No description available.

No description available.

Ethylbenzene (EB) is currently produced via acid catalyzed benzene alkylation with ethene, which is a product of highly endothermic and energy intensive processes. The new reaction, which uses ethane for benzene alkylation, instead of ethene, would eliminate the ethene production step, thus, leading to the commercial and environmental benefits in the EB manufacturing. Benzene alkylation with ethane into EB can be achieved using bifunctional zeolite catalysts, which combine ethane dehydrogenation into ethene over metal sites with benzene alkylation by ethene over Brønsted acid sites. The benzene alkylation with ethane into EB over Pt-containing (1 wt.%) ZSM-5 bifunctional catalyst was investigated at six different temperatures (290, 330, 370, 410, 450 and 490oC). The optimum reaction temperature as well as the effect of temperature on the catalyst performance and reaction pathways were established. Excellent catalyst performance was obtained at 370oC, at which very stable catalyst operation (46 h on stream) is observed and the EB selectivity above 90 mol.% is achieved at benzene conversion of 12.5%, which is very close to the maximum equilibrium conversion of benzene into EB at this temperature (13.6%). The obtained results have shown that the temperature has different effects on the rates of the different reaction steps, leading to the different product distributions at different temperatures.

This thesis describes the synthesis and properties of a number of novel substituted 1 ,2,4,5-tetrakis(amino )benzenes for which synthetic methods have only recently become available. Similar compounds have previously been observed as very electron rich systems; this thesis therefore explores some of the behaviour of these compounds that stems from this observed property. Chapter 1 details a proposed architecture for using single organic molecules as storage or processing units for single bits of binary data. This involves a bottom-up approach of creating single molecules, which could be used to fulfil the role of components in an integrated circuit. The design criteria that a molecule would need to fulfil in order to perform this task are discussed and substituted 1,2,4,5- tetrakis(amino )benzenes are suggested as possible candidates. Chapter 2 reports the results of a theoretical and computational study into the effects of ion-pairing on the observed electrochemical behaviour of tertiary 1,2,4,5-tetrakis(amino)benzenes. Compounds 1 - 6 are modelled using Density Functional Theory in the gas phase, in solution and as ion-pairs with [PF6] and [CI04] anions. The results of this study provide some insight as to why some of the tertiary tetrakis( amino )benzenes exhibit two-electron oxidation processes under certain conditions. Chapter 3 goes on to explore the synthesis of a selection of novel secondary tetrakis(amino)benzenes 9a - 11a based on recently published methods employing palladium catalysis. These new compounds have aromatic substituents on the nitrogen atoms and methyl or methoxy groups on the 3 and 6 positions of the central benzene ring. The ease with which these compounds can be oxidised to the corresponding benzoquinonediimines 9 - 11 is noted. Chapter 4 reports the discovery that these benzoquinonediimines can be oxidatively cyclised to produce the novel riminophenazines 12 and 13 or tetra(aza)pentacenes 14 and 15. The oxidative synthesis of these compounds is optimised and the tetra(aza)pentacenes are observed to be stable with regard to further oxidation and can form dications. Chapter 5 explores the ability of the benzoquinone diimines to form stable coordination compounds with a variety of rhodium-containing fragments producing a selection of binuclear complexes. These compounds were observed to be redox active. The effect on the redox potentials caused by changes to substituents on the central ring as well as the ancilliary ligands was investigated. Chapter 6 summarises the conclusions drawn in each of the preceding chapters to give an overall picture of the properties and behaviour of the compounds studied. These observations are linked to the electron rich nature of these compounds. Some comments are offered regarding how the compounds studied would meet the specification laid out for 'molecular bits'. A number of interesting observed properties are highlighted. Potential future applications of the compounds detailed herein are explored, and a range of derivative compounds which would be worthy of further study are highlighted.

