Thesis (M.S.)--University of Michigan, 1961.

The tropospheric reactions of toluene, acting as a model VOC, are investigated using an electron bombardment-matrix isolation system coupled with Fourier transform infrared spectroscopy. Initial experiments to produce the hydroxyl radicals used to initiate the toluene reactions via electron bombardment of water-argon mixtures are performed. The effects of electron current, water concentration, and gas flow rate are investigated. A more efficient method of initiating the toluene reactions, by directly creating benzyl radicals through electron bombardment of toluene is then investigated, and the effects of toluene concentration and electron current on the production of the benzyl radicals is quantified. Benzyl radicals are successfully produced, and identified via FT-IR. The next step is the formation of benzylperoxy radicals, via electron bombardment of toluene-oxygen-argon gas mixtures. Experiments are performed using increasing concentrations of toluene and oxygen, in an attempt to observe the benzylperoxy radical. Two new absorptions are observed in the infrared spectra and are tentatively identified as due to the peroxy group on the benzylperoxy radical. Computational work is also performed to confirm that benzylperoxy radicals can in fact be produced from benzyl radicals and oxygen. The vibrational frequencies of the benzylperoxy radical are also calculated, and used to confirm the possibility that the new absorptions seen in the infrared spectra could in fact be due to benzylperoxy radicals. The overall results from this work demonstrate that it is likely to be possible to use electron bombardment-matrix isolation systems to investigate tropospheric reactions of volatile organics, and that further experiments could be enhanced by structural modifications to the system. / Thesis (Master, Chemistry) -- Queen's University, 2013-11-26 15:57:59.4

The gas-phase chemistry of butanal, propanal, and acetaldehyde has been investigated using electron bombardment matrix isolation techniques. Each aldehyde was diluted in excess argon gas and subjected to electron bombardment with 300eV electrons. The products of subsequent reaction processes were matrix isolated and analyzed by FTIR absorption spectroscopy. Ionized butanal produced a variety of decomposition products including propane, propene, propyne, ethene, ethyne, CCCO, ketene, formaldehyde, CO, CH2=CHCH2•, CH2CHO•, HCO• and methane. Products resulting from ionized propanal included the ethyl radical, ethane, ethene, ethyne, CO, CH2CHO•, HCO• and methane. In both cases the products are believed to be formed from C—C cleavages of the parent ion followed by hydrogen atom scavenging and/or hydrogen atom abstraction from proximally located species. Dehydrogenation products of propane and ethane are proposed to result from product secondary ionization, a process dependent on high electron currents. Surprisingly, in the case of butanal, the McLafferty Rearrangement, a dominant process in electron ionization mass spectrometry, was not observed to occur. Electron bombardment of acetaldehyde:Ar mixtures produced many decomposition products including methane, CO, HCO•, CH3CO•, CH2CHO•, CH3• and ketene. The isomerization product, vinyl alcohol, was also observed. As way of investigating the mechanisms of the above products, experiments were performed in which the acetaldehyde:Ar mole ratio was varied. Variations in the acetaldehyde:Ar mole ratio produced dramatic variations in the products formed, demonstrating a transition from unimolecular chemistry at low acetaldehyde mole ratios, to processes consistent with bimolecular processes at intermediate mole ratios. Variations in the total flow rate of gas resulted in nonsystematic changes in product yields but provided further evidence for unimolecular methane formation via the elimination of neutral CO. Finally, an investigation into the mechanism of vinyl alcohol using the acetaldehyde isotopomer, CD3CHO, in conjunction with computational methods provided further evidence that enol formation occurs as a result of a direct 1,3-H-transfer and not consecutive 1,2-H-transfers. / Thesis (Master, Chemistry) -- Queen's University, 2009-06-26 10:51:32.331