Kinetics and mechanisms of iron

Additional relevant details of the kinetics and mechanisms of iron chelation reactions may be found in other recent reviews (10,22,134,160,161). 

The kinetics and mechanism of iron-siderophore complex formation are influenced by the oxidation state and composition of the first coordination shell of iron. The iron sequestration... 

Macara, I.G. HoyT.G. Harrison, P.M. (1972) Formation of ferritin from apoferritin. Kinetics and mechanism of iron uptake. Bio-chem. J. 126 151-152... 

The kinetics and mechanism of iron removal from siderophore complex to a free ligand has been examined using spectrophotometric or 55Fe3+ labeling techniques. 

In summary, the kinetics and mechanism of iron exchange between siderophores have revealed that iron bound in these complexes is not in general readily exchanged. However, catecholate complexes display more rapid reaction kinetics compared to their hydroxamate counterparts. 

The purpose of this section is to review recent literature on the kinetics and mechanisms of iron oxide dissolution. Particular emphasis is placed on pure iron oxides and iron oxides on steel surfaces. The limited scope of this review precludes complete coverage of the vast amount of work on passive film formation and dissolution. However, some aspects of passivation that apply directly to chemical clening are reviewed in Chapter 4. 

The main insight into the kinetics and mechanism of iron dissolution and corrosion has come from electrochemical studies using complex E-t or I-t perturbation programs. Some of the conclusions that have emerged from this large body of work are summarized here. 

Hung H-M, Hoffmann MR (1998) Kinetics and mechanism of the enhanced reductive degradation of CC14 by elemental iron in the presence of ultrasound. Environ Sci Technol 32(19) 3011—3016... 

Fe(III) displacement of Al(III), Ga(III), or In(III) from their respective complexes with these tripodal ligands, have been determined. The M(III)-by-Fe(III) displacement processes are controlled by the ease of dissociation of Al(III), Ga(III), or In(III) Fe(III) may in turn be displaced from these complexes by edta (removal from the two non-equivalent sites gives rise to an appropriate kinetic pattern) (343). Kinetics and mechanism of a catalytic chloride ion effect on the dissociation of model siderophore-hydroxamate iron(III) complexes chloride and, to lesser extents, bromide and nitrate, catalyze ligand dissociation through transient coordination of the added anion to the iron (344). A catechol derivative of desferrioxamine has been found to remove iron from transferrin about 100 times faster than desferrioxamine itself it forms a significantly more stable product with Fe3+ (345). 

Tang, WZ Chen, RZ. Decolorization kinetics and mechanism of commercial dyes by H202/iron powder system. Chemosphere, 1996 32 (5), 947-958. 

A review of iron(III) in aqueous solution covers hydrolysis and polymerization, the formation and dissociation of binuclear species, and kinetics and mechanisms of water exchange and complex formation. " Kinetic and equilibrium data for hydrolytic reactions of iron(III) have been conveniently assembled. Reviews of hydrolysis of Fe aq, and subsequent precipitation of hydrated oxide-hydroxide species, cover a very wide range of media, from geochemistry to biology to human metabolism. Added anions or pH variation can affect which form... 

Equilibrium constants for formation of iron(III) complexes of several oxoanions, of phosphorus, arsenic, sulfur, and selenium, have been reported. The kinetics and mechanism of complex formation in the iron(III)-phosphate system in the presence of a large excess of iron(III) involve the formation of a tetranuclear complex, proposed to be [Fc4(P04)(0H)2(H20)i6]. The high stability of iron(III)-phosphate complexes has prompted suggestions that iron-containing mixed hydroxide or hydroxy-carbonate formulations be tested for treatment of hyperphosphatemia. " ... 

Information on the formation and decomposition of iron(III)-sulfur(IV) complexes, in the presence and absence of dioxygen, is vital to the understanding of iron-catalyzed autooxidation of sulfur(IV). The kinetics and mechanism of formation of mono-, bis-, and tris-sulfito-iron(III) from Fe " aq/FeOH aq, have been established, together with estimates of their stability... 

Pyman, M.A.F. Posner, A.M. (1978) The surface areas of amorphous mixed oxides and their relation to potentiometric titration. J. Colloid Interface Sci. 66 85-93 Pyzik, A. Sommer, S.E. (1981) Sedimentary iron monosulfides kinetics and mechanism of formation. Geochim. Cosmochim. Acta 45 687-698... 

Brandt, C., I. Fabian, and R. van Eldik, Kinetics and Mechanism of the Iron(III)-Catalyzed Autooxidation of SulfuKIV) Oxides in Aqueous Solution—Evidence for the Redox Cycling of Iron in the Presence of Oxygen and Modeling of the Overall Reaction Mechanism, Inorg. Chem., 33, 687-701 (1994). 

Recently we presented (23) the results of an experimental study on the kinetics and mechanisms of the reaction of lepidocrocite (y-FeOOH) with H2S. With respect to the interaction between iron and sulfur, lepidocrocite merits special attention. It forms by reoxidation of ferrous iron under cir-cumneutral pH conditions (24), and it can therefore be classified as a reactive iron oxide (19). The concept of reactive iron was established by Canfield (19), who differentiated between a residual iron fraction and a reactive iron fraction (operationally defined as soluble in ammonium oxalate). The reactive iron fraction is rapidly reduced by sulfide or by microorganisms. 

Pyzik, A.J., and Sommer, S.E. (1981) Sedimentary iron monosulfides kinetics and mechanism of formation. Geochim. Cosmochim. Acta 45, 687-698. 

Zang, V. and van Eldik, R., 1990, Kinetics and mechanism of the autoxidation of iron(II) induced through chelation by ethylenediaminetetraacetate and related ligands, Inorg. Chem., 29,... 

Bhattacharjee369, who has brominated acetanilide suspended in aqueous solution of potassium bromide and hydrogen peroxide in presence of vanadium pent oxide catalyst. Chloroperoxidase has been mimicked using supported manganese phorphyrin catalyst in the oxychlorination of dimedone370 and by clay-supported iron(III) chloride in the oxy-chlorination of toluene and anisole371. The kinetics and mechanism of the haloper-oxidases have been studied extensively372,373. 

In the presence of iron(II) sulfate, /cH-butyl hydroperoxide decomposes to yield acetone and methyl radicals, For a discussion of the kinetics and mechanism of purine C8 methylation by methyl radicals see ref 50. Reaction of adenine with benzenediazonium ions yields ( )-6-(3-phenyl-2-triazen-l-yl)purinc (7, Ar = Ph), which undergoes a C-arylation reaction, probably involving an intermolecular free-radical substitution at C8, to give 8. " ... 

Most theories of anomalous deposition in this case are based on the studies on kinetics and mechanism of electrodeposition of iron by Bockris et al. [66]. They proposed the following mechanism for the electrodeposition of Fe... 

Pyzik, a. j., and S. E. Sommer. 1981. Sedimentary iron tnonosullides Kinetics and mechanisms of formation. Geochim. Cosmochim. Acto 45 687-98. 

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