Tesi: "Ethers" – Grafiati

1

Huang, Zilin. "Synthesis and Complexation Studies of Novel Functionalized Crown Ethers and Azacrown Ethers". Thesis, University of North Texas, 2006. https://digital.library.unt.edu/ark:/67531/metadc5593/.

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Novel cage-functionalized azacrown ethers, i.e. 51, 52, 53, 55, 57, 61 and 62, which have various crown cavity and different number of nitrogen atoms incorporated, have been prepared. X-ray structures of 53, 55 and 57 have been obtained for the study of the crown topological structure. The complexation properties of crown 51, 52, 57, 61 and 62 have been evaluated via alkali metal picrate extraction, silver picrate extraction and ESI-MS study. The novel cage-fuctionalized azacrown ethers generally exhibit high avidity and selectivity towards Ag+ versus alkali metal ions and some transition metals i.e. Cu2+, Mn2+, Zn2+, Ni2+ and Pb2+. Crown 61 displays significant avidity and selectivity toward K+ in alkali metal picrate extraction experiments vis-à-vis the remaining alkali metal picrates. Three types of ditopic ion-exchange receptors for sodium hydroxide extraction study have been designed. All of the crown ether molecules have proper cavity for selective sodium complexation and have weakly acidic ionizable alcohols for sodium-proton exchange under strongly basic conditions. Crown 80 and 81 were synthesized; key intermediates for the synthesis of crown 82, 83 and 84 have been prepared. The preparation of 99 afforded an unexpected crown 103. The preparation of 109 had been attempted, but could not be successfully isolated. Four novel cage-functionalized calix[4]arene crown-5, i.e. 113-116, have been synthesized. The structures of 113 and 116 have been established by X-ray crystal structural analysis and NMR spectral analysis. The complexation properties of the four ionic receptors have been studied via alkali metal picrate extraction experiments. Crown 115 and 116 display more than modest avidity toward alkali metal ions and are most selective toward K+ vis-à-vis 113 and 114.

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2

Welsh, Gwendolyn L. "Polybrominated diphenyl ethers". Cincinnati, Ohio : University of Cincinnati, 2008. http://rave.ohiolink.edu/etdc/view.cgi?acc_num=ucin1216928488.

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Thesis (M.S.)--University of Cincinnati, 2008.
Advisors: Jodi Shann PhD (Committee Chair), Brian Kinkle PhD (Committee Member), Anne Vonderheide PhD (Committee Member), Stacy Pfaller PhD (Committee Member) Title from electronic thesis title page (viewed Oct. 5, 2008). Includes abstract. Keywords: Brominated Flame Retardants; PBDE; GC-MS; Soil Sorption; Bioavailability; GC-ECD; Microbial Degradation Includes bibliographical references.

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3

Lousenberg, Robert Daniel. "Synthesis of trifluorovinyl ethers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29227.pdf.

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4

Rico, Joseph G. "Directed lithiations of enol ethers : stereoselective synthesis and reactions of substituted enol ethers". Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/27166.

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5

Yassin-Hussan, Saad. "Photolyse des ethers aromatiques halogenes : bromo phenetole, paradibromo phenetole, parabromo phenetole, parabromodiphenyl ether". Toulon, 1990. http://www.theses.fr/1990TOUL0004.

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Nous avons etudie la photolyse, par rayonnement ultra-violet, de quatre ethers halogenes aromatiques (bromophenetole, parabromophenetole et parabromobiphenylether) dans l'acenotrile, l'eau et dans les melanges eau-acetonitrile, eau-methanol, en presence ou en absence de peroxyde d'hydrogene, compose jouant le role de photooxydant. L'irradiation ultra-violette de ces composes genere de nombreux photoproduits qui ont ete identifies, apres extraction liquide-liquide, par analyse en chromatographie liquide et gazeuse et c. P. V. Couplee a la spectrometrie de masse. Les cinetiques de photodecomposition de chaque ether aromatique halogene ont ete quantifiees. Ces travaux ont permis de preciser les processus complets de photodecomposition de chaque produit: deshalogenation, fixation de l'oxygene moleculaire par les radicaux hydrocarbones, formation et evolution photochimique des peroxydes, action des radicaux hydroxyles et du brome, ouverture du cycle aromatique avec formation d'acides carboxyliques, decomposition de ces acides avec liberation de gaz carbonique et caracterisation d'un residu, a structure macromoleculaire comparable a celle d'un acide humique. Les resultats de ces travaux permettent d'apporter une double contribution: d'abord dans le domaine de la determination des mecanismes reactionnels en chimie radicalaire, ensuite dans le domaine de la chimie appliquee au traitement, par irradiation ultra-violette, des effluents industriels contamines par les ethers halogenes aromatiques

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6

Starkey, Darren Paul. "The tropospheric oxidation of ethers". Thesis, University of Hull, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322331.

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7

Jones, D. "The synthesis of aryl ethers". Thesis, Swansea University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637726.

