Theses and Dissertations - Department of Chemistry & Biochemistry

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Acetic Anhydride
(University of Alabama Libraries, 1929) Hanna, Carl; University of Alabama Tuscaloosa
Acetic anhydride is a colourless, volatile liquid having an odor like that of glacial acetic acid, but stronger. It is very corrosive and its vapors are extremely irritating to the eyes and lungs. Care should therefore be exercised in working with it, and any spilled upon the hands should be immediately washed off. It is a condensation of two molecules of acetic acid with elimination of water. The reaction, however, is reversible, and there is always present some acetic acid due to action of water.
Air-stable palladium(II) precatalysts: synthesis, properties, and applications in cross-coupling reactions
(University of Alabama Libraries, 2017) Barnett, Kerry Lynn; Shaughnessy, Kevin H.; University of Alabama Tuscaloosa
Palladium catalyzed cross-coupling reactions are a versatile tool in organic chemistry to produce small molecules. Current research interests involve the development of new catalyst systems for various palladium catalyzed reactions. Previous work has suggested the active species for palladium-catalyzed cross-coupling reactions to be a mono-ligated palladium(0) species when sterically demanding ligands are used. Therefore, the my work focused on the synthesis of precatalysts with an established 1:1 L:Pd. Specifically, we were focused on the synthesis of mono-ligated palladium(II) precatalysts of general formula [(R_3P)PdCl_2]_2, using di-tert-butylneopentylphosphine (DTBNpP), tert-butyldineopentylphosphine (TBDNpP), and trineopentylphosphine (TNpP) as ligands. Under optimized conditions, both [(DTBNpP)PdCl_2]_2 and [(TNpP)PdCl_2]_2 were effective precatalysts for the Suzuki cross-coupling of a wide range of aryl bromides. Comparison studies with the air-stable precatalysts versus the in-situ generated catalyst showed the precatalysts to have improved conversions and higher rates of reaction under both inert and ambient atmospheres. The precatalyst activation pathways were investigated by 31P NMR spectroscopy. The spectra obtained from 31P NMR experiments revealed a side reaction resulting in a catalytically inactive palladacycle species. The results obtained from the mechanistic investigations led to further optimization of reaction conditions to decrease the amounts of catalytically inactive side products formed.
Anionic polymerization of activated aziridines
(University of Alabama Libraries, 2018) Mbarushimana, Pierre Canisius C.; Rupar, Paul A.; University of Alabama Tuscaloosa
Polyethyleneimine, also referred to as polyaziridine, is a polymer that has a repeat unit of (-CH2CH2NH-). Due to its high amine density, PEI finds application in several domains including gene transfection, antimicrobial/antibacterial medicine, CO2 capture, thin film metal deposition, industrial wastewater treatments, and more. Commercially, PEI is obtained via the uncontrolled polymerization of aziridine and the cationic ring opening polymerization (CROP) of oxazolines. However, the available cationic polymerization techniques of aziridines are poorly controlled. In order to synthesize well-defined PEIs, recent literature approaches have used the anionic ring opening polymerization (AROP) of various N-substituted aziridines. The present research, done at The University of Alabama, has focused on the synthesis and AROP of N-substituted aziridines, without the substitution at the 2-position of the aziridine ring. The studied monomers include three tert-butylcarboxy-protected aziridine monomers, specifically tert-butyl aziridine-1-carboxylate, tert-butyl 2-methylaziridine-1-carboxylate, tert-butyl 2-decylaziridine, and six 1-(alkylsulfonylsulfonyl) aziridine monomers, i.e. 1-(methylsulfonyl)aziridine, 1-(toluenesulfonyl)aziridine, 1-(octylsulfonyl)aziridine, 1-(sec-butylsulfonyl)aziridine, 1-((2-nitrophenyl)sulfonyl)aziridine, and 1-((4-nitrophenyl)sulfonyl)aziridine. After characterization, the synthesized monomers were homopolymerized by AROP using various nucleophilic initiators. Except for BOCDecAz, all the synthesized monomers were successfully converted into the corresponding polymers. However, only short oligomers of the resulting homopolymers were formed, as high molecular weight polymer chains were insoluble. The synthesized polymers can potentially be used as precursor to pure linear polyamines A single sulfonyl aziridine, namely1-((ortho-nitrophenyl)sulfonyl)aziridine (oNsAz) was found to produce high molecular weight poly(oNsAz) that was soluble in DMF and DMSO. This is significant as it is the first example of a soluble poly(1-sulfonylaziridine) homopolymer; prior examples were limited to random copolymer. The deprotection of poly(oNsAz) was also attempted in effort to synthesize linear PEI. Although evidence was found for the formation of linear PEI, satisfactory purification of the linear PEI was not achievable.
