Dissertations / Theses on the topic 'Nitrogen – Chemistry'
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1
Wheildon, Andrew R. "Novel nitrogen chemistry." Thesis, University of Nottingham, 1999. http://eprints.nottingham.ac.uk/13326/.
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Chapter One contains a brief overview of zeolites, their structure, uses and synthesis. Chapter Two relates to the attempted synthesis of quinuclidines via a novel 6-endo-trig radical cyclisation. Chapter Three contains a review of the 'Zip reaction' and the attempted synthesis of triazacyclopentadecane derivatives. Chapter Four relates to the synthesis of pyrrolidines via retro-Cope cyclisation methodology. Reviews of the Cope and retro-Cope reactions, nitrone synthesis and nucleophilic addition of carbon nucleophiles to nitrones are included. The synthetic work is split into three sections relating to the electron withdrawing group used to stabilise the carbanion of the nucleophile - ester, sulphone and sulphoxide - and attempts to indicate the utility of the retro-Cope reaction in the diastereoselective synthesis of substituted pyrrolidines.
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Henderson, Neil. "Studies in nitrogen heterocyclic chemistry." Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280300.
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Harrison, James Thomas Henry. "Electrical discharge chemistry of nitrogen oxides." Thesis, University of York, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292592.
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Griffith, Jeraime A. "Nitrogen-based ligands for asymmetric chemistry." Thesis, University of Sussex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418713.
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Simcox, Michael Thomas. "Some aspects of nitrogen heterocyclic chemistry." Thesis, Loughborough University, 1997. https://dspace.lboro.ac.uk/2134/10544.
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Chapter One reviews the use of scandium and lanthanide trifluoromethanesulfonates (triflates) in organic synthesis. Their ability to act as Lewis acids and so promote a wide variety of reactions are illustrated. In particular the review highlights the advantages of scandium and lanthanide triflates over more conventional Lewis acids, such as aluminium(I1I) chloride. Chapter Two describes the use of scandium and lanthanide trifiates in the reaction of acetals with amines to produce imines. The extension of this methodology to the synthesis of nitrogen-containing heterocycles such as isoindolones, isoquinolinones and ~-carboline derivatives are elaborated on. Some limitations of the methodology and the problems encountered with its application to the synthesis of enamines are covered. Chapter Three reports our approach to a novel synthesis of ~-carboline derivatives. The formylation of indole-3-acetic acid derivatives in the 2- position proved difficult and several approaches to this problem are discussed. The attempted cyclisation of imines prepared from 2-formyl- and 2- acetyl-3-indolyl acetic acid compounds are also covered. Chapter Four describes a modified Clauson-Kaas pyrrole procedure using trimethylsilyl trifiate. The selection of reaction conditions in an effort to optimise the procedure are discussed. Chapter Five provides full experimental procedures and analytical data for the reactions described in Chapters Two, Three and Four.
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Pandya, Ashish. "Novel nitrogen containing polymers via Reissert chemistry." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/40120.
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Southcott, M. R. "The chemistry of some novel nitrogen-containing spirocyclohexadienes." Thesis, Nottingham Trent University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379799.
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Montgomery, J. "Synthesis and chemistry of novel bridgehead nitrogen compounds." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/24991.
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Four isomers of pyridpyrrolizinones were made by FVP of the appropriately substituted pyrrole pyridine esters. The mechanism of the cyclisation is believed to follow the cascade mechanism. The structure of two of the ismoers has been confirmed by X-ray crystallography, the NMR properties of all four ismoers is also discussed in detail. The chemistry of 9-azapyrrolo[2,l-a]isoindol-5-one was also investigated, it was shown to undergo ring opening with LAH the product of which can then be repyrolysed to give a pyridopyrrolizine. Ring opening also occurs in methanol to give a nicotinate and the pyrrole ring can be hydrogenated to give a tetrahydropyridopyrrolizinone. The synthesis of pyrrolizin-l-one has been achieved by the FVP of methyl-3- (pyrrol-1-yl)-acrylate over W03 catalyst, the reaction is believed to proceed via an intramolecular electrophilic substitution reaction. The chemistry of pyrrolizin-l-one was investigated, reaction with nucleophiles proceeds via addition across the enone double bond. When a nitrogen nucleophile is used ring opening occurs. Hydrogenation occurs at the enone bond to give a dihydrpyrrolizin-l-one. Pyrrolinzin-l,3-dione was made by the oxidation of l-hydroxypyrrolizin-3-one using pyridinium dichromate. The dione shows ketone properties (eg. Formation of DNP derivative) and, in common with other pyrrolizinones, the lactam unit is readily ring opened by methanol under basic conditions. The active methylene unit of pyrrolinine-l,3dione couples readily with diazonium salts to provide a hydrazone whose structure was confirmed by X-ray crystallography. It also reacts with methoxymethylene Meldrum's acid to give a Meldrumsated pyrrolizine-l,3-dione whose FVP at 700 c gives a pyronopyrrolizinine. Reaction of pyrrolizine-l,3-dione with DMF acetal gives the 2-dimethylaminomethylene derivative which exists as a mixture of rotomers at room temperature. 8-Azaindolizine was made by FVP of DBN over a W03 catalyst. 8-Azaindolizine shows reactivity towards electrophiles in substitution reactions at the 3-position. It also reacts with methoxymethylene Meldrum's acid to give a Meldrumsated derivated whose FVP at 950 C reacts with 3-t-butyl-4-[l-methoxymethylene]-4H-isoxazol-5-one to give a isoxazolone whose FVP at 950 C gives a cyclazine.
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Lunga, Mayibongwe J. "A medicinal chemistry study in nitrogen containing heterocycles." Thesis, Rhodes University, 2018. http://hdl.handle.net/10962/63521.
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Moss, James Russell. "Assessment of Vineyard Nitrogen Management upon Grape Chemistry." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/78150.
