A microcalorimeter of the Tian-Calvet type has been constructed for the purpose of measuring heats of combustion. The instrument consists of a differentially-connected system of two iron-constantan thermopiles, each being constructed of sixteen thermocouples. The recording of the heat liberated is accomplished by means of a d.c. amplifier; the areas thus recorded are integrated by an electronic integrator. The apparatus is capable of measuring heats of the order of 10-3cal. The microcalorimeter is discussed from the theoretical and practical points of view.

The interpretation of mass spectra has made great progress over the past decade, as experimental methods have been developed for assigning structures to organic ions in the gas phase. This thesis describes the important experiments in gas phase ion chemistry whose correct interpretation can lead to the assignment of structures, and the elucidation of fragmentation mechanisms of organic positive ions. The low energy fragmentations of five isomeric [H3,C,N,O 2]+· ions. The low energy fragmentation characteristics of the [H3,C,N,O2]+· isomers, H3CNO2+·, 1, H2C=N(O)OH+·, 2, H3CONO +·, 3, HC(O)NHOH+·, 4, and HC(OH)=NOH+·, 5, were studied in detail by metastable ion mass spectrometry. Appearance energy measurements established the potential energy surface of the isomers 1, 2 and 3 showing the intricate interrelation between them. For isomers 4 and 5, it was concluded that they do not intercommunicate with ions 1, 2 and 3 prior to fragmentation. Neutralization-reionization mass spectrometry indicated that the enol form of formohydroxamic acid structures as well as the keto analogue are stable in the gas phase. The neutral counterparts of the C2H7O + isomers. The neutral counterparts of the C2H 7O+ isomers, CH3O+(H)CH 3, CH3CH2OH2+ and C 2H4···H-OH2+ have been studied by means of neutralization-reionization mass spectrometry. It was observed that the internal energy of protonated dimethyl ether ions is directly related to the stability of the neutrals generated by electron transfer, and on their dissociation. With regard to CH3CH 2OH2+ and C2H4···H-OH 2+, it was concluded that the former ion can be obtained as a neutral species in the gas phase, whereas the latter isomer could not be produced as a neutral species. Classical and non-classical forms of the ethyl cation and their participation in the ions RO+(C2H5)R'. Oxonium ions formed via ion/molecule reactions between several oxygen centered molecules and the ethyl cation were studied. Significant H/D mixing in these oxonium ions was observed only when a labeled ethyl cation was reacted with a non-labeled ROR' molecule. The degree of H/D mixing depends only on the size of R and R', being independent of the observational timeframe from 1-30 mus. When non-labeled ethyl cations were reacted with labeled ROR' molecules, H/D mixing was not observed. The results were interpreted as arising from the classical and non-classical forms of the ethyl cation having different reactivities with ethers of different sizes. Homologous hydrogen-bridged intermediates R1R 2O···H···C(O)R3 from ionized beta-hydroxyethers. The unimolecular dissociations of several beta-hydroxyethers and some of their isotopomers were studied by metastable ion and collision induced dissociation mass spectrometry. It was found that molecular ions of the form R1OCH(R2)CH(OH)R 3 yield protonated ethers, R1O+(H)R2 , via intermediates of the type R1R2O···H···C(O)R 3+·.

