NMR study of coupling effects

Bzhezovskii, V. M.; Trofimov, B. A.; Калабин, Г. А.; Keiko, V. V.; Кушнарев, Д. Ф.; Мирскова, А. Н.; Zorina, E. F.; Atavin, A. S.

doi:10.1007/bf00921500

Cited by 5 publications

(4 citation statements)

References 2 publications

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“…They were fully characterized and their data appear in the Supporting Information. All the other vinyl ethers have been previously reported . Although characterization data for compounds 1a − c , 1e − i, and 8a − c are in agreement with those reported, they were also fully characterized, except for 1e for which a satisfactory HRMS was not obtained (see the Supporting Information).…”

Section: Methodssupporting

confidence: 82%

A New Method for the Preparation of Aryl Vinyl Ethers

Blouin

Frenette

2001

J. Org. Chem.

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Section: Methodssupporting

confidence: 82%

A New Method for the Preparation of Aryl Vinyl Ethers

Blouin

Frenette

2001

J. Org. Chem.

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“…Such variation in the rotamer populations in going from ether VII to VIII is accompanied by an appreciable increase (by 0.21 ppm) of the difference in the chemical shifts of the β-protons in the vinyl group (Δδ = δ B -δ A ), as well as by decrease of the absolute values of the coupling constants 2 J AB , 3 J AX , 3 J BX , and 1 J(C α , H X ) by 1.6, 0.8, 0.6, and 8.4 Hz, respectively (see table). In addition, the chemical shift of C α in ether VIII decreases by 6.8 ppm, whereas the chemical shift of C β increases by 5.5 ppm, as compared to the corresponding values for ether VII, due to different polarization of the vinyl group [12]. Thus the above spectral parameters reliably reflect populations of different conformers in the series of aryl vinyl ethers I-VI, depending on the position and size of substituents in the aromatic ring.…”

mentioning

confidence: 83%

Effect of aromatic ring anisotropy on the 1H NMR shielding constants and conformational equilibrium of sterically strained aryl vinyl ethers

Afonin

2011

Russ J Org Chem

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According to the 1 H and 13 C NMR data and quantum-chemical calculations, phenyl vinyl ether exists mainly in the s-trans conformation which is characterized by concurrent p-π* interaction of the oxygen atom with both unsaturated fragments. Introduction of two methyl groups into the ortho positions of the benzene ring forces the latter to go out from the vinyloxy group plane, leading to loss of p-π* conjugation with the aromatic ring, enhancement of p-π* conjugation with the vinyl group, and transition of the molecule to s-cis conformation. The 1 H and 13 C NMR data indicated that replacement of both o-methyl groups by tert-butyl makes the s-cis conformer sterically overcrowded even when the aromatic ring is oriented orthogonally with respect to the vinyl group; as a result, conformational equilibrium is displaced again toward s-trans rotamer.I-VI, X = O; IX, X, X = S; I, IX, R 1 = R 2 = R 3 = H; II, R 1 = Me, R 2 = R 3 = H; III, R 1 = R 3 = H, R 2 = Me; IV, X, R 1 = R 2 = R 3 = Me; V, R 1 = R 3 = t-Bu, R 2 = H; VI, R 1 = R 3 = t-Bu, R 2 = Me; VII, R = Me; VIII, R = t-Bu.It was shown previously that stereospecificity of shielding constants of different magnetically active nuclei may be regarded as an effective tool for studying steric and electronic structure of unsaturated heteroatom compounds [1][2][3][4]. The procedure for performing structural studies on organic molecules with the aid of NMR spectroscopy is attractive due to its accessibility and simplicity, for NMR chemical shift is one of the most readily and reliably measurable spectral parameters of a substance. Conformational equilibria in the series of fluorinated aryl vinyl sulfides [5] and selenides [6] were studied previously by analysis of their 1 H and 13 C NMR spectra. In the present study stereochemical relations inherent to 1 H and 13 C shielding constants were used to examine rotational isomerism in the series of sterically strained aryl vinyl ethers having a bulky substituent in the ortho position with respect to the vinyloxy group. Prevalence of one or another rotamer was confirmed by analysis of 1 H-1 H and 13 C-1 H coupling constants in the vinyl group.The 1 H and 13 C NMR parameters of aryl vinyl ethers I-VI, as well as of alkyl vinyl ethers VII and VIII and aryl vinyl sulfides IX and X taken for comparison, are collected in table. As "reference" structure for estimation of the effect of substituents in the aromatic ring on conformational equilibria of aryl vinyl ethers we selected unsubstituted phenyl vinyl ether (I). The steric structure of its molecule is determined by the weight-average torsion angles φ and ψ at the O-C α and O-C i bonds, respectively (structure A).The 13 C NMR spectrum of phenyl vinyl ether (I) revealed pronounced excess shielding of the β-carbon atom in the vinyl group as compared to ethylene (δ C 95 and 123 ppm, respectively), which indicated considerable p-π* interaction in the vinyloxy group [7,8]. Therefore, compound I was presumed to exist as equilibrium mixture of nearly planar s-cis and s-trans conformers (see...

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“…19' ;he two-line ,' Cl spectrum of (ClCH,),.P(O)CHS (36.241 and 36.950 MHz) shows that in the crystal only one of the two possible conformers is present, that with the trans-orientation of the C-Cl bonds, in agreement with other evidence from its i.r. s ectrum, dipole moment and Kerr PClC6Hs groups in aminochlorotriphosphazatrienes, N3P,Cl6_,R, (R=N(CH3), for II = 1-4 and R = NCSHlo for n = 1-3) are found in the ranges [26][27][28][29][22][23][24][25] respectively; in the monoamino derivatives the PCl, frequencies fall between 26.8 and 28.6 MHz, and the PClNR, frequencies fall between 24.3 and 25.0 MHz Furthermore the smaller temperature dependence of the PClR frequencies relative to PCl,, together with the above conclusions, has permitted a distinction to be made between the various possible geometrical isomers of these compounds. Because the n.q.r.…”

Section: Ymentioning

confidence: 99%

Progress in nuclear quadrupole resonance investigations of halogen‐containing organic and organometallic compounds

Воронков

Фешин

1977

Org. Magn. Reson.

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Recent nuclear quadrupole resonance (n.q.r.) investigations of halogen-containing organic and organometallic compounds, covering the period between 1970-1976, are reviewed. Special attention is paid to n.q.r. studies of the stereochemistry of organic molecules with particular emphasis on the interactions of geminal atoms, and the application of Stark effects to the study of the coordination and hybridization of atoms.

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NMR study of coupling effects

Cited by 5 publications

References 2 publications

A New Method for the Preparation of Aryl Vinyl Ethers

A New Method for the Preparation of Aryl Vinyl Ethers

Effect of aromatic ring anisotropy on the 1H NMR shielding constants and conformational equilibrium of sterically strained aryl vinyl ethers

Progress in nuclear quadrupole resonance investigations of halogen‐containing organic and organometallic compounds

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