Chapter One begins with an introduction to enzymology and leads into a discussion on BSSL beginning with the physical properties and the source of the enzyme. The literature concerning the kinetic properties of BSSL is reviewed, followed by a discussion on how the structure of enzymes influences their catalytic activity and specificity. The use of X-ray crystallographic techniques is addressed as a means of elucidating the three dimensional structure of enzymes. The chemicals, apparatus and standard methodologies used in this present investigation are described in Chapter Two. The means by which kinetic data measured for an enzyme-substrate system are analysed and compared are also discussed. Chapter Three describes the purification of bile salt-stimulated human milk lipase (BSSL) from whole human milk. A detailed study of the activity of the purified protein has been conducted against both lipid and ester substrates in order to monitor the progress of the purification. A further determination of the physical properties of the protein has also been conducted. Results from these studies have identified the protein as BSSL. In Chapter Four the methods used for determining the partial amino acid sequence of the enzyme are described. This study has revealed interesting homologies with enzymes from other species. The sequence of that part of the enzyme which includes the active site has been determined and has been found to be identical to the consensus sequence found in the active site of pancreatic lipase, serine proteases and cholinesterases. It may therefore be postulated that the similarity observed for some of the kinetic behaviour of enzymes arises from homology in their amino acid sequences and, in particular, those portions of the protein comprising the active site. The use of kinetic isotope effects, to gain insight as to the mechanism of BSSL catalysed hydrolysis of lipid substrates, is the subject of Chapter Five. A mechanism has been proposed which explains the observed effects and takes into account information from the literature. The mechanism also incorporates findings made from the amino acid sequence study and the literature reports on the residues involved in catalysis. Chapter Six begins within a literature survey of detergent less microemulsions and continues with an account of the kinetic properties of BSSL in this new and novel medium in which enzymic reactions involving substrates of low water solubility may be conducted. The advantage of this medium is that it allows one to monitor the reaction by spectrophotometric means. In more traditional methods of assay of lipid substrates this is not normally possible. This advantage has also been exploited in the study of the kinetics of BSSL against triolein in reversed micelles, which is the subject of Chapter Seven. A detailed description is given of an FT-IR technique which allows one to monitor the course of reaction of biologically important substrates.

A wide range of compounds elicit the sweet taste response but currently it is not known what causes this response. In Chapter 3 a number of sweeteners, and representatives of all the taste groups are investigated using NMR spectroscopy. The T1 relaxation times of the tastants were determined in aqueous solution and in solution with liposomes, a model membrane system. The observed changes in T1, values are analysed to determine which regions of the tastants are involved in the interaction with the membrane. In Chapters 4 and 5 an investigation is reported of the interaction of tastants with a liquid membrane system, which is reportedly able to distinguish between classes of chemicals. The interest lies in developing a simple experiment that will enable taste qualities to be predicted, something that is currently not possible. In Chapters 6 and 7 the NMR assignments of some sweeteners is discussed. NMR assignments are a necessary precursor before their sweetening properties can be studied by NMR.

Despite the vast amount of research reported on the acid-catalysed hydrolysis of amides, the mechanism of reaction has remained a source of controversy. The various literature results have been summarised in the introduction. Two series of amides have been studied in this investigation, one a series of N-substituted, 4-chlorobenzamides, the other a series of substituted acetanilides. Their basicity (or acid-dissociation) constants have been evaluated in sulphuric acid, and the rates of hydrolysis measured over a wide range of acid concentrations. Within each series, variation of the substituent causes the rate constant to vary in a way which is typical of a bimolecular reaction involving rate-determining nucleophilic attack of water on the protonated intermediate. By drawing a comparison between the two series of amides, (i.e. the difference in basicities and rates of hydrolysis) it becomes apparent that the 0-protonated amide, which is thermodynamically favoured, is not the kinetically active species, A new rate equation is proposed, the equation being based on a mechanism in which water attacks the carbonyl carbon in the rate-determining step. The equation confidently predicts the experimental rate-profiles for the acid-hydrolysis of simple amides. It has been applied, in two forms, to the experimental rate data; the first form allows for the involvement of three water molecules in the slow step of hydrolysis, and the second form allows for the involvement of only two water molecules. The rate equation, in these two forms, has also been applied to much of the hydrolysis data reported in the literature and again it has proved to be very successful. In contrast to the amides, ureas have not been subjected to extensive research. In this investigation, the basicity constants of a series of substituted phenylureas have been measured, (if not already available) and the hydrolysis reactions carried out over a wide range of sulphuric acid concentrations, as well as in water. The 4-methyl and 4-chloro-phenylureas have also been hydrolysed in a range of hydrochloric and perchloric acid solutions; the effects of added salt were studied and the solvent isotope effects on the rate were evaluated. All these results, together with information obtained from application of the Hammett equation to the rate data, were in agreement with a mechanism involving a pre-equilibrium protonation to form the minor, N-protonated conjugate acid. This is followed by a slow transfer of the proton attached to the alternate nitrogen atom to form the appropriately substituted phenylisocyanate, and rapid reaction of this intermediate to form products. The substituent effects on the n.m.r. spectra of the substituted acetanilides and phenylureas have also been reported.

