Aerosol particles have profound impacts on human health, atmospheric radiation, and cloud microphysics and these impacts are strongly dependent on particle sizes. However, formation and growth of atmospheric particles are currently not well understood. In this work, laboratory and theoretical studies have been performed to investigate the formation and growth of atmospheric particles. The first two parts of the dissertation are a laboratory investigation of new particle formation and growth, and a theoretical study of atmospheric molecular complexes and clusters. The nucleation rate was considerably enhanced in the presence of cis-pinonic acid and ammonia. The composition of the critical cluster was estimated from the dependence of the nucleation rate on the precursor concentration and the time evolution of the clusters was then simulated using molecular dynamic simulations. Results from quantum chemical calculations and quantum theory of atoms in molecules (QTAIM) reveal that formation of strong hydrogen bonding between an organic acid and sulfuric acid is likely responsible for a reduction of the nucleation barrier by modifying the hydrophobic properties of the organic acid and allowing further addition of hydrophilic species (e.g., H2SO4, H2O, and possibly NH3) to the hydrophilic side of the clusters. This promotes growth of the nascent cluster to overcome the nucleation barrier and thus enhances the nucleation in the atmosphere. The last part of this dissertation is the laboratory investigation of heterogeneous interactions of atmospheric carbonyls with sulfuric acid. Direct measurement has been performed to investigate the heterogeneous uptake of atmospheric carbonyls on sulfuric acid. Important parameters have been obtained from the time-dependent or timeindependent uptake profiles. The results indicated that the acid-catalyzed reactions of larger aldehydes (e.g. octanal and 2, 4-hexadienal) in sulfuric acid solution were attributed to aldol condensation in high acidity. However such reactions do not contribute much to secondary organic aerosol (SOA) formation due to the low acidity under tropospheric conditions. On the other hand, heterogeneous reactions of light dicarbonyl such as methylglyoxal likely contribute to SOA formation in slightly acidic media. The reactions of methylglyoxal in the atmospheric aerosol-phase involve hydration and subsequent polymerization, which are dependent on the hygroscopicity, rather than the acidity of the aerosols.

Thesis (M.S.)--University of Missouri, School of Mines and Metallurgy, 1927. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed February 23, 2010) Includes bibliographical references (p. 34).

The chemical industry of today is under increased pressure to develop novel green materials, bio-fuels as well as sustainable chemicals for the chemical industry. Indeed, the endeavour is to move towards more eco-friendly cost efficient production processes and technologies and chemical transformation of renewables has a central role considering the future sustainable supply of chemicals and energy needed for societies. In the Nordic countries, the importance of pulping and paper industry has been particularly pronounced and the declining European demand on these products as a result of our digitalizing world has forced the industry to look at alternative sources of revenue and profitability. In this thesis, the production of levulinic and formic acid from biomass and macromolecules has been studied. Further, the optimum reaction conditions as well as the influence of the catalyst and biomass type were also discussed. Nordic sulphite and sulphate (Kraft) cellulose originating from two Nordic pulp mills were used as raw materials in the catalytic synthesis of green platform chemicals, levulinic and formic acids, respectively. The catalyst of choice used in this study was a macro-porous, cationic ion-exchange resin, Amberlyst 70, for which the optimal reaction conditions leading to best yields were determined. Cellulose from Nordic pulp mills were used as raw materials in the catalytic one-pot synthesis of ‘green’ levulinic and formic acid. The kinetic experiments were performed in a temperature range of 150–200 °C and an initial substrate concentration regime ranging from 0.7 to 6.0 wt %. It was concluded that the most important parameters in the one-pot hydrolysis of biomass were the reaction temperature, initial reactant concentration, acid type as well as the raw material applied. The reaction route includes dehydration of glucose to hydroxymethylfurfural as well as its further rehydration to formic and levulinic acids. The theoretical maximum yield can hardly be obtained due to formation of humins. For this system, maximum yields of 59 mol % and 68 mol % were obtained for formic and levulinic acid, respectively. The maximum yields were separately obtained in a straight-forward conversion system only containing cellulose, water and the heterogeneous catalyst. These yields were achieved at a reaction temperature of 180 °C and an initial cellulose intake of 0.7 wt % and belong to the upper range for solid catalysts so far presented in the literature. The reaction network of the various chemical species involved was investigated and a simple mechanistic approach involving first order reaction kinetics was developed. The concept introduces a one-pot procedure providing a feasible route to green platform chemicals obtained via conversion of coniferous soft wood pulp to levulinic and formic acids, respectively. The model was able to describe the behaviour of the system in a satisfactory manner (degree of explanation 97.8 %). Since the solid catalyst proved to exhibit good mechanical strength under the experimental conditions applied here and a one-pot procedure providing a route to green platform chemicals was developed. A simplified reaction network of the various chemical species involved was investigated and a mechanistic approach involving first order reaction kinetics was developed.

