Oxidation-reduction reactions examples

Electrochemistry is the study of reduction-oxidation reactions (called redox reactions) in which electrons are transferred from one reactant to another. A chemical species that loses electrons in a redox reaction is oxidized. A species that gains electrons is reduced. A species that oxidizes is also called a reducing agent because it causes the other species to be reduced likewise, an oxidizing agent is a species that is itself reduced in a reaction. An oxidation-reduction reaction requires that one reactant gain electrons (be reduced) from the reactant which is oxidized. We can write the reduction and the oxidation reactions separately, as half-reactions the sum of the half-reactions equals the net oxidation-reduction reaction. Examples of oxidation half-reactions include ... 

Calculating the free-energy change from electrode potentials Given standard electrode potentials, calculate the standard free-energy change for an oxidation-reduction reaction. (EXAMPLE 20.9)... 

Although essentially inert m acid-base reactions alkanes do participate m oxidation-reduction reactions as the compound that undergoes oxidation Burning m air (combus tion) IS the best known and most important example Combustion of hydrocarbons is exothermic and gives carbon dioxide and water as the products... 

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. 

Another example is the siliciditing of tantalum, basically an oxidation— reduction reaction. The packing is sodium duoride and siUcon. After deposition, the coating diffuses continuously into the substrate, according to the following reactions ... 

Oxidation—Reduction. Redox or oxidation—reduction reactions are often governed by the hard—soft base rule. For example, a metal in a low oxidation state (relatively soft) can be oxidized more easily if surrounded by hard ligands or a hard solvent. Metals tend toward hard-acid behavior on oxidation. Redox rates are often limited by substitution rates of the reactant so that direct electron transfer can occur (16). If substitution is very slow, an outer sphere or tunneling reaction may occur. One-electron transfers are normally favored over multielectron processes, especially when three or more species must aggregate prior to reaction. However, oxidative addition... 

In an electrochemical cell, electrical work is obtained from an oxidation-reduction reaction. For example, consider the process that occurs during the discharge of the lead storage battery (cell). Figure 9.3 shows a schematic drawing of this cell. One of the electrodes (anode)q is Pb metal and the other (cathode) is Pb02 coated on a conducting metal (Pb is usually used). The two electrodes are immersed in an aqueous sulfuric acid solution. 

As described in Section 4-1. one important class of chemical reactions involves transfers of protons between chemical species. An equally important class of chemical reactions involves transfers of electrons between chemical species. These are oxidation-reduction reactions. Commonplace examples of oxidation-reduction reactions include the msting of iron, the digestion of food, and the burning of gasoline. Paper manufacture, the subject of our Box, employs oxidation-reduction chemishy to bleach wood pulp. All metals used in the chemical industry and manufacturing are extracted and purified through oxidation-reduction chemistry, and many biochemical pathways involve the transfer of electrons from one substance to another. 

There are also examples of induced complex formation, an essential step of which is always an oxidation-reduction reaction. Rich and Taube found that the rate of exchange between PtCl and Cl was considerably increased by addition of cerium(rV). In the presence of this oxidizing agent a labile complex of Pt(III) is formed, the chloride of which is easily exchangeable. Exchange of platinum between PtCl and PtClg is similarly rapid via the intermediate labile PtCIs complex formed by cerium(IV). 

Although in the fifties of the last century it had already been recognized that in several oxidation-reduction reactions the co-existence principle i.e. the assumption that the individual processes take place independently of each other) was not valid and to date many examples of chemical induction have been found, there are only a few cases known where the mechanism of the induced reaction has been satisfactorily elucidated. There are several reasons for this. Some of the induced reactions take place too rapidly to be investigated by conventional kinetical methods in other cases a thorough investigation was frustrated by the lack of appropriate analytical methods. 

Examples of tunneling in physical phenomena occur in the spontaneous emission of an alpha particle by a nucleus, oxidation-reduction reactions, electrode reactions, and the umbrella inversion of the ammonia molecule. For these cases, the potential is not as simple as the one used here, but must be selected to approximate as closely as possible the actual potential. However, the basic qualitative results of the treatment here serve to explain the general concept of tunneling. 

Oxidation-reduction reactions may affect the mobility of metal ions by changing the oxidation state. The environmental factors of pH and Eh (oxidation-reduction potential) strongly affect all the processes discussed above. For example, the type and number of molecular and ionic species of metals change with a change in pH (see Figures 20.5-20.7). A number of metals and nonmetals (As, Be, Cr, Cu, Fe, Ni, Se, V, Zn) are more mobile under anaerobic conditions than aerobic conditions, all other factors being equal.104 Additionally, the high salinity of deep-well injection zones increases the complexity of the equilibrium chemistry of heavy metals.106... 

It is convenient to divide organic chemical reactions between acid-base and oxidation-reduction reactions as in inorganic chemistry. In acid-base reactions the oxidation states of carbon do not change, e.g. in hydrolysis, where reaction is, for example,... 

CH3CO.OR + H20 - CH3COOH + ROH In oxidation-reduction reactions the oxidation states of carbon change, for example, CH3COOH + H2 - CH3CHO + h2o... 

