Alcohol, electrolytic oxidation

Tripotassium hexakiscyanoferrate [13746-66-2] K2[Fe(CN)g], forms anhydrous red crystals. The crystalline material is dimorphic both orthorhombic and monoclinic forms are known. The compound is obtained by chemical or electrolytic oxidation of hexacyanoferrate(4—). K2[Fe(CN)g] is soluble in water and acetone, but insoluble in alcohol. It is used in the manufacture of pigments, photographic papers, leather (qv), and textiles and is used as a catalyst in oxidation and polymerisation reactions. 

The 2,5-dialkoxy-2,5-dihydrofurans can be obtained by electrolytic oxidation of furan in alcoholic ammonium bromide or by bromine oxidation of furan in the appropriate alcohol. ... 

Electrolytic oxidation of tetrahydrofuran Addition of alcohols to aldehydes or ketones... 

The direct electrochemical oxidation of aliphatic alcohols (1) to carbonyl compounds (2) (Eq. 1) is not a convenient way for synthesis because of the high oxidation potentials of alcohols. The oxidation always competes with the oxidation of a solvent and supporting electrolyte, leading to low current efhdencies and side products. 

The nickel oxide electrode is generally useful for the oxidation of alkanols in a basic electrolyte (Tables 8.3 and 8.4). Reactions are generally carrried out in an undivided cell at constant current and with a stainless steel cathode. Water-soluble primary alcohols give the carboxylic acid in good yields. Water insoluble alcohols are oxidised to the carboxylic acid as an emulsion. Short chain primary alcohols are effectively oxidised at room temperature whereas around 70 is required for the oxidation of long chain or branched chain primary alcohols. The oxidation of secondary alcohols to ketones is carried out in 50 % tert-butanol as solvent [59], y-Lactones, such as 10, can be oxidised to the ketoacid in aqueous sodium hydroxide [59]. 

Bromine or electrolytic oxidation of furan in alcoholic solution gives the corresponding... 

Although NaI04 or KI04 are the secondary oxidants used in the vast majority of cases in which alcohols are oxidized with catalytic Ru04, the employment of sodium hypochlorite (NaOCl),31 sodium bromate (NaBrOj )32 or Cl+, electrolytic-ally generated by oxidation of chloride ion,33 have also been reported. 

While these experiments, which were carried out without giving a theoretical insight into the nature of the electrochemical reaction, yielded almost all the possible oxidation products in the oxidation of methyl alcohol, Elbs and Brunner 2 have discovered a method which gives 80% of the current yield in formaldehyde. This is exactly the substance which could not be proven present up to that time among the electrolytic oxidation products of methyl alcohol. Elbs and Brunner electrolyzed an aqueous solution of 160 g. methyl alcohol and 49 to 98 g. sulphuric acid in a litre. They employed a bright platinum anode in an earthenware cylinder, using a current density of 3.75 amp.1 and a temperature of 30°. Only traces of formic acid and carbonic acid and a little carbon monoxide, aside from the 80 per cent, of formaldehyde, were formed. Plating the platinum anode with platinum decreased the yield of formaldehyde at the expense of the carbon dioxide. With an anode of lead peroxide the carbon dioxide exceeded the aldehyde. 

Dony-Henault observed that alcohol is oxidized in sulphuric-acid solution already at an anode potential of 1.3 volts, as measured in connection with the hydrogen electrode. The oxidation of acetaldehyde, on the contrary, requires a potential of 1.66 volts to convert the aldehyde into acetic acid. Hence, the alcohol can be oxidized only to aldehyde between 1.3 and 1.66 volts. The experiment proved that, when a platinized platinum electrode is employed, only acetaldehyde is formed, and this quantitatively. The aldehyde yield decreases at a higher potential, the acid content of the electrolytes increases, and, at the same time, ethyl-sulphuric acid can be detected, as already shown by Itenard. Dony-Henault ascribes the formation of tliis acid to the discharge of the SCVions. According to Elbs, a purely chemical action of the sulphuric acid (which becomes concentrated at the anode) on the alcohol is the more probable. 