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The synthesis of biaryl ethers is a process of importance in many fields within the chemical industry. Generally, the Ullmann ether synthesis is employed, though improvements in the general method have not been commonplace since the inception of the process at the turn of the century. By reinvestigating the parameters present, it was found that the use of cuprous iodide in a solventless reaction led to high yields of diaryl ethers. Further improvements were developed by the implementation of ultrasound in conjunction with lower reaction temperatures, with similarly high yields being afforded. Study was then undertaken to investigate the applicability of electrophilic bromination of various aromatic moieties. Thus, phenol, 2-methoxyphenol and aniline were examined in relation to the amount of ortho-bromination occurring with reagents such as 1,3-dibromo-5,5-dimethylhydantoin and N-bromosuccinimide in the presence of solid supports. These studies indicated that the use of solid supports, especially Amberlyst 15 and XN1010 and Montmorillonite K10 realised high degrees of bromination, though in the case of aniline the natural tendency to realise bromination in the para-position reduced the observed effectiveness of the process. By the implementation of acetyl hypobromite and N,N-dibromourethane, good para selectivity was found for the bromination of toluene in the presence of solid supports, though when applied to nitrobenzene, bromination of the straight chain alkane present at the internal standard present for gas chromatography analysis occurred. The use of molecular bromine in conjunction with solid supports such as Montmorillonite K10 led to high yields of 1-bromonaphthalene.

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8

Vile, Sadie. "Alpha-sulphonyl ethers in synthesis". Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46595.

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9

Wild, Carl. "Trifluoroethyl enol ethers, dienol ethers, and acetals: an investigation of their preparations, reactivities, and synthetic applications". Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/54459.

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The major portion of this work details our investigation of trifluoroethoxy (TFE) substituted compounds with particular emphasis given to their preparation and possible applications. The three types of compounds studied were trifluoroethoxy substituted ketals, enol ethers, and dienol ethers. The ketal and enol ether work involved developing methodology for the large scale preparation of these structures as well as studies detailing their behavior. For the TFE ketals, preparation involved an acid-catalyzed alcohol exchange reaction. Applications included their use as non-complexing/acid-stable carbonyl protecting groups. The TFE enol ether work also involved preparation and applications studies. These structures were synthesized from propargyl ketones via a conjugate addition reaction. The applications were synthetic in nature mainly involving utilization of these compounds in cycloaddition and conjugate addition reactions. The last portion of this work involved our investigation into behavior of trifluoroethoxy substituted dienol ethers (substituted 1-trifIuoroethoxy-3-trialkylsiloxy-1,3- butadienes). Their preparation was accomplished by a method similar to that used by Danishefsky in his synthesis of the 1-methoxy analogs. The applications portion of this study focused on the use of these compounds as 4 carbon synthons in [4+2] cyclcoaddition reactions. Information gained from these studies provided insight into the effect the electron-withdrawing trifluoroethoxy group has on the reactivities of structures into which in has been incorporated.
Ph. D.

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10

Landry, Denis Joseph Carleton University Dissertation Chemistry. "Approaches to the synthesis and sterochemical analysis of aza crown ethers". Ottawa, 1989.

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11

Huang, Zilin. "Synthesis and Properties of Novel Cage-Annulated Crown Ethers". Thesis, University of North Texas, 2003. https://digital.library.unt.edu/ark:/67531/metadc5523/.

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Three cage-functionalized polyoxacrown ethers (9, 10 and 12) and four novel cage-functionalized polyoxamonoazacrown ethers (18, 20, 25 and 29) that contain 3,5-disubstituted-4-oxahexacyclo[5.4.0.02,6.03,10.05,9.08,11]dodecane ("oxahexacyclic") moiety have been synthesized and their respective alkali metal picrate extraction profiles along with that of three analogues 13, 14 and 21 have been obtained. The observed avidities and selectivities of the host molecules toward complexation and transport of alkali metal picrates can be related to the size and shape of their respective macrocyclic cavity and the number of donor atoms. The effect of N-alkyl substitution on the complexation properties of azacrown ethers has been studied. The avidity of N-Et azacrown ethers toward complexation with alkali metal cations is generally higher than that of the corresponding non-N-alkylated hosts. However, the presence of an N-Et group appears to have a negligible effect upon their relative selectivities in their regards. The effect of pH on extraction process was studied; it was thereby determined that the alkali metal picrate extraction experiments are best performed at high pH (ca. 11-12).

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12

Kleissler, Charles Richard. "Comparison of poly(vinyl alcohol) backbone-grafted ethers and chain-growth crown ether polymers in selective cation adsorption". Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/10115.

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13

Lightfoot, Andrew Philip. "Chiral oxime ethers : applications in synthesis". Thesis, Loughborough University, 1996. https://dspace.lboro.ac.uk/2134/28182.

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Chapter One reviews the literature, discussing the role of nucleophilic additions to oximes and their derivatives. This introduction is primarily concerned with the formation of new carbon–carbon bonds, this is achieved by the addition of organometallic reagents to the carbon–nitrogen double bond functionality of oximes and their derivatives.

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14

Fowler, Tom. "Claisen rearrangments of bicyclic enol ethers". Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414088.

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15

Telford, Peter T. "New routes to highly fluorinated ethers". Thesis, Durham University, 1986. http://etheses.dur.ac.uk/6835/.

