Organic Chemistry Commons^™

Heterogeneous Base Metal Catalyzed Oxidative Depolymerization Of Lignin And Lignin Model Compounds, John Adam Jennings

Theses and Dissertations--Chemistry

With the dwindling availability of petroleum, focus has shifted to renewable energy sources such as lignocellulosic biomass. Lignocellulosic biomass is composed of three main constituents, lignin, cellulose and hemicellulose. Due to the low value of cellulosic ethanol, utilization of the lignin component is necessary for the realization of an economically sustainable biorefinery model. Once depolymerized, lignin has the potential to replace petroleum-derived molecules used as bulk and specialty aromatic chemicals. Numerous lignin depolymerization strategies focus on cleavage of β-aryl ether linkages, usually at high temperatures and under reductive conditions.

Alternatively, selective benzylic oxidation strategies have recently been explored for …

Formation Of The Ether Bridge In The Loline Alkaloid Biosynthetic Pathway, Minakshi Bhardwaj

Theses and Dissertations--Chemistry

Lolines are specialized metabolites produced by endophytic fungi, such as Neotyphodium and Epichloë species, that are in symbiotic relationships with cool-season grasses. Lolines are vital for the survival of the grasses because their insecticidal and antifeedant properties protect the plant from insect herbivory. Although lolines have various bioactivities, they do not have any concomitant antimammalian activities.

Lolines have complex structures that are unique among naturally occurring pyrrolizidine alkaloids. Lolines have four contiguous stereocenters, and they contain an ether bridge connecting C(2) and C(7) of the pyrrolizidine ring. An ether bridge connecting bridgehead C atoms is unusual in natural products and …

Acenes, Heteroacenes And Analogous Molecules For Organic Photovoltaic And Field Effect Transistor Applications, Devin B. Granger

Theses and Dissertations--Chemistry

Polycyclic aromatic hydrocarbons composed of benzenoid rings fused in a linear fashion comprise the class of compounds known as acenes. The structures containing three to six ring fusions are brightly colored and possess band gaps and charge transport efficiencies sufficient for semiconductor applications. These molecules have been investigated throughout the past several decades to assess their optoelectronic properties. The absorption, emission and charge transport properties of this series of molecules has been studied extensively to elucidate structure-property relationships. A wide variety of analogous molecules, incorporating heterocycles in place of benzenoid rings, demonstrate similar properties to the parent compounds and have …

Towards The Total Synthesis Of 7-Epi-Clusianone, Shubhankar Dutta

Theses and Dissertations--Chemistry

Polycyclic polyprenylated acylphloroglucinols (PPAPs) are plant- (Guttiferae) derived natural products. They have fascinating bicyclo[3.3.1]nonane-2,4,9-trione or [3.2.1]nonane-2,4,8-trione cores decorated with prenyl or geranyl groups. More than 200 PPAPs have been isolated, but only a few of them have been synthesized, although most of the synthesized PPAPs are of type A and have an exo substituent at C (7). Here, we are trying to make a type B 7-endo PPAP, 7-epi-clusianone. The synthetic plan involves an alkynylation–aldol strategy to construct the bicyclic core. Having established the bicyclic core, the synthesis presents a new challenge: the oxidation of a very hindered …

Organometallic Materials: Ferroceno[C]Thiophenes And 1,2-Bisthienylmetallocenes, Surya R. Banks

Theses and Dissertations--Chemistry

Development of synthetic routes toward two general organometallic frameworks was undertaken. The first project involved synthetic attempts of substituted and unsubstituted ferroceno[c]thiophene while the second one was the synthesis of 1,2-dithienylmetallocenes. The long-term goal of this work is to lay the foundations for study of electronic, electrochromic, redox, and optical properties of thiophene-based materials integrated with organometallic systems such as ferrocene, ruthenocene and cymantrene. The synthetic pathway for the target molecule in the first project involved converting 1,2-bis(hydroxymethyl)ferrocene to 1,2-bis(thiouroniummethyl)ferrocene with thiourea under acidic conditions. Refluxing the salt in base followed by acidification resulted in 1,2-bis(mercaptomethyl)ferrocene, which is …

The Development Of Colorimetric Assays To Determine The Identity And Frequency Of Specific Nucleobases In Dna Oligomers, Elizabeth Marie Thomas