This work contains some fundamental investigations on Triton X series nonionic surfactants from different aspects. Techniques, such as viscometry, densimetry, diffusion measurement, ultra-violet spectrophotometry, differential scanning calorimetry, surface tension measurement and optical microscopy were employed to acquire the information. Some theoretical analyses were given to the results of these measurements. Triton X surfactants show different properties when they dissolve in different solvents. Aggregation can occur in some solvents, depending on the interactions between solvent and solute. The addition of a surfactant to a solvent will give rise to a solute-solvent interaction and change the solute-solute and solvent-solvent interactions as well. From mass transport properties of the surfactant solutions, these interactions were studied and the contributions to them from each species of the solutions were calculated with a transition-state theory model which is usually used for small molecule systems. Under some reasonable assumptions, a new theoretical method was set up and was able to give a reasonable explanation for the experimental results. The surfactants can also associate with some dyes in both polar and apolar media. The ultra-violet spectra of the surfactant-dye solutions show that surfactant-dye complexes might be formed in the polar and apolar media where the surfactants form regular and reversed micelles respectively. The mechanism of the complexation reactions was studied with equilibrium theory and the charge-transfer nature of the association between the surfactant and dye revealed. The surface tension and. cloud point changes due to the addition of polyethylene glycol were determined to discover the interaction between the water-soluble polymer PEG and the surfactants at the air-solution interface and in the bulk solutions respectively. The mass distribution of the two materials between the two phases produced in the segregation (at the cloud point) of the solutions were determined by their ultra-violet adsorption spectra and densities. The analysis of the cloud point changes was given with the new concepts of polysoap and depletion flocculation. The results show that the size of the micelles, the length of the polymer chains, and the structures of the intra - chain micelles can change the mechanisms of polymer-surfactant interaction and influence the properties of the polymer/surfactant solutions. In a certain range of concentrations, the surfactants aqueous solutions can form liquid crystalline structures which can be observed under a cross-polarised microscope and determined by differential scanning calorimetry. The phase diagrams and their variations with additions of the third component, such as xylene, polyethylene glycol and BaCl2 2H2O have been determined. The effects of temperature and each of the additives on the ordered structures were analysed separately in the light of concepts of spontaneous mean curvature and "salting out" effect. Osmotic coefficients of the surfactant aqueous and methanol solutions were determined with a vapour pressure osmometer, and the activity coefficient of the solvent can be calculated with the osmotic coefficients. The change of the activity coefficient with increase of surfactant concentration shows the interactions of the surfactant with the solvent. In aqueous solution, the addition of surfactant frees the solvent molecules, leading to an activity coefficient larger than 1. In methanol solution, the surfactant addition reduces the fugacity of methanol molecules, resulting in an activity coefficient less than 1. Chemical shift changes of protons of the surfactant molecules in the lH NMR spectra show some information about the configuration of the chains, hydration, and phase structure of the solution system when the surfactant concentration changes over the whole concentration range. From 40% w/w the associated water molecules begin to be lost, and the association number ratio of water molecules and the ethylene oxide unit of the surfactant is 4:1. Electric conductance of electrolytes in the surfactant aqueous solutions are reduced by the addition of the surfactants. The reduction is more significant for large size cations, and the longer the EO chain of the surfactant, the larger the reducing effect on conductance.

