Assessment of the host properties of selected optically pure, racemic and achiral compounds
- Authors: Jooste, Daniel Victor
- Date: 2017
- Subjects: Organic compounds -- Synthesis Cyclic compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/18826 , vital:28735
- Description: This study focussed on the synthesis and host properties of four different broad categories of potential host compounds, namely optically active and racemic TADDOL [(4R,5R)-α,α,α’,α’-tetraphenyl-1,3-dioxolane-4,5-dimethanol] and derivatives, TTFOL [(3R,4R)-2,2,5,5-tetraphenyltetrahydrofuran-3,4-diol], amino acid ester-derived compounds [(S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol], and compounds derived from xanthone [9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine]. The potential hosts were recrystallized from a range of possible guest species and the resulting solids analysed by 1H-NMR spectroscopy. If inclusion was observed by this technique, the complexes were analysed further using single crystal X-ray techniques and thermal experiments where possible. Competition studies were carried out where these were deemed appropriate. Optically active and racemic TADDOLs were synthesized using L-(+) and DL-(±)-tartaric acid respectively. Two further derivatives were prepared whereby the hydroxyl groups were substituted for chlorine and azide in order to assess the effect of this change on the inclusion ability. Both the optically active and racemic TADDOLs displayed similar host abilities, complexing with guests with 1:1 host:guest ratios as determined through 1H-NMR spectroscopy. Competition experiments showed that both forms of TADDOL exhibited similar guest preferences for pyridine and the methylpyridine isomers. Pyridine however was preferred over 2-methylpyridine by optically active TADDOL while the racemic form preferred this methyl-substituted guest over pyridine. Thermal analysis studies showed, surprisingly, that the TADDOL complexes containing pyridine had higher relative thermal stabilities than those containing the methylpyridines, whether the host was optically active or not. The preference order of these hosts for these guests can, therefore, not be used as a predictor for the relative thermal stability of the complexes. TTFOL was found to include only ethanol, 2-methylpyridine and dioxane from the range of guest species used; the complex with dioxane did not produce X-ray quality crystals. The L-tyrosine derivative, (S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol, was an ineffective host incapable of including any of the guests used in these experiments. The two xanthone derivatives, 9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine each formed complexes with one guest species (morpholine and DMF, respectively).
- Full Text:
- Date Issued: 2017
- Authors: Jooste, Daniel Victor
- Date: 2017
- Subjects: Organic compounds -- Synthesis Cyclic compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/18826 , vital:28735
- Description: This study focussed on the synthesis and host properties of four different broad categories of potential host compounds, namely optically active and racemic TADDOL [(4R,5R)-α,α,α’,α’-tetraphenyl-1,3-dioxolane-4,5-dimethanol] and derivatives, TTFOL [(3R,4R)-2,2,5,5-tetraphenyltetrahydrofuran-3,4-diol], amino acid ester-derived compounds [(S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol], and compounds derived from xanthone [9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine]. The potential hosts were recrystallized from a range of possible guest species and the resulting solids analysed by 1H-NMR spectroscopy. If inclusion was observed by this technique, the complexes were analysed further using single crystal X-ray techniques and thermal experiments where possible. Competition studies were carried out where these were deemed appropriate. Optically active and racemic TADDOLs were synthesized using L-(+) and DL-(±)-tartaric acid respectively. Two further derivatives were prepared whereby the hydroxyl groups were substituted for chlorine and azide in order to assess the effect of this change on the inclusion ability. Both the optically active and racemic TADDOLs displayed similar host abilities, complexing with guests with 1:1 host:guest ratios as determined through 1H-NMR spectroscopy. Competition experiments showed that both forms of TADDOL exhibited similar guest preferences for pyridine and the methylpyridine isomers. Pyridine however was preferred over 2-methylpyridine by optically active TADDOL while the racemic form preferred this methyl-substituted guest over pyridine. Thermal analysis studies showed, surprisingly, that the TADDOL complexes containing pyridine had higher relative thermal stabilities than those containing the methylpyridines, whether the host was optically active or not. The preference order of these hosts for these guests can, therefore, not be used as a predictor for the relative thermal stability of the complexes. TTFOL was found to include only ethanol, 2-methylpyridine and dioxane from the range of guest species used; the complex with dioxane did not produce X-ray quality crystals. The L-tyrosine derivative, (S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol, was an ineffective host incapable of including any of the guests used in these experiments. The two xanthone derivatives, 9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine each formed complexes with one guest species (morpholine and DMF, respectively).
