Initial Single Electron Transfer Research Articles

Etude de la réaction de germyllithiums sur la di-t-butyl-3,5 orthoquinone: mise en évidence d'un mécanisme par transfert monoélectronique

Reactions between organogermyllithiums R 3GeLi and 3,5-di-t-butylorthoquinone mainly give digermanes but also O-germylcatechol and germadioxolanes. It appears that these reactions start after an initial single electron transfer (SET) which is supported by an ESR study of the reaction. ESR analysis shows the transient formation of an O-semiquinonic species and also germanium centered radicals R 3Ge · (stable at 20°C for R = Mes). The digermane formation can occur through germanium centered radicals duplication. But it appears that other by-reactions lead also to digermane as O-germylcatechol lithiogermolysis and unexpected successive SET reactions. All these reactions which work to form digermanes are highly dependent on the nature of the R group linked to germanium and specially on their steric hindrance.

Photochemical oxygenation of styrene by pyrimido[5,4, [formula omitted]]pteridine 10- oxide as a chemical mimic of hemin-catalysed oxygenation

Irradiation of styrene ( 5) in the presence of pyrimido[5,4- g ]Pteridine 10-oxide ( 1) with u.v.-visible light resulted in the formation of styrene oxide ( 6) and phenylacetaldehyde ( 7) which are proved as primary metabolites of ( 5). Chemical and physico-chemical facts showed that the photooxygenation of ( 5) by ( 1) involves an initial single-electron transfer followed by oxygen-atom transfer, accommodating the oxygenation mode of cytochrome p -450 and other hemoproteins. Comparative experiments with 3-methylpyridazine 2-oxide ( 3) and pyridine N -oxide ( 4) demonstrated the simplicity and the mechanistic characteristic of the photooxygenation by ( 1).

The Photochemical Debromination of Bromocyclopropane in the Presence of Amine

Abstract The irradiation of bromoarylcyclopropanes (1) in the presence of tertiary amine resulted in the formation of the debrominated cyclopropanes as a mixture of geometrical isomers, whose ratios were essentially similar regardless of the stereochemistry of the bromide. The reactions were not, however, observed in the absence of amine. The results are interpreted as indicating that the reactions proceed through an initial single-electron transfer to the excited 1, followed by debromination and hydrogen-abstraction.

Single-electron transfer processes and the reaction mechanism of enzymic degradation of lignin

The lignin-degrading, ‘H 2O 2-dependent oxygenase’ from Phanerochaete chrysosporium oxidised veratryl alcohol without incorporating oxygen into the substrate. It also catalysed α-β cleavage of a non-phenolic diarylpropane substrate in the absence of oxygen. Studies with tris(phenanthroline)iron(III) established the importance of single-electron transfer in bringing about α-β cleavage. We propose that the lignin-degrading enzyme functions not as an oxygenase but as a peroxidase and that the oxidation reactions are brought about by initial single-electron transfer between the aromatic ring and a high redox oxy-ferryl active site in the enzyme. Lignin degradation Single-electron transfer Cα-Cβ bond cleavage Phanerochaete chrysosporium Peroxidase compound I

Reactions of oxiranes with alkali metals: intermediacy of radical-anions

Reaction of oxiranes with alkali metals in aprotic solvents yields a variety of products depending on the nature of the metal and the structure of the oxirane. Deoxygenation to olefins is the major reaction in case of lithium. Rearrangement to carbonyl compounds, reduction to alcohols and formation of dimeric products occur when oxiranes are treated with sodium. All the reactions could be rationalised by a mechanism involving an initial single electron transfer leading to the formation of a radical-anion intermediate.

D.C. and sine-wave polarographic studies of the nitrophenols. II. Mechanism of inhibited reduction with special reference to m-nitrophenol

The modes of the free and inhibited reduction of the nitrophenols, and in particular m-nitrophenol, in basic media are discussed using sine- wave and conventional d.c. polarography. The mechanism of the initial single-electron transfer step of m-nitrophenol in the presence of inhibitor is attributed to the stabilization of the m-nitrophenol radical ion.