Electroreduction Subject

In contrast to the porphyrin case, Fe-Pc appears to be a more promising candidate than Co-Pc for the electroreduction of 02 to II2C).126 411-413 A large number of papers has been published on this subject and some authors have attributed the four-electron reduction to give H20 to the catalytic activity of the Fe-Pc in chemically decomposing electrogenerated H202 on the electrode surface. 

Organic electroreductive coupling reactions using transition-metal complexes as catalysts have been widely investigated. Reviews on the subject have been published [89, 90]. The method involving the most common transition-metal complexes (nickel, cobalt, palladium) appears to be a useful tool to synthetize heterocycles from organic halides via radical intermediates. Nickel catalyst precursors are nickel(II) salts that are cathodically reduced either to nickel(I) or to nickel(O) and cobalt catalyst... 

Recently, chloro-, bromo-, and iodoben-zenes have been subjected to electroreduction using Ni(0) complex mediators to yield biphenyl. NiCl2L2 and NiBr2L2 [L= P(Ph)3, (Ph)2PCH2CH2P(Ph)2] have been used as catalysts [259-265]. Pro-tic media such as alcohols, that is, methanol, ethanol or alcohol-water mixtures are found to be suitable solvents for achieving the electrosynthesis of biaryls from aryl halides according to a procedure that involves a catalytic process by nickel-2,2 -bipyridine complexes [266]. Electrochemical cross-coupling between... 

The problem of the kinetics and mechanism of electroreduction of N02 and NO3 has been the subject of several studies since the 1960s [4-16]. 

The influence of varying the electrode material upon proton electroreduction has been the subject of extensive study . This reaction can be regarded as inner-sphere in that it often involves a rate-limiting, proton-transfer step to form an adsorbed hydrogen atom . Although superficially different, the conventional treatment of substrate effects upon such reactions is similar to that presented here. Thus the marked increase in the rate constants seen for Hj evolution as the metal-hydrogen atom bond energy... 

Electrochemical reduction has been applied occasionally on benzotriazinones. Thus, compound 19n was reduc-tively degraded to indazolin-3-one 137, aniline, and benzanilide (Equation 50) the latter was the sole product (90%) upon electroreduction of 19n in DMF. 3-Phenyl-3,4-dihydro-l,2,3-benzotriazine, when subjected to cathodic reduction, gave only 18% of A -benzylaniline along with more than eight minor, unidentified products <1979ACB233>. 

The electroreduction of acetophenone in acidic electrolytes has been the subject of detailed studies of both the electrode kinetics and the reaction products. One important question that has arisen from this work... 

Reductive Electropolymerization. Besides the oxidative anodic electropolymerization of the monomer, which is the most convenient and the most widely used method, polythiophene can also be prepared by a cathodic route involving the electroreduction of the complex Ni(2-bromo-5-thienyl)(PPh3)4Br in acetonitrile. This method, initially proposed for the synthesis of poly(p-phenylene) [374-376], has been extended to polythiophene [520]. The major drawback is that the polymer is produced in its neutral insulating form, which leads rapidly to a passivation of the electrode and limits the attainable film thickness to approximately 100 nm. On the other hand, this technique presents the advantage of being applicable to electrode materials subject to anodic corrosion such as small-bandgap semiconductors [521]. 

Laccases are used at the cathode of a BFC to catalyze the four-electron electroreduction of 02(which acts as the terminal electron acceptor) to water. They belong to a group of enzymes called blue copper oxidases," due to the presence of a type 1 (T1) copper site in the enzyme. This copper site acts as the primary electron acceptor and imparts laccases with a blue color. Additional copper ions in type 2 and type 3 (T2/T3) sites form a trinuclear cluster that acts as a binding site for molecular oxygen. Here, the electrons transferred firom the T1 site reduce oxygen to water. Laccases have been the subject of study for several decades, and have found use in fields ranging firom wastewater treatment to the paper industry [19,20], However, it is their DET ability and high redox potential that have led to their use in biosensors and BFCs. 

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