In this study, a series of carboxylic acid functionalised pyrrole derivatives and ferrocene- and ruthenocene-containing dipyrromethanes were synthesised. Porphyrin complexes bearing a mono-carboxylic acid functional group in the β-position as well as ferrocene or ruthenocene in the -5-, or -5,10-, or -5,15- meso positions have been prepared from these pyrrole derivatives. A series of metal-free tetraphenylporphyrins containing nitro, amino or carboxylic acid functional groups on the para position of one of the phenyl rings were synthesised from pyrrole and a substituted benzaldehyde. In addition, a series of metal-free porphyrins containing an electron-withdrawing CF3 group in the ortho, meta or para positions of a phenyl group in one or two of the four meso porphyrin position as well as three or two electron-donating ferrocenyl or ruthenocenyl group in the other meso porphyrin positions were synthesised though a modified statistical condensation procedure of a substituted dipyrromethane and an appropriately functionalised benzaldehyde. Copper and nickel were also inserted into the cavities of these porphyrins. Techniques to synthesise water-soluble polymers bearing a porphyrin side chain were also developed. All complexes were fully characterised inter alia with 1H NMR, IR and UV/vis spectroscopic methods and by electrochemical studies. The new porphyrins described in this study may enhance cancer therapy by synergistic effects between the chemotherapeutically active metallocene groups and the photodynamically active porphyrin macrocycle. The availability of water-soluble porphyrins via the water-soluble ADF quantum chemical computations were performed on peripherally and non-peripherally substituted phthalocyanines to optimise gas phase structures and to generate theoretically predicted UV/vis spectra. The result indicated that DFT calculations could be utilised to design a phthalocyanine that possesses Q-band λmax values in its electronic spectra that is red-shifted enough to render the phthalocyanine appropriate for application in photodynamic therapy of cancer. polymeric drug delivery systems synthesised in this study may enhance clinical administration of these new antineoplastic drugs to patients. Electrochemical studies revealed that all ferrocene-containing porphyrins exhibited chemically and electrochemically reversible one-electron transfer steps for the Fc/Fc+ couple. Because of the use of [NBu4][B(C6F5)4] as supporting electrolyte, an electrochemical reversible Rc/Rc+ couple could be identified, rather than the usual irreversible Cp2RuII/Cp2RuIV couple. The metallocenefree porphyrins exhibited two one-electron oxidation waves as well as two one-electron reduction waves. The metallocene-containing porphyrins exhibited only one one-electron oxidation wave; the second went-off scale in the potential window that CH2Cl2 as solvent allows.

Mimosa (Acacia mearnsii) also known as black wattle, and quebracho (Schinopsis balansae, Schinopsis lorentzii) are the major commercial sources of natural condensed tannins (proanthocyanidin oligomers) used today. Mimosa bark is harvested from commercial plantations in South Africa which, according to a survey done by the Department of Water Affairs and Forestry for 2001, cover an area of about 107 000 hectares in South Africa. Quebracho is extracted from the wood of natural forests in Brazil and Argentina. Mimosa bark is extracted with water (about 50% by weight). Tara (Cæsalpinia spinosa) and Italian chestnut (Castanea sativa) are the major commercial sources of hydrolysable tannins. The ability of water soluble hydrolysable and condensed tannins (polyphenols) to react with proteins, presumably via hydrogen bonds, lies at the heart of their ability to transform raw hide into leather and their commercial application as tannin agents. It explains their existence in nature as anti-feeding agents as it renders plants indigestible to insects and herbivores. It also explains the use of milk in tea where the complexation of milk proteins with tea tannins reduces astringency. The chemistry of this process however remains uncertain. The polyphenolic nature also renders tannin extracts very susceptible to oxidation and further polymerisation and rearrangements that render the extracts even more complex. This is evident in the transformation of green tea (high flavan-3-ol content and low condensed tannin content) into Indian or black tea (low flavan-3-ol content and high condensed tannin content). The quality of red wine is to a large extent determined by the amount and composition (which changes during ageing in a poorly understood way) of its condensed tannin. The tannins react with protein receptors on the tongue to impart âmouth feelâ characteristics. Wood-aged wine not only contains condensed tannins from grape skin, but also hydrolysable tannins from the wooden barrels it is aged in. The polyphenolic nature of the aromatic rings allows reaction with electrophiles. This forms the basis of adhesive manufacturing, where formaldehyde is used to polymerise tannin extracts to form adhesives. Other commercial applications of tannin extracts include the use as anti-foaming agents in oil drilling and the manufacturing of amine containing resins (via the Mannich reaction) for water purification applications (removal of heavy metals). The production of mimosa condensed tannin is a sustainable process as trees are harvested