archives@tulane.edu / A catalyst is a substance that increases the rate of a reaction without itself being consumed. Catalysis is an enabling technology due to its importance in a wide range of industrial applications. Processes responsible for more than 95% of all produced chemical products by volume employ catalysis, more than 85% of the added value in the chemical industry is produced by means of catalysis, and ca. 20% of the world economy depends directly or indirectly on catalysis. Generally, catalysts are classified into three categories: heterogeneous, homogeneous, or bio catalysts. A heterogeneous catalyst is one that is not in the same phase as the reactants while in homogeneous catalysis, the catalyst is in the same phase as the reactants. Heterogeneous catalysis is currently the most dominant catalysis route due to its advantages. A very important feature is that heterogeneous catalysts can be regenerated and reused for several catalytic cycles, which makes their application highly economical. Zeolites, which are porous crystalline aluminosilicates, offer great potential as heterogeneous catalysts due to their unique structural characteristics. For example, they can be employed in important chemical reactions such as aromatization, alkylation, dehydration, disproportionation, hydroalkylation, hydrocracking, and hydrogenation. To achieve unique selectivities in these processes, knowing the topology of zeolites is essential because it controls the size and shape of molecules that can be admitted in the framework, and their possible pathways. Since the properties of zeolites are associated with their structure, the synthesis of zeolites with improved topologies and compositions and their fundamental understanding has been and continues to be the objective of many researchers. Even though significant improvements in zeolites have been achieved in the last century, there is still space for growth in some areas including the diversification of zeolite chemical compositions to expand their applications as catalyst. The present dissertation attempts to give an understanding of how different parameters can be linked to the activity of heteroatom-containing zeolites in certain oxidation reactions. Chapter (1) of the dissertation covers the fundamentals of zeolite materials science and their applications in industry. Chapter (2) describes the experimental methods and analytical tools used in this dissertation. Synthesis and detail characterization of Sn, Sn-Al, and Sn-B substituted into MFI zeolites are discussed in chapter (3). We found that Sn-Al- MFI have both Lewis and Brönsted acidities while Sn-B-MFI shows strong Lewis acidity and weak Brönsted acidity. Moreover, the presence of the second element (Al/B) impacts the Sn uptake. In chapter (4), we report the synthesis of Fe-ZSM-5 zeolites made by a novel method called steam-assisted crystallization and their use in benzene hydroxylation to phenol in the presence of hydrogen peroxide as the oxidant. These materials showed a superior catalytic activity for benzene hydroxylation as compared to conventional Fe- ZSM-5 zeolites. Chapter (5) describes the effect of different trivalent elements (Ga, Al, B) on the acidity of Fe-MFI materials and their relation to the catalytic activity methane partial oxidation to oxygenated compounds including formic acid, methanol, and methyl hydroperoxide. We found that acidity plays a crucial role in the activation of hydrogen peroxides and ultimately methane oxidation. Chapter (6) and (7) present conclusions and potential future works, respectively. / 1 / Meysam Shahami

High-valent metal-oxo complexes are vital as active oxidants in enzymatic and synthetic catalytic oxidations. Inspired by the ubiquitous cytochrome P450 enzyme, researchers have explored the power of metalloporphyrins to mimic one of Nature’s premier catalytic entities. In this work, four manganese(III)porphyrin systems, including three electronwithdrawing ligands and one electron-donating ligand, were investigated with regard to their ability to form high-valent manganese(IV)-oxo porphyrin systems. The porphyrin ligands studied were 5,10,15,20-tetra(2,6-difluorophenyl)porphyrin [H2(2,6-F2TPP)], 5,10,15,20-tetra(4-trifluoromethylphenyl)porphyrin [H2(4-CF3TPP)], 5,10,15,20-tetra(4- fluorophenyl)porphyrin [H2(4-FTPP)], and 5,10,15,20-tetra(2,6- dimethoxyphenyl)porphyrin [H2(TDMPP)]. All were synthesized purified and characterized spectroscopically. Using the mild oxidant iodobenzene diacetate, manganese(IV)-oxo porphyrins [MnIV(Por)O] were successfully generated in all systems as confirmed through spectroscopic methods. Meanwhile, a new photochemical approach was explored for its efficacy in producing the MnIV-oxo complexes by visible light irradiation of manganese(III) precursors containing the photolabile chlorate as the axial ligand. More importantly, the MnIV-oxo complexes obtained by chemical generation were tested for their abilities as oxygen atom transfer agents (OATs) with aryl alkenes, alkenes and thioanisoles in CH3CN. The apparent second-order rate constants for sulfoxidation ranged between (2.29 ± 0.08) and (12.9 ± 2.0) M-1s-1 x 10-2 which were, on average, a magnitude larger than the rates for epoxidation of the aryl alkenes. Most notably in reactions with substrate, the order of reactivity of [MnIV(Por)O] was [(4-F)TPP] > [(4- CF3)TPP] > [(2,6-F2)TPP], which is inverted from the expected result based on the electron-demands of the porphyrin ligands. The apparent rate constants for reaction with cyclohexene was found to be 1 to 2 orders of magnitude larger than those with sulfide substrates. The kinetic results are consistent with a reaction model involving disproportionation of MnIV(Por)O to give MnIII(Por) and MnV(Por)O species, the latter of the two being the active oxidant. Alternatively, the results from the sulfoxidations are consistent in part with a direct oxygen atom transfer by [MnIV(Por)O]

