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1
Karunaratne, Veranja. "Donor-Acceptor reagents derived from 4-chloro-2-trimethylstannyl-1-butene, application to the total syntheses of (±)-\delta]9(12)-capnellene and (±)-pentalenene." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25810.
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This thesis describes the preparation of 4-chloro-2-trimethyl-stannyl-1-butene (8̲4̲) and its conversion into a number of structurally interesting and synthetically useful donor-acceptor reagents. Thus, transmetalation of (8̲4̲) with methyllithium produced 4-chloro-2-lithio-1-butene (9̲5̲), which reacted smoothly at -78°C in tetrahydrofuran with aldehydes, ketones and α,β-unsaturated N,N',N'-trimethylcarboxhydrazides to provide the addition products (1̲0̲8̲)-(̲1̲1̲3̲) and (̲1̲2̲8̲)-(̲1̲3̲0̲). When the reaction mixtures were treated with hexamethylphosphoramide and were then allowed to warm to room temperature, the 3-methylenetetrahydro-furan derivatives (̲1̲1̲4̲)-(̲1̲1̲9̲) and the 3-methylenecyclopentanecarboxylic acid derivatives (̲1̲3̲1̲)-(̲1̲3̲3̲) were produced in good yields.
Treatment of reagent (̲9̲5̲) with 1 equiv of phenylthiocopper or cuprous cyanide provided solutions of the corresponding cuprate reagents (̲1̲7̲9̲) and (̲1̲8̲0̲). Conjugate addition of the latter species to the cyclic enones (̲1̲8̲1̲)-(̲1̲8̲6̲) afforded very good yields of the ketones (̲1̲8̲7̲)-(̲1̲9̲2̲), which, when treated with potassium hydride in tetrahydrofuran, provided the methylenecyclopentane annulation products (̲1̲̲9̲3̲)-(̲1̲9̲8̲), respectively.
This methylenecyclopentane annulation method served as a key
process in the total synthesis of two structurally interesting triquinane
sesquiterpenoids, (±)-Δ⁹⁽¹²⁾ -capnellene (̲2̲0̲5̲) and (±)-pentalenene (̲2̲5̲1̲). Thus, copper bromide - dimethylsulfide catalyzed addition of the Grignard reagent (̲2̲3̲3̲) to 2-methyl-2-cyclopenten-1-one (̲1̲8̲4̲), followed by intramolecular
alkylation of the resultant chloro ketone (̲1̲9̲0̲), gave the annulation product (̲1̲9̲6̲). This material was converted into the enone (̲2̲3̲1̲) , which was subjected to an annulation sequence identical with
that used in the conversion of (̲1̲8̲4̲) into (̲1̲9̲6̲). Removal of the
carbonyl group from the resultant product (̲2̲3̲2̲) provided (±)-Δ⁹⁽¹²⁾ capnellene (̲2̲0̲5̲).
Transformation of the readily available keto acetal (̲2̲8̲̲7̲) into the enone (̲2̲8̲4̲), followed by subjection of the latter substance to the methylenecyclopentane annulation sequence, gave the tetracyclic keto olefin (̲2̲8̲5̲). Treatment of an acetic acid solution of this material with hydrogen in the presence of platinum metal produced a mixture of the epimeric ketones (2̲9̲8̲) and (2̲9̲9̲), which was converted into a mixture of (±)-pentalenene (2̲5̲1̲) and (±)-9-e̲p̲i̲-pentalenene (2̲6̲9̲), respectively. [Formula Omitted]Science, Faculty of
Chemistry, Department of
Graduate
2
Holt, Jay. "1,8-Diarylanthracenes as reagents for asymmetric synthesis." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/29902.
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3
Wang, Lanquing. "Characterization of selenide drugs and their metabolites by hydride generation ICP-MS and HPLC/ICP-MS." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/28041.
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4
Adeosun, Adetenu Adebisi. "Novel alkylidenation, epimetallation and hydrometallation reactions of group 4 metal alkyls." Diss., Online access via UMI:, 2004. http://wwwlib.umi.com/dissertations/fullcit/3150494.
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5
Bodzay, Steve J. "Organotin reagents toward the preparation of cyclic disulfides and related compounds." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72827.
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6
Nielsen, Randall Gunnar. "Preparation and characterization of immunological reagents for analytical applications." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184395.
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Immunochemical reagents were characterized under carefully controlled laboratory conditions using conventional high performance liquid chromatography instrumentation. The stationary phase was prepared by attaching antigen molecules to an insoluble support through a covalent linkage. Experiments were carried out by introducing antibody molecules into the mobile phase and monitoring their interaction with the stationary phase. Monoclonal antibodies were employed because of their more homogeneous properties compared to polyclonal antisera. Radioisotopes were employed to study low level adsorption on the stationary phase. Recovery experiments were carried out in which it was possible to account for all of the material introduced into the mobile phase. Antibodies were purified over a preparative scale antigen affinity column following labeling to insure high immunoreactivity. Studied under normally dissociating conditions, irreversible adsorption of picomole amounts of protein on the antigen stationary phase was greater than on other ligand modified stationary phases. This accumulation decreased with repeated use of the affinity column. The present study provides a framework for evaluation of other immunoaffinity systems and demonstrates that reproducible recovery of immunologically active material in high yield is possible. Monoclonal antibodies labeled with fluorescein were different from unlabeled molecules in binding and physical characteristics. Computer simulations were used to describe binding behavior. Although fluorescein labels improve detection sensitivity over native protein absorbance, their use in this case decreased binding affinity significantly. Heterogeneity of affinity purified fluorescein labeled and unlabeled monoclonal antibodies was examined with two dimensional gel electrophoresis. In addition to increased charge heterogeneity in the labeled antibody fragments, both light and heavy chains possessed more negative character. These results agree with each other. Fluorescein contains a carboxylic acid group, and modification of antibody light chains may interfere with binding affinity. The number and location of labels covalently attached to antibodies must be carefully controlled to obtain maximum detection sensitivity and preserve immunoreactivity.