The anionic ring-opening polymerization of cyclic imines
(University of Alabama Libraries, 2019) Reisman, Louis; Rupar, Paul A.; University of Alabama Tuscaloosa
One important class of polymers is polyimines. Polyimines have a wide range of applications such as CO2 capture and non-viral gene-transfection. Despite their many applications, the use of these polymers is limited due to difficulties in controlling the polymerization. To increase the feasibility of polyimines in the aforementioned high-value applications, the research in this dissertation focuses on controlled routes to produce linear polyimines using living anionic ring-opening polymerization (AROP). The early work of this dissertation focuses on an AROP route to linear polyethylenimine (LPEI). Due to the insolubility of p(N-sulfonylaziridine)s (i.e. non-2-substituted) in all common solvents, this was achieved using a copolymerization strategy. Utilizing two N-sulfonylaziridines, N-(methanesulfonyl)aziridine (MsAz) and N-(sec-butylsulfonyl)aziridine (sBsAz), with similar reactivities, a soluble random copolymer with narrow molecular weight distributions is produced. Removal of the sulfonyl groups of p(MsAz-r-sBsAz) affords the first example of LPEI by living, controlled AROP. The later work in this dissertation focuses on the AROP of N-sulfonylazetidines in route to linear poly(trimethylenimine) (LPTMI). Initially, the polymerization of N-(methanesulfonyl)azetidine (MsAzet) was investigated. The kinetics of this polymerization were studied, and the reaction found to be first order with respect to monomer and the number of active chain ends remains constant throughout the polymerization. Interestingly, activation occurs at the methanesulfonyl group, leading to polymer branching. This branching precludes p(MsAzet) from being a precursor to LPTMI. By more judicial selection of N-sulfonylazetidine monomers, a living, controlled AROP approach to LPTMI was achieved by copolymerizing two similar N-sulfonylazetidines, N-(p-tolylsulfonyl)azetidine (pTsAzet) and N-(o-tolylsulfonyl)azetidine (oTsAzet), to produce a statistical copolymer. Copolymerization was required as the homopolymers resulting from these monomers were insoluble in all common solvents. The copolymerization is living and controlled, producing polymers with narrow molecular weight distributions. The kinetics of the copolymerization, and the reactivity ratios of the two monomers, were studied and the sulfonyl groups of the polymer were removed to provide the first example of LPTMI by living, controlled AROP. Finally, the high barrier to polymerization of N-sulfonylazetidines was utilized to produce block copolymers, containing no homopolymer impurities, in a closed system in which all monomers are present in solution at the time of initiation.
Application of hydrogen deuterium exchange mass spectrometry in protein-ligand and protein-protein interactions
(University of Alabama Libraries, 2016) Guan, Siqi; Frantom, Patrick A.; University of Alabama Tuscaloosa
Proteins are not static objects. They have a great variety of internal motions with different amplitudes and different timescales. These internal motions play an important role in catalytic processes. Therefore, the existence of an intimate relationship between protein dynamics and protein function is widely accepted. Due to the significance of protein dynamics, techniques have been developed to study protein dynamics including nuclear magnetic resonance (NMR) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and mass spectrometry (MS). Compared with NMR and EPR spectroscopy, MS has less stringent sample requirements, including protein concentration and protein size. Moreover, the mass accuracy, sensitivity, and faster data analysis also have contributed to the rapid growth of MS based techniques. Hydrogen-deuterium exchange mass spectrometry (HDX-MS), a combination of HPLC and MS, has become a common and sensitive tool to probe protein structural flexibility and solution dynamics. In this dissertation, HDX-MS was applied to study dynamic changes of proteins due to substrate binding and protein-protein interactions. The GT-A glycosyltransferase glucosyl-3-phosphoglycerate synthase from Mycobacterium tuberculosis (MtGpgS) catalyzes the first step of biosynthesis of 6-O-methylglucose lipopolysaccharides (MGLPs), which are essential to growth and existence of mycobacterium. The HDX-MS data revealed that the two substrates UDP-glucose (UDPG) and 3-phosphoglycerate (3PGA) can bind to MtGpgS independently, disagreeing with the previous proposal that 3PGA can only bind to MtGpgS after UDPG. Moreover, 3PGA was found to bind to or allosterically affect the UDPG binding site. Furthermore, the HDX-MS data revealed that MtGpgS may provide a necessary conformation for UDPG binding, while it goes through a large conformational change on 3PGA binding. The GT-B glycosyltransferase MshA from Corynebacterium glutamicum (CgMshA) catalyzes the initial step of mycothiol biosynthesis. A large conformational change was observed in CgMshA on nucleotide binding by superimposing APO structure of CgMshA and