Iron substitution

The magnetic properties of the new solid solution series SrFe Rui 3 3, (0 < X < 0.5) with distorted perovskite structure, where iron substitutes exclusively as Fe(in) thereby causing oxygen deficiency, has also been studied by Greenwood s group [147] using both u and Fe Mossbauer spectroscopy. Iron substitution was found to have little effect on the magnetic behavior of Ru(IV) provided that X remains small (x < 0.2). 

Another Ti-catalyzed domino reaction has been developed by Riick-Braun and coworkers [313] using 3-cyclopentadienyl (dicarbonyl)iron-substituted enals 6/4-129 and primary amines 6/4-130 to give dihydropyrrolones 6/4-131 (Scheme 6/4.32). 

Scheme 1. Iron-substituted Silanimines. Synthesis and Reactions with Alcohols, Amins and Acetone.

Zinc protoporphyrin IX is a normal metabolite that is formed in trace amounts during haem biosynthesis. However, in iron deficiency or in impaired iron utilization, zinc becomes an alternative substrate for ferrochelatase and elevated levels of zinc protoporphyrin IX, which has a known low affinity for oxygen, are formed. This zinc-for-iron substitution is one of the first biochemical responses to iron depletion, and erythrocyte zinc protoporphyrin is therefore a very sensitive index of bone-marrow iron status (Labbe et ah, 1999). In addition, zinc protoporphyrin may regulate haem catabolism by acting as a competitive inhibitor of haem oxygenase, the key enzyme of the haem degradation pathway. However, it has been reported... 

F. Yamakura, K. Kobayashi, H. Ue, and M. Konno, The pH-dependent changes of the enzymic activity and spectroscopic properties of iron-substituted manganese superoxide dismutase. A study on the metal-specific activity of Mn-containing superoxide dismutase. Eur. J. Biochem. 227, 700—706 (1995). 

Figure 22 Mechanism of 2-propanol oxygenation in an iron-substituted aluminophos-phate molecular sieve.

Due to the availability of multiple salt forms, close attention is warranted when administering iron. Substitution of 1 salt for another without proper adjustment may result in serious over or under dosing. 

Schwertmarm, U. Gasser, U. Sticher, H. (1989) Chromium-for-iron substitution in synthetic goefhites. Geochim. Cosmochim. Acta 53 1293-1297... 

Oxygenation of alkanes with hydrogen peroxide in homogeneous reactions can be obtained also with Keggin-type iron-substituted polyoxometalates. Evidence against radical reactions has been offered. 

Bismuth Molybdates And Iron Substituted Bismuth Molybdates... 

Figure 3. XRD patterns for the iron substituted composition having the empirical formula of Bi 2-2x) 2x 030i2 where x = 0.40. The top powder diffraction pattern is for the aerosol prepared material as directly obtained from the reactor. The bottom diffraction pattern is for the material after calcining in air for 4 hr at 450°C.

The selectivity to acrolein as a function of iron substitution is shown in Figure 9. It is interesting to note that the selectivity profile vs iron concentration follows that observed for rates vs iron concentration. The unusual aspect of these data is the fact that selectivity increased in the regime where the catalyst was performing at highest conversion. 

Bart, F., Leturcq, G. Rabiller, H. 2003. Iron-substituted barium hollandite ceramics for cesium immobilization. I05th American Ceramic Society Symposium Proceedings, Nashville, TN, USA, 27 April-2 May. 

Iron-substituted heteropolytungstates such as XW, 1Fe3 + Oj9 (P, As, Si, Ge) are the catalysts for the electroreduction of nitrite to ammonia (Table XXXVII)... 

Electrocatalytic Reduction of Nitrite to Ammonia in the Presence of Iron-Substituted Heteropolytungstates, XWnFe3 Os9 (416, 417)... 

The y-isomer Keggin-type silicodecatungstate [y-SiWio036]8- has been used as a structural motif for di-metal-substituted POMs with bis- i-oxo(or hydroxo)-dimetal cores [97-102]. The di-iron-substituted silicotungstate [y-SiWi0 Fe(OH2) 2O3g]6 was synthesized by the reaction of [y-SiWi0O36]8- with Fe(N03)3 in acidic aqueous... 

Fp-substituted enones and enals undergo cyclocarbonylations on treatment with metal hydrides or metal alkyls to provide y-lactones (Scheme 1.15) [45], Similarly, electron-rich primary amines afford dihydropyrrolones with iron-substituted (Z)-enals in the presence of titanium tetrachloride and triethylamine [46],... 

Figure 3. Absorbance spectra of the 1985 set of MarSAMs. a) absorbance spectra of five variably Ca/Fe-exchanged materials prepared from SWy montmorillonite of nominal iron substitutions of 0, 20, 50, 80 and 100 % of the exchange capacity. b) absorbance spectra of two replicate samples of the crude parent SWy, a 100% exchanged form of SWy prepared in 1982, the crude parent Otay, and a 100% Fe-exchanged form of Otay.

Preferred conditions for the reaction of the zeolite with the metal ammonium fluoride are as follows. A zeolite-water slurry containing about 10-25 gm of zeolite per 100 cm3 of water is preheated to 75-95°C. When substituting Ti, the titanium salt is added to the zeolite as a water slurry containing finely divided crystals, 10 gm of (NH4>2T1F6 per 100 cm3 of water. With iron substitution, the iron salt, when added as (NH4>3FeF6, is added from a 10 wt.% solution of the salt in water. Alternatively, FeF3 can be added to a solution of NH4HF2 or NH F such that the stoichiometry of fluorine (F2) to Fe3+ is 3.0 and the total amount of salt in solution is about 10 wt.%. The addition rate of the metal ammonium fluoride salt to the zeolite slurry is about 0.005 moles of the metal ion per minute per mole of aluminum in the zeolite. 

The hydronium exchanged synthetic mordenite does have a band, as shown in spectrum 10 in Figure 1. The iron substituted mordenite samples (spectra 8 and 9) do not show the presence of the band it was "removed" as a result of the substitution reaction. An absorption band at 950 cm- is normally attributed to an Si-OH stretch vibration (14, 15), and is typically observed in some acid or hydrothermally treated zeolites. 

Figure 1. Comparison of the Framework Region Infrared Spectra of Some Titanium or Iron Substituted Zeolites with the Untreated Starting Materials.

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