Effect of the structural change of an iron–iron oxide mixture on the decomposition of trichloroethylene

The effect of the structure of a mixture of industrially produced iron and iron oxide on the decomposition of trichloroethylene (TCE) was investigated by gas chromatography, scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray analysis, X-ray diffractometry, and ⁵⁷Fe-Mössbauer spectroscopy. The concentration of 10 mg L^?1 TCE aqueous solution decreased to 0.41, 0.52, 0.26, and 0.09 mg L^?1 when stirred for 7 days with iron–iron oxide mixtures having mass ratios of 2:8, 3:7, 4:6, and 5:5, respectively. The Mössbauer spectra of the mixtures after leaching were composed of two sextets with respective isomer shifts (δ) and internal magnetic fields (H) of 0.29_±0.01 mm s^?1 and 48.8_±0.1 T, and 0.64_±0.01 mm s^?1 and 45.5_±0.1 T, attributed to the Fe³⁺ species in tetrahedral (T _d) and the Fe²⁺ and Fe³⁺ mixed species (Fe^2.5+) in octahedral (O _h) sites, respectively. Mössbauer spectra of a 3:7 mass ratio iron–iron oxide mixture showed a gradual decrease in the absorption area (A) of zero valent iron (Fe⁰) from 40.6. to 12.6, 13.2, 3.8 2.8, and 1.0_±0.5 % and an increase in A of Fe₃O₄ from 31.8 to 59.4, 71.4, 93.2, 95.6, and 98.0_±0.5 % after leaching with 10 mg L^?1 TCE aqueous solution for 1, 2, 3, 7, and 10 days, respectively. Consistent values of the first-order rate constant were calculated as 0.32 day^?1 for Fe⁰ oxidation, 0.34 day^?1 for Fe₃O₄ production, and 0.30 day^?1 for TCE decomposition, which indicates that the oxidation of Fe⁰ was the rate-controlling factor for Fe₃O₄ production and TCE decomposition. It is concluded from the experimental results that an iron–iron oxide mixture is very effective for the decomposition of TCE.     

Mössbauer study of the effect of boron and iron contents on the dynamic behavior of iron in sodium phosphate glass system

Mössbauer measurements were performed at different temperatures in order to examine the dynamic behavior of iron in the glass system: 42.5% P₂O₅, 42.5% Na₂O, 15% Fe₂O₃. Variation of the dynamic behavior was traced by substituting B₂O₃ for P₂O₅ [30 P₂O₅, 12.5 B₂O₃, 42.5 Na₂O, 15 Fe₂O₃] and by increasing the amount of iron at the expense of Na₂O [42.5 P₂O₃, 15 Na₂O, 42.5 Fe₂O₃]. The Mössbauer measurements gave the values of Debye temperature (_D), mean square displacement <²>, mean square velocity <v ² > of oscillation, the lattice time () and the strength parameter (B) for each glass. These values were discussed with the results of DTA, density, hardness and D. C. conductivity.     

Investigation of the kinetics of the chain-radical process in the system iron carbonyl–Lewis base

An ESR spectroscopy investigation of the kinetics of accumulation and consumption of iron carbonyl radical anions, Fe₃(CO)₁₂⁻ and Fe₃(CO)₁₁⁻, arising in the reaction of Fe₃(CO)₁₂ with (Et₄N)SEt in THF at 19.5°C, was carried out using the stopped-flow technique. The solution of the inverse kinetic problem showed a satisfactory agreement between calculated and experimental data. This supports the principal idea that chain radical processes including preliminary complex formation followed by one-electron redox-initiation lie at the heart of the interaction of iron carbonyls with Lewis bases, and that the following transformations are due to electron and ligand changes in the coordination sphere of seventeen-electron coordinatively unsaturated species.     

Study of the relationship of small variations of the molecular structure and the iron state in iron containing proteins by Mössbauer spectroscopy: biomedical approach

This review considers the results of experimental M?ssbauer studies and theoretical calculations of the effect of small variations of protein molecular structure on the iron electronic structure and stereochemistry in order to understand the proteins structural heterogeneity and functional variety. Structural changes in iron containing proteins during various diseases are also considered. These results show the relationship of the small structural variations and M?ssbauer parameters of iron containing proteins and demonstrate the possibilities of M?ssbauer spectroscopy to obtain new information at the molecular level in biomedical research.     

