With use of deuterium-labeled isotopes of RRR-and all-rac-α-tocopheryl acetate, the transport of vitamin E in pregnancy was evaluated to determine whether the placenta discriminates between these compounds. Fifteen pregnant subjects were recruited 5 d before delivery to receive 15, 30, 75, 150, or 300 mg vitamin E/d in capsules containing d3-RRR-α-tocopheryl acetate and d6-all-rac-α-tocopheryl acetate (1:1, by wt). Maternal blood was obtained before dosing, at hospital admission, and at parturition. Cord blood samples were obtained at parturition. Deuterium-labeled and unlabeled tocopherol contents were determined by gas chromatography-mass spectrometry in plasma and lipoproteins (chylomicrons, VLDL, LDL, and HDL). Maternal plasma and lipoproteins obtained at delivery had higher concentrations of d3-RRR-α- tocopherol than d6-all-rac-α-tocopherol regardless of the vitamin E dose administered (P < 0.05). Cord plasma at delivery also had higher concentrations of d3-RRR-α-tocopherol than d6-all-rac-α-tocopherol in plasma irrespective of the dose administered (P < 0.05). In lipoproteins isolated from cord blood, tocopherol concentrations were greatest in the HDL fraction (P < 0.05), whereas in maternal blood they were greatest in the LDL fraction (P < 0.05). We conclude that the placental-fetal unit, the fetal liver, or both further discriminate between RRR- and all-rac-α-tocopherol.

Estudos do mecanismo de reações unimoleculares, das moléculas de acetato de metila e etila, induzidas por absorção multifotônica e de reações bimoleculares com os radicais OH e Cl, usando cálculos ab initio e de funcional de densidade foram realizados neste trabalho. A análise dos cálculos das barreiras de energia e das constantes de velocidade microcanônicas das reações unimoleculares com o formalismo da teoria RRKM, permitiu prever algumas reações cujos produtos não foram determinados experimentalmente. Além disso, semelhanças das geometrias e dos valores de energia de algumas estruturas entre diferentes superfícies de energia, analisadas com cálculos de IRC, permitiram a explicação da viabilidade de determinada via de reação em detrimento de outra. Em outro método, relatado por Forst(1), na determinação das constantes de velocidade variacionais, comparadas com a variação da energia de Gibbs, verificou-se constantes de velocidade microcanônicas menores e a localização dos estados de transição em comprimentos de ligação, também, menores. Nas reações com o radical OH e Cl, a via predominante de reação é o ataque aos hidrogênios do grupo ligado diretamente ao oxigênio da molécula, responsável pelo valor da constante final de mais de 93% nas reações com OH e 99% nas reações com Cl, a 298K, em concordância com os resultados experimentais, em detrimento do ataque ao grupo CH3 da porção carboxilato da molécula. Nas reações com OH, os valores de constante de velocidade calculados mais próximos dos valores experimentais foram obtidos a partir dos resultados com os funcionais mPW1B95-41, para o acetato de metila, e mPW1B95-44, para o acetato de etila, enquanto que nas reações com Cl foram obtidos com o os métodos CCSD(T)//B3LYP para o acetato de metila e CCSD(T)//MP2 para o acetato de etila. Os valores de constante de velocidade da reação com cloro são cerca de dez vezes maiores que aquelas para as reações com radicais OH. As reações com OH e Cl ocorrem em uma única etapa, sem estabilização do intermediário e sem efeito de tunelamento significante. Por sua vez, cálculos da constante de velocidade, pelo método da relação estrutura reatividade (SAR), sobreestimam a reatividade dos hidrogênios dos grupos CH3 na porção carboxilato, em ambos os acetatos, e na porção etóxido do acetato de etila. Este método falha ao descrever a participação de cada grupo na reação com Cl, pois prevê que a reação no grupo CH3 da porção alcóxido passa a ser predominante sobre a reação ao grupo CH2 nas reações do acetato de etila, oposto aos nossos cálculos onde a reação com o grupo CH2 é a predominante. Outra falha do método é na previsão de mesma reatividade para ambos os grupos CH3 no acetato de metila, pois por nossos cálculos a reação ocorre predominantemente no grupo CH3 na porção alcóxido da molécula. / Computational studies on methyl and ethyl acetates molecules using ab initio and density functional calculations exploring the unimolecular mechanism, induced by multiphoton absorption, and the bimolecular reactions with OH and Cl radicals, have been performed in this work. Analysis of the calculated energy barriers and rate constants of unimolecular reactions with the RRKM microcanonical theory, predicts the occurrence of some reactions whose products were not determined experimentally. Furthermore, similarities on geometrical and energetic of some structures between different energy surfaces, analyzed with IRC calculations, allowed the explanation of the viability of a particular reaction pathway over another. Forst\'s method, used to determine variational rate constants, when compared with the variation of Gibbs energy, generates microcanonical rate constants with smaller values and location of transition states in smaller bond lengths. With OH and Cl, the predominant reaction route is the attack on the hydrogens of the group bonded directly to oxygen in the molecule, responsible for more than 93% of the final constant value in reactions with OH and 99% in reactions with Cl , at 298 K, in agreement with the experimental results, while the attack to the CH3 group in the carboxylate portion of the molecule is the less likely to occur. In reactions with OH, the values of the rate constant calculated closer to the experimental values were obtained from the results with functional mPW1B95-41, for methyl acetate, and mPW1B95-44 for ethyl acetate, whereas in reactions with Cl, were obtained with the CCSD(T)//B3LYP method for the methyl acetate and the CCSD(T)//MP2 method for ethyl acetate. The rate constant for the reaction with chlorine are about ten times larger than those for reactions with OH radicals. Reactions with OH and Cl occur in a single step, without stabilization of the intermediary and without significant tunneling effect. The rate constant obtained by the structure-reactivity relationship (SAR) overestimates the reactivity of the hydrogens of the CH3 groups at the carboxylate portion, in both acetates, and at the ethoxide portion of ethyl acetate. This method fails to describe the participation of each group in the reaction with Cl, predicting that the reaction on the CH3 portion of the alkoxide becomes predominant over the reaction on the CH2 group of ethyl acetate, relative to our calculations where the reaction with the CH2 group is predominant. Another flaw by providing the same reactivity for both the CH3 in methyl acetate, is in disagreement with our calculations which indicate that the reaction occurs predominantly in the CH3 group at the alkoxide portion of the molecule.

