In this research, silicon carbide (SiC) has been confirmed to be catalytically active for the formation of polycyclic aromatic hydrocarbons (PAHs) from acetylene (C2H2). Aromatization reactions of C2H2wasexamined by gas-phase experiments in vacuo using α-SiC and β-SiC respectively, characterized with in situ time-of-flight mass spectrometry (TOF-MS)in which abundant information of intermediates was record-ed. The significance of this catalytic reaction lies in the fact that the reagents –acety-lene, the catalyst –SiC, and the PAH products are all coexisting in interstellar environment and this reaction indicates one of the possible channels for the formation of PAHs. Reaction products obtained were further confirmed by gas chromatography mass spectrometry (GCMS). The SiC catalysts were analyzed before and after the re-action using high-resolution transmission electron microscopy (HRTEM), X-ray dif-fraction(XRD) and derivative thermogravimetry (DTG).Results of experiments indicate that SiC catalyzes aromatization of C2H2starting from 400℃with activities dependent on temperature and notable difference has been observed between α and β crystal forms. For a long-time reaction at a particular temperature, the changes in productions of the four major PAH products, i.e. naphthalene, anthracene, phenan-threne and pyrene showed the transition from small PAHs to larger PAHs. Carbon deposition on the catalyst depends on temperature, which explains the deactivation of SiC catalyst at high temperatures. Based on experimental results, two new mechanisms for activation of acetylene on SiC that are closely connected with SiC surface dangling bonds have been proposed: 1)breakage of C-H bond by interaction of H with dangling bonds; 2) radical addition of hydrocarbon to form a surface ring structure which is then desorbed from the surface. Subsequent ring-growth process is suggested to follow the H abstraction / C2H2addition (HACA) mechanism. The activation effect of SiC dangling bonds was then extended to aromatization of propylene (C3H6) and propane (C3H8) starting from 650℃ and 750 ℃respectively in similar conditions. Comparison among reactions of C2H2, C3H6and C3H8provides further evidence for the proposed mechanism. / published_or_final_version / Chemistry / Master / Master of Philosophy

The structures of the six new compounds and the TNF molecular complex were substantiated by satisfactory elemental analyser. The infrared and ultraviolet absorption spectra of the six new compounds were recorded. / Master of Science

Ravidomycin is a yellow antitumor antibiotic produced by Streptomyces ravidus. Ravidomycin shows strong antitumor activity against P388 lymphocytic leukemia, the colon 38 tumor, and the CD8Fl mammary tumor. It is also very active against Gram positive bacteria. Biosynthetic studies have shown that the aglycone unit comes from the folding of a polyketide chain with the vinyl unit arising from propionic acid. Since this vinyl functionality is believed to playa role in the antitumor activity of the antibiotic, it is of interest to elucidate the stereochemical selectivity in its formation from propionic acid. The synthesis of (R) and (S)-L2-²H₁ j propionate, incorporation of the labelled material, and chemical analysis of the resulting antibiotic was be used to determine the stereochemistry of formation of the vinyl side chain. It was found that propionate was incorporated with ravidomycin with stereospecific loss of the 2-(pro-R)-proton. / Master of Science

The synthesis of a novel, cage spiro-oxetane was carried out. Pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane-8- one (PCUD-8-one) undergoes one-carbon homologation to a mixture of endo- and exo- PCUD-carboxaldehydes which then are converted into 8,8-bis(hydroxymethyl)PCUD. The monotosylate obtained via reaction of 8,8- bis(hydroxymethyl)PCUD with tosyl chloride(1 equivalent) reacts with sodium hydride to afford the corresponding spiro-oxetane via intramolecular Williamson reaction. Six new substituted heptacyclo[6.6.0.0^2,6.0^3,13.0^4,11. 0^5,9.0^10,14]tetradecanes (HCTD) were synthesized. These compounds will be used as substrates in a photoelectron spectroscopic study. The ring-expansion reaction of PCUD-8-one with ethyl diazoacetate in the presence of BF_3:OEt_2 was performed. The major product was converted into an alcohol, and the structure of the 3,5-dinitrobenzoate of this alcohol was elucidated by single crystal x-ray structural analysis.

