Thesis (Ph. D.)--University of Illinois, 1919. / Biographical.

Kinetics of the iodination of a number of substituted benzenes and thiophenes by iodine and nitric acid in acetic acid solution have been studied. The reaction is catalysed by dinitrogen tetroxide and hydrogen ions and evidence is presented to show that the iodinating species is protonated nitryl iodide, which reacts in a slow step with the substrate. Acidity function data for nitric acid in 10% aqueous acetic acid are presented and the charge-transfer complex formation between iodine and m-xylene in acetic acid has been studied. The conversion of 4-iodoanisole into 2-iodo-4-nitroanisole by nitric acid, has been shown to occur by rapid nitrodeiodination and iodination to give 2,4-di-iodoanisole and 4-nitroanisole; gradual nitrodeiodination of the former compound at the 4-position with the production of free iodine, and then very slow iodination of the latter compound at the 2-position, Nitrous acid and hydrogen ions act as catalysts and the preliminary step is thought to be nitrosodeiodination. The ortho:para ratio for the methoxy-group in nitrosodeiodination is very low. The ipso factors of Perrin and Skinner are discussed in the light of this and other work. Transient intermediates observed in the nitrodeiodination reaction have been investigated using stopped-flow techniques and a water soluble substrate. These species are tentatively suggested to be o-complexes. The anomalously high rate of nitration of iodobenzene has been investigated and it has been found that this phenomenon is not due to a nitrodeiodination reaction, as had been suggested previously. Work on the nitration of ioclomesitylone has been investigated and it has been found that nitrosodeiodination is significant in this reaction, which is contrary to the findings of the previous workers. A computer programme has been written to assist calculations on data obtained from radio-isotopic dilution experiments where two products are formed simultaneously from a single substrate. Another computer programme has been written to assist in the calculation of rate constants for reactions of the first and half order.

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Cesium adsorption on Pt(111) and its coadsorption with iodine and oxygen is studied in this dissertation. The work function during Cs dosing first decreases and at Δφ≈ 3 eV ( Cs = 0:15) the surface undergoes surface transition between a disordered anomalous state (Pt(111)(anom)-Cs) and islands of a Pt(111)(2 x 2)-Cs causing a change in the slope of the work function curve. The work function curve reaches minimum at -5:5 eV where the surface is fully covered with the Pt(111)(2 2)-Cs structure (θCs = 0:25). Further Cs dosing results in a work function increase and the surface undergoes a phase transition to Pt(111)(p3 p3)-Cs. The Cs saturated structure (Pt(111)(ihcp)-Cs) has an hexagonal symmetry with the unit cell vector aligned with the h1; 0i direction of the substrate. Cs in the anomalous state desorbs from the surface in a high-temperature TDS peak (> 1000 K). When the lock-in TDS detection technique is used, this peak appears to be phase shifted by 180 when compared to the desorption peak of normally adsorbed Cs ( Cs > 0:15) . This phase shift is a consequence of a positive charge of desorbing Cs. The TDS and work function behavior were explained by a Monte Carlo desorption model incorporating di¤erent desorption behavior for all four observed adsorption phases. When O2 is dosed on a Pt(111)-Cs surface, the maximum coverage of oxygen bonded to the surface is significantly increased in comparison to Pt(111). Anomalously adsorbed Cs activates the O2 bond but does not interact strongly with coadsorbed O. However, when O2 is dosed on Pt(111)(ihcp)-Cs, the oxygen first adsorbs to a sub-layer adsorption site and strongly interacts with Cs. The oxygen in this state is responsible for thermal stabilization of coadsorbed Cs. When iodine is coadsorbed on a Pt(111)-Cs surface, it also strongly interacts with and thermally stabilizes Cs. During the desorption of Cs,I layers, some Cs and I desorb together in the form of a CsxIy cluster. The surface structures observed by LEED during the coadsorption of Cs and I are in good agreement with atomic arrangements predicted for ionic layers. The validity of this conclusion and the general behavior of ionic layers was checked by an electrostatic energy calculation for various structures. / Graduate / 0494 / 0748

