Chemistry Commons^™

The Use Of Heterocycles As Important Structures In Medicinal Chemistry, Sayre Weast

Honors Theses

Heterocycles have many applications in the discipline of medicinal chemistry. These structures are found in various natural products with relevant biological activity. Our research group, in collaboration with two others, is particularly interested in one heterocycle, quinoline, as a scaffold for HIV-1 integrase inhibitors. A synthetic route has been developed to produce a derivatized structure on small scale. One goal of this thesis was to expand the scale of this route to provide increased quantities of the quinoline scaffold. Procedures were adapted to accommodate the increase in scale to convert commercially available anthranilic acids to quinolines via the isatoic anhydride. …

Synthesis, Characterization, And Utilization Of Iron Ii Ion Sensing Fluorescent Probes For Detection Of Early Onset Anodic Corrosion, Dane N. Wedgeworth

Honors Theses

Corrosion effects can be seen in infrastructure all around the world. From rusted bridges, ships, and other steel surfaces, the price of corrosion adds up quickly with repairs, maintenance, and complete replacement. Common approaches to corrosion detection and prevention require slow, optical inspection to begin the repair and maintenance process, which can also be very slow and costly. However, recent literature suggests that metal chelating probes can yield new understanding of the processes of corrosion faster and with greater specificity in location and diversity in mechanisms for early onset of corrosion. Earlier corrosion detection can be characterized by several ways. …

A Study On The Modifications Of [2.2]Paracyclophane And Their Effects On The Enantioselectivity Of The Copper Catalyzed Cyclopropanation Reaction, Yousef Dawoud

Honors Theses

The use of chiral [2.2]paracyclophane Schiff-base ligands has been shown to induce enantioselectivity in the copper catalyzed cyclopropanation of styrene with diazoesters. ¹ Previous research by Dr. Masterson tested Schiff-base ligands based on 4- amino[2.2]paracyclophane with moderate enantioselectivity. In this project, the Schiff-base N- salicylidene-4-amino[2.2]paracyclophane, was modified by way of Grignard addition to the imine carbon and its enantioselective properties were explored with the copper catalyzed cyclopropanation. The methyl Grignard addition to N- salicylidene-4-amino[2.2]paracyclophane was successful in producing the amino alcohol and the amino alcohol was characterized. The amino alcohol was produced from the R enantiomer of the Schiff-base and …

Low Molecular Weight Fluorescent Probes (Lmfps) To Detect The Group 12 Metal Triad, Ashley D. Johnson, Rose M. Curtis, Karl J. Wallace

Faculty Publications

Fluorescence sensing, of d-block elements such as Cu²⁺, Fe³⁺, Fe²⁺, Cd²⁺, Hg²⁺, and Zn²⁺ has significantly increased since the beginning of the 21st century. These particular metal ions play essential roles in biological, industrial, and environmental applications, therefore, there has been a drive to measure, detect, and remediate these metal ions. We have chosen to highlight the low molecular weight fluorescent probes (LMFPs) that undergo an optical response upon coordination with the group 12 triad (Zn²⁺, Cd²⁺, and Hg²⁺), as these metals have …

Large Fatty Acid-Derived Aβ42 Oligomers Form Ring-Like Assemblies, Wenhui Xu, Dexter N. Dean, Kelli A. Stockmal, Sarah E. Morgan, Ulrich H.E. Hansmann, Vijayaraghavan Rangachari

Faculty Publications

As the primary toxic species in the etiology of Alzheimer disease (AD) are low molecular weight oligomers of Aβ, it is crucial to understand the structure of Aβ oligomers for gaining molecular insights into AD pathology. We have earlier demonstrated that in the presence of fatty acids, Aβ42 peptides assemble as 12-24mer oligomers. These Large Fatty Acid-derived Oligomers (LFAOs) exist predominantly as 12mers at low and as 24mers at high concentrations. The 12mers are more neurotoxic than the 24mers and undergo self-replication, while the latter propagate to morphologically distinct fibrils with succinct pathological consequences. In order to glean into their …

Functional Polymers Through Mechanochemistry, Stephen Schrettl, Diedrik W.R. Balkenende, Céline Calvino, Marc Karman, Ana Lavrenova, Laura N. Neumann, Yoshimitsu Sagara, Ester Verde-Sesto, Michela Di Giannantonio, Yoan C. Simon, Katharina M. Fromm, Marco Lattuada, Christoph Weder

Faculty Publications

While coupling mechanical and chemical processes is widespread in living organisms, the idea to harness the mechanically induced dissociation of weak covalent and non-covalent bonds to create artificial materials that respond to mechanical stimulation has only recently gained attention. Here we summarize our activities that mainly revolve around the exploitation of non-covalent interactions in (supramolecular) polymeric materials with the goal to translate mechanical stresses into useful, pre-defined events. Focusing on mechano- chromic polymers that alter their optical absorption or fluorescence properties, several new operating principles, mechanosensitive entities, and materials systems were developed. Such materials are expected to be useful for …

Spatial Patterns Of Particulate Organic Carbon Concentrations And Isotopic Signatures Across A Salinity Gradient In A River Dominated Estuary, Lauren E. Alvaro, John C. Lehrter, Mai Fung

Gulf and Caribbean Research

No abstract provided.

A New Generation Of Functional Polyisobutylenes For Advanced Applications, Corey M. Parada

Dissertations

Polyisobutylene (PIB) is a fully saturated, aliphatic polymer of high commercial importance due to its superior gas barrier properties and high chemical/oxidative stability. One commercial end-use for PIB is in insulated glass windows (IGU), where it acts as a gas/moisture barrier and sealant. Under certain adverse conditions, catastrophic failure of the PIB sealant may result in aesthetic and functional failure of the IGU, which necessitates replacement of the unit. Thus, there exists a need to improve current generations of thermoplastic PIB sealants to be able to withstand the harsh environments found in current real-world applications.

In the first project, we …

Polyhedral Oligomeric Silsesquioxane-Phosphate Glass Matrix Nanocomposites With Additional Chapter On Phosphate Glass-Poly(Ethylene Terephthalate) Matrix Composites, Kyoungtae Kim

Dissertations

Preparation and characterization of tin fluorophosphate glass (Pglass) matrix nanocomposites incorporating polyhedral oligomeric silsesquioxane (POSS) were investigated on the structural, thermal, morphological, mechanical, and rheological properties. Various processes including synthesis, extrusion and sintering processes were applied to prepare the nanocomposite samples. Another application of POSS with hydrophobic functional groups on the well-structured nanoscale silicate cage with three silanol groups was investigated to present the feasibility to use POSS molecule as a coating material on the surface of the hydrophilic inorganic glass. In addition, Poly(ethylene terephthalate) polymer matrix composites incorporating Pglass was studied to present the benefits of the Pglass with …

Effect Of Network Structure On Free Volume And Gas Transport Properties Of Thiol-Ene And Epoxy-Amine Networks, Ramesh Krishnan Ramakrishnan

Dissertations

Network parameters such as cross-link density or intermolecular interactions were used as effective parameters to control polymer chain packing or free volume and thereby control the mass transport properties of networks.

A series of polyethylene glycol (PEG) based thiol-ene elastomeric networks having a broad range of molecular weight between cross-links, M_c, (inverse of cross-link density) was prepared. The specific volume of the networks was studied as a function of temperature and pressure using high pressure dilatometry, and the obtained PVT data was fit using Simha-Somcynsky equation of state (S-S eos) analysis. Fractional free volume, quantified through S-S eos …

Structure-Property Relationships Of Solvent-Cast Organic Thin Films For Model Corrosion Control Coatings, Austin Maples

Dissertations

This dissertation aimed at answering several fundamental questions, specifically: 1) What is the effect of scribing parameters on visual corrosion assessments? 2) What role do molecular weight, residual solvent, and polymer composition have on morphological changes in organic thin films? 3) What alternatives to visual assessments could be implemented to better understand and detect corrosion before macroscopic failure? This research definitively proved that scribes can vary in type and dimensions, and yet are still comparable if the scribe dimensions before exposure are known. Furthermore, it demonstrated that solvents common to a variety of coating industries could become trapped within the …

