Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / Please refer to full text for abstract. Abstract contains special characters.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Please refer to full text for abstract

Thesis (MSc (Chemistry and Polymer Science))--Stellenbosch University, 2008. / N,N-dialkyl-N-acyl(aroyl)thiourea ligands form stable chelated complexes in a cis configuration with the platinum group metals. Such chelated complexes are generally considered substitutionally “inert” in solution, however, it was found that cis-bis(N,Ndialkyl- N-acyl(aroyl)thioureato)M(II) complexes (M = Ni(II), Pd(II) or Pt(II)) readily undergo facile chelate metathesis reactions in solution at room temperature. Upon mixing two different parent complexes, a mixed-ligand product formed in solution, with an equilibrium, or steady state, between the two parent complexes and the mixed-ligand product being attained after a period of time: M(LA)2 + M(LB)2 M(LA)(LB). All three complexes remained in solution even with a ten-fold excess of one parent complex. The presence of the mixed-ligand products in solution was confirmed by liquid chromatography-mass spectrometry (LC-MS), nuclear magnetic resonance (NMR) spectra and a crystal structure of the mixed-ligand complex cis-Pd(L3-S,O)(L4-S,O). Though a number of attempts were made, it was not possible to either isolate or synthesise the mixed-ligand complexes exclusively. The equilibrium distribution and the rate of the metathesis reaction were influenced by a number of factors, including the central metal ion, the substituents on the complexed ligands and the reaction medium. In addition to these, a number of other factors, some unexpected, also played a role in the rate of the reaction. Initial concentration of the parent complexes, the age of the solutions upon mixing and the presence of impurities or additives all contributed to the overall rate of reaction. The results from these rate studies highlighted the necessity for extensively purified compounds. In addition to chelate metathesis reactions, the exchange between a cis-Pd(L-S,O)2 complex and an unbound HL ligand in solution was also investigated. Again, even with an excess of unbound ligand, all three possible complexes were present in solution. It has been shown previously that these complexes undergo a photoinduced cis-trans isomerisation under intense light, and it has been proposed that the reverse trans-cis process, which occurs in the dark, may be a metathesis reaction. In light of this, the relationship between these chelate metathesis reactions and the reverse trans-cis reaction was briefly investigated. Though the metathesis reactions were a general phenomenon in the Ni(II), Pd(II) and Pt(II) complexes of the aforementioned ligands, the experiments focused mainly on the cis-Pd(L-S,O)2 complexes due to the favourable timescales of their metathesis reactions. The primary technique to observe these reactions was reversed-phase high-performance liquid chromatography (rp-HPLC). The timescales involved in the cis-Pd(L-S,O)2 metathesis reactions as well as the stability of the Pd(II) complexes under the HPLC conditions made this technique ideal.

Thesis (MSc (Chemistry and Polymer Science))--Stellenbosch University, 2007. / In this study, ten selected boron-nitrogen compounds and three borane carbonyl complexes were investigated by a number of computational methods. It is well known that the B-N dative bond is shorter in the solid state than in the gas phase. The B-CO distance, on the other hand, displays the opposite effect. Quantum mechanical techniques at the Hartree-Fock, Møller-Plesset second-order and Density Functional Theory level were used to calculate the geometries of the isolated molecules and to compare them with those found in molecular clusters built to model the solid state. It was found that calculated geometries were very sensitive to the choice of the basis set. The effects of dipole-dipole interactions were further investigated by applying an external electric field with varying strength to isolated molecules, and by replacing the central molecule in a cluster with a different compound. The B-N bond was found to respond much more to the applied field than the B-CO bond. An effort was made to correlate the lengthening or shortening of the dative bond to the strength of the crystal field, the latter being calculated classically from point charges. Unfortunately, large differences were noted between the charges calculated with common methods like Mulliken or Merz-Kollman-Singh. Furthermore, an analysis of 67 crystal structures taken from the Cambridge Structural Database did not reveal a correlation between the length of the B-N bond and the crystal field calculated with Charge Equilibration charges. Finally, a valence force field was developed for H3N-BH3. It was shown that a much better fit of the vibrational spectrum can be obtained if the B-N stretching mode is assigned to the 603 cm-1 band rather than the peak observed at 968 cm-1.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2008. / In this study linear low density polyethylene (LLDPE), a copolymer consisting of ethylene and 1-butene, was fractionated by the use of temperature rising elution fractionation (TREF). These fractions were then analyzed by crystallisation analysis fractionation, 13C NMR, high temperature size exclusion chromatography and DSC. The molecular distribution of the polymer was investigated. It was found that the polymer had a very broad distribution in its chemical composition. From these results it was also clear that the catalysts used for the polymerisation consist out of different active sites, producing chains with different molecular architecture. Subsequently the polymer was fractionated again by TREF and certain fractions were removed and the remaining material recombined. The removed fractions and recombined material were analyzed by 13C NMR, high temperature size exclusion chromatography, DSC and DMA. The results were compared with the bulk material and from this we could conclude the influence of the fractions removed on the material properties. This gave us more information on the influence of the chemical structure of the polymer on its mechanical properties. It was clear that by removing certain fractions with a certain chemical composition, the properties of the polymer are significantly influenced.

Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The choice of the sample preparation technique used in combination with a chromatographic technique in environmental analysis strongly influences the performance of the method as a whole. The main aim of this work was to evaluate methods like: micro liquid-liquid extraction (цLLE)and solid phase micro extraction (SPME) in combination with gas chromatography-electron capture detector (GCECD) and a recently developed technique named stir bar sorptive extraction (SBSE) combined with thermal desorption system-programmable temperature vaporizationgas chromatography-mass spectrometer (TDS-PTV-GC-MS) for the analysis of organochloro-pesticides (OCPs) in natural water and to make a comparison between them. The most suitable method was then selected for the analysis of water samples collected from Eritrea. An additional goal was to develop a sensitive method for the analysis ofOCPs in soil and sediment samples. цLLE-GC-ECD and SPME-GC-ECD methods were evaluated for the analysis of OCPs in water. The former allowed achieving a sensitivity of less than 100 ppt and the latter was able to detect down to the 1 ppt level. Both methods were found to be repeatable with %RSD of3% to 19% and 5% to 12% as well as linear with a range of 1:103 and 1:5x103 respectivey. SBSE-TDS-GC-MS was also investigated for the analysis of OCPs in water samples. With this technique a good sensitivity down to 1 ppt was also obtained. The less sensitive nature of the MS compared to ECD was hereby compensated for by the large amount of polydimethylsiloxane (PDMS) phase on the stir bar. The method was repeatable and linear with a range of 1:5000, which is similar to the one obtained for the SPME-GC-ECD method. All three methods were also tested with real contaminated water samples and a comparison of the three techniques in terms of sensitivity, linearity, repeatability, availability and cost effectiveness was done. As a method of choice in terms of the above criteria, SPMEGC- ECD was applied to the water samples collected from Eritrea. The presence of some oePs such as a-BBC (benzenehexachloride), heptachlor, heptachlor epoxide, endosulfan I, p,p'-DDE (dichlorodiphenylchloroethylene), endosulfan II, p,p'-DDD (dichlorodiphenyldichloroethane), endosu!fan sulfate and p,p'-DDT (dichlorodiphenyltrichloroethane) in some of the Eritrean water samples was demonstrated The SPME-GC-ECD technique for the analysis OCPs in soil and sediment samples was investigated. It was shown to be able to detect down to 1 pg/g (lppt) with good linearity and repeatability. The method was also evaluated for authentic soil samples. Due to a lack of time the method could not be applied for the analysis of the soil and sediment samples collected from Eritrea. / AFRIKAANSE OPSOMMING: Die keuse van 'n gepaste monster-voorbereidingsmetode wat gebruik word tesame met 'n chromatografiese skeidingtegniek in omgewings-analise het 'n beduidende effek op die algehele metode. Die doel van hierdie werk was om metodes soos mikrovloeistof- vloeistof ekstraksie (цLLE) en soliede fase mikro ekstraksie (SPME) in kombinasie met gaschromatografie met elektronvangs deteksie (GC-ECD) te ontwikkel vir die analise van organochloor-pestisiede (OCPs) in natuurlike water. Vervolgens is hierdie metodes vergelyk met die onlangs-ontwikkelde roerstaaf