Organic Chemistry Commons^™

New Methods For Synthesis Of Organic Peroxides And Application Of Peroxide Electrophiles To Synthesis Of Functionalized Ethers, Shiva Kumar Kyasa

Department of Chemistry: Dissertations, Theses, and Student Research

New Method for Synthesis of Alkyl Hydroperoxides: There are a number of methods reported for synthesis of alkyl hydroperoxides, but most of them suffer either from poor yields or the formation of unwanted side products. I will be discussing new methodology for efficient synthesis of pure samples of 1° and 2° alkyl hydroperoxides via alkylation of readily available cyclododecanone 1,1-dihydroperoxide followed by hydrolysis of the resulting bis peroxyacetals.

Peroxide Electrophiles for Synthesis of Functionalized Ethers: Peroxides are underexplored functional groups as precursors for C-O bond formation and ether synthesis. The reactivity of dialkyl peroxides towards organometallics such as alkyl lithium …

Hydrolytically Stable Analogues Of Sugar Phosphates And A Miniaturized In Situ Enzymatic Screen, Xiang Fei

Department of Chemistry: Dissertations, Theses, and Student Research

The glmS riboswitch undergoes self-cleavage upon binding its metabolic product GlcN6P, thereby providing a negative feedback mechanism limiting translation of the glmS protein when GlcN6P is abundant. As a first step toward the development of novel antimicrobials, we have synthesized a series of GlcN6P analogues bearing phosphatase-inert surrogates in place of the natural phosphate ester functionality. The self-cleavage assay identified two such compounds that display significant riboswitch actuator activity; namely those bearing a 6-phosphonomethyl group or a 6-O-malonyl ether. These two analogues exhibit a 22-fold and a 27-fold higher catalytic efficiency, respectively, than does glucosamine. Docking experiments were …

Studies In Asymmetric Synthesis: Supramolecular Catalysis, C–H Activation, And D-Cycloserine Synthesis, Nathan C. Thacker

Department of Chemistry: Dissertations, Theses, and Student Research

Rh-catalyzed asymmetric hydrogenation has emerged as a powerful tool for the manufacturing of chiral pharmaceuticals. While the mechanism is well understood, catalyst design a priori is not yet possible. Supramolecular catalysis, the use of non-covalent forces to affect a catalytic process, can afford the catalyst diversity required to uncover efficient catalysts and further our understanding. Using a modular design and self-assembly, a large scale supramolecular catalyst screening in a catalyst scaffold optimization study of rhodium-catalyzed asymmetric hydrogenation was carried out. Analyzing the data yields some new insights into the roles of each module making up the supramolecular catalyst. Perhaps most …

A, Catalysis Of Co-Prox By Water-Soluble Rhodium Fluorinated Porphyrins. B, Studies Toward Fluorination Of Electron Rich Aromatics By Nucleophilic Fluoride, Shri Harsha Uppaluri

Department of Chemistry: Dissertations, Theses, and Student Research

The rhodium(III) derivative of a water soluble, heavily fluorinated porphyrin is shown to catalyze the low temperature, low pressure selective oxidation of carbon monoxide in hydrogen gas streams for use in fuel cell applications. The catalytic activity is a direct result of the removal of electron density from the metal center. Selectivity for CO oxidation is a direct consequence of fluorination of the porphyrin periphery, since these substituents enhance the rate of the reaction and prevent the formation of Rh(II)-Rh(II) dimmers. Significantly, the dramatic increase in rhodium hydride acidity caused by fluorination precludes hydrogen activation and generation, thereby permitting preferential …

Qualitative And Quantitative Analysis Of Lignocellulosic Biomass Using Infrared Techniques: A Mini-Review, Feng Xu, Jianming Yu, Tesfaye Tesso, Floyd Dowell, Donghai Wang

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Current wet chemical methods for biomass composition analysis using two-step sulfuric acid hydrolysis are time-consuming, labor-intensive, and unable to provide structural information about biomass. Infrared techniques provide fast, low-cost analysis, are non-destructive, and have shown promising results. Chemometric analysis has allowed researchers to perform qualitative and quantitative study of biomass with both near-infrared and mid-infrared spectroscopy. This review summarizes the progress and applications of infrared techniques in biomass study, and compares the infrared and the wet chemical methods for composition analysis. In addition to reviewing recent studies of biomass structure and composition, we also discuss the progress and prospects for …

