Chemistry Commons^™

Acylpyrazolones: Synthesis, Self-Assembly And Lanthanide Metal Ion Separation, Jun Yang

Dissertations

The central hypothesis that nanoscale self-assemblies can provide excellent metal ion recognition has been substantiated by employing acylpyrazolones and trivalent lanthanide metal ions as model systems. Several novel acylpyrazolones and their amphiphilic analogs have been designed, synthesized, and characterized. Their lanthanide metal ion recognition efficacies have been demonstrated through baseline separations of a mixture of light, middle, and heavy lanthanide metal ions by employing them in the aqueous mobile phase of high performance liquid chromatography (HPLC) with octadecylsilanized silica (ODS) as the stationary phase. The complex separation mechanism is influenced by the structures of acylpyrazolone and amphiphilic moieties, and spontaneous …

Ionic Liquid As Catalysts In The Cycloaddition Of Co2 To Styrene Oxide In Supercritical And Subcritical States, Joy Mwalimu

Masters Theses

Supercritical fluids (SCFs) have fascinated researchers ever since the discovery of a critical temperature more than a century ago.¹ Initial studies focused mainly on the physical properties of supercritical phases.² However, their use as reaction media has sparked mainly during the last five to ten years.²

The coupling of CO₂ and Ionic Liquids (ILs) in the synthesis of cyclic carbonates comes from an increasing need for environmentally and toxicologically benign processes for the production of high-value compounds. In my research, CO₂ was utilized as both a replacement solvent and a C₁ feedstock in its …

Synthesis And Spectroscopic Characterization Of Manganese Doped Zinc Sulfide Quantum Dot Nanocrystals, Pedro A. Gonzalez Beerman

Dissertations

Zinc sulphide quantum dots were synthesized in aqueous media using sodium polyphosphate as the stabilizer. The nanoparticles were 2.5 ± 0.5 nm and 5.0 ± 0.5 nm diameter depending on the synthetic procedure employed and the amount of Mn doped varied from 0.003 to 0.32% (w/w). The nanoparticles were characterized by UV-Vis absorption, luminescence, EPR, near edge x-ray absorption fine structure (NEXAFS), and x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD), and transmission electron microscopy (TEM). These quantum dots show a strong emission at 590 nm due to the ⁴T₁ -⁶A₁ transition characteristic of Mn …

Synthetic And Structural Studies Of Novel 1, 10-Phenanthroline Derivatives, Eunjoo Kim

Masters Theses

Asymmetric catalysis can provide a general approach to the preparation of enantiomerically enriched compounds in organic synthesis. Very often these asymmetric catalysts consist of a chiral ligand-metal complex. Because of the growing demand to develop enantioselective reactions in organic chemistry one focus of this area of research is the design and characterization of new chiral ligands for asymmetric synthesis.

The focus of my research is in the design, synthesis, and characterization of novel 1, 10-phenanthroline derivatives that could be used as chiral ligands in enantioselective reactions. Central to these studies have been the effect of substituents on the B-ring of …

Rhizopine Synthesis – Potential Mediators For Nitrogen Fixation In Legume Plants, Venkat Reddy Guduru

Masters Theses

This research project focused on novel and efficient synthetic approaches of inosamine derivatives (rhizopines). The preparation of specific rhizopines would help elucidate the microbial pathway of rhizopine catabolism and degradation, and determine the role of corresponding genes during nitrogen fixation. We have investigated regio - and stereoselective transformations of myo-inositol derivative 28 utilizing an organostannane as key intermediate towards rhizopine 1a. The synthesis involved several protection and deprotection strategies to control competing reactivities of six hydroxyl groups of myo-inositol. Rhizopine 1a was prepared efficiently as a single isomer in 8 steps and 13% yield by controlling reactions …

Effect Of Antioxidants On Cadmium Induced Oxidative Stress And Signal Transduction, Deepti Goel

Masters Theses

A study was done to establish if reactive oxygen species (ROS) participate in the signal transduction pathway through which cadmium induces gene transcription. Cadmium has become a concern in the health care community in the past few years as evidence suggests that cadmium can induce the development of tumors, influence cell signaling and cause damage to organs, tissue, cells and DNA. The mechanism by which cadmium exerts its action on cellular processes or induces toxicity is however unclear although there is evidence to suggest that ROS play a role. Our laboratory is interested in understanding the mechanisms of differentially regulated …

