Substituent effects on the 13C chemical shifts of monosubstituted twistanes

1977 ◽  
Vol 55 (17) ◽  
pp. 3161-3165 ◽  
Author(s):  
Helmut Beierbeck ◽  
John K. Saunders
Keyword(s):  
Chemical Shift ◽  
Substituent Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
13C Chemical Shifts ◽  
Bond Interaction ◽  
Chemical Shift Data ◽  
Shift Data ◽  
Deshielding Effect

The 13C chemical shift data for some hydroxy, chloro, bromo, and oxo twistane derivatives are presented and compared to the shifts observed in corresponding adamantanes. The substituent effect at the α and β carbons is more pronounced in twistanes than in adamantanes. The substituent shift induced at an antiperiplanar γ carbon is shown to depend on the presence or absence of 1,3-diaxial hydrogen–hydrogen interactions between the substituted and γ carbons. If such an interaction is present the effect is of shielding whereas if it is absent, the effect is of deshielding. The deshielding effect appears to occur via a through bond interaction.

Organometallic compounds in synthesis. VIII. Carbon-13 nuclear magnetic resonance spectroscopic study of tricarbonylcyclohexadienyliron salts

1976 ◽  
Vol 29 (8) ◽  
pp. 1671 ◽  
Author(s):  
AJ Birch ◽  
PW Westerman ◽  
AJ Pearson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Spectroscopic Study ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Organometallic Compounds ◽  
Nucleophilic Attack ◽  
Chemical Shift Data ◽  
Shift Data

The carbon-13 N.M.R. spectra of eleven substituted tricarbonylcyclohexadienyliron salts (1) have been determined and individual resonances assigned. Substituent effects have been deduced and compared with corresponding effects in cyclohexadienyl cations. The structures of the tricarbonylcyclohexadienyliron salts are discussed with reference to chemical shift data. The proportions of irreversible nucleophilic attack at the terminal positions in the unsymmetrical 2-substituted salts are compared with the observed chemical shifts at these carbon atoms.

scholarly journals A computerized approach to the analysis of oligosaccharide structure by high-resolution proton n.m.r

1984 ◽  
Vol 223 (1) ◽  
pp. 129-143 ◽  
Author(s):  
E F Hounsell ◽  
D J Wright ◽  
A S R Donald ◽  
J Feeney
Keyword(s):  
Sialic Acid ◽  
High Resolution ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Oligosaccharide Structure ◽  
Chemical Shift Data ◽  
Computer Library ◽  
Shift Data

The 500 MHz proton-n.m.r. spectra of 21 oligosaccharides, predominantly of the lacto-N and lacto-N-neo series and their derivatives containing non-reducing terminal fucose, sialic acid or N-acetylgalactosamine and reduced-end hexitol or hexosaminitol, were examined with 2H2O as solvent. The chemical-shift data obtained from analysis of the spectra were collated with data from other laboratories who have used 250-500 MHz n.m.r. in the analysis of secreted and chemically synthesized oligosaccharides and of the O- and N-linked chains of glycoproteins. A referenced computer library was constructed that includes the chemical shifts of monosaccharides within oligosaccharide sequences that make up the majority of the carbohydrate structures found in mammalian glycoproteins. Examples are given of the computerized interrogation of this library for the assignment of possible structures of unknown oligosaccharides.

17O nuclear magnetic resonance spectroscopic study of substituted phthalic anhydrides and phthalides

1987 ◽  
Vol 65 (6) ◽  
pp. 1214-1217 ◽  
Author(s):  
David W. Boykin ◽  
Alfons L. Baumstark ◽  
Margaret M. Kayser ◽  
Chantal M. Soucy
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Carbonyl Groups ◽  
Chemical Shift Data ◽  
The Relationship ◽  
Electronic Character ◽  
Shift Data ◽  
Phthalic Anhydrides

17O chemical shift data (natural abundance) for 3-substituted phthalic anhydrides and 4- and 7-substituted phthalides in acetonitrile at 75 °C are reported. Steric interactions of substituents ortho to the carbonyl groups result in deshielding effects (9–22 ppm) relative to parent compounds regardless of the electronic character of the substituents. Factors contributing to the deshielding effects are discussed. The relationship between 17O chemical shifts and regiochemistry of the phthalic anhydrides is discussed.

