Sugar chlorosulphates of furanoid and pyranoid derivatives bearing chlorosulphonyloxy groups at primary and secondary positions, were synthesized and examined mainly with a view to determine their extent of reactivity in terms of nucleophilic substitution reactions, especially with azide. Inversion of configuration occurred at reactive chiral centres, whereas intermediate azidosulphonyloxy derivatives (azidosulphates) were formed via S-Cℓ bond fission of the chlorosulphonyloxy group at less reactive primary or secondary centres, e.g. 1,2:3,4-diO̲isopropyl idene-α-D-galactopyranose 6-azidosulphate, 1,2-O̲isopropylidenea- D-xylofuranose 3-azidosulphate and 1,2:5,6-di-O̲-isopropyl idene-α-Dglucofuranose 3-azidosulphate. 1,2:3,4-Di-O̲-isopropylidene-α-Dgalactopyranose 6-azidosulphate ultimately afforded the 6-azidodeoxy derivative probably by an SN2 mechanism. Some SNi characteristics were,however, evident when substitution occurred at a reactive primary centre (e.g. methyl 2,3,4-tri-O̲-methyla- D-glucopyranoside 6-chlorosulphate), as the 6-azidodeoxy derivative obtained, appeared to be contaminated with a trace amount of the corresponding 6-chlorodeoxy sugar, which had presumably formed via an internal SNi mechanism, while no intermediate azidosulphonyloxy derivative was isolated. In another study, the reaction pathways for the synthesis of benzylated chlorodeoxy sugars having potential biological properties as exemplified by the multivalent drug, tribenoside, were also investigated

The reactions between the lanthanide nitrate salts and the ligand triphenylphosphine oxide (TPPO) gave rise to nine-coordinated complexes of the nature Ln(TPPO)3(NO3)3, for Ln = La – Dy, Er, Tm, in which the Ln(III) centre is coordinated to three phosphoryl oxygen atoms and three bidentate nitrate ligands. Generally, the geometry can be described as being mer-octahedral, where the nitrate ligands are considered as monoatomic species. The product of the reaction between Yb(NO3)3·5H2O and TPPO, however, was a highly symmetrical eight-coordinated complex, in which the Yb(III) centre was coordinated to two bidentate nitrate groups and four TPPO molecules. The geometry in this case is best described as being trans-octahedral, with the two nitrate ligands coordinated practically perpendicular to one another. The complexes isolated from the reactions of lanthanide nitrate salts with the ligand bis(pentamethylene)urea (PMU) had the general formula Ln(PMU)3(NO3)3, where Ln = La – Dy, Yb, Lu. The complexes were found to be nine-coordinated with distorted trigonal prismatic geometry, in which the one base of the prism is composed of the oxygen atoms of the three PMU ligands and the other base is made up by one oxygen atom from each of the bidentate nitrate groups. The second oxygen atoms of each of the nitrate groups protrude upward, occupying capping positions. The reactions of the La and Pr nitrate salts with the ligand 2,2’-dipyridyl-N,N’-dioxide (DPDO) produced two novel complexes of the nature [Ln(DPDO)(H2O)2(NO3)3]. These complexes are remarkable in that their crystal structures reveal the Ln(III) centres to be ten-coordinated. The geometry around the Ln(III) centres was complex, due to the presence of a seven-membered chelate ring, formed by the bidentate coordination of the oxygen atoms from the DPDO ligands to the metal centres. The chelate ring did not lie in a single plane, but was twisted at the pyridyl bridgeheads to lie above and below the coordination plane.

The compounds in the series from triphenylphosphine to triphenylbismuthine were examined as acceptors in oxygen transfer reactions involving the l-pyrroline-l-oxides. Triphenylphosphine was found to offer a useful route from the l-pyrroline-l-oxides to the corresponding pyrrolines. The second part of this work is centred on the structural investigation of Sanno's base (XV) (l), obtained as a by-product in the reductive cyclization of ethyl 2-acetyl-2-ethyl-4-methyl-3-nitromethyl valerate (aγ -nitro-ketone) and formulated by the author as having the Δ’ -pyrroline structure; this compound has since been found to be a cyclic nitrone (XVI). In the case of this complex nitrone, the oxygen transfer reaction to triphenylphosphine has been successful, yielding two isomeric Δ' -pyrrolines. The isolation of a Δ -pyrroline structure is confirmation of the proposed cyclic nitrone (XVI) structure for Sanno's base and as this provides a practical application of this reaction in structural work as well as showing that triphenylphosphine will reduce N-oxides in the presence of an ester group. / Science, Faculty of / Chemistry, Department of / Graduate

