The Determination of the Aqueous Oxidation Potentials of Aniline and Sixteen of its Derivatives via Ultrafast Cyclic Voltammetry to Model the Photocatalyzed Degradation of Organic Pollutants in Natural Bodies of Water
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Redox reactions of organic pollutants are important processes to consider when studying the effect of pollutants on the environment. Having accurate aqueous formal oxidation potentials (E0’) for pollutants is essential to understanding their redox chemistry and how they might react with photoactivated dissolved organic matter in natural bodies of water. Aniline and sixteen of its derivatives were studied with cyclic voltammetry and ultrafast cyclic voltammetry in order to determine their aqueous oxidation potentials. Due to the rapid polymerization of aniline upon oxidation, cyclic voltammetry at macroelectrodes is unable to detect reduction, and thus measures an irreversible process. Using a 3.00 mm glassy-carbon macroelectrode and scan rates on the order of 1 Vs-1 the irreversible oxidation of the anilines was observed, and the reversible E0’ was approximated by the inflection points of their oxidation peaks. This data was further analyzed based on the resonance and electron donating / withdrawing effects of the various aniline substituents. In order to study the reversible process, ultrafast cyclic voltammetry was used in an attempt to reduce aniline radical cations before they are consumed by the polymerization reaction. An 11 μm carbon fiber, a 10 μm gold, and a 10 μm platinum microelectrode were employed at scan rates between 200 Vs-1 and 1,000 Vs-1. This technique was successful at measuring a reversible redox couple for some of the anilines; however, further experimentation is required to collect accurate data for all anilines.