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Artifacts in two-dimensional electrophoresis (2-DE) caused by the presence of salts in isoelectric focusing (IEF) have been previously described as a result of increasing conductivity and inducing electroosmosis. However, electrolysis induced by the presence of salts should not be disregarded. In this study, electrolytic reduction-oxidation reaction (redox) was found to be enhanced in the presence of salts in IEF. The consequence of the electrolytic redox leads to acidification of the low-pH region and alkalization of the high-pH region within the immobilized pH gradient (IPG) strip. As a result, a breakdown of immobilized pH buffer near the high pH region of IPG strips along with reduction of basic proteins resulted in uncharacterized artifacts in 2-DE. Electrolytic reduction in the presence of alkali and alkaline metal ions was demonstrated to reduce 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), protein disulfide bonds, and protein carboxylic acids. Importantly, semipreparative electrolytic reduction of proteins can be carried out in the presence of sodium ions in a homemade electrolytic apparatus. These findings give additional explanations to the observed artifacts in 2-DE and reveal the unknown effects of salts in IEF. Moreover, we have provided a method with the potential to convert proteins or peptides to corresponding modified products containing aldehyde groups that can be used for conjugation with amine-containing compounds.

In order to ensure a stable and efficient separation in microfluidic free-flow electrophoresis (FFE) devices, various methods and chips have been presented until now. A major concern hereby is the generation of gas bubbles caused by electrolysis and the resulting disturbances in the position of the separated analyte lanes. Instable lane positions would lead to a decreased resolution in sample collection over time which certainly would be problematic when incorporating a stationary detector system. In contrast to our previous publications, in which we implemented laborious semipermeable membranes to keep bubbles outside the separation region, here we describe an electrochemical approach to suppress the electrolysis of water molecules and therefore bubble formation. This approach allowed a simpler and additionally a closed chip device with integrated platinum electrodes. With the use of this chip, the successful separation of three fluorescent compounds was demonstrated. Quinhydrone, which is a complex of hydroquinone and p-benzoquinone, was added only to the local flow streams along the electrodes, preventing mixing with the separation media and sample. The electrical current was generated via the oxidization and reduction of hydroquinone and p-benzoquinone up to a certain limit of the electrical current without gas formation. The separation stability was investigated for the chip with and without quinhydrone, and the results clearly indicated the improvement. In contrast to the device operating without quinhydrone, a 2.5-fold increase in resolution was achieved. Furthermore, separation was demonstrated within tens of milliseconds. This chemical approach with its high miniaturization possibilities offers an interesting alternative, in particular for low-current miniaturized FFE systems, in which large and open electrode reservoirs are not tolerable.

pH-stating is a common technique for monitoring kinetics of various biochemical reactions that involve the generation of hydrogen or hydroxyl ions. In this work, we describe a reagentless electrochemical micro-pH-stat where the titrant of acid or base is produced by water electrolysis on the rotating sample system (RSS) platform. RSS originated from the authors' laboratory as a convective platform to support different analytical techniques in microliter-sized samples. As water electrolysis induces no volume change and the current that generates the reagent can be precisely measured even at low levels, very small samples in the microliter range become accessible for pH-stating: a reduction of more than an order of magnitude in specimen size relative to the most sensitive conventional methods. Nearly 100% current efficiency has been achieved with this system using a 250 [micro]m Pt minidisc working electrode for electrolysis. The developed micro-pH-stat has been validated by the determination of the activity of erythrocyte acetylcholinesterase as a function of substrate concentration and pH. The optimal pH and activity profile obtained are in good agreement with those determined with standard techniques. The micro-pH-stat has the potential for applications for enzyme assays, reagentless pH control, acidity/alkalinity, and buffer capacity measurements in very small samples of biomedical and environmental origin.