complex structure with UDP. HDX-MS was utilized to study conformational changes of CgMshA on substrate binding from the aspect of dynamics, providing a complementary to static structures. The HDX-MS data showed that both substrates uridine diphosphate glucose-N-acetylglucosamine (UDP-GlcNAc) and 1-L-myo-inositol-1-phosphate (I1P) can bind to CgMshA independently, but the I1P binding is not productive since it binds to an uncorrect site. Moreover, the I1P binding can lead to dynamic changes of CgMshA, while only UDP-GlcNAc can induce the major conformational change of CgMshA. Furthermore, the 3PGA binding cannot induce further dynamic changes of CgMshA in the presence of UDP. HDX-MS was also employed to study dynamic changes of protein complex SufBC2D from Escherichia coli on ADP/Mg2+ binding. This complex is responsible for Fe-S cluster assembly under oxidative stress. The crystal structure of SufBC2D complex has been determined, while little dynamic information is known. So HDX-MS was applied to study dynamic changes of the SufBC2D complex. The HDX-MS data revealed that SufC has a significant conformational change, which may be required by ATP binding and hydrolysis. Moreover, SufB and SufD are detected to have dynamic changes due to SufC conformational changes. These dynamic changes suggest that SufB-SufD protomer may have a conformational change in order to provide a suitable conformation for Fe-S cluster assembly. This work demonstrates that HDX-MS can be effectively used to study protein-ligand and protein-protein interactions, as well as the accompanying changes in structural dynamics. HDX-MS data detects substrate binding mechanism and conformational changes that are not available through x-ray crystallography. With these advantages, HDX-MS has been applied in study of protein structure and dynamics, studying protein-ligand and protein-protein interactions, protein folding, as well as protein therapeutics discovery and development.
Applications of polyamidoamine dendrimers in polymer electrolyte membrane fuel cells
(University of Alabama Libraries, 2009) Zhu, Huizhen; Thrasher, Joseph S.; University of Alabama Tuscaloosa
Dendrimers are highly branched macromolecules with well-ordered three- dimensional architectures. Polyamidoamine (PAMAM), the most common class of dendrimers, have been widely studied due primarily to the following three features: 1) the interior amine and amide groups that can interact with ionic metal precursors through ligand exchange reactions; 2) the presence of an interior void space in the higher generation dendrimers; and 3) the exterior primary amine groups that permit further functionaliztion. These unique structural features have inspired many potential applications. This dissertation describes two applications of PAMAM dendrimers in polymer electrolyte membrane fuel cells (PEMFCs). First, in an effort to improve the utility of Pt in PEMFCs, PAMAM G4 was used as both a template and a stabilizer to synthesize dendrimer encapsulated Pt nanoparticles (Pt DENs) by photoreduction. These nanoparticles are highly monodisperse, exhibit high specific activity for the oxygen reduction reaction, and are inert to methanol oxidation, showing great potential for application in PEMFCs. Then, a simplified membrane electrode assembly (MEA) has been fabricated by the electrostatic self-assembly between Nafion® and Pt DENs and characterized. Two methods were proposed to increase Pt loading: layer-by-layer self-assembly and immobilization of Pt DENs and carbon powder on carbon fibers. Approximately 80 layers were proposed to reach the required loading using a dipping machine. Immobilization of Pt DENs and carbon powder simultaneously on carbon fibers can easily be achieved by electrochemical coupling, which is promising for replacing the conventional method of electrode fabrication. Secondly, in order to reduce the methanol crossover in direct methanol fuel cells (DMFCs), PAMAM G0 doped Nafion® membranes were prepared. Direct TEM imaging of the Naifon® embedded with nanoparticles demonstrates that PAMAM G0 can penetrate into the bulk of Nafion® through cluster channels to re-organize the distribution of sulfonate clusters by interacting with the sulfonic acid groups in different clusters. The presence of PAMAM G0 in the Nafion® membrane causes reduction of both methanol permeability and proton conductivity, but a very beneficial trade off can be reached when a doping concentration of 10⁻⁴ M PAMAM G0 is used. The fuel cell performance is much improved When Nafion® was treated with 10⁻⁴ M PAMAM G0.
Approaches to the Synthesis of Qinghaosu
(University of Alabama Libraries, 1984) Muse, David Earl; University of Alabama Tuscaloosa
The object of this research was to develop new syntheses of bicyclic peroxides and to apply these new methods to the total synthesis of qinghaosu (Arteannuin A), a previously reported anti-malarial compound. 4 Qinghaosu has shown clinical activity in humans against chloroquineresistant strains of malaria. The most challenging feature of qinghaosu, and the biologically active portion of the compound was the peroxide bridge.