7
Fu, Yunyi Michael. "Development of a polymer-supported reagent for Trost-Lu isomerization reactions and reagents for Mitsunobu reactions." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B39793989.
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8
Fu, Yunyi Michael, and 付運毅. "Development of a polymer-supported reagent for Trost-Lu isomerization reactions and reagents for Mitsunobu reactions." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B39793989.
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9
Terhune, Tammy Lee 1962. "Preparation of immunochemical reagents for a non-competitive assay for the detection of haptens." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276829.
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The strategy required for the development of the immunochemical reagents needed for a non-competitive assay for the detection of haptens was investigated. For this work, these reagents were termed "anti-complex" antibodies. To preserve the integrity of such an assay, these "anti-complex" antibodies should not react with either the free anti-hapten antibody or the free hapten and they should not compete with the hapten for binding to the anti-hapten antibody. Anti-hapten hybridomas were developed using standard hybridoma technology. The development of anti-complex hybridomas was investigated using standard hybridoma technology and the novel approach of intrasplenic immunization. Both immunization protocols addressed the three questions concerning the strategy for developing such hybridomas, namely the type of immunization (snygeneic or allogeneic), the physico-chemical nature of the hapten in the complex (free or conjugated) and the physico-chemical nature of the anti-hapten antibody in the complex (intact or fragmented). (Abstract shortened with permission of author.)
10
Lau, Kwok-kin. "The chemistry of lanthanide complexes with amide and carboxylate ligands /." View the Table of Contents & Abstract, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36584654.
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Lau, Kwok-kin, and 劉國健. "The chemistry of lanthanide complexes with amide and carboxylate ligands." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B45015491.
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12
Harden, John Michael. "Elucidation of key interactions between in situ chemical oxidation reagents and soil systems." Diss., Mississippi State : Mississippi State University, 2006. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
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13
Spratt, Michael Phillip. "Solution and solid state NMR studies of fluorine tagging reagents." Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/49865.
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A series of studies are presented in which fluorine tagging reagents are used to analyze complex mixtures for compounds containing active hydrogen functional groups (e.g., hydroxyl, amine, thiol, and carboxylic groups). The existence of these derivatized functional groups is determined by utilizing a number of solution and solid-state nuclear magnetic resonance (NMR) techniques.
In solution NMR studies p-fluorobenzoyl chloride was the fluorine tagging reagent of choice because of a large ¹⁹F chemical shift range for the different derivatized substrates (~10 ppm) and generally good reaction yields. Various classes of sterol and amino acid p-fluorobenzoyl derivatives were characterized on the basis of their ¹⁹F NMR isotropic chemical shifts. The presence (or absence) of hydroxyl, amine, and carboxylic acid functional groups in coal extract and pyrolysis products was also determined.
The versatility of the p-fluorobenzoyl chloride as the fluorine tagging reagent in ¹⁹F NMR was enhanced by: a) enriching the carbonyl carbon of the acid chloride with labeled ¹³C isotope, thus synthesizing a dual ¹⁹F and ¹³C NMR sensitive reagent and b) using the reagent in conjunction with LC-NMR. The extension to either technique added another dimension to the NMR spectral data obtained from the p-fluorobenzoyl tagging reagent in solution NMR.
Finally, preliminary data is presented illustrating how fluorine tagging reagents may be used to study functional groups (and atoms present in the immediate proximity of the group) existing on solid material utilizing solid-state NMR. Functional groups on the solid material are tagged with a fluorinated reagent. The sample is then analyzed using solid-state NMR with cross-polarization (CP), magic angle spinning (MAS), and high-power proton decoupling. The ¹⁹F dipolar coupling interactions, created by the presence of the fluorine tag, attenuate signals for these nuclei in the immediate proximity of the tagged site. A series of 1-adamantanol, steroid, and silica gel fluorinated derivatives show that the effects of the ¹⁹F dipolar interactions were modulated by complex anisotropic molecular motions (i.e., solid system with little motion, exhibiting greater signal attenuations due to ¹⁹F dipolar coupling).Ph. D.
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14
Kan, Tze-wai Jovi. "Development of new polymer-supported reagents for organic synthesis, solvent effects in samarium promoted allylic alcohol cyclopropanation reactions and time resolved resonance studies of the photodeprotection of p-hydroxyphenacyl caged phototrigger compounds." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37925660.
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Shelton, Kathy Rhea. "Kinetics of 3,5-diacetyl-1,4-dihydrolutidine in formaldehyde detection." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54420.
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Formaldehyde, a hazardous and toxic substance, can be found in most resin treated durable press fabrics. The current formaldehyde regulations are limited to worker exposure in an industrial setting and the possibility of government regulation of formaldehyde release from textiles is of concern to the textile industry. The most common test of formaldehyde release used by the U.S. textile industry is the AATCC Test Method 112, a colorimetric determination based on the Hantzsh reaction between ammonia, formaldehyde, and acetylacetone. The chromophore formed is 3,5-diacetyl-1,4-dihydrolutidine (DDL). In the AATCC test the ammonia and acetylacetone are in the Nash reagent and the formaldehyde is extracted from the fabric by trapped steam. The formaldehyde in solution and the Nash reagent are mixed and the color developed.