Philosophiae Doctor - PhD / Maleic acid (MA) is a key intermediate for the synthesis of polyester resins, surface coatings, lubricant additives, plasticizers, copolymers, pharmaceuticals and agricultural chemicals. The current industrial production of MA is an energy-intensive gas-phase oxidation process of n-butane. The dwindling fossil resources and environmental issues have brought about a worldwide paradigm shift from fossil feedstocks to biomass resources for the sustainable production of fuel and chemicals. Furfural (FFR) and 5-hydroxymethylfurfural (HMF) are excellent biomass-derived platform chemicals, which present an alternative route for the production of renewable bio-based MA. There has been considerable success achieved in the oxidation of furfural and HMF to maleic acid and maleic anhydride with different catalysts in recent years.

Baeyer-Villiger oxidation of 1,9-dibromopentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione (1,9-dibromo-PCU-8,11-dione) was performed by using an excess amount of m-chloroperbenzoic acid (3 equivalents) and resulted in the formation of the corresponding monolactone. The reaction would not proceed to the dilactone stage. The structure of the reaction product was established unequivocally via single crystal X-ray diffraction. Baeyer-Villiger oxidation of 1,9-dibromo-PCU-8,11-dione using ceric ammonium nitrate (CAN) was also performed and afforded a mixture of lactones. Only one of these lactones, which also contained an alkene functionality, could be isolated and characterized. 1,7-dibromo-PCU-8,11-dione was also reacted with CAN, yielding the mono-lactone, which has also been characterized.

No description available.

The genus Gluconobacter consists of acetic acid bacteria which have the ability to generate acidic products from their substrates, particularly acetic acid from ethanol. For this reason, the gluconobacters live in acidic, sugary environments such as flowers, honey bees, fruits, cider, vinegar, wine and beer. The gluconobacters carry out a strictly respiratory type of metabolism using only oxygen as a terminal electron acceptor. They do not completely oxidize a substrate to carbon dioxide. Instead, they partially oxidize the substrate using membrane-bound dehydrogenases and excrete the product into the surrounding growth medium. It is these limited oxidations that make the gtuconobacters industrially useful. Although much is known about the physiology of the limited oxidations in the gluconobacters, little is known of their genetics, particularly, their plasmids. The overall purpose of this dissertation was to determine if Gluconobacter plasmids correlate with oxidative capability and/or antibiotic resistance. To achieve this goal, I first needed a way to screen strains of Gluconobacter for their ability to oxidize many different substrates. 'developed an assay that used an unusual artificial electron acceptor, tetranitroblue tetrazolium (TNBT) and then tested the ability of six strains to oxidize 13 chemical compounds. Although most strains were able to oxidize the 13 compounds tested, they accomplished this with varying extents of oxidation. These differences were noted even with strains representing the same species. / Ph. D.

Perfumery compounds isoeugenol and isosafrole can be oxidized to their aldehydes, vanillin and heliotropin respectively. The aldehydes obtained are very useful and commercially valuable products. Apart from their importance as perfumery compounds, they form important intermediates in the Pharmaceuticals and pesticide industries. Liquid phase oxidation of isosafrole using different oxidizing agents were tried. Sodium dichromate as oxidizing agent in aqueous acetic acid was found to be most suitable because of its higher yields and mild reaction conditions. This reaction was taken up for detailed study. Since the kinetic study of dichromate oxidation in aqueous acetic acid medium of isosafrole has not been mentioned in the literature, various parameters like isosafrole, dichromate and acetic acid concentrations were studied. The experiments were conducted at different temperatures to estimate the activation energy of the reaction. The effect of added salts like manganese sulfate, manganese acetate and cobaltous acetate has also been studied. For all the experiments the change in isosafrole concentration was observed. The rate of reaction increases with increase in isosafrole concentration. The order of the reaction with respect to isosafrole concentration is found to be one. The rate of reaction increases with increase in initial sodium dichromate concentration. The reaction is found to be half order in dichromate ion concentration. The rate of reaction increases with increase in acetic acid concentration with an order two. The atmospheric oxygen does not affect the reaction rate suggests that the reaction may not be free radical reaction. The rate of reaction increases with increase in temperature. The activation energy was found to be equal to 14.59 kcal/mol.

