scholarly journals NMR diffusion measurements under chemical exchange between sites involving a large chemical shift difference

2010 ◽  
Vol 36A (2) ◽  
pp. 127-137 ◽  
Author(s):  
S. Leclerc ◽  
L. Guendouz ◽  
A. Retournard ◽  
D. Canet
Keyword(s):  
Chemical Shift ◽  
Chemical Exchange ◽  
Chemical Shift Difference ◽  
Nmr Diffusion

Circular dichroism spectra of tetraamminecobalt(III) complexes of amino alcohols

1978 ◽  
Vol 31 (11) ◽  
pp. 2399 ◽  
Author(s):  
CJ Hawkins ◽  
GA Lawrance ◽  
JA Palmer
Keyword(s):  
Circular Dichroism ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Amino Alcohols ◽  
Circular Dichroism Spectra ◽  
Chemical Shift Difference ◽  
Solvent Dependence ◽  
Cotton Effects ◽  
Circular Dichroïsm ◽  
Chiral Amino Alcohols

The circular dichroism spectra are reported for tetraamminecobalt(III) complexes with the chiral amino alcohols 2-aminopropan-1-ol, 2- aminobutan-1-ol, 1-aminopropan-2-ol, 2-amino-1-phenyl-ethanol, ψ- ephedrine and ephedrine with the alcohol groups protonated (OH) and deprotonated (O-). The solvent dependence of the chemical shifts of the NH protons was investigated to determine the effects of stereoselective solvation on the circular dichroism, but, in contrast to some other related systems, the chemical shift difference between the two NH2 protons was relatively insensitive to solvent. Consistent with this, the circular dichroism spectra of the tetraphenylborate salts of the deprotonated complexes were found not to be markedly dependent on solvent. Tetraammine-{(-)-ψ-ephedrine)cobalt(III) and tetraammine{(-)- ephedrine}cobalt(III) were found to have the same signs of Cotton effects for the various d-d transitions, whereas bis{(-)-ψ- ephedrine}copper(II) and bis{(-)-ephedrine}copper(II) had opposite signs. This has been explained in terms of different conformer populations in the cobalt(III) and copper(II) systems.

Correlations of NHN hydrogen bond energy with geometry and1H NMR chemical shift difference of NH protons for aniline complexes

2019 ◽  
Vol 150 (11) ◽  
pp. 114305 ◽  
Author(s):  
E. Yu. Tupikina ◽  
M. Sigalov ◽  
I. G. Shenderovich ◽  
V. V. Mulloyarova ◽  
G. S. Denisov ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Chemical Shift ◽  
Bond Energy ◽  
Nmr Chemical Shift ◽  
Hydrogen Bond Energy ◽  
Chemical Shift Difference

A concise approach for determining the relative configuration of H-7 and H-8 in 8,4′-oxyneolignans by 1H NMR spectroscopy

2019 ◽  
Vol 6 (7) ◽  
pp. 886-891 ◽  
Author(s):  
Ya-Nan Yang ◽  
Bing Han ◽  
Peng-Fei Yang ◽  
Zi-Ming Feng ◽  
Jian-Shuang Jiang ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
1H Nmr ◽  
1H Nmr Spectroscopy ◽  
Relative Configuration ◽  
Chemical Shift Difference

The chemical shift difference between H-9a and H-9b can be used to accurately and rapidly determine the relative configuration of H-7 and H-8 in three types of 8,4′-oxyneolignan glucosides.

109Ag NMR-Study of the Selective Solvation of the Ag+ Ion in Solvent Mixtures of Water and the Organic Solvents: Pyridine, Acetonitrile, and Dimethyl Sulfoxide

1984 ◽  
Vol 39 (1) ◽  
pp. 83-94 ◽  
Author(s):  
L. Guinand. K. L. Hobt. E. Mittermaier ◽  
E. Rößler ◽  
A. Schwenk ◽  
H. Schneider
Keyword(s):  
Chemical Shift ◽  
Dimethyl Sulfoxide ◽  
Organic Solvents ◽  
Mole Fraction ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Equilibrium Constants ◽  
Solvent Mixtures ◽  
Nmr Study ◽  
Solvent Molecules