The consistency of the labelling and assignments of the vibrations of the monosubstituted benzenes in the ground electronic state are investigated in this thesis. In doing so, many inconsistencies are uncovered, the origin of which is determined to be a result of the inherent problems in the previously employed assignment schemes. As a consequence, a new assignment scheme based on the vibrations of tluorobenzene is proposed. The SI electronic states of toluene and a -trideuterated toluene (toluene-d3) are investigated using resonance enhanced multi photon ionization, REMPI, spectroscopy. Using many of the observed SI vibrational levels as intermediates, two-colour, zero kinetic energy (ZEKE) spectroscopy has been employed in order to investigate the cationic ground states of these two toluene isotopologues. The vibrations are assigned using the nomenclature proposed in this thesis, and the activity of the vibrations in the REMPI and ZEKE spectra are discussed. Using high level ab initio techniques, potential energy curves, PECs, are calculated for the metal cation/rare gas, M+-RG (M = B, AI, Ga, and In) complexes. From these, spectroscopic parameters are derived, which are compared to previously reported experimental and theoretical values. The interactions between the moieties are examined by analyzing the orbital wavefunctions. The trends in the spectroscopic parameters determined for these complexes are compared with those previously determined for the RG complexes of the alkali metal, and the alkaline earth metal cations. Finally, the PECs of the ground electronic states of the coinage metal/rare gas complexes are calculated using high level ab initio techniques, with the interactions which occur within these complexes investigated

Kinetic and equilibrium studies have been made of the reactions of a series of ring-substituted anilines with l,3,5-trinitrobenzene (TNB) and with 4- nitrobenzofuroxan (4-NBF) in dimethyl sulfoxide (DMSO). There is evidence from (^1)H NMR spectroscopy that in the presence of Dabco these reactions yield anionic σ-adducts. Kinetic studies are compatible with a two-step process involving initial nucleophilic attack by amine to give a zwitterionic intermediate which can transfer an acidic proton to Dabco. In the case of TNB the proton transfer step is rate-limiting due to the high rate of reversion of the zwitterion to reactants. Measurement of substituent effects shows that values of the equilibrium constant K(_1) for the initial zwitterions formation decrease by a factor of ca 1000 as R, the ring substituent in the anilines, is changed from 4-OMe to 3-CN (p=-3.82), while values of K(_Dabco) for the proton transfer equilibrium increase by a similar factor (p=+3.62). Hence overall values of K(_1)Doabco show only a small variation with the nature of R. Related studies with 4-NBF indicate that there is a balance between nucleophilic attack and proton transfer as the rate limiting step. This is due to the lower value for the rate of reversion of the zwitterion to reactants in the case of 4- NBF, relative to TNB. Values of K(_Doabco) are found to be larger for the 4-NBF reaction than for the TNB reaction, indicating greater electron withdrawing ability for the 4- NBF system than for TNB .(_pKa) values in DMSO for the nine aniline derivatives used were measured using the proton transfer equilibrium with 2,4-dimtrophenol. (^1)H NMR studies in d(_6)-DMSO show that the carbanions of nitromethane, nitroethane and 2-nitropropane add to 4-nitrobenzofiirazan derivatives to give carbon- bonded σ-adducts. With time there is evidence for the base-catalysed elimination of nitrous acid from the adducts to yield anionic alkene derivatives. Kinetic and equilibrium results for the corresponding reactions in methanol have been measured. Three ring-substituted benzyl triflones were prepared and reactions of the carbanions formed from them with 4,6-dinitrobenzofuroxan, 1,3,5-trinitrobenzene and benzofurazan derivatives were examined. There is evidence for the initial formation of σ-adducts followed by rapid elimination of HSO2CF3. Rate constants for these reactions in methanol are reported.

The research described in this thesis is concerned with the exploitation of a nonracemic chiral base to create enantiomerically enriched chiral centres on the benzylic positions of arene chromium tricarbonyl complexes. The first chapter is in two parts. The first part contains a historical overview of chiral bases and their use in asymmetric synthesis, as well as demonstrating the versatility of chiral base reactions. The latter part deals with the chemistry of arene chromium tricarbonyl complexes and how these molecules have been used in asymmetric synthesis and as ligands in asymmetric catalysis. The second chapter looks at the synthesis of a novel benzyl phosphine chromium tricarbonyl complex and attempts to asymmetrically deprotonate the molecule in order to create a new chiral monophosphine. The third chapter describes the generation of a range of novel monophosphine ligands, based on an arene chromium tricarbonyl core, by exploitation of an asymmetric deprotonationlelectrophilic quench sequence. the novel monophosphines have been assayed in the asymmetric hydrosilylation reaction, and the results are presented and discussed. The fourth chapter is a study of arene chromium tricarbonyl complexes of dibenzyl ethCl and a dibclIzy laminc, dnd their as) mmetr ie dept otonatiol'l. The genet [tHon of new C2-symmetric ethers with high enantioselectivity is demonstrated. The fifth chapter describes the attempted construction of a novel chiral C3-symmetric triol using the chiral base mediated asymmetric benzylic functionalisation approach. The sixth chapter contains the experimental details of the work presented in Chapters two, three, four and five. Chapter seven provides the bibliographic information.

