No abstract available. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2001.

Thesis (Ph. D.)--University of Washington, 2005. / Vita. Includes bibliographical references (p. 116-121).

This is a study involving some of the chemistry of osmium tetroxide in perchloric acid solution. The research was originally instigated from a seminar report on the ruthenium III thiocyanate complex ion which was studied in perchloric acid solution. The seminar report given by Craig Townsend discussed how a spectrophotometric study by Yaffe and Voight (1951) was made of the ruthenium III thiocyanate complex ion, Similar possibilities were recognized as being possible in attacking the problem of an osmium thiocyanate complex or complexed. Some of the chemistry involved in the study of the ruthenium III thiocyanate complex will be discussed later. It will now suffice to say that the complex was studied by reacting ruthenium IV perchlorate and sodium thiocyanate to produce the complex ion. Townsend (1953), following the general procedure of Yaffe and Voight, took osmium tetroxide and sodium thiocyanate in a perchloric acid solution and reacted them to produce a rose colored osmium thiocyanate complex ion. He then determined a general formula and a value for the dissociation constant for the complex. Many problems were encountered in the Townsend study; and, therefore, there was reason for further study along these same lines. Some of the general characteristics of osmium and its related elements will be noted first.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Bibliography: leaves 190-192. / by James Edwin Garmirian. / Ph.D.

Platinum-gold and nanoceria-modified platinum-gold electrodes were prepared on a platinum surface via electrochemical reduction of solutions of platinum and gold salts in the dispersion of nanoceria. The molar ratios of Pt and Au were varied in both PtAu and PtAu/CeO₂ electrodes while the total concentration of the metals was maintained at 2 x 10⁻³M and the concentration of nanoceria was maintained constant at 5 x 10⁻³M. The electrodes were characterized by their cyclic voltammetry curves in 0.5M sulfuric acid solution. The electrochemically active area of the electrodes was determined using the copper underpotential deposition method. The linear sweep voltammograms of the PtAu and PtAu/CeO₂ electrodes were plotted from -1V to 0V vs. Ag/AgCl, 3M KCl reference electrode using the rotating disk electrodes for the rotation speeds from 200 to 3600rpm in an oxygen saturated 0.1M sodium hydroxide solution. The values of the kinetic controlled current density were determined from the rotating disk voltammetry. The values of the limiting current density for each rotation speed were used to plot the Koutecky-Levich plots for the electrodes. The rate constants were obtained from the Koutecky-Levich plots for each composition of the electrode. The values of kinetic current density and the rate constants indicated that the addition of Au enhances the ORR rates in both the PtAu and the PtAu/CeO₂ electrodes. The values of the kinetic current densities of the PtAu/CeO₂ were lower than that of the PtAu electrodes owing to the poor electrical conductivity of ceria. The Koutecky-Levich plots for the PtAu and the PtAu/CeO₂ electrodes are linear for the four-electron reduction of oxygen in the alkaline media, which indicates that the overall reaction follows the first order kinetics. The electron transfer rate constants obtained from the Koutecky-Levich plots for the PtAu and the PtAu/CeO₂ electrodes both were found to increase in values with the addition of Au. The Tafel plots were plotted for the PtAu and PtAu/CeO₂ electrodes and the values of Tafel slopes were found to be in a small range for lower amounts of Au which indicated that the ORR rates were enhanced in lower amounts of Au. The values of Tafel slopes were found to be much higher for the ceria-modified PtAu electrodes as compared to the PtAu electrodes, which indicate the lower rates of ORR after the modification with ceria. Also, the ORR rates for the electrodes with smaller amounts of Au in PtAu/CeO₂ were higher than those in the larger amounts of Au.

