Chemical reactions reduction-oxidation

Chemical reactions—oxidation, reduction, dehydration, hydrolysis, acid rain... 

It is thus obvious that for all the cases described above the oxide reacted with the element to form a volatile oxide. A chemical reaction (oxidation-reduction reaction... 

The solution came, in part, by the application of biotransformations. These can be defined as biological processes that modify organic compounds via simple chemical reactions (oxidations, reductions) by means of enzymes contained in microbial, plant, or even animal cells. The aim is usually a one-step reaction to a recoverable product in a sequence of steps in which the majority of conversions are chemical steps (i.e., synthesis). In fermentation processes the whole sequence of reactions is carried out by microorganisms, be it a carbohydrate breakdown to alcohol (or other solvents), the production of antibiotics, or even enzymes. 

An important property of an element is the oxidation state in which it exists in a compound or ion. We begin with learning how to assign oxidation numbers, part of a bookkeeping system that helps us keep track of what goes on in an important class of chemical reactions—oxidation-reduction reactions. 

The third remarkable aspect of enzyme catalysis is the versatility of these species. They catalyze an extremely wide variety of reactions— oxidation, reduction, polymerization, dehydration, dehydrogenation, etc. Their versatility is a reflection of the range and complexity of the chemical reactions necessary to sustain life in plants and animals. 

As for chemical reactions, the reduction/oxidation (redox) reactions in an homogeneous medium (i.e., in the bulk of the solution) have been experimentally studied with proper intensity only in the past decades. There has been some development of the bulk reactions. However, as earlier, a comparison of the same compound in chemical and electrochemical electron/charge-transfer reactions is still of current interest. Such a comparison is made in this section. The examples offered are intended to invoke novel interpretations or discover new colors in pictures, which have already been drawn. 

Subsequent ion exchange of the metal cation with the quaternary ammonium ion catalyst provides a lipophilic ion pair (step 2), which either reacts with the requisite alkyl electrophile at the interface (step 3) or is partitioned into the electrophile-containing organic phase, whereupon alkylation occurs and the catalyst is reconstituted. Enantioselective PTC has found apphcation in a vast number of chemical transformations, including alkylations, conjugate additions, aldol reactions, oxidations, reductions, and C-X bond formations." ... 

The goal of this chapter is to give you a stronger handle on the basics of chemical reactions, which were introduced in Chapter 2. Then in the following chapters we ll look at specific classes of chemical reactions, such as acid-base reactions, oxidation-reduction reactions, and reactions involving organic chemicals. 

Any time electrons are transferred between reactants in a chemical reaction, the reaction is called an oxidation-reduction reaction. Oxidation-reduction reactions are also called redox reactions. 

If electrons are liberated, they will not remain as free charges. They will be absorbed somewhere else in a complete reaction. Thus in a complete chemical reaction, oxidation and reduction reactions are coupled as in the case of a galvanic cell where electrons are liberated by an anode and are subsequently absorbed by a cathode. Thus, these coupled reactions are redox reactions. 

Biological degradation—fungi, bacteria, insects, termites Enzymatic reactions—oxidation, hydrolysis, reduction Chemical reactions—oxidation, hydrolysis, reduction Mechanical—chewing... 

There is another common way to classify chemical reactions acid-base reactions, oxidation-reduction reactions, and reactions of more complicated types (beyond the scope of this book). Acid-base reactions are considered to involve the reactions of hydrogen ions with hydroxide ions. The reactions of acids and bases will be taken up in this section, and a more sophisticated view of these reactions is presented in Chapter 19. Oxidation-reduction reactions involve the transfer of electrons from one substance to another. Many combination reactions, many decomposition reactions, all single substitution reactions, and all combustion reactions are of this type, but more complex examples are presented in Chapters 16 and 17. 

In solid phase reaction s3mthesis, there are three types of chemical reactions oxidation or reduction of a solid, thermal decomposition of a solid, and solid state reaction between two t3 s of solid. With liquid phase ssmthesis of ceramic powders, there are five different methods drying of a liquid, precipitation, sol-gel sjmthesis, hydrothermal S5m-thesis, and reactions of a liquid metal melt with a gas to give a solid ceramic. There are basically three operational principles for precipitation temperature change, evaporation, and chemical reaction. Sol—gel... 

Simultaneous occurrence of oxidation and reduction in a chemical reaction. Oxidizing agent reducing agent oxidation-reduction pair (couple). 