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The aim of this research project was to devise a viable synthetic route to perfluoropolyethers. Current commercial processes are elaborate but inefficient and hence are limited in application by cost. The approach undertaken in this project consisted of essentially two steps; (1) the free radical addition of a polyether to a fluorinated olefin and (2) the direct fluorination of the polyadducts derived from the addition process (scheme i) (Rf = polyfluoroalkyl, Rf(^1) = perfluoroalkyl) The research work was carried out in two phases. The initial investigation examined the free radical addition of simple mono-, di-, and poly-ethers to various fluorinated olefins. The participation of a 1, 5 hydrogen transfer process was found to have a major influence onthe production of poly-adducts. The second phase of the process involved the development of techniques for the further fluorination of the simple adduct systems. Fluorination was achieved using cobalt trifluoride for volatile systemsbut the approach was limited by fragmentation of the substrate as the molecular weight of the adduct increased.Techniques for direct fluorination have been developed and a range of simple ether adducts were successfully fluorinated producing the corresponding perfluoroetherso The findings from the model compound studies were applied to polyethylene glycol diethyl ether (avo molecular weight 456). Addition of the polyether to hexafluoropropene followed by fluorination of the resulting polyadduct with elemental fluorine~ produced a perfluoroether with the following structural featurasin good yield:

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16

Owens, K. A. "Polycyclic crown ethers incorporating cyclophane units". Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370864.

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17

Laurent, Pierre. "Asymmetric synthesis using chiral oxime ethers". Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248161.

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18

Hunt, James Charles Atlee. "Chiral oxime ethers in asymmetric synthesis". Thesis, University of Exeter, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302639.

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19

Wilson, Mark James. "Activity relationships for aromatic crown ethers". Thesis, University of Strathclyde, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249872.

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20

Dawkins, David Anthony. "Asymmetric synthesis using chiral vinyl ethers". Thesis, University of Leicester, 1992. http://hdl.handle.net/2381/33644.

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Using chiral alcohol precursors, a number of chiral vinyl ethers were prepared by mercuric acetate-catalysed transetherification with butyl vinyl ether. a-Lithiation of (1R)-menthyl vinyl ether was unsuccessful under a variety of conditions. (1S)-(Menthylthio)ethene was prepared from (1S)-menthanethiol but deprotonation was not possible as the thioether was found to decompose rapidly at room temperature. The deprotonation of (R)-phenethyl vinyl ether, (S)-l-(2-naphthyl)-l-ethyl vinyl ether and (S)-l-phenyl-1-butyl vinyl ether and attempted reaction with benzaldehyde yielded none of the a-alkylated adduct but a Wittig rearrangement reaction was seen. The cycloaddition reaction of benzonitrile oxide with a range of chiral vinyl ethers was investigated. The isoxazoline product was isolated as a mixture of two diastereoisomers after flash column chromatography. In most cases the diastereoisomer ratio neared 1:1, but (S)-l-(2-naphthyl)-l-ethyl vinyl ether and 1-phenyl-1-butyl vinyl ether gave a single diastereoisomer of the isoxazoline product, after chromatography, with a variety of nitrile oxides. Conditions have been developed for the removal of the chiral auxiliary but as yet only achiral isoxazolines have been obtained by this method. Attempts at ring deprotonation/alkylation and also the addition of a nucleophile or radical to the isoxazoline C=N bond were hindered by the instability of the isoxazoline adducts. A chiral vinyl pyrrolidinone was also prepared and found to undergo an asymmetric cycloaddition reaction with benzonitrile oxide to yield a single diastereoisomer of the isoxazoline product. The equivalent acrylamide was synthesised and, although this gave a 1:1 mixture of diastereoisomers with both benzonitrile oxide and 2,2-dimethylpropanenitrile oxide, these diastereoisomers could be separated. Removal of the chiral auxiliary yielded hydroxyisoxazolines with an enantiomeric excess of 90-94%. Attempts to investigate the extent of any asymmetric induction in the cycloaddition of nitrile oxides to chiral vinyl sulphoxides were hampered by the instability of the isoxazoline product, which underwent an immediate syn-elimination. In an effort to determine the potential of chloromethyl-(1R)-menthyl ether as a chiral OH protecting group, a series of (1R)-menthoxymethyl ethers were prepared from a variety of racemic and homochiral alcohols. Conditions for deprotection were developed which did not lead to the racemisation of homochiral alcohols. The usefulness of the (1R)-menthoxymethyl ether group as a simple means of measuring enantiomeric excess was demonstrated in a silicon-directed diene synthesis.

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21

Awad, Amneh. "Palladium Catalyzed Reactions of Enol Ethers". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1398070523.

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22

Snelling, Jeff Barnett Mark O. "Higher ethers as replacement oxygenates for methyl tertiary butyl ether in gasoline synthetic and environmental aspects /". Auburn, Ala., 2007. http://repo.lib.auburn.edu/2006%20Fall/Dissertations/SNELLING_JEFF_42.pdf.

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23

Bodvik, Rasmus. "Bulk and interfacial properties of cellulose ethers". Doctoral thesis, KTH, Yt- och korrosionsvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95379.