Information-Driven Inverse Approach To Disordered Solids: Applications To Amorphous Silicon, Dil K. Limbu, Raymond Atta-Fynn, David A. Drabold, Stephen R. Elliott, Parthapratim Biswas

Faculty Publications

© Physical Review Materials

Publisher's Version

Pva/Chitosan/Silver Nanoparticles Electrospun Nanocomposites: Molecular Relaxations Investigated By Modern Broadband Dielectric Spectroscopy, Mohammad K. Hassan, Ahmed Abukmail, Alaa J. Hassiba, Kenneth A. Mauritz, Ahmed A. Elzatahry

Faculty Publications

In this study, we used broadband dielectric spectroscopy to analyze polymer nanofibers of poly(vinyl alcohol)/chitosan/silver nanoparticles. We also studied the effect of incorporating silver nanoparticles in the polymeric mat, on the chain motion dynamics and their interactions with chitosan nanofibers, and we calculated the activation energies of the sub-T_g relaxation processes. Results revealed the existence of two sub-T_g relaxations, the first gets activated at very low temperature (−90 °C) and accounts for motions of the side groups within the repeating unit such as –NH₂, –OH, and –CH₂OH in chitosan and poly(vinyl alcohol). The second …

Unexpected Effects Of Inorganic Phosphate Glass On Crystallization And Thermo-Rheological Behavior Of Polyethylene Terephthalate, Kyoungtae Kim, Shahab Kashani Rahimi, Todd M. Alam, Eric G. Sorte, Joshua U. Otaigbe

Faculty Publications

The effects of ultra-low glass transition temperature (T_g) phosphate glass (Pglass) on the thermal, morphological, rheological, mechanical, and crystallization properties of hybrid Pglass/poly(eththylene terephthalate)(PET) were investigated. Nano- and micro-scale distribution of the Pglass in the PET polymer matrix was observed. The polydispersed Pglass in the PET matrix functioned as a nucleation agent, resulting in increasing crystallization temperature. The Pglass in the PET matrix decreased the T_g, indicating a plasticizing effect of the Pglass in the hybrids that was confirmed by the significantly decreased complex viscosity of the PET matrix. In addition, with increasing temperature, a non-terminal …

Quinolines From The Cyclocondensation Of Isatoic Anhydride With Ethyl Acetoacetate: Preparation Of Ethyl 4-Hydroxy-2-Methylquinoline-3-Carboxylate And Derivatives, Nicholas Jentsch, Jared D. Hume, Emily B. Crull, Samer M. Beauti, Amy H. Pham, Julie A. Pigza, Jacques Kessl, Matthew G. Donahue

Faculty Publications

A convenient two-step synthesis of ethyl 4-hydroxy-2-methylquinoline-3-carboxylate derivatives has been developed starting from commercially available 2-aminobenzoic acids. In step 1, the anthranilic acids are smoothly converted to isatoic anhydrides using solid triphosgene in THF. In step 2, the anhydride electrophiles are reacted with the sodium enolate of ethyl acetoacetate, generated from sodium hydroxide, in warm N,N-dimethylacetamide resulting in the formation of substituted quinolines. A degradation–build-up strategy of the ethyl ester at the 3-position allowed for the construction of the α-hydroxyacetic acid residue required for the synthesis of key arylquinolines involved in an HIV integrase project.

