Dissertations / Theses: 'Fundamental chemistry'

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Tun, Zin-Min. "Fundamental Chlorophosphazene Chemistry." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1321278169.

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Wheatley, James Ernest. "Fundamental chemistry of carbon dioxide capture." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/18363/.

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Carbon dioxide capture is an urgently needed pathway to mitigation of climate change, yet the amine-based solvents currently considered the leading industrial technologies suffer from many shortcomings; namely their high operating cost, poor stability and potentially damaging environmental impact from emission of degradation products. This work is a study of possible routes to improved CO2 capture technologies from a fundamental chemistry perspective. Initial work focused on the development of a straightforward and adaptable protocol for studying the species formed by CO2 capture into amine solvents, using 1H NMR spectroscopy for its combination of speed and accuracy. The applicability of this approach to diverse blended-amine solvents was demonstrated. This method was then applied to the study of phenoxide as a novel possible capture agent in conjunction with amines. Blends of potassium phenoxide with monoethanolamine were found to have an excellent capture capacity and favourable speciation that suggests a low energy consumption in practical use. This demonstrates the feasibility of blended solvents with a reduced amine component. Finally, a possible amine-free route to CO2 capture, exploiting the high susceptibility of carboxylate acidity to solvation, was explored. The first systematic study of the pKa of CO2 in mixtures of organic solvent and water was carried out, finding that this value is relatively insensitive to the makeup of the solvent and therefore in organic-rich solutions, carboxylate salts can be used as a CO2-absorbing base. CO2 capture using a system developed along these principles was demonstrated, and the possible basis for the observed insensitivity was discussed with particular emphasis given to the thermodynamics of the process.

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Stiel, Jason A. "Fundamental Chemistry of Chlorophosphazenes and Polysilanes." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1467990664.

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Lamm, Ashley, and Ashley Lamm. "Fundamental Chemistry of 1,2-Dihydro-1,2-Azaborines." Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12514.

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Benzene and its derivatives are ubiquitous in chemical research, with applications ranging from material science to biomedical research. 1,2-Dihydro-1,2-azaborine is a benzene mimic which replaces a CC bond with a BN bond. The basic science and applications of 1,2-azaborines is relatively underdeveloped. This thesis expands the fundamental understanding of 1,2-azaborines. Chapter I describes the air and moisture stability of 1,2-azaborines. Chapter II introduces nucleophilic aromatic substitution reactions that the parent 1,2-dihydro-1,2-azaborine will undergo. Chapter III discusses a trimerization reaction that 1,2-dihydro-1,2-azaborine can perform, which is unique from benzene. Chapter IV examines a novel protection free synthesis of 1,2-azaborines, which provides a more direct route to functionalized 1,2-azaborines. Chapter V discusses the novel deprotection of the N-silicon using an amide, giving one of the first 1,2-azaborine pharmaceutical mimics. Finally, chapter VI summarized miscellaneous contributions I have made to the basic science of 1,2-azaborines. This dissertation includes previously published and unpublished co-authored material.
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Saleh, Nidal. "Chiral complexes : from fundamental chirality to helicene chemistry." Thesis, Rennes 1, 2013. http://www.theses.fr/2013REN1S112/document.

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Au cours de ce travail de doctorat, nous avons d'abord étudié un aspect fondamental de la chiralité au niveau moléculaire visant à observer des différences d'énergie entre deux énantiomères provenant d'effets de violation de la parité (PV). Nous avons en particulier examiné les complexes oxorhénium chiraux dont les deux énantiomères présentent théoriquement des énergies d'absorption infrarouge différentes. Leur propriétés chiroptiques, en particulier leur dichroïsme circulaire vibrationnel (VCD), ont été examinées. D'autres complexes métalliques chiraux comme des complexes de platine portant un carbone asymétrique fluoré ont été préparés. Par ailleurs, nous avons étudié la chiralité hélicoïdale provenant de la fusion en ortho de plusieurs cycles aromatiques. Ainsi, des hélicènes portant des fonctionnalités bi-pyridines ont été synthétisés et ont montré des propriétés photophysiques et chiroptiques intéressantes. La présence d'unité chélatantes de type N^N’ ou N-C nous a permis d'étudier l'influence de la coordination de divers métaux de transition (Re(I) et Pt(II)) sur les propriétés et de concevoir de nouveaux commutateurs chiroptiques acido-basiques
In this PhD work, we first investigated a fundamental aspect of chirality at the molecular level aiming to determine the parity violation (PV) energy difference between two enantiomers. We focused on chiral oxorhenium complexes for which the two corresponding enantiomers show theoretically different infrared absorption energies. Their chiroptical properties and especially their vibrational circular dichroism (VCD) were examined. Other chiral metal complexes such as platinum complexes bearing an asymmetric fluorinated carbon have also been prepared. Furthermore, we have investigated the helical chirality derived from the skew shape of ortho-fused aromatic ring. Indeed, helicenes bearing 2,2’-bipyridine functionalities were synthesized and they showed interesting photophysical and chiroptical properties. The presence of N^N’ or N-C chelating moieties enabled us to study the coordination effect of different transition metals (Re(I) and Pt(II)) on their properties and to conceive new acid-base triggered chiroptical switches

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McKay, Hayley. "Fundamental studies of surface reaction mechanisms." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/252213.

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Wood, David John. "Fundamental studies on ionomer glasses." Thesis, University of Greenwich, 1993. http://gala.gre.ac.uk/6347/.

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Composition-structure-property relationships were studied in glasses of the type used to produce glass lonomer dental cements. These materials are currently being developed as a bone cement in joint replacement surgery. Initially, a simple quaternary (25i02-Al203-CaO-CaF2) glass was produced and was found to undergo minimal fluorine loss. This results in a glass whose composition is reproducible between batches. This composition, however, was too reactive to form a glass ionomer cement. A glass-ceramic approach was pursued to deactivate the glass and following heat treatments, cements were produced whose properties varied depending upon the precise heat treatment used. The heat treatments above the glass transition temperature resulted in amorphous phase separation, probably by a spinodal decomposition mechanism, followed by a two stage crystallization of calcium fluoride (fluorite) and anorthite. The anorthite phase crystallized from fluorite nuclei and, in effect, crystallization occurred by a bulk nucleation mechanism. The glass will also undergo significant crystallization to fluorite below the glass transition temperature, with surface nucleation the dominant mechanism. This explains the deactivation of ionomer glasses used commercially to control the setting properties of dental glass ionomer cements. The structural role of fluorine in these glasses was also investigated. It seems that fluorine is present in the glass network, rather than existing as a discreet entity bonded to a modifying cation. There is evidence that the fluoride ions are bonded only to aluminium sites and act to disrupt network connectivity. A commercial glass was examined and was found to be clearly phase separated. This glass was found to crystallize to apatite and mullite. Apatite is the mineral phase of bone and enamel and this may explain the excellent biocornpatability of glass ionomer cements. Glasses containing sodium and phosphate ions have also been produced. The sodium containing glasses were all found to crystallize from the melt to calcium fluoride. The phosphate containing glasses formed cements without any subsequent modification, and following a simple heat treatment, all of the phosphate containing glasses were found again to crystallize initially to an apatite phase. Selected compositions additionally crystallized to mullite. These glass-ceramics were tougher than the base glasses and this is attributed to the presence of interlocking needles of the two phases. Some of the glasses were easily castable to produce optically clear glasses, and in addition the glasses underwent bulk nucleation via prior amorphous phase separation, to give needles of apatite and mullite. These glass-ceramics thus show tremendous potential for use as a bloactive bone substitute material or as a castable crown.

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Han, Qi. "Electrocatalysis at the Electrode-Adsorbate-Solution Interface: Fundamental Studies." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1574855036013662.

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Pappas, Iraklis. "Fundamental investigations into dinitrogen fixation by group 4 metals." Thesis, Princeton University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10120357.

