Browsing by Subject "Crown ethers"
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Item Covalent attachment of 18-crown-6 to polystyrene(Texas Tech University, 1992-05) Knobeloch, John MNot availableItem Crown ether compounds: synthesis and alkali metal cation complexation(Texas Tech University, 1991-05) Goo, Mi-jaNOT AVAILABLEItem Design and synthesis of benzo-18-crown-6 carboxylic acids and diazadibenzo crown ethers and lariat ethers with neutral and proton-ionizable side arms(Texas Tech University, 2001-12) Kim, MyeongseobA series of proton-ionizable benzo-18-crown-6 lariat ethers has been prepared to probe the optimal host structure for a ferrioxamine B guest. Host-guest supramolecular assembly formation constants involving second-sphere complexation of the siderophore ferrioxamine B by a lariat ether carboxylic acid host were obtained from liquid-liquid extractions at high and low pH. The formation constant, Ka, determined at pH = 3.2 is compared to those from other lariat ether carboxylic acids of different chain lengths. These constants are similar to the parent crown ether. At pH = 9.3, the lariat ethers are ionized and this results in a more stable complexes. According to the comparison of formation constants at pH =9.3, an optimal host structure for the complexation of ferrioxamine B guest is determined. To study the complexation behavior of nitrogen containing macrocyclic ligands toward transition metal cations, series of diazadibenzocrown ethers and diazadibenzo lariat ethers with neutral side arms and proton-ionizable side arms were synthesized. Solvent extraction and membrane transport studies were performed with 1,13- diazadibenzo-15-crown-5, 1,13-diazadibenzo-18-crovra-6, 1,13-diazadi(?er^butylbenzo)- 18-crown-6 and l,13-diazadibenzo-18-crown-6 diester and showed that 1,13-diazadi (?ert-butylbenzo)-18-crown-6 and a l,13-diazadibenzo-18-crown-6 diester selectively forms complexes with Pb^2+ in the presence of Cd^2+ and Zn^2+.Item Immobilization of lariat ether carboxylic acids on polystyrene(Texas Tech University, 1996-08) Corley, Leo JamesThe research presented in thesis has three objectives. The first objective was to obtain a synthetic route which would allow the linkage of proton-ionizable crown ethers to commercially available, flinctionalized polystyrene. The proton-ionizable crown ethers used in this research could not be directly attached to chloromethylated polystyrene. Therefore an appropriate intermediate had to be incorporated prior to crown ether attachment. The second objective was to determine the characteristics of the base resin which allow the greatest degree of alkali metal cation binding. Structural characteristics of the base resin include the degree of crosslinking and extent of chloromethylation. These two factors could play a very significant role in the metal cation sorption ability of the various crown ether-coupled polystyrene resins. The final objective was to determine if the polymer bound proton-ionizable crown ethers maintained the metal ion binding abilities of the corresponding non-polymeric proton-ionizable crown ethers.Item Lariat ethers in silver-selective polymeric membrane electrodes(Texas Tech University, 1995-08) Liu, YiThere have been many studies of crown compounds as neutral carriers of ion-selective electrodes. The investigations of these complexing agents have focused mainly upon obtaining high affinity and selectivity for given metal ions. When considering the coordination features of heavy metal cations such as Ag+, it is known that soft donor atoms in the host lonophores are more effective than just hard atom donors based on the hard-soft acid and base (HSAB) concept. One aspect of this thesis is to investigate the influence of nonionizable side arm which contain soft atom donor sites in sym-dibenzo- 16-crown lariat ethers upon their complexation and selectivities for silver ion versus alkali, alkaline-earth, transition, and heavy metal cations in solvent polymeric membrane electrodes. The second goal of this thesis is to obtain highly efficient Ag+ selective lonophores.Item Metal ion complexation and separation by crown ether compounds(Texas Tech University, 1996-12) Eley, Mark DwightThe objective of this research is to probe the influence of structural variations within macrocyclic multidentate ligands upon their interactions with metal ions. For this evaluation mono-, bi-, and triphasic experimental systems will be utilized. The biphasic (picrate extraction technique) and the triphasic (bulk liquid membrane transport technique) systems all employ neutral ligands. The monophasic system (titration calorimetry) uses proton-ionizable lariat ethers.Item Metal ion complexation by acyclic and cyclic multidentate ligands(Texas Tech University, 1999-08) Elkarim, Nazar Saied AwadThe objective of this work is to evaluate the different factors that dictate the binding ability of multidentate polyether ligands towards alkali metal and some heavy metal cations with special emphasis on crown ether compounds. The evaluation will involve the use of different analytical techniques, such as solvent extraction, ion-selective electrodes and fluorometry. A primary objective is to investigate the influence of structural variations within a crown ether compound upon the selectivity and efficiency of alkali metal cation extraction. The research will involve a series of new crown ethers with different ring sizes containing multiple benzo or cyclohexano groups in the polyether ring. The conventional picrate extraction method will be used and the results will be compared with those from other more sophisticated extraction methods. Other factors (solvent and anion effects) that influence the complexing ability of crown ethers in solvent extraction will be probed. Assessment of anion and solvent effects on the extraction efficiency and selectivity by a series of crown ether compounds with varying ring sizes will be conducted. The complexing ability of crown ethers will also be evaluated in solvent polymeric membrane electrodes. Crown ethers will be incorporated as active components in PVC-matrix type membrane electrodes and their selective binding towards alkali metal cations will be tested. Special attention will be paid to Na selective ligands due to the importance of this cation in the field of medicine. Solvent extraction will be performed with lipophilic pseudocyclic polyether dicarboxylic acids. In solvent extraction, these ligands do not require concomitant transfer of the aqueous phase anion into the organic phase. The ligands are known to have good binding ability towards Pb(n) which is an environmentally hazardous metal cation. A supplementary study will be performed to evaluate the stoichiometrics of Pb(II) and Cu(II) complexes formed with these ligands. The final part of this work will be contribution to the growing field of chemosensors. A new calixarene-based fluorogenic reagent for selective Hg(II) recognition will be tested as a prospective chemosensor.Item Metal ion complexation, extraction and transport by crown and lariat ether compounds(Texas Tech University, 1997-08) Lu, JianpingA wide variety of crown ethers have been employed for alkali and alkaline earth metal cation separations due to their superior binding ability for these metal ions. Lariat ethers are crown ethers with one or more donor-groupbearing arms. Attachment of one or more side arms with potential metal ion coordination sites to a crown ether framework may enhance metal selectivity. To investigate the influence of nonionizable side arms upon the complexation of alkali metal cations by lariat ethers, solvent polymeric membrane electrodes containing the lariat ethers as ionophores were utilized. For dibenzo-16-crown-5 lariat ethers, Na* selectivity over other alkali and alkaline earth metal ions was enhanced by increasing the basicity of an oxygen atom in the side arm and by preorganizing the metal ion binding site through attachment of a hydrocarbon group geminal to the oxygen-containing side arm. The effect of structural variation within N-(R) sulfonyl lariat ether carboxamides upon the extraction efficiency and selectivity was explored in solvent competitive extraction. Very high Na* selectivity and extraction efficiency were achieved for N-(R)sulfonyl sym-(alkyl)dibenzo-16-crown-5-oxyacetamides. N-(R)sulfonyl lariat ether carboxamides were used also as metal ion carriers for transport across polymeric inclusion membranes. For N-(R)-sulfonyl syA77-(alkyl)dibenzo-16-crown-5-oxyacetamides, high Na* transport selectivity was noted. The flux was influenced by R variation. Also the flux was proportional to the diffusion coefficient of the complexed lariat ether in the membrane.Item Metal ion separations by acyclic and cyclic polyethers and their polymers(Texas Tech University, 1994-12) Hankins, Matthew G.The serendipitous discovery by Charles J. Pedersen'^ that cychc polyether compounds, such as dibenzo-18-crown-6 (Figure l.lf), possess specific cation complexation capabihties catalyzed an avalanche of synthetic efforts to estabhsh novel polyether compounds which could be utilized for complexation of a wide variety of metal ions. The field progressed to include not only cychc polyether compounds, but also bicyclic, tricychc and other related three-dimensional structures. In 1987 the Nobel prize was jointly awarded to D. J. Cram, J.