Copper Exchange Studies Between The First And Fourth N-Terminal Metal-Binding Domains Of Wilson Disease Atpase, Jennifer Bunce

Masters Theses

The human copper-transporting ATPase Wilson's disease protein was one of the first proteins shown to be actively involved in cellular copper homeostasis. The protein includes six N-terminal metal binding domains. The individual capabilities of the domains to bind and transfer copper are not yet fully understood. Each metal-binding domain is about 72 amino acid residues long and contains the conserved binding motif GMTCXXC, of which the cysteines are involved in the copper coordination. Studies have shown that the protein binds six copper atoms suggesting the potential involvement of each metal-binding domain. Separate functional roles for the latter domains have been …

Synthesis And Characterization Of A Recombinant Thrombin Inhibitor, Joel Lwande

Masters Theses

The final step of the blood coagulation cascade is catalyzed by thrombin, a serine protease. Like most enzyme activities, thrombin activity encounters inhibition from both direct and indirect inhibitors. A new thrombin inhibitor peptide named theromin was recently isolated from the leech Theromyzon tessulatum, and it is the most potent thrombin inhibitor isolated to date. Theromin is made up of 67 amino acid residues, out of which 16 are cysteines engaged in 8-disulfide bridges.

We synthesized the theromin gene and expressed the protein in Eschericia coli. We purified the recombinant protein and carried out thrombin inhibition assays that …

Analysis Of Benzo(A)Pyrene-Induced Gene Expression Changes In Fisher 344 Rat Liver By Affymetrix Microarray And Quantitative Real-Time Pcr, Alhaji Umar N’Jai

Dissertations

No abstract provided.

Metal Ion Imprinted Polymers For Biomolecular Recognition, Len A. Harris

Masters Theses

Protein recognition by HPLC, based on histidine residues, was achieved by incorporating a copper chelating ligand covalently bonded to a polystyrene/divinyl benzene substrate, into column packing. The metal ion was bonded to the substrate in two ways: randomly, where the copper was bound to the ligand after the substrate polymerization and imprinted, where the copper was bound to the ligand before the substrate polymerization. The effect of this templating was measured by protein separation parameters of the resulting HPLC chromatographs. The hypothesis of this thesis is the imprinted substrate will have a higher copper content, and with coppers affinity toward …

A Comparative Study Of Photomultiplier Tubes And Charge Coupled Devices In Glow Discharge-Optical Emission Spectrometry, Robert James Broadwater

Masters Theses

This Masters Thesis compared two glow discharge-optical emission spectrometers designed around two different types of detectors: the photomultiplier tube (PMT) and the charge-coupled device (CCD). The two instruments compared were the LECO SA2000 (PMT-based) and the LECO GDS500a (CCD-based). Detection limit, dynamic range, precision, accuracy, and drift were determined to compare the detection systems between 165 and 450nm.

The PMT-based system outperformed the CCD-based system in all five of the categories studied based on the initial protocol. However, it was shown that improvements could be made in four of the five categories studied by exploiting the CCDs ability to monitor …

Capillary Electrophoretic Separations Of Metal Ions, Elena Hofman

Masters Theses

Transition-metal (Zn(II), Co(II), Ni(II) and Cu(II)) ion separation was studied using 8-hydroxyquinoline-5-sulfonic acid and 2-methyl-8-hydroxyquinoline ligands with surfactants (cationic and anionic) by capillary electrophoresis under a variety of conditions (like pH, ionic strength, voltage and ion, ligand and surfactant amounts) and has debuted a clear separation mechanism. With cationic surfactants, ligands compete with capillary surface silanols for the metal ions; with anionic surfactants, ligands, silanols and micelles compete.