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Addition of terminal or internal alkynes to a base free titanocene oxide results in synthesis of the corresponding oxometallocyclobutene. With appropriate cyclopentadienyl substitution, these compounds undergo reversible C-C reductive elimination offering a unique approach to cyclopentadienyl modification. Subsequent reactivity demonstrates the complete scission of the Ti=O multiple bond.

Cycloaddition of monosubstituted allenes with a monomeric, base free titanocene oxide resulted in isolation and crystallographic characterization of the corresponding oxatitanacyclobutanes. In solution these compounds are a mixture of (E) and (Z) isomers and interconvert by mechanisms that are dependent on the specific substitution of the allene. Facile carbonylation of the oxatitanacyclobutanes was also observed to yield rare examples of structurally characterized oxatitanacyclopentanones. These studies highlight the new chemistry available from synthesis of base free titanocene oxide compounds enabled by appropriate cyclopentadienyl substitution.

The hydrogenolysis of titanium nitrogen bonds in a family of bis(cyclopentadienyl) titanium amides, hydrazides, and imides via proton coupled electron transfer (PCET) is demonstrated. (η⁵-C₅Me₅)(py-Ph)Rh-H (py-Ph = 2-pyridylphenyl, [Rh]-H) and (η⁵- C₅R₅)(CO)₃CrH ([Cr]^R-H, R= H, Me) were used as catalysts for homolytic H₂ activation followed by PCET to the nitrogen-containing fragment. Detailed mechanistic studies and an analysis of the underlying thermochemistry are employed to explain the decreased catalytic efficiency of [Cr]^R-H compared to [Rh]-H. The N-H bond dissociation free energies (BDFEs) in 12 structurally similar compounds were determined through a combination of experimental and computational methods, providing a foundation for the use of N-H BDFEs as a metric to enable NH₃ synthesis from H₂ and N₂ at a well-defined metal center.

Combination of the readily available a-diimine ligand, ((ArN=C(Me))₂ Ar = 2,6-ⁱPr₂-C₆H₃), (^iPrDI) with air-stable nickel(II) bis(carboxylates) generated a highly active catalyst exhibiting anti-Markovnikov selectivity for the hydrosilylation of alkenes with (EtO)₃SiH. The exclusive selectivity for formation of terminal alkyl silanes was also observed with internal alkenes via a tandem isomerization-hydrosilylation pathway. The hydrosilylation of 1-octene with triethoxysilane, a reaction performed commercially in the silicones industry on a scale of > 12,000,000 lbs/year, was performed on a 10 g scale with 96 % yield and >98 % selectivity for the desired product.

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Pastor, Michael B. "Bimetallic Complexes| The Fundamental Aspects of Metalmetal Interactions, Ligand Sterics and Application." Thesis, University of the Pacific, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10932512.

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Metal containing complexes have been used to catalyze various organic transformations for the past few decades. The success of several mononuclear catalysts led to transition metal catalysts used in pharmaceuticals, environmental, and industrial processes. While mononuclear complexes have been used extensively, bimetallic systems have received far less attention. Bimetallic or polynuclear sites are commonly found in metalloenzymes that perform elegant transformation in biological systems, underlying their significance. Inorganic chemists take inspiration from nature and design model bimetallic complexes to further study this cooperativity effect. A bimetallic platform offers many structural and functional differences such as the identity of the metal atoms and the bonding interactions between metals, which have been reflected in their unique catalytic ability and reactivity.

This dissertation encompasses work related to the computational study of metal-metal interactions of bimetallic systems, the ¹H NMR study of stereochemical and conformational changes in solution of N,N'-diarylformamidines, the synthesis of dizinc formamidinate complexes, and the synthesis and catalytic ability of dicopper formamidinate complexes.

In the first part, DFT calculations are used to study factors that influence metal-metal bond lengths in various complexes. Several experimentally obtained X-ray crystal structures were used as the basis for the study. Differences in metal-metal separations were investigated through various functionals, indicating the importance of charge, orbital interactions, and formal bond order. BH&HLYP SDD/aug-CC-PVDZ geometry optimizations of octahalodimetalate anions Tc₂X₈^n- (X = Cl, Br; n=2, 3), Re₂X₈^2- (X = Cl, Br), and Mo₂Cl₈^4- reproduced M-M bond distance trends observed experimentally. The study demonstrated that the increase in σ and π bond strength resulted in the shortening in Tc-Tc bond distance from Tc₂X₈^2- to Tc₂X₈^3-, which was further supported by the short Mo-Mo bond in the Mo₂Cl₈^4- ion. This study was expanded further through the inclusion of [M₂Cl₄(PMe₃)₄]ⁿ⁺ (M = Tc, Re, n = 0-2) and [Mo₂E₄]^n- (E = HPO₄ or SO₄, n = 2-4), allowing a systematic study on the role of charge on the metal atoms. PBEO SDD/aug-CC-PVDZ calculations revealed that both formal bond order and formal charge on the metal atoms dictate the trends in M-M bond strength.

The second half of this dissertation focuses on the synthesis and characterization of bimetallic Zn- and Cu-formamidinate complexes. The stereochemical exchange of substituted N,N'-diarylformamidines were studied through ¹H NMR in various solvents. Alkyl substituents placed on the ortho positions were found to shift the isomeric equilibrium in solution through destabilization of the hydrogen-bond dimer evident in X-ray crystal structures. The Z-isomer of substituted N,N'-diarylformamidines is observed in CDCl₃, C₆D₆, and DMSO-d₆ when the ligands feature significant steric hinderance. Similar ortho substituted N,N'-diarylformamidines were also used to enforce steric interactions to limit the nuclearity of Zn-formamidinate complexes. Various dizinc formamidinate complexes were synthesized through direct and transmetalation routes. NMR and mass spectrometry were used alongside X-ray crystal structures to fully characterize the dizinc complexes. Dicopper formamidinates formed through a transmetallation route were synthesized and feature distinct short Cu^…Cu separations thought to be brought about by metalophillic interactions. Preliminary results suggest catalytic ability of dicopper formamidinates in cyclopropanation and aziridination of styrene with various diazo compounds. The catalytic activity suggests the formation of dicopper carbene and nitrene intermediates, of which only few published experimentally observed examples exist in the literature.

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Colson, Sophie. "Fundamental flame characteristics and combustion chemistry for ammonia/methane blended fuels." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI103.

