Teses / dissertações: "Chemistry"

1

Walls, Bethany M. "Becoming a chemist graduate students' perspectives on chemists and chemistry /". Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1233080675/.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

2

Sato, Hiroki. "Chemistry /". Online version of thesis, 2008. http://hdl.handle.net/1850/7747.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

3

Dinescu, Adriana Cundari Thomas R. "Metals in chemistry and biology computational chemistry studies /". [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-3678.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

4

Jiang, Jian. "Studies of supramolecular chemistry through Schiff-base chemistry". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27809.

Texto completo da fonte

Resumo:

This thesis describes the synthesis, characterization, and host-guest studies of a series of Schiff-base macrocycles. New [2+2] Schiff-base macrocycles were prepared by Schiff-base condensation. These macrocycles were shown to be wide-mouthed supramolecular hosts that can include organic cations such as pyridinium, paraquat and ammonium derivatives. A new kind of donor-acceptor-donor 3-in-1 complex was obtained in solution by combining macrocycle, cyclobis(paraquat-p-phenylene) and tetrathiafulvalene. Variations of these [2+2] Schiff-base macrocycles were prepared by modifying the substituents of the diformyl diol unit. In this way naphthalene-based macrocycles that undergo keto-enamine tautomerization were synthesized. These macrocycles can also combine with organic cations to form host-guest complex. The naphthalene-based [2+2] macrocycles can form lyotropic liquid crystals in chloroform and 1,2-dichloroethane. From the polarizing optical microscopy, it is proposed that the mesophases are lyotropic nematic liquid crystals based on a bilayer structure. A further study of these macrocycles shows that the host-guest complex can also form a lyotropic liquid crystalline phase. Covalently-linked macrocycles with isosceles triangle shapes were prepared by Schiff-base condensation. The molecular isosceles triangles proved to also be supramolecular hosts for pyridinium and ammonium cations, based on ¹H NMR, 2D-ROESY NMR, and mass spectrometry studies. In addition to the Schiff-base macrocycles, conjugated Schiff-base containing oligomers were synthesized via Gilch polymerization methods. The oligomers were characterized by gel permeation chromatography (GPC), thermogravimetric analysis (TGA) and UV-Vis spectroscopy. For further proof of the oligomeric structure, a model compound was prepared by the Wittig reaction.

Estilos ABNT, Harvard, Vancouver, APA, etc.

5

Dinescu, Adriana. "Metals in Chemistry and Biology: Computational Chemistry Studies". Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc3678/.

Texto completo da fonte

Resumo:

Numerous enzymatic reactions are controlled by the chemistry of metallic ions. This dissertation investigates the electronic properties of three transition metal (copper, chromium, and nickel) complexes and describes modeling studies performed on glutathione synthetase. (1) Copper nitrene complexes were computationally characterized, as these complexes have yet to be experimentally isolated. (2) Multireference calculations were carried out on a symmetric C2v chromium dimer derived from the crystal structure of the [(tBu3SiO)Cr(µ-OSitBu3)]2 complex. (3) The T-shaped geometry of a three-coordinate β-diketiminate nickel(I) complex with a CO ligand was compared and contrasted with isoelectronic and isosteric copper(II) complexes. (4) Glutathione synthetase (GS), an enzyme that belongs to the ATP-grasp superfamily, catalyzes the (Mg, ATP)-dependent biosynthesis of glutathione (GSH) from γ-glutamylcysteine and glycine. The free and reactant forms of human GS (wild-type and glycine mutants) were modeled computationally by employing molecular dynamics simulations, as these currently have not been structurally characterized.

Estilos ABNT, Harvard, Vancouver, APA, etc.

6

Grange, Helen. "Good Chemistry". True Love, 2011. http://hdl.handle.net/10962/d1006276.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

7

Mant, Barry Peter. "Antimatter chemistry". Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230606.