Investigations Of Inter- And Intramolecular C-O Bond Forming Reactions Of Peroxide Electrophiles, Benjamin W. Puffer

Department of Chemistry: Dissertations, Theses, and Student Research

A common reaction to yield ethers relies on an alkoxide nucleophile and a carbon electrophile (Williamson ether formation). Ethers can also be formed by reactions with carbon nucleophiles and oxygen electrophiles by way of the peroxide functional group. We screened a number of carbon nucleophiles suitable for attack on dialkyl peroxides to form new C-O bonds. Also a novel approach using a peroxyketal electrophile is shown to increase the efficiency of this intermolecular reaction. This method of C-O bond formation can also be implemented intramolecularly, not seen before in the literature, to yield cyclic ethers. This approach requires the generation …

The Use Of Rhenium(Vii) Oxide As A Catalyst For The Substitution Of Hemiacetals, Michael W. Richardson

Department of Chemistry: Dissertations, Theses, and Student Research

Rhenium (VII) oxides have proven to be mild and versatile catalysts in organic chemistry. They have previously been utilized to catalyze the transposition of allylic aclohols, Prins reaction, and reductive amination to name a few examples. This thesis reports the application of Re(VII) oxide in the substitution of hemi-acetals with a wide array of nucleophiles including oxo-, thio-, and peroxy-nucleophiles. These reactions proceed efficiently with rapid reaction times and high yields.

Adviser: Patrick H. Dussault

Data Mining Of Protein Databases, Christopher Assi

School of Computing: Dissertations, Theses, and Student Research

Data mining of protein databases poses special challenges because many protein databases are non-relational whereas most data mining and machine learning algorithms assume the input data to be a relational database. Protein databases are non-relational mainly because they often contain set data types. We developed new data mining algorithms that can restructure non-relational protein databases so that they become relational and amenable for various data mining and machine learning tools. We applied the new restructuring algorithms to a pancreatic protein database. After the restructuring, we also applied two classification methods, such as decision tree and SVM classifiers and compared their …

I, Synthesis Of Β-Sitosterol And Phytosterol Esters. Ii, New Methodology For Singlet Oxygen Generation From 1,1-Dihydroperoxides, Jiliang Hang

Department of Chemistry: Dissertations, Theses, and Student Research

Phytosterols are steroid compounds structurally similar with cholesterol and vary in the nature of carbon side chain. β-Sitosterol is commercially available in preparative amount only as mixtures with other phytosterols. New semipreparative synthesis of pure β-sitosterol and sidechain-modified phytosterols is discussed in this dissertation. This new synthesis is achieved via a temporary masking of the stigmasterol 5,6-alkene as an epoxide. Following performance of the desired modification, the alkene is regenerated through a mild deoxygenation. Preparation of phytosterol esters for cholesterol metabolism study is also discussed in this dissertation.

Singlet oxygen (¹O₂) is the lowest excited state …

Rhodium-Catalyzed Hydroboration Of 1,1-Disubstituted Alkenes, Scott A. Pettibone

Department of Chemistry: Dissertations, Theses, and Student Research

Enantioselective rhodium-catalyzed hydroboration is becoming an increasingly important asymmetric transformation of alkenes based upon the utility of the organo boranate ester intermediate. The newly acquired asymmetric C-B bond can be converted to C-O, C-N, C-C bonds and the organo borante can be coupled to SP2 hybridized halogen bonds, all with retention of configuration. Catalyzed hydroboration of 1,1-disubstituted alkenes are an especially challenging substrate class for this enantioselective transformation. The difficulty for catalysts to distinguish between the two enantiotopic faces of the olefin is one of the major issues that have to be overcome to achieve a desirable level of enantioselectivity. …

High Yield Synthesis Of Positron Emission Tomography Ligands For Metabotropic Glutamate Receptor Imaging, Saraanne E. Hitchcock

Department of Chemistry: Dissertations, Theses, and Student Research

Positron Emission Tomography (PET) is a powerful and non-invasive imaging technique used for human and animal organ imaging. Currently, the market for PET is project to reach $5.4 billion per year by 2015.5 This research focuses on the direct incorporation of [18F]-fluoride into PET ligands. The widespread use of PET imaging is currently frustrated, in part, by the lack of efficient fluorination chemistry.