Theses and Dissertations--Chemistry

Colorimetric methods combined with color-changing chemical probes are widely used as simple yet effective tools for identifying and quantifying a wide variety of molecules in solution. For nucleic acids (DNA and RNA), perhaps the most commonly used colorimetric probe is potassium permanganate, which can be used to identify single-stranded pyrimidines (thymine and cytosine) in polymers. Unfortunately, permanganate is not an effective probe for identifying purines (adenine and guanine), especially in the presence of the more reactive pyrimidines. Therefore, robust methods for discriminating between the purines remain elusive, thereby creating a barrier toward developing more complex colorimetric applications. In this dissertation, …

Spectroscopic Characterization Of Lanthanum-Mediated Hydrocarbon Activation, Dilrukshi C. Hewage

Theses and Dissertations--Chemistry

Lanthanum (La)-promoted hydrocarbon activation reactions were carried out in a laser vaporization metal cluster beam source. Reaction products were identified by time-of-flight mass spectrometry, and the approximate ionization thresholds of La-hydrocarbon complexes were located with photoionization efficiency spectroscopy. The accurate ionization energies and vibrational frequencies of the La complexes were measured using mass analyzed threshold ionization (MATI) spectroscopy. Their molecular structures and electronic states were investigated by combing the MATI spectroscopic measurements with quantum chemical and Franck-Condon factor calculations.

In this dissertation, La-mediated C-H and C-C bond activation reactions were investigated for several small alkynes (acetylene, propyne) and alkenes (propene, …

Unhindered Triangulene Salt Pairs: Substitution-Dependent Contact Ion Pairing And Complex Solvent-Separated Discotic Ions In Solution, Subrahmanyam Modekrutti

Theses and Dissertations--Chemistry

This work sought to enforce aromatic interactions between compatible π-molecular orbital systems with ionic bonding. In this case the interacting partners are oppositely charged discotic triangulene derivatives. The observed properties of the heterodimeric ion-pairs likely arise due to a hypothetical synergy between electrostatics and π-interactions. The work presented here describes investigation of putative covalency arising from this hypothetical synergy in the electrostatics driven π-stacking. In order to probe this, various hypotheses were made and experiments were designed to test their validity. The results from the experiments show existence of contact ion-pairs and complex solvent-separated discotic ions in solution. The formation …

Electrode And Electrolyte Additives For Lifetime Extension In Lithium-Ion Batteries, Kishore Anand Narayana

Theses and Dissertations--Chemistry

Lithium-ion batteries (LIBs) are the most commonly used type of rechargeable batteries with a global market estimated at $11 billion, which is predicted to grow to $60 billion by 2020. The global commercialization of Li-ion batteries is impeded by issues such as poor cycle life (5000 cycles achieved in some LIBs) in high energy and power density applications because of the rising internal resistance due to aging and safety concerns such as overcharge which ultimately leads to thermal runaway and explosions. A battery’s performance mainly depends on external factors such as electrode thickness and degree of compacting, and the type …

Optimization Of The Optical And Electrochemical Properties Of Donor-Acceptor Copolymers Through Functional Group And Side Chain Modification, Mark J. Seger

Theses and Dissertations--Chemistry

Donor-acceptor copolymers have received a great deal of attention for application as organic semiconductors, in particular as the active layers in low-cost consumer electronics. The functional groups grafted to the polymer backbones generally dictate the molecular orbital energies of the final materials as well as aid in self-assembly. Additionally, the side chains attached to these functional groups not only dictate the solubility of the final materials, but also their morphological characteristics. The bulk of the research presented in this dissertation focuses on the synthesis and structure-property relationships of polymers containing novel acceptor motifs. Chapter 2 focuses on the synthesis of …

Hydrogenation And Hydrogenolysis Of Furan Derivatives Using Bipyridine-Based Electrophilic Ruthenium(Ii) Catalysts, Anitha Shankaralinge Gowda

Theses and Dissertations--Chemistry

The catalytic activity of ruthenium(II) bis(diimine) complexes cis-[Ru(6,6′-Cl₂bpy)₂(OH₂)₂](Z)₂ (2, Z = CF₃SO₃; 3, Z = (3,5-(CF₃)₂C₆H₃)₄B ,i.e. BArF), cis-[Ru(4,4′-Cl₂bpy)₂(OH₂)₂](Z)₂ (4, Z = CF₃SO₃; 5, Z = BArF) and cis-[Ru(bpy)₂(PR₃)(OH₂)](CF₃SO₃)₂ (7, bpy = 2,2’-bipyridine, PR₃ = P(C₆H₄F)_{3 …}

