One of the main objectives of this Thesis was to explore the use of thiophenes to synthesize several more complex aromatic systems. Thus starting from 2,4-dimethyl 5- amino-3-methylthiophene-2,4-dicarboxylate 115, the synthesis of the first cis-thia[ 13]annulene, 4-bromo-cis-9b,9c-dimethyl-9b,9c-dihydrophenyleno[1,9-bc]thiophene 116a, as well as the trans-isomer, 116b have been achieved in 11 steps. Introduction of a bromo-substituent at an early stage, facilitated rearrangement of the thiacyclophanes 119a and 119b to permit easier isolation of the product annulenes. Both the cis-thia[ 13]annulene 116a and the trans-thia[ 13]annulene 116b were found to be diatropic on the basis of their 1H NMR chemical shifts. Using thiophene dioxide 150 and 152 as key intermediates to generate multifunctional azulenes, the novel azulene containing thiacyclophane 105 has been synthesized in 9 steps. Even though this was not able to be converted to the [18]annulene 100, discovery of a new route to thiacyclophanes from thiolacetates was achieved. This has been tested successfully on a variety of other examples, including the unusual bis thiophene containing cyclophanes 194 and 195, as well as the unsymmetrical 191 which was subsequently converted to the dihydropyrene 236a and 236b. During the course of this work, we discovered a new mild method to electrophilically brominate reactive aromatics using NBS in [special characters omitted] at room temperature. This reagent was investigated for several thiophenes, azulenes and dihydropyrenes. The products from the latter were successfully coupled using Ni(0) catalysis to generate 28% of the first unsymmetrically connected dimer of DMDHP, 249, as well as 33% of the symmetrical dimer 102. Unlike 102, the bi-annulenyl 249 has a significant barrier to rotation, which is estimated as 11.0 kcal/mole from [special characters omitted] measurement, compared to a PCMODEL calculated barrier of 12 kcal/mole. This is the first measurement of the barrier to rotation in a 1,2'-binaphthyl type system. Electrophilic substitution in DMDHP using the diazonium salts 277 and 283 was also studied, and several novel cross-coupling products have been synthesized and isolated, such as 278 from 279 and 280. As well the very unusual isomeric quinones, 7-(10b, 10c-dimethyl-7-oxo- 2,7,10b, 10c-tetrahydro-2-pyrenyliden)-10b, 10c-dimethyl-2,7-10b, 10c-tetrahydro-2- pyrenone 263 and 264 have been successfully prepared by reacting 102 with NBS or PDC. Compounds 263 and 264 have highly extended conjugated systems. / Graduate

The synthesis of trans-11b,11c-dimethyl-11b,11c-dihydro-7H-cyclopent [a] pyrene, 109, from trans-10b,10c-dimethyl-10b,10c-dihydropyrene, 32, was achieved in six steps in an overall yield of 29%. Deprotonation of 109 gave the first annuleno-fused cyclopentadienide, trans-11b,11c-dimethyl-11b,11c-dihydrocyclopent[a] pyrene, ion(1-), 101. Experimental and theoretical proton NMR results for the anion in the presence and absence of the counter cation were analysed. The cyclopentadienyl anion, when fused to 32, has 53% of the effective bond-fixing ability of benzene fused to the same system. In terms of benzene resonance energy units, cyclopentadienyl anion has an effective resonance energy of 0.53. Metal complexation of the cyclopent[a]dihydropyrene, 101, was investigated, and gave the first two cyclopent-fused large annulene metal complexes, (6a,7,8,9,9a- μ5]-trans-11b,11c-dimethyl-11b,11c-dihydrocyclopent[a] pyrene-pentamethylcyclopentadienylruthenium(II), 139, and (6a,7,8,9,9a- μ5) trans-11b,11c-dimethyl-11b,11c-dihydrocyclopent[a] pyrene-tricarbonylmanganese (I), 141. Experimental and theoretical 1H NMR results for the two complexes were analysed. Ruthenocene, when fused to 32, was found to be 1.38 times more bond-fixing than benzene itself. Similarly, cyclopentadienylmanganesetricarbonyl is 1.33 times more bond-fixing than benzene. In terms of benzene resonance energy units, the two complexes have effective experimental resonance energies of 1.42 and 1.36, respectively. The diamagnetic susceptibility, X, of a cyclopentadienylruthenium moiety, with the center of anisotropy located at the metal atom, was calculated as -330x10-36 m3 per molecule. The same parameter for a manganese tricarbonyl moiety, with the center of anisotropy being located at 3.2 A° down from the manganese atom, was calculated as -635x10-36 m3 per molecule. An X-ray structure determination of 32 was finally achieved some 25 years after its first synthesis. The structural data confirm the planarity and lack of bond alternation in the bridged annulene, indicating that it is aromatic. / Graduate

