Reductant species

In Landolt -type reactions, iodate ion is reduced to iodide tlirough a sequence of steps involving a reductant species such as bisulfde ion or arsenous acid (H AsO ). The reaction proceeds through two overall... 

According to the depth profile of lithium passivated in LiAsF6 / dimethoxyethane (DME), the SEI has a bilayer structure containing lithium methoxide, LiOH, Li20, and LiF [21]. The oxide-hydroxide layer is close to the lithium surface and there are solvent-reduction species in the outer part of the film. The thickness of the surface film formed on lithium freshly immersed in LiAsF /DME solutions is of the order of 100 A. 

In order for there to be a reaction between the two, the element must be above the cation in the activity series. Since Mg is higher on the table, it will oxidize (react as shown in the table). (Note only Mg, not Mg2+, undergoes oxidation.) If a substance undergoes oxidation then something must also undergo reduction. In this problem, the only option for a reduction species is the H+. The reduction is the reverse of the equation in the table. 

An almost complete description of both OH radical-mediated and one-electron oxidation reactions of the thymine moiety (3) of DNA and related model compounds is now possible on the basis of detailed studies of the final oxidation products and their radical precursors. Relevant information on the structure and redox properties of transient pyrimidine radicals is available from pulse radiolysis measurements that in most cases have involved the use of the redox titration technique. It may be noted that most of the rate constants implicating the formation and the fate of the latter radicals have been also assessed. This has been completed by the isolation and characterization of the main thymine and thymidine hydroperoxides that arise from the fate of the pyrimidine radicals in aerated aqueous solutions. Information is also available on the formation of thymine hydroperoxides as the result of initial addition of radiation-induced reductive species including H" atom and solvated electron. 

In short, the central heteroatom was admitted to intervene in the reduction of these POMs essentially by the overall ionic charge it imposes to the molecule. Recently, however, the Si center was shown, by XP S, FT IR, and E S R, to be partly reduced in the one-electron reduction species of a-[SiMoi204o]" [55]. 

Another point worth mentioning is the reduction of substituted nitro-benzenes by sodium disulfide in aqueous methanolic solution. This reaction was shown to be largely influenced by the presence of electron- donating or electron-withdrawing substituents (ref.8). The effect of substituents fits the Hammett equation well, the slope p-value being + 3.55, thus leading the authors to propose the disulfide anion as the reductive species. 2- and... 

I III (excess reduction species) slow and mostly irreversible. 

Quantity Selenium Tumor Site 2 Carcinogen Tumor Reduction Species (% Controls) Reference ... 

Given radiation chemical yields expressed as G values, it is possible to calculate the concentrations of oxidative and reductive species in pure water at a known absorbed dose. The SI unit of dose is the gray (Gy), which equals an energy deposition of 1 J kg-1. For example, the concentration of OH-produced in pure, neutral water by absorbing 1 kGy is ... 

Typical reactions and products are listed in Table 1. Reductions involving in NaCl-AlClj solvents or Hj in the presence of Na involve AlClj jH or NaH, respectively, as reductant species. 

Polarograms and cyclic voltammograms for tris(bipy) complexes of Cr and Cr in DMF have been reported. On the basis of the half-wave potential shift caused by methyl substitution on the bipy ligands it was concluded that each excess electron of the reductant species of the redox systems Cr(bipy)3/Cr(bipy)3 Cr(bipy)3 /Cr(bipy)3 and Cr(bipy) /Cr(bipy)3 " occupies a ligand n orHtal. The electrochemical reduction of [CrPh2(bipy)2]I at Pt and Au electrodes in MeCN and Me2SO has been investigated. Two reversible one-electron reductions were observed, as in reaction... 

In a metal catalysed reaction of a Cirignard reagent the reductive species is either the free metal in a colloid stale ora metal salt in a suhvalenl state like Co". ... 

The catalyst powder (0.8 g) was placed in a tubular quartz reactor. The composition of the gas flow was obtained by mixing the different components (CO, O2, NO, CsHg) diluted in N2 with the use of gas flowmeters. For all experiments the ratio (oxydant species/reductive species) was taken equal to 1. Before each reaction, the reactor is bypassed in such a way as to know precisely the composition of the gas flow before reaction. 

Cu(I) formation observed here Is probably the result of a combination of primary and secondary processes. Primary processes may be Important In destroying Cu(II) complexes which are Inert to secondary reactions, thereby making secondary processes more Important. The decay of Cu(I) after Irradiation Is much slower than the expected, since Its half life In the presence of 0. Is under 6 minutes. Therefore, the presence of relatively long lived reductant species such as must be Invoked. Artificial seawater containing ultrafiltrate also produced Cu(I) upon solar Irradiation, but chloride free media did not ( ), In agreement with kinetic expectations based on the extremely rapid oxidation of Cud) In chloride free media. 

For biological systems this tendency is expressed by the standard reduction potential, Eq, defined as the electromotive force (emf) in volts given by a half-cell in which the reductant and oxidant species are both present at 1.0 M concentration unit activity, at 25°C and pH 7.0 in equilibrium with an electrode which can reversibly accept electrons from the reductant species, according to the equation ... 

Fig. 2.19 Energy level model for electron transfer from a redox species in the electrolyte to a photogenerated hole in the semiconductor valence band. The density of states Z red depend on the concentration of the reductant species according to = c edlFredfE). A large overlap of the redox DOS with the energy of the hole (left) gives higher currents than a small overlap (right)...

Chitosan could react with the OH radicals, which are derived from the radiolysis of water and H2O2, in which the reduction species H and e q" are transformed into "OH. The results suggest that the addition of a small amount of H2O2 could greatly increase the degradation of chitosan with y-irradiation. 

As shown in Figure 2.1, due to the electron-treinsfer reaction occuring on the electrode surface, only those oxidant species with a concentration of Co(0,t) and reductant species with a... 

Figure 2.1 Schematic of the electrode electron-transfer and reactant diffusion process in an electrochemical system. Cb(0,t) is the surface concentration of oxidant species, ChlO.t) is the surface concentration of reductant species, Co(x,f) is the bulk solution concentration of oxidant, and Cr(x, ) is the bulk solution concentration of reductant species. In these four expressions of concentration, tis the reaction time. (For color version of this figure, the reader is referred to the online version of this book.)...

Oxygen is the common cathodic reduction species found in water, which is responsible for continued corrosive attack on some engineering materials, such as low carbon steel. However, passive engineering alloys utilize the oxygen to form thin, tenacious, and adherent protective oxide films. Some common alloys with protective films are stainless steels, nickel alloys, copper-base alloys and aluminum alloys. The oxygen concentration at ambient temperatures and atmospheric pressure is approximately 6-8 mg/L. An increase in temperature decreases oxygen solubility, whereas an increase in pressure increases oxygen solubility. 

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