Electrolysis in the presence of ultrasound: cell geometries for the application of extreme rates of mass transfer in electrosynthesis

Marken, Frank; Compton, Richard G.; Davies, Stephen G.; Bull, Steven D.; Thiemann, Thies; Melo, M. L. Sá e; Neves, André Campos; Castillo, José L.; Jung, Céline; Fontana, André

doi:10.1039/a701004d

Cited by 24 publications

(15 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Applications of this dual stimulation have been found in electroplating [3], reaction mechanism and kinetic analysis [4,5], synthesis [6][7][8][9][10][11][12][13][14][15][16] and most recently electroanalysis [17][18][19][20][21]. The dominant ultrasonic effects in all of these uses are those of greatly enhanced mass transport of electroactive substrate to the electrode and the activation of the electrode surface through cavitational cleaning action.…”

Section: Introductionmentioning

confidence: 99%

Electroanalysis of Ascorbic Acid: A Comparative Study of Laser Ablation Voltammetry and Sonovoltammetry

Akkermans

Bain

et al. 1998

Electroanalysis

View full text Add to dashboard Cite

The electroanalytical detection of L-ascorbic acid via its two electron oxidation in aqueous solution is the subject of a comparison of two voltammetric methodologies both of which rely in part on electrode abrasion. First in sonovoltammetry cavitational collapse at the electrodesolution interface can lead to electrode erosion and activation. Second in laser ablation voltammetry (LAV) a 10 Hz pulsed laser (532 nm, 0.7 mJ per pulse) is used to abrade the electrode. In both cases the concomitant agitation of the solution leads to regular refreshment of the diffusion layer so that at sufficiently extreme potentials sustained currents (transport limited currents) are observed which scale with the concentration of ascorbic acid present and permit quantitative electroanalysis.Comparison of the methods as applied to ascorbic acid shows that for LAV the laser light intensity can be adjusted for maximum ablation of surface adsorbed blocking species but with minimum damage to the platinum surface itself. In contrast the sonovoltammetry technique does not facilitate selective erosion of surface adsorbed species. Instead the mass transport, amount of cavitation and damage to the electrode are all interlinked with the intensity of ultrasound employed. Thus while the amount of cavitation at the electrode surface can be controlled the relative adsorbate/electrode abrasion cannot. The limiting currents under insonation were found to be substantially (ca. 15 times) larger than for LAV suggesting that the major benefit of sonovoltammetry is in terms of enhanced mass transport whereas LAV shows more selective cleaning activation. The development of a novel sono-LAV is therefore reported which retains the merits of both the separate experiments in isolation. Thus the cleaning potential of LAV is coupled with the mass transport enhancement of ultrasound. Application to the quantitative electroanalysis of ascorbic acid is reported.

show abstract

Section: Introductionmentioning

confidence: 99%

Electroanalysis of Ascorbic Acid: A Comparative Study of Laser Ablation Voltammetry and Sonovoltammetry

Akkermans

Bain

et al. 1998

Electroanalysis

View full text Add to dashboard Cite

show abstract

“…The observed limiting currents may be compared to the limiting currents obtained from a numerical simulation and a quantitative mechanistic analysis employing the following reactions scheme (Eqs. [3][4][5]. The limiting current observed in the absence of cis-1,2-cyclopentanediol defines the diffusion layer thickness here given by Equation 1.…”

Section: The Electrocatalytic Cleavage Of Cis-cyclopentane-12-diol Imentioning

confidence: 99%

“…Increasing the mass transport to the electrode has the advantage of simultaneously discriminating against the undesirable background processes [4] which could cause problems if only the electrode surface area rather than the mass transport is increased. The extremely high rate of mass transport and surface cleaning action of power ultrasound in electrochemical systems would be ideally suited for this purpose and is studied here in conjunction with the use of electrogenerated Pb(IV).…”

Section: The Sonoelectrochemical Reduction and Oxidation Of Pb(ii) Inmentioning

confidence: 99%

See 1 more Smart Citation

Sonoelectrochemically Enhanced Electrocatalytic Processes: The Pb(IV) Catalyzed Cleavage of 1,2-cis-Cyclopentanediol at Graphite and Glassy Carbon Electrodes

Marken¹,

Compton²,

Buston³

et al. 1998

Electroanalysis

View full text Add to dashboard Cite

In this study, the electrocatalytic (EC 0 -type) carbon-carbon bond cleavage of cis-1,2-cyclopentanediol by Pb(IV) benzoate generated in situ is shown to be possible under extremely fast mass transport conditions. Based on the comparison of data obtained experimentally and by the numerical simulation of sonoelectrochemical limiting currents with commercially available software (Digisim 2.0), excellent agreement with the theoretical model of a planar diffusion layer can be achieved and allows the straightforward prediction and optimization of sonoelectrochemcial processes involving homogeneously coupled chemical steps. The ultrasonic cleaning of the electrode surface strongly affects the Pb deposition process at glassy carbon and basal plane pyrolytic graphite electrodes, but is not efficient enough to prevent electrode fouling which accompanies the anodic process at positive potentials. The overall rate and efficiency of the electrochemical process is enhanced due to fast mass transport in the presence of ultrasound.