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This work summarizes several studies that all concern cellulose ethers of the types methylcellulose (MC) hydroxypropylmethylcellulose (HPMC) and ethyl(hydroxyethyl)cellulose (EHEC). They share the feature of negative temperature response, as they are soluble in water at room temperature but phase separate and sometimes form gels at high temperatures. The different types of viscosity transitions occurring in these three cellulose ethers are well-known. However, earlier studies have not solved the problem of why both HPMC and EHEC, as the temperature increases, exhibit a viscosity decrease just before the viscosity increases, whereas MC only has one transition temperature where the viscosity increases. With our investigations we have aimed to compare the effect of temperature on bulk solutions and on adsorbed layers of the different polymers using a range of techniques. Light scattering and cryo transmission electron microscopy (cryo-TEM) was employed to study aggregation of MC, HPMC and EHEC in solution. The solvent quality of water is reduced for all three polymers in solution as the temperature increases, and this infers an onset of aggregation at a certain temperature. The aggregation rate follows the order EHEC > HPMC > MC. Cryo-TEM pictures of solutions frozen from high temperatures showed closely packed fibrils forming dense networks in MC solution. Some fibrils were also found in HPMC solution above the transition temperature, but they did not interconnect readily. This is explained by the bulky and hydrophilic hydroxypropyl groups attached to HPMC. EHEC has similar substituents, while MC only has short and hydrophobic methyl groups attached to the main chain. An amphiphilic liquid, diethyleneglycolmonobutylether (BDG) was used as an additive to change the properties of MC solutions in water. With 10 wt% BDG added, the effect was similar in viscosity and light scattering measurements as well as cryo-TEM pictures, inducing a temperature response resembling that of HPMC in pure water. 5 wt% of BDG was enough to change the aggregation type and induce a transition temperature with viscosity decrease. The effect of the additive is rationalized by BDG acting as a hydrophobic and bulky substituent in MC, similar to the large substituents in HPMC and EHEC. Two instruments, a quartz crystal microbalance with dissipation (QCM-D) and an ellipsometer, were used in parallel to determine the changes with temperature on an adsorbed layer of MC and HPMC on silica kept in water and in polymer solution. The silica needed to be hydrophobized for significant adsorption to take place. Adsorption was similar for both polymers at low temperatures, whereas a sharp transition in several layer properties occurred for HPMC, but not for MC, close to the solution viscosity transition temperature. Atomic force microscopy (AFM) was used to measure attractive and repulsive forces and also friction forces between MC layers in polymer solution. The small changes in normal forces with temperature infer that the hydrophobic groups in MC are mostly depleted from the surface. The surface–polymer interactions increase with increasing temperature and the layer becomes more cohesive, which induces a higher load bearing capacity and lower friction when measured at high loads. AFM imaging was employed to obtain the height distribution in MC adsorbed layers. These images indicate that fibril-like structures were formed at a lower temperature in the surface layer than in bulk solution. The different preferences for adsorption and for aggregation in MC and HPMC above the solution transition temperatures are explained by the fibril formation in MC shielding hydrophobic parts of the polymer from the solution, and thus counteracting adsorption, but also fast aggregation. The viscosity decrease in HPMC and EHEC is conferred to intra-chain contraction and aggregation into less extended structures.

QC 20120523

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24

Gorgy, Tamer George Alexan. "Polybrominated diphenyl ethers in biosolids-amended soils". Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/35020.

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Polybrominated diphenyl ethers (PBDEs) are added to many consumer products as flame retardants. Their hydrophobic characteristics and high n-octanol-water coefficients make them partition in organic media such us sludge and biosolids, by-products of wastewater treatment which are commonly applied to agricultural soils to promote crop growth or discarded in landfills. Biosolids-amended soils have been found to contain up to 7x10⁶ pg PBDEs/g dry weight, whereas leachates from biosolids and flame-retarded products in landfills, contained up to 4,000 pg PBDEs/litre. PBDEs in the environment could potentially cause serious health effects. Research was conducted to determine the concentration and mobility of PBDEs in biosolids, biosolids-amended soil, and clay liners used to retain PBDEs. A field study investigated the degree of PBDE contamination due to the application of biosolids at an agricultural site near Kamloops and an agricultural field in Totem Field at the University of British Columbia in Vancouver. PBDEs were found to migrate downwards to depths of at least 0.85 m. Laboratory experiments determined leachability of PBDEs from biosolids. PBDEs sorbed on fine particles suspended in the leachate, allowing PBDEs to exceed their aqueous phase solubilities. Concentrations were much higher on ultra-fine than on fine particles. Leaching column tests demonstrated that PBDEs leached from biosolids-amended soils and migrated through the soils. PBDEs in soils upgradient and downgradient of solid waste facilities in Northern Canada varied widely from location to location. There was evidence that PBDE contamination in Iqaluit is due to long-range atmospheric transport, whereas that found at Yellowknife is mainly from the solid waste facility. Laboratory experiments showed that sand-bentonite partially retained PBDEs. The hydraulic conductivity decreased with leaching, and then gradually increased. The decrease is attributed to swelling, whereas the increase is due to shrinkage of the clay interlayer, owing to the hydrophobicity of the permeant. The research may be helpful in establishing regulations on land application of biosolids, regulating waste disposal and landfill design requirements.

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25

Fruteau, de Laclos Anne-Marie F. (Anne-Marie François). "Cleavage of benzyl aryl ethers by chlorine". Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70291.

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In order to extend application of the gel-degradation mechanism of delignification, model compounds of the general structure (3,4-dimethoxyphenyl)-CH(OR)R$ sp prime$ were treated at room temperature with increasing charges of molecular Cl$ sb2$ in glacial HOAc.
Catalytic amounts of Cl$ sb2$ cleaved benzyl aryl ether bonds (OR=2-methoxy-4-methylphenoxy) before any ring chlorination occurred. Yields of cleavage decreased in the order: R$ sp prime$=H; R$ sp prime$=$-$CH$ sb2$-2-methoxyphenoxy; R$ sp prime$=$-$CH(CH$ sb2$OH)-2-methoxyphenoxy. These results support the concept that the delignification of wood pulp by chlorine results from benzyl aryl ether cleavage. The conditions of the reaction, as well as control reactions with hydrochloric acid, suggest that the cleavage is due to conventional acid hydrolysis induced by chlorine. The experimental evidence does not rule out another possible mechanism in which the cleavage is initiated by molecular chlorine.
Benzyl ether links were generally stable in models of the benzyl alkyl type, whose primary reactions were ring chlorination. A large excess of chlorine caused side-chain displacement, hitherto considered the primary reaction in the solubilization of lignin.

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26

Scullion, Lisa. "Single molecular conductance of ethers and peptides". Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539474.

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27

Wadman, S. N. "Stereoselective alkene syntheses from cyclic enol ethers". Thesis, University of Southampton, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233924.

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28

Engel, García Paloma. "Novel coupling reactions for complex polycyclic ethers". Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4339/.

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Development of cascade RCM reactions, where two different approaches are proposed. The first route involves a ruthenium-catalysed enyne RCM reaction, followed by a metallotropic [1,3]-shift and a final alkene RCM. The second route incorporates an enyne RCM reaction followed by direct alkene metathesis. These methodologies provide access to common bicyclic and tricyclic polyether skeletons such as those present in tamulamide, prymnesin, gambierol and maitotoxin, respectively. The second project is concerned with the synthesis of the C-G ring fragment of gambieric acid and the development of novel methodology for the formation of the seven membered E ring.

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29

Taylor, Piers. "Aza-enolate alkylation reactions of lactim ethers". Thesis, University of Bath, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425801.

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30

Denike, John Kane Carleton University Dissertation Chemistry. "The synthesis and complexation of bis-crown ethers and polymers bearing pendant crown ethers and the study of molecular motion of crown ethers in solids using solid state 2H NMR". Ottawa, 1992.

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31

Höglund, Anders. "Controllable degradation product migration from biomedical polyester-ethers". Licentiate thesis, KTH, Fibre and Polymer Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4366.

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The use of degradable biomedical materials has during the past decades indeed modernized medical science, finding applications in e.g. tissue engineering and drug delivery. The key question is to adapt the material with respect to mechanical properties, surface characteristics and degradation profile to suit the specific application. Degradation products are generally considered non-toxic and they are excreted from the human body. However, large amounts of hydroxy acids may induce a pH decrease and a subsequent inflammatory response at the implantation site.

In this study, macromolecular design and a combination of cross-linking and adjusted hydrophilicity are utilized as tools to control and tailor degradation rate and subsequent release of degradation products from biomedical polyester-ethers. A series of different homo- and copolymers of -caprolactone (CL) and 1,5-dioxepan-2-one (DXO) were synthesized and their hydrolytic degradation was monitored in phosphate buffer solution at pH 7.4 and 37 °C for up to 546 days. The various materials comprised linear DXO/CL triblock and multiblock copolymers, PCL linear homopolymer and porous structure, and random cross-linked homo- and copolymers of CL/DXO using 2,2’-bis-(ε-caprolactone-4-yl) propane (BCP) as a cross-linking agent.

The results showed that macromolecular engineering and controlled hydrophilicity of cross-linked networks were useful implements for customizing the release rate of acidic degradation products in order to prevent the formation of local acidic environments and thereby reduce the risk of inflammatory responses in the body.

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32

Merilis, Giorvanni. "Distribution of Polybrominated Diphenyl Ethers Among Demographic Categories". Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6903.

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Polybrominated Diphenyl Ethers (PBDEs) are flame retardants widely used within the United States in various products such as plastics, electronics, textiles and furniture. With an increase in production and usage, PBDEs have recently emerged as a contaminant of concern. Due to their chemical structure, PBDEs have the propensity to bioaccumulate in mammals. In fact, elevated PBDE concentrations have been recorded in human breast milk. Due to the potential widespread exposure to PBDEs, this study investigates human blood concentrations of PBDEs generated through the 2003-2004 National Health and Nutrition Examination Survey. Through the use of statistical modeling, a comparison of mean PBDE concentrations in ng/g lipid is conducted based on age, gender and ethnicity. From a sample of 2337 individuals, the average blood concentration of PBDEs was approximately 81 ng/g lipid. The average PBDE concentration of males was significantly higher than females, using a 95% confidence level. In addition, PBDEs detected in human blood ranged approximately from 0.05 to 3676 ng/g lipid, with the highest concentrations found in black males. Also, a logistic regression analysis is conducted to determine whether an increase in background PBDE concentrations is a risk factor for obesity. Furthermore, the analyses of PBDEs are repeated for phthalates and polychlorinated Biphenyls for comparison. Finally, the measured concentrations of PBDEs are also compared to health outcome data known to show potential risk.

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33

Rolland, de Denus Christine Marie. "Controlled molecular design and polymerization of polyaromatic ethers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq23656.pdf.

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34

Teclechiel, Daniel. "Synthesis and characterization of highly polybrominated diphenyl ethers". Doctoral thesis, Stockholm : Department of Environmental Chemistry, Stockholm university, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7410.

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35

Danon-Schaffer, Monica N. "Polybrominated diphenyl ethers in landfills from electronic waste". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/20740.

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Abstract (sommario):

Previous research on Brominated Flame Retardants (BFRs), including Polybrominated Diphenyl Ethers (PBDEs), has largely focused on their concentrations in the environment and their adverse effects on human health. This thesis explores how these compounds reach the environment, how they are transferred from waste streams to water and soil, and how they are transported to distant locations like Northern Canada. Landfills, which receive a large proportion of society’s discarded consumer waste products, including electronic wastes (e-waste), are the major focus of attention. Leachate was collected and analysed from 27 landfills across southern Canada and 11 dump sites in the Canadian North. There was wide variability in the results, both in terms of the total concentrations of PBDEs and in the distribution of congeners. Northern sites tended to have lower PBDE concentrations than southern ones, but some levels were significant despite the low population density and lack of industry in the north. The North provides a sink for PBDE contaminants. Significant differences in PBDE levels in leachate in contact with wastes originating in different 5-year time intervals suggest that the time-of-manufacture of electronic goods plays an important role in determining the rate of PBDE release into the environment. Electronic components manufactured in the 1985-89 period were found to have especially high PBDE concentrations. Experiments were carried out in which e-waste was contacted with distilled water and leachate from a major urban landfill in a custom-built contactor. There was transfer of PBDEs to the aqueous phase which increased with greater contact time and increasing temperature. Exposing e-waste to distilled water led to lower PBDE concentrations, probably due to dislodgement of fine dust from the surface of e-waste particles. A comprehensive mole balance model was prepared to assist in predicting the concentration of PBDEs in and near landfills. The balances were applied to different homologue groups and different subsystems - field e-waste, non-e-waste solids, and aqueous phase. Mass transfer parameters were obtained from solid-liquid contacting experiments with crushed e-waste. Simulations indicate that PBDEs will persist for decades in the environment even if they are no longer manufactured and incorporated in plastics.

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36

Gallimore, A. R. "The biogenesis of terrestrial and marine polycyclic ethers". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599282.

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The widely accepted hypothetical model for polyether biosynthesis involves a polyene intermediate that undergoes an oxidative cyclisation via the corresponding polyepoxide. Recently, a triene shunt metabolite from monensin-producing Streptomyces cinnamonensis lent great support to this model. Sequencing of the gene cluster also supported this model. However, the role of two novel genes, monBI and monBII, was unclear. Deletion of these genes resulted in the production of a number of apparent monensin analogues, whilst abolishing monensin production itself. By isolating and characterising novel epimers of monensin, from one of these mutants, a role of the monB genes in the cyclisation of the final monensin intermediate is proposed. Acid-catalysed cyclisation of surmised cyclisation intermediates from this mutant served to confirm this proposal. An approach to trapping a triepoxide intermediate analogue that is unable to spontaneously cyclise was then explored. The preliminary results suggest that such an approach might lead to the isolation and characterisation of such a triepoxide. The closest marine relatives of the terrestrial polyethers are the ladder polyethers, such as brevetoxin and ciguatoxin. By extrapolating the polyepoxide model to all known marine ladder polyethers, a simple biosynthetic model is proposed, based on the development and justification of the “stereochemical uniformity rule”. Interestingly, application of this model and rule to the largest known ladder polyether, maitotoxin, reveals a stereochemical discrepancy at one of the ring junctions. It is thus suggested that this new rule may have uncovered an error in the established structure of this molecule, as well as being a potentially useful rule in the assignment of new ladder polyether ladder structures.

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37

Bird, P. M. "Stereocontrol in the synthesis of substituted spirocyclic ethers". Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596658.

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This thesis describes the synthesis of spirocyclic ethers with substituents in both rings. The strategy employed is considered in stepwise manner starting with the two-step synthesis of the substituted cyclic α-phenylsulfanylcarbaldehydes A and B from the corresponding cyclic ketones, paying particular attention to the stereoselectivity in the first step and the stereospecificity of the second. Simple aldol reactions of these aldehydes with ester and ketone enolates are reported, along with the conversion of the aldol products C to (1,3)-diols D by reduction (including the[1,3]-stereoselective reduction of β-hydroxyketones) or addition of an organometallic reagent. The stereospecific cyclisation of these diols to the targeted spirocyclic ethers E was achieved by treatment with catalytic amounts of p-touenesulfonic acid. Elucidation of the stereochemistry of these tetrahydrofurans and their precursors - and the implications of these assignments - by the examination of 2-D NMR spectra is discussed.

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38

Trmcic, Jelena. "Electrophilic fluorination of ethers and deactivated benzene derivatives". Thesis, Durham University, 2005. http://etheses.dur.ac.uk/2769/.

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Abstract (sommario):

Chapter 1 - Chapter 1 provides a literature review of the relevant topics for this thesis in organofluorine chemistry: effect of fluorine as a substituent on the molecule, synthesis of C-F bond from C-H bond using electrophilic reagents with discussions of mechanisms. Chapter 2 ― Direct fluorination of electron-rich systems such as alkyl and cyclic saturated ethers using elemental fluorine results in the formation of unexpected products: fluorinated aldal acetáis. Selectfluor™ was also used to prepare these products in good yield, but also to gain information about mechanism. Chapter 3 - Same methodology for fluorination of deactivated benzene derivatives using elemental fluorine was applied and resulted in a selective substitution of hydrogen by fluorine and allowed the synthesis of a diverse collection of polyfunctional monofluorinated aromatic products. Chapter 4 - Fluorination of 1,3- and 1,4-disubstituted benzaldehyde derivatives was studied in the reactions with elemental fluorine and resulted usually in mixtures of two products. It is concluded that the distribution of the two competing products is dependent on the total electric effect of the substituent (σ-value) attached to the aromatic ring. Chapter 5 - Our research group has developed a microreactor for the purpose of selective fluorination of a wide range of compounds such as benzaldehydes and nitrobenzenes. Low inventories of fluorine gas, in contact with reagents, provide increased safety. Optimization was obtained by varying substrate flow rate, and often resulted in a good conversion and superior yields. Chapter 6-9- Experimental details of the work discussed in Chapters 2-5.