sorptiewe ekstraksie tegniek (SBSE) in kombinasie met termiese desorbsie-GCmassaspektrometriese deteksie (TDS-GC-MSD). Die mees geskikte metode is vervolgens gebruik vir die analise van Eritreaanse watermonsters. Daarbenewens was die doelook om 'n sensitiewe metode te ontwikkel vir die analise van OCPs in gronden sedimentmonsters. Beide цLLE en SPME-GC-ECD metodes is gekarakteriseer deur goeie herhaalbaarheid en lineariteit. Die sensitiwiteit van bogenoemde metodes was minder as 100 dele per triljoen (ppt) en 1 ppt, respektiewelik. Ook met SBSE-TDS-GC-MSD kon 'n deteksielimiet van 1 ppt bereik word. In hierdie geval is vir die verlies van sensitiwiteit van die MSD in vergelyking met die ECD, gekompenseer deur die groter hoeveelheid PDMS op die roerstaaf in vergelyking met 'n SPME apparaat. Die herhaalbaarheid en lineariteit van die metode is vergelykbaar met dié van die SPMEGC- ECD metode. Al drie metodes is vergelyk vir die analise van gekontamineerde watermonsters in terme van sensitiwiteit, liniêre bereik, herhaalbaarheid, toeganklikheid en kosteeffektiwiteit. SPME-GC-ECD is vervolgens gekies as metode van voorkeur vir die analise van Eritreaanse watermonsters. Die teenwoordigheid van sekere OCPs soos a-BHC, heptachloor, heptachloorepoksied, endosulfan I, p,p'-DDE, endosulfan II, p,p' -DDD, endosulfan sulfaat en p,p' -DDT in die monsters is gedemonstreer. Die toepasbaarheid van die SPME-GC-ECD metode vir die analise van OCPs in grond-en sedimentmonsters is ook geëvalueer, en dit was moontlik om so min as 1 pg/g waar te neem. Weens tydbeperkings was dit nie moontlik om Eritreaanse grondmonsters met die ontwikkelde metode te analiseer nie.

Thesis (PhD (Chemistry and Polymer Science))--Stellenbosch University, 2008. / The successful preparation and structural characterization of a number of N,N-dialkyl-N’-benzoyl(thio)selenourea ligands is described; where the intermolecular interactions are characterized by the presence of Resonance Assisted Hydrogen Bonding (RAHB), π- π interactions between neighbouring benzene residues only being evident amongst the longer alkyl chain derivatives. The first structural characterization of an asymmetrically substituted N,N-dialkyl- N’-benzoylselenourea ligand reveals an increased stability of the Z isomer in the solid state, this being reflected by the sulfur analogue. Attempts to synthesise N,N-dicyclohexyl-N’-benzoylselenourea led to the isolation and structural characterization of a novel 1,3,5-oxaselenazine salt and dicyclohexylaminobenzoate. The first structural characterization of a “bipodal” N,N-dialkyl-N’-benzoylselenourea ligand, 3,3,3’,3’-tetrabutyl-1,1’- isophthaloylbis(selenourea), reveals RAHB in the crystal lattice similar to that exhibited by the “monopodal” analogue, N,N-dibutyl-N’-benzoylselenourea. The successful complexation of the N,N-dialkyl-N’-benzoyl(thio)selenourea ligands to a number of different transition metal ions is reported allowing the preparation of several potential single source precursors. Coordination through the O and Se/S donor atoms to Pd(II) results in the formation of square planar metal complexes, with a cis conformation, several of which could be structurally characterized. In particular, the first structural elucidation of an asymmetrically substituted N,N-dialkyl-N’-benzoylselenourea metal complex, cis-bis(N-benzyl-N-methyl-N’- benzoylselenoureato)palladium(II) indicates