every eight years. Tannins will become a more important source of feedstock nutrients, as crude oil, which is currently used, becomes depleted. It also creates employment in rural areas. Higher oligomers of condensed tannins are built up by successive addition of flavan-3-ol monomer extension units via C-4 to C-8 or C-4 to C-6 interflavanyl bonds. Higher oligomers are impossible to purify by chromatography and other methods of analysis are required. Acid catalysed fission of the interflavanyl bonds and trapping of the monomer intermediates with toluene-α-thiol or floroglucinol followed by analysis of the trapped products with HPLC is normally used to analyse condensed tannin composition. The analysis of mimosa and quebracho tannins is however compounded by the resorcinol type A-ring in these compounds. The absence of a 5-OH group imparts stability to the interflavanyl bond against acid hydrolysis. The high temperatures thus required to hydrolyse the interflavanyl bond in mimosa and quebracho tannins leads to decomposition. Mass spectrometry and 13C NMR (nuclear magnetic resonance) spectrometry in solution have also been used with varying degrees of success. The analysis of hydrolysable tannins is even more complex than that of condensed tannins. As a result, the composition of condensed and hydrolysable tannin extracts remains uncertain, after more than 50 years of research. Of particular interest are the average chain length of tannin extracts from different sources and the composition of the constituent monomers. In this thesis the potential of solid state NMR and electrospray mass spectroscopy to solve vexing problems in tannin chemistry was investigated. Solid state NMR is particularly useful to investigate insoluble samples, overcoming problems associated with selective extraction, chemical modifications during extraction and sample preparation and uncertainty regarding compounds that are not extracted. Electrospray mass spectrometry complements MALDITOF mass spectrometry in that molecules with masses below 500 Dalton are detected. We were able to assign all the resonances in solid state NMR of hydrolysable and condensed tannins by comparing liquid and solid state spectra of pure flavonoids and tannin extract. This allowed us to distinguish unequivocally between condensed tannins and hydrolysable tannins with a simple routine experiment, avoiding laborious chemical tests. A method was developed to identify and distinguish with confidence between quebracho and mimosa condensed tannins. This method is the only available method to identify quebracho, which is of interest to oenology (quebracho tannins are added to wine) and could hitherto only be identified chemically because it tests negatively for all the available tests for tannins. We established that no insoluble higher oligomeric condensed tannins or tannins covalently bonded to other insoluble bark components remain in spent mimosa bark (after extraction of tannins). It promises an easy way for the wattle industry to investigate lower extraction temperatures and extraction time and the associated energy savings. A fingerprinting method for mimosa was developed and is already used by the industry (Annex A). As the gum resonances do not overlap with the tannin resonances, the bark can be analysed directly without the requirement of manufacturing an extract. The only sample preparation required is to grind the bark (about 100mg) finely and pack the solid state NMR rotor. As carbon is magnetised via hydrogen, less than 30 minutes NMR time is required per sample. This provides an easy way to identify the bark of quebracho, mimosa and hydrolysable tannins. A solid state NMR spectrum of the spent bark not only indicated that no condensed tannins remain, but also supports the conclusion that spent bark consists of water insoluble gums (polymers of glucose and other sugars). We believe that this method will find application in identifying novel sources of tannins from indigenous plants. We expanded our investigation into tanned leather and developed an easy method to determine whether leather was tanned with mimosa, quebracho, Italian chestnut, tara, synthetic tanning material, chromium or aluminium. We believe this method can be used by the leather industry to determine tannin loading of tanned leathers. By combining our electrospray mass spectrometry data with published MALDI-TOF mass spectrometry data we could calculate the relative composition of monomers, dimers, trimers, tetramers etc. in condensed tannin sample. These calculations were used by the mimosa and quebracho tannin industry to comply with new European Union (EU) REACH (Registration, Evaluation, Authorisation and Restriction of Chemical substances) legislation. Without compliance mimosa extract cannot be exported to the EU. Sulfitation (treating mimosa and particularly quebracho extract with bisulfite) is routinely used in industry to enhance the extractâs properties (e.g. increase water solubility) and products with different levels of sulfitation are commercially available. The chemical changes associated with sulfitation remain speculation. The solid state NMR indicated that the C-ring is opened during the process. The electrospray MS conclusively demonstrated the existence of condensed tannin-sulfonate molecules for the first time. The m/e values correspond with ring opening and introduction of a sulfonate group on the C-2 position.

