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Over the past decade, many studies have been done on the semiconductor photominieralization of water pollutants. There is still an apparent lack of knowledge or further calcification required concerning details of the photocatalytic degradation mechanism, and factors associated with the reaction. The aim of this thesis is to address various fundamental aspects of semiconductor photocatalysis. Thus in Chapter three, the often used concept that O<SUB>2</SUB> is a necessary reactant in the semiconductor photocatalysis of organic pollutants is challenged in a detailed study of the kinetics of photomineralisation of 4-chlorophenol and acetone, sensitised by TiO<SUB>2</SUB> using metal ions, such as Fe<SUP>3+</SUP>, Cu<SUP>2+</SUP> and Hg<SUP>2+</SUP>, rather than, and in addition to, O<SUB>2</SUB>, as the electron acceptors. Chapter four highlights the poorly understood world of semiconductor photocatalysis kinetics and mechanisms with a study of the effect of light intensity upon the apparent Langmuir-Hinshelwood constants found for the photomineralisation of 4-chlorphenol, sensitised by Degussa P25 powder dispersions. Chapter five describes the results of a detailed study of the kinetics of photomineralisation of 4-CP, sensitised by a film of Degussa P25 - the first example of such a study. The similarities and differences in kinetics of photomineralisation of the dye methylene blue sensitised by TiO<SUB>2</SUB> are explored. This dye features widely in semiconductor photocatalysis as test organic pollutant and is used to evaluate the activities of different photocatalysts. However, the kinetics and underlying mechanisms for photobleaching are much more complex than previously recognised, as revealed by the results of this study.

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Chapter I. Bismuth-Catalyzed Benzylic Oxidation The first chapter is a description of the development of new catalytic methods using bismuth chelates and I-butyl hydroperoxide for the oxidation of alkylarenes and diarylmethanes to aromatic ketones and for the oxidation of methylarenes to the corresponding carboxylic acids. The reactions have been applied to a large variety of substrates. Mechanistic studies of the benzylic oxidation' reaction and the use of bismuth(II1) salts in combination of oxaziridines in the benzylic oxidation reaction are also reported. Chapter II. Synthesis of Amides Using the Ritter Reaction with Bismuth Triflate Catalysis ' This chapter is a description of the synthesis of N-tertiary-alkyl and aryl amides by the Ritter reaction of various nitriles ,vith tertiary alcohols in the presence of a catalytic amount of bismuth triflate. Chapter III. Studies Towards Novel Chiral Sulfur Based Ligands The use of bidentate ligands to modify the chiral space around a metal centre is a well documented strategy for effecting stereocontrol in asymmetric synthesis using metal organic catalysts. Previous studies within the group have centered upon the development of bidentate, mono-anionic, chiral-atsulfur ligands containing nitrogen Lewis basic sites. Particular success was achieved with the imino sulfinamidine ligands. Thus, any chiral versions of these complexes can be expected to possess a highly asymmetric environment in close proximity to the metal centre. This first part describes attempts to synthesise non-racemic p-imino sulfinamidines containing a chiral binaphtyl derived group. . The second part of the section is a description the synthesis of a series of novel compounds containing a N-S-N backbone to produce a C2-symmetric ligand where the two sulfur (IV) atoms generate the chirality of the compound.

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