Estudos do mecanismo de reações unimoleculares, das moléculas de acetato de metila e etila, induzidas por absorção multifotônica e de reações bimoleculares com os radicais OH e Cl, usando cálculos ab initio e de funcional de densidade foram realizados neste trabalho. A análise dos cálculos das barreiras de energia e das constantes de velocidade microcanônicas das reações unimoleculares com o formalismo da teoria RRKM, permitiu prever algumas reações cujos produtos não foram determinados experimentalmente. Além disso, semelhanças das geometrias e dos valores de energia de algumas estruturas entre diferentes superfícies de energia, analisadas com cálculos de IRC, permitiram a explicação da viabilidade de determinada via de reação em detrimento de outra. Em outro método, relatado por Forst(1), na determinação das constantes de velocidade variacionais, comparadas com a variação da energia de Gibbs, verificou-se constantes de velocidade microcanônicas menores e a localização dos estados de transição em comprimentos de ligação, também, menores. Nas reações com o radical OH e Cl, a via predominante de reação é o ataque aos hidrogênios do grupo ligado diretamente ao oxigênio da molécula, responsável pelo valor da constante final de mais de 93% nas reações com OH e 99% nas reações com Cl, a 298K, em concordância com os resultados experimentais, em detrimento do ataque ao grupo CH3 da porção carboxilato da molécula. Nas reações com OH, os valores de constante de velocidade calculados mais próximos dos valores experimentais foram obtidos a partir dos resultados com os funcionais mPW1B95-41, para o acetato de metila, e mPW1B95-44, para o acetato de etila, enquanto que nas reações com Cl foram obtidos com o os métodos CCSD(T)//B3LYP para o acetato de metila e CCSD(T)//MP2 para o acetato de etila. Os valores de constante de velocidade da reação com cloro são cerca de dez vezes maiores que aquelas para as reações com radicais OH. As reações com OH e Cl ocorrem em uma única etapa, sem estabilização do intermediário e sem efeito de tunelamento significante. Por sua vez, cálculos da constante de velocidade, pelo método da relação estrutura reatividade (SAR), sobreestimam a reatividade dos hidrogênios dos grupos CH3 na porção carboxilato, em ambos os acetatos, e na porção etóxido do acetato de etila. Este método falha ao descrever a participação de cada grupo na reação com Cl, pois prevê que a reação no grupo CH3 da porção alcóxido passa a ser predominante sobre a reação ao grupo CH2 nas reações do acetato de etila, oposto aos nossos cálculos onde a reação com o grupo CH2 é a predominante. Outra falha do método é na previsão de mesma reatividade para ambos os grupos CH3 no acetato de metila, pois por nossos cálculos a reação ocorre predominantemente no grupo CH3 na porção alcóxido da molécula. / Computational studies on methyl and ethyl acetates molecules using ab initio and density functional calculations exploring the unimolecular mechanism, induced by multiphoton absorption, and the bimolecular reactions with OH and Cl radicals, have been performed in this work. Analysis of the calculated energy barriers and rate constants of unimolecular reactions with the RRKM microcanonical theory, predicts the occurrence of some reactions whose products were not determined experimentally. Furthermore, similarities on geometrical and energetic of some structures between different energy surfaces, analyzed with IRC calculations, allowed the explanation of the viability of a particular reaction pathway over another. Forst\'s method, used to determine variational rate constants, when compared with the variation of Gibbs energy, generates microcanonical rate constants with smaller values and location of transition states in smaller bond lengths. With OH and Cl, the predominant reaction route is the attack on the hydrogens of the group bonded directly to oxygen in the molecule, responsible for more than 93% of the final constant value in reactions with OH and 99% in reactions with Cl , at 298 K, in agreement with the experimental results, while the attack to the CH3 group in the carboxylate portion of the molecule is the less likely to occur. In reactions with OH, the values of the rate constant calculated closer to the experimental values were obtained from the results with functional mPW