-M. Lehn, and C. J. Pedersen^ for their achievements in this area of host-guest chemistry. Polyether metal ion chelates, both cychc (crown ethers) and pseudocychc (podands) have been apphed in organic synthesis, metal ion separation processes, and analytical chemistry. As phase transfer catalysts, crown ethers and related compounds have provided an additional tool to the organic chemist for dual phase synthesis. Thus, the facile transfer of reactive salts, such as KMn04, into the organic phase may be performed with polyether compounds. A variety of analytical methods, primarily for the determination of Groups 1 and 2 metal ions, but also for the detection of heavy metal ions and anions, have been developed which incorporate crown ether hgands. Selective chromogenic agents for the colorimetic determination of alkah and alkaline earth metal ions have potential for apphcation in environmental and clinical laboratories. The principle by which these ligands fimction is a color change that occurs upon complexation with the metal ion. Molecules of this type generally have a side arm that mteracts with the bound metal ion and perturbs molecular conjugation. The superior complex stabihty of certain aza-crown ethers for Ca has enabled these polyether hgands to be used effectively as masking agents for the determination of other less concentrated metal ions in water. ^ In research for which the primary objective is the development of ion-selective electrodes, polyether hgands are a primary source of lonophores due to their selectivity and resihence. A promising analytical apphcation of crown ether compounds is in chromatography. Cation and anion separations may be performed with water, methanol or aqueous methanol eluents on columns packed with polystyrene or sihca gel-bound neutral polyether hgands. Good resolution of alkah metal saks has been demonstrated by sihca gel-bound benzo-15-crown-5.'^ Tliese separations are unique since conductivity detection may be used without the requirement for background suppression.Item Metal ion separations by proton-ionizable macrocyclic and acyclic polyether ligands(Texas Tech University, 2000-08) Amiri-Eliasi, BijanNot availableItem New syntheses of crown and proton-ionizable lariat ethers(Texas Tech University, 1999-05) Hanes, Robert E.Macrocyclic polyethers (crown ethers) are known for their ability to bind metal ions within their central cavities. This allows crown ether compounds to be utilized in the separation and determination of metal ion species. Traditional routes for crown ether synthesis often give only low yields due to competitive cyclization and oligomentation reactions. The efficacy of cesium-assisted cyclizations for the preparation of lipophilic benzocrown ether compounds and of di-, tri-, and tetrabenzocrown ethers has been explored. In the synthesis of lipophilic benzocrown ethers by cesium-assisted cyclizations, the desired [1+1] cyclization products were found to be contaminated with corresponding [2-1-2] adducts. The influences of reactant concentrations, stirring method and rate, reactant addition method and rate, and leaving group identity were investigated to determine optimized conditions for formation of the highest possible proportion of the [l + l] adduct in the product mixture. For formation of 18-membered rings or larger, the synthesis of di-, tri-, and tetrabenzocrown ether compounds by cesium-assisted cyclizations produced only the desired [1+1] adducts in good-to-excellent yields. These results provide insight into the nature of the "cesium effect" in cylization reactions. Solid-state structures for several of the benzo group-substituted crown ether compounds and for one crown ether-metal salt complex have been determined. Alkali metal cation binding selectivity for the lipophilic benzocrown ether compounds was assessed by solvent extraction and with solvent polymeric membrane electrodes. For use in the study of ring size effects upon the efficiency and selcctivity of alkali metal cation complexation by proton-ionizablc lanat ethers (crown ethers with an attached arm bearing a teminal acidic group), a series of N-(X) sulfonyl sym-(dccyl)diben/o-13-crown-4-oxyacctamides was prepared. In this series, variation of X is used to "tunc" the acidity of the pendant acidic function.Item Synthesis and metal cation separation of chelating polymers containing crown ether units(Texas Tech University, 1995-05) Zhao, QiangEach of the three parts of this dissertation research involves organic synthesis, monomer polymerization and polymer characterization, analytical chemistry and host-guest chemistry. The overall goal is to synthesize several different types of novel monomers and polymers which contain crown ether units and then study their complexation behavior with metal cations by sorption measurement, liquid-liquid or liquid-solid extraction or membrane transport techniques. The types of crown ether polymers described in the dissertation include formaldehyde condensation crosslinked resins, linear styryl-type polymers and polyamides. In the first part of the research, the influence of adding alkali-metal cations in the formaldehyde polymerization of dibenzo polyethers was investigated. It was found that cation complexation of the dibenzocrown ether monomer diminished the efficiency of the polymerization process, neutral crown ether resins and crown ether carboxylic acid resins with different levels of crosslinking were also prepared and their alkali-metal ion sorption efficiency and selectivity have been studied. Lastly, formaldehyde dibenzo- 18-crown-6 resins with varying levels of phosphonic monoacid and diacid group substitution were also prepared. The effect of the identity and level of the phosphonic acid groups on alkali-metal cation sorption by the resins was investigated. The second part of the research in the dissertation was the synthesis of some novel linear styryl-type crown ether polymers, some of which include ion-exchange sites in the polymer structure. The influence on metal picrate extractions for variation of the crown ether substituent group, side arm and spacer group between crown ether unit and polymer backbone in the polymers was studied. Factors, including the introduction of crown ether units and preorganization of the ion-exchange site relative to crown ether cavity, were also examined with regard to their effects on the metal cation sorption behavior of the ion-exchange crown ether polymers. The final part of the research in the dissertation involves the synthesis and characterization of a number of novel crown ether polyamide esters and acids. The crown ether units were incorporated within the polymer backbones. Some of the prepared polyamides could be cast to form mechanically strong membranes. This feature is crucial for potential applications in industry. Alkali-metal cation sorption by the crown ether polyamide acids and transport of alkali-metal cations across crown ether polyamide carboxylic acid membranes were investigated.Item Synthesis and metal ion sorption by proton-ionizable, acyclic and cyclic polyether resins(Texas Tech University, 1994-12) Laney, Evelyn E.In 1967 Pedersen published the first of four fundamental papers on the synthesis and properties of macrocyclic polyether compounds. 1 "4 This class of compounds was discovered by accident during the preparation of bis-(<9-hydroxyphenoxy)ethyl ether (1) by reaction of bis chloroethyl) ether with the sodium salt of o-hydroxyphenoxytetrahydropyran followed by acid hydrolysis. Along with the anticipated product 1, Pedersen isolated a small quantity of a by-product. Investigation into the structure of the byproduct identified the compound as macrocyclic polyether 2 which was formed by the cyclic condensation of 2 moles of unprotected catechol, a small amount of which was present in the reactant, with 2 moles of bis(chloroethyl) ether.Item Synthesis and modeling of crown ethers(Texas Tech University, 2003-08) Gwyn, Angela ChristineNot availableItem Synthesis of crown and lariat ether compounds(Texas Tech University, 1996-05) Ivy, Sheryl N.The following thesis describes the design and synthesis of crown and lariat ether compounds for two purposes. The first objective is to compare a synthetic route to dibenzocrown ethers with a method developed earlier by J. C. Lee. The second goal is to synthesize a new type of proton-ionizable lariat ether. To access the degree that starting materials affect crown ether yields in cesium ion-assisted cydizations, a synthetic route developed by Lee will be followed with different combinations of reactants. The effect on yield will be examined.Item Synthesis of lariat ethers with proton-ionizable and non-ionizable side arms and their acyclic analogues(Texas Tech University, 1995-05) Jang, YoungchanLariat ethers are crown ethers (macrocychc polyethers) which have one or more donor-group-bearing side arms. Functionalization of crown ethers by addition of a pendent ann(s) substituted v^th a proton-ionizable group(s) or non-ionizable donor group(s) is an effective method to improve the metal ion binding ability and selectivity of crown ethers due to the extra coordination sites. To study the nature of the polyether unit (i.e., acychc or cychc) upon the efiSciency and selectivity of metal ion complexation, the synthesis of acyclic polyethers which have two proton-ionizable side arms was performed. Several series of proton-ionizable lariat ethers with structural variations which include the crown ether ring size, length of the linkage which joins the acidic fimction to the crown ether ring, and the identity of the proton-ionizable group were prepared. For the lariat ether carboxyhc acids, dibenzo-16-crown-5, dibenzo-19-crown-6, tribenzo-19-crown-6, and benzo-18-crown-6 compounds were synthesized. Investigations of metal ion complexation behavior of these lariat ether carboxyhc acids and their