Analysis of 13C nuclear magnetic resonance chemical shifts of acyclic hydrocarbons

1980 ◽  
Vol 58 (12) ◽  
pp. 1258-1265 ◽  
Author(s):  
Helmut Beierbeck ◽  
John K. Saunders
Keyword(s):  
Chemical Shifts ◽  
Aliphatic Hydrocarbons ◽  
Bond Rotation ◽  
Molecular Asymmetry ◽  
13C Nuclear Magnetic Resonance ◽  
Cyclic Molecules ◽  
Chain Conformations ◽  
Acyclic Hydrocarbons ◽  
C Nmr

The 13C nmr chemical shifts of aliphatic hydrocarbons were derived from chemical shifts and probabilities of individual chain conformations. Conformer resonances were calculated with parameters developed for conformationally homogeneous cyclic molecules. Conformer populations were derived from bond rotation potentials and steric energy contributions, available from independent sources. This analysis contains non adjustable parameters. It represents a unified treatment of cyclic and acyclic hydrocarbon resonances, which is capable of dealing with molecular asymmetry and thus permits the determination of configuration in aliphatic hydrocarbons.

Determination of chemical shifts in 6-condensed syringylic lignin model compounds

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Lucas Lagerquist ◽  
Jani Rahkila ◽  
Patrik Eklund
Keyword(s):  
Chemical Shift ◽  
Methoxy Group ◽  
Chemical Shifts ◽  
Model Compounds ◽  
Correlation Peak ◽  
Lignin Model Compounds ◽  
Benzylic Alcohols ◽  
Lignin Model ◽  
C Nmr

Abstract A small library of 6-substituted syringyl model compounds with aliphatic, carboxylic, phenylic, benzylic alcohols and brominated substituents were prepared. The influence of the substituents on the chemical shifts of the compounds was analyzed. All of model compounds showed a characteristic increase in the 13C NMR chemical shift of the methoxy group vicinal to the substitution. This 13C NMR peak and its corresponding correlation peak in HSQC could potentially be used to identify 6-condensation in syringylic lignin samples.

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.

13C nuclear magnetic resonance and Raman investigations of aqueous carbon dioxide systems

1982 ◽  
Vol 60 (8) ◽  
pp. 1000-1006 ◽  
Author(s):  
Theresa M. Abbott ◽  
Gerald W. Buchanan ◽  
Peeter Kruus ◽  
Keith C. Lee
Keyword(s):  
Carbon Dioxide ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Linear Relationship ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Carbonate Ion ◽  
13C Nuclear Magnetic Resonance ◽  
Wide Range ◽  
C Nmr

13C-nmr spectra of carbon dioxide in water are reported for a wide range in pH. Chemical shifts were determined for the following species: CO2(g), CO2(aq), HCO3−(aq), CO32−(aq). A linear relationship was found between the shift of the 13C line and the fraction of carbonate ion calculated to be present, as well as between the ratio of the area under the 1067 cm−1 (carbonate) Raman peak to the sum of the area under the 1067 cm−1 and 1017 cm−1 (bicarbonate) peaks and the fraction carbonate.

The determination of the stereochemistry of epoxides located at the 5,6-positions of decalinic systems: An empirical method based on 13C NMR chemical shifts

2002 ◽  
Vol 80 (7) ◽  
pp. 774-778 ◽  
Author(s):  
Raquel M Cravero ◽  
Guillermo R Labadie ◽  
Manuel González Sierra
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Empirical Method ◽  
Nmr Chemical Shifts ◽  
13C Nmr Chemical Shifts ◽  
Empirical Rule ◽  
C Nmr

The 13C NMR spectra of a series of 5,6-epoxides in decalinic systems were studied. The interpretation of the chemical shifts allowed us to formulate an empirical rule to predict the epoxide stereochemistry. A discussion of the scope and limitations of this method and its extension to larger carbon skeletons is also presented.Key words: epoxide stereochemistry, 13C NMR, NMR, decalinic systems, oxiranes.

The Determination of Substituent Effects by 13C Nuclear Magnetic Resonance Spectrometry. The Effect of Solvent on CH2X Groups

1985 ◽  
Vol 38 (2) ◽  
pp. 337
Author(s):  
DAR Happer ◽  
BE Steenson
Keyword(s):  
Inductive Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Side Chain ◽  
Polar Solvents ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic Resonance Spectrometry ◽  
Magnetic Resonance Spectrometry ◽  
Lines Of Force

A previous study of the effect of meta- and para-CH2X substituents on the 13C n.m.r. chemical shifts of the α and β side-chain carbons of β- methoxycarbonylstyrenes (methyl cinnamates ) in ethanol has been extended to cover five additional solvents (Me2SO, Me2CO, CDCl3, CCl4 and C6H6). The results support the earlier claim that, for most substituents , the magnitudes of the substituent -induced shifts are proportional to the inductive effect of X. The major contributor to the latter appears to be the field effect generated by the C-X dipole, with the lines of force passing mainly through the molecule. In non-polar solvents, however, there is evidence that lines of force passing directly through the solvent can also influence the shifts in both the meta and para series.

scholarly journals Alternative probe for the determination of the hydrogen-bond acidity of ionic liquids and their aqueous solutions

2017 ◽  
Vol 19 (18) ◽  
pp. 11011-11016 ◽  
Author(s):  
Pedro P. Madeira ◽  
Helena Passos ◽  
Joana Gomes ◽  
João A. P. Coutinho ◽  
Mara G. Freire
Keyword(s):  
Hydrogen Bond ◽  
Ionic Liquids ◽  
Aqueous Solutions ◽  
Chemical Shifts ◽  
Nmr Chemical Shifts ◽  
Hydrogen Bond Acidity ◽  
C Nmr

The alternative probe pyridine-N-oxide allows the determination of the hydrogen-bond acidity of both neat ionic liquids and their aqueous solutions based on 13C NMR chemical shifts.

Solvent and α-substituent perturbations of the 2H/1H isotope shifts in the 13C nuclear magnetic resonance of toluene-α-d3

1987 ◽  
Vol 65 (3) ◽  
pp. 534-537 ◽  
Author(s):  
Ted Schaefer ◽  
James Peeling ◽  
Rudy Sebastian
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Refractive Index ◽  
Magnetic Resonance ◽  
Isotope Effect ◽  
Electron Donor ◽  
Chemical Shifts ◽  
Aromatic System ◽  
Expectation Value ◽  
13C Nuclear Magnetic Resonance ◽  
C Nmr

The 2H/1H isotope effect on 13C nmr chemical shifts, nΔ, n being the number of intervening bonds between 2H and 13C nuclei, in toluene-α-d3 is solvent dependent. For example, 1Δ ranges from 817 ppb in CD3OH to 869 ppb in acetone-d6 solutions, a positive number indicating increased shielding in the deuterated species. 1Δ is linearly dependent on a function of the refractive index, nD, of the solvent, allowing extrapolation to nD = 1. The hyperconjugative model, in which the C—D bond is a poorer electron donor to the aromatic system than is a C—H bond, is tested for the substituents CH2D, CHD2, CD3, CHDCH3, CD2CH3, CD(CH3)2, C6H5CHD, and (C6H5)2CD. For these substituents, the negative 5Δ is linearly related to the expectation value of sin2 θ; θ is the angle by which the C—D bond twists out of the benzene plane. The model fails quantitatively for C6H5CD2X (X = Cl, COOH, CN, OH). For X = OH, very large negative 5Δ and 3Δ values are observed. nΔ is also reported for 4-ethyltoluene-α-d3 and benzaldehyde-α-d1. For the latter, all nΔ values are positive other than 5Δ, which vanishes in acetone-d6 solution.

Alkanes with multiple asymmetric centers: synthesis, identification, and 13C nuclear magnetic resonance spectra

1979 ◽  
Vol 57 (4) ◽  
pp. 367-376 ◽  
Author(s):  
Pierre Lachance ◽  
S. Brownstein ◽  
Arthur M. Eastham
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Nmr Spectra ◽  
Aliphatic Hydrocarbons ◽  
Capillary Chromatography ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Capillary Glc ◽  
C Nmr ◽  
Magnetic Resonance Spectra

The identification of aliphatic hydrocarbons containing multiple asymmetric centers can be difficult because of the complexity of the nmr spectra and because in capillary chromatography the diastereomers may be resolved to varying degrees. We suggest that the most effective method for identifying such hydrocarbons is through the pattern of retention times developed by the mixture of diastereomers on a suitable capillary glc column.This paper presents the results of some studies of a series of alkanes having the general form C2H5—(CH—CH3)n—R, where n = 1 to 4, and includes the syntheses and 13C nmr spectra of the compounds.

Substituent effects of phosphorus-containing groups on aromatic reactivity. Determination of substituent constants by 13C nuclear magnetic resonance spectroscopy

1977 ◽  
Vol 55 (21) ◽  
pp. 3681-3685 ◽  
Author(s):  
Tomasz A. Modro
Keyword(s):  
Substituent Effects ◽  
Resonance Spectroscopy ◽  
Benzene Derivatives ◽  
13C Nuclear Magnetic Resonance ◽  
Phosphorus Containing ◽  
Substituent Constants ◽  
Parameter Approach ◽  
Reactivity Determination ◽  
C Nmr

13C nmr spectra have been obtained for a series of benzene derivatives substituted with phosphorus-containing groups of the type PZ2, P(O)Z2, and P(S)Z2. Inductive and resonance substituent constants were determined from the shielding of meta and para carbon atoms according to the dual-substituent parameter approach. Possible mechanisms of substituent effects of PIII and PV derived functional groups are discussed and in some cases compared with effects of the analogous nitrogen derivatives.

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