Studies of the structure and properties of the double-layer at the Hg electrode interface by measurements of the adsorption of urea and of a series of n-propylammonium salts in water, have been carried out by means of electrocapillary measurements using a drop-time tensiometer. Since the adsorption of surface-active substances at charged interfaces involves solvent displacement, an appropriate adsorption isotherm is chosen in which the relative size ratio x, of adsorbate and solvent is taken into account. The following isotherm was applied to the results obtained in the present work: Kc = theta/exp(x-1)(1-theta)x or a corresponding one with a lateral interaction term exp(-2atheta) included. Electrocapillary curves were obtained for urea adsorption but did not exhibit the striking adsorption behaviour found experimentally with thiourea in previous work, where a strong Hg-S interaction predominates. Urea was found to adsorb in a more or less perpendicular orientation to the surface with its C=O group oriented towards the solvent. The Esin and Markov coefficients and the surface pressure behavior were evaluated for urea and tend to confirm the proposed orientation. It is determined by the H-bonding between the C=O function in urea and surrounding urea molecules as well as with other surrounding water molecules in the interphase. The experimental results for the series of n-propyl-ammonium perchlorates, n-PrN+ nH4-nC10-4 , show that all the organic cations tend to adsorb more strongly when qM is negative as expected on electrostatic grounds. The increase of adsorbability with increasing number of propyl chains corresponds to increasing hydrophobicity and decreasing accessibility of the N+ charge-center to the H2O dipoles of the solvent. Evaluation of the standard free energies of adsorption for this series of cations shows that, in a general way, the DG°ads becomes more negative with increasing surface excess, Gamma, suggesting that apparent attractive interactions take place among the adsorbed cations in the interphase. At first sight, this is unexpected since repulsion between ions of the same sign in an ad-layer would be the more expected behavior. These results suggest, however, that the interaction effects amongst hydrated ions must be considered not only in terms of the electrostatic interactions involved but also in terms of interactions between overlapping hydration co-spheres of the ions in the sense of Gurney. The co-sphere overlap of R4N+ ions, as in regular solutions of R4N+ salts, gives an attractive interaction which accounts for the unusual behavior of DG°ads with increasing surface coverage. Attempts to study the structure of the mercury-electrolyte solution interphases in acetonitrile was unsuccessful. This unfortunate situation was apparently caused by the presence of traces of water and oxygen in the solvent resulting in the hydrolysis of acetonitrile to acetamide which in turn becomes the predominantly adsorbed species at the mercury surface. This difficulty, noted in other work, prevented any reliable results being obtained in this solvent.

In this thesis, infrared spectroscopy has been used to study adsorbed species on silica-supported nickel and platinum catalysts. The chemisorption of the oxides of nitrogen (particularly nitric oxide) was studied initially, followed by a study of the chemisorption and oxidation of pyridine on bare and oxidized nickel and platinum. The results of these studies will be described below. Infrared spectral data have shown that nitric oxide chemisorbs on Ni/SiO 2 to form a single adsorbed species, which has been attributed to linear, neutral Ni-NO. On Pt/SiO2 two major surface species were produced and these have been assigned to linear, neutral Pt-NO and bent Pt-NO. In addition, the spectral data have indicated that, at high surface coverage, other nitrogen-oxygen containing species are formed one of which has been tentatively identified as PtONO2. The study of nitrogen dioxide chemisorption has demonstrated that nitrogen dioxide dissociates on both Ni/SiO2 and Pt/SiO2 to form adsorbed nitric oxide and oxygen. Isotopic substitution experiments have shown that carbon monoxide and nitric oxide react over Ni/SiO2 to form a surface nickel isocyanate species and the formation of this species is independent of the order of the addition of the reactants. However, on Pt/SiO2 a surface isocyanate species was generated only if the nitric oxide was preadsorbed at low surface coverage. In both studies, it has been concluded that very little M-NCO is produced (M = Ni or Pt). When hydrogen was added to chemisorbed nitric oxide on Pt/SiO2, two new surfaces species are formed and these have been identified as Pt-NH 3 and Pt2O2NH. In addition to the above results, this thesis also contains extensive reviews of the chemisorption of nitric oxide and nitrogen dioxide and of the formation of surface isocyanate species on the transition metals. Pyridine. Infrared spectral data have indicated that pyridine dissociatively chemisorbs on Pt/SiO2 to form a Pt-C sigma bond at the 'ortho' position and a coordinate bond with the N-atom such that the molecule lies perpendicular to the surface. On Ni/SiO2 a different strongly adsorbed species is formed which has been identified as a simple nitrogen-coordinated pyridine which also lies perpendicular to the surface, and, as proposed by others, the coordination of this species is promoted if the nickel surface is pretreated with either CO or O2. When oxygen is added to chemisorbed pyridine on Pt/SiO2 two new adsorbed species are formed and these have been assigned to a surface (N=0) containing species of the type, PtNOx (x = 2 or 3) or Pt2NO, and a cyclic C5 derivative of unknown structure. The same species were formed on oxidized Pt/SiO2, but, in addition, coordinated pyridine is formed.

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.