The purpose of this study was to determine if a more effective formulation of the Nash reagent than currently used by industry can be produced. The reaction between the Nash reagent and formaldehyde is first order in formaldehyde, therefore pseudo-first order kinetics was used as the basis of the study. Reagent effectiveness was determined by comparisons and calculations based on the molar extinction coefficient, maximum absorbance, and rate constant. The study was set up in phases to investigate the effect of different ammonia sources, the effects of varying concentrations of the reactant components, the effect of ageing, and the effect of different temperatures on the formation of DDL. In the final phase the best reformulated reagent was compared to the Nash reagent under the conditions of the AATCC Test Method 112.
Several reformulations were found to be comparable to Nash, but none was found to be more effective in formaldehyde detection. This study has shown some of the complexities of the reaction and that the Nash reagent is not able to obtain 100% conversion of formaldehyde to DDL. Therefore, any test that uses the Nash reagent is underestimating the releasable formaldehyde concentration in the fabric.Ph. D.
16
Lau, Chi-yin. "Reductive aldol cyclizations using Stryker's reagent and polystyrene-supported triphenylarsine in carbon-carbon bond forming reactions." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B39634450.
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Lau, Chi-yin, and 劉志賢. "Reductive aldol cyclizations using Stryker's reagent and polystyrene-supported triphenylarsine in carbon-carbon bond forming reactions." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39634450.
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Kan, Tze-wai Jovi, and 簡紫慧. "Development of new polymer-supported reagents for organic synthesis, solvent effects in samarium promoted allylic alcohol cyclopropanationreactions and time resolved resonance studies of the photodeprotectionof p-hydroxyphenacyl caged phototrigger compounds." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37925660.
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Kirchhoefer, Patrick L. "A bridgehead organolithium reagent, the Retro-Nazarov reaction, and 4+3 cycloadditions with a nicotinic acid derivative /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p3164519.
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Shi, Yunqing Nancy. "¹H NMR and HPLC studies of tetraarylporphyrin atropisomers." Scholarly Commons, 1993. https://scholarlycommons.pacific.edu/uop_etds/2250.
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This thesis includes NMR studies of free base meso-tetra(otolyl) porphyrin (TTP) and meso -tetraphenylporphyrin (TPP) and their dications protonated by trifluoroacetic acid (TFA). The chemical shift changes of the -NH resonance are very unusual and have never been reported. At the beginning of the titration, the N-H resonances broaden considerably but do not shift; when the ratio of [TFA]/[TTP] or [TFA]/[TPPf are over 2, the N-H resonances shift markedly to lower field by as much as 1.6 ppm. At acid levels well above the equivalence point, the NH resonances moves back to higher field. Moreover upon protonation the NH line of TTP becomes a complex multiplet which changes as a function of [TFA]/[TTP]. The NH line of TPP remains a singlet at all acid levels.
We also report here a way of isolating atropisomers of mesotetra( o -tolyl)porphyrin through HPLC by using an analytical C-18 bond pack reverse phase column eluted by a 1 %THF + 99%Me0H solvent combination. A preliminary study by HPLC was also carried out on ZnTTP(II) with aliquots of 2,6-dimethylpyridine, and the retention time of the separation decreased markedly, but this study needs to be repeated and improved.
TTP and TPP dications at two different acid levels were studied by VT-NMR, and the downfield shift of -NH resonance of TTP dications was more pronounced at higher temperatures than those of TPP dications.
21
Brumbaugh, William G. "Development of an integrative sampler for bioavailable metals in water /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9842510.
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Learmonth, Robin Alec. "Studies in asymmetric synthesis." Thesis, Rhodes University, 1991. http://hdl.handle.net/10962/d1005018.
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The concept of combining two well established areas of organic chemistry, viz., organosilicon chemistry and the use of chiral auxiliaries, into a viable, alternative method of asymmetric synthesis has only very recently begun to receive attention. At the outset of this investigation, no asymmetric reactions of silyl enol ethers, chiral by virtue of optically active substituents on the silicon, had been reported. A range of novel chiral silyl enol ethers have thus been prepared from a variety of ketones, including pinacolone, cyclohexanone, and α-tetralone, and employing menthol, borneol, and cholesterol as chiral auxiliaries. These preparations have been achieved via several distinct routes, including a novel convergent approach involving the isolation of either the chloro(menthyloxy)dimethylsilane or the (bornyloxy)chlorodimethylsilane. The MS and NMR spectra of these silyl enol ethers were examined in detail and, in the case of the crystalline cholesteryloxy silyl enol ether, the X-ray structure has been determined. The potential of chloroalkoxysilanes to act as general, chiral derivatizing agents has been established by the preparation of diastereomeric silyl acetal mixtures of racemic secondary alcohols (e.g. I-phenylethanol and 2-octanol). The experimental diastereomeric ratios, obtained by GLC and ¹H NMR spectroscopy, approached the expected value of unity, confirming the potential of the alkoxychlorosilanes as chiral probes. The chiral silyl enol ethers have been successfully oxidized to the corresponding α-siloxy ketones employing MCPBA, MMPP, and 2-(phenylsulphonyl)-3-phenyloxaziridine as oxidizing agents and the diastereomeric excesses obtained, which varied from 0 to 16%, indicated some potential for stereochemical control. Alkylation and hydroxyalkylation reactions of the silyl enol ethers have yielded the expected α-iert-butyl and β-hydroxy ketones in good to excellent material yields, with the enantiomeric excesses, as determined by chiral shift reagent studies, reaching 14%. To improve the stereo control in these reactions, attempts have been made to prepare chiral silyl enol ethers with auxiliaries possessing the potential for transition state complex co-ordination in the reactions under consideration. The preparation of such silyl enol ethers, incorporating the proline-derived auxiliaries, N-methyl-2-hydroxymethylpyrrolidine and 2-methoxymethylpyrrolidine met with only limited success. In an alternative approach, three derivatives of 2,3-dihydroxybornane have been prepared. However, two of these auxiliaries, viz., 3-exo-benzyloxy-2-exo-hydroxybornane and 3-exo-(1-methoxyethoxy)-2-exo-hydroxybornane failed to form silyl enol ethers, even under considerably more vigorous conditions than normally employed. The third derivative, 3,3-ethylenedioxy-2-hydroxybornane has been successfully utilized in the preparation of a pinacolone-derived chiral silyl enol ether. Hydroxyalkylation of this compound with benzaldehyde has yielded the β-hydroxyketone with significantly improved enantiomeric excess (26%) and a transition state complex has been proposed to rationalize this improvement.