Phase change materials based on polyethylene (LDPE, LLDPE and HDPE) and copper (micro and nano) blended with soft paraffin wax were studied in this work. The purpose of this study was to form composites that can store energy as well as conduct heat. The influence of wax content, as well as copper content and copper particle size, on the morphology and thermal, mechanical and conductivity properties was investigated. The scanning electron microscopy results show that both the Cu micro-and nano-particles were well dispersed in the matrix. The nano-particles, did, however, also form agglomerates. The results also show that the Cu micro-particles have a greater affinity for the wax than for the polyethylenes, giving rise to preferable crystallization of the wax around the Cu particles. The differential scanning calorimetry results show that the Cu micro- and nano-particles influence the crystallization behaviour of the polyethylenes in different ways. The extent to which the copper particles influence the crystallization behaviour of the polyethylenes also depends on the respective morphologies of the different polyethylenes. All the polyethylene/wax blends are immiscible or only partially miscible at wax contents of 30, 40 and 50%. The presence of wax in the polyethylene/wax blends reduces the melting temperatures of all three polyethylenes, indicating the plasticizing effect of the molten wax in the polyethylene matrix. The thermogravimetric analysis results show observable influence of both the presence of copper and the sizes of the copper particles, as well as the presence and amount of wax, on the thermal stabilities of the blends and composites. The thermal conductivities of the composites show a non-linear increase with an increase in Cu particle content. The presence of wax slightly decreases these values, confirming the preferable crystallization of wax around the Cu particles. The thermal conductivities of the Cu nano-particle containing composites, at the same copper contents, are almost the same as those of the micro-particle containing composites. Youngâs moduli increased with an increase in copper content in both the polyethylene composites and the polyethylene/wax blend composites, except in the case of HDPE where a decrease was observed. The dynamic mechanical analysis storage moduli determined through dynamic mechanical analysis show the same trends as the Youngâs moduli. The tensile strengths show variable behaviour, but mostly these values decrease with increasing Cu and wax contents. The energy storage results show that the heat transport is faster in the case of the blend composites compared to the polyethylene/wax blends, and the heat transport in the polyethylene/wax blends is also faster than in the neat polyethylene

Flavonoids are polyphenolic naturally occurring compounds with a wide variety of biological and physiological activities, like anti-platelet, anti-inflammatory, antioxidant, antiviral, antiallergenic, and antitumor properties. The potential therapeutic value of these compounds gave impetus to the development of numerous synthetic routes to not only get access to more material than possible through the isolation thereof from natural sources, but also to have access to flavonoids with substitution patterns different to those of naturally occurring analogues. Existing synthetic methodologies, however, involve tedious multistep processes, stoichiometric amounts of sometimes toxic reagents that produce large amounts of waste, harsh reaction conditions and are not always high yielding. With this in mind, it was envisaged that isoflavonoids might be accessible via a catalytic process entailing hydroesterification of 2-hydroxystilbenes. If the desired regio-isomer could be obtained during this reaction, cyclization between the 2-hydroxy group and the introduced ester moiety would give rise to the heterocyclic C-ring of the corresponding isoflavonoid. Although it is known that steric factors play a prominent role in regioselective control during hydroesterification processes, little is known about the role of the electronic environment around the double bond during these reactions. To address this issue and determine the feasibility of hydroesterification methodology for the synthesis of isoflavonoids, various stilbenes with electron-withdrawing and electron-donating groups, respectively on the two aromatic rings were envisaged as substrates to be subjected to palladium catalysed hydroesterification reactions. Since the Wittig reaction is well-known for the formation of alkenes such as the envisaged stilbenes, this approach was followed in order to prepare the required starting materials. Although the phosphonium salts, benzyltriphenylphosphonium bromide and p-methoxybenzyltriphenylphosphonium chloride, required as reactant in the Wittig reaction, could easily be prepared from the benzyl halide and triphenylphosphine (PPh3) in good yields (98 % and 76 %, respectively), preparation of the p-methoxybenzyl bromide/chloride were more challenging and led to an overall yield for the phosphonium salt of only 45 %. Other methodologies towards the synthesis of substituted phosphonium salts, i.e. treatment of p-methoxybenzyl alcohol with PPh3 in trifluoroacetic acid and cleavage of the benzyl methyl ether, p-methoxybenzyl methyl ether, with PPh3 .HBr, were therefore investigated but yields of only 10 and 38 %, respectively, were obtained. With the best methodology for the synthesis of phosphonium salts determined, attention was subsequently turned towards the final step in the preparation of the envisaged starting materials, i.e. synthesis of the oxygenated stilbenes. Methoxystilbene was therefore prepared according to the traditional Wittig reaction between benzyltriphenylphosphonium bromide and p-anisaldehyde, with BuLi as base and the product obtained in only 33 %. In an effort to improve on the yield, the same Wittig reaction was performed utilizing an organic/aqueous (aldehyde and aq. NaOH) biphasic solvent system with NaOH as base, which led to an increase in yield (54 %). Application of the same methodology to the synthesis of 2- methoxystilbene and 4-ethoxymethoxystilbene resulted in the formation of the desired products in 53 and 55 % yields, respectively. The latter compound, 4-ethoxymethoxystilbene, was subsequently subjected to acid catalysed deprotection (quantitative yield) followed by reaction with trifluoromethanesulfonyl chloride and triethylamine to obtain a stilbene, 4-trifluorosulfonyloxystilbene, protected with an electronwithdrawing substituent in 54 % yield. In an effort to improve the yields obtained for the stilbene preparation process to beyond ca. 50 %, a microwave assisted Perkin-type reaction between phydroxybenzaldehyde and phenylacetic acid with a piperidine-imidazole catalyst system and PEG-400 as solvent, was embarked upon and hydroxystilbene obtained in 42 % yield. Although the yield was almost the same as what was found with the Wittig method, this