Neste trabalho apresenta-se o estudo do comportamento eletroquímico anódico - direto (oxidação na superfície do eletrodo) e indireto (oxidação através de um oxidante eletrogerado, ou mediador) de β-ceto-sulfetos e βhidróxi-sulfetos de estruturas variadas. Foram utilizadas as técnicas de voltametria cíclica (anodo:pérola de Pt; referência: Ag/AgI; solvente: MeCN anidra e NaClO4 0,1 M como eletrólito de suporte) e de oxidações anódicas preparativas (potencial controlado ou corrente constante; eletrodos de Pt polida 4 cm2; solvente:MeCN/H2O (9:1v/v); NaClO4 0,2 M). Foram sintetizadas e estudadas as seguintes cetonas α-sulfeniladas: 2-etiltio- (I.1), 2-etiltio-2-metil (I.2) e, 2-feniltio-(I.3)-ciclo-hexano-1-onas; 2-metiltio-(II.1) e 2-metiltio-2-metil-(II.2)-1-tetralonas; 1-fenil-2-metiltio-butano-1-ona (III.1); 2-etiltio-1,2-difenil-etano-1-ona (IV.1) e três derivados aril-substituídos [4.4-OMe (IV.2); 4-OMe (IV.3); 2.2-Cl (IV.3); 2,2-Cl (IV.4)]. Os mediadores preparados e eletroquimicamente investigados foram os derivados bromados da trifenilamina (V.1): tris(4-bromofenil)amina (V.2) e tris(2,4-dibromo-fenil)amina (V.3). Os álcoois correspondentes foram preparados por redução direta das cetonas. Os resultados dos estudos eletroquímicos das cetonas demonstraram que o diferente comportamento eletroquímico deve-se a fatores estereoeletrônicos. Somente (III.1) e (IV.1, 2 e 3) eram oxidados indiretamente. As oxidações anódicas diretas dos β-hidróxi-sulfetos mostraram-se mais seletivas que as das cetonas relativas. Além do mais, a comparação entre as oxidações direta e indireta destes álcoois revelou que enquanto diretamente obtem-se dois ou três produtos, indiretamente os sulfóxidos correspondentes são obtidos. Como único produto, de todos álcoois exceto daqueles relativos às cetonas (IV. 2, 3 e 4). Também foi observado que a estereoquimica cis entre os grupos hidroxila e alquiltio é fator determinante para as oxidações eletroquímicas indiretas. Os estereoisômeros trans não eram oxidados indiretamente. Um intermediário cíclico, formado durante o processo de oxidação, é sugerido como explicação para estes fatos. Também foi observado que ocorre clivagem da ligação carbono-carbono entre os grupos hidroxila e alquiltio na oxidação anódica, quando os carbonos substituídos são terciários (no caso de 2-etiltio-1,2-dimetil-ciclohexan-1-ol), ou estão ligados a grupos fenila (IV.1, 2, 3 e 4). São obtidos os compostos carbonílicos correspondentes em bons rendimentos. / In the present work a study of the electrochemical oxidation behaviour under direct (oxidation at the electrode) and indirect (oxidation by on in situ electrogenerated species, a mediator) conditions of several β-keto and β-hydroxysulphides is reported. Cyclic voltammetry (anode: Pt bead, reference: Ag/AgI, 0.1 M NaClO4) in anhydrous acetonitrile) and preparative scale electrolysis under controlled potential or at constant current (anode: Pt 2 x 2 cm, 0.2 M NaClO4 in acetonitrile - water (9:1 v/v) were employed. The studied mediators were tris-(4-bromophenyl) and tris-2,4-dibromophenyl)amines. The following α-sulphenylated ketones were synthesized: 2-ethylthio-(I.1), 2-ethylthio-2-methyl (I.2) and 2-phenylthio-(I.3)-cyclohexan-1-ones; 2-methylthio-(II.1) and 2-methylthio-2-methyl-(II.2)-1-tetralones; 1-phenyl-2-methylbutan-1-one (III.1); 2-ethylthio-1,2-diphenylethan-1-one (IV.1) and three aryl derivatives [4,4\'-OMe (IV.2), 4\'-Ome (IV.3), 2,2\'-Cl (IV.3)]. The corresponding alcohols were prepared by direct reduction of the ketones. The results of the electrochemical studies for the investigated ketones demonstrated that their different behaviour is due to stereoelectronic effects. Only (III.1, IV.1, IV.2 and IV.3) were indirectly oxidized. The direct anodic oxidations of the β-hydroxy-sulphides were more selective than those of the corresponding ketones. Moreover, a comparison between direct and indirect oxidations of such alcohols reveal that while the former can give two or three products, the latter yields the relatives sulphoxides as the only products with all the alcohols except the ones related to (IV.2, 3 and 4). It was also noticed that the cis stereochemistry between hydroxyl and alkylthio groups is the determining feature in the indirect electrochemical oxidation of cyclic alcohols. No oxidation was observed in the case of the trans stereoisomers. A cyclic intermediate, formed during the oxidation process, is suggested to explain these facts. In addition, a cleavage of the carbon-carbon bond between the hydroxyl and alkylthio groups was observed in the anodic oxidation, when the substituted carbons are tertiary (in the case of 2-ethylthio-1,2- dimethylciclohexan-1-ol), or linked to phenyl groups (IV.1, 2, 3 and 4). In these cases, the corresponding carbonyl compounds were obtained in good yields.