A specialized vacuum electrolysis reactor was designed, constructed, and utilized for 13-carbon isotope analysis of formic acid-13C and acetic [acid-sup.13]C, each highly enriched at the C1-position. This reusable reactor was equipped with two platinum wire electrodes, miniature stir bar, and sidearm reaction chamber. The associated technique developed for 13-carbon isotope analysis is based upon electrolytic generation of carbon dioxide into the preevacuated reactor followed by gas inlet mass spectrometry. It proved practical to degas and electrolyze 95% formic acid (without added electrolyte) due to adequate ionic conductivity. Formic [acid-sup.13]C (nominally 99 at. [%.sup.13]C) was measured by electrolytic C[O.sub.2] generation to be 98.9 at. % 13C. To analyze various [sup.13]C-isotopic permutations of acetic acid, lithium and acid were separately added to reactor compartments, vacuum degassed, and stirred to produce an acidic solution. Thus, acetic [acid-l-sup.13]C that was nominally 99 at. % [sup.13]C1 was determined by vacuum electrolysis to be 98.9 at. % [sup.13]C1. Further, acetic [acid-2-sup.13]C that was isotope depleted at the C1-position (and known to be 99 at. % [sup.13]C at C2) gave 0.8 at. % [sup.13]C by mass spectrometry.

Nickel(II) secochlorins, chlorophin and homoporphyrins are examined with reference to their electrochemical properties for the first time.The effect of macrocycle rigidity on electroreduction is presented.

Research was conducted to examine the electrolysis of Au(sub 145)(SC6)sub 50 monolayer-protected clusters (MPCs), wherein the cores throughout the solution have known quanta of double layer charge, as well as the application of the electronic charges in stoichiometrically quantified chemical reactions. Results indicate that electronic charges associated with double layer charges of MPCs can serve as a controllable and quantifiable way to drive electron transfer reactions.

The electrochemical oxidation and reduction of anthracene (AN) and thianthrene (TH) incorporated within pentasil and mordenite zeolites in the presence of H20 showed a distinctive pattern. This indicated that the electrochemically generated radical ions located at the outermost layers of the zeolite particles experienced an effective protection against the attack of external reagents. This effect was believed to arise from some degree of spatial constraints experienced by the guests adsorbed on the surface of microporous solids, suggesting partial penetration through pore entrances.

A study was conducted to analyze a way of preparing cyclopropanone N,O-acetals using an electrochemical method and a number of transformations of the resulting products under acidic conditions. Electrolyses were performed in a divided cell using a platinum anode. The enamines were electrolyzed under a constant current until the 2F/mol of charge had passed through the cell. Moreover, 1H and 13C nuclear magnetic resonance spectra were obtained at 90 and 22.4 MHz, respectively.

Polycrystalline diamonds have the requisite surface structure and chemical composition needed to support and sustain the polyamine oxidation reaction. This was gleaned from the results of an investigation of the oxidation of five polyamines at polycrystalline, boron-doped, diamond thin-film electrodes via cyclic voltammetry and flow injection analysis with amperometric detection. A scheme for polyamine oxidation at diamond that is similar to the model for anodic oxygen-transfer reactions is also presented.

New methodology for the measurement of electrogenerated chemiluminescence (ECL) has been developed by using a dual-electrolysis stopped-flow system. Using this method, the ECL from 'energy-sufficient' systems composed of different kinds of ion radicals can be easily observed by mixing both the electrolyzed solutions directly. The apparatus and method have been described in detail as well as the ECL observations for various energy-sufficient systems. In particular, in the reaction between the thianthrene (TH) cation radical and the pyrene (PY) anion radical, it was found that the emission spectra changed with the addition of the precursors, reflecting both complex electron- and energy-transfer processes in solution. The present results indicate that the electron- and energy-transfer reactions changed significantly, depending on the type of molecules. The ECL observation with the addition of the third molecule was also informative to compare the ease of the formation of the excited states. It was clarified that the excited states of 9,10-diphenylanthracene and rubrene are easily formed compared with those of TH and PY.

Research was conducted to examine the electrooxidative inter- and intramolecular carbon-carbon bond formation using organothio groups as electroauxiliaries. The objective was to show that the anodic oxidation of alpha-organothio-substituted ethers in the presence of carbon nucleophiles leads to the bond formation. Results demonstrate the generality of the concept of electroauxiliary and its possible use in the control of stereochemistry.

