Oxidation-reduction reactions described

Isomerization reactions rearrange particular atoms within the molecule. Their role is often to prepare a molecule for subsequent reactions such as the oxidation-reduction reactions described in point 1. 

Which of the following half-reactions for this oxidation-reduction reaction describes the oxidation, and which one describes the reduction ... 

Iodine, I2, has many uses, including the production of dyes, antiseptics, photographic film, pharmaceuticals, and medicinal soaps. It forms when chlorine, CI2, reacts with iodide ions in a sodium iodide solution. Which of the following half-reactions for this oxidation-reduction reaction describes the oxidation, and which one describes the reduction ... 

Plutonium found in soils may undergo the same oxidation/reduction reactions described for surface waters in places where soil contacts water. In addition to oxidation/reduction reactions, plutonium can react with other ions in soil to form complexes. These complexes may then be absorbed by roots and move within plants however, the relative uptake by plants is low. In plants, the complex can be degraded but the elemental plutonium will remain. 

The term electrochromism was apparently coined to describe absorption line shifts induced in dyes by strong electric fields (1). This definition of electrocbromism does not, however, fit within the modem sense of the word. Electrochromism is a reversible and visible change in transmittance and/or reflectance that is associated with an electrochemicaHy induced oxidation—reduction reaction. This optical change is effected by a small electric current at low d-c potential. The potential is usually on the order of 1 V, and the electrochromic material sometimes exhibits good open-circuit memory. Unlike the well-known electrolytic coloration in alkaU haUde crystals, the electrochromic optical density change is often appreciable at ordinary temperatures. 

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. 

Various options for the production of tantalum from pure tantalum compounds are summarized in Figure 4.26. The oxide and halide reduction reactions described above have been carried out in basically different types of reactors, using processes that are characteristically different because the forms and the physico-chemical nature of the feed materials are different. A relatively recent development with regard to process metallurgical equip-... 

In the reaction presented above, oxygen shares electrons with sulfide ion which is unlike that from oxidation-reduction processes described later where transfer of electrons occurs. 

Harry B. Gray and Walther Ellis,13 writing in Chapter 6 of reference 13, describe three types of oxidation-reduction centers found in biological systems. The first of these, protein side chains, may undergo oxidation-reduction reactions such as the transformation of two cysteine residues to form the cystine dimer as shown in equation 1.28 ... 

In addition to the physical effects previously described, animals can change the soil s biological and chemical reactions. For instance, animal paths become devoid of plants and compacted, thereby changing water infiltration and percolation and oxidation-reduction reactions, particularly when there is continual use of the paths [1-4]. 

From the viewpoint of inorganic chemistry, the reaction of potassium nitrate with sulfur and charcoal can be described as an oxidation-reduction reaction in which electron transfer between reacting species involves a loss or gain of electrons resulting in an oxidation or reduction process respectively. 

Today, many reactions in aqueous solutions can be described as oxidation-reduction reactions (redox reactions). Oxidation is the process in which the oxidation number of atoms increases. Reduction is the process in which the oxidation number of atoms is decreased or made more negative. In another definition, oxidation is the loss of electrons by an atom, and reduction is the gain of electrons. Let us look at the following reaction ... 

Metal Ion Catalysis Metals, whether tightly bound to the enzyme or taken up from solution along with the substrate, can participate in catalysis in several ways. Ionic interactions between an enzyme-bound metal and a substrate can help orient the substrate for reaction or stabilize charged reaction transition states. This use of weak bonding interactions between metal and substrate is similar to some of the uses of enzyme-substrate binding energy described earlier. Metals can also mediate oxidation-reduction reactions by reversible changes in the metal ion s oxidation state. Nearly a third of all known enzymes require one or more metal ions for catalytic activity. 

Although oxidation and reduction must occur together, it is convenient when describing electron transfers to consider the two halves of an oxidation-reduction reaction separately. For example, the oxidation of ferrous ion by cupric ion,... 

The principles of oxidation-reduction energetics described above apply to the many metabolic reactions that involve electron transfers. For example, in many organisms, the oxidation of glucose supplies energy for the production of ATP. The complete oxidation of glucose ... 

Biological oxidation-reduction reactions can be described in terms of two half-reactions, each with a characteristic standard reduction potential, E °. 

Oxidation/reduction reactions. They have fitted ReaxFF against a wide range of metal oxidation states to ensure that ReaxFF describes redox reactions accurately. 