Sialic acids are prevalent in many organisms and facilitate a range of cellular processes in both bacteria and mammals. Whilst a variety of sialic acids are present in nature, N-Acetylneuraminic acid (NANA) is the most common and plays a key role in the pathogenesis of a select number of neuroinvasive bacteria such as Neisseria meningitidis. These pathogens coat themselves with polysialic acids, mimicking the exterior surface of mammalian cells and consequentially concealing the bacteria from the host’s immune system. NANA is synthesised in prokaryotes via a condensation reaction between phosphoenolpyruvate and N-acetylmannosamine. This reaction is catalysed by the domain swapped, homodimeric enzyme, N-acetylneuraminic acid synthase (NANAS). Each NANAS monomer is comprised of two distinct domains; a catalytic domain linked to an antifreeze protein-like (AFPL) domain. This thesis outlines research into the role of the AFPL domain using a range of structural and kinetic analyses to compare variant enzymes to the natural, NmeNANAS enzyme. An investigation was also made into the evolutionary relationships between NANAS and other bacterial sialic acid synthases such as Legionaminic acid synthase and Pseudaminic acid synthase.

Selenenic acids and other organoselenium compounds are important both in organic and biochemistry. In organic chemistry, syn-elemination of selenoxides is used to prepare alkenes, giving a selenenic acid by-product. In biochemistry, selenocysteine is catalytically active in a variety of selenoenzymes, which have antioxidant properties, and is oxidized to a selenenic acid intermediate. For example, glutathione peroxidase (GPx) plays a role in fighting oxidative damage by catalyzing the reduction of hydroperoxides. Previous studies have shown that the lighter chalcogen analogue of selenenic acid, sulfenic acid, is a powerful antioxidant and that the known antioxidant activity of garlic is attributable to the 2-propenesulfenic acid derived from the compound allicin. This has prompted questions concerning the role of selenenic acid in the antioxidant activity of organoselenium compounds. In order to study the physiochemical properties of selenenic acids –a functional group about which little is known—and to evaluate their potential as antioxidants, a persistent selenenic acid is needed. Herein, the model compound, 9-triptyceneselenenic acid, is prepared by a previously reported procedure and a new pathway is designed, such that its properties and reactivity can be studied. The oxidation of thiols is important in cell signalling, leading to the disulfide bonds implicated in post-translational modification, among other biological roles. While this reaction is presumed to occur through the reaction of thiol with an oxidant that forms sulfenic acid, and from a subsequent reaction of sulfenic acid with another thiol, sulfenic acids are so reactive that they are not usually seen as intermediates. Given the stability of the 9-triptycenesulfenic acid previously synthesized, preliminary kinetic study of the oxidation of 9-triptycenethiol to its corresponding sulfenic acid is made possible.

Mud acid, which is composed of HCl and HF, is commonly used to remove the formation damage in sandstone reservoirs. However, many problems are associated with HCl, especially at high temperatures. Formic-HF acids have served as an alternative of mud acid for a long period. Several factors may influence the outcome of an acidizing job in sandstone formations. In this research, effects of mineralogy, temperature, and HF concentration were studied. Various clay minerals (kaolinite, chlorite, and illite) were examined to react with formic-HF acid mixtures which contain different concentrations of HF. Coreflood experiments on sandstone cores featured by different mineralogy with dimensions of 1.5 in. x 6 in. were also conducted at a flow rate of 5 cm^3/min. Formic or acetic acids were used in preflush stage to remove the carbonates. A series of formic-HF acid mixtures with different ratios and concentrations were tested, and temperature varied from 77 to 350 degrees F. Inductively coupled plasma (ICP), scanning electron microscopy (SEM) and 19F nuclear magnetic resonance (19F NMR) were employed to follow the reaction kinetics and products. Besides, acetic-HF acid system, which is another important alternative of mud acid, was also investigated to compare with formic-HF acids. The species and amounts of reaction products of different clay minerals in organic-HF acids depend on mineral type, acid composition and ratio, and this is further confirmed by coreflood experiments, in which sandstone cores with different mineral compositions give quite different responses to the same acid mixture. As preflush, formic acid becomes more effective in removing carbonate minerals in sandstone cores at higher temperatures. In main flush stage, more concentrated HF can react with more clay minerals, but can also cause higher risk of CaF2 precipitate. Both formic-HF and acetic-HF acids are much milder than mud acid. When reacting with clay minerals, there is no big difference in the behaviors of 13 wt% acetic-HF acids and 9 wt% formic-HF acids, as long as the HF concentrations are the same.

Thesis (MAppSc in Pharm) -- University of South Australia, 1993

Typescript (photocopy) / iv, 201 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.) Dept. of Organic Chemistry, University of Adelaide, 1981

Thesis (Ph.D.) Dept. of Organic Chemistry, University of Adelaide, 1981. / Typescript (photocopy).

Thesis (M.Med.Sc.)--University of Western Australia, 2004.