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L’étude de combustibles décarbonés, tel que l’ammoniac, est essentielle dans le contexte du réchauffement climatique. Sa combustion nécessite cependant de relever plusieurs défis, notamment concernant la stabilisation des flammes et la production de NOx. Afin de pallier les problèmes de stabilisation, une solution consiste à utiliser un mélange d’ammoniac avec un autre combustible. Cette thèse a pour objectif l’analyse des caractéristiques fondamentales de la combustion d’un mélange ammoniac-méthane, encore peu étudié. Il s’agira de comprendre les mécanismes cinétiques conduisant à la formation de polluants et ceux contrôlant la stabilisation. Dans ce but, le travail portera d’abord sur la chimie de combustion de ces mélanges, afin de clarifier leurs propriétés, notamment la structure de la flamme et les émissions engendrées. L’étude des mécanismes réactionnels, déjà validés dans un domaine limité de conditions, a montré de réelles disparités lorsque les conditions d’étude étaient élargies. Il est donc essentiel d’évaluer ces mécanismes dans des configurations diversifiées et sur une plus large base de résultats expérimentaux. Quatre mécanismes ont été sélectionnés et évalués dans une configuration à contre-courant, via l’étude du taux d’étirement à l’extinction et l’analyse des profils d’espèces OH et NO. La stabilisation de ces flammes a ensuite été étudiée, en examinant l’influence de l’ajout d’ammoniac sur une flamme de méthane de type jet non-pré-mélangée. L’évolution des limites de suspension, de rattachement et l’étendue de la zone d’hystérésis ont notamment été examinés. La dynamique de (dé)stabilisation de la flamme attachée au brûleur, sa suspension et son rattachement ont été étudiés pour comprendre l’évolution particulière de ces régimes. Les résultats montrent une forte diminution du domaine de stabilisation avec l’ajout d’ammoniac ainsi qu’un comportement singulier de la limite de ré-attachement. Enfin, l’étude de la flamme attachée a souligné l’importance des couplages aérodynamique et chimique dans la dynamique de stabilisation du bout de flamme
The study of low-carbon fuels, such as ammonia, is essential in the context of global warming. However, its combustion is challenging, particularly regarding flame stabilization and NOx emission. One solution to overcome the stabilization issues is to use a mixture of ammonia with another fuel. The aim of this thesis is the analysis of the fundamental combustion characteristics of an ammonia-methane mixture, which remains merely investigated in the literature. The objective is to understand the kinetic mechanisms leading to the formation of pollutants and the mechanisms controlling stabilization. For that purpose, this work will first focus on the combustion chemistry of these mixtures, to clarify their properties, and more specifically the structure of the flame and the emissions generated. The study of the reaction mechanisms, already validated in a limited range of conditions, showed real disparities when the range of experimental conditions is broadened. It is therefore essential to evaluate these mechanisms in diverse configurations and on a broader range of experimental results. Four detailed chemistry mechanisms were selected and evaluated in a counterflow configuration, studying the extinction stretch rate and analyzing OH and NO species profiles. The stabilization of these flames was then studied, by examining the influence of the addition of ammonia to a methane non-premixed jet flame in an air coflow. The evolution of liftoff and re-attachment limits and the hysteresis region were investigated. The dynamics of stabilization of the flame attached to the burner, its liftoff and its re-attachment have been studied to understand the particular evolution of these regimes. The results show a strong decrease in the stabilization domain with the addition of ammonia as well as a singular behavior of the re-attachment limit. Finally, the study of the attached flame highlighted the importance of aerodynamic and chemical couplings in the stabilization dynamics of the flame tip

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Whittle, Carl. "Fundamental Investigations of Mechanistic Pathways of Selected Organic Reactive Intermediates." TopSCHOLAR®, 1997. http://digitalcommons.wku.edu/theses/360.

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Part 1 of this thesis deals with the role that it -electron density plays in the formation of it -complexes in electrophilic aromatic substitution. Using commercial and synthetic compounds of varying it-electron density, the fact that % -complexes actually exist in these species was determined by a mass spectral investigation that was designed to monitor alkyl side-chain isomerizaitons. Also, the amount of it-complex was determined for each compound by measuring the amount of alkyl carbenium ion loss in each compound's mass spectrum. Found within the systems was an internal trend showing that the greater the amount of 7t-electron density in the ring, the less it-complex formed. This trend was further studied utilizing a Spartan 3.0 computational system, and all data found was internally consistant with the experimental data. It was found that the compounds with the greatest nelectron density used the excess tc-electron density for greater covalency in the complex. In Part 2, the gas-phase reaction between the ethylene oxide radical cation and neutral ethylene oxide, when performed in the high-pressure source of a tandem mass spectrometer, forms a C4Hg02 radical cation adduct. The collisionally activated dissociation (CAD) mass spectrum of the C4H802 adduct is nearly identical to that of the 1,4-dioxane radical cation. Computational investigations utilizing semi-empirical AMI, MNDO, and PM3 methodologies were invoked to determine the mechanistic pathways involved in the reaction. The most likely mechanism is a step-wise process involving a long-chain distonic radical cation intermediate that subsequently forms a non-distonic cyclic radical ion. A calculated thermodynamic driving force of ca. 10 Kcal/mol exists for the cyclization of the long-chain distonic radical cation. For Part 3, an array of acyclic long-chain distonic radical cations was generated and analyzed by semi-empirical AMI computational methods. In general, an enthalpic driving force for the isomerization of the distonic ions to cyclic non-distonic ions was observed. The enthalpies of the isomerizations were evaluated as a function of chain length, identity of the atom (C, O, N) bearing the radical site, and substitution of the radical and carbenium ion sites. The structures, electron distribution, free spin distribution, and thermodynamic stabilities of the cyclic ions generated upon isomerization of the distonic ions were nearly identical to those formed by direct removal of an electron from the corresponding cyclic neutral precursor.

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Pritchard, Keith L. "Fundamental processes governing calcite dissolution at high pH." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238178.

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Hansen, Neils Richard Stewart. "Fundamental and applied studies with fuel cell sensors." Thesis, Cardiff University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274561.

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Tao, Ye Ph D. Massachusetts Institute of Technology. "Fundamental efforts for improving the sensitivity of magnetic resonance force microscopy." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68547.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2011.
"July 2011." Cataloged from PDF version of thesis.
Includes bibliographical references (p. 20-24).
Introduction: Complete understanding of the mechanisms of biological processes, indispensable for the rational design and testing of therapeutic strategies, can be greatly facilitated by easy and rapid access to macromolecular structures at the atomic resolution. As of 2011, a general method for rapid rendering of macromolecular and cellular structures with atomic resolution represents both a major challenge and a major need in science. Such a method would prove all the more valuable to understanding the conformational complexities of protein misfolding diseases and amyloid formation phenomena , caused by complex networks of structural transition reactions linking the monomeric, oligomeric, and polymorphic fibrillar forms of disease-causing proteins, the structures of which have only been rigorously characterized in a small number of cases. To date, the majority of protein and RNA structures known have been solved by either X-ray crystallography or by NMR spectroscopy. Many requirements on the sample prevent these methods from being generally applicable to biological specimens. First, since X-ray crystallography and NMR spectroscopy are techniques based on assessing the average properties of a macroscopic sample, a high degree of sample heterogeneity undermines their ability to solve structures. Second, X-ray crystallography requires the sample protein to form ordered crystals. However, the procedure for crystallizing proteins remains a daunting trial-and-error process and important proteins like membrane proteins are impossible to crystallize in their native forms. Recent advances in solid state NMR (ssNMR) spectroscopy have made it possible to study membrane proteins, but the technique is still limited by protein size and by the need for order, at least at the local level. For these reasons, the structural studies of macromolecule that contain high degrees of conformational heterogeneity and that are large in size have remained challenging, rare, and largely tackled, with difficulty, by computational approaches.
by Ye Tao.
S.M.

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Phillips, Shannon L. "Fundamental studies and applications of liquid chromatography at the critical condition /." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu148640254458979.

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Nichols, Jason M. "The redox chemistry of dirhodium carboxamidates from fundamental structures to catalytic functions /." College Park, Md. : University of Maryland, 2008. http://hdl.handle.net/1903/8051.

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Thesis (Ph. D.)--University of Maryland, College Park, 2008.
Thesis research directed by: Dept. of Chemical and Biomolecular Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Pinkerton, Tim D. "Fundamental studies of the effect of electric fields on water-surface chemistry /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9900.

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Livshits, Maksim Y. "Fundamental Investigation of PhotoActive Materials From Small Molecules to Materials." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1490713190973503.

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Sheridan, Phillip Michael. "High-resolution millimeter-wave spectroscopy of metal-containing species: Examining fundamental ligand interactions." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/284335.

