Electro-organic chemistry

We found that conventional electrolysis (of the partially-neutralised salt) in methanol produced a very rapid increase in applied cell-voltage and the attainment of no effective product (Column I). This was due to the production of a pale coloured coating at the anode which caused the reaction to cease. This is a well known occurrence in electro-organic chemistry [61] and the remedy is to add pyridine to keep the electrode dean, presumably by solubilising the inhibiting layer. Column II shows the product ratios from the silent reaction in the presence of 13 % (v/v) of pyridine. Here there is 60 % of... 

Electro-organic chemistry at the cathode is essentially that of radicals, radical-anions, carbanions, and polyanions (which range from dianions to hexa-anions (Scheme 1). The anions may behave as nucleophiles, bases, and as single electron reductants the factors governing the competition between these roles are not yet fully understood. 

Electro-organic chemistry is the study of the oxidation and reduction of organic molecules and ions, dissolved in a suitable solvent, at an anode and cathode respectively in an electrolysis cell, and the subsequent reactions of the species so formed. The first experiment of this type was reported in 1849 by Kolbe, who described the electrolysis of an aqueous solution of a carboxylate salt and the isolation of a hydrocarbon. The initial step involves an anodic oxidation of the carboxylate anion to a radical which then dimerises to the alkane. 

Putter, El. (2001) Industrial electro organic chemistry. Chapter 31 in H. Lund and O. Hammerich (Eds) Organic Electrochemistry (4th edn). Dekker, New York. 

Nevertheless, the discovery that high electronic conductance could be induced in organic polymers is a most important event in electro-organic chemistry, and progress in research to develop the electrochemistry of such compounds (which began in the 1980s) is still far from reaching the exponential part of its S-shaped plot. 

We are well aware that this discussion of the electrode material and its role in electro-organic chemistry is severely limited, both with respect to the number of examples quoted and to the number of possible factors involved. However, we think that the mere fact that hardly any synthetic investigations dealing with the problem have adequately characterized the surfaces of the electrode materials used gives us a good excuse for refraining from such a discussion. Let us first get the experimental facts on this point ... 

The historical development of electro-organic chemistry is well documented by several authors, e.g. in refs. 514 and 521-527, and therefore will not be repeated here. Much of the pioneering work in the field was carried out at Pt, i.e. Pt covered with an oxide film of monolayer dimensions in the case of anodic reactions. Electro-organic reactions at Pt have been analyzed in considerable detail by Conway [517] and will not be discussed here. Rather, attention will be focussed on oxide electrocatalysts and metal anodes covered with oxide films of multilayer dimensions, e.g. Ni and Pb. However, before commencing with a discussion of such oxide catalysts, some important factors in electroorganic chemistry will be briefly reviewed. 

C. J. Brockman, Electro-organic Chemistry, Wiley, New York, 1926. 

Rossman, J., Electro-organic Chemistry in the Patent OflSce, Electrochemical Society, Preprint (1943). 

ALLEN J. BARD holds the Norman Hackerman/Welch Chair in Chemistry at the University of Texas at Austin, is editor-in-chief of the Journal of the American Chemical Society, and is a member of the National Academy of Sciences. He attended the City College of New York (B.S., summa cum laude, 1955) and completed his graduate work (A.M., 1956 Ph.D., 1958) at Harvard University. In 1958 he joined the faculty of the University of Texas at Austin. His research interests have included investigations in electro-organic chemistry, photoelectrochemistry, electrogenerated chemiluminescence, and electroanalytical chemistry, and he has published about 400 papers and several books and holds six patents in these areas. 

A special and very important case of EC-type processes is denoted as the catalytic or EC (or ErevC rev) electrode reaction. In this reaction sequence (see Eq. II. 1.24), the heterogeneous electron transfer produces the reactive intermediate B, which upon reaction with C regenerates the starting material A. The redox system A/B may therefore be regarded as redox mediator or catalyst, and numerous applications of this scheme in electro-organic chemistry are known [97]. Furthermore, a redox... 

The junction between an electronic conductor and a polymeric proton conductor gives a very interesting tool for the study of mass and charge transfer in solids and in solutions. In addition, the perfluorosulphonic proton conductor gives new synthesis routes in organic or electro-organic chemistry. Future developments in this family of proton conductors are to be expected for the preparation of low price perfluorinated materials. 

K. Scott, Developments in Chemical Engineering and Mineral Processing, 1993, 1, 71. D.E. Danly, Emerging Opportunities for Electro-organic Chemistry, 1984, Marcel Dekker, New York. 

Unfortunately, mechanisms of elementary steps, e.g., electron transfer, in electrode processes were not at all well understood during the period of early development of electro-organic chemistry, and the significance of the fundamental relation between overpotential ( polarization ) and current density was not appreciated until the work of Volmer, Gurney, Bowden,... 

Figure 1. Illustrating developments in electro-organic chemistry.

In this chapter, emphasis will be placed on same basic electrochemical mechanistic aspects of studies in electro-organic chemistry rather than the myriad of specific, essentially organic reaction mechanisms that involve eventual product formation from the initial, electrochemically generated intermediate. We shall, however, refer in a later section of this chapter to a selection of reactions that are mechanistically better understood and may lead, or have led, to commercially viable processes (Section 13). In other chapters in this series of volumes " will be found accounts of electroorganic reactions which are presented more specifically from the point of view of the organic chemistry involved, e.g., in follow-up reactions after electron transfer. 

The Mass Transport Problems In Preparative Electro-Organic Chemistry and Cell Design... 

Brockman, Electro-organic Chemistry, John Wiley and Sons, New York, 1926. 5 Conway and Dzieciuch, Can. J. Chem. 41 (1963) 21, 38, 55. 

Tafel had been active also in the field of electro-organic chemistry, an area that had been already extensively investigated in earlier years of the 19th century, e.g. by Kolbe, but more from the preparative than the kinetic-mechanistic directions. 

Possible and actual relationships between electro-organic chemistry and natural product chemistry will be discussed. Attempts to carry out bio-genetic type reactions at in electrode surface will be summarized. Some specific examples of unique electrochemistry that have been discovered in natural materials or materials similar to natural materials will be described. 

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