Toluene.—According to Renard,1 this compound, by electrolytic oxidation in alcoholic-sulphuric acid, forms benzaldehyde and phenose, C6H6(OH)6( ). According to Puls,2 there are produced in the same electrolyte, using a diaphragm and a platinum anode, benzaldehyde, benzoic acid, benzoic ethyl ester, and, as chief product, p-sulphobenzoic acid. Under the same conditions, Merzbacher and Smith3 had obtained a poor yield of benzoic ethyl ester. 

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. 

Bromine or electrolytic oxidation of furan in alcoholic solution gives the corresponding 2,5-dialkoxy-2,5-dihydrofuran 159 (R = Alk). Lead tetraacetate in acetic acid oxidation yields 2,5-diacetoxy-2,5-dihydrofuran 159 (R = Ac). 

Non-Reversible Processes. —Reactions of the non-reversible type, i.e., with systems which do not give reversible equilibrium potentials, occur most frequently with un-ionized organic compounds the cathodic reduction of nitrobenzene to aniline and the anodic oxidation of alcohol to acetic acid are instances of this type of process. A number of inorganic reactions, such as the electrolytic reduction of nitric acid and nitrates to hydroxylamine and ammonia, and the anodic oxidation of chromic ions to chromate, are also probably irreversible in character. Although the problems of electrolytic oxidation and reduction have been the subject of much experimental investigation, the exact mechanisms of the reactions involved are still in dispute. For example, the electrolytic reduction of the compound RO to R may be represented by... 

Electrolytic oxidation with nickel anodes and stainless steel cathodes and sodium hydroxide or potassium hydroxide as the electrolyte converts saturated, unsaturated, acetylenic, and aromatic alcohols into acids at 25-75 in yields ranging from 51 to 92% (equation 229) [116]. 

The further oxidation of phenol may also result in the formation of catechol, C,iH4(OH) (1 2). The transformation may be effected by fusion with sodinm hydroxide.85 The snbstance may also be obtained by oxidizing benzene with hydrogen peroxide in the presence of ferrous sulfate88 and by reducing o-benzoquinone with aqueous sulfurous acid in the cold.81 Quinol may be prepared from phenol by oxidation with potassium persulfate in alkaline solution.38 It can also be obtained directly from benzene by the electrolytic oxidation of an alcohol solution to which... 

Iodoform can be prepared economically by the electrolytic oxidation at 60 of an aqueous solution of alcohol containing potassium iodide and sodium carbonate. The iodine set free by the current converts the alcohol and the sodium carbonate into iodoform and sodium iodide. The latter serves as a source for more iodine. Theoretically, all the iodine should be recovered... 

Benzaldehyde is a liquid with an agreeable odor, which boils at 179°, and has the specific gravity 1.0504 at 15°. It can be formed by oxidizing benzyl alcohol, or distilling calcium benzoate with calcium formate. It is manufactured by heating benzal chloride with milk of lime, or by oxidizing benzyl chloride with a solution of lead nitrate. It has been prepared from toluene directly by electrolytic oxidation or by oxidation with air in the presence of a catalyst. 

The general hemi-reactions for a CnH2n+iOH mono-alcohol that oxidizes completely to CO2 in a DAFC employing an acid electrolyte are ... 

Wallach found that azoxybenzene in presence of acids rearranges into 4-hydroxyazobenzene, but his main work was on terpenes, on which he published 126 papers. He studied limonene (and its tetrabromide), pinene, and terpineol. Limonene tetrabromide was independently discovered by Guillaume Adolphe Renard (Rouen 10 May 1846-April 1919), who also obtained methylcyclohexane from rosin spirit, and worked on the electrolytic oxidation of alcohol, turpentine, benzene, toluene, etc. (1880 f.). 

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