Qualitative Applications of the NMR Spectra of Alkylpyridines: Part I. Chemical Shifts of the Ring Protons

1968 ◽  
Vol 22 (4) ◽  
pp. 325-329 ◽  
Author(s):  
F. R. McDonald ◽  
A. W. Decora ◽  
G. L. Cook
Keyword(s):  
Chemical Shift ◽  
Nmr Spectra ◽  
Pyridine Ring ◽  
Structural Information ◽  
Chemical Shifts ◽  
Shale Oil ◽  
Nmr Chemical Shift ◽  
Chemical Shift Data ◽  
Spectroscopic Identification ◽  
Shift Data

Spectroscopic identification of pyridine compounds isolated from complex substances such as shale oil is greatly aided by NMR chemical-shift data on the pyridine-ring protons. Chemical shifts of the ring protons in CCl4 and C6H6 solution and the differential shift of the protons in these two solvents are reported. A paramagnetic shift is observed in the directional character of the proton alpha to the nitrogen in the pyridine ring. These data are used to determine structural information from the spectrum of a mixture of pyridine homologs.

13C Nuclear Magnetic Resonance Spectra of Organic Sulfur Compounds: Cyclic Sulfides, Sulfoxides, Sulfones, and Thiones

1975 ◽  
Vol 53 (19) ◽  
pp. 2880-2890 ◽  
Author(s):  
M. S. Chauhan ◽  
I. W. J. Still
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Limited Data ◽  
Organic Sulfur Compounds ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Chemical Shift Data ◽  
Derivatives Of ◽  
Shift Data ◽  
Methyl Phenyl

13C Chemical shift data have been obtained for more than 50 thiochromanone and related sulfoxide and sulfone derivatives. The assignments of the various resonances in the most important of these have been made using the limited data already available and also by comparison with certain model compounds, such as thioanisole, diphenyl sulfide, and the corresponding sulfoxides and sulfones.Within each of these three series and in a fourth which comprises derivatives of thiochromone, including three α, β-unsaturated thiones, we have examined the effects on 13C chemical shift of substitution at various positions in the thiochromanone skeleton. Among the substituents examined in this context are methyl, phenyl, methoxyl, bromine, and carbomethoxyl. Attempts to compare the 13C chemical shifts for the thiochromanone series with those in a few oxygen containing analogs and in a small number of structurally similar analogs are also discussed.

Carbon-13 Nuclear Magnetic Resonance Spectra of Isothiazole, 1,2-Dithiole, and 1,3-Dithiole Derivatives

1975 ◽  
Vol 53 (6) ◽  
pp. 836-844 ◽  
Author(s):  
N. Plavac ◽  
I. W. J. Still ◽  
M. S. Chauhan ◽  
D. M. McKinnon
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Carbonyl Compounds ◽  
Heterocyclic Compounds ◽  
Chemical Shifts ◽  
Conjugated Systems ◽  
Nuclear Magnetic Resonance Spectra ◽  
Chemical Shift Data ◽  
Shift Data

Carbon-13 chemical shift data have been obtained for a number of isothiazole, benzo[c]isothiazole, 1,2-dithiole, and 1,3-dithiole derivatives. A number of these compounds are thiones and the chemical shifts of the C=S carbons are discussed in the light of recent attempts to predict such chemical shifts from those of the analogous carbonyl compounds. Comparisons of substituent chemical shift (s.c.s.) effects in these heterocyclic compounds with those in simpler aromatic or conjugated systems have been made and additivity correlations tested in a number of cases.

scholarly journals Revisit to 25R/25S Stereochemical Analysis of Spirostane-type Steroidal Sapogenins and Steroidal Saponins via 1H NMR Chemical Shift Data