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Apresentamos uma revisão bibliográfica sobre a formação de complexos no sistema iodo/iodeto. Efetuamos uma apreciação geral sobre métodos de cálculo de constantes de equilibrio em sistemas mononucleares, incluindo os métodos desenvolvidos neste Instituto de Química. Desenvolvemos uma sistemática de cálculo de constantes de equilibrio de complexos mononucleares, baseada no princípio dos mínimos quadrados, a qual é um aperfeiçoamento de uma sistemática anteriormente proposta pelo grupo de trabalho. Estudamos o sistema iodo/iodeto em meio homogêneo, através de medidas de potencial, evidenciando duas espécies mononucleares, I-3 e I2-4, com as seguintes constantes de formação, obtidas a 25ºC, e condições de força iônica 1,0 M, mantida com perclorato de sódio: [Ver esquema no PDF] Efetuamos estudos em meio heterogêneo, na mesma temperatura e condições de força iônica, com a fase solida em equilíbrio com íons iodeto. Através de medidas de potencia1 e de solubilidade, evidenciamos quatro especies binucleares: I-5, I-7, I-9 e I2-6. Combinando os dados obtidos em meio homogêneo e em meio heterogêneo obtivemos os valores das constantes de formação dessas espécies binucleares: [Ver esquema no PDF] A obtenção desses valores envolveu uma série de recursos de cálculo, processos de ensaio e erro e considerações de diversas hipóteses de tratamento de dados. Foram considerados outros equilíbrios correlatos e ainda perspectivas de trabalhos futuros. Medidas de solubilidade de iodo em soluções de brometo levaram à evidência da espécie I2Br-. / A bibliographie review on complex formation at the iodine/iodide system is presented. An outline and discussion about calculation of equilibrium constant was considered, including those methods developed at this Chemistry Institute. A systematie approach to calculate equilibrium constants from potentiometric data was developed, on basis of the use of the least square treatment of data. This procedure is an extension of former studies in this group of work. The iodine/iodide system was studied in a homogenium aqueous medium, at 25,00C, and ionie strength 1,0 M, held with NaClO4. The following final results were obtained, for the constants of the mononuclear species: [See squeme on PDF] A series of measurements were carried out in a heterogenium medium where solid iodine was in equilibrium with iodide ions in the working solutions. The eombination of such solubility data with the potentiometric ones lead to evaluate the presence of the following binuclear species: I-5, I-7, I-9 e I2-6. The following formation constant were determined at the conditions above mentioned: [See squeme on PDF] To obtain this formation constant several strategies were used as to solve a cumbersome puzzle, with several hypothesis being worked out and checked. Other related equilibria were considered as well as prospect for future work. Measurements of the solubility of iodine in bromide solutions lead to evidence of I2Br- specie.

The adsorption of iodine on a platinum(111) single-crystal surface has been investigated using LEED, Auger spectroscopy, and work function measurements. The phase transformations and work function changes have also been measured during desorption. Mass spectroscopy shows that above 300 K the main desorption product is atomic iodine with a small amount of molecular iodine detected as well. The desorption kinetics at these temperatures were studied by different techniques to extract the kinetic parameters and the orders of the desorption reactions. There are two main desorption features, one displaying zero-order desorption kinetics typical of a phase transition and the other displaying first-order kinetics with a coverage-dependent activation energy. The work function changes during adsorption and desorption were shown to be a function of coverage rather than having a site dependence. The adsorption of iodine at temperatures below 200 K was also studied. Multilayers of molecular iodine are formed that desorb with essentially zeroth order kinetics. Two multilayer desorptions were observed with thermal desorption spectroscopy. One of the multilayer desorptions had a significant work function change associated with it. The work function changes were modelled by calculating the hybridization dipole moment using extended-Hückel theory with Bloch wavefunctions. The calculations are sensitive to the atomic position of the adsorbate and require further refinement. Due to the protective nature of the iodine layer and its high polarizability, the iodine layers were used to study the ambient pressure adsorption of fluorinated carbosilane dendrimers. These dendrimers are stable in vacuum but do not form an ordered structure at ambient temperature. Heating the adsorbed dendrimer in vacuum to 1100 K produced a new ordered structure on the platinum surface. This structure was shown not to be an intact dendrimer molecule as two different dendrimers with similar structural moieties produced the same (√19x√19)R23.4° LEED pattern. The ordered structure was studied by Auger spectroscopy to determine the carbon coverage. This structure is proposed to be islands of a coincidental lattice of graphite. / Graduate