Studies show that the three (Me3[9]aneN3)MoIIIX3 complexes phosphoresce and undergo photooxidation in solution at room temperature. C(NO2)4 was also found to promote the permanent one-electron photooxidation of (Me3[9]aneN3)MoIIIBr3 and (Me3[9]aneN3)MoIIII3. In the presence of water, disproportionation of photogenerated MoIV intermediates promotes the two-electron oxidation of the complexes.

The electrochemical reductions of cyclooctatetraenes (COT) and their derivatives were studied in terms of the heavier carbon group substituents. The order of the reduction was difficult in the order of Si

The construction and characterization of a nitrate reductase-based amperometric electrode for determination of nitrate ion is described. The electrode consisted of nitrate reductase held by dialysis membrane onto a Nation-coated glassy carbon electrode. Methyl viologen was allowed to absorb into the Nation layer, which acted as a reservoir for the electron mediator. The utility of the electrode to assay fertilizer and water sample for nitrate was demonstrated. The assays conducted with this electrode compared well with colorimetric and potentiometric assays of the same samples.

The positioning of the capillary relative to the electrode in the electrolyte vial and buffering of the background electrolyte (BGE) in capillary zone electrophoresis have been found to have a crucial influence on the magnitude of pH changes of the BGE in the separation capillary. Oncapillary measurement of the pH changes was accomplished by adding a suitable pH indicator dye to the BGE and employing absorbance detection in the visible region. This method has been demonstrated using xylenol blue in a chromate BGE commonly used for anion analysis (pH 8.0) and bromocresol green in an acetate BGE (pH 4.8). Using the chromate BGE, high pH changes of more than 2.5 pH units were observed when the capillary end was positioned close to the electrode surface in the inlet electrolyte vial, but changes of less than [+ or -]0.3 pH unit resulted if the capillary end was displaced at least 1 mm laterally from the electrode and/or at least I mm vertically below the electrode end. These effects were explained by direct observations of pH changes around a platinum electrode placed in a photometric cell serving as a BGE reservoir. These observations showed a zone of altered pH being generated close to the electrode and spreading over time through the surrounding BGE by thermal convection. Further, a simple way of buffering the chromate electrolyte with a suitable cation (Tris) is presented, with the buffered electrolyte showing pH fluctuations in the capillary of less than [+ or -]0.2 pH unit. Practical implications of these findings on the practice of capillary zone electrophoresis are discussed.

The kinetic and mechanistic properties of the oxidation of three hexosamines, D-mannosamine, D-glucosamine and D-galactosamine by CAB in alkaline medium at 40 degrees C are presented. Results indicate that oxidation occurs through the cleavage of both C-H and C-C bonds to form a mixture of aldonic acids from the hexosamines. Based on experimental data, a new pathway for the oxidation of hexosamines by CAB is proposed.

Voltammetric data obtained at a rotated ring - disk electrode for oxidation of dimethyl sulfoxide (DMSO) to dimethyl sulfone support the conclusion that anodic O-transfer and [O.sub.2](aq)-evolution reactions are in competition for a common reaction precursor. That species is concluded to be the adsorbed OH radical generated by anodic discharge of [H.sub.2]O. Because of this competition, an increase in the flux of the reactant in the O-transfer reaction causes a decrease in the rate of [O.sub.2](aq) evolution. Therefore, difference voltammetry and hydrodynamically modulated voltammetry cannot be considered reliable for accurate deconvolution of the total electrode current resulting from these concomitant processes. A simple mathematical model is developed to describe the total current resulting from these simultaneous processes, and results of preliminary tests of this model are in good agreement with experimental data for DMSO oxidation.

