Oxidation-reduction half-reactions

The half-reactions and reduction potentials in Table 21.1 can be used to analyze energy changes in redox reactions. The oxidation of NADH to NAD can be coupled with the reduction of a-ketoglutarate to isocitrate ... 

To monitor the transfer of electrons in a redox reaction, you can represent the oxidation and reduction separately. A half-reaction is a balanced equation that shows the number of electrons involved in either oxidation or reduction. Because a redox reaction involves both oxidation and reduction, two half-reactions are needed to represent a redox reaction. One half-reaction shows oxidation, and the other half-reaction shows reduction. 

Write the oxidation half-reaction, the reduction half-reaction, and the overall cell reaction for each of the following galvanic cells. Identify the anode and the cathode in each case. In part (h), platinum is present as an inert electrode. 

Write the oxidation half-reaction, the reduction half-reaction, and the overall cell reaction for the following galvanic cell. 

In this method, the reaction is broken down into two half-reactions, oxidation and reduction half-reactions. Each half-reaction is balanced separately, so that the same number of electrons appear in each half-equation. Then, the two halfreactions are summed up to get a balanced net equation. 

The energy available from spontaneous cell reactions can be used to power vehicles or generate electricity (Box 12.2). To calculate the standard cell potential for a spontaneous process, we must combine the standard potential of the cathode half-reaction (reduction) with that of the anode half-reaction (oxidation) in such a way as to obtain a positive... 

Polyphenols could act as effective chain-breaking antioxidants (AH = POH) through the one-electron transfer reactions 4 and 5 if they produce a stable and relatively nonreactive antioxidant radical (A = PO) [Jovanovic et al., 1994], Reactions 4 and 5 can be represented by the reaction 8, where L or LOO represents the oxidant free radical. This reaction can be decomposed in two half-reactions one reduction (reaction 9) and one oxidation (reaction 10) ... 

Standard potentials (reactants and products at unit activity, hydrogen ion activity of 1, i.e. pH = 0), of reduction, oxidation, net reaction, the ith redox-active species, and any half-reaction Standard reduction potential at hydrogen ion activity of 10 7 (pH = 7.0)... 

The reaction can be written as the difference of two half-reactions whose reduction potentials are listed in Table 19-1. The nE° values can be calculated as standard reduction potentials so long as one is reversed to an oxidation. The reversal of the reaction results in the opposite sign for the potential. 

Redox reactions may always be written as two half-reactions, a reduction halfreaction with electrons as a reactant and an oxidation half-reaction with electrons as a product. 

In an oxidation-reduction reaction, or redox reaction, one or more electrons are transferred completely from one species to another. Every redox reaction may be separated into a reduction half-reaction and an oxidation half-reaction. A reduction half reaction, in which a chemical species accepts electrons, may usually be written in the form... 

The second step requires you to separate the equation into two separate half-reactions. A half-reaction only shows what is going on in half of the reaction. The first half-reaction shows the oxidation and the second half-reaction the reduction ... 

Write the reduction and oxidation half-reactions Oxidation C —> CO2... 

Oxidation is defined as a gain in oxidation number, caused by a loss of electrons or of control of electrons. Reduction is defined as a loss in oxidation number, caused by a gain of electrons or of control of electrons. Complicated oxidation-reduction equations must be balanced according to some systematic method because they are too complex to be balanced by inspection. Although neither can take place alone, the oxidation and the reduction can occur in different locations if suitable electrical connections are provided. (Chapter 17) In the halfreaction method, the equation for the half-reaction involving oxidation and that for the half-reaction involving reduction are balanced separately then the two are combined. Each may be multiplied by a small integer if necessary to balance the numbers of electrons involved. 

The catalytic cycle of each flavoenzyme consists of two distinct processes, the acceptance of redox equivalents from a substrate and the transfer of these equivalents to an acceptor. Accordingly, the catalyzed reactions consist of two half-reactions a reductive half-reaction in which the flavin is reduced and an oxidative half-reaction, in which the reduced flavin is reoxidized. This review summarizes the chemistry of simple flavoprotein reductases, dehydrogenases, (di)thiol oxidoreductases, oxidases, and monooxygenases (Table 1) (5 0) This grouping provides a good appreciation about what type of common mechanisms can be distinguished and what type of substrates can be converted. Information on the chemistry of complex flavoenzymes can be found in the Further Reading section. 

The set of reactions that creates the complex redox environments of landfill leachate plumes consists of combinations of two half-reactions oxidation half-reaction and reduction halfreaction. Table 3 presents the most prominent overall redox reactions, along with their calculated Gibbs free energy change under standard conditions (AGo(W)). The lower (the more negative) the AGq(W), the more energy is gained. 

Multiply oxidation half-reaction. Multiply reduction half-reaction by 5 and add to oxidation half-reaction. 

To convert these oxidation potentials to electrode potentials as defined by the lUPAC convention, one must mentally (1) express the half-reactions as reductions and (2) change the signs of the potentials. 

Reduction half-reaction Oxidation half-react ion ... 

The oxidized form of a species in a half-reaction is capable of oxidizing the reduced form of a species in a half-reaction whose reduction potential is more negative than its own, and vice versa The reduced form in a half-reaction is capable of reducing the oxidized form in a half-reaction with a positive potential. 

Subtracting haif-ceii of the tin half-reaction (anode, oxidation) from haif-ceii of the silver half-reaction (cathode, reduction) gives a positive n that is,... 

Reduction Half-Reaction Oxidation Half-Reaction Complete Reaction ... 

Label each half-reaction as reduction or oxidation. 

Half reaction of oxidation Half reaction of reduction... 

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