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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

Sintese van amino-arielaldehied verbindings / Marlene Prinsloo

Prinsloo, Marlene January 2015 (has links)
Die soeke na sterk hoë-verrigtingspolimere het gelei tot die idee om ʼn volledig gekonjugeerde polimeer te ontwikkel vir moontlike gebruik in die motorindustrie. Hierdie polimeer moet soortgelyke eienskappe as dié van Kevlar besit, aangesien die beoogde polimeer vir die bakwerk van battery-aangedrewe voertuie gebruik sou kon word. Die selfpolimerisasie van 4,6-diaminobenseen-1,3-dikarbaldehied is as die gewenste gekonjugeerde polimeer beskou. Tydens die studie is daar gefokus op die sintese van die monomeer 4,6-diaminobenseen- 1,3-dikarbaldehied. Die sintese van monomere wat beide funksionele groepe wat aan die polimerisasie deelneem, op dieselfde molekuul besit, was uitdagend, omdat hierdie monomere baie maklik selfpolimerisasie kan ondergaan. Hierdie studie het ook na groener en korter sinteseroetes om 4,6-diaminobenseen-1,3-dikarbaldehied of derivate daarvan te sintetiseer gekyk, aangesien die sintese van 4,6-diaminobenseen-1,3-dikarbaldehied in die verlede met baie lang sinteseroetes en gevaarlike chemikalieë uitgevoer is. Sintese van 1,5-dibromo-2,4-dimetielbenseen (1), 1,5-dibromo-2,4-bis(dibromometiel)- benseen (2), 4,6-dibromobenseen-1,3-dikarbaldehied (3) en 1,3-bis([1,3]dioksolaan)-4,6- dibromobenseen (5) is suksesvol uitgevoer, maar tydens die koper-gekataliseerde Ullmanntipe reaksies om 4,6-diaminobenseen-1,3-dikarbaldehied (4) te sintetiseer, het slegs poeiers gevorm wat nie oplosbaar in organiese oplosmiddels is nie. Om die selfpolimerisasie moontlikhede van 4 uit te skakel is 5 gesintetiseer. ʼn Poging om 1,3-bis([1,3]dioksolaan)- 4,6-diaminobenseen (6a) vanaf 5 te sintetiseer het egter tot geen reaksie gelei nie. Molekuulmodellering van die Ullmann-tipe reaksies om 6a en 4,6-dimetielbenseen-1,3- diamien te sintetiseer is gedoen om die reaksie te ondersoek. Daar is gevind dat ʼn 1,3- diketoonligand wat aan die koperkatalisator bind, nodig is om die reaksie te verbeter. Vanuit die resultate van die studie is ook gevind dat ʼn Ullmann-tipe reaksie nie met 5 sal plaasvind nie, aangesien dit energeties nie so voordelig is nie. Spektroskopiese analise van die poeiers wat tydens die sintese van 4 gevorm het, bevestig dat die poeiers polimere is. Dit blyk egter dat dit nie die voorgestelde rigiede polimeer is wat gevorm het nie, maar dat dit eerder ʼn amorfe kinasolientipe produk is. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2015
2