reaction did not require protection of the free phenolic hydroxy group or the time consuming preparation of starting materials and needed reaction times of only 10 minutes, as well as the added advantage of it being an environmentally more favourable procedure compared to the Wittig reaction. Since Pd(OAc)2 together with PPh3 and the Lewis acid activator/co-catalyst Al(OTf)3 have been reported as one of the best catalyst systems for the methoxycarbonylation of many different aliphatic alkenes, this catalyst system was utilized in the methoxycarbonylation (35 bar CO pressure, 95 °C) of model substrates like hex-1-ene, styrene and allylbenzene and obtained conversions to the corresponding methyl ester products of 70, 99 and 57 %, respectively. When trans-stilbene was, however subjected to the same reaction conditions and catalyst system, virtually no product was formed, so it was decided to use the model substrate, trans-β-methylstyrene, for determining the best catalyst system and reaction conditions for the methoxycarbonylation of substrates that has the double bond in conjugation with an aromatic ring. While it was found during this investigation that the reaction conditions of 35 bar and 95 °C was indeed the optimum for trans-β-methylstyrene, PdCl2 proved to be more reactive than Pd(OAc)2 when applied to the methoxycarbonylation of substrates with conjugated double bonds, with a 90 % conversion to the products, methyl 4-phenylbutanoate, methyl 2-methyl-3-phenylpropanoate and methyl 2-phenylbutanoate, in a 6:2:1 ratio. Due to the insolubility of trans-stilbene in pure methanol, a solvent study was embarked upon and MeOH:THF (1:1) was found to be the best alternative to pure methanol (conversion of 61 vs. 90 % in pure MeOH). With the optimum reaction conditions determined, the influence of a higher degree of substitution around the double bond as well as position of substituents attached to the double bond were investigated, it was also decided to evaluate the effect of the electron-donating and electron-withdrawing substituents attached to the aromatic ring, on the outcome of the reaction. Subjecting α-methylstyrene and 2-methyl-1- phenylprop-1-ene to the reaction conditions, led to the conversion (38 and 22 %, respectively) and isolation of the expected products, methyl 3-phenylbutanoate and methyl 3-methyl-4-phenylbutanoate, indicating that the steric environment around the double bond indeed has a significant influence on the reaction. The electronic effects were studied through the methoxycarbonylation of trans-anethole (the p-methoxy equivalent of trans-β-methylstyrene) and 1-(4'-trifluoromethanesulfonyloxyphenyl)prop-1-ene and, while the three expected products were obtained, it was found that an aromatic methoxy substitutent has an inhibiting effect on the reaction (21 % vs. 90 % conversion of trans-β-methylstyrene), while the substrate with the deactivating group showed a much improved conversion (31 %) compared to the p-methoxy analogue. Performing the methoxycarbonylation of trans-β-methylstyrene (in MeOH) in the presence of anisole (1:1) proved that aromatic methyl ethers indeed have a detrimental effect on the reaction, since only trace amounts of the products could be detected in this instance. Since chiral induction during the enantioselective synthesis of isoflavonoids has been achieved through utilization of amide chiral auxiliaries, like 2-imidazolidinones, it was decided to investigate the possibility of transforming an alkene into an amide in a one-step reaction and therefore circumvent the need for a second reaction to obtain the desired amide. Trans-β-methylstyrene was therefore subjected to the methoxycarbonylation conditions developed before [PdCl2/Al(OTf)3/PPh3, 35 bar CO, 95 °C], but in an inert solvent (THF) containing aniline as nucleophile and 53 % conversion to N,2-diphenylbutanamide and 2-methyl-N,3-diphenylpropanamide in a 6:1 ratio was obtained. Encouraged by the success of the first ever palladium catalysed aminocarbonylation reaction, the scope of the reaction was extended to include substrates like benzamide, n-butylamine and piperidine, but these nucleophiles were found to be unreactive, so more work is clearly needed to determine the conditions necessary for the successful utilization of these compounds in aminocarbonylation reactions. Finally, attention was turned to the methoxycarbonylation of the stilbenes, therefore trans- and cis-stilbene as well as trans-2-methoxystilbene were subjected to the palladium catalysed reaction, but only very low conversions (trace amounts up to 4 %) were found. Since everything pointed towards the electronic effect of conjugation, which deactivates the double bond to such an extent that the reaction with the palladium catalyst is supressed, being the cause of the failure of stilbenes to undergo methoxycarbonylation, 1,3- diphenylprop-1-ene, a substrate with the double bond not in conjugation with the two aromatic rings, were therefore subjected to the reaction and a conversion of 27 % to the product, methyl 2,4-diphenylbutanoate, was obtained. This result clearly demonstrates that the failure of stilbenes to undergo hydroesterification reactions originates in the fact that the double bond is in conjugation with two aromatic rings.

A series of MnIII(β-diketonato)3 complexes (β-diketonato = acac, ba, dbm, tfaa, tfth, tffu, tfba and hfac) were synthesized and characterized with the aid of mass spectroscopy, elemental analysis, X-ray diffraction (crystallography) and melting point measurements. The electrochemical study (cyclic voltammetry) showed that for MnIII(β-diketonato)3 complexes with more electron withdrawing R and R' groups on the β-diketonato ligands (RCOCHCOR')-, the redox potential of the [MnIII(β-diketonato)3] + e- [MnII(β-diketonato)3] redox reaction was found to shift to more positive potentials. The reduction potential of the the MnIII/MnII couple was correlated to electronic parameters (acid dissociation constant (pKa) of the uncoordinated b- diketones (RCOCH2COR'), the total group electronegativities [Σ(cR + cR')] and total Hammett sigma meta constant [Σ(ÏR + ÏR')] of the R and R' side groups of the b-diketonato ligands (RCOCHCOR') and the calculated electron affinity of Mn(β-diketonato)3 complexes. DFT computational studies were done on the Mn(acac)3 and Mn(dbm)3 complexeto understand the Jahn-Teller distortion that that MnIII(β-diketonato)3 complexes undergo. Electrochemical (cyclic voltammetry) studies were done on M(acac)3 complexes where M = V, Cr, Mn, Fe and Co. The reduction potential of the MIII/MII couple was correlated to electronic parameters such as the metal electronegativity (cPauling and cMulliken), calculated electron affinity and LUMO energy. DFT computational studies were done on the symmetry of V(acac)3 to investigate the Jahn-Teller distortion of the V(acac)3 complex. A DFT computational study was used to illustrate the d-orbital occupations of the M(acac)3 complexes ( M = V, Cr, Mn, Fe and Co).

