Browsing by Subject "Reactive intermediate"
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Item Photochemical Production of Reactive Intermediates in Inland Surface Waters(2017-09) McCabe, AndrewReactive intermediates form when dissolved natural organic matter (DOM) absorbs sunlight in surface waters. These reactive intermediates include triplet excited states of dissolved organic matter (T*), reactive oxygen species, carbonate radical, and halide radicals. They are associated with a variety of physicochemical processes, including carbon and metal cycling, pathogen inactivation, and reactions with trace organic contaminants. T* is particularly important in these processes because it can react either through electron or energy transfer mechanisms and it is responsible for the formation of secondary reactive intermediates, such as singlet oxygen and radicals. The quantity and composition of DOM are key variables that control the rate and efficiency of T* formation, defined as the ratio of the rate of T* formation to the total rate of light absorption. As DOM is transported through aquatic environments, its composition is altered by natural and anthropogenically-influenced biogeochemical processes. Here, DOM composition is related to the reactivity of T* in stormwater and in temperate wetlands, two important aquatic systems involved in the production and transport of DOM. The rate and efficiency of T* formation were measured with two chemical probes, 2,4,6-trimethylphenol and trans,trans-2,4-hexadienoic acid, that quantify rates of T* electron transfer and energy transfer, respectively. DOM composition was characterized using absorption spectrophotometry, fluorescence spectroscopy, and Fourier transform ion cyclotron mass spectrometry. Within our sample set, the observed range in the efficiency of T* formation is <1%–14%, and shows a distinct dependence on watershed vegetative land cover and open water extent. The rate of T* formation increases with the concentration of dissolved organic carbon (DOC) while the efficiency of T* formation is independent of DOC. The data reported here suggests that DOM derived from vascular plants has a dual role, controlling both the rate of light absorption and the efficiency of T* formation.Item Studies toward the total synthesis of rac-Leuconolam, modified Julia Olefination approach to access functionalized steroidal side chains, proton-NMR Studies of Mosher-like esters, and exploring a non-enzymatic Diels Alder reaction to account for the methyl sarcophytoate core(2012-09) Izgu, Enver CagriThis Ph.D. thesis is composed of five chapters, two of which are closely related and are presented at the begining. In Chapter-I, an extensive study toward the total synthesis of a plant natural product, namely leuconolam, will be discussed. In the course of this project, two different routes have been explored, where novel synthetic methods have been developed. In particular, some of the key bond-forming events such as Ireland-Claisen rearrangement, arene-alkene coupling (via either Stille reaction or C-H bond functionlization) and allylative ring closure are highlighted.A side project that has emerged during my investigations in Chapter-I will be covered in Chapter-II. This work focuses on the synthesis of two new organometallic reagents and their utility in organopalladium mediated cross-couling reactions with various alkenyl and aryl halides. Chapter-III encompasses the studies in the area of steroid chemistry, more specifically, in chemical construction of important steroid side chains. In order for a convergent strategy, a modified Julia olefination method has been performed on a common sulfone donor with a series of uselful aldehyde acceptors. Biologically relevant derivatives of alkyl and alkoxy branched side chains have been successfully synthesized. In Chapter-IV, synthetic and spectroscopic studies in Mosher ester analysis technique will be discussed. This NMR based tool is critical in determining the absolute configuration of a stereogenic carbon center and is commonly used by organic chemists. Finally, in Chapter-V, our efforts in generating a reactive pyrylium dienophile to facilitate a Diels-Alder reaction will be outlined.