13C N.M.R. Spectra of ortho-Substituted Phenyl N,N-Dimethyl-Carbamates and N-Methyl Carbamates

1987 ◽  
Vol 40 (12) ◽  
pp. 2005 ◽  
Author(s):  
C Yamagami ◽  
T Sai ◽  
N Takao
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Chemical Shift ◽  
Aromatic Ring ◽  
Side Chain ◽  
Carbon Nucleus ◽  
Carbonyl Carbon ◽  
Upfield Shift ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Monosubstituted Benzenes

We measured 13C nuclear magnetic resonance spectra of O-substituted phenyl N,N- dimethyland N-methyl- carbamates and compared the results with those for the corresponding m- and p-substituted derivatives. The additivity relationship on the basis of the substituent chemical shift for monosubstituted benzenes ( scsphx ) did not hold well because of the ortho effect. However, the scs of C2(ipso), C3(ortho) and C5(para) was correlated excellently with scsphxX . Dual substituent parameter (DSP) analyses of the scs of C5 and the carbonyl carbon in the fixed side chain showed that correlation was very good for C5 but moderate for C=O. These observations suggested that the X substituent lay in almost the same plane as the aromatic ring, whereas the OCONMe2 group may have changed its conformation somewhat. In O-substituted derivatives, the carbon nucleus that is directly attached to the aromatic ring (γ to the oxygen; OCONMe2)had a pronounced upfield shift relative to the corresponding m- and p-substituents by 4-5 ppm . This phenomenon was explained by the γ-effect caused by the oxygen atom.

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 Nuclear magnetic resonance studies. XIII. 13C Carbonyl carbon shieldings of some β,γ-unsaturated ketones

1969 ◽  
Vol 47 (19) ◽  
pp. 3601-3604 ◽  
Author(s):  
Gurudata Gurudata ◽  
J. B. Stothers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Qualitative Assessment ◽  
Carbonyl Carbon ◽  
Olefinic Bond ◽  
Magnetic Resonance Studies ◽  
Unsaturated Ketones ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

The 15.1 MHz 13C nuclear magnetic resonance spectra of 13 aliphatic and alicyclic ketones having an olefinic bond in the β,γ position with respect to the carbonyl group have been recorded and the carbonyl shieldings measured. The major aim of this study was to investigate the possibility of detecting homo-conjugative interactions between the π-systems by comparing the carbonyl shieldings with those for the corresponding saturated and α,β-unsaturated systems. Some evidence of homoconjugation is presented on the basis of our previous interpretation of the factors governing carbonyl shieldings. A qualitative assessment of the observed geometrical dependence of the effect is offered.

13C-nuclear magnetic resonance spectra of oxiranes. Configuration of 1,2-epoxypropyl side chains in fungal metabolites

1978 ◽  
Vol 56 (24) ◽  
pp. 3117-3120 ◽  
Author(s):  
Suzanne Lesage ◽  
Arthur S. Perlin
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Side Chain ◽  
Fungal Metabolites ◽  
Trans Isomers ◽  
Model Compounds ◽  
Nmr Data ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Cis And Trans ◽  
C Nmr

13C nmr data indicate that the epoxypropyl side chain of 'asperlin' (1) has a trans configuration. This assignment follows from associated measurements on model compounds, showing that the 13C chemical shift of an epoxypropyl CH3 group is close to either 17 ppm (trans isomers) or 13 ppm (cis isomers). Synthesized as oxirane derivatives related to 1 are diastereomeric pairs of 8-deoxy-6,7-cis- and -trans-epoxy-1,2:3,4-di-O-isopropylidene-α-D-galacto-octopyranoses.

13C Nuclear Magnetic Resonance Spectra of Bridged 10π-Electron Systems. The Extent of Electron Delocalization

1973 ◽  
Vol 51 (5) ◽  
pp. 767-771 ◽  
Author(s):  
A. V. Kemp-Jones ◽  
Alan J. Jones ◽  
M. Sakai ◽  
C. P. Beeman ◽  
S. Masamune
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Ring Current ◽  
Electron System ◽  
Electron Delocalization ◽  
Electron Systems ◽  
Upfield Shift ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra

The 13C n.m.r. spectrum of the cation 4 suggests the presence of considerable 1,7-bonding, indicating that it should be described as a substituted homotropylium cation rather than a monocyclic 10π-electron system. The intra-annular carbon atoms of 3 and 4 do not show a significant upfield shift due to the ring current. Explanations are offered.

13C nuclear magnetic resonance spectra of steroids: the assignments of chemical shifts for C-15 and C-16 in 17β-acetyl steroids

1976 ◽  
Vol 54 (23) ◽  
pp. 3766-3768 ◽  
Author(s):  
Dong Je Kim ◽  
Lawrence D. Colebrook ◽  
T. J. Adley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Chemical Shift Assignments ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

Previously reported 13C chemical shift assignments for C-15 and C-16 of a number of 17β-acetyl steroids related to progesterone have been shown to be reversed. Based on the revised assignment the effect of bromo- and hydroxy-substitution at C-17 on C-12, C-14, C-15, and C-16 is assessed.

13C nuclear magnetic resonance study of cyclodipeptides containing 13C enriched hydrophobic amino acids

1980 ◽  
Vol 45 (2) ◽  
pp. 482-490 ◽  
Author(s):  
Jaroslav Vičar ◽  
François Piriou ◽  
Pierre Fromageot ◽  
Karel Bláha ◽  
Serge Fermandjian
Keyword(s):  
Amino Acids ◽  
Nuclear Magnetic Resonance ◽  
Nuclear Magnetic Resonance Study ◽  
Coupling Constants ◽  
Side Chain ◽  
Amino Acid Residues ◽  
Magnetic Resonance Study ◽  
Side Chain Conformation ◽  
13C Nuclear Magnetic Resonance ◽  
Hydrophobic Amino Acids

The diastereoisomeric pairs of cyclodipeptides cis- and trans-cyclo(Ala-Ala), cyclo(Ala-Phe), cyclo(Val-Val) and cyclo(Leu-Leu) containing 85% 13C enriched amino-acid residues were synthesized and their 13C-13C coupling constants were measured. The combination of 13C-13C and 1H-1H coupling constants enabled to estimate unequivocally the side chain conformation of the valine and leucine residues.

13C Nuclear Magnetic Resonance Spectra of Natural Undiluted Lipids:  Docosahexaenoic-Rich Phospholipid and Triacylglycerol from Fish

2004 ◽  
Vol 52 (13) ◽  
pp. 4250-4255 ◽  
Author(s):  
C. Leigh Broadhurst ◽  
Walter F. Schmidt ◽  
Michael A. Crawford ◽  
Yiqun Wang ◽  
Rong Li
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic
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