This study includes the investigation of enaminoketones as ligand systems in rhodium complexes with possible future application in catalysis. In order to evaluate the influence of substituents on the phenyl ring on activity of the complex, a range of 4-(phenylamino)pent-3-en-2-onate (PhonyH) derivatives with chloride substituents on different positions on the phenyl ring were synthesized and characterized through X-ray crystallography as well as infrared and NMR spectroscopy. The compounds crystallize in a range of space groups and varying crystal systems, are stable in air over a period of several years and soluble in most solvents. The optimized structures of these compounds were calculated using DFT methods. The relative energies of the optimized structures adopt a cumulative nature â the relative energy of 2,4-Cl2-PhonyH with regard to unsubstituted PhonyH is roughly equal to the sum of the relative energies of 2-Cl- PhonyH and 4-Cl-PhonyH, while the relative energy of 2,6-Cl2-PhonyH is twice the relative energy of 2-Cl-PhonyH. The distortion of the phenyl ring from the ideal planar position presented in the calculated structures corresponds to the distortion observed in the solid state. The synthesis of the uncoordinated compounds was followed by the synthesis and characterization of a range of substituted dicarbonyl-[4-(phenylamino)pent-3-en-2-onato]- rhodium(I) complexes. The complexes crystallized in varying crystal systems and space groups. The trans influence of nitrogen was confirmed through the difference in the Rh-CO bonds: the Rh-C bond trans to the nitrogen atom is longer than the Rh-C bond trans to oxygen. The impact of the chloride substituents was observed from differences in geometrical parameters and is supported by information from the calculated structures and literature. The optimized structures of these complexes were calculated using DFT methods, and their optimized energies follow the same cumulative trend as observed in the uncoordinated compounds. A range of carbonyl-[4-(phenylamino)pent-3-en-2-onato]-triphenylphosphine-rhodium(I) {[Rh(N,O-Bid)(CO)(PPh3)]} complexes were synthesized and characterized, containing both electron-withdrawing chloride atoms and electron-donating methyl groups. These complexes displayed poor solubility, but once dissolved, were stable over a period of several months. Isomorphism was observed between [Rh(2,6-Cl2-Phony)(CO)(PPh3)] and [Rh(2,6-Me2- Phony)(CO)(PPh3)]. [Rh(2,6-Cl2-Phony)(CO)(PPh3)] and [Rh(2,6-Me2-Phony)(CO)(PPh3)] were chosen to investigate the exchange of triphenylphosphine coordinated in [Rh(N,O-Bid)(CO)(PPh3)] complexes with the uncoordinated phosphine, allowing for the comparison of the electronic effect of the substituents on the phenyl rings. The method chosen for the investigation was magnetization spin transfer, an NMR technique which utilizes the magnetic properties of nuclei and determines the kinetic properties of the exchange reaction by following the rate at which magnetic equilibrium is restored. The rate of the phosphine exchange reaction in [Rh(2,6-Cl2-Phony)(CO)(PPh3)] was determined as approximately three times faster than the rate of reaction for phosphine exchange in [Rh(2,6- Me2-Phony)(CO)(PPh3)]. The decreased electron density surrounding the rhodium atom in [Rh(2,6-Cl2-Phony)(CO)(PPh3)] allows for the reversal of the reaction as indicated by the k-1 values of approximately 11 s-1 calculated from the [Rh(2,6-Cl2-Phony)(CO)(PPh3)] exchange reaction. This value is absent in the reaction of the [Rh(2,6-Me2-Phony)(CO)(PPh3)] complex. The activation parameters of the exchange reaction in [Rh(2,6-Cl2-Phony)(CO)(PPh3)] (ÎHâ¡ = 25(3) kJ.mol-1 and ÎSâ¡ = -117(9) J.K-1.mol-1) correlate well with the parameters of the exchange reaction in [Rh(2,6-Me2-Phony)(CO)(PPh3)] (ÎHâ¡ = 24(4) kJ.mol-1 and ÎSâ¡ = -124(12) J.K-1.mol- 1). In both cases the value for entropy, ÎSâ¡, is negative, indicating an associative mechanism. The relative contribution of TÎSâ¡ to ÎGâ¡ is approximately 60% for both complexes, whereas the enthalpy (ÎHâ¡) terms are correspondingly small. This indicates that the activation process is primarily controlled by entropy and involves the formation of a stable, well-ordered transition state while bond weakening is less important. The relatively constant values for ÎGâ¡ imply that the exchange reaction is not very sensitive to changes in temperature.