Three modes of selectivity based on charge-selective partitioning, electrolysis potential, and spectral absorption wavelength were demonstrated simultaneously in a new type of spectroelectrochemical sensor. Operation and performance of the three modes of selectivity for detection of analytes in the presence of direct interferences were investigated using binary mixture systems. These binary mixtures consisted of Fe[[(CN).sub.6].sup.3-] and Ru[[(bpy).sub.3].sup.2-] and of Fe[[(CN).sub.6].sup.4-] and Ru[[(CN).sub.6].sup.4-] in aqueous solutions. Results on the Fe[[(CN).sub.6].sup.3-]/Ru[[(bpy).sub.3].sup.2-] binary mixture showed that an anion-exchange coating consisting of PDMDAAC-Si[O.sub.2] [where PDMDAAC is poly(dimethyldiallylammonium chloride)] and a cation-exchange coating consisting of Nafion-Si[O.sub.2] can trap and preconcentrate analytes with charge selection. At the same time, such coatings exclude interferences carrying the same type of charge as that of the exchange sites in the sensor coating. Using the Fe[[(CN).sub.6].sup.4-]/Ru[[(CN).sub.6].sup.4-] binary mixture, the Fe[[(CN).sub.6].sup.4-] component can be selectively detected by restricting the modulation potential cycled to a range specific to the redox-active Fe[[(CN).sub.6].sup.4-] component and simultaneously monitoring the optical response at the overlapping wavelength of 420 nm. It was also shown that, when the wavelength for optical monitoring was chosen as 500 nm, which is specific to the Ru[[(CN).sub.6].sup.4-] component, interference from the Fe[[(CN).sub.6].sup.4-] component for spectroelectrochemical detection of Ru[[(CN).sub.6].sup.4-] was significantly suppressed, even though the cyclic modulation potential encompassed the redox range for the Fe[[(CN).sub.6].sup.4-] component.

Electrochemical reduction leads to a dimer in the case of the cis(Cl) isomer, while the trans(Cl) isomer prompts the formation of a polymeric film of [Ru(bpy)(CO)2]n. The presence of a single chloride ligand in a mixed trans-(chloro/ester) complex also leads to the creation of a similar dimer. The dimers show very strong electrocatalytic activity toward CO2 reduction. They have intense coloration and characteristic spectroscopic properties.

An exact treatment derives the steady-state limiting current of a one-electron reduction for the N [in equilibrium] [O.sup.+] + [A.sup.-] mixture at a hemispherical microelectrode. Either or both of the neutral N and cationic [O.sup.+] species may be electroactive. A supporting salt is present at any concentration, including zero or excess; its ions are electropassive and do not interact with the other solutes or each other. The various species are treated as having distinct diffusivities, linked to their mobilities through the Nernst-Einstein relationship. Universal electroneutrality is assumed. The predictions of the model are compared with published experimental data on the reduction of aqueous weak acids; agreement is excellent at intermediate, but poor at low, support ratios. Analysis of the unsupported case shows that the neutral N species dissociates in a narrow zone close to the electrode, and the injection of ions there serves to increase the electric field in the outer region of the transport zone. This enhances cationic migration enormously, leading to an unsupported limiting current that is much more than double the supported value. However, the limiting current is drastically diminished by traces of foreign electrolyte. Curiously, the limiting current with full support adopts the same value when equilibration is fast as when it is very slow, although the mechanisms are totally different.

Gas chromatography and infrared spectroelectrochemistry were employed to observe the electrocatalytic reduction of carbon monoxide by the hexafluorophosphate salt and tetraphenylborate salt of the binuclear complex (Ir2(dimen)4)2+. The reaction, which proceeds via several pathways depending on the conditions, yielded formate and bicarbonate as the major products of the reduction of CO2 and residual water, respectively.

A single irreversible cyclic voltammetric wave that corresponds to the two-electron cleavage of the carbon-halogen bond was observed for each compound in the electrochemical reduction of several mono- and dihalothiophenes at carbon cathodes in dimethylformamide containing tetramethylammonium perchlorate. The reduction of dihalothiophenes exhibited a stepwise trend.The first stage of the reduction involves two-electron cleavage of one carbon-halogen bond to yield mixtures of mono- and dihalothiophenes, while the second stage corresponds to an overall four-electron process to give thiophene. An electrolytically induced halogen dance appear to generate product distributions during electrolyses.

