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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.

Intramolecular bifunctional catalysis of the racemization of phenyl benzenethiosulfinate /

Moguin, Alan Lathrop. January 1969 (has links)
Thesis (M.S.)--Oregon State University, 1969. / Typescript. Includes bibliographical references (leaves 59-67). Also available on the World Wide Web.

Studies of racemization rates in solvents of intermediate dielectric constant

Morgan, Lyman Wallace 08 1900 (has links)
No description available.

Relative rates of base-catalyzed racemization and deuterium exchange of aryl 2-octyl sulfones stereochemistry of the acetolysis of endo-Bicyclo-[2.2.2]-oct-5-en-2-yl p-Toluenesulfonate.

Towns, Donald Lionel, January 1963 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 85).

Synthesis, clathrate inclusion properties and racemization studies of Benzo-fused tetraphenylenes.

January 1988 (has links)
by Yuet-ming Man. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1988. / Bibliography: leaves 49-52.

Ion-pair return associated with the solvolysis of [alpha]-methyl-[gamma]-phenylallyl p-nitrobensoate in aqueous acetone

Linday, Ernest Charles, January 1968 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Pacific and Atlantic coast mollusk shells chromatographic amino acid racemization kinetics and interlaboratory comparisons /

Bakeman, Valerie R.. January 2006 (has links)
Thesis (M.S.)--University of Delaware, 2006. / Principal faculty advisor: John F. Wehmiller, Dept. of Geological Sciences. Includes bibliographical references.

Studies in peptide synthesis

Antonovics, Ieva January 1965 (has links)
No description available.

Racemization of amino acids in wood: experimental results, problems, and perspectives

Engel, Michael H. January 1976 (has links)
No description available.

Mechanistic Investigations of Gold(I) Catalyzed Hydrofunctionalizations of C-C Multiple Bonds

Harris, Robert Joseph January 2015 (has links)
<p>Cationic gold(I) complexes containing phosphine and N-heterocyclic carbene based ligands are a powerful catalysts for the hydrofunctionalization of C-C multiple bonds with carbon and heteroatom based nucleophiles as well as the cycloisomerization of enynes and related &#960;-systems. Mechanisms involving outer sphere, nucleophilic attack an activated gold &#960;-complex are typically invoked for both hydrofunctionalizations and cycloisomerizations, however, direct experimental evidence for these mechanisms remain limited.</p><p>Gold(I) catalyzed allene racemization is an important background reaction in the hydrofunctionalization of 1,3 disubstituted allenes. It can compromise chirality transfer or be exploited to realized stereoconvergent synthesis of allylic alcohols and amines. The kinetics of the racemization of aromatic 1,3-disubstituted allenes catalyzed by gold(I) phosphine complexes has been investigated. The rate of racemization displayed first order dependence on allene and gold concentration. Kinetic analysis gold(I) catalyzed racemization of allenes as a function of allene and phosphine donor ability established a depletion of electron density on the terminal allene carbons and an accumulation of electron density on the phosphine ligand in the rate-limiting transition state.</p><p>Investigation of the mechanism of gold(I) catalyzed hydrofunctionalization of allenes with alcohols, carbamates, and anilines established a variable catalyst resting state depending on the equilibrium binding affinities of the nucleophile and the relative concentrations of allene and nucleophile that are employed. Reversible C-X bond formation may explain the difference in regioselectivity observed for hydroalkoxylation and hydroamination with carbamates. Additionally, in situ analysis of the hydrofunctionalization of enatiopure 1,3-disubstituted allenes for enatiopurity of the allene and product ruled out trapping of an achiral &#951;1-intermediate and established concomitant allene racemization as the cause of loss of enatiopurity.</p><p>Finally we report the two gold(I) carbene complexes not stabilized by &#960;-conjugated heteroatoms. First, we report the hydride abstraction from a neutral gold cycloheptatrienyl complex that was isolated and characterized in solution and by single crystal X-ray diffraction. This complex represents the first example of a gold carbenoid complex that lacks conjugated heteroatom stabilization. Second we report the synthesis of the first gold(I) vinylidene via hydride abstraction from a gold (disilyl)ethylacetylide complex to form a cationic &#946;,&#946;-disilacyclopentyl vinylidene complex. The C1 and C2 carbon atoms of the vinylidene complex underwent facile interconversion presumably through the gold &#960;-disilacyclohexyne.</p> / Dissertation

Synthesis of (S,R,S)- and (R,S,R)-1,4,5,8,9,16- hexahydroxytetraphenylenes. / CUHK electronic theses & dissertations collection

January 2006 (has links)
*Please refer to dissertation for diagrams. / In addition, a precursor of tetraphenylene-based monodentate ligand ( S,S)-114 was also prepared, and the structures of five compounds, namely 89, 124, 125, 133 and 137 were examined by X-ray crystallographic analysis. These structural determinations were relevant in establishing regiochemistry and absolute stereochemistry.* / In the synthesis of enantiopure (S,R,S)-48 and (R,S,R)-48, two routes were successfully employed. One way was to follow the same pathway for the synthesis of racemic 48 by using enantiopure (S,S)- and (R,R)-1,8,9,16-teramethoxytetraphenylenes [(S,S)-89 and (R,R)- 89] as staring materials. Another way was by direct resolution of racemic 48 via derivatization into its two diastereomeric hexakis-(S)-camphorsulfonates 135 and 136. / In the synthesis of racemic 48, 3-nitrophenol (115) was employed as the starting material which upon a series of standard reactions provided 2,2'-diiodo-1,1'-biphenyl (119). Through sequential lithium-iodine exchange and Cu(II)-mediated oxidative cyclocoupling, 119 was converted to 1,8,9,16-tetramethoxytetraphenylene (89) . The key intermediate 1,8-dihydroxy-9,16-dimethoxytetraphenylene (87) was obtained by partial demethylation of 89. This intermediate was transformed to 1,4,5,8-tetrahydroxy-9,16-dimethoxytetraphenylene (126) by a quinone-hydroquinone strategy. Demethylation of 126 furnished the target compound 48. / This thesis describes the synthesis of 1,4,5,8,9,16-hexahydroxytetraphenylene (48)* in its racemic and enantiopure (S,R,S) and ( R,S,R) forms. Some essential background and previous works in this area are presented in the first chapter. / Wu Anhui. / "August 2006." / Adviser: Henry N. C. Wong. / Source: Dissertation Abstracts International, Volume: 68-03, Section: B, page: 1649. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 80-85). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

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