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1
Sacramento, José Augusto Amorim Silva do. "Estoques e fluxos de C e N em Sistemas agrícolas tradicional e agroflorestais no Semiárido brasileiro." reponame:Repositório Institucional da UFC, 2012. http://www.repositorio.ufc.br/handle/riufc/9049.
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SACRAMENTO, J. A. A. S. Estoques e fluxos de C e N em Sistemas agrícolas tradicional e agroflorestais no Semiárido brasileiro. 2012. 76 f. Dissertação (Mestrado em Agronomia/Solos e Nutrição de Plantas) - Centro de Ciências Agrárias, Universidade Federal do Ceará, Fortaleza, 2012.Submitted by Francisco Lacerda (lacerda@ufc.br) on 2014-09-11T16:46:18Z No. of bitstreams: 1 2012_dis_jaassacramento.pdf: 1162810 bytes, checksum: 1709bb3360f0140cdbc1f905255069ac (MD5)
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The objective was to assess the changes promoted in the stocks and flows of C and N from the soil by farming systems agroforestry (agrosilvipasture - AGP and silvipasture - SILV) and traditional (TR), compared to natural vegetation of Caatinga (VN), after 13 years, the experiment was installed on a typical Ortic Chromic Luvisol, the city of Sobral, Ceará. Soil samples were collected at depths 0-6, 6-12, 12-20, 20-40 and 40-60 cm, relief in four replicates per. Was determined by the total carbon carbon (TOC); total nitrogen (NT) and bulk density. The gas flow was measured using an analyzer in the field of O2, CO2, NO / NO x and SO 2 (UNIGAS Eurotron 3000). To this end, were used for still cameras based on galvanized steel and PVC cover installed in the field. The sampling was done in three replicates, considering the relief plan, convex and concave in each study situation. For each determination were performed triplicate, totaling nine chambers for relief. Soil samples were collected for determination of soil bulk density (Ds) and particle (Dp) and gravimetric moisture (Ug), which allowed the calculation of total porosity (Pt) and the pore space filled with water (EPPA). Among the agroforestry systems studied, the silvipasture, long-term, promoted greater reductions in C stocks and N, the system promoted agrossilvipastroil lower losses and represents a sustainable alternative to sequestration of soil C and N in the Brazilian semi-arid conditions. The traditional cropping system provided a reduction of 58.87 and 9.57 (Mg ha-1), which meant, a reduction of 6.5 and 1.06 (Mg ha-1), for those of TOC and TN, respectively. These results demonstrate the inadequacy of this system for the Brazilian semi-arid conditions. The concave topography (AGP) and flat (SILV) showed the highest values of TOC. For NT the concave shape (VN, AGP, and SILV) showed the highest values. Flows of C-CO2 varied with the time, AGP and SILV being similar to NV in the wet season, while in the dry season are higher. The TR has a different behavior, being higher during the wet season and similar to AGP and SILV in the dry. The flow behavior of NO present without a tendency similar to C-CO2: AGP and SILV presents similar to each other in the wet season, but smaller than VN. During the dry SILV and VN are larger than AGP. In TR NO was not detected in the two periods. The convex shape of relief TR system showed the highest values of C-CO2 fluxes in the wet season. In the dry season were found higher values of C-CO2 flows in AGP, SILV and RT, compared to NV flat terrain. Soil moisture was the variable most correlated with the fluxes of NO, what might be observed in systems SILV and AGP and VN convex reliefs.
Objetivou-se avaliar as alterações promovidas nos estoques e fluxos de C e N do solo por sistemas agrícolas agroflorestais (Agrossilvipastoril – AGP e Silvipastoril – SILV) e tradicional (TR), comparativamente à vegetação natural de Caatinga (VN), após 13 anos, em experimento instalado sobre um Luvissolo Crômico Órtico típico, no município de Sobral, Ceará. Amostras de solo foram coletadas nas profundidades de 0-6, 6-12, 12-20, 20-40 e 40-60 cm, em quatro repetições, considerando os relevos plano, convexo e côncavo em cada situação de estudo. Nestas amostras foram determinados o carbono orgânico total do solo (COT), nitrogênio total (NT), densidades do solo (Ds) e de partícula (Dp) e a umidade gravimétrica (Ug), o que possibilitou o cálculo da porosidade total (Pt) e o espaço poroso preenchido por água (EPPA). O fluxo dos gases foi quantificado no campo utilizando um analisador de O2, CO2, NO/NOX e SO2 (Unigás Eurotron 3000). Para tanto, foram utilizadas câmaras estáticas com base de aço galvanizado e tampa de PVC instaladas no campo em triplicatas, totalizando nove câmaras por relevo. Entre os sistemas agroflorestais estudados, o silvipastoril, em longo prazo, promoveu maiores reduções nos estoques de C e N, enquanto que agrossilvipastoril promoveu menores perdas, representando uma alternativa sustentável para o sequestro de C e N do solo nas condições semiáridas brasileira. O sistema de cultivo tradicional (TR) apresentou redução no período 13 anos de 58,87 e 9,57 Mg ha-1 (6,5 e 1,06 Mg ha-1 ano-1) dos estoques de COT e NT, respectivamente, o que comprova a não adequação deste sistema para as condições semiáridas brasileiras. Os relevos côncavo (AGP) e plano (SILV) apresentaram os maiores valores de estoques de COT, enquanto que para o NT, a forma côncava apresentou os maiores valores, no caso VN, AGP e SILV. Os fluxos de C-CO2 variaram com a época, sendo AGP e SILV semelhantes à VN no período úmido, enquanto no período seco estes mesmos sistemas foram maiores. O TR apresenta comportamento diferenciado, sendo maior no período úmido e semelhante ao AGP e SILV no seco. Os fluxos de NO apresentaram comportamento com tendência diferente do C-CO2: AGP e SILV apresentaram-se semelhantes entre si no período úmido, porém menores que VN. No período seco, SILV e VN foram maiores que AGP. No TR, o NO não foi detectado nos dois períodos. O relevo convexo no TR apresentou os maiores valores de fluxos de C-CO2 no período úmido. No período seco foram encontrados maiores valores de fluxos de C-CO2 em AGP, SILV e TR em relação à VN no relevo plano. A umidade do solo foi a variável que mais se correlacionou com os fluxos de NO, o que pôde ser observado nos sistemas SILV e AGP e na VN relevos convexos.
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Deon, Diana Signor. "Mudança de uso da terra e impacto na matéria orgânica do solo em dois locais no Leste da Amazônia." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-03072013-084639/.
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Mudanças de uso da terra afetam a dinâmica da matéria orgânica e o acúmulo de C e N no solo e estão associadas a emissões de gases de efeito estufa (GEEs). A região Amazônica é relevante para as emissões brasileiras de GEEs oriundas das mudanças de uso da terra. O objetivo deste trabalho foi determinar alterações quantitativas e qualitativas nos estoques de C e N no solo em função de mudanças de uso da terra em Santarém-PA e São Luís-MA. Foram coletadas amostras de solo sob diferentes usos da terra: vegetação nativa, vegetação secundária, pastagem degradada, pastagem melhorada e agricultura anual. Adicionalmente, foram avaliadas áreas de mata queimada em Santarém-PA e de fruticultura e horticultura em São Luís-MA. Houve diferenças entre os solos de vegetação nativa nos dois locais, apesar dos estoques de C e N terem sido similares. Em Santarém, fósforo e granulometria relacionaram-se aos estoques de C e N. Em São Luís a acidez potencial ajudou a estimar o estoque de C; granulometria e capacidade total de troca de cátions estimaram o estoque de N. Os estoques de C e N na vegetação secundária foram similares aos da vegetação nativa nos dois locais e relacionaram-se com a acidez potencial do solo. Em Santarém o estoque de C (0-30 cm) na pastagem melhorada foi maior que na vegetação nativa. Em São Luís, o estoque de C foi semelhante ao da vegetação nativa. Os estoques de N tiveram comportamento similar aos estoques de C. Na pastagem melhorada de Santarém a soma de bases foi importante para estimar os estoques de C e N; em São Luís houve efeito negativo da densidade do solo. Estoques de C e N nas pastagens degradadas foram semelhantes à vegetação nativa, mas foram influenciados por parâmetros diferentes. Áreas de agricultura anual apresentaram estoques de C inferiores aos das pastagens melhoradas e da vegetação nativa e a sua manutenção relaciona-se com a redução da acidez potencial e com o aumento das bases trocáveis. A qualidade da matéria orgânica do solo foi avaliada nas amostras de São Luís. A mudança de uso da terra reduziu o C na fração orgânica (75-2000 ?m), mas os usos mais conservacionistas aumentaram o C nas formas estáveis (< 53 ?m). Vegetação secundária e pastagem recuperada apresentaram índice de manejo de C semelhantes aos da vegetação nativa. A conversão de vegetação nativa para agricultura ou pastagem reduziu o C na biomassa microbiana, mas os sistemas com grande aporte de material orgânico e com reduzida mobilização do solo apresentaram teor de C microbiano similar à vegetação nativa. Pastagem e agricultura também apresentaram os menores quocientes microbianos, indicando condição de estresse da biomassa microbiana.Land use changes affect organic matter dynamics and the accumulation of C and N in the soil and are associated with greenhouse gas emissions (GHGs). Amazon region is relevant to Brazilian GHG emissions from land use changes. The aim of this study was to determine quantitative and qualitative changes in C and N stocks in the soil due to land use changes in Santarém (PA) and São Luís (MA). Soil samples were collected under different land uses: native vegetation, secondary vegetation, degraded pasture, improved pasture and annual agriculture. Additionally, we evaluated burnt forest areas in Santarém (PA) and fruit-growing and horticulture in São Luís MA. There were differences between the soils of native vegetation in both sites, despite the C and N stocks were similar. In Santarém, phosphorus and soil particle size were related to C and N stocks. In São Luís potential acidity was used to estimate C stock; soil particle size and total cation exchange capacity estimated N stock. C and N stocks in secondary vegetation were similar to those of native vegetation in both sites and related with the soil potential acidity. In Santarém C stock (0-30 cm) in improved pasture was greater than in native vegetation. In São Luís, C soil stock was similar to that of native vegetation. N stocks had similar behavior to C stocks. In improved pasture of Santarém sum of bases was important to estimate the C and N stocks; in São Luís there was negative effect of soil density. C and N stocks in degraded pastures were similar to native vegetation, but were influenced by different parameters. Annual agricultural areas had C stocks below those of improved pastures and native vegetation and its maintenance is related to the reduction of soil potential acidity and to the increase of soil exchangeable bases. Quality of soil organic matter was evaluated in samples of São Luís. Land use changes reduced the content of C in organic fraction (75-200 ?m), while more conservationists uses have increased the C in stable shapes (< 53 ?m). Secondary vegetation and improved pasture presented carbon management index similar to native vegetation. Conversion of native forest to agriculture or pasture reduced the C microbial biomass, but systems with large organic material input and with reduced tillage presented microbial C content similar to native vegetation. Pasture and agriculture also presented the smallest ratios of microbial biomass C to total organic C, indicating stress of microbial biomass.
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Durigan, Mariana Regina. "Mudanças nos estoques de carbono e nitrogênio do solo em função da conversão do uso da terra no Pará." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/11/11140/tde-03062013-093119/.
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A atividade de mudança do uso da terra na Amazônia vem sendo apontada como principal fonte de CO2 para a atmosfera em função das emissões de C e N provenientes do solo. A prática de manejo adotada pode influenciar significativamente nos estoques de C e N do solo funcionando como dreno ou fonte de C e N para a atmosfera. Além disso, podem ser alterados: a fertilidade e a densidade do solo bem como as frações e a origem da MOS. Com o objetivo de avaliar o impacto das mudanças de uso da terra na região leste da Amazônia foram coletadas amostras de terra nos principais usos da terra na região de Santarém-PA, em três profundidades: 0-10, 10-20 e 20-30 cm. Através das amostras foi realizada a caracterização físico-química das áreas e foram determinados os teores de C e N do solo e os isótopos ? 13C e ? 15N com a finalidade de quantificar os estoques de C e N do solo e avaliar a dinâmica e origem da MOS. Para um subconjunto de amostras foi realizado o fracionamento físico da MOS e a determinação do C da biomassa microbiana para compreender como a mudança de uso da terra interferiu nessas frações. Somado a essas determinações foi realizada a estimativa dos fatores de emissão com base na metodologia descrita pelo IPCC. Através da caracterização físicoquímica as áreas de estudo são caracterizadas por solos argilosos a muito argilosos. Os maiores valores de pH, macronutrientes, CTC, SB e V% foram observados nas áreas de agricultura (AGR) sugerindo que a utilização de práticas como adubação e calagem, são capazes de alterar os padrões de fertilidade do solo na Amazônia, aumentando seus índices de fertilidade. Para os estoques de C e N pode-se dizer que a mudança de uso da terra na região estudada está contribuindo para as perdas de C e N do solo, principalmente quando a conversão é realizada para áreas de agricultura (AGR) e pastagem (PA) sendo que os estoques de C observados na camada de 0-30 cm nessas áreas foram 49,21 Mg C ha-1 (PA) e 48,60 Mg C ha-1 (AGR). O maior valor de ? 13C foi encontrado nas áreas de pastagens, -25,08?, sugerindo que para as áreas de PA existe diluição isotópica e que parte do C do solo ainda é remanescente da floresta. As frações da MOS apresentaram alterações na quantidade de C e na proporção das frações leve e oclusa, principalmente nos usos AGR e PA. A fração lábil da MOS (C da biomassa microbiana) também apresentou grande diferença entre os usos FLO e AGR (526,21 e 296,78 ?g g-1de solo seco), indicando que a AGR foi o uso que mais alterou os estoques de C e N do solo e também as frações da MOS. Os fatores de emissão calculados confirmam todos os resultados observados em relação a conversão de FLO para AGR, sendo que para esse uso o fator de emissão foi de 0,93 ± 0,033, sendo então o uso que mais emitiu C. Com base nos resultados conclui-se que a introdução de áreas agrícolas na região de Santarém, é a principal causa de perda de C e N do solo e consequentemente é o uso que mais contribui com as emissões de gases do efeito estufa.The land use change in the Brazilian Amazon has been identified as the main source of CO2 to the atmosphere due to emissions of soil carbon and nitrogenl. The management practice adopted can strongly influence the soil C and N stocks and may works like a sink or source of C and N to the atmosphere. Furthermore, can be changed: the soil fertility and bulk density as well as the SOM fractions and C source of the SOM. With the objective of evaluate the impact of the land use change in eastern Amazonia soil samples were collected in the main land uses in Santarém region, Para State of Brazil, at three depths: 0-10, 10-20 and 20-30 cm. Through the samples was performed the physicochemical characterization of the areas and were determined the soil C and N contents as well the isotopes ? 13C and ? 15N in order to quantify the soil C and N stocks and understand the SOM dynamics and evaluate the SOM origin. For a subset of samples were performed the physical fractionation of SOM and the determination of microbial biomass C to understand how the land use change may interfere in these fractions. Added to these determinations were estimated the emission factors based on the methodology described by the IPCC. Through the physicochemical characterization study areas can be characterized as a clayey loamy soils. The highest values of pH, macronutrients, CEC , sum of bases and base saturation were observed in croplands (CP), suggesting that the use of practices such as fertilization and liming are able to change the soil fertility patterns in the Amazon, increasing their fertility. For C and N stocks can be said that the land use change in the study area is contributing to the loss of soil C and N, especially when the conversion is done for croplands (CP) and grasslands (GS) areas and the value observed for soil C stocks in the 0-30 cm layer in these areas were 49.21 Mg C ha-1 (GS) and 48.60 Mg C ha-1 (CP). The highest ? 13C value was found in GS, -25.08 ?, suggesting that for these areas is occurring an isotope dilution and that part of the soil C is still remaining from forest. The SOM fractions showed changes in the amount of C and in the proportion of light and occluded fractions, especially in the uses CP and GS. The labile SOM fractions (microbial biomass) also showed a large difference between the UF and CP uses (526.21 and 296.78 mg g-1 of dry soil), indicating that CP affects the soil C and N stocks and also the SOM fractions. The emission factors calculated confirm all results observed for the conversion of UF for CP, and for this use the emission factor was 0.93 ± 0.033, and then this was the use that emitted more C. Based on the results we conclude that the introduction of croplands in Santarem region is the main cause of soil C and N loss and consequently contributes more to the greenhouse gases emission.
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Frazão, Leidivan Almeida. "Conversão do Cerrado em pastagem e sistemas agrícolas: efeitos na dinâmica da matéria orgânica do solo." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/64/64135/tde-18092007-113334/.
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A mudança de uso da terra no Cerrado acarreta em alterações na dinâmica da matéria orgânica do solo (MOS). Práticas de manejo com revolvimento das camadas de solo aceleram a decomposição da MOS, favorecendo as emissões de gases do efeito estufa do solo para atmosfera. Dessa forma, o objetivo desse trabalho foi avaliar as mudanças na dinâmica da MOS de um Neossolo Quartzarênico submetido a diferentes usos e sistemas de manejo, utilizando como referência o sistema nativo (Cerrado). O presente estudo foi realizado no município de Comodoro - MT (13º50\'00\" a 13º50\'03\" S e 59º37\'18\" O). Foi empregado o delineamento experimental inteiramente casualizado com sete áreas de estudo. As coletas foram realizadas em julho de 2005 e fevereiro de 2006 e as áreas amostradas foram: Cerrado nativo (CER); pastagem (CAP22); plantio convencional com a cultura da soja (CS1), sucessão de culturas arroz-soja (CAS3) e sucessão arroz-soja-sorgo ou milheto (CAS/Sor3 e CAS/M3); e plantio direto (CAP13S/M5). Foram estudadas as seguintes variáveis: atributos físicos e químicos do solo, estoques de carbono (C) e nitrogênio (N) do solo, teores de C e N nas frações granulométricas da MOS, quantidades de N inorgânico, C e N microbiano do solo, quociente metabólico (qCO2) e fluxos de gases do solo (CO2, N2O e CH4). Os resultados deste estudo indicaram que os sistemas com plantio convencional e plantio direto avaliados apresentaram melhoria nos atributos físicos e químicos do solo em relação a pastagem (CAP22), com menor compactação do solo e aumento na disponibilidade de fósforo, cálcio e magnésio. Foram obtidos maiores estoques de C e N em CAS/Sor3 e CAS/M3, áreas com maiores teores de argila. A área CAP13S/M5 também mostrou maiores teores de argila, porém baixos estoques de C e N, resultado atribuído ao uso da terra por treze anos com pastagem sem reforma e ao pouco tempo de implantação do sistema plantio direto. Analisando as frações granulométricas da MOS verificou-se maiores teores de C e N na fração menor que 50 \'mü\'m. As maiores quantidades de N inorgânico em relação ao CER foram observados na área CAS/M3, e com exceção desta área, a forma predominante de N inorgânico foi o amônio. Foram obtidas maiores quantidades de C e N microbiano na época úmida, quando todas as áreas estavam com cobertura vegetal. Entre as áreas de estudo, as maiores quantidades de C e N microbiano foram obtidos em CAP22. Os fluxos de C-CO2, com exceção da área CAS/Sor3, foram maiores na época úmida, enquanto que os fluxos de N-N2O e C-CH4 foram semelhantes entre as épocas de estudo. Os fluxos de gases em C equivalente não apresentaram diferenças significativas entre as áreas de estudo devido ao alto desvio padrão verificado para cada gás. A mudança de uso da terra promove alterações na dinâmica da MOS, porém neste estudo não foi possível distinguir qual o melhor sistema de uso para o Neossolo Quartzarênico devido ao pouco tempo de implantação dos sistemas plantio convencional e plantio direto, e a degradação da pastagem (apesar do maior tempo de implantação)Land-use changes of Brazilian savanna (Cerrado) result in alterations of the soil organic matter (SOM). Managements practices with tillage accelerate the SOM decomposition, enhancing greenhouse gases emissions from the soil to the atmosphere. Therefore, the objective of this work was to evaluate the changes in the SOM dynamics of a Typic Quartzipisamment submitted to different uses and managements systems, using as reference the native system (Cerrado). The present study was conducted in areas located at Comodoro (Mato Grosso state, Brazil) (from 13º50\'00\" till 13º50\'03\" S and 59º37\'18\" W). At each site, samples were taken randomly within seven areas. Sampling activities were performed in July 2005 and February 2006 and the sample sites consist of an area of \"Cerrado\" (CER); pasture (CAP22); conventional tillage with soybean (CS1), rice-soybean succession (CAS3) and rice-soybean-sorghum or millet (CAS/Sor3 and CAS/M3) successions; and a field with no-tillage system (CAP13S/M5). Studied variables were: physical and chemical attributes, C and N stocks, isotopic composition of 13C/12C and 15N/14N, C and N content in the SOM fractions, quantity of inorganic N, microbial C and N biomass, metabolic quotient (qCO2), and the soil gases fluxes (CO2, N2O and CH4). The results of this study showed that all evaluated fields under conventional or no-tillage systems result in physical and chemical attribute improvement in relation to the pasture (CAP22), with soil compaction decrease, pH increase and improvement of the availability in phosphorus, calcium and magnesium. The C and N stocks were higher in areas CAS/Sor3 and CAS/M3, corresponding to the highest clay content. The area CAP13S/M5 showed similar clay content, but smaller C and N stocks, this result was attributed to the land-use: thirteen years as pastures without reform and also the short time of no-tillage implantation. Analyzing the SOM fractions, it was verified higher C and N contents in the 50 \'mü\'m fraction. The higher quantities of inorganic N in relation to the CER were found in area CAS/M3, and with exception of this area, ammonium was the predominant form of inorganic N. Higher quantities of the microbial C and N were obtained during the wet season, when all areas presented a cover crop. Among areas, the higher quantities of microbial C and N were obtained in CAP22. The fluxes of C-CO2, excepting area CAS/Sor3, were higher during the wet season, while the fluxes of N-N2O and C-CH4 were similar between seasons studied, because high standard deviations were calculated for each gas. The land use promoted alterations in SOM dynamic, however it was not possible to differentiate the best land use for this Typic Quartzipisamment, mainly due to the short time of no-tillage implantation, and the degradation of the pasture (although of the implantation time was higher)
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SANT?ANNA, Selenobaldo Alexinaldo Cabral de. "Balan?o de gases de efeito estufa em ?rea de cultivo de cana-de-a??car." Universidade Federal Rural do Rio de Janeiro, 2013. https://tede.ufrrj.br/jspui/handle/jspui/2120.
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CNPq
The study aimed to evaluate the changes in the soil stocks of C and N under non-burnt sugarcane grown in an area previously with pasture, and to quantify greenhouse gas emissions (N2O and CH4) and ammonia volatilization losses when using fertilizer and vinasse. The study was conducted in an area of a clayey Oxisol (LVef) in Ribeir?o Preto-SP. For the evaluation of C and N it was considered a chronosequence of two sugarcane areas, with 3 and 25 years of cultivation, and areas with pasture and over 30 years secondary forest. The stocks of C and N were estimated for the 0-30 cm and 0-100 cm layers. There was no statistical difference for the depth 0-30 cm, after correction for soil equal mass between forest, pasture and sugarcane of 3 years, which amounted to, respectively, 55.05, 48.85 and 49.96 Mg C ha-1 and 4.27, 3.74 and 3.83 Mg N ha-1. The area under the > 25 years sugarcane, for this depth range, showed statistically lower values of C stocks (46.04 Mg C ha-1) and N (3.45 Mg Nha-1) compared to secondary forest; but these values did not differ from the other two systems of land use. In the 0-100 cm layer, the forest showed a value significantly higher (118.36 Mg C ha-1) than the > 25 years sugarcane (103.25 Mg C ha-1) and the pasture (102.29 Mg C ha-1). The C stock (109.97 Mg C ha-1) in the 3 years sugarcane did not differ from the other systems. The forest and the 3 years sugarcane had higher N stock, respectively 8.52 and 8.02 Mg N ha-1, when compared with the sugarcane > 25 years (7.04 Mg N ha-1), but they were not different from the pasture (7.79 Mg N ha-1), which was not different from the > 25 years sugarcane. For sampling of gases and volatilization losses of NH3, a study was conducted in a completely randomized block design with six treatments: CSP-control without straw, FSP-fertilizer without straw, FCP-fertilizer with straw, CCP-control with straw, VSP-vinasse without straw and VCP-vinasse with straw, with five replications and three sampling periods in the years 2010, 2011 and 2012. The treatments consisted of applying 160 m3 ha-1 equivalent to 59 kg N ha-1 vinasse in 2010, 70 kg N ha-1 in 2011, and 108 kg N ha-1 in 2012, application of urea at a dose of 52 kg N ha-1 in 2010, and 100 kg N ha-1 in 2011 and 2012, and controls. The temporal variation of N2O fluxes in the three years was from 5.12 to 42.49 ?g N2O-N m2 h-1. In 2010 there was no difference among treatments, and in 2011 and 2012 it followed the FSP = FCP > CSP = CCP = VCP = VSP order. The emission factors ranged from 0.01 to 0.4%. The average flow rates of CH4 were negative. The NH3 volatilization losses in the three years of evaluation were less than 15% and 2% for doses of fertilizers and vinasse, respectively. The results suggest that the planting of sugarcane in pastures with low production does not significantly modify the stocks of C and N in the soil, although they reach values below the secondary forest (> 30 years) ones. The usage of nitrogen fertilization induces the production of N2O from the soil; the same tends to occur with vinasse application. Also, even with the maintenance of the straw, the emission levels are too low to be credited to these practices a risk of compromising the ethanol program.
O trabalho teve como objetivo avaliar as mudan?as nos estoques de C e N no solo em ?rea de cana-de-a??car cultivada sem queima em ?rea antes ocupada por pastagem e quantificar as emiss?es de gases (N2O e CH4) e as perdas por volatiliza??o de am?nia do solo pelo uso de fertilizante e vinha?a. O estudo foi realizado em uma ?rea de LATOSSOLO VERMELHO Eutrof?rrico (LVef), textura argilosa, no Munic?pio de Ribeir?o Preto-SP. Para avalia??o dos estoques de C e N foi considerada uma cronossequ?ncia com duas ?reas de cana-de-a??car, uma com mais de 25 anos e outra com 3 anos de cultivo respectivamente, e uma ?rea ocupada com pastagem e outra com floresta secund?ria com mais de 30 anos. Os estoques de C e N foram estimados para as camadas de 0-30 cm e de 0-100 cm. N?o houve diferen?a estat?stica para a profundidade 0-30 cm corrigido para massa igual de terra entre a floresta, pastagem e cana 3 anos, que somaram, respectivamente, 55,05, 48,85 e 49,96 Mg C ha-1 e 4,27, 3,74 e 3,83 Mg N ha-1. A ?rea sob cana > 25 anos para esse intervalo de profundidade apresentou estatisticamente menores valores dos estoques de C (46,04 Mg C ha-1) e N (3,45 Mg N ha-1) em rela??o a floresta secund?ria, por?m esses valores n?o diferiram dos outros dois sistemas de uso do solo. Na camada 0-100 cm a floresta apresentou valor significativamente maior (118,36 Mg C ha-1) do que as ?reas de cana > 25 anos (103,25 Mg C ha-1) e a pastagem (102,29 Mg C ha-1). A ?rea de cana com 3 anos apresentou estoque de C (109,97 Mg C ha-1) que n?o diferiu entre os tr?s outros sistemas. A floresta e a cana com 3 anos apresentaram maiores estoque de N, respectivamente (8,52 e 8,02 Mg N ha-1), comparada com a ?rea de cana > 25 anos (7,04 Mg N ha-1), mas n?o diferente da ?rea de pastagem (7,79 Mg N ha-1), a qual n?o diferenciou da ?rea de cana > 25 anos. Para as amostragens de gases e as perdas por volatiliza??o de NH3 o trabalho foi realizado em delineamento experimental em bloco inteiramente casualizado, com seis tratamentos: CSP - controle sem palha, FSP - fertilizante sem palha, FCP - fertilizante com palha, CCP - controle com palha, VSP - vinha?a sem palha e VCP - vinha?a com palha e com cinco repeti??es e em tr?s per?odos de amostragens correspondentes aos anos de 2010, 2011 e 2012. Os tratamentos consistiram na aplica??o de 160 m3 ha-1 de vinha?a equivalente a 59 kg N ha-1 em 2010, a 70 kg N ha-1 em 2011 e a 108 kg N ha-1 em 2012, aplica??o de ureia na dose de 52 kg N ha-1em 2010 e 100 kg N ha-1 em 2011 e 2012 e controles. A varia??o temporal dos fluxos de N2O nos tr?s anos foi 5,12 a 42,49 ?g N-N2O m2 h-1. Em 2010 n?o houve diferen?a entre tratamentos e em 2011 e 2012 seguiram a ordem FSP = FCP > CSP = CCP = VCP = VSP. Os fatores de emiss?o variaram entre 0,01 e 0,4%. Os fluxos m?dios de CH4 foram negativos. As perdas por volatiliza??o de NH3 nos tr?s anos de avalia??o foram menores que 15% e 2% para as doses de fertilizantes e vinha?a respectivamente. Os resultados sugerem que o plantio da cana-de-a??car em ?reas de pastagens de baixa produ??o n?o modifica significativamente os estoques de C e N do solo, mas alcan?am n?veis inferiores aos da floresta secund?ria (>30 anos). O uso da fertiliza??o nitrogenada induz a produ??o de N2O do solo, assim como tende a ocorrer com a aplica??o da vinha?a, e mesmo com a manuten??o da palhada, os n?veis de emiss?o s?o muito baixos para se atribuir a essas opera??es um risco de comprometimento do programa de etanol.
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Santos, Josiane Bürkner dos. "Alterações no estoque e taxa de sequestro de carbono em um Latossoto vermelho submetido a sistemas de manejo." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2006. http://tede2.uepg.br/jspui/handle/prefix/2193.
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Previous issue date: 2006-05-17The objective of this study was to quantify the changes of the total carbon (C) and total nitrogen (N) stock, and the variation of the C pool’s in monthly soil samples, and the C balance and C sequestration rates provoked by the soil tillage systems. The soil samples were accomplished in a long term experiment implanted in 1988, in the experimental station of Fundação ABC located in Ponta Grossa city, Center-South area of the Paraná State. The soil tillage systems were comprised: a) Conventional Tillage (CT); b) Minimum Tillage (MT); c) No-tillage with chisel plow (NTCP) each three years; and d) No-tillage – Continuous (NTC). Soil samples for each treatments were obtained by digging 3 profiles of 20-cm x 50-cm (surface area) x 50-cm deep for each replicate, and collected from three depths (0,0- to 2.5- cm, 2.5- to 5-cm, 5- to 10-cm). In the samples collected in October of 2003, May of 2004 and November of 2004, the total organic carbon (TOC) and the total nitrogen in all of the depths was measured. The particle size fractionation was accomplished, separating the soil in fractions in the size of 2000 - 210 Wm, 210 - 53 Wm and <53 Wm. In all these fractions TOC was determined. The treatments had significant effects on TOC and TN contents and pools. The total C and N stock in NTC was superior to the other systems demonstrating larger maintenance of C in the soil. The larger concentration of C was observed in the 210 to 53 Wm particle size fraction in the NTC. In the 2000 - 210 Wm fraction of the 0,0-2,5 cm layer were observed larger changes in the C stock due to the management systems in the samples at all long year. The greatest change was accomplished to CT. In NTP, the stock of C was larger in all soil samples, indicating that the maintenance of the cultural residues in the associated surface protection of the aggregates allows larger accumulation of C. Although the C stock in the particle size fraction <53 Wm not to present significant differences among the management systems, and was observed the C migration of the coarse fractions (210-53 and 2000-210 Wm) to the recalcitrant particle size fraction, indicating a continuous C flow. The C balance model adjusted for the local conditions revealed that the oxidation rate acted by K2 is inferior to the simulations accomplished by other authors, demonstrating the importance of the local conditions. With this model, the minimum amount of crop residues to maintain NTC system in steady-state was 8,05 Mg ha-1 year-1 while in the PC treatment it won't be possible to reach the balance with the amount of crop residues placed in this long term experiment, being a deficient system.
RESUMO Este estudo teve por objetivo quantificar as alterações provocadas pela adoção de sistemas de manejo do solo sobre o estoque total de carbono (C) e nitrogênio (N), a variação do estoque do C nas épocas de coleta, o balanço de C e as taxas de seqüestro de C. As coletas do solo foram realizadas em um experimento de longa duração, implantado em 1988, na estação experimental da Fundação ABC em Ponta Grossa, Meso Região Centro-Oriental do Estado do Paraná. Os sistemas de manejo do solo foram avaliados: a) Preparo convencional (PC), Preparo mínimo (PM), plantio direto escarificado (PDE) e plantio direto permanente (PDP). As amostras foram coletadas em 12 épocas com intervalos mensais e nas profundidades de 0,0-2,5; 2,5-5,0 e 5,0-10 cm de profundidade. As amostras deformadas foram coletadas em mini-trincheiras nas camadas de 0,0-2,5 e 2,5-5,0 cm e na camada de 5,0- 10,0 cm com o auxílio do trado. Nas amostras coletadas em outubro de 2003, maio de 2004 e novembro de 2004 foi determinado o carbono orgânico total (COT) e o nitrogênio total (NT) em todas as profundidades amostradas. Nas amostras coletadas mensalmente foi realizado o fracionamento granulométrico da matéria orgânica, separando o solo em frações no tamanho 2000 – 210 Wm, 210 – 53 Wm e < 53 Wm. Em todas estas frações foi determinado o COT. O estoque total de C e N no PDP foi superior aos demais sistemas de manejo demonstrando maior manutenção do C no solo. O estoque de C nas frações granulométricas apresentaram diferenças significativas entre as camadas amostradas, observando-se maior concentração de C na fração 210 a 53 Wm do PDP. Na fração 2000 – 210 Wm da camada de 0,0-2,5 cm observaram-se maior alteração no estoque de C devido aos sistemas de manejo durante as épocas de coleta, sendo a maior amplitude de variação atribuída ao PC. No PDP, o estoque de C foi maior em todas as épocas de coleta indicando que a manutenção dos resíduos culturais na superfície associada à proteção dos agregados permite maior acúmulo de C. Embora o estoque de C na fração < 53 Wm não apresentar diferenças significativas entre os sistemas de manejo, observou-se uma migração do C das frações mais grosseiras (210-53 e 2000-210 Wm) para esta fração mais recalcitrante, indicando um fluxo contínuo de C. O modelo de balanço de C proposto por Henin e Dupuis (1945) e ajustado para as condições locais revelou que a taxa de oxidação representada pelo K2 é inferior às simulações realizadas por outros autores, demonstrando a importância das condições locais. Com este modelo, a quantidade mínima de resíduos culturais para manter sistema PDP em equilíbrio foi de 8,05 Mg ha-1 ano-1 enquanto no PC não será possível atingir o equilíbrio com a quantidade de resíduos culturais aportada, sendo um sistema deficitário.
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Soares, Paula Fernanda Chaves. "Varia??o de atributos e din?mica de carbono e nitrog?nio em Organossolos em fun??o de uso e manejo agr?cola no Rio de Janeiro." Universidade Federal Rural do Rio de Janeiro, 2011. https://tede.ufrrj.br/jspui/handle/jspui/1226.
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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPQ
The Histosols are characterized by high organic content, distinguishing this class from others in the Brazilian System of Soil Clasification. Because of this characteristic they are more fragile in face of agricultural use and management than mineral soils. The agricultural drainage is the most important practice that changes soil properties and it is the cause of subsidence, which impacts on other attributes. On the other hand, Histosols are an important natural reservoir of carbon in the soil. However, there are few studies on the dynamics of carbon and nitrogen and potential contribution of greenhouse gases as a result of agricultural usage. The study aims to identify changes in edaphic attributes and dynamics of carbon and nitrogen of Histosols in a floodplain environment in State of Rio de Janeiro, according to types of land use and agricultural management. Three areas with different managements were selected. Two areas are located in Macae municipality, under pasture and annual crop rotation, and the third in Santa Cruz, in Rio de Janeiro city, cultivated with cassava (Manihot esculenta). They were evaluated: chemical and physical attributes, including aggregate stability and specific attributes of Histosols; content soil organic matter (SOM), carbon in the fractions - humin (HUM-C), humic acid (HAF-C) and fulvic acid (C-FAF); stocks of C and N; and flux of gases CO2 and N2O from soil to atmosphere. In general, the area cultivated with cassava had the highest values for the exchangeable cations at all depths; in the first sampling the H value varied from 32.1 to 33.2 cmolc kg-1, and Ca from 20.4 to 15.7 cmolc kg-1. In the second sampling K and P (5.16 to 4.36 cmol c kg-1, and 4 mg kg-1, respectively) were highest in the cassava crop area. The levels of (SOM) were highest in the pasture for the two sampling periods, with values ranging from 306.3 to 249.0 g kg-1 (WB method) and 297.8 to 278,5 g kg-1 (oven method) for the first sampling, and from 303.2 to 153.9 g kg-1 (WB) and 322.9 to 176.1 g kg-1 (oven) in the second period, indicating that this usage is less aggressive to the soil. The physical properties of Histosols may be used to indicate degree of subsidence. Thus, the high values of particle density and bulk density (1.9 and 0.8 Mg m-3); the total volume of pores that ranged from 54 to 60% with the lowest values in the two samplings; and minimum residue and mineral material highest than other usages (0.49 to 0.44 cm and 85.1 cm-1 to 80.7%, respectively) in the cassava area point to the high subsidence ot these soil. As for SOM chemical fractionation, the C_HUM indicated that this fraction had highest expression in all areas. In the second sampling the cassava area showed the lowest values of C-HUM (79.05 to 76.27 g kg-1), followed by C_FAH (44.56 to 40.05 g kg-1) and C_FAF (20.37 to 14.36 g kg-1). The stocks of C and N were highest in the pasture area, indicating better preservation of SOM, with values from 72.93 to 117.12 mg kg-1 for C and from 8.35 to 2,67 mg kg-1 for N. The values of CO2-C flux were within the range of variation proposed by the IPCC, where the highest emission value corresponded to 0.09 Mg CO2 ha-1 day-1 in the pasture area. The values of N2O-N flux were lower than the emission rate proposed by the IPCC, with the highest value around 270 g N2O-N m-2 day-1 in the area with beans. In general, the area with pasture management stood up as management that caused the least damage to the Histosols properties, among the land use evaluated.
Os Organossolos caracterizam-se pelo alto teor de material org?nico, que distingue essa classe das demais no Sistema Brasileiro de Classifica??o de Solo. Ainda, por essa caracter?stica s?o solos mais fr?geis diante do uso e manejo agr?cola que solos com dom?nio de minerais. Dentre as pr?ticas que mais alteram as propriedades ed?ficas, a drenagem ? a mais importante e ? respons?vel pelo processo de subsid?ncia com impactos em v?rios atributos. Por outro lado, os Organossolos s?o importante reservat?rio natural de carbono no solo. Ainda assim s?o poucos os estudos sobre a din?mica de carbono e nitrog?nio e o potencial de contribui??o com gases de efeito estufa diante do manejo agr?cola. O estudo visa identificar altera??es nos atributos ed?ficos e na din?mica de carbono e nitrog?nio de Organossolos em ambiente de v?rzea no Estado do Rio de Janeiro, em fun??o de tipos de uso e manejo agr?cola. Foram selecionadas tr?s ?reas com manejos distintos. Duas ?reas localizam-se em Maca?, com pastagem e rota??o de culturas anuais, e a terceira em Santa Cruz, no Rio de Janeiro, com mandioca (Manihot esculenta). Foram avaliados: atributos qu?micos e f?sicos, incluindo estabilidade de agregados e atributos espec?ficos de Organossolos; teores de mat?ria org?nica do solo (MOS) e o teor de C nas fra??es humina (C-HUM), ?cido h?mico (C-FAH) e ?cido f?lvico (C-FAF); estoques de C e N; e fluxos dos gases CO2 e N2O do solo para a atmosfera. Em geral, a ?rea com mandioca apresentou os maiores valores para o complexo sortivo em todas as profundidades; na primeira coleta o H variou de 32,1 a 33,2 cmolc kg-1, e o Ca entre 20,4 e 15,7 cmolc kg-1. Na segunda coleta destacam-se os valores de K e P (5,16 e 4,36 cmolc kg-1 e 4 mg kg-1, respectivamente) tamb?m maiores na ?rea com mandioca. A MOS mostrou maior teor na ?rea de pastagem para as duas coletas, com valores variando entre 306,3 a 249,0 g kg-1 (m?todo WB) e 297,8 a 278,5 g kg-1 (m?todo da mufla) na primeira coleta, e para a segunda coleta de 303,2 a 153,9 g kg-1 (WB) e 322,9 a 176,1 g kg-1 (mufla), o que indica que esse manejo ? menos agressivo ao solo. As propriedades f?sicas dos Organossolos podem indicar o seu grau de subsid?ncia. Assim, os valores altos de densidade da part?cula e densidade do solo (em torno de 1,9 e 0,8 Mg m-3) mais o volume total de poros, que variou de 54 a 60% sendo os menores nas duas coletas, e o res?duo m?nimo e material mineral com valores maiores (0,49 a 0,44 cm cm-1 e 85,1 a 80,7%, respectivamente) indicam para a ?rea de mandioca maior grau de subsid?ncia. No fracionamento qu?mico da MOS o C_HUM indicou que essa fra??o teve maior express?o em todos as ?reas. Na segunda coleta a ?rea de mandioca apresentou os menores valores de CHUM (79,05 a 76,27 g kg-1) seguidos de C_FAH (44,56 a 40,05 g kg-1) e C_FAF (20,37 a 14,36 g kg-1). Os estoques de carbono e nitrog?nio foram mais altos no solo sob pastagem, indicando melhor conserva??o da MOS, com valores entre 117,12 e 72,93 Mg kg-1 para C e 8,35 e 2,67 Mg kg-1 para N. Os valores de fluxo de C-CO2 estiveram dentro da faixa de varia??o proposta pelo IPCC, em que o maior valor de emiss?o correspondeu a 0,09 Mg CO2 ha-1 dia-1 na ?rea de pastagem. Os valores de N-N2O foram menores que a taxa de emiss?o proposta pelo IPCC, com o valor mais elevado em torno de 270 ?g N-N2O m-2 dia-1 e na ?rea com feij?o. Em geral, a pastagem se destacou como o manejo que causou menor altera??o nas propriedades dos Organossolos, dentre as formas de uso da terra avaliadas.
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Ahern, J. M. "Radical hydroacylation of C-C and N-N double bonds in air." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1309819/.
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The formation of C-C and C-N bonds in modern organic synthesis is a key target for methodological advancement. Current methods of C-C and C-N bond formation often involve the use of expensive catalysts, or sub-stoichiometric reagents, which can lead to the generation of undesirable waste products. This thesis describes a novel and environmentally benign set of reaction conditions for the formation of C-C and C-N bonds by hydroacylation and this is promoted by mixing two reagents, an aldehyde and an electron-deficient double bond, under freely available atmospheric oxygen at room temperature Chapter 1 will provide an introduction to the thesis and mainly discusses methods for C-C bond formation, in particular, radical chemistry and hydroacylation. Chapter 2 describes the hydroacylation of vinyl sulfonates and vinyl sulfones (C-C double bonds) with aliphatic and aromatic aldehydes with a discussion and evidence for the mechanism of the transformation. Chapter 3 details the synthesis of precursors for intramolecular cyclisations and studies into aerobic intramolecular cyclisations. Chapter 4 describes the hydroacylation of vinyl phosphonates (C-C double bonds) and diazocarboxylates (N-N double bonds) with aliphatic and aromatic aldehydes bearing functional groups. In addition, the hydroacylation of diazocarboxylates with chiral aldehydes will be discussed. In conclusion, a new, facile and clean set of reaction conditions for the formation of C-C and C-N bonds has been developed via aerobic C-H activation of aldehydes providing access to unsymmetrical ketones.
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Qian, Xin. "Cobalt-Catalyzed C-C and C-N Coupling reactions." Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00943479.
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Ce travail de these a permis le déveloippement de nouvelles reactions de couplage catalysées par des sels de cobalt(II) Le premier chapitre décrit l'allylation cobalta catalysée d'halogénures d'alkyles. La méthode est facile à mettre en œuvre, efficace avec une grande variété d'halogénures d'alkyes et des acétates ou carbonates d'allyle substitués. Les rendements vont de bons à excellents et la tolérance fonctionnelle élevée. Dans le cas d'acétates d'allyle substitués le produit linéaire est obtenu majoritairement ou exclusivement. Quelques expériences ont permis de mettre en lumière la formation d'espèce radicalaire lors du cycle catalytique. Les premiers essais pour étendre cette méthodologie aux couplages allyle-allyle et alkyle-alkyle sont également décrits. Le deuxième chapitre porte sur l'amination catalysée au cobalt d'organozinciques fonctionnalisés en utilisant des N-chloroamines. La procédure est simple et générale et demande des conditions plus douces que celles précédemment décrite, tout en tolérant un très large éventail de substrats, avec une bonne tolérance à de nombreux groupes fonctionnels. Les premiers essais pour étendre la méthodologie à la réaction entre un organozincique et une source électrophile de soufre en vue de former des liaisons C-S sont également exposés. Enfin le dernier chapitre décrit la réaction d'organozinciques engendrés par catalyse au cobalt avec une source " verte " de cyanure électrophile, N-cyano-N-phenyl-p-methyl-benzenesulfonamide (NCTS), pour conduire avec de bons rendements aux arylnitriles correspondants. Des sources analogues de CN+ ont également été testées.
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Simayi, Rena. "Synthesis and reaction chemistry of various N,N,C- and O,N,C- palladium pincer complexes." Thesis, University of Leicester, 2017. http://hdl.handle.net/2381/39392.
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In this thesis, the synthesis, characterisation and complexation chemistry of a series of related NNC and ONC pyridine based pincer ligands, together with some reaction chemistry of the metal complexes is described. The pro-ligands and the metal complexes have been characterised by a combination of multinuclear NMR spectroscopic techniques, IR spectroscopy, mass spectrometry and, for selected examples, by single crystal X-ray crystallography; remarkable spectroscopic and structural data are discussed. In Chapter 2, the synthesis and characterization of thirteen NNC and ONC pyridine based pincer ligands is described, including nine novel pincer ligands and four pyridine based pincers which have been previously reported. In Chapter 3, the palladium/platinum chemistry of NNCaryl and ONCaryl pyridine based pincer ligands is explored. Variation on the donor atoms has allowed an investigation of donor property influences on C-H activation, by giving peri-activated palladium pincer complexes for the ketimine-, aldimine-, amine- and biyridine-armed ligands and generating ortho-activated ONC palladium pincer complexes in the case of the alcohol-armed pro-ligand. Use of different palladium salts also led to different regioselective C-H activations. With the ketimine-armed naphthyl ligand (HL1ket-nap) as the example, the interconversion chemistry between the ortho- and peri-C-H activated products is also explored. In Chapter 4, sp3 C-H activation of the Et-armed ligand HL4Et with both palladium acetate and palladium chlorides has been unsuccessful, giving the N,N-coordinated bidentate species. The reaction of palladium acetate with the iPr-armed pro-ligand HL4iPr has resulted in minor amounts of C-H activated vinyl species with the major product being the non-activated palladium diacetate complex. Noticeably, upon reaction with Na2PdCl4, a mixture of the non-activated bis-chloride palladium complex and the sp3 C-H activated NNC-tridentate palladium species has been obtained, in a ratio of 1:1.5. Moreover, the sp3 C-H activation and the isolation of a rare sp3 C-H activated palladium complex have been achieved by reacting the tBu-armed pro-ligand HL4tBu with palladium acetate. The reaction of this ligand with Na2PdCl4 also resulted in the successful C-H activation of the tBu-arm to give a palladium pincer complex with a yield of 95%. Other than the NMR and FABMS analyses, the solid state X-ray structure of the latter complex confirmed the formation of the material as a rare sp3 C-H activated palladium complex. The stoichiometric reactivity of the (NNC/ONC)PdCl species towards AgBF4/AgPF6, and the subsequent ligand exchange reactions are disclosed in Chapter 5, together with the application of twelve palladium complexes as a series of promising catalysts in the allylic arylation of various allylic acetates with sodium tetraphenylborate.
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Huang, Xiaohua 1973. "Palladium-catalyzed C-C, C-N and C-O bond formation." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29639.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2003.Vita.
Includes bibliographical references.
New methods for Pd-catalyzed cross-coupling reactions of aryl halides or arenesulfonates are described. Key to the success of these transformations is the proper choice of ligand and reaction conditions. Palladium catalysts supported by bulky, monodentate phosphine ligands with a biaryl backbone or the bidentate ligand, Xantphos, effectively promote the formation of ca-aryl carbonyl compounds. Base-sensitive functional groups are better tolerated when a weak base, such as K3PO4, is used. One of the most difficult transformations in Pd catalysis, the intermolecular C-O bond formation between primary alcohols and electron-neutral or even electron-rich aryl halides, was effectively promoted by the use of a new generation of ligands, 3-methyl-2-di-t-butylphosphinobiaryl. The one-step synthesis of ligands from cheap starting materials, as well as the mild reaction conditions employed for the coupling reactions, enables the practical use of Pd catalysis to access aryl alkyl ethers for the first time. Continuing study of Pd-catalyzed C-N bond-forming processes using biaryl monophosphine ligands led to the discovery of a structural derivative of these ligands, 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl. This ligand, in combination with a Pd source, produces a catalyst system with both a greater degree of activity and of stability than those that use our previous ligands. Substrates that were not amenable to Pd catalysis previously are reexamined using this new catalyst system, and excellent results are obtained.
by Xiaohua Huang.
Ph.D.
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Cómbita, Merchán Diego Fernando. "Formación de enlaces C-C, C-N y N-N con catalizadores de óxido de cerio y de oro/óxido de cerio." Doctoral thesis, Universitat Politècnica de València, 2016. http://hdl.handle.net/10251/62780.
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[EN] Heterogeneous catalysis is one of the most important tools in the advancement of green chemistry, understood it as one that efficiently uses (preferably renewable) raw materials, eliminate waste and avoids the use of toxic and/or dangerous reagents and solvents in chemicals production and application.
In this thesis we have investigated the reaction mechanisms and the nature of the active centers in C-C, C-N and N-N bond forming reactions over cerium oxide and over gold nanoparticles supported on cerium oxide heterogeneous catalysts.
As C-C bond formation reaction, we had been studied Sonogashira reaction catalyzed by a heterogeneous Au/CeO2 catalyst, wherein the CeO2 nanoparticle is about 5 nm in diameter.
The second part of the thesis comprises the study of C-N bonds formation during carbamoylation reaction between diaminotoluene and dimethyl carbonate, catalyzed by cerium oxide, studying the effect over the reaction of the crystal planes available for reactants adsorption.
In a third part, the N-N bond formation in the reductive coupling reaction of nitrocompounds to obtain azocompounds was studied, using Au/CeO2 as heterogeneous catalyst. Also in this section we report, by first time, an active and selective heterogeneous catalyst for the Mills reaction between nitroso compounds and anilines to obtain symmetric and asymmetric azocompounds.[ES] La catálisis heterogénea es una de las más importantes herramientas para el desarrollo de la Química Sostenible, entendida como aquella que utiliza eficientemente las materias primas (preferiblemente renovables), elimina los desechos y evita el uso de reactivos y solventes tóxicos y/o peligrosos en la manufactura y aplicación de los productos químicos. En esta tesis doctoral se han investigado los mecanismos de reacción y la naturaleza de los centros activos, en reacciones de formación de enlaces C-C, C-N, y N-N sobre catalizadores heterogéneos de óxido de cerio y de nanopartículas de oro soportadas en óxido de cerio. Como reacción de formación de enlaces C-C se ha estudiado la reacción de Sonogashira catalizada con un catalizador heterogéneo de Au/CeO2, en donde el CeO2 está en forma de nanopartículas de cerca de 5nm de diámetro. En la segunda parte de la tesis se profundiza en el estudio de la formación de enlaces C-N durante la reacción de carbamoilación del diaminotolueno con dimetilcarbonato catalizada por el óxido de cerio, estudiando el efecto que tiene sobre la reacción la naturaleza de los planos cristalinos disponibles para la adsorción de los reactivos. En una tercera parte se estudia la formación de enlaces N-N en la reacción de acoplamiento reductivo de nitrocompuestos para obtener azocompuestos en presencia de un catalizador heterogéneo de Au/CeO2. Es este mismo apartado se reporta por primera vez un catalizador heterogéneo de alta actividad y selectividad para la Reacción de Mills entre un nitrosocompuesto y una anilina para obtener azocompuestos simétricos y asimétricos.
[CAT] La catàlisi heterogènia és una de les ferramentes més importants per al desenvolupament de la Química Sostenible, entesa com aquella que utilitza eficientment les matèries pimes (preferiblement renovables), elimina els rebutjos i evita l'ús de reactius i dissolvents tòxics i/o perillosos en la manufactura i aplicació dels productes químics. En esta tesi doctoral s'han investigat els mecanismes de reacció i la natura dels centres actius, en reaccions de formació d'enllaços C-C, C-N i N-N sobre catalitzadors heterogenis d'òxid de ceri i nanopartícules d'or suportades en òxid de ceri. Com reacció de formació d'enllaços C-C s'ha estudiat la reacció de Sonogashira catalitzada amb un catalitzador heterogeni d'Au/CeO2, on el CeO2 està en forma de nanopartícules amb un diàmetre proper als 5nm. En la segona part de la tesi s'aprofundeix en l'estudi de la formació d'enllaços C-N durant la reacció de carbamilació del diaminotoluè amb dimetilcarbonat catalitzada per l'òxid de ceri, estudiant l'efecte que té sobre la reacció la natura dels plans cristal·lins disponibles per a l'adsorció dels reactius. En una tercera part s'estudia la formació d'enllaços N-N en la reacció d'acoblament reductiu de nitrocompostos per a obtenir azocompostos en presència d'un catalitzador heterogeni d'Au/CeO2. En aquest mateix apartat es reporta per primera vegada un catalitzador heterogeni d'alta activitat i selectivitat per a la Reacció de Mills entre un nitrocompost i una anilina per a obtenir azocompostos simètrics i asimètrics.
Cómbita Merchán, DF. (2016). Formación de enlaces C-C, C-N y N-N con catalizadores de óxido de cerio y de oro/óxido de cerio [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/62780
TESIS
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Roberts, Deborah Elizabeth. "Palladium N-neterocyclic carbene complexes as catalysts for C-N, C-Si and C-S bond formations." Thesis, University of Sussex, 2013. http://sro.sussex.ac.uk/id/eprint/45342/.
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This work is foremost a study of various palladium-bearing N-heterocyclic carbenes complexes and their catalytic potential to form C-N bonds. Both alkyl amination and aryl amination are considered. Further elucidation on the mechanism of such catalytic activity is investigated. The viability of alkyl amination using palladium complexes bearing the ligands, ITMe, 1,2,3,4- tetramethylimidazol-2-ylidene, and ICy, 1,3- bis-cyclohexylimidazol-2-ylidene, as catalysts, is investigated. This includes the synthesis of [Pd(ITMe)(neopentyl)Cl]2,[Pd(ITMe)2(neopentyl)Cl], [Pd(ITMe)(neopentyl)(tbutylamine)Cl], [Pd(ITMe)(neopentyl)(hexylamine)Cl], with successful elimination of the alkyl-amination reaction product in low yield from the latter complex. [Pd(ICy)(neopentyl)Cl]2, [Pd(ICy)2(neopentyl)Cl] are also isolated. Unsuccessful attempts were made to vary the electronic properties of the complexes by replacing the amine with a hydrazine. Work was also done on indirect alkylation using tBuLi which led to a new method for synthesis of [Pd(ItBu)2] and novel complex, [Pd(ItBu)Cl3. ItBuH] (ItBu = 1,3- bis-tertbutylimidazol-2-ylidene). Aryl amination catalysed by complexes of palladium bearing the ligand, ITMe, is considered. This includes an improved synthesis of [Pd(ITMe)2] and synthesis of [Pd(ITMe)2(anisole)Cl]. Unsuccessful attempts at the elucidation of the mechanism of [Pd(ITMe)2(anisole)] formation led to the unexpected formation of [Pd(ITMe)2(SiMe3)(Si(SiMe3)3)] and [Pd(ITMe)2(SiMe3)2]. Aryl amination with using [Pd(ITMe)2(SiMe3)2] led to two aryl amination products, 4-ortho-methoxyphenyl morpholine as well as the expected para isomer. The use of complexes [Pd(ItBu)2] and [Pd(SIPr)2] (SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) in C-S bond formation was explored. Addition of mesityl magnesium bromide to Pd(1,5-COD)Cl2 led to addition of mesityl substrate across 1,5-COD double bond and the addition of ITMe formed the Heck cycle intermediate [Pd(8-mesityl-1,4,5-η3 – C8H12)X2] (X=Cl, Br). Addition of 4-tolyl magnesium chloride resulting in the formation of Pd(ItBu)2(tolyl)Cl via an indirect route.
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Neal, Richard J. "The loosely-bound proton in ¹³N and the transfer reaction ¹¹B(¹³N,¹²C)¹²C." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/1783.
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The radioactive nucleus ¹³N (t½ = 10 min, Jπ = ½) contains one loosely bound proton (Sp = 1.94 MeV) which can be considered to be bound to a core of ¹²C. Taking advantage of the recent availability of beams of radioactive nuclei at Louvain-la-Neuve, Belgium, a beam of ¹³N has been used to investigate the transfer reaction ¹¹B(¹³N,¹²C)¹²C. Particle-γ coincidence data was taken, using the LEDA silicon strip array and BaF₂ modules, gating on the 15.11 MeV γ-decay from the T = 1 state in ¹²C*. Two final states, corresponding to ¹²Cgs + ¹²C*(15.11 MeV) and ¹²C*(4.44 MeV)+ ¹²C*(15.11 MeV) have been observed and angular distributions have been measured for both transitions at each of two beam energies, 29.5 MeV and 45 MeV. The results are discussed with special reference to the loosely bound nature of the valence proton in ¹³N; the transfer reaction has been modelled using a DWBA code, with the ¹³N ground state constructed as a mixture of states: a p½ proton bound to ¹²Cgs , or a p3/2 proton bound to ¹²C*₂₊ (4.44 MeV). Fits to the experimental data have been obtained using a very shallow set of optical potentials, which are found to be energy dependent. The agreement with experiment is good, with the exception of the ¹²C*(4.44)+¹²C*(15.11) transition at the lower beam energy, which is significantly underestimated by the calculations, suggesting a contribution from a different reaction mechanism.
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Ounaïes, Myriam. "Ensembles inévitables pour les applications holomorphes de C [exposant] n dans C [exposant] n." Toulouse 3, 1995. http://www.theses.fr/1996TOU30140.
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En une veriable complexe, l'image d'une fonction meromorphe evite au plus deux points de la sphere de rieman: c'est le theoreme de picard. De plus, grace a la theorie de nevanlinna, nous savons que chaque valeur est prise dans le disque de rayon r avec la meme frequence asymptotique sauf pour un ensemble denombrable de valeurs. En plusieurs variables, on observe un phenomene different. Il existe en effet des applications holomorphes, injectives, de c#n dans c#n dont l'image n'est pas dense dans c#n: ce sont les applications de fatou-bieberbach. Rosay et rudin ont montre qu'il existe pourtant des ensembles discrets qui doivent rencontrer l'image de toute application holomorphe non degeneree ; nous les appellerons ensembles inevitables. L. Gruman a construit explicitement une famille de tels ensembles e(a) parametres par a dans c*#n. Nous montrons que chaque ensemble e(a) est rencontre dans la boule de rayon r avec la meme frequence asymptotique pour tout a dans c*#n. Ceci constitue une sorte d'analogue a la theorie de nevanlinna en plusieurs variables
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Mudarra, Alonso Ángel Luis. "Coinage complexes in C-C and C-N bond-forming reactions." Doctoral thesis, Universitat Rovira i Virgili, 2020. http://hdl.handle.net/10803/670357.
Full textAbstract:
Els complexos organometàl·lics de coure, plata i or juguen un paper fonamental com espècies reactives
en diverses transformacions químiques. Aquesta tesi aporta coneixement sobre el comportament
d’aquests complexos en la formació d’enllaços C-C i/o C-N. En concret, estudiem: i) el mecanisme de
reacció a través del qual els complexos de coure co-catalitzen un acoblament oxidant en el context de
sistemes bimetàl·lics de rodi i coure; ii) el potencial de nucleòfils de plata com a agents transmetal·lants
en reaccions de trifluorometilació catalitzades per pal·ladi; iii) el mecanisme de reacció de sistemes
bimetàl·lics de Pd/Ag emprant un sistema model; i iv) el comportament de complexos bis(trifluorometil)
cuprat, argentat i aurat com a nucleòfils. En aquesta tesi, on s´han combinat estudis experimentals i
computacionals, s’ha adquirit nou coneixement sobre els processos estudiats, i s’ha contribuït al camp de
la recerca química basada en el coneixement.Los complejos organometálicos de cobre, plata y oro juegan un papel fundamental como especies reactivas en diversas transformaciones químicas. Esta tesis aporta conocimiento sobre el comportamiento de estos complejos en la formación de enlaces C-C y/o C-N. En concreto, estudiamos: i) el mecanismo de reacción por el cual complejos de cobre co-catalizan un acoplamiento oxidante en el contexto de sistemas bimetálicos de rodio y cobre; ii) el potencial de nucleófilos de plata como agentes transmetalantes en reacciones de trifluorometilación catalizadas por paladio; iii) el mecanismo de reacción de sistemas bimetálicos de Pd/Ag usando un sistema modelo; y iv) el comportamiento de complejos bis(trifluorometil) cuprato, argentato y aurato como nucleófilos. En esta tesis, donde se han combinado estudios experimentales y computacionales, se ha adquirido nuevo conocimiento sobre los procesos estudiados, y se ha contribuido al campo de la investigación química basada en el conocimiento.
Organometallic coinage metal complexes are be key reactive species for promoting a wide variety of chemical transformations. This thesis improves the understanding the behavior of these complexes in relevant C-C and/or C-N bond-forming reactions. Specifically, we have explored: i) the mechanistic intricacies of copper species as co-catalyst in the context of rhodium/copper-catalyzed oxidative coupling reactions; ii) the capability of silver nucleophiles as transmetalating agents in palladium-catalyzed trifluoromethylation reactions; iii) the reaction mechanism of Pd/Ag bimetallic reactions using a model system as probe; and, iv) the study of bis(trifluoromethyl) coinage metallates as nucleophiles. The fundamental insights gathered in this Thesis, encompassing both experimental and computational approaches, improve our understanding of the processes under study and make a contribution to the general field of knowledge-driven research in Chemistry.
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Kanuru, Vijaykumar. "Understanding surface mediated C-C and C-N bond forming reactions." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608956.
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Raghuvanshi, Keshav. "Ruthenium(II)-Catalyzed C-N, C-O and C-C Formations by C-H Activation." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://hdl.handle.net/11858/00-1735-0000-002B-7D4C-2.
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Laren, Martijn Wouter van. "Palladium-catalyzed C-H and C-N bond formation." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/75422.
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Bollwein, Tobias. "Metallierung, oxidative C-C-Kupplung und C-N-Aktivierung mit Zinkorganyl-Verbindungen." Diss., [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963033077.
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Desmarchelier, Alaric. "Cascades réactionnelles organocatalysées : création stéréosélective de liaisons C-N et C-C." Versailles-St Quentin en Yvelines, 2012. http://www.theses.fr/2012VERS0031.
Full textAbstract:
Les travaux exposés dans ce manuscrit ont pour objectif l’étude de cascades réactionnelles organocatalysées permettant de former stéréosélectivement des liaisons C-N, et C-C. Plusieurs approches « one-pot » séquentielles ont été développées à partir de substrats simples, conduisant à des produits hautement fonctionnalisés. Le premier chapitre se focalise sur la formation énantiosélective d’aziridines portant un centre quaternaire, à partir d’énals α-substitués. La difonctionnalisation en position α d’aldéhydes a ensuite été étudiée par double activation énamine. Le deuxième chapitre traite ainsi d’une séquence réaction de Mannich/amination électrophile sur l’acétaldéhyde, pour accéder à des diamines vicinales. Le troisième chapitre décrit la cascade réaction de Michael/amination électrophile, conduisant à la formation d’hydrazinoaldéhydes possédant un centre quaternaire. Enfin, le dernier chapitre se concentre sur l’amination électrophile d’aldéhydes α,α-disubstitués, et son application en cascade organocatalysée pour former des hétérocycles azotés, les 3-pyrrolines, portant un centre quaternaireThe work presented in this manuscript aims at the study of organocascade reactions enabling the stereoselective formation of C-N and C-C bonds. Several sequential one-pot approaches yielding highly functionalized products from simple substrates have been developed. The first chapter describes the enantioselective synthesis of aziridines from α-substituted enals. α-difunctionalization of aldehydes has then been studied via double-enamine activation. The second chapter presents a one-pot Mannich reaction/electrophilic amination of acetaldehyde, leading to vicinal diamines. The third chapter studies a Michael reaction/electrophilic amination cascade, giving rise to hydrazinoaldehydes bearing a quaternary stereocenter. Finally, the last chapter focuses on the electrophilic amination of α,α-disubstituted aldehydes, and its application in an organocascade reaction, leading to 3-pyrrolines with a quaternary stereocenter
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Wolfe, John P. (John Perry) 1970. "Late transition metal catalyzed C-N and C-C bond forming reactions." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9521.
Full textAbstract:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1999.Includes bibliographical references.
New methods for the palladium-catalyzed amination of aryl halides are described. Key to these is the development of new catalysts and reaction conditions for these transformations. Initially, P(o-tol)3 ligated palladium catalysts were investigated but gave way to systems that used chelating phosphine ligands which substantially expanded the scope of the catalytic amination methodology. Palladium catalyst systems based on BINAP ((2,2'-diphenylphosphino)-1, 1 '-binaphthyl) allowed for the transformation of a much wider range of amines and aryl halide substrates, as well as aryl triflates. Of practical significance was that the use of cesium carbonate as a base at 100 °C substantially increased the functional group tolerance of the method. Palladium catalysts supported by novel, bulky, electron-rich phosphine ligands are exceptionally effective in the C-N, C-0, and C-C coupling procedures. For some substrate combinations, these palladium catalysts are effective for the room-temperature catalytic amination of aryl chlorides. These palladium catalysts are also highly effective for Suzuki coupling reactions of aryl bromides and chlorides at room temperature. Suzuki coupling reactions of aryl bromides and aryl chlorides are effective at very low catalyst loadings (0.000001-0.005 mol % Pd for ArBr, 0.02-0.05 mol % for ArCI) at 100 °C, and reactions of hindered aryl halides or boronic acids are effected at moderate catalyst loadings (1 mol % Pd). The high reactivity of these catalysts towards aryl chlorides challenges the conventional dogma that chloride substrates cannot be transformed under mild conditions with palladium catalysts, and significantly expands the pool of substrates available for cross-coupling chemistry.
by John P. Wolfe.
Ph.D.
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Kulchat, Sirinan. "Dynamic covalent chemistry of C=N, C=C and quaternary ammonium constituents." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF018/document.
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Cette thèse décrit la Chimie Covalente Dynamique (CCD) des échanges imine/imine, Knoevenagel/imine et Knoevenagel/Knoevenagel. La L-proline est un excellent organocatalyseur pour la formation de Bibliothèques Covalentes Dynamiques (BCDs). Cependant, l’interconversion entre des dérivées Knoevenagel de l’acide diméthylbarbiturique et des imines se déroule rapidement sans catalyseur. Une nouvelle classe de CCD basée sur des échanges par substitutions nucléophiles (SN2/SN2’) entre des sels d’ammonium quaternaires et des amines tertiaires est développée, impliquant la catalyse par l’iodure. Les réactions d’échange entre des sels de pyridinium et un dérivé de pyridine génèrent des liquides ioniques dynamiques. Enfin, la sélection cinétique et thermodynamique de la formation d’imines dans la CCD est réalisée en solution aqueuse e ten solvant organiqueThis thesis describes the dynamic covalent chemistry (DCC) of imine/imine, Knoevenagel/imine, and Knoevenagel/Knoevenagel exchange. L-proline is shown to be an excellent organocatalyst to accelerate the formation of dynamic covalent libraries (DCLs). The interconversion between Knoevenagel derivatives of dimethylbarbituric acid and imines is found to occur rapidly in the absence of catalyst. A new class of DCC based on nucleophilic substitution (SN2/SN2’) component exchange between quaternary ammonium salts and tertiary amines is developed, by the use of iodide as a catalyst. The exchange reactions between pyridinium salts and a pyridine derivative generate dynamic ionic liquids. Finally, kinetic and thermodynamic selection of imine formation in a DCC is perfomed in aqueous solution and organic solvent
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Jäschke, Britta [Verfasser]. "Neue multinäre nitridische Keramiken in den Systemen B/P/N/(C), Al/P/N/(C) und Si/N/C aus molekularen und polymeren Vorläufern / Britta Jäschke." Aachen : Shaker, 2003. http://d-nb.info/1172611645/34.
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Treffert, Harald. "N,O- und N,C,N-koordinierte Platinmetallkomplexe : Synthesen, Strukturen und katalytische Anwendungen." kostenfrei, 2008. http://deposit.d-nb.de/cgi-bin/dokserv?idn=989135500.
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Monnehan, Georges. "Résonances dans les réactions nucléaires ¹⁵N + ¹²C et ¹⁵N +¹⁶O." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376081864.
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Ruiz-Castillo, Paula. "Palladium-catalyzed C-N and C-O cross-coupling reactions." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105048.
Full textAbstract:
Thesis: Ph. D. in Organic Chemistry, Massachusetts Institute of Technology, Department of Chemistry, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 375-410).
Chapter 1: This chapter describes a general method for the of the Pd-catalyzed N-arylation of hindered [alpha],[alpha],[alpha]-trisubstituted primary amines. The reaction utilized catalysts based on two biaryl phosphine ligands, which were developed via kinetics-based mechanistic analysis and rational design. These studies led to the first example of catalyst based on a hybrid (alkyl)aryl biaryl phosphine ligand that provides better results that its dialkyl- or diarylbiaryl analogues. The C-N coupling was efficient for a wide range of (hetero)aryl chlorides and bromides under mild conditions. Chapter 2: This chapter relates the development of the Pd-catalyzed C-O coupling of primary alkyl alcohols. The reaction of primary aliphatic alcohols bearing [beta]-hydrogen atoms can lead to undesired [beta]-hydride elimination pathways instead of the target reductive elimination from the [LPd(Ar)OAlk] intermediate, especially when using electron-rich aryl halides. Additionally, aryl chlorides have been shown to be more challenging coupling partners than the corresponding aryl bromides. The use of catalysts based on commercially available ligand t-BuBrettPhos and a novel hybrid ligand, AdCyBrettPhos, have allowed the C-O coupling reaction to proceed effectively at room temperature, minimizing the side reaction. A variety of functionalized primary alcohols have been successfully coupled with (hetero)aryl bromides and chlorides giving rise to medicinally interesting products. Chapter 3: This chapter is a compilation of the applications of Pd-catalyzed C-N coupling in various fields of chemical research since 2008. This work includes the reactions of nine classes of nitrogen-based coupling partners in the 1) synthesis of heterocycles, 2) medicinal chemistry, 3) process chemistry, 4) synthesis of natural products, 5) organic materials and chemical biology, and 6) synthesis of ligands. The large number of applications highlights the versatility and utility of this transformation both in academic and industrial settings.
by Paula Ruiz-Castillo.
Ph. D. in Organic Chemistry
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Le, Roux Anabel-Lise. "N-Myristoylation-Dependent c-Src Interactions." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/346927.
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c-Src is the leading member of the Src family of non-receptor tyrosine kinases, which are involved in many signaling pathways. Its deregulation affects cell migration, proliferation and survival. c-Src is composed of the intrinsically disordered N-terminal SH4 and Unique domains, of the folded SH3, SH2, kinase domains and of a C-terminal tail. c-Src is myristoylated at its N-terminal region and anchored to membranes via cooperative electrostatic and hydrophobic interactions. Weak interactions with lipids in the Unique and SH3 domains and intramolecular interactions between them were recently found in the non-myristoylated form. These interactions involve the Unique Lipid Binding region (ULBR) in the Unique domain, and the RT and nSrc loops in the SH3 domain. Our objective consisted in obtaining and characterizing the myristoylated form of the Unique and SH3 domains (MyrUSH3).
Protocols for the efficient production of myristoylated proteins were developed. The incorporation of shorter acyl chains was characterized as a general problem in the preparation of myristoylated proteins, and conditions enabling to minimize their formation were found, in particular in the case of expression in minimum media. A well-defined myristoylation-induced cleavage site was identified and characterized in the Unique Lipid Binding Region of the Unique Domain of c-Src. Conditions to obtain degradation-free samples for structural studies were established.
The kinetics of MyrUSH3 binding to liposomes was followed using surface plasmon resonance (SPR) and revealed two MyrUSH3 populations, a dominant form binding with relatively fast association and dissociation, and a minor persistently bound (PB) population not described earlier. This PB form was studied in an assay involving detection by a secondary antibody and the model better explaining the experimental results described these PB species to be dimer forms of MyrUSH3. In a construct in which the SH3 domain was replaced by the GFP protein, single molecule photobleaching experiments of these PB species bound to supported lipid bilayers were conducted. A major population of dimers over the bilayer surface was detected. When binding of the myristoylated SH4 (MyrSH4) peptide to liposomes by SPR, a PB population was also observed. Monitoring of the surface activity of MyrSH4 revealed the micelar behavior of the peptide at low concentrations.
Nuclear Magnetic Resonance (NMR) measurements permitted to study the effect of the myristoyl group on the intramolecular interactions between the Unique and SH3 domains, as well as on the binding of the ULBR and RT loops to liposomes when the protein was anchored in the
bilayer. 1H-15N spectra of the myristoylated Unique domain (MyrUSrc) confirmed the propensity of the ULBR to bind liposomes, but in a different manner depending on the nature of the lipid in the bilayer. These measurements of MyrUSrc also pointed out some intermolecular propensities in the MyrSH4 domain. 1H-15N spectra of MyrUSH3 in solution revealed the presence of a myristoyl binding site has been found in the RT loop. Interaction of the myristoyl chain with lipids results in the loss of other lipid binding interactions in the Unique and SH3 domains that were observed in the non-myristoylated form. The interaction between the SH4 and the SH3 domains that restricts the conformational space of the Unique domain was preserved in the myristoylated forms and in the presence of lipids.
The SPR and single molecule fluorescence studies revealed the formation of self-associated complexes of limited size upon binding of MyrUSH3 or MyrUGFP to liposomes, possibly driven by the presence of the MyrSH4 domain. The NMR data highlighted the interplay between the lipid binding regions of the Unique and SH3 domains, in presence or absence of liposomes. Therefore, the myristoylated intrinsically disordered Unique domain may act in c-Src regulation at the lipid bilayer interface.c-Src es miembro de una importante familia de tirosina quinasas, que está involucrada en la transducción de señales en las células. c-Src está formada por una región N-terminal desordenada (compuesta de los dominios SH4 y Único), por los dominios plegados SH3, SH2, SH1 (el dominio quinasa), y por una cola C-terminal. c-Src es una proteína miristoilada en su extremo N-terminal, lo cual permite su unión a membranas, unión reforzada por la interacción del dominio SH4 polibásico con los lípidos cargados negativamente. En ausencia del grupo miristoilo, se encontraron zonas de unión a lípidos y de interacciones intramoleculares en los dominios Único y SH3. El objetivo de este trabajo es la obtención y la caracterización de la forma miristoilada de los dominios Único y SH3 (MyrUSH3). Se desarrollaron protocolos que permitieron la producción de proteínas miristoiladas. La cinética de unión de MyrUSH3 a liposomas se estudió con resonancia de plasmones superficiales. Se observó una población mayoritaria con una asociación y una disociación relativamente rápidas, y una población minoritaria con una unión persistente a liposomas. Esta segunda especie se estudió por detección secundaria via un anticuerpo y se dedujo que estaba posiblemente formada por dímeros. El dominio SH3 se remplazó por una proteína verde fluorescente (MyrUGFP) y se estudió la unión de MyrUGFP a liposomas, mediante su observación con microscopía confocal, usando la técnica de fotoblanqueo de moléculas individuales. Se observó una población mayoritaria de dímeros. A continuación, se estudió la proteína MyrUSH3 con resonancia magnética nuclear, en solución o unida a liposomas. En solución, se encontró un sitio de unión al grupo miristoil en el dominio SH3. Tras la inserción del grupo miristoil en la bicapa lipídica, se perdió la capacidad de unión a lípidos en los dominios Único y SH3 (excepto el dominio SH4), y algunas interacciones intramoleculares fueron afectadas.
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Flournoy, Cecil Buford Jr. "N-parameter Fibonacci AF C*-Algebras." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/1221.
Full textAbstract:
An n-parameter Fibonacci AF-algebra is determined by a constant incidence matrix K of a special form. The form of the matrix K is defined by a given n-parameter Fibonacci sequence. We compute the K-theory of certain Fibonacci AF-algebra, and relate their K-theory to the K-theory of an AF-algebra defined by incidence matrices that are the transpose of K.
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Graham, Alan. "New C-C and C-N bond forming reactions mediated by chromium complexation." Thesis, University of Bath, 1996. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760696.
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Barron, Benedict James. "Evaluation of asymmetric catalysts in C–C and C–N Michael type transformations." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/45060.
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The first chapter of this thesis presents a literature survey of recent developments in asymmetric C–C and C–N conjugate addition reactions using metal mediated and organocatalytic protocols, focusing on the limitations and strengths of each system. The aim of this study will also be presented. The second chapter discusses the study of two asymmetric Pd (II) catalytic protocols in the aza-Michael reaction of N-containing arylamines with N-carbamates. The main body of work focuses on the utilisation of N-protected phenylenediamine substrates. In one case, these nucleophilic amines are poorly tolerated, with an interesting deactivation pathway uncovered. For the second protocol, high yields and ee are achieved with an interesting water effect observed. The afforded aza-adduct substrates were subsequently cyclised into tetrahydroquinoline derivatives, with particular attention paid to the regioselectivity of the transformation. This chapter also highlights the limitations of ortho-substituted anilines under these two protocols. The third chapter highlights the attempts to further extend these aza-Michael Pd(II) catalysed protocols to the reactions of substituted hydroxylamines with N-carbamates, with the overall objective of furnishing enantio-enriched aziridine products. Variation of the Michael acceptor was also explored, focusing on the utilisation of α-substituted α,β-unsaturated 1,3-dicarbonyls and alkylidene malonates in the aza-Michael addition with simple aniline derivatives. In the fourth chapter, Pd(II) catalytic protocols are applied to the asymmetric C–C Michael addition of β-ketoester and β-ketoamides to β-substituted α,β-unsaturated thioesters with little success. In contrast, the employment of an asymmetric MBI-derived phase transfer organocatalyst in the Michael addition of glycine Schiff base with various oxo and thio-ester Michael acceptors provided facile access to chiral γ-lactam derivatives. Chapter 5 contains experimental procedures and characterisation data for all synthesised compounds.
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Kilaru, Praveen. "New Strategies for Transition Metal Catalyzed C-C and C-N Bond Formation." Diss., North Dakota State University, 2018. https://hdl.handle.net/10365/31710.
Full textAbstract:
Transition metal catalysis emerged as an essential tool in the field of organic chemistry. In this context, transition metal catalyzed C-H bond functionalization is considered as an alluring strategy as it occurs with the high atom-and-step economy. In the recent years, significant attention has been paid for the conversion of C-H bond into C-X (X = C, N, O, S, P..etc) bonds using transition metal catalysts. This thesis presents the development of new catalytic systems for the construction of C-C and C-N bonds through late transition metal-mediated C-H activation and decarboxylation reactions. Chapter 1 introduces the background of transition metal catalyzed C-H bond functionalization. This chapter provides reported catalytic methods for the conversion of arene C-H bonds into various functional groups through transition metal mediated chelation-assisted C-H bond activation.
Chapter 2 describes the development of a new method for the synthesis of oxindoles via intramolecular alkene hydroarylation with N-aryl acrylamides using a Ru(II)/N-heterocyclic carbene (NHC) catalyst system. This reaction occurs with good substrate scope and synthetically useful tolerance of functional groups and does not require the assistance of additional directing group. Preliminary mechanistic results support a tandem sequence involving amide-directed aromatic C-H bond activation and intramolecular alkene arylmetalation. Chapter 3 describes ruthenium-based decarboxylative alkenylation of heteroarenes through carboxylate directed C-H bond functionalization. The decarboxylative functionalization of heteroarenes occurs with high regioselectivity and a broad range of functional group tolerance. This decarboxylation proceeds without stoichiometric amounts of bases or oxidants and it is applicable for functionalization of various heteroarenes such as indole, pyrrole, thiophene, benzothiophene, and benzofuran at both C-2 and C-3 positions. The current protocol provides a straightforward approach for the synthesis of trisubstituted olefins with heteroarenes. Chapter 4 explains the development of Rh/Ag-bimetallic catalyst system for decarboxylative amidation of ortho-substituted benzoic acids with 3-aryldioxazolones. The nature of ortho-substituents determines regioselectivity of this reaction through two forms of proposed chelation assistance: (1) A wide range of non-directing ortho-substituents led to ortho-amidation products via carboxylate-directed C-H amidation and subsequent decarboxylation. (2) 2-Pyridyl and analogous DGs led to ipso-amidation products via DG-assisted decarboxylation and subsequent amidation.
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Bowen, John George. "C-H activation in the formation of C-N and C-O Bonds." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.685335.
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The regioselective activation of C-H bonds and subsequent transformation into desirable functional groupS is an attractive prospect in organic synthesis. We have developed two novel C-H functionalisation reactions; the first is an intramolecular, sulfonamide directed, C-H amination reaction for the synthesis of 3_phenylisoindolinone derivates and the second is a sulfonamide directed ortho C-H acetoxylation reaction. Both isoindolinones and phenol derivatives of sulfonamides are important motifs in numerous pharmaceutically relevant compounds. The Cull-catalysed intramolecular C-H amination reaction for the synthesis of substituted 3-phenylisolindolinone derivatives (Scheme i) was found to be tolerant to substitution on both aromatic rings, however, no reaction was observed on exchanging the tethered aryl group for an alkyl group. Mechanistic investigations revealed that C-H cleavage was not part of the rate-determining step which is likely to be coordination of the copper catalyst to the sulfonyl amide. Substitution of the tethered phenyl ring (R2 ) and a subsequent Hammett analysis indicated that this coordination may be accelerated by a cation-IT interaction between CU11 and the pie system of the aryl group.
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Lee, Alison Victoria. "Catalyst and methodology development for regioselective C-N and C-C bond formation." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31377.
Full textAbstract:
The related investigations of catalytic hydroamination as a key step in synthetic methodology development and the synthesis of new hydroamination catalysts are reported in this thesis. The first section focuses on methodology development for the application of a bis(amidate)bis(amido) titanium hydroamination precatalyst towards the synthesis of functionalized small molecules via a tandem C-N, C-C bond forming reaction sequence. The development of two tandem sequential reactions will be described, as well as their applications in the synthesis of α-cyanoamines, α-amino acid derivatives, β-amino alcohols, diamines, imidazolidinones, and β-amino acid derivatives. These tandem reactions show an expanded substrate scope and increase synthetic flexibility by allowing for alternative starting materials in the preparation of highly functionalized small molecules. The second section describes progress towards the development of an asymmetric tandem reaction sequence, including investigations into the mode of activation for the tandem reaction. It has been established that a nucleophilic activation mode is required to generate an active species for the C-C bond forming step. Furthermore, it is postulated that the coordination environment and steric congestion about the activator impacts reaction efficiency and stereoselectivity. This information will be valuable in the design of future generations of activators. The final section reports the development of two novel group 4 metal complexes for catalytic hydroamination. The synthesis and full characterization of these complexes will be described, as well as the results of the catalytic investigations. Through this investigation it has been postulated that while a change in the electronic nature of the metal complex does enhance catalytic reactivity, the degree of orbital overlap between the ligand and the metal center is also an important consideration in the design of electrophilic hydroamination precatalysts. Hydroamination catalysis is currently an attractive area of intense research. The work in this thesis has demonstrated the use of hydroamination catalysis in the synthesis of highly functionalized small molecules, and has furthered the fundamental understanding of the hydroamination reaction. This increase in understanding can then be applied towards the rational design of more powerful hydroamination catalysts and further their application in the synthesis of functionalized N-containing compounds.Science, Faculty of
Chemistry, Department of
Graduate
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Enouz-Védrenne, Shaïma. "Elaboration et analyses structurales et chimiques de nanotubes hétéroatomiques de type C-N et C-B-N." Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2007. http://tel.archives-ouvertes.fr/tel-00147980.
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Il existe actuellement deux structures nanotubulaires largement étudiées : les nanotubes de carbone (CNTs) possédant un gap de l'ordre de 1 eV et ceux de nitrure de bore (BN-NTs) dont le gap est compris entre 5 et 6 eV. Parvenir à doper ces nanotubes par substitution d'éléments chimiques pouvant introduire des états donneurs ou accepteurs est supposé être une approche prometteuse pour moduler les propriétés électroniques et optiques de ces nanostructures. Les objectifs de cette thèse ont été doubles. D'une part, il s'est agi de développer des procédés de synthèse modulables pour pouvoir produire différents types de tubes hétéroatomiques. La technique CVD assistée par aérosol et la technique de vaporisation laser ont été utilisées à cette fin. D'autre part, une analyse fine à l'échelle macroscopique et sub-nanométrique des échantillons a été réalisée principalement par microscopie électronique en transmission (HRTEM) et spectroscopie de pertes d'énergies des électrons résolue spatialement (SR-EELS).Il a ainsi été mis en évidence dans ce manuscrit la possibilité de réaliser des nanotubes de type CNx et CBxNy mono- et multi-feuillets. Par ailleurs, une forte tendance à la ségrégation en domaines de type C et BN a été observée avec un localisation préférentielle et une taille des domaine spécifique, fonction de la technique de synthèse utilisée.
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GERVAIS, CHRISTEL. "Etude par resonance magnetique nucleaire a l'etat solide de divers polymeres, precurseurs de ceramiques b-n, si-c-n, si-b-c-n et si-b-c-o." Paris 6, 1999. http://www.theses.fr/1999PA066210.
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L'elaboration de ceramiques a partir de precurseurs polymeres est une voie de synthese qui s'est beaucoup developpee recemment pour permettre l'elaboration de materiaux composites et remedier a la fragilite des ceramiques massives. Les grandes possibilites de mise en forme offertes par des polymeres solubles ou fusibles va en effet faciliter la fabrication de composites a renfort fibreux presentant d'excellentes proprietes mecaniques et qui trouvent par exemple leur application dans le secteur aeronautique et spatial. L'objet de ce travail est d'evaluer les potentialites qu'offre la rmn a l'etat solide pour caracteriser la conversion de precurseurs polymeres en ceramiques de type nitrure et borure. Cette voie d'elaboration conduit a l'obtention de composes complexes et peu organises dont la caracterisation structurale est relativement difficile. Toutefois, un reel developpement de ces procedes necessite une bonne comprehension des processus mis en jeu lors de la transformation du polymere en ceramique. Nous nous sommes interesses a differents polymeres preceramiques dans les systemes b-n, si-c-n, si-b-c-n et si-b-c-o : nous avons ete amenes a mettre en oeuvre differentes methodes rmn haute resolution a l'etat solide axees plus particulierement sur l'etude des noyaux 1 1b et 1 5n en essayant de contourner les difficultes afferentes a ces derniers (l'existence d'une interaction quadripolaire difficile a moyenner pour 1 1b et une tres faible sensibilite pour 1 5n). Nous avons d'une part tire profit de la presence de protons : elle a permis d'augmenter la sensibilite de spins peu abondants ( 1 3c, 1 5n et 2 9si) mais aussi de sonder l'environnement protone des differents noyaux etudies grace aux techniques de polarisation croisee. Les methodes les plus recents de rmn haute resolution des noyaux quadripolaires ont egalement ete mises en oeuvre (mq-mas, mas a hauts champs) afin d'apprehender les differents environnements du bore au sein d'une meme coordinence.
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Grünberg, Matthias F. [Verfasser], and Lukas [Akademischer Betreuer] Gooßen. "Nachhaltige Konzepte zur C-C, C-N und C-S Bindungsknüpfung / Matthias Grünberg. Betreuer: Lukas Gooßen." Kaiserslautern : Technische Universität Kaiserslautern, 2015. http://d-nb.info/1080521704/34.
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Wrigglesworth, Joseph W. "The development of new palladium(II) catalysed C-C, C-N and C-O bond formations." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601218.
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Cassirame, Bénédicte. "Couplages C-C utilisant des triarylbismuthines catalysés par le PEPPSI." Thesis, Paris Est, 2012. http://www.theses.fr/2012PEST1116.
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Les réactions de couplage métallocatalysées mises en avant par l'attribution du Prix Nobel de Chimie 2010 permettent la création de liaison C-C impossible par les réactions de type SN1 ou SN2. Or, les composés auxquels elles donnent accès sont très utilisés dans le domaine pharmaceutique, agrochimique ou encore dans celui de la chimie supramoléculaire. Si les réactions sont efficaces, les agents de couplages sont souvent peu accessibles et/ou peu éco(nomique/logique)-compatibles. Les triarylbismuthines lèvent en partie ces limitations, car tous les atomes de ces organométalliques participent aux processus et ces composés sont considérés comme non toxiques mais les réactions engageant ce type d'organométalliques souffrent de leur dimérisation. Afin de lever cette limitation, nous avons développé un système catalytique plus " vert" utilisant le PEPPSI comme pré-catalyseur sur une réaction test. Ces nouvelles conditions donnent généralement d'excellents rendements en série biarylique comme hétérobiarylique. La gamme des substituants sur le dérivé halogéné est très étendue mais plus limitée sur la bismuthine. Ce système catalytique a ensuite été utilisé sans modification dans les réactions domino d'élimination/couplage. Une étude cinétique comparative par GC/MS et RMN 13C a permis de montrer qu'une élimination d'ordre 2 avait lieu avant le couplage. De plus il y a un effet coopératif entre les ions fluorures et la bismuthine : celle-ci joue donc un double rôle : agent organométallique doux de couplage et base. L'ambiguïté mécanistique ainsi levée, il a été permis d'envisager une chimiosélectivité en fonction des divers états d'hybridation du carbone portant le brome au moment du couplage. Plusieurs méthodes d'accès à des molécules de structures Ar-Ar-C C-Ar à géométries variables peuvent être obtenues rapidement. Le système catalytique a également permet l'activation de liaison C-Br de bromocoumarines. Ainsi, il est possible de réaliser le couplage sur les positions 3-, 4- et 6-. L'ordre de réactivité a été déterminé ce qui a permis de réaliser des monocouplages parfaitement sélectifs sur les 3,4- ou 3,6- dibromocoumarines, dont les applications biologiques suscitent un grand intérêt. Le nouveau système catalytique a donc éliminé le problème de dimérisation des triarylbismuthines et donne potentiellement accès à des molécules intéressantes pour leurs propriétés physiques ou biologiquesMetallocatalysed crosscoupling reactions have been highlighted by the attribution of the 2010 Nobel Chemistry Price since they allow CC bond formation when classical SN1 or SN2 do not permit it. Furthermore, they give access to many pharmaceutics and agronomic compounds but also molecules used for their supramolecular properties. Nowadays, reactions are really efficient but reactants are not always readily accessible and can't be classified as green reagents. Since all its atoms act over the catalytic process and because they are not considered as toxic so far, triarylbismuthines may be a good alternative to circumvent the limitation described above. However, they suffer a main drawback, their reductive dimerisation. In order to avoid this side-reaction, a new greenest process has been developed on a benchmark reaction based on PEPPSI, an NHC/Pd catalyst. These conditions gave usually excellent yields, either for the biaryle or heterobiaryle crosscoupling reaction. The range of substituents is really wide on the aryle halide moiety but slightly more limited on the triarylbismuthine reagents. Then, this catalytic process has been applied without modification to an elimination/crosscoupling domino reaction. A GC/MS and 13C NMR supported comparative kinetic study showed that a 2nd order elimination take place before the C-C bond formation. Fluoride anion and triarylbismuthine act together. Therefore triarylbismuthine play a dual role: base and aryl transfer reagent. This mechanism study led to chimioselective reactions that allow many paths for the synthesis of Ar-Ar-C C-Ar containing compounds with a good control on geometry of this highly conjugated structure. This catalytic process allows also bromocoumarine C-Br bond activation. Thus, crosscoupling may be selectively performed at the 3-, 4- or 6- position of coumarines. The reactivity order difference of these positions even allow hightly selective mono crosscoupling reaction on 3,4- or 3,6-dibromocoumarines for further biological application. To conclude, our PEPPSI based greenest process avoid the dimerisation of bismuthines and give easy access to many compounds of great interest either for their biological or physical properties
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Owen, Gareth Richard. "Palladium-mediated transformationand activation of unsaturated C-N, C-S and C-O bonds." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408281.
