Reduction of Iron(III) Ion by Activated Carbon Fiber

The mechanisms of adsorption of iron(II) ion, iron(III) ion, and reduced iron(III) ion onto an activated carbon fiber and the ability of carbon fibers to reduce iron(III) ion were investigated on the basis of the amounts of iron ion adsorbed. The amount of iron(II) ion adsorbed onto the activated carbon fiber increased with increasing adsorption temperature. Iron(II) ion was more easily removed by the activated carbon fiber than iron(III) ion. Iron(III) ion was adsorbed onto the activated carbon fiber after being reduced to iron(II) ion. The reduction ability of A-20 was stronger than that of A-10 because the hydrophilic groups of A-20 were larger than those of A-10. It is concluded that the activated carbon fiber has a reduction effect on iron(III) ion and that the reduction effect of the activated carbon fiber depended on the number of hydrophilic groups on the activated carbon fiber. Copyright 2000 Academic Press.     

Kinetics of Reduction of Some Surfactant-Cobalt(III) Complexes by Iron(II)

The electron transfer kinetics of the reaction between the surfactant-cobalt(III) complex ions, cis-[Co(en)₂(C₁₂H₂₅NH₂)₂]³⁺, cis-α-[Co(trien)(C₁₂H₂₅NH₂)₂]³⁺(en:ethylenediamine, trien:triethylenetetramine, C₁₂H₂₅NH₂ : dodecylamine) by iron(II) in aqueous solution was studied at 298, 303, 308 K by spectrophotometry method under pseudo-first-order conditions using an excess of the reductant in self-micelles formed by the oxidant, cobalt(III) complex molecules, themselves. The rate constant of the electron transfer reaction depends on the initial concentration of the surfactant cobalt(III) complexes. ΔS^# also varies with initial concentration of the surfactant cobalt(III) complexes. By assuming outer-sphere mechanism, the results have been explained based on the presence of aggregated structures containing cobalt(III) complexes at the surface of the self-micelles formed by the surfactant cobalt(III) complexes in the reaction medium. The rate constant of each complex increases with initial concentration of one of the reactants surfactant-cobalt(III) complex, which shows that self micelles formed by surfactant-cobalt(III) complex itself has much influence on these reactions. The electron transfer reaction of the surfactant-cobalt(III) complexes was also carried out in a medium of various concentrations of β-cyclodextrin. β-cyclodextrin retarded the rate of the reaction.     

Kinetics and Mechanisms of Reactions of some complexes of Chromium(III). Formation of Oxalatobis(biguanide) chromium(III) Ion from Diaquobis(biguanide) chromium(III) Ion and its Dissociation in Acid Medium

The kinetics of formation of oxalatobis(biguanide)chromium(III) ion from diaquobis(biguanide)chromium(III) ion and oxalate has been studied in aqueous solution (pH ca. 3–4). The results indicate ion-pair formation between the reacting species followed by reaction by an essentially dissociative mechanism (S_N1IP). The kinetics of dissociation of the oxalatobis(biguanide)chromium(III) ion in acid medium has also been studied. The reactions involved are the loss of the two biguanide ligands in stages and by proper choice of acid concentrations and temperature the rates of the two steps could be followed separately. The results indicate S_N2CA mechanism.     

二过碘酸合铜(III)氧化乙醇胺的动力学及机理

近年来，三价铜的过碘酸配合物作为氧化剂在有机物的定量测定中得到广泛的应用问．Movius风和Murthy门分列报导了二过碘酸合铜（Ill）氧化一元醇的反应动力学，但二者所得结果有一定的差别·由于C“m）处于最高氧化态，反应体系又比较复杂·目前人们对它的认识并不太清楚·本文就CU（）氧化乙醇胺（则进行了动力学及机理的研究·1实验部分所用仪器及测定人。s的实验手续同前文＊．2结果与讨论2．1准一级速车常教k。bs的求得在D川。三IO可＊u（m）IO条件下，以w人一＊。）对时间土的图为直线，表明反应对［Cb（Ill）］为一级·准一级速…     

Hydrolysis of americium(III)

A generalized scheme of americium(III) hydrolysis is proposed for a wide range of pH (1–10) and concentrations (10^–1–10^–10M). The data on Am(III) hydrolysis are presented in the form of three-dimensional isothermal diagram. This approach to the study of hydrolysis can be used for investigation of hydrolytic behaviour of most polyvalent ions.     

Kinetics and the Mechanism of Iron(II) Reduction of cis-α-halogeno(cetylamine) (triethylenetetramine)cobalt(III) Complex Ion in Aqueous Acid Medium

The kinetics and mechanism of iron(II) reduction of cis- α-chloro/bromo(cetylamine)(triethylenetetramine) cobalt(III) surfactant complex ions were studied spectrophotometrically in an aqueous acid medium by following the disappearance of Co^III using an excess of the reductant under pseudo-first-order conditions: [Fe^II = 0.25 mol dm⁻³, [H⁺ = 0.1 mol dm⁻³, [μ = 1.0 mol dm⁻³ ionic strength in a nitrogen atmosphere at 303, 308 and 313 K. The reaction was found to be second order and showed acid independence in the range [H⁺ = 0.05−0.25 mol dm⁻³. The second order rate constant increased with Co^III concentration and the presence of aggregation of the complex itself altered the reaction rate. The effects of [Fe^II], [H⁺] and [ μ] on the rate were determined. Activation and thermodynamic parameters were computed. It is suggested that the reaction of Fe²⁺(aq) with Co^III complex proceeds by an inner-sphere mechanism.     