Glutamate, one of the 20 most abundant naturally occurring amino acids, serves as a neurotransmitter in the central nervous system. Glutamate functions in this capacity by binding to ionotropic and metabotropic receptors. Metabotropic receptors are Gcoupled proteins …

I, An Improved Procedure For Alkene Ozonolysis. Ii, Exploring A New Structural Paradigm For Peroxide Antimalarials., Charles Edward Schiaffo

Department of Chemistry: Dissertations, Theses, and Student Research

The use of ozone for the transformation of alkenes to carbonyls has been well established. The reaction of ozone with alkenes in this fashion generates either a 1,2,4-trioxolane (ozonide) or a hydroperoxyacetal, either of which must undergo a separate reduction step to provide the desired carbonyl compound. There is considerable interest in being able to perform a reductive ozonolysis to directly provide the carbonyl. Previous reports from the Dussault lab have shown that amine N-oxides are able to perform a reductive ozonolysis. In the course of efforts to expand this reaction to other oxyanions it was realized that water was …

Ultrasonic Activation Of Triacetone Triperoxide, Latravia R. Dobson

Department of Chemistry: Dissertations, Theses, and Student Research

Triacetone triperoxide (TATP) is an organic peroxide that has received widespread attention in recent years. TATP is a ketone peroxide with a high active oxygen content. It is relatively shock sensitive, with explosive decomposition easily initiated, and is therefore considered a primary explosive. However, TATP is also a powerful explosive possessing about 83 % of the power of TNT. TATP can be prepared quickly and easily from inexpensive household chemicals in the absence of any specialized facilities, making it the explosive of choice for modern day terrorists. TATP poses a major challenge for security and law enforcement services around the …

I, A New Synthetic Approach To The Synthesis Of N-(Phosphonoacetyl)-L-Ornithine. Ii, The Influence Of Pyridine On The Ozonolysis Of Alkenes, Bradley M. Johnson

Department of Chemistry: Dissertations, Theses, and Student Research

Part I. The use of chemical inhibitors to manipulate the level of amino acids in cells has proven to be invaluable in the mechanistic study of gene expression in bacteria and fungi. Here we present a new approach to the synthesis of δ‐N‐ (phosphonoacetyl)‐L‐ornithine (PALO), a potent ornithine transcarbamylase inhibitor, using a new amino acid protecting group, 9‐borabicyclononane (9‐BBN). Starting from commercially available reagents and utilizing mild reaction conditions, we were able to form PALO in fewer synthetic steps and in greater yields than previous attempts.

Part II. Ozonolysis is widely used to transform alkenes into oxygen‐rich functional groups (e.g.– …

I, Development Of The In Situ Reductive Ozonolysis Of Alkenes With Tertiary Amine N-Oxides. Ii, Progress Toward The Asymmetric Synthesis Of Peroxyplakoric Acid A3, Christopher P. Schwartz

Department of Chemistry: Dissertations, Theses, and Student Research

Ozone, first discovered in the mid 1800’s, is a triatomic allotrope of oxygen that is a powerful oxidant. For over a century, research has been conducted into the synthetic application and mechanism of reactions of ozone with organic compounds. One of the major areas of interest has been the ozonolysis of alkenes. The production of carbonyl compounds is the most common synthetic application of ozonolysis. The generally accepted mechanism developed by Rudolf Criegee for this reaction involves the 1,3-electrocyclic addition of ozone to the π bond of the alkene to form a 1,2,3-trioxolane or primary ozonide. The primary ozonide is …

Controlling Reductive Elimination From Novel I(Iii) Salts Using A Secure Method, Joseph W. Graskemper

Department of Chemistry: Dissertations, Theses, and Student Research

Positron Emission Tomography (PET) is a valuable clinical, research, and diagnostic technique for human and animal organ imaging. The current market for PET in the United States is $500 million per year and is projected to be $5.4 billion per year globally by 2015. To synthesize labeled radiotracers, we are most interested in using ¹⁸F as the isotope of choice because it is a nearly ideal positron emitting radionuclide.

