The oxidation of 1,1-dimethylhydrazine by bromine has been studied using a coulometric method of bromine generation, and a dual intermediate system of bromide and cupric ions in solution. The system allowed over-generation of bromine and back-titration by cupric ion. The results of the investigation showed that the mechanism of oxidation is not fixed, but is a function of the concentration of bromine in the solution at any time. Additional studies have been recommended, whereby the mechanisms of the reactions may be determined.

No description available.

The kinetics for the reaction of the oxidation of acetaldehyde by chromic acid in aqueous medium has been studied in an attempt to extend the present knowledge of oxidation by chromic acid. In particular, these experiments were undertaken in order to see if there are any similarities between this reaction and the oxidation of isopropyl alcohol in aqueous medium, which other investigators have studied. The main runs were carried out at 25°, at an ionic strength of 0.3. The reaction was followed by the decrease in chromic acid concentration as determined with the Beckman Spectrophotometer. In all of the runs, the concentrations of acetaldehyde and H⁺ were in excess of the chromic acid concentrations. It was found that the oxidation of acetaldehyde is first order in acetaldehyde and first order in HCrO₄⁻, (but not strictly first order in total chromic acid). The reaction is roughly second order in H⁺. Mn⁺² has an inhibitory effect upon the rate, as has been found in the isopropyl alcohol oxidation. Because of the similarity in kinetic behavior between acetaldehyde and isopropyl alcohol, the mechanisms are probably very similar. This mechanism for acetaldehyde oxidation has been discussed in some detail. / Master of Science

The purpose of thIs investigation was to determine whether correlation exists between the O-R potential and the biochemical oxygen demand of settled sewage. The source of the samples was the effluent end of the primary clarifier at the V.P.I. Sewage Disposal Plant. The investigation consisted essentially of performing the standard biochemical oxygen demand determination and the oxidation-reduction potential determination on similar sewage samples. The data obtained were statistically analyzed and graphically presented. The standard deviation was ascertained and a ninety percent confidence limit was established. The final results based on statistical methods of analysis show that no valid correlation exists between O-R potential and B.O.D. of settled sewage. / Master of Science

The making and breaking of O-O bonds has implications ranging from artificial photosynthesis and water oxidation to the use of O₂ as a selective, green oxidant for transformations of small molecules. Oxidative generation of O₂ from coupling of two H₂O molecules remains challenging, and well defined systems that catalytically evolve O₂ are exceedingly rare. Recent theoretical studies have invoked metal oxyl radicals (L[subscript n]M=O*) containing a singly occupied M-O π-type orbital as precursors to O-O bond forming events in both biological and synthetic water oxidation catalysts. However, the lack of stable metal oxyl complexes makes it difficult to explore and understand this hypothesis. The activation of dioxygen (breaking of O-O bonds) to produce terminal metal oxos also remains a challenge. There is an inherent kinetic barrier to the spin-forbidden reactions of triplet dioxygen, and features that engender selective O₂ reduction are not easily transferable from system to system. The primary thrust of this thesis work has been to elaborate new methods to generate well-defined metal oxyl radicals for studies of their reactions in radical bond-forming reactions similar to the radical coupling hypothesis of water oxidation. A library of >20 5- and 6-coordinate high-valent oxorhenium complexes containing redox-inert and redox-active ligands has been prepared. The complexes containing redox-active ligands have shown the ability for ligand-mediated radical coupling reactions. Mechanistic studies of bimetallic O₂ homolysis (the microscopic reverse of water oxidation) and nitroxyl radical deoxygenation at five-coordinate oxorhenium(V) reveal that, in both net 2e⁻ reactions, coupling to a redox-active ligand lowers the kinetic barrier to the reaction by facilitating formation and stabilization of 1e⁻ oxidized intermediates. Coordinatively unsaturated high-valent oxorhenium complexes containing redox-active ligands direct bond-forming reactions towards the metal center. This is undesirable towards the goal of forming O-O bonds. To address this problem coordinatively saturated Re(V) and Re(VII) complexes were prepared. Oxidation of these species by chemical oxidants allowed for the isolation of "masked" oxyl species. These complexes showed reactivity towards Si and trityl radicals to produce new Si-O and C-O bonds, whereas their closed-shell congeners were inert. We have successfully developed a method for the preparation and isolation of "masked" oxyl radicals and shown their utility in ligand-mediated radical coupling reactions.

