Acids electrolytic reduction

Cyclohexanones are readily reduced to the hydrocarbon in a sulphuric acid electrolyte. Reduction of ketosteroids in dioxan - aqueous sulphuric acid at a lead cathode in a divided cell is a convenient process for converting the carbonyl group to methylene [84,85] and affords as good yields as the alternative non-electrocheniical processes. Menthone is reduced to the hydrocarbon under mild conditions at a mercury cathode when the electrolyte is either magnesium chloride or zinc perchlorate in ethanol [86]. 

Reduction of Nitric Acid. Electrolytic reduction of HN03 in the presence of HC1 produces hydroxylammonia chloride ... 

All the mono- and diarylarsines may be prepared by the reduction of the corresponding arsinic acids, whether the benzene nucleus is substituted or not. Such reduction may be effected with zinc dust and hydrochloric acid, and, in the case of phenylarsinic acid, electrolytic reduction in aqueous alcohol solution has also been used. The primary arsines show no basic properties and readily undergo oxidation in air, forming oxides, acids, and arseno- compounds. Halogens react with these arsines, replacing the hydrogen ... 

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... 

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 ... 

Alkaline Fuel Cell. The electrolyte ia the alkaline fuel cell is concentrated (85 wt %) KOH ia fuel cells that operate at high (- 250° C) temperature, or less concentrated (35—50 wt %) KOH for lower (<120° C) temperature operation. The electrolyte is retained ia a matrix of asbestos (qv) or other metal oxide, and a wide range of electrocatalysts can be used, eg, Ni, Ag, metal oxides, spiaels, and noble metals. Oxygen reduction kinetics are more rapid ia alkaline electrolytes than ia acid electrolytes, and the use of non-noble metal electrocatalysts ia AFCs is feasible. However, a significant disadvantage of AFCs is that alkaline electrolytes, ie, NaOH, KOH, do not reject CO2. Consequentiy, as of this writing, AFCs are restricted to specialized apphcations where C02-free H2 and O2 are utilized. 

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). 

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). 

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

Good yields of phenylarsine [822-65-17, C H As, have been obtained by the reaction of phenylarsenic tetrachloride [29181-03-17, C H AsCl, or phenyldichloroarsine [696-28-6], C3H3ASCI25 with lithium aluminum hydride or lithium borohydride (41). Electrolytic reduction has also been used to convert arsonic acids to primary arsines (42). Another method for preparing primary arsines involves the reaction of arsine with calcium and subsequent addition of an alkyl haUde. Thus methylarsine [593-52-2], CH As, is obtained in 80% yield (43) ... 

As the reduction of the cathode proceeds through equation 1 and the potential decreases, the reduction equation 2 becomes more favorable. First the divalent Mn(OH)2 is solubili2ed to some extent in the mildly acidic electrolyte. 

Dithionites. Although the free-dithionous acid, H2S2O4, has never been isolated, the salts of the acid, in particular zinc [7779-86-4] and sodium dithionite [7775-14-6] have been prepared and are widely used as industrial reducing agents. The dithionite salts can be prepared by the reaction of sodium formate with sodium hydroxide and sulfur dioxide or by the reduction of sulfites, bisulfites, and sulfur dioxide with metallic substances such as zinc, iron, or zinc or sodium amalgams, or by electrolytic reduction (147). 

The tritylone ether is used to protect primary hydroxyl groups in the presence of secondary hydroxyl groups. It is prepared by the reaction of an alcohol with 9-phenyl-9-hydroxyanthrone under acid catalysis (cat. TsOH, benzene, reflux, 55-95% yield).It can be cleaved under the harsh conditions of the WolfT-Kishner reduction (H2NNH2, NaOH, 200°, 88% yield), " and by electrolytic reduction (-1.4 V, LiBr, MeOH, 80-85% yield). It is stable to 10% HCl, 55 h. ... 

A benzyl carbonate was prepared in 83% yield from the sodium alkoxide of glycerol and benzyl chloroformate (20°, 24 h). It is cleaved by hydrogenolysis (H2/ Pd-C, EtOH, 20°, 2 h, 2 atm, 76% yield) and electrolytic reduction (-2.7 V, R4N X, DMF, 70% yield). A benzyl carbonate was used to protect the hy-droxyl group in lactic acid during a peptide synthesis. 

The diphenyl-4-pyridylmethyl group is cleaved by Zn/AcOH, 1.5 h, 91% yield H2/Pd-C, 91% yield or by electrolytic reduction, 2.5 h, 0°, 87% yield. The Dppm group is stable to trifluoroacetic acid. " ... 

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