Whole document restricted, see Access Instructions file below for details of how to access the print copy. / Aluminium smelters emit upwards of 6 kg of gaseous hydrogen fluoride per tonne of aluminium metal produced. Since the 1960's, many aluminium smelters have used the dry scrubbing process to capture the HF on the surface of smelter grade alumina. In this way, dispersion of the emitted HF is prevented and the fluoride is returned to the aluminium electrolysis cells. The surface adsorption reactions on which the dry scrubbing process relies have been studied by various researchers. It is common knowledge that there occurs a relatively strong bond between HF and alumina and that the quantity of water in the gas effects the maximum fluoride adsorption capacity of the alumina. It has also been considered that FIF adsorption is a combination of strong chemisorption and reversible physisorption at the temperatures at which the dry scrubbing process operates. Some researchers have postulated the formation of Al-F bonds at the alumina surface, while others have postulated the existence of hydrogen bonds between surface fluoride or hydroxyl ions and molecular H2O and HF. However, these models do not agree with the experimental data which was gathered during the course of researching this thesis, nor do they agree with much of the experimental data presented earlier. The major finding of this research was that hydrogen fluoride adsorption is irreversible under the temperature and gas composition conditions of the dry scrubbing process. The maximum fluoride adsorption capacity of smelter grade alumina depends on the relative humidity during adsorption, as well as the specific surface area of the alumina. Both factors indicate that HF adsorption is a surface process. The most likely product of reaction is a thin layer of crystalline aluminium hydroxyfluoride, AIFx(OH)3-x 6H2O, formed in an aqueous reaction at the alumina surface. The reaction mechanism involves the steps of: H2O adsorption to form an aqueous layer on the alumina surface; HF adsorption to acidify the surface water layer; dissolution of the alumina surface to form AlO2- and AlO2-; precipitation of AlFx(OH)3-x.nH2O. The overall adsorption rate appears to be controlled by the rate of the surface chemical reactions rather than by transport phenomena such as fluid phase mass transfer and intraparticle diffusion. At relative humidity greater than 35% the adsorption capacity of smelter grade alumina increases dramatically and small crystallites of AIFx(OH)3-x.6H2O and AIF3.3H2O are formed. Under these conditions the reaction mechanism is similar, except that water-filled pores provide an environment which is conducive to the formation of larger crystallites of product. At temperatures below 450°C the aluminium hydroxyfluoride hydrate phase dehydrates, and at temperatures above 450°C hydrolysis of aluminium hydroxyfluoride results in the release of HF. Samples which are produced under dry scrubbing conditions and aged under ambient conditions, are indefinitely stable. However, when aged at high humidity the product layer is transformed into distinct crystallites of aluminium hydroxyfluoride by a dissolution/re-precipitation mechanism involving water filled pores. Samples which are hydrofluorinated at greater than 35% humidity show continued growth of A1Fx(OH)3-x 6H2O and AlF3.3H2O under all storage conditions due to residual water condensed within the alumina pores.

Organometallic chemistry is concerned with the study of metal-carbon bonded species. A wide variety of bonding modes have been discovered ranging from simple σ- through to more complex π- and μ-interactions. This thesis deals with the synthesis and chemistry of just three classes of compound, those containing formal TM-C single, double and triple bonds. These species are normally referred to as transition metal alkyl (σ-aryl), carbene and carbyne complexes respectively. The material is divided into five chapters and each is introduced by a relevant review. In chapter 1 the syntheses of σ-alkyl and -aryl complexes of ruthenium and osmium are described. These species are produced from organomercury reagents either by oxidative addition to the zerovalent complex Ru(CO)₂(PPh₃) ₃ or by reaction with the hydrido complexes MClH(CO)(PPh₃) ₃ (M = Ru, Os). This latter reaction provides a new route to organotransition metal complexes and some possible mechanisms are discussed. The organo-complexes formed by this latter method are coordinatively unsaturated and the structure of RuCl(p-tolyl)(CO)(PPh₃)₂ has been obtained by X-ray crystallography. The migratory insertion and reductive elimination reactions of these new compounds are discussed in chapters 2 and 3. Predictably, the Lewis base CO rapidly adds to these 16 electron species and the expected octahedral derivatives are formed. In some cases these are in equilibrium in solution with the corresponding dihapto-acyl complexes. The positions of the equilibria, the rates of interconversion and the relative solubilities of the two forms are such that in each case either essentially pure dicarbonyl or essentially pure dihapto-acyl can be isolated from solution. The dihapto-mode of bonding has been confirmed by X-ray crystallography for two of the derivatives. CNp-tolyl also adds to the 16 electron organo-compounds in an analogous fashion and equilibrium with the corresponding dihapto-iminoacyl compounds is attained in some cases. The dihapto-iminoacyl formulation has been confirmed by X-ray crystallography. Factors affecting the positions of all these equilibria are discussed and the possible relevance of these dihapto-acyl and -iminoacyl complexes as models for the proposed intermediates in the CO and CNR insertion reactions is noted. Compounds containing cis-H,R ligands are rarely stable since reductive elimination of R-H usually occurs very readily. Species of this type, therefore, appear to be ideal precursors for reactive, low valent complexes which are unobtainable by other means. A synthetic route has been developed by which an hydrido ligand can be incorporated into the coordination sphere of the new organo-derivatives described in chapter 1. The key step involves the thermal decarboxylation of a dihapto-formate ligand. In this way remarkably stable cis-H, tolyl complexes of osmium have been prepared. Toluene is eliminated from these derivatives only under forcing conditions. In contrast, reductive elimination from the analogous ruthenium complexes proceeds much more rapidly and in only one case has a stable hydrido, aryl complex been isolated. Other compounds that have been formed by this route are the zerovalent complex Ru(CO)(dppe)₂ and the ortho-metallated complex Ru(C6H₄PPh₂)H(CO)(PPh₃)₂. Factors affecting the rates of all these reactions are discussed. Some reactions of Ru(C₆H₄PPh₂)H(CO)(PPh₃)₂ have been investigated, and most notably a methyl, formate complex is produced with formaldehyde and a small amount of a dichlorocarbene complex with CCl₄. The reactions of this ortho-metallated compound may proceed via the intermediate "Ru(CO)(PPh₃)₃". Extension of the synthetic procedure described in chapter 1 has led to the production of the dichlorocarbene complex OsCl₂ (CO)(CCl₂)(PPh₃)₂, the structure of which has been determined by X-ray crystallography. This compound, which formally contains an Os-Ccarbene double bond, provides the subject matter for chapter 4. The carbene carbon atom is attacked by nucleophiles and the chloride substituents are easily displaced. This species therefore behaves as a remarkably versatile synthetic intermediate. Reaction with the chalcogen hydrides HX⁻ (or H₂X) leads to the corresponding chalcocarbonyl derivatives and OsCl₂ (CO)(CTe)(PPh₃)₂ is the first tellurocarbonyl complex to be isolated. Characterization of this complex includes an X-ray crystallographic analysis. Primary mines react with OsCl₂ (CO)(CCl₂)(PPh₃)₂ to form the corresponding coordinated isocyanides and reactions with other nucleophiles are also discussed. The most important of these, however, is the reaction with Li(p-tolyl). This produces the monomeric carbyne complex, Os(Cp-tolyl)Cl(CO)(PPh₃)₂, the structure of which has been determined by X-ray crystallography. This compound has an extremely short Os-Ccarbyne bond length and this is consistent with a triple bond formulation. The synthesis and chemistry of this compound is discussed in chapter 5. Although other carbyne complexes have been isolated previously this is a relatively new area of organometallic chemistry and reports of the chemistry of these species are restricted mainly to compounds of the GpVIa and VIIa metals. Os(Cp-tolyl)Cl(CO)(PPh₃)₂ displays a rather different chemistry from these compounds and some new reactions have been observed. Electrophiles such as H₊ and Cl₂ readily attack Ccarbyne and the corresponding carbene complexes are formed. This suggests that Ccarbyne is nucleophilic. The elements S, Se and Te add to the Os-Ccarbyne triple bond under ambient conditions to give the corresponding dihapto-chalcoacyl complexes. Adducts of the Os-Ccarbyne triple bond are also formed with the GpIb metals and the structure of Os(C{p-tolyl}AgCl)Cl(CO)(PPh₃)₂ has been determined by X-ray crystallography. Analogues of all these reactions are to be found in acetylene chemistry. In contrast to the cationic carbyne complexes of the GpVIa and VIIa metals, Ccarbyne in [Os(Cp-tolyl)(CO)₂ (PPh₃)₂]ClO₄ is not attacked by nucleophiles. Instead LiBHEt₃ preferentially attacks the para-carbon atom of the Ccarbyne p-tolyl substituent and an Os(O) vinylidene complex is formed. The structure of this compound has been confirmed by X-ray crystallography. Although the aromatic ring is destroyed in this reaction it is replaced by an extensively conjugated system which reaches through to the osmium atom. Further reactions of this species and the cationic carbyne complex [Os(Cp-tolyl)(CO)(CNp-tolyl)(PPh₃)₂]ClO₄ are also discussed. / Note: Whole document restricted due to copyright restrictions, but available by individual request use the feedback form to request access.