An empirical parameter, K_e, (electrophoretic-mobilities based) rationalizing the separation was proposed, experimentally analyzed and supported; it provides a silanol group per cm² value of the capillary surface, an equilibrium …

Mechanistic Studies On The Antagonistic Effect Of Chromium On Bpde Mutant Frequency In Human Fibroblasts, Felicia Codrea

Masters Theses

The purpose of this study was to investigate the possible mechanisms involved in the decrease in mutant frequency when cells are treated with two different types of carcinogens: chromium (VI) in combination with benzo(a)pyrene diol epoxide (BPDE). Three of our working hypotheses are: Cr alone or Cr and BPDE synergistically activate detoxifying enzyme glutathione-S-transferase (GST), Cr alone or Cr and BPDE act synergistically to inhibit cell cycle at the G₁/S boundary thus allowing more time for DNA repair, and Cr alone or Cr and BPDE synergistically activate DNA repair systems which result in more efficient repair of DNA …

Metal Ion Separation Mediated By Organized Molecular Assemblies, Hong Cao

Masters Theses

We have investigated the separation of Co(II), Ni(II), Cu(II) and Zn(II) by the ligands 8-hydroxyquinoline- 5-sulfonic acid and 7-iodo-8-hydroxy-quinoline- 5-sulfonic acid in the presence of the anionic surfactant sodium dodecyl sulfate (SDS) and the cationic surfactant octyltrimethylammonium bromide (OTAB) . Baseline separations have been achieved by HPLC employing an octadecylsilanized silica (ODS) column. The underlying mechanisms of separation have been determined.

The significant new results of our studies are: (1) separation is not possible without the presence of surfactants and hence organized assemblies; (2) separations can be achieved under submicellar concentrations; (3) the separations are not driven by micelles; and …

Separation Of Enantiomers With Chiral Dendrimer, Jie Zhuang

Masters Theses

Chiral dendrimers with .unique ordered structures are especially attractive for the recognition of chiral molecules based on the three point contact model. We have successfully synthesized first generation chiral dendrimers containing L- and D- tryptophan methyl ester moieties and characterized them by NMR, IR, UV-Visible, MS, and optical activity. L-tryptophan methyl ester dendrimer was converted to its acid form in order to attach it to aminopropyl silica for the HPLC separation of enantiomers. The aminopropyl silica containing 1.52mmols/g of NH₂ groups binds about 0.3mmols of dendrimer per gram and has about 0.4mmols of free NH₂ groups per gram. …

Pan, Ppn And Mpan Measurements And The Quantitative Relationship Of Pan And Mpan In Biogenic Hydrocarbon Conditions, Chen Wangchun

Masters Theses

Simultaneous measurements of PAN, PPN and MPAN were made during the SOS 1999 Nashville campaign at Dickson site. The PANs data at this site were rich and complex. PAN and MP AN showed obvious diurnal change but PPN did not during this period. PAN and ozone have a clear positive relationship. Due to the special location of the site, winds from different directions bring anthropogenic hydrocarbons (AHCs) or biogenic hydrocarbons (BHCs) to the site. The data showed that the influence of AHCs and BHCs on PANs compounds varied on different days. Average values of PAN/PPN and PAN/MPAN from MLR may …

Characterization Of Organo-Tin And Organo-Mercury Compounds With Electrospray Mass Spectrometry, Kan Zhu

Masters Theses

Metal-containing compounds are often found as pollutants in the environment. Obtaining speciation information about these compounds is important to understanding toxieity and bioaccumulation. Electrospray Mass Spectrometry (ESMS) is a technique that has the potential to provide rapid and direct speciation information of solution phase metal compounds. The ionization behavior of chemical species is related to their electron affinities. The higher the electron affinity, the easier it will be reduced during the ionization process. Additionally, solvent with different polarity and surface tension will also affect the ionization and reduction products. Organo-tin compounds with more alkyl groups will be ionized more efficiently, …

Alkyl Nitrates In Dickson During The Sos 1999 Field Campaign, Mei Ma

Masters Theses

Measurements of alkyl nitrates were performed during the Southern Oxidants Study (SOS) 1999 Summer Field Campaign in Dickson, TN from June 10 to July 15, 1999. The developed GC-ECD method was tested and used successfully. Nine alkyl nitrates were measured and six alkyl nitrates were quantified. The measured alkyl nitrates expect methyl nitrate showed higher mixing ratios under northeasterly and southeasterly wind, which brought anthropogenic sources to the measurement site, and lower mixing ratios when wind came from northwest and southwest, which brought NOx and clean air, respectively. The contribution of the measured alkyl nitrates to the total oxidized nitrogen …

A Qualitative Investigation Of The Polymerization Process In The Ihss Humic Substances Extraction Procedure Using Model Phenolic Compounds, Roger J. Germay

Masters Theses

Achard (1786) extracted peat with alkali and reported obtaining dark compounds now called humic substances. These are complex, high molecular weight, polyphenolic compounds naturally occurring in soil, in fresh-water and in marine environments. They are biodegradation products of plant materials.