This work reports on the preparation and characterization of polyhedral oligomeric silsesquioxanes (POSS)-containing polymer nanocomposites. The nanocomposites investigated in this study consist of two different types of POSS particles [octamethyl-T8- POSS and poly((propylmethacryl-heptaisobutyl-POSS)-co-(methyl-methacrylate))] dispersed in two different polymer matrices such as linear low-density polyethylene (LLDPE) and poly(methyl methacrylate) (PMMA). The melt-blending technique was used for the preparation of various nanocomposites. The morphology and structure of various nanocomposites were characterized by using x-ray diffraction (XRD), small angle x-ray scattering (SAXS), field-emission scanning electron microscopy (FE-SEM) and polarized optical microscopy (POM). The influence of different loadings of POSS particles on the thermal, thermomechanical, tensile, impact, and melt-state viscoelastic properties of nanocomposites was investigated. The morphology of the freeze-fractured surfaces of the LLDPE/POSS nanocomposites investigated by means of FE-SEM, revealed a homogeneous dispersion of the octamethyl-T8- POSS particles into the LLDPE matrix at a low filler content. The thermal properties of pure LLDPE and various nanocomposites showed double melting behaviour of the neat LLDPE matrix and the nanocomposite samples. The thermomechanical properties were investigated by stress-strain controlled rheometry using a solid-state rectangular fixture. The results showed a moderate improvement in both the storage and loss moduli of the neat LLDPE upon the incorporation of the POSS particles. The thermal stability of pure LLDPE and its nanocomposites was investigated in both air and nitrogen atmospheres. Two degradation steps were observed for all studied samples under nitrogen atmosphere. An improvement in the thermal stability of the samples studied in air in the high-temperature region was observed. The melt-state rheological properties measurements showed that the POSS particles were highly immiscible with the LLDPE matrix. POSS-containing LLDPE composites did not show any improvement in tensile properties. A decrease in impact properties of the LLDPE at higher POSS loadings was observed. The heat distortion temperature of the LLDPE samples increased with increasing the POSS loading in the polymer matrix. In the case of PMMA/POSS nanocomposites, the FE-SEM results did not give any information about the dispersion of the POSS particles in the PMMA matrix. However, the XRD studies indicated that the POSS particles were dispersed throughout the PMMA matrix. Both differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) showed a single glass transition for all the investigated samples. A decrease in the glass transition temperature was observed with increasing POSS loading in the polymer matrix. The rheological studies showed a gel-like character for all the investigated samples. An increase in the storage modulus for the 5 wt % POSS-containing sample was observed when compared with pure PMMA.

Phase change material (PCM) composites based on high-density polyethylene (HDPE) with soft (M3) and hard (H1) Fischer-Tropsch paraffin waxes and alkali-treated wood flour (WF) were investigated in this study. Both the blends and composites were prepared using a meltmixing method with a Brabender-Plastograph. SEM, DSC, TGA, DMA, tensile testing and water absorption were used to characterize the structure and properties of the blends and composites. The HDPE as the supporting matrix kept the molten waxes in compact shape during its phase transition from solid to liquid. Immiscibility of the PCMs (waxes) and the supporting matrix (HDPE) is a necessary property for effective energy storage. M3 wax blends were immiscible, whereas H1 wax blends seemed to be partially miscible and cocrystallized with the polymer matrix. In the presence of WF, the wax seems to crystallize around and in the pores of the WF particles, thus reducing co-crystallization with the HDPE and improving the energy storage capacity. TGA results showed a reduction in the thermal stabilities of the blends and composites in the presence of both WF and waxes. The storage modulus was reduced in the presence of wax, but improved when both WF and wax are present, although the improvement was less significant in the case of the M3 wax. Depending on the type of wax, the γ- and α-transitions were influenced differently, and there was an emergence of a β-relaxation in the case of the M3 wax blends. Both waxes had different influences on the tensile modulus and strength of the blends, with H1 increasing and M3 decreasing these properties. The PCM composites, on the other hand, had high moduli. High content of WF in the composites showed high water absorption. However, in the wax containing composites, there was a general decrease in water uptake.

Flavonoids and isoflavonoids are known to exhibit many important physiological properties and are especially promising candidates for cancer chemoprevention. Similar to most natural products, studies directed at the synthesis of flavonoids have, therefore, emerged from the search for new compounds with beneficial biological properties. Metabolic studies related to flavonoids are, however, frequently hampered by the inaccessibility of a variety of optically active compounds. While a single method for the synthesis of enantiomerically enriched isoflavonoids has been published, this process utilizes phenylacetic acid derivatives which are not always readily available in all naturally occurring substitution patterns. Even though the synthesis of phenylacetic acids are possible via a number of routes, these are based on ancient low yielding chemical processes utilizing harsh reaction conditions, stoichiometric quantities of reagents and in many cases, poisonous heavy metals like lead and thallium. In order to address the availability of phenylacetic acid derivatives of variable substitution patterns, the current study was aimed at the development of methodology for the synthesis of phenylacetic acid derivatives that would be high yielding, environmentally benign, have a limited number of process steps, and are applicable to all naturally occurring flavonoid substitution patterns. In this regard it was envisaged that ozonolysis of substituted allylbenzenes would comply with all of the stated criteria and was therefore investigated as methodology for the synthesis of phenylacetic acid derivatives that could serve as building blocks during isoflavonoid preparations. Since substituted allylbenzenes of all oxygenation patterns are not available commercially, the allylic moiety was introduced into the required phenols by means of a allyl phenyl ether intermediate, through utilization of Williamson ether synthesis (allyl bromide; K2CO3, refluxing CH3CN) followed by Claisen rearrangement of the neat allyl phenyl ethers, allyl 3- methoxyphenyl ether and allyl 3,5-dimethoxyphenyl ether, under microwave irradiation (at 200 ºC in 15 min. intervals and 0ô¯200 W variable power) to obtain the desired allylphenols, 1-allyl-2-hydroxy-4-methoxybenzene and 1-allyl-2-hydroxy-4,6-dimethoxy-benzene, in 44 and 88 % yield, respectively. Apart from the desired allylphenol, Claisen rearrangement of allyl 3-methoxyphenyl ether, however, also led to the formation of 1-allyl-2-hydroxy-6- methoxybenzene in 45% yield, indicating a lack of selectivity towards the formation of the sterically less hindered product under the prevailing reaction conditions. Since free phenolic substituents on the aromatic rings of the envisaged substrates might have a negative effect during ozonolysis reactions, the commercially available allylphenols as well as the two substrates prepared by allylation and Claisen rearrangement (vide supra) were subjected to methylation (MeI; K2CO3; refluxing acetone or acetonitrile) and the respective fully methylated analogues, 1-allyl-3,4-dimethoxybenzene, 1-allyl-2,4-dimethoxybenzene, 1-allyl- 2,4,6-trimethoxy-benzene, and 1-allyl-3,4,5-trimethoxybenzene, obtained in 79, 96, 80, and 77% yield, respectively. Ozonolysis [O3 (6ô¯8 min.), DCM, 0 °C] with reductive work-up [N-methylmorpholine-Noxide (NMMO)] of 1-allyl-2-methoxybenzene, 1-allyl-4-methoxybenzene, and 1-allyl-3,4- dimethoxybenzene afforded the corresponding phenylacetaldehydes in 58, 88 and 15% yield, respectively. Ozonolysis of the highly oxygenated substrates, 1-allyl-2-hydroxy-4- methoxybenzene, 1-allyl-2,4,6-trimethoxybenzene, and 1-allyl-3,4,5-trimethoxybenzene, however, only led to cleavage of the aromatic ring and formation of unidentifiable product mixtures. Cleavage of the aromatic rings of these substrates was confirmed by 1H NMR analysis of the reaction mixture [O3 (6ô¯8 min.), CDCl3, -78 °C] where the formation of the 1,2,4-trioxolane intermediate could be detected for the substrates that gave the desired phenylacetaldehydes but not for the highly oxygenated analogues. In order to reduce electron density on the aromatic ring of the highly oxygenated substrates and prevent ring ozonolysis in this way, the free hydroxy function on each substrate was changed into a trifluoromethanesulfonyl ester and the subtrates, 1-allyl-2- trifluoromethanesulfonyloxy-4-methoxybenzene, 1-allyl-4-trifluoromethanesulfonyloxy-3- methoxybenzene, 1-allyl-4-trifluoromethanesulfonyloxy-3,5-dimethoxybenzene, and 1-allyl- 2-trifluoromethanesulfonyloxy-4,6-dimethoxybenzene submitted to ozonation with NMMO work-up again. While the phloroglucinol based sulfonyl ester gave the desired phenylacetaldehyde in 71% yield, the other three substrates furnished NMMO induced double bond migration with the subsequent formation of the benzaldehyde equivalent products. When the ozonation reaction was repeated on the resorcinol, catechol and pyrogallol trifluoromethanesulphonyl esters, with replacement of the NMMO with dimethyl sulphide (DMS) as reductant, the desired phenylacetaldehydes or trioxolanes were, however, obtained in 63, 32 and 31% yield, respectively. Ozonolysis with oxidative work-up [(i) O3/MeOH; (ii) Ac2O-Et3N] applied to the monomethoxy substrates, 1-allyl-2-methoxybenzene and 1-allyl-4-methoxybenzene, afforded the desired methyl phenylacetates in 91 and 32% yield, respectively. Similar to what was found for the reductive work-up procedure, the higher oxygenated substrates had to be converted to their respective triflates before ozonolysis of the allylic double bond could be effected successfully and the phenylacetic acid esters, methyl 4-trifluoromethanesulfonyloxy- 3-methoxyphenyl acetate, methyl 4-trifluoromethanesulfonyloxy-3,5- dimethoxyphenyl acetate, and methyl 2-trifluoromethanesulfonyloxy-4,6-dimethoxyphenyl acetate obtained in 9, 17 and 65% yield, respectively. Since the published process for the stereoselective synthesis of isoflavonoids would require the phenyl acetates prepared through ozonolysis to be transformed into the corresponding amides, the possibility of direct formation of the nitrogen derivatives, like anilides, during the ozonolysis reaction was subsequently investigated. While first attempts at having the aniline present during the ozonolysis reaction only led to nitrogen oxidation, the process was amended to addition of the nitrogen nucleophile after formation of the 1,2,4-trioxolane, which resulted in the desired 2-methoxyphenylacetanilide being formed in 37% yield. The scope of this novel reaction was subsequently extended to the reaction of 1-allyl-4- methoxybenzene with acetamide leading to the product being obtained in 39% yield. While this reaction gave indications that deactivated nitrogen nucleophiles could also be used in this process, the reaction with 2-imidazolidinone, a secondary amide, did not succeed indicating that the new reaction still needs to be optimized to be useful in the enantioselective synthesis of isoflavonoids. Finally, it was shown during the current study that the phenylacetic acid derivatives prepared via ozonolysis could be transformed into deoxybenzoins, another isoflavonoid precursor, through formation of the acid chloride followed by reaction with a phenyl Grignard reagent. Thus phenylacetyl chloride could be reacted successfully with phenylmagnesiumbromide at - 78 oC in diethyl ether to give the deoxybenzoin in almost 60% yield.