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Millimeter-wave spectroscopy has been used in this thesis to accomplish two main goals: (1) to study bonding, structural, and electronic properties of small, metal-bearing molecules in their ground electronic states, in particular how individual metal atoms bond to small ligands, and (2) to provide rest frequencies for radio astronomical searches of metal containing species in the interstellar medium. The types of molecules studied in this thesis can be broadly classified into three groups: (1) alkali and alkaline-earth amides (MNH₂), (2) diatomic molecules in high electron spin or high orbital angular momentum electronic ground states (MX), and (3) transition metal cyanides (MCN). In this first category, the pure rotational spectra of LiNH₂ (X¹A₁), LiND₂ (X¹A₁), NaND₂ (X¹A₁), MgNH₂ (X²A₁), and MgND₂ (X²A₁), were recorded and analyzed. For each, the first experimental monomer r₀ structures were determined. These species were found to be planar and not invert, in contrast to ammonia. In addition, for the alkaline-earth amides, the M-N bond appears to become less ionic from Sr to Ca to Mg. The second class of molecules investigated, high-spin diatomcs, includes: NaC(X⁴Σ⁻), CrN(X⁴Σ⁻), CrO(X⁵Πᵣ), MnF(X⁷Σ⁺), FeN(X²Δᵢ), FeC(X³Δᵢ), and TiF(X⁴Φᵣ). These species represent examples of electronic states that have never or seldom been observed by high-resolution millimeter-wave spectroscopy, due to their high values of electron spin and orbital angular momenta. The analysis of their spectra has been used to test the adequacy of the effective Hamiltonians developed to model their rotational spectra; in particular the use of theoretically predicted higher order parameters. The final group studied includes the transition metal cyanides CoCN (X3Φᵢ ) and NiCN (X2Δᵢ). Unlike their alkali, alkaline-earth, and group 13 counterparts, these species were determined to be linear cyanides with the metal atom bonded to carbon, similar to both CuCN (X1Σ⁺) and ZnCN (X2Σ⁺). For both molecules, complications in the rotational spectra due to the Renner-Teller effect were observed and analyzed.

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Xu, Jing. "FUNDAMENTAL STUDIES OF ELECTROCATALYTIC SYSTEMS WITH RELEVANCE TO ENERGY CONVERSION AND STORAGE." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1449139728.

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Lampard, Graham S. "Mineral tanning mechanisms : a fundamental study." Thesis, University of Northampton, 2000. http://nectar.northampton.ac.uk/2676/.

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A review across the periodic table of tanning effects of simple inorganic compounds reveals that many elements are capable of being used to make leather. But, if the practical criteria of effectiveness, availability, toxicity and cost are applied, the useflul options reduce to chromium (III) the benchmark orto titanium (IV) zucomum (V) iron (II/III) and aluminium (II) For mainly environmental reasons, alternative tanning agents to chromium are needed, However. none so far investigated match the all round properties achieved with chromium (III) salts. In tanning terms, the chemistry of titanium (IV) is dominated by the titanyl ion, TiO2, limiting its reactivity with collagen. An alternative approach to titanium tanning, using metastable titanium (III) salts as possible tanning agents, was investigated in this study. A method to determine the titanium content in leathers was developed. Complexes of Ti (III) were investigated using various spectroscopic techniques, including uv/vis spectroscopy, electron spin resonance, electron nuclear double resonance and nuclear magnetic resonance dispersion spectroscopies. The complexes used in subsequent tanning studies were based on titanium (III) citrate, gluconate and tartrate. However, in comparative trials with chromium (III) salts, the study highlighted that titanium (III) salts were not suitable for tanning collagen. Titanium (III) saks were found to be useflul in the production of semi- metal tamlages. The research was extended to investigate the hydrothermal shrinking of tanned collagen. Techniques such as extended x-ray absorption — fine structure and x-ray absorption near structure were used to investigate the interaction of chromium (III) tanning salts and titanium (III) complexes with collagen. The research demonstrated that the shrinking reaction is independent of the tannage. It involves instead the breaking of hydrogen bonds, rather than the breakdown of the tannin-collagen molecule. From this work, and a reappraisal of older work on the shrinking reaction, a new theory of tanning has been formulated based on co-operating units and the role of crystallinity in stabilising the collagen structure. The influence of the solvent is also discussed

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Creamer, Neil J. "Fundamental and industrial aspects of the crystallisation of amorphous silica." Thesis, Open University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288580.

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Chakar, Fadi S. "Fundamental delignification chemistry of laccase-mediator systems on high-lignin-content kraft pulps." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/7017.

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McCrystal, Conor B. "Characterisation of the fundamental interactions between water and cellulose ether polymers." Thesis, Liverpool John Moores University, 1998. http://researchonline.ljmu.ac.uk/4912/.

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Heffernan, John Vincent Thomas. "A fundamental surface study of phosphorus based antiwear films on iron." Thesis, University of Southampton, 1994. https://eprints.soton.ac.uk/365531/.

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Hunter, Katherine. "Fundamental studies of electrochemical oxide formation on platinum single crystal electrodes." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/100871/.

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Platinum single crystal electrodes were used to investigate electrochemical oxides and related surface species and their impact upon important catalytic reactions such as the oxygen reduction reaction (ORR). Notions of perchlorate anions being “non-specifically adsorbed” were re-evaluated and challenged. For example, the voltammetry of Pt single crystal electrodes as a function of perchloric acid concentration (0.05–2.00 M) was studied in order to test the assertion by Watanabe et al. that perchlorate anions specifically adsorb on polycrystalline platinum. Specific adsorption of perchlorate anions was found in varying degrees for Pt(hkl) surfaces. By flame-annealing and cooling a series of Pt n(110)x(111) and Pt n(110)x(100) single crystal electrodes in a CO ambient, new insights into the nature of the electrosorption processes associated with Pt{110} voltammetry in aqueous acidic media were elucidated. For Pt n(110)x(111) electrodes, a systematic change in the intensities of voltammetric peaks indicated a lack of surface reconstruction (in contrast to hydrogen cooled analogues). Pt n(110)x(100) stepped electrodes displayed a marked tendency towards surface reconstruction irrespective of cooling environment. Pt(110) terrace sites were found to afford a specific affinity for sulphonate groups contained within a Nafion adlayer. Pt n(100)x(110) surfaces showed rapid quenching of the Nafion ‘spike’ as a function of increasing step density. Reactivity measurements involving oxygen reduction and hydrogen peroxide oxidation/reduction largely revealed the importance of adsorbed oxide/OH in regulating activity. Kinetic studies suggested that for Pt(100) terraces, oxide formation was also accompanied by rapid surface reconstruction. Fast potential cycling of all electrode surfaces confirmed the likelihood of structural changes occurring in real fuel cells. It is deduced that roughened catalyst particles should actually exhibit an enhanced ORR activity, even in the presence of Nafion.

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Liu, Qiang. "Fundamental Study and Method Development for Surface-based Laser Desorption Ionization Imaging Mass Spectrometry." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-02262009-143514/.

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By providing both the chemical identity and the spatial organization of each component in biological samples, Imaging Mass Spectrometry (IMS) becomes an emerging tool in clinic and pharmacological study. Most work in IMS has been focused on protein and peptide mapping in biological samples to take advantage of effective analyte ionization in MALDI-MS, and also partially due to the limitation of MALDI-MS in small molecule detection. The focus of my research is to develop novel tools to image spatial distribution of small molecules in biological samples. A surface-based mass spectrometric imaging method, i.e. Desorption/Ionization on Silicon (DIOS), was used for biological surface analysis in the concept-proof investigation. More over, possible proton transferring pathways and impact of local chemical environment have been systematically investigated in the fundamental understanding of ionization mechanism of SALDI-MS. Based on the finding on the SALDI mechanism, a hybrid ionization approach, ME-SALDI has been developed by combing the strength of the conventional MALDI matrix and SALDI, where the improved detection sensitivity with reduced matrix-analyte interference and the improved imaging capability through analysis of mouse brain and heart sections has been demonstrated. In addition, the impact of vacuum stability of matrix in ME-SALDI-IMS applications has been examined. A solvent free, homogenous and reproducible sublimation method has been developed for ionic matrix in ME-SALDI, by which improved vacuum stability and MS detection have been achieved. Furthermore, a new generation of meso-porous oxide substrate was developed as a novel ME-SALDI substrate with a superior storage stability, extended detectable mass range and robust substrate preparation.