The preparation of 5-ethoxycarbonyltetrazole, 5-phenyltetrazole, 1-methyl-5-phenyltetrazole, 2-methyl-5-phenyltetrazole, 5-p-nitrophenyltetrazole, 1-methyl-5-p-nitrophenyltetrazile, 2-methyl-5-p-nitrophenyltetrazole, 1-methyl-3,5-diphenyl-1,2,4-triazole and 2-methyl-4,5-diphenyl-1,2,3-triazole have been described. Photolysis of 5-phenyltetrazole produces 3,6-diphenyl-s-tetrazine and 1,4-dihydro-3,6-diphenyl-s-tetrazine, whereas the latter undergoes smooth oxidation with bromine producing 3,6-diphenyl-s-tetrazine. Several attempts were made to trap the possible nitrilimine intermediate by photolysing 5-phenyltetrazole in the presence of norbornene and ethyl acrylate, but in neither case was any pyrazoline derivative obtained. The production of 1-4-dihydro-3,6-diphenyl-s-tetrazine through the possible photodimer or free radicals formations has also been discussed. Photolysis of 2-methyl-5-phenyltetrazole produces 2-methyl-4,5-diphenyl-1,2,3-triazole in addition to some other yet unidentified products. The structure of 2-methyl-4,5-diphenyl-1,2,3-triazole has been confirmed by its independent synthesis starting from benzil. Several attempts were made to trap the possible C-phenyl-N-methyl-nitrilimine by photolysing 2-methyl-5-phenyltetrazole with benzonitrile, but no change in the total yield of 1,2,3-triazole derivative was observed. The formation of 2-methyl-4,5-diphenyl-1,2,3-triazole through a possible photodimer of 2-methyl-5-phenyltetrazole has also been assumed. As 2-methyl-4,5-diphenyl-1,2,3-triazole on heating up to 220-225° for 6 hours did not produce any 1-methyl-3,5-diphenyl-1,2,4-triazole, the idea of the formation of 1-methyl-3,5-diphenyl-1,2,4-triazole via 2-methyl-4,5-diphenyl-1,2,3-triazole during the thermolysis of 2-methl-5-phenyltetrazole was given up. It has been shown, by using the Vycor filter, that radiations above 2400 A are responsible for effecting the photolysis of 2-methyl-5-phenyltetrazole. Several attempts were made to effect the photolysis of 1-methyl-5-phenyltetrazole by direct irradiation and once with the sensitizer, benzophenone, but in all cases 1-methyl-5-phenyltetrazole was found to be stable towards ultraviolet irradiation. 2-methyl-5-p-nitrophenyltetrazole, which has been isolated in 93% yield by methylation of 5-p-nitrophenyltetrazole, has been found to be stable towards the direct ultraviolet irradiation. The magnetic anisotropy-effects on the ortho protons of the phenyl rings of 2-methyl-5-phenyltetrazole, 5-phenyltetrazole, 5-p-nitrophenyltetrazole, 2-methyl-5-p-nitrophenyltetrazole and 1-methyl-3,5-diphenyl-1,2,4-triazole and 3,6-diphenyl-s-tetrazine have been discussed. Infrared, ultraviolet and n.m.r. spectra were used extensively in the structure determinations of these compounds.

In the work described in the present thesis, which deals with simulation of the kinetic behaviour of various reaction mechanisms, conditions which give rise to particular and characteristic current-potential profiles under different "experimental" conditions for the reaction process in question have been sought. Attention has been focussed on parameters such as the reduced sweep-rate s/k and the ratio of the rate constants governing the individual processes in a given complex reaction mechanism, which in turn give rise to particular shapes of i-V profiles. It is shown that relative values of electrochemical and chemical rate constants, k, interaction parameters, g, and standard electrode potentials, E°, can be derived using the characteristic kinetic features which are shown to be generated by a given reaction mechanism. Such features are the half-width potentials, DeltaV1/2, the peak currents, ip, the coverage of the chemisorbed species up to the current peak, theta p, etc. Where appropriate, comparisons of the simulated kinetic behaviour derived in the present work have been made with experimental results for various systems recorded in the literature. First, the kinetic behaviour of a single step, 1-e surface reaction is treated theoretically as a simple reference case, especially with regard to: (a) characteristic aspects of its behaviour when significant attractive or repulsive interactions arise between the atoms in the electrodeposited monolayer film and (b) formulation of characteristic features of its kinetic and equilibrium behaviour which provide a reference case for distinguishing the behaviour of other, more complex reactions. The analytical derivations of characteristic parameters, derived previously by some other workers only for Langmuir behaviour, are made more general by extension to cases where two-dimensional interactions are significant. For surface processes involving parallel steps in which two chemisorbed species are involved, it is shown how a "kinetic relaxation method" can be developed and used for resolution of the behaviour of the two species when the electrochemical reactions in which they are deposited or desorbed occur over the same potential range. This method can be applied when one of the two chemisorbed species behaves more "irreversibly" than the other. It is shown how experimental results for acetonitrile at Pt electrode obtained by other workers in this laboratory can be treated by this technique. The potentiodynamic linear sweep method has often been applied to sequential reactions involving at least one chemisorbed intermediate species. The simulation calculations were extended to cases of this kind. The mechanisms which were analyzed involve a first-order chemical surface step coupled with a simple 1-e electro-chemical process, thus giving rise to either an "ec" or a "ce" type of overall mechanism. Characteristic features of the kinetic behaviour derived from the computed current-potential profiles were compared with those for the simple 1-e surface reaction case. Holding of the potential, especially at the end of the sweep, proves to be of great importance as it affects the i-V curves obtained on the subsequent reverse sweep in characteristic ways for these types of processes. (Abstract shortened by UMI.)

Abstract not available.

Abstract not available.