23
Aluoch, Austin Ochieng. "Metal enhanced detection of salivary proteins, Bacillus globigii and novel reagents for bioimaging & sensing." Diss., Online access via UMI:, 2007.
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Silva, Aline Santana da [UNESP]. "Desenvolvimento de métodos quantitativos e de sistemas de screening para a determinação de glifosato." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/105723.
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silva_as_dr_araiq.pdf: 2860868 bytes, checksum: 0a5366c12c615d912dea72ff05ef8e46 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O produto comercial Roundup®, contendo o glifosato como principal ingrediente ativo, é vendido mundialmente por ser um herbicida sistêmico, pós-emergente e não seletivo. Além disso, a alta eficiência no processo de remoção de plantas indesejadas e o aumento de culturas transgênicas favorecem seu uso extensivo. Embora não seja considerado um sério contaminante para o homem, o controle e monitoramento destes herbicidas são muito importantes. Desta forma, o presente projeto propõe o desenvolvimento de sistemas de screening e métodos analíticos limpos que possam ser aplicados à determinação de glifosato, uma vez que a literatura dispõe de poucos métodos de análise que visam à aplicação dos princípios da Química Verde. Os métodos propostos neste estudo foram espectroscopia de reflectância difusa, espectrofotometria e sistemas em fluxo, empregando análise por injeção em fluxo (FIA) e multi-bombas (MPFS), com detecção na região do UV-Vis. Os métodos de análise propostos são baseados na reação entre glifosato e p-dimetilaminocinamaldeído (p- DAC), em meio acidificado, com um máximo de reflecção ou absorção em 495 nm. Após a otimização das condições experimentais e validação dos métodos propostos, através de parâmetros como linearidade da curva analítica, exatidão, precisão, limite de detecção, limite de quantificação, recuperação e estudos de possíveis íons interferentes, estes foram aplicados em amostras de herbicidas comerciais e águas (naturais e de consumo humano). Os resultados obtidos na determinação de glifosato nas amostras de herbicidas comerciais empregando reflectância difusa concordaram com os resultados obtidos empregando análise por injeção em fluxo, os quais apresentaram teores de 378,8 g L-1 para a amostra A, 392,4 g L-1 para a amostra...
The commercial product Roundup®, containing the glyphosate as its main active ingredient, is marketed worldwide because it is a nonsystemic, post-emergent and nonselective herbicide. Moreover, the high efficiency in the process of the removal of unwanted plants and the increase in the introduction transgenic plants favor their extensive use. Although it has not been considered a serious contaminant to humans the control and monitoring of this herbicide are very importants. The present project proposes the development of screening systems and clear analytical methods that can be applied to determine the presence of glyphosate, since in the literature there are few methods of analysis that apply Green Chemistry’s principles. The proposed methods in this study were diffuse reflectance spectroscopy, spectrophotometry and flow systems, employing flow injection analysis (FIA) and multi-pumping (MPFS), with detection in the Uv-vis region. The proposed analysis methods are based in the reaction between glyphosate and p-dimethylaminocinnamaldehyde (p-DAC), in acid medium, it presents a reflection or absorption maximum in 495 nm. After the optimization of the experimental conditions and validation of the proposed methods, through parameters such as: linearity of the analytical curve, accuracy, precision, limit of detection, limit of quantification, recovery and study of possible interference ions, these were applied to commercial herbicides and water samples (naturals and for human consumption). The results obtained in the determination of glyphosate in the commercial herbicides employing diffuse reflectance were agree with the results obtained by employing flow injection analysis, which presented levels of 378.8 g L-1 to the A sample, 392.4 g L-1 to the B sample and 330.6 g L-1 to the C sample... (Complete abstract click electronic access below)
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Silva, Aline Santana da. "Desenvolvimento de métodos quantitativos e de sistemas de screening para a determinação de glifosato /." Araraquara : [s.n.], 2012. http://hdl.handle.net/11449/105723.
