of the hindered rotation ∆G ≠ are in 59-77 kJ mol -1 range. Using difference mode NOE NMR experiments, the structures of the major and minor rotation isomers were proved. The DFT B3LYP/6 31G* calculations were performed. The difference between the calculated rotation barriers and the experimental values obtained by line shape analysis is less than 7.6 kJ mol -1 . The height of the rotation barrier varies in a 18 kJ mol -1 range depending on the substituents in the triazine ring.

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Section: Resultssupporting

confidence: 85%

Section: Resultssupporting

confidence: 82%

Synthesis, structure, and dynamic behavior in solution of arylamino-1,3,5-triazines

2005

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“…In 1,1-bis-methylthio-2,2-diacetyl ethylene and 1,1-bis-methylthio-2,2-dicarbomethoxy ethylene, the S-cis-S trans arrangement of the carbonyl groups with respect to the C-C double bond approximates the EZ conformation. 2 However, in 3-bis(methylthio)methylene-pentane-2,4-dione, which is closely related to the title compound ( Fig. 1), it approximates the EE conformation.…”

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confidence: 92%

Crystal Structure of 3-(1,3-Dithiolan-2-ylidene)pentane-2,4-dione

et al. 2007

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In 1,1-diacetyl ethylenes, three conformations (EE, EZ and ZZ) must be taken into account. In 1,1-bis-methylthio-2,2-diacetyl ethylene and 1,1-bis-methylthio-2,2-dicarbomethoxy ethylene, the S-cis-S trans arrangement of the carbonyl groups with respect to the C-C double bond approximates the EZ conformation. However, in 3-bis(methylthio)methylene-pentane-2,4-dione, which is closely related to the title compound ( Fig. 1), it approximates the EE conformation. 3 The title compound was obtained by the reaction of acetyl acetone with carbon disulfide in the presence of a base, followed by alkylation with 1,2-dibromoethane.To a suspension of KOH (5.6 g, 0.1 mol) in acetonitrile (30 ml) a mixture of acetyl acetone (10 ml, 0.1 mol) and carbon disulfide (0.1 mol, 6.5 ml) was added and stirred for 2 h at room temperature. A solution of 1,2-dibromoethane (8.5 ml, 0.1 ml) in 10 ml acetonitrile was added to this, and stirred for another 24 h. The obtained crude solid was washed with water, evaporated in a vacuum and recrystallized from dichloromethane.Colorless prismatic crystals used for data collection were obtained by slow evaporation from an acetone solution. X-ray intensity data were collected on a Enraf-Nonius CAD-4 diffractometer with Cu Kα radiation (λ = 1.5418 Å) in the ω-2θ scan mode. Then, 868 reflections were measured (hmax = 0; kmax = 17; lmax = 9), of which 849 were treated while being observed with I > 2σ(I). Data were corrected for Lorentz, polarization and extinction effects.Crystal data, intensity collection conditions and refinement parameters are given in Table 1.The structure was solved by direct methods using SHELXS97. Isotropic refinements of the hydrogen atoms and anisotropic refinements of the non-hydrogen atoms lowered the R-factor to 0.0309. All hydrogen atoms were fixed by the program. The absolute structure of this crystal was determined by Flack's parameters-0.02(3). The maximum and minimum electron densities in the final difference Fourier map were at 0.49 e Å -3 x221 ANALYTICAL SCIENCES 2007, VOL. 23 X-ray Structure Analysis OnlineCrystal Structure of 3-(1,3-Dithiolan-2-ylidene)pentane-2,4-dione Kerala, India This compound with molecular formula C8H10O2S2 crystallized in the orthorhombic space group Pca21 (Z = 4) with unitcell parameters a = 7.3576(9)Å, b = 14.2238(11)Å, c = 8.714(2)Å. The structure was solved by direct methods and refined to R = 0.0309. This compound approximates the rare ZZ conformation in which both the ketenedithioacetal group and the oxygen atoms are on the same plane with the sulfur atoms close to the respective oxygen atoms.

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“…The temperatures were measured as described in Part I. 12 In order to facilitate the assignment of the signals a selection of solvents and solvent mixtures was used. Fluorobenzene was used instead of benzene because of the lower melting point of the former solvent.…”

Section: E X P E R I M E N T a Lmentioning

confidence: 99%

“…In these compounds the substituents on C, are the same as in Ref. 12, but the capacity of the substituent on C, to donate electrons and stabilise a positive charge is considerably enhanced. In (compounds 1A to IOA, restricted rotations have been observed around the C-N bonds, the C=C bond and in some cases also around the C-X and/or C-Y bonds.…”

mentioning

confidence: 96%

Studies of polarised ethylenes—IV: Barriers to rotation around formal double bonds and formal single bonds in 1, 1‐bis‐dimethylaminoethylenes

Wennerbeck

Sandström

1972

Org. Magn. Reson.

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1 .l-Bis-dimethylaminoethylenes with electron attracting substituents on C , show rotations around the C-=C and C-N bonds, the rates of which are in most cases measurable by the N M R line shape method. The temperature-dependent four-and eight-site N M R spectra have been analysed and the barricrs to rotation around the different bonds have been evaluated by a complete line shape treatment based on the Bloch formalism. Assignment of sites to methyl groups has been made with the aid of aromatic solvent induced shifts and anisotropy effects.

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Studies of Polarized Ethylenes. Part I. Barriers to Rotation Around the Carbon-Carbon Double Bond in 1,1-Bis-alkylthio-ethylenes.

Cited by 80 publications

References 0 publications

Synthesis, structure, and dynamic behavior in solution of arylamino-1,3,5-triazines

Synthesis, structure, and dynamic behavior in solution of arylamino-1,3,5-triazines

Crystal Structure of 3-(1,3-Dithiolan-2-ylidene)pentane-2,4-dione

Studies of polarised ethylenes—IV: Barriers to rotation around formal double bonds and formal single bonds in 1, 1‐bis‐dimethylaminoethylenes

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