2012 ◽  
Vol 7 (6) ◽  
pp. 1934578X1200700
Author(s):  
Pawan K. Agrawal ◽  
Torsten Burkholz ◽  
Claus Jacob
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Steroidal Saponins ◽  
Methyl Group ◽  
H Nmr ◽  
Stereochemical Analysis ◽  
Chemical Shift Data ◽  
The Difference ◽  
Shift Data ◽  
1H Nmr Chemical Shift

An approach based on the difference (Δab = δa – δb) between 1H NMR chemical shifts (δa, δb) of the geminal protons of oxymethylene (H2-26) (Δab = <0.2 for 25 R; Δab = >0.5 for 25 S) is proposed for ascertaining 25 R/25 S orientation of the 27-methyl group for (22 R)-spirostane-type steroidal sapogenins and steroidal saponins. These studies suggested the 25 R-orientation of the 27-Me group for the steroidal saponins isolated by Temraz et al. from Tribulus alatus.

13C NMR spectroscopy of heterocycles: 1-phenyl-3-aryl/t-butyl-5-arylpyrazoles

2017 ◽  
Vol 23 (2) ◽  
pp. 125-131 ◽  
Author(s):  
Amy N. Hockstedler ◽  
Beatrice A. Edjah ◽  
Saajid Z. Azhar ◽  
Hadrian Mendoza ◽  
Nicole A. Brown ◽  
...  
Keyword(s):  
Chemical Shifts ◽  
Substituent Effects ◽  
Phenyl Group ◽  
13C Nmr Spectroscopy ◽  
Aryl Group ◽  
Torsion Angles ◽  
Chemical Shift Data ◽  
Molecular Modeling Studies ◽  
Shift Data ◽  
C Nmr

AbstractA series of chalcones 1–12 were converted to pyrazolines (1Pi–12Pi) by reaction with phenylhydrazine followed by DDQ oxidation to produce the corresponding pyrazoles (1Pz–12Pz). Three 1-phenyl-3-t-butyl-5-arylpyrazoles (13Pz–15Pz) were synthesized using an analogous approach. Molecular modeling studies predicted the 5-aryl group of the pyrazoles for both series to have a torsion angle of 52°–54° whereas the 1-phenyl group was predicted to have 35°–37° torsion angles. The 3-aryl group was predicted to be essentially coplanar (−3°) with the pyrazole system in the first series. 13C NMR data for both series, 1Pz–12Pz and 13Pz–15Pz, were collected in DMSO-d6 at 50°C. A plot of the C4 chemical shifts for 1Pz–12Pz versus Hammet constants for 5-aryl substituents yielded a very good linear correlation (R2=0.96) with a slope of 1.5. The chemical shift data for C4 showed little or no dependence on 3-aryl substituents. The result for 13Pz–15Pz, despite only three points, was consistent with the first series results and yielded a ρ value of 2.0. Distal transmission of substituent effects (5-aryl groups) to C4 of the pyrazole system was reduced by roughly 50–60% of that of the analogous planar isoxazole system, but are not consistent with results for the similarly twisted 4-bromoisoxazoles.

Metabolites of bird's nest fungi. Part 10. Carbon-13 nuclear magnetic resonance studies on the cyathins

1978 ◽  
Vol 56 (16) ◽  
pp. 2197-2199 ◽  
Author(s):  
William A. Ayer ◽  
Thomas T. Nakashima ◽  
Dale E. Ward
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Magnetic Resonance Studies ◽  
Chemical Shift Data ◽  
Related Compounds ◽  
Shift Data ◽  
Methyl Acetal ◽  
Magnetic Resonance Spectra

The carbon-13 magnetic resonance spectra of cyathin A3 and several related compounds have been measured and the chemical shifts have been assigned. The chemical shift data have been used to determine the stereochemistry at C-1 in cyafrin A4 and to determine the position of the bromine in 1-bromoallocyathin A3 methyl acetal.

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