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.

109Ag NMR-Studies of the Selective Solvation of the Ag+ -Ion in Water-Ethylamine-Mixtures and of the Coordination of Halide-Anions to the Silver-Ethylamine Solvate Complexes

1980 ◽  
Vol 35 (3) ◽  
pp. 319-328 ◽  
Author(s):  
J. Kronenbitter ◽  
U. Schweizer ◽  
A. Schwenk
Keyword(s):  
Chemical Shift ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Equilibrium Constants ◽  
Relaxation Times ◽  
Solvent Mixtures ◽  
Nmr Studies ◽  
Selective Solvation ◽  
Halide Anions ◽  
Chlorine Ion

Abstract109Ag chemical shift measurements of 0.02 up to 3 molar solutions of AgNO3, AgCl, and AgBr in solvent mixtures of H2O (W) and ethylamine (ea) were performed. The extremely long relaxation times T1 and T2 were determined with new techniques. The Ag+ -ion in solvent mixtures of W and ea shows a strongly selective solvation by ea. The 109Ag chemical shift of the solvate complex [Ag ea2]+ surrounded solely by W is δ2 = (335 ± 2) ppm (referred to the Ag+-ion in W). A further solvation in addition to the inner solvation sphere was determined; this solvation is not or only weakly selective. There is a rapid chemical exchange; the lifetime of the inner solvation sphere is long compared with the Larmor period, whereas the solvation outside this sphere is changed in times shorter than the Larmor period. In contrast to the NO3- -anion, the halide anions Cl- and Br- are partly coordinated to the [Ag ea2]+ complex. The equilibrium constants for this coordination were determined as well as the chemical shifts of the [Ag ea2 · Cl] and the [Ag ea2 · Br] complexes. The bromine ion is coordinated for shorter times than the Larmor period, whereas the time of the coordination of the chlorine ion may be comparable to the Larmor period or shorter.

Chemical shifts for compounds of the group IV elements silicon and tin

1968 ◽  
Vol 46 (8) ◽  
pp. 1399-1414 ◽  
Author(s):  
B. K. Hunter ◽  
L. W. Reeves
Keyword(s):  
Chemical Shift ◽  
Complex Formation ◽  
Chemical Shifts ◽  
Equilibrium Constants ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Shielding Effect ◽  
Spin Lattice ◽  
Group Iv Elements

Chemical shifts for 29Si in seven series of molecules of the type XnSiY4−n have been measured where Y is an alkyl group and X varies widely in electronegativity. A considerable amount of proton and fluorine chemical shift data has been obtained for the same compounds and in one series (CH3)nSiCl4−n the 13C chemical shifts in the methyl groups have been measured.The gross features of the 29Si chemical shifts are understood by considering the series (Alkyl)3SiX with the electronegativity of X widely varied. The hybridization at silicon is approximately conserved in these series and the theoretically anticipated linear dependence on electronegativity of X is demonstrated. The ligands X = O, N, and F are exceptional and these 29Si chemical shifts have a high field shift. This additional shielding has been associated with (p → d)π bonding. The approximate nature of present chemical shift theories is not likely to provide a measure of the order of (p → d)π bonding.The 29Si chemical shifts in the series XnSiY4−n are discussed and also indicate a net shielding effect with (p → d)π bonding. A comparison is always made with corresponding 13C chemical shifts. A long range proton–proton coupling in molecules Me3SnX and Me2SnX2, H—C—Si—C—H, is observed when and only when X = O, (N?), F.119Sn chemical shifts in a series of alkyltin compounds have been measured. The same dependence on the electronegativity of X in the series (Alkyl)3SnX is noted, but the variation of X is much more limited. Some shielding due to (p → d)π bonding in the series (n-Butyl)nSnCl4−n is suggested. The tin chemical shift has been measured as a function of concentration and solvent for simple methyltin bromides and chlorides. In donor solvents, it has been possible to obtain equilibrium constants for complex formation from tin dilution chemical shifts. The nature of the bonding in complexes suggested previously is consistent with the variations in the coupling constant |JSn–C–H| with concentration. The distinction between ionization and complex formation with the solvent for (CH3)2SnCl2 can be made on the basis of the concentration dependence of |JSn–C–H|The spin–lattice relaxation time T1for 13C and 29Si in natural abundance in several pure degassed compounds has been measured. These are not in the case of 13C (as has been suggested) of the order several minutes, but are always less than 50 s and in one case as low as 3–4 s. Both 29Si and 13C T1 values follow what might be expected on the basis of a dipole–dipole mechanism from the closest protons. The short value of 35 s in CS2 is probably a result of spin–rotation interaction in the liquid state.