Acenes And Acenequinones For Optics And Organic Electronics, Matthew Bruzek

Theses and Dissertations--Chemistry

Acenes have been explored by a number of research groups in the field of organic electronics with a particular emphasis on transistor materials. This group has been actively studying acene‐based organic semiconductors for more than a decade using a crystal engineering approach and has developed acene derivatives for applications in field‐effect transistors, light‐emitting diodes, and photovoltaics. In addition to organic electronics, crystal engineering has important applications in a number of other fields, quite notably in the design of metal‐organic frameworks. Chapters 2 and 3 of this dissertation focus on applying crystal engineering to the synthesis of acene derivatives for use …

N-Doped Multiwalled Carbon Nanotubes: Functionalization, Characterization And Application In Li Ion Batteries, Aman Preet Kaur

Theses and Dissertations--Chemistry

The focus of this dissertation is to utilize chemical functionalization as a probe to investigate the reactivity of N-doped multiwalled carbon nanotubes (N-MWCNTs). The surface of N-MWCNTs, being a set of potentially reactive graphene edges, provides a large number of reactive sites for chemical modification, so considerable changes in chemical and physical properties can be envisaged. We observed that both reduction (dissolving metal reduction/alkylation) and oxidation (H₂SO₄/HNO₃ and H₂SO₄/KMnO₄ mixtures) of N-MWCNTs lead to formation of interesting spiral channels and spiraled carbon nanoribbons. A variety of techniques, including TGA, SEM, …

Efficient Electrochemical Functionalization Of Carbon Nanotubes And Carbon Nanotube Membranes For Energy, Drug Delivery And Potential Catalysis Applications, Xin Zhan

Theses and Dissertations--Chemistry

Electrochemical diazonium grafting offers versatile functionalization of chemically inert graphite under mild condition, which is particularly suitable for CNT composite modification. Tetrafluorinated carboxylphenyl diazonium grafting provides the most controllable functionalization chemistry allowing near monolayer levels of functionality on carbon nanotubes. The functional density was successfully quantified by anion selective dye-assay and X-ray photoelectron spectroscopy (XPS) of thiol-Au self-assembled monolayers (SAM) as a calibration reference. This technique enables monolayer functionality at the tips of carbon nanotube membranes for biomimetic pumps and valves as well as thin conductive layers for CNT-based high area electrochemical support electrodes.

Double-walled carbon nanotube (DWCNT) membranes were …

Fluorinated Arene, Imide And Unsaturated Pyrrolidinone Based Donor Acceptor Conjugated Polymers: Synthesis, Structure-Property And Device Studies, Arawwawala Don T. Liyanage

Theses and Dissertations--Chemistry

FLUORINATED ARENE, IMIDE AND LACTAM-FUNCTIONALIZED DONOR ACCEPTOR CONJUGATED POLYMERS: SYNTHESIS, STRUCTURE-PROPERTY AND DEVICE STUDIES

After the discovery of doped polyacetylene, organic semiconductor materials are widely studied as high impending active components in consumer electronics. They have received substantial consideration due to their potential for structural tailoring, low cost, large area and mechanically flexible alternatives to common inorganic semiconductors. To acquire maximum use of these materials, it is essential to get a strong idea about their chemical and physical nature. Material chemist has an enormous role to play in this novel area, including development of efficient synthetic methodologies and control the …

Novel Aromatic Ion–Pairs: Synergy Between Electrostatics And Π-Face Aromatic Interactions, Pramod Prasad Poudel

Theses and Dissertations--Chemistry

This dissertation focuses on the design and study of charged aromatic molecules where weak π-π interactions synergize with electrostatic interactions to enhance the overall interaction between aromatic moieties. Each chapter investigates some aspect of this hypothetical synergy between electrostatics and π-face aromatic cohesion.

The first chapter unveiled the importance of electrostatics in the intramolecular stacking of flexible aromatic molecular templates 1-2Br and 2a. While our previous studies found dicationic molecular template 1-2Br to have intramolecular π-stacking between electron poor pyridinium and electron rich xylylene moieties, no such stacking interaction was observed in the neutral analog 2a.

Chapter two systematically …

Development Of Novel Chemical Tools For Proteasome Biology & A New Approach To 1-Azaspirocyclic Ring System, Lalit Kumar

Theses and Dissertations--Chemistry

The proteasome, a multiprotease complex, is clinically validated as an anticancer target by the FDA approval of bortezomib and carfilzomib for the treatment of multiple myeloma. The emergence of resistance to proteasome inhibitors however remains a major clinical challenge. Recently, distinct types of proteasomes termed ‘intermediate proteasomes’, which contain unconventional mixtures of catalytic subunits, have been implicated with drug resistance of tumor cells. In elucidating the role of intermediate proteasomes in drug resistance, a crucial step is to unequivocally determine the subunit composition of intermediate proteasomes in cells. With this in mind, the goal of the studies reported in this …