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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.
191

The analysis and discrimination of pyrolysis products from biological and non-biological sources

Gabriel, Gina Francesca January 2015 (has links)
This work involves the limited use of human tissue samples. These samples were obtained through body donation and under full ethical approval from the University of Strathclyde ethics committee. Products generated through pyrolysis of common materials can act as background compounds, interfering with the analysis and identification of potential human remains. The development of a robust methodology for the generation and analysis of volatile products from biological (porcine and human tissues) and non-biological (textile materials) sources stands at the core of this study, combined with examining various factors that causes these profiles to deviate. This process began with the validation of porcine samples as a substitute of human samples through the identification of similar key indicators, characteristic to both tissues. Interestingly, different temperature ranges (pre- and post-ignition) and type of porcine tissues utilised were found to effect the type of key indicators detected; and as such, has convincingly resolved key indicators reported in previous research literature. In addition, key indicators of pure and blended textiles were also established and the effects of blended fibres towards the overall thermal properties of the textile, highlighted. Alterations to the key indicators of individual porcine and textile samples were examined, subjectively and objectively, when both samples were burnt together (combined samples). Subjective analysis involved the scrutiny of the chromatographic output, revealing the dominance of key indicators of porcine samples over textiles for majority of the combined samples. EIC and EIP proved to be a beneficial tool in extracting key indicators of porcine samples in the presence of contamination (textiles). At 70% presence, SOFM provided an objective and successful classification and discrimination of pyrolytic data according to the type of pyrolysis product detected across textiles, porcine bones and also in the combined textile-bone samples while underlining meaningful associations amongst similar groups. Overall, although this work suggests that pyrolytic data can be unpredictable, such as its dependence on various factors, with suitable analytical and statistical techniques, it has revealed pertinent information on the key indicators of porcine, human and textiles samples and the inter- and intra-molecular changes that occur to them during pyrolysis.
192

Catalytic approaches towards amidation of unactivated ester derivatives

Caldwell, Nicola January 2015 (has links)
Amide bond forming reactions are commonly encountered within a synthetic chemistry environment. Traditionally, a stoichiometric coupling reagent is employed to facilitate the condensation of a carboxylic acid and an amine. However, a number of disadvantages are inherent in this process, including by-product formation, poor atom economy, elevated cost, and variable yields. An organocatalytic approach using N-heterocyclic carbenes (NHCs) would provide a more atom-economical route towards the synthesis of amides, addressing some of the issues outlined above. However, upon investigating anhydrous reaction conditions required for handling NHCs, a novel base-catalysed amidation manifold was identified. Catalytic amounts of base were found to mediate amidation of unactivated esters using amino alcohols in the absence of carbene catalyst. Based on this initial observation, full optimisation of the base-catalysed amidation process was carried out using a combination of linear screening and Design of Experiments (DoE) techniques. Optimised conditions (Scheme 1a) were used to examine substrate scope, demonstrating that a wide range of products could be prepared using this methodology (53 examples, 40-100%), including oxazolidinone derivatives and medicinally-relevant compounds. Mechanistic investigations indicated formation of a transesterification intermediate, followed by intramolecular rearrangement to the more stable amide product. Subsequently, optimisation of a more sustainable base-catalysed amidation process (Scheme 1b) was carried out in order to address the green credentials of this reaction (16 examples, 42-100%). Additionally, by employing an alcohol additive to facilitate in situ formation of the activated ester species, the base-catalysed amidation methodology could be adapted to the direct synthesis of amide products (25 examples, 32-95%). Finally, several novel NHC systems were designed and evaluated for their ability to catalyse a direct amidation reaction.
193

Synthesis and reactivity of superelectrophilic amidine disalts

Scullion, Callum January 2014 (has links)
This work describes the successful synthesis and full characterization of amidine disalt 4.1, which was made from the reaction of a tertiary amide with triflic anhydride and an amine; this disalt contains a dication which can be considered as a superelectrophile. Various related disalts (not limited to, but including disalts 3.43, 5.1 and 6.13) have also been synthesised and their reactivities further investigated. Chapter 1 gives an introduction to the concept of superelectrophiles, including the original discoveries in this area of chemistry. Chapter 2 focuses on reviewing the chemistry of [Fe]-hydrogenase, which converts amidine molecule 2.1 into diamino methylene 2.2; the possibility of a mechanism involving superelectrophiles is briefly highlighted. Chapter 3 reviews the previous work carried out within the Murphy group regarding superelectrophiles, leading on to the synthesis of disalt 3.43. Chapter 4 discusses the route to synthesising and isolating disalt 4.1. Additionally, Chapter 4 describes attempts at carrying out [Fe]-hydrogenase-related reactivity with disalt 3.43 and also describes the limitations of this disalt due to side-reactivity. The reasoning behind the synthesis of disalt 5.1 is discussed in Chapter 5; this chapter also discusses the successful reduction of this disalt with an iron hydride in a reversible process - the first successful model reaction of amidine disalts and iron hydrides, intended to mimic the possible reactivity within [Fe]-hydrogenase. Chapter 6 discusses non-hydrogenase reactivity of amidine disalts; evidence for the formation of monocationic carbene 6.1, the synthesis and reactivity of further substituted disalt 6.13 and the possibility of oxygen-containing disalts of type 6.56 are all discussed.
194

Synthesis and characterization of novel organic semiconducting materials for organic field effect transistors (OFETs) and photovoltaics (OPVs)

Arumugam, Sasikumar January 2015 (has links)
No description available.
195

New materials for electrochemical synthesis of ammonia

Amar, Ibrahim Ali Ahmed January 2014 (has links)
This thesis has mainly focused on the electrochemical synthesis of ammonia at atmospheric pressure using three different catalyst types (nitride, spinel and perovskite). Attention also has been given to developing new electrolyte materials based on oxide-carbonate composites, with the aim of exploring their application in ammonia synthesis at low operating temperature (< 500 °C). Ammonia was synthesised from H₂ and N₂ using an electrolyte supported cell based on LiAlO₂-(Li/Na/K)₂CO₃ as electrolyte, Ag-Pd as anode and either nitride (e.g. Co₃Mo₃N) or spinel (CoFe₂O₄) as cathode. The maximum rate of ammonia formation (3.27 x 10⁻¹⁰10 mol s⁻¹ cm⁻² at 450 °C and 0.8 V) was obtained when Co₃Mo₃N was used as a cathode. Ammonia was also synthesised from H₂ and N₂ in an electrolytic cell based on Sm-doped ceria-carbonate composite (SDC-(Li/Na/K)₂CO₃) as an electrolyte, NiO-SDC as anode and perovskite oxide La₀.₆Sr₀.₄Fe₀.₈Cu₀.₂O₃-δ (LSFCu) catalyst as a cathode. The maximum rate was found to be 5.39 x 10⁻⁹ mol s⁻¹ cm⁻² at 450 °C and 0.8 V. Ammonia was also synthesised successfully from water vapour (3% H₂O) and nitrogen, using a new electrolyte material based on Ca and Gd co-doped ceria-carbonate composite (CGDC-(Li/Na/K)₂CO₃). Perovskite oxide Sm₀.₅Sr₀.₅CoO₃-δ (SSCo) was used as an anode and either spinel or perovskite based catalysts were used as cathodes. The maximum rate of ammonia formation (4.0 x 10⁻¹⁰ mol s⁻¹ cm⁻² at 375 °C and 1.4 V) was attained with a La₀.₇₅Sr₀.₂₅Cr₀.₅Fe₀.₅O₃-δ (LSCrF) cathode. Ammonia was synthesised directly from air and water vapour (3% H₂O) in a symmetrical cell composed of LSCrF as electrodes (cathode and anode) and CGDC-(Li/Na/K)₂CO₃ composite as electrolyte. The maximum rate was found to be 1.94x10⁻¹¹ mol s⁻¹ cm⁻² at 375 °C with an applied voltage of 1.2 V.
196

