Ruthenium (II) polypyridine complexes in general have been extensively studied because of their unique redox and photochemical properties. A typical example of such complexes is tris(2,2’-bipyridyl) ruthenium (II). In this study, this complex was synthesized and then characterized using electronic spectroscopy and cyclic voltammetry. It was also shown that the ruthenium concentration could be accurately determined using ICP-MS. It was found that the complex is very stable in various chemical environments. It was observed from spectrophotometric investigations that persulphate and lead dioxide easily oxidize Ru(bpy)3 2+ to Ru(bpy)3 3+ in the presence of heat and H2SO4, respectively. It was also observed that the oxidation between Ru(bpy)3 2+ and cerium (IV) occurred at approximately 3:2 [Ce(IV)]/[Ru(II)] mole ratio. The resultant Ru(bpy)3 3+ solution was unstable in the presence of light and recovery of Ru(bpy)3 2+ occurred gradually. The regeneration of Ru(bpy)3 2+ from Ru(bpy)3 3+ was found to be a multistep process, which appears to involve the formation of an intermediate species. The following reaction model was found to best explain the kinetic data obtained: Ru(bpy)3 2+ + Ce(IV) → Ru(bpy)3 3+ Ru(bpy)3 3+ → Ru(bpy)3 2+ Ru(bpy)3 3+ → Ru* intermediate Ru* intermediate → Ru(bpy)3 2+ Theoretical rate constants were also calculated for the same process under the experimental conditions. The comparison between the experimental and theoretical results gave good agreement. In addition, the factors that influence the rate of the regeneration of Ru(bpy)3 2+ from Ru(bpy)3 3+ were also discussed.

The reaction of alkyl iodides with phenyl-iodo-arsines in the presence of mercury has been found to yield arsonium derivatives of triiodomercury (II). Extension of these reactions to other iodides of the Group V elements showed that when reacted with iodomethane and mercury, phosphorus triiodide gave the 1:1 complex of trimethylphosphine and mercuric iodide; antimony triiodide gave tetramethylstibonium triiodomercury (II); diiodophenylstibine reacted only to a limited extent; and bismuth triiodide gave an unstable product. Trifluoroiodomethane failed to react with the Group V iodides in the presence of mercury. Because of the possibility that 1:1 tertiary arsine mercuric iodide complexes are intermediates in the reactions which give rise to arsonium triiodomercury (II) derivatives, the reaction of these complexes with alkyl iodides was investigated. In all cases investigated using iodomethane, direct reaction occurred with the formation of arsonium triiodomercury (II) derivatives. Iodoethane, bromoethane and trifluoroiodomethane were found to react only to a slight extent, if at all, with tertiary arsine mercuric iodide complexes. / Science, Faculty of / Chemistry, Department of / Graduate

When deoxybenzoin oxime was reacted with carbon monoxide and hydrogen in the presence of dicobalt ootacarbonyl at elevated temperatures and pressures 3-benzylphthalimidine and 3-phenyl-3,4-dihydroisocarbostyryl were produced. When 2-acetonaphthone oxime was reacted under similar conditions 2-(β-naphthyl)-4-methyl-benzo[h] quinoline, 3-methylbenzo[f]phthalimidine and 1- (β-naphthyl)ethylurea were produced. Verification of the structure of 2-(β-naphthyl)-4-methylbenzo[h]-quinoline was attained in part through the hydrochloride salt, the methiodide salt, the picrate derivative and the 2-(β-naphthyl)-4-formylbenzof[h]-quinoline derivative. 2-(β-Naphthyl)-4-methyl-benzof[h] quinoline was also synthesized by reacting 2- acetonaphthone oxime with 2-acetonaphthone at elevated temperatures. The infrared spectra of the above compounds are described. / Science, Faculty of / Chemistry, Department of / Graduate

When oxygen is passed through a microwave discharges, the oxygen atoms being destroyed by distilling mercury through the discharges an excited molecule O₂(¹△g) was observed to be the primary discharge product. This excited molecule was found to be immune to collisional deactivation by a wide range of added foreign gasses, with the exception of certain substituted ethylenes which it oxidized. The principal mode of decay of O₂(¹△g) was nonradiative decay, with knonrad. equal to 0,178 sec.-¹ The excited molecule O₂(¹△g) however, was observed to undergo two novel energy pooling processes, [ Formulas omitted ] The first of these energy pooling processes gave rise to two broad structureless bands at 6340 A and 7030 A which had not previously been observed in discharged oxygen. These bands, the intensity of which is proportional to the square of the O₂(¹△g) concentration and independent of the total pressure in the systems are believed to result from a simultaneous electronic transition in two O₂(¹△g) molecules with the emission of a single photon. The 6340 A band appears if both molecules undergo a (0-0) transition in the [ Formula omitted ] system and the 7030 A. band if one molecule undergoes a (0-0) transition and the other a (0-1) transition. The second of these energy pooling processes is a disproportionation reaction which leads to the formation of a second excited molecule [ Formula omitted ]. Tne rate constant, for this reaction was found to be 1.3 x 10³ l.moles -¹sec.-¹, in disagreement with the results of Young and Black by a factor of 10⁴ Both energy pooling processes are believed to have a common intermediate, { O₂(¹△g) }2, which is either a metastable double molecule or a colliding pair of molecules. The principal mode of decay of [ Formula omitted ]was nonradiative decay, with knonrad. equal to 64.6 sec.-¹ Unlike O₂(¹△g) , [ Formula omitted ] was found to be collisionally deactivated by a wide variety of added foreign gases, with the most effective deactivator tried being water. The rate constants for the reaction [ Formula omitted ] were determined for fourteen different quenchers. A good correlation between quenching efficiency and the magnitude of the intermolecular potential between the quencher and [ Formula omitted ] has been obtained. Two additional energy pooling processes involving excited oxygen molecules and either molecular iodine or nitrogen dioxide were observed. Both resulted in the formation of an excited molecule[ Formula omitted ]or NO₂, which emitted in the visible. / Science, Faculty of / Chemistry, Department of / Graduate