Texto completo da fonte

Resumo:

This thesis concerns the theoretical study of the low-energy interaction of antihydrogen atoms (¯H) with hydrogen molecules and antiprotons (p¯) with hydrogen molecular ions. Both systems are of interest to experiments currently under way at CERN aiming to trap and study antihydrogen atoms. To date limited work has been carried out on these systems. Only four papers on the ¯H-H2 system have been published and so far only semi-classical results have been published for p¯-H+ 2 . For both systems potential energy surfaces are constructed by ﬁtting analytical functions to ab initio calculated energies. A combination of a neural network and suitable long-range asymptotic functions are used to ﬁt the surfaces of both systems. The resulting surfaces are more accurate than those of previous work and should be useful for further studies. Quantum mechanical scattering calculations are carried out using the S-matrix Kohn variational method. It is shown that basis sets which are eﬀective for normal chemical systems are not suitable for mixed matter/antimatter interactions. Instead, a basis set of multidimensional Gaussian functions, tailored to the potential, is used to converge the scattering calculations. For ¯H-H2 scattering the diatomic is approximated as a rigid rotor. Elastic and rotationally inelastic scattering calculations are presented. Hadronic annihilation calculations are also presented along with the ﬁrst calculation of leptonic annihilation cross sections for this system. Scattering calculations for the p¯-H+ 2 system are carried out with approximations made to the potential. The strength of the interaction between the antiproton and hydrogen molecular ion, which at long range becomes Coulombic, requires large basis sets. The necessary modiﬁcations required to use the Kohn method with a Coulomb potential are discussed. A preliminary calculation of Pn-H elastic scattering is also carried out.

Estilos ABNT, Harvard, Vancouver, APA, etc.

8

Qureshi, Tariq. "Spin chemistry". Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365292.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

9

Polywka, R. "Epoxide chemistry". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258024.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

10

Fitchett, Christopher Mark. "Metallosupramolecular chemistry". Thesis, University of Canterbury. Chemistry, 2002. http://hdl.handle.net/10092/5964.

Texto completo da fonte

Resumo:

This thesis describes the preparation and characterisation of a number of metallosupramolecular assemblies. Such species were constructed by the reaction of ligands based on nitrogen containing heterocycles with metal atoms. The coordinate bonds used to hold these species together provide a mixture of strength and lability that aids the formation of interesting structures. The twenty six ligands utilised for the formation of metallosupramolecular species can be divided into three types; rigid sym-biheterocycles, ligands with added flexibility, and chiral ligands for the formation of polymers. These investigations used a range of metal atoms to allow the examination of the metallosupramolecular chemistry of these ligands. The structure of forty three complexes was determined using single crystal X-ray crystallography. The complexes isolated and characterised had a diverse range of structures, with discrete and polymeric species formed. The rigid sym-biheterocycles gave mostly monomeric and oligomeric complexes, with two polymeric complexes also formed; all ligands failed to coordinate through all donor atoms. Ligands with added flexibility gave mostly one- and two- dimensional polymers, with discrete complexes such as M2L2 macrocycles and mononuclear structures also formed. The chiral ligands prepared using camphor gave a range of clural polymers, and in two cases these possessed directionality. The variety of metallosupramolecular assemblies synthesised exemplifies the structural complexity that may be formed using metal atoms and N-heterocyclic ligands as structural components for molecular construction.

Estilos ABNT, Harvard, Vancouver, APA, etc.

11

Sudkeaw, Pravit. "Theoretical chemistry". Thesis, University of Canterbury. Chemistry, 1991. http://hdl.handle.net/10092/8785.

Texto completo da fonte

Resumo:

Ab initio Molecular Orbital and Valence-Bond methods and the semiempidcal, AM1 method are applied in the studies of: 1. The proton affinity of diacetylene The gas-phase ion-molecule reaction between diacetylene and a proton was studied theoretically at the MP4SDQ/6-311G** level. The geometries, calculated harmonic vibrational frequencies and the proton affinity of the most stable structures are compared. The results from this study are supported by selected ion flow tube measurements and are compared with other calculations 2. The gas-phase reaction of CH₃CN and CH₃⁺. The reaction between CH₃CN and CH₃⁺ was studied at the MP4SDQ/6-31G* level of theory in order to determine the products and establish the multistep dissociation pathway of the reaction. The location and height of the transition states in the process is used as a criteria for the feasibility of the proposed pathway. The result is compared with the expediential and theoretical studies of the same system done by Wincel and coworkers [146]. 3. The geometries and force constants of small-sized organotin compounds The calculations on 12 small-sized organotin compounds were done at the HF/3- 21G* level of theory. The objective of this study was to provide the force constants of SnX and X-Sn-Y types for the use in Molecular Mechanic calculations of organotin compounds. The calculated geometries and harmonic vibrational frequencies of stannane and methyl stannane are compared with experimental results in order to measure the reliability of the calculations. 4. The chemical properties of CnO, CnO⁺, CnHO⁺, CnS, CnS⁺ and CnHS⁺ species in the instellar clouds CnO and CnS when n = 2 and 3 have been reported to be found in some interstellar clouds. These species in such environments are subjected to ionization and protonation processes. Theoretical studies of these species were done at the MP4SDQ/6-311G** level of theory. The calculations suggest that these species are more stable in protonated forms and could be intermediates of some steady state processes. 5. Theoretical study of C₆H₄+ formation in acetylenic flames C₆H₄⁺ has been detected as an intermediate in acetylenic flames. The semiempirical AM1 method was used to determine the most stable products and to establish a chemical mechanism of the reaction between C₄H₂⁺ and C₂H₂. The results from AM1 method were refined by ab initio calculations at the HF/4-31G andMP4SDQ/6-31G* level. From this study, only chemical pathways involved acyclic structure isomers are feasible. 6. A Valence-Bond study of BH2 radical In this study a Valence-Bond program was used on IBM PC/AT microcomputer to study the correlation between the nuclear bond angle and the angle of hybrid orbitals of BH₂. The energies of BH₂ from the Valence-Bond calculations were also compared with the energies from the Molecular Orbital method at the HF, MP4SDQ and CI level with best orbital energy basis sets, 10s6p/2s1p for boron atom and 6s/1s for hydrogen atoms. GAUSSIAN series programs, the MICROMOL package, the GAMESS program, a Valence-Bond program and the MOPAC program were used to perform the calculations.

Estilos ABNT, Harvard, Vancouver, APA, etc.

12

Alcock, S. "Tobacco chemistry". Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356015.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

13

Salan, Umit. "Feverfew chemistry". Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336046.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

14

Bown, M. "Organoruthenaborane chemistry". Thesis, University of Leeds, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377857.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

15

Potterton, Michael Andrew. "Diazopeptide chemistry". Thesis, Open University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337282.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

16

Phiri, Aretha. "Illuminating chemistry". Rhodos, 2006. http://hdl.handle.net/10962/d1006407.

Texto completo da fonte

Resumo:

Every year the Chemistry Department hosts a visiting lecturer for a week in memory of Professor William Francis Barker, former Professor of Chemistry in the Rhodes Chemistry Department (1925 -1961). This year's Barker Lecturer was Professor Mike Cook from the Department of Chemistry and Pharmaceutical Sciences at the University of East Anglia in Norwich, England. Professor Cook has an ongoing collaboration with Professor Tebello Nyokong in the Department of Chemistry in the field of phthalocyanine.

Estilos ABNT, Harvard, Vancouver, APA, etc.

17

San, Martín Luis Ortega. "Peruvian Chemistry Olympiad, twenty years promoting chemistry among youngsters". Revista de Química, 2015. http://repositorio.pucp.edu.pe/index/handle/123456789/100005.

Texto completo da fonte

Resumo:

La olimpiada peruana de Química cumple su vigésimo aniversario y en este artículo se hace una pequeña recopilación de la participación de alumnos en los últimos años, de las regiones de las que proceden y de los éxitos internacionales obtenidos por nuestra delegación.
The Peruvian Chemistry Olympiad celebrates its 20th anniversary and, in this report, a short review of the student participation in the event along with their origin and the international results obtained by each year’s winners is given.

Estilos ABNT, Harvard, Vancouver, APA, etc.

18

Goei, Elisabeth Rukmini. "Using Green Chemistry Experiments to Engage Sophomore Organic Chemistry". Miami University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=miami1280437800.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

19

Orrling, Kristina M. "On the Versatility of Microwave-Assisted Chemistry : Exemplified by Applications in Medicinal Chemistry, Heterocyclic Chemistry and Biochemistry". Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-101356.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

20

Erickson, John Timothy. "Chem flash cards online chemistry tutorials for beginning chemistry students /". Connect to online resource, 2004. http://www.csun.edu/%7Ejte35633.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

21

Humphrey, Mark Graeme. "Aspects of organometallic chemistry, particularly metal alkynyl and cluster chemistry". Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09SD/09sdh9267.pdf.