The electrochemical hydroxylation of aromatic substrates was investigated in some detail, with the view to develop a method, which could produce dihydroxybenzenes in acceptable yields. Of particular interest was the selectivity and yield of the 1,4-dihydroxybenzenes. Two distinctly different methods were investigated in order to achieve this goal, acyloxylation and direct electrochemical hydroxylation. Acyloxylation is the process where radical cations generated at the anode undergoes nucleophilic attack by acetate anions. The resulting aromatic acetates so produced can then be hydrolysed to the phenolic compounds. Two nucleophile systems were considered in the investigation, acetates (acetoxylation) and trifluoro-acetates (trifluoro-acetoxylation). These investigations were conducted under a variety of conditions using phenol and phenyl acetate as starting materials. From the results it was, however, concluded that the acetoxylation of these aromatic compounds occurs in unacceptable product and current yields. Trifluoro-acetoxylation on the other hand showed promise, but due to the nature and cost of the reagents it was deemed to be an impractical process. Direct electrochemical hydroxylation: in which the radical cations produced at the anode undergoes nucleophilic attack by water producing the corresponding dihydroxybenzenes. These dihydroxybenzenes are then further oxidised to the benzoquinones, which then undergo reduction at the cathode in order to produce the corresponding dihydroxybenzene. In this process phenol, 2-tert-butylphenol and 2,6-di-tert-butylphenol were investigated as substrates. The results indicated that the yield towards the 1,4-dihdroxybenzenes increased as the degree of substitution on the ring increased.

No description available.

Polarographic results for the reduction of a number of aromatic compounds in anhydrous acetic acid were obtained. The compounds studied included: o-, m- and p-nitroanilines and nitro-phenols; o-nitrobenzoic acid; 2,4-dinitro substituted phenol, benzoic acid and toluene; 3,5-dinitro substituted phenol and benzoic acid; 2,4,6-trinitro substituted phenol, benzoic acid and toluene. It has been shown that activating substituents on the benzene nucleus hinder the reduction of nitro groups on the ring, the effect being most pronounced for the o- and p- positions. Hydrogen bonding has been shown to occur to a lesser extent in acetic acid than in aqueous solution. Deactivating groups have been shown to cause nitro substituents to be more easily reduced, the effect decreasing in the order o<m<p. The polarographic reduction of a nitro group has been postulated to proceed with the same mechanism as in aqueous solvents. This reduction has been assumed to be a four or six electron irreversible reaction to the hydroxylamino or amino group repectively. Acetic acid, although limited in the potential range available, has been determined to be a suitable solvent for polarographic studies of organic compounds. / Science, Faculty of / Chemistry, Department of / Graduate

The transfer of energy from one species of hydrocarbon to another has been observed. The conditions under which such transfer occurs indicate that one aromatic hydrocarbon may be absorbed onto crystals of the other forming a surface complex with a binding energy of a few hundred calories. Transfer of energy occurs readily between the components of this complex but not between molecules of different hydrocarbons when both are in solution. However, evidence for resonance transfer of energy between pairs of molecules of the same substance when both are in solid solution has been found. Studies of a large number of hydrocarbons have failed to reveal any single electronic property of the molecule which determines its ability to form complexes of the type found. The techniques developed were applied to a preliminary study of the rate of disappearance of carcinogenic hydrocarbons applied to the skin of mice. Also included are literature surveys on the known interactions of polycyclic hydrocarbons, the mode of reaction of carcinogenic hydrocarbons with living cells, and the spectral properties of chlorophyll. / Science, Faculty of / Chemistry, Department of / Graduate