Azobenzene and 2,3-dichloro-5,6-dicyanobenzoquinone donor-acceptor complexation and analysis of the magnetic anisotropy of the nitroso substituent in aromatic systems
(University of Alabama Libraries, 2015) Reach, Savannah; Blackstock, Silas C.; University of Alabama Tuscaloosa
The first part of this thesis describes the evaluation of a new electron donor-acceptor (DA) bond between azobenzene (AB) with the electron deficient quinone 2,3-dichloro-4,5-dicyanobenzoquinone (DDQ), the former acting as an electron-donor and the latter as an electron acceptor. A novel feature of AB is that it may exist in one of two interconvertable isomer forms, cis-AB (contracted structure) and trans-AB (extended structure). Since both of these isomers have different shapes and electronic properties, my research is designed to test the binding of the cis/trans AB isomers to DDQ in solution. Another goal is to grow cocrystals of the AB isomers with DDQ for imaging these molecular aggregates in the cocrystal state by X-ray diffraction analysis. AB/DDQ association in solution is observed optically for the trans-isomer as newly formed red complexes. Concentration of the red solutions results in trans-AB/DDQ cocrystals whose X-ray diffraction structure has been determined. Attempts to cocrystallize cis-AB/DDQ complexes have been attempted, so far without success. The second part of this thesis involves experimental and computational studies of nitrosobenzenes to evaluate the dramatic anisotropic magnetic shielding effects of the nitroso group on the NMR chemical shifts of nearby nuclei. The large magnetic anisotropy gives a ∆∂ of 3.5 ppm for the syn and anti ortho 1H NMR signals and a ∆∂ of 34 ppm for the syn and anti ortho 13C NMR signals. Fifty-six proton chemical shifts in 14 nitrosobenzene structures have been calculated using B3LYP density functional theory with several different basis sets and correlated with experimental values. In addition, forty-four proton chemical shifts from a series of simple aromatic structures lacking the nitroso group (e.g. styrene, benzaldehyde, benzonitrile, and anilines) have been added to the correlation for comparison. The best linear fit of the calculated shifts to experimental values for 1H-NMR is obtained for B3LYP/6-31G*, with an rms deviation of 0.074 ppm for 1H NMR. For 13C NMR, the best linear fit is for B3LYP/DZVP2//TZVP, with an rms deviation of 3.140 ppm. By modeling NMR shifts of nitrosobenzene, we aim to better understand the basis of the large magnetic anisotropy observed for the nitroso group.
Benzoic acid (C₆H₆COOH)
(University of Alabama Libraries, 1920) Hood, Edward P.; University of Alabama Tuscaloosa
The acid juice of apples and various other fruits was employed for preparing different medicines before any attempt was made to isolate the acid itself. Free benzoic acid, however, obtained by subliming benzoin, was discovered and minutely discussed by the French physician, Blaise de Vigenial (1522-96) toward the end of the sixteenth century. Benzoic acid was discovered in gum benzoin in 1608 and prepared from urine by Sholle in 1785. Its composition was established by Liebig and Wohler's classical research in 1832. In 1832 Wohler discovered the relationship between benzoic acid and hippuric acid, and in 1832, Liebig and Wohler determined the true composition of benzoic acid and established its relation to the other benzoyl compounds.