Texto completo da fonte

Resumo:

Includes bibliographical references. Details research carried out into the nonlinear optical properties of metal alkynyls, chiefly organoruthenium complexes, showing that these complexes can be designed to have very large NLO coefficients. Also demonstrates the utility of spectroscopic, electrochemical and copmutational aids as predictive tools for NLO materials. Also examines cluster synthesis, reactivity and physical properties using ruthenium clusters and hard-donor ligands, affording a series of cluster complrxes that provide structural models for industrially-important hydrotreating intermediates.

Estilos ABNT, Harvard, Vancouver, APA, etc.

22

Leste-Lasserre, Pierre. "Sulfur allotrope chemistry". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38218.

Texto completo da fonte

Resumo:

The synthesis of the sulfur homocycles S6, S9, S10, S12 and S20, which belong to the group of sulfur allotropes, has been achieved based on existing procedures. Polymeric sulfur Smu was also prepared.
The parameters of a small scale model reaction between 2,3-diphenyl-1,3-butadiene and S10 were optimized. Products were identified and 1H-NMR yields were calculated by comparison with an internal standard. The experimental parameters of this model served as a base for further reactions of S 10 with a variety of simple or conjugated olefins. The products of these reactions were fully isolated and characterized using standard spectroscopic techniques. The structures of a new bis-sulfurated compound having a norbornane framework and of the product obtained from the dimerization of norborn-5-ene-2,3-dithiol were also confirmed by single crystal X-ray crystallography.
The sulfur homocycles S9, S12 and S20 were also found to react with norbornene and two different 1,3-dienes. Products were identified and 1H-NMR yields for these small scale reactions were calculated by internal standard comparison. Differences and similarities with the products obtained with S10 are discussed. Sulfuration efficiencies of the different allotropes towards selected substrates are also compared.
A mechanistic study was carried out. The implication of sulfur radicals in the thermal decomposition of S10 has been suggested. Reaction mechanisms accounting for the formation of the different products observed are proposed.

Estilos ABNT, Harvard, Vancouver, APA, etc.

23

York, Andrew P. E. "Methane conversion chemistry". Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334954.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

24

Chatakondu, Kalyan. "Organometallic intercalation chemistry". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258017.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

25

Seward, Christopher M. P. "Stereoselective glycosylation chemistry". Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270281.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

26

Polywka, M. E. C. "Mechanistic organometallic chemistry". Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253399.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

27

Duggan, Andrew Charles. "Fullerene intercalation chemistry". Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298749.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

28

Henry, Paul Francis. "Fullerene intercalation chemistry". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363757.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

29

Bishop, Alexander James. "Actinide surface chemistry". Thesis, Cardiff University, 2010. http://orca.cf.ac.uk/54193/.

Texto completo da fonte

Resumo:

The surface reactivity of thorium and uranium, and how this links to the 5f electrons, has been investigated under UHV conditions using X-ray photoelectron spectroscopy (XPS), ultra violet photoelectron spectroscopy (UPS), and inverse photoemission spectroscopy (IPES). Water and ammonia adsorption on a polycrystalline thorium surface has been investigated at 100 and 298 K. Water adsorbs and dissociates upon the surface, leading to the formation of oxide and hydroxide species at 298 K, and oxide, hydroxide, and physisorbed water at 100 K. The surfaces after adsorption at both temperatures proved to be unstable when exposed to the low energy electron gun utilised in IPES. Ammonia adsorbs and dissociates upon the surface, leading to the formation of nitride and NH₂ species at 298 K, and nitride, NH₂, and physisorbed ammonia at 100 K. Upon reaction only the mononitride ThN is formed, the metallic nature of which was confirmed by UPS and IPES. The surface was unstable under the low energy electron gun utilised in IPES, with the ThN species being converted to the non-metallic Th₃N₄. Water and ammonia adsorption on a polycrystalline uranium surface has also been investigated at 100 and 298 K. Water adsorbs and dissociates upon the surface, leading to the formation of oxide and hydroxide species at 298 K, and oxide, hydroxide, and physisorbed water at 100 K. The rate of reaction of water with uranium is substantially reduced in the presence of residual oxygen on the surface. The small band-gap of semi-conducting UO₂ can be observed directly with UPS and IPES. Ammonia adsorbs and dissociates upon the surface, leading to the formation of nitride and NH₂ species at 100 and 298 K.

