Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1952. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [93-94]).

Thesis (Ph. D.)--University of Wisconsin, 1964. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

In all the studies reported in the subsequent sections a common method of approach has been followed. As a preliminary to the kinetic work, detailed investigations have been made of the precise nature and stoichiometry of the decompositions occurring. Since the conditions chosen for the work involve low concentrations of reactants as a means of minimising secondary processes, the analytical techniques to determine the precise stoichiometry have faced considerable difficulties peculiar to each case investigated. The general techniques of gas analysis, ultra violet spectrophotometry, mass spectrometry, and chromatography have been enlisted to solve the problems involved. Although many of these techniques have been common to all three substances, the problems were sufficiently individual to merit their discussion in separate sections. 1. Triphenyl Methane a. The pyrolytic decomposition of this substance yielded 9-phenyl fluorine and hydrogen in equimolecular proportions. A hydrocarbon C23H18 was also produced in a very small amount. b. The decomposition proceeded by a first order mechanism, obeying the rate equation k=1.26 x 1014 e −71, 1°°/RT. 2. Carbazole a. The thermal decomposition of this compound has been shown not to give the dimer 9:9' of dicarbazyl under usual pyrolytic conditions. b. It is more probably that hydrogen and a phenazine type of compound are produced by the reaction of two carbazyl radicals. c. There appeared to be some heterogenous decomposition on the walls of the reactor during carbazole pyrolysis and a carbon coated surface is necessary. d. The kinetic data obtained were rather scattered due to poor reproducibility, but first order rate constants are of a magnitude given by k = 1013e 75,°°°/RT. e. If the energy of activation is ascribed to the dissociation of the N-H link in the molecule, it is shown that the resonance energy of the radical is in rough agreement with expectations from other data. 3. Toluene. a. Since two values for the energy of activation of the primary decomposition of toluene have been reported, a brief re-examination of the problem has been made, using the nitrogen carrier gas technique. b. The value of 77.5 k.cals./mole found was in agreement with the previous work of Szwarc, and the products were those anticipated on the basis of his proposed mechanism c. An examination is made of the papers by Szwarc and Steacie.

No description available.

No description available.

An investigation has been made of the pyrolysis of n-hexane, S-methyl-pentane, 3-methyl-pentane, 2, 8-dimethyl-butane and 2,3-dimethyl-butane in a static system at temperatures between 490° and 530°C. The normal pyrolysis and also the pyrolysis inhibited by nitric oxide have been studied. The effect of variation of initial hydrocarbon pressure on the distribution of products and on energies of activation and frequency factors was determined for the uninhibited reactions. The effect of variation in surface-to-volume ratio on rates and on product distribution has also been investigated. A study of factors governing overall reaction rates has provided information on the kinetics of chain termination processes. All pyrolyses at low pressures are significantly inhibited by reactions occurring on the surface of the quartz vessel. Mechanisms have been proposed to account qualitatively for observed decomposition products and the kinetics of pyrolysis of each of the isomers. In the reactions inhibited by nitric oxide, the effect of the pressure of nitric oxide on the rates and product distributions has been examined. The effect of an increase in surface-to-volume ratio on reaction rates and on product distributions has been investigated. The pressure of NO required for maximum inhibition appears to be independent of the partial pressure of the hydrocarbon and also of the nature of the latter. The kinetic and analytical evidence indicates that nitric oxide acts "both homogeneously and heterogeneously as an inhibitor. Significant consumption of nitric oxide was found for all branched isomers. The reduction in inhibition observed as the branching of the isomers increases is attributed in part to increased heterogeneous initiation reactions, from an increase in the extent of adsorption of the more branched isomers relative to the less-branched isomers. A mechanism is proposed for the inhibited pyrolysis of each of the isomers, which accounts qualitatively for the experimental results. A major conclusion drawn from the present study is that nitric oxide acts as an inhibitor through reactions occurring on the surface of the reaction vessel as well as through reactions occurring in the gas phase. / Science, Faculty of / Chemistry, Department of / Graduate

The thermal decomposition of cyclobutane is a homogeneous,unimolecular reaction;ethylene being the only product.The rate law :- K = 10¹⁵•³ e⁻⁶¹’⁰⁰⁰[symbol omitted] sec.⁻¹ was found to be obeyed in the pressure region 10 to 40 mm. and temperature range 398° to 450°C. Cyclobutane undergoes a wall reaction to form propylene and 1-butene. The high pressure rate constant falls off at low pressures and reaches a limiting low pressure rate when activation is maintained by collision with the walls of the reactor. The low pressure limiting rate decreases as the size of the reactor increases. The fall off curves gave best agreement with values of the Slater parameter, n, between 5 and 8, and values of the Kassel parameter, s, between 3 and 7. It was concluded that the ring vibrations are of major importance in the dissociation, and that the C—H bond vibrations are relatively unimportant. No evidence for a tetramethylene biradical intermediate was found. The reaction mechanism probably involves the simultaneous splitting of two opposite C—C bonds. / Science, Faculty of / Chemistry, Department of / Graduate

The pyrolysis of azoethane has been studied in a static system in the temperature range 245 to 308°C., and at initial pressures between 15 and 110 mm. using gas chromatographic analysis. In the initial stages of the reaction, products identified are methane, ethane, ethylene, propane, propylene, n-butane, nitrogen and di- and tri- ethyl amines. At large extents of the reaction radical-olefin reactions occur extensively and produce a complex distribution of products. Compounds containing carbon, hydrogen and nitrogen are also formed at higher percentage decompositions. The orders of formation of major products with respect to azoethane, as well as activation energies, have been determined. The activation energy for the initiation reaction C₂H₅N₂C₂H₅ → 2 Ċ₂H₅ + N₂ has been found to be 47.2 ± 1.0 kcal per mole. The effects of additives such as cis-butene-2, butene-1 and carbon dioxide on the initial rates of formation of various products have been investigated. All the additives have a common effect of lowering the initial rate of formation of ethane. Increase in surface: volume ratio has the effect of lowering the time rate of pressure change by 10 to 20% and this has been attributed to the increased surface recombination of radicals. The rate of formation of ethane is also decreased in the packed reaction vessel. This study has pointed out that there is a short chain in the thermal decomposition of azoethane due to the formation and subsequent decomposition of CH₃ĊH-N=N-CH₂CH₃ radical. A mechanism has been proposed for the pyrolysis of azoethane which accounts qualitatively for the nature and distribution of products. The flash photolysis of azoethane has also been investigated at room temperature in pyrex and quartz reaction vessels. Thermally equilibrated radicals are produced in the pyrex cell with outer pyrex jacket. Addition of large amounts of carbon dioxide in the flash photolysis of azoethane decreases the product yields indicating the collisional deactivation of excited azoethane molecules. The ratio of ethyl radicals disproportionation to combination has been found to be 0.12 ± 0.02. Reactions have been postulated to account for the products of flash photolysis of azoethane. / Science, Faculty of / Chemistry, Department of / Graduate

The thermal and photolytic decomposition of cis and trans_-3,5-dimethyl-3-acetyl-Δ¹-pyrazoline have been found to give six products. They have been separated and identified as 2,3,5-trimethyl-Δ²-dihydrofuran, cis and trans-1,2-dimethyl-1- acetyleyclopropane, cis and trans-3-methyl-3-hexen-2-one and 3-methyl-4-hexen-2-one. The formation of cyclopropanes by photolysis showed some degree of stereospecifIcity. Both pyrolysis and photolysis yielded olefins with high degree of stereospecificity. 2,3,5-TrImethyl-Δ²-dihydrofuran was a major product from the decomposition of cis-3,5-dimethyl-3-acetyl-Δ¹ -pyrazoline only. Pyrolysis gave a higher ratio of olefins to cyclopropanes than photolysis. These decomposition reactions gave results analogous to those of cis and trans-3,5-dimethyl-3-carbomethoxy-Δ¹-pyrazoline. The product compositions from both the pyrolysis and photolysis of cis and trans_-3,5-dimethyl-3-carbomethoxy-Δ¹-pyrazoline have been found to show a small and regular influence of the solvent and this has been related to the dielectric constant of the solvent. Pyrolysis and photolysis gave an olefin to cyclopropane ratio of 57:43 and 21:79, respectively, in formamide, and 7:93 and 5:95, respectively, in cyclohexane. A small kinetic solvent effect has been observed for the pyrolysis of 3,5-dimethyl-3-carboraethoxy-Δ¹-pyrazoline. The rate of pyrolysis as followed by the rate of nitrogen evolution has been found to decrease for the following series of solvents: dl-n-butyl ether, tetralin, nitrobenzene and form-amide. These rates were all within a factor of three. The absence of rate enhancement in a solvent of high dielectric constant has been used as an argument against an ionic Intermediate in these reactions. Liquid phase photolysis of trans-3,5-dimethyl-3-carbo- methoxy-Δ¹-pyrazolIne at various temperatures ranging from -55ᵒ to 58ᵒ did not show appreciable change in the product compositions attributable to the influence of temperature. The solvent temperature therefore does not affect the amount of quenching of any "hot" intermediate. Photolysis and pyrolysis of cis and trans-3,5-dimethy1-3-carbomethoxy-Δ¹ -pyrazoline under identical conditions did not give the same product composition. This suggested the two reactions do not have a common Intermediate. No isomerization between the cis and trans-3,5-dimethyl-3-carbomethoxy-Δ¹-pyrazolines has been observed as shown by the partial pyrolysis and photolysis of the trans-pyrazoline. These results are discussed In view of current mechanistlc proposals for the pyrolysis and photolysis of Δ¹-pyrazolines. / Science, Faculty of / Chemistry, Department of / Graduate