Borafluorenes and polyborafluorenes boron doped varients of fluorene
(University of Alabama Libraries, 2017) Adams, Ian; Rupar, Paul A.; University of Alabama Tuscaloosa
A series of novel boron containing variants of fluorene were synthesized. Boron was incorporated synthetically via lithium halogen exchange and Grignard reaction pathways. Once incorporated, the borafluorene could be polymerized or undergo further functionalization via Yamamoto and Stille coupling reactions. This incorporation of boron into a conjugated system imparted Lewis acidic and electron deficient properties into a conjugated system. It is our hope that this will dope fluorene and create novel n-type semiconductors. A novel polymer of borafluorene, poly(9-borafluorene) (P9BF) was synthesized. HOMO and LUMO levels of P9BF were estimated by cyclic voltammetry. As predicted in prior DFT studies, P9BF has a reduced band gap and a lower lying LUMO compared with polyfluorene. To examine how the HOMO and LUMO levels of borafluorene systems could be tuned, copolymers of 9-borafluorene were synthesized. Four of the copolymers were a series of donor-acceptor (DA) type copolymers. A borafluorene-fluorene (P9BF-OF) copolymer and borafluorene-diketopyrrolopyrrole (P9BF-DPP), as an acceptor-acceptor (AA) copolymer were also synthesized. The series of DA copolymers showed higher energy HOMO and LUMO levels in correlation with the relative donating ability of the donor monomer. P9BF-OF has a reduced LUMO level in comparison with P9BF. P9BF-DPP has a very low band gap (1.8eV), with absorption well into the near-IR region. To examine ways to make borafluorene more air stable, a series of borafluorenes bearing bismethylmethoxyphenyl (BMMP) ligands were investigated. Interestingly, ii bismethylmethoxyphenyl-borafluorene (BMMP-BF) exhibits an exceptionally large Stokes shift of 16000 cm-1. To extend the conjugation and change the Stokes shift, thiophene containing derivatives BMMP-BF-T, BMMP-BF-2T, and BMMP-BF-3T were synthesized. These thiophene containing compounds exhibited anomalous two wavelength fluorescence. During our fluoride titration experiments, we noticed spectral impurities when using tetrabutylammonium fluoride (TBAF) as our fluoride source. Examining this more closely, we found that commercial samples of TBAF were found to absorb light at 295 and 370 nm and fluoresce as 435 nm. This was not expected for analytically pure TBAF, so we concluded that there must be an impurity present in commercial TBAF. The source of this impurity was found to be I3- which occurs from the oxidation of I-.
Carbohydrate sensing using boronic acid modified polymers
(University of Alabama Libraries, 2019) Liang, Xiaoli; Bonizzoni, Marco; University of Alabama Tuscaloosa
Polyelectrolytes have attained a more prominent role in the design of supramolecular systems in recent years. In particular, commercially available poly(amidoamine) (PAMAM) dendrimers have been widely used because they have high loading capacities and good solubility in water. We focus here on using optical spectroscopy to investigate the application of PAMAM dendrimer derivatives as receptors in carbohydrate sensing, and to study the multivalent behavior of receptors covalently appended to the surface of these macromolecules. We then extended the design principles obtained from this work to linear water-soluble anionic polyelectrolytes developed in collaboration with the Kharlampieva group at the University of Alabama at Birmingham (UAB), using polymethacrylate-acrylamide co-polymers synthesized by their group. In chapters 2 and 3, we describe a carbohydrate sensing system that can operate in neutral water, using covalently modified polyelectrolytes as receptors, and common commercially available dyes as optical signaling units. Particularly, in chapter 2, boronic acid modified PAMAM dendrimers were used as receptors to differentiate common monosaccharides in water at millimolar concentration. This is a significant improvement in affinity and sensitivity over simple boronic acid receptors, particularly for work in aqueous environment, which is considered a challenging medium for carbohydrate detection. In chapter 3, these design concepts were also extended to using boronic acid modified polymethacrylate-acrylamide copolymers synthesized at UAB. Binding affinity trends of carbohydrates to boronic acid moieties were then investigated from a fundamental perspective. In chapter 4, the multivalent behavior of boronic acid moieties on surface-modified PAMAM dendrimers was characterized in detail to determine the factors influencing the onset of multivalent behavior, including the surface density of receptor sites and the overall size of the polymeric scaffold.
Catalytic small molecule reduction using late transition metal complexes of carbon and nitrogen donor chelates
(University of Alabama Libraries, 2017) Siek, Sopheavy; Papish, Elizabeth T.; University of Alabama Tuscaloosa
Hydrogenation reactions can be used to store energy in chemical bonds, and if these reactions are reversible that energy can be released on demand. A new bidentate chelating ligand was designed and synthesized for this project, using an N-heterocyclic carbene ring bound directly to a pyridinol ring (NHC-pyOR). This new ligand was used to make iridium complexes that were studied as catalysts for the hydrogenation of CO2 and dehydrogenation of formic acid. For comparison, analogous bipy derived iridium and ruthenium complexes were also tested. In general, the NHC-pyOR complexes demonstrated modest activity, where hydroxyl-pyridines found in the bipy derived systems are more active for CO2 hydrogenation under basic conditions. However, the trends were quite different for formic acid dehydrogenation reaction which will be discussed in Chapter 2. Other ruthenium (II) and iridium (III) complexes of the NHC-pyOR ligand with difference counter anions from above complexes were also synthesized. The ruthenium complexes were tested for their ability to accelerate CO2 (de)hydrogenation, but our studies show that these complexes all undergo transformations in solution and thus they are not true catalysts, but rather pre-catalysts. The use of new tridentate pincer ligands derived from NHC and pyridinol is also described. A new ligand containing (NHC-pyOR-NHC) rings binding to a metal with the pyridinol derivative were synthesized. A series of metal complexes of the type LnM were synthesized (n = 1 and 2; M = Fe2+, Co3+, and Ru2+). Preliminary results of photocatalytic reduction of CO2 to CO show that ruthenium complexes are the most active catalysts followed by cobalt and iron, respectively. The activation of carbon dioxide and nitrite utilizing bio-inspired and proton responsive catalysts were also studied with tris(triazolyl)hydroborate (Ttz) complexes of zinc(II) and copper(II). For the biomimetic zinc complexes for CO2 activation, the synthetic result was found to be greatly depend on the steric bulk of Ttz ligand which will be discussed in detail in Chapter 6. Moreover, the electrochemical reduction of Ttz-Cu(II) complexes in the presence and absence of a proton source shows processes that are relevant to enzymatic nitrite reduction which also will be studied in Chapter 7.