Estilos ABNT, Harvard, Vancouver, APA, etc.

30

Song, Chuanjun. "New heteroaromatic chemistry". Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/56011/.

Texto completo da fonte

Resumo:

The current literature for the synthesis of pyrazole derivatives has been reviewed. A silver nitrate-induced 5-endo-dig approach to pyrazolines and pyrazoles is discussed. A brief review of the 5-endo-dig cyclisation is included. The propargylic hydrazine precursors are synthesized by four different routes. The key step for the first route is a Mitsunobu reaction of propargylic alcohols with hydrazine derivatives. A short review of the Mitsunobu reaction is also included. The second route applied is a nucleophilic attack onto imines by lithium acetylides followed by electrophilic Anamination of the resulting propargylic amine with a oxaziridine. The third route involves 7V-nitrosation of a propargylic amine and subsequent reduction of the nitroso functional group. The final route is a simple nucleophilic substitution of propargyl bromide with hydrazine. Oxidation of pyrazoline to pyrazole and iodination of pyrazole have also been briefly studied. Two examples of 5-endo-dig iodocyclisation and one example of palladium-induced 5-endo-dig cyclisation are also reported. Current literature for pyrrole acylation has been reviewed. Representative 2-aryl-7V-tosylpyrroles were synthesized by Suzuki coupling of 2-bromo-Af-tosylpyrrole and arylboronic acids. A brief review of Suzuki coupling reaction is included. A new method for the acylation of Af-tosylpyrroles using carboxylic acids and trifluoroacetic anhydride is discussed. When applied to a,/-unsaturated acids, a in situ Nazarov cyclisation follows acylation to give cyclopenta 6 pyrrol-6(l//)-ones. The Nazarov cyclisation is reviewed. TV-Detosylation of acylpyrroles has been briefly examined. A study towards the construction of the macrocyclic core of roseophilin by the new pyrrole acylation strategy is discussed.

Estilos ABNT, Harvard, Vancouver, APA, etc.

31

Norbury, A. M. "Novel organoboron chemistry". Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638337.

Texto completo da fonte

Resumo:

The first part of the thesis deals with an investigation into some aspects of the chemistry of di-(2,4,6-triisopropylphenyl)boranes, a novel class of highly hindered organoborones. Chapter one investigates the synthesis of such compounds and discusses the formation of organoboranes in general. Chapter two discusses the chemistry of carbanions, especially those stabilized by an adjacent boron atom. The results of a study of the lithiation of ditripylboranes are reported. It is shown that the compounds are readily lithiated by unhindered bases. Chapters three, four and five report some of the reactions of the carbanions prepared in chapter two. Included are alkylation and acylation reactions, and also the reaction with halogenometal derivatives. Chapter six contains a brief dicusssion of the chemistry of allylboranes, including that of ditripylallyborane. Chapter seven reports the use of ditripylborane (a borane which is uniquely monomeric in the solid state) in the hydroboration reaction. Its properties are compared to those of other common diorganylboranes. Chapter eight charts the formation of ditripylalkylhydroborates, a novel class of highly hindred reducing agents, which display good diasteroselectivity in the reduction of methylcyclohexanones. Chapter nine discusses the hindered rotation present in some ditripylboranes. Section A of the thesis contains the results of a study on the diastereoselectivity of the condensation of aldehydes with allenyldiorganylboranes. In general the results obtained were disappointing since only low levels of stereoselectivity were obtained.

Estilos ABNT, Harvard, Vancouver, APA, etc.

32

Meade, Susie J. "Primary Metabolic Chemistry". Thesis, University of Canterbury. Chemistry, 1999. http://hdl.handle.net/10092/5794.