Neste trabalho apresenta-se o estudo do comportamento eletroquímico anódico - direto (oxidação na superfície do eletrodo) e indireto (oxidação através de um oxidante eletrogerado, ou mediador) de β-ceto-sulfetos e βhidróxi-sulfetos de estruturas variadas. Foram utilizadas as técnicas de voltametria cíclica (anodo:pérola de Pt; referência: Ag/AgI; solvente: MeCN anidra e NaClO4 0,1 M como eletrólito de suporte) e de oxidações anódicas preparativas (potencial controlado ou corrente constante; eletrodos de Pt polida 4 cm2; solvente:MeCN/H2O (9:1v/v); NaClO4 0,2 M). Foram sintetizadas e estudadas as seguintes cetonas α-sulfeniladas: 2-etiltio- (I.1), 2-etiltio-2-metil (I.2) e, 2-feniltio-(I.3)-ciclo-hexano-1-onas; 2-metiltio-(II.1) e 2-metiltio-2-metil-(II.2)-1-tetralonas; 1-fenil-2-metiltio-butano-1-ona (III.1); 2-etiltio-1,2-difenil-etano-1-ona (IV.1) e três derivados aril-substituídos [4.4-OMe (IV.2); 4-OMe (IV.3); 2.2-Cl (IV.3); 2,2-Cl (IV.4)]. Os mediadores preparados e eletroquimicamente investigados foram os derivados bromados da trifenilamina (V.1): tris(4-bromofenil)amina (V.2) e tris(2,4-dibromo-fenil)amina (V.3). Os álcoois correspondentes foram preparados por redução direta das cetonas. Os resultados dos estudos eletroquímicos das cetonas demonstraram que o diferente comportamento eletroquímico deve-se a fatores estereoeletrônicos. Somente (III.1) e (IV.1, 2 e 3) eram oxidados indiretamente. As oxidações anódicas diretas dos β-hidróxi-sulfetos mostraram-se mais seletivas que as das cetonas relativas. Além do mais, a comparação entre as oxidações direta e indireta destes álcoois revelou que enquanto diretamente obtem-se dois ou três produtos, indiretamente os sulfóxidos correspondentes são obtidos. Como único produto, de todos álcoois exceto daqueles relativos às cetonas (IV. 2, 3 e 4). Também foi observado que a estereoquimica cis entre os grupos hidroxila e alquiltio é fator determinante para as oxidações eletroquímicas indiretas. Os estereoisômeros trans não eram oxidados indiretamente. Um intermediário cíclico, formado durante o processo de oxidação, é sugerido como explicação para estes fatos. Também foi observado que ocorre clivagem da ligação carbono-carbono entre os grupos hidroxila e alquiltio na oxidação anódica, quando os carbonos substituídos são terciários (no caso de 2-etiltio-1,2-dimetil-ciclohexan-1-ol), ou estão ligados a grupos fenila (IV.1, 2, 3 e 4). São obtidos os compostos carbonílicos correspondentes em bons rendimentos. / In the present work a study of the electrochemical oxidation behaviour under direct (oxidation at the electrode) and indirect (oxidation by on in situ electrogenerated species, a mediator) conditions of several β-keto and β-hydroxysulphides is reported. Cyclic voltammetry (anode: Pt bead, reference: Ag/AgI, 0.1 M NaClO4) in anhydrous acetonitrile) and preparative scale electrolysis under controlled potential or at constant current (anode: Pt 2 x 2 cm, 0.2 M NaClO4 in acetonitrile - water (9:1 v/v) were employed. The studied mediators were tris-(4-bromophenyl) and tris-2,4-dibromophenyl)amines. The following α-sulphenylated ketones were synthesized: 2-ethylthio-(I.1), 2-ethylthio-2-methyl (I.2) and 2-phenylthio-(I.3)-cyclohexan-1-ones; 2-methylthio-(II.1) and 2-methylthio-2-methyl-(II.2)-1-tetralones; 1-phenyl-2-methylbutan-1-one (III.1); 2-ethylthio-1,2-diphenylethan-1-one (IV.1) and three aryl derivatives [4,4\'-OMe (IV.2), 4\'-Ome (IV.3), 2,2\'-Cl (IV.3)]. The corresponding alcohols were prepared by direct reduction of the ketones. The results of the electrochemical studies for the investigated ketones demonstrated that their different behaviour is due to stereoelectronic effects. Only (III.1, IV.1, IV.2 and IV.3) were indirectly oxidized. The direct anodic oxidations of the β-hydroxy-sulphides were more selective than those of the corresponding ketones. Moreover, a comparison between direct and indirect oxidations of such alcohols reveal that while the former can give two or three products, the latter yields the relatives sulphoxides as the only products with all the alcohols except the ones related to (IV.2, 3 and 4). It was also noticed that the cis stereochemistry between hydroxyl and alkylthio groups is the determining feature in the indirect electrochemical oxidation of cyclic alcohols. No oxidation was observed in the case of the trans stereoisomers. A cyclic intermediate, formed during the oxidation process, is suggested to explain these facts. In addition, a cleavage of the carbon-carbon bond between the hydroxyl and alkylthio groups was observed in the anodic oxidation, when the substituted carbons are tertiary (in the case of 2-ethylthio-1,2- dimethylciclohexan-1-ol), or linked to phenyl groups (IV.1, 2, 3 and 4). In these cases, the corresponding carbonyl compounds were obtained in good yields.

