Aerosols have significant impacts on earth's climate and hydrological cycle. They can directly reflect the amount of incoming solar radiation into space; by acting as cloud condensation nuclei (CCN), they can indirectly impact climate by affecting cloud albedo. Our current assessment of the interactions of aerosols and clouds is uncertain and parameters used to estimate cloud droplet formation in global climate models are not well constrained. Organic aerosols attribute much of the uncertainty in these estimates and are known to affect the ability of aerosol to form cloud droplets (CCN Activity) by i) providing solute, thus reducing the equilibrium water vapor pressure of the droplet and ii) acting as surfactants capable of depressing surface tension, and potentially, growth kinetics. My thesis dissertation investigates various organic aerosol species (e.g., marine, urban, biomass burning, Humic-like Substances). An emphasis is placed on the water soluble components and secondary organic aerosols (SOA). In addition the sampled organic aerosols are acquired via different media; directly from in-situ ambient studies (TEXAQS 2006) environmental chamber experiments, regenerated from filters, and cloud water samples. Novel experimental methods and analyses to determine surface tension, molar volumes, and droplet growth rates are presented from nominal volumes of sample. These key parameters for cloud droplet formation incorporated into climate models will constrain aerosol-cloud interactions and provide a more accurate assessment for climate prediction.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemistry, 1978 / Vita. / Includes bibliographical references. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Chemistry

The work presented in this thesis has broadly established a few findings about the structure¬hyperpolarizability relation in molecular compounds: First, by measuring βHRS of an organic keto-enol tautomer, benzoylacetanilide in a binary solvent, I have shown that the first hyperpolarizability can be manipulated favourably by changing the composition of the solvent or by altering the pH of the solution. BA which exists in the pure keto form in water and as a keto-enol tautomer in ethanol, co-exists in equilibrium with the keto and enol forms at pH 11 in aqueous solution. The β value of the anion form is 709 x 10¬30 esu , whereas that of the enol is 232 x 10-30 esu and of the keto is 88 x 10-30 esu. There is an enhancement of β by ~ 8 times for the anion and ~3 times for the enol compared to the keto form. This opens up the possibility of finding large nonlinearities in organic molecules by simply ionizing it. Second, in organometallic complexes of divalent Ru, the first hyperpolarizability could be manipulated by altering the valence state of the metal center by oxidation or reduction or by introducing highly polarisable halogen atoms as substitutions in ligands attached to the metal center. The enhancement of first hyperpolarizability was observed in mononuclear [RuII(acac)2(CH3CN)2] complex by 1.7 times when the metal center was oxidized from RuII to RuIII. As it is already known that the complexes like [(acac)2Ru-bptz-Ru(acac)2] produce stable mixed valent compound, the enhancement of β by ~1.6 times is appearing because of that species only. Exploring Large Nonlinearity in Tautomers In this thesis I have taken a linear ketone for studying the effect of structure on β via the enol and anion formation mediated by solvent and pH of the medium. In the present study the proton transfer in BA took place in the ground state of the ketone and the enol or anion are produced in the ground states. The proton transfer reaction (tautomerism) can also happen in the excited state as well in some molecules where there is a substantial barrier to the proton transfer reaction in the ground state. In such systems, once the ketone is excited using ultraviolet light the barrier to proton transfer in the medium is overcome and a proton transfer in the excited state takes place and the enol is produced. Since such a system will be at higher energy, it will be interesting to do a two-laser experiment where the excited state hyperpolarizability is measured in a time resolved manner and the β value is determined in the excited state. Building Molecular Nonlinearity in Step-by-Step Electron Transfer In this thesis, I have dealt with a binuclear complex of Ru(II) which in one-step electrochemical oxidation produced a mixed valence compound which had substantially higher β value compared to the unoxidized complex. In this way it is possible to build a multicentered complex and see if sequential one-electron transfer and subsequent oxidation/reduction of the metal centers produce a mixed-valent metal compound with large molecular nonlinearity. The indication from the present study is that such a scheme should double the β value in each one-electron transfer step. Also the linker group/moiety between the successive metal centers will play an important role in dictating the efficiency of electron transfer. If the metal d-electrons in a multinuclear complex are linked through a π-conjugation, one would expect manifold enhancement of β. Such metal arrays can also be designed in 2 or 3 dimensions. The dimensionality of the multinuclear metal complexes can easily be changed by supramolecular design and synthesis strategy. Such metal networks may or may not generate large β molecules since electronic polarization in such systems may not be superimposable in a coherent fashion and may not add in a positive sense. All these remain to be tested and explored in the future.