Diperiodatoargentate(III) Oxidation of D-Galactose in Absence and Presence of Anionic and Cationic Surfactants

Diperiodatoargentate(III) (DPA) was used as an oxidizing titrant in the spectrophotometric degradation of D-galactose for the first time. The kinetics is based on the reduction of silver(III) to silver(I) by D-galactose at specified experimental conditions. Effects of added [H⁺] and [periodate] have also been investigated. The premicellar environment of cetyltrimethylammonium bromide (CTAB) and sodiumdodecyl sulphate (SDS) strongly inhibits the reaction rate. The observed rate constant is strongly affected by [CTAB] and [SDS] changes for [surfactant] <cmc. Surfactant concentration range above the cmc does not influence the reaction rate. The monoperiodatoargentate(III) ions act as an active oxidant in comparison to that of DPA. A suitable mechanism involving a two-electron transfer from D-galactose to the silver(III) species has been proposed and hence a corresponding rate equation has been derived.     

La（III）催化磷酸二（4－硝基苯酚）酯水解研究

The catalytic hydrolysis of bis（4-nitrophenyl）phosphate （BNPP） by lanthanum（Ⅲ） ion in the presence of amino-alcoholic ligands： diethanolamine （DEA） and triethanolamine （TEA）, was investigated kinetically at 30 ℃. The results indicated that the dinuclear dihydroxo complexes formed by lanthanum（Ⅲ） ion with aminoalcoholic ligands might be the catalytically active species which catalyze the hydrolysis of BNPP to different extents and the catalytic mechanism was believed to involve the synergism of double Lewis acid activation of the substrate and an intramolecular nucleophilic attack of a bridging oxo ligand.     

Comparative Reactivity of Phosphate Ester Hydrolysis Catalyzed by Mononuclear and Hetero-Dinuclear Complexes Containing the Lanthanum Ion (III)

The hydrolysis of bis(p-nitrophenyl phosphate)(BNPP) and p-nitrophenyl phosphate (NPP) were strongly promoted by the mononuclear La^III[(N,N-bis(3-carboxyl)-2-hydroxysalicylidene)ethylenediamine] and the hetero-dinuclear Cu^IILa^III[(N,N-bis(3-carboxyl)-2-hydroxysalicylidene)ethylenediamine] complexes at 35 °C in 50% aqueous DMSO. The results indicated that the hetero-dinuclear Cu^IILa^III complex exhibited a relatively higher catalytic function on NPP hydrolysis, while the hydrolysis of BNPP was slightly more efficient in the presence of the mononuclear La^III complex than that in the presence of the Cu^IILa^III complex, and this case was discussed by the different spacer requirements for NPP and BNPP hydrolysis. In addition, widely differing pH-rate profiles were obtained: saturated curves for NPP hydrolysis and bell-shaped curves for BNPP hydrolysis, and thus different kinetic treatments were employed to obtain the relative parameters.     

Studies on Cobalt(III) Metallosurfactants. Kinetics and Mechanism of Reduction of Cobalt(III) by Iron(II) in Aqueous Acid Medium

The kinetics and mechanism of reduction of the surfactant complex ions, cis-chloro/bromo(dodecylamine)(triethylenetetramine)cobalt(III) by iron(II) in aqueous solution were studied at 303, 308 and 313 K by spectrophotometry under pseudo-first-order conditions using an excess of the reductant. The second-order rate constant increases with cobalt(III) concentration and the presence of aggregation of the complex itself alters the reaction rate. The reductions are acid-independent in the range [H⁺] = 0.05–0.25 mol dm⁻³. Variation of ionic strength (μ) influences the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested that the reaction of Fe²⁺(aq) with the cobalt(III) complex proceeds by an inner-sphere mechanism. The critical micelle concentration (CMC) values of these surfactant metal complexes in aqueous solution were obtained from conductance measurements. Specific conductivity data (at 303, 308 and 313 K) served for the evaluation of the temperature-dependent CMC and the standard Gibbs energy of micellization (ΔG_m⁰).     

