iv, 190 leaves : ill. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Organic Chemistry, 1970

Thesis (Ph.D.) -- University of Adelaide, Dept. of Organic Chemistry, 1970.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1937. / Typescript. Includes abstract and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

This project was concerned with the evaluation of three potential synthetic routes for 3-tert-butyl-4-methoxybenzaldehyde, a useful fine chemical intermediate and ingredient in many sunscreen agents. The three synthetic routes all involved the selective oxidation of the 3-tert-butyl-4-methoxytoluene to the desired benzaldehyde by (a) catalytic air oxidation, (b) direct electrochemical oxidation, and (c) indirect electrochemical oxidation. In order to decide whether catalytic oxidation should precede the alkylation of 4-methoxytoluene, the selective oxidation using the well-known cobalt(II)- bromide catalyst system in acetic acid solutions were investigated with the view to determine whether increased electron density on the aromatic ring improves selectivity to the desired benzaldehyde or not. In addition, the effect of various important reaction variables was also investigated. These studies showed that increased electron density, hence increased substitution, increases the desired benzaldehyde selectivity. In addition, while reaction conditions such as reaction temperature, catalyst concentration, water concentration, etc. may be optimised for maximum 3-tert-butyl-4- methoxybenzaldehyde yields (~80 percent), such yields can only be achieved at relatively low (<40 percent) alkoxytoluene conversions. The direct electrochemical oxidation of 3-tert-butyl-4-methoxytoluene was investigated in methanol solutions containing various supporting electrolytes and using constant current electrolysis with the intention of optimizing the production of 3-tert-butyl-4-methoxybenzyl dimethyl acetal which can later be hydrolyzed using sulfuric acid to the 3-tert-butyl-4-methoxybenzaldehyde. In this study, various parameters such as supporting electrolyte and electrodes were studied. Previous studies showed undoubtedly that methanol as a solvent gave better results amongst the rest of the solvents. Indirect route was also studied as a method of synthesizing 3-tert-butyl-4- methoxybenzaldehyde and compared to the direct electro synthesis.

A study of the oxidation kinetics of galena crystals in ammonium acetate solutions under oxygen pressures was carried out toy following the changes in the lead ion concentration toy means of a cathode ray polarograph. The oxidation rate-exhibits a parabalic rate law character similar to the rate growth curves obtained by E. Gulbransen (8) for oxides on metals. The lead is preferentially oxidized and leached from the galena crystal leaving sulphur, which builds up a sulphur film on the surface. Application of the transition state theory (4) shows that the rate controlling step has a low entropy of activation, and a diffusion coefficient of the magnitude associated with the electron diffusion mechanism. The presence of a sulphide layer on the galena crystal has been established. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

In the first part of this work, the reaction between cis- and trans-2-butenes and oxygen atoms was studied at room temperature in a flow reactor in the essential absence of molecular oxygen. Products were mainly analysed by gas chromatography. These reaction products were found to consist of hydrocarbons and oxygenated products in the ratio of approximately 2:1. The hydrocarbon products were mainly ethane, some ethylene, a little propane and isobutane, and trace amounts of methane, n-butane and isobutene. The oxygenated products were mainly acetaldehyde and propanal, some cis- and trans-2, 3-butene oxide, acetone, isobutanal, butanone-2 and traces of other products. Peroxides were also detected. Cis-trans isomerisation, previously unobserved by other workers, was found to occur during the course of the oxidation reaction. The disappearance of the oxygen atoms could not be accounted for by the amount of oxygenated products nor by the disappearance of the 2-butene, as observed by several previous authors. The reaction order for the rate of production of the various products and for the rate of disappearance of the 2-butene was found not to be simply unity with respect to each of the reactants 2-butene and oxygen atoms. The formation of products is explained in terms of an initial oxygen atom attack at the 2-butene to form a biradical [formula omitted] which is thought to decompose in one of three ways: [formula omitted]. Other products are formed through the interaction of the radicals thus produced, and from the reactions between these radicals and the parent 2-butene. Ring closure occurs to produce epoxides. Cis-trans isomerisation is effected by rotation about the centre C-C bond in the biradical and subsequent scission of the C-0 bond. The disappearance of oxygen atoms is explained through an olefin-catalysed recombination of oxygen atoms via a complex (π or charge transfer) formation between 2-butene and the oxygen atom [formula omitted] or by way of a 4-centre reaction scheme involving the biradical [formula omitted]. The formation of peroxides is thought to be due to the reaction between the radicals present and molecular oxygen thus produced. In the second part of this work, the thermal oxidation of. cis- and trans-2-butenes by molecular oxygen was investigated in a conventional static system. Pressure-time studies were made at 289°C and at a total initial pressure of 51 mm Hg. Cool flames were observed at the end of an induction period when the ratio (po₂/p₂-butene) was greater than unity but not very large. When this ratio became very large, no cool flame was observed but the pressure-time curve took on a simple S-shape. When this ratio became less than unity, no pressure increase was detected at the end of the induction period. The relationship between the overall pressure increase and the initial pressure of 2-butene at a total initial pressure of 51 mm Hg was found to be ΔP/p₂-butene = 1.66 - 6.0xl0⁻² p₂-butene where ΔP is the overall pressure increase and p₂-butene the initial 2-butene pressure. The induction period ⊤ at 289°C and at a total pressure of 51 mm Hg was found to relate to the initial 2-butene pressure by the following expression [formula omitted] where ⊤ is in minutes and p₂-butene is the initial pressure of 2-butene in mm of Hg. Products formed during the induction period were mainly acetaldehyde, some propanal, isobutanal and butanone-2. After the end of the induction period, large quantities of hydrocarbons and other products such as formaldehyde, methanol and carbon dioxide appeared. Methane and carbon monoxide appeared in large amounts immediately after the end of the induction period but it appeared they were subsequently consumed. The maximum in the methane concentration occurred later than that observed for the carbon monoxide concentration. Crotonaldehyde was not detected. Kinetic studies were made at total pressure of 10-75 mm Hg. It was found that [formula omitted]. The value of [formula omitted] was determined over six temperatures each for cis- and trans-2-butenes in the range of 289-357°C. There was no appreciable difference in [formula omitted] between using cis- and trans-2-butenes as reactant. It was found that [formula omitted] Thermal isomerisation of 2-butenes to isobutene and the catalysed cis-trans isomerisation of 2-butenes have also been observed. A mechanism has been proposed to explain the observations involving the initial abstraction of hydrogen from the 2-butene by oxygen to form a butenyl radical and a HO₂ radical: [formula omitted] The butenyl radical is thought to react rapidly with oxygen to form a peroxy radical [formula omitted] Acetaldehyde is probably produced through the isomerisation and subsequent decomposition of the A-butenyl peroxy radical [formula omitted] The B-butenyl radical is likely to undergo isomerisation to the A-form. [formula omitted] Other products are probably formed through the interaction of radicals produced and through the reaction between these radicals and the parent 2-butene and oxygen. This mechanism must be incomplete since the rate law thus derived, employing the stationery state treatment, is in disagreement with the observed expression. A satisfactory mechanism which would give the observed rate law has not been found. / Science, Faculty of / Chemistry, Department of / Graduate

