Iron disulfide FeS

PCP-phenolic radical that possesses an absorption spectrum in H2O at 440 nm and decays via second-order kineties with k = 9. x 10 /M/s, as evidenced by pulse radiolytie studies. The PCP-phenolic radical can attach covalently to the C8-site of dG to generate the C8-OPCP adductIn the presence of GSH, redox cyeling of the phenoxyl radieal with thiyl radieal generation will yield a GSH disulfide anion radieal that ean reduetively aetivate O2 to generate the superoxide radieal anion (02 ) that ean generate free ferrous iron Free Fe " " may... 

Iron disulfide is obtained from its naturally occurring minerals, pyrite and marcasite. In the laboratory it may be prepared along with iron(II) sulfide by passing dry hydrogen sulfide through a suspension of hydrated iron (III) oxide or iron(III) hydroxide in alkaline medium. The unstable product formed decomposes to FeS2 and FeS. 

In iron disulfide, commonly called fool s gold because of its resemblance to gold, iron has an oxidation number of 2-I-. The complex ionic structure has the formula Fe 2. 

This iron sulfide, or FeS, has 1 iron atom and 1 sulfur atom in each molecule. It is quite similar to iron disulfide (pyrite), the formula for which is FeSa. 

A similar system under development employs iron disulfide [12068-85-8], FeS2, as the positive electrode. Whereas this system offers a higher theoretical energy density than does Li—Al/FeS, the FeS2 cell is at a lower stage of development (64,65). 

Most of the studies of the interaction between metallic iron and organic monosulfides or disulfides are based on the premise that the rate of formation of iron sulfides (FeS, FeS2) is a valid measure of additive reactivity. This was the premise used by Dorinson and Broman [24] in their comparison of the reactivities of di-t-octyl disulfide and di-n-octyl disulfide with iron powder. The kinetic data for 25% of additive in white oil fitted the following equations ... 

The furnace is used to further heat the feed before it enters the reactor. The tubes will always be an alloy. We have found these tubes to vary from 1% Cr alloys to Series 321 stainless steel. The furnaces can be cleaned by the same method as outlined in the section on preheat bundles, but care should be taken to ensure that no coke or iron disulfide is present, as both of these deposits are not soluble in the aldehyde/acid solvent used to dissolve FeS. If the furnace is coming down, then the reactor also will be taken off line. In this case, the reactor will be regenerated. The furnace will be used... 

Pyrite or marcasite (iron disulfide [FeS2]) decomposes to iron sulfide (FeS) at reducing atmospheres in a temperature range of 400 to 1000 °C. At temperatures above 1000 °C, a-Fe is formed and the presence of silicates produces iron sihcate melts [15]. 

Previous reactions of FeClg and tetramethylthiuram disulfide and [Fe(R2dtc)s] or [Fe(R2dtc)2Cl] with CI2 or Br2 resulted in the formation of complexes of the following type. Iron(IV) and iron(II) complexes con-... 

Fig. 6. A schematic view of the [3Fe-4S] Emd [4Fe-4S] cores, as versatile structures. The absence of one site leads to the formation of a [3Fe-4S] core. The cubane structure can incorporate different metals (in proteins, M = Fe, Co, Zn, Cd, Ni, Tl, Cs), and S, N, O may be coordinating atoms from hgands (Li). The versatihty csm be extended to higher coordination number at the iron site and a water molecule can even be a ligand, exchangeable with substrate (as in the case of aconitase (,87)). The most characteristic binding motifs are schematically indicated, for different situations proteins accommodating [3Fe-4S], [4Fe-4S], [3Fe-4S] + [4Fe-4S], and [4Fe-4S] -I- [4Fe-4S] clusters. A disulfide bridge may replace a cluster site (see text).

Both iron (II) and iron (III) form complexes with mercaptoacetic acid, SRSH2 (5, 11). The ferrous complexes, Fe(II) (RS)2-2 and Fe(II) (OH) (RS) , are highly air-sensitive and are rapidly oxidized to the intense red ferric complex, Fe(III)OH(RS)2 2 (5). Under air-free conditions the color of this latter complex is observed to fade at moderate to fast rates because of a redox reaction in which the iron is reduced to the ferrous state and the mercaptoacetate is oxidized to the disulfide. Michaelis and Schubert (9) proposed that the catalysis takes place through the alternate oxidation and reduction of iron ions in a sequence similar to that just described, but Lamfrom and Nielsen (4) were able to show that under mildly acid conditions the rate of oxygen uptake of solutions containing iron and... 

The mercaptoacetate dependence and the effects of the scavengers indicate that competition exists between Fe(III) (OH) (RS)2 2 and RSH- for the intermediates H02 and HO The reactions of these radicals result in their reduction and, also, when Fe(III) (OH) (RS)2 2 is involved, in the reduction of the iron to the ferrous state. The best source of electrons in this latter reaction is the ligands coordinated to the iron ion. Thus, it appears that H02 and H02 react with Fe(III) (OH)(RS)2 2 to give disulfide in a manner similar to that suggested by Lamfrom and Nielsen for RS ... 

A set of values of tetrahedral covalent radii 7 for use in crystals of these types is given in Table 7-13 and represented graphically in Figure 7-7. These values were obtained from the observed interatomic distances in crystals of these tetrahedral types and of other types in which the atom of interest forms four covalent bonds with neighboring atoms which surround it tetrahedraliy. For example, in pyrite, FeS. each sulfur atom is surrounded tetrahedraliy by three iron atoms and one sulfur atom, with all of which it forms essentially covalent bonds (Fig. 7-8) the substance is a derivative of hydrogen disulfide, H2S2. That the Fe—S bonds are essentially covalent is shown by the magnetic eri-... 

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