The Photochemically Produced Ketyl of Perfluorobenzophenone: Electron Spin Resonance Studies of Solvent Effects

1973 ◽  
Vol 51 (19) ◽  
pp. 3211-3216 ◽  
Author(s):  
Frederick Peter Sargent ◽  
Marshall Grant Bailey
Keyword(s):  
Electron Spin Resonance ◽  
Equilibrium Constant ◽  
Mole Fraction ◽  
Electron Spin ◽  
Solvent Effects ◽  
Chemical Exchange ◽  
Solvent Molecule ◽  
Solvent Mixtures ◽  
Ketyl Radical ◽  
Spin Resonance

The ketyl radical is formed when solutions of perfluorobenzophenone are photolyzed with u.v. light. The radical was identified by electron spin resonance (e.s.r.) studies of the effects of solvent, temperature, chemical exchange, and deuteration on the spectra. Solvent mixtures of cyclohexane and ethanol gave spectra which were very sensitive to the mole fraction of alcohol in the range 0–1%. An equilibrium constant for solvent molecule exchange has been deduced.

scholarly journals Carbon-13 NMR Chemical Shift of Methyl Group: A Useful Parameter for Structural Analysis of C-Methylated Flavonoids

2006 ◽  
Vol 1 (11) ◽  
pp. 1934578X0600101
Author(s):  
Pawan K. Agrawal ◽  
Chandan Agrawal ◽  
Shravan Agrawal
Keyword(s):  
Structural Analysis ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Nmr Chemical Shift ◽  
Methyl Group ◽  
Nmr Chemical Shifts ◽  
Nmr Study ◽  
Pterocarpus Santalinus ◽  
Group A ◽  
C Nmr

The 13C NMR resonances corresponding to the C-Me group of C-6 and/or C-8 C-methylated-flavonoids absorb between 6.7–10.0 ppm and typically between 6.7–8.7 ppm. A comparative 13C NMR study reflects that the 13C NMR chemical shifts reported for 6-hydroxy-5-methyl-3′,4′,5′-trimethoxyaurone-4-O-α-L-rhamnoside from Pterocarpus santalinus and 8-C-methyl-5,7,2′,4′- tetramethoxyflavanone from Terminalia alata are inconsistent with the assigned structures, and therefore need reconsideration.

Reactions of vanadate with N,N- dimethylhydroxylamine: aqueous equilibria and the crystal structure of the uncharged oxygenbridged dimer of bis(N,N-dimethylhydroxamido)hydroxooxovanadate

1997 ◽  
Vol 75 (4) ◽  
pp. 429-440 ◽  
Author(s):  
Pradip C. Paul ◽  
Sarah J. Angus-Dunne ◽  
Raymond J. Batchelor ◽  
Frederick W.B. Einstein ◽  
Alan S. Tracey
Keyword(s):  
Crystal Structure ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Variable Temperature ◽  
Crystalline Solid ◽  
Resonance Spectroscopy ◽  
Reaction Products ◽  
Orthorhombic Space Group ◽  
Ph Variation ◽  
Nmr Study

51V nuclear magnetic resonance spectroscopy has been utilized in the investigation of the reactions of vanadate with N,N-dimethylhydroxylamine in aqueous medium. The major components of the reaction products were mono- and bisliganded mononuclear vanadate compounds with 51V chemical shifts near −630 and −740 ppm, respectively. Variation of the concentration of the reactants enabled the determination of stoichiometry and formation constants of the products. The two major signals near −740 ppm were assigned to two stereoisomers of a bisligand product. The proton stoichiometrics and pKa values of the major products were determined from pH variation studies. A crystalline product of the type [V(O)(ONMe2)2]2O was isolated from the reaction of vanadate with dimethylhydroxylamine and its structure determined from X-ray diffraction studies. The compound possesses a dimeric oxo-bridge structure with a six-coordinate vanadium core. The arrangement about each vanadium may be described as approximately tetrahedral considering the center of the N—O bond in each dimethylhydroxamide ligand as one vertex. Hydrolysis of the crystalline solid in D2O provided two isomers that corresponded to the two bisligand products. A variable temperature 1H NMR study in D2O and 50% D2O/(CD3)2CO mixture revealed the existence of reasonably fast chemical exchange between the two predominant isomers. The nature of coordination of these and related compounds is discussed. Crystal structure of [V(O)(ONMe2)2]2O: orthorhombic, space group P22121;Z = 2;a = 7.0955(9) Å; b = 10.2313(12) Å; c = 11.5942(11) Å; V = 841.69 Å3; T = 213 K; RF = 0.021 for 1141 data (I0 ≥ 2.5σ(I0) ) and 137 variables. Keywords: bis(N,N-dimethylhydroxamido)hydroxooxovanadate, vanadate, dimethylhydroxylamine, vanadium NMR, aqueous equilibria, peroxovanadate.

