13C nuclear magnetic resonance chemical shifts in styrenes; substituent and solvent effects

1984 ◽  
pp. 1673 ◽  
Author(s):  
Duncan A. R. Happer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Solvent Effects ◽  
Chemical Shifts ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

13C Nuclear Magnetic Resonance of Oximes. I. Solvent and Isotope Effects on the 13C Chemical Shifts of Acetoxime

1972 ◽  
Vol 50 (12) ◽  
pp. 1956-1958 ◽  
Author(s):  
N. Gurudata
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Solvent Effects ◽  
Chemical Shifts ◽  
Isotope Effects ◽  
Solvent Interactions ◽  
13C Chemical Shifts ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

The 13C n.m.r. spectrum of acetoxime has been obtained in five representative solvents and the chemical shifts of the three carbon atoms measured. The solvent effects on the chemical shifts are found to reflect specific solute–solvent interactions. The effect of deuteration of the α-protons on the chemical shift of the oximino carbon is also discussed.

Semiempirical calculation of 13C nuclear magnetic resonance chemical shifts of acyclic hydrocarbons. Application to the stereochemical analysis of steroidal side chains

1988 ◽  
Vol 66 (1) ◽  
pp. 71-75 ◽  
Author(s):  
Manuel Gonzalez-Sierra ◽  
Daniel A. Bustos ◽  
Edmundo A. Ruveda ◽  
Alejandro C. Olivieri ◽  
Mariano Grasselli
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Side Chains ◽  
Stereochemical Analysis ◽  
Microcomputer Program ◽  
Semiempirical Approach ◽  
13C Nuclear Magnetic Resonance ◽  
Acyclic Hydrocarbons ◽  
Nuclear Magnetic

A semiempirical approach for predicting 13C nuclear magnetic resonance chemical shifts of acyclic hydrocarbons has been adapted to a microcomputer program. A series of methyl and dimethyl substituted cholesterols has been studied using this program, and the predicted shifts are in agreement with literature reports. Preferred conformations of the steroidal side chains have been also predicted and agree with previous studies. A simple rule for analyzing the trends in the chemical shift of the carbon C-20, which is sensitive to changes in the configuration at C-22, is also given, not only for hydrocarbon side chains but also for hydroxy substituted compounds.

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.

A Study of Solvent Effects on the 13C Nuclear Magnetic Resonance Spectra of Cholesterol, Pyridine, And Uridine

1973 ◽  
Vol 51 (9) ◽  
pp. 1384-1391 ◽  
Author(s):  
H. H. Mantsch ◽  
Ian C. P. Smith
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Solvent Effects ◽  
Chemical Shifts ◽  
Dipole Interaction ◽  
Simple Relation ◽  
The Other ◽  
Solvent Interaction ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance

The 13C n.m.r. chemical shifts for cholesterol in five solvents are reported. All carbon atoms were subject to solvent effects of varying sign and magnitude. The chemical shifts in the solvent pair dioxane–chloroform 1:1 could be predicted on an additivity basis. Pyridine was studied in 24 solvents; the chemical shifts of all carbons were solvent-dependent. Solvent effects at positions β and γ were correlated, while those at position α bore no simple relation to those of the other carbons. A small isotope effect was noted on comparing the data for H2O and 2H2O. Coupling between 13C and 14N was observed in some cases; its magnitude was solvent-dependent. Uridine was studied in four solvents. While all carbons were subject to solvent-induced shifts, evidence for specific solvent interaction at C-4, -5, -1′, and -2′ was obtained. An appreciable contribution to the relaxation of carbonyl C-2 and -4 from dipole–dipole interaction with the hydrogen on N-3 was observed. Solvent effects can result in scrambling and misassignment of 13C resonances if care is not taken with choice of solvent.

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.

13C nuclear magnetic resonance and reactivity of 4H-3,1-benzoxazin-4-ones

1988 ◽  
Vol 66 (3) ◽  
pp. 416-419 ◽  
Author(s):  
Valerie J. Robinson ◽  
Robin W. Spencer
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shifts ◽  
Resonance Assignments ◽  
Human Leukocyte ◽  
Leukocyte Elastase ◽  
13C Nuclear Magnetic Resonance ◽  
Tissue Degradation ◽  
Alternate Substrate ◽  
Nuclear Magnetic

Complete carbon-13 nuclear magnetic resonance assignments have been made for 22 4H-3,1-benzoxazin-4-ones. These compounds are alternate substrate inhibitors of human leukocyte elastase, a serine protease involved in tissue degradation. Correlations between the carbon chemical shifts and rates of alkaline hydrolysis are consistent with hydrolysis via attack at C4, and are also useful in the selection of parameters for structure–activity analysis.

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