The infrared spectra of single crystals of naphthalene-d₈, anthracene-h₁₀ and anthracene-d₁₀ are reported with the plane of the incident radiation parallel to all three principal optical directions of the crystals. The polarized measurements extend down to 50 cm⁻¹and all low-energy infrared-active molecular vibrations and many lattice vibrations have been assigned. The laser-excited Raman spectra of single crystals of naphthalene-d₈ and anthracene-d₁₀ also are reported and this data was supplemented by depolarization ratio measurements from solution and from the melt. With the new information available from these studies a re-evaluation of the assignments of the molecular fundamentals of these three molecules has been made. When the list of fundamentals was as complete as possible, attention was directed to the force fields. The out-of-plane field of benzene was reconsidered, and the assumption that interaction constants should be as small as possible was completely supported. Transfer of these force constants to naphthalene was successful; however, it proved to be impossible to fit all the observed non-planar frequencies of anthracene with the force constants developed for benzene. An in-plane modified valence force field designed for benzene was extended to naphthalene and anthracene and refined to fit simultaneously the observed frequencies of all three molecules and their three perdeuterated analogues. The results were compared with the results of a similar calculation carried out by Neto, Scrocco and Califano and presented elsewhere, and certain differences were noted, particularly in the anthracene-h₁₀ and -d₁₀ B₂[subscript u] ring modes. In order to find out how well force fields developed for these molecules would transfer to related but less similar molecules, the vibrations of pyrene and acenaphthene were considered. The infrared spectra of single crystals of pyrene-h₁₀, pyrene-d₁₀ and acenaphthene were measured, with emphasis on the low-frequency regions not previously studied. The data obtained were supplemented by Raman measurements carried out by others in this laboratory and fairly complete assignments of the normal vibrations were possible. The fundamental frequencies of these molecules were calculated with force fields synthesized from the two planar fields mentioned earlier and from the out-of-plane fields of benzene and (for acenaphthene) cyclopentane. Comparison of the observed and calculated frequencies showed that although some fairly large discrepancies did arise, they were few in number and located only in the region of the ring stretching vibrations (above about 1200 cm⁻¹) . The fit to the fundamentals below that energy was most encouraging, and indicated that the transfer of force constants from one molecule to another in order to calculate approximate frequencies was certainly possible. / Science, Faculty of / Chemistry, Department of / Graduate

Claisen first synthesized Chalcone in 1881 by condensing acetophenone with benzaldehyde using sodium methoxide as a condensing agent. Chalcone and its derivatives have been prepared primarily as intermediates for the synthesis of anthocyanins and other related pigments. In recent years extensive preparation and study of chalcones has been carried out utilizing chalcones for their biological effects in medical and pharmaceutical fields. It has been shown that certain highly substituted compounds present in the flower pigments as additives to adhesive absorb ultraviolet radiation. Carboxylic acid chalcones have become known for their therapeutic action in the treatment of chronic kidney diseases, diseases of the eye, and rheumatoid diseases, such as bursitis and osteoarthritis. Treatment of chalcones with sulfuric acids to obtain α-ketosulfones, used as chemotherapeutic agents, has been under investigation and useful results have been obtained. Many of these α-ketosulfones are used to identify small amounts of sulfuric acid obtained from the cleavage and rearrangement of certain sulfones. In the research of genetic factors which regulate the formation of flavonoids factors in organisms, a suitable method for determining these compounds in small amounts in plant tissues is of very great importance and chalcones have been under investigation to serve this purpose. The observation of insecticidal bacteriostatic and tuberculostatic activities in chalcones has led to extensive investigation of chalcones.

No description available.

No description available.