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Resumo: O produto comercial Roundup®, contendo o glifosato como principal ingrediente ativo, é vendido mundialmente por ser um herbicida sistêmico, pós-emergente e não seletivo. Além disso, a alta eficiência no processo de remoção de plantas indesejadas e o aumento de culturas transgênicas favorecem seu uso extensivo. Embora não seja considerado um sério contaminante para o homem, o controle e monitoramento destes herbicidas são muito importantes. Desta forma, o presente projeto propõe o desenvolvimento de sistemas de screening e métodos analíticos limpos que possam ser aplicados à determinação de glifosato, uma vez que a literatura dispõe de poucos métodos de análise que visam à aplicação dos princípios da Química Verde. Os métodos propostos neste estudo foram espectroscopia de reflectância difusa, espectrofotometria e sistemas em fluxo, empregando análise por injeção em fluxo (FIA) e multi-bombas (MPFS), com detecção na região do UV-Vis. Os métodos de análise propostos são baseados na reação entre glifosato e p-dimetilaminocinamaldeído (p- DAC), em meio acidificado, com um máximo de reflecção ou absorção em 495 nm. Após a otimização das condições experimentais e validação dos métodos propostos, através de parâmetros como linearidade da curva analítica, exatidão, precisão, limite de detecção, limite de quantificação, recuperação e estudos de possíveis íons interferentes, estes foram aplicados em amostras de herbicidas comerciais e águas (naturais e de consumo humano). Os resultados obtidos na determinação de glifosato nas amostras de herbicidas comerciais empregando reflectância difusa concordaram com os resultados obtidos empregando análise por injeção em fluxo, os quais apresentaram teores de 378,8 g L-1 para a amostra A, 392,4 g L-1 para a amostra... (Resumo completo, clicar acesso eletrônico abaixo)Abstract: The commercial product Roundup®, containing the glyphosate as its main active ingredient, is marketed worldwide because it is a nonsystemic, post-emergent and nonselective herbicide. Moreover, the high efficiency in the process of the removal of unwanted plants and the increase in the introduction transgenic plants favor their extensive use. Although it has not been considered a serious contaminant to humans the control and monitoring of this herbicide are very importants. The present project proposes the development of screening systems and clear analytical methods that can be applied to determine the presence of glyphosate, since in the literature there are few methods of analysis that apply Green Chemistry's principles. The proposed methods in this study were diffuse reflectance spectroscopy, spectrophotometry and flow systems, employing flow injection analysis (FIA) and multi-pumping (MPFS), with detection in the Uv-vis region. The proposed analysis methods are based in the reaction between glyphosate and p-dimethylaminocinnamaldehyde (p-DAC), in acid medium, it presents a reflection or absorption maximum in 495 nm. After the optimization of the experimental conditions and validation of the proposed methods, through parameters such as: linearity of the analytical curve, accuracy, precision, limit of detection, limit of quantification, recovery and study of possible interference ions, these were applied to commercial herbicides and water samples (naturals and for human consumption). The results obtained in the determination of glyphosate in the commercial herbicides employing diffuse reflectance were agree with the results obtained by employing flow injection analysis, which presented levels of 378.8 g L-1 to the A sample, 392.4 g L-1 to the B sample and 330.6 g L-1 to the C sample... (Complete abstract click electronic access below)
Orientador: Helena Redigolo Pezza
Coorientador: Leonardo Pezza
Banca: Ademir dos Santos
Banca: Matthieu Tubino
Banca: Carlos Roberto Bellato
Banca: Graziella Ciaramella Moita
Doutor
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Goddard-Borger, Ethan D. "Some synthetic carbohydrate chemistry : natural product synthesis, rational inhibitor design and the development of a new reagent." University of Western Australia. School of Biomedical, Biomolecular and Chemical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2009.0043.
Full textAbstract:
Earnest carbohydrate research was initiated in the nineteenth century by several talented organic chemists. Carbohydrates, now known to play essential roles in a range of fundamental biological processes, are presently studied by a throng of scientists from many fields, including: biochemistry, molecular biology, immunology, structural biology, medicine, agriculture, pharmacology and, of course, chemistry. Organic chemistry remains as relevant to carbohydrate research as it has ever been; its practitioners, with their skills in synthesis and fundamental understanding of molecules, are truly indispensable. This thesis details various synthetic endeavours within the field of carbohydrate chemistry. It describes four projects with goals as diverse as natural product synthesis, rational inhibitor design and the development of new reagents in organic synthesis. The first chapter provides an account of the synthesis of compound 1, a potent germination stimulant present in smoke, from D-xylose. Many analogues of 1 were prepared from carbohydrates and evaluated as germination stimulants, which permitted the dissemination of several structure-activity relationships. Subsequent chapters describe the design and preparation of inhibitors for various carbohydrate-processing enzymes. Compounds 55 and 56 were sought after as putative synergistic inhibitors of a Vitis vinifera (grape) uridine diphospho-glucose:flavonoid 3-O-glucosyltransferase (VvGT1). It was hoped that crystallographic investigations of VvGT1-UDP-2/3 complexes by a collaborator, structural biologist Professor Gideon Davies, would aid in clarifying mechanistic aspects of this enzyme.Compounds 114, 115 and 118 were prepared as putative arabinanase inhibitors. Once again, this work was undertaken to assist in crystallographic studies that might provide a better understanding of how these enzymes operate. The thesis concludes by describing the development of compound 152.HCl, a novel reagent for the diazotransfer reaction. Previously, this reaction utilised trifluoromethanesulfonyl azide (TfN3), an expensive and explosive liquid with a poor shelf-life, to convert a primary amine directly into an azide. Reagent 152.HCl was developed to replace TfN3 in this useful synthetic transformation. A one-pot procedure enabled the simple and inexpensive preparation of 152.HCl, which was demonstrated to be shelf-stable, crystalline and, crucially, effective in the diazotransfer reaction.