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Pastor, Michael Bernard. "Bimetallic complexes: The fundamental aspects of metal-metal interactions, ligand sterics and application." Scholarly Commons, 2018. https://scholarlycommons.pacific.edu/uop_etds/3559.

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Metal containing complexes have been used to catalyze various organic transformations for the past few decades. The success of several mononuclear catalysts led to transition metal catalysts used in pharmaceuticals, environmental, and industrial processes. While mononuclear complexes have been used extensively, bimetallic systems have received far less attention. Bimetallic or polynuclear sites are commonly found in metalloenzymes that perform elegant transformation in biological systems, underlying their significance. Inorganic chemists take inspiration from nature and design model bimetallic complexes to further study this cooperativity effect. A bimetallic platform offers many structural and functional differences such as the identity of the metal atoms and the bonding interactions between metals, which have been reflected in their unique catalytic ability and reactivity. This dissertation encompasses work related to the computational study of metal-metal interactions of bimetallic systems, the 1H NMR study of stereochemical and conformational changes in solution of N,Nʹ-diarylformamidines, the synthesis of dizinc formamidinate complexes, and the synthesis and catalytic ability of dicopper formamidinate complexes. In the first part, DFT calculations are used to study factors that influence metal-metal bond lengths in various complexes. Several experimentally obtained X-ray crystal structures were used as the basis for the study. Differences in metal-metal separations were investigated through various functionals, indicating the importance of charge, orbital interactions, and formal bond order. BH&HLYP SDD/aug-CC-PVDZ geometry optimizations of octahalodimetalate anions Tc2X8n- (X = Cl, Br; n=2, 3), Re2X82- (X = Cl, Br), and Mo2Cl84- reproduced M-M bond distance trends observed experimentally. The study demonstrated that the increase in σ and π bond strength resulted in the shortening in Tc-Tc bond distance from Tc2X82- to Tc2X83-, which was further supported by the short Mo-Mo bond in the Mo2Cl84- ion. This study was expanded further through the inclusion of [M2Cl4(PMe3)4]n+ (M = Tc, Re, n = 0-2) and [Mo2E4]n- (E = HPO4 or SO4, n = 2-4), allowing a systematic study on the role of charge on the metal atoms. PBEO SDD/aug-CC-PVDZ calculations revealed that both formal bond order and formal charge on the metal atoms dictate the trends in M-M bond strength. The second half of this dissertation focuses on the synthesis and characterization of bimetallic Zn- and Cu-formamidinate complexes. The stereochemical exchange of substituted N,Nʹ-diarylformamidines were studied through 1H NMR in various solvents. Alkyl substituents placed on the ortho positions were found to shift the isomeric equilibrium in solution through destabilization of the hydrogen-bond dimer evident in X-ray crystal structures. The Z-isomer of substituted N,Nʹ-diarylformamidines is observed in CDCl3, C6D6, and DMSO-d6 when the ligands feature significant steric hinderance. Similar ortho substituted N,Nʹ-diarylformamidines were also used to enforce steric interactions to limit the nuclearity of Zn-formamidinate complexes. Various dizinc formamidinate complexes were synthesized through direct and transmetalation routes. NMR and mass spectrometry were used alongside X-ray crystal structures to fully characterize the dizinc complexes. Dicopper formamidinates formed through a transmetallation route were synthesized and feature distinct short Cu…Cu separations thought to be brought about by metalophillic interactions. Preliminary results suggest catalytic ability of dicopper formamidinates in cyclopropanation and aziridination of styrene with various diazo compounds. The catalytic activity suggests the formation of dicopper carbene and nitrene intermediates, of which only few published experimentally observed examples exist in the literature.

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Hua, Wei. "Interfacial Water Organization and Ion Distributions Investigated with Vibrational Sum Frequency Spectroscopy: Answering Fundamental Questions for Environmental Chemistry." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1385593745.

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Cai, Yu. "Theory for Fundamental Reactions in Fuel Cells." Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1120759456.

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Palencsar, Iozsef Attila. "SINGLE PARTICLE MICROELECTRODES AND MICROBATTERIES: FUNDAMENTAL STUDIES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=case1144340892.

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33

Zhu, Qian. "Fundamental aspects of carbon gasification and NOâ†x release from carbon combustion." Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362414.

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34

Greenhalgh, Edward T. "Fundamental understanding of microwave assisted ring-opening polymerisation and co-polymerisation." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14265/.

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The work presented in the thesis attempted to gain in-depth understanding of the effect that the microwave energy has on various facets of the ring-opening polymerisation of cyclic esters with a view to synthesising novel bio-degradable homopolymers, branched structures and copolymers. Chapter 1 introduces the various synthetic polymer procedures and lists possible final product architectures. The main technique that is used throughout this thesis, ring-opening polymerisation, is discussed in great detail. The various targeted linear aliphatic polyesters are introduced. Finally, the fundamental theory behind microwave dielectric heating is discussed. Chapter 2 outlines the various characterisation techniques that are used to analyse the various synthesised materials throughout the work in this thesis. The polymerisation techniques used, particularly using the microwave reactor, is also discussed. In Chapter 3, the effect that microwave heating has upon the homopolymerisation of poly(ε-caprolactone) is investigated. Detailed analysis of the dielectric properties of the reagents and accurate temperature monitoring is applied at various stages of the reaction mechanism to compare and contrast the effect of microwave and conventional heating. Chapter 4 describes the impact that microwave energy has upon the copolymerisation reactions when a second cyclic ester is introduced, D/L-lactide. Various procedures are utilised in an attempt to synthesise bio-degradable block copolymers with interesting mechanical properties and degradation rates. The dielectric properties of the reagents and their polymer structures are used to rationalise any experimental observations. The work presented in Chapter 5 investigates the synthesis of branched polymers using a di-lactone branching agent, composed to two joined ε-CL units. Various analytical techniques are employed to guarantee successful branching. The effect of microwave energy is scrutinised, with a view to creating faster rates of reaction and altering the final product structure using direct dielectric heating. Finally, Chapter 6 provides the overall conclusions obtained from the work presented in this thesis, before providing possible routes of subsequent study for further research into this area.

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35

Burton, Lyle Lorrence. "Fundamental studies and spectral simulation of the inductively coupled argon plasma." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30964.

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The objectives of this work are twofold: firstly, to understand the inductively coupled argon plasma (icp) from a fundamental point of view and, secondly, to attempt to put that knowledge to practical use. In an effort to realize this first objective, a simple two-level rate model was developed which allows the estimation of the deviations (due to radiative decay) of analyte level populations in the icp from local thermodynamic equilibrium (lte). The results were found to agree very well with experiment for analyte elements (Fe, Cr and Ba) which did not exhibit charge transfer with the argon support gas. A comprehensive study of magnesium excited-state level populations was performed. It was found that charge transfer between argon ions and ground state magnesium atoms caused ionic magnesium to be overpopulated (with respect to the simple rate model calculations mentioned above). It was also found that, due to appreciable self-absorption, argon itself conforms to an lte model. Electron temperatures (Te) were measured in the icp. It was found that, for electron densities greater than about 2x10¹⁵ cm⁻³, Te was within experimental uncertainty of the so-called lte temperature (Te,lte - calculated from the electron density). At lower electron densities, due to the large experimental errors involved, it was difficult to draw definitive conclusions regarding their agreement. The plasma was also extensively characterized when an extra argon flow was added to the aerosol gas. It was found that at low values of the aerosol gas flow rate, mixing between it and the plasma gas was relatively complete, whereas at higher flow rates there was relatively little mixing. It was also found that the introduction of water into the plasma had a limited effect on sample excitation. In order to fulfil the second objective, a method was developed to simulate emission spectra from an icp. The method involved the use of a computer program, which worked by combining basic physical data for atomic species, the results of icp fundamental studies, and a realistic instrumental line profile (described in detail). The method was used to simulate a hypothetical silver determination in NBS coal fly ash showing the effects of spectrometer bandpass, silver concentration, and line choice on spectral overlaps.
Science, Faculty of
Chemistry, Department of
Graduate

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36

Briand, Glen G. "Bifunctional ligands in discerning and developing the fundamental and medicinal chemistry of bismuth(III)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0015/NQ49247.pdf.