Electron-rich aromatic substrates can be particularly difficult to fluorinate. We show that reductive elimination of I(III) diaryliodonium salts provide increased fluorination of electron-rich aromatic substrates. Modest yields of fluorinated product …

Rhodium-Catalyzed Hydroboration: Directed Asymmetric Desymmetrization, Judy L. Miska

Department of Chemistry: Dissertations, Theses, and Student Research

Rhodium-catalyzed asymmetric hydroboration in conjunction with directing groups can be used control relative and absolute stereochemistry. Hydroboration has the potential to create new C–C, C–O, and C–N bonds from an intermediate C–B bond with retention of stereochemistry. Desymmetrization resulting in the loss of one or more symmetry elements can give rise to molecular chirality, i.e., the conversion of a prochiral molecule to one that is chiral. Unsaturated amides and esters hold the potential for two-point binding to the rhodium catalyst and have been shown to direct the regiochemistry and impact stereochemistry in asymmetric hydroborations of acyclic β,γ-unsaturated substrates. In …

Functionalization Of Aromatic Organic Molecules By Anhydrous Fluorides And By Reductive Elimination Of Iodine(Iii), Bijia Wang

Department of Chemistry: Dissertations, Theses, and Student Research

Solution phase reactivity of nucleophilic fluoride reagents is attenuated by ion-pairing interactions. ¹H-¹⁹F HOESY competition experiments permit generation of a fluoride ion affinity scale in the weak-binding regime. Direct DFT calculations of ion pair interaction energies as well as calculated cation electrostatic potential maps can be used to predict solution phase ion pairing tendencies for closely related ammonium cations. It was found by studying the decomposition of tetra-substituted ammonium cations by fluoride that: 1) rates of E2 decomposition is faster than the S_N2 pathway; 2) aryl substituents destabilize the cations; 3) steric strain tends to …

Relatin Dissolved Oxygen Concentration To Fish Distribution In Jarecki Lake, Adam Sutton

Department of Environmental Studies: Undergraduate Student Theses

Abstract Water temperature and dissolved oxygen (DO) profiles were measured once every month from mid July to mid February in a relatively deep sand-pit lake in southeast Nebraska. These profiles showed depleted DO concentrations below the thermocline during summer stratification indicating areas fish will likely avoid in summer months. Colder temperatures in fall caused complete mixing of the water column allowing fish to inhabit all depths of the lake. An inverse temperature stratification occurred directly below the ice during winter months as ice cover cooled the surface water to below 4 degrees Celsius. Ice cover also blocked air – water …

Herbicides And Amphibian Populations, Zach Shirk

Department of Environmental Studies: Undergraduate Student Theses

Amphibians are a unique class of species that are found worldwide except Antarctica and Greenland. They range in size from a few millimeters to over six feet long. Amphibian’s habitats are as various as their size, but one thing in common is that amphibians require an aquatic location to breed. Amphibians live in deserts, mountain prairies, rain forest, wetlands, and almost everywhere in between. Amphibians are an integrated part of most natural ecosystems across the world. Amphibians are a critical part of many food chains; they provide the important link between secondary and tertiary consumers. Amphibians are indicator species in …

Oligo(Vinylidene Fluoride) Langmuir-Blodgett Films Studied By Spectroscopic, Rafal Korlacki, J. Travis Johnston, Jihee Kim, Stephen Ducharme, Daniel W. Thompson, Vladimir M. Fridkin, Zhongxin Ge, James M. Takacs

Stephen Ducharme Publications

Thin films of amphiphilic vinylidene fluoride oligomers prepared by Langmuir–Blodgett deposition on silicone substrates were investigated by comparing experimental and theoretical mid-infrared (IR) spectra. The experimental spectra were obtained using infrared spectroscopic ellipsometry. Theoretical spectra were calculated using density functional theory. Excellent correspondence of major IR bands in both data sets shows that the molecular backbone is oriented with the long axis normal to the substrate plane. This is in contrast to poly vinylidene fluoride[1] LB films, in which the polymer chains are parallel to the substrate.