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Zhang, Yang. "Mechanistic studies and synthetic applications of Ce (IV) reagents /." Diss., 2005. 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:3203831.
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Van, der Linde Gert Johannes. "Studie van die wisselwerking tussen reagense en minerale by die flottasie van apatiet." Thesis, 2015. http://hdl.handle.net/10210/14804.
Full textAbstract:
D.Sc. (Chemistry)The Phosphate Development Corporation (FOSKOR) recovers apatite from foscorite ore by a process of froth flotation. Four reagents are used viz. sodium hydroxide, water-glass, nonylphenol tetraglycol ether (EMU) and a fatty acid. The fatty acid is mainly composed of a mixture of oleic and linoleic acid in a ratio of 1,2:1. The aim of this study was to investigate the influence of the first three above-mentioned reagents on the adsorption of oleic, linoleic and linolenic acids on apatite and The Phosphate Development Corporation (FOSKOR) recovers apatite from foscorite ore by a process of froth flotation ...
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Shen, Yang. "Chemical Fate Studies of Mining Reagents: Understanding the Decomposition Behavior under Various Conditions." Thesis, 2016. https://doi.org/10.7916/D8WS8T57.
Full textAbstract:
The decomposition behavior of several mining reagents (i.e., xanthate, dithiocarbamate, dithiophosphate and dithiophosphinate) used widely in mineral processing operations was studied. Decomposition has been reported to generate toxic compounds such as CS₂ (carbon disulfide) and COS (carbonyl sulfide), causing severe concerns to SHE (safety, health and environment). With the global trend of becoming sustainable/green and the increasingly strict regulations, the mining industry is facing an unprecedented pressure to handle the problematic reagents that can lead to the adverse impacts. Unfortunately, the interests of the prior research are biased on the performance of the reagents to optimize the efficiency and lower the cost, while the examination of the decomposition behavior is almost neglected. Under the circumstance of poor endeavor found in the prior investigations, the knowledge gap awaits to be filled in a systematic and integrated manner to recommend countermeasures for those problematic reagents.
It can be seen from those fragmented studies collected from literature that only a limited understanding of thermal or aqueous decomposition behavior is achieved. It is far from sufficient for industrial guidance of mitigation. One key reason is the lack of robust methods to investigate decomposition under various conditions that are interesting to the mining companies (e.g., the flotation conditions). Consequently, the method development has always been considered of the utmost importance upon the start of this work to align with our overall goal of understanding the decomposition behavior under the various conditions.
Three methods under a consistent strategy were designed to examine the decomposition under three conditions from Simple (in aqueous solutions alone), to Complex (in ore pulp under flotation conditions), to Specific (in solution containing metal ions). These three conditions were chosen based on the general interests from several prominent mining companies (Vale, Barrick, Freeport McMoRan and Newmont) to understand the decomposition mechanism and kinetics. The Simple is to serve as control for all other conditions. Besides, most of the prior studies in the literature are only conducted for the Simple condition. Therefore, the Simple is to resolve all discrepancies and conflicts, and provide a relatively comprehensive summary of the decomposition under the control condition. The Complex puts decomposition in a new environment that has never been explored before: the ore pulp under the simulated batch flotation conditions. Conclusions drawn from this part provide the most practical guidance for industrial mitigation. The Specific goes after the Complex to thoroughly understand the effect of a specific factor on decomposition. The decomposition responding to the variation of a certain factor is followed within a closed system with the compositional changes measured in all phases. The integrated analysis enables the correlation of the decomposition behavior to its original causes, which are the interactions of the reagent with other components in the system.
Through the systematic investigation of decomposition of various reagents under various conditions, it is concluded that decomposition depends heavily on those parallel or sequential interactions that occur along with the decomposition reaction. For example, the decomposition reaction of xanthate throughout our entire study is regarded as ROCS₂⁻→CS₂. When xanthate forms xanthic acid, monothiocarbanate or dixanthogen with the change of pH, its breakup into CS₂ is altered. When xanthate interacts with Cu²⁺ forming Cu₂X₂, decomposition is depressed, but with Fe³⁺ forming FeX₃ decomposition is promoted. The CS₂ generated from decomposition could interact with OH- to form CS₃²⁻ or dissolve in solution or adsorb on minerals, leading to the decrease of CS₂ detected. The bonding properties between the –CS₂ moiety and other atoms or radicals in the molecule affect the stability of the reagents and the subsequent decomposition. The necessity to include a list of the side-interactions as complete as possible is key to understand and predict the decomposition behavior.
With experimental efforts taken to develop methodologies to measure the decomposition under various conditions, the attempt to model the decomposition behavior is also initiated in this work. Based on the conclusions from experimental results, major components determining the output of the final decomposition products are identified. Unsurprisingly, the decomposition reaction together with its parallel and sequential interactions is critical. Simulation using Matlab to assess the decomposition of a simplified system containing SIBX and Cu²⁺ ions has achieved preliminary success by matching well with the experimental measurements. This establishes the groundwork for furthering the simulation of more complex systems and model development.
Reagents decompose differently, although they might be applied to function similarly during an operation. As flotation collectors used for sulfide ore beneficiation, dithiocarbamate and xanthate possess some similarities in the decomposition in terms of generating CS₂. Their decomposition also decreases with the chain length. On the other hand, the decomposition of dithiophosphate and dithiophosphinate are different as the breakup of the molecule is mainly at their alkyl chain to generate moieties such as olefins.
