This investigation has been geared towards several aspects of chromone chemistry. Selected 2-(N,N-dimethylarnino)chromones have been synthesized via 2-hydroxyacetophenone boron difluoride complex intermediates, and potentiometric analysis of these compounds in ethanolwater has been used to determine the influence of substituents on their basicity. The pKa values have been found to lie within a narrow range (1.92 - 2.52), and the observed substituent effects have been rationalized with the aid of semi-empirical and ab initio molecular orbital calculations. An efficient route has been developed for the synthesis of the naturally-occurring chromone, "granulosin" [7,8-(methylenedioxy)-2-propylchromone], and several C-2 side chain analogues in good yields, by condensing 2'-hydroxy-3',4'-(methylenedioxy)acetophenone with a range of ethyl carboxylate esters. These compounds show significant cytotoxic activity against the brine shrimp, Artemia salina, and two of them, the 2-ethyl and 2-benzyl derivatives also show 100% activity as pesticides on Beet army worms (BAW). Another naturally-occurring chromone derivative, 5-hydroxy-2-isopropyl-7-methoxychromone, and four C-2 side chain analogues have been prepared in moderate yields. These compounds also show significant cytotoxic activity against the brine shrimp, Artemia salina, and it is apparent that the presence of the hydroxyl group at C-5 is critical for such activity. The electronimpact mass spectra of both series of chromone derivatives have been investigated, permitting the elucidation of characteristic fragmentation patterns. In work directed towards the synthesis of potential HIV -1 protease inhibitors, five novel chromone-containing analogues of the clinically useful drug, ritonavir, have been synthesized. The design strategy has involved the coupling of substituted chromone-2- carboxylic acids with a specially prepared, hydroxyethylene dipeptide isostere to afford ritonavir analogues containing chromone termini. An interactive docking procedure has been used to explore the docking of ritonavir and the novel chromone-containing analogues into ' the active site of the enzyme, and has indicated the capacity of the ritonavir analogues to form hydrogen-bonds with the HJV-l enzyme receptor. Various substituted cbromone-3-carbaldehydes, which have been synthesized from the corresponding o-hyclroxyacetophenones using Vilsmeier-Haack methodology, have been examined as substrates for Morita-Baylis-Hillman reactions, using 3-hyclroxyquinuclidine as the catalyst and arcylonitrile and methyl acrylate as the activated alkenes. Optimization of the reaction conditions has permitted efficient conversion of the cbromone-3-carbaldehydes to the Morita-Baylis-Hillman products and, in some cases, dimeric products, within 24 h. Heating of the Morita-Baylis-Hillman products, arising from reactions with methyl acrylate, at 80 ºC for 3 h in the presence of DABCO as catalyst, has been shown to effect transformation to the corresponding dimers in good yield.

[From Introduction, p. 3] Raw marine oils are subject to considerable variation in composition with season and are moreover very unbalanced oils for direct use in the paint industry. Further refining is undertaken chiefly by Messrs Marine Oil Refiners of Africa Ltd., whose factory is situated at Simonstown. In their plant marine oils and others are treated by the Solexol process involving counter current extraction of the oil with liquid propane in a tower over which a temperature gradient is maintained. The process achieves the removal of a large proportion of the relatively saturated glycerides, the natural antitioxidants, and the relatively highly unsaturated components, all of which are detrimental to the eventual formation of good paint films. The segregated marine oil from the Solexol process is then bodied or polymerised at high temperatures to yield a "drying oil" which is used as a substitute for bodied linseed oil in paints. The chemical reactions taking place during the polymerisation and drying of these oils are of an exemely complex nature, and for their understanding it is necessary to have an accurate knowledge of the chemical nature of the component fatty acids in the natural glycerides ... The term "marine oils" in this work should be understood to mean marine fish body oils, marine mammal oils being excluded from consideration.

