Étude en résonance magnétique nucléaire du 13C des F-méthyl-4 coumarines

1987 ◽  
Vol 65 (6) ◽  
pp. 1356-1360 ◽  
Author(s):  
Raphaël E. Pastor ◽  
Joëlle Fabron ◽  
Aimé Cambon ◽  
You-Chuan Hu
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Alkyl Substituent ◽  
Coupling Constant ◽  
Methyl Substituent ◽  
Slight Effect ◽  
Nuclear Magnetic Resonance Spectra ◽  
Résonance Magnétique ◽  
Magnetic Resonance Spectra

Analysis of 13C nuclear magnetic resonance spectra of six 4-F-methyl coumarins are reported. This 4-F-alkyl substituent has a very slight effect on the chemical shifts of different carbon atoms. Only the C-10, C-4, and C-5 atoms are really affected and are shifted towards higher fields. The size of these effects was evaluated and compared with the corresponding effects of a 4-methyl substituent. The most important fact is the appearance of a 4JCF (and 5JCF for 6) coupling constant. We have shown that this effect is a through-space coupling.

The metal nuclear magnetic resonance spectra of some tin(II) and lead(II) complexes with polydentate phosphines

1983 ◽  
Vol 61 (8) ◽  
pp. 1795-1799 ◽  
Author(s):  
Philip A. W. Dean
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Narrow Range ◽  
Chemical Shifts ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The previously reported 1:1 complexes formed in MeNO2, between M(SbF6)2 (M = Sn or Pb) and Ph2P(CH2)2PPh2, PhP[(CH2)2PPh2]2, MeC(CH2PPh2)3, P[(CH2)2PPh2]3, and [Formula: see text] have been studied by metal (119Sn or 207Pb) nmr. The metal chemical shifts span the comparatively narrow range of −586 to −792 ppm and 60 to −269 ppm, relative to the resonance of MMe4, for 119Sn and 207Pb nmr, respectively. The implications of these data regarding the denticity of the ligand in M(P[(CH2)2PPh2]3)2+ are discussed, and a comparison with the metal nmr spectra of related stannous and plumbous complexes is made.

15N Nuclear Magnetic-Resonance Spectra of ortho-Substituted Phenylacetanilides: The Origin of γ-syn Effects

1989 ◽  
Vol 42 (4) ◽  
pp. 463 ◽  
Author(s):  
C Yamagami ◽  
N Takao ◽  
Y Takeuchi
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Aromatic Ring ◽  
Chemical Shifts ◽  
Van Der Waals ◽  
Side Chains ◽  
Upfield Shift ◽  
Nuclear Magnetic Resonance Spectra ◽  
The Difference ◽  
Magnetic Resonance Spectra

The 15N chemical shifts of X α and Y α, i.e., the nuclei through which the side chains, X and Y, respectively, of o-substituted phenylacetanilides (2a) are bonded to the aromatic ring were determined. There was observed a uniform upfield shift (γsyn effect). In order to explore the origin of the γ effect, other o-disubstitutes benzenes (2b-d) were also examined. The values of D, defined as the difference between γ α substituent chemical shifts of the ortho (2) and para (3) series of compounds, and considered as a measure of the γ-syn effect, were correlated with various electronic and steric substituent parameters. Correlations with electronegativity and van der Waals terms were successful. Examination of the correlations indicated that the γ-syn effect is mostly governed by electronegativity. The classic steric compression theory does not seem very convincing as a means of explaining the shielding γ-syn effect observed in the present study.

13C N.M.R. STUDIES: VIII. 13C SPECTRA OF SOME SUBSTITUTED ANISOLES

1966 ◽  
Vol 44 (23) ◽  
pp. 2855-2866 ◽  
Author(s):  
K. S. Dhami ◽  
J. B. Stothers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Aromatic Ring ◽  
Steric Hindrance ◽  
Steric Effect ◽  
Chemical Shifts ◽  
Methoxyl Group ◽  
Side Chains ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra

The 13C nuclear magnetic resonance spectra of a series of 40 substituted anisoles have been obtained to investigate the effects of substitution on the aromatic and methoxyl carbon shieldings. This work extends our studies on the variations of chemical shifts of carbon nuclei in side chains of aryl derivatives. The question of steric hindrance to conjugative interaction of a methoxyl group with an aromatic ring is considered on the basis of the present results. Evidence of a steric effect in compounds in which both ortho positions are substituted is presented.

SOLVENT EFFECTS IN THE NUCLEAR MAGNETIC RESONANCE SPECTRA OF BENZALMALONONITRILES

1965 ◽  
Vol 43 (9) ◽  
pp. 2585-2593 ◽  
Author(s):  
M. A. Weinberger ◽  
R. M. Heggie ◽  
H. L. Holmes
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Solvent Effects ◽  
Benzene Solution ◽  
Chemical Shifts ◽  
Olefinic Proton ◽  
Solvent Molecule ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

The nuclear magnetic resonance spectra of a series of substituted benzalmalononitriles were examined in various solvents. The chemical shifts for the olefinic protons are susceptible to large solvent effects which are interpreted as arising from association of a solvent molecule with the olefinic proton (acetone) or a site in its vicinity (benzene). With acetone this leads to a downfield shift from values observed in chloroform. In benzene solution the association produces increased shielding and is present in addition to a second solvation complex, the arrangement of which is governed by the substituent. The difference in behavior of the ethylenic proton in benzalmalononitriles from the formyl proton in benzaldehyde is ascribed to its more highly acidic nature.

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