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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.
1

Radical cyclisation in routes to cis-fused heterocycles

Fletcher, Rodney Justin January 1995 (has links)
No description available.
2

Contaminants and decomposition products in naturally aged pentaerythritol tetranitrate (PETN)

Brackett, Claudia L. 01 January 2005 (has links) (PDF)
PETN is characterized by its sensitivity to environmental conditions. However, anhydrous low-temperature decomposition is poorly understood. This research undertook the search for the decomposition products of naturally aged PETN. This study did not detect any decomposition products. The methods tried were NMR, HPLC, mass spectrometry, and HPLC. PETN's behavior was sensitive to mass spectral conditions and resulted in adduct formation and artifactual decomposition. Artifacts could be sources of misinterpretation for true decomposition. Such behaviors included PETN's autonitration and nitrate's clinging to instrument surfaces. Additionally, PETN seemed able to autooxidize which produced an [M] − ion and [M+H] − ion that obscured isotopic information. Conditions that enhanced the abundance of the [M−H] − ion also increased PETN artifactual decomposition. Because an ion at m/z 330 could represent PETRIN, it was studied and candidated to be an artifact. This PETRIN-acetate isobar was formed from PETN in the presence of acetate. An illusion that a new mass at m/z 330 materialized could be due to spray chamber temperatures. The ion stayed relatively constant throughout a temperature increase while the abundance for other PETN ions decreased. This created an illusion of increasing abundance when the mass spectrum was displayed in normalized mode. An HPLC gradient of acetonitrile/water with addition of 3% NH 4 OH and 0.1 M ammonium acetate in methanol produced chromatographic peaks. However, these species were artifacts formed in the presence of hydroxide ion. Hydroxide accelerated the disappearance of the ion at m/z 315, but not the ion at m/z 378. A second HPLC system used an acetonitrile/water gradient with added 3.3 M ammonium acetate in methanol. However, no difference between PETN and naturally aged PETN chromatograms was evident. In an additional experiment, with the HPLC effluent collected in aliquots and analyzed separately, no condensed phase decomposition product was observed. Because the NMR, HPLC and mass spectrometry experiments did not detect condensed phase decomposition products, the decomposition products might be gas(es). In support, the explosives HMX and RDX are known to decompose in gas phase reactions. It is reasonable that naturally aged PETN proceeds through the same mechanism. The findings of this dissertation supported this viewpoint.
3

SYNTHESIS, TESTING AND CRYSTALLOGRAPHIC STUDIES OF ALLOSTERIC MODIFIERS OF HEMOGLOBIN

Deshpande, Tanvi 05 July 2013 (has links)
The major physiological function of hemoglobin (Hb) is to bind, transport and deliver oxygen to tissues; made efficient by endogenous effectors, such as protons and 2,3-diphosphoglycerate. Synthetic allosteric effectors of Hb (AEHs) are also known to modulate Hb oxygen affinity, showing potential for the treatment of sickle cell disease (SCD) and ischemic-related diseases. In this project, AEHs which increase Hb affinity for oxygen, including derivatives of the anti-sickling compounds, 5HMF and benzaldehydes, as well as an AEH that decreases Hb affinity for oxygen, RSR-13, were synthesized for their effects on Hb oxygen binding property and their capability to release NO from substituted nitrate ester moieties. Compounds that were found to increase Hb affinity for oxygen were further tested for their anti-sickling activities. Structural studies were carried out to gain insight into the compound’s mode of action. Development of these agents could be a therapeutic strategy for SCD or ischemic-related diseases.

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