A study of the color reaction of iron with “TTA”

Summary TTA, or 2-Thenoyltrifluoroacetone, gives with ferric ion, in various concentrations colorations ranging from blood red to light pink. The advantages of this test are that it is simple to perform, that it is applicable in different acid media of fairly high concentrations, and that it is somewhat sensitive in the presence of ions that usually interfere with such tests. The sensitivity (limit of identification) was found to be 0,5 and the limit of concentration 1 : 100000 when a benzene solution of the reagent was reacted with a slightly acid solution of ferric ion on spot paper.

---

Zusammenfassung TTA (2-Thenoyltrifluoraceton) gibt mit Ferriionen je nach Konzentration der letzteren eine blutrote bis blaßrosa Färbung. Die Probe ist einfach ausführbar und wird durch die Gegenwart von Säuren bis zu ziemlich hohen Konzentrationen sowie durch die Gegenwart störender Ionen wenig beeinträchtigt. Wenn eine Lösung des Reagens in Benzol zu einer leicht angesäuerten Ferrisalzlösung zugesetzt wird, beträgt die Erfassungsgrenze 0,5 bei einer Grenzkonzentration von 1 : 100000.

---

Résumé Le TTA, thénoyl-2 trifluoracétone, donne avec les ions ferriques, suivant leur concentration, une coloration rouge sang à rose pâle. L'essai est simple à effectuer et à peine troublé par la présence des acides jusqu'à des concentrations passablement élevées et par la présence des ions gênants. Quand on ajoute une solution du réactif dans le benzène à une solution peu acide de sel ferrique, on observe une limite de sensibilité de 0,5 pour une limite de dilution de 1 : 100000.

     

The catalytic condensation of ω-phenyl-substituted alcohols in the presence of an iron oxide

The results of gas-phase conversion of ω-phenyl-substituted alcohols (benzyl alcohol, 2-phenylethanol, 3-phenyl-1-propanol) and their equimolar mixtures with primary normal alcohol (1-octanol) are presented. Reactions were carried out at atmospheric pressure in the presence of an iron catalyst in the temperature range of 568–673 K and load of 2.0 h⁻¹. 2-Phenylethanol and 3-phenyl-1-propanol undergo dehydrogenation to aldehydes and condensation to esters. At higher temperatures symmetrical ketones containing ω-phenyl group as substituent are formed. Mixtures of these alcohols with 1-octanol give among others asymmetrical aromatic-aliphatic ketones.     

Formation of calcium in the products of iron oxide–aluminum thermite combustion in air

The composition of condensed products resulting from the combustion of thermite mixtures (Al + Fe₂O₃) in air is studied by precise methods. It is shown that during combustion, calcium is formed and stabilized in amounts of maximal 0.55 wt %, while is missing from reactants of 99.7 wt % purity. To explain this, it is hypothesized that a low-energy nuclear reaction takes place alongside the reactions of aluminum oxidation and nitridation, resulting in the formation of calcium (Kervran–Bolotov reaction).     

β-Nitro derivatives of iron corrolates

Two different methods for the regioselective nitration of different meso-triarylcorroles leading to the corresponding β-substituted nitrocorrole iron complexes have been developed. A two-step procedure affords three Fe(III) nitrosyl products-the unsubstituted corrole, the 3-nitrocorrole, and the 3,17-dinitrocorrole. In contrast, a one-pot synthetic approach drives the reaction almost exclusively to formation of the iron nitrosyl 3,17-dinitrocorrole. Electron-releasing substituents on the meso-aryl groups of the triarylcorroles induce higher yields and longer reaction times than what is observed for the synthesis of similar triarylcorroles with electron-withdrawing functionalities, and these results can be confidently attributed to the facile formation and stabilization of an intermediate iron corrole π-cation radical. Electron-withdrawing substituents on the meso-aryl groups of triarylcorrole also seem to labilize the axial nitrosyl group which, in the case of the pentafluorophenylcorrole derivative, results in the direct formation of a disubstituted iron μ-oxo dimer complex. The influence of meso-aryl substituents on the progress and products of the nitration reaction was investigated. In addition, to elucidate the most important factors which influence the redox reactivity of these different iron nitrosyl complexes, selected compounds were examined by cyclic voltammetry and thin-layer UV-visible or FTIR spectroelectrochemistry in CH(2)Cl(2).     