Enhancement Of Triplet-Sensitized Upconversion In Rigid Polymers Via Singlet Exciton Sink Approach, Steponas Raišys, Saulius Juršėnas, Yoan C. Simon, Christoph Weder, Karolis Kazlauskas

Faculty Publications

To increase the practical usefulness of solid-state sensitized upconversion (UC) materials as components of solar energy harvesting systems, it is important to identify and suppress loss mechanisms, and increase the UC quantum yield (Φ_UC). Here we focus on a benchmark UC system consisting of the emitter 9,10-diphenylanthracene (DPA) and the sensitizer platinum octaethylporphyrin (PtOEP) in a rigid poly(methyl methacrylate) (PMMA) matrix, and show that one of the major losses originates from Förster resonant energy transfer (FRET) from DPA back to PtOEP. Even though DPA emission lies within the PtOEP transparency window, the quantitative assessment of singlet exciton diffusion …

Rational Design Of Superhydrophilic/Superoleophobic Surfaces For Oil-Water Separation Via Thiol-Acrylate Photopolymerization, Li Xiong, Wei Guo, Benjamin M. Alameda, Reese Sloan, William D. Walker, Derek L. Patton

Faculty Publications

We report a simple, rapid, and scalable strategy to fabricate surfaces exhibiting in-air superoleophobic/superhydrophilic wetting via sequential spray deposition and photopolymerization of nanoparticle-laden thiol–acrylate resins comprising both hydrophilic and oleophobic chemical constituents. The combination of spray deposition with nanoparticles provides hierarchical surface morphologies with both micro- and nanoscale roughness. Mapping the wetting behavior as a function of resin composition using high- and low-surface-tension liquid probes enabled facile identification of coatings that exhibit a range of wetting behavior, including superhydrophilic/superoleophilic, superhydrophobic/superoleophobic, and in-air superhydrophilic/superoleophobic wetting. In-air superhydrophilic/superoleophobic wetting was realized by a dynamic rearrangement of the interface to expose a greater …

Role Of Stone-Wales Defects On The Interfacial Interactions Among Graphene, Carbon Nanotubes, And Nylon 6: A First-Principles Study, Sanjiv K. Jha, Michael Roth, Guido Todde, J. Paige Buchanan, Robert D. Moser, Manoj K. Shukla, Gopinath Subramanian

Faculty Publications

We investigate computationally the role of Stone-Wales (SW) defects on the interfacial interactions among graphene, carbon nanotubes (CNTs), and Nylon 6 using density functional theory (DFT) and the empirical force-field. Our first-principles DFT calculations were performed using the Quantum ESPRESSO electronic structure code with the highly accurate van der Waals functional (vdW-DF2). Both pristine and SW-defected carbon nanomaterials were investigated. The computed results show that the presence of SW defects on CNTs weakens the CNT-graphene interactions. Our result that CNT-graphene interaction is much stronger than CNT-CNT interaction indicates that graphene would be able to promote the dispersion of CNTs in …

Synthetic And Theoretical Studies For Cyclization Reactions To Form C-C And C-N Bonds, Nicholas Jentsch

Dissertations

Natural product total synthesis provides an alternative method for obtaining medicinally relevant compounds in a more efficient process with higher yields than what nature can provide. Natural products pose significant synthetic challenges due to the unique heterocyclic skeletons with fused and spirocyclic ring systems. Therefore, it is paramount to develop efficient reaction methodologies targeting substructures such as cyclic ureas and spiro[4.5]decanes which are prominent among marine natural products and Lycopodium alkaloids, respectively. Presented here is a compilation of research seeking to develop synthetic methods for the construction of cyclic moieties such as those previously mentioned. The objectives that are addressed …

A System For Conducting Laser-Induced Fluorescence Measurements On Gas Mixtures Exposed To Alpha Radiation, Patrick Ables

Master's Theses

This paper documents modifications to an existing vacuum system to allow laser-induced fluorescence spectroscopy measurements within simulated atmospheres under a variety of conditions. This added capability will expand the laboratory’s ability to experimentally validate a computational model that calculates the effects of radiation within the atmosphere. The computational model could reveal radiation-induced chemical products that can be used to develop an alternative detection method that can be implemented from a safe distance. The selection of molecules for experimental validation has been limited to those which can be detected utilizing cavity ringdown spectroscopy. The current model indicates nitric oxide and ozone …

Hiv-1 Integrase-Targeted Short Peptides Derived From A Viral Protein R Sequence, Xue Zhi Zhao, Mathieu Métifiot, Evgeny Kiselev, Jacques Kessl, Kasthuraiah Maddali, Christophe Marchand, Mamuka Kvaratskhelia, Yves Pommier, Terrence R. Burke Jr.