- Full Text:
- Date Issued: 2017
Macrophyte distribution and responses to drought in the St Lucia Estuary
- Nondoda, Sibulele Phefumlela
- Authors: Nondoda, Sibulele Phefumlela
- Date: 2012
- Subjects: Estuaries -- South Africa -- Saint Lucia, Lake , Lakes -- South Africa -- Saint Lucia, Lake , Vegetation mapping -- South Africa -- Saint Lucia, Lake , Estuarine sediments -- South Africa -- Saint Lucia, Lake , Wetland mapping -- South Africa --Saint Lucia, Lake
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10632 , http://hdl.handle.net/10948/d1012330 , Estuaries -- South Africa -- Saint Lucia, Lake , Lakes -- South Africa -- Saint Lucia, Lake , Vegetation mapping -- South Africa -- Saint Lucia, Lake , Estuarine sediments -- South Africa -- Saint Lucia, Lake , Wetland mapping -- South Africa --Saint Lucia, Lake
- Description: This study investigated the response of the macrophytes in St Lucia Estuary, northern KwaZulu-Natal to drought. The present distribution of vegetation (2010 / 2011) was mapped and changes over time recorded from past aerial photographs. The changes in macrophyte cover in response to environmental factors (sediment and groundwater characteristics) was measured along four transects in 2010 and compared with results from previous years, in 2005 and 2006. In the current study, 1960 images were digitized to illustrate macrophyte distribution and cover of the Narrows, Makakatana and the Eastern Shores during a low rainfall period which started in 1958. The 2001 images were digitized to illustrate vegetation distribution and cover of the same area prior to the current drought which started in June/ July 2002. The 2008 images were digitized to illustrate vegetation distribution and cover of estuarine vegetation within the floodplain during the drought (after 6 years). The sites were visited in June 2011 for verification of the distribution and boundaries of each macrophyte habitat. The area covered by the water column varied over time. In 1960 during a low rainfall period the water was 32705 ha, 33320 ha in 2001 and reduced to 30443 ha in 2008. The area cover of inundated and dry reeds fluctuated with the water level. Under high water levels, low-lying areas such as Fanies Island and Selley‟s Lake were flooded and under low water levels, intertidal sand and mudflats were exposed and colonised by succulent salt marsh (Sarcocornia spp. and Salicornia meyeriana). Similar conditions were observed at Makakatana. Mangroves were observed from the mouth to the Forks. Avicennia marina was the dominant mangrove species and primary colonizer of dredge spoil. The area cover of mangroves in the vicinity of the mouth fluctuated as a result of fluctuating water levels, dredging operations, excavation of the Back Channel and Cyclone Gamede which killed intertidal vegetation. Between 2001 and 2008, mangrove expansion was faster in the Mfolozi Swamps area (± 1.4 ha yr -1) compared to the Narrows (± 0.4 ha yr -1). Long term monitoring transects were set up in 2005, at Makakatana, Charters Creek, Catalina Bay and at Listers Point to document changes in sediment conditions and vegetation cover. These were sampled in July 2005, October 2005, February 2006 and May 2010. Silt was the dominant particle size at Catalina Bay, Charters Creek and Makakatana. At Makakatana, average ground water salinity was 17.2 ± 6.6 ppt, 4.1± 4.9 ppt at Catalina Bay and 32.9 ± 19.3 ppt at Charters Creek. Drought resulted in the accumulation of salt on the surface sediment layer at Listers Point and Charters Creek due to low rainfall. Listers Point, the site with the lowest freshwater input and habitat diversity had the lowest macrophyte species richness with only three species. The dominant species at this site were Sporobolus virginicus and Chenopodium album L. which are highly salt tolerant species. Catalina Bay had the highest species richness (18 to 27); as a result of freshwater input via groundwater seepage from the sand dune aquifers on the Eastern Shores. Along the Eastern Shores, vegetation was dominated by species of Cyperaceae, Juncaceae and Juncaginaceae. Fluctuations in groundwater depth were observed at all sites, Listers Point groundwater depth in February 2006 was 80 cm and the ground water level was not reached during the May 2010 field trip. During the May 2010 field trip, the water column salinity of the St Lucia system was highly variable, Makakatana had the lowest water column salinity of 7.1 ppt, 42.1 ppt at Catalina Bay, 44 ppt at Charters Creek and Listers Point had the highest water column salinity of 95 ppt. An assessment of the changes in macrophyte cover along the transects showed that cover fluctuated in response to rainfall, water level and drought. At Listers Point, there was a continuous decline in the abundance of Sporobolus virginicus over time which was sparsely distributed in the first 40 m of the transect. Sarcocornia natalensis, a succulent