Formation of variable-composition iron(III) hydrosilicates with the сhrysotile structure

The process of formation of iron hydrosilicates (Mg²⁺,Fe³⁺)_2–3Si₂O₅(OH)₄ was studied. It was shown that the stage of coprecipitation of magnesium and iron hydroxides in the presence of silica nanoparticles forms poorly crystallized layered Mg–Fe double hydroxides having Fe³⁺ ions in the octahedral sites. Hydrothermal treatment of the mixtures of coprecipitated hydroxides and silica nanoparticles gives rise to layered hydrosilicates, where Fe³⁺ ions occupy both the octahedral (preferentially) and tetrahedral sires. The possibility of the formation and a fairly stable existence of the variable-composition layered hydrosilicate (Mg²⁺,Fe³⁺)_2–3Si₂O₅(OH)₄ was shown to correlate with the stability range of its precursor brucite-like Mg–Fe layered double hydroxide.     

Specific features of the structures of iron(II) α-benzyl dioxymate solvates with pyridine

Coordination compounds [Fe(DfgH)₂Py₂] (I) and [Fe(DfgH)₂Py₂] · A, where DfgH is the α-benzyldioxime monoanion and A = Py (II), DMF (III), and methyl ethyl ketone (IV), have been synthesized and studied by X-ray diffraction analysis. Diamagnetism and the gamma-resonance (GR) spectral parameters confirm that iron exists in the oxidation state +2 in the low-spin state. The octahedral trans configuration of the iron polyhedra is a common feature of all complexes. The equatorial plane of the octahedron contains two intramolecular hydrogen bonds O-H...O between two organic anions DfgH⁻ affording a pseudomacrocycle. The axial coordinate of the octahedron is occupied by the pyridine molecules, which are almost perpendicular to the equatorial plane N₄(oxime) in complexes I–IV. The structure of the compounds is a framework with allowance for weak interactions C-H...O and C-H...C. The manner of inclusion of solvents into the crystal and their functioning in structure formation of compounds II–IV are discussed.     

Mössbauer properties of the diferric cluster and the differential iron(II)-binding affinity of the iron sites in protein R2 of class Ia Escherichia coli ribonucleotide reductase: a DFT/electrostatics study

The R2 subunit of class-Ia ribonucleotide reductase (RNR) from Escherichia coli (E. coli) contains a diiron active site. Starting from the apo-protein and Fe(II) in solution at low Fe(II)/apoR2 ratios, mononuclear Fe(II) binding is observed indicating possible different Fe(II) binding affinities for the two alternative sites. Further, based on their M?ssbauer spectroscopy and two-iron-isotope reaction experiments, Bollinger et al. (J. Am. Chem. Soc., 1997, 119, 5976-5977) proposed that the site Fe1, which bonds to Asp84, should be associated with the higher observed (57)Fe M?ssbauer quadrupole splitting (2.41 mm s(-1)) and lower isomer shift (0.45 mm s(-1)) in the Fe(III)Fe(III) state, site Fe2, which is further from Tyr122, should have a greater affinity for Fe(II) binding than site Fe1, and Fe(IV) in the intermediate X state should reside at site Fe2. In this paper, using density functional theory (DFT) incorporated with the conductor-like screening (COSMO) solvation model and with the finite-difference Poisson-Boltzmann self-consistent reaction field (PB-SCRF) methodologies, we have demonstrated that the observed large quadrupole splitting for the diferric state R2 does come from site Fe1(III) and it is mainly caused by the binding position of the carboxylate group of the Asp84 sidechain. Further, a series of active site clusters with mononuclear Fe(II) binding at either site Fe1 or Fe2 have been studied, which show that with a single dielectric medium outside the active site quantum region, there is no energetic preference for Fe(II) binding at one site over another. However, when including the explicit extended protein environment in the PB-SCRF model, the reaction field favors the Fe(II) binding at site Fe2 rather than at site Fe1 by ~9 kcal mol(-1). Therefore our calculations support the proposal of the previous M?ssbauer spectroscopy and two-iron-isotope reaction experiments by Bollinger et al.     