This chapter mainly focuses on the reactivity of 02 and its partially reduced forms. Over the past 5 years, oxygen isotope fractionation has been applied to a number of mechanistic problems. The experimental and computational methods developed to examine the relevant oxidation/reduction reactions are initially discussed. The use of oxygen equilibrium isotope effects as structural probes of transition metal 02 adducts will then be presented followed by a discussion of density function theory (DFT) calculations, which have been vital to their interpretation. Following this, studies of kinetic isotope effects upon defined outer-sphere and inner-sphere reactions will be described in the context of an electron transfer theory framework. The final sections will concentrate on implications for the reaction mechanisms of metalloenzymes that react with 02, 02 -, and H202 in order to illustrate the generality of the competitive isotope fractionation method. 

Trichlorogermane reactions involving participation of dichlorogermylene are not oxidation-reduction reactions in the usual sense of this term, though they are described by Gen/GeIV transfers. At the same time, the reductive properties of trichlorogermane can be illustrated by the reduction of nitrobenzenes to anilines. 

Redox reactions are not limited to single replacement reactions. They really describe a wide variety of reactions, but each shares the common theme of involving an oxidation and a reduction. An oxidation occurs when a substance loses electrons and becomes more positively charged. Earlier in the book we discussed a similar phenomenon in the formation of ionic compounds. Substances don t just lose electrons for no reason. They lose electrons because another substance takes them. When a substance acquires additional electrons and becomes more negatively charged, it is called a reduction. An oxidation cannot take place without a reduction, so these processes must occur simultaneously. These reactions describe the simultaneous oxidation and reduction of materials, which has earned them the name oxidation-reduction reactions. 

One purpose of this paper is to examine the evidence that the rates of oxidation—reduction reactions are related to the conductivity of the medium separating the oxidant and reductant. This survey will then describe experiments now in progress to investigate systematically the nonadiabatic regime in oxidation—reduction reactions. First the relationship between what has loosely been referred to as the conductivity of the medium and the title term, nonadiabatic, should be defined. 

Before describing experiments designed to study the nonadiabatic regime for electron transfer in oxidation-reduction reactions systematically, some systems in which electron tunnelling, in the sense that it... 

Pai et al. (1983) measured hole mobilities of a series of bis(diethylamino)-substituted triphenylmethane derivatives doped into a PC and poly(styrene) (PS). The mobilities varied by four orders of magnitude, while the field dependencies varied from linear to quadratic. In all materials, the field dependencies decreased with increasing temperature. The temperature dependencies were described by an Arrhenius relationship with activation energies that decrease with increasing field. Pai et al. described the transport process as a field-driven chain of oxidation-reduction reactions in which the rate of electron transfer is controlled by the molecular substituents of the hopping sites. 

The reaction I have just described is an example of a special class of chemical reactions known as oxidation-reduction reactions, or redox reactions for short. When an atom or molecule loses electrons in a reaction, we say the substance is oxidized. When an atom or molecule gains electrons in a reaction, we say the substance is reduced. " In a redox reaction, at least one atom or molecule gains electrons, and at least one atom or molecule loses electrons. 

The concept of oxidation states (also called oxidation numbers) provides a way to keep track of electrons in oxidation-reduction reactions. Oxidation states are defined by a set of rules, most of which describe how to divide up the shared electrons in compounds containing covalent bonds. However, before we discuss these rules, we need to discuss the distribution of electrons in a bond. 

The principal abiotic processes that transform uranium in water are formation of complexes and oxidation-reduction reactions that have been described in Section 5.3.1. In seawater at pH 8.2, it was shown that U(IV) exists as 100% neutral hydroxo complexes, and U02 " and U(VI) exist as 100% carbonate complexes. In freshwater at pH 6, U(IV) was shown to exist as 100% hydroxo... 

The assignment of electrons is somewhat arbitrary, but the procedure described below is useful because it permits a simple statement to be made about the valences of the elements in a compound without considering its electronic structure in detail and because it can be made the basis of a simple method of balancing equations for oxidation-reduction reactions. 

The experimental observations on the actinide oxidation-reduction reactions are described, and the empirical results are tabulated. The rate laws have been interpreted in terms of net activation processes, and these have been tabulated togther with the associated activation parameters— aF, AH, and AS. An electrical analog is described which has been useful in interpreting complicated rate laws. Empirical correlations have been found between the formal entropies of the activated complexes and their charges, and for sets of similar reactions, between the hydrogen ion dependence and AF°, between AF and aF°, and between AH and AH°. The kinetic and physical evidence for binuclear species is discussed. 

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