A presente tese fornece uma revisão bibliográfica dos trabalhos mais importantes sobre as reduções catódicas e anódicas do grupo carbonila em aldeídos, cetonas, dicetonas, cetonas α, β-insaturadas, cetoácidos, cetoésteres, e ésteres α, &#946 -insaturados. São descritas as sínteses por nós efetuadas de 13 hidroxi e cetoésteres metílicos, a saber: mandelato , 4-carbometoxi, 4-cloro, 4-nitro e 4-metoximandelatos, α-fenil-β-hidroxibutirato, fenilglioxilato, 4-carbometoxi, 4-cloro, 4-nitro e 4-metoxifenilglioxilatos,benzilpiruvato e piruvato. A pureza desses compostos foi testada por meio de espectroscopia no I.V .e R.M.N., cromatografia de gás ou em camada delgada e, em alguns casos, por análise elementar. 4-nitrofenilglioxilato, 4-carbometoxifenilglioxilato e 4-carbometoximandelato, compostos ainda não descritos na literatura, foram caracterizados e analisados. O trabalho fornece as eletrólises, com eletrodos de platina em metanol, de 10 cetoésteres que incluem, além dos acima enumerados, o α -cetobutirato de metila, 4-cetopimelato de etila e o cetomalonato de etila. Os produtos de reação obtidos foram identificados por métodos cromatográficos e espectroscópicos. São apresentadas dois tipos de experiências eletrolíticas: as simples e as que foram acompanhadas em tempos periódicos pela análise cromatográfica, sendo as primeiras, em alguns casos, repetidas, variando-se o tempo da eletrólise. Os resultados obtidos demonstram que são reduzidos aos hidroxiésteres correspondentes os seguintes cetoésteres contendo anel aromático: fenilglioxilato, 4-cloro e 4-carbometoxifenilglioxilatos e benzilpiruvato, como também, os 2 cetoésteres alifáticos -α -cetobutirato e piruvato. Entretanto, verifica-se que tanto 4-nitro e 4-metoxifenilglioxilatos como cetomalonato e 4-cetopimelato não sofrem redução. Estes resultados comparados com os anteriores do nosso laboratório, permitem sugerir a seguinte ordem de velocidade da redução: α -cetovalerato > α-cetobutirato > piruvato > fenilglioxilato) > 4-clorofenilglioxilato > 4-carbometoxifenilglioxilato. São fornecidas provas de que a falta de reatividade de 4-nitrofenilglioxilato e cetomalonato e a diminuição de reatividade de 4-cloro e 4-carbometoxifenilglioxilatos, como também, de piruvato são devidas à existência do equilíbrio cetoéster-semiacetaléster nestes compostos, em metanol. Finalmente, é apresenta.da uma discussão do mecanismo da redução de cetoésteres que justificaria a diminuição de reatividade de fenilglioxilato em relação aos α-cetoésteres alifáticos e a falta de reatividade. de 4-cetopimelato e 4-metoxifenilglioxilatonilglioxilato. / The present work describes the syntheses of some aliphatic and aromatic α-hydroxy - and α-keto-methyl esters and reports the electrolyses of the latter, in methanol, at a platinum cathode Some simple electrolytic experiments, varying the experimental conditions as well as those in which the transformations occurring during the electrolyses were followed by gas chromatography, are described. The reactivities towards cathodic reduction are reported and the following order of the relative rate for the reduction is suggested: α-oxovalerate > α-oxobutyrate > pyruvate> phenylglyoxylate > 4-chlorophenylglyoxylate > 4-methoxycarbonylphenylglyoxylate .No reduction is found to occur with 4-methoxyphenylglyoxylate 4-nitrophenylglyoxylate or 4-oxopymelate .An explanation for these differences in reactivities is suggested on the basis of electronic effects, steric inhibition of coplanarity, and hemiacetal formation

