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To enable the rational development of CO2 utilisation processes, it is vital to understand the mechanisms of involved reactions. This thesis reports studies to improve the mechanistic understanding of two catalytic CO2 utilisation reactions and work towards the development of a novel CO2 utilisation process. In Chapter 2, the role of guanidines in the reaction of propargylamines and CO2 to give cyclic carbonates is discussed. Guanidines have multiple potential mechanisms of catalytic activity. Through correlating the catalytic activity and solvent effects with observed guanidine-CO2 complexation, the origin of catalytic activity was determined. Chapters 3-5 report results of a mechanistic investigation into the guanidine catalysed reductive functionalisation of CO2 with amines and hydrosilanes to yield formylamides, methylamines and aminal products. Through monitoring the reaction using GC, 1H & 13C NMR, in situ FT-IR and mass spectrometry, a number of competitive intertwined reaction pathways and intermediates were identified. At low temperatures formylamides are produced via transformylation of a formoxysilane intermediate with an amine. However, at higher temperatures a competing pathway enables further reduction of the formoxysilane to a bis(silyl)acetal, its subsequent reaction with amines yields aminal intermediates which can be further reduced under reaction conditions to yield methylamines and formylamides. A catalyst deactivation pathway was identified whereby formylation of the catalyst itself occurs. By using alkylated guanidines, the deactivation pathway was prevented and the alkylated catalysts could be used at 0.1 mol% loadings and achieved TON of 805 and TOF of 33.5 h-1. In Chapter 6, efforts towards the development of a novel CO2 utilisation reaction are discussed. α-Ketocarboxylic acids were targeted from the insertion of CO2 into an aldehyde C-H bond, inspired by analogous hydroacylation chemistry. A range of reaction conditions, rhodium catalysts and substrates were investigated; however, although a number of products were identified, no incorporation of CO2 was observed.

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The aim of this work has been to obtain reliable experimental data which can be used to obtain constraints on the tritium breeding cross-sections of 6-Li and 7-Li; and, to develop a technique for rapid estimation of tritium production in a fusion reactor blanket. A range of experimental and calculational techniques were used during the project, but the main approach was to circumvent problems in direct measurement of tritium production by using other reactions, which behave in the same way as the 6-Li(n, alpha)t and 7-Li(n, n'alpha)t reactions. The measurement regime was optimised, and then compared with Monte-Carlo predictions made by the MORSE code. To check the calculations an NE-213 spectrometer was used to give differential (in energy) neutron information. Significant modifications were made to an existing spectrometer, before it was used for the measurements described here. The matrix unfolding technique was used to obtain neutron energy spectrum information from the measured NE-213 pulse-height response, and the code 05S was used to predict the mono-energetic detector responses that this requires. The data input to 05S was updated as part of this work, particularly the cross-section and angular distribution used for the 12-C(n, alpha)9-Be reaction.

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The various groups into which the triterpenes are divided are defined and emphasis is placed on the structural relationships which exist between these groups. A brief description is given of the methods used in the determination of the structure of triterpenes with particular reference to β-asyrin (I), a member of the oleanane (II) group. Recent progress in the problems of biogenesis and the total synthesis of triterpenes is reviewed. All approaches, so far investigated, to the synthesis of pentacyclic triterpenes involve the fusion of two bicyclic moities representing rings A and B and rings D and E of the proposed structure. This thesis describes attempts to synthesise pentacyclic triterpenes of the oleanane (II) group, via the tetracyclic-cis-ketone (IIIa), the tetracyclic-trans-ketone (IIIc) or the tetracyclic-αβ-unsaturated-ketone (IVa).

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The manganese halide complexes, [Mn2(μ-dppO2)4X2]X2.2H2O (X = Cl, Br, I; dppO2 = Ph2P(O)(CH2)3P(O)Ph2) have been synthesised and structurally characterised by single crystal X-ray diffraction. Powder diffraction studies of the complexes have been performed at room temperature and at 120°C. The reactivity of the complexes towards sulfur dioxide has been studied using thermogravimetric techniques and X-ray powder diffraction and two sulfur dioxide adducts have been crystallographically characterised; that of [Mn2(μ-dpp02)4(NCS(2(NCS)2.2S02 and [Mn2(μdpp02) 4Br2]Br2.2CH30H.S02. Thermodynamic studies have been performed on the reactivity of the manganese complexes [Mn2(μ-dpp02)4X2]X2 (X = Cl, Br, I, NCS) in order to calculate approximate values for the enthalpy of formation of the sulfur dioxide adducts.

In this thesis, the development and applications of the Hydrated Torsions (HT) method are discussed. The method is designed to study the incremental solvation of biomolecules and thus is ideal for the study of zwitterion formation. A reduced dimensionality approach, torsional path integral Monte Carlo, is used to explicitly treat the torsional motion of the biomolecules to provide anharmonic and quantum corrections of the torsional free energy. Four amino acids are treated with the HT method in this work; glycine, alanine, proline and serine. The initial development was performed using glycine. Microsolvated amino acid clusters were studied, with the number of solvent molecules ranging from one to six. The low energy structures identified in the work using density functional theory are in good agreement with structures found in the literature. The hydrogen bond networks formed in the structures were found to resemble hydrogen bond networks found in analogous water clusters. The incremental addition of water molecules to glycine and alanine reduced the electronic ,energy difference between the zwitterionic and neutral systems by a linear amount, up until the fourth water molecule due to stabilization of the more polar zwitterion. After four water molecules the stabilization is diminished and the make-up of the hydrogen bond network becomes more important. This change in electronic energy difference after four water molecules was not observed for proline and serine. Water molecules added to the systems beyond four water molecules do not affect the free energy difference as much as when one to four water molecules are added. Calculations indicate that the zwitterionic systems are not been fully stabilized at four, five or six water molecules, so this change in free energy behaviour must be due to the vibrational characteristics of the systems. Frequency analysis of the systems reveals that the difference in frequency of the torsional vibrational modes is not enough to cause this, so other low frequency modes are likely to be affecting the free energy.

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