Call number: LD2668 .T4 1984 K55 / Master of Science

The 2-aryl-2,3-dihydroquinolin-4(1H)-ones were prepared via acid-catalyzed cyclization of the corresponding 2-aminochalcones, which were in turn, prepared by base-promoted Claisen-Schmidt aldol condensation of 2-aminoacetophenone and benzaldehyde derivatives. The 2-aryl-6,8-dibromo-2,3-dihydroquinolin-4(1H)-ones were prepared by reacting 2-aryl-2,3-dihydroquinolin-4(1H)-ones with N-bromosuccinimide (NBS) in carbon tetrachloride-chloroform mixture at room temperature. The 2-aryl-6,8-dibromo-2,3-dihydroquinolin-4(1H)-ones were subjected to palladium-catalyzed Suzuki-Miyaura cross-coupling reaction with arylboronic acid using dichlorobis(triphenylphosphine)palladium(II)-tricycohexylphosphine as catalyst mixture and potassium carbonate as a base in dioxane-water under reflux to afford the corresponding novel 2,6,8-triaryl-2,3-dihydroquinolin-4(1H)-ones in a single-pot operation. The latter were subjected to thallium(III) p-tolylsulfonate in dimethoxyethane under reflux to yield the 2,6,8-triarylquinolin-4(1H)-ones. The 2,6,8-triaryl-2,3-dihydroquinolin-4(1H)-ones were treated with molecular iodine in refluxing methanol to afford the corresponding 2,6,8-triaryl-4-methoxyquinolines. All the new compounds were characterized using a combination of 1H NMR & 13C NMR spectroscopy, IR and mass spectroscopic techniques. / Chemistry / M.Sc. (Chemistry)

Thesis submitted in fulfilment of the requirements for the Degree of Master of Technology: Organic Chemistry, Durban University of Technology, 2011. / Malaria, the most prevalent parasitic disease, is considered a neglected disease owing to insufficient research and development in synthesis and therapy worldwide. Therapy failures are frequent and are due to a variety of factors such as the intrinsic characteristics of the disease, conditions of transmission, and the difficult control of spreading through tropical areas. Primary factors are the complexity of the parasite life cycle and the development of drug resistance. Another critical factor is the increasing number of immune-compromised patients that suffer from malaria and human immunodeficiency virus (HIV) co-infections. Most of the drugs currently available to treat malaria are quinoline derivatives modelled on the quinine molecule, found in the bark of Cinchona trees. Over the last 50 years the use of quinine has declined owing to the development of synthetic 4-aminoquinolines such as chloroquine. However, the malaria parasite is rapidly becoming resistant to the drugs currently available. Recently bisquinoline compounds were found more potent than chloroquine against both chloroquine-sensitive and resistant strains of malaria; this improved efficacy and prompted an increased interest in the design of these anti-malarial drugs. Although several synthetic methods are available to synthesise bisquinolines, we report the synthesis of bisquinolines from simple, readily available and cost- effective starting compounds. The synthesis was accomplished in four reaction steps using the Claisen condensation, Vilsmeir-Haack reaction, formation of a Schiff base and thermal cyclization, sequentially. We used a conventional energy source and microwave irradiation for the synthesis, wherever possible, of 2, 4-dichloro-3, 4'-biquinoline and 2, 4-dichloro-7'-methoxy-3, 4'-biquinoline. In the first step, 3-acyl-2, 4-dihydroxyquinoline is synthesised from an equimolar mixture of methyl-2-aminobenzoate and ethyl acetoacetate by microwave irradiation for 3 minutes; the yield is 90 % whereas by 6 hours refluxing the yield is 75 %. This is followed by the synthesis of 3-chloro-3-(2,4-dichloroquinolin-3yl) acrylaldehyde, by combining DMF and POCl3 at 00C to form the electrophile which reacts with 3-acyl-2,4-dihydroxyquinoline under microwave irradiation for 5 minutes; the yield is 65 % whereas by 6 hours refluxing the yield is 50 %. In the next step, several protocols to prepare a Schiff base 3-chloro-3-(2, 4-dichloroquinolin-3-yl) allylidene aniline are investigated with the best yield of 75% obtained by microwave irradiation for 5 minutes. Subsequently three aniline derivatives viz, 4-methoxyaniline, 4-chloroaniline and 4-methylaniline, are used as substrate to prepare 3-chloro-3-(2,4-dichloroquinolin-3-yl) allylidene-4-methoxyaniline, 3-chloro-3-(2 ,4-dichloroquinolin-3-yl) allylidene-4-methylaniline and 3-chloro-3-(2, 4-dichloroquinolin-3-yl) allylidene-4-chloro aniline at 68, 78 and 64 % yield, respectively. In the final step, 2, 4-dichloro-3, 4'-biquinoline is prepared; several methods were investigated, however, the best yield is 24 % which is obtained under alkaline conditions in the presence of K2CO3 and DMF by microwave irradiation for 10 minutes. The 2, 4-dichloro-7'-methoxy-3, 4'-biquinoline derivative is also prepared in 18 % yield under the same alkaline conditions. The outline of the total synthesis of bisquinoline is presented graphically below. / National Research Fund.

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The primary objective of the work was to investigate the negative thermal expansion of organic materials and to determine the mechanisms governing this phenomenon by using the principles of crystal engineering. To this end, the following three compounds were studied in detail: • 4,4'-Diiodobiphenyl • 4-Iodobenzoic acid • Methyl Paraben The rationale behind this work was to determine the mechanisms responsible for the observed negative thermal expansion and to uncover the structural factors that induce negative thermal expansion. Single-crystal X-ray diffraction was employed as the primary analytical tool, owing to the unique information it can provide regarding intermolecular interactions in the solid state. A total of twenty organic compounds were analysed, of which three exhibited negative thermal expansion. Each compound employs a specific mechanism for negative thermal expansion, two of which are closely related and the third distinct. / AFRIKAANSE OPSOMMING: Die hoof doel van hierdie studie was om ondersoek in te stel in die verskynsel van ‘negative thermal expansion’ in organiese materiale en gevolglik die meganisme vas te stel deur die beginsels van kristalmanipulsie (‘crystal engineering’) te gebruik. Gevolglik was drie organise stowwe ondersoek: • 4,4'-Diiodobiphenyl /4,4'-Diiodobifeniel • 4-Iodobenzoic acid /4-Iodobensoësuur • Methyl Paraben Die redenasie hieragter is om die meganisme verantwoordelik vir die ‘negative thermal expansion’ vas te stel en die verskillende faktore wat bydra tot dit te bevestig. Enkel-kristal diffraksie word benut as die primêre analitiese tegniek as gevolg van die unieke inligting wat verkry kan word met betrekking tot die intermolekulêre interaksies. 'n Totaal van twintig stowwe is geanaliseer waarvan drie die spesifieke termisie eienskap besit. Elk van die drie stowwe het ‘n ander meganisme te vore laat kom waarvan twee baie ooreenstem en die derde verskil.