Synthesis of substituted benzoxazoles by the iron(Ⅲ)-catalyzed aerobic oxidation process

The FeCl3-catalyzed aerobic oxidation process for the synthesis of benzoxazoles,benzothiazole and benzimidazole has been discovered.This method has proved to be effective to a wide range of substrates,and it has been applied for the synthesis of JTP-426467.     

DFT modeling of the first step of plastoquinol oxidation by the iron–sulfur protein of the cytochrome b6f complex

1. Download high-res image (126KB)
2. Download full-size image

     

Fe doped aluminoborate PKU-1 catalysts for the ketalization of glycerol to solketal: Unveiling the effects of iron composition and boron

An inexpensive Fe doped aluminoborate consisted of 18% Fe in PKU-1 material that exhibits high selectivity of 4-hydroxymethy-2,2-dimethyl-1,3-dioxolane(Solketal, 98.3%), considerable activity(TOF 51.7 h-1),and recyclable ability in the ketalization of glycerol to Solketal with acetone at 318 K has been developed.Our study demonstrated that the structure of Fe(less agglomerated iron species vs. Fe Oxclusters) can be tuned by changing Fe loading in the PKU-1 material, which correlated well with ex...     

Liquid-liquid extraction of α-activation products of iron with HDEHP

The carrier-free radiotracers,^52,56Mn,^55,56,58Co and^56,57Ni were produced simultaneously by accelerated -particle activation of iron. They were subsequently studied through LLX using the liquid cation exchanger, HDEHP, as an extractant. A considerable enrichment of individual carrier free radionuclides of manganese, cobalt and nickel was achieved. Production and verification of purity of the carrier-free radiotracers at different stages of their extraction were carried out by -ray spectroscopic studies.     

Cytochrome P-450 modelling oxygenation of olefins within the space-restricted cavity of iron “binap porphyrin”: Rate enhancement in the presence of imidazole

In the presence of 1,5-diphenylimidazole, iron porphyrin modified by binaphthyl groups on one side exhibited increased rate in epoxidation of olefins and shape selective oxidation. Spectrophotometric study supports the inhibition of the formation of the six-coordinated bisimidazole complex. Oxidation within the modified cavity is proposed.     

Preparation of iron—polysiloxane vertically ordered microneedles from a suspension of iron microparticles in liquid silicone rubber

Russian Chemical Bulletin - A simple method for the preparation of the vertically located flexible iron—polysiloxane magnetic needles up to 12 mm long by the self-organization of iron...     

Does the valence state of an ion affect its diffusivity? Part I: Oxygen activity dependence of the diffusion of iron in alumina-doped MgO

To investigate whether a change in the valence state of tracer ions affects their diffusivity or not, the iron tracer diffusion in Al₂O₃-doped MgO, in which 0.5% of the cations were Al³⁺ ions, has been studied experimentally. Samples were prepared from high purity aluminum and magnesium nitrates using a chemical solution method and from powders of high purity Al₂O₃ and MgO. Because the concentration of the Al³⁺ dopant ions present in the samples was much larger than that of all other impurities, the concentration of the majority point defects, cation vacancies, was determined by the Al³⁺ concentration. Therefore, when changing the oxygen activity, the diffusivity of iron tracer ions can only be altered by changes in their valence state. Measurements of iron tracer diffusion coefficients were performed as a function of the oxygen activity at 1100 and 1200 °C. The experimental results indicate that the mean diffusivity of iron ions in Al₂O₃-doped MgO increases with increasing oxygen activity at both temperatures, suggesting that Fe³⁺ ions diffuse in Al₂O₃-doped MgO faster than Fe²⁺ ions.