Electroreduction benzene

Electroreduction, vinyl fluoride, 30 282 Electrosorbed species, nonreactant, electrocatalytic action, 40 166-167 Electrosoiption, 30 240 benzene versus potential, 30 259-260 isotherms, 30 244... 

Phenol (508) is found to be produced continuously from benzene (507) by aerial oxidation in aqueous sulfuric acid when a Cu(I)/Cu(II) redox couple is used as a mediator (Scheme 176) [581]. The Cu(I)-mediated electroreduction of oxygen in the presence of chloride is found to be effective for toluene oxidation, leading to benzaldehyde and benzyl chloride [582]. Recently, benzene has also been oxidized... 

Triple bonds in side chains of aromatics can be reduced to double bonds or completely saturated. The outcome of such reductions depends on the structure of the acetylene and on the method of reduction. If the triple bond is not conjugated with the benzene ring it can be handled in the same way as in aliphatic acetylenes. In addition, electrochemical reduction in a solution of lithium chloride in methylamine has been used for partial reduction to alkenes trans isomers, where applicable) in 40-51% yields (with 2,5-dihydroaromatic alkenes as by-products) [379]. Aromatic acetylenes with triple bonds conjugated with benzene rings can be hydrogenated over Raney nickel to cis olefins [356], or to alkyl aromatics over rhenium sulfide catalyst [54]. Electroreduction in methylamine containing lithium chloride gives 80% yields of alkyl aromatics [379]. 

Some nickel(II) tetraaza macrocycles have been proved to act as efficient catalysts for the electrochemical reduction of C02 in H20/MeCN medium. This indirect electroreduction occurs at potentials in the range -1.3 to -1.6 V vs. SCE and mainly produces either CO or a CO/H2 mixture, depending upon the type of complex.2854 The five-coordinate complexes [NiL] (394) formed by some deprotonated dioxopentamine macrocycles have been found to display very low oxidation potentials Nin/Nira in aqueous solution (about 0.24-0.25 V vs. SCE at 25 °C and 0.5 M Na2S04). Air oxidation of the same complexes in aqueous solution yields 1 1 NiL-02 adducts (5 = 1) which are better formulated as superoxo complexes, NimL-02 (Scheme 56). The activation of Ni-bound oxygen is such that it attacks benzene to give phenol.2855... 

Fig. 5. Cyclic Voltammograms for the Catalytic Electroreduction of Benzene H) sessile hanging mercury drop electrode, reversal potential —3.2 V (SCE), v = 10 V s 1, a) 0.5 M (C4H,)4NBF4 in THF-2% HzO b) a + benzene (0.25 M)...

Fig. 6. Cyclic Voltammograms for the Catalytic Electroreduction of Benzene201 (data collected digitally and plotted with a scale change at the end of the first half cycle) hanging mercury drop electrode, v = 5 V s 1, a) 1.0 M (C4H9)4NOH in H20 b) 5 ml (a) + 15 pL benzene...

Fleszar B, Sobkowiak A. Hydroxylation of benzene and phenol during electroreduction of oxygen. Electrochim Acta 1983 28 1315-1318. 

The electrooxidation of 1,4-diaminobenzene [2] exhibits the linear dependence of /Ts on Tl In this case also, the reaction in alcohols was faster than in solvents without hydrogen bonding. The one-electron electroreduction of 2,4,6-trimethylnitro-benzene to the corresponding radical anion was studied in five organic solvents [150] ... 

Jaworski et al. [186] found that the reaction constants from the Hammett equation, in the case of the irreversible electroreduction of substituted chloro- and bromo-benzenes in a number of organic solvents, are linearly dependent on the logarithms of the solvent longitudinal relaxation times. 

Stereoselective electroreduction of some organometal complexes has been reported. The reduction of o -oxotetramethylene-cyclopentadienyl-iron - 7 -benzenes in an acidic solution occurs specifically from the exo side to give only the en /o-alcohol, as in Eq. (38) in alkaline solution the corresponding stereoisomeric (d, 1 and mso) pinacols are formed but the stereochemistry has not been determined [257]. 

This step differs from the rds proposed for gas phase hydrogenation of benzene, for which hydrogen adsorption is considered slow, inhibited by strongly adsorbed benzene (559). If a similar step were operative in the electroreduction, the Tafel slope would be twice the observed value. However, insensitivity of the electrocatalytic reaction to temperature (56) indicates strong benzene chemisorption, in agreement with catalytic results. 

The use of a heterogeneous system under nitrogen consisting of a stirred suspension of silica gel with adsorbed ferric-catechol complex in benzene treated with 35% hydrogen peroxide has been reported to result after 2.5 hours in a 60% yield of phenol (ref. 14). The formation of phenol in 56% yield resulted from a mixture of benzene and vanadium(V) catalyst in acetonitrile under nitrogen when reacted for 2 hours at ambient temperature (ref. 15). More recent studies have involved the conversion of benzene in trifluoromethanesulphonic acid to phenol by the electroreduction of dioxygen (ref. 16) and from generation... 

Dicyanobenzene was converted into 3-cyanobenzoic acid by using the bacterium Rhodococcus rhodochrocus ". Intramolecular electron transfer involving isomeric forms of dicyanobenzene was investigated in detaiP and the mechanisms of electroreduction of all three isomers were studied. When dicyanobenzene was used as catalyst in photoamination reactions of arenes, the first step of the reaction was the formation of an aryl radical cation by electron transfer from the aromatic hydrocarbon to m-dicyano-benzene. ... 

Electroreduction of 1,3,5-tricyanobenzene was studied. When 1,3,5-tricyanobenzene was reacted with silyl and germyl radicals, 1,3,5-tricyanocyclohexadienyl radicals were obtained and detected by ESR spectroscopy. A charge-transfer complex of 1,3,5-tricyanobenzene with l,3,5-tris(dimethylamino)benzene was reported. Small amounts of isomeric tricyanobenzenes have been obtained by photochemical cycloaddition reactions ... 

Photocatalytic decomposition of alcohol Electro-oxidation of hydrogen Electroreduction of oxygen Ammonia synthesis Carbon monoxide methanation Carbon monoxide methanation Carbon monoxide oxidation Propene hydrogenation Benzene hydrogenation Oxidation of ethylene Coal liquefaction Electroreduction of oxygen Dehydrogenation of butadiene... 

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