Characterization and catalytic applications of silver nanoparticles supported on hierarchically porous SiO_2 and Co_3O_4 monoliths
(University of Alabama Libraries, 2017) Yildirim, Yasemin; Bakker, Martin G.; University of Alabama Tuscaloosa
Hierarchically porous materials are of great interest in such applications as catalysis, drug delivery, chromatography, and electrochemical sensor arrays due to properties such as high surface area, large void volume, and tunable surface chemistry. In this study, we give the detailed report of the synthesis of supported Ag nanoparticles by nanocasting on to hierarchically porous SiO2 (silica) and Co3O4 (cobalt oxide) monoliths, as well as the use of these materials as heterogeneous catalysts for the hydrogenation and oxidation reactions. In the preliminary work, we investigated the synthesis of Ag supported on hierarchically porous SiO2 and Co3O4 monoliths, and the catalytic activity of these monoliths for the hydrogenation of MB (methylene blue) and MO (methyl orange) dyes in the presence of NaBH4 (sodium borohydride). The SiO2 monoliths were synthesized using a sol-gel technique. The Co3O4 monoliths were prepared by nanocasting, using the SiO2 monoliths as a template. The loading of Ag nanoparticles on the SiO2 and Co3O4 monoliths was done by a solution infiltration method using aqueous AgNO3 (silver nitrate) solution followed by reduction with ethylene glycol and hydrazine hydrate. Such monoliths also were used as continuous flow monolithic microreactors for the catalytic activity and stability studies for the hydrogenation of EO (eosin-Y) dye in the presence of NaBH4. Finally, the use of these monoliths for the oxidation of cyclohexene was investigated including the effects of temperature, oxidant, catalyst loading, and substrate to oxidant ratio. All these studies are presented in different sections depending on the different synthesis, procedures, and catalytic activity occurring in each heterogeneous catalyst.
Characterization and thermoelectric performance of polymer/inorganic hybrid films using spectroscopic and microscopic techniques
(University of Alabama Libraries, 2019) Sutch, Tabitha Patricia; Szulczewski, Greg J.; University of Alabama Tuscaloosa
The main goal of this dissertation was to investigate the thermoelectric performance of films of silver telluride (Ag2Te), bismuth sulfide (Bi2S3) and bismuth telluride (Bi2Te3) nanowires (NWs) dispersed in P(NDI2OD-T2). We hypothesize that the electrical properties of the films made with Ag2Te, Bi2S3, and Bi2Te3 will be n-type and behave like composite materials. Ag2Te was synthesized to make three different lengths of NWs. Powder x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS) confirmed that β-Ag2Te was synthesized with the anticipated stoichiometry. Scanning electron microscopy (SEM) of Ag2Te NWs in P(NDI2OD-T2) revealed that the longest Ag2Te NWs produced homogeneous composites whereas the shorter Ag2Te NWs phase-separated. Electrical conductivity and Seebeck coefficients for each composite film were determined and theoretical models were used to investigate charge-transport behavior. Seebeck coefficients confirmed that all composites were n-type. The longest Ag2Te NWs produced the highest electrical conductivities with parallel transport behavior and are promising to the field of thermoelectrics. Bi2S3 and Bi2Te3 NWs were synthesized, and their stoichiometry and structures were confirmed using XRD and EDS. SEM images of the NW/P(NDI2OD-T2) films revealed that both Bi2S3 and Bi2Te3 phase-separated. The electrical conductivity for each composite film was determined and theoretical models were applied. The electrical conductivity of the Bi2S3 and Bi2Te3 composites were slightly higher than pristine P(NDI2OD-T2), further indicating that the NWs phase-separated. Seebeck coefficients for both systems confirmed that the composites were n-type. Despite the various strategies for improving the film morphology, composites made with Bi2Te3 and Bi2S3 NWs did not produce promising results. The spin-dynamics of P(NDI2OD-T2) doped with cobaltocene were studied with continuous-wave electron paramagnetic resonance (EPR). Additionally, the electrical conductivity of cobaltocene doped P(NDI2OD-T2) films increased several orders of magnitude compared to pristine P(NDI2OD-T2). A sputter depth profile in conjunction with x-ray photoelectron spectroscopy was used to analyze how the dopant dispersed in the polymer matrix. Temperature-dependent pulsed EPR of two different doping concentrations suggested two different relaxation rates. Overall, this study investigated the temperature-dependent spin dynamics of cobaltocene doped P(NDI2OD-T2) films and lays the foundation for further investigations on n-doped polymer system.
Characterization of the carotenoid cis-bixin
(University of Alabama Libraries, 2018) Tay-Agbozo, Sefadzi; Street, Shane C.; Bowman, Michael K.; University of Alabama Tuscaloosa
Bixin, a carotenoid found in annatto, Bixa orellana, is unique among natural carotenoids by being sparingly water-soluble. Bixin free radicals have been stabilized on the surface of silica alumina and TiO2 and characterized by pulsed electron nuclear double resonance (ENDOR). Least-square fitting of experimental ENDOR spectra calculated from density functional theory (DFT) calculations hyperfine couplings characterized the radicals trapped on silica alumina and TiO2. DFT predicts that the trans bixin radical cation is more stable than the cis bixin radical cation by 1.26 kcal/mol. While this small energy difference is consistent with the 26% trans and 23% cis radical cations in the ENDOR spectrum for silica alumina, the TiO2 spectrum could not be fitted due to poor signal. The ENDOR spectrum for silica alumina shows several neutral radicals formed by loss of a H+ ion from the 9, 9′, 13, or 13′ methyl group, a common occurrence in all water-insoluble carotenoids studied in literature. In addition, the continuous wave (CW) electron paramagnetic resonance (EPR) spectroscopy signal of bixin on silica alumina was intense prior to irradiation. Upon irradiation, the intensity is reduced 4-fold. On the other hand, unlike on TiO2 there was no signal prior to irradiation but signal was observed upon irradiation. The extinction coefficient bixin in chloroform is determined to be 1.1 x 105 ± 0.49 and 1.0 x 105 M-1cm-1 ±0.05 at 472 and 503 nm, respectively, while the redox potential in THF is found to be 0.94 ± 0.01V by cyclic voltammogram (CV) measurements. Based on the irreversibility of the CV, the bixin radical cation is estimated to have a short lifetime and decay rapidly at ambient temperature.
The Chemical Refining of Natural Graphite
(University of Alabama Libraries, 1930) Anderson, Ross Eugene; University of Alabama Tuscaloosa
It is the purpose of this paper to present some of the more important aspects of the graphite industry, such as countries producing graphite, economic conditions, uses of graphite, and the nature of graphite deposits; and it is the special purpose of this paper to present the experimental efforts and results of the writer to chemically purify natural Alabama graphite, along the general lines of the Lloyd-Kennedy Process. *NOTE: This is the best available copy.*
Chemistry of Butenolides Derived from D-Ribonolactone
(University of Alabama Libraries, 1988) Blazis, Vincent Joseph; University of Alabama Tuscaloosa
Acetomycin was first reported by Prelog and coworkers as an antibacterial agent isolated from Streptomyces ramulosus, strain ETH 17633. This natural product has been subsequently found in culture of Streptomyces ramulosus Tue-32. The stereochemistry and absolute configuration of acetomycin was established by X-ray crystallography carried out in our laboratories on the antibiotic itself and elsewhere on a bromo derivative.
