Metal ions-hydrogen peroxide, oxidation

The mechanism and rate of hydrogen peroxide decomposition depend on many factors, including temperature, pH, presence or absence of a catalyst (7—10), such as metal ions, oxides, and hydroxides etc. Some common metal ions that actively support homogeneous catalysis of the decomposition include ferrous, ferric, cuprous, cupric, chromate, dichromate, molybdate, tungstate, and vanadate. For combinations, such as iron and... 

Enthalpies, Entropies, and Gibb s Energies of Transition Metal Ion Oxidation-Reduction Reactions with Hydrogen Peroxide in Aqueous Solution (T = 298 K) [23]... 

Transition metals have the ability to form a complex with an electron donor. In this complex, the outermost set of five stable d electron orbitals of the transition metal is partially filled. When transition metal salts, such as ferrous sulfate, are combined with hydrogen peroxide, the resulting oxidation power is known as Fenton s reagent. Instead of forming a complex with hydrogen peroxide, the ferrous ion loses one electron to the peroxide bond of hydrogen peroxide. As a result, a hydroxyl radical and a hydroxide ion are formed. 

For instance, quantification of ultratrace levels of sulfide is feasible with inexpensive flow analyzers relying on the catalytic action of the target analyte on the hydrogen peroxide-luminol chemiluminescent (CL) reaction. Furthermore, in combination with online gas diffusion processes, it is possible to suppress matrix effects, e.g. metals, ions, oxidants, and organic compounds, and improve selectivity as a result. The MSFIA-CL method depicted in Figure 7.9 features a linear working range... 

The activation energy in Eqs. 1.13 and 1.14 is lower than the activation energy of monomolecular degradation of hydrogen peroxides. Thus the oxidation of plastics is accelerated by the presence of metal ions. Relevant metal ions include iron (Fe y Fe " ), cobalt (Co yCo ), copper (CuyCu ), chromium (Cr yCr ), manganese... 

Many polyoxo complexes have metal ions such as Mo, W, V in their highest possible oxidation states. This makes them candidates for potential selective epoxidation catalysts. A heteropolyoxo anion [y-SiW Oj was found to show high epoxidation activity as a precatalyst with 30% hydrogen peroxide as the oxidant. 

The mechanism of inhibition by the salts of the long chain fatty acids has been examined . It was concluded that, in the case of the lead salts, metallic lead was first deposited at certain points and that at these points oxygen reduction proceeded more easily, consequently the current density was kept sufficiently high to maintain ferric film formation in addition, any hydrogen peroxide present may assist in keeping the iron ions in the oxide film in the ferric condition, consequently the air-formed film is thickened until it becomes impervious to iron ions. The zinc, calcium and sodium salts are not as efficient inhibitors as the lead salts and recent work has indicated that inhibition is due to the formation of ferric azelate, which repairs weak spots in the air-formed film. This conclusion has been confirmed by the use of C labelled azelaic acid, which was found to be distributed over the surface of the mild steel in a very heterogeneous manner. ... 

Iron(III) salts also activate the oxidation of sulphoxides by hydrogen peroxide in dry acetonitrile although the yields are typically lower than for the iron(II) system35. With iron(III) salts the hydrogen peroxide seems to be activated by direct complexation between the metal ion and the peroxide moiety. 

C19-0050. What are the half-reactions for these redox processes (a) Aqueous hydrogen peroxide acts on Co, and the products are hydroxide and Co , in basic solution, (b) Methane reacts with oxygen gas and produces water and carbon dioxide, (c) To recharge a lead storage battery, lead(II) sulfate is converted to lead metal and to lead(IV) oxide, (d) Zinc metal dissolves in aqueous hydrochloric acid to give ions and hydrogen gas. 

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