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Mechanism of iodine-catalyzed multicomponent cyclocondensation reactions: Synthesis of polysubstituted quinoline "archipelago" asphaltene mimics
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- Author / Creator
- Scott, David
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Asphaltenes constitute the heaviest and least understood sub-class of bitumen. The degree of difficulty regarding upgrading arises from the diverse and complex mixture of organic and organometallic molecules characteristic of heavy petroleum. It is hypothesized that these molecular constituents are entwined and tightly aggregated to form complex suprastructures. The numerous structural properties of asphaltenes (vast polycyclic aromatics, heteroatoms, polar functional groups, aliphatic segments and substituents, etc.) instigate inter- and intramolecular interactions causing irreversible aggregation. To increase the value and/or use of this material, efficient new upgrading procedures are required in order to address global, ever-expanding, energy needs.
Significant achievements in analytical technology has surpassed the basic understanding of the bulk properties of bitumen. Analytical methods such as ICP-MS, VPO, SANS, ITC, and AFM/ STM have begun to intimately define the structural make-up of complex asphaltene molecules. Initial modeling of asphaltene components was limited to commercial aromatic compounds; however, rational molecular design and modern organic synthesis have begun to build a library of structural candidates, to accurately represent the supramolecular behaviour of native asphaltenes.
This dissertation describes a new catalytic cyclocondensation procedure, allowing us to prepare a range of quinoline-core asphaltene model compounds. The concise synthetic methodology utilizes a multicomponent reaction (MCR) to build compounds that incorporate a basic nitrogen entity. As a result of low yields and irreproducible results, substantial effort was applied to improve the reaction. Extensive optimizations were conducted to generalize and control the MCR. New mechanistic detail was obtained by our in-depth analysis and we identified the true role of the catalyst, the necessary requirement of added oxygen, and the need for other additives. Effectively, once optimized, a wide range of quinoline-core compounds were synthesized in high purity and yield. These quinoline-based compounds have tremendous value in assessing the behaviour of authentic asphaltene samples. As a result of the complex solubility characteristics of asphaltenes, model compounds have been used to study the difference in solubility and chemical structure using Hansen solubility parameters. Though early work using quinoline-based model compounds has shown that solubility of model compounds is complex due to slight changes in structure, the need for further investigation requires a diverse library of models. Furthermore, the model compounds will be needed to test aggregation, which is expected to differentiate when one or a mixture of compounds are studied (ITC, NMR, IR, etc.). Overall, the key to this methodology is the simplicity to modulate the individual components and increase the complexity required for the types of compounds required. -
- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Doctor of Philosophy
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- License
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