Na+ and K+ Binding by Fulvic Acid

1973 ◽  
Vol 51 (19) ◽  
pp. 3217-3222 ◽  
Author(s):  
Donald S. Gamble
Keyword(s):  
Aqueous Solution ◽  
Fulvic Acid ◽  
Free Energies ◽  
Acid Base ◽  
Titration Curves ◽  
Electrostatic Binding ◽  
Binding Regions

The electrostatic binding of Na+ and K+ by fulvic acid in aqueous solution has been measured with cation electrodes at 25.00 °C ± 0.05. The binding equilibria were followed during the course of acid–base titrations, and have revealed distinct binding regions in the titration curves. In one of these regions Na+ is more strongly bound than is K+. The standard free energies of binding were 11.7 × 103 to 20.5 × 103 J/mol ± 2% for Na+, and 11.5 × 103 to 17.8 × 103 J/mol ± 1%, for K+.

scholarly journals Effect of the ionic strength on the acid-base titration curves of a soil fulvic acid

Analusis ◽  
1999 ◽  
Vol 27 (5) ◽  
pp. 414-417 ◽  
Author(s):  
A. Ramos ◽  
S. López ◽  
R. López ◽  
S. Fiol ◽  
F. Arce ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Fulvic Acid ◽  
Acid Base ◽  
Titration Curves ◽  
Acid Base Titration

scholarly journals The combination of proteins, amino-acids, &c., with acids and alkalis. Part II.—Titration curves of amino-acids in presence of formaldehyde

1929 ◽  
Vol 104 (732) ◽  
pp. 412-439 ◽  
Keyword(s):  
Aqueous Solution ◽  
Amino Acids ◽  
Detailed Examination ◽  
Acid Base ◽  
Base Equilibrium ◽  
Titration Curves ◽  
Maximum Accuracy ◽  
Acid Base Equilibrium ◽  
Derivatives Of

Grounds for an Investigation. 1.A detailed examination of the acid-base equilibrium and the titration curves of amino-acids in aqueous solution has already been made (1), but data have hitherto been lacking for these solutions in the presence of formal-dehyde, i . e ., relating to the methylene derivatives of the amino-acids. 2.The addition of formaldehyde to amino-acids and the resulting increase in their acidity towards phenol phthalein (or thymol phthalein) constitutes the basis of the well-known Sørensen (“formol”) method (2) for their estimation by titration with soda; accordingly some knowledge of the acid-base constants and the titration curves of the systems in question is necessary before one can formulate the conditions (viz., the concentrations of formaldehyde and amino-acids, and the initial and final p h readings, etc.) under which this estimation may be carried out with maximum accuracy.

2-Deoxyribose Radicals in the Gas Phase and Aqueous Solution. Transient Intermediates of Hydrogen Atom Abstraction from 2-Deoxyribofuranose

2005 ◽  
Vol 70 (11) ◽  
pp. 1769-1786 ◽  
Author(s):  
Luc A. Vannier ◽  
Chunxiang Yao ◽  
František Tureček
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Atom ◽  
Gas Phase ◽  
Computational Study ◽  
Hydrogen Atom Abstraction ◽  
Oh Radical ◽  
Free Energies ◽  
Intramolecular Hydrogen ◽  
Solvation Free Energies ◽  
Transient Intermediates

A computational study at correlated levels of theory is reported to address the structures and energetics of transient radicals produced by hydrogen atom abstraction from C-1, C-2, C-3, C-4, C-5, O-1, O-3, and O-5 positions in 2-deoxyribofuranose in the gas phase and in aqueous solution. In general, the carbon-centered radicals are found to be thermodynamically and kinetically more stable than the oxygen-centered ones. The most stable gas-phase radical, 2-deoxyribofuranos-5-yl (5), is produced by H-atom abstraction from C-5 and stabilized by an intramolecular hydrogen bond between the O-5 hydroxy group and O-1. The order of radical stabilities is altered in aqueous solution due to different solvation free energies. These prefer conformers that lack intramolecular hydrogen bonds and expose O-H bonds to the solvent. Carbon-centered deoxyribose radicals can undergo competitive dissociations by loss of H atoms, OH radical, or by ring cleavages that all require threshold dissociation or transition state energies >100 kJ mol-1. This points to largely non-specific dissociations of 2-deoxyribose radicals when produced by exothermic hydrogen atom abstraction from the saccharide molecule. Oxygen-centered 2-deoxyribose radicals show only marginal thermodynamic and kinetic stability and are expected to readily fragment upon formation.

A QM/MM study combined with the theory of energy representation: Solvation free energies for anti/syn acetic acids in aqueous solution

2006 ◽  
Vol 419 (1-3) ◽  
pp. 240-244 ◽  
Author(s):  
Takumi Hori ◽  
Hideaki Takahashi ◽  
Masayoshi Nakano ◽  
Tomoshige Nitta ◽  
Weitao Yang
Keyword(s):  
Aqueous Solution ◽  
Free Energies ◽  
Solvation Free Energies ◽  
Acetic Acids

The influence of β-cyclodextrin on acid–base and tautomeric equilibrium of fluorescein dyes in aqueous solution

2010 ◽  
Vol 345 (13) ◽  
pp. 1882-1890 ◽  
Author(s):  
Larisa N. Bogdanova ◽  
Nikolay O. Mchedlov-Petrossyan ◽  
Natalya A. Vodolazkaya ◽  
Alexander V. Lebed
Keyword(s):  
Aqueous Solution ◽  
Tautomeric Equilibrium ◽  
Acid Base ◽  
Fluorescein Dyes

Acid-Base Titration Curves in Disproportionating Redox Systems

1994 ◽  
Vol 71 (8) ◽  
pp. 632 ◽  
Author(s):  
Tadeusz Michalowski ◽  
Andrzej Lesiak
Keyword(s):  
Redox Systems ◽  
Acid Base ◽  
Titration Curves ◽  
Acid Base Titration

Acid–base titration curves of solid humic acids

2008 ◽  
Vol 68 (1) ◽  
pp. 242-247 ◽  
Author(s):  
Pavel Janoš ◽  
Sylvie Kříženecká ◽  
Libuše Madronová
Keyword(s):  
Humic Acids ◽  
Acid Base ◽  
Titration Curves ◽  
Acid Base Titration
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