The photochemical dissociation of hexafluoroacetone vapour (HFA) has been studied at room temperature using five exciting wavelengths between 2500 and 3500 Å, and at -78°, using 3130 Å excitation. The effect of the presence of biacetyl during the photolysis has been investigated. Complementary experiments on the visible emission from HFA were performed, paying particular attention to the quenching action of oxygen and biacetyl. Plots of reciprocal quantum yield of carbon monoxide versus HFA pressure have either a positive and constant, or positive and decreasing slope, down to 1 mm pressures there is virtually no evidence that a weak (multistage) collision mechanism is operative in deactivation of the excited molecules. A simple extension of classical unimolecular theory is examined, in order to account, for observed photo-dissociation rate constants, k₂(λ, T). The model shows that Arrhenius plots of k₂(T) at constant wavelength will not, in general, be linear, but that upper and lower limits for the critical (activation) energy, may still be obtained. For HFA, this energy is placed between 5.7 and 8.6 kcals/mole. Agreement in order-of-magnitude is found between calculated and observed values of k₂(T), only if it is assumed that a fraction (rather more than half) of the normal modes participate in intramolecular energy exchange. This fraction has to be increased with decreasing wavelength to explain the observed k₂(λ) values. The inadequacy of a classical treatment of the system is recognized. The emission spectrum of HFA consists of both fluorescence and phosphorescence. Small concentrations of biacetyl quench phosphorescence and triplet dissociation. The phosphorescence to fluorescence ratio is 2.77 at 25º and 9.95 at -78°, while the total emission yield increases by a factory of 16.7 on decreasing the temperature over this range. From a study of biacetyl emission, direct and sensitized by HFA, it is shown that nearly 50% of HFA molecules excited with 3130 Å, eventually reach the triplet state at 25º. The phosphorescence yield of HFA at -78°was estimated to be 0.51. At relatively high pressures, dissociation yields are apparently greater when less energetic excitation is used. Various modifications to the intersystem crossing mechanism are discussed to account for this, but no definite conclusion can be reached. / Science, Faculty of / Chemistry, Department of / Graduate

Tetramethyldiarsine Is found to add across the double bond of fluoroölefins of the type CF₂=CFX (X = F,Cl,Br), to give addition products. Thus 1:1 adducts, i.e. (CH₃)₂As-CF₂-CFX-As(CH₃)₂, are obtained in the reactions of tetramethyldiarsine and CF₂=CFX (X = CI,Br). The reaction of tetramethyldiarsine and tetrafluoroethylene, however, gives (CH₃)₂Aa-(CF₂-CF₂)₄-As(CH₃)₂, a 1:4 adduct. Iodotrifluoroethylene and tetramethyldiarsine react to give an adduct which Is unstable in air, but this reaction yields dimethylperfluorovinylarsine, b.p. 71°. The above arsine is also prepared by the reaction of iododimethylarsine and iodotrifluoroethylene in the presence of mercury. Tetramethyldiarsine does not react with ethylene at 20°. Bromotrifluoroethylene does not give an addition product with tetrakis(trifluoromethyl) diarsine. Hexafluoro-2-butyne reacts with tetramethyldiarsine at 20° to yield a 1:1 adduct, trans-1,2-bis(dimethylarsino)-1,2-bis(trIfluoromethyl)ethylene. Tetrakis (trifluoromethyl)diarsine and arsenobenzene do not react with hexafluoro-2—butyne to give adducts. Iodotrifluoromethane reacts with arsenobenzene to produce iodophenyltrifluoromethylarsine, phenylbis(trifluoromethyl) arsine and phenyIdliodoarsine. The mechanism of this reaction has been suggested. The iodophenyltrifluoromethylarsine reacts with silver chloride to yield chlorophenyltrifluoromethylarsine. The chloroarsine and bis(trifluoromethyl)arsine react with the elimination of hydrogen chloride to form a diarsine, which Is believed to be the symmetrical 1,2-bis(phenyl)-!, 2-bis (trifluoromethyl) diarsine. This same diarsine is probably formed by the coupling of two iodophenyltrifluoromethylarsine molecules in the presence of mercury. Paranitroarsenobenzene reacts with iodotrifluoromethane with explosive violence. Trimethylarsine does not undergo exchange reaction with bromotrifluoroethylene to give dimethylperfluorovinylarsine. Hexafluoro-2-butyne does not give an addition compound with iodo- dimethylarsine. Tetrakis(trifluoromethyl)diphosphine fails to yield adduct with bromotrifluoroethylene at 120°. Hexafluoro-2-butyne also does not give adducts with tetrakis(trifluoromethyl)diphosphine, hexa-phenylditin and hexabutylditin. / Science, Faculty of / Chemistry, Department of / Graduate

