School of Chemistry - Theses
Permanent URI for this collection
Search Results
1 - 5 of 5
-
ItemNMR studies of amyloid ab-peptide in membranes(University of Melbourne, 2006)
-
ItemIon trap studies of single microparticles: optical resonances and mass spectrometry( 2006-12)Microparticle experiments conducted using a newly commissioned quadrupole ion trap (QIT) are reported. Single polystyrene microparticles are confined using three dimensional electrodynamic quadrupole fields and characterised by their fluorescence emission and secular frequency measurements. The advantages of this confinement technique are that single particle properties can be measured free from ensemble averaging effects and unperturbed by solvents and (or) substrates. (For complete abstract open document)
-
ItemHigh power carbon-based supercapacitors( 2006)Energy storage devices are generally evaluated on two main requirements; power and energy. In supercapacitors these two performance criteria are altered by the capacitance, resistance and voltage. (For complete abstract open document)
-
ItemThe chemistry of Salvia divinorum( 2006-04)Salvia divinorum is a hallucinogenic sage used to treat illness by the Mazatec Indians of Mexico. Salvinorin A (1a), a neoclerodane diterpenoid isolated from the plant, is a potent, selective agonist at the kappa opioid receptor (KOR), and is the first non-nitrogenous opioid. The plant is used recreationally as a hallucinogen, but is unpopular due to its dysphoric effects. 1a has been prohibited in Australia under an invalid systematic name. An early report of psychoactive alkaloids in S. divinorum proved to be irreproducible. Similarly, tests in mice suggesting the presence of psychoactive compounds other than 1a were confounded and therefore unreliable. In this work, an improved isolation method for 1a was developed, using filtration through activated carbon to decolourise the crude extract. Six new diterpenoids were isolated: salvinorins D–F (1d–1f) and divinatorins A–C (28a–28c). Five known terpenoids not previously reported from this species were also isolated. The structure–activity relationships of 1a were evaluated via selective modifications of each functional group. Useful synthetic methods are reviewed, including the first thorough review of furanolactone hydrogenations. Testing of the derivatives at the KOR suggests that the methyl ester and furan ring of 1a are required for activity, but that the lactone and ketone functionalities are not. Other compounds from S. divinorum did not bind to the KOR, suggesting that 1a is the plant’s active principle.
-
ItemPerformance chemistry of novel urethane coatings( 2006)This work has assessed the durability of a series of polyurethane polymer coatings for use on steel. Using standard industry techniques, a variety of polyurethane polymers were prepared which were subsequently subjected to different weathering exposure environments. The performance of these polyurethane coatings were then assessed using a range of methods including standard industry tests and advanced spectroscopy and microscopy techniques. This analysis highlighted the specific polymers that possessed the greatest durability after exposure in harsh weathering environments. In order to gain more insight into the different durability performance of these polyurethane polymers, theoretical DFT calculations were utilised to help identify sites within the polymer matrix that may be susceptible to free-radical degradation processes that may occur during oxidative stress. The DFT calculations identified that the thermodynamic product was not always kinetically favoured. As such, further calculations investigated possible intermolecular vs. intramolecular hydrogen atom transfer processes; identifying that intermolecular hydrogen atom transfer was more energetically favoured. The Radical Trapping technique was utilized as an independent method of determining sites within the polymer matrix that are susceptible to free radical oxidative attack. Model substrates designed to reflect key linkages within the polyurethanes of interest, were combined with tert-butoxyl radicals in the presence of the stable nitroxide TMIO. The product mixture was analysed by HPLC, which revealed that several nitroxide trapped products were generated. These adducts were isolated and characterised by standard spectroscopic techniques. The results from this trapping experiment were in good agreement with the DFT calculations, thus verifying our theoretical approach for determining potential sites of degradation.