Each year there are accidents involving oil tankers, pipelines, and storage facilities resulting in the release of large quantities of oil into the environment. As a result, oils are usually characterized for identification purposes. Nitrogen-containing aromatic compounds (NCACs) such as substituted pyridines, indoles, quinolines and carbazoles are known to occur in the low to high molecular weight fractions of crude oil. Use of the popular SARA fractionation procedure allows oils to be separated into fractions containing Saturates, Aromatics, Resins, and Asphaltenes. This allows for the individual and chemical class identification of many of the constituents present in oils worldwide. The objective of this research was to use Electrospray Ionization Tandem Mass Spectrometry (ESI-MS/MS) to study a variety of NCACs for use in the analysis of the Resins fraction of several crude oils. In addition, the affect of weathering on these oil resins was studied using a technique employing Electrospray Ionization Mass Spectrometry (ESI-MS).

Highthroughput methods have been increasingly applied to catalyst screening, however, efforts to use these for enantioselective measures are still lacking. We propose to apply Fluorescence Resonance Energy Transfer (FRET) as a highthroughput screening method to fulfill such a purpose. This concept is applied to the desymmetrization of meso substrates. The meso compound will be equipped with a recognition element for catalyst binding, two different fluorescence donor molecules to distinguish between the chiral centres and also a fluorescence acceptor molecule to suppress fluorescence. Upon catalytic hydrolysis, the fluorescence acceptor molecules will be discharged into solution and thus can be detected by use of a spectrophotometer. As each donor molecule has a characteristic fluorescence emission wavelength, measuring the respective fluorescence intensities will ultimately allow for one to rapidly determine the enantiomeric excess. Efforts towards establishing this FRET based assay are discussed herein.* *Please refer to dissertation for diagrams.

Structure determination of membrane proteins by solution nuclear magnetic resonance spectroscopy requires that they can be incorporated into detergent micelles in order to ensure that they are maintained in a folded, water-soluble state. However, some detergents appear to disrupt structurally important interactions between transmembrane (TM) helices, while others produce micelle-protein complexes that may be too large for solution NMR. As a result there are a limited number of detergents suitable for solution NMR studies, making the search for better solution conditions one of the remaining challenges for structure elucidation of membrane proteins by this technique. This thesis presents the development and application of methods to address this problem by characterizing detergents for suitability for membrane protein solution NMR. Since the overall size of the membrane protein-detergent complex is one of the major factors that affects the quality of NMR spectra, modified versions of pulsed field gradient (PFG) NMR pulse programs for translational diffusion measurement were set up to estimate the size of these complexes. These methods were applied to a model membrane protein-detergent system allowing an approximate complex size and composition to be determined. 15N relaxation parameters were also measured for this complex and provided evidence that extensive motion of the protein within the micelle can occur to improve the quality of the resulting NMR spectrum. In addition to these experiments that probe complex molecular weight, a model system was also established to help identify detergent characteristics that can promote helix-helix interactions. This system is based on the properties of the single transmembrane segment from the M13 bacteriophage major coat protein (MCPTM) which forms homodimers in both lipid membranes and detergent micelles. Using solution NMR in combination with paramagnetic probes, oligomerization of this peptide under a range of detergent conditions was investigated. The results show that both denaturing and non-denaturing detergents are capable of preserving the TM-helix homodimer interaction. In accord with previous studies on this dimer, results from this study indicate that this peptide exists as a parallel dimeric structure at low concentrations of detergents. Together the methods described in this thesis have the potential to be used in the characterization of a wider range of detergent-protein complexes to assist in the development of new solvents that can ultimately advance the utility of solution NMR of membrane proteins.

Silver nanoparticles can be readily generated in micellar environments by ketyl radicals formed from the photoreduction of benzophenone in the presence of a suitable hydrogen donor. The yield of these ketyl radicals can be increased by extending the lifetime of the triplet radical pair through Zeeman splitting of the triplet sublevels in an externally applied magnetic field. This provides control over the rate of photogeneration of nanoparticles under very mild conditions. The rate of photogeneration can be monitored by the distinctive surface plasmon resonance absorption around 420 nm. In this work, micelles of sodium dodecyl sulphate (SDS) were employed, and 1,4-cyclohexadiene (1,4-CHD), an excellent hydrogen donor, was used to promote the generation of ketyl radicals. When benzophenone and a silver salt are added to this system and it is irradiated in the presence of a magnetic field, the rate of appearance of the plasmon band is enhanced. In addition to serving as a hydrogen donor, 1,4-CHD also has a stabilising influence on the nanoparticles, adsorbing onto the surface and preventing aggregation. 1,4-CHD added to a solution of nanoparticles synthesised without the diene present will even break up existing aggregates.