the increased stability of the EZ isomer in the solid state. Structural elucidation of the novel (N,N-diphenyl-N’-benzoylselenoureato)cadmium(II) reveals a bimetallic complex in the solid state, where the expected 2:1 ligand : metal ratio is maintained, and the two Cd(II) centres are 5 and 6 coordinated, with O and Se donor atoms. Multinuclear Nuclear Magnetic Resonance (NMR) Spectroscopy has been employed in the thorough characterisation of the potential single source precursors, 77Se NMR spectroscopy indicating a decreased shielding of the 77Se nucleus as the “hardness” of the central metal ion increases i.e. Pd(II) > Zn(II) > Cd(II). Use of 113Cd NMR spectroscopy indicates the preferential binding of N,N-diethyl-N’- benzoylselenourea to Cd(II) over that of its sulfur analogue, and initial studies suggest a form of chelate metathesis taking place in solution. 31P NMR spectroscopy is used to gain insight into the formation of cis-bis(N,N-diethyl-N’- benzoylselenoureato)Pt(II). Thermolysis of (N,N-diethyl-N’-benzoylselenoureato)cadmium(II) and its sulfur analogue led to the successful synthesis of CdSe and CdS quantum dots respectively, where thermolysis over a range of temperatures allows a degree of size control over the resulting nanoparticles. The effect of precursor alkyl chain length on nanoparticle morphology was investigated for both the N,N-dialkyl-N’-benzoylthio- and –selenoureas. A correlation between the two for the (N,N-dialkyl-N’-benzoylselenoureato)Cd(II) complexes is described and possible growth mechanisms are discussed. Preliminary investigations into the use of other N,N-dialkyl-N’-benzoyl(thio)selenourea metal complexes as single source precursors reveal that both (N,N-diethyl-N’-benzoylselenoureato)Zn(II) and its sulfur analogue show potential as single source precursors for the formation of ZnO and ZnS nanoparticles respectively. Initial studies into the use of N,N-dialkyl-N’-benzoyl(thio)selenourea metal complexes as single source precursors for the synthesis of core-shell nanoparticles is briefly described. The Aerosol Assisted Chemical Vapour Deposition (AACVD) of several N,N-dialkyl-N’-benzoyl(thio)selenourea metal complexes is reported, where both (N,N-diethyl-N’-benzoylselenoureato)Cd(II) and its sulfur analogue allow the deposition of crystalline CdSe and CdS respectively. The AACVD of (N,N-diethyl-N’- benzoylselenoureato)Zn(II) leads to the deposition of crystalline ZnSe, ZnS being deposited by (N,N-diethyl-N’-benzoylthioureato)Zn(II). The deposition of heazelwoodite (Ni3S2) with varying morphologies results from the AACVD of cis-bis(N,N-diethyl-N’-benzoylthioureato)Ni(II). Thermal annealing of the amorphous material deposited by the AACVD of cis-bis(N,N-diethyl-N’-benzoylthioureato)Pd(II), allows the formation of highly crystalline palladium. The deposition of metallic platinum using cis-bis(N,N-diethyl-N’-benzoylthioureato)Pt(II) is described as well as the deposition of crystalline Pd17Se15 from cis-bis(N,N-diethyl-N’-benzoylselenoureato)Pd(II). This, to the best of our knowledge, is the first time that AACVD has been performed, using the N,N-dialkyl-N’- benzoyl(thio)selenourea metal complexes as single source precursors, in addition, we believe it to be the first time that palladium selenide has been deposited using the AACVD technique.