[No abstract available] / Science, Faculty of / Chemistry, Department of / Graduate

The kinetics and mechanism of the "roast-reaction" of lead sulfide have been examined. The investigation, partitioned by the nature of the problem, included a study of (a) the "roast" which is the several reactions between galena (lead sulfide) and oxygen (or air) yielding oxides, sulfates and basic sulfates of lead, and (b) the reduction "reaction", between lead sulfide and the oxidation products of the roast leading to the production of lead metal. The mechanism of the roasting of lead sulfide does not lead to the formation of distinct PbO and PbSO₄ phases. The products appear to be a mixture of basic sulfates throughout. The rate of the reaction between PbS and PbO or PbSO₄ has been shown to be controlled by the transport of SO₂ from the reacting surface with gas velocities up to 5 cm./min. Under conditions of reduced pressure (<5mm. of Hg) the reduction reactions are shown to be heterogeneous and probably proceed by the adsorption of PbS vapor on the oxidized surface to form a (PbS.xPbO)‡ basic sulfate type activated complex which subsequently decomposes to lead metal. The stoichiometry of this heterogeneous reaction has been checked for the PbS-PbO case with the use of a Pb²¹² tracer. The average value was measured to be 1PbS + 3.4 PbO →4.4Pb + - - - . / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

The work described in this thesis is in two essentially independent parts. In Chapter 3, we have studied the infrared spectra of the alkaline earth and first-row transition metal bisfluorosulfates over the frequency range 4000 – 250 cm⁻¹ in an attempt to resolve discrepancies in the literature on the infrared spectra of these compounds. We have obtained spectra for these compounds which are easily assigned and we suggest that the discrepancies in the literature may be due to differences in crystalline modifications studied by the different workers. We have also checked the reliability of infrared frequency shifts as measures of cation-anion interaction in fluorosulfate compounds. We observe a general increase in frequencies for the symmetric SO₃ stretching and S-F stretching modes with increasing interaction, but no quantitative relationship is present. However, the S-F stretching mode is shown to give a good indication of cation-anion interaction for compounds with predominantly ionic character. In the second part of this thesis, described in Chapter 4, we have prepared tetrakis(pyridine) complexes of nickel(II), copper(II) and zinc(II) fluorosulfates. In order to determine the coordination strength of the fluorosulfate ion relative to other ions, we have also prepared and characterized complexes of the general formula Cu(py) ₄X₂ (X = C10₄ˉ, BF₄ˉ, N0₃ˉ, CH₃C₆H₄SO₃ˉ, CF₃COOˉ ) by infrared, electronic, and electron paramagnetic resonance spectroscopy, electrical conductivity, and magnetic susceptibility measurements. The results indicate that on the whole, the coordination strength of SO₃Fˉ towards metals is similar, but slightly stronger than CIO₄ˉ and BF₄ˉ , definitely stronger than PF₆ˉ, and weaker than ReO₄,ˉ, CH₃C₆H₄SO₃ˉ and CF₃C00ˉ . / Science, Faculty of / Chemistry, Department of / Graduate

