Thesis (Ph. D.)--University of Rochester. Dept. of Chemistry. / Bibliography: leaves 86-88.

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--University of Notre Dame, 1941. / Cover title. Vita. Bibliography: p. 33.

Thesis (Ph. D.)--University of Chicago, 1942. / Reproduced from type-written copy. Description based on print version record. Bibliographical foot-notes.

Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xii, 108 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 97-108).

Dialkyl carbonates are important industrial compounds that have a low toxicity and are readily biodegrade, also replacing some highly toxic and corrosive reagents in organic chemistry. There are a number of synthetic routes towards the synthesis of dialkyl carbonates, including two commercial processes (ENIChem S.p.A. and UBE Industries, LTD). The ENIChem process involves the carbonylation of methanol in the presence of CuCl2 as a catalyst. The major drawback of this process is in the use of an explosive gas mixture (CO/O2) under certain conditions. The UBE process is a two step reaction, whereby the methanol reacts with O2 and NO in the presence of a PdCl2 catalyst to form methyl nitrite and water, followed by carbonylation of methyl nitrite to form DMC and reform NO. The major drawback associated with this process is in the combination of methanol, nitric oxide and oxygen which is also explosive under some conditions. The transesterification reaction between a cyclic carbonate and an alcohol in the presence of a catalyst provide an alternative route towards synthesis of dialkyl carbonates, producing a glycol as by-product. This synthetic route is environmentally friendly, decreases explosion possibilities, and the reagents employed in this process are less hazardous than those of other processes. The main aim of this study was to identify and optimise the catalyst systems that could promote the transesterification reaction effectively. A number of homogeneous and heterogeneous, acidic or basic catalysts were evaluated during this study. The study revealed that basic homogeneous catalysts such as TBD, DBU, DBN, MTBD, DABCO, and Verkade bases are effective for the transesterification reaction. The basic heterogeneous catalysts such as Amberlites® IRA 96, IRA 67 and IRA 400 showed good catalytic behaviour, but they eventually became deactivated. On the other hand, homogeneous Lewis acids such as La(OTf)3, Gd(OTf)3, and Sm(OTf)3 demonstrated good activity, even though they need high temperatures, i.e. 150 °C. The heterogeneous acidic systems such as Amberlyst® 15, Amberlyst® 36, silica, alumina, etc., showed much lower activity, if any was observed. ix Due to the fact that these reactions were carried out above room temperature and analysed at room temperature in the GC, it was important to understand the equilibrium shift under such temperature variations, and NMR studies were used here. There was no significant difference in equilibrium conversion between the NMR reactions and the autoclave reactions (analysed in a GC), indicating slight influence of temperature variation. The results obtained from the NMR study were used to calculate the reaction kinetics. The calculations indicated a direct proportional increase of the rate with respect to the catalysts pKa values. / Prof. D.B.G. Williams

Ph.D. / The sensitivity of Petunia hybrida flowers to the plant hormone ethylene increases during the early stages of senescence and directly after pollination of the flowers. During these early stages .of senescence, ethylene production is very low and only increases after ethylene sensitivity had already increased. The increase in ethylene sensitivity is due to the forming of short-chain saturated fatty acids that accumulate in the petal tissue during the early stage of senescence. Following pollination, these acids are formed in the stylar tissue and transported to the corolla where it causes a rapid increase in ethylene sensitivity. The synthesis of short-chain saturated fatty acids is controlled by the enzyme acetyl-GoA carboxylase. As the acitivity of this enzyme decreases, the concentrations of short-chain fatty acids increase due to the lack of malonyl-GoA required for chain lengthening. During the early stages of senescence, the activity of this enzyme decreases simultaneously with an increase in short-chain fatty acids and ethylene-sensitivity. The results of this study indicate that acetyl-GoA carboxylase is a key enzyme involved in the control of ethylene sensitivity in petunia flowers.

The hydrogenation of ethylene reaction was studied over small catalyst beds of powdered nickel, nickel spheres, alumina supported nickel, powdered copper, and platinum wire. The reactor was positioned between the pole faces of an electromagnet, so that a magnetic field of strengths up to 10⁴ gauss could be applied across the catalyst bed. The reaction was studied at conditions of constant flow over the temperature range of 25° C to 550°C. The reaction rate was measured by means of a gas chromatograph, which had the sampling port installed in the system. Two magneto-catalytic effects were studied in this work: (i) the change in catalytic activity of a ferromagnetic catalyst as it is heated through its Curie temperature (internal magneto-catalytic effect); (ii) the change in catalytic activity of either a ferromagnetic or non-ferromagnetic catalyst, due to the presence of an external magnetic field (external magneto-catalytic effect). A clearly observable internal magneto-catalytic effect was found for the runs done on the ferromagnetic catalyst, nickel, which has an approximate Curie temperature of 360°C. In order to confirm this effect, runs were done over the temperature range of 300°C to 500°C on the non-ferromagnetic catalysts, copper and platinum. No change in reaction rate was found near 360°C, as was found using a nickel catalyst. No external magneto-catalytic effect was observed at any temperature. The hydrogenation of ethylene was found to be a rapidly self-poisoning reaction at temperatures above 100°C. Published literature indicates that at moderately high temperatures, desorption of reacting ethylene complexes off the catalyst surface causes the decrease in reaction rate. In this work a significant mole fraction of methane was detected in the reactor effluent gas, at temperatures above 300°C, and an accompanying carbon deposit was observed to form on the catalyst surface. The rapid decrease in catalytic activity at high temperatures was believed to be due to this carbon deposit. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Optical techniques have been used to study the behaviour of ethylene and hydrogen near their liquid-vapour critical points. From measurements of the coexistence curve of ethylene over the reduced temperature range 1.5 x 10⁻⁶ < t < 4.5 x 10⁻², where t — (Tc — T)/Tc and Tc is the critical temperature, we find the critical exponent β = 0.327±.002 and the corrections-to-scaling exponent ∆ = 0.46±.02. Similar measurements for hydrogen over the range 3.2 x 10⁻⁵ < t < 7.0 x 10⁻² give β = 0.326 ± .002 and ∆ = 0.46 ± .02. Measurements of the compressibility of hydrogen give the critical exponent [Formula Omitted] = 1.19 ± .05 and the critical amplitude ratio [Formula Omitted] = 5.2 ± .4. With the exception of ∆, which is slightly lower than its predicted value of 0.5, the results for these universal quantities are in agreement with theoretical predictions. The leading coexistence curve amplitude for hydrogen, B₀ = 1.19±.03, is lower than the corresponding values for ethylene, B₀ = 1.56 ± .03, and for other room-temperature fluids. This decrease is in qualitative agreement with the predictions of a theory of quantum effects on critical behaviour. Measurements of the coexistence curve diameter for both fluids show an anomaly near the critical point having a form consistent with the predicted t¹⁻α temperature dependence. These results are in agreement with a recent theory of the effects of many-body forces on the diameter; the hydrogen data indicate that these forces are attractive in that fluid. This suggests that quantum mechanical exchange interactions are important near the critical point of hydrogen. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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