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To combat excessive vine vigor, many vintners have employed intensive cover cropping techniques. While cover crops provide a multitude of benefits to the farming system, they can compete for nutrients and water. The seemingly ubiquitous adoption of cover crops in the Eastern United States has led to vines and grape musts which are deficient in nitrogen (N). A must that is deficient in yeast assimilable nitrogen (YAN) can lead to the production of off aromas and stuck or sluggish fermentations. It has also been suggested that musts with limited amino nitrogen sources can result in wines with less fruity aromas than those with a higher starting amino acid content. Varying rates of calcium nitrate were applied to the soil at bloom and foliar urea was sprayed at a Sauvignon blanc and Petit Manseng (Vitis vinifera L.) vineyard. Perennial White and Crimson clover as well as foliar urea applications at véraison were utilized at a Vidal blanc (Vitis spp.) site. Foliar urea was effective at significantly increasing YANs in all experiments with some year to year variation in efficacy. Foliar urea applications slightly favored the production of ammonia over primary amino nitrogen. While most of the measured amino acids in fruit increased in concentration with the application of either soil or foliar N, foliar applications were more effective at increasing fruit amino acids. Of the amino acids measured, arginine and glutamine were the most increased by foliar urea applications, whereas proline was relatively unaffected. The use of clover as a perennial under-vine cover crop did not increase berry YAN. The application of foliar urea sprays may present an effective means by which vintners can easily increase must YANs and amino acid contents.Master of Science in Life Sciences
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Ritter, Halle (Halle Caitlan). "Nitrogen chemistry in an urban bioretention system in Singapore." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82824.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 35-37).
An investigation into the nitrogen chemistry of the anoxic layer of an urban constructed wetland in Singapore was conducted. This pilot-scale wetland treats stormwater runoff from the Balam Estate housing development for several water quality parameters of concern, including nitrate. Earlier sampling in the wetland had indicated that the concentration of nitrate was lower in the outflow from the rain garden than in its inflow, but no research had been done on other nitrogen species or transformation pathways. Preliminary analyses suggest that, although the saturated layer is sufficiently anoxic and denitrification is occurring as per performance objectives, organic nitrogen is being added to the infiltrating water throughout this layer, causing a net export of total nitrogen from the anoxic zone. This organic nitrogen could be either re-released from reserves adsorbed onto organic material during previous storm events, or leached directly from the anoxic layer material which includes wood chips and sand. Readings at outflow pipes indicate that a percentage of this nitrogen is likely re-mineralizing to ammonia upon exposure to more oxygen-rich conditions in the outflow pipes. Further study in the Balam Rain Garden using isotope labeling to more clearly delineate nitrogen fate and transport is suggested.
by Halle Ritter.
M.Eng.
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Ho, Yee-Ping. "Some studies in nitrogen heterocyclic chemistry using Reissert compounds." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/33250.
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The thesis reports the first examples of Reissert compounds prepared from five-membered ring heterocycles. The method utilises trimethylsilyl cyanide as the key reagent in a single phase non-aqueous medium. Previous attempts to synthesise such compounds have failed because, under the conventional two phase conditions, the reaction either does not proceed or ring opening of the heterocycle occurs. Reaction of benzothiazole with an acid chloride (aliphatic, aromatic or chloroformate) and trimethylsilyl cyanide in dichloromethane has been shown to give rise to 3-acyl-2-cyano-2,3-dihydrobenzothiazoles. Eight such five-membered ring Reissert compounds have been prepared, mostly in yields exceeding 70%. The mechanistic involvement of trimethylsilyl cyanide is discussed. The novel Reissert compounds have been shown to be versatile intermediates for the further modification of the starting heterocycles.
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Elder, Susan Margaret. "The coordination chemistry of some polydentate nitrogen-donor ligands." Thesis, University of Cambridge, 1990. https://www.repository.cam.ac.uk/handle/1810/272957.
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Palmer, Catherine Ann. "The coordination chemistry of some nitrogen-sulphur donor ligands." Thesis, University of Cambridge, 1990. https://www.repository.cam.ac.uk/handle/1810/272977.
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Crossland, Justin L. 1982. "Iron coordination chemistry of nitrogen, diazene, hydrazin, and ammonia : Investigating the mechanism of nitrogen reduction to ammonia." Thesis, University of Oregon, 2009. http://hdl.handle.net/1794/10336.
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xvi, 233 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.The coordination chemistry of iron with N 2 is becoming increasingly important as chemists try to find alternative routes to the production of ammonia. Current biological and industrial processes use iron to catalyze the formation of ammonia from N 2 ; however, huge amounts of energy are required for this conversion. Understanding how dinitrogen and other intermediates of dinitrogen reduction interact with iron could lead to energy efficient processes for the production of ammonia. This dissertation explores the synthesis and reactivity of an iron dinitrogen complex that reacts with acid to produce ammonia at room temperature and pressure. This dissertation also explores the progress toward determining the mechanism of this reaction in hopes of improving the yields of ammonia. Chapter I describes both the biological nitrogen fixation process and the industrial production of ammonia and provides an in-depth look at progress toward an alternative route to ammonia using iron complexes described in the literature thus far. Chapter II details the synthesis, characterization, and reactivity of dihydrogen and dinitrogen complexes of iron. These complexes are precursors to the active ammonia producing complex and are among a handful of dihydrogen and dinitrogen complexes that have been structurally characterized. Chapter III explores the synthesis and stability of Fe(DMeOPrPE) 2 N 2 . This complex produces ammonia and hydrazine upon protonation with a strong acid. Optimizing the yield of ammonia from this protonation is also described. Chapter IV discusses the synthesis and reactivity of several complexes of iron containing intermediates relevant to dinitrogen reduction, including diazene (N 2 H 2 ), hydrazine (N 2 H 4 ), and ammonia. By studying these intermediates, a mechanism of ammonia formation from the protonation of Fe(DMeOPrPE) 2 N 2 is proposed that may also provide insights into the mechanism of nitrogenase. Chapter V provides a summary of this research. This dissertation includes previously published and unpublished co-authored material.
Committee in charge: Darren Johnson, Chairperson, Chemistry; David Tyler, Advisor, Chemistry; Michael Haley, Member, Chemistry; Kenneth Doxsee, Member, Chemistry; Scott Bridgham, Outside Member, Biology
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Cornell, Sarah Elizabeth. "Dissolved organic nitrogen in rainwater." Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296336.
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McGuigan, H. "Synthetic studies on nitrogen heterocycles." Thesis, University of Glasgow, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375469.
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Ritchie, Robert B. "Chemical routes to atomic nitrogen." Thesis, University of Aberdeen, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359346.
