Kinetics and Equilibrium of Binding of Fe3+ by a Fulvic Acid: A Study by Stopped Flow Methods

1975 ◽  
Vol 53 (20) ◽  
pp. 2979-2984 ◽  
Author(s):  
Cooper H. Langford ◽  
Tahir R. Khan
Keyword(s):  
Ionic Strength ◽  
Complex Formation ◽  
Fulvic Acid ◽  
Metal Ion ◽  
Equilibrium Constants ◽  
Acid Dissociation ◽  
Stopped Flow ◽  
Solution Ph ◽  
Sulfosalicylic Acid ◽  
Flow Measurements

The first report of a rate of binding of a metal ion (Fe3+) by a soluble fulvic acid is derived from stopped flow measurements. The rate of complex formation is normal in Wilkins' sense and similar to that for sulfosalicylic acid. Dissociation is slow (t1/2 > 10 s). The binding of Fe3+ by the fulvic acid in acid solution, pH = 1–2.5, was investigated by kinetic analysis in which the reaction of free Fe3+ with sulfosalicylic acid was followed by stopped flow spectrophotometry on a time scale short compared to release of Fe3+ by fulvic acid. Conditional equilibrium constants found were 1.5 ± 0.3 × 104 at pH = 1.5 and 2.5, and 2.8 ± 0.3 × 103 at pH = 1.0 at 25 °C (ionic strength 0.1).

Kinetic and Thermodynamic Studies of the Reactions of Sulfite Ion with Picramide, N-Methylpicramide, and N,N-Dimethylpicramide in Aqueous Solution

1974 ◽  
Vol 52 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Erwin Buncel ◽  
Albert Richard Norris ◽  
Kenneth Edwin Russell ◽  
Peter Jura Sheridan
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Complex Formation ◽  
Equilibrium Constants ◽  
Specific Rate ◽  
Stopped Flow ◽  
Primary Role ◽  
Kinetics Of ◽  
Kinetic And Thermodynamic Studies ◽  
Sulfite Ion

The kinetics of the reactions between sulfite ion and picramide, N-methylpicramide, and N,N-dimethylpicramide, to form 1:1 σ-complexes in aqueous solutions of constant ionic strength 0.14 M, have been investigated using a stopped-flow spectrophotometer. Specific rate constants for the formation and decomposition of these three complexes at 25.0 °C are 5.7 ± 0.2 × 104M−1 s−1 and 7 ± 1 s−1, 1.4 ± 0.1 × 104M−1 s−1 and 0.20 ± 0.02 s−1, and 4.1 ± 0.2 × 103M−1 s−1 and 0.14 ± 0.04 s−1, respectively. Enthalpies and entropies of activation characterizing the formation of the 1:1 σ-complexes have been determined. Equilibrium constants, determined spectrophotometrically at a number of temperatures, have been used to calculate the enthalpy (ΔH0) and entropy (ΔS0) changes associated with 1:1 and 2:1 σ-complex formation. These values are compared with corresponding ones for complex formation of sulfite ion with 1,3,5-trinitrobenzene and 2,4,6-trinitrobenzaldehyde. The extent of solvation of the σ-complexes is considered to play a primary role in determining the observed trends in the enthalpies and entropies of reaction.

scholarly journals Sensing Zn2+ in Aqueous Solution with a Fluorescent Scorpiand Macrocyclic Ligand Decorated with an Anthracene Bearing Tail

Molecules ◽  
2020 ◽  
Vol 25 (6) ◽  
pp. 1355 ◽  
Author(s):  
Matteo Savastano ◽  
Matteo Fiaschi ◽  
Giovanni Ferraro ◽  
Paola Gratteri ◽  
Palma Mariani ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Metal Ion ◽  
Equilibrium Constants ◽  
Macrocyclic Ligand ◽  
Fluorescence Emission ◽  
Zinc Complexes ◽  
Large Excess ◽  
Macrocyclic Ring ◽  
Ph Range

Synthesis of the new scorpiand ligand L composed of a [9]aneN3 macrocyclic ring bearing a CH2CH2NHCH2-anthracene tail is reported. L forms both cation (Zn2+) and anion (phosphate, benzoate) complexes. In addition, the zinc complexes of L bind these anions. The equilibrium constants for ligand protonation and complex formation were determined in 0.1 M NaCl aqueous solution at 298.1 ± 0.1 K by means of potentiometric (pH-metric) titrations. pH Controlled coordination/detachment of the ligand tail to Zn2+ switch on and off the fluorescence emission from the anthracene fluorophore. Accordingly, L is able to sense Zn2+ in the pH range 6–10 down to nM concentrations of the metal ion. L can efficiently sense Zn2+ even in the presence of large excess of coordinating anions, such as cyanide, sulphide, phosphate and benzoate, despite their ability to bind the metal ion.

