Browsing by Subject "Metal ions -- Physiological transport"
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Item Synthesis and conformational studies of proton-ionizable polyethers(Texas Tech University, 1993-05) Kim, Jong SeungProton-ionizable lariat ethers are crown ethers (macrocyclic polyethers) which possess a pendent addic group (carboxylic add, sulfonic add, phosphonic acid). Compared with neutral crown ethers, the protonionizable lariat ethers have an important advantage that transfer of a metal ion into an organic medium in a separation process does not require concomitant transport of an aqueous phase anion. This factor is of immense importance for potential practical applications in which hard, hydrophilic aqueous phase anions, such as chloride, nitrate and sulfate, would be involved. Attachment of an alkyl group to the central carbon of the three-carbon bridge on the polyether ring in sym-dibenzo-16-crown-5- xyacetic acid gives rise to significant enhancement in the metal extraction selectivity. To explore the causative factors for this phenomenon, the synthesis of several series of proton-ionizable polyethers with structural variations which include the identity of the proton-ionizable group, the crown ether cavity size, and the length of the linkage which joins the proton-ionizable group to the polyether ring was undertaken. Synthetic strategies for the preparation of these proton-ionizable polyethers are described. Pre-organization of the binding site by intramolecular hydrogen bonding of the carboxylic acid function for sym-(R)dibenzo-16-crown-5- oxyacetic adds, where R is an alkyl, alkenyl, alk5myl or aryl group, in homogeneous solution has been studied by ^H NMR spectroscopy, which utilized 2-D techniques as well as solvent-dependent and temperature dependent measurements. Results of these conformational studies are supported by X-ray crystal structure determinations, as well as association constant measurements.Item Synthesis of cyclic and acyclic lipophilic complexing agents for metal ions(Texas Tech University, 1990-12) Whaley, Louis WayneNot availableItem Synthesis of mono- and dibenzocrown ethers with fluorinated or chromogenic substituents(Texas Tech University, 1999-12) Campbell, Martin JMacrocyclic polyethers (crown ethers) are known for their ability to bind metal cations within their central cavities. This allows crown ethers to be utilized in the separation and determination of metal ion species. Since their discovery in 1967, a number of structural modifications have been evaluated to enhance the performance of crown ethers in solvent extraction systems requiring high organic phase solubility coupled with low aqueous phase solubility to ensure extraction efficiency. In addition, the attachment of chromogenic side arms has enhanced their utility in the spectroscopic determination of metal ions. The advent of new extraction technologies, such as supercritical fluid extraction, and fluorous biphasic extraction systems, has brought about the need for crown ethers with enhanced solubility in these nontraditional solvents. Unrelated research has proven the high solubility of highly fluorinated compounds in these systems. Therefore, the synthesis of crown ethers with highly fluorinated side arms has been explored. The use of suitable protected and derivatized benzenes as starting materials made possible the development of a new series of dibenzocrown ethers which are ideally suited for incorporation of perfluoroalkyl groups and, potentially, for use in many other organic transformations. Substituted benzene moieties incorporating polyfluorinated tails were developed as precursors for the construction of other crown ethers. Methods for attaching highly fluorinated alkyl and aromatic groups directly to the polyether macroring were explored. Novel crown ethers with perfluorinated benzene side arms were prepared. Several mono- and dialcohols were prepared which contained both a traditional hydrocarbon alcohol unit and a perfluorocarbon chain remote from the alcohol functionality. These alcohols are expected to be useful building blocks for the construction of additional crown ethers in which partially fluorinated side groups are attached directly to the macroring. A new series of proton-ionizable lariat ethers with chromogenic side groups was developed. In these chromoionophores, the proton-ionizable chromogenic groups were attached to the macroring in a way previously unexplored. The interesting solution-phase and solid state geometries which resulted from this rigid, planar attachment were explored. These lariat ethers exhibited significant color changes under basic conditions.