Oxidation-reduction reactions applications

Since the experimental evidence at hand is no more against than in favor of the view that electrons are responsible for valence in the case of non-electrolytes than in the case of electrolytes, while indirect evidence is in favor of this view, it is much simpler to adopt the view of one kind of force acting between atoms in all compounds, that is, that due to the electron associated with the atom. This at once furnishes one definition for all oxidation-reduction reactions applicable to all cases and easily understood. 

It is now possible to calculate the equilibrium constants of oxidation-reduction reactions, and thus to determine whether such reactions can find application in quantitative analysis. Consider first the simple reaction ... 

For a number of applications curing at room temperature is desirable. This so-called cold cure is brought about by using a peroxy initiator in conjunction with some kind of activator substance. The peroxy compounds in these cases are substances such as methyl ethyl ketone peroxide and cyclohexanone peroxide, which as used in commercial systems tend not to be particularly pure, but instead are usually mixtures of peroxides and hydroperoxides corresponding in composition approximately to that of the respective nominal compounds. Activators are generally salts of metals capable of undergoing oxidation/reduction reactions very readily. A typical salt for this purpose is cobalt naphthenate, which undergoes the kind of reactions illustrated in Reactions 4.6 and 4.7. 

Oxidation-reduction reactions represent yet another type of reaction that titrimetric analysis can utilize. In other words, a solution of an oxidizing agent can be in the buret, and a solution of a reducing agent can be in the reaction flask (and vice versa). In this section, we review the fundamentals of oxidization-reduction chemistry and discuss the titrimetric analysis applications. 

Oxidoreductases, which catalyze oxidation-reduction reactions and are acting, for example, on aldehyde or keto groups. An important application is the synthesis of chiral molecules, especially chiral PFCs (22 out of 38 chiral products produced on large industrial scale are already made using biocatalysis). 

In me previous chapter we discussed acid-base reactions, which are chemical reactions involving the transfer of pro Lons from one reactant to another. In this chapter, we explored oxidation-reduction reactions, which involve the transfer of one or more electrons from one reactant to another. Oxidation-reduction reactions have many applications, such as in photography, batteries, fuel cells, the manufacture and corrosion of metals, and the combustion of non-metallic materials such as wood. 

In cyclic voltammetry, the potential applied to the working electrode is varied linearly (Fig. 2.1) between potentials Ex and E2, E2 being a potential more positive (for oxidation) or negative (for reduction) than the peak maximum observed for the oxidation/reduction reaction concerned. At E2, the voltage scan is reversed back to E3 or to another end potential value, E3. The application of this type of potential ramp can be done in a number of ways, varying the starting potential Eu the reverse potential E2, the end potential E3 and the scan rate. The latter is the rate that is applied to vary the potential as a function of time, commonly represented in Vs 1 or mVs"1. 

The above classification highlights the common analytical methods. There is, however, a great deal of overlapping as far as the chemistry of the process is involved. For example, iodometric method involves an oxidation-reduction reaction between thiosulfate anion and iodine. It is, however, classified here under a separate heading because of its wide application in environmental analysis. 

Phenylarsine oxide, C6H5As = O, is as effective as sodium thiosulfate in reducing iodine. It is more stable than thiosulfate. An advantage is that it is stable even in dilute solution. This substance is, however, highly toxic and is a suspected carcinogen. Because of its toxicity, its application is limited. One such application is in the amperometric titration of residual chlorine. The oxidation-reduction reaction of PAO is similar to thiosulfate. Its equivalent weight in iodine reaction is 168. 

Oxidation-reduction reactions similar to the Cannizzaro process are brought about in the living cell by certain enzyme systems. Numerous exanfples 7-8- 10 of these have been studied in vitro by the aid of tissue preparations, and certain of them 6 suggest possible application in preparative methods. The dismutation. of aldehydes in basic or neutral solution also has been effected by catalytic metals, such as nickel and platinum.11 12 It seems likely that there is a closer analogy between... 

Classification of Solvents. Solvent classification helps to identify properties useful in solvent selection for individual applications for example, the study of acid-base reactions, oxidation-reduction reactions, inorganic coordination chemistry, organic nucleophilic displacement reactions, and electrochemistry. 

Oxidoreductases comprise a large class of enzymes that catalyze biological oxidation/reduction reactions. Because so many chemical transformation processes involve oxidation/reduction processes, the idea of developing practical applications of oxidoreductase enzymes has been a very attractive, but quite elusive, goal for many years [83], Applications have been sought for the production of pharmaceuticals, synthesis and modification of polymers, and the development of biosensors for a variety of clinical and analytical applications [83], In recent years, the use of oxido-reductive enzymes to catalyze the removal of aromatic compounds from... 

Batteries are a practical application of the galvanic cell in that an oxidation-reduction reaction generates an electric current. A battery that has an enormous impact on our lives is the automobile battery, shown in Figure 10.3. 

Chemical/physical treatment processes are those in which a chemical reaction is used to alter or destroy a hazardous waste component. Chemical treatment techniques can be applied to both organic and inorganic wastes, and may be formulated to address specific target compounds in a mixed waste. Typical chemical treatment processes include oxidation-reduction reactions such as ozonation, alkaline chlorination, electrolytic oxidation and chemical dechlorination. Physical treatment processes separate waste component by either applying physical force or changing the physical form of the waste. Various physical processes include adsorption, distillation, or filtration. Physical treatment is applicable to a wide variety of waste streams but further treatment is usually required. 

Cyano metal complexes undergo a variety of oxidation-reduction reactions. One of the most studied is the fast self-exchange reaction of the [Fe(CN)4] /" anions information from this research was instrumental in establishing the outer-sphere mechanism (see Outer-sphere Reaction) for transition metal oxidation-reduction reactions (see Electrochemistry Applications in Inorganic Chemistry). The nature... 

Applications of coulometric titrations involving oxidation-reduction reactions are shown in Table 4. Electrogenerated oxidizing agents such as bromine have proved to be useful, especially in organic analysis. 

The types of voltammetry that u.se the various excitation signals are also listed in Figure 23-1. The first three of these techniques in parts a-c of Figure 23-1 are discussed in detail in the sections that follow. Cyclic voltammetry has found considerable application as a diagnostic tool that provides information about the mechanisms of oxidation/reduction reactions under various conditions. Cyclic voltammetry is discussed in Section 23D. 

Cyclic voltammetry (CV) is an important and widely used electroanalytical technique. Although CV is infrequently used for quantitative analysis, it finds wide applicability in the study of oxidation/reduction reactions, the detection of reaction intermediates, and the observation of follow-up reactions of products formed at electrodes. In CV, the applied potential is swept in first one direction and then the other while the cunent is measured. A CV experiment may use one full cycle, a partial cycle, or several cycles. 

We learn much about chemical reactions from the study of electrochemistry. The amount of electrical energy consumed or produced can be measured quite accurately. All electrochemical reactions involve the transfer of electrons and are therefore oxidation-reduction reactions. The sites of oxidation and reduction are separated physically so that oxidation occurs at one location, and reduction occurs at the other. Electrochemical processes require some method of introducing a stream of electrons into a reacting chemical system and some means of withdrawing electrons. In most applications the reacting system is contained in a cell, and an electric current enters or exits by electrodes. 

Gray, Harry B., John D. Simon, and William C. Trogler. Braving the Elements. Sausalito, Calif. University Science Books, 1995. This book is an introduction to the basic principles of chemistry, with elementary explanations of radioactive decay, chemical bonding, oxidation-reduction reactions, and acid-base chemistry. Practical applications of specific chemical compounds and classes of compounds are presented. 

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