Compared to the studies carried out to understand the performance of the reagents when being used, research on decomposition requires more attention. Therefore, derivative work can be conducted based on results achieved in this work. For example, it is useful to further examine how reagents decompose after adsorbing on the mineral surfaces. It complements the knowledge to thoroughly understand decomposition at different spots within a complex system.
The chemical fate studies of mining reagents with respect to the understanding the decomposition open up the window of developing methodologies to examine adverse behaviors. The experimental setups are applicable to simulate various conditions under which the reagent is being used and generating the adverse impacts. The strategy of analyzing decomposition within a complex system as shown in this study also provides insight into systematically investigating the other types of adverse behaviors.
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"Spectrofluorimetric determination of aluminium in food and antacid drugs with 8-hydroxyquinoline as reagent." Chinese University of Hong Kong, 1993. http://library.cuhk.edu.hk/record=b5887797.
Full textAbstract:
by Kwong Tsz-kin.Thesis (M.Phil.)--Chinese University of Hong Kong, 1993.
Includes bibliographical references (leaves 90-96).
Chapter I. --- Abstract --- p.i
Chapter II. --- Acknowledgment --- p.ii
Chapter III. --- Table of contents --- p.iii
Chapter IV. --- List of Tables and Figures 、 --- p.iv
Chapter Chapter 1. --- Introduction --- p.1
Chapter 1.1. --- General introduction
Chapter 1.2. --- Review of analytical methods for aluminium analysis
Chapter 1.3. --- Spectrofluorimetric determination of aluminium
Chapter 1.4. --- Project aim
Chapter Chapter 2. --- Experimental --- p.14
Chapter 2.1. --- Apparatus
Chapter 2.2. --- Reagents & Material
Chapter 2.3. --- Procedure
Chapter 2.4. --- Treatment of data
Chapter Chapter 3. --- Results and discussion --- p.24
Chapter 3.1. --- Optimization of experimental conditions
Chapter 3.2. --- Analytical Parameters
Chapter 3.3. --- Analytical results
Chapter Chapter 4. --- Conclusion --- p.89
Chapter Chapter 5. --- References --- p.90
Appendix --- p.97
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Willemse, Johannes Alexander. "Carbon monoxide as reagent in the formylation of aromatic compounds." Thesis, 2008. http://hdl.handle.net/10210/433.
Full textAbstract:
Sasol endeavors to expand its current business through the beneficiation of commodity feedstreams having marginal value into high-value chemicals via cost-effective processes. In this regard Merisol, a division of Sasol has access to phenolic and cresylic feedstreams, which have the potential to be converted to fine chemicals. Targeted products include para-anisaldehyde, ortho- and para-hydroxybenzaldehyde which are important intermediates for the manufacture of chemicals used in the flavor and fragrance market and various other chemicals. The use of CO technology (HF/BF3) to produce these aldehydes in a two-step process from phenol as reagent is economically attractive due to the relative low cost and other benefits associated with syngas as reagent. The aim of the study was to evaluate and understand this relatively unexplored approach to the formylation of aromatic compounds. The reactivity of both phenol and anisole proved to be much lower than that of toluene. The main aldehyde isomer (para) produced in these HF/BF3/CO formylations as well as of other ortho-para directing mono-substituted benzenes tested in our laboratories were in accordance with published results. Efforts to increase substrate conversion resulted in substantial secondary product formation and mechanistic investigations showed this to be a consequence of the inherent high acidity of the reaction environment. The effect of different substituents on the relative formylation rates of benzene derivatives was investigated. These results showed that methyl groups are activating while halogens are deactivating relative to benzene as substrate. The decrease in reactivity from fluorobenzene> chlorobenzene> bromobenzene is in accordance with formylation trends observed in other acidic systems. Deuterium labeling experiments were applied to gain additional information on the formylation reaction mechanism. This study provided interesting but inconclusive results in support of the so-called intra-complex mechanism. All reported studies as well as our own work suggested that HF and BF3 in (at least) stoichiometric amounts are required for effective formylation with CO. Under these conditions this methodology for effecting aromatic formylation is not economically viable. Industrial application of formylation using CO will require the development of new catalysts or methodology to allow the use of HF/BF3 in a catalytic way. In this regard ionic liquids as a new and ecological-friendly field was explored. Chloro-aluminate ionic liquids promote the carbonylation of alkylated aromatic compounds, but fails in the case of oxygenated aromatics. Aldehyde yields of formylation in the acidified neutral ionic liquids were generally similar compared to reactions conducted in HF as solvent/catalyst. Formylation of anisole and toluene, but not of phenol in the neutral ionic liquids resulted in increased secondary product formation in comparison with hydrogen fluoride used as solvent/catalyst. This difference in behavior is not understood at present, but suggests that phenol is a good substrate for formylation in this medium, particularly with the development of a system catalytic with respect to HF/BF3 in mind.Prof. C.W. Holzapfel
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Elephant, Dimpho Elvis. "A comparative study of the BCR sequential and batch extractions for wastes and waste-amended soil." Thesis, 2010. http://hdl.handle.net/10413/7357.
Full textAbstract:
The use of standard soil tests to assess waste materials has become a common practice in waste management. However, the suitability of using standard soil tests on waste materials is questionable. Therefore, this investigation was undertaken to compare commonly used chemical extraction methods for their ability to extract elements from soil, waste, and soil-waste mixtures. This was carried out by:
· Assessing the effects of extraction time on the extractability of Al,Ca, Co, Cu, Fe, Mg, Mn, Ni, Pb, S, Si, and Zn;
· Assessing the comparability between single and sequential extraction.
Two manganese rich wastes namely electro-winning waste (EW) and silicate-rich smelter slag (SS) and an acid soil (Inanda, Ia) were used for this study. Waste amended soils were obtained by incubating the EW and SS with Ia soil at field capacity at a rate of 20 g kg-1 and 120 g kg-1 soil respectively, and were sampled at day 0, 7, 28, 56, and 140.
The effect of extraction time was assessed on the EW, SS, and Ia soil with carbonated water used in the acid rain test conducted at 16, 20, 30, and 50 hours. The equilibration time was different for different materials and elements. The concentration of Al and Zn did not change appreciably with increasing extraction time in the EW. Similar results were found for Mg, S, and Si in the SS and S in the Ia soil. This was attributed to ‘equilibrium’ being reached before 16 hours. The equilibration time of 20 hours which would release the exchangeable and specifically adsorbed elements was obtained for Co, Mg, Si, S, and Mn in the EW. The concentration of Ca decreased with extraction time in the EW and was attributed to readsorption. The concentration of Ca and Mn in the SS and Al, Fe, and Si in the Ia soil increased with extraction time and the ‘equilibrium’ was not reached even after 50 hours. This was attributed to the release of elements due to dissolution of minerals.
In the comparison between Community Bureau of Reference (BCR) sequential and batch extraction, the concentrations of Ca, Co, Mg, Mn, and S were higher in batch extraction than in sequential extraction, particularly for the EW and the EW treated soils. This was possibly caused by the readsorption of released elements during water extraction. On the contrary, sequential extraction had higher concentration of Al and Fe compared to batch extraction for the EW, Ia soil, SS treated soils, and EW treated soils. These were attributed to a continued desorption of elements and dissolution of minerals due to exposed surfaces which occurs in sequential extraction.
The comparison between single and sequential extraction for the BCR sequential extraction showed that hydroxylammonium chloride (HAC) applied in sequential extraction had higher concentration of Al, Co, Fe, Pb, and Zn than the single HAC extraction. This was probably due to incomplete dissolution of minerals, precipitation of amorphous minerals, and readsorption of released elements occurring for a single HAC extraction. These were minimised for hydrogen peroxide (H2O2) extraction and hence comparability between single and sequential H2O2 extraction was observed. This was probably due to the presence of complexing agent in the extracting reagent which would minimise the formation of secondary precipitates and hence, improved dissolution of minerals was obtained. Similarly, the concentrations of elements were comparable between single and sequential aqua regia extraction. These results indicated that comparability is improved between single and sequential extraction when aggressive conditions are used.
The results from this investigation indicated that when chemical extraction methods are applied to wastes, the effects of the waste properties on the results of extraction need to be well understood. Consequently, when the chemical extraction methods are used in waste management scenarios certain modifications might have to be made. These modifications include the use of a high solution:solid ratio and an extracting solution which has high complexing abilityThesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.
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"The enhancement of the activity of commercial antifungal agents using Aspalathus linearis synthesized gold nanoparticles." Thesis, 2015. http://hdl.handle.net/10210/13844.
Full textAbstract:
M.Sc.(Nanoscience)The synthesis and application of gold nanoparticles (AuNPs) has been intensively studied worldwide. However, the toxicity of these nanoparticles is still a concern. We considered that various physiochemical methods used to synthesize AuNPs are energy driven, costly and require the use of harmful chemicals. Thus, this makes them not environmentally-friendly. The aim of this study was therefore to synthesize AuNPs via a greener route using Aspalathus linearis tea leaves. The AuNPs were used to coat eight commercial antifungal discs (i.e. amphotericin B, fluconazole, clotrimazole, econazole, flucytosine, ketoconazole, miconazole and nystatin) against four Aspergillus spp. for enhanced antifungal activity. The aqueous extract of A. linearis was characterized by high performance liquid chromatography and liquid chromatography–mass spectroscopy. The AuNPs were characterized using ultravioletvisible (UV-vis) spectroscopy, dynamic light scattering, nanoparticle tracking analysis, Fourier transforms infrared spectroscopy (FTIR), high-resolution transmission electron microscopy and X-ray diffraction. The toxicity of the synthesized AuNPs was studied by 3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium) assay and xCELLigence test on HepG-2 cell lines and results revealed very little to no toxicity of the AuNPs. The pristine antifungal and AuNPs coated antifungal discs were characterized by FTIR, scanning electron microscopy (SEM) and antifungal activity performed using the disc diffusion method. A strong resonance peak was observed at 529 nm of the AuNPs measured using UV-vis spectroscopy. Average size of AuNPs was ~44±1 nm and demonstrated excellent in-vitro stability under various solutions (5% NaCl, phosphate buffered saline) at varying pH levels. The SEM images revealed that the AuNPs were attached onto the coated antifungal discs when compared with the pristine antifungal discs. Antifungal results indicated that AuNPs significantly (p<0.001) enhanced the antifungal activity of the coated antifungal discs against the tested fungi when compared to the pristine antifungal discs. The AuNPs coated econazole disc exhibited the greatest (broad spectrum) activity than other antifungal agents tested. In conclusion, A. linearis can be used as a reducing agent in the synthesis of stable AuNPs. Furthermore, the AuNPs coated antifungal discs demonstrated considerable antifungal activity over the pristine antifungal discs...