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Chapter 1 contains a general introduction and review of the field of atomic nitrogen chemistry. Included here is mention of the occurrences, generation, detection and analysis, reactions and uses of atomic nitrogen. A summary of previous work towards the chemical generation of atomic nitrogen in solution is given, this being stated as the overall aim of the thesis. This aim encompasses bond-breaking: (a) in nitrogen containing heterocycles upon mild photolysis or thermolysis, (b) in azidyl radicals. Chapter 2 describes the benzocinnoline N-imine system along with its isomeric 5H-dibenzo[1,2,3][d,f]triazepine with a view to the selective derivatisation of the latter. The photochemical and oxidative reactions of these systems are investigated by esr. 1H-Benzotriazole and selected derivatives are examined as triazenyl models for the triazepinyl system. Chapter 3 considers the chemistry of the 1,3,4-dioxazol-2-ones particularly the unreported 5-O-linked derivatives which are sought as possible precursors to the novel 1,3,4-dioxazolidine-2,5-diones themselves potential atomic nitrogen precursors. Chapter 4 concerns the 1,2,4-dithiazolidine-3,5-diones as potential atomic nitrogen precursors and two routes are pursued to the little reported unsubstituted parent 1,2,4-dithiazolidinedione. Chapter 5 departs from the heterocyclic theme of chapters 2-4 and considers the generation and fragmentation of the azidyl radical as a possible source of atomic nitrogen. Evidence for the production of atomic nitrogen from this radical, generated from the persulphate oxidation of azide anion, is discussed.
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Lamm, Ashley, and Ashley Lamm. "Fundamental Chemistry of 1,2-Dihydro-1,2-Azaborines." Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12514.
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Benzene and its derivatives are ubiquitous in chemical research, with applications ranging from material science to biomedical research. 1,2-Dihydro-1,2-azaborine is a benzene mimic which replaces a CC bond with a BN bond. The basic science and applications of 1,2-azaborines is relatively underdeveloped. This thesis expands the fundamental understanding of 1,2-azaborines. Chapter I describes the air and moisture stability of 1,2-azaborines. Chapter II introduces nucleophilic aromatic substitution reactions that the parent 1,2-dihydro-1,2-azaborine will undergo. Chapter III discusses a trimerization reaction that 1,2-dihydro-1,2-azaborine can perform, which is unique from benzene. Chapter IV examines a novel protection free synthesis of 1,2-azaborines, which provides a more direct route to functionalized 1,2-azaborines. Chapter V discusses the novel deprotection of the N-silicon using an amide, giving one of the first 1,2-azaborine pharmaceutical mimics. Finally, chapter VI summarized miscellaneous contributions I have made to the basic science of 1,2-azaborines.
This dissertation includes previously published and unpublished co-authored material.10000-01-01
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Georgiou, George Cleovoulos. "Nitrogen-rich oximic complexes." Thesis, London Metropolitan University, 1988. http://repository.londonmet.ac.uk/3051/.
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Chua, Zhijie. "Coordination chemistry of high oxidation nitrogen containing amides and heterocycles." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119473.
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The catalytic reduction of nitrous oxide (N2O) to dinitrogen (N2) by nitrous oxide reductase (N2OR) is poorly understood. The N2O molecule is a poor ligand with relatively sparse coordination chemistry. We proposed the synthesis of probable nitrous oxide precursors which can be coordinated to transition metals prior to conversion to nitrous oxide. Nitramide, H2NNO2, 2-1, and the related nitrogen amide acids N-nitroamide 2-2, 2-3; N-nitrocarbamate 2-4, 2-5, N-nitrosocarbamate 2-6, 2-7; N-nitrosulfonamide 2-8 have been synthesized as possible nitrous oxide precursors for coordination studies with transition metals. The silver salts of the conjugate base of the nitrogen acids N-nitroamide 2-2Ag; N-nitrocarbamate 2-4Ag, 2-5Ag; N-nitrosocarbamate 2-6Ag; N-nitrosulfonamide 2-8Ag are synthesized from the reaction of the acids with Ag2CO3. Similarly the potassium salts of the nitrogen acids N-nitroamide 2-2K; N-nitrocarbamate 2-4K; N-nitrosocarbamate 2-6K; N-nitrosulfonamide 2-8K are synthesized from the reaction of the nitrogen acids with K2CO3 or CH3OK. To investigate the pi-acidity of the nitrogen acids, a series of Ir(I) complexes of the nitrogen acids, trans-Ir(η1-X)(CO)(PPh3)2, (X = nitrogen acid) N-nitroamide 3-3; N-nitrocarbamate 3-4, 3-5; N-nitrosocarbamate 3-6; N-nitrosulfonamide 3-7 are synthesized from the reaction of Vaska's complex, trans-Ir(Cl)(CO)(PPh3)2 (3-1) with the silver salts of the conjugate base of the nitrogen acids (N-nitroamide 2-2Ag; N-nitrocarbamate 2-4Ag, 2-5Ag; N-nitrosocarbamate 2-6Ag; N-nitrosulfonamide 2-8Ag). Comparative studies with the related amides, dinitramide and bistriflimide, have also been done.The oxidative addition of the nitrogen acids (N-nitroamide 2-2, 2-3; N-nitrocarbamate 2-4, 2-5) to trans-Ir(Cl)(N2)(PPh3)2 (3-2) afford the Ir(III) complexes of the nitrogen acids, Ir(η2-X)(H)(Cl)(PPh3)2, (X = nitrogen acid) N-nitroamide 3-11, 3-12; N-nitrocarbamate 3-13, 3-14. The 31P, 1H NMR and IR spectroscopic reaction monitoring profiles of the oxidative addition reactions give evidence of reaction intermediates that eventually convert to the final product. The reaction of 3-11 with CO and P(CH3)2Ph result in the formation of multiple isomers of the addition products and also phosphine substitution. Addition of methyl triflate to 3-11 in CH3CN is found to result in the substitution and loss of the nitrogen acid. The Re(I) complexes of the nitrogen acids , trans-Re(η2-X)(CO)2(PPh3)2, (X = nitrogen acid) N-nitroamide 4-8; N-nitrocarbamate 4-9; N-nitrosulfonamide 4-12 are synthesized from the reaction of trans-[Re(CH3CN)2(CO)2(PPh3)2](Y), (Y = ClO4: 4-3, BF4: 4-7) with the potassium salts of the conjugate base of the nitrogen acids 2-2K, 2-4K and 2-8K respectively. The reaction of 4-7 with N-nitrosocarbamate 2-6K at room temperature gives mostly the kinetic isomer trans-Re(η2-X)(CO)2(PPh3)2 (4-10). The same reaction at reflux conditions gives mostly a thermodynamic isomer Re(η2-X)(CO)2(PPh3)2 (4-11A). Complex 4-9 and 4-10 are found to crystallize in an unusual space group R-3 that gives a large unit cell with huge solvent channels between the Re complexes and CH2Cl2 solvate molecules. The Dimroth/amidine rearrangement of benzotriazoles has been shown to exist in solution for 5-1 by variable temperature 19F NMR. The reaction of 3-2 with the benzotriazoles 5-1 and 5-2 gives the new Ir(I) complex, trans-Ir(Cl)(η1-5-1)(PPh3)2 (5-7) and Ir(III) complex, trans-Ir(Cl)(η3-5-2)(PPh3)2 (5-8) respectively. Complex 5-7 undergoes addition and substitution reactions readily to give multiple isomers while 5-8 is inert towards nucleophiles.La réduction de l'oxyde nitreux (N2O) en diazote (N2) par le réductase de l'oxyde nitreux (N2OR) est très peu comprise. La molécule N2O n'est pas un très bon ligand et à une coordination chimique limité. Nous proposons la synthèse de précurseurs de l'oxyde nitreux qui peuvent se coordonner aux métaux de transitions avant leurs conversions en oxyde nitreux. Nitramide, H2NNO2, 2-1, et les acides d'azotes amidés N-nitroamide 2-2, 2-3; N-nitrocarbamate 2-4, 2-5, N-nitrosocarbamate 2-6, 2-7; N-nitrosulfonamide 2-8 ont étés synthétisés en tant que de possible précurseurs de l'oxyde nitreux pour des études de coordination avec des métaux de transitions. Les sels d'argents des bases conjugués des acides d'azotes N-nitroamide 2-2Ag; N-nitrocarbamate 2-4Ag, 2-5Ag; N-nitrosocarbamate 2-6Ag; N-nitrosulfonamide 2-8Ag ont étés synthétisés par les réactions des ces acides avec Ag2CO3. Similairement, les sels de potassium des bases conjugués des acides d'azotes N-nitroamide 2-2K; N-nitrocarbamate 2-4K; N-nitrosocarbamate 2-6K; N-nitrosulfonamide 2-8K ont étés synthétisés par les réactions des ces acides soit avec K2CO3 ou CH3OK. Pour examiner l'acidité du système pi de ces acides d'azotes, des séries the complexes d'acides d'azotes d'Ir(I) trans-Ir(η1-X)(CO)(PPh3)2, (X = acide d'azote) N-nitroamide 3-3; N-nitrocarbamate 3-4, 3-5; N-nitrosocarbamate 3-6; N-nitrosulfonamide 3-7 ont étés étés synthétisés par les réactions du complexe de Vaska, trans-Ir(Cl)(CO)(PPh3)2 (3-1), avec les sels d'argents des bases conjugués des acides d'azotes (N-nitroamide 2-2Ag; N-nitrocarbamate 2-4Ag, 2-5Ag; N-nitrosocarbamate 2-6Ag; N-nitrosulfonamide 2-8Ag). Des études comparatives avec des amides reliés, dinitramide et bistriflimide, ont aussi étés faites. Les complexes de Re(I) des acides d'azotes, trans-Re(η2-X)(CO)2(PPh3)2, (X = acide d'azote) N-nitroamide 4-8; N-nitrocarbamate 4-9; N-nitrosulfonamide 4-12 ont étés synthétisés par les réactions de trans-[Re(CH3CN)2(CO)2(PPh3)2](Y), (Y = ClO4: 4-3, BF4: 4-7) aves les sels de potassium des bases conjugués des acides d'azotes 2-2K, 2-4K et 2-8K respectivement. La réaction de 4-7 avec N-nitrosocarbamate 2-6K à température de la pièce procure principalement l'isomère cinétique trans-Re(η2-X)(CO)2(PPh3)2 (4-10). La même réaction en condition de reflux procure principalement l'isomère thermodynamique Re(η2-X)(CO)2(PPh3)2 (4-11A). Les complexes 4-9 et 4-10 cristallisent dans un groupe d'espace insolite, soit R-3, qui à une grande unité cellulaire avec de larges canaux de solvant entre les complexes de Re et les molécules de solvant de CH2Cl2.Le réarrangement Dimroth/amidine des benzotriazoles ont démontré leur existence en solution pour 5-1 via la RMN 19F en température variable. Les réactions de 3-2 avec les benzotriazoles 5-1 et 5-2 donnent de nouveaux complexes d'Ir(I), trans-Ir(Cl)(η1-5-1)(PPh3)2 (5-7) et d'Ir(III), trans-Ir(Cl)(η3-5-2)(PPh3)2 (5-8) respectivement. Le complexe 5-7 subit facilement des réactions de substitution et d'addition pour donner de multiples isomères tandis que le complexe 5-8 est inerte envers les nucléophiles.
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Rahman, Mohammed Shoponur. "Chemistry of mixed donor phosphorus-nitrogen ligands : towards asymmetric catalysis." Thesis, King's College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271393.
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Zhang, Qi. "Chemistry of organic nitrogen in atmospheric waters and fine particles /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
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Togrou, Maria. "Iron, titanium and vanadium coordination chemistry related to nitrogen fixation." Thesis, University of Sussex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364587.
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Coates, Brian. "The stereoselective synthesis of nitrogen heterocycles." Thesis, Queen's University Belfast, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334524.
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Barker, S. J. "Nitrogen heterocycles by flash vacuum pyrolysis." Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383390.
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Kemp, Mark Ian. "Zirconocene mediated synthesis of nitrogen heterocycles." Thesis, University of Southampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242197.
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Wongtap, Hathaichanuk. "A radical approach to nitrogen heterocycles." Thesis, University of Warwick, 1999. http://wrap.warwick.ac.uk/109826/.