Whole document restricted, see Access Instructions file below for details of how to access the print copy. / Mammalian liver and skeletal muscle glycogens were extracted using mild procedures and characterised according to their fine structure, molecular weight distribution and electron microscopic appearance. The role of protein in their structure was investigated. Rat, rabbit and mouse liver and muscle glycogens were polydisperse ranging in size up to more than one thousand million daltons. Whilst there are reports of liver glycogen covering such a size range, skeletal muscle glycogen of this size has not been previously reported. The glycogens contained a significant level of protein, some of which could be removed without altering the molecular weight distribution. The residual protein accounted for approximately 1% by weight of the purified glycogen, and it was concluded that this protein was covalently bound. Protease or concentrated alkali treatment of the glycogen digested the protein and resulted in a dramatic lowering of the molecular weight of glycogen, indicating that it was covalently bound protein which was responsible for the formation of high molecular weight material. Disulphide bond reduction also caused a lowering of molecular weight, indicating that high molecular weight glycogen arises by disulphide bridging between the protein backbones upon which the low molecular weight glycogen is synthesised. Thus liver and skeletal muscle glycogens are constructed in a similar manner. The fine structure of the glycogens was typical of that previously reported. When observed by electron microscopy the material appeared as spherical β-particles and large aggregates of these, the α-particles, thus confirming the presence of a high molecular weight component of skeletal muscle glycogen. The sizes of the products of TCA or KOH extraction of tissue glycogen were explained by the effects of these agents upon the glycogen molecule. Alkali digests the protein backbone and splits the glycogen β-particles, while TCA causes insolubility of the high protein content, high molecular weight glycogen. The protein backbone of rat liver glycogen was isolated. It had a molecular weight of 60,000 daltons and was rich in serine, glutamate, and the hydrophobic amino acids. Lysosome-enriched fractions were isolated from rat liver and skeletal muscle. Both contained glycogen; approximately 10% of tissue glycogen for the liver fraction and approximately 5% for the muscle fraction. The lysosomal glycogen of both tissues was enriched in the high molecular weight component. Thus in both tissues glycogen metabolism is compartmentalised, and degradation is via both phosphorolytic and hydrolytic pathways. The lysosomal acid α-glucosidases showed a preference for low rather than high molecular weight glycogen as substrate. A model for the regulation of lysosomal breakdown of glycogen was proposed. High and low molecular weight liver and muscle glycogens showed inhomogeneous responses upon starvation and rapid post mortem glycogenolysis. Both phosphorolysis and hydrolysis were involved. The increase in glycogen level upon refeeding following starvation was inhomogeneous with respect to glycogen size, in both tissues. The metabolic inhomogeneity of glycogen was related to its structural inhomogeneity and the association of the high molecular weight component with the lysosome.