Thesis (PhD (Chemistry and Polymer Science))--Stellenbosch University, 2008. / Novel gold(I) trithiophosphite complexes were synthesised by utilising the ligands P(SR)3 (R = Me, Ph) and 1,2-bis(1,3,2-dithiaphospholan-2-ylthio)ethane (2L). Reaction with (tht)AuCl or (tht)AuC6F5 readily yielded the corresponding complexes (RS)3PAuX and 2L(AuX)2 (X = Cl, C6F5) as well as {Au[P(SMe)3]2}CF3SO3. Structural characterisation by X-ray diffraction revealed linear complexes in part associating by Au…Au and/or Au…S contacts, two polymorphs of one compound associating by either Au…S interactions or p-stacking was also obtained. (MeS)3PAuCl and (MeO)3PAuCl were found to be isostructural in the solid state. The complex chloro[tris(4-methylthiazol-2-yl)phosphane]gold, A, was used to probe the electronic influence tris(azol-2-yl)phosphanes exert upon gold(I) by substituting the chloride with various thiolates. In contrast to Ph3PAuCl, only NCS– and PhC(O)S– afforded stable compounds which could be attributed to a weaker donating capability of the tris- (azolyl)phosphane ligand class. The compounds A and chloro[tris(thiazol-2-yl)phosphane]- gold, B, were shown to crystallise in 4 new polymorphs and solvates bringing the total to an exceptional seven. Among the solid-state structures of A the rare instance of a polymorph and a thf solvate not exhibiting aurophilic interactions as opposed to the original structure were observed. Complex B was shown to crystallise in polymorphs where dimers are associated either by Au…Au or Au…Cl interactions but otherwise exhibit similar arrangements of the ligand, this set of polymorphs is unprecedented amongst gold complexes. An NMR experiment proved that tris(thiazolyl)phosphane complexes are subject to hydrolysis under alkaline conditions. A trimeric gold(I) heterometallacycle, obtained by reacting (tht)AuCl with 4,4-dimethyl-2-(2- thienyl)oxazoline deprotonated at C-5 of the thiophene ring, was structurally characterised. Intramolecular Au…S interactions were found to be present which precluded interaction of the gold atoms with other metal centres such as Me3CNCAuCl or AgNO3. A second solvate obtained additionally exhibits Au…Au interactions. The scope of uncommon bis-imine coordination to AuI was expanded by utilising 1,2-bis(1-imidazolylmethyl)-2,4,6-trimethylbenzene (2L) to synthesise the [Au2(μ-2L)2]2+ cation. The triflate salt forms the first porous crystal structure of gold and the co-crystallised solvent could be partially removed by evacuation at elevated temperatures. Utilising a ditopic phosphite ligand instead of the commonly used ditopic phosphane ligands, a new cationic species of the type [Au2(μ-2L)3]2+ was characterised in the solid state for the first time. Finally, employing 2-phenylthiazole and 1-(thiazol-2-yl)piperidine which can be deprotonated at C-5 of the thiazole ring, Fischer-type pentacarbonyltungsten carbeniate complexes were prepared and structurally characterised. Starting from these complexes, the analogous Fischertype methoxycarbene as well as carbyne complexes could be obtained by alkylation and formal oxide abstraction, respectively. The latter products readily formed dinuclear adducts with AuCl. A Fischer-type methoxycarbene could be transferred to AuI affording the first such gold(I) complex exhibiting Au…Au interactions in the solid state as well as a rare agostic Au…H interaction which was examined by low-temperature 1H NMR measurements. Transfer of the carbeniate ligand derived from 1-(thiazol-2-yl)piperidine to Ph3PAu+ afforded an aurated thiazole product (by an unprecedented loss of CO) which may be represented as a pseudoabnormal azolylidene complex owing to W(CO)5-coordination at a distant nitrogen. The carbeniate originating from 2-phenylthiazole, on the other hand, afforded, by rare W(CO)5- trapping and without CO-loss, a pseudo Fischer-type carbene complex. Carbene transfer to gold was complemented by the first transfers of rNHC ligands from chromium and tungsten to gold(I) affording a novel class of complexes, all of which were structurally characterised. This work bridges the unnatural divide created between Fischer and N-heterocyclic carbene complexes.