Cyclohexane electrochemical oxidation

Benzyl alcohol can be smoothly converted to benzaldehyde by electrochemi-cally recycled BrO as an oxidizing catalyst in an emulsion system prepared from a mixture of water, amyl acetate, and 2% BU4NHSO4 [60]. A different hypobromite reagent is provided by an electrochemical oxidation of a cross-linked poly-4-vinylpyridine in an MeCN-H20-HBr-(Pt) system [61]. Secondary alcohols can be oxidized by this method to give ketones in high yields. The electrooxidation of A-monoalkyltosylamides (42) in a two-phase system consisting of cyclohexane... 

The molecule has been found to be an efficient electron carrier in electrochemical oxidation, converting secondary alcohols to ketones. Daicel of Tokyo has used NHPI in the development of custom production in proprietary air-oxidation technology , and it can also be used to oxidize cyclohexane to adipic acid and p-xylene to p-toluic acid in the presence of Mn + or Co + salts. The new process produces no nitrogen oxides, is more environmentally friendly and does not require the use of denitration equipment. 

De Lijser, H.J.P. and Arnold, D.R., Interconversion and rearrangement of radical cations. Part 2. Photoinduced electron transfer and electrochemical oxidation of l,4-bis(methylene)cyclohexane, /. Chem. Soc., Perkin Trans. 2, 1369, 1997. 

Concern for the conservation of energy and materials maintains high interest in catalytic and electrochemistry. Oxygen in the presence of metal catalysts is used in CUPROUS ION-CATALYZED OXIDATIVE CLEAVAGE OF AROMATIC o-DIAMINES BY OXYGEN (E,Z)-2,4-HEXADIENEDINITRILE and OXIDATION WITH BIS(SALI-CYLIDENE)ETHYLENEDIIMINOCOBALT(II) (SALCOMINE) 2,6-DI-important industrial method, is accomplished in a convenient lab-scale process in ALDEHYDES FROM OLEFINS CYCLOHEXANE-CARBOXALDEHYDE. An effective and useful electrochemical synthesis is illustrated in the procedure 3,3,6,6-TETRAMETHOXY-1,4-CYCLOHEX ADIENE. ... 

The photo-induced electron transfer of l,4-bis(methylene)cyclohexane in acetonitrile-methanol solution with 1,4-dicyanobenzene (DCB) affords two products, both consistent with nucleophilic attack on the radical cation followed by reduction and protonation or by combination with DCB ).63 In the absence of a nucleophile, the product mixture is highly complex, as is the case under electro-oxidative conditions. Under UV irradiation, /nmv-stilbene undergoes dimerization and oxygenation (to benzaldehyde) by a single-electron mechanism in the presence of a sensitizer such as 2,4,6-triphenylpyrilium tetrafluoroborate (TPT).64 This reaction was found to yield a similar product mixture with the sulfur analogue of TPT and their relative merits as well as electrochemical and photophysical properties are discussed. 

Several electrochemical methods for alkane oxidation have been used by Fleischmann and his cowork-ers. These proceed via carbonium ion intermediates and, as expected, extensive rearrangement can be observed for example, cyclohexane in FSO3H gives l-acetyl-2-methyl-l-cyclopentene as major product ... 

Electrochemical methods have played an important role in the recognition of cation radicals as intermediates in organic chemistry and in the study of their properties. An electrode is fundamentally an electron-transfer agent so that, given the proper solvent system, anodic oxidation allows formation of the cation radical without any associated proton or other atom transfer and without the formation of a reduced form in the immediate vicinity of the cation radical. Moreover, because the potential of the electrode can be adjusted precisely, its oxidizing power can be controlled, and further oxidation of the cation radical can often be avoided. Finally, the electrochemical experiment can involve both production of the cation radical and an analysis of its behavior, so that information about the thermodynamics of its formation and the kinetics of its reaction can be obtained, even if the cation radical lifetime is as short as a few milliseconds. There are some limitations, however, in the anodic production of cation radicals. The choice of solvent is limited to those that show reasonable conductivity with a supporting electrolyte (e.g. tetra-n-butylammonium perchlorate, TBAP). Acetonitrile, methylene chloride and nitrobenzene have been employed as solvents, but other favorites, such as benzene and cyclohexane, cannot be used. The relatively high dielectric constant of the suitable... 

The chemical (Gif system) and the electrochemical conversion (Gif-Orsay system) have been compared in the oxidation of six saturated hydrocarbons (cyclohexane, 3-ethylpentane, methylcyclopentane, cis- and traus-decalin and adamantane). The results obtained for pyridine, acetone and pyridine-acetone were similar for both systems. Total or partial replacement of pyridine for acetone affects the selectivity for the secondary position and lowers the ratio ketone secondary alcohol. The formation of the same ratio of cis- and traws-decal-9-ol from either cis- or trans-deca in indicates that tertiary alcohols result from a mechanism essentially radical in nature. The C /C ratio between 6.5 and 32.7 rules out a radical mechanism for the formation of ketones and secondary alcohols. Ratios of 0.14 and 0.4 were reported for radical-type oxidations of adamantane and cis-decalin. Partial replacement of pyridine by methanol, ethanol or f-propanol results in diminished yields and a lower selectivity. Acetone gives comparable yields however, the C /C ratio drops to 0.2-10.7. 

Various electrochemical [3 -l- 2] cycloaddition reactions havebeen achieved between alkoxyphenols and olefin nucleophiles in lithium perchlorate/nitromethane electrolyte solution [18]. In these reactions, alkoxyphenols are anod-ically oxidized to generate the corresponding phenoxonium cations, which are then trapped by olefin nucleophiles to form the desired [3 + 2] cycloadducts. However, because the oxidation potentials of these [3 + 2] compounds are relatively lower than those of starting alkoxyphenols, overoxidation of the desired products can take place. To address this problem, cyclohexane is... 

A marginally catalytic oxidation of cyclohexane using a Ru(OEP)(PPh3)Br/PhIO system was mentioned above (Section 3.3.). The Ru(TMP)(0)2 species is thermally unreactive toward cyclooctane at 1 atm O2 at 70°C, but some O-atom insertion into saturated C-H bonds has been achieved under photolytic conditions and with the electrochemically generated Ru(TMP XOX species few details are available, but the latter system showed for adamantane oxidation the usual radical selectivity (tertiary > secondary carbon). 

Simultaneously, other scientists also explored the electrochemical catalytic properties based on electrospun Pt and PtRh nanowires for dehydro-genative oxidation of cyclohexane to benzene (Figure 9.25). In contrast to the conventional Pt nanoparticle catalysts (e.g., carbon/Pt or Pt black), Pt and PtRh electrospun nanowires electrocatalysts exhibited higher catalytic... 

Figure 2). The removal of surface oxides was accomplished by polishing the electroactive surface in a reduced oxygen environment (degassed cyclohexane). The simultaneous detection of multiple analytes is possible providing that both molecules react electrochemically at sufficiently separated potentials. This... 

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