A presente tese fornece uma revisão bibliográfica dos trabalhos mais importantes sobre as reduções catódicas e anódicas do grupo carbonila em aldeídos, cetonas, dicetonas, cetonas α, β-insaturadas, cetoácidos, cetoésteres, e ésteres α, &#946 -insaturados. São descritas as sínteses por nós efetuadas de 13 hidroxi e cetoésteres metílicos, a saber: mandelato , 4-carbometoxi, 4-cloro, 4-nitro e 4-metoximandelatos, α-fenil-β-hidroxibutirato, fenilglioxilato, 4-carbometoxi, 4-cloro, 4-nitro e 4-metoxifenilglioxilatos,benzilpiruvato e piruvato. A pureza desses compostos foi testada por meio de espectroscopia no I.V .e R.M.N., cromatografia de gás ou em camada delgada e, em alguns casos, por análise elementar. 4-nitrofenilglioxilato, 4-carbometoxifenilglioxilato e 4-carbometoximandelato, compostos ainda não descritos na literatura, foram caracterizados e analisados. O trabalho fornece as eletrólises, com eletrodos de platina em metanol, de 10 cetoésteres que incluem, além dos acima enumerados, o α -cetobutirato de metila, 4-cetopimelato de etila e o cetomalonato de etila. Os produtos de reação obtidos foram identificados por métodos cromatográficos e espectroscópicos. São apresentadas dois tipos de experiências eletrolíticas: as simples e as que foram acompanhadas em tempos periódicos pela análise cromatográfica, sendo as primeiras, em alguns casos, repetidas, variando-se o tempo da eletrólise. Os resultados obtidos demonstram que são reduzidos aos hidroxiésteres correspondentes os seguintes cetoésteres contendo anel aromático: fenilglioxilato, 4-cloro e 4-carbometoxifenilglioxilatos e benzilpiruvato, como também, os 2 cetoésteres alifáticos -α -cetobutirato e piruvato. Entretanto, verifica-se que tanto 4-nitro e 4-metoxifenilglioxilatos como cetomalonato e 4-cetopimelato não sofrem redução. Estes resultados comparados com os anteriores do nosso laboratório, permitem sugerir a seguinte ordem de velocidade da redução: α -cetovalerato > α-cetobutirato > piruvato > fenilglioxilato) > 4-clorofenilglioxilato > 4-carbometoxifenilglioxilato. São fornecidas provas de que a falta de reatividade de 4-nitrofenilglioxilato e cetomalonato e a diminuição de reatividade de 4-cloro e 4-carbometoxifenilglioxilatos, como também, de piruvato são devidas à existência do equilíbrio cetoéster-semiacetaléster nestes compostos, em metanol. Finalmente, é apresenta.da uma discussão do mecanismo da redução de cetoésteres que justificaria a diminuição de reatividade de fenilglioxilato em relação aos α-cetoésteres alifáticos e a falta de reatividade. de 4-cetopimelato e 4-metoxifenilglioxilatonilglioxilato. / The present work describes the syntheses of some aliphatic and aromatic α-hydroxy - and α-keto-methyl esters and reports the electrolyses of the latter, in methanol, at a platinum cathode Some simple electrolytic experiments, varying the experimental conditions as well as those in which the transformations occurring during the electrolyses were followed by gas chromatography, are described. The reactivities towards cathodic reduction are reported and the following order of the relative rate for the reduction is suggested: α-oxovalerate > α-oxobutyrate > pyruvate> phenylglyoxylate > 4-chlorophenylglyoxylate > 4-methoxycarbonylphenylglyoxylate .No reduction is found to occur with 4-methoxyphenylglyoxylate 4-nitrophenylglyoxylate or 4-oxopymelate .An explanation for these differences in reactivities is suggested on the basis of electronic effects, steric inhibition of coplanarity, and hemiacetal formation

Thesis: Sc. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 1976 / Bibliography: p. 361-366. / Sc. D. / Sc. D. Massachusetts Institute of Technology, Department of Chemical Engineering

Le présent travail a pour but d'évaluer les potentialités électrocatalytiques du cuivre sous différentes formes pour les réactions de réduction du dioxyde de carbone et de réduction de l'ion nitrate.<p><p>Dans la première partie du travail, nous avons comparé, à l’aide de la voltampérométrie, d’électrolyses à potentiel contrôlé et d’analyses chromatographiques, l'activité d'électrodes polycristalline et monocristallines de Cu et d'alliages AuxCuy de différentes orientations cristallines pour l'électroréduction de CO2.<p>Nous avons pu établir une étroite corrélation entre l'activité de l'électrode de Cu et l'arrangement atomique de sa surface. L'activité et la sélectivité pour CH4 de Cu décroissent selon la séquence :Cu (111) > Cu (100) > Cu (poly). La réduction du CO2 et la formation de CH4 sont favorisées sur les surfaces lisses et denses à l'échelle atomique.<p>La sélectivité des alliages AuxCuy est considérablement orientée vers CO quand la fraction superficielle de Au augmente. L'alliage de composition 50-50 conduit à la formation exclusive de CO.<p><p>La seconde partie de la thèse est consacrée à l'étude de l'activité d'électrodes massives de Cu polycristallin et monocristallin d’orientation (111) et de dispersions de Cu pour la réduction électrochimique de NO3-. <p>Nous avons mis en évidence l'importance des conditions de pH pour le déroulement des processus à l'électrode de cuivre. En milieu acide, NO3- est directement réduit en NH4+ alors qu’en milieu neutre, les réactions de réduction de NO3- en NO2- et de NO2- en NH4+ s’observent successivement en fonction du potentiel.<p>L'activité des dispersions de Cu dans un film de polyaniline dépend fortement des conditions de dépôt. Le cuivre incorporé au film sous sa forme réduite est plus actif que le cuivre incorporé au film initialement oxydé. Par ailleurs, nous avons montré que la concentration de H+ dans le polymère est limitée. En conséquence, le processus de réduction de NO3- sur le cuivre dispersé dans un film de polyaniline est modifié en milieu acide.<p>L’utilisation d’un film de poly-3,4-éthylènedioxythiophène déposé sur une surface de Pt s'est quant à elle révélée inadéquate comme support pour l'incorporation de Cu dans le cadre de l'étude de la réduction de NO3- en milieu acide.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished