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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Nova classe de porfirinas substituídas com éter coroa: Aplicação analítica e atividade catalítica na oxidação de hidrocarbonetos e do fármaco carbamazepina / New class of crowned porphyrins: analytical application and catalytic activity in the oxidation of hydrocarbons and carbamazepine drug.

Silva Filho, Juvenal Carolino da 10 November 2006 (has links)
Neste trabalho foi realizada a síntese, purificação e caracterização de uma tetra crowned porfirina, a 5,10,15,20-tetraquis[2-(hexaoxacicloexadecano-3-amidafenil)]-porfirina, H2TCP, bem como a correspondente ferroporfirina, (FeTCP)Cl. Foi investigado a atividade catalítica desta ferroporfirina e da ferroporfirina mono-crowned substituída, (FeMCP)Cl, sintetizada anteriormente, na oxidação dos substratos (z)-ciclooocteno, estireno, cicloexano e do fármaco carbamazepina, por vários oxidantes: iodosilbenzeno, ácido meta-cloroperbenzóico e hipoclorito de sódio, em meio homogêneo (MeOH ou ACN) e bifásico (C2H4Cl2/H2O). Os resultados revelaram que estes sistemas metaloporfirinicos podem ser considerados bons modelos biomiméticos das enzimas citocromo P450, para oxidação dos substrados estudados, levando ao mesmo produto obtido in vivo na oxidação do fármaco carbamazepina, o cabamazepina-epóxido. Os rendimentos dos produtos de oxidação catalisada pelas ferro crowned porfirinas são, na maioria dos casos, mais expressivos do que aqueles observados com as metaloporfirinas amino-substituídas precursoras. Estes resultados indicam que o substituinte éter coroa confere maior estabilidade e reatividade ao catalisador, e leva à maior seletividade, resultado da interação do éter corôa com o substrato, direcionando-o para o sítio catalítico. Uma outra propriedade importante das crowned porfirinas estudadas é sua capacidade de atuar como agente transferidor de fases nas reações em meio bifásico, utilizando hipoclorito de sódio como oxidante. Os resultados catalíticos nestes sistemas mostraram que as unidades éter corôa foram capazes de carregar o oxidante do meio aquoso para o meio orgânico, onde se encontra o substrato. Foram avaliadas também as propriedades destas novas porfirinas e metaloporfirinas em extrair íons metálicos sódio e potássio do meio aquoso para o meio orgânico. As crowned porfirinas foram bastante eficientes na extração destes metais, principalmente utilizando a técnica de extração por fase única, levando a extrações superiores a 90 % do cátion potássio, e mostrando maior seletividade para este cátion, devido ao tamanho adequado da cavidade do éter corôa para ligar este íon. Foi realizada também a caracterização das porfirinas e ferroporfirinas crowned substituídas por voltametria cíclica, visando sua aplicação futura na análise eletroanalítica de íons potássio e/ou sódio. Observou-se que as porfirinas crowned substituídas sofrem reduções mais fáceis e oxidações mais difíceis quando comparadas com as porfirinas precursoras, mostrando o efeito sacador de elétrons dos substituintes éter corôa. Estes resultados ajudam a explicar os melhores resultados catalíticos obtidos com as ferro porfirinas crowned substituídas, mostrando o efeito do éter coroa em formar a metaloporfirina mais eletrofílica e aumentando a reatividade da espécie catalítica. / In this work we carried out the synthesis, purification and characterization of a tetra crowned porphyrin, 5,10,15,20-tetrakis[2- (hexaoxacyclohexanedecane-3-amidephenyl)]porphyrin, H2TCP, and its corresponding ironporphyrin, (FeTCP)Cl. We investigated the catalytic activity of both this ironporphyrin and the previously synthesized mono-crowned substituted (FeMCP)Cl in the oxidation of the substrates Z-cyclooctene, styrene, cyclohexane and the drug carbamazepine by oxidants like iodosylbenzene, metachloroperbenzoic acid and sodium hypochlorite, in homogeneous (methanol or acetonitrile) and biphasic (C2H2Cl2/H2O) media. Our results demonstrated that these metalloporphyrin systems can be considered good biomimetic models of the cytochrome P450 enzymes in the case of the substrates studied herein, since they led to the same product obtained in the in vivo oxidation of carbamazepine, the carbamazepine-epoxide. The product yields obtained in the oxidation reactions catalyzed by the crowned ironporphyrins were, in the majority of the cases, higher than those achieved with the precursor aminosubstituted metalloporphyrins. This indicates that the crown-ether substituent renders the catalyst more stable and reactive, thus leading to higher selectivity. This selectivity results from the interaction between the crown-ether and the substrate, which directs the latter toward the catalytic site. Another important feature of the studied crowned ironporphyrins is their ability to act as phase-transfer agent in the reactions carried out in biphasic medium, using sodium hypochlorite as oxidant. The catalytic results using such a system gave evidence that the crown ether entities were capable of carrying the oxidant from the aqueous to the organic medium, where the substrate was located. We also evaluated the ability of these novel porphyrins and ironporphyrins to extract sodium and potassium ions from aqueous solution to organic medium. The crowned porphyrins were efficient at extracting these metals, especially when the one-phase extraction technique was employed, leading to potassium ion extraction as high as 90 %. The complexes were more selective toward this latter ion due to the fact that the size of the crown ether cavity was more suitable for binding the larger K+. The crowned porphyrins and ironporphyrins were also characterized by cyclic voltammetry, aiming at their future application in the electroanalytical determination of sodium and potassium ions. When compared with the precursor aminosubstituted porphyrins, we observed that the crowned porphyrins undergo reduction more easily, but their oxidation is harder to achieve. This gives evidence of the electronwithdrawing effect of the crownether substituent. These results help explain the better catalytic results obtained with the crowned ironporphyrins, showing that the crown-ether entity must render the metalloporphyrin more electrophilic, thus increasing the reactivity of the active species.
82

Seven- and Eight-Membered Ether Formation via Sulfonium Ylide Rearrangement Processes and Application in an Approach to (+)-Laurencin

Cao, Liya 06 1900 (has links)
Given the large number of biologically active natural products containing medium-sized ether motifs, many organic chemists have shown great interest for developing new methodologies to access these structures. In particular, numerous synthetic methodologies for the construction of seven-membered and eight-membered ethers have been developed by research groups around the world. Recent advances in the synthesis of seven-membered and eight-membered ethers will be reviewed in chapter one. This chapter will cover some of the more notable publications from the last five years (from 2005 to 2009). In chapter two, the development of ring expansion reactions via [1,2]-shift rearrangements of thioacetal-derived sulfonium ylides will be described. A variety of functionalized diazoketones and diazoketoesters were made from commercially available starting materials. Sulfur-bridged seven-membered and eight-membered ethers were constructed upon treatment of these diazo precursors with suitable metal catalysts. It was found that Rh2(OAc)4 was a better catalyst for diazoketones, while Cu(hfacac)2 proved to be more effective for diazoketoesters. This methodology provides a convenient route to the seven- and eight-membered ethers in relatively few steps. In chapter three, the methodology for construction of sulfur-bridged ethers was employed as the key step in the attempted formal synthesis of (+)-laurencin. In this approach, the relative and absolute stereochemistry was established by a highly enantioselective and diastereoselective allylboration, a facially selective Michael addition, and a thermodynamically controlled acetal formation. The eight-membered sulfur-bridged ether was efficiently constructed using our [1,2]-shift reaction of a sulfonium ylide in toluene at 100 oC in the presence of Cu(hfacac)2. The following desulfurization and decarboxylation was effective at affording an advanced intermediate in this synthesis. The chemistry demonstrated in this chapter outlines a promising strategy for the formal synthesis of (+)-laurencin.
83

The Sulfonated Poly(arylene ether)s for Fuel Cell

Wu, Sheng-feng 06 September 2010 (has links)
PEM (Proton Exchange Membrane) fuel cell is one of the most important green energy, because it has high energy density, lifetime, small and light.etc advantages. Nafion , the major material for PEM now, However, has some disadvantages such as high cost ($600¡V1000/m2) and limited choices for operation temperature about 25¢J~80¢J. Consequently, there is an increasing interest in the development of alternative ionomer membranes with lower cost, and higher proton conductivity, and that are more easily processed. Here we present polymeric membranes made of sulfonic Poly(arylene ether)s (PAEs) which is achieved by nucleophilic displacement reactions of dihalo or dinitro compounds with alkali metal bisphenolates and direct polymer sulfonation was carried out in heterogeneous media using chlorosulfonic acid as both solvent and sulfonating agent. In our PAEs which has high Tg values about 225¡ã250¢XC depends on the barriers to rotation along the main polymer chain. And weight losses above 500 ¢XC by thermogravimetric (TGA) analysis, indicative of their high thermal stability. After FTIR analysis we preparation sulfonated polymer successfully by using chlorosulfonic acid as sulfonating agent. Thermogravimetric analysis (TGA) studies were carried out to investigate the thermal stability of sulfonated PAEs (Td≈ 500¢XC). The proton conductivity of polymer s(DFB+M3) sulfonated with chlorosulfonic acid about 10-6¡ã10-7S cm-1 .Compared with Nafion membrane measured in the same condition, the conductivity of our membrane is smaller than 3~4 order. In the future, it is possible to improve the conductivity of our membrane with optimization.
84

Characteristics of carbony compounds from a heavy-duty diesel engine fueled with dimethyl ether-diesel blend

Cheng, Yi-Jie 23 June 2011 (has links)
In this research, used dimethyl ether as second fuel blended with diesel (mixed quantity with 10 L/min to 60 L/min, interval 10L/min), which test behavior of diesel engine and carbonyls emission investigated. The engine operated at steady-state condition of 1600 rpm, 145 Nm torque , eight kinds of carbonyls were sampling and analysis, and discuss the performance of the ozone formation potential (OFP). The results of regulated pollutant emissions, CO, THC and PM emission could increasing with the addition of DME, NOX emissions, along with the mixed rate of per minute from 10 L, 20 L, 30 L, 40 L, 50 L and 60 L of its reduction rate was 6.8%¡B8.3%¡B10.0%¡B10.6%¡B13.1% and 15.4%, shows that the DME can reduce NOX emissions. Add a various amount of dimethyl ether , which carbonyl compounds emission from the gas flow 0 L(with neat diesel), 10 L, 20 L, 30 L, 40 L, 50 L and 60 L concentrations were 2507.44 g/m3, 2665.27 g/m3, 2726.67 g/m3, 2958.07 g/m3, 4645.87 g/m3, 5470.20 g/m3 and 7279.91 g/m3; the emission factor of 143.58 mg/bhp-hr, 152.65 mg/bhp-hr, 156.62 mg/bhp-hr, 168.69 mg/bhp-hr, 266.22 mg/bhp-hr, 312.38 mg/bhp-hr and 416.36 mg/bhp-hr, shows the addition of DME will rising the carbonyl compound emissions of diesel engine. Gas of dimethyl ether (10,20,30,40,50 and 60 L/min) into the neat diesel fuel (0 L/min) as a mixture fuel additives, the effect of ozone formation potential as increase in the total ozone formation potential, 21945.93 g-O3/m3, 23698.40 g-O3/m3, 24427.46 g-O3/m3, 26672.98 g-O3/m3, 42683.69 g-O3/m3, 50519.26 g-O3/m3 and 67710.60 g-O3/m3 respectively, and ozone manufacturability will 0 L/min of 8.75 increased to 60 L/min of 9.30.
85

Performance Study on the Treatment of MTBE-Borne Waste Gas by Activated Sludge Aeration and Biotrickling Filtering Processes

Su, Li-Chun 14 June 2005 (has links)
In this study, a laboratory-scale activated sludge reactor and a biotrickling filter were constructed to study the removal of methyl tert-butyl ether (MTBE) from air vented from contaminated sites. The activated sludge tank (0.4 m¡Ñ0.4 m cross-sectional area, 3.0 m height, and 480 L total volume) was made by acrylic resin. A mixed liquor suspended solids (MLSS) concentration of 2000-3000 mg/L was maintained in the experimental mixed liquor and the sludge was acclimated for 30 days under selected conditions of a Food to Microorganism Ratio (F/M) of 0.3 g BOD/(g MLSS¡Dday) and an influent gas MTBE concentration (C0) of 180 mg/Am3 (@27oC). Results on performance tests show that an average MTBE removal efficiency of 93.6% was obtained with the operation conditions of C0 of 610 mg/Am3 (@27oC), volumetric aeration rate of 0.063 m3/m3¡Dmin, MLSS of 2600 mg/L, and submerged liquid depth of 1.0 m. The biotrickling filter was made by combining two same type of acrylic resin columns (each 0.2 m inner diameter, 2.0 m height, and packed with 900 pieces of polypropylene Pall rings to a height of 1.35 m) in series for the test gas flow and in-parallel for the trickling liquid flow. Each test was operated for 8 hours to reach a steady state for a set of selected conditions (gas flow rate 0.050 m3/min and superficial gas velocity 0.027 m/s, trickling liquid flow rate 0.004 m3/min and pH: 6.8-7.2, and liquid/gas flow ratio: 80 L/m3). Results show that the MTBE removal efficiencies from the influent gas were 40%, 22% and 15%, respectively, with C0 of 50,100 and 230 mg/Am3 (@27oC).
86

Design and Synthesis of HAT-core as New Materials

Liao, Su-Chih 19 July 2005 (has links)
The common discotic mesogen molecules are known to have a flat structure, comprising a rigid core, e.g., polynuclear aromatic structure, and a ring of four to nine flexible aliphatic side chains. We take the electron deficient heterocyclic hexaazatriphenylene (HAT) as our central core and readily synthesized by the condensation of hexaketocyclohexane with the respective 1,2-bis-alkoxy-4,5-diaminobenzene. The new molecules with electron deficient discotic liquid crystal properties are successfully.
87

Crown ether Linked Aza-Triphenylene Derivatives As New Materials

Shih, Wen-li 05 September 2005 (has links)
The crown ether derivative application have been widely reported,but is very difficult to see by the liquid crystal primarily report. We have used dibezn-18-crown-6 as the starting material to synthesis and study their properties of liquid crystal.
88

Synthesis of Hexaazatrinaphtjylene with Polyether Side Chain

Mao, Yuan-Chi 30 July 2001 (has links)
We solved the problem of purification and successfully synthesized water-solubled hexaazatrinaphthylene with polyether and crown ether side chain under our biomimic and new material goal.
89

Preparation and Study of Electro-Optical Properties of Novel Flexible Substrate Materials

Huang, Kuan-lung 29 July 2008 (has links)
Monomer 4,4¡¦¡¦¡¦¡¦-Difluore-3,3¡¦¡¦¡¦¡¦-bis(trifluoromethyl)-2¡¦¡¦,3¡¦¡¦,5¡¦¡¦,6¡¦¡¦-triphenyl (M4) were converted to novel poly(arylene ether)s by nucleophilic displacement reaction with several bisphenols in this study, then we called them : P-A1, P-A2, P-B1, P-B2. These polymers exhibit weightaverage molecular weight (Mw) between 2.2¡Ñ10^4 to 2.2¡Ñ10^5 g/mol. The molecular weight were investigated and confirmed by Mass and GPC. The molecular structures were investigated and confirmed by NMR and FT-IR.Thermal analysis physics studies with these polymers confirmed by Thermogravimetric analyzer (TGA) and differential scanning calorimetry (DSC). It is indicated that Td 5% of these polymers were 450¢XC ~ 548¢XC in TGA and Tg of these polymers were 303¢XC ~ 324¢XC in DSC.Besides, these polymers not were observed apparent crystallizing point, so we consider that they are not easy crystallized. Therefore, they could make manufacture in higher temperature and have higher thermal stability.In photophysical property of polymeric thin films, we obtained absorption wavelength that was 232nm ~ 300nm in UV-Vis absorption spectra and excitation wavelength that was 362nm ~ 368nm in PL spectra. Furthermore, the transmission spectra of polymeric thin films showed that visible light transparency were up to 83%. Besides, we used Ellipsometer to measure refractive index(n) that is 1.33 ~ 1.49.In drop shape analysis system, contact angles of the polymeric thin films are more than 109.8¢X. They show that the polymer thin films have low polarity and good hydrophobicity. By above material properties of these polymers, they have high thermal stabilities, high optical transparency, low polarity and good hydrophobicity. These good material properties are doing as a plastic substrate of devices or panel display.
90

Microbial degradation of the fuel oxygenate methyl tert-bytyl ether (MTBE)

Youngster, Laura K. G., January 2009 (has links)
Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Microbiology and Molecular Genetics." Includes bibliographical references (p. 112-131).

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