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

Technological developments have enabled mass spectrometry (MS) to evolve asone of the most versatile, sensitive and widely used analytical methods. Key areas ofresearch in biological MS include the development of analyte-selective MSmethodologies, along with the design of MS compatible separation technology. Analytesof interest range from small, biologically active molecules in disease progressionresearch, to macromolecules such as proteins, in proteomics investigations. Advances inthese areas are vital to maintaining the level of sophistication that has become thebenchmark for MS analyses.Mass spectrometry has found a permanent station in disease progression studies,particularly in biomarker discovery. This is especially true for Alzheimer's disease (AD),a condition marked by widespread lipid peroxidation (LPO) in the brain. The mainhypothesis of the first part of this dissertation is that LPO produces aldehydes that canpotentially be exploited as AD biomarkers. Design of novel LC-MS/MS methods forbrain aldehyde analysis is described. The methods were applied towards aldehydequantification in the hippocampus, superior and middle temporal gyrus and cerebellum ofsubjects with early AD (EAD), mild cognitive impairment (MCI) and age-matchedcontrols. Results obtained indicated elevation of neurotoxic aldehydes in MCI and EADbrain and suggested that LPO occurred early in AD. Understanding AD progression hasbecome important for developing diagnostic methods and treatments.Mass spectrometry is also the major analytical tool in proteomics, where gelelectrophoresis is dominant in pre-MS separations. The main hypothesis of the latter partof this dissertation is that exposure of microbe fermenters including Clostridiumthermocellum to an external stimulus, such as ethanol, can alter the membrane proteome.Design of novel doubled-SDS-PAGE (dSDS-PAGE) methods for membrane proteinanalysis is described, as these proteins are under-represented in standard 2D-PAGE. Thenewly developed Bicine-dSDS-PAGE offered superior separation over other methods andwas applied towards analysis of wild type and ethanol-adapted C. thermocellum cellmembranes. Significant differences in protein expression were observed. Anunderstanding of ethanol adaptation will promote the design of more ethanol-tolerantstrains. Such an outcome can have dramatic effects in the fuel industry as the trendtowards more efficient fuel development gathers momentum.

Intact strawberry fruit did not produce detectable t-2-H which is derived from -linolenic acid (18:3). However, in response to wounding by gentle bruising, strawberry fruit emitted t-2-H with the largest quantity produced within 10 min following injury. The level of total lipid 18:3 in the fruit increased two-fold in response to wounding whereas free 18:3 declined slightly (about 30%). At 10 min following wounding, fruit exhibited a 25% increase in 13-lipoxygenase (LOX) activity, which leads to the production of 13-hydroperoxyoctadecatrienoic acid (13-HPOT) from 18:3. The activity of hydroperoxide lyase (HPL), which catalyzes formation of cis-3-hexenal (c-3-H), the precursor of t-2-H, from 13-HPOT, increased two-fold at 10 min after wounding. Thus, within 15 min after wounding, free 18:3 substrate availability and the activity of two key enzymes, LOX and HPL, changed in a manner consistent with increased t-2-H biosynthesis. The site and mode of interaction of C6 aldehydes with Botrytis cinerea, a common pathogen of many plant species, was characterized using radiolabeled six carbon (C6) aldehydes, including c-3-H and t-2-H. An approximately 25% molar conversion of 18:3 to C6 aldehydes was obtained by enzymatic manipulation with LOX and HPL extracts. Following exposure of Botrytis cultures to radiolabeled aldehydes, radiolabeled aldehydes were recovered in protein fractions, but not in the lipid fraction. They were incorporated into conidia at a 20-fold higher level than mycelia (per mg fresh weight). About 95% of the radiolabeled aldehyde was recovered in proteins on the surface (wash protein) of the fungal tissue, while 5% was from protein in internal tissue (cell wall and membrane and cytosol). Supplementing radiolabeled aldehydes with nonradiolabled C6 aldehydes to increase the vapor phase concentration affected distribution of radiolabel in each protein fraction. The t-2-H at both 5.4 and 85.6 mol affected protein expression patterns, changing the intensity of expression in over one third of all proteins. Both up- and down-regulation of specific proteins were observed. Though five proteins of interest were analyzed, their identities were not determined. However, the data indicate a clear effect of t-2-H on protein expression in Botrytis cinerea.

The Knoevenagel reaction was applied to form a carbon-carbon double bond between the aldehydes (HMF, furfual) and an alpha di-carbonyl compound. The alpha di-carbonyl compound used was malonic acid, which can be bio-derived from glucose along fermentation routes. The effects of solvents (THF, water, ethanol, isopropanol, ethyl ether, toluene) and catalysts (e.g. homogeneous and heterogeneous amines, solid basic oxides) on the yields of alpha-beta unsaturated acids were investigated. It was found that the homogeneous amines worked well in THF solvent (90-100% conversion, 99% selectivity for furfural and HMF), while the poly(styrene) supported ethylenediamine gave a higher conversion and selectivity for HMF (65± 5%, 99% selectivity) over furfural (58 ± 7%, 99% selectivity). This trend was also present in competition reactions where both HMF and furfural were reacted in the same vessel. á-â Unsaturated mono-acids for both HMF and furfural were identified as minor side products. However, levulinic acid did not work as well under the conditions studied. Lastly, among the solvents studied, several caused precipitation of the Knoevenagel products.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2004. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Thesis (M.S.)--University of Michigan, 1982.

Thesis (M.S.)--University of Michigan, 1982.

Thesis (M.S.)--The University of North Carolina at Greensboro, 2009. / Directed by Gregory M. Raner; submitted to the Dept. of Chemistry and Biochemistry. Title from PDF t.p. (viewed May 17, 2010). Includes bibliographical references (p. 56-57).

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaf: [36] )