Biotransformation of xenobiotics takes place in two phases. In phase I (= functionalization reactions), reactive groups are either activated or inserted into the substance molecule, thus providing the lipophilic molecule with a functional hydrophilic group. (In phase II, a hydrophilic residue is added to this group transferases hereby catalyze the conjugation with an endogenous substance.) Phase I elfects the insertion of reactive (polar) groups (such as -OH, -COOH, -SH, -NH2) by means of four chemical processes oxidation, reduction, hydrolysis, and hydration. 

A battery is a complex device that delivers electrical energy by transforming chemical energy. The electrical energy is provided by electrochemical reactions (oxidation-reduction reactions) that take place at the anode and the cathode of the battery. While the term battery is often used, the basic electrochemical unit being referred to is the cell [1]. A battery is composed of several cell units that are connected in series or in parallel... 

Standard substances in clinical chemistry include primary standards, which can be obtained sufficiently pure to be used for the preparation of solutions by weighing or by reference to other definable physical characteristics (e.g., constant-boiling hydrochloric acid). Primary standard chemicals are available for acid-base reactions, precipitation reactions, oxidation-reduction reactions, etc. (V3), and are used in these various categories of analytical determination to validate the preparation of solutions of other chemical substances which cannot be obtained in a form suitable to meet the criteria demanded for a primary standard. Following their calibration in terms of a primary standard, these other chemieals can act as secondary standards. 

Are these reactions oxidation-reduction reactions Are electrons transferred Simply reading a chemical equation does not always tell us whether oxidation and reduction have occurred, so chemists have developed a numerical system to help identify a reaction as redox. For redox reactions, this system also shows us which element is oxidized, which is reduced, what the oxidizing agent is, and what the reducing agent is. 

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. 

In an electrochemical cell, electricity is produced by a spontaneous chemical reaction. Oxidation and reduction take place separately at the anode and cathode, respectively, and the electrons flow through an external circuit. 

A battery is a collection of one or more electrochemical cells that convert chemical energy into electrical energy via electrochemical reactions (oxidation-reduction reactions). These reactions take place at the battery s anode and cathode. The electrochemical cells are connected in series or in parallel depending on the desired voltage and capacity. Series connections provide a higher voltage, whereas parallel connections provide a higher capacity, compared with one cell. 

Chemical transformations in the liver are greatly facilitated by the action of enzymes within the smooth endoplasmic reticulum of hepatocytes (often called the microsomal fraction). Phase I reactions (oxidation, reduction, and hydrolysis reactions) convert molecules into more polar forms that usually differ in biological activity from the parent form. Oxidation reactions occur primarily under the direction of a family of enzymes called P450- Non-specific esterases in the liver, plasma, and other sites catalyze the hydrolysis of esters, whereas amides are hydrolyzed in the liver. Protein drugs are often degraded by proteases and peptidases, which are abundant in many tissues, including the intestinal tract and plasma. Phase II reactions are conjugation reactions. 

Transformation/degradation processes biodegradation, chemical hydrolysis, oxidation-reduction reactions and photolysis, the last only at the surface of the soil. Biological transformations comprise the main degradation pathway in the soil layer, where there is an active bacterial community, possibly up to some tens of centimetres deep. 

The most conventional kinetic scheme of FRP includes initiation, propagation, and bimolecular termination reaction steps. Additional reactions such as chain transfer are introduced to improve the process description. Free radicals are highly reactive chemical species produced by the homolytic dissociation of covalent bonds. Such species are produced through physical (thermoexcitation, radiation) or chemical methods (oxidation-reduction, addition, etc.). Generally, their survival time is less than a second, except for those radicals highly stabilized by specific chemical groups the hybridization state is sp. ... 

As we discussed in Chapter 4, oxidation is the loss of electrons in a chemical reaction, and reduction is the gain of electrons. (Section 4.4) Thus, oxidation-reduction (redox) reactions occur when electrons are transferred from an atom that is oxidized to an atom that is reduced. Redox reactions are involved not only in the operation of batteries but also in a wide variety of important natural processes, including the rusting of iron, the browning of foods, and the respiration of animals. 

The chemistry of these elements is closely associated with a ver important type of chemical reaction oxidation and reduction. An atom which has been oxidized is one that, in the course of a chemical reaction, loses control - totally or partially - over one or more of its valency electrons, in favour of a more electronegative atom. Reduction occurs simultaneously, since the reduced atom gains control over an electron from a less electronegative atom. 

Like any chemical system, oxidation-reduction reactions will progress toward equilibrium. Because of this fact, the cell potential provides a way to measure equilibrium constants or free energy changes. 

---