13C Nuclear Magnetic Resonance Studies. 38. Examination of the Long-range Shielding Effects of the Hydroxyl Group in Alicyclic Systems

1974 ◽  
Vol 52 (6) ◽  
pp. 870-878 ◽  
Author(s):  
S. H. Grover ◽  
J. B. Stothers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Spectral Analysis ◽  
Magnetic Resonance ◽  
Substituent Effects ◽  
Hydroxyl Group ◽  
Magnetic Resonance Studies ◽  
13C Nuclear Magnetic Resonance ◽  
Steric Crowding ◽  
Direct Contrast ◽  
Shielding Effects

The substituent effects of the hydroxyl group on the 13C shieldings of the trans-decalols and the 10-methyl-trans-decalols have been determined. The shifts for the carbons three and four bonds from the site of substitution depend strongly on their orientation with respect to the hydroxyl group. While the latter have not been widely recognized, these δ effects are valuable for spectral analysis and stereochemical assignments since these range up to 3.4 p.p.m. In direct contrast to the well established trends for γ effects, steric crowding of δ nuclei causes marked downfield shifts. The corresponding effects in several steroids are illustrated.

scholarly journals 13C nuclear magnetic resonance studies. 64. The 13C spectra of a variety of bicyclo[3.2.1]octanols

1977 ◽  
Vol 55 (5) ◽  
pp. 841-848 ◽  
Author(s):  
J. B. Stothers ◽  
C. T. Tan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Substituent Effects ◽  
Ring System ◽  
Hydroxyl Group ◽  
Magnetic Resonance Studies ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr ◽  
Shielding Effects

The 13C nmr spectra of a series of 20 bicyclo[3.2.1]octanols and -octenols have been determined to examine the shielding effects of the hydroxyl group on the skeletal carbons in this ring system. For comparison, the previously unreported data for a few closely related alcohols in the [2.1.1], [2.2.1], and [3.2.2] systems were also collected. The utility of these substituent effects for configuraional and conformational assignments is discussed.

Configurationally dependent hydroxyl group effects on 13C nuclear magnetic resonance chemical shifts of olefinic carbons in cyclic six-membered allylic alcohols

1988 ◽  
Vol 66 (12) ◽  
pp. 3128-3131 ◽  
Author(s):  
Teodoro S. Kaufman
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Hydroxyl Group ◽  
Allylic Alcohols ◽  
Stereochemical Assignment ◽  
13C Nuclear Magnetic Resonance ◽  
Group Effects ◽  
Nuclear Magnetic

The differences in chemical shifts of olefinic carbons, Δδ(sp2), of pseudoequatorial and pseudoaxial six-membered allylic alcohols were correlated with the Δδ(sp2) values of their parent olefins. The results obtained reflect configurationally dependent substituent effects, the magnitude of which could be used for the stereochemical assignment of the hydroxyl group in these compounds.

13C Nuclear Magnetic Resonance Studies. 29. 13C Spectra of Some Alicyclic Methyl Esters

1973 ◽  
Vol 51 (13) ◽  
pp. 2092-2097 ◽  
Author(s):  
M. Gordon ◽  
S. H. Grover ◽  
J. B. Stothers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Carboxylic Acid ◽  
Magnetic Resonance ◽  
Methyl Esters ◽  
Membered Ring ◽  
Model Compounds ◽  
Magnetic Resonance Studies ◽  
13C Nuclear Magnetic Resonance ◽  
Acid Esters ◽  
Shielding Effects

The shielding effects of the carbomethoxyl group on neighboring carbons in the cyclohexane and trans-decalin ring systems have been characterized by 13C n.m.r. examination often model compounds. The data show that sufficient differences are exhibited by axial and equatorial groups to permit stereochemical assignments in related systems. The observed trends are compared with those produced by other functional groups. The three-, four-, and five-membered ring cycloalkae carboxylic acid esters were also examined.