Kinetics and Mechanism of the Reduction of Dihydroxydiperiodatoargentate(III) by 1,2-butylene Glycol in Alkaline Medium

Kinetics and mechanism of the reduction of dihydroxydiperiodatoargentate(III) by 1,2-butanediol in alkaline medium were studied by spectrophotometry in the 298.2–318.2 K range. The reaction rate showed pseudo-first order dependence in oxidant and 1 < n_ap< 2 in reductant. The associated rate law is: -d[Ag(III)]_t/dt = { kK₁K₂K₃[CH₃CH₂CHOHCH₂OH]² [Ag(III)]_t/[H₂IO^3-₄][OH^-]+K₁K₂+K₁K₂K₃[CH₃CH₂CHOHCH₂OH] = k.[Ag(III)]_t. A plausible mechanism involving a pre-equilibrium of adduct formation between the complex and reductant was proposed. The activation parameters along with rate constants of the rate-determining step were calculated.     

Kinetics of Fe(III) → Fe(0) Reduction on Aluminum in Aqueous Solutions

The reduction of iron(III) ions by dispersed aluminum in chloride-containing aqueous solutions and the influence exerted by the initial iron(III) ion concentration and the degree of aluminum dispersion on the kinetics of the process were studied.     

First Hydrolysis Constant of Lutetium (III) by Solvent Extraction

The solvent extraction method involving diglycolic acid (dicarboxy methyl ether) as a competitive ligand to lutetium and N-tris[hydroxymethyl]methyl-2-aminoethanesulfonic acid (TES) as a buffer was used to study the hydrolysis of lutetium in 1 mol⋅dm⁻³ NaCl ionic strength at 303 K. Acid dissociation constants of H₂DG and TES were determined and the possible formation of lutetium–TES compounds was investigated. It was found that lutetium does not form compounds with TES under the experimental conditions. The solvent extraction method using ¹⁷⁷Lu as a tracer was applied and the first hydrolysis constant of lutetium was determined by means of the relationship of the equilibrium constant of the complex Lu(DG)⁺ in the absence and in the presence of hydrolysis. The value obtained was log ₁₀ β _Lu,H=−7.9±0.3.     

Reduction of rhodium(III) trifluoroacetate by norbornadiene

It was shown that the action of heat on rhodium(III) trifluoroacetate with norbornadiene (NBD) leads to its reduction and the formation of red crystals of [Rh(CF₃COO)NBD]₂. The formation of the complex was confirmed by elemental analysis and IR, electronic, and x-ray photoelectron spectra. The reaction shows that Rh-Rh compounds can disproportionate under the influence of NBD with the formation of Rh(I) and Rh(III).Institute of Chemical Physics at Chernogolovka, Russian Academy of Sciences, 142432 Chernogolovka. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1438–1440, June, 1992.     

A Selective Colorimetric and Fluorescent Chemodosimeter for Fe(III) Ion Based on Hydrolysis of Schiff Base

An efficient colorimetric and fluorescent chemodosimeter for Fe³⁺ ions has been developed. The visual and fluorescent behaviors of the receptor toward various metal ions were investigated. The receptor shows exclusive response toward Fe³⁺ ions and also distinguishes Fe³⁺ from other cations by color change and unusual fluorescence enhancement in aqueous solution (DMSO/H₂O = 4/1, v/v). Thus, the receptor can be used as a colorimetric and fluorescent sensor for the determination of Fe³⁺ ion. The visual color detection limit and the fluorescence detection limit of the receptor towards Fe³⁺ are (1.42 ± 0.01) × 10^‐6 M and (7.57 ± 0.04) × 10^‐8 M, respectively. The fluorescence microscopy experiments showed that the receptor is efficient for detection of Fe³⁺ in vitro, developing a good image of the biological organelles. The sensing mechanism is proven to be a hydrolysis process     

Hydrolysis of antimony(III) fluoride complexes

Vibrational and ¹⁷O NMR spectroscopy in combination with quantum chemical calculations are used to investigate the hydrolysis of antimony(III) fluoride complexes. A hydrolytic decomposition of SbF₃ and [SbF₄]^? is accompanied by oligomerization with the formation of edge-and corner-connected dimers ([Sb₂O₂F₄]^2?, [Sb₂OF₈]^4?) and trimers ([Sb₃O₃F₆]^3?, [Sb₃OF₉]^2?) with bridging oxygen atoms. The hydrolysis of [SbF₄]^? is also characterized by the presence in the solution of a discrete cation of [SbF₅]^2? which is least hydrolized. Only a partial isomorphic substitution of fluoride ion by hydroxide one is possible, which is reflected in the composition of K₂Sb(OH)_xF_5?x (x = 0.3) crystals isolated from the fluoride aqueous solution.     

Kinetics of anation of chromium(III) by L-phenylalanine

Summary The kinetics of anation of chromium(III) species, [Cr(H₂O)₆]⁴⁺ and [Cr(H₂O)₅OH]²⁺, by L-phenylalanine in aqueous acid has been studied spectrophotometrically. Effects of varying [substrate], [ligand], [H⁺], , % ethanol and temperature were investigated. The kinetic data suggest a mechanism where outersphere-associations [between chromium(III) species and phenylalanine in the zwitterionic form] precede anation. Comparison of the results with published data suggest an I_a path for the [Cr(H₂O)₆]³⁺ reaction and I_d path for the [Cr(H₂O)₅OH]²⁺ reaction.