Texto completo da fonte

Resumo:

Thioesters and acyl phosphates are important metabolites throughout the biosphere. This may imply that they were involved in prebiotic chemistry. The study of the reactivity of thioesters and acyl phosphates may therefore provide some insights into the possible roles for these molecules in prebiotic chemistry. The work described in this thesis demonstrates that acetyl phosphate and inorganic phosphate react to form pyrophosphate in the presence of salts of some divalent metals. Divalent metal ions and nitrogen containing compounds act in synergy to promote pyrophosphate formation in some cases. Ferrous salts were much more efficient at promoting the formation of pyrophosphate than similar reactions containing magnesium ions, Addition of pyridine, or a variety of other nitrogen containing compounds, did not enhance the pyrophosphate yield. The promotion of pyrophosphate formation at near neutral pH by ubiquitous metal salts is considered to be a feasible route for prebiotic production of pyrophosphate. One chemoautotrophic origin of life theory concentrates on the oxidative formation of pyrite (FeS2) from ferrous sulfide and hydrogen as a possible source of prebiotic reductive power. N-Phenyl acetamide can be prepared from mercaptoacetic acid and aniline in water using FeS/H2S as a reagent system. We have established that one possible intermediate, N-phenyl mercaptoacetamide does react to give the product, and that this reaction is fast. Ferrous ions were observed to promote the formation of N-acetyl alanine from alanine and thioacetic acid. Zinc and cadmium ions on the other hand, promote the hydrolysis of thioacetic acid to acetic acid in preference to the N-acylation reaction. Both ferrous ions and ferro cyanide ions were observed to promote the peptide bond formation between protected amino acid derivatives. The results described in this thesis are consistent with the proposal that iron chemistry may have been important in prebiotic chemistry.

Estilos ABNT, Harvard, Vancouver, APA, etc.

33

Wheildon, Andrew R. "Novel nitrogen chemistry". Thesis, University of Nottingham, 1999. http://eprints.nottingham.ac.uk/13326/.

Texto completo da fonte

Resumo:

Chapter One contains a brief overview of zeolites, their structure, uses and synthesis. Chapter Two relates to the attempted synthesis of quinuclidines via a novel 6-endo-trig radical cyclisation. Chapter Three contains a review of the 'Zip reaction' and the attempted synthesis of triazacyclopentadecane derivatives. Chapter Four relates to the synthesis of pyrrolidines via retro-Cope cyclisation methodology. Reviews of the Cope and retro-Cope reactions, nitrone synthesis and nucleophilic addition of carbon nucleophiles to nitrones are included. The synthetic work is split into three sections relating to the electron withdrawing group used to stabilise the carbanion of the nucleophile - ester, sulphone and sulphoxide - and attempts to indicate the utility of the retro-Cope reaction in the diastereoselective synthesis of substituted pyrrolidines.

Estilos ABNT, Harvard, Vancouver, APA, etc.

34

Bates, Richard Simon. "Arene ruthenium chemistry". Thesis, University of Nottingham, 1990. http://eprints.nottingham.ac.uk/11890/.

Texto completo da fonte

Resumo:

This thesis describes the synthesis and reactivity studies of new arene-ruthenium(II) and arene-ruthenium(O) complexes. Ultrasound has been investigated as an alternative energy source, with the overall aim of synthesising arene ruthenium clusters. Chapter 1 gives an introduction and summary of the known arene ruthenium chemistry reported to date. Chapter 2 reports the synthesis of (CGH6)Ru(C2H4)2 and (MeC6H4CHMe2)Ru(C2H4)2. Low temperature protonation studies generated (C6H6)Ru(H)(CZH4)2' and (MeC6H4CHMe2)Ru(H)(C2H4)7ý. These are observed by 1H nmr spectroscopy to undergo two dynamic processes, rotation of the ethylene ligands and an exchange between the hydride and the hydrogens of the ethylenes. On protonation with trifluoroacetic acid (C6H6)Ru(02CCF3)2 has been shown to be the final product. Nucleophilic substitution investigations of the bis(ethylene) complexes has determined that the arene is more labile than the coordinated ethylene. Chapter 3 reports the generation of a reactive intermediate, [(MeC6H4CHMez)Ru(THF)2]", and the reactions it undergoes. The synthesis and stereochemistry of the new complexes [(MeC6H4CHMe2)RuBr(C3H5)] and Ru(H)[(C6H40) (OPh)2][P(OPh)3]3 are reported. Chapter 4 describes the successful synthesis of the project goal, with the formation of the trimer [(MeC. H., CHMe2)3Ru3Se,_1` and the tetra nuclear species [(MeC6H4CHMe2)4Ru4H4]2'. Electrochemistry shows both complexes undergo two, one-electron reversible reductions to generate their neutral analogues. Ru3(CO)12 was formed when arene ruthenium carbonyl clusters were sought. Chapter 5 reports the formation and reactivity of arene ruthenium complexes containing nitrogen based ligands. The half sandwich complexes, (arene)RuCl2(NH2R) (arene = C6H6, R= Et, CMe, C6H4Me; McC6H4CHMe2, R=CMe3) and (C. H6)RuCl(NHZCGH4Me)Z' have been synthesised in good yield. However, these complexes are not synthetically useful as substrates for cluster synthesis, although (C6H6)RuC12(NH2CMe3) can be converted to the mixed ethoxide-halide dimer, [(C6H6)Ru(OEt)]2Cl`. Me3SiN3 on reaction with [(MeC6H4CHMe2)RuC12]2 affords [(MeC6H4CHMe2)RuCl(N3)]Z. An X-ray crystal structure determination of this complex showed the nitrogens bridging the two ruthenium atoms are pyramidal rather than the expected planar in geometry. [(MeC6H4CHMe2)RuCl(N3)]2 undergoes chloride loss to form the triply bridged dimer, [(MeCGH4CHMe2)RuCl(N3)z]', and bridge cleavage to form [(MeC, H4CHMe2)RuCl(N3)PPh3]. The latter complex is believed to undergo disproportionation in solution. Conclusions and future directions of the project are discussed in chapter. 6. The appendix provides a discussion of ultrasound proposed structure.

Estilos ABNT, Harvard, Vancouver, APA, etc.

35

Brown, Stephen L. "Mechanistic organometallic chemistry". Thesis, University of Oxford, 1986. http://ora.ox.ac.uk/objects/uuid:96218480-9b1d-4d53-9d1d-033e2b451818.

Texto completo da fonte

Resumo:

A number of organometallic transformations related to proposed elementary steps in the reductive polymerization of carbon monoxide are discussed. The use of isonitrile as model ligands for carbon monoxide, with which they are isoelectronic, is proposed. Investigations show that alkyl migration to isonitrile is preferred over migration to carbon monoxide. Iminoformyl products due to hydride migration to isonitrile are not, however, observed. Syntheses of a range of cationic complexes of the type [ (η⁵-C₅H₅)M(L)₂(CNR)]⁺, [(η⁵-C₉H₇)Ru(L)₂(CNR)]⁺ and [(η⁵-C₉H₇)M(L)₂(CO)]⁺ (M = Fe, Ru; L = CO, phosphine) are described. In two cases, addition of hydride to the isonitrile cations is followed by protonation on work-up to give aminocarbene complexes. These are inert to further reduction under the conditions employed. The majority of isonitrile cations lose the isonitrile ligand to give good yields of metal hydride complexes. A mechanism involving ring-slippage of the hydrocarbon ligand is implicated. Hydride addition to η⁵-C₉H₇ complexes results, in the majority of cases, in loss of the hydrocarbon ligand from the complex and recovery of indane. Evidence for the intermediacy of metal formyl complexes in a number of hydride donation reactions is presented. These formyl complexes are formed from carbonyl hydride complexes either under moderate CO pressure or in THF solution. Hydride complexes lacking a carbonyl ligand are found to be inert. Finally, two reactions, one involving an alkyl migration reaction catalyzed by silver(I) salts, and the other involving the reduction of a metal acyl ligand to metal alkyl, are combined to demonstrate a model for carbon chain growth at a metal centre. The synthesis of an iron pentanoyl complex, followed by a decomplexation reaction, gives pentanoic acid in which all the catbon atoms are potentially directly derived from carbon monoxide. This is the first synthesis of a single homologous acid from carbon monoxide.

Estilos ABNT, Harvard, Vancouver, APA, etc.

