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One-electron Transfer (one-electron + transfer)
Selected AbstractsElectrochemical Approach to the Radical Anion Formation from 2,-Hydroxy Chalcone DerivativesELECTROANALYSIS, Issue 5 2006P. Quintana-Espinoza Abstract Three 2,-hydroxy chalcone derivatives were electrochemically reduced to the radical anion by a reversible one-electron transfer followed by a chemical dimerization reaction. Under suitable conditions of the medium, the one-electron reduction produces very well resolved cyclic voltammograms due to the formation of the radical anion. By using appropriately the wide versatility of the cyclic voltammetric technique, was possible to study the generation of the radical anion and its stability. [source] Free-radical 4-nitrophenylation of thieno[2,3- b]pyridine.JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2001Part 3: Consideration of mechanistic, selectivity factors involved in the substitution process A 1:1 geometrically oriented encounter complex between thieno[2,3-b]pyridine (1) and 4-nitrophenyldia-zoacetate (2) is proposed to account for the dominant formation (ca. 64%) of the 2-isomer in the mixture of 4-nitrophenyl-l isomers obtained previously. A mechanism involving one-electron transfer from 1 to 2 plus fragmentation of 2· into 4-nitrophenyl free radical, N2, and acetate ion is invoked. Formation of other isomers is discussed. It is noted that there is a close correlation between orientational rules plus mechanisms of reaction for numerous free-radical substitutions (SR) with SN reactions of alkyllithiums on furan, thiophene, N -alkylpyrroles, pyridine, and their condensed aromatic molecules, including 1, as substrates. Also isomeric selectivities for SE, SN, and SR substitutions into 1 were shown to be qualitatively consistent with one another. While SE reactions occur largely at position 3 and then at 2, SN and SR reactions occur either at 2 or 6. Selectivity for positions 4 or 5 is small or zero. [source] Electrochemical, ESR and quantum chemical study of 1-substituted naphthalenes and their radical anions,,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2008N. V. Vasilieva Abstract Electrochemical reduction and oxidation of a series of 1-substituted naphthalenes (1-X-naphthalenes) have been studied by the method of cyclic voltammetry (CV). The first reduction peak of the majority of these compounds corresponds to a one-electron transfer to form the relatively stable radical anion (RA). For these species, ESR spectra have been registered and interpreted, the life time has been estimated. The first oxidation peaks of 1-X-naphthalenes are irreversible and correspond to a transfer of two or more electrons. Copyright © 2007 John Wiley & Sons, Ltd. [source] Raman and pulse radiolysis studies of the antioxidant properties of quercetin: Cu(II) chelation and oxidizing radical scavengingJOURNAL OF RAMAN SPECTROSCOPY, Issue 5 2005Armida Torreggiani Abstract Quercetin (Querc), a pentahydroxyflavonol, is suggested to give protection to living organisms by both direct scavenging of free radicals and metal chelation. The scavenging ability of Querc towards oxidizing radicals, such as ,OH, N3, and NO2,, was evaluated by pulse radiolysis studies in aqueous solutions at different pH. Phenoxyl radicals are the final transient products and are formed either by water elimination from ,OH-adducts or by one-electron transfer from the deprotonated OH groups. Their formation rate is strongly affected by pH and reaches the maximum values in alkaline medium. The Raman and IR spectra were useful to assess the relevant interaction of Querc with Cu(II) ions, which play an important role in the metal-catalysed generation of reactive oxygen species. Depending on pH and the metal-to-ligand ratio, the different chelating sites of Querc change their ability to complex copper ions. Under neutral conditions, the 5-OH group of ring A and CO-4 of ring C have a chelating power superior to that of the catechol group (ring B), whereas the complexation in alkaline medium occurs in the reverse order. In addition, experiments with Querc and Zn(II) ions, carried out at basic pH in order to verify the possible Cu(II)-catalysed oxidation of the ligand, indicated the absence of the above process. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||