show abstract

“…Its use 15 during electrolysis increases mass transport of the substrate to the electrode and of the product from the electrode in many cases. 16 An increase in current at constant potential was noted when using ultrasound. The reaction time of the oxidative SO-extrusion can be shortened without altering the product distribution.…”

mentioning

confidence: 99%

Preparation and Electrooxidative SO-Extrusion of Halogenated 7-Thiabicyclo[2.2.1]heptene 7-Oxides†

Thiemann¹,

Melo²,

Neves³

et al. 1998

J. Chem. Res.

Self Cite

View full text Add to dashboard Cite

Halogenated thiophenes have been cycloadded oxidatively to maleimides to give halogenated thiabicyclo[2.2.1]heptene S-oxides which have been subjected to an electrochemical extrusion of SO to give various halogeno-substituted phthalimides. Torssell1 and Fallis and co-workers 2 have shown that oxidative cycloaddition occurs on treating alkyl-substituted thiophenes with m-chloroperbenzoic acid (m-CPBA) in the presence of an electron-poor dienophile. We have studied the reaction in greater detail and found it valuable to synthesize novel alkyl-substituted 7-thiabicyclo[2.2.1]heptene 7-oxides in connection with crown ether systems. 3 Recently, it was shown that the yield for the oxidative cycloaddition of alkyl-substituted thiophenes, proceeding via intermediate thiophene S-monoxides, could be greatly enhanced by adding BF 3 Á Et 2 O to m-CPBA.4 While the uncatalysed reaction can be run at 0 8 8C to ambient temperature, the catalysed reaction is run typically at À78 8 8C. The greater stability of thiophene S-oxides towards further oxidation under catalysed conditions was demonstrated. 4,5 The further oxidation of thiophene S-monoxides to the S,S-dioxides is a main side reaction in the oxidative cycloaddition.Oxidation of thiophenes at sulfur proceeds readily when the thiophenes are substituted with electron donors such as alkyl groups. Electron-withdrawing or more ambidentate substituents hinder the oxidation. For this reason the oxidative cycloaddition of halogenated thiophenes does not proceed well at room temperature. Nevertheless, at more elevated temperatures, 7-thiabicyclo[2.2.1]heptene S-oxides from readily in the reaction of 2,5-chlorinated or brominated thiophenes with such idenophiles as maleimides or maleic anhydride (Scheme 1). The products are not very soluble in dichloromethane and partly precipitate during the reaction. Further precipitation can be induced by addition of diethyl ether. Apart from diligent washing with diethyl ether, the products need no additional puri®cation for a further transformation, although for analytical purposes column chromatography and recrystallization have been performed.It has been found that the addition of BF 3 Á Et 2 O has no bene®cial eect on the reaction, if the thiophene is halogenated at position 2 and/or 5. In the case of 3,4-dibromo-2,5-dimethylthiophene 1d, however, an acceptable yield of the cycloadduct was obtained when the reaction was run at À20 8 8C in presence of BF 3 Á Et 2 O. In the cycloaddition ®ve stereocentres are created. Nevertheless, only one isomer is isolated. Although no crystal structural analysis has been performed, it is thought to be the endo-product with the lone-electron pair of the sulfur directed to the newly formed ole®nic bond. This is evidenced by comparison to compounds formed in cycloadditions with donor-substituted compounds. On the other hand, 3 may be viewed as precursors for corresponding arenes. Photochemical 6 and oxidative extrusion 3 of SO in 3 has been found to proceed at much lower temperatures than the purely thermal e...

show abstract

Electrolysis in the presence of ultrasound: cell geometries for the application of extreme rates of mass transfer in electrosynthesis

Cited by 24 publications

References 31 publications

Electroanalysis of Ascorbic Acid: A Comparative Study of Laser Ablation Voltammetry and Sonovoltammetry

Electroanalysis of Ascorbic Acid: A Comparative Study of Laser Ablation Voltammetry and Sonovoltammetry

Sonoelectrochemically Enhanced Electrocatalytic Processes: The Pb(IV) Catalyzed Cleavage of 1,2-cis-Cyclopentanediol at Graphite and Glassy Carbon Electrodes

Preparation and Electrooxidative SO-Extrusion of Halogenated 7-Thiabicyclo[2.2.1]heptene 7-Oxides†

Contact Info

Product

Resources

About