This thesis describes synthetic work directed towards the synthesis of the dimeric pyranonaphthoquinone antibiotic crisamicin A 1.46 and its regioisomer 2.77. The synthetic strategy adopted is based on a double furofuran annulation/oxidative rearrangement strategy that has been successfully used by this research group to prepare a related dimeric pyranonaphthoquinone based on the actinorhodin skeleton. The retrosynthesis that was adopted (see Scheme 1.47, page 59) required the initial preparation of a key bis-naphthoquinone 1.267 which in turn is available from bisnaphthalene 1.268 that bears acetyl groups at C-7 and C-7’. Initial work concentrated on the construction of the biaryl linkage of bis-7- acetylnaphthalene 1.268 using a palladium(0)-mediated Suzuki-Miyaura homocoupling of the key triflate 1.269 (prepared in 10 steps from vanillin 1.271) using bis(pinacolato)diboron 1.179. This coupling method successfully afforded binaphthyls 2.8b and 2.8d which were subjected to attempts to effect either double bromination, double acetylation or double Fries rearrangement to a more functionalised biaryl system. Disappointingly, none of these methods allowed introduction of the key acetyl group at C-7 and C-7’ onto the initial biaryls 2.8b and 2.8d. Attention then turned to the synthesis of the bis-7-acetylnaphthalene 1,268 that was required for the ensuing furofuran annulation reaction starting from triflate 2.7 that already contained an acetyl group at C-7, then effecting formation of the key biaryl linkage. Attempts to prepare 7-acetyltriflate 2.7 via either Fries rearrangement of acetates 2.33a or 2.9a, or via bromination of acetate 2.33a, naphthol 2.56 or benzyl ether 2.6 were unsuccessful. An alternative approach for the preparation of 7-acetyltriflate 2.7 involved the preparation of 2-acetylcarbamate 2.74 from carbamate 2.64 via a directed ortho-metalation, followed by reaction of the derived ortho-lithiated species with N-methoxy-N-methylacetamide 2.71. However, this strategy resulted only in low yields of the desired 2-acetylcarbamate 2.74, although initial model work did provide methodology for the successful conversion of carbamate 2.68 to 2-acetyl-l-naphthol 2.73. The synthetic target of this thesis shifted to the regioisomer of crisamicin A 2.77 when attempts to introduce an acetyl group atC-7 of triflate 2.9 failed. However formation of the 6-acetyltriflate 2.81b was successful from triflate 2.9b. A subsequent one-pot in situ Suzuki-Miyaura homocoupling of triflate 2.81b with boronate 2.89 furnished dimmer 2.76b. Oxidation of dimer 2.76b to bis-naphthoquinone 2.80 was then accomplished using silver(II) oxide and 6 M nitric acid. With the key bis-6-acetylnaphthoquinone 2.80 in hand, an efficient double furofuran annulation reaction was carried out using 2-trimethylsilyloxyfuran 1.88 affording the desired bis-furonaphthofuran adduct 2.79 as an inseparable l:l mixture of diastereomers 2.79a and 2.79b. However, initial experiments to effect the double oxidative rearrangement of bis-furonaphthofuran adducts 2.79 using either silver(Il) oxide and 6 M nitric acid or with ceric ammonium nitrate in aqueous acetonitrile to the bisfuronaphthopyran 2.7 8 were unsuccessful. Attention then turned to the preparation of bis-furonaphthopyran 2.78 from the 6-acetyltriflate 2.81b via initial oxidation of triflate 2.81b to naphthoquinone 3.3 followed by furofuran annulation and then oxidative rearrangement. Attempts to effect the key Suzuki-Miyaura homocoupling of furonaphthofuran 3.2 to bis-furonaphthofuran 2.79, or of furonaphthopyran 3.1 to bis-furonaphthopyran 2.78, using catalyst PdCl2(dppf) and ligand dppf were unsuccessful. The work achieved herein constitutes the synthesis of an advanced intermediate for the synthesis of the crisamicin analogue 2.79. The final synthesis of the regioisomer of crisamicin A 2.77 can be completed by preparing bis-furonaphthopyran bis-lactol 2.78 using more powerful palladium(0) catalysts and ligands for the Suzuki-Miyaura homocoupling of the monomeric furonaphthopyran 3.1. Subsequent reduction af 2.78 using triethylsilane and trifluoroacetic acid will then afford the bis-cyclic ether 3.15, which can undergo deprotection of the methyl ether and epimerisation at C-5 upon treatment with excess boron tribromide to finally furnish the regioisomer of crisamicin A 2.77. An investigation into the double oxidative rearangement of bis-furonaphthofuran 2.79 to the bis-lactol 2.78 could also be carried out by the use of several alternative oxidising agents, such as phenyliodine(III) bis(trifluoroacetate) (PIFA), phenyliodine(III) diacetate (PIDA), polymer-supported (diacetoxyiodo)benzene (PSDIB), Fremy's salt, iron trichloride or CrO3.