scholarly journals 1H-NMR characterization of l-tryptophan binding to TRAP, the trp RNA-binding attenuation protein of Bacillus subtilis

1996 ◽  
Vol 315 (3) ◽  
pp. 895-900 ◽  
Author(s):  
Vasudevan RAMESH ◽  
Tom BROWN
Keyword(s):  
Bacillus Subtilis ◽  
Complex Formation ◽  
1H Nmr ◽  
Rna Binding ◽  
Chemical Exchange ◽  
Chemical Shifts ◽  
Large Change ◽  
Binding Pocket ◽  
Nmr Study ◽  
Nmr Characterization

A 1H-NMR study of the binding of L-tryptophan to the trp RNA-binding attenuation protein of Bacillus subtilis (TRAP), an ondecamer (91.6 kDa), has been implemented. The assignment of the aromatic indole ring proton resonances of the bound tryptophan ligand has been successfully carried out by two-dimensional chemical exchange experiments. The observation of only a single set of chemical shifts of the bound ligand demonstrates that the tryptophan binding site is identical in all the 11 subunits of the protein. Further, the large change in ligand chemical shifts suggests that the conformation of tryptophan ligand undergoes a significant rearrangement after complex formation with TRAP. This is further substantiated by the extensive ligand-induced chemical shift changes observed to the protein resonances and identification of several strong ligand–protein intermolecular nuclear Overhauser effects. A correlation of these preliminary NMR data with the X-ray crystal structure of the TRAP–tryptophan complex also suggests, tentatively, that the observed changes to the NMR spectra of the protein might correspond to changes associated with residues surrounding the tryptophan binding pocket owing to complex formation.

The ortho effect in ortho-substituted 2-(X-benzal)-1,3-indanediones, 3-(2-X-benzal)phthalides and 3-(2-X-benzal)-5,6-dihydro-4,7-dithiaphthalides: A 1H-NMR study

1980 ◽  
Vol 45 (5) ◽  
pp. 1589-1594 ◽  
Author(s):  
Ľudovít Krasnec ◽  
Eva Solčániová ◽  
Pavol Hrnčiar
Keyword(s):  
Chemical Shift ◽  
Field Effect ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Methine Proton ◽  
Electronic Effects ◽  
H Nmr ◽  
Nmr Study ◽  
Considerable Distortion ◽  
The Common

The 1H-NMR spectra of ortho-substituted 2-(X-benzal)-1,3-indanediones, 3-(2-X-benzal)-phthalides and 3-(2-X-benzal)-5,6-dihydro-4,7-dithiaphthalides have been studied. The chemical shifts observed for the methine proton were correlated with various constants of the substituents. In addition to simple correlations, two- and three-parameter correlations were also made. Statistically most important one-parameter correlations were observed for σp-constants. Apart from the common electronic effects, in the transfer of effects of the substituents from the ortho-position upon the chemical shift of the methine proton the field effect plays also an important role. The deviations observed in the case of substances substituted in both ortho-positions confirm the assumed considerable distortion of the coplanarity of the studied systems.

