• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 258
  • 50
  • 25
  • 19
  • 10
  • 10
  • 10
  • 10
  • 10
  • 10
  • 4
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 431
  • 431
  • 96
  • 77
  • 60
  • 50
  • 49
  • 48
  • 44
  • 41
  • 38
  • 37
  • 31
  • 29
  • 25
  • 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.
101

Study of factors affecting the synthesis of carbon nanotubes by spray pyrolysis

Xiao, Jiajia, January 2007 (has links)
Thesis (M.S.)--University of Texas at El Paso, 2007. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.
102

Half-sandwich ruthenium (II) complexes of 1,3,5-triaza-7-phosphaadamantane syntheses, reactivity, and catalytic application /

Assoua, Mebi Charles. January 2007 (has links)
Thesis (Ph. D.)--University of Nevada, Reno, 2007. / "May, 2007." Includes bibliographical references. Online version available on the World Wide Web.
103

Factors affecting the photodegradation rates of polymers that contain (-C₅H₄(CO)₃Mo-Mo(CO)₃C₅H₄-) in the backbone /

Daglen, Bevin Colleen, January 2008 (has links)
Thesis (Ph. D.)--University of Oregon, 2008. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 131-143). Also available online in Scholars' Bank; and in ProQuest, free to University of Oregon users.
104

The chemistry of triosmium alkylidyne carbonyl clusters /

Wong, Wai-yeung. January 1995 (has links)
Thesis (Ph. D.)--University of Hong Kong, 1995. / Includes bibliographical references (leaf 320-343).
105

Preparation and reactions of alkyl- and arylpentacarbonyltungsten anions

Polichnowski, Stanley Whitmore. January 1977 (has links)
Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 270-278).
106

Electronic properties of cyclopentadienyl ytterbium complexes ; Copper (1) complexes as synthetic precursors to cadmium sulfide/curprous sulfide photovoltaic cells

Schlesener, Connie Joann. January 1982 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
107

Aryloxy tungsten-based classical catalytic systems and group 14 metal-containing dienes in acyclic diene metathesis polymerization /

Gómez, Fernando José, January 2000 (has links) (PDF)
Thesis (Ph. D.)--University of Florida, 2000. / Printout. Vita. Includes bibliographical references (leaves 150-156). Also available on the World Wide Web; PDF reader required.
108

Vibrational spectroscopy of immobilized cobalt and rhodium carbonyls used to effect the catalytic hydroformylation of propylene

Woo, Seong Ihl. January 1983 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. Includes bibliographical references (leaves 467-476).
109

Synthesis of viridamine analogues for use in selective metal complexation studies

Caddy, Judy 24 November 2011 (has links)
M.Sc. / The aim of this project was the synthesis of viridamine analogues, to be used for selective metal complexation. This, therefore, required the synthesis of diketopiperazines, containing an imidazole-type side chain. The imidazole functionality was introduced into the synthesis via peptide acid coupling reaction between histidine and another amino acid. Before any coupling reactions were possible it was necessary to protect the carboxylic acid functionality of one of the two amino acids being used and the amine functionality of the other. This was to prevent mixed products forming. Owing to the continued difficulty at achieving selective N-protection of histidine, it was decided to make use of the corresponding methyl ester instead. After some initial attempts, it was found that the methyl ester of histidine, which was bought as the dihydrochloride salt, could be readily coupled to a variety of Boc protected amino acids. The Boc protected amino acids could be prepared under various conditions using di-tertbutyl dicarbonate. A range of conditions was investigated for the coupling of the two amino acids, i.e. the histidine methyl ester dihydrochloride and a Boc protected amino acid. Successful coupling was finally achieved using tetrahydrofuran as solvent, N-hydroxy benzotriazole as reaction promoter, N-methyl morpholine as a base and dicyclohexylcarbodiimide as the coupling agent. After varying the reaction conditions the optimised reaction conditions gave yields in the region of 76%. Once coupling had been achieved, it remained to cyclise the dipeptide. Cyclisation was preceded by the removal of the Boc protecting group either in situ or in a two step process. In the absence of the imidazole functionality, removal of the Boc group was readily achieved using trifluoroacetic acid. However, attempted deprotection of dipeptides containing the imidazole functionality led to decomposition of the dipeptide under identical conditions. It was therefore necessary to find an alternative form of deprotection. This was found in the form of formic acid, which proved to be successful in removing the Boc group and in effecting cyclisation to the analogous diketopiperazine. This particular form of in situ cyclisation proved to be very low yielding. This problem was circumvented by following the formic acid treatment by a period of reflux in a toluene I 2-butanol mixture. Cyclisation was effected with pure products being obtained in high yield, after column chromatography. Complexation reactions were initiated with the synthesised diketopiperazines but unfortunately no X-Ray diffraction studies could be carried out, due to the formation of amorphous solids instead of crystalline materials.
110