Alkali–metal ion coordination in uranyl(vi) poly-peroxo complexes in solution, inorganic analogues to crown-ethers. Part 2. Complex formation in the tetramethyl ammonium-, Li+-, Na+- and K+-uranyl(vi)–peroxide–carbonate systems

2015 ◽  
Vol 44 (37) ◽  
pp. 16565-16572 ◽  
Author(s):  
Pier Luigi Zanonato ◽  
Zoltán Szabó ◽  
Valerie Vallet ◽  
Plinio Di Bernardo ◽  
Ingmar Grenthe
Keyword(s):  
Complex Formation ◽  
Alkali Metal ◽  
Crown Ethers ◽  
Metal Ion ◽  
Equilibrium Constants ◽  
Peroxo Complexes ◽  
Alkali Metal Ion ◽  
Alkali Ions ◽  
Tetramethyl Ammonium

Equilibrium constants and 17O-NMR demonstrate that alkali ions act as templates for the formation of [(UO2)(O2)(CO3)]n rings.

Metal-ion oxidations in solution. Part XVIII. Characterization, rates, and mechanism of formation of the intermediates in the oxidation of thiols by chromium(VI)

1977 ◽  
Vol 55 (18) ◽  
pp. 3328-3334 ◽  
Author(s):  
Alexander McAuley ◽  
M. Adegboyega Olatunji
Keyword(s):  
Complex Formation ◽  
Thermodynamic Parameters ◽  
Rate Constants ◽  
Metal Ion ◽  
Formation Mechanisms ◽  
Stopped Flow ◽  
Mechanism Of Formation ◽  
Chromium Vi ◽  
Kinetics Of ◽  
Absorbance Data

The stopped-flow technique has been used to study the reactions of [HCrO4−] and penicillamine, glutathione and β-mercaptoethylamine (RSH) in perchlorate media, [H+] = 0.02−0.100 M, I = 1.00 M over the temperature range 10–30 °C. The transient orange species formed as intermediates are 1:1 chromate esters,[Formula: see text]with λmax ∼ 420–430 nm and K1 ∼ 700 (DL-penicillamine) to 1440 M−1 (glutathione) at T = 25 °C. Thermodynamic parameters for complex formation have been derived from initial absorbance data and the evidence for sulphur bonding is discussed. Kinetics of the reactions conform to the rate law[Formula: see text]Activation enthalpies lie in the range 6–10 kcal/mol but ΔS≠ values vary considerably possibly reflecting solvation effects. The rate constants kfH+ are several orders of magnitude lower than those found for this parameter in other reactions of this type. The complex formation mechanisms are discussed and the possibility of some associative character in the present reactions is considered.

scholarly journals Interaction of Salicylamide and Salicylic Acid with Iron and Cobalt and their Comparative Study by IR and NMR

2021 ◽  
pp. 53-62
Author(s):  
Mr. Mohd Waseem Wani ◽  
Dr. G. K. Chandok
Keyword(s):  
Salicylic Acid ◽  
Ionic Strength ◽  
Complex Formation ◽  
Comparative Study ◽  
Metal Ions ◽  
Equilibrium Constants ◽  
Spectroscopic Technique ◽  
Essential Metal ◽  
Vis Spectroscopy ◽  
Derivatives Of

The complexes formed by salicylic acid and several substituted derivatives of salicylic acid (Salicylamide) with essential metal ions of the soil (iron and cobalt) have been investigated at 25° and in a medium of variable ionic strength using pH. The equilibrium constants of complex formation of the 1 : 1 , 1 : 2 and1 : 3 mole ratio metal–acid complexes formed are discussed with reference to the activity degradation of substituents. Salicylic acid and Salicylamide after disposal can also react with the various metal ions present in the soil to form complexes. The rate at which these complexes are formed is done with the help of UV-vis. Spectroscopy. The complexes formed are characterized by various Spectroscopic technique viz. FTIR and NMR.