We have already come across a few examples in which oxidation-reduction reaction can initiate vinyl polymerisation. Such a polymerisation reaction is known as redox polymerisation. In such reactions the oxidant is generally referred to as initiator and the reductant as activator. 

Metals react with nonmetals. These reactions are oxidation-reduction reactions. (See Chapters 4 and 18). Oxidation of the metal occurs in conjunction with reduction of the nonmetal. In most cases, only simple compounds will form. For example, oxygen, 02, reacts with nearly all metals to form oxides (compounds containing O2-). Exceptions are the reaction with sodium where sodium peroxide, Na202, forms and the reaction with potassium, rubidium, and cesium where the superoxides, K02, Rb02, and Cs02 form. 

In addition, potentiometric titration methods exist in which an electrode other than an ion-selective electrode is used. A simple platinum wire surface can be used as the indicator electrode when an oxidation-reduction reaction occurs in the titration vessel. An example is the reaction of Ce(IV) with Fe(II) ... 

Material balances can be written for moieties which are conserved during the reaction, such as the atoms of a particular element or the total charge, or for reactant or product species if the stoichiometry is unambiguous. Oxidation-reduction reactions may be particularly troublesome. In the following situation, for example, one cannot write a material balance relating protons to water molecules. Consider the oxidation of O2 to H2O and the equilibrium dissociation of I O. 

The proper location of data is also important in parameter-estimation situations. For the nitric oxide reduction reaction (K11), for example, the relative sizes of the three-dimensional confidence regions calculated after each observation are shown in Fig. 27. The size of the confidence region after 12 points taken according to a one factor at a time variation of hydrogen and nitric oxide partial pressures is seen to be equivalent the size of the region... 

We have stressed the direct relationship of specific nutritional needs to enzyme building, but this is only one possibility. In the case of nicotinamide, for example, which in the form of coenzymes I and II functions in oxidation-reduction reactions, an individual s need may be great because of the genetic ineffectiveness of the mechanism for building nicotinamide into enzyme systems, but the difficulty may lie at another site. Possibly there is difficulty in digestion (of the combined forms) or more likely absorption, which precludes the individual from getting a substantial portion of the nicotinamide out of his food to the cells that need it. Even the mechanism for transport may be at fault. We wish to emphasize that the effectiveness or ineffectiveness of the structures and mechanisms which may be... 

Various catalytic reactions are known to be structure sensitive as proposed by Boudart and studied by many authors. Examples are the selective hydrogenation of polyunsaturated hydrocarbons, hydrogenolysis of paraffins, and ammonia or Fischer-Tropsch synthesis. Controlled surface reactions such as oxidation-reduction reactions ° or surface organometallic chemistry (SOMC) " are two suitable methods for the synthesis of mono- or bimetallic particles. However, for these techniques. 

A primary goal of chemical separation processes in the nuclear industry is to recover actinide isotopes contained in mixtures of fission products. To separate the actinide cations, advantage can be taken of their general chemical properties [18]. The different oxidation states of the actinide ions lead to ions of charges from +1 (e.g., NpOj) to +4 (e.g., Pu" " ) (see Fig. 12.1), which allows the design of processes based on oxidation reduction reactions. In the Purex process, for example, uranium is separated from plutonium by reducing extractable Pu(IV) to nonextractable Pu(III). Under these conditions, U(VI) (as U02 ) and also U(IV) (as if present, remain in the... 

Fire is a self-sustaining, exothermic oxidation-reduction reaction. The fire reaction usually involves oxygen which forms the oxides of the fuel. The most important examples in petrochemical and hydrocarbon processing facilities are combustion reactions of hydrocarbons with oxygen. 

A major class of enzymes that catalyze oxidation-reduction reactions. This class includes dehydrogenases, reductases, oxygenases, peroxidases, and a few synthases. Examples include alcohol dehydrogenase (EC 1.1.1.1), aldehyde oxidase (EC 1.2.3.1), orotate reductase (EC 1.3.1.14), glutamate synthase (EC 1.4.1.14), NAD(P) transhydrogenase (EC 1.6.1.1), and glutathione peroxidase (EC 1.11.1.9). 

If a chemical reaction can make electricity it should not be surprising to learn that electricity can make a chemical reaction. Using an electric current to cause a chemical reaction is called electrolysis, a technique widely used to win elements from their compounds. For example, pure sodium metal (Na) and chlorine gas (CI2) are obtained by passing electricity through molten sodium chloride (NaCl). The study of the interplay of electricity and oxidation-reduction reactions is called electrochemistry. 

Bacterial ferredoxins function primarily as electron carriers in ferredoxin-mediated oxidation reduction reactions. Some examples are reduction of NAD, NADP, FMN, FAD, sulfite and protons in anaerobic bacteria, CO -fixation cycles in photosynthetic bacteria, nitrogen fixation in anaerobic nitrogen fixing bacteria, and reductive carboxylation of substrates in fermentative bacteria. The roles of bacterial ferredoxins in these reactions have been summarized by Orme-Johnson (2), Buchanan and Arnon (3), and Mortenson and Nakos (31). 

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 redox reactions, oxidation and reduction processes occur at the same time. The following reaction is an oxidation-reduction reaction. For example,... 

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