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39

Merithew, Andrew William. "Differential Self-Assembly of Novel Redox Crown Ethers". Thesis, University of California, Santa Barbara, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3645672.

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Abstract (sommario):

Retinal prosthesis relies on the stimulation of living nerve tissue behind the rods and cones of the eye. The current state of the art relies on electrodes controlled by cameras which directly stimulate the nerve tissue to elicit a response to an image. These types of retinal implants have allowed for short-term crude vision in patients but have had limited long term success due to external battery packs and electroplating of the implanted electrodes.

Ionic stimulation is one of the principle mechanisms that sensory neurons utilize in the generation of an action potential. In a complex transduction pathway, ionic gradients are constantly altered inside the neuron by voltage sensors or mechanically controlled gates embedded in the neuronal cell membrane; responsible for the open and close state of these ion channels.

It has been demonstrated that local concentration increases of K⁺ by direct injection proximal to the nerve can elicit nerve firing at a concentration of 15-20 mM (3-4X normal concentration) increase in K⁺ concentration. As part of a larger concept of integrating biotechnology with nanofabrication, the materials for the development of potassium selective sequestration/storage and delivery were developed in the form of a redox-gated K⁺ selective crown ether.

The structure of the anthraquinone-based crown was deduced by computational simulation and stoichiometry of the complex confirmed by mass spec. along with 2D diffusion NMR techniques. In this instance, the stoichiometry could be controlled by the addition of different salts to give a 1:1 complex with large, aromatic anions and a 2:1 complex with smaller anions such as triflate. The synthesis of the molecule was optimized by computational modeling and simulations of transport through an artificial membrane. The selectivity of the architecture developed was specific for K⁺ over Na+, the other major ionic species present in the blood. The mechanism influencing the self-assembly of this class of compounds has much to do with the breakage of intramolecular π-stacking interactions and the formation of stronger intermolecular π-stacking interactions.

Finally, the transport of K⁺ through nanoporous membranes and single nanopores with novel PEG-type polymeric dispersions is demonstrated. This thesis concludes with future work toward developing more advanced transporters and proposes novel uses for anthraquinone-appended polymers as proton exchange membranes and DNA-base pair interchelators.

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40

Fregapane, Giuseppe. "Chemo-enzymatic synthesis of sugar fatty acid ethers". Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357150.

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41

Cooper, Tracey Sara. "Synthesis of amino acids from chiral oxime ethers". Thesis, University of Exeter, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432786.

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42

Heslin, J. C. "Synthesis of cyclic ethers and approaches to zoapatanol". Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47108.

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43

Wikström, Linus. "Surface treatment of cellulose ethers Ytmodifiering av cellulosaetrar". Thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-17977.

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The aim of this diploma work was to execute surface treatment of non-ionic cellulose ethers EHEC that AkzoNobel provides under the tradename Bermocoll®. In order for the cellulose ether to dissolve without forming lumps, some surface treatment is commonly required. In this work glyoxal has been used for this surface modification using two different lab-scale methods that in different ways mimic the full scale production. It is an everlasting challenge for the chemical industry to reduce the consumption of chemicals and also reduce energy consumption in the production. Therefore one objective of this work was to gain fundamental understanding about the glyoxal reaction with EHEC in terms of required equivalents glyoxal, reaction temperature and reaction time. Another aim of this work was to compare the two lab scale methods with regards to their predictivity and reproducibility of results.One method is called the dry method in which a water solution of glyoxal was added to dry, non-glyoxal treated EHEC at varying temperature during heavy agitation. The second method is called the acetone method where the EHEC and glyoxal were first suspended in acetone at room temperature, and then heated at different temperature for various time periods. The parameters in the experiments made was chosen using a design of experiments (DoE) approach in order to gain as much information as possible from a few experiments and also facilitating a statistical analysis of the results.This diploma work indicates that the acetone method have a better reproducibility and would be the better choice when investigating various parameters for the reaction. On the other hand the dry method might be better suited for the further analysis of temperature dependence of the glyoxal reaction with cellulose ethers. The most important factor for the reaction was the amount of glyoxal used, whereas it is indicated that the reaction temperature had a minor effect on the reaction yields.
Program: Högskoleingenjörsexamen i Kemiingenjör – tillämpad bioteknik

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44

WELSH, GWENDOLYN L. "Polybrominated Diphenyl Ethers: Soil Sorption and Microbial Degradation". University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1216928488.

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45

Ji, Mingzhe. "Explorations with optically active, cage-annulated crown ethers". Thesis, University of North Texas, 2003. https://digital.library.unt.edu/ark:/67531/metadc4207/.