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The generation of amidyl radical and carbon centred radicals using both tin hydride and non-tin hydride methods are described. The effect of the nitrogen substituent upon the stereoselectivity of amidyl radical cyclisations onto the alkyl side chain using the tin hydride method was investigated The O-benzoyl hydroxamic acid derivatives were chosen as precursors for these radicals. The results indicated that the tram isomers were the major isomers from the cyclisation reaction. The greatest diastereoselectivity was found when the nitrogen substituent was a methoxy group. However, the cyclisations afforded low yields of the desired sample products due to the difficulty in removing the tin residues from the crude. Amidyl radicals were also generated from cyclohexadienyl functionalised hydroxamide acid derivatives using peroxides as initiators. Due to the rapid reduction of the amidyl radical by hydrogen abstraction from the initial cyclohexadienyl system under these conditions, the cyclisations were not successful. The atom transfer radical cyclisation of allyl trichloroacetate was investigated N- pentyl-2-pyridylmethanimine [164] was reported as an effective ligand in copper mediated cyclisation using Cu(I)Cl The reaction was optimised in order to investigate the effect of ligand concentration, of catalyst concentration, of substrate concentration, and of solvent It was found that two equivalents of ligand with CuCI provided the most effective catalyst while the use of 30mol% of catalyst was essential for the success of the cyclisation A lower yield of product was obtained if the amount of catalyst was lowered and this may be due to its gradual decomposition The reaction was best carried out at a concentration between 0.065 to 0.13M solution in order to suppress telomerisation processes and intermolecular addition and reduction processes due to hydrogen abstraction reactions At higher concentrations more telomers were obtained. In toluene solution, the CuCl-[164] catalyst system provided faster reactions when compared with the same reaction in acetonitrile solution. The Cu(I)Cl-[164] was also used as an effective catalyst system for the atom transfer radical cyclisations of N-allyl trichloroacetamides. Intermolecular capture of cyclised radicals by a highly radicophilic reagent such as diphenyl diselenide was possible whereas the transfer of a cyano group by ethyl cyanoformate not. The cyclisation of tribromoacetamide derivatives using Cu(I)Br-[164] was also investigated. In addition, the effect of the structure of the ligand on the rate and diastereoselectivity of the cyclisation of N-allyl-N-tosyl dichloromethylacetamide was also studied The cyclisation afforded the trans isomer as the major product. Ligands with more bulky N-substituents gave slower cyclisations and smaller diastereomer excesses. Finally, the synthesis of medium-size lactams was investigated. Unexpectedly, attempts to synthesis the bigger ring lactams failed completely. The precursors underwent [1,5] aromatic rearrangement instead of cyclisation. In addition, the intramolecular 1,5 hydrogen abstraction of the starting amide radicals afforded significant amounts of reduced products.
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Jordan, Philip Henry. "The photocatalytic abatement of nitrogen oxides." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296578.
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Fox, Peter Anthony 1965. "Synthesis and reactivity of organotantalum complexes containing nitrogen ligation." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290672.
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This work examines various aspects of hydrodenitrogenation catalysis. Various tetrahydroquinolinyl (THQ) and indolinyl (DHI) complexes of tantalum were synthesized including: Ta(THQ)ₓCl₅₋ₓ(x = 1 to 5), Ta(DHI) ₓCl₅₋ₓ(THF) (x = 1 and 2). In addition, THQ and DHI complexes containing aryloxide (OAr = 2,6-diisopropylphenoxide) and alkyl complexes were also synthesized: Ta(THQ)(OAr)Cl₃(OEt₂), Ta(THQ)₂(OAr)₂Cl, Ta(THQ)(OAr)R₃Cl (R = Me and Et), Ta(THQ)₂(OAr)₂R (R = Me and Et), Ta(DHI)(OAr)Cl₃(OEt₂), and Ta(DHI)₂(OAr)₂Cl. The effects of sulfur ligation versus oxygen ligation was examined by comparison of the crystal structures of Ta[η²(N,C)-2,4,6-tri-t-butylpyridinel](OAr)₂(OᵗBu) and Ta[η²(N,C)-2,4,6-tri-t-butylpyridine](OAr)₂(SᵗBu). The sulfur ligand donates less π density to the metal center, resulting in a longer Ta-C bond for the pyridine ligand. The arene complexes (η⁶C₆Me₆)Ta(OAr)(SAr')Cl and (η⁶-C₆Me₆)Ta(OAr)(SAr'')Cl were also synthesized. These arene-thiolate complexes do not appear to bind quinoline, unlike the oxygen analogs A number of Ta(η⁴-diene)(OAr)₃ complexes were synthesized (diene = butadiene, isoprene, 2,3-dimethylbutadiene, 1,3-cyclohexadiene) and their reactivity with respect to nitriles examined. Nitriles typically insert into Ta(η⁴-isoprene)(OAr)₃ to form (ArO₃Ta(CH₂CHCMeCH₂CRN) which can then be thermally rearranged to (ArO) ₃Ta(=NCRCH₂CHCMeCH₂) (R = Me, Ph, ᵗBu). Similar reactivity is observed with butadiene and 2,3-dimethylbutadiene diene complexes. The Ta(η⁴-C₄H₆)(OAr)₃ complex is also capable of inserting two nitriles to form (ArO)₃Ta(NCRCH₂CHCHCH₂CRN), whereas Ta(η⁴-1,3-cyclohexadiene)(OAr)₃ only forms the bis-insertion product. Aspects of the formation of the above complexes with specific concentration on the tantalum-nitrogen interactions are presented.
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DeGraffenreid, Allison Lynne. "Studies on boron - nitrogen and boron - gadolinium compounds." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1294835746.
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Burnett, Duane Arthur. "Synthesis of nitrogen containing heterocycles /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487264603219377.
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Selim, Masud Ahmed. "Detailed and reduced chemistry for NOx formation and destruction in flames." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297270.
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Donnelly, Shileen Agnes. "Electrochemical and related reactions of nitrogen heterocycles." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282130.
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Afzal, A. "Effects of nitrogen on CVD diamond growth." Thesis, Manchester Metropolitan University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286081.
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Martin, Nicolas. "Gold-catalysed reactions of Nitrogen containing molecules." Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/1222/.
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The development of several new gold-catalysed reactions are described. Two new strategies have been employed to access pyrroles by the cycloisomerisation of alkynyl aziridines, and the formation of α,β-unsaturated imides by the oxidation of ynamides has been developed. A rare gold-mediated vinylidene rearrangement of brominated or silylated alkynes has been used to prepare brominated or silylated 2,4-substituted pyrroles regioselectively. The practical applicability of this process was limited by instability of products under the reaction conditions. Cationic gold catalysis was used in a synthesis of 2,4- and 2,5-substituted pyrroles from alkynyl aziridines. The role of counterion in these processes was studied and shown to be important in determining reaction outcomes. A Ph\(_3\)PAuCl/AgOTs catalyst system, allows 2,5-substituted pyrroles to be regioselectively synthesised in an atom-economical manner in near quantitative yield. From the same aryl-substituted starting materials the 2,4-substituted pyrrole isomer were accessed preferentially when a Ph\(_3\)PAuCl/AgOTf catalytic system was employed. A reaction mechanism accounting for the reaction outcome was proposed on the basis of \({^13}\)C- and deuterium-labelling studies. A new gold-catalysed synthesis of α,β-unsaturated imides was developed using a ynamide oxidation approach. Gold carbenoid intermediates can be formed regioselectively by action of an external oxidising agent, and were used in 1,2-insertion reactions.
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Zhao, Hailiang. "Computational study of the boron-nitrogen dative bond." Thesis, Stellenbosch : Stellenbosch University, 2008. http://hdl.handle.net/10019.1/2846.
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Thesis (MSc (Chemistry and Polymer Science))--Stellenbosch University, 2007.In this study, ten selected boron-nitrogen compounds and three borane carbonyl complexes were investigated by a number of computational methods. It is well known that the B-N dative bond is shorter in the solid state than in the gas phase. The B-CO distance, on the other hand, displays the opposite effect. Quantum mechanical techniques at the Hartree-Fock, Møller-Plesset second-order and Density Functional Theory level were used to calculate the geometries of the isolated molecules and to compare them with those found in molecular clusters built to model the solid state. It was found that calculated geometries were very sensitive to the choice of the basis set. The effects of dipole-dipole interactions were further investigated by applying an external electric field with varying strength to isolated molecules, and by replacing the central molecule in a cluster with a different compound. The B-N bond was found to respond much more to the applied field than the B-CO bond. An effort was made to correlate the lengthening or shortening of the dative bond to the strength of the crystal field, the latter being calculated classically from point charges. Unfortunately, large differences were noted between the charges calculated with common methods like Mulliken or Merz-Kollman-Singh. Furthermore, an analysis of 67 crystal structures taken from the Cambridge Structural Database did not reveal a correlation between the length of the B-N bond and the crystal field calculated with Charge Equilibration charges. Finally, a valence force field was developed for H3N-BH3. It was shown that a much better fit of the vibrational spectrum can be obtained if the B-N stretching mode is assigned to the 603 cm-1 band rather than the peak observed at 968 cm-1.
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Tundel, Rachel E. (Rachel Elizabeth). "Advances in palladium-catalyzed carbon-nitrogen bond forming processes." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36283.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.Vita. Leaf 68 blank.
Includes bibliographical references.
Chapter 1. Microwave-assisted, palladium-catalyzed C-N bond-forming reactions with aryl/heteroaryl nonaflates/halides and amines using the soluble amine bases DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) or MTBD (7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene) and a catalyst system consisting of Pd2dba3 and ligands (XantPhos, 2-dicylcohexylphosphino-2',4',6'-triisopropyl-1,1 '-biphenyl (XPhos) and 2-di-tert-butylphosphino-2',4',6'-triisopropyl-1, '-biphenyl) resulted in good to excellent yields of arylamines in short reaction times. Chapter 2. Using a catalyst comprised of the bulky, electron-rich monophosphine ligand di-tert-Butyl XPhos (2-di-tert-butylphosphino-2',4',6'-triisopropyl-1,1'-biphenyl) and Pd2dba3 with sodium tert-butoxide as the base, amino heterocycles were coupled successfully with aryl/heteroaryl halides in moderate to excellent yields.
by Rachel E. Tundel.
S.B.
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England, Anthony F. (Anthony Francis). "The thorium benzyne and the cerium(IV)-nitrogen bond." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36549.
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George, Linda Acha. "Development of a Direct, Low Pressure, Laser-Induced Fluorescence Measurement Technique for NO2., Ambient Measurements and Urban NOx Chemistry." PDXScholar, 1991. https://pdxscholar.library.pdx.edu/open_access_etds/1144.
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Nitrogen oxides control the global formation of ozone in the lower atmosphere and influence the much higher levels of ozone formed in areas subjected to photochemical air pollution. As an important member of the nitrogen oxide family, N02 plays a significant role in serving as the only known source of ozone (through photolysis) in the lower atmosphere and as sink for HO via the formation of nitric acid. Ozone can be destroyed by reaction with another member of the nitrogen oxide family, nitric oxide (NO), to reform N02. This cycle between NO, N02 and 03 is known as the NOx-03 photostationary state (PSS). Imbalances in this cycle have been used to calculate ambient levels of oxidants (such as R02 and H02) responsible for ozone production. Consequently, accurate N02 measurements are critical to making meaningful measurements of the imbalances in the NOx-03 photostationary states (PSS). A low pressure laser-excited fluorescence technique (FAGE) for the direct determination of atmospheric N02 has been developed. This technique has been explored with both a Nd-YAG laser (1.4 W, 532nm, 30Hz) and a Cu-vapor (1.2 W, 511nm, 5.6kHz) laser. The detection limits for these instruments, under laboratory conditions and a signal collection time of 20s (lOs each signal and background), have been determined to be 450 and 350pptv N02, respectively. In these systems, the background was measured by chemically reducing N02 with FeS04°7H20. Ambient measurements of the NOx-03 photostationary state (PSS) were undertaken on a rooftop monitoring site in downtown Portland, Oregon. N02 was monitored with the Cu-vapor system. Nitric oxide and ozone were monitored with standard instruments. Data for three days in 1990 are presented. Overall these data sets clearly show that despite daily changes in concentration of NO, N02 and 0 3 of factors of 4-10 each, the PSS remains relatively constant to within -50%. This is in itself strong confIrmation of the primary importance of the NOx-03 photo stationary state in controlling the concentrations of these species at these levels. In addition, these experiments also serve to demonstrate that the monitoring instruments, including FAGE-N02, are not subject to serious interferences or artifacts at these concentration levels.
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Phanopoulos, Andreas. "The coordination chemistry and catalytic applications of nitrogen-centred triphosphine ligands." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/30832.
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Tripodal triphosphine ligands featuring a heteroatomic apical moiety of general formula R'E(CH2PR2)3 are under-investigated compared to mono- or bidentate phosphines, and to the carbon-centred analogue CH3C(CH2PPh2)3. The work presented in this thesis is an investigation of the nitrogen-centred triphosphine ligands N(CH2PR2)3 (NP3R), including coordination behaviour and catalytic applications. behaviour and catalytic applications. The modular synthesis of NP3R ligands allowed the substituents at phosphorus to be replaced, generating novel symmetrical ligands (with three identical phosphine arms), as well as unsymmetrical "mixed-arm" derivatives with PPN coordinating moieties. Coordination of these, and previously reported ligands to tungsten(0) precursors afforded complexes with the NP3R ligands in either a bi- or tridentate coordination mode. Evaluation or the steric and electronic properties of the NP3R ligands suggest that the diff erent coordination modes observed are primarily electronically controlled, with more electron-donating phosphines coordinating in a bidentate fashion. A comparative study of the phenyl and cyclopentyl ligands NP3Ph and NP3Cyp coordination to ruthenium precursors displayed similar trends to those observed during tungsten coordination. The electronic parameters of the ligands, as well as oxidation state of the metal were crucial in determining the denticity of NP3R coordination. A facile route to synthesise the dihydride complexes, including [RuH2(CO)(k3-NP3Ph)], was established, which proceeded under mild conditions and via the air- and moisture-stable carbonate complex [Ru(CO3)(CO)(k3-NP3Ph)]. Three pre-formed ruthenium complexes, as well as systems generated in situ were evaluated as catalysts for the hydrogenation of the biomass-derived levulinic acid to value-added compounds. In the absence of acidic co-catalyst, quantitative conversion of levulinic acid to 1,4-pentanediol was achieved using the pre-formed ruthenium complex [RuH2(PPh3)(k3-NP3Ph)], which crucially featured a labile PPh3 ligand. The addition of catalytic amounts of a strongly acidic component that also features a highly non-coordinating conjugate base (HNTf2) allowed the conversion of levulinic acid to 2-MTHF in 87% yield, making this one of the most active systems reported for this reaction under relatively mild conditions.
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Suddick, Emma C. "Nitrogen photo-chemistry and the dynamics of CDOM in aquatic environments." Thesis, University of Aberdeen, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485377.
Full textAbstract:
Photochemical ammonium production and photo-bleaching of chromophoric dissolved organic matter (CDOM) kinetics were studied in a variety of aquatic environments including freshwater samples of peatland origin, Caithness, a Tyne Estuary (NE, U.K.) estuary and the Iberian Sea. The main aims of the study were to assess seasonal variability within the peatland catchments, in conjunction with a study of regional and geographical variability of dissolved organic matter (DOM) and ammonium photo-production. Samples collected from a variety of aqueous environments covered the CDaM .absofPtion coefficient at 350 nm (a350) range 0.3 to 69.0 m-I. Selected, filtered samples (n=21) were exposed to natural and artificial light, in order to study ~+ photo-production CDaM photo-bleaching. The photo-chemical degradation of CDaM, as indicated by decreases in a350 over time, also led to increases in the spectral slope of sample absorbance over the wavelength range 290-350 nm, and losses of total fluorescence intensity. In addition we observed hypsochromic shifts of long-wave, humic-like fluorescence (fluorophore A). Photo-chemical ammonium release was observed in 19 of the total 21 irradiation experiments. However the kinetics of ammonium production were complex with 4 of the 21 samples showing a near-linear increase in NH/ concentration while other samples showed an initial lag phase, followed by production and then a decline in NH/ concentrations. In order to assess possible impacts of ~+ release on N balance we estimated NH4+ photoproduction potentials from concentration differences between the initial values and maximum ~+ values divided by irradiation time (i1t). Thus obtained ~+ photo-production potentials between sites ranged from 0 to 3.57 JIM r1 h-I (mean ± stdev 0.7) under solar noon irradiance levels. Using calculated daily sky irradiance and seasonal correction factors, annual depth integrated ~+ photo-production rates were estimated, ranging from 0.06 to 8.05 JIMNm-2 yrI( mean ± stdev 2.73). The photo-chemical production ofNH/ indicates that photo-chemically induced nitrogen release could potentially be an important source of biologically labile nitrogen to aquatic ecosystems, with severe impacts upon the biogeochemistry and nutrient limitation of these environments when compared to N-reservoir size and other N fluxes. However, compared to N deposition photo-ammonification is not a major source ofN. Key words: Dissolved organic matter, chromophoric dissolved organic matter, photoammonification, peatlands, estuaries, marine, and fluorescence.
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De, Souza Jaisa Soares. "Aspects of vanadium, iron and titanium chemistry related to nitrogen fixation." Thesis, University of Sussex, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283147.
Full textAbstract:
This project concerned the basic chemistry of VD, Vm and FeD (iJ because of interest in the role of vanadium and iron in the electron-transfer processes catalysed by the nitrogenases, and (iiJ to try to rationalise the fragmented data available on the chemistry of low-oxidation-state vanadium and its reactions with iron(II) compounds. In order to increase the range of FeD materials available for reaction with VD, the dinuclear complex [{FeCI(tmeda)h{Jt-Cl)2] and the mononuclear [FeCI2(tmeda)2] (tmeda = N,N,N',N'-tetramethylethylenediamine) were synthesised and characterised by chemical and physical methods including X-ray diffraction. The reaction between vanadium(II) or iron(II) compounds, such as [MCI2(tmeda)z], and chloride-abstracting agents (e.g. M~SiI or NaBPh4) afforded trinuclear ionic complexes containing [M3Cl3Y2(LL)3]+ , where M = FeDor VD, Y = chloride and LL = bidentate amine or phosphine; complexes containing Y = methoxide and M = yD were isolated from methanol solutions. The planar {M3CI3} core is highly stable and remains intact during substitution of the axial Y groups and the neutral ligands. Mixed clusters containing both vanadium(II) and iron(II) can also apparently be synthesised, but the similarity of the metal radii in oxidation state II makes characterisation by X-ray diffraction analysis difficult. Attempts to produce yD_ or ym -bridging N2 compounds containing the ligand 2- [(N,N-dimethylamino)methyl]ferrocenyl (L) were not successful. In order to obtain additional information on the reactivity of L towards early transition metals, the cyclopentadienyltitanium (IV) complexes [Cp2Ti(L)CI] and [CpTiLxCl3.J (x = 1-3) were prepared. X-ray diffraction analyses of [Cp2Ti(L)CI] and [CpTi(L)CIJ have shown that L can be monodentate or bidentate, depending on steric constraints about the metal atom. The complex [CpTi(L)(L')] has also been synthesised; L' is a tridentate ligand apparently generated upon heating by intramolecular C-H activation of a methyl substituent on one of the tertiary amino groups of [CpTi(L)3], followed by elimination of neutral [(N,N-dimethylamino)methyl] ferrocene. The complexity of this system and the formation oftrinuclear vanadium(II) complexes possibly account for some of our difficulties in understanding vanadium-dinitrogen chemistry.
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Alias, Yatimah. "Molybdenum-nitrogen chemistry : electrochemical ligand cleavage and coupling reactions; routes to chiral complexes." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267707.
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Strieter, Eric R. "Mechanistic studies on metal-catalyzed carbon-nitrogen bond forming reactions." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32427.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2005.Vita.
Includes bibliographical references.