No description available.

The bidentate ligand 1,2-bis(ditertbutylphosphinomethyl)benzene has been shown to be a very efficient catalyst for operating the alkoxycarbonylation of alkenes and unsaturated esters and carboxylic acids giving a very high selectivity to the linear product with very few exceptions to this general rule. Due to the increasing prices of petroleum feedstock and petroleum-derived chemicals, the preparation of chemicals starting from renewable resources and waste products from the industry becomes an interesting alternative. Fatty acids and fatty esters, due to the existence of one or more unsaturation in their alkyl chain are subjected to the alkoxycarbonylation reactions in presence of 1,2-bis(ditertbutylphosphinomethyl)benzene, palladium, methane sulfonic acid, carbon monoxide and methanol, yielding diesters with a long carbon chain (up to 19 carbon atoms). The diesters are shown to be readily prepared from unpurified olive, rapeseed or sunflower oils as well as from tall oil. In the last case triesters are also formed. The diesters are subjected to hydrogenation in the presence of 1,1,1-tris(diphenylphosphinomethyl)ethane, ruthenium and hydrogen, in a mixture of dioxane and water at high temperature, yielding the corresponding diols. The resulting products of the reactions are monomers for preparing polyesters having the potential to replace some existing petroleum-based polymers (for instance polyethylene). The aminocarboxylation reaction in the presence of the same palladium/1,2-bis(ditertbutylphosphinomethyl) benzene catalyst, in the presence of aniline, 2{naphthol and potassium iodide in diethylether, is employed for preparing esteramides, which are subjected to hydrogenation. Aromatic polyamides are prepared by melting together an aromatic diamine and diacids obtained from methoxycarbonylation. Finally, N-Heterocyclic Carbene (NHC) ligands are employed for preparing new palladium complexes which are used in the Suzuki-Miyaura cross-coupling reaction in a water/isopropanol mixture. Other complexes based on copper are employed for developing an inexpensive transmetallation reaction for transferring a NHC ligand from copper to palladium and gold.

Les polymères de phtalonitrile sont obtenus par des réactions d'addition des groupements cyano à haute température et pour un temps long à partir de dérivés de phtalonitrile. Ils trouvent de nombreuses applications dans les domaines de pointe comme l'aérospatiale et la marine. Cependant, leurs performances sont limitées par les inconvénients suivants : (1) fragilité liée intrinsèquement à leur réseau structural, (2) température de fusion élevée, fenêtre de conditions de mise en forme étroite, température de cuisson élevée, cinétique de cuisson faible, (3) Selon la litérature, le traitement du bisphthalonitrile pour obtenir la résine correspondante s'effectue souvent à des températures inférieures à 500°C. Il y a peu d'études sur les matériaux formés à des températures supérieures à celle-ci, (4) Il n'y a pas beaucoup d'études sur la fonctionnalisation de la résine bisphthalonitrile et son domaine d'application doit être élargis. Cette thèse porte sur le dévelopement de méthodes permettant la modification et la fonctionnalisation de la résine bisphthalonitrile conduisant à une amelioration des propriétés mécaniques de celle-ci. De plus, des nanotubes de carbone ayant une morphologie différente et des matériaux capables d'absorber les hyperfréquences ont été obtenus par pyrolyse de la résine bisphthalonitrile en présence de différents catalyseurs de fer et sur une plage de température allant de 600 a 900°C / Bisphthalonitrile polymers are obtained by addition curing reaction of cyano groups upon heating phthalonitrile derivatives at elevated temperature and for an extended period of time. They have found many applications in advanced technologies such as aerospace and marine. However, their performances are limited by the following disadvantages: (1) high brittleness of the inherent network structure; (2) high melting temperature, narrow processing window, high curing temperature, low curing rate and long curing time; (3) according to the literature, the processing temperature of bisphthalonitrile resin-based composites is controlled at 500°C or less, whereas there are few studies on materials formed above 500°C; (4) studies on the functionalization of bisphthalonitrile resins are not abundant and its application range needs to be expanded. Based on the above statement, this thesis is focused on the modification and functionalization of bisphthalonitrile resins. The latter were modified by a variety of methods, resulting in improved mechanical properties. Moreover, carbon nanotubes with different morphologies and microwave absorbing materials were obtained by pyrolysing bisphthalonitrile resins with different metal iron catalysts in the range of 600 to 900°C