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Frogneux, Xavier. "Transformations réductrices du CO2 pour la formation de liaisons C-N et C-C." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112136/document.
Full textAbstract:
Dans le monde actuel, le dioxyde de carbone (CO2) est le déchet majoritaire issu de l’utilisation des ressources fossiles mais il est encore peu utilisé dans les applications à grande échelle. Afin de tirer parti de son abondance, le développement de nouvelles transformations chimiques du CO2 pour accéder à des produits de chimie fine connait un intérêt croissant au sein de la communauté scientifique. Tout particulièrement, la formation de liaison(s) C-N à partir du CO2 et d’un substrat azotés permet d’accéder à des produits à hautes valeurs énergétiques et commerciales. Un second type de transformation désirable est la formation de liaison C-C à partir du CO2 afin de synthétiser des dérivés d’acides carboxyliques comme des esters. L’utilisation d’hydrosilanes, réducteurs doux, permet de travailler sous 1 bar de CO2 avec des catalyseurs à base de métaux peu coûteux et abondants tels que le fer et le zinc ou bien avec des organocatalyseurs. Les synthèses de formamides, de méthylamines ou d’aminals à partir du CO2 ont ainsi été développées par hydrosilylation. Enfin, la carboxylation des carbosilanes à partir du CO2 a été développée pour la première fois avec un catalyseur à base de cuivre. Dans le cas des 2-pyridylsilanes, l’utilisation de sels de fluorures pentavalents permet d’activer le substrat efficacement sans catalyseurIn the current world, carbon dioxide (CO2) is the major waste of the massive utilization of fossil resources but only few applications have been developed using this compound. In order to take advantage of its abundancy, the development of novel chemical transformation of CO2 to produce fine chemicals is of high interest in the scientific community. In particular, the formation of C-N bond(s) from CO2 and amine compounds unlocks a new way to access high energy and value-added. A second type of highly desirable transformation is the formation of C-C bonds with CO2 so as to synthesize carboxylic acid derivatives. The utilization of hydrosilanes as mild reductants allows the reactions to proceed under 1 bar of CO2 with abundant and cheap metal-based catalysts (iron, zinc) or with organocatalysts. The synthesis of formamides, methylamines and aminals from CO2 are described herein. Ultimately, the catalytic carboxylation of carbosilanes has been achieved for the first time using copper-based complexes. In the specific case of 2-pyridylsilanes, the use of pentavalent fluoride salts allowed us to perform the reaction without catalyst
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Sabour, Abdelouahed. "Étude expérimentale et thermodynamique de systèmes binaires des n-alcanes pairs-impairs (nc₂₃ : n-c₂₄ et nc₂₃ : c₂₂)." Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL064N.
Full textAbstract:
Dans les coupes pétrolières ou gazoles, le dépôt solide cristallise lors de baisses sensibles de la température est constitué en partie de solutions solides de n-alcanes. Compte tenu de la complexité de ces mélanges, la connaissance de leur comportement est nécessaire pour une analyse thermodynamique permettant d'approcher une modélisation du point de trouble des coupes pétrolières paraffiniques ou gazoles. Dans ce travail nous avons détermine les diagrammes de phases des deux systèmes binaires (nc₂₃: nc₂₄ nc₂₃: nc₂₂par l'utilisation conjointe de l'analyse thermique différentielle, de l'analyse enthalpimétrique, de l'analyse thermomécanique et de la diffraction des rayons X. Ceci nous a permis de mettre en évidence plusieurs phases intermédiaires et une systématique dans le comportement de n-alcanes pour les systèmes binaires pairs-impairs. L'étude thermodynamique comporte le représentation des mesures de la variation d'enthalpie en fonction de la température par un modèle du solide d'Einstein, les expressions analytiques des fonctions thermodynamiques sont exploitées pour le calcul des diagrammes de phases en représentant les grandeurs d'excès pour un modèle de margules à deux paramètres
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Hall, Jack Kingsbury Mathematics & Statistics Faculty of Science UNSW. "Some branching rules for GL(N,C)." Awarded by:University of New South Wales. Mathematics and Statistics, 2007. http://handle.unsw.edu.au/1959.4/29473.
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This thesis considers symmetric functions and algebraic combinatorics via the polynomial representation theory of GL(N,C). In particular, we utilise the theory of Jacobi-Trudi determinants to prove some new results pertaining to the Littlewood-Richardson coefficients. Our results imply, under some hypotheses on the strictness of the partition an equality between Littlewood-Richardson coefficients and Kostka numbers. For the case that a suitable partition has two rows, an explicit formula is then obtained for the Littlewood-Richardson coefficient using the Hook Length formula. All these results are then applied to compute branching laws for GL(m+n,C) restricting to GL(m,C) x GL(n,C). The technique also implies the well-known Racah formula.
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Nikolussi, Marc. "Cementite in the Fe-N-C system." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-38396.
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Damak, Mondher. "C*-algebres et probleme a n-corps." Cergy-Pontoise, 2000. http://www.theses.fr/2000CERG0091.
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Le but de cette these est l'etude par des methodes algebriques de certaines generalisations du probleme a n-corps. Notre point de vue est, au depart, celui des chapitres 8 et 9 de abg. Nous montrons dans un premier article (constituant le chapitre 2 de cette these) que les techniques abstraites developpees dans ce livre permettent de retrouver et d'ameliorer les resultats de c. Gerard sur les hamiltoniens dispersifs. Nous montrons aussi que le resultat de lewis, siedentop and vugalter concernant le spectre essentiel des systemes a n particules relativistes decoule facilement de la version algebrique du theoreme hvz de abg. Dans les chapitres 3 et 4 de la these nous allons au-dela du formalisme algebrique pour les systemes a n corps tel qu'il est expose dans le chapitre 9 de abg. Ces deux parties constituent en fait deux papiers en collaboration avec vladimir georgescu. Notre but est d'etudier des c*-algebres d'operateurs suggerees par le probleme a n corps mais en meme temps naturellement associees a des espaces vectoriels de dimensions finies, et de faire l'analyse spectrale des operateurs auto-adjoints qui leurs sont affilies. Cette classe d'operateurs est tres riche, elle permet par exemple de traiter de maniere unifiee les hamiltoniens des systemes dispersifs (avec des interactions dependantes du moment) et ceux des systemes stratifies ou pluristratifies. Abg w. Amrein, a. Boutet de monvel and v. Georgescu, c 0-groups, commutator methods and spectral theory of n-body hamiltonians (birkhauser, progress in math. Ser. Nr. 135, 1996).
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Anderson, Kevin William. "Expanding the substrate scope in palladium-catalyzed C-N and C-C bond-forming reactions." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36255.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.Vita.
Includes bibliographical references.
Chapter 1. The first detailed study of the palladium-catalyzed amination of aryl nonaflates is reported. Use of bulky electron-rich monophosphinobiaryl ligands or BINAP allow for the catalytic amination of electron-rich and -neutral aryl nonaflates with both primary and secondary amines. Using XantPhos, the catalytic amination of a variety of functionalized aryl nonaflates resulted in excellent yields of anilines; even 2-carboxymethyl aryl nonaflate is effectively coupled with a primary alkyl amine. Moderate yields were obtained when coupling halo-aryl nonaflates with a variety of amines, where in most cases the aryl nonaflate reacted in preference to the aryl halide. Overall, aryl nonaflates are an effective alternative to aryl triflates in palladium-catalyzed C-N bond-forming processes due to their increased stability under the reaction conditions. Chapter 2. A catalyst comprised of a Pd precatalyst and 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl is explored in C-N bond-forming processes. This catalyst displayed unprecedented stability and scope allowing, for the first time, the coupling of substrates bearing a carboxylic acid or a primary amide.
(cont.) Also, the more bulky catalyst system Pd/2-tert-butylphosphino-2',4',6'-triisopropylbiphenyl was found to be effective for the Narylation of 2-aminoheterocycles and weakly basic HN-heterocycles: pyrazole and indazole. The chemoselectivity for amination using these catalysts was explored where the rough order of reactivity for amines is: aryl amines >> primary and secondary alkyl amines > 2-aminoheterocycles > primary amides - HN-heterocycles. Chapter 3. The palladium-catalyzed Suzuki-Miyaura coupling of haloaminoheterocycles and functionalized organoboronic acids using a highly active and stable monophosphinobiaryl ligand, 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl, efficiently produced aminoheterocyclic biaryl derivatives. This same catalyst was effective in coupling 2-haloaminoaryl compounds with 2-formyl or 2-acetylphenyl boronic acids, providing the fused heterocyclic compounds phenanthridine, benzo[c][1 ,8]naphthridine and benzo[c][1,5]naphthridine in excellent yields. Chapter 4. A water-soluble monophosphinobiaryl ligand, sodium -dicyclohexylphosphino-2',6'-dimethoxybiphenyl-3'-sulfonate, was synthesized by electrophilic sulfonation of the lower-aromatic ring of 2-dicyclohexylphosphino-2',6'- dimethoxybiphenyl.
(cont.) This ligand was utilized in the palladium-catalyzed Suzuki-Miyaura reaction of water-soluble aryl/heteroaryl halides and organoboronic acids. The catalyst displays unprecedented reactivity and stability for Suzuki-Miyaura reactions conducted in water. Chapter 5. A water-soluble monophosphinobiaryl ligand, sodium 2'-(dicyclohexyl-osphanyl)-2,6-diisopropyl-biphenyl-4-sulfonate, was synthesized by a proposed electrophilic ipso-substitution/reverse Friedel-Crafts alkylation of the lower-aromatic ring on 2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl. This ligand was utilized in the palladium-catalyzed Heck alkynylation (copper-free Sonogashira coupling) of hydrophobic and hydrophilic aryl halides and terminal alkynes conducted in an aqueous acetonitrile solvent system. For the first time, an electron-deficient terminal alkyne, propiolic acid, was successfully coupled with aryl bromides. We also demonstrated that this catalyst is useful in the reaction of benzyl chlorides and terminal alkynes to provide benzyl alkynes in good yields. We show that by using an excess amount of base (> 1.0 equiv.) and higher reaction temperatures ( 80 °C), base-catalyzed isomerization to the corresponding aryl allenes can be achieved in a one-pot process.
by Kevin W. Anderson.
Ph.D.
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Chudasama, V. "The use of aerobic aldehyde C-H activation for the construction of C-C and C-N bonds." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1324525/.
Full textAbstract:
This thesis describes a series of studies directed towards the use of aerobic aldehyde C-H activation for the construction of C-C and C-N bonds by the process of hydroacylation. Chapter 1 provides an introduction to the research project and an overview of strategies for hydroacylation. Chapter 2 describes the application of aerobic aldehyde C-H activation for the hydroacylation of vinyl sulfonates and sulfones. A discussion on the mechanism of the transformation, the effect of using aldehydes with different oxidation profiles and the application of chiral aldehydes is also included. Chapter 3 describes the functionalisation of γ-keto sulfonates with particular emphasis on an elimination/conjugate addition strategy, which provides an indirect approach to the hydroacylation of electron rich alkenes. Chapters 4 and 5 describe the application of aerobic aldehyde C-H activation towards the hydroacylation of α,β-unsaturated esters and vinyl phosphonates, respectively. An in-depth discussion on the mechanism and aldehyde tolerance of each transformation is also included. Chapter 6 describes acyl radical approaches towards C-N bond formation with particular emphasis on the synthesis of amides and acyl hydrazides.
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Söllner, Johannes [Verfasser]. "C^C*-Cyclometallierende N-heterocyclische Carbenliganden in photophysikalisch aktiven Übergangsmetallkomplexen / Johannes Söllner." München : Verlag Dr. Hut, 2020. http://d-nb.info/1219477540/34.
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Baalbaki, Zein El-A. "Vibrational relaxation of N₄O, C₄H₄, and C₄H₄-Ar mixtures." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4666.
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Persson, Andreas K. Å. "Palladium(II)-Catalyzed Oxidative Cyclization Strategies : Selective Formation of New C-C and C-N Bonds." Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-75435.
Full textAbstract:
The main focus of this thesis has been directed towards preparation and oxidative carbocyclization of en-, dien- and aza-enallenes. In the first part of this thesis, a stereoselective oxidative carbocyclization of dienallenes was realized. By employing cheap and readily available palladium trifluoroacetate we were able to efficiently cyclize a variety of dienallenes into hydroxylated carbocycles in high yield and high selectivity. This oxidative process was compatible with two different reoxidation protocols: one relying on p-benzoquinone (BQ) as the oxidant and the other employing molecular oxygen as the oxidant. In the second part of the thesis the carbocyclization methodology was extended to include carbocyclization of aza-enallenes. This was achieved in two distinct steps. First, a copper-catalyzed coupling of allylic sulfonamides with bromoallenes was developed, giving access to the corresponding aza-enallenes. Subjecting these substrates to catalytic amounts of palladium acetate, along with BQ as the oxidant, rendered N-heterocycles in good yield. The reactivity of these N-heterocycles towards activated dienophiles was later exploited in a tandem (aerobic) oxidative carbocyclization/Diels-Alder reaction. The third topic involves efficient oxidative arylative/borylative carbocyclization of enallenes. These reactions, catalyzed by palladium acetate, relies on transmetallation of a (σ-alkyl)palladium(II) intermediate with diboranes or arylboronic acids. With this novel methodology we were able to obtain an array of arylated or borylated carbocycles, as single diastereomers, in high yield. Finally, we developed a palladium(II)-catalyzed cyclization of allylic carbamates. This mild, operationally simple, and scalable catalytic reaction opens up access to an array of oxazolidinones in high yield and excellent diastereoselectivity.At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 6: Manuscript.