Electrolysis Electrolytic oxidation

Electrolysis Electrolytic oxidation Aldehydes from ethers... 

Ttinitroparaffins can be prepared from 1,1-dinitroparaffins by electrolytic nitration, ie, electrolysis in aqueous caustic sodium nitrate solution (57). Secondary nitroparaffins dimerize on electrolytic oxidation (58) for example, 2-nitropropane yields 2,3-dimethyl-2,3-dinitrobutane, as well as some 2,2-dinitropropane. Addition of sodium nitrate to the anolyte favors formation of the former. The oxidation of salts of i7k-2-nitropropane with either cationic or anionic oxidants generally gives both 2,2-dinitropropane and acetone (59) with ammonium peroxysulfate, for example, these products are formed in 53 and 14% yields, respectively. Ozone oxidation of nitroso groups gives nitro compounds 2-nitroso-2-nitropropane [5275-46-7] (propylpseudonitrole), for example, yields 2,2-dinitropropane (60). 

Electrolysis 1.5 V, CH3CN, H2O, UCIO4 or Bu4N-"C104, 50-75% yield. " 1,3-Dithiolanes were not cleaved efficiently, by electrolytic oxidation. 

The fluoride and chloride ions are very difficult to oxidize (Elx F = —2.889 V E°x Cl- = —1.360 V). Hence the elements fluorine and chlorine are ordinarily prepared by electrolytic oxidation, using a high voltage. As pointed out in Chapter 18, chlorine is prepared by the electrolysis of aqueous sodium chloride ... 

Both inter- and intramolecular [5 + 2] cycloaddition modes have been utilized in the synthesis of natural products. Successful intermolecular cycloaddition depends on making an appropriate selection of solvent, supporting electrolyte, oxidation potential, and current density. This is nicely illustrated in Schemes 23 to 25. For example, in methanol the controlled potential oxidation of phenol (101) affords a high yield (87%) of (102), the adduct wherein methanol has intercepted the reactive intermediate [51]. In contrast, a constant current electrolysis conducted in acetonitrile rather than methanol, led to an 83% yield of quinone (103). 

The nitrosodisulfonate salts, particularly the dipotassium salt called Fremy s salt, are useful reagents for the selective oxidation of phenols and aromatic amines to quinones (the Teuber reaction). - Dipotassium nitrosodisulfonate has been prepared by the oxidation of a hydroxylaminedisulfonate salt with potassium permanganate, " with lead dioxide, or by electrolysis. This salt is also available commercially. The present procedure illustrates the electrolytic oxidation to form an alkaline aqueous solution of the relatively soluble disodium nitrosodisulfonate. This procedure avoids a preliminary filtration which is required to remove manganese dioxide formed when potassium permanganate is used as the oxidant. " ... 

Electrolytic oxides are responsible for the passivity of corroding metals, for example Ti02 and NiO. However, this is not generally the case under O2 evolution conditions. If an oxide passivates a surface, it is not a good electrocatalyst for O2 evolution. On the other hand, oxides that are good catalysts for O2 evolution very often are unstable under O2 evolution and dissolve. For instance, NiO passivates Ni in alkali and is also a good electrocatalyst for O2 evolution. However, it dissolves in acids and the metal cannot be used for water electrolysis at low pH. Similarly,... 

Potassium manganate obtained above is oxidized to the permanganate either by electrolysis or by chemical oxidation. Electrolytic oxidation is more common. Electrolytic cells have cathodes made of iron rods and nickel-plated anodes. Potassium manganate melt is extracted with water prior to its electrolysis and then electrolyzed at a cell voltage of 2.3V and current of about 1,400 amp. Permanganate is produced at the anode and water is reduced to gaseous hydrogen and hydroxyl ions at the cathode ... 

E. C. Szarvasky found that the electrolysis of hydroxylamine was accompanied by the spontaneous transformation of hydroxylamine into ammonia. Secondary reactions always occur—the base being reduced to ammonia at the cathode and at the anode oxidized to nitrogen oxides. F. Balia found that with various electrodes the percentage current yield of NaN02 NaN03 in the electrolytic oxidation of hydroxylamine with anodes of different metals was as follows ... 

Some general considerations which require variations in the simple electrolysis cell construction described above to meet the requirements for electrolytic oxidations and reductions of a wide range of organic compounds may be briefly summarised, but attention is drawn to the very extensive surveys which are available.32... 

Many O-centered radicals undergo facile P-fragmentation. For example, acyl-oxyl radicals which are intermediates in the electrolytic oxidation of acids (Kolbe electrolysis), rapidly decompose into alkyl radicals and C02 [reaction (1)]. The rate of these reactions is in the order of 109 s 1 and increases with increasing branching of the alkyl substituent, i.e., decreasing C-C02 bond energy (Table 7.1). 

These laws (determined by Michael Faraday over a half century before the discovery of the electron) can now be shown to be simple consequences of the electrical nature of matter. In any electrolysis, an oxidation must occur at the anode to supply the electrons that leave this electrode. Also, a reduction must occur at the cathode removing electrons coming into the system from an outside source (battery or other DC source). By the principle of continuity of current, electrons must be discharged at the cathode at exactly the same rate at which they are supplied to the anode. By definition of the equivalent mass for oxidation-reduction reactions, the number of equivalents of electrode reaction must be proportional to the amount of charge transported into or out of the electrolytic cell. Further, the number of equivalents is equal to the number of moles of electrons transported in the circuit. The Faraday constant (F) is equal to the charge of one mole of electrons, as shown in this equation ... 

Electrolytic oxidation of cyanide is carried out by anodic electrolysis at high temperatures. It has been more successful for wastes containing high concen-... 

Law and Mollwo Perkin 4 report on the electrolytic oxidation of toluene, the three xylenes, mesilylene, and pseudocumene. In a sulphuric-acid-acetqne solution of toluene they obtained a little benzaldehyde and perhaps benzyl alcohol. The electrolysis of an emulsion of toluene and dilute sulphuric acid leads to a complete combustion of the toluene to carbonic acid and water. 

With regard to an economically beneficially synthesis an organic reactant is dissolved in supercritical C02 and brought in contact with the aqueous electrolyte in a two-phase reaction column. The mediator, dissolved in the electrolyte, oxidizes (or reduces) the reactant to the desired product. In an ideal case the formed product stays in the SF-C02 phase, leaves the column with the C02 and can be isolated in an expansion step. The electrolyte is recycled outside the pressure apparatus in a conventional electrolytic cell. Electrolysis gases and C02 dissolved in the electrolyte leave the apparatus from the electrolytic cell. 

Potassium chlorate, KC103.—The chlorate is obtained by methods similar to those employed for the corresponding sodium salt. The electrolysis of the chloride 4 affords a means of manufacture, and it is also obtained by the interaction of potassium chloride and calcium chlorate. Large quantities are made by the electrolytic oxidation of sodium chloride to chlorate, and conversion of this salt into potassium chlorate by treatment with potassium chloride. Sodium chlorate is much more soluble than potassium chlorate, so that the electrolytic process is not impeded by crystallization of the salt. 

Chlorine can be obtained in the laboratory by oxidation of HCl with a strong oxidizer such as manganese dioxide (equation 1). The industrial production of chlorine is a major section of the heavy chemical industry and is based on electrolytic oxidation of the chloride anion. Chlorine, sodium hydroxide, and hydrogen are produced by the electrolysis of... 

Cyclic voltammetry of the ferrocenylboron-capped oximehydrazonate iron(II) complexes with the same ribbed substituents (Table 39) reveal a reversible one-electron oxidation of the ferrocenyl iron at 320-H340 mV vs SCE. Electrolytic oxidation of the ferrocenyl iron at a potential of 750 mV in solution produces a stable mixed-valence complex. Cyclic voltammograms at this potential the solution before and after electrolysis indicate that the integrity of the complexes is maintained as the ferrocenyl is cycled between the +2 and +3 oxidation states. The redox potentials associated with the encapsulated iron ion are not affected by the oxidation state of the ferrocenyl iron, i.e., there is no apparent interaction between the two... 

Electrolytic oxidation takes place at the anode of an electrolytic cell, which may or may not contain a diaphragm to separate cathodic and anodic spaces. The anode must be made of a metal that resists oxidation, such as lead [775], nickel [776], or, most frequently, platinum. The anode is usually in the shape of a cylinder made of a wire gauze [777, 775]. The possible electrolytes are dilute sulfuric acid [777] or sodium methoxide prepared in situ from methanol and sodium [775]. The direct-current voltage is 3-100 V, the current density is 10-20 A/dm, and the electrolysis temperature is 20-80 C. 

DMSO is an excellent solvent for many inorganic salts and organic compounds. It is difficult to reduce and fairly resistant to electrolytic oxidation. Its dielectric constant is high (s = 47). It thus has many of the qualities desirable for a solvent for electrolysis, and it shows promise of being one of the most important electrochemical media [387]. The liquid range is from 18 to 189°C, which makes it somewhat inconvenient to get rid of DMSO in the workup. When used as solvent for electrolysis it must be considered that DMSO is not always inert but has a fair reactivity in certain reactions. DMSO is unfit for UV spectroscopy. Its autoprotolysis constant is 31.8. 

The cause of these effects is in the spacing of the metal runners, which is 1 to 2 pm in today s circuits, and will be of 0.5 to 1 pm within a decade. Because of the small distances, the electric fields are high and the transport of ions on the surfaces of the microcircuits, when ions are present, is rapid. The electrolytic processes corrode the metal runners and lead to accumulation of certain anions and cations on different regions of the surface. Because some ions are more strongly adsorbed than others, their transport introduces local electric fields that perturb the operation of microcircuits. The metal runners corrode either directly or indirectly. In direct corrosion, the metal, usually aluminum, is electrolytically oxidized to compounds of Al3+. In indirect corrosion, electrolysis causes a local change in pH. Aluminum is attacked both at excessively high and at excessively low pH. 

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