and obligate halophyte, was recorded, in areas with high sediment conductivity. In May 2010, bare ground increased to an average percentage cover of 96.5% and was covered with dead organic matter and a salt crust at Listers Point. At Makakatana, there was a significant decrease in bare ground from July 2005 to May 2010 (H = 24.58, N = 197, p<0.001) as bare areas were colonized by salt marsh. Multivariate analysis showed that the abundance of Sporobolus virginicus was positively influenced by sediment moisture content and Paspalum vaginatum abundance was strongly influenced by the water column salinity. At Catalina Bay, low sediment conductivity at the groundwater seepage area resulted in terrestrial vegetation encroaching on estuarine vegetation. Sarcocornia natalensis became more abundant towards the water column. During the period of study, species richness at St Lucia ranged from 2 (Listers Point, May 2010) to 27 (Catalina Bay, February 2006). Salinity and water level fluctuation have a significant impact on the distribution of macrophytes at St Lucia during the drought. In saline areas salt marsh plants have colonized exposed shorelines and along the Eastern Shores groundwater seepage has increased macrophyte species richness. Low water levels have resulted in the exposure and desiccation of submerged macrophytes, which are replaced by macroalgae.
- Full Text:
- Date Issued: 2012
- Authors: Nondoda, Sibulele Phefumlela
- Date: 2012
- Subjects: Estuaries -- South Africa -- Saint Lucia, Lake , Lakes -- South Africa -- Saint Lucia, Lake , Vegetation mapping -- South Africa -- Saint Lucia, Lake , Estuarine sediments -- South Africa -- Saint Lucia, Lake , Wetland mapping -- South Africa --Saint Lucia, Lake
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10632 , http://hdl.handle.net/10948/d1012330 , Estuaries -- South Africa -- Saint Lucia, Lake , Lakes -- South Africa -- Saint Lucia, Lake , Vegetation mapping -- South Africa -- Saint Lucia, Lake , Estuarine sediments -- South Africa -- Saint Lucia, Lake , Wetland mapping -- South Africa --Saint Lucia, Lake
- Description: This study investigated the response of the macrophytes in St Lucia Estuary, northern KwaZulu-Natal to drought. The present distribution of vegetation (2010 / 2011) was mapped and changes over time recorded from past aerial photographs. The changes in macrophyte cover in response to environmental factors (sediment and groundwater characteristics) was measured along four transects in 2010 and compared with results from previous years, in 2005 and 2006. In the current study, 1960 images were digitized to illustrate macrophyte distribution and cover of the Narrows, Makakatana and the Eastern Shores during a low rainfall period which started in 1958. The 2001 images were digitized to illustrate vegetation distribution and cover of the same area prior to the current drought which started in June/ July 2002. The 2008 images were digitized to illustrate vegetation distribution and cover of estuarine vegetation within the floodplain during the drought (after 6 years). The sites were visited in June 2011 for verification of the distribution and boundaries of each macrophyte habitat. The area covered by the water column varied over time. In 1960 during a low rainfall period the water was 32705 ha, 33320 ha in 2001 and reduced to 30443 ha in 2008. The area cover of inundated and dry reeds fluctuated with the water level. Under high water levels, low-lying areas such as Fanies Island and Selley‟s Lake were flooded and under low water levels, intertidal sand and mudflats were exposed and colonised by succulent salt marsh (Sarcocornia spp. and Salicornia meyeriana). Similar conditions were observed at Makakatana. Mangroves were observed from the mouth to the Forks. Avicennia marina was the dominant mangrove species and primary colonizer of dredge spoil. The area cover of mangroves in the vicinity of the mouth fluctuated as a result of fluctuating water levels, dredging operations, excavation of the Back Channel and Cyclone Gamede which killed intertidal vegetation. Between 2001 and 2008, mangrove expansion was faster in the Mfolozi Swamps area (± 1.4 ha yr -1) compared to the Narrows (± 0.4 ha yr -1). Long term monitoring transects were set up in 2005, at Makakatana, Charters Creek, Catalina Bay and at Listers Point to document changes in sediment conditions and vegetation cover. These were sampled in July 2005, October 2005, February 2006 and May 2010. Silt was the dominant particle size at Catalina Bay, Charters Creek and Makakatana. At Makakatana, average ground water salinity was 17.2 ± 6.6 ppt, 4.1± 4.9 ppt at Catalina Bay and 32.9 ± 19.3 ppt at Charters Creek. Drought resulted in the accumulation of salt on the surface sediment layer at Listers Point and Charters Creek due to low rainfall. Listers Point, the site with the lowest freshwater input and habitat diversity had the lowest macrophyte