polymers, which were prepared by their reaction with formaldehyde condensation in formic acid, have been undertaken.Item Synthesis of lipophilic acid crown ethers(Texas Tech University, 1987-05) Robison, Thomas WayneNot availableItem Synthesis of neutral and proton-ionizable crown ethers(Texas Tech University, 1990-05) McDonough, Joseph AloysiusCyclization studies show that the CS2CO3 instigated reaction of the dimesylate of triethyleneglycol with 2,2'-bis[4(5)-tert-butyl-6- hydroxyphenoxy]-ethyl ether in MeCN is the best available method for preparation of sym-di[4(5)-tert-butylbenzo]-21 -crown-7. The lipophilicity and substitution pattern of hydrocarbon substituents are varied in a series of novel lipophilic 18-crown-6 compounds. Two synthetic methods are used. The first involves cyclization of a functionalized primary bis-hydroxy intermediate with its ditosylate. The second method implements a DMF-THF(4:1) solvent mixture to facilitate the cyclization of functionalized vicinal diols with the ditosylates of polyethylene glycols. The synthesis of a series of proton-ionizable crown ethers is described, lonizable pendant arms are attached by alkylation and subsequent hydrolysis, if appropriate, of hydroxy- and (hydroxymethyl)crown alkoxides with BrCH2C02H, BrCH2C02Et and CH2=CHCN. The (hydroxymethyl)crown ethers are derived by hydroboration-oxidation of novel vinylidene crown ethers, which are produced by cyclization of methallyl dichloride and bisphenols. A series of proton-ionizable azacrown ethers are synthesized by incorporation of a tosylaza group into a bisphenol that is cyclized with epichlorohydrin. The N-tosyl hydroxycrown ethers are then alkylated with BrCH2C02H or BrCH2C02Et. The ring nitrogen is alkylated with bromodecane in one compound and with BrCH2C02Et in another. Two di(proton-ionizable) crown ethers are prepared by alkylation of a primary amine substituted dibenzo-16-crown-5 with 2 equivalents of BrCH2C02Et followed by basic hydrolysis.Item Synthesis of new crown ether compounds(Texas Tech University, 1999-05) Zhang, QianIn 1967, Pedersen published the first practical synthesis of a variety of cyclic polyether compounds and assessed their complexation abilities for alkali and alkaline-earth metal ions. As shown in Equation 1.2, when Pedersen tried to prepare bisphenol 4 from bis(2-chloroethyl) ether and monotetrahydropyranylprotected catechol, which was contaminated with 10% of unprotected catechol, a small amount of white crystalline solid with a silky, fibrous nature was obtained as a by-product. The structure of this by-product was deduced to be crown ether 5 by elemental and mass spectroscopic analysis. Pedersen found that the yield of crown ether 5 could be increased to 45% when pure catechol was utilized as a reactant. Subsequently Pedersen prepared more than 60 macrocyclic polyethers and investigated the formation of complexes between the cyclic polyethers and metal salts. For his work, Pedersen together with Cram and Lehn was awarded the 1987 Nobel Prize in Chemistry.Item Synthesis of new ligands for metal ion complexation(Texas Tech University, 2001-05) Zhao, QingxiangThe ability of crown ethers to selectively bind alkali and alkaline earth metal cations was discovered in 1967 and tremendous developments in this field have been achieved to date. Many dibenzocrown ethers with a substituent on each benzo unit have been obtained and investigated in various studies as mixtures of regioisomers. Since the regioisomers may have different complexing properties, a synthetic route has been developed in this thesis to prepare disubstituted dibenzocrown ethers in which the two substituents are in specific positions. Allyl groups were incorporated into these disubstituted dibenzocrown ethers which can be utilized for further transformation. Nuclear waste treatment is an important and worldwide problem. Recently, interest in applying tridentate organophosphoryl ligands to separate actinides from nuclear waste arose. A synthetic intermediate to these tridentate ligands was synthesized in this thesis with a much improved yield from previous work. In solvent extraction of actinides, long chain carboxylic acids have been used as co-extractants with crown ethers and were found to enhance the extraction efficiency and selectivity. A highly lipophilic carboxylic acid was prepared on large scale to be utilized in actinide extraction. Calixarenes were developed in the late 1970's and have been investigated as complexing ligands for molecular, cationic and anionic species. However, p-t-butylcalix- [4]arene, the most widely studied calixarene, and its derivatives have limited solubility in organic solvents. A series of calix[4]arenes with r-octyl groups as the para substituents were synthesized and increased solubility in organic solvents was observed.