D/H Exchange In Nitro Diastereomers, Charles A. Kingsbury

Department of Chemistry: Faculty Publications

The two diastereomers of 4-nitro-1,3-diphenylpentan-1-one behave differently in deuterium for hydrogen exchange in DMSO-d6/D2O solutions using various bases as catalyst. Reaction of the erythro diastereomer gives largely the same diastereomer upon D/H exchange (retention), i.e., exchange exceeds epimerization. Pyridine and acetonitrile as solvents lead to faster epimerization than exchange. In the threo diastereomer (DMSO-d6 solution), epimerization exceeds exchange, and the anion to some extent regains the same hydrogen originally removed by the base on the opposite face. 2-Bromo-4-nitro-1,3-diphenylbutan-1-one undergoes ring closure to the cyclopropane faster than exchange (within seconds). The cyclopropane shows faster exchange than equilibration, i.e., retention of configuration, …

A Study Of Euplotes Crassus Telomere Proteins And Related Genes, John Scott Perez

Department of Chemistry: Dissertations, Theses, and Student Research

A novel PCR technique used to amplify Euplotes crassus macronuclear chromosomes was developed to provide scientific proof that an Euplotes crassus 1.0 kb gene is not genetically related to an Oxytricha nova 1.8 kb β-telomere protein gene. Theories and experimental procedures associated with the development of this PCR technique were the product of research that will have a profound impact on future studies of telomere protein genes and telomeric DNA in a multitude of eukaryotic cells. The hypothesis that a β-telomere protein does not exist in Euplotes crassus was supported by the result of this study.

Expression of the recombinant …

Axial Asymmetry In The Nuclear Magnetic Resonance Spectra Of Deuterated Methyl Groups: An Alternative Explanation, Mieng-Hua Wann, Gerard S. Harbison

Gerard S. Harbison Publications

The deuterium nuclear magnetic resonance (NMR) powder spectra of methyl groups at ambient temperatures are invariably averaged by rotation or hopping about the C₃ axis. The canonical result for a perfectly threefold symmetric methyl is an axially symmetric Pake doublet whose splitting, in the case of perfect tetrahedral angles around the group, is averaged by a factor of exactly three. However, deuterium NMR spectra of methyl groups are often somewhat axially asymmetric, indicating a significant deviation either of the methyl group, or of its environment, from threefold symmetry. Previous explanations for this phenomenon have hinged on either an additional …

Viscosities Of Vegetable Oils And Fatty Acids, Hossein Noureddini, B. C. Teoh, L. Davis Clements

Papers in Biomaterials

Data for viscosity as a function of temperature from 24 to 110°C (75 to 230°F) have been measured for a number of vegetable oils (crambe, rapeseed, corn, soybean, milk- coconut, lesquerella) and eight fatty acids in the from Cg to CZZ The viscosity measurements were performed according to ASTM test methods D 445 and D 446. Several correlations were fitted to the experimental data. Correlation constants for the best fit are presented. The range of temperature in which the correlations are valid is from 24°C (75°F), or the melting point of the substance, to 110°C (230°F). The correlation constants are …

Syntheses In The Thiophene Series, Alfred William Weitkamp

Department of Chemistry: Dissertations, Theses, and Student Research

Summary

The Friedel-Crafts reaction has been used in the preparation of thiophene ketones, some of which were hitherto unknown. Certain limitations of the reaction have been noted.

The mercuration of thiophene ketones has been systematically investigated for the first time. Many new halogen derivatives of benzothienone have been synthesized. These were employed in the elucidation of the structure of a complex mercurial· derived from this ketone.

A new modification of an old reaction has been developed whereby benzothienone can be mercurated quickly and almost quantitatively. Interesting derivatives of this little known ketone have been synthesized. Chief among these are the …