Faculty Publications

HIV-1 integrase (IN) inhibitors represent a new class of highly effective anti-AIDS therapeutics. Current FDA-approved IN strand transfer inhibitors (INSTIs) share a common mechanism of action that involves chelation of catalytic divalent metal ions. However, the emergence of IN mutants having reduced sensitivity to these inhibitors underlies efforts to derive agents that antagonize IN function by alternate mechanisms. Integrase along with the 96-residue multifunctional accessory protein, viral protein R (Vpr), are both components of the HIV-1 pre-integration complex (PIC). Coordinated interactions within the PIC are important for viral replication. Herein, we report a 7-mer peptide based on the shortened Vpr …

Unraveling Substituent Effects On The Glass Transition Temperatures Of Biorenewable Polyesters, Xiaopeng Yu, Junteng Jia, Shu Xu, Ka Un Lao, Maria J. Sanford, Ramesh K. Ramakrishnan, Sergei I. Nazarenko, Thomas R. Hoye, Geoffrey W. Coates, Robert A. Distasio Jr.

Faculty Publications

Converting biomass-based feedstocks into polymers not only reduces our reliance on fossil fuels, but also furnishes multiple opportunities to design biorenewable polymers with targeted properties and functionalities. Here we report a series of high glass transition temperature (T_g up to 184 °C) polyesters derived from sugar-based furan derivatives as well as a joint experimental and theoretical study of substituent effects on their thermal properties. Surprisingly, we find that polymers with moderate steric hindrance exhibit the highest T_g values. Through a detailed Ramachandran-type analysis of the rotational flexibility of the polymer backbone, we find that additional steric hindrance does …

Thermosetting Polymers Via Azide Alkyne Cycloaddition, Richard H. Cooke Iii

Dissertations

This dissertation exploits properties inherent to azide-alkyne cycloaddition and applies practical solutions to difficult problems. Chapter II addresses structure-property relationships in glassy azido-alkyne matrices by varying the identity of the central linkage within tetrapropargyl bis-aniline-type crosslinkers, and by the addition or omission of Cu(I) catalyst. This systematic study showed that an ether or methylene linkage yielded lower melting tetrapropargyl crosslinkers that were soluble in, and produced homogeneous, networks when cured with, a standard azido resin, di(3-azido-2-hydroxypropyl) ether of bisphenol-A; in contrast, a sulfone linkage yielded a relatively insoluble crosslinker and poorly dispersed, heterogeneous networks when reacted with the same …

Nearly Defect-Free Dynamical Models Of Disordered Solids: The Case Of Amorphous Silicon, Raymond Atta-Fynn, Parthapratim Biswas

Faculty Publications

It is widely accepted in the materials modeling community that defect-free realistic networks of amorphous silicon cannot be prepared by quenching from a molten state of silicon using classical or ab initio molecular-dynamics (MD) simulations. In this work, we address this long-standing problem by producing nearly defect-free ultra-large models of amorphous silicon, consisting of up to half a million atoms, using classical MD simulations. The structural, topological, electronic, and vibrational properties of the models are presented and compared with experimental data. A comparison of the models with those obtained from using the modified Wooten-Winer-Weaire bond-switching algorithm shows that the models …

Small-Angle X-Ray Scattering In Amorphous Silicon: A Computational Study, Durga Paudel, Raymond Atta-Fynn, David A. Drabold, Stephen R. Elliott, Parthapratim Biswas

Faculty Publications

We present a computational study of small-angle x-ray scattering (SAXS) in amorphous silicon (α-Si) with particular emphasis on the morphology and microstructure of voids. The relationship between the scattering intensity in SAXS and the three-dimensional structure of nanoscale inhomogeneities or voids is addressed by generating large high-quality (α-Si networks with 0.1%–0.3% volume concentration of voids, as observed in experiments using SAXS and positron annihilation spectroscopy. A systematic study of the variation of the scattering intensity in the small-angle scattering region with the size, shape, number density, and the spatial distribution of the voids in the networks is presented. Our results …

