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No description available.

Thesis (Ph.D.)--University of Iowa, 2009. / Thesis supervisor: Edward G. Gillan. Includes bibliographical references (leaves 184-194).

Thesis, 1928. / Includes bibliographies.

Thesis (Ph. D.)--University of Chicago, 1946. / Includes bibliographical references.

D.Phil. / The topic of this thesis centres around the construction of carbocycles from carbohydrates involving the use of SmI2 as reagent. Carbocycles, in particular functionalised cyclopentanes, form important substructures in a plethora of natural compounds, many of which are biologically active. The conversion of carbohydrates into stereodefined cyclopentanoids represents an attractive means of generating this type of compounds. The SmI2-mediated cyclisation of hex-5-enals, derived from suitably substituted carbohydrate precursors via a zinc-mediated Grob-fragmentation reaction, was found to be a facile reaction generating stereodefined cyclopentanols in moderate yields. The effect of varying stereochemistry and substitution pattern on the outcome of the cyclisation was also investigated. In order to achieve a more efficient route to the cyclic products, a Grobfragmentation based on SmI2 was investigated. The substituent at the anomeric position of the carbohydrate was found to be crucial to the success of the fragmentation. This protocol gave rise to conditions under which fragmentation and cyclisation could be effected in a tandem fashion mediated by SmI2. Various attempts at intermolecular trapping of the organosamarium species generated after cyclisation proved fruitless. In order to circumvent these obstacles a tandem radical bicyclisation reaction was investigated for the construction of highly functionalised bicyclic ring systems. This approach proved to be a successful alternative for incorporating functionality at the exocyclic carbon atom which is otherwise difficult to achieve. The second part of this work is directed at the synthesis of stereodefined alkoxyaminocyclopentanes from carbohydrates promoted by SmI2. The intramolecular trapping of a radical by an oxime ether represents an attractive means of generating these compounds. The preparation of the iodo oxime ether starting materials from suitably substituted carbohydrates is discussed. The radical cyclisation under the action of SmI2 was found to be a facile process providing a rapid route to aminocyclopentanes which are used as key intermediates for the preparation of carbocyclic glycosidase inhibitors and analogues. In the third part of this work, the construction of functionalised cyclobutanols from carbohydrate precursors is discussed. The 4-exo-trig cyclisation holds promise as a general route for the stereoselective synthesis of highly functionalised cyclobutanols. Initial attempts at the 4-exo-trig cyclisation proved fruitless. It was subsequently established that the radical acceptor plays a crucial role in the success of the transformation. This led to the isolation of the first carbohydrate derived cyclobutanol. The final part of this thesis involves the development of a new approach for the conversion of suitably functionalised pentose derivatives into chiral cyclopentanols. Cyclisation of a ribose derived hemiacetal via its in situ formed hex-5-ynal is discussed. This approach opens new possibilities for the construction of complex carbocycles from readily available carbohydrate starting materials.

Calorimetric heats of mixing per mole, ΔH_x^M, and a solid-liquid phase diagram were obtained for the system water--p-dioxane at 25°C over the entire range of composition. From these data are derived values for the partial molar heat contents, activities and free energies and entropies of mixing. The excess free energy-composition curve, which is roughly parabolic in shape, gives little indication of the extent of interaction in this system. The ΔH_x^M values, however, range from 115 cal./mole endothermic to 142 cal./mole exothermic. A sharp exothermic dip occurs at a mole fraction of 0.143, which corresponds to a ratio of 6.00 water molecules to each dioxane molecule. Minimum values for the freezing points and entropies of mixing also occur at approximately this same composition. Possible short range structures that could contribute to the properties of this system are discussed. ΔH_x^M data were determined calorimetrically for the ternary and the three binary systems that can be formed from carbon tetrachloride (1), cyclohexane (2), and benzene (3). The following analytical equations, in which x_i is the mole fraction of component i, summarize these data: ΔH_12^M = x_1x_2 [ 160.8 / 18.9 (x_1 - x_2) - 20.2(x_1 - x_2)^2 ] 15,25,and 35°c ΔH_13^M = x_1x_3 [ 103.2 / 11.0 (x_1 - x_3) - 13.3(x_1 - x_3)^2 ] 25°C ΔH_13^M = x_1x_3 [ 96 / 4.17 (x_1 - x_3) - 13.19 (x_1 - x_3)^2 ] 10°C ΔH_23^M = x_2x_3 [ 3105 - 7.980 T - (1303-4.370 T) (x_2 - x_3) / (1738 - 5.486 T) (x_2 - x_3)^2 ] 15,25,and 35°C ΔH_123^M = x_1x_2 [ 160.8 / 18.9 (x_1 - x_2) - 20.2 (x_1 - x_2)^2 ] / x_1x_3 [ 103.2 / 11.0 (x_1 - x_3) - 13.3 (x_1 - x_3)^2 ] / x_2x_3 [ 726.0 / 102.4 (x_2 - x_3)^2 ] 25°C Solid-liquid phase equilibria data were also obtained for these systems. This information for the system cyclohexane-benzene, together with the thermal data, made possible the calculation of the partial molar heat contents, L_i, and the excess free energies, ΔF_x^E, and entropies, ΔS_x^E, of mixing per mole as functions of composition. These data are summarized by the following expressions: L_2 = x_3^2 [ (6146 - 17.836T) - (19116-61.368T) x_2 / (20856-65.832T) x_2^2 ] L_3 = x_2^2 [ (3540-9,096T) - (8692-26.408T) x_3 / (20856-65.832T) x_3^2 ] ΔF_x^E = x_2x_3 [ 310.6 / 2.33 (x_2 - x_3) / 40.0 (x_2 - x_3)^2 / 130.8 (x_2 - x_3)^3 ] 25°C TΔS_x^E = x_2x_3 [ 415.4 - 2.33 (x_2 - x_3) / 62.4 (x_2 - x_3)^2 - 130.8 (x_2 - x_3)^3 ] 25°C The system carbon tetrachloride-benzene proved to be especially interesting in that the phase diagram of this "near-to-ideal" system reveals a complex of approximately one benzene molecule to one carbon tetrachloride molecule composition. It is suggested that TT bonding between the electron cloud of the aromatic ring and the empty 3-d shell of chlorine may be responsible for the formation of the compound. Replacing benzene with p-xylene to increase the electron density of the ring enhanced the formation of the complex. On the other hand, either decreasing the electron density of the ring by using nitrobenzene, or decreasing the electronegativity of the chlorine atoms by substituting CHCl_3 for CCl_4 prevented complex formation. The results of this study of carbon tetrachloride-cyclohexane-benzene mixtures seem to indicate that the system carbon tetrachloride-cyclohexane is very nearly ideal, the system carbon tetrachloride-benzene is much more complex than was previously considered, and the high entropy in the system cyolohexane-benzene is probably due partially to volume change on mixing and partially to lack of randomness in the pure benzene.

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No description available.

The specific heat of a material is simply the measure of the amount of energy required to raise the temperature of a unit mass of the material by one degree. The specific heat of a material depends on the structure, pressure, and temperature of the material. Hence, measurement of specific heat can indicate structural changes and transitions in the material.Previous work at the State University of New York at Buffalo, shored anomalies in the specific heats of Glassy Carbon samples which had been exposed to neutron irradiation. Neutron irradiation of the carbon introduced defects in the material and the specific heat was dependent on the time of sample irradiation. The specific heat plotted as a function of temperature showed peaks at temperatures below 2.0°K. This indicates some kind of transition in the material. Also the specific heat values, which were measured up to 4.5°K, were much lower than the specific heat of the original nonirradiated material. Measurements indicated that the two kinds of samples had the same specific heat at room temperature. This kind of change in the specific heat of carbon has not been explained.The purpose of this project was to investigate the specific heats of these samples above 4.50K to determine where and how the anomalies in the specific heat disappeared at higher temperatures. The specific heats were measured by cooling the sample with liquid helium. This enabled the sample to obtain temperatures of 2.5°K and up. The specific heat was measured by electrically heating the thermally isolated sample and measuring the change in its temperature with a germanium resistance thermometer.