The International Humic Substances Society (IHSS) adapted Achard's method to separate humic substances into three fractions: (1) humic acids (HA), soluble only at high pH; (2) fulvic acids (FA), water-soluble at any pH; and (3) humin, insoluble at any pH. The IHSS method involves contact of soil with 0.1N.NaOH solution, followed by acidification with HCl.

In this study, 0.01 N. …

Surface Modification Of Diamond And Determination Of Kinetics And Mechanism Of Modification Reactions, Humera Farooq

Masters Theses

A series of photochemically modified diamond surfaces were prepared. Surface functional groups added included, chlorine, bromine, methoxy, amine, methylamine, dimethylarnine and trimethylammonium chloride. Photochemically chlorinated and brominated diamond surfaces were used as synthetic intermediates. The modified diamond surfaces were characterized by Diffuse Reflectance Infrared Spectroscopy (DRIFT) and X-ray Photoelectron Spectroscopy (XPS).

The study was mainly focused on understanding the kinetic processes and reaction mechanism of modified surfaces. The observed rate constants for surface hydrogen loss and HCl (g) evolution were found to be identical. Similar rate constants were observed for amine substitution and consumption of ammonia.

The study of action …

Quantification Of Benzo[A]Pyrene-Guanine Adducts In In Vitro And In Vivo Tissue Samples By Lc Tandem Mass Spectrometry, Po-Chang Chiang

Dissertations

No abstract provided.

An Investigation Of Friedel-Crafts Alkylation Reactions In Super- And Subcritical Carbon Dioxide And Under Solventless Reaction Conditions, Kan Nie

Masters Theses

This study investigates the Friedel-Crafts alkylation reaction of triphenylmethanol with methoxybenzene (anisole) in supercritical and subcritical carbon dioxide, and under solventless reaction conditions. The reaction was initiated using trifluoroacetic acid to produce triphenylmethylcarbocation as the reaction intermediate. Isolated product yields of the Friedel-Crafts product, p-methoxytetraphenylmethane, are reported. The possibility of using the above reaction as an alternative synthesis in an undergraduate organic laboratory to teach some of the tenets of green chemistry is also presented. Additionally, we have investigated the use of benzhydrol, 9-hydroxyxanthene and 9-phenylxanthen-9- ol as potential carbocation sources for supercritical carbon dioxide synthesis and we report those …

Allosteric Tuning Of Ruthenium 2,2’-Bipyridyl Luminescent Sensor Systems, Daqing Gan

Masters Theses

A series of new ruthenium bipyridyl crown supramolecular sensor systems containing two binding sites were synthesized. The crystal structure and photophysical properties of the developed sensor systems were thoroughly studied using x-ray, nuclear magnetic resonance and photoscopy methods. It turned out that the chelation of transition metal on the remote sites of the bipyridyl crown ligands greatly reduced the reactivity of the crown cavity. It is believed that the chelation of transition metal on the nitrogen atoms forces the bipyridyl function towards coplanarity and restricts the conformational freedom of the crown ring. The conformational rigidity in turn influences the binding …

Photophysical Study Of Linked 1,4,7-Triazacyclonane Cr (Iii) Complexes, Weizhen Tu

Masters Theses

A series of mono and bimetallic Cr(III) complexes based on the 1,4,7- triazacyclonoane(TACN) were prepared. Complexes of the Cr(TACN)X₃ , and Cr₂(DTNE)X₆ demonstrated marked difference of photophysical properties on the nature of X. In cases where X is more easily oxidized, enhanced extinction coefficient in the ⁴A₂ ➔ ²T, absorption and larger quantum yield of emission at 77K were observed in the dimer complexes. Shorter lifetime and enhanced decay rate were also found in the dimer complexes suggests that there might exists weak coupling behavior between the two Cr(III) metal cents in the …