A novel route for the synthesis of the polycyclic aromatic hydrocarbon peropyrene (Pp) is reported along with the efforts to synthesize derivatives of Pp, 2,2′- and 5,5′-linked tetracene dimers as candidates for study as singlet fission materials in photovoltaic devices. Peropyrene was synthesized by the McMurry coupling conditions from phenalenone and low-valent titanium species. The crystal structure of Pp is formed by π-stacked molecular pairs in a herringbone arrangement. The direct functionalization of Pp was studied, and several indirect methods for the functionalization of Pp via phenalenone derivatives are reported. Nucleophilicly dependent, regioselective Michael addition pathways for phenalenone are described. Phenalenone forms a nucleophilic complex with bispinacolatodiboron and yields chiral 3,3′-linked phenalenone dimers and a bicyclo[3.2.1]octane derivative product of an unusual 3,4 addition. An active complex product of phenalenone and (dimethylphenylsilyl)boronic acid pinacolic ester forms Pp directly. The synthesis of 2,2′- and 5,5′-linked tetracene dimers led to the study of the reduction of 1-arylprop-2-yn-1-ol derivatives via TFA-catalyzed hydride transfer from triethylsilane. Substrates with terminal and TMS-protected alkynes showed silane exchange upon reduction. A TMS-protected, terminal alkyne became triethylsilyl-protected by about 50% whereas only triethylsilyl-protected, terminal alkyne was observed from the reduction of an unprotected, terminal alkyne. A new conformational polymorph of 1,4-bis(triisopropylsilyl)buta-1,3-diyne is reported. Five other rotamers are studied by density functional theory as possible candidates of conformational polymorphism by the analysis of torsional strain energies. The relative stabilities and interconversion equilibria of the seven conformational isomers are studied.

Poly(arylene ether phosphine oxide)s (PEPO) are a recently identified subset of an important macromolecular series which includes industrially important high performance thermoplastics, such as the polysulfones, e.g. UDEL@ and polyether ketones, e.g. PEEK@, PEKK@, etc. The PEPO materials show an elevated glass transition temperature, high thermal and oxidative stability, improved solubility, and increased flame resistance. It has been demonstrated that a variety of metal salts including metals such as iron, zinc, cobalt, and copper, can be complexed at a molecular level with the phosphoryl group in films of these polymers producing novel transparent metal/polymer "composites". A procedure for obtaining homogeneous films from solutions of the metal halide complexed polymers has been developed. FTIR experiments as well as Tl phosphorus (31 P) NMR measurements were conducted to demonstrate the existance of metal complexation in the solid state. The effect of the chemical composition of the chain, type of metal salt, molar concentration of the metal salt, and heating cycle were investigated and found to influence properties of the films such as solubility, glass transition temperature, thermal stability, and storage mexiulus. Additionally, linear poly(arylene ether phosphine oxide)s were reduced to different extents to the corresponding phosphine containing polymers. Properties such as intrinsic One of these phosphine polymers was subsequently used in the generation of a rhodium catalyst for the hydroformylation of octene-l. The utilization of polymer-supported catalysts has important advantages such as catalyst recovery and the ease of separation of the product. The catalyst activity of the polymeric rhodium complex was studied as a function of reaction time as well as ligand to rhodium ratio. For a phosphorus/rhodium ratio of two these heterogeneous catalysts suffer in tenns of reaction rate in relation to their homogeneous counterparts. However, at phosphorus/rhodium ratios of approximately eight the reaction is almost quantitative after three hours, and the selectivity is greatly improved over that of monomeric homogeneous catalysts for the same P/Rh ratio. / Master of Science