No description available.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Electron transfer to and between the redox centers of milk xanthine oxidase was investigated by laser flash-photolysis. Evidence is presented for slow equilibration of electrons (k < 38 s⁻¹) between the various redox centers of the enzyme. The enzyme-bound flavin and the heme moieties of the flavoprotein and cytochrome subunits of p-cresol methyl hydroxylase from Pseudomonas putida are both reduced rapidly in a second order manner by 5-dRF generated by the laser flash, followed by slower first order intramolecular electron transfer (k = 220 s⁻¹) from the protein-bound neutral flavin radical to the oxidized cytochrome. Complex formation between spinach ferredoxin:NADP⁺-reductase (FNRₒᵪ), spinach ferredoxin (Fdₒᵪ), rubredoxin (Rdₒᵪ) from Clostridium pasteurianum, two homologous HIPIP's from Ectothiorhodospira halophila (iso-1 and iso-2) and two homologous cytochromes (cytochromes-c₂ from Paracoccus denitrificans and Rhodospirrilum rubrum) have been investigated. Evidence is presented supporting the formation of 1:1 complexes that are stabilized by attractive electrostatic interactions at low ionic strength. Kinetic studies of the above-mentioned complexes provide evidence for extremely rapid to relatively slower intracomplex electron transfer rates (k 7000 s⁻¹ to 4 s⁻¹). In addition the effect of complexation on the degree of accessibility of the various redox centers of the respective complexes to reduction by small reductants such as 5-dRF· and LfH· generated by the laser flash has been evaluated. The effect of both pH and ionic strength on the second order rate of reduction and the intracomplex rates in the respective complexes have also been investigated. The results have been interpreted in terms of redox potential differences, electrostatic and structural features that influence the electron transfer rates in these systems.

The Effect of Sulindac was studied on an animal model of ischemic stroke. Sulindac, a non steroid anti inflammatory drug (NSAID) could protect cell death due to hypoxia/reoxygenation. This drug was given 2 days before and 24 hrs after ischemia until animals were sacrificed on 3rd or 11th day. Infarct size was measured for these animals. Sulindac induced Hsp 27 in ischemic penumbra and core on Day 3 & 11 with uncoated nylon suture which shows its cell-survival and anti-apoptotic activity. Also, it increased expression of cell survival markers such as Akt, Bcl2 & Grp 78 in ischemic penumbra and core. With silicon suture it reduced expression of Hsp 27 in ischemic penumbra and core, alleviating cell stress and having pro-survival and anti-stress effects. In conclusion sulindac may have excellent potential as neuro protective agent against oxidative stress in cerebral ischemia. / by JIgar Modi. / Thesis (M.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.

The enzyme Methionine sulfoxide reductase A (MsrA) repairs oxidized proteins, and may act as a scavenger of reactive oxygen species (ROS), making it a potential therapeutic target for age-related neurodegenerative diseases. The anoxia-tolerant turtle offers a unique model to observe the effects of oxidative stress on a system that maintains neuronal function following anoxia and reoxygenation, and that ages without senescence. MsrA is present in both the mitochondria and cytosol, with protein levels increasing respectively 3- and 4-fold over 4 hours of anoxia, and remaining 2-fold higher than basal upon reoxygenation. MsrA was knocked down in neuronally-enriched cell cultures via RNAi transfection. Propidium iodide staining showed no significant cell death during anoxia, but this increased 7-fold upon reoxygenation, suggesting a role for MsrA in ROS suppression during reperfusion. This is the first report in any system of MsrA transcript and protein levels being regulated by oxygen levels. / by Lynsey Erin Bruce. / Thesis (M.S.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.