Dihydroxybenzaldehyde (DHB) isomers can be oxidatively electrodeposited onto glassy carbon electrodes previously activated in base solution. We have studied the mechanism of such electrodeposition as well as the electrochemical features of films derived from 2,3-DHB, 3,4-DHB, 2,5-DHB, and 2,4-DHB isomers as well as related analogs including 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, and 4-nitrocatechol. The electrodeposition process and the electrochemical behavior of the modified electrodes were strongly dependent on pH as anticipated for quinone/hydroquinone functionalities. Glassy carbon electrodes modified with films derived from 2,3-DHB and 3,4-DHB exhibit catalytic activity in the electrooxidation of NADH. The catalytic currents are proportional to the concentration of NADH over the range 0.01-1.2 and 0.01-0.9 mM for films derived from 3,4-DHB and 2,3-DHB, respectively. These modified electrodes can be used in the design of biosensors based on coupled dehydrogenase enzymatic activities.

Carbon-carbon (C-C) bond-forming reactions in microemulsions and in DMF were investigated. The Co(I)L complex vitamin B12 mediated the reactions of alkyl iodides with 2-cyclohexen-1-one and the cyclization of 2-(4-bromobutyl)2-cyclohexen-1-one to 1-decalone. The Co(I)L complex reacted with alkyl halides to produce a Co-alkyl complex. A comparison of the C-C bonds formed following the cleavage of the Co-alkyl complexes revealed wide variations in selectivity. The cyclization reaction in a microemulsion gave remarkable stereoselectivity in comparison with the other reactions.

A method is presented for utilizing the unique characteristics of a pair of microband electrodes to initiate and study the products of a paired electrosynthesis employing short-lived species. The oxidation of anthracene is combined with the simultaneous reduction of dioxygen in acetonitrile to produce the anthracene radical cation and the superoxide anion. The cation and the anion react with a femtoliter scale volume to yield initially 9,10-dihydro-9,10-epidoxyanthracene, which rearranges into 9,10-anthracenedione and dihydrogen by electron transfer catalysis.

Growth hormone releasing peptide (GHRP, sequence His-D-Trp-Ala-Trp-D-Phe-Lys-N[H.sub.2]) is a synthetic hexapeptide under consideration for transdermal iontophoretic drug delivery. Cyclic voltammetry, controlled-potential electrolysis, HPLC/UV analysis, LC/MS/MS analysis, and EPR spin-trapping studies indicate that the electrolysis-induced oxidative degradation of GHRP is likely to be mediated by electrogenerated oxygen radicals from the electrolysis of water. Within 2 h and up to 2.5 V versus an Ag/AgCl reference electrode, the peptide backbone remains largely intact. The chemical modifications are selectively on imidazole (histidine) and indole (tryptophan). Strategies for alleviating the electrolysis-induced degradation of GHRP are proposed.

Lithium aluminum hydride reduces the addition product formed between diethyl vinylphosphonate and primary phosphines to prepare small organophosphine dendrimers containing 12 and 15 phosphorus atoms. 31P NMR spectroscopy helps characterize the dendrimers. Metalated dimers formed by the reaction between these dendrimers and (Pd(CH3CN)4)(BF4)2 catalyze the electrochemical reduction of CO2.

Examination of the electrophilic addition of bromine to benzonorbornadiene at different temperatures reveals that at low temperatures the addition reaction produces 2-eno-7-anti-dibromide, while the reaction at higher temperatures produces non-arranged and rearranged products in a ratio of 8:2. Presence of a free radical inhibitor inhibits the formation of non-arranged products, revealing a competition between radical and ionic reactions. Benzonorbornadiene on electrolysis produces 2,7-disubstituted benzonorborn-5-ene derivatives.

Microscopical Monte Carlo simulations of electrochemical reduction of alkyl halides in water indicate that a straight forward application of linear response approximation is not valid for dissociative electron transfer reactions in solution. The validity of Marcus' relationship depends on the solute internal potential energy. Control field theorem supports the applicability of Marcus' relationship to outersphere electron transfer reactions.

The effect of following chemical reactions during chronoamperometry and cyclic voltammetry at microelectrodes has been evaluated by digital simulation and the results have been compared to experiments. This study was motivated by the demonstrated utility of microelectrodes to monitor catecholamine secretion from individual biological cells. Since following chemical reactions can increase the total number of coulombs passed, such an occurrence can affect the calibration of the measured response. However, at microelectrodes, products formed by chemical reactions after electron transfer are less likely to return to the electrode because of the divergent diffusion field that can exist at electrodes of small dimensions. The degree to which these effects are apparent has been evaluated quantitatively by digital simulation of the DISP1 scheme for a disk-shaped electrode. The predictions of the simulation are verified in an experimental study of the anodic oxidation of diphenylanthracene in acetonitrile containing pyridine. In contrast, the DISP1 reaction of catecholamines at carbon-fiber microelectrodes exhibits much less enhanced current than predicted by theory. The experimental data suggest this is due to the heterogenous nature of the carbon surface with respect to electron transfer. Thus, for most applications of carbon-fiber microelectrodes as sensors of catecholamine secretion from cells, the effect of the DISP1 reaction can be ignored.

Examination of the catalytic ability of three copper-phenanthroline complexes adsorbed on graphite electrodes toward electroreduction of dioxygen reveals that all three complexes catalyze the four-electron reduction of oxygen. Adsorbed complexes having Cu with a single ligand coordination exhibit more catalytic ability than complexes having two coordinated ligands at the Cu center. Kinetic studies reveal the coordination of O2 to the Cu(I) form of the complexes as the rate-determining step, and the kinetic behavior of the complexes adsorbed on graphite electrode is different from that of the complexes in solution.

A 0.29-mm-diameter flexible electrode designed for subcutaneous in vivo amperometric monitoring of glucose is described. The electrode was designed to allow 'one-point' in vivo calibration, i.e., to have zero output current at zero glucose concentration, even in the presence of other electroreactive species of serum or blood. A valid zero point, along with a measurement of the glucose concentration in a withdrawn sample of blood at which the current is known, defined the sensitivity in the linear response range. The electrode was four-layered, with the layers serially deposited within a 0.125-mm recess upon the tip of a polyimide-insulated 0.25-mm gold wire. The recessed structure reduced the sensitivity to movement and allowed, through control of the depth of the recess, control of the transport of glucose and thus the range of linearity. The recess contained the four polymeric layers, with a total mass less than 5 [[micro]gram] and no leachable components. The bottom glucose concentration-to-current transducing layer consisted of the enzyme 'wiring' redox polymer [poly[(vinylimidazole)Os[(bipyridine).sub.2]Cl].sup.+/2+], complexed with recombinant glucose oxidase and cross-linked with poly (allylamine), on which an immobilized interference-eliminating horseradish peroxidase based film was deposited. An outer biocompatible layer was formed by photo-cross-linked poly(allylamine), on which an immobilized interference-eliminating horseradish peroxidase based film was deposited. An outer biocompatible layer was formed by photo-cross-linking derivatized poly(ethylene oxide). The current output of a typical electrode at 10 mM, glucose and at 37 [degrees] C was 35 nA, the apparent [K.sub.m] was 20 mM, and the 10-90% response time was [approximately] 1 min. The sensitivity varied only by [+ or -] 5% over a 72-h test period. The electrode tracked the blood glucose concentration in a rat model before, during, and following intraperitoneal glucose infusion. Two failure modes were observed. The first, deactivation of hydrogen peroxide-producing lactate oxidase in the interference-eliminating layer, resulted in inadequate preoxidation of interferants. The second was an abrupt drop in the sensitivity of implanted electrodes, [approximately] 7 h after implantation. The failed electrodes promptly regained their sensitivity in buffer.

The adsorption of multiply charged, heteropolytungstate anions on mercury electrodes is extraordinarily strong. For the chromium(III)-substituted anion, [[Alpha].sub.2]-[[[P.sub.2][W.sub.17][O.sub.61]Cr(O[H.sub.2])].sup.7-], the mercury surface is half-saturated at concentration of the heteropolyanion of only 5 X [10.sup.-9] M. In the presence of the adsorbed anions, the rate of reduction of the unadsorbed heteropolytungstates in solution is greatly diminished. The decreased reduction rates appear to result from increases in the negative diffuse layer potentials produced by the anion adsorption. The spontaneous adsorption of heteropolytungstates on mercury may prove useful in their electroanalysis at very low levels and in electrocatalytic applications.

The anion-sensitive membrane electrodes based on lipophilic metalloporphyrin derivatives [(FeTPP).sub.2]O show similar anti-Hofmeister selectivity sequence: [SCN.sup.-] > [I.sup.-] > Cl[[O.sub.4].sup.-] > N[[O.sub.2].sup.-] > [Br.sup.-] > [Cl.sup.-] > N[[O.sub.3].sup.-]. The electrode with an optimum membrane composition has a linear response for [SCN.sup.-] between [10.sup.-6] and [10.sup.-1] mol/L, with a slope of 53.0 mV/p-[SCN.sup.-] (25 [degrees] C). The origin of the anti-Hofmeister response characteristics has been discussed in view of the coordination chemistry of the metalloporphyrins. The interaction mechanism between [(FeTPP).sub.2]O and [SCN.sup.-] is studied by UV/vis and IR spectroscopy. The transfer process of [SCN.sup.-] across the membrane interface is investigated by ac impedance measurements.

Oxidation of ferrocene in acetonitrile resulted in films on Pt electrodes under voltammetric conditions. Films were more readily formed with tetrabutylammonium tetrafluoroborate as the electrolyte than with perchlorate salts. No films were detected when ferrocene was oxidized in aqueous 0.05 M cetyltrimethylammonium bromide (CTAB). Analysis of the films by FT-IR and Auger spectroscopy confirmed iron-containing oxidation products on Pt, presumably from chemical reactions of ferricinium ions. Oxidation of 50-100 mM ferrocene in acetonitrile on Pt yielded insoluble precipitates. Analyses by MS, FT-IR, and UV-visible (water extract), suggested a mixture of oligomeric material and a small fraction of ferricinium ions. Film formation had much less influence on voltammograms on 12.5-micrometer-radius Pt microdisks than on 0.5-mm-radius Pt. This is consistent with the smaller sensitivity of microelectrodes to chemical reactions following charge transfer. The smaller apparent heterogeneous rate constants (k convolution prime) found for ferrocene on macroelectrodes than on microelectrodes could possibly be influenced by film formation on larger Pt electrodes. Correlations between macro- and microelectrode kinetic data suggest that macroelectrode k convolution prime values may be valid in a relative sense when ohmic drop is negligible. Bias in k convolution primes on conventional-sized electrodes should be small in solutions giving minimal film formation, such as micellar CTAB.

A straightforward and accurate procedure has been developed for the quantitation of volatile products that are formed from electrolyses of organic compounds. This methodology, which eliminates the need for external cold traps, utilizes an internal standard that is present in both the solution and gas phases of a gas-tight electrochemical cell. By sampling the gas and solution phases of the cell at the end of an electrolysis and by using gas chromatography to determine the quantities of the various volatile products in each phase with respect to the internal standard, one can ascertain the absolute yield of each product derived from the electrolysis of the starting material. In this paper, we present the theoretical background for this technique, including the formulation and use of experimentally measured gas chromatographic response factors, and we demonstrate the applicability of the approach for the quantitation of seven volatile products that are formed by the electrolytic reduction of 1,4-dibromobutane at a reticulated vitreous carbon cathode in dimethylformamide containing tetramethylammonium perchlorate. This method can be readily adapted to any compound whose electrolysis gives rise to volatile products.

The reaction of complex cis-(Os(bpy)2(CO)H)+ (bpy = 2,2'-bipyridine) and some related complexes with CO2 in acetonitrile was investigated. The twice- reduced form of the osmium complex was found to be reactive with CO2. Cyclic voltammograms showed a greater current-CO2 concentration proportionality than with H2O. The kinetics of reduction of CO2 by related complexes showed a current increase upon reduction in the bpy wave. Two pathways resulted in the formation of separate intermediates.

The frozen solutions of singly, doubly and triply reduced C60 anions in benzonitrile, dichloromethane, pyridine and tetrahydrofuran solvents have been subjected to ESR spectroscopic analysis. The results reveal that the C60 anions feature ESR resonances with linewidths and g values that facilitate direct recognition of the reduced states of the anion. Moreover, the mono- and trianion have ESR spectral linewidths that increase as a function of temperature.