13C Nuclear Magnetic Resonance Studies. 47. 13C Spectra of some exo-Methylenecycloalkanes and -norbornanes

1975 ◽  
Vol 53 (4) ◽  
pp. 589-595 ◽  
Author(s):  
S. H. Grover ◽  
J. B. Stothers
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Carbonyl Group ◽  
Ring System ◽  
Magnetic Resonance Studies ◽  
13C Nuclear Magnetic Resonance ◽  
Methylene Group ◽  
Shielding Effects ◽  
Nuclear Magnetic

The shielding effects of the exo-methylene group on neighboring carbons in several cycloalkanes, methylcyclohexanes, and in the norbornane ring system have been characterized by 13C n. m. r. examination of 28 compounds. The results are compared with those for the carbonyl group and the utility of these data for structural elucidations is discussed. The more distinctive trends exhibited by the methyl carbons in these systems are compared with those for cyclohexanes, cyclohexanones, norbornanes, and norcamphors.

13C Nuclear Magnetic Resonance Studies of Methylated Anthracenes

1975 ◽  
Vol 53 (13) ◽  
pp. 1958-1969 ◽  
Author(s):  
Myron L. Caspar ◽  
J. B. Stothers ◽  
Nancy K. Wilson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Regression Analysis ◽  
Standard Deviation ◽  
Magnetic Resonance ◽  
Substituent Effects ◽  
Methyl Substituent ◽  
Magnetic Resonance Studies ◽  
Charge Densities ◽  
13C Nuclear Magnetic Resonance ◽  
Proton Decoupling

The 13C n.m.r. spectra of anthracene and 11 methylated anthracenes have been examined. Analysis of the 1H spectra allowed unequivocal assignments for most of the protonated carbons by selective proton decoupling. Parameters describing the methyl substituent effects on the aryl carbon shieldings were defined and refined by regression analysis so that the 13C shieldings were predicted for 67 independent aryl positions in anthracenes without peri-methyls with a standard deviation of 0.12 p.p.m. Peri methyl-methyl interactions cause considerable deviations from the predicted substituent effects. The relationships of the 13C shieldings to charge densities calculated by the CNDO/2 method were briefly examined. Syntheses of 2,7,9-trimethyl-, 1,4,5,8- and 1,4,5,9-tetramethyl-, and 1,4,5,8,9-pentamethylanthracene are described.

13C nuclear magnetic resonance studies. 55. A comparison of the stereochemical dependence of γ- and δ-substituent effects on 13C shieldings in several norbornanols and norbornenols

1976 ◽  
Vol 54 (8) ◽  
pp. 1211-1221 ◽  
Author(s):  
J. B. Stothers ◽  
C. T. Tan ◽  
K. C. Teo
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Substituent Effects ◽  
Magnetic Resonance Studies ◽  
Considerable Potential ◽  
13C Nuclear Magnetic Resonance ◽  
Insight Into ◽  
C Nmr ◽  
Nuclear Magnetic

The 13C nmr spectra of a series of 50 methyl substituted norbornanols have been determined to gain further insight into the nature of stereochemical effects on the shieldings of carbons having closely neighboring substituents. The relatively rigid norbornyl skeleton permits examination of a variety of orientations of substituents separated by three and four bonds, the γ and δ interactions, respectively. While methyl carbons close to γ substituents exhibit upfield shifts, as is well established, methyl carbons close to δ substituents are significantly deshielded. Even more striking shifts are found for the carbons bearing these closely lying groups. The penultimate carbons in a fragment having a δ interaction between terminal groups show deviations of up to +11 ppm from the shieldings predicted by simple additivity. For fragments having a corresponding γ interaction, the penultimate carbons absorb as much as −10 ppm from the values expected by additivity. These deviations have considerable potential for stereochemical assignments and offer a challenge for theoretical interpretation.Some norbornenols and the acetates of several of the norbornanols were also included in this series and the latter shieldings are compared briefly with those observed for the parent alcohols.

X-Ray crystallographic and 13C nuclear magnetic resonance studies of 3,4,5,6-tetrahydro-2H-1,3,4-oxadiazin-2-ones derived from ephedrine and pseudoephedrine

Tetrahedron ◽  
2001 ◽  
Vol 57 (49) ◽  
pp. 9789-9798 ◽  
Author(s):  
Shawn R Hitchcock ◽  
George P Nora ◽  
David M Casper ◽  
Michael D Squire ◽  
Christopher D Maroules ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Studies ◽  
X Ray ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic
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