species richness with only three species. The dominant species at this site were Sporobolus virginicus and Chenopodium album L. which are highly salt tolerant species. Catalina Bay had the highest species richness (18 to 27); as a result of freshwater input via groundwater seepage from the sand dune aquifers on the Eastern Shores. Along the Eastern Shores, vegetation was dominated by species of Cyperaceae, Juncaceae and Juncaginaceae. Fluctuations in groundwater depth were observed at all sites, Listers Point groundwater depth in February 2006 was 80 cm and the ground water level was not reached during the May 2010 field trip. During the May 2010 field trip, the water column salinity of the St Lucia system was highly variable, Makakatana had the lowest water column salinity of 7.1 ppt, 42.1 ppt at Catalina Bay, 44 ppt at Charters Creek and Listers Point had the highest water column salinity of 95 ppt. An assessment of the changes in macrophyte cover along the transects showed that cover fluctuated in response to rainfall, water level and drought. At Listers Point, there was a continuous decline in the abundance of Sporobolus virginicus over time which was sparsely distributed in the first 40 m of the transect. Sarcocornia natalensis, a succulent and obligate halophyte, was recorded, in areas with high sediment conductivity. In May 2010, bare ground increased to an average percentage cover of 96.5% and was covered with dead organic matter and a salt crust at Listers Point. At Makakatana, there was a significant decrease in bare ground from July 2005 to May 2010 (H = 24.58, N = 197, p<0.001) as bare areas were colonized by salt marsh. Multivariate analysis showed that the abundance of Sporobolus virginicus was positively influenced by sediment moisture content and Paspalum vaginatum abundance was strongly influenced by the water column salinity. At Catalina Bay, low sediment conductivity at the groundwater seepage area resulted in terrestrial vegetation encroaching on estuarine vegetation. Sarcocornia natalensis became more abundant towards the water column. During the period of study, species richness at St Lucia ranged from 2 (Listers Point, May 2010) to 27 (Catalina Bay, February 2006). Salinity and water level fluctuation have a significant impact on the distribution of macrophytes at St Lucia during the drought. In saline areas salt marsh plants have colonized exposed shorelines and along the Eastern Shores groundwater seepage has increased macrophyte species richness. Low water levels have resulted in the exposure and desiccation of submerged macrophytes, which are replaced by macroalgae.
- Full Text:
- Date Issued: 2012
Slow delivery of low-income housing at munipal level with special reference to the Nelson Mandela Bay Munipality
- Authors: Scheepers, Mario Jacques
- Date: 2011
- Subjects: SLow-income housing -- South Africa -- Port Elizabeth , Municipal services -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9671 , http://hdl.handle.net/10948/d1015968
- Description: The provision of adequate housing is an important part of government's commitment towards providing a better quality of life to the people of South Africa. Housing delivery is, however, not taking place to the extent and speed that will eliminate the backlog in housing delivery. The researcher aims to (i) evaluate and investigate the reasons why housing delivery at municipal level is slow, (ii) discuss the effect of inefficient implementation on delivery, (iii) examine the influence of the lack of infrastructure and the lack of skilled municipal officials and employees of construction organisations and the processes followed to make a success of housing delivery. Chapter 2, Section 26(1), Act 108 0f 1996 of the Constitution of South Africa states that everyone has the right to have access to adequate housing. This places an obligation on government to provide adequate housing to all citizens, within the restriction of available resources. The lack of land hampers the speed at which municipalities can deliver low-income housing. Housing and basic infrastructure (water, sewer and roads) form an integral part of the governments commitment to reduce poverty and improve the quality of life of South Africans. The fact that municipalities do not have capacity to address housing delivery and the fact that most artisans are near retirement age also influence the rate that houses can be delivered. Adequate housing processes are needed for housing delivery to take place, without it government will not succeed in delivering adequate housing. The results of the survey and the literature review confirm that housing delivery at municipality level is slow, that municipal officials need training and more employees to insure that housing delivery improves. The results also show the importance of infrastructure and land, the importance of implementing housing policies and processes adequately.
- Full Text:
- Date Issued: 2011
- Authors: Scheepers, Mario Jacques
- Date: 2011
- Subjects: SLow-income housing -- South Africa -- Port Elizabeth , Municipal services -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9671 , http://hdl.handle.net/10948/d1015968
- Description: The provision of adequate housing is an important part of government's commitment towards providing a better quality of life to the people of South Africa. Housing delivery is, however, not taking place to the extent and speed that will eliminate the backlog in housing delivery. The researcher aims to (i) evaluate and investigate the reasons why housing delivery at municipal level is slow, (ii) discuss the effect of inefficient implementation on delivery, (iii) examine the influence of the lack of infrastructure and the lack of skilled municipal officials and employees of construction organisations and the processes followed to make a success of housing delivery. Chapter 2, Section 26(1), Act 108 0f 1996 of the Constitution of South Africa states that everyone has the right to have access to adequate housing. This places an obligation on government to provide adequate housing to all citizens, within the restriction of available resources. The lack of land hampers the speed at which municipalities can deliver low-income housing. Housing and basic infrastructure (water, sewer and roads) form an integral part of the governments commitment to reduce poverty and improve the quality of life of South Africans. The fact that municipalities do not have capacity to address housing delivery and the fact that most artisans are near retirement age also influence the rate that houses can be delivered. Adequate housing processes are needed for housing delivery to take place, without it government will not succeed in delivering adequate housing. The results of the survey and the literature review confirm that housing delivery at municipality level is slow, that municipal officials need training and more employees to insure that housing delivery improves. The results also show the importance of infrastructure and land, the importance of implementing housing policies and processes adequately.
- Full Text:
- Date Issued: 2011
An investigation into the role of school-governing bodies with reference to the Kuyasa Secondary School, King William's Town District
- Authors: Radoni, Bonisile Wellington
- Date: 2009
- Subjects: School boards -- South Africa -- King Williams Town , School personnel management -- South Africa -- King Williams Town , School management and organization -- South Africa -- King Williams Town
- Language: English
- Type: Thesis , Doctoral , DPA
- Identifier: vital:8206 , http://hdl.handle.net/10948/1164 , School boards -- South Africa -- King Williams Town , School personnel management -- South Africa -- King Williams Town , School management and organization -- South Africa -- King Williams Town
- Description: The introduction of school governing bodies provided communities with an opportunity to play a significant role in the organisation and governance of their schools. This involvement of significant stakeholders is purported to oversee that schools offer education of high quality to the learners. However, school governance is a legal responsibility, which requires the skills, knowledge and expertise to ensure that SGB members will be able to fulfil their concomitant legal duties. The aim of the study was to investigate the impact of the SGBs role in school governance in Kuyasa Secondary School, King Williams Town District. The findings revealed that the SGBs knowledge and understanding of their roles and responsibilities, and the type of training they receive have a marked effect on their functionality. There is also a need to recruit SGB members with a particular level of education, knowledge, understanding and expertise to minimise the chances of failure.
- Full Text:
- Date Issued: 2009
- Authors: Radoni, Bonisile Wellington
- Date: 2009
- Subjects: School boards -- South Africa -- King Williams Town , School personnel management -- South Africa -- King Williams Town , School management and organization -- South Africa -- King Williams Town
- Language: English
- Type: Thesis , Doctoral , DPA
- Identifier: vital:8206 , http://hdl.handle.net/10948/1164 , School boards -- South Africa -- King Williams Town , School personnel management -- South Africa -- King Williams Town , School management and organization -- South Africa -- King Williams Town
- Description: The introduction of school governing bodies provided communities with an opportunity to play a significant role in the organisation and governance of their schools. This involvement of significant stakeholders is purported to oversee that schools offer education of high quality to the learners. However, school governance is a legal responsibility, which requires the skills, knowledge and expertise to ensure that SGB members will be able to fulfil their concomitant legal duties. The aim of the study was to investigate the impact of the SGBs role in school governance in Kuyasa Secondary School, King Williams Town District. The findings revealed that the SGBs knowledge and understanding of their roles and responsibilities, and the type of training they receive have a marked effect on their functionality. There is also a need to recruit SGB members with a particular level of education, knowledge, understanding and expertise to minimise the chances of failure.
- Full Text:
- Date Issued: 2009
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