Chromium, question of essentiality for mammals: its subcellular mechanism, toxicity, uses as a probe for DNA binding
(University of Alabama Libraries, 2011) Rhodes, Nicholas Ryan; Vincent, John B.; University of Alabama Tuscaloosa
Chromium was proposed to be an essential trace element over 50 years ago and was accepted as an essential element for over thirty years. Several studies were performed to address the question of essentiality. Male Zucker lean rats were housed in specially designed metal-free cages for six months and fed the purified AIN-93G diet with no added chromium in the mineral mix component of the diet, the standard purified AIN-93G diet, the standard purified AIN-93G diet supplemented with 200 Μg Cr/kg, or the standard purified AIN-93G diet supplemented with 1000 Μg Cr/kg. This study revealed that a diet with as little chromium as reasonably possible had no effect on body composition or glucose metabolism or insulin sensitivity compared to a chromium "sufficient" diet. The diets supplemented with Cr had beneficial effects on the rats; the effects at these doses are pharmacological effects, the mechanism of which requires further research. Zucker obese and Zucker diabetic fatty (ZDF) rats were used to establish whether rats under stress (diabetes and obesity associated insulin resistance) have altered levels of chromium absorption compared to Zucker lean rats. If these conditions lead to increases in chromium absorption, then increased urinary Cr losses resulting from the conditions are unlikely to lead to chromium deficiency. The study revealed that increases in urinary Cr loss associated with insulin resistance or diabetes are offset by increased absorption. Together with the results of other recent studies, these results clearly indicate that chromium can no longer be considered an essential element. Chromium(III) picolinate, [Cr(pic)_3 ], is a commonly used nutritional supplement in humans, that has also been approved for use in animals. Health concerns have arisen over the use of [Cr(pic)_3 ] in high doses. Male CD-1 mice were used to further assess the potential for reproductive or developmental toxicity at a dose of 200 mg/kg/day [Cr(pic)_3 ]. The results suggest that paternal dietary exposure to [Cr(pic)_3 ] has little potential for adverse reproductive effects. Studies with chromium nicotinate and chromium basic carboxylate complexes containing trifluoroacetate, 3-fluoropyridine, 3-trifluoromethylpyridine, and 4-trifluoromethylpyridine are described.
Chromium: binding studies with transferrin and peptide eeeegdd and its effect on colorectal cancer
(University of Alabama Libraries, 2016) Deng, Ge; Vincent, John B.; University of Alabama Tuscaloosa
Chromium as the trivalent ion has been proposed as an essential element for decades. Although that status has recently been discredited, doses of Cr3+ have been shown to generate improvements in insulin sensitivity and blood cholesterol levels in animals that have problems with their glucose and lipid metabolism systems, especially in type 2 diabetic rodent models. The mechanism for these effects at a molecular level is unknown. Transferrins are a class of protein that can reversibly bind 2 equivalents of metal ions. Biologically, transferrins are the main iron transport proteins in plasma. A role for transferrin in the delivery Cr3+ from plasma to tissues has been proposed. Studies have shown that Cr3+ readily binds to the two metal-binding sites in the two lobes of apotransferrin. The Cr3+ binding is accompanied by intense changes in the transferrin’s ultraviolet spectrum. This intense changes arises from chromic ion binding to two tyrosine residues in the two iron-binding sites of transferrin and allow the binding of Cr3+ to transferrin to be monitored. The rate at which Cr3+ binds to transferrin and the stability of Cr-transferrin recently has received considerable attention. In vitro spectroscopic studies previously found that the generation of Cr2-transferrin needs two weeks to guarantee a stoichiometric amount of Cr3+ binding. However, this study indicates that in the presence of 25 mM (bi)carbonate, the concentration in human blood, two Cr3+ ions bind rapidly and tightly to apotransferrin. Glycation of transferrin alters how tightly the protein binds iron and may alter the conformation of diferric transferrin, presumably changing its ability to deliver the iron to tissues. Given that Cr3+ complexes has been proposed as nutritional supplements to improve symptoms of type 2 diabetic subjects, understanding the ability of glycated transferrin to bind and transport Cr is significant, especially for determining the appropriate dose of Cr. This study examined the binding ability of Cr3+ to glycated serum transferrin and the transport of Cr in vivo by glycated transferrin. The results suggest that glycation of transferrin in subjects with elevated blood glucose levels should lower the ability of Cr from pharmacological agents to enter tissues. Additionally, these studies with glycated transferrin also indicate that heat treatment of transferrin makes dramatic change on its conformation and Cr binding ability.
Comparative Reactivities of Axial and Equatorial Carbinol Derivatives
(University of Alabama Libraries, 1961) Williams, George C.; University of Alabama Tuscaloosa
In an earlier work, rates of reaction of iodide ion with cyclopentylmethyl bromide and cyclohexylmethyl bromide in dry acetone were determined. These two compounds reacted at about the same rate, but there were differences in the entropies of activation and in the energies of activation. Cyclopentylmethyl bromide was found to have the lower entropy of activation. This lower value suggests that it is more difficult for the cyclopentylmethyl bromide molecule to assume the transition state. Since the favorable conformation for the bromomethyl group in cyclohexylmethyl bromide is the equatorial one, and since the bromomethyl group of cyclopentylmethyl bromide is similarly oriented, it was decided to study bromides in which the bromomethyl group is rigidly held in the axial or in the equatorial position. Then, by determining rates of reaction of iodide ion with these bromides, the effects of the different conformations would be apparent.

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