The influence of ligands and co-catalysts on selected catalytic transformations

Bredenkamp, Tyler 21 November 2011 (has links)
M.Sc. / There were two main objectives of the research presented m this dissertation. Firstly, the synthesis of bulky electron withdrawing phosphine-alkene ligands for classic ligand testing in the Suzuki cross-coupling reaction was performed. Previously, a range of electron deficient phosphine-alkenes was prepared from 2- ( diphenylphosphino )benzaldehyde, using both Wittig and Knoevenagel chemistry. These were tested for catalysis and gave high yields for the Suzuki reaction. In the present instance, 2-( di-otolylphosphino) benzaldehyde was synthesised making use of Grignard technology from acetyl protected 2-bromobenzaldehyde and chloro(di-o-tolyl)phosphine (itself prepared from PCh. And the appropriate o-tolyl Grignard reagent. This material served as a building block for the generation of P-alkene ligands which were synthesised making use of Wittig, Knoevenagel and transesterification chemistry. These o-tolyl analogues of the P-alkene ligands prepared in the previous study were used in ligand testing experiments in the Pd-catalysed Suzuki cross-coupling reaction. The results of the catalysis showed an enhanced activity with these ligands over the previous cases The second part of this dissertation involved determining the role (influence on activity) of the non coordinating counterion in the catalyst system in the methoxycarbonylation reaction. To this end discrete Pd complexes were synthesised and used directly in the methoxycarbonylation reaction. There have been a few reports on the role of the non-coordinating counterions of the catalyst systems in the methoxycarbonylation reaction. The catalyst is typically a palladium compound in the presence of a Bmnsted acid co-catalyst. Changes to the Bmnsted co-catalyst cause two variables to change, namely the acidity of the acid and the nature of the counterion that the acid provides. The work presented in this dissertation shows the results of only one variable being changed (that of the counterion) and as such allowed the specific role of the counterion in the outcome of the reaction to be determined. Previous work done in our laboratories made use of the Lewis acid Al(OTf)3 to co-catalyse the methoxycarbonylation reaction with rates and high yields being observed. In the present instance discrete Pd complexes were synthesised from Pd(OAc)2 using p-TsOH, MsOH and TfOH as the acids containing the weakly coordinating counterions. These Bnmsted acids have the ability to displace the OAc- anion from the Pd and as such formed the discrete L2PdX2complexes (L = PPh3; X = Mso-, p-Tso-, TfO} Synthesis of these discrete complexes was impeded by a lack of knowledge of the specific conditions under which to prepare the complexes and many avenues were pursued before successful isolation of these complexes was achieved. These discrete catalysts were used in the methoxycarbonylation reaction co-catalysed by Al(OT£)3. Here, the Al(OTt)3 forms the basis of a constant acid cocatalyst allowing only the counterion to be changed with the view to determining its role in these reactions. It was found that the counterion appears to play no role at all (Aco-, p-Tso-, Mso-, TfO-) in the outcomes of these reactions under the conditions employed. A comparative study is also detailed herewithin of the effects of both ex situ and in situ catalyst generation on the activity in the methoxycarbonylation reaction, which provides some insightful results.

Page generated in 0.0922 seconds