The kinetic parameters in acetonitrile of the nucleophilic substitution reaction: N₃P₃C1₆ + KCNS -> N₃P₃C1₅NCS + KC1 have been determined. The Arrhenius activation energy is 15.5 ± 5 Kcal moleˉ¹ and the common logarithm of the pre-exponential factor is 10.2 ± 3. The reaction is first order in each reagent and is probably bimolecular. Comparison with similar reactions indicates a lone pair electron donation from the nitrogen to the phosphorus atoms of the ring. The compound, N₄P₄(NMe₂)₈HCuCl₃ was prepared by the reaction of tetrameric phosphonitrilic dimethylamide with copper (II) chloride in butanone. The infra-red spectrum indicates that the copper atom is bound to one ring nitrogen atom, and the proton to the opposite nitrogen atom. The ring is found to be too small to allow chelation of the copper atom. The salt, N₆P₆(NMe₂)₁₂CuCl⁺CuCl₂ˉ was prepared by the dehydro-halogenation of N₆P₆(NMe²)₁₂HClCu₂Cl₃. The hydrochloride was prepared by the reaction of hexameric phosphonitrilic dimethylamide (H.P.D.) with ' copper (II) chloride in the reducing solvent butanone. The salt was also produced by the reaction of H.P.D. with an equimolar mixture of copper (I) chloride and copper (II) chloride in acetonitrile. Chemical and magnetic studies on the salt showed it to have one copper (II) atom per molecule. The x-ray crystal structure showed the copper (II) atom to be in a distorted square pyramidal environment, bonded to four ring nitrogen and one chlorine atom. The salt contains the first known example of the CuC1₂ˉ anion. This is linear with a Cu-C1 bond length of 2.11A. The anion is also one of the few examples of a finite species containing a two co-ordinate copper (I) atom. The infra-red spectrum of the salt was very similar to that of the parent H.P.D. The main difference was in the frequencies of the stretching modes of the phosphorus nitrogen ring bonds; which is consistent with copper chelation. Conductiometric and analytical studies showed that the salt does not retain the form form N₆P₆(NMe₂)₁₂CuCl⁺CuCl₂ˉ in acetonitrile solution; the limiting molecular conductance 377 ± 10 Ohmsˉ¹ being too large to be consistent with a 1:1 electrolyte. / Science, Faculty of / Chemistry, Department of / Graduate

Monoaniline and monopyridine adducts of copper (II) ortho-methyl-, meta-methyl-, ortho-bromo-, and meta-bromobenzoate, and mono-aniline adducts of copper (II) ortho-chloro-, para-methyl-, and para-bromobenzoate were prepared. Magnetic susceptibility measurements of these compounds were made at room temperature on Gouy and Faraday apparatus. Variable temperature susceptibility measurements over the range 77 - 330°K were made employing a Gouy apparatus. Visible diffuse reflectance spectra as well as solution spectra of these compounds were also recorded. Molecular weight measurements could be obtained only for a few of the compounds because of their marked insolubility. Structure and bonding are discussed in the light of the results. / Science, Faculty of / Chemistry, Department of / Graduate

The reactions of the ethyl radical with a series of allyl compounds were examined experimentally in the gas phase, and the results were seen to conform to a general mechanism. Specifically, the ethyl radical can abstract a hydrogen atom from the allyl compound, or add to the olefinic linkage of the allyl compound. Dismutation reactions of the product radicals formed in the addition or abstraction reactions were also observed in this study. The metathesis reactions of some allyl compounds were too slow to be measured unless the functional group was deuterated. When this was done in the case of allyl alcohol and allyl formate, primary isotope effects in metathesis could be measured, and were in good agreement with the values predicted on the basis of zero point energy differences. The activation energies of the dismutation reactions of the adduct radicals ranged from 15 to 27 Kcal/mole and were found to depend on the estimated enthalpies of this reaction. In certain cases, a choice between two different reaction routes of the dismutation reaction could be made by comparing the activation energy with the estimated enthalpy change. The dismutation reaction offers a convenient method for the generation of free radicals at low temperatures. In this way, the allyl and ethoxy radicals were generated, and their disproportionation-combination ratios with the ethyl radical were measured. The kinetics of interaction of the ethyl radical with an allyl compound in the gas phase can be compared with the polymerization of that monomer in the liquid phase. Specifically the ratio of the addition rate constant to the metathesis rate constant in the gas phase can be related to the degree of polymerization and a linear relationship between these quantities was found in this study. / Science, Faculty of / Chemistry, Department of / Graduate