Dependence of geminal1H−1H and31P−1H spin-spin coupling constants on the specific intramolecular C−H...X interaction

Afonin, A. V.; Perez, D. E.; Azúa, Martín C. Ruiz de; Contreras, Rubén H.; Lazzeretti, Paolo

doi:10.1007/bf02494365

Cited by 4 publications

(2 citation statements)

References 9 publications

(3 reference statements)

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“…24,25 This causes a downfield shift of the H b signal which results in an increase in the υ parameter, an increase in the one-bond 1 J(Cˇ,H b ) coupling constant and, hence, a decrease in the J parameter and an algebraic increase in the 2 J(H a ,H b ) coupling constant. 26,27 The υ parameter for O-vinyl ketoximes 1-8 is increased by ¾0.2 ppm and the J parameter is decreased by ¾1 Hz compared with those in divinyl ethers 13 and 14 having a similar conformational equilibrium. 12,28 The electron-withdrawing effect of the C N moiety should cause a significant decrease in the geminal 2 J(H a ,H b ) coupling constant in O-vinyl ketoximes 1-8 relative to divinyl ethers 13 and 14.…”

Section: Rotation In the Vinyloxy Fragmentmentioning

confidence: 99%

Configurational and conformational analysis ofO-vinyl ketoximes by1H and13C NMR spectroscopy

Afonin¹,

Ushakov²,

Zinchenko³

et al. 2000

Magn. Reson. Chem.

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1H and 13C chemical shifts and 1H,1H, 13C,1H and 13C,13C coupling constants were determined for a series of O‐vinyl ketoximes. The analysis suggests that O‐vinyl ketoximes are conformationally homogeneous. These exist as a mixture of s‐trans/s‐trans and s‐trans/s‐cis conformers, the former being energetically preferable. The proximity effects for 1H and 13C NMR parameters allow one to detect the stereo‐orientation of asymmetric substituent relatively to the ketoxime moiety. Copyright © 2000 John Wiley & Sons, Ltd.

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Section: Rotation In the Vinyloxy Fragmentmentioning

confidence: 99%

Configurational and conformational analysis ofO-vinyl ketoximes by1H and13C NMR spectroscopy

Afonin¹,

Ushakov²,

Zinchenko³

et al. 2000

Magn. Reson. Chem.

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“…The intermolecular hydrogen-type interactions have been earlier observed in heterocyclic N-vinyl derivatives, Adam Mickiewicz University, Department of Chemistry, Grunwaldzka 6,koroniak@amu.edu.pl;Fax: +48 (61) where the b-cis hydrogen atom of the vinyl group participated in specific C-HÁ Á ÁX interactions with an endocyclic or exocyclic heteroatom. 8 According to G. R. Desiraju, who addressed some questions related to the now well-established C-HÁ Á ÁX hydrogen bonds, the observed interactions could belong to this category. 9 The hydrogen bond plays an essential role in chemistry and biochemistry.…”

Section: Introductionmentioning

confidence: 99%

Fluorinated enamines of nucleobases as precursors of nucleoside analogues. Synthesis, spectroscopic and structural studies

et al. 2010

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The 1 H and 19 F NMR spectra of N-a-fluoro-b-trifluoromethylenamines and isostructural N-b-fluoro-b-trifluoromethylenamines of nucleobases dissolved in CDCl 3 and DMSO-d 6 have shown distinct differences associated with the conformational conversion between the Z and E stereoisomers. In the E stereoisomer the tetrafluoropropenyl group is rotated relative to the heteroring plane, whereas the Z stereoisomer assumes the most planar structure. The flat conformation of the Z stereoisomer is stabilised by internal hydrogen bonding between C a -H and the carbonyl oxygen (pyrimidinic bases) or the endocyclic nitrogen (purinic bases). Large variations in the magnitudes of the chemical shifts of C b -H, C a -F, C 6 -H and C 8 -H were observed, i.e. the chemical shift increased with increasing polarity and ability of DMSO-d 6 to establish intermolecular hydrogen bonds in competition with intramolecular hydrogen bonds. The (Z)-N 4 -benzoyl-N 1 -(1,3,3,3-tetrafluoroprop-1-enyl)cytosine crystals undergo a phase transition at 230 K induced by the tetrafluoropropenyl substituent reorientations. Between 300 and 230 K the molecules are present in two conformations, and below 230 K the molecules gradually assume five conformations, remaining in a stable equilibrium with intermolecular forces, evidenced by single-crystal X-ray diffraction.

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Advances in theoretical and physical aspects of spin-spin coupling constants

Contreras¹,

Peralta²,

Giribet³

et al. 2000

Annual Reports on NMR Spectroscopy

128

114

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Dependence of geminal1H−1H and31P−1H spin-spin coupling constants on the specific intramolecular C−H...X interaction

Cited by 4 publications

References 9 publications

Configurational and conformational analysis ofO-vinyl ketoximes by1H and13C NMR spectroscopy

Configurational and conformational analysis ofO-vinyl ketoximes by1H and13C NMR spectroscopy

Fluorinated enamines of nucleobases as precursors of nucleoside analogues. Synthesis, spectroscopic and structural studies

Advances in theoretical and physical aspects of spin-spin coupling constants

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