Reduction redox reactions

The most usual synthetic routes to the derivatives of platinum group metals are the exchange reactions of the complexes containing halide ligands with alkali metal alkoxides (method 5), alcoholysis of the same kind derivatives (usually by phenols, method 4), alcoholysis of hydroxide complexes (method 3), and redox reactions — reduction of chlorides or 0s04 in alcohol media (method 7) (Table 12.25). 

Triazenes can be prepared by the following three methods (Scheme 1) (1) redox reactions (reduction of azides, oxidation of triazanes), (2) building or splitting of nitrogen chains, and (3) exchange of substituents (mutual transformation of triazenes). 

Redox Reactions.—Reduction of [Coi i(TPPS)] by Cr + follows a two-term rate law with an observed rate constant / obs= 173 + (2.0/[H+]) [Cr ]. The first term is interpreted as outer-sphere reduction of the bis-aquo-Co (TPPS) complex but ambiguity exists for the term between an inner-sphere... 

Strand breakage, either single strand or double strand, may be effected by metal complexes which are capable of undergoing redox reactions. Reduction of the metal complex, subsequent reaction of the reduced species to produce active oxygen moieties has been demonstrated to produce strand breaks. Photolytic reduction of the complex can also result in strand cleavage. 

Redoxreaktion redox reaction, reduction-oxidation reaction, oxidation-reduction reaction... 

Redoxpaar redox couple Redoxpotential redox potential Redoxreaktion redox reaction, reduction-oxidation reaction, oxidation-reduction reaction Reduktion reduction Reduktionsmittel reducing agent Redundanz redundancy reduzieren reduce... 

The cationic monomeric complexes Re(CO)4(diimine) formed in the reaction of Eq. (6,39) when L=CO show excited state redox reactions. Reductive quenching experiments of the excited state with substituted methoxybenzenes and with chloride ion leads to an sq)proximate value of 1.5 V being found for the Re(CO)4(di-imine) /Re(CO)4(diimine) excited state potential. Photosubstitution is also observed with these complexes, although a definitive assignment of the photoactive states that lead to these different reactions has not yet been achieved. 

Highly protective layers can also fonn in gaseous environments at ambient temperatures by a redox reaction similar to that in an aqueous electrolyte, i.e. by oxygen reduction combined with metal oxidation. The thickness of spontaneously fonned oxide films is typically in the range of 1-3 nm, i.e., of similar thickness to electrochemical passive films. Substantially thicker anodic films can be fonned on so-called valve metals (Ti, Ta, Zr,. ..), which allow the application of anodizing potentials (high electric fields) without dielectric breakdown. 

In a complexation reaction, a Lewis base donates a pair of electrons to a Lewis acid. In an oxidation-reduction reaction, also known as a redox reaction, electrons are not shared, but are transferred from one reactant to another. As a result of this electron transfer, some of the elements involved in the reaction undergo a change in oxidation state. Those species experiencing an increase in their oxidation state are oxidized, while those experiencing a decrease in their oxidation state are reduced, for example, in the following redox reaction between fe + and oxalic acid, H2C2O4, iron is reduced since its oxidation state changes from -1-3 to +2. 

Redox reactions, such as that shown in equation 6.22, can be divided into separate half-reactions that individually describe the oxidation and the reduction processes. 

Selecting a Constant Potential In controlled-potential coulometry, the potential is selected so that the desired oxidation or reduction reaction goes to completion without interference from redox reactions involving other components of the sample matrix. To see how an appropriate potential for the working electrode is selected, let s develop a constant-potential coulometric method for Cu + based on its reduction to copper metal at a Pt cathode working electrode. 

Determining Equilibrium Constants for Coupled Chemical Reactions Another important application of voltammetry is the determination of equilibrium constants for solution reactions that are coupled to a redox reaction occurring at the electrode. The presence of the solution reaction affects the ease of electron transfer, shifting the potential to more negative or more positive potentials. Consider, for example, the reduction of O to R... 

Catalyst Selection. The low resin viscosity and ambient temperature cure systems developed from peroxides have faciUtated the expansion of polyester resins on a commercial scale, using relatively simple fabrication techniques in open molds at ambient temperatures. The dominant catalyst systems used for ambient fabrication processes are based on metal (redox) promoters used in combination with hydroperoxides and peroxides commonly found in commercial MEKP and related perketones (13). Promoters such as styrene-soluble cobalt octoate undergo controlled reduction—oxidation (redox) reactions with MEKP that generate peroxy free radicals to initiate a controlled cross-linking reaction. 

A number of reductive procedures have found general applicability. a-Azidoketones may be reduced catalytically to the dihydropyrazines (80OPP265) and a direct conversion of a-azidoketones to pyrazines by treatment with triphenylphosphine in benzene (Scheme 55) has been reported to proceed in moderate to good yields (69LA(727)23l). Similarly, a-nitroketones may be reduced to the a-aminoketones which dimerize spontaneously (69USP3453279). The products from this reaction are pyrazines and piperazines and an intermolecular redox reaction between the initially formed dihydropyrazines may explain their formation. Normally, if the reaction is carried out in aqueous acetic acid the pyrazine predominates, but in less polar solvents over-reduction results in extensive piperazine formation. 

Ox and Red are general symbols for oxidation and reduction media respectively, and n and (n-z) indicate their numerical charge (see Section 2.2.2). Where there is no electrochemical redox reaction [Eq. (2-9)], the corrosion rate according to Eq. (2-4) is zero because of Eq. (2-8). This is roughly the case with passive metals whose surface films are electrical insulators (e.g., A1 and Ti). Equation (2-8) does not take into account the possibility of electrons being diverted through a conductor. In this case the equilibrium... 

REDOX Biological reductions/oxidations. These reactions usually require enzymes... 

Reduction Potentials—An Accounting Device for Free Energy Changes in Redox Reactions... 

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