Exhaustive Electrolysis Research Articles

Studies on electroreduction mechanisms of selected aromatic hydrocarbons in tetrahydrofuran

Detailed mechanisms of electrochemical reductions of seven polynuclear aromatic hydrocarbons (PAHs) including benzo[a]pyrene (BaP), benzo[e]pyrene (BeP), dibenz[a,h]anthracene, dibenz[a,c]anthracene, 3-methylcholanthrene, 7,12-dimethylbenz[a]anthracene, and benz[a]anthracene were studied using cyclic voltammetry, single potential step chronoamperometry, voltammetry at rotating disk electrodes, and controlled potential coulometry in tetrahydrofuran solution using 0.1 M tetra-n-butylammonium perchlorate as a supporting electrolyte. Results indicate that these compounds undergo ECE reactions to a final product reduced at L-regions of each PAH with the exception of BaP and BeP. For these two PAHs, unreduced hydrocarbons were identified after exhaustive electrolysis. Heterogeneous electron-transfer rate constants, as well as homogeneous reaction rate constants, for the addition of the proton to electrogenerated anion radicals are also reported.

Studies on electroreduction mechanisms of selected aromatic hydrocarbons in tetrahydrofuran

Detailed mechanisms of electrochemical reductions of seven polynuclear aromatic hydrocarbons (PAHs) including benzo[a]pyrene (BaP), benzo[e]pyrene (BeP), dibenz[a,h]anthracene, dibenz[a,c]anthracene, 3-methylcholanthrene, 7,12-dimethylbenz[a]anthracene, and benz[a]anthracene were studied using cyclic voltammetry, single potential step chronoamperometry, voltammetry at rotating disk electrodes, and controlled potential coulometry in tetrahydrofuran solution using 0.1 M tetra-n-butylammonium perchlorate as a supporting electrolyte. Results indicate that these compounds undergo ECE reactions to a final product reduced at L-regions of each PAH with the exception of BaP and BeP. For these two PAHs, unreduced hydrocarbons were identified after exhaustive electrolysis. Heterogeneous electron-transfer rate constants, as well as homogeneous reaction rate constants, for the addition of the proton to electrogenerated anion radicals are also reported.

The reduction of propyleneglycol dinitrate, nitroglycerin, dinitrotoluene, and trinitrotoluene on silver electrodes

The nitrate esters propyleneglycol 1,2-dinitrate and nitroglycerin, as well as the aromatic nitro compounds, dinitrotoluene and trinitrotoluene, are electrochemically reducible on silver electrodes. Concentrations as low as 0.5 mg l −1 are readily detectable at scan rates of 5 mV s −1 in unstirred solutions. Peak potentials vary with the nature of the electrolyte anion. The ortho, meta, and para isomers of dinitrotoluene yield different voltammograms; the ortho and para isomers show two reduction peaks but only a single peak is found for the three meta isomers. Constant-current, exhaustive electrolysis studies of 2,5-dinitrotoluene show two reduction stages, corresponding to three-electron and five-electron reductions.

The reduction of propylene glycol dinitrate and other related nitrate esters on silver electrodes

The electrochemical reduction of propylene glycol 1,2-dinitrate (PGDN) on solid electrodes is sensitive to the choice of the electrode material and is not detectable on many transition metals. The reduction of PGDN occurs readily at 100 mV s −1 on silver electrodes to give a peak potential that is independent of the pH, but varies with the nature of the electrolyte anion. Slower potential scan rates give a more sensitive detection of the nitrate ester, and concentrations as low as 0.5 ppm can be readily measured at 5 mV s −1 in unstirred solutions. The reduction of PGDN on silver is found to be a diffusion-controlled, irreversible reaction. Nitroglycerin (NG) and n-propyl nitrate (PN) show electrochemical responses similar to those observed for PGDN. Constant-current, exhaustive electrolysis experiments in stirred solutions show a four-electron reduction per PGDN molecule and a six-electron reduction for the NG molecule. Based upon the standard potential calculated for the reduction of simple nitrate esters: RONO 2+H 2O+2 e −→ROH+NO 2 −+OH −, these electrode reactions are characterized by high overvoltages. The transfer of the first electron involving breakage of the O−N bond is postulated to be the slow step in the reaction mechanism.

Electro-organic reactions. Part 13. The anodic acetoxylation of methyl oleate

Efficient anodic mono- and di-acetoxylation of methyl oleate is described. Acetoxylation is consecutive and conditions may be adjusted to give a maximum of either 60% monoacetoxylation or 85% diacetoxylation. Both mono- and di-substituted products are a complex mixture of isomers but the products of exhaustive electrolysis are mainly 9,10-diacetoxyoctadec-7- or -11-enoate. A mechanistic rationalisation is proposed.

A coulometric thin layer flow cell for trace amount detection and its application to adsorption studies

A flow cell assembly is described featuring ultra-low electrolyte flow propulsion rates (10 −5 to 10 −3 cm 3 s −1) in combination with a working electrode compartment of thin layer dimensions (thickness < 10 −2 cm), enabling thus the exhaustive electrolysis of electroactive species at a potential-controlled detector electrode. The cell can be used to detect trace amounts (>10 −12 mol) of electroactive species delivered into or withdrawn from the streaming electrolyte, such as compounds adsorbed at or desorbed from an ideally polarizable electrode, allowing the independent determination of Δ q- and Λ-isotherms of cation adsorbates. The flow cell has been used to study the adsorption of Tl on polycrystalline Ag in KCl solution. The isotherms obtained can be interpreted in terms of competitive Cl − adsorption within the Tl + adsorption range.

A coulometric thin layer flow cell for trace amount detection and its application to adsorption studies

A flow cell assembly is described featuring ultra-low electrolyte flow propulsion rates (10 −5 to 10 −3 cm 3 s −1 ) in combination with a working electrode compartment of thin layer dimensions (thickness < 10 −2 cm), enabling thus the exhaustive electrolysis of electroactive species at a potential-controlled detector electrode. The cell can be used to detect trace amounts (>10 −12 mol) of electroactive species delivered into or withdrawn from the streaming electrolyte, such as compounds adsorbed at or desorbed from an ideally polarizable electrode, allowing the independent determination of Δ q - and Λ-isotherms of cation adsorbates. The flow cell has been used to study the adsorption of Tl on polycrystalline Ag in KCl solution. The isotherms obtained can be interpreted in terms of competitive Cl − adsorption within the Tl + adsorption range.

Design of a new type of enclosed cell for rapid exhaustive electrodeposition of metal ions

Abstract A new type of an enclosed electrolysis cell has been developed for rapid exhaustive electrolysis of trace level metal ions. The cell was machined from plexiglass and houses a rotating tantalum auxiliary electrode, a silver‐silver chloride reference, in addition to a wax impregnated graphite working electrode. Rapid exhaustive depositions were obtained for copper in the parts‐per‐billion range with NaCl‐MgSO4 electrolyte. The tantalum auxiliary electrode circumvented the interference of soluble chlorine normally generated at auxiliary electrodes that attacks metal deposition films.

Controlled-potential electrolysis and the rates of homogeneous reactions

Abstract