This thesis deals with the design of ligands for efficientasymmetric catalysis and studies of the conformation of theligands in the catalytically active complexes. All ligandsdeveloped contain chiral oxazoline heterocycles. The conformations of hydroxy- and methoxy-substitutedpyridinooxazolines and bis(oxazolines) during Pd-catalysedallylic alkylations were investigated using crystallography,2D-NMR techniques and DFT calculations. A stabilising OH-Pdinteraction was discovered which might explain the differencein reactivity between the hydroxy- and methoxy-containingligands. The conformational change in the ligands due to thisinteraction may explain the different selectivities observed inthe catalytic reaction. Polymer-bound pyridinooxazolines and bis(oxazolines) weresynthesised and employed in Pd-catalysed allylic alkylationswith results similar to those of monomeric analogues;enantioselectivities up to 95% were obtained. One polymer-boundligand could be re-used several times after removal of Pd(0).The polymer-bound bis(oxazoline) was also used in Zn-catalysedDiels-Alder reactions, but the heterogenised catalyst gavelower selectivities than a monomeric analogue. A series of chiral dendron-containing pyridinooxazolines andbis(oxazolines) were synthesised and evaluated in Pd-catalysedallylic alkylations. The dendrons did not seem to have anyinfluence on the selectivity and little influence on the yieldwhen introduced in the pyridinooxazoline ligands. In thebis(oxazoline) series lower generation dendrimers had a postiveon the selectivity, but the selectivity and the activitydecreased with increasing generation. Crown ether-containing ligands were investigated inpalladium-catalysed alkylations. No evidence of a possibleinteraction between the metal in the crown ether and thenucleophile was discovered. A new type of catalyst, an oxazoline-containing palladacyclewas found to be very active in oxidations of secondary alcoholsto the corresponding aldehydes or ketones. The reactions wereperformed with air as the re-oxidant. Therefore, this is anenviromentally friendly oxidation method. <b>Keywords:</b>asymmetric catalysis, chiral ligand,oxazolines, conformational study, allylic substitution,polymer-bound ligands, dendritic ligands, crown ether,oxidations, palladacycle.