The amount of reaction between pyrite and vapor state nitric acid-has been analytically determined at 130°, 145°, 160° and 175° C. for one hour reaction time, and for one-half, one and two hour reaction times at 160°C. The variation of pressure with time for constant-boiling (68.2 per cent) nitric acid was studied at 130° and 160°C The reaction observed between pyrite and vapor state nitric acid followed the possible chain of reactions given below: (formula omitted) with the possible reaction: Fe₂(S0₄)₃ + H₂S0₄⇄Fe₂(S0₄)₃ . H₂SO₄. At 160°C the overall reaction was found to be of an apparent zero-order as was also that for the formation of ferric sulfate and ferric oxide, over the range of almost 100 per cent decomposition of the nitric acid. The maximum amount of pyrite used was about 11 per cent. Experimental results show that reactions (3), (4),(5) and (6) must all be surface reactions. A decrease in the rates of the reactions was noted between 145° and 160°C. This was most probably caused by the change in the physical and chemical properties of sulfur in this range, and indicates that elemental sulfur has a significant retarding effect on the rate of the overall reaction / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

A thesis submitted in fulfillment of the requirements for the degree of Doctor of Philosophy to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, Johannesburg, August 2018 / This work details findings of an analytical, numerical and experimental investigation into the physical nature of three-dimensional shock reflection transition. Steady flow shock reflections comprise two types: regular reflection and Mach reflection. Reflection studies have previously been conducted using double-wedge symmetrical test piece configurations. It had been found by previous researchers that the expansion waves resulting from the side edges of the wedges would influence the reflection plane. The three-dimensional nature of real experimental flows gives rise to there generally being a coexistence of regular reflection (at the central portions) and Mach reflection (towards the outer peripheral portions) in between which transition occurs. It is the object of this work to understand three-dimensional transition for flow fields in which edge effects do not influence the reflection plane. Specially modified test piece geometry was developed for this purpose. Experimental tests were required for validation of the numerical models of the flow field. This was achieved by obtaining oblique shadowgraphs with optical orientation in both yaw and roll to assist in visualising the three-dimensional features of the flow field. These were compared with numerically reconstructed images at the same oblique orientations using a novel reconstruction technique. The main objective of this work was to identify the degree of correspondence of the threedimensional transition conditions to those of two-dimensional flows. This was facilitated by means of reducing the three-dimensional analysis to an effective two-dimensional one. It was found that the three-dimensional transition points occur at a higher effective angle than predicted by twodimensional criteria, and tend towards two-dimensional criteria at reduced free-stream Mach numbers and increased model geometrical spreads. Another important aspect of this work was the nature of the intersection line in the vicinity of the transition point, i.e., the point of impingement of the incident wave and its Mach surface on the horizontal symmetry plane in between the test pieces. Here it was found that a cusp exists in the sweep profile of the intersection line at the transition point. This was proved from a theoretical standpoint based on a model developed for the analysis of the flow in the vicinity of transition. Evidence of this from the numerical and experimental results is given as well. Higher geometrical spreads and lower free-stream Mach numbers were found to create flatter intersection line profiles at the horizontal symmetry plane on which the transition points were located further forward towards the apex of this line and which gave rise to greater transverse deflections for the streamlines passing through the regular reflection portions. Further discussion revolves around the nature of the shear and Mach surfaces. The Mach surface heights (representative of the triple line trajectories) are shown to increase monotonically. The shear layer edge trajectory, which originates at the sweep cusp, was found to show considerable transverse divergence but in keeping with the nature and extent of the transition cusp sweep differential, which in some cases was found to be large enough to cause a strong shock solution for the Mach reflection portion. In this case the shear surface edge trajectory diverted from trends seen for other models. The nature of the shear surface as a whole revealed interesting insights into the negative triple configuration of the Mach reflection portions which comprised of convex Mach surfaces. This is in contrast to the geometry obtained for the Mach surface for full Mach reflection numerically studied with a highly-spread geometry. Here, the flat Mach surface was found to increase monotonically towards the periphery in contrast to what was found for flows with edge influences on the Mach surface. It is suggested that this is what precludes complex reflection (central Mach reflection, transitioning to regular reflection further out, with a further transition to Mach reflection at the periphery) from being obtained in such flow fields / MT 2019

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