Mechanistic studies on copper and palladium-catalyzed C-N bond forming reactions are described. To understand the mechanistic details of these processes, several principles of physical organic chemistry have been employed. Chapter 1. We have investigated the mechanism of the copper-catalyzed N-arylation of amides using aryl iodides, i.e., the Goldberg reaction. The focus of the work has been directed towards amides since this reaction remains the most versatile in the presence of Cu(I)/1,2- cliamine catalyst systems. The results provide insights into the role of 1,2-diamines in modulating the coordination environment around Cu(I). The catalyst is more efficient at high concentrations of 1,2-diamine and high concentrations of amide, as revealed by a nonlinear dependence of the rate on 1,2-diamine concentration. Extended premixing times between the Cu(I) precatalyst and the amide lead to an extensive induction period which can be attenuated by replacing the Cu(I) precatalyst with a Cu(II) precatalyst. Evidence for the reduction of the Cu(II) precatalyst through the oxidation of the amide is also presented. Furthermore, we demonstrate that a 1,2-diamine ligated Cu(I)-amidate may potentially serve as the reactive species that undergoes aryl halide activation. This was established through both its chemical and kinetic competency in the stoichiometric N-arylation process. This behavior has important consequences for new catalyst development since these results show the significance of both the diamine and amide in modulating the overall reactivity of the system. Chapter 2.
(cont.) A systematic mechanistic analysis of Pd(OAc)₂/ monophosphino- biaryl-catalyzed C-N bond forming reactions with aryl chlorides has been performed. The results provide insights into the relationship between the steady-state concentration of active Pd and the size and substitution pattern of the monophosphinobiaryl ligands. These insights into the nature of catalyst activation help highlight the importance of establishing a high concentration of active catalyst. The catalyst derived from the bulkiest ligand in the series, the tri-i-propyl ligand 13, exhibits both accelerated rate and the increased stability required for practical application of this reaction.
by Eric R. Strieter
Ph.D.
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Houmes, Joel David. "New routes to nitride materials : oxide precursors and nitrogen plasmas." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/41411.
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Klingensmith, Liane M. (Liane May). "Mechanistic studies on palladium-catalyzed carbon-nitrogen bond forming reactions." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32489.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2005.Vita.
Includes bibliographical references (leaves 68-69).
Precatalyst species present in a solution of Pd₂(dba)₃ and Xantphos were identified as Pd(Xantphos)(dba) and Pd(Xantphos)₂ by use of ³¹p NMR and independent syntheses. Pd(Xantphos)₂ was found to form at high ligand concentrations. To determine whether the formation of this species affected reaction rates, reaction calorimetry was used to explore the rate of the palladium-catalyzed coupling of 4-t-butylbromobenzene and morpholine using the ligand Xantphos at varying palladium to ligand ratios. It was found that catalyst activity is dramatically dependent on the concentration of ligand relative to palladium, due to formation of Pd(Xantphos)₂. Two plausible hypotheses for the low activity of Pd(Xantphos)₂ as a precatalyst are (1) a slow rate of dissociation of a ligand from the bis-ligated species, and (2) the high degree of insolubility of Pd(Xantphos)₂. Magnetization transfer experiments were used to probe the rate of dissociation of ligand for the bis-ligated species, and reaction calorimetry experiments were performed using the more soluble t-butylXantphos in comparison to Xantphos to determine whether the insolubility of' Pd(Xantphos)₂ causes it to have relatively low activity. It was found that solubility is not the main cause for the low activity of Pd(Xantphos)₂, and evidence was given to support the hypothesis that low activity results from the slow dissociation of a ligand from the bis-ligated species.
by Liane M. Klingensmith.
S.M.
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Chang, Kevin Kai. "Custom built atomic force microscope for nitrogen-vacancy diamond magnetometry." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68549.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 27).
The nitrogen-vacancy (N-V) center in diamonds have the potential to be an ultra-sensitive magnetic field sensor that is capable of detecting single spins. Implementing this sensor for general and nontransparent samples is not trivial. For N-V centers to be a useful probe, a way of positioning the NV center with nanometer accuracy while simultaneously measuring its fluorescence is needed. Here, a method of using N-V centers as magnetometer probes by combining this sensor with Atomic Force Microscopy (AFM) is described. A custom AFM was built that allows optical monitoring of the cantilever tip and collection of fluorescence with a high-NA objective from the same side. The AFM has a large open bottom and top and thus provides dual optical access. The motion of the cantilever is measured by optical beam deflection so that a wide range of commercial cantilevers can be used. The AFM and the confocal microscope objective can be locked in position while a piezoelectric stage allows raster scanning of the substrate.
by Kevin Kai Chang.
S.M.
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Leroy, Vincent. "Studies relevant to the synthesis of nitrogen-containing natural products /." The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487864485229217.
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Guy, Collette S. "New approaches to nitrogen heterocycles via radical cyclisations." Thesis, University of Warwick, 2013. http://wrap.warwick.ac.uk/63951/.
Full textAbstract:
The work presented in this thesis focuses on the use of radical cyclisations to synthesise nitrogen heterocycles. Chapter 1 provides an introduction to radical cyclisations and the development of conditions over the past couple of decades. It also gives an introduction to atropisomerism, a phenomenon present in a number of cyclisation precursors, and how this has been exploited to achieve chirality transfer in the cyclisation of acrylanilides. Chapter 2 describes investigations into the effects of alkene substitution on the barrier to rotation about the N-alkenyl bond in enamides. A range of enamides were synthesised and their barriers to rotation were investigated by both 1H VT NMR and racemisation of an enriched atropisomer. Tetrasubstituted enamides were found to have significantly higher barriers to rotation, and in some cases it was possible to separate the two atropisomers at room temperature by chiral HPLC. Chapter 3 describes the results of 5-endo cyclisations of tetrasubstituted enamides. Dependant on the starting material, cyclisations were carried out mediated by both Bu3SnH and copper. Cyclisations of tetrasubstituted enamides proved to be more challenging than previous reported cyclisations of less hindered substrates with a number of by products produced. We have also examined the possibility of whether chirality transfer would be possible in the cyclisation of an enamide with a high barrier to rotation. In Chapter 4 studies into the cyclisations of 2-bromobenzyl enamides are presented. Initial cyclisations were carried out into the Bu3SnH mediated cyclisation of a trisubstituted enamide and the rate of both the 5-exo and 6-endo cyclisation was calculated. The cyclisation of tetrasubstituted 2-bromobenzyl enamides was then attempted, however it proved less successful. The hindered nature of the tetrasubstituted enamides was found to slow the rate of cyclisation significantly leading to the formation of other products. Chapter 5 describes studies into the synthesis of oxindoles via radical cyclisation. Reactions in methanol with CuBr and TPA at 50 oC gave three main products, a reduced compound, an eliminated compound and the target oxindole. Reactions repeated in toluene at 110 oC were much cleaner giving the oxindole product in high conversions.