Taro Sekine

Mechanism of Hydrocarbon Formation in the Electrolytic Reduction of Acetone in Aqueous Sulfuric Acid

A tentative mechanism or hydrocarbon formation is proposed which, by combining the usual mechanism of pinacol and isopropanol formation, will contribute to one clarification of the over‐all electrode process of acetone reduction (see PDF for formula). The main point lies in the fact that the radical is further reduced with dehydration of propane through the isopropyl radical which is combined with the cathode metal. In certain cases (mercury and lead, etc.) the reaction products with metal (organometallic compound) can be isolated in a relatively stable form. Generally speaking, cathode material having a negative standard electrode potential tends to follow this hydrocarbon formation process.

Anodic Processes of Acetate Ion in Methanol and in Glacial Acetic Acid at Various Anode Materials

The anodes used in this study were platinum, gold, palladium, lead dioxide, and graphite. The normal Kolbe process, the formation of ethane (and methane) and carbon dioxide, can be realized at a potential higher than 2.0v (vs. SCE) in both methanol and glacial acetic acid. In methanol, only platinum and gold seem to be suitable for realizing the process. In glacial acetic acid, however, all of the anodes except graphite can be used successfully for the same process. Another process, the formation of methyl acetate, occurs in both solvents at graphite in the potential range 1.4–2.0v. A side reaction observed in methanol at palladium, graphite, and lead dioxide was the formation of formaldehyde (and methyl formate in case of lead dioxide) which occurs at potentials as low as 1.2v.

Electroreduction of substituents on a pyridine ring in aqueous sulfuric acid

Abstract Hydroxymethyl, aminomethyl, carboxyl, methoxycarbonyl, carbamoyl, hydrazinocarbonyl, formyl, vinyl and phenyl groups attached to various positions of a pyridine ring were reduced at a mercury cathode in an aqueous sulfuric acid solution. These groups, except for the phenyl group, at the 2- and 4-positions could be reduced, while the reduction of the groups at the 3-position seemed to be difficult. The reduction potential of the groups at the 4-position was generally less negative than that of the same group at the 2-position. Current efficiencies for the reduction of hydroxymethyl, aminomethyl and vinyl groups were higher in the case of 4-substituted-pyridines than 2-substituted-pyridines, while this tendency reversed in the case of the other groups. An obvious steric hindrance effect on the current efficiency was also observed in the reduction of substituted-hydroxymethyl groups attached to the 2-position. On the basis of these results, reduction mechanism is discussed and also the synthetic scope is described.

Electrolytic Reduction of 2‐Amino‐4‐chloropyrimidine, 2‐Amino‐4‐choro‐6‐methylpyrimidine, and 2‐Aminopyrimidine

2‐Amino‐4‐chloropyrimidine and its 6‐methyl derivative give two polarographic waves in the pH region of 7.4–8.9; 2‐aminopyrimidine and 2‐amino‐6‐methylpyrimidine yield but a single wave in this region. Macroscale electrolysis at lead or mercury cathodes in ammoniacal medium shows that the first wave of the chlorocompounds arises from reductive dehalogenation. The second wave of the chlorocompounds coincides with the single wave of their parent compounds, the 2‐aminopyrimidines, and is ascribed to reduction of the pyrimidine nucleus in both cases. The macroreduction of 2‐aminopyrimidine takes place easily at lead or mercury cathodes in ammoniacal medium to yield 2 ‐aminodihydropyrimidine. The mechanism of reduction is tentatively identified as pure electrolytic reduction.The reduction of 2‐amino‐4‐chloropyrimidine to 2‐aminopyrimidine at cathodes of lead and mercury in aqueous methanolic ammonium sulfate was found to be impractical on a preparative scale. On the other hand at spongy cadmium the reduction takes place in 90% yield. At spongy zinc the yield is poorer due to further reduction of the pyrimidine nucleus. However, for the reduction of 2‐amino‐4‐chloro‐6‐methylpyrimidine zinc is superior to cadmium as a cathode.

Cathodic crossed hydrocoupling XIII. Synthetic aspect of the cathodic crossed hydrocoupling reaction of aliphatic carbonyl compounds with electrophiles in aqueous sulfuric acid

Abstract For the purpose of organic electrosynthesis, the cathodic crossed hydrocoupling of aliphatic carbonyl compounds with some electrophiles was investigated. When mixtures of carbonyl compounds (such as ketone and aldehyde) and electrophiles (such as activated olefin, pyridine, and cyanamino compound) were electrolysed with various kinds of cathodes in aqueous sulfuric acid, these compounds were coupled reductively to give many useful products in the field of synthetic organic chemistry. In most of the couples of carbonyl compounds and electrophiles, the reduction potentials of the formers were more positive than those of the latters under the electrolysis condition. The yield, current efficiency, and selectivity of products depended on electrolytic conditions, especially cathode material.