The anodic oxidation of aryl substituted ketene imines takes a course nearly opposite that of the analogous chemical-based process. In the presence of protons, almost quantitative amounts of amides are formed. As the condition becomes increasingly dry, the amide yield gives way to bicyclic, tricyclic and tetracyclic dimerization and trimerization products, along with the formation of stable carbocations. Several possible mechanisms, including intramolecular radical and electrophilic attacks to effect ring closure or formation, are discussed.

The synthesis of alpha-acetoxy-3,3,3-trifluoropropyl sulfides provides the material for a study of their nucleophilic substitution reactions at the beta position. Acetoxylation is achieved by electrochemical means under very high substrate and electrolyte strengths. The subsequent study shows that nucleophilic attack on the beta position, otherwise difficult because of sulfur's stabilization of the nearby carbocation, proceeds efficiently with the use of electrogenerated acids rather than ordinary Lewis acids.

Sodium benzophenone in solution allows controlled room-temperature reduction of three perfluorocycloalkanes to perfluoro and polyfluoro aromatics. Other perfluorocycloalkanes either are overreduced or yield low reduction products, with substrates bearing tertiary carbons being the most reactive. Electrochemical studies show that selectivity and reaction rates are determined by the reduction potentials of the substrate, the reducing agent and the product. Optimum results are obtained when the reduction potential decreases in that order.

The (Mo2Fe6S8 SEt 9 3-)-catalyzed alpha-keto acid conversion of thioesters of the type RC(O)SEt via carbon dioxide fixation through the application of controlled potential electrolysis was studied. Analysis of the products revealed that H2O and excess EtS anions hindered the progress of the reaction. Furthermore, strong acylating agents decomposed the catalyst and prevented ester anion formation. A possible mechanism of the electrochemical carbon fixation reaction was theorized and presented.

Seven Ni(I)- and Ni(II)-CO2 complexes considered as possible models of the electrocatalytic reduction of CO2 using NiCl2(cyclam) were subjected to ab initio molecular orbital/SD-CI calculations. Data showed that CO2 reacted with Ni(I)F(NH3)4 to form the Ni(I)F(NH3)4(n1-CO2) complex which had an O p(pi) orbital-based highly occupied molecular orbital. However, CO2 failed to react with (Ni II F NH3 4)+, (Ni I NH3 4)+ and (Ni I NH3 5)+.

The electrochemical analysis of iron(2) complexes of 2,2'-bipyridine, 2,2'-bipyrimidine, 1,10-phenanthroline and 2, 2':6',2''-terpyridine showed that all the complexes undergo a three-step one-electron reversible reduction except for terpyridine complexes which involve a two-step one-electron reduction. Moreover, all the four complexes featured a single one-electron reversible oxidation with electrochemical potentials ranging from +0.785 to +1.036. In addition, the application of ultraviolet-vis-near-infrared spectroscopy in the examination of the products provided reliable results.

The complete conversion of L-lactate into D-lactate is undertaken by making full use of the stereospecificity of L-lactate dehydrogenase with the electrochemical regeneration of NAD+ at the anode and the electrochemical reduction of pyruvate at the cathode. The conversion process is kinetically controlled via the rate of pyruvate reduction. The method may be extended to the deracemization or complete conversion of all types of chiral alpha-alcohol-acids, as long as the dehydrogenase corresponding with the isomer to be inverted is available.

2-oxomorpholyn-3-yl (TM-3 and DEM-3) dimers undergo symmetric bond cleavage to yield their corresponding monomer radicals that serve as reducing agents for the viologens propyldiquat and paraquat. The homolysis produces oxazinone and oxazinonium byproducts, the latter being reduced further to oxomorpholine. The equilibrium dynamics for theviologen radicals as well as their reduction potentials establish the corresponding reduction potentials for the dimers. The kinetics of reduction, along with a comparative study of the two reducing agents with dithionite, are discussed.

Isostructural layered oxyhydroxides result from the anodic oxidation of the layered hydroxides of the pyroaurite-type. Anions and H2O molecules are interjected between the layers to neutralize the charges. Oxidation of the cobalt cation influences the size of the interlayers and unit cell dimensions. The cations exist in oxidation states of +4 or more, but are reduced to lower oxidation states on heating. When phase transition occurs, they may exist in trivalent states.