Browsing by Subject "Radicals (Chemistry)"
Now showing 1 - 12 of 12
Results Per Page
Sort Options
Item Ion radical cycloadditions and the synthesis of novel, electron-rich polymer structures(2002) Roh, Yeonsuk; Bauld, Nathan L.The aminium salt initiated cation radical chain cycloaddition polymerization of various oxygenated difunctional monomers is investigated in order to minimize a limiting factor, a competing carbocation pathway, by applying a dichloromethane/water binary solvent mixture. Polymerizations have also been initiated by electrochemical oxidation and photosensitized electron transfer. The synthesis of cation radical cycloaddition polymers of difunctional carbazole monomers which contain reactive trans-1-propenyl groups for polymerization in the N-, 3- or 6- positions of carbazole, is presented. All polymers containing carbazole units in the polymer main chain show good solubility in halogenated organic solvents, high molecular weights, and high thermal stabilities. The reaction appears to proceed via a highly efficient cation radical chain mechanism which circumvents the usual hole transfer step of the propagation cycle. This polymerization represents the first observation of direct cation radical Diels-Alder cycloaddition polymerization and affords a novel polymer structure. The cation radical Diels-Alder cycloadditions of monofunctional, highly electron-rich substrates such as N-(trans-1-propenyl)carbazoles and N-phenyl-3- (trans-1-propenyl)carbazole to generate monomers of interest in connection with ring-opening metathesis polymerization are also presented. The cycloadditions of various electron-rich monomers to 1,3-cyclopentadiene efficiently generate norbornene monomers, which readily undergo ring-opening metathesis polymerization to yield electron rich polymers. Both ring-opened homopolymers and copolymers containing carbazole groups are synthesized. In addition, investigations of photorefractive effects resulting from a combination of photoconductive and electro-optic effects (change in refactive index in response to an electric field) in composites which utilize new carbazolecontaining polymers as charge transport components are carried out, and their photorefractive performances are compared with the performance of the standard composites based upon poly(N-vinyl carbazole). Finally, some studies of anion radical chain cycloadditions of tethered enones by cathodic reduction, which involve intramolecular anion radical cyclobutanation and unprecedented Diels-Alder cycloaddition, are reported. Evidence for stepwise cycloaddition involving distonic anion radical intermediates has been illustrated.Item Isolation of Phenoxathiin cation radical Perchlorate and the study of its Chemistry(Texas Tech University, 1976-08) Mani, Serugudi R.The present study was undertaken to investigate the chemistry of phenoxathiin cation radical perchlorate. Work with the phenoxathiin cation radical in the past has been confined mainly to characterization by ESR spectroscopy, while its chemistry has gone largely unexplored. Although the cation radical can be prepared quite easily in solution, the use of these solutions to study its chemistry is usually complicated by several factors. It is desirable therefore to isolate the cation radical as a stable solid and then to investigate its chemistry in homogeneous solution. The purpose of this dissertation is to describe the method of making crystalline phenoxathiin cation radical perchlorate and to explore the reactions of the cation radical with various nucleophiles.Item Oxidative decomposition reactions of azoalkanes(Texas Tech University, 1990-05) Robertson, Donald TsuyoshiNot availableItem Radical and radical cation chemistry of azoalkanes and oximes(Texas Tech University, 1990-05) Lee, Wang-keunNot availableItem Reactions induced by cation radicals and studies of oxidation of o-nitrobenzeneselenenyl compounds(Texas Tech University, 1988-12) Chiou, ShishueNot availableItem Reactions of Thianthrene cation radical perchlorate with nucleophiles(Texas Tech University, 1975-08) Kim, KyongtaeNot availableItem Study of 10-methylphenothiazine cation radical chemistry.(Texas Tech University, 1975-08) Padilla, Amphlett GregNot availableItem Study of Thianthrene cation radical chemistry(Texas Tech University, 1972-05) Silber, Juana Josefa ChessaNot availableItem The chemistry of 10-phenylphenoxazine cation radical perchlorate(Texas Tech University, 1977-05) Wu, Shi-MingPhenoxazine cation radicals had been made as early as 1902, when Kehrmann oxidized phenoxazine with bromine in benzene and with ferric chloride in glacial acetic acid, but Kehrmann had no way of knowing that the phenoxazine cation radical was formed. It was not until the advent of esr spectroscopy that chemists rediscovered these reactive intermediates and characterized them spectroscopically by esr and electronic absorption spectroscopy. In the last decade, cation-radical chemistry has been studied rather extensively as cited in the most recent review. In the case of 10-phenylphenoxazine cation radical, only a few spectroscopic characterizations have been published, and the nature of the cation-radical chemistry is fully unexplored. It is the main goal of this investigation to study the nucleophilic substitution reactions of 10-phenyJ phenoxazine cation radical perchlorate with a variety of nucleophiles, and to recognize the competition between nucleophilicity and oxidizability of a nucleophile in reaction with cation radical species. Throughout the course of this study, there was an attempt to compare the chemical reactivity of 10-phenylphenoxazine cation radical with other well-studied heteroaromatic cation radicals, especially its structural analogue: 10-phenyphenothiazine cation radical.Item The chemistry of dibenzo-p-dioxin cation-radical(Texas Tech University, 1973-12) Shade, LewisNot availableItem The reaction of aromatic cation radicals with fluoride ion(Texas Tech University, 1981-05) Stephenson, Michael ThomasNot availableItem The use of bulky ligands for the stabilization of group 15 radicals and cations(2002-05) Wiacek, Robert Johnny; Cowley, Alan H.A variety of bulky ligands have been utilized for the stabilization of group 15 radicals and cations. The molecular structures of the stable phosphinyl and arsinyl radicals, • PnR2 (Pn = P, As; R = CH(SiMe3)2), have been determined by gas-phase electron diffraction (GED) in conjunction with ab initio molecular orbital calculations. The X-ray crystal structures of the corresponding dipnictines, the "dimers", R2PnPnR2, and the corresponding chloro derivatives R2PnCl have also been determined. Collectively, these gas-phase and solid-state structural investigations demonstrate that large distortions of the ligands attached to phosphorous and arsenic occur when the pnictinyl radicals unite to form the corresponding dipnictine dimers. Theoretical studies indicate that in the process of pnictinyl radical dimerization, the molecules accumulate substantial amounts of potential energy and are thus primed to spring apart upon release from the solid state by melting, dissolution, or evaporation. The first example of group 15-containing “constrained geometry” complexes, [Me2Si(η-C5Me4)(N-t-Bu)]PnCl (Pn = P, As, Sb), have been prepared and isolated. In the case of the chlorophosphine, [Me2Si(η-C5Me4)(N-t-Bu)]PCl, an unprecedented shift of the µ-SiMe2 group from the ipso to the α-position on the Me4C5 ring occurs. Treatment of [Me2Si(η-C5Me4)(N-t-Bu)]PnCl (Pn = P, Sb) with AlCl3 results in chloride ion abstraction and formation of the pnictocenium salt, {[Me2Si(η-C5Me4)(N-t-Bu)]Pn}{AlCl4}. The structures of these salts were established by X-ray crystallography. The chloropnictines (η-C5Me5)2PnCl (Pn = As, Sb, Bi) have been synthesized and structurally characterized, and exhibit the expected periodic trend toward increased multihapto bonding with increasing atomic number. The arsenocenium and stibocenium tetrachloroaluminates salts were prepared by chloride anion abstraction from the precursor chlorides and the structures of the cations in these salts were found to be different than those in previously reported examples.