Quebracho (Schinopsis lorentzii and Schinopsis balansae) heartwood and black wattle (Acacia mearnsii) bark extracts are important renewable industrial sources of proanthocyanidins (PACs). These extracts are used industrially in leather tanning and adhesive manufacturing. These applications are derived from their chemical properties. The poly hydroxy groups of PACs complex with proteins via hydrogen bonds and thus transforms raw skin into leather. The phloroglucinol or resorcinol type A-rings are nucleophilic and polymerise with aldehydes to form natural adhesives. The ortho hydroxy group on the B-ring form insoluble complexes with heavy metals and can be used in water purification applications. The extracts are often treated with sodium hydrogen sulphate (sulfitation) to enhance their industrial usefulness. From a literature search and discussions with role players in the black wattle and quebracho PAC extract manufacturing industry, it became evident that knowledge on the composition of commercial PACs extracts and chemical changes that takes place during sulfitation is unsatisfactory. These PAC extracts are complex due to variable hydroxylation patterns of the constituent flavan-3-ol aromatic rings, different configurations of the C-2, C-3 and C-4 stereogenic centres, different degrees of polymerisation, and the existence of angular oligomers. Gel or paper chromatography fractionations of the complex extracts are hampered by poor resolution due to their hydrophilic polyphenolic nature and efforts to isolate pure compounds have been restricted to the isolation of mainly monomers and a few dimers and trimers. PACs of the commercially important quebracho (Schinopsis lorentzii and Schinopsis balansae) and black wattle (Acacia mearnsii) extracts have a strong and stable interflavanyl bond. This stability is important from an industrial point of view as it leads to durable leather and adhesive products. It is attributed to the absence of 5-OH groups in the aromatic moieties of the extender fisetinidol and robinetinidol flavan-3-ols units. However, from an analytical point of view it is not advantageous. The high temperatures thus required to hydrolyse the interflavanyl bonds with weak acids; leads to decomposition of the intermediate monomers that renders conventional thiolysis and phloroglucinolysis based analytical methods unreliable. In this thesis we used electrospray mass spectrometry (ESI-MS) to investigate the composition of PACs in black wattle extract and the changes that takes place in the chemical composition of quebracho PACs during sulfitation. We furthermore use all the information available from literature on the phytochemistry of flavan-3-ols and PACs and the syntheses of flavan-3-ol oligomers to guide us in our ESI-MS interpretations. Previous research in our group established that quebracho PACs always consist of a catechin starter unit to which one, two or more fisetinidol extender units are attached. The first and second extender units are always attached to the relatively reactive phloroglucinol A-ring of the catechin starter unit to form predominantly dimers and angular trimers. Further extender units are attached to the relatively less reactive resorcinol A-rings of already incorporated fisetinidol extender units. This explains the relatively short degree of polymerisation of quebracho PAC extracts and their popularity as a tanning agent. Large PACs will not penetrate the spaces between skin proteins and cannot act as a tanning agent. In this thesis we established that black wattle PACs have, in addition to catechin starter units, also gallocatechin starter units and, in addition to fisetinidol extender units, also robinetinidol extender units. Acacia PACs are thus more complex combinations of catechin, gallocatechin, fisetinidol and robinetinidol monomers. This contrasts with quebracho PACs that only contain catechin and fisetinidol monomers. The higher degree of hydroxylation of gallocatechin and robinetinidol explains the higher water solubility of black wattle PACs and the less frequent need for sulfitation. We also established that during sulfitation of quebracho PACs, a sulfonic acid moiety is introduced in both the C-2 and C-4 position of the pyran heterocyclic C-ring. In the case of C-2 sulfitation, the heterocyclic ring is opened. This enhances the reactivity of the A-ring towards the reaction with formaldehyde (adhesive formation) and increases water solubility due to removal of rigidity and introduction of a polar sulfonic acid group. In the case of C-4 sulfitation, the interflavanyl bond is broken. Polarity and water solubility is thus not only increased via an additional sulfonic acid moiety, but due to the presence of shorter oligomers and a smaller average chain length. We also developed a chromatographic method to estimate the degree of sulfitation of quebracho PAC extract. We believe that we have made a valuable contribution towards a better understanding of the composition of black wattle and sulfited quebracho PAC extracts and have identified a number of misconceptions.