PART I A general introduction is given to the mechanisms of olefin-forming β-elimination. The development of mechanistic criteria and their application to the various reactions is discussed. Conflicting theories concerning the nature of the transition states of E2H reactions in protic solvents as well as the Winstein-Parker E2C-like transitions states for elimination by weak bases in dipolar aprotic solvents are described. PART II The use of primary deuterium isotope effects: structure-reactivity relationships, and rate-acidity correlations as mechanistic criteria for the E2 mechanism and the variants of the E1cB mechanism is reviewed. These criteria have been applied to the dehydrochlorination of the 1,1-diaryl-2, 2, 2-trichloroethanes (DDT-type compounds) with methoxide-methanol and t-butoxide-t-butanol. Literature comparisons indicate that the kinetic evidence for these two systems is in accord with an "irreversible" E1cB elimination pathway. PART III Characteristics of weak base-promoted eliminations in dipolar aprotic advents are reviewed. The evidence is not entirely consistent with either E2C or the E2H mechanism. Deuterium isotope effects and equilibrium constants are reported for the chloride ion-promoted elimination of the 1, 1-diary1-2,2,2-trichloroethanes in dimethylformamide and acetone respectively. The results are in accord with an E2H mechanism.

The results to be described and discussed in this thesis concern synthesis and reactivity of iridium(I) and (III) complexes containing thiocarbonyl or selenocarbonyl ligands. Chapter 1 comprises: a review of Vaska's compound, IrCl(CO) (PPh3)2 and related species, covering syntheses, structure and bonding and reactions of this very widely studied moiety; and brief reviews of metal-thiocarbonyl syntheses and reactions and metal-selenocarbonyl chemistry. These three reviews background the themes developed in this work; of preparations and reactions, particularly ligand reactions, of thiocarbonyl and selenocarbonyl analogues of Vaska's compound and species derived from IrCl(CE)(PPh3)2, E = S, Se. A new synthesis of IrCl(CS)(PPh3)2 is described in Chapter 2. The route employed involves preparation of dithioester complexes and facets of the reactivity of these species have been considered and a number of metallocycle derivatives prepared. Reductions of coordinated-thiocarbonyl groups have been considered; IrH(CS)(PPh3)3 was transformed into IrH2(SMe)(PPh3)3 by treatment with hydrogen, while the thiocarbonyl cation complexes [IrClX(CO)(CS)-(PPh3)2]+ were treated with borohydride to afford thioformyl species. Iridium alkyl, thiocarbonyl complexes have been prepared, and transformed by reaction with dithiocarbamate ion to yield monohapto-thioacetyl derivatives. The preparation of IrCl(CSe)(PPh3)2, the selenocarbonyl analogue of Vaska's compound is reported in Chapter 3. The synthesis utilizes carbon diselenide as the selenocarbonyl source, and involves a four-step conversion of a dihapto-carbon diselenide adduct complex to the iridium(I) selenocarbonyl species. Reactions of a range of iridium(I) complexes with carbon diselenide are described, including the preparation of a complex including three CSe2 groups. Reactions of IrCl(CSe)(PPh3)2 have been studied and several iridium(I) and (III) selenocarbonyl compounds prepared. The ready reduction of IrCl(CSe)(PPh3)2 (in the presence of phosphine) by borohydride to give IrH2(SeMe)(PPh3)3 is described and comparisons are drawn between the relative reactivities of iridium thiocarbonyl and selenocarbonyl groups, in analogous species, with nucleophiles. It is concluded the Ir-CSe system is more reactive under similar conditions. Metallocycle derivatives of iridium selenocarbonyl, diselenomethylester complexes have been characterised.