Thesis (PhD)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The aim of this thesis is to use tin-mediated reactions to differentiate between the four zones in the myo-inositol ring that consists of five contiguous equatorial and one axial hydroxyl groups. It is expected to give chemical control over the hexitol that can be put to good use in commercializing the phosphate derivatives of myo-inositol that are of pharmaceutical value. As point of departure 1,2-0-cyclohexylidene-myo-inositol (II.I) was synthesized that contains a tetrol with one end adjacent to an axial acetal oxygen and the other end adjacent to an equatorial acetal oxygen. The selective protection of position 3 (Dmyo- inositol) was investigated. Various problems lead to the selective silylation of the acetal at position 5. The silane forms the basis of the subsequent investigation because the cyclitol is now divided into an isolated mono-ol and a trans-diol allowing for easier differentiation between the various hydroxyl groups. It was indeed possible to differentiate the trans-diol from the mono-ol by using carbonylation and allylidenation. Ring closure occurs in both cases. In the carbonylation case the resultant five-membered ring is less stable than that of the allylidene due to the Sp² hybridized carbon atom of the carbonate compared to theSp³ hybridized carbon of the allylidene group. Preliminary work was done on the racerrue 1,2-0-cyclohexylidene-myo-inositol (II.VII) in order to use the acquired technology on the chiral camphor analog. The transition from racemic to chiral proved problematic since the camphor acetal is difficult to prepare and its selective silylation differs from that observed for cyc1ohexylidene. The camphor acetal itself was silylated in the process. (S)-( -)-Camphanic chloride was therefore used as chiral auxiliary in the protection of position six of the racemic 1,2,3,4,5-protected myo-inositol, thus solving the problems encountered in the protection of position six whilst combining the protection and chiral induction steps. The resultant diastereomers could both be used in the synthesis of IP₃ and IP₄ respectively, eliminating the disposal of half ofthe product. This project lead to the development of useful chiral differentially protected myoinositol derivatives, which could be useful in synthesis of various other myo-inositol derivatives. Besides the synthesis of useful chiral differentially protected myo-inositol derivatives, this investigation developed new applications in the tin-mediated derivatization of sugars. The following compounds were synthesized during this investigation. Bold numbers indicates novel compounds. / AFRIKAANSE OPSOMMING: Die doel van hierdie proefskrif is om met behulp van tin-bemiddelde reaksies onderskeid te maak tussen die vier sones in die mia-inositolring, wat bestaan uit vyf aaneenlopende ekwatoriale hidroksigroepe en een aksiale hidroksigroep. Die verwagting was om vinnig, effektiewe chemiese beheer oor die genoemde heksitol te verkry om sodoende chemies en kommersiëel munt te slaan uit die farmaseutiese werking van die fosfaatafgeleides van mia-inositol. As eerste uitgangspunt is 1,2-0-sikloheksilideen-mia-inositol (II.I) berei, wat lei tot die vorming van 'n tetrol waarvan die een punt naasliggend aan 'n aksiale asetaalsuurstofatoom en die ander punt naasliggend aan 'n ekwatoriale asetaalsuurstof is. As voortsetting is die selektiewe beskerming van posisie 3 (D-mia-inositol) ondersoek. Velerlei probleme lei tot die selektiewe sililering van die asetaal by posisie 5 (II.VII). Die silieleter vorm die basis van al die daaropvolgende ondersoeke omdat dit die siklitol in 'n trans-diol en 'n geïsoleerde mono-ol verdeel en die verskillende hidroksigroepe daarvan makliker van mekaar onderskei kan word. Dit is inderdaad moontlik om die trans-diol van die mono-ol te onderskei deur karbonilering of allilidenering. In albei gevalle vind ringannulering plaas. In die geval van die karbonilering is die gevormde vyflidring minder stabiel as wat die geval is vir die allilideengroep. Die rede hiervoor is dat die karbonaatkoolstofatoom Sp²- gehibridiseer is terwyl die ooreenstemmende koolstofatoom van die allilideen Sp³- gehibridiseer is. Ontwikkelingswerk is op die rasemiese 1,2-0-sikloheksilideen-mia-inositol (II.VII) gedoen ten einde dit op die chirale kamferasetaalanaloog toe te pas. Die oorgang van rasemies na chiraal is egter problematies aangesien die kamferasetaal moeiliker vorm en selfs as dit vorm toon die reaksies, soos byvoorbeeld die sililering, ander selektiwiteit as wat die geval is vir die rasemiese mengsel. Sililering van die kamferasetaallei tot sililering van die kamfer self. (S)-(-)-kamfanoïelchloried is gevolglik as chirale hulpreagens gebruik om posisie 6 van die rasemiese 1,2,3,4,5-beskermde-mia-inositol te beskerm. Hierdie benadering los die problematiek rondom die beskerming van posisie 6 sowel as die induksie van chiraliteit op. Die twee diastereomere wat op hierdie wyse vorm, kan albei in die sintese van onderskeidelik IP₃ en IP₄ gebruik word, wat die verlies aan helfte van die produk verhoed. Behalwe die daarstelling van bruikbare chirale differensiëel-beskermde mioinositolafgeleides wat gebruik kan word om 'n verskeidenheid chirale mioinositolafgeleides te berei, het hierdie ondersoek nuwe toepassings in tin-bemiddelde derivatisering van suikers daargestel. Die volgende verbindings is gedurende die verloop van hierdie ondersoek gesintetiseer, waar verbindings vir die eerste keer gesintetiseer is word dit aangedui deur die verbinding se nommer vet (bold) te druk.

Digitized from microfiche to pdf. / Please refer to full text.

Digitized from microfiche to pdf format. / Thesis (PhD (Chemistry))--University of Stellenbosch, 1977. / Please refer to full text.