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37

Li, Zhao. "The Kinetics and Mechanisms of Some Fundamental Organic Reactions of Nitro Compounds." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1407.

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The central topic of this dissertation is to seek the answer to the question: Is the single transition state model appropriate for (1) the proton transfer reactions of nitroalkanes and (2) the aromatic nucleophilic reactions of trinitroarenes? If not, what are the real mechanisms? This objective has been accomplished by careful kinetic and mechanistic studies which take advantage of modern digital acquisition of absorbance - time data, combined with extensive new data analysis of results from pseudo-first-order kinetic measurements. Several new analysis procedures for pseudo-first-order kinetics that are capable of distinguishing between single-step and multi-step mechanisms have been introduced and intensively confirmed during the application in the kinetic study of the target reactions. The procedures include (1) half-life dependence of apparent rate constant, (2) sequential linear pseudo-first-order correlation, (3) approximate instantaneous rate constant analysis, and (4) time-dependent apparent kinetic isotope effects. Various conventional and nonconventional pseudo-first-order kinetic analyses of the reactions of nitroalkanes in aqueous solutions revealed that the reactions are complex and involve kinetically significant intermediates. The spectral evidence for the formation of reactive intermediates was obtained by carrying out the kinetic experiments at the isosbestic points where changes in reactant and product absorbance cancel. The apparent deuterium kinetic isotope effects studies indicated that the deuterium kinetic isotope effects are not associated with the formation of the intermediates. The observations of anomalous Brønsted exponents previously found for this reaction series could be rationalized well with the complex mechanisms proposed in this work, which indicate that the nitroalkane anomaly does not exist, but arises from an interpretation based upon the incorrect assumption that the reactions follow a simple one-step mechanism. Simulations revealed that the generally accepted competitive mechanism was not appropriate to describe the Meisenheimer complex formation during the reaction of 2,4,6-trinitroanisole with methoxide ion in methanol. This conclusion is supported by the conventional pseudo-first-order kinetic analysis. A reversible consecutive mechanism that accounts for the kinetic behavior has been proposed, which involves an intermediate dianion complex that is formed reversibly from the initial 1,3-σ-complex, and then eliminates methoxide ion to form the 1,1-σ-complex product.

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Korzyński, Maciej Damian. "Functionalization of metal-organic frameworks with early transition metals : from fundamental studies to catalytic applications." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121781.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 191-215).
Metal-organic frameworks (MOFs) have established themselves as some of the most versatile materials available, with applications ranging from gas sorption to separation to sensing to catalysis. With a large abundance of structural motifs published to date, research efforts have shifted towards further framework elaboration via post-synthetic modification (PSM), a method to alter the chemical structure of preformed MOFs. The secondary building units (SBUs) of MOFs, which are commonly small inorganic clusters, have been particularly interesting targets for this synthetic approach. The aim of this thesis is to further our understanding of how metal cations interact with these inorganic nodes. Additionally, the node functionalization approach is used to synthesize novel catalysts for the olefin metathesis reaction. In Chapter 1, the reader is introduced to post-synthetic modification of MOFs with a focus on early transition metal species. A review of pertinent literature is presented. Chapter 2 describes how a desire to challenge the limits of the well-precedented cation exchange process led to a serendipitous discovery of a long-sought binding mode in the iconic MOF-5 system using NbCl₄(THF)₂ as a precursor of niobium. In Chapter 3, attention shifts from fundamental studies to the development of new catalysts for olefin metathesis, a process that to (late has been not been extensively studied in MOFs. After a short introduction about the traditional olefin metathesis catalysis, the prospect of using the inorganic nodes of MOFs as supports akin to the classical platforms used in heterogeneous catalysis is explored. Chapter 4 expands the concepts developed in the previous chapter to rhenium oxide-based olefin metathesis, which is unique compared to catalysis using molybdenum and tungsten oxide systems.
by Maciej Damian Korzyński.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Chemistry

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39

Rozsnyai, Lawrence Francis 1968. "Applications and fundamental studies of self-assembled monolayers : conducting polymer deposition and chemical force microscopy." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/45972.

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40

Knopf, Ioana. "Carbon dioxide utilization : from fundamental reactivity to catalysis using transition metals supported by macrocyclic diphosphines." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112359.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 2017.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis. Page 308 blank.
Includes bibliographical references.
Molybdate, a molecular metal oxide, readily binds CO₂ at room temperature to produce a robust monocarbonate complex, [MoO₃(k²-CO₃)]²-. In the presence of excess CO₂, a pseudo-octahedral dioxo dicarbonate complex, [MoO₃(k²-CO₃)₂]²-, is formed. The monocarbonate [MoO₃(k²-CO₃)]²- reacts with triethylsilane to produce formate together with silylated molybdate. A different system investigated in the context of CO₂ reduction to formate was sodium borohydride. The uptake of three equivalents of CO₂ by NaBH₄ is described, along with full spectroscopic and crystallographic characterization of the resulting triformatoborohydride, Na[HB(OCHO)₃]. In order to develop catalytic transformations for CO₂ utilization, we undertook an extensive investigation into the synthesis of novel phosphine ligand architectures that could support transition metal catalysts. A new, chelating, cationic P,N-ligand, [pyP₂dmb₂][SbF₆], was synthesized by treatment of the robust bicyclic diphosphane, 3,4,8,9-tetramethyl-1,6-diphosphabicyclo(4.4.0)deca-3,8-diene or P₂dmb₂, with 2-iodopyridine, followed by an anion exchange. This phosphino-phosphonium salt was investigated as a ligand for group 6 and group 10 transition metals. Other cationic and zwitterionic ligand frameworks were also briefly investigated. A family of cis-macrocyclic diphosphines was prepared in just three steps from white phosphorus and commercial materials using a modular synthetic approach. Alkylation of bicyclic diphosphane P₂dmb₂ produced phosphino-phosphonium salts [RP₂dmb₂]X, where R is methyl, benzyl, isobutyl, or neopentyl. Treatment of these salts with organometallic reagents yielded macrocyclic diphosphines of the form cis-1-R-6-R2-3,4,8,9-tetramethyl-2,5,7,10-tetrahydro-1,6-DiPhospheCine, or R,R2-DPC, in which R2 is methyl, cyclohexyl, phenyl, mesityl or neopentyl. Alternatively, symmetric diphosphine Cy₂-DPC was synthesized from the dichlorodiphosphine Cl₂P₂dmb₂. Multidentate ligands with additional S, P and N donor atoms have also been prepared. The coordination chemistry of these cis-macrocyclic diphosphines was explored, with a focus on nickel and cobalt complexes. An unusual iodide-bridged cobalt(I) dimer, [(Cy₂-DPC)CoI]₂, was prepared and structurally characterized. These nickel and cobalt complexes supported by cismacrocyclic diphosphines were investigated as potential catalysts for the coupling of carbon dioxide and ethylene to produce acrylate, a valuable polymer precursor. The nickel complexes studied showed similar or better turnover numbers for acrylate production compared to complexes of commercial diphosphine ligands. Although not yet catalytic, the first examples of cobalt complexes capable of mediating acrylate formation from CO₂ and ethylene are reported.
by Ioana Knopf.
Ph. D.

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41

Menderes, Özlem. "Fundamental aspects of the chrome tanning reaction." Thesis, University of Leicester, 2002. http://hdl.handle.net/2381/30258.

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Fundamental elements of chrome-collagen interactions and the crosslinking mechanism at the molecular level have been investigated to gain detailed understanding that can be translated into improvements in the commercial process. Amide group hydrolysis during conventional liming proceeds by two mechanisms: direct hydrolysis with hydroxyl catalysis or intramolecular catalysed hydrolysis that can be measured by the degree of racemisation at L- asparagine. Gas chromatography mass spectrometry analysis of limed collagen demonstrated that there was no initial rise in the amount of D-aspartic acid during the first 24 hours of liming, indicating that, within the conventional period of liming, collagen remained intact. Circular dichroism has demonstrated that beamhouse processing has dispersive and relaxing effects on the collagen triple helices, but without disruption. Attenuated total reflection Fourier transform infrared spectroscopy analysis provided information regarding changes in the secondary structure of collagen during tanning. Complete breakdown of chrome tanned collagen was achieved by the use of a cocktail of proteolytic enzymes: this allowed an analysis of the isolated crosslinks, which indicated preferred reaction at aspartate sidechain carboxyls. This is supported by chrome tanning studies following treatment of collagen by amidase enzymes. Geometric details of chromium(lll) species involved in the tanning reaction were elucidated by extended X-ray absorption fine structure analysis. Linear tetrameric chromium species were found to be predominant in the tanning process. Direct measurements of the mechanism were made using electron spin resonance spectroscopy. A two-stage reaction mechanism is postulated: physical interaction and chemical complexation, affected by reaction conditions such as pH, temperature and the presence of neutral salts. Nuclear magnetic relaxation dispersion measurements confirmed changes in the speciation of chromium(lll) under tanning conditions.

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Qiao, Geng. "Fundamental understanding of thermophysical properties of molten salts containing nanoparticles." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8453/.

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Molten salts have been widely used as thermal energy storage (TES) materials as they offer favourable specifications which enable them to be employed in TES applications. Finding a cost-effective method to enhance the energy storage capability of molten salts has caught the attention of many researchers. It was reported that by adding a small amount of nanoparticles, a major enhancement of the specific heat capacity was observed in molten salts. Though different studies argued that the enhancement was not found in other thermal storage materials, the observation of the enhancement was continuously reported. This work studied the thermal properties of molten salt based nanosuspensions synthesized with a novel method modified based on other studies. Molecular dynamics (MD) simulations were employed to study the thermodynamic properties of the nanosuspension systems. By the analysis of the effect on the internal energy of the nanosuspensions I draft general conclusions and explain why molten salt have this specific heat enhancement while other materials (e.g. water) does not. I use MD simulation to support, for the first time, a theory that can explain the apparently contradictory behaviour of the experimental data. Moreover, the main impact factor affecting the enhancement was investigated and discussed.

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Edwards-Gau, Gregory R. "X-ray Birefringence Imaging and other fundamental aspects of solid organic inclusion compounds." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/75370/.

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This thesis presents new experimental techniques and utilizes these strategies in the analysis of solid organic inclusion compounds. This thesis also reports the production of a new series of co-crystals and examines their crystal structures. Chapter 1 acts as an introduction to the materials studied in this research. It explains the properties of inclusion compounds and lists the chemical materials used for these experiments. Chapter 2 explains the experimental techniques used in this research. Specifically it explains X-ray diffraction, X-ray birefringence and in-situ solid-state NMR. Chapter 3 presents a new technique for spatially resolved mapping of specific bond orientations in anisotropic solid materials using wide beam linearly polarized X-rays and an area detector. Earlier work with a focussed beam and a point detector showed the sensitivity of X-ray Birefringence to the orientation of specific energy-matching bonds inside a material, but these experiments only probed a small section of the crystal. Our wide beam imaging technique (X-ray Birefringence Imaging) shows similar sensitivity but allows us to investigate the full crystal simultaneously, which allows us to identify different domains within a single crystal. We apply this technique to a model material (1 bromocyclohexane/thiourea) which undergoes a low temperature phase transition and serves to demonstrate the usefulness of imaging techniques - in the high temperature phase the relevant C−Br bonds are isotropically disordered and no birefringence is observed, in the low temperature phase the relevant C−Br bonds are ordered but there are three possible orientations for the bromocyclohexane molecule so different regions of the crystal exhibit different birefringent signal. This behaviour is very clear on an imaging technique, but can appear highly confusing when using point-detector techniques. Chapter 4 utilizes X-ray Birefringence Imaging to investigate the dynamic rotational properties of guest molecules in a different set of solid organic inclusion compounds. By studying the known structures of 1,10-dibromodecane/urea and 1,8-dibromooctance/urea we have determined that XBI is a time-averaged and space-averaged technique. Additionally this chapter utilizes a Ge(555) analyzer instead of the Si(555) analyzer, which results in better spatial resolution and a different beam shape on the final images. Chapter 5 utilizes solid-state in-situ NMR to monitor crystallization processes as they occur and gain insight on competitive uptake of different guest molecules within the inclusion compound. These experiments use alkane and α,ω-dibromoalkane guest molecules inside urea inclusion compounds where the urea host structure (created in-situ) acts like a one-dimensional tunnel confining the guest. Every position within the urea tunnel is equivalent (a property of the incommensurate structure) which serves to simply the solid-state NMR spectra and means that for a given atom at the end of an alkane chain the only difference in NMR site comes from the neighbour molecule along the tunnel. This means in the solid phase we can observe peak splitting on certain atoms based on neighbour environment (e.g. the -CH3 in undecane will give a slightly different chemical shift if the neighbouring guest molecule is another undecane compared to if the neighbouring guest molecule is 1,8-dibromooctane) which in turn allows us to extract some information about the ordering within the inclusion compound. In these experiments we can also clearly distinguish between the same molecules in different phases, so as crystallization occurs we observe the loss of solution signal alongside the gain of solid signal. Additionally these experiments show no evidence of any intermediate structures or transition states. Chapter 6 describes a new set of organic co-crystals formed by reacting thiourea with α,ω-diiodoalkane chains and examines the crystal structures of these materials. Chapter 7 details further work and potential applications of this research. Digital data includes animated videos of the X-ray birefringence imaging data obtained in Chapter 3 and CIF files of the structures determined in Chapter 6.

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Williams, Joshua R. "Fundamental investigations of skutterudite phase formation by the modulated elemental reactant method /." view abstract or download file of text, 2002. http://wwwlib.umi.com/cr/uoregon/fullcit?p3055721.

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Thesis (Ph. D.)--University of Oregon, 2002.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 124-128). Also available for download via the World Wide Web; free to University of Oregon users.

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Jenkins, Judith Lynn. "Spectroscopic and Spectroelectrochemical Characterization of Fundamental Interfacial Charge Transfer Processes Relevant to Efficient Solar Energy Conversion." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/255173.

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Solar energy conversion is accomplished by multilayered devices consisting of various conducting and semiconducting materials. Because the layers are only 10s - 100s of nm thick, device behavior is governed primarily by interfacial molecular dynamics that often differ from the bulk behavior of these materials. The thermodynamics and kinetics of the interfacial interactions are particularly interesting, as interfacial electron transfer strongly influence the efficiency of photovoltaics and devices used in solar hydrogen production. This work focuses specifically on interfacial charge transfer processes occurring at three interfaces relevant to thin film organic/inorganic solar energy conversion devices. i) A potential-step polymer electrochemical deposition and doping procedure was developed and used to create poly(3-hexylthiophene) (e-P3HT) interlayer films for organic photovoltaics. Photoelectron spectroscopies suggest that an interface dipole forms spontaneously at the polymer donor/fullerene acceptor interface through partial interfacial charge transfer prior to photoexcitation; this doping-dependent interfacial dipole was correlated to the electrical properties of these critical heterojunctions. ii) Potential-modulated fluorescence spectroscopy (PMF) was developed and used examine the kinetics of the reversible oxidation of the (e-P3HT) films in attempt to elucidate the ITO/e-P3HT charge transfer rates. However, the optical switching increased linearly as the polymer film decreased, indicating that the molecular-level process probed by PMF was rate-limited by counter-ion movement into and out of the polymer film. iii) Potential-modulated attenuated total reflectance spectroscopy (PM-ATR) was used to examine the reversible reduction of CdSe semiconductor nanocrystals tethered to indium tin oxide electrodes as well as the surface-coverage dependent bleaching of these nanocrystals. A new equivalent circuit model describing the CdSe/ITO electrode is proposed, and a PM-ATR simulation program was used to quantify Faradiac resistances to interfacial charge transfer that trend with the magnitude of overpotential. The insights gained through these experiments add to a growing understanding of the fundamental, molecular-level competition between photoinduced charge generation and parasitic charge recombination at these critical interfaces.

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Widanalage, Dona Tharanga Kumudini Wijethunga. "Hydrogen- and halogen-bond driven co-crystallizations: from fundamental supramolecular chemistry to practical materials science." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/20497.

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Doctor of Philosophy
Chemistry
Christer B. Aakeroy
A series of co-crystallizations between four biimidazole based compounds with nine symmetric aliphatic di-acids and fifteen perfluorinated halogen-bond donors were carried out to determine if a MEPS based ranking can be used to effectively assign selectivity in hydrogen- and halogen-bond interactions. The results suggested that a simple electrostatic view provides a reliable tool for successfully implementing the practical co-crystal synthesis with desired connectivity. MEPS based selectivity guidelines for halogen-bond interactions were explored in co-crystallizations between twelve asymmetric ditopic acceptors and nine halogen-bond donors. If the difference between the two acceptor sites is below 35 kJ/mol, no selectivity was observed; above 65 kJ/mol halogen bond selectivity dominates and mid ΔE range was recognized as the grey area where predictions cannot be made. To examine competition between hydrogen and halogen bonds, five heteroaryl-2-imidazoles were co-crystallized with fifteen halogen-bond donors. It was found that halogen bonds prefer best the acceptor site, demonstrating that a suitably activated halogen-bond donor can compete with a strong hydrogen-bond donor. The benefits of ‘double activation’ for promoting halogen bond effectiveness was explored with nine haloethynylnitrobenzenes. The positive potential on halogen atoms was enhanced through a combination of an sp-hybridized carbon and electron-withdrawing nitro group(s). Iodoethynylnitrobenzenes were identified as the most effective halogen-bond donors reported to date and the compounds were exploited for the interaction preferences of nitro group and nitro⋯X-Csp interactions were identified as synthetic tools for energetic co-crystal assembly. A synthetic strategy for the deliberate assembly of molecular polygons was developed utilizing bifurcated halogen bonds constructed from N-oxides and complementary halogen-bond donors via co-crystallization. A convenient, effective, and scalable protocol for stabilizing volatile liquid chemicals with co-crystallization was achieved. Through the use of halogen-bonding, liquid iodoperfluoroalkanes were transformed into crystalline materials with low-vapor pressure, considerable thermal stability and moisture resistance. To stabilize the energetic compound ethylenedinitramine, a co-crystallization approach targeting the acidic protons was employed. Eight co-crystals were obtained and the acceptors were identified as supramolecular protecting groups leading to diminished reactivity and enhanced stability while retaining the desirable energetic properties.

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47

Chan, George C. Y. "Fundamental mechanisms and diagnostic tools for interference effects in inductively coupled plasma-atomic emission spectrometry." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3274247.

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Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2007.
Source: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4435. Adviser: Gary M. Hieftje. Title from dissertation home page (viewed Apr. 15, 2008).

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Topçu, Türker. "Time dependent studies of fundamental atomic processes in Rydberg atoms /." Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Dissertations/TOPCU_TURKER_31.pdf.

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WEBB, BRYAN DOUGLAS. "FUNDAMENTAL INVESTIGATIONS OF A 148 MEGAHERTZ INDUCTIVELY COUPLED PLASMA DISCHARGE." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188138.

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Fundamental investigations have been carried out on an Inductively Coupled Plasma (ICP) operated at 148 MHz, a frequency which is nearly three times higher than any previously reported for analytical ICPs used in spectrochemical analysis. High frequency operation is expected to provide easier sample introduction into the discharge, with a consequence of less energetic conditions in the central channel. Several plasma diagnostic techniques were employed in order to determine the conditions experienced by the analyte species in this source for spectrochemical analysis. Three different torch systems were investigated at 148 MHz and compared to the "standard" 27 MHz configuration. The highest excitation temperatures and electron densities were obtained in the 27 MHz configuration, and the lowest values in the largest torch at 148 MHz. Intermediate values were obtained in the intermediate-size torches at 148 MHz. These observations correlate reasonably well with the ratio of the plasma radius to the skin depth (r/s). The skin depth defines the region in which the majority of the electrical energy is deposited into the discharge, and is smaller at 148 MHz than at 27 MHz. The measurement of electron densities also allows the estimation of how closely a particular discharge approaches Local Thermal Equilibrium (LTE). As may be expected, LTE is most closely approached in the 27 MHz arrangement. The less energetic conditions characterized by lower temperatures and electron densities result in less intense analyte emission from the high frequency ICPs. Signal-to-Background ratios and detection limits reflect this trend, but the linearity of the calibration curves and freedom from vaporization interferences are not degraded. Finally, the introduction of organic solvents is much easier, and better detection limits in an organic matrix are obtained at 148 MHz. These investigations have shown the utility of classifying the effects of changing torch sizes and operating frequencies by means of the r/s ratio. This provides the analyst with a means of selecting the general range of conditions to be employed in a particular analysis.

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Grasseschi, Daniel. "Uma abordagem fundamental sobre nanopartículas de ouro." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-20072015-141715/.

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O estudo sistemático de nanopartículas de ouro utilizando conceitos fundamentais de química de coordenação e físico-química é o foco principal desta tese, que trata principalmente da natureza das interações moleculares na superfície de nanopartículas. Para tal finalidade, estudou-se como as variações dos parâmetros experimentais influenciam no mecanismo de formação das partículas pelo \"método de Turkevich\". Observou-se que, não somente, a morfologia e as propriedades ópticas estão atreladas aos processos de nucleação e crescimento, mas também a composição e as propriedades químicas da camada molecular ao redor das partículas. Dessa forma, foi possível comprovar, teórica e experimentalmente, que um intermediário instável da reação de oxidação do citrato de sódio, a acetonadicarboxilato, se torna estável devido a coordenação aos átomos superficiais de ouro. Isto leva a propriedades químicas e espectroscópicas distintas, principalmente, frente a reações de troca de ligantes na superfície das partículas. Foi feito um estudo, teórico e experimental, sistemático das propriedades das moléculas de etanobis(tioamida) na superfície de diferentes nanopartículas de ouro, comprovando que a presença de acetonadicarboxilato, ao final da síntese das partículas, influencia drasticamente nas propriedades do sistema.
The systematic study of gold nanoparticles using fundamental concepts of coordination and physical chemistry is the focus of this thesis, devoting an especial attention for molecular interactions nature at the particles surface. For this goal, the effects of many experimental parameters on the gold nanoparticles formation by the Turkevich method have been studied. It has been shown that not only the morphology and optical properties are controlled by the nucleation and growth processes, but also the chemical properties of the molecular layer at the particles surface. In this way, it has been proved, theoretical and experimentally, that an instable oxidation product of the sodium citrate reaction with the gold salt, a ketonedicarboxilate species, is stabilized by coordination with the superficial gold atoms. This fact leads to distinct chemistry and spectroscopic properties, mainly, related to the reactions at the gold surface. IN addition, a carefully theoretical and experimentally study has been carried out exploring the characteristics of the ethanebis(thioamide) molecules on the surface of different particles. It has been demonstrated that the ketonedicarboxilate presence, from the synthesis process, drastic influences the system properties.

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Dissertations / Theses on the topic 'Fundamental chemistry'

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