Anodic oxidation reactivity

These apparent contradictions can be resolved if one keeps in mind that the competition between several reaction paths is dependent upon both the reactivities of the anodically oxidized parent species and the polymer film as well as the reactivity of the surrounding solvent-electrolyte medium. 

Figures 3 and 4, respectively, show thin-layer current-potential curves for polycrystalline Au and Ir in molar sulfuric acid before and after exposure to a 2 mM HQ solution. For smooth Au, no changes in the voltammetric curves are seen. In comparison, a prominent anodic oxidation peak is observed for Ir after pretreatment with HQ. These observations, which indicate that Ir is reactive towards HQ but Au is not, are consistent with what is known from the literature on homogeneous organometallic chemistry (21) Ir and Pt complexes are reactive towards a variety of organic compounds, whereas Au is inert.

Recently, Germain et al. have also shown that the indirect anodic oxidation in fluorosulfuric add of fluorocarbon derivatives of the type RfCF2X (X — H, COOH, S03H, CH2OH, Br), which are not directly oxidizable, leads to fluorosulfates of the type FSG3CF3Rf (Eqs. 18 and 19) [37, 38], in these reactions, the peroxide (FS03)2, partially dissociated in its free radicals, is the in-situ electrochemically produced reactive intermediate as shown in Scheme 5.1. 

Since the chemical reactivity of a cyclopropane ring is sometimes compared with that of a carbon-carbon double bond, it is interesting to study the electrochemical behaviour of silyloxycyclopropanes. Torii et al. described the anodic oxidation of silyloxycyclopropanes in the presence of Fe(N03)3 which resulted in the opening of the cyclopropane ring as shown in Scheme 27 [61]. The reaction temperature has a profound effect on the yields of the products the best resuls are obtained at —13 to —10 °C. 

The work on the electrochemical generation of a solution of ceric sulphate from slurry of cerous sulphate in 1-2 M sulphuric acid was abandoned by BCR due to difficulties encountered in handling slurried reactants. A 6kW pilot reactor operated at 50 °C using a Ti plate anode and a tungsten wire cathode (electrolyte velocity about 2ms 1) produced 0.5 M Ce(S04)2 on the anode with a current efficiency of 60%. The usefulness of Ce(IV) has been limited by the counter anions [131,132], Problems include instability to oxidation, reactivity with organic substrates and low solubility. Grace found that use of cerium salts of methane sulfonate avoids the above problems. Walsh has summarized the process history, Scheme 6 [133],... 

This chapter deals with anodic oxidation of saturated hydrocarbons, olefins, and aromatic compounds. Substituted hydrocarbons are included, when the substituents strongly influence the reactivity. Anodic functional group interconversions (FGI) of the substituents are covered in Chapters 6, 8-10 and 15. 

The oxidation of an amine can benefit from the use of an electroauxiliary [19-28]. Electroauxiliaries are substituents that both lower the initial oxidation potential of the substrate and control the formation of the subsequent reactive intermediates. To this end, the anodic oxidation of the 6-membered ring a-silylamines in the presence of cyanide was shown to afford a net displacement of the silyl... 

Heterocycles are of great interest in organic chemistry due to their specific properties. Many of these cycles are widely present in natural and pharmaceutical compounds. Electrochemistry appears as a powerful tool for the preparation and the functionalization of various heterocycles because anodic oxidations and cathodic reductions allow the selective preparation of highly reactive intermediates (radicals, radical ions, cations, anions, and electrophilic and nucleophilic groups). In this way, the electrochemical technique can be used as a key step for the synthesis of complex molecules containing heterocycles. A review of the electrolysis of heterocyclic compounds is summarized in Ref. [1]. 

Various reactive intermediates have been postulated in the formation of heterocycles by anodic oxidation. 

The photoelectrochemical behavior of a given photoanode is dependent on its method of synthesis. Various methods, some of which we now briefly consider, such as anodic oxidation, spray pyrolysis, reactive sputtering and vapor deposition are commonly employed to make polycrystalline thin films. 

A specific and peculiar additional possibility was suggested " from the observation that an ordered array of Ti02 nanocoils forms in particular conditions of synthesis by anodic oxidation.The interesting aspect is that in such nanostructures, photo-induced current generates a local magnetic field which influences the reactivity properties of catalytic... 

Schemes 24 and 34. Not all specific examples follow these generalized pathways. Although 78h does decompose predominately into 99 (Scheme 44) at neutral pH, evidence suggests that it may not do so via an addition-elimination mechanism. This intermediate is detectable in reaction mixtures, but it has never been isolated due to its high reactivity. The N-benzoyl analogue 78h has been prepared by anodic oxidation of N-benzoyl-2-aminofluorene and has been shown by labeling experiments to generate 99 by an intramolecular pathway presumably involving the intermediate 100. ...

Nonetheless, a number of electroorganic synthesis reactions are known whose outcome i.e., whose yield and selectivity, is decisively determined by the nature of the electrode so that heterogeneous acceleration of at least one of several competitive reactions of the electrogenerated reactive intermediates might be anticipated. A famous case is the Kolbe reaction, which is essentially the anodic dimerization of alkyl radicals that are generated at platinum anodes by anodic oxidation of the anions of carboxylic acids ... 

The a-methoxylated derivatives are shown to be versatile synthons because of the reactivity of the methoxy group near the nitrogen atom, a-Methoxycarbamates, prepared by anodic oxidation, were used as key intermediates in the synthesis of a-amino acids,200 a new carbon-phosphorus bond-forming reaction,200 and in a new method of acylation of aliphatic amines at the -position.201 The application of this reaction to the synthesis of pyrrolidine, piperidine, and tropane alkaloids is also described.202... 

Another model for giving an explanation of the pH dependence of the reactivity of halide ions may be that surface cations serve as effective sites for adsorption of reaction intermediates which are produced in the course of the anodic oxidation of halide ions. Usually, the anodic oxidation of halide ions is believed to... 

The anodic oxidation of iodide, bromide and chloride ions at illuminated ZnO electrodes, which occurs in competition with the anodic decomposition of the electrode itself, was studied as functions of halide ion concentration, illumination intensity and solution pH in order to investigate factors which affect the degree of competition. The reactivity of halide ions, obtained under fixed conditions, was in the order of I >Br >Cl, reflecting the importance of the redox potential in determining the reactivity. 

To get insight into the reactivity of olefin radical cations toward oxygen, anodic oxidation of olefins under oxygen was attempted. DPE was electrolyzed at 1.5 V vs SCE in a mixture of... 

The apparent dichotomy between good yields of pyrrolidine products from anodic oxidation of lithium alkenylamides and the generally low reactivity of neutral aminyl radicals toward cyclization might be explained by the presence of lithium cations in the electrochemical reactions. The lithium cation has been shown to act as a Lewis acid in promoting aminyl... 

In particular, (diacyloxyiodo)benzene such as phenyliodine(III) diacetate (PIDA) and phenyliodine(III) bis(trifluoroacetate) (PIFA) have received a great deal of attention due to their reactivities similar to those of heavy metal reagents or anodic oxidation, low toxicity, ready availability and easy handling. Accordingly, a variety of useful oxidation reactions using iodine(III) or iodine(V) reagents have been developed recently. A number of previous review articles and... 

Fig. 39 compares results of the anodic oxidation of starch in acidic and alkaline solution, the former showing the lower reactivity. D-Glucuronic acid is also available by oxidation in an electrolyzer in which chlorine is electrochemically generated from a solution of sodium chloride.326... 

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