Sintese van amino-arielaldehied verbindings / Marlene Prinsloo

Prinsloo, Marlene January 2015 (has links)
Die soeke na sterk hoë-verrigtingspolimere het gelei tot die idee om ʼn volledig gekonjugeerde polimeer te ontwikkel vir moontlike gebruik in die motorindustrie. Hierdie polimeer moet soortgelyke eienskappe as dié van Kevlar besit, aangesien die beoogde polimeer vir die bakwerk van battery-aangedrewe voertuie gebruik sou kon word. Die selfpolimerisasie van 4,6-diaminobenseen-1,3-dikarbaldehied is as die gewenste gekonjugeerde polimeer beskou. Tydens die studie is daar gefokus op die sintese van die monomeer 4,6-diaminobenseen- 1,3-dikarbaldehied. Die sintese van monomere wat beide funksionele groepe wat aan die polimerisasie deelneem, op dieselfde molekuul besit, was uitdagend, omdat hierdie monomere baie maklik selfpolimerisasie kan ondergaan. Hierdie studie het ook na groener en korter sinteseroetes om 4,6-diaminobenseen-1,3-dikarbaldehied of derivate daarvan te sintetiseer gekyk, aangesien die sintese van 4,6-diaminobenseen-1,3-dikarbaldehied in die verlede met baie lang sinteseroetes en gevaarlike chemikalieë uitgevoer is. Sintese van 1,5-dibromo-2,4-dimetielbenseen (1), 1,5-dibromo-2,4-bis(dibromometiel)- benseen (2), 4,6-dibromobenseen-1,3-dikarbaldehied (3) en 1,3-bis([1,3]dioksolaan)-4,6- dibromobenseen (5) is suksesvol uitgevoer, maar tydens die koper-gekataliseerde Ullmanntipe reaksies om 4,6-diaminobenseen-1,3-dikarbaldehied (4) te sintetiseer, het slegs poeiers gevorm wat nie oplosbaar in organiese oplosmiddels is nie. Om die selfpolimerisasie moontlikhede van 4 uit te skakel is 5 gesintetiseer. ʼn Poging om 1,3-bis([1,3]dioksolaan)- 4,6-diaminobenseen (6a) vanaf 5 te sintetiseer het egter tot geen reaksie gelei nie. Molekuulmodellering van die Ullmann-tipe reaksies om 6a en 4,6-dimetielbenseen-1,3- diamien te sintetiseer is gedoen om die reaksie te ondersoek. Daar is gevind dat ʼn 1,3- diketoonligand wat aan die koperkatalisator bind, nodig is om die reaksie te verbeter. Vanuit die resultate van die studie is ook gevind dat ʼn Ullmann-tipe reaksie nie met 5 sal plaasvind nie, aangesien dit energeties nie so voordelig is nie. Spektroskopiese analise van die poeiers wat tydens die sintese van 4 gevorm het, bevestig dat die poeiers polimere is. Dit blyk egter dat dit nie die voorgestelde rigiede polimeer is wat gevorm het nie, maar dat dit eerder ʼn amorfe kinasolientipe produk is. / MSc (Chemistry), North-West University, Potchefstroom Campus, 2015
3

Local and global contaminants in Swedish waters : studies on PCBs, DDTs, 4,5,6-trichloroguaiacol and their transformation products in fish and sediments

Söderström, Maria January 2002 (has links)
This thesis is focused on studies on the environmental fate and methodological improvements for determination of the global contaminants, PCBs and DDTs, and locally discharged phenolics, e.g. 4,5,6-trichloroguaiacol (4,5,6-TCG), and their transformation products. 4,5,6-TCG is released from bleached pulp mills, and was chosen as a model substance, to study its fate and effects in aquatic environments. In a brackish water model ecosystem, 4,5,6-TCG was shown to be transformed via demethylation, dechlorination, and methylation reactions. Marine periphyton exposed to 4,5,6-TCG was shown to form demethylated, brominated and dimeric metabolites. Several of these metabolites were identified and quantified. Also more tightly bound chlorophenolics were recovered from the substrate, after harsh extraction procedures had been applied. Conjugates of chlorophenols in fish bile were determined as useful tracers for monitoring effluents from bleached pulp mills, even in areas far from the discharge point. To facilitate calculations of water concentrations, bile to water bioconcentration factors (bBCF-values) were determined for several phenolics, including also alkali-labile chlorocatechols. PCBs and DDTs, were assessed in Swedish lakes with background exposure of these global contaminants. A methodological study focus on the contamination risks of airborne PCBs, during freeze-drying and storage of dry sediment samples. Eutrophication has been proposed to cause lower levels of pollutants in biota in lakes due to biomass dilution but in this thesis examples of higher levels of PCBs in sediment traps, sediment and in perch, and also in higher fluxes of PCBs to the sediment, were observed. Phytoplankton are supposed to be responsible for most of the transport of the contaminants. The composition of DDTs in soil, sediment traps and in dated sediment cores was studied in some detail. PCBs, DDTs, HCB and HCHs were measured in sediments from 100 reference lakes included in the National Swedish Environmental Program. The lakes have a large variation in lake characteristics, representative for different areas in Sweden. A gradient was observed for sPCB with decreasing levels from the south west towards the north. The results suggests that longrange transport is the dominating mechanism for distribution of the contaminants analysed. In this study the levles of PCBs and DDTs were lower in eutrophic lakes than in oligotrophic lakes, in an area with similar atmospheric exposure. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 6: Manuscript.</p>

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