Reactions Without Oxidation-Reduction

Varma has run many types of reactions on nontoxic supports, such as alumina, silica, and clay, using microwaves.45 (For more on the use of microwaves, see Chap. 15.) The method offers selectivity under safe, fast, mild reaction conditions in open vessels. The supports can be recycled. The reactions include oxidations, reductions, nitrations, aldol condensations, and others. Solvents were used in the workups. Other workers have devised a condensation (8.3) of aromatic aldehydes with malonic acid (without a support) that uses no solvents at all.46 The workup consisted of pouring the glassy reaction mixture from the Erlenmeyer flask into ice water, filtering off the solid, and drying it. The conventional procedure for this reaction requires heating at 120°C for 3 h to give the product in 96% yield. 

Equilibrium reactions at the solid-aqueous solution interface may be characterized by those in which oxidation or reduction does or does not occor, A reaction without oxidation or reduction may be repreaenred by the reaction... 

If n = 0. the reaction is a chessical reaction without oxidation or reduction. For n 0. A represents the reactant in the oxidized stale while B is in the reduced state. According to the Nemst equation,... 

The aim of a titration is the addition of a quantity of the standard solution CHEMICALLY EQUIVALENT to the quantity of the unknown. This means the MOLAR RATIO of the known added to the unknown must conform to the ratio in the chemical equation. Addition of an excess or insufficient quantity of the known solution results in an incorrect analysis. The reaction may be an acid-base reaction, an oxidation-reduction, the precipitation of a slightly soluble salt, or any other reaction which goes practically to completion, without complicating side reactions. 

Gotman I (1997) Characteristics of metals used in implants. J Endourol 11(6) 383-389 Guyton DL, Hambrecht FT (1973) Capacitor electrode stimulates nerve or muscle without oxidation-reduction reactions. Science 181 74-76... 

The control of chemical reactions (e.g., esterification, sulfonation, nitration, alkylation, polymerization, oxidation, reduction, halogenation) and associated hazards are an essential aspect of chemical manufacture in the CPI. The industries manufacture nearly all their products, such as inorganic, organic, agricultural, polymers, and pharmaceuticals, through the control of reactive chemicals. The reactions that occur are generally without incident. Barton and Nolan [1] examined exothermic runaway incidents and found that the principal causes were ... 

Other corrosion inhibitors also enhance passivity without electrochemical reduction, by depositing insoluble oxidation products into the passivating film. For example benzoate ions cause deposition of ferric benzoate into the oxide, but do not provide any cathodic reaction. 

Of course, there is no oxidation without a concurrent reduction. However, we classify reactions as oxidations or reductions depending on whether the organic compound is oxidized or reduced. In some cases both the oxidant and reductant are organic those reactions are treated separately at the end of the chapter. 

Co(Y)CP and Co(HY)Cl react with Fe " " at comparable rates. Comparisons are instructive between this redox reaction and other cation-catalysed chloride-abstraction reactions which occur without simultaneous oxidation-reduction. The intimate mechanisms are likely to be... 

Deprotection of X, and subsequent oxidation, reduction, and acetylation reactions can, with care, be carried out without decomposition of the inorganic backbone. Reactions of this type are of particular interest for the synthesis of bioactive or biocompatible polyphosphazenes. 

Preliminary observations of the reactions of Fe(II) and Fe(III) in an ultrasonic field revealed conversion of Fe(II) to Fe(III) and vice-versa, even without any external oxidant/reductant, which were subsequently confirmed experimentally and sequentially through the following four qualitative conversions. The details are available in the literature [35]. 

There are further theoretical objections to this RNA-world hypothesis, especially since we know of no organisms based on RNA without DNA and proteins. Moreover, RNA is not able to act as a catalyst for many essential simple molecule reactions, e.g. of CO, H2, N2, nor for most oxidation/reduction changes, and RNA... 

The Noyori reduction of various diketo esters in this series was very dependent upon the amount of add present in the reaction. Without the presence of a stoichiometric amount of add, the rate of reduction as well as the selectivity in the reduction dropped off. At higher pressures, the chemoselectivity of the reduction was poor resulting in die reduction of both alkene groups. Further, the carbonyl at C5 was never reduced under these reaction conditions but was absolutely necessary for the reduction of the C3 carbonyl. When C5 was in the alcohol oxidation state, no reduction was seen. A. Balog, unpublished results. 

In a related study, the oxidation-reduction sequence was carried out in the presence of an olefin (Scheme 21). Two products were formed. The major product resulted from the net reduction of the carboxylic acid to an aldehyde. The minor product resulted from trapping of the radical anion intermediate generated from the reduction reaction by the olefin. It should be noted that, in the absence of a trapping group, the acid can be selectively reduced to the aldehyde without any over-reduction. Although not in the scope of this review, this is a very useful transformation in its own right [35]. At this time, the yields of the cyclized products from the cyclization reaction of the radical anion with the olefin remain low. 

Figure 10. Cyclic voltammetric response at the NPyeCME for the oxidation/ reduction reaction of benzyl alcohol (32 mM)/C10 in aqueous 4.1 mol NaOCl (A) and nonaqueous CH2CI2 (B) solutions at a scan rate of 50 mV/s. (C) Cartoon for the NPyeCME. Inset (A) corresponds to an enlarged version of the oxidation part without (a) and with (b) benzyl alcohol. In order to marntam the electrical conductivity, 0.1 M tetrabutylammonium bromide (TBAB) is added into the CH2CI2 solution.

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