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Abstract (sommario):

A variety of optically active macrocyclic crown ethers that serve as "host" systems that are capable of differentiating between enantiomeric "guest" molecules during host-guest complexation have been prepared via incorporation of chiral elements into the crown ring skeleton. The ability of these crown ethers to recognize the enantiomers of guest salts, i.e., (+) a-methyl benzylamine and to transport them enantioselectively in W-tube transport experiments were studied. The ability of these crown ethers to perform as chiral catalysts in an enantioselective Michael addition was studied. The extent of asymmetric induction, expressed in terms of the enantiomeric excess (%ee), was monitored by measuring the optical rotation of the product and comparing to the literature value.

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46

Gouardères, Frédéric P. "The cationic ring-opening polymerization of cyclic ethers". Thesis, Aston University, 1995. http://publications.aston.ac.uk/9681/.

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Abstract (sommario):

The kinetics and mechanisms of ring opening polymerization and copolymerizntion of different cyclic ethers were studied using mainly a cationic system of iinitiation. BF30Et2/ethanediol. The cyclic ethers reacted differently showing that ring strain and basicity are the main driving forces in cationic ring opening polymerizaion. In most cases it was found that the degree of polymerization is controlled kinetically via terminations with the counterion and the monomers, and that the contribution of each type of reaction to the overall termination differs markedly. The Gel permeation chromatography studies showed that the molecular weight distribution of the samples of polyoxetanes were bimodal. This was in accordance with previous work establishing that the cyclic tetramer is found in much higher proportions than any of the other cyclic oligomers. However the molecular weight distribution of the copolymers made from oxetane and THF or from oxetane and oxepane were shown to be unimodal. These observations could be explained by a change in the structure of the growing end involved in the cationic polymerization. In addition crown ethers like dibenzo-crown-6 and compounds such as veratrole are believed to stabilise the propagating end and promote the formation of living polymers from oxetane.

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47

Page, Abigail. "Atropisomeric diaryl ethers and other non-biaryl atropisomers". Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/atropisomeric-diaryl-ethers-and-other-nonbiaryl-atropisomers(84281e1e-416b-4d2e-834b-1d215d6767cf).html.

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Atropisomerism is a property exhibited by molecules where rotation about one or more bonds is restricted. Along with biaryls, which are widely utilised in asymmetric catalysis, several other classes of compounds display atropisomerism. These molecules have applications in enantioselective synthesis, asymmetric catalysis and have been used to relay stereochemical information. There are, however, a number of challenges associated with their asymmetric synthesis (Chapter 1). This thesis describes research carried out on the synthesis and asymmetric synthesis of atropisomeric diaryl ethers. Chapter 2.1 explains how these ethers are synthesised in multi-gram quantities and to allow the incorporation of large ortho substituents. Having a number of diaryl ethers with suitable substitution patterns to achieve atropisomerism, Chapter 2.2 goes on to report two novel and complimentary biocatalytic approaches to the enantioselective synthesis of diaryl ethers by desymmetrisation. This chapter also describes a possible route towards the synthesis of a diaryl ether based ligand. Chapter 2.3 reports the lateral lithiation of meso diaryl ethers to yield diastereomeric atropisomers stereoselectively. Our attempts to use (-)-sparteine in lateral lithiations to desymmetrise a diaryl ether enantioselectively is also described. We go on to determine the configurational integrity of our organolithiums and the reaction pathway that exists in lithium substitution. Finally, the diastereoselective synthesis of both a diaryl ether (via a stereoselective reduction of a pro-chiral ketone) and a diaryl sulfide (via an addition reaction) is described in chapter 2.4. This chapter also reports the conformational behaviour of a diaryl amide in solution.

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48

LLORENS, GILBERT. "Contribution a l'etude des ethers d'alcool gras polyoxyethylene". Strasbourg 1, 1993. http://www.theses.fr/1993STR15021.

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49

D'Souza, Lawrence Joseph. "Bile Acid Based Molecular Tweezers And Crown Ethers". Thesis, Indian Institute of Science, 1995. https://etd.iisc.ac.in/handle/2005/114.

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Abstract (sommario):

Chapter 1. Introduction to Molecular Tweezers Whitlock and Zimmerman developed a class of molecular hosts, popularly known as molecular tweezers, which sandwich aromatic guests by ii=ii interaction. Chapter 1 summarizes molecular tweezers of various kinds which have recently been synthesized. Chapter 2. Design and synthesis of "Bile Acid-Based Molecular Tweezers" Bile acids have a rigid backbone, and the array of hydroxyl groups separated by 5-7 A provides opportunities for the attachment of binding surfaces such as two extended chromophoric units.

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50

D'Souza, Lawrence Joseph. "Bile Acid Based Molecular Tweezers And Crown Ethers". Thesis, Indian Institute of Science, 1995. http://hdl.handle.net/2005/114.

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Abstract (sommario):

Chapter 1. Introduction to Molecular Tweezers Whitlock and Zimmerman developed a class of molecular hosts, popularly known as molecular tweezers, which sandwich aromatic guests by ii=ii interaction. Chapter 1 summarizes molecular tweezers of various kinds which have recently been synthesized. Chapter 2. Design and synthesis of "Bile Acid-Based Molecular Tweezers" Bile acids have a rigid backbone, and the array of hydroxyl groups separated by 5-7 A provides opportunities for the attachment of binding surfaces such as two extended chromophoric units.

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Tesi sul tema "Ethers"

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