36

Helmer, Magdalena. "Meteoric metal chemistry". Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318079.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

37

Thornton, Steven Rupert. "Novel nitrone chemistry". Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335298.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

38

Bristow, N. "Infrared laser chemistry". Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353552.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

39

Smith, Paul David. "Arene-ruthenium chemistry". Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357040.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

40

Rodriguez-Cruz, N. M. "Chemistry of coal". Thesis, University of Newcastle Upon Tyne, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372569.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

41

Bancroft, Matthew N. "Molybdenum-sulfur chemistry". Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301264.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

42

Stone, Jon C. "Allenylidene diruthenium chemistry". Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341487.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

43

English, Russell Fowke. "New dithiazole chemistry". Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47424.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

44

Wells, C. H. J. "Studies in chemistry". Thesis, University of Edinburgh, 1989. http://hdl.handle.net/1842/11536.

Texto completo da fonte

Resumo:

Studies have been carried out in the following areas: (1) Photochemistry The photochemical behaviour of selected aromatic carbonyl compounds has been studied, especially in relation to the nature of the excited state involved in chemical reaction. The photochemistry of certain pyrimidine-based agrochemicals and related compounds has been investigated from a kinetic and product viewpoint. The dye sensitised photooxidation of these compounds has also been studied. (2) Spectroscopy and Charge-Transfer Complexation The spectroscopic properties and electron acceptor ability of a variety of organic compounds has been reported upon. (3) Chemistry of Polynitroaromatic Compounds The synthesis of a number of new polynitronaphthalenes and polynitro-acenaphthenes has been achieved, and the properties of many of these compounds has been studied by nmr, esr, electronic spectroscopy and by mass spectrometry. The reaction of base with such compounds has also been investigated. (4) Education Articles have been published in educational journals on molecular complexes, colour, solar energy and spectroscopy. Textbooks on molecular spectroscopy and photochemistry have been published.

Estilos ABNT, Harvard, Vancouver, APA, etc.

45

Marillo, Sialer Estephany. "Chemistry with lasers". Revista de Química, 2017. http://repositorio.pucp.edu.pe/index/handle/123456789/123958.

Texto completo da fonte

Resumo:

El número de aplicaciones de la energía laser en el campo científico crece día a día. Estas no solo se han extendido en los campos de química, física y ciencia de materiales, sino también en biología y medicina. Este artículo es una breve introducción a los principios fundamentales del funcionamiento del láser, así como a su aplicación en el campo de la química.
The number of applications of lasers in science is constantly growing, with applications stretching from chemistry, physics and materials science to biology and medicine. This article provides a short overview of the fundamentals of lasers and an introduction to the application of lasers and laser ablation in chemistry.

Estilos ABNT, Harvard, Vancouver, APA, etc.

46

Lastovetska, Ludmila. "Chemistry of emotions". Thesis, Київський національний університет технологій та дизайну, 2019. https://er.knutd.edu.ua/handle/123456789/13080.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

47

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

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

48

Inokuma, Yasuhide. "Chemistry of Subporphyrin". 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124434.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

49

Garcia, Carmen Alicia. "Tracking Chemistry Self-Efficacy and Achievement in a Preparatory Chemistry Course". Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1638.

Texto completo da fonte

Resumo:

Self-efficacy is a person's own perception about performing a task with a certain level of proficiency (Bandura, 1986). An important affective aspect of learning chemistry is chemistry self-efficacy (CSE). Several researchers have found chemistry self-efficacy to be a fair predictor of achievement in chemistry. This study was done in a college preparatory chemistry class for science majors exploring chemistry self-efficacy and its change as it relates to achievement. A subscale of CAEQ, Chemistry Attitudes and Experiences Questionnaire (developed by Dalgety et al, 2003) as well as student interviews were used to determine student chemistry self-efficacy as it changed during the course. The questionnaire was given to the students five times during the semester: in the first class and the class before each the four tests taken through the semester. Twenty-six students, both men and women, of the four major races/ethnicities were interviewed three times during the semester and events that triggered changes in CSE were followed through the interviews. HLM (hierarchical linear modeling) was used to model the results of the CSE surveys. Among the findings, women who started at significantly lower CSE than men accomplished a significant gain by the end of the semester. Blacks' CSE trends through the semester were found to be significantly different from the rest of the ethnicities.

Estilos ABNT, Harvard, Vancouver, APA, etc.

50

Brent, Bill M. "The achievements of Chemistry in the Community students compared to traditional chemistry students in an introductory university chemistry course /". free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9901220.

Texto completo da fonte

Estilos ABNT, Harvard, Vancouver, APA, etc.

Teses / dissertações sobre o tema "Chemistry"

Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos