Electrolyte Reduction

Consequently, considerable attention has been paid to lowering the operating temperature, in either of two ways  

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Europium(TTI) salts are typical lanthanide derivatives. Europium(ll) salts are pale yellow in colour and are strong reducing agents but stable in water. EuX2 are prepared from EuX -hEu (X=C1, Br, I) or EuFa + Ca EuCl2 forms a dihydrale. EUSO4 is prepared by electrolytic reduction of Eu(III) in sulphuric acid. Eu(II) is probably the most stable +2 stale of the lanthanides... 

It is prepared by reduction of nitrobenzene with iron and NaOH. It is also prepared by an electrolytic reduction of nitrobenzene. It is widely used for the preparation of benzidine. 

NH2-C0-NH NH2,CH5N30. Colourless crystalline substance m.p. 96" C. Prepared by the electrolytic reduction of nitrourea in 20% sulphuric acid at 10 "C. Forms crystalline salts with acids. Reacts with aldehydes and ketones to give semicarbazones. Used for the isolation and identification of aldehydes and ketones. 

Hydroxylamine is derived from ammonia by replacing one hydrogen atom by a hydroxyl group. It is prepared by the electrolytic reduction of nitric acid, using a lead cathode ... 

Aldehydes are more generally prepared by electrolytic reduction of amides, the reduction of carboxylic adds being possible only when they are activated by a strongly electron-withdrawing group (58). 

The 2-bromothiazole can also be reduced to thiazole by zinc (18) in CH3COOH, or by electrolytic reduction (68). The deuterated thiazoles can also be obtained starting from the corresponding halogenothiazoles, by Zn/Cu in CH3COOD (18). 

Reduction. These hydroxybenzaldehydes can be reduced by catalytic hydrogenation over palladium or platinium to yield the corresponding hydroxybenzyl alcohols, but the electrolytic reduction in an alkaline medium gives the coupling product l,2-bis(4-hydroxyphenyl)ethane-l,2-diol in very good yield from 4-hydroxybenzaldehyde (49—51). 

It is easy to reduce anhydrous rare-earth hatides to the metal by reaction of mote electropositive metals such as calcium, lithium, sodium, potassium, and aluminum. Electrolytic reduction is an alternative in the production of the light lanthanide metals, including didymium, a Nd—Pt mixture. The rare-earth metals have a great affinity for oxygen, sulfur, nitrogen, carbon, silicon, boron, phosphoms, and hydrogen at elevated temperature and remove these elements from most other metals. 

Selective Reduction. In aqueous solution, europium(III) [22541 -18-0] reduction to europium(II) [16910-54-6] is carried out by treatment with amalgams or zinc, or by continuous electrolytic reduction. Photochemical reduction has also been proposed. When reduced to the divalent state, europium exhibits chemical properties similar to the alkaline-earth elements and can be selectively precipitated as a sulfate, for example. This process is highly selective and allows production of high purity europium fromlow europium content solutions (see Calcium compounds Strontiumand strontium compounds). 

Electrolytic Reduction. The largest manufacturers of magnesium use processes based on the electrolytic reduction of magnesium chloride... 

During electrolytic reduction of to and the subsequent reduction of Pu to inextractable Pu hydrazine is added as a holding agent to destroy excess nitrite ions and prevent reoxidation of and Pu to their higher valence states. 

Reduction Products. Glyoxyhc acid [298-12 ], HOOCCHO, mol wt 74.04, is produced as aqueous solution by the electrolytic reduction of oxahc acid. It is used for the manufacture of vanillin. 

Glycohc acid [79-14-1], HOOCCH2OH, mol wt 76.05, can be obtained by the electrolytic reduction of oxaUc acid or the catalytic reduction of oxaUc acid with hydrogen in the presence of a mthenium catalyst. Because of its acidity it is used as a cleaning agent for metal surface treatments and for boiler cleaning. It also serves as an ingredient in cosmetics (qv). 

Aluminum can be produced by metaHothermic, carbothermic, or electrolytic reduction processes. The earliest commercial process for producing aluminum (1855—1893) was sodiothermic reduction of aluminum haUdes. Once the HaH-HAroult process became commercial, however, sodiothermic reduction was not competitive. 

Electrolytic Reductions. Both nitro compounds and nitriles can be reduced electrochemically. One advantage of electrochemical reduction is the cleanness of the operation. Since there are a minimum of by-products, both waste disposal and purification of the product are greatiy simplified. However, unless very cheap electricity is available, these processes are generally too expensive to compete with the traditional chemical methods. 

Electrolytic reductions generally caimot compete economically with chemical reductions of nitro compounds to amines, but they have been appHed in some specific reactions, such as the preparation of aminophenols (qv) from aromatic nitro compounds. For example, in the presence of sulfuric acid, cathodic reduction of aromatic nitro compounds with a free para-position leads to -aminophenol [123-30-8] hy rearrangement of the intermediate N-phenyl-hydroxylamine [100-65-2] (61). 

Nitriles. The electrolytic reduction of nitriles requires a high negative potential, but can lead to amines in good yields under the right conditions. This reaction occurs in acidic media according to the following equation (62). 

Aminophenols are either made by reduction of nitrophenols or by substitution. Reduction is accompHshed with iron or hydrogen in the presence of a catalyst. Catalytic reduction is the method of choice for the production of 2- and 4-aminophenol (see Amines BY reduction). Electrolytic reduction is also under industrial consideration and substitution reactions provide the major source of 3-aminophenol. 

Sodium nitrite has been synthesized by a number of chemical reactions involving the reduction of sodium nitrate [7631-99-4] NaNO. These include exposure to heat, light, and ionizing radiation (2), addition of lead metal to fused sodium nitrate at 400—450°C (2), reaction of the nitrate in the presence of sodium ferrate and nitric oxide at - 400° C (2), contacting molten sodium nitrate with hydrogen (7), and electrolytic reduction of sodium nitrate in a cell having a cation-exchange membrane, rhodium-plated titanium anode, and lead cathode (8). 

Electrolytic reduction with a mercury or platinum electrode produces equimolar amounts of sulfide and sulfite ... 

A hexahydrate is also known and may be prepared by the electrolytic reduction of the tetrabromide in hydrobromic acid solution. 

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