A 139La NMR study of the interactions between the La(III) cation and D-ribose in aqueous solution

1994 ◽  
Vol 72 (7) ◽  
pp. 1753-1757 ◽  
Author(s):  
Zhigang Chen ◽  
Nicole Morel-Desrosiers ◽  
Jean-Pierre Morel ◽  
Christian Detellier
Keyword(s):  
Aqueous Solution ◽  
Nmr Spectroscopy ◽  
Chemical Shift ◽  
Stability Constant ◽  
Chemical Shifts ◽  
Similar Treatment ◽  
Calorimetric Measurements ◽  
Nmr Study ◽  
The Stability ◽  
Good Agreement

The interactions of the La(III) cation with D-ribose and with D-arabinose in aqueous solution were investigated by 139La NMR spectroscopy. In the case of D-ribose, the formation of a La(III)-sugar complex was indicated by variations of the 139La chemical shift and linewidth with an increase of the sugar concentration in solution. In contrast, the complexation of La(III) by arabinose is very weak and almost undetectable by 139La NMR. On the basis of a 1:1 stoichiometry, the stability constant for the complex of La(III) with D-ribose was calculated from the observed 139La chemical shift values. A similar treatment was done for the viscosity corrected 139La linewidths using arabinose as an uninteractive reference. The stability constants, K, obtained independently from 139La chemical shifts and linewidths are in good agreement, 2.8 ± 0.5 and 2.2 ± 0.6 M−1 respectively at 299.0 ± 0.5 K. The thermodynamic parameters for the complexation of La(III) by D-ribose could also be obtained: ΔH0 = −12 ± 2 kJ mol−1, and ΔS0 = −31 ± 5 J K−1 mol−1. These values are in very good agreement with those obtained by calorimetric measurements.

13C NMR chemical shift calculations of charged surfactants in water — A combined density functional theory (DFT) and molecular dynamics (MD) methodological study

2013 ◽  
Vol 91 (7) ◽  
pp. 529-537 ◽  
Author(s):  
T. Mineva ◽  
Y. Tsoneva ◽  
R. Kevorkyants ◽  
A. Goursot
Keyword(s):  
Chemical Shift ◽  
Density Functional ◽  
Chemical Shifts ◽  
Water Solution ◽  
Basis Set ◽  
Conformational Sampling ◽  
Sodium Octanoate ◽  
Solvent Molecules ◽  
Isotropic Chemical Shifts ◽  
C Nmr

Structural and magnetic properties of one anionic and one cationic amphiphile molecule (sodium octanoate and hexadecyltrimethylammonium chloride, respectively) in water are studied comparing different methods to account for the presence of the solvent. Calculated 13C NMR chemical shifts are used as the probe for accuracy of the theoretical electronic structures obtained with different descriptions of the surfactants in water solution. The best agreement with the experimental data are obtained by averaging 13C NMR isotropic chemical shifts over a large number of conformational structures of sodium octanoate while considering the electronic structure of the solvent molecules. The 13C chemical shift values of the hexadecyltrimethylammonium alkane chain are systematically overestimated by 10–15 ppm even if an extensive conformational sampling and water as the polarized continuum medium have been taken into consideration. The role of the basis set quality has been studied and discussed as well.

An NMR study of ligand binding by maltodextrin binding protein

1998 ◽  
Vol 76 (2-3) ◽  
pp. 189-197 ◽  
Author(s):  
Kalle Gehring ◽  
Xiaochen Zhang ◽  
Jason Hall ◽  
Hiroshi Nikaido ◽  
David E Wemmer
Keyword(s):  
Chemical Shift ◽  
Ligand Binding ◽  
Conformational Changes ◽  
Chemical Exchange ◽  
Binding Protein ◽  
Difference Spectra ◽  
One Dimensional ◽  
Beta Cyclodextrin ◽  
Nmr Study ◽  
Maltodextrin Binding Protein

Proton NMR spectra of maltodextrin binding protein from Escherichia coli were used to monitor conformational changes that accompany ligand binding. Chemical shift changes associated with the binding of different maltodextrins to maltodextrin binding protein were studied using one-dimensional difference spectra. Line-shape analysis of an isolated upfield methyl resonance was used to measure the kinetics of maltose binding at several temperatures. Maltose and linear maltodextrins caused similar changes to the upfield protein spectrum with no detectable differences between alpha and beta sugar anomers. Binding of a cyclic ligand, beta-cyclodextrin, caused smaller chemical shift changes than binding of linear maltodextrins. Two maltodextrin derivatives were also studied. Both maltohexaitol and maltohexanoic acid gave one-dimensional difference spectra that were intermediate between those of linear maltodextrins and beta-cyclodextrin. The methyl resonances at -1 and -0.35 ppm were assigned to leucine 160 on the basis of homonuclear COSY and TOCSY experiments and theoretical chemical shift calculations using the X-ray crystal structure of maltodextrin binding protein.Key words: maltose binding protein, chemical shifts, chemical exchange, sugar anomer specificity.

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