Remote oxidation at the C-5 position of isobornyl acetate (37) by chromium trioxide in glacial acetic acid/acetic anhydride, and the application of this oxidation to monoterpenes having the bicyclo[2.2.1] heptane framework is described. Subsequent conversion of 5- ketoisobornyl acetate (38) to 5-ketocamphene (42) and the relevance of this sequence to the proposed synthesis of the sesquiterpenes, culmorin (95), helminthosporol (99) and helmintho-sporal (97) is discussed. The oxidation of dihydroisocampherenyl acetate (87) at C-5 and subsequent conversion to b-ketodihyriro-p-santalene (90) is also described. The postulate that "certain compounds are susceptible to oxidation at positions remote from functionality" is further tested by the oxidation of fatty acid esters. The formation of a mixture of mono-ketoesters from the oxidation of methyl stearate (72;n=16), methyl docosanoate (72;n=20), methyl myristate (72;n=12), methyl palmitate (72;n=14), and methyl decanoate (72;n=8) by Cr03-Ac20/AcOH, and the procedure used to obtain a quantitative estimation of the relative amounts of isomeric ketoesters present in the product mixtures, is reported. Evidence is given for the validity of the analytical method used to estimate the relative amounts of isomeric ketoesters. / Science, Faculty of / Chemistry, Department of / Graduate

The objective of this study was to obtain information on the role of iron in the oxidation of sulfide minerals. Activated carbon, a catalyst for the oxidation of iron (II), was used as a tool. Activated carbon was an effective catalyst for the oxidation of iron (II) using percolators. The catalytic action increased at decreasing pH. The optimum amount of carbon to be used in the percolator was 0.5 g. The bubbling rate of the percolator was not critical. The presence of activated carbon increased the rate of oxidation of copper (II) sulfide. Increasing the iron concentration increased this rate, but not linearly. The bacteria had an optimum iron concentration in the oxidation of copper (II) sulfide. The activated carbon had little effect upon the biological activity. Iron (III) was not as effective in oxidizing copper (II) sulfide as iron (II) and carbon. Cuprite was rapidly oxidized by air at pH 1.0. The rate was increased by the presence of activated carbon and iron (II). Iron (III) had a greater effect on the oxidation of pyrite than iron (II) and carbon. The oxygen in the air was essential to the oxidation of pyrite. The bacteria produced the greatest rate of oxidation of the pyrite. Bornite, covellite, and chalcocite were all oxidized by iron (III). Chalcopyrite showed very limited oxidation by iron (II) and iron (III) solutions but gave very rapid oxidation with an iron (II) solution and carbon at pH 1,0. Varying the temperature on runs with covellite gave a biological optimum when the bacteria were present. The sterile run gave the effect of air oxidation with an iron (II) solution. The state of the soluble iron in these runs demonstrated biological activity, the reduction of iron (III) by the mineral, and the air oxidation of the iron at various temperatures.

Berlin, Techn. Univ., Diss., 2002. / Computerdatei im Fernzugriff.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy