Association of a Europium Shift Reagent with Dialkylnitrosamines

1974 ◽  
Vol 52 (2) ◽  
pp. 315-324 ◽  
Author(s):  
Richard A. Perry ◽  
Yuan L. Chow
Keyword(s):  
Chemical Shifts ◽  
Equilibrium Constants ◽  
Molecular Geometry ◽  
Shift Reagent ◽  
Nitroso Group ◽  
Contact Shift ◽  
Substrate Ratio ◽  
The Eu

The Eu(fod)3 induced shifts of the n.m.r. signals of various nitrosamines were studied at a constant lanthanide concentration and also at constant nitrosamine concentration. The bound chemical shifts (ΔB) and binding equilibrium constants (K) were determined. The stoichiometry of the complexes appears to be 1:1 in CDCl3 in agreement with the criteria of two types of existing tests designed to determine Eu–substrate ratio. On the basis of the experimental ΔB values, the molecular geometry of Eu–nitrosamine complexes were computed according to the principle of pseudo-contact shift. It was concluded that the Eu atom complexed at the oxygen of the nitroso group and that the conformations of nitrosamines in the complexes were basically the same as those of uncomplexed nitrosamines.

scholarly journals Application of Lanthanide Shift Reagent to the 1H-NMR Assignments of Acridone Alkaloids

Molecules ◽  
2020 ◽  
Vol 25 (22) ◽  
pp. 5383
Author(s):  
Sio-Hong Lam ◽  
Hsin-Yi Hung ◽  
Ping-Chung Kuo ◽  
Daih-Huang Kuo ◽  
Fu-An Chen ◽  
...  
Keyword(s):  
Least Squares ◽  
Nmr Assignments ◽  
Least Squares Method ◽  
Chemical Shifts ◽  
Shift Reagent ◽  
Spectral Studies ◽  
Lanthanide Shift Reagent ◽  
Planar Structures ◽  
Acridone Alkaloids ◽  
The Eu

This study investigates the application of the paramagnetic shift reagent tris(dipivaloylmethanato)-europium(III) in NMR spectral studies of permethoxyacridone alkaloids (1–3) and pyranoacridone alkaloids (4–6). The induced chemical shifts (∆δ) of all protons were observed for the same molecule, and were compared to deduce the positions resulting from the distance nearby the Eu(dpm)3. Assignment of the H-2, H-4 and H-8 of polysubstituted acridones could be distinguished based on the least-squares method of lanthanide-induced shifts plotted against the mole ratios of Eu(dpm)3 to the substrate. The developed method is not only potentially useful for determining the planar structures of polysubstituted compounds, such as acridones, anthraquinones, xanthones, flavonoids, and phenanthrenes, but also applicable for their stereochemistry.

Evaluation of the Binding Constants, Bound Chemical Shifts, and Stoichiometry of Lanthanide–Substrate Complexes

1972 ◽  
Vol 50 (13) ◽  
pp. 2119-2129 ◽  
Author(s):  
Ian Armitage ◽  
G. Dunsmore ◽  
L. D. Hall ◽  
A. G. Marshall
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Binding Constants ◽  
Shift Reagent ◽  
Accurate Solution ◽  
Conventional Procedure ◽  
Equilibrium Binding ◽  
Straight Line ◽  
Equilibrium Binding Constant ◽  
The Eu

A theoretical analysis of the equilibrium between a lanthanide shift reagent, L, and a substrate, S, is presented. When [Formula: see text] then a plot of [S]0vs. (1/δ) at constant [L]0 gives a straight line whose slope is [L]0ΔB and whose y-intercept is −{(1/KB) + [L]0}, where KB is the equilibrium binding constant, δ is the induced chemical shift, and ΔB is the bound chemical shift. A more general and accurate solution using a computer programme is applicable for all ratios of [L]0/[S]0. It is also shown that the conventional procedure for evaluating ΔB leads to varying values for ΔB that are generally too small, even under the most optimal conditions. Eu(DPM)34 has a KB of ca. 34.21 mol−1 with n-propylamine and KB of ca. 9.71 mol−1 with neo-pentanol. These values increase by at least 10-fold (to ≥ 1001 mol−1) for the corresponding complexes with Eu(FOD)34 shift reagent. However, the bound chemical shifts for the Eu(FOD)3 complexes are nearly the same as for the Eu(DPM)3 complexes. Finally, it is shown definitively that the association between Eu(DPM)3 and either n-propylamine or neo-pentanol has 1:1 stoichiometry; with Eu(FOD)3 a tentative assignment of 1:1 stoichiometry can be made.

Synthesis and structure of 2?-substituted 1-(1,3-dioxan-5-yl)uracils. Positive role of the Eu(fod)3 nmr shift reagent

1981 ◽  
Vol 17 (11) ◽  
pp. 1112-1119
Author(s):  
Yu. Yu. Samitov ◽  
I. N. Goncharova ◽  
N. P. Ramzaeva ◽  
A. F. Mishnev ◽  
Ya. Ya. Bleidelis
Keyword(s):  
Shift Reagent ◽  
Positive Role ◽  
Substituted 1 ◽  
The Eu

Ligand Redistribution Equilibria in Aqueous Fluoroberyllate Solutions

1998 ◽  
Vol 53 (11) ◽  
pp. 1294-1300 ◽  
Author(s):  
Michael Schmidt ◽  
Hubert Schmidbaur
Keyword(s):  
Experimental Data ◽  
Ligand Exchange ◽  
Room Temperature ◽  
Chemical Shifts ◽  
Equilibrium Constants ◽  
Individual Species ◽  
Ph Values ◽  
Exchange Processes ◽  
The Individual ◽  
Good Agreement

The composition of aqueous fluoroberyllate solutions has been studied by 9Be and 19F NMR spectroscopy for various ratios of the beryllium and fluorine concentrations, and at different pH values. The equilibrium constants have been determined for the ligand exchange processes, which involve the species [Be(OH2)4]2+, [BeF(OH2)3]+, [BeF2(OH2)2], [BeF3(OH2)]- , and [BeF4]2-. These equilibria are shifted towards [BeF4]2- at high pH. No polynuclear fluoroberyllates have been detected. The fluoride exchange between the individual species is slow on the NMR time scale at room temperature, and separate sharp signals with the expected multiplicity are therefore recorded. Calculated 9Be chemical shifts are in good agreement with experimental data.

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.

1-Iodoacétylènes. IV. Relations structure–réactivité pour la complexation des 1-iodoacétylènes substitués avec des bases de Lewis

1983 ◽  
Vol 61 (1) ◽  
pp. 135-138 ◽  
Author(s):  
Christian Laurence ◽  
Michèle Queignec-Cabanetos ◽  
Bruno Wojtkowiak
Keyword(s):  
Complex Formation ◽  
Triple Bond ◽  
Vibrational Frequency ◽  
Chemical Shifts ◽  
Structural Parameters ◽  
Equilibrium Constants ◽  
Lewis Acidity ◽  
Frequency Shifts ◽  
Substituent Constants ◽  
Substituted 1

The equilibrium constants for complex formation between the substituted 1-iodoacetylènes 1–8 and the vibrational frequency shifts induced by complex formation are related to the electronic substituent constants. The 13C chemical shifts of the triple bond are also useful structural parameters for predicting the Lewis acidity of iodoalkynes.

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