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

The products of vanadium metal atom reactions with propene and some propene isotopomers (propene-d6 and propene-3,3,3-d3) are investigated using FT-IR matrix isolation. The major product from the condensation of V atoms with propene at elevated mole ratios is found to be propane (C3H8), the production of which is seen to increase as concentration of propene increases. Additionally a matrix isolated product formed after metal atom insertion into the C-H bond of propene at low propene mole ratios is isolated and identified. The location of the insertion site is identified as one of the methyl hydrogen carbon bonds. The structure of the product is identified as an allyl vanadium hydride complex, through a FT-IR matrix isolation study of propene isotopomers. It is also shown that this primary product acts as an intermediate in the formation of propane. A full mechanism for the proposed formation of propane from sacrificial hydrogenation is proposed and compared with the reported mechanism for the similar reaction involving ethene. The mechanistic identification of the hydrogenation of propene is shown as a generalization of the previous reaction involving ethene. Photochemistry of reactants and intermediates trapped in the matrix are investigated. Irradiation of matrices with several different UV-visible wavelength ranges indicate that no further chemistry occurs after formation of the matrix and further irradiation has no effect on intermediates or reactants. Additionally the reactivity of water with vanadium and propene under low propene concentration conditions is also studied. Results from this study show that under all conditions studied no incorporation of water into the propene molecule is found. / Thesis (Master, Chemistry) -- Queen's University, 2009-08-10 11:15:55.312

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Thesis (Ph. D.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 104-113.

The research reported here deals with a study of the reaction of atomic oxygen in the first excited electronic state with hexafluoroacetone (HFA). Matrix Isolation (MI) Spectroscopy was used to elucidate the reaction.

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The literature relevant to the generation of volatile hydrides for analytical atomic spectroscopy has been reviewed, with particular reference to atomic absorption spectrometry (AAS). This reveals some conflicting information concerning the nature of various interference effects and strategies to overcome them. The use of flow injection (FI) procedures has been demonstrated by several research groups, to be beneficial. A review of the literature concerning the application of FI techniques to AAS shows that there is a sustained interest in the use of such a combination for analytical purposes. In particular, an interest in the on-line coupling of chemical pretreatment of samples is evident. Atomic absorption spectrometry has a limited working range and requires frequent calibration, consequently, there is a need for a rapid, precise on-line dilution procedure. The potential of FI systems with wide bore manifold tubing for on-line dilution was assessed and found to be limited by variations in dispersion coefficient arising from differences in specific gravities between the sample and carrier fluids. This could be overcome only by the use of unrealistically high flow rates. The use of FI procedures for the generation of volatile hydrides of selenium and arsenic was investigated. Optimization studies of system parameters, including the atomization step, were undertaken which demonstrated the benefits in applying FI in hydride generation atomic absorption spectrometry (HGAAS). Analytical methods were devised and evaluated for the determination of Se in copper metal and As in nickel alloy. These procedures involved the use of an on-line matrix removal step in which potentially interfering matrix elements were retained on a strong cation exchange resin (Dowex 50W). The manifold was designed so that the FI value acted as the interface between the matrix isolation stage and the vapour generation stage, a strategy which allowed independent optimization of each stage. Location of the ion exchange resin in the sample loop of a six-port rotary valve allowed the resin to be regenerated easily and rapidly, with a throughput capability of the order of 50 h⁻¹ and permit the proposed full automation of the whole analytical procedure. In the determination of As in nickel alloy a novel stopped-flow pre-reduction step was developed to permit AsIII quantification, therefore, achieve optimum sensitivity. The two systems permitted limits of detection for Se and As of 2.1 and 3.9 ng ml⁻¹ respectively. Direct comparisons were made with existing matrix isolation systems to emphasise the benefits of system design.

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No description available.