Imidazolidinones in amine catalysis

Rowley, Julian H. January 2014 (has links)
No description available.
197

Alkali-metal-mediated cleave and capture chemistry

Ramsay, Donna Louise January 2015 (has links)
Whilst metallation, a fundamental reaction in synthetic chemistry, is well established with mono-metallic organolithium reagents, recently a second generation of bimetallic reagents has been gathering momentum, evading some of the limitations associated with organolithium reagents. This study extends the current research in this area of synergic bimetallic chemistry and reports the synthesis and characterisation of new compounds from reactions of bases with different substrates, as well as detailed studies of the starting reagents. A new method for synthesising the utility organoamidolithium reagent LiTMP by way of a transmetallation reaction between tBuLi and Zn(TMP)₂ is described. This realised a new crystalline polymorph of LiTMP in the cyclotrimer (LiTMP)₃ 2.1. Remarkably an interrogation of the two most popular aluminating reagents “LiTMP·Al(iBu)₃” 3.1 and “LiTMP·Al(TMP)(iBu)₂” 3.2 established that 3.1 is not a single species as previously reported but in fact a complex mixture of five distinct species all in equilibria with each other. Additionally it was discovered that the modus operandi of both reagents is a two-step lithiation - trans-metaltrapping protocol, and not by direct alumination. The pharmacologically relevant amine DMPEA was studied with a range of bimetallic base mixtures. Post metallation and subsequent β-elimination the NMe₂ fragment was captured in three different crystalline compounds: [TMEDA·Na(TMP)(NMe₂)Zn(tBu)] 4.2, [PMDETA·Li(NMe₂)Zn(tBu)₂] 4.3 and [THF·Li(TMP)(NMe₂)Al(iBu)₂] 4.4. The first crystal structure where DMPEA is bonded to a metal has also been revealed in [DMPEA·Li(TMP)Zn(Me)₂] 4.5. Probing ferrocene with bimetallic mixtures afforded a range of mono- and dideprotonated products depending on the stoichiometry used. Both zincations in TMEDA·Na(μ-TMP)[μ-(C₅H₄)Fe(C₅H₅)]Zn(tBu) 5.1 and [TMEDA·Na(μ-TMP)Zn(tBu)]₂(C₅H₄)₂Fe 5.2 and aluminations in THF·Li(μ-TMP)[μ- (C5H4)Fe(C5H5)]Al(iBu)2 5.4, [THF·Li(μ-TMP)Al(iBu)2]2(C5H4)2Fe 5.5, [TMP(H)·Li(μ-TMP)Al(iBu)2]2(C5H4)2Fe 5.6 and TMP(H)·Li(TMP)[(C5H4)Fe(C5H5)]Al(iBu)2 5.7 were possible. The zinc system also provided the novel ferrocenophane type structure [{Fe(C₅H₄)₂}₂{Na₂Zn₂(tBu)₂·(THF)₆}] 5.8, as well as hints of a possible polymetallated product.
198

Exploration of a template-directed approach for the synthesis of silver nanoparticles

Kashmery, Heba Abbas January 2015 (has links)
The aim of this thesis is to develop a facile one-pot synthesis of silver nanoparticles (AgNPs) using Tollens' reagent as a silver source. The project focuses on the preparation of a series of sugar triazole ligands to template the formation of monodisperse AgNPs in a size- and shape-controlled manner. Chapter 1 introduces the optical properties of metal nanoparticles and the common methods for the preparation of AgNPs, highlighting the limitations of typical methods and the motivations of this research. Chapter 2 describes the influence of the structural parameters of these sugar triazole ligands (i.e., sugar units, triazole and aromatic core) on the size, shape, stability and dispersity of AgNPs. The work highlights how the Ag(I) binding affinity of these ligands is a key parameter to tune the size and shape of the resultant AgNPs formed. Weaker Ag(I) binding ligands with a phloroglucinol core form monodisperse angular AgNPs over a range of sizes (12 ± 1 nm - 33 ± 7 nm), whereas resorcinol core triazole ligands exhibiting a higher Ag(I) binding affinity produce monodisperse spherical AgNPs of a single size (8 ± 5 nm). Chapter 3 describes the synthesis of AgNPs using sugar triazole ligands and Tollens' reagent using silver trifluoroacetate to investigate the counter-ion effect of silver salts on the size and the morphology of formed AgNPs. This salt produces AgNPs with similar shapes and sizes compared to that formed using silver nitrate. Chapter 4 describes the synthesis of PEG-functionalised sugar triazoles bearing PEG groups to investigate their effects on the formation of AgNPs. This work identifies the southernmost triazole as a modular site to tune the size and shape of AgNPs. Installation of PEG chains into the southernmost triazole ring shows a significant reduction in the Ag(I) binding affinity and produces monodisperse angular AgNPs with diameters ranging from 15 ± 4 nm to 38 ± 7 nm. The surface enhanced Raman scattering properties of formed AgNPs are also discussed. Chapter 5 describes the synthesis of sugar-modified peptides to template the synthesis of AgNPs using Tollens' reagent. Increasing the sugar units using octamer peptide produces angular and smaller AgNPs (10 ± 2 - 23 ± 2) compared to that formed using pentamir peptide (16 ± 2 - 32 ± 4). In conclusion, this thesis reports a novel template-directed triazole ligand strategy for the one-step synthesis of AgNPs in a size- and shape-controlled fashion. The mild synthetic methodology outlined in this thesis opens up new opportunities for the development of optical biosensing and imaging applications.
199

Dynamic supramolecular hydrogels with adaptive biological functionality

Abul-Haija, Yousef Mustafa Yousef January 2015 (has links)
No description available.
200

Synthesis and characterisation of conjugated 4,8-benzobisthiazole derivatives for organic electronics

Conboy, Gary January 2015 (has links)
No description available.

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