The photolysis of azomethane, di-isopropyl ketone and azoisobutane has been examined briefly in the gas phase and these compounds have been found to be convenient sources of the methyl, isopropyl and tert-butyl radicals respectively. The photolysis of the mixed vapours of cyclohexadiene-1,4 with each of azomethane, di-isopropyl ketone and azoisobutane has been examined over a series of temperatures. These studies afforded the Arrhenius parameters for the abstraction of the methylenic hydrogen atom from cyclohexadiene-1,4 by the methyl, isopropyl and tert-butyl radicals. There was found no significant difference in the reactivities of these radicals towards the cyclohexadiene-1,4 substrate. The rate constants measured were [formula omitted]. The cyclohexadienyl radical is generated in this metathetical reaction, and the interaction of the cyclohexadienyl radical with the various mentioned initiator radicals was examined kinetically. It was found that the interaction of alkyl radicals with the cyclohexadienyl radical produced either benzene and the hydrocarbon, RH, (disproportionation) or 1-alkylcyclohexadiene-2,4 (combination, I) or 1-alkylcyclohexadiene-2,5 (combination, II). The ratio of the rates of formation of the two combination products (I/II) has been found to have the constant value 0.77 ± 0.17 within the experimental error for all the alkyl radicals studied. The ratio of the rate of disproportionation to the combined rates of combination was found to vary systematically over the values 0.27 ± 0.07, 0.52 ± 0.09, and 1.33 ± 0.24 for the methyl, isopropyl and tert-butyl radicals respectively. A previous study of the ethyl radical's reactions with the cyclohexadienyl radical in this laboratory had shown that this ratio for the ethyl radical was 0.38 ± 0.03. The measured values of the termination rate ratios for the various systems are consistent with the expectation that the product of greater entropy should form preferrentially and the results are considered to support the disproportionation transition state model of Bradley and Rabinovitch. During the photolysis of azomethane-cyclohexadiene-1,4 mixtures at lower intensisties, there was observed the formation of cyclohexene and greater than the expected amount of benzene. This was considered to arise from the decomposition reaction C₆H₇→C₆H₆ + H˙. Kinetic analysis of this system has afforded an estimate of the heat of formation of the cyclohexadienyl radical, (45 ± 5 kcal./mole), and consequently of its resonance energy, (24 ± 5 kcal./mole). This has been considered to be evidence that there is an interaction of the delocalized system across the methylenic carbon bridge, since the resonance energy is substantially greater than that measured in another laboratory for the straight chain pentadienyl radical (15.5 kcal./mole). The reactions of the isopropyl radical with the cyclohexadiene-1,3 molecule have been studied in the gas phase. The isopropyl radical adds to the unsaturated linkages with a rate constant [formula omitted]. The abstraction of a methylenic hydrogen atom procedes with a rate governed by the rate constant [formula omitted]. Thus the metathetical reaction procedes more slowly for the conjugated cyclohexadiene than for the unconjugated system by a factor of 1.9 at 100°. This behavior was also found for the reactions of the ethyl radical with the cyclohexadiene isomers in a previous study, and probably arises from a slightly lower free energy of the cyclohexadiene-1,3 molecule. The ratio of addition to abstraction between isopropyl and cyclohexadiene-1,3 is low, (4.3 at 100°) and degradative chain transfer has been suggested as the reason for the very low tendency of the cyclohexadiene-1,3 molecule to polymerize under homogeneous, free radical conditions. / Science, Faculty of / Chemistry, Department of / Graduate

Reliable design of artificial metalloenzymes (ArMs) to access transformations not observed in nature remains a long-standing and important challenge. We report that a monomeric streptavidin (mSav) Rh(III) ArM permits asymmetric synthesis of α,β-unsaturated-δ-lactams via a tandem C-H activation and [4+2] annulation reaction. These products are readily derivatized to enantioenriched piperidines, the most common N-heterocycle found in FDA approved pharmaceuticals. Embedding a Rh cyclopentadienyl (Cp*) catalyst in the active site of mSav results in improved stereocontrol and a seven-fold enhancement in reactivity relative to the isolated biotinylated Rh(III) cofactor. With the goal of using protein engineering to improve the activity of monomeric streptavidin (mSav) ArM complexed to Rh(III), we also report computational calculations that demonstrate the effects of modifying the secondary coordination sphere. These findings have allowed us to engineer a more active mutant G49A that provides up to 67 more TON compared to WT mSav ArM. Directed evolution techniques, when applied to ArMs, allows us to mimic the natural selection process and thereby dramatically increase the TON of the ArM. This technology has been used to develop an artificial aminobrominase with up to 2587 TON.

Addition reactions of pentafluorosulfur bromide with unsaturated substrates were studied and four new compounds containing the pentafluorosulfur group have been prepared. The mechanism for these reactions seems to involve a radical addition pathway. In reaction with CH2=CFC1, CF3C≡CH and CH3C≡CH the SF5 radical attacks the carbon atoms carrying the most hydrogens. The reaction with CF2=CHCl is interesting, as by analogy with other fluoroolefins, the SF5 primary attack should occur.at the CHCl group, however, SF5CF2CHC1Br was found as the only product for this reaction. The reaction of SF5Br with CF3C≡CH produced two isomers but with CH3C≡CH only one isomer was forrmed. Analytical data, infrared, nmr .and mass spectra are presented supporting the proposed structures for these new compounds.

No description available.

No description available.

No description available.