Water solvent exchange rates of primary amides. Acid-catalyzed NMR saturation transfer as an indicator of rotation and structure of the protonated form

1979 ◽  
Vol 101 (21) ◽  
pp. 6151-6162 ◽  
Author(s):  
A. G. Redfield ◽  
S. Waelder
Keyword(s):  
Exchange Rates ◽  
Protonated Form ◽  
Solvent Exchange ◽  
Saturation Transfer ◽  
Water Solvent ◽  
Acid Catalyzed

scholarly journals 3D printing of a biocompatible low molecular weight supramolecular hydrogel by dimethylsulfoxide water solvent exchange

2020 ◽  
Vol 33 ◽  
pp. 101162
Author(s):  
Anaïs Chalard ◽  
Morgane Mauduit ◽  
Sandrine Souleille ◽  
Pierre Joseph ◽  
Laurent Malaquin ◽  
...  
Keyword(s):  
Molecular Weight ◽  
3D Printing ◽  
Low Molecular Weight ◽  
Solvent Exchange ◽  
Supramolecular Hydrogel ◽  
Water Solvent

scholarly journals Modeling size controlled nanoparticle precipitation with the co-solvency method by spinodal decomposition

Soft Matter ◽  
2016 ◽  
Vol 12 (34) ◽  
pp. 7231-7240 ◽  
Author(s):  
Simon Keßler ◽  
Friederike Schmid ◽  
Klaus Drese
Keyword(s):  
Exchange Rates ◽  
Spinodal Decomposition ◽  
Scaling Relations ◽  
Solvent Exchange ◽  
Nanoparticle Sizes ◽  
Size Controlled

Experimentally observed scaling relations between nanoparticle sizes and solvent exchange rates can be explained by spinodal decomposition.

A Carbon-13 Nuclear Magnetic Resonance Study of Cation Solvation in Alcohols

1974 ◽  
Vol 52 (5) ◽  
pp. 744-748 ◽  
Author(s):  
Gerald W. Stockton ◽  
John S. Martin
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Exchange Rates ◽  
Low Temperatures ◽  
Solvation Shell ◽  
Nuclear Magnetic Resonance Study ◽  
Solvent Exchange ◽  
Magnetic Resonance Study ◽  
Sign Reversal ◽  
Solvation Complex

Natural abundance 13C spectra of solvent coordinated to the cation have been observed in solutions of Mg(II) and Al(III) salts in alcohols. Carbon shielding changes induced by cations resemble those induced by electronegative substituents; a sign reversal between the β and γ positions is found in both instances. Solvent exchange rates correspond to those found by 1H n.m.r.; this confirms that whole molecule exchange is dominant. Selective relaxation of the solvation shell signals at low temperatures reflects differences in conformational mobility within the solvation complex.

Study of the exchange rates of ethanol and water on ferriprotoporphyrin IX by n.m.r. line broadening

1969 ◽  
Vol 47 (17) ◽  
pp. 3217-3224 ◽  
Author(s):  
N. S. Angerman ◽  
B. B. Hasinoff ◽  
H. B. Dunford ◽  
R. B. Jordan
Keyword(s):  
Exchange Rates ◽  
Temperature Jump ◽  
Aqueous Ethanol ◽  
Ion Pair ◽  
Solvent Composition ◽  
Water Proton ◽  
Solvent Exchange ◽  
Line Broadening ◽  
Kcal Mole ◽  
Ethanol Molecule

The nuclear magnetic resonance (n.m.r.) line broadening technique has been used to determine the rate of solvent exchange from the first coordination sphere of ferriprotoporphyrin IX (hemin) in aqueous ethanol. The line broadenings of the methyl and methylene protons of ethanol and the water protons have been studied as a function of solvent composition at 35° and of temperature in 48.8 mole % ethanol.The average values of the kinetic parameters for ethanol molecule exchange, taken from the CH3 and CH2 proton broadening are ΔH≠ = 6.2 ± 1.0 kcal mole−1 and ΔS≠ = −9.1 ± 4.4 cal mole−1 deg−1. Both proton transfer and water molecule exchange contribute to the water proton line broadening with a net value of ΔH≠ = 6.3 ± 0.5 kcal mole−1 and ΔS≠ = −3.8 ± 2.0 cal mole−1 deg−1.From the n.m.r. study at varying solvent composition, it is concluded that monomeric and dimeric hemin undergo solvent exchange at the same rate. The equilibrium constant for formation of the monoethanol solvated hemin from hydroxyhemin is determined as 8.7 at 35° from this study.A comparison of the rate of ethanol exchange (1.8 × 106 s−1 at 25°) and the rate of imidazole binding to hemin (from a separate temperature jump study) indicates that the imidazole substitution occurs through an SN1 ion pair mechanism.

Hydration of the carbonyl group — Acetic acid catalysis in the co-operative mechanism

2005 ◽  
Vol 83 (6-7) ◽  
pp. 769-785 ◽  
Author(s):  
Yih-Huang Hsieh ◽  
Noham Weinberg ◽  
Kiyull Yang ◽  
Chan-Kyung Kim ◽  
Zheng Shi ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Carbonyl Group ◽  
Isotope Shift ◽  
Acid Catalysis ◽  
Water Molecules ◽  
Hydration Reaction ◽  
Water Solvent ◽  
General Acid ◽  
O Isotope ◽  
Acid Catalyzed

In a co-operative reaction, solvent molecules, specifically water molecules, participate actively in the mechanism to circumvent the formation of charged intermediates. This paper extends our earlier theoretical treatment of the neutral co-operative hydration of acetone to include general acid catalysis by acetic acid. As before, the predominant neutral channel employs three catalytic water molecules. The principal acetic acid catalyzed channels employ one catalytic water molecule and, in approximately equal proportions, one or both oxygens of the carboxyl group. The theoretical rate constant for general acid catalysis is calculated to be 0.49 M–1 s–1 at 298 K. This compares to an estimated experimental value of 0.30 M–1 s–1 for acetic acid catalyzed hydration of acetone at 298 K in water solvent, determined by using the 18O-isotope shift in the 13C NMR spectrum of 2-13C-labelled acetone as a kinetic probe. It is concluded that the notion of co-operativity can be extended to include general acid catalysis of the hydration of a carbonyl group in water solvent. This creates an obvious problem for the generally accepted view that multistep ionic mechanisms are operative in the low dielectric media that exist at the active sites of hydrolytic enzymes. The relevance of this finding to the mechanisms of action of β-lactam antibiotics has been noted.Key words: hydration, reaction mechanism, co-operativity, general acid catalysis, ab initio, SCRF, 18O-isotope shift.

scholarly journals Exchange rates of creatine kinase metabolites: feasibility of imaging creatine by chemical exchange saturation transfer MRI

2012 ◽  
Vol 25 (11) ◽  
pp. 1305-1309 ◽  
Author(s):  
Mohammad Haris ◽  
Ravi Prakash Reddy Nanga ◽  
Anup Singh ◽  
Kejia Cai ◽  
Feliks Kogan ◽  
...  
Keyword(s):  
Creatine Kinase ◽  
Exchange Rates ◽  
Chemical Exchange ◽  
Chemical Exchange Saturation Transfer ◽  
Saturation Transfer

15NH/D-SOLEXSY experiment for accurate measurement of amide solvent exchange rates: application to denatured drkN SH3

2010 ◽  
Vol 46 (3) ◽  
pp. 227-244 ◽  
Author(s):  
Veniamin Chevelkov ◽  
Yi Xue ◽  
D. Krishna Rao ◽  
Julie D. Forman-Kay ◽  
Nikolai R. Skrynnikov
Keyword(s):  
Exchange Rates ◽  
Solvent Exchange ◽  
Amide Solvent ◽  
Amide Solvent Exchange
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