Reaction Of Caffeic Acid With Amino Acids, Yonggang Wang

Masters Theses

The reaction of caffeic acid with tryptophan was studied as a model for the reaction of caffeic acid with amino acids in the aquatic environment. Although the autoxidation reaction of caffeic acid in aqueous solution with subsequent dimerization had been previously studied, it was examined as well for comparison purposes. The present studies demonstrate that oxidized caffeic acid would react with tryptophan. The reaction, like the dimerization reaction, was catalyzed by the presence of iron(III) ions at low pH ( <4) and by hydroxide ions at high pH (10). The reaction of caffeic acid with itself yielded six products, four of which were identified by mass spectroscopy as dimers, with the other two being trimers. The reaction of caffeic acid with tryptophan yielded three product peaks. Two of the product peaks had similar retention times to the dimers from the self-reaction of caffeic acid; the third was a new product resulting from the reaction of caffeic acid with the tryptophan.

A mechanism for the reaction of caffeic acid with tryptophan has been proposed. This mechanism was based on the analysis …

Photodegradation Of Pcbs In Natural Waters, Adriana R. Nicolaescu

Masters Theses

PCBs are widely distributed in the environment and they are biologically refractory and toxic compounds. There is great interest in understanding their fate in the environment, and also for finding safe and effective degradation methods.

This study is concerned with the photodegradation of four PCB congeners: PCB 5, PCB 18, PCB 77, PCB 128 in natural waters. Natural waters contain humic substances which can greatly influence the environmental fate of the PCBs. The different degradation of the four congeners was studied in standardized systems and in humic acid or nitrate solutions, under environmental conditions. DMDE and Methoxyclor (whose environmental half-lifetimes …

Alkyl Nitrates During The Prophet ’98 Summer Intensive, Kristi A. Ostling

Masters Theses

As part of the PROPHET intensive held at the University of Michigan Biological Station in northern Michigan, a gas chromatography system for making fast-turnaround measurements of C1 to C5 alkyl nitrates was developed and deployed from July 19 to August 21, 1998. Every 30 minutes, samples were automatically acquired on a small Tenax trap made from silicosteel column and injected on a GC column by thermal desorption prior to ECD detection. Tests performed to measure breakthrough and on-trap destruction indicated no breakthrough for C3, C4, and C5 nitrates and excellent stability for these compounds on the trap. Chromatographic resolution of …

Spectroscopic And Kinetic Investigation Of Carbocation Reactivity In Supercritical Carbon Dioxide, Hongshu Jin

Masters Theses

Recent interest in the use of supercritical CO₂ as an environmentally benign reaction medium has included the development of solvent systems that may support polar and ionic chemistry. Carbocations are key intermediate in a variety of synthetically important reactions and characterization of their reactivity is the focus of this work. UV-visible absorption, and steady-state and time-resolved fluorescence spectroscopy has been used to identify and monitor the reaction kinetics of 9- phenylxanthenium carbocation. The arylcarbocation is conveniently generated from 9- phenylxanthen-9-ol in supercritical CO₂ under mildly acidic conditions. Under these conditions 9-phenylxanthenium ion is extremely stable and persists for …

Gas Sparging And Humic Acid Sorption/Desorption, Masaki Sakakibara

Masters Theses

Partition coefficients (K_DOC) for sorption of PAHs and chlorinated benzenes to dissolved humic acids (HA) were measured using gas-sparging methodology. The resulting K_DOC values were significantly lower than the K_OW-based K_DOC values, which generally appear to provide reliable estimates for K_DOC values. The K_DOC values measured by gas sparging were also strongly influenced by the concentration of HA in solution, as measured by dissolved organic carbon content (DOC). Increasing DOC concentration consistently resulted in decreased K_DOC values for all compounds investigated. Previous studies have claimed that K_DOC values measured using …

Synthesis, Characterization And Photophysical Behavior Of A Cr(Iii) Bimetallic System, Yan Chen

Masters Theses

Many binuclear transition metal complexes have been studied to understand the nature of interactions between the metal centers. People have found Simultaneous Pair Excitation phenomenon in some bimetallic system that can serve as a potential source of Non-Linear Optical behavior.

Thus a series of Cr₂ -([14]aneN₄)₂-X₄ⁿ⁺ complexes were synthesized and characterized. Only the cis,cis configuration was found. The results were compared with those of their monomer analogs. The electronic structures are very similar in both monomer and dimer complexes. The quantum yield, UV-Vis absorption and lifetime studies suggested a possible coupling between the …