An Exploration Of Pyrrole Groups On The Enantioselectivity Of Pig Liver Esterase, Brian Long

Honors Theses

Pig Liver Esterase (PLE) is a serine protease enzyme that can interact with one side of a diester to hydrolyze the ester to a carboxylic acid, and research has found that the level of hydrophobicity of side groups can impact the enantioselectivity of PLE hydrolysis.1, 2 The Jones Model is what current researchers use to model the active site of PLE, but the nature of its binding pockets, namely the Hydrophobic Long (HL) pocket, has been called into question.3 Dimethyl 2-((pyrrole-2-yl)methyl)-2-methylmalonate was prepared to be subjected to PLE hydrolysis to see whether enantioselectivity was found. Chiral HPLC revealed 25.32% enantiomeric …

Biocompatible, Responsive Polysoaps Via Raft Copolymerization For The Delivery Of Model Cancer Therapeutics, Mason Dearborn

Honors Theses

Many chemotherapeutic drugs are small, hydrophobic molecules that require water-soluble, biocompatible nanocarriers for enhanced vascular circulation. Existing polymeric carriers either conjugate the drug along a copolymer backbone or sequester drugs within a protected interior domain to be delivered to specific sites in the body. Such therapeutic systems must overcome a myriad of hurdles, beginning with complex, multi-step syntheses, followed by other inherent barriers that limit the efficiency of drug delivery at the targeted site. This work aims to circumvent a number of these issues using biocompatible, stimuli-responsive polysoaps that are capable of unimeric micelle formation, hydrophobic drug delivery, and triggered …

Understanding The Coating-Substrate Interface Changes And Degradation Caused By Environmental Acclimation With Water And Electrolytes, Russell Vick

Honors Theses

While it is well known that polymeric coatings are used to protect metals from corrosion, efficient and reliable protocols for quantifying and estimating protective coatings’ lifetimes have yet to match real-time results in rate or in detected mechanisms of material failure. Alkoxysilane pretreatments are widely utilized for substrate preparation and improved coating system performance by changing the metal substrate surface morphology to improve adhesion at the coating-substrate interface by creating a foundation and excluding water from the system. Three pretreatments used were 3-aminopropyltriethoxy silane (APS), tetraethylortho silicate (TEOS), N-[3-(trimethoxysilyl)propyl]ethylenediamine (DAS). They were investigated to improve the understanding of the relationships …

Diastereoselective Synthesis Of 2,4,6-Trisubstituted Piperidines Via Aza-Prins Cyclization, John A. Hood

Honors Theses

The nitrogen heterocycles are shared amongst 59% of Food and Drug Administration (FDA) approved small molecule pharmaceuticals with the six-membered piperidine representing the most common moiety. Given the versatility and potential to yield derivatives with broad biological activities, the discovery of new chemical methods to generate these heterocycles in a more time and cost-efficient manner is desired. While there are existing racemic methods to access this class of molecule, the objective of this research is to pioneer a new novel six-step method to generate 2,4,6-trisubstituted piperidines with stereoselective control.

The first step is a condensation between a nonenolizable aldehyde and …

Functional Emulsions Via Thiol-Ene Chemistry, Douglas Amato

Dissertations

Polymer particles (micro to nano) with tunable functionality have emerged as a promising and viable technology platform for applications including coatings, cosmetics, nanomedicine, and imaging. Unfortunately, the lengthy polymerization time and lack of intrinsic functionality in the monomers used to fabricate particles is an industrial challenge. Thiol-ene chemistry cirmcumvents these limitations with very rapid polymerization kinetics, high reaction yields, with supressed side reactions and inherent functionality. This dissertation demonstrates the utility of thiol-ene/yne polymerization in miniemulsion and microfluidics to generate functional materials in a one-pot-method. The functionality is typically generated via off-stoichiometry thiol-ene (OSTE) resins which allow for either excess …