Redoxpotentiale von Phenol/Phenoxyl-Systemen

Nickel, Bernhard; Mauser, Heinz; Hezel, Ute

doi:10.1524/zpch.1967.54.3_4.196

Cited by 10 publications

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“…The anodic peak potentials obtained with Pt electrodes during the first potential scan were 0.46 and 0.20V vs. SSCE in electrolytic solutions II and III, respectively, and those with BPG electrodes were 0.62 and 0.16V vs. SSCE for solutions II and III, respectively (at a scan rate of 50 mVs-'). According to the literature (8,(28)(29)(30), in a neutral or acidic solution a two-electron removal from the neutral, nonionized phenolic compound occurs to give a phenoxonium ion, while in a strongly basic solution a one-electron removal from phenoxide anion occurs to give a phenoxy free radical. These two reactions have been accepted as the basic mechanisms of anodic oxidation of phenolic compounds.…”

Section: Science and Technologymentioning

confidence: 99%

“…On the other hand, in basic solutions such as electrolytic solutions II and III, 2,6-dimethylphenol is dissoci-ated to 2,6-dimethylphenoxide ion (II) (R4) (8,29,30). In this case, the primary anodic product is a phenoxy radical (IV, V) formed via one-electron removal (R5).…”

Section: Tmdpqmentioning

confidence: 99%

“…134, No. 12 ANODIC OXIDATION 3073 ated to 2,6-dimethylphenoxide ion (II) (R4) (8,29,30). In this case, the primary anodic product is a phenoxy radical (IV, V) formed via one-electron removal (R5).…”

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confidence: 99%

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Anodic Oxidation of 2,6‐Dimethylphenol in Various Electrolytic Solutions

Oyama

Ohsaka

Ohnuki

et al. 1987

J. Electrochem. Soc.

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The electrolytic synthesis of poly(2,6-dimethyl-!A-phenylene0xide) (PPO), 3,3',5,5'-tetramethyl-4,4'-diphenoquinone (TMDPQ), and 2,2',6,6'-tetramethyl-1, l'-biphenol (TMBP) from 2,6-dimethytphenol in various electrolytic solutions was carried out. They were Characterized by chemical (using IR absorption spectroscopy, 1H-and~3C-NMR technique, etc.) and electrochemical means. The results were compared with those obtained for the oxidative coupling of 2,6-dimethylphenol in the presence of oxygen using a copper-amine complex as the catalyst. The electrolysis conditions favorable for the preparation of the above compounds were as follows. The electrolysis at a Pt electrode in basic electrolytic solutions such as NaOH-containing methanol and (C2Hs)2NH-containing acetonitrile sOlutions is preferable for PPO preparation, while neutral acetonitrile solution is suitable for the preparation of TMDPQ and TMBP. In addition on the basis of the results obtained, the possible mechanism of the anodic oxidation of 2,6-dimethylphenol is discussed.A number of papers have reported the oxidative coupling of phenolic compounds since poly(2,6-dimethyl-l,4-phenyleneoxide) was first prepared by Hay et at. (1,2) from 2,6-dimethylphenol in the presence of oxygen using a copper.amine complex as the catalyst. The previous papers (1-7) demonstrate that the oxidative coupling of a 2,6-disubstituted phenol mainly leads to two kinds of products, i.e., poly(2,6-disubstituted-l,4-phenyleneoxide) and diphenoquinone via carbon-oxygen coupling and carbon-carbon coupling, respectively, depending on the preparation conditions (e.g., the kind of the catalyst, the kind of the substituent group, the presence or absence of basic additives, and temperature) (Scheme 1)The electrochemical oxidation of phenolic compounds has also been carried out by replacement of the catalytic oxidation with anodic oxidation and has been summarized in several recent review articles (8-18). Two main types of the electrolysis products have been prepared; the polymerie eompounds of the polyoxyphenylene type and the dimeric compounds. Bruno et al. (11) have reported that the anodic polymerization of substituted phenols is performed successfully in alcohols containing alkaline bases. They have found that passivating protective polyoxyphenylene films, which have thicknesses ranging from -0.05 to 0.15 ~xm and which are homogeneous and adherent, can be formed on several metal substrates. Mengoli et at. (9,17,18) have found that the electrolysis of systems based on the phenol (as the main monomer)/2-ehlorophenol/ethylenediamine gives thiek homogeneous eoatings of more than 20 fxm. This behavior, which is mainly due to the presence of ethylenediamine, was explained by assuming that ethylenediamine may adsorb on the anode in competition with phenoxide anions. Thus the electropolymerization no longer takes place in situ but develops into the solution as the competitive adsorption of the amine breaks the coupling reaction along the plane of the electrode. Recently, Tsuchida et al. (19) hav...

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Section: Science and Technologymentioning

confidence: 99%

Section: Tmdpqmentioning

confidence: 99%

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Anodic Oxidation of 2,6‐Dimethylphenol in Various Electrolytic Solutions

Oyama

Ohsaka

Ohnuki

et al. 1987

J. Electrochem. Soc.

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“…According to literature [44][45][46][47], phenol oxidation occurring in acidic medium (pH \ 9.89 (pKa)) involves two electrons per molecule to give a mesomeric phenoxonium ion (reaction 2) while in basic solution (pH [ 9.89) it corresponds to a one-electron exchange from phenoxide anion to give a mesomeric phenoxy radical (reaction 3).…”

Section: Influence Of the Successive Potential Scans At Different Temmentioning

confidence: 99%

Electropolymerization of phenol on a vitreous carbon electrode in acidic aqueous solution at different temperatures

Tahar

Savall

2011

J Appl Electrochem

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Electrochemical oxidation of phenol in acidic aqueous solution was studied on a vitreous carbon electrode at different temperatures in the range of 25-85°C by cyclic voltammetry and chronoamperometry. The kinetic aspect of the phenol oxidation was investigated as a function of its concentration and temperature. The electrode deactivation by formation of an adherent, compact, and insulating polymeric film was examined by monitoring the decrease in the peak current of phenol oxidation during the course of successive potential scans. Repeated potential scans in the region of water stability did not reactivate the electrode whatever the temperature used. Chronoamperometric curves recorded at different potentials in the region of water decomposition shown that the electrochemical activity of the electrode was partially restored even when performed at low temperature (25°C).

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10.3.1 Phenols

Steenken¹

Proton and Electron Transfer. Biradicals

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Redoxpotentiale von Phenol/Phenoxyl-Systemen

Cited by 10 publications

References 0 publications

Anodic Oxidation of 2,6‐Dimethylphenol in Various Electrolytic Solutions

Anodic Oxidation of 2,6‐Dimethylphenol in Various Electrolytic Solutions

Electropolymerization of phenol on a vitreous carbon electrode in acidic aqueous solution at different temperatures

10.3.1 Phenols

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