The changes in the level of circulating thyroid hormone, or protein-bound iodine (PBI), in the male Holstein calf and the Wistar Albino rat during a portion of the growth period have been determined. Two levels of nutrition were employed.in each case to determine if the nutritional status exerted an appreciable effect on the measured PBI level. Repetitive measurements of the serum PBI were conducted with each of eight calves in order to assess age changes, while with the rats single determinations were made on animals killed at regular weight intervals. Carcass analysis of the rats, including body fat and water determinations of the individual animals, and protein and ash analysis of a pooled sample from each group, was conducted with the intent of relating age changes of the serum PBI to a measure of "metabolically active tissue". The PBI level of the Holstein calf was found to increase with age in the growth interval considered. The rate of change of the PBI level of the low plane calves appeared to be less than in the high plane animals; the degree of variability was such, however, that a definite effect of nutrition could not be shown. No correlation was found between either the initial PBI level or the level at slaughter and the daily rate of gain. The resting metabolic rate of the calves was determined prior to the removal of a blood sample for PBI analysis. No relationship between the serum PBI level and the metabolic rate existed. In the case of the rats, no correlation was found between the serum PBI level and chronological age, body weight or fat-free body weight. A great deal of variability of the PBI level among animals in the same group was observed. Possible reasons for this variability are discussed. The body composition data of the high plane rats followed accepted trends, with the body water, protein and ash fractions exhibiting differential growth with respect to body weight and fat-free body weight. The composition of the low plane rats was not appreciably different from that of the high plane animals at equal body weights. The realimentation period was characterized by the deposition of large quantities of body fat. The significance of these findings in terms of the results of other investigators is discussed. Various workers have attempted to relate the serum PBI level of a young animal with its potential productive worth. No evidence was obtained in this study of such a relationship; a discussion of the many factors affecting the serum PBI level is offered to support the contention that no such relationship should be anticipated. / Land and Food Systems, Faculty of / Graduate

The lower British Columbia mainland waterways are inhabited by two races of the prickly sculpin Cottus asper Richardson. One race lives in the lower part of rivers or in estuaries and spends at least part of its life, particularly during the spawning season, under tidal influence. This race is the "coastal". The other race, called "inland", is confined entirely to fresh water where it is found in scattered, more or less isolated populations. By investigating the effects of ambient salinity on the oxygen consumption and on the utilization of injected radioiodine, it was found that salinity profoundly effects the iodine metabolism and, to a lesser degree, standard metabolic rates of the fish. In fresh water the thyroids of both races appear relatively quiescent but with increasing salinity, particularly in hyperosmotic environment, there is a marked increase in thyroid uptake of tracer iodine and also in the levels of circulating thyroid hormone. The inland fish demonstrate a greater ability than coastal fish to retain iodide in fresh water, and in sea water their thyroids appear more active. The inland fish also have a lower oxygen consumption in fresh water than do coastal fish. Viewed together, the results lead to the conclusion that the inland fish, with respect to their osmoregulating ability, show genetic divergence from the coastal forms. The latter probably more closely resemble the ancestral form. / Science, Faculty of / Zoology, Department of / Graduate

The diffusion of iodine implanted 6H-SiC has been investigated using Rutherford backscattering Spectrometry (RBS). SiC is used as the main barrier in the modern high temperature gas cooled reactors. An understanding of the transport behaviour of iodine in 6H-SiC will shed some light into SiC’s effectiveness in the retention of fission products. Room temperature iodine implantations were performed to a fluence of 1 x 1016 iodine ions per cm2. Iodine depth profiles were determined by Rutherford backscattering spectroscopy. Previous studies indicate that iodine diffusion cannot be detected for temperatures below 1000oC. Isochronal annealing experiments for 5 hours cycles were then performed starting from 1000oC. 5 hour annealing cycles at 1200oC and 1300oC were also performed. These relatively short annealing cycles were used to study the evolution of the iodine depth profiles and to determine the temperature where the first noticeable broadening of the iodine implanted profile is observed. Broadening of the iodine profile was initially observed at temperatures around 1200oC. Isothermal annealing cycles were then performed at this temperature of 1200oC where the broadening was first observed. The annealing experiments were performed for a total annealing time of 60 hours. Isothermal annealing experiments were also performed at a lower temperature of 1100oC also for a total annealing time of 60 hours. The experimental data was analyzed by fitting the iodine depth profiles to a Gaussian function using the GENPLOT program. Diffusion coefficients were obtained by comparing the full widths at half maximum, (FWHM) of the iodine profiles before and after annealing. Results for 1100oC show that the diffusion coefficient is below 10-21 m2 s-1 . Solving the diffusion equation numerically for this diffusion coefficient shows that the iodine does not traverse more than 2 ìm through SiC after annealing for one year. Intact SiC coatings which have a thickness of 35 ìm in the fuel particles will therefore be able to prevent iodine release from the particle at this temperature. Results for 1200oC show that the diffusion coefficient is in the order of 10-20 m2 s-1. The results also reveal that iodine loss through the front surface is relatively low with only 15% of iodine loss observed after annealing for a total time of 60 hours. Further indications of SiC ability to retain iodine are observed when an iodine peak is still present after annealing for 30 hours at a temperature of 1500oC. Radiation damaged produced during ion implantation was investigated by Rutherford backscattering in conjunction with channeling. The results of the RBS/channeling reveal that the room temperature implantations produce an amorphous layer from the surface up to a depth of 260 nm. Some epitaxial regrowth is observed starting at approximately 1000oC. / Dissertation (MSc)--University of Pretoria, 2011. / Physics / unrestricted