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Honeybush tea, also known as “South Africa’s sweetest tea”, is a herbal tea made from the leaves and twigs of Cyclopia spp., indigenous to the fynbos biome in the Western and Eastern Cape provinces of South Africa. The pleasant sweet aroma and taste of fermented honeybush, its low tannin content and the absence of caffeine have led to widespread interest in the commercial cultivation and processing of honeybush tea since the mid-1990s. Although more than 20 species of honeybush grow in the wild, only a few species are commercially exploited for the manufacture of tea. Currently the more prominent species are C. intermedia, C. subternata, C. genistoides, and C. sessiliflora. The present research contributes to a comprehensive honeybush research programme being conducted at the Agricultural Research Council (ARC) Infruitec-Nietvoorbij in South Africa. The first phase of the present study, using C. genistoides as representative species, was aimed at developing the necessary methodology for the analysis of extremely low concentrations of honeybush volatiles. A high-capacity headspace sample enrichment probe was applied successfully in conjunction with gas chromatography-mass spectrometry (GC-MS) to analyse the volatile organic compounds present in dry or infused unfermented and fermented honeybush. A total number of 255 volatile compounds were identified in unfermented and fermented honeybush, the majority of which are terpenoids (138; 54%) comprising mostly terpenes, terpene ketones, terpene alcohols and terpene ethers. Of the other compound classes, the aldehydes are the largest group, followed by esters, hydrocarbons and ketones. The stereochemistry of the identified compounds was determined whenever possible. This is the most comprehensive chemical characterisation of the volatile compounds in a South African herbal plant reported to date. A comparative study of green and fermented honeybush showed that the same compounds are, to a large extent, present in both, albeit in different relative concentrations. Not all of the identified honeybush volatiles are necessarily odour-active compounds contributing to the overall typical honeybush aroma. An important aspect of this research was thus the identification of the 46 odour-active compounds in fermented honeybush by means of gas chromatography-olfactometry (GC-O), using detection frequency and aroma extract dilution analysis methods. Fifteen of these compounds, mainly terpenoids, were singled out as the most intense individual contributors to the honeybush aroma based on consideration of all the relevant GC-O data. The odours of certain compounds, i.e. (6E,8Z)-megastigma-4,6,8-trien-3-one, (6E,8E)-megastigma- 4,6,8-trien-3-one, (7E)-megastigma-5,7,9-trien-4-one, 10-epi- -eudesmol, epi- -muurolol and epi- - cadinol, were perceived by GC-O assessors as typically honeybush-like. The quantitative GC-MS data of seven different Cyclopia samples (including four different species and variants thereof) were compared with respect to all the volatile components and particularly with respect to the odour-active compounds. Interesting variations were found in the concentrations of certain odour-active compounds in the various samples. The quantitative data obtained for the odour-active honeybush volatiles and data obtained from the sensory analysis of eight Cyclopia samples (including four different species and variants thereof) were subjected to statistical analysis and interesting associations between compounds with certain sensory aroma attributes were established. The present study has made a major contribution to the scientific knowledge regarding one of South Africa’s most popular indigenous herbal teas. / AFRIKAANSE OPSOMMING: Heuningbostee, wat ook bekend staan as “Suid-Afrika se soetste tee”, word gemaak van die blare en takkies van Cyclopia spp. wat inheems is en voorkom in die fynbosbioom van die Wes- en Oos-Kaapprovinsies van Suid-Afrika. Die aangename soet smaak en aroma van gefermenteerde heuningbos, die lae tannnien-inhoud en die feit dat die tee kafeïenvry is, het gelei tot belangstelling in die kommersiële verbouing en prosessering van heuningbostee gedurende die 1990s. Meer as 20 heuningbosspesies kom in die natuur voor, maar slegs ‘n paar spesies word kommersieel verbou vir die vervaardiging van heuningbostee waarvan C. intermedia, C. subternata, C. genistoides en C. sessiliflora tans die belangrikste spesies is. Die navorsing maak deel uit van ‘n omvattende heuningbos navorsingsprogram wat onder leiding staan van die Landbounavorsingsraad Infruitec- Nietvoorbij in Suid-Afrika. In die eerste fase van die huidige studie is die nodige analitiese metodologie ontwikkel vir die monsterneming en analise van die vlugtige organiese verbindings wat in uiters lae konsentrasies in heuningbos voorkom, deur van ‘n verteenwoordigende spesie, C. genistoides, gebruik te maak. ‘n Sogenaamde “sample enrichment probe” (SEP) is ontwikkel en suksesvol in kombinasie met gaschromatografie-massaspektrometrie (GC-MS) aangewend vir die analise van die vlugtige verbindings aanwesig in die bodamp van sowel droë plantmateriaal as infusies van ongefermenteerde en gefermenteerde heuningbos. ‘n Totaal van 255 vlugtige verbindings is geïdentifiseer, waarvan die meeste hoofsaaklik terpenoïede is (138, 54%) en terpene, terpeenketone, terpeenalkohole en terpeeneters insluit. Die ander verbindingsgroepe, waarvan die aldehiede die grootste groep is, sluit in esters, koolwaterstowwe en ketone. Indien haalbaar, is die stereochemie van die geïdentifiseerde verbindings ook bepaal. Hierdie studie is die mees omvattende chemiese karakterisering van die vlugtige verbindings in ‘n Suid-Afrikaanse kruieplant wat tot dusver onderneem is. ‘n Vergelykende studie het getoon dat ongefermenteerde en gefermenteerde heuningbos tot ‘n groot mate dieselfde verbindings, hoewel in verskillende relatiewe konsentrasies, bevat. Nie al die geïdentifiseerde vlugtige verbindings in heuningbos is noodwendig aroma-aktiewe verbindings wat ‘n bydrae tot die algehele tipiese heuningbosaroma lewer nie en daarom was die identifisering van die 46 aroma-aktiewe verbindings in geferementeerde heuningbos deur gebruik te maak van gaschromatografie-olfaktometrie (GC-O) deur middel van deteksiefrekwensie en aroma ekstrak verdunningsanalise, ‘n belangrike aspek van die navorsing. Na oorweging van al die tersaaklike GC-O data is 15 van hierdie verbindings, hoofsaaklik terpenoïede, uitgesonder as die verbindings wat die belangrikste bydrae tot die heuningbosaroma lewer. Die reuke van sekere van die verbindings, nl. (6E,8Z)-megastigma-4,6,8-triën-3-oon, (6E,8E)-megastigma-4,6,8-triën-3-oon, (7E)-megastigma-5,7,9-triën-4-oon, 10-epi- -eudesmol, epi- -muurolol, en epi- -cadinol, is deur sommige van die GC-O paneellede as tipies heuningbosagtig beskryf. Die kwantitatiewe GC-MS data van sewe verskillende Cyclopia monsters (insluitende vier verskillende spesies en variante daarvan) is vergelyk met betrekking tot al die vlugtige verbindings, asook veral met betrekking tot die aroma-aktiewe verbindings. Interessante variasies in die konsentrasies van sekere aroma-aktiewe verbindings is in die verskillende monsters waargeneem. Die kwantitatiewe data van die aroma-aktiewe heuningbosverbindings en data verkry uit die sensoriese analise van agt Cyclopia monsters (insluitende vier verskillende spesies en variante daarvan), is onderwerp aan statistiese analises waaruit interessante assosiasies tussen verbindings met sekere sensoriese aroma-eienskappe waargeneem is. Hierdie studie lewer ‘n groot bydrae tot die wetenskaplike kennis aangaande een van Suid- Afrika se mees populêre inheemse kruietees.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Due to the commercial, nutritional and health value of vegetable oils, seeds and beans, the analysis of their components is of much interest. In this dissertation oil-containing food products, specifically vegetable oils, seeds and beans, were investigated. Selected minor components of three locally produced vegetable oils, namely apricot kernel, avocado pear and macadamia nut oils were investigated using 31P NMR spectroscopy. These minor components, including 1,2 diacylglycerols, 1,3 diacylglycerols and free fatty acids, were identified in the 31P NMR spectra of each of the three vegetable oils for the first time. Two approaches were used for the quantification of the minor components present in the spectra. A calibration curve approach used known concentrations of standard minor components to establish calibration curves while a direct correlation approach calculated the unknown concentration of minor components in the vegetable oils using a known amount of standard compound within the analysis solution. These approaches aided in determining the concentration of minor components during storage studies in which vegetable oils were stored in five different ways: exposed to light, in a cupboard, in a cupboard wrapped in tin foil, at -8 °C and at 5 °C. It was found that determining the best storage condition for each oil was difficult since individual minor components were affected differently by the various storage conditions. However, in general the best storage conditions appeared to be 5 °C and -8 °C. The oil, protein and carbohydrate contents of sesame, sunflower, poppy, and pumpkin seeds, and soy, mung, black and kidney beans were analysed by thermogravimetric analysis and 13C NMR solid state NMR spectroscopy. It was shown that the first derivative of TGA data for seeds and beans can give valuable information about the carbohydrate, moisture, protein and fat content. This has not been previously demonstrated. For the seeds, the integration of a region between 270–480 ºC was equal to the sum of the oil and protein content and compared well to quantitative results obtained by other conventional methods. For beans the integration of a region between 180-590 ºC, gave a value which represented the sum of the oil, protein and carbohydrate content. 