Metal-ion oxidations in solution. Part XXI. Kinetics and mechanism of the reaction of ascorbic acid, hydroquinone, and catechol with 12-tungstocobaltoate(III)

1977 ◽  
Vol 55 (20) ◽  
pp. 3581-3586 ◽  
Author(s):  
Zahid Amjad ◽  
Jean-Claude Brodovitch ◽  
Alexander McAuley
Keyword(s):  
Ascorbic Acid ◽  
Ionic Strength ◽  
Dissociation Constant ◽  
Metal Ion ◽  
Outer Sphere ◽  
Hydrogen Ion ◽  
Stopped Flow ◽  
Acid Media ◽  
Temperature Range ◽  
Mechanism Of The Reaction

The mechanisms of oxidation of the three di-hydroxy substrates in the title reactions have been investigated in acid media [HClO4] = 0.04–1.00 M, at an ionic strength of 1.0 M [LiClO4] over the temperature range 5–35 °C using the stopped-flow method. In contrast to the reactions of hydroquinone (k2(25 °C) = 1.43 × 104 M−1 s−1, ΔH≠ = 3.6 ± 0.4 kcal mol−1, ΔS≠ = −34 ± 8 cal deg−1 mol−1) and catechol (k2(25 °C) = 9.5 × 102 M−1 s−1, ΔH≠ = 5.9 ± 0.9 kcal mol−1, ΔS≠ = 27 ± 8 cal deg−1 mol−1) where no hydrogen ion dependence is observed over the range studied, the rate variations of oxidation of ascorbic acid (H2A) are consistent with two reactions involving H2A (k5 = 77.4 M−1 s−1, ΔH≠ = 4.5 ± 0.6 kcal mol−1, ΔS≠ = −35 ± 5 cal deg−1 mol−1) and HA− (k6 = 2.41 × 105M−1 s−1, ΔH≠ = 2.0 ± 1 kcal mol−1, ΔS≠ = −17 ± 6 cal deg−1 mol−1). The dissociation constant of ascorbic acid has been re-determined over the temperature range studied. Solvation effects are considered important in these outer-sphere systems, which may be discussed in terms of the Marcus relationship. Comparisons with related reactions are discussed.

Protonation effects on dynamic flux properties of aqueous metal complexes

2009 ◽  
Vol 74 (10) ◽  
pp. 1543-1557 ◽  
Author(s):  
Herman P. Van Leeuwen ◽  
Raewyn M. Town
Keyword(s):  
Complex Formation ◽  
Metal Ion ◽  
Good Description ◽  
Minor Component ◽  
Outer Sphere ◽  
Metal Species ◽  
Central Metal ◽  
Inner Sphere ◽  
A Minor ◽  
Protonated Ligand

The degree of (de)protonation of aqueous metal species has significant consequences for the kinetics of complex formation/dissociation. All protonated forms of both the ligand and the hydrated central metal ion contribute to the rate of complex formation to an extent weighted by the pertaining outer-sphere stabilities. Likewise, the lifetime of the uncomplexed metal is determined by all the various protonated ligand species. Therefore, the interfacial reaction layer thickness, μ, and the ensuing kinetic flux, Jkin, are more involved than in the conventional case. All inner-sphere complexes contribute to the overall rate of dissociation, as weighted by their respective rate constants for dissociation, kd. The presence of inner-sphere deprotonated H2O, or of outer-sphere protonated ligand, generally has a great impact on kd of the inner-sphere complex. Consequently, the overall flux can be dominated by a species that is a minor component of the bulk speciation. The concepts are shown to provide a good description of experimental stripping chronopotentiometric data for several protonated metal–ligand systems.

Corrigendum to: Effect of humic acid, fulvic acid, pH, ionic strength and temperature on 63Ni(II) sorption to MnO2

2020 ◽  
Vol 108 (7) ◽  
pp. 591
Author(s):  
Guodong Sheng ◽  
Jun Hu ◽  
Han Jing ◽  
Shitong Yang ◽  
Xuemei Ren ◽  
...  
Keyword(s):  
Humic Acid ◽  
Ionic Strength ◽  
Fulvic Acid ◽  
Acid Ph
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