Notizen: 67Zn NMR Anomalous Solvent Isotope Effect in Aqueous Solutions

1974 ◽  
Vol 29 (4) ◽  
pp. 660-661 ◽  
Author(s):  
B. W. Epperlein ◽  
H. Krüger ◽  
. Lutz ◽  
A. Schwenk
Keyword(s):  
Aqueous Solutions ◽  
Isotope Effect ◽  
Solvent Isotope Effect ◽  
Zinc Bromide ◽  
The Difference ◽  
Solvent Isotope

For 67Zn NMR lines of solutions of ZnCl2, ZnBr2, and ZnI2 in H2O and D2O an anomalous solvent isotope effect is reported. In D2O solutions the lines are shifted to higher frequencies. The difference between the shieldings in H2O and D2O is e.g. σ(H2O) - σ(D2O) = (13.1 ±0.7) ppm for a concentration of 0.02 moles zinc bromide per mole solvent.

11B and 10B NMR Investigations in Aqueous Solutions

1986 ◽  
Vol 41 (5) ◽  
pp. 737-742 ◽  
Author(s):  
R. Balz ◽  
U. Brändle ◽  
E. Kämmerer ◽  
D. Köhnlein ◽  
O. Lutz ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Isotope Effect ◽  
Chemical Shifts ◽  
Relaxation Mechanism ◽  
Magnetic Shielding ◽  
Solvent Isotope Effect ◽  
Weighted Averages ◽  
Dilute Aqueous Solutions ◽  
Ph Dependent ◽  
Solvent Isotope

11B NMR chemical shifts and linewidths have been measured in very dilute aqueous solutions of boric acid and borates. The results can be explained bv taking pH dependent weighted averages over the species B(OH)3 and B(OH)4−. The11B−10B primary isotope effect on the magnetic shielding is smaller then 3 · 10-8. The H2O - D2O solvent isotope effect on T1 has been established for 11B and 10B in the species mentioned, and from the ratios of T1 the quadrupolar origin of the relaxation mechanism has been inferred.

Calculation of the Thermodynamic Solvent Isotope Effect for Ferrousand FerricIons in Water

1989 ◽  
Vol 44 (5) ◽  
pp. 385-394 ◽  
Author(s):  
Charles L. Kneifel ◽  
Harold L. Friedman ◽  
Marshall D. Newton
Keyword(s):  
Isotope Effect ◽  
Correlation Functions ◽  
Hydration Shell ◽  
Power Spectra ◽  
Large Degree ◽  
Model Potential ◽  
Solvent Isotope Effect ◽  
The Difference ◽  
Dynamics Simulations ◽  
Solvent Isotope

Molecular dynamics simulations of molecular models of Fe2+ and Fe3+ in water (L2O = H2O or D2O) are used to generate various correlation functions that characterize the respective hexaaquo hydration complexes. The static Fe2+-oxygen and Fe2+-hydrogen correlation functions are compared in detail with the first difference neutron diffraction results of Enderby et al. for Ni2+ . Velocity autocorrelation functions and corresponding power spectra are generated and analyzed for those modes of hydration shell water molecules whose reduced masses are most sensitive to the changes from H2O to D2O. Various approximations are applied to these data to calculate the solvent isotope effect on the difference in hydration free energies for Fe2+ and Fe3+ . These different approximations all lead to the qualitative conclusion that the net solvent isotope effect reflects a large degree of cancellation between the OL stretching modes and the librational modes. The simulation results generally agree with the results of earlier quantum chemical calculations applied to the same system, but in some respects the new results are not as realistic as the earlier ones. It is proposed that the agreement with experiment would be improved by changes in the model potential which are motivated by other, independent considerations.

Neutral Solvolysis of Acyl Carbon and the Temperature Dependence of the Kinetic Solvent Isotope Effect

1975 ◽  
Vol 53 (6) ◽  
pp. 869-877 ◽  
Author(s):  
B. Rossall ◽  
R. E. Robertson
Keyword(s):  
Temperature Dependence ◽  
Isotope Effect ◽  
Solvent Isotope Effect ◽  
Acyl Carbon ◽  
Rate Of Hydrolysis ◽  
Solvent Isotope ◽  
Neutral Conditions ◽  
Hydrolysis Of

The temperature dependence of the rate of hydrolysis of benzoic, phthalic, and succinic anhydrides have been determined in H2O and D2O under "neutral" conditions. Corresponding data have been obtained for methyl trifluoroacetate. While both series supposedly react by the same BAc2 mechanism, remarkable differences are made obvious by this investigation. Possible sources of such differences are proposed.

An Unusual Solvent Isotope Effect in the Reaction of W(CO)5(solv) (solv = Cyclohexane or Cyclohexane-d12) with THF

2000 ◽  
Vol 19 (9) ◽  
pp. 1682-1691 ◽  
Author(s):  
Riki Paur-Afshari ◽  
J. Lin ◽  
Richard H. Schultz
Keyword(s):  
Isotope Effect ◽  
Solvent Isotope Effect ◽  
Solvent Isotope

scholarly journals One-proton catalysis by the α-l-arabinofuranosidase III of Monilinia fructigena

1988 ◽  
Vol 254 (3) ◽  
pp. 899-901 ◽  
Author(s):  
T Selwood ◽  
M L Sinnott
Keyword(s):  
Isotopic Composition ◽  
Isotope Effect ◽  
Solvent Isotope Effect ◽  
Monilinia Fructigena ◽  
Single Proton ◽  
Solvent Isotope ◽  
Hydrolysis Of

1. Michaelis-Menten parameters for the hydrolysis of p-nitrophenyl alpha-L-arabinofuranoside were measured as a function of pL (pH or pD) in both 1H2O and 2H2O. 2. The variation of both Vmax. and Vmax./Km with pL is sigmoid, the pK governing Vmax. shifting from 6.34 +/- 0.05 in 1H2O to 6.84 +/- 0.07 in 2H2O, and that governing Vmax./Km from 5.89 +/- 0.03 in 1H2O to 6.38 +/- 0.05 in 2H2O. 3. In the plateau regions there is a small inverse solvent isotope effect on Vmax./Km (0.92), and one of 1.45 on Vmax. 4. The variation of Vmax. with isotopic composition is strictly linear, indicating that the isotope effect arises from the transfer of a single proton.

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