13C solid state NMR spectroscopy, including SPE-MAS, CP-MAS and variable contact time experiments, was carried out on these seeds and beans and gave valuable information on the solid-like and liquid-like components. To our knowledge these seeds and beans have never been previously analysed using this technique. 13C SPE-MAS NMR spectroscopy indicated that the seeds contained more liquid-like components than the beans. In turn the 13C CP-MAS NMR spectra indicated that beans had higher levels of solid-like components than the seeds. These conclusions correlated well with the quantities of liquid-like components and solid-like components that were determined by conventional methods and TGA. Preliminary studies using T1pH experiments on the components present in the seeds and beans led to a few observations. Most interesting is that a model using a two- phase fit in order to determine T1pH values appears to be more accurate than a one-phase model. / AFRIKAANSE OPSOMMING: Groente olies, sade en bone is ‘n onderwerp van groot belang omrede hul kommersiële, voeding en gesondheidswaardes. In hierdie tesis is olie-bevattende voedselprodukte, spesifiek groente-olies, sade en bone geanaliseer. Geselekteerde komponente teenwoordig in klein hoeveelhede in drie lokaal geproduseerde groente-olies, naamlik appelkoos-pit, avokadopeer en makadamia-neut olies is geanaliseer met behulp van 31P KMR spektroskopie. Hierdie komponente, insluitend 1,2 diasielglyserole, 1,3 diasielglyserole en ongebonde vetsure, is vir die eerste keer geïdentifiseer in die 31P KMR spektra van die drie groente olies. Twee benaderings is gebruik vir die hoeveelheids-bepaling van die komponente in die spektra. ‘n Yking-kurwe metode het gebruik gemaak van bekende hoeveelhede konsentrasies standaard komponente vir die opstel van yking-kurwes, terwyl ‘n direkte korrelasie metode gebruik is om die onbekende konsentrasie van komponente in groente olies te bepaal met behulp van ‘n bekende hoeveelheid standaard verbinding teenwoordig in die oplossing. Hierdie metodes het gelei tot die bepaling van die konsentrasies van die komponente gedurende vyf verskillende berging toestande wat ingesluit het: Blootgestel aan lig, in ‘n donker kas, in ‘n donker kas toegevou in tin foelie, bevries by -8 °C en in ’n koelkas by 5 °C. Dit was bevind dat bepaling van die beste bergingstoestand vir elke olie moeilik is aangesien die individuele komponente verskillend geaffekteer word deur die verskeie berging toestande. Die beste bergings toestand oor die algemeen blyk egter om by 5 °C en -8 °C te wees. Sesamsaad, sonneblomsaad, papawersaad en pampoensaad sowel as sojaboontjie, mungboontjie, swartboontjie en pronkboontjie se olie, protein en koolhidraat komponente was geanaliseer met behulp van termogravimetriese analise (TGA) en 13C soliede toestand KMR spektroskopie. Dit was bevind dat die eerste afgeleide van die TGA data waardevolle inligting lewer oor die komponent inhoud van elk van die sade en bone. Hierdie is nog nie vantevore bevind nie. Vir die sade, was die integrasie van ‘n area tussen 270–480 ºC gelyk aan die som van die olie en proteïen inhoud en het goed vergelyk met die waardes verky deur algemene analitiese metodes. Vir die boontjies, was die integrasie van ‘n area tussen 180-590 ºC gelyk aan die som van die olie, protein en koolhidraat inhoud. 13C vaste staat KMR spektroskopie, insluitende SPE-MAS, CP-MAS en variëerbare kontak-tyd eksperimente, was gedoen en het waardevolle inligting gelewer omtrent die solied-agtige en mobiel-agtige komponente. Hierdie sade en bone is tot ons kennis nog nie van te vore met die tegnieke ondersoek nie. 13C SPE-MAS NMR spektroskopie het aangedui dat daar ‘n groter hoeveelheid mobiel-agtige komponente in sade as in bone teenwoordig is. 13C CP-MAS NMR spektroskopie het weer aangedui dat daar ‘n groter hoeveelheid solied-agtige komponente in bone as in sade teenwoordig is. Hierdie gevolgtrekkings het goed vergelyk met die waarnemings verkry deur konvensionele analitiese metodes en TGA. Voorlopige studies op die komponente van sade en bone deur T1pH eksperimente het tot ‘n paar gevolgtrekkings gelei waarvan die mees interessantste was dat ‘n twee-fase model vir die bepaling van T1pH waardes beter resultate lewer as ‘n een-fase model.