- Electrochemical generation of a Michael acceptor: A green method for the synthesis of 4-amino-3-(phenylsulfonyl)diphenylamine derivatives
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Electrochemical oxidation of 4-aminodiphenylamine in aqueous solution and in the presence of some arylsulfinic acids as nucleophiles was studied and its reaction mechanism was discussed. Using the voltammetric data, a one-pot and environmentally friendly
- Salahifar, Eslam,Nematollahi, Davood
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- Enhanced study and control of analyte oxidation in electrospray using a thin-channel, planar electrode emitter
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A thin-channel, planar electrode emitter device is described and utilized for the study and control of electrochemical oxidation of analytes at the emitter electrode in an electrospray ion source. For analytes that are not particularly susceptible to oxid
- Van Berkel, Gary J.,Asano, Keiji G.,Kertesz, Vilmos
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p. 5047 - 5056
(2007/10/03)
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- Electrochemical polymerization of aniline investigated using on-line electrochemistry/electrospray mass spectrometry
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A thin-layer electrochemical flow cell coupled on-line with electrospray mass spectrometry (EC/ES-MS) was used to investigate the soluble products from the controlled-potential anodic polymerization of aniline in H2O and H2O/CH3O H (1/1 v/v) with ammonium acetate and acetic acid or ammonium hydroxide as electrolytes (pH 4, 6.5, or 9). At a working electrode (glassy carbon) potential of 1.0 V versus Ag/AgCl, singly protonated aniline oligomers containing as many as 10 aniline units (10-mer) were observed in the ES mass spectra when the polymerization in H2O/CH3OH at pH 4 was carried out. The abundance of the higher n-mers decreased at higher solution pH and in 100% H2O at pH 4. Most of the oligomers were observed in more than one redox state ranging from fully oxidized (all imine nitrogens) to fully reduced (all amine nitrogens). The number of different redox states observed for the n-mers increased with increasing n. The structures of the reduced (m/z 185) and oxidized (m/z 183) aniline dimer ions (head-to-tail, tail-to- tail, or head-to-head) produced from the polymerization of aniline at pH 4, 6.5, and 9 in H2O/CH3OH were revealed to vary as a function of pH by comparison of their tandem mass spectrometry product ion spectra with the product ion spectra of the dimer standards. EC/ES-MS potential scan experiments, in which the working electrode current and major n-mer ions for n = 2, 3, and 4 were monitored as a function of electrode potential, were used to probe the growth mechanism to higher aniline oligomers. Under the conditions used, the controlled-current electrolytic process inherent to the operation of the ES ion source did not significantly influence the formation or nature of the oligomers observed. Beyond the current application, the results presented here serve to demonstrate the utility of EC/ES-MS as a tool in identifying the initial products of electropolymerization and in studying the products of electrode reactions in general.
- Deng, Haiteng,Van Berkel, Gary J.
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p. 4284 - 4293
(2007/10/03)
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- Kinetics of the p-aminodiphenylamine radical in organic solution: An electrochemical and electron spin resonance study
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In studying the reaction mechanism of anodic aniline oxidation the dimer p-aminodiphenylamine (ADPA) was found to be the main intermediate product in acidic solution. It is oxidized in both the free amine and the protonated form. The cyclic voltammograms have been simulated by taking into account an electrochemical reaction of both the protonated and the nonprotonated forms. Thus, it was also found that the ADPA concentration is determined by the protonation equilibrium. The oxidation product N-phenylquinone diimine (PQDI) undergoes a symproportionation reaction with ADPA forming the ADPA?+ cation radical. The equilibrium constant for this reaction of PQDI in dimethyl sulfoxide was determined and found to be independent of the concentration of the protons in solution. The ADPA?+ cation radical decay can be described by a rate equation based on a second-order reaction for the radical dimerization and a pre-equilibrium for the radical formation by symproportionation. The reaction mechanisms of the anodic oxidation of p-aminodiphenylamine and its chemical follow-up reactions are given.
- Petr,Dunsch
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p. 4867 - 4872
(2007/10/03)
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- Surface-Enhanced Raman Spectroscopy as a Probe of Electroorganic Reaction Pathways. 2. Ring-Coupling Mechanisms during Aniline Oxidation
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The adsorbed ring-coupling products formed during aniline electrooxidation at gold-aqueous interfaces have been identified by means of real-time surface-enhanced Raman-spectroscopy (SERS) in conjunction with linear sweep voltammetry.In the absence of solution species, the electrooxidation of irreversibly adsorbed aniline yields predominantly adsorbed benzidine.In the presence of solution aniline, however, the "head-to-tail" dimer N-phenyl-1,4-phenylenediamine (PPDA) as well as benzidine is formed at the interface, the proportion of the former adsorbate increasing toward higher pH and larger aniline concentrations.A distinction between these interfacial reaction products can readily be made from the characteristic and intense SER spectra of the two-electron oxidation products formed from PPDA and benzidine.Markedly different ring-coupling product distributions were formed in solution (i.e., within the diffusion layer) as deduced voltammetrically, PPDA predominating except in strong acidic media.Possible reasons for these observed differences are discussed.In alkaline media, azobenzene is observed to be the major ring-coupling product in both adsorbed and solution-phase environments.
- Gao, Ping,Gosztola, David,Weaver, Michael J.
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p. 3753 - 3760
(2007/10/02)
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- REAKTIONEN AN KOMPLEXGEBUNDENEN LIGANDED. XXXVI. SYNTHESE UND OXIDATIONSVERHALTEN VON M(CO)5-KOMPLEXEN (M = Cr, Mo, W) MIT AMIN- UND BENZOCHINONDIIMIN-LIGANDEN
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The oxidation of yellow Cr(CO)5NH2R complexes (NH2R = aniline, m-toluidine, 3,5-xylidine, m-anisidine) with Pbac4 gives deep blue to deep purple coloured compounds, which have been identified as the respective complexes.Oxidation of the p-phenylenediamine complex yields , which is also deep blue.The binuclear blue complex 2HN=C6H4=NC6H5> is obtained by treating Cr(CO)5THF with the free ligand in THF/hexane; it dissociates rapidly in acetone to form and Cr(CO)5.Analogous Mo(CO)5 and W(CO)5 complexes could not be obtained.The oxidation of W(CO)5(m-anisidine)> by I2 yields 2.All the compounds were characterized by spectroscopic methods as well as by elemental analysis.
- Sellmann, Dieter,Mueller, Juergen
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p. 379 - 394
(2007/10/02)
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- POLAROGRAPHY OF SOME AROMATIC AND HETEROCYCLIC NITROSO COMPOUNDS
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The electrochemical reduction of 4-nitrosodiphenylamine, 3-methyl-4-amino-5-nitrosouracil and 1,3-dimethyl-4-amino-5-nitrosouracil was studied in connection with the development of methods of electrosynthesis of some amino derivatives, intermediate compounds in the production of medicinal preparations and antioxidants of polymeric materials.
- Avrutskaya, Inna,Fioshin, Michail
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p. 196 - 202
(2007/10/02)
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