In mixtures of water (W) and one of the organic solvents pyridine, acetonitrile, and dimethyl sulfoxide (O), the silver ion forms the following solvate complexes: AgW2, AgWO, and Ag02. The chemical shift of 109Ag is strongly affected by the ligating solvent molecules, and replacing the ligand W by one of the three organic ligands yields a higher Larmor frequency. In solvent mixtures, only a single resonance line has been observed because of rapid chemical exchange. The measured chemical shifts in the range up to 400 ppm are mean values of the chemical shifts of the different solvate species in a given mixture, weighted with their relative concentrations. The 109Ag chemical shifts were determined for 0.05 to 0.15 molal solutions of AgNO3, as functions of the mole fractions of the solvent components. Using a Gaussian least squares fitting routine, the individual chemical shifts of the Ag+ solvate complexes and the corresponding equilibrium constants were determined. This fit was successful for the whole mole fraction range of DMSO, while in the solvent systems with acetonitrile and with pyridine at higher concentrations of the organic component the chemical shift is influenced by more than two solvent molecules. In these cases equilibrium constants were calculated from chemical shift data for solutions of low mole fraction of acetonitrile and pyridine.

Michael additions to metallocene analogues of chalcones

1987 ◽  
Vol 52 (1) ◽  
pp. 174-181 ◽  
Author(s):  
Jozef Federič ◽  
Štefan Toma
Keyword(s):  
Double Bond ◽  
Chemical Shift ◽  
Aryl Group ◽  
Chemical Shift Difference ◽  
Michael Additions ◽  
Methyl Malonate

Eleven analogues of chalcones were synthesized; the variously substituted ferrocenyl, ruthenocenyl or η5-cyclopentadienyltricarbonylmanganese are attached to the β-carbon of the chalcone double bond. Methyl malonate was added to eight selected chalcones. The effect of an aryl group on the chemical shift difference of diastereotopic -COOCH3 groups is discussed. The Vilsmeier-Haack formylation was employed to prepare 1'-chloro and 1'-bromoferrocenecarbaldehydes. The synthesis of 2-chloroferrocenecarbaldehyde from 2-chloroferrocenylmethyldimethylamine is also described.

Determination of the Chemical-Shift Difference between the Lactate Multiplets and Its pH Dependence

1996 ◽  
Vol 112 (3) ◽  
pp. 236-239 ◽  
Author(s):  
Michael Bunse ◽  
Wulf-Ingo Jung ◽  
Günther Dietze ◽  
Otto Lutz
Keyword(s):  
Chemical Shift ◽  
Ph Dependence ◽  
Chemical Shift Difference

An investigation into the origins of polar substituent effects upon 19F chemical shifts, using 4-substituted β,β-difluorostyrenes

1980 ◽  
Vol 58 (8) ◽  
pp. 839-845 ◽  
Author(s):  
William F. Reynolds ◽  
Victoria G. Gibb ◽  
Nick Plavac
Keyword(s):  
Chemical Shift ◽  
Electron Density ◽  
Molecular Orbital ◽  
Excellent Agreement ◽  
Field Effect ◽  
Chemical Shifts ◽  
Substituent Effects ◽  
Molecular Orbital Calculations ◽  
Chemical Shift Difference ◽  
Polar Substituent

19F, 13C, and 1H chemical shifts have been determined for β,β-difluorostyrene and eight 4-substituted derivatives. The β-fluorine chemical shift difference, ΔδF, is used to evaluate the constant in the Buckingham equation. A = 3.0 × 10−11 esu for C—F bonds which is in excellent agreement with the value derived by Adcock and Khor. This allows accurate estimates of direct field effect contributions to 19F chemical shifts in aryl fluorides. Substituent parameter correlations demonstrate that the primary polar effect on 19F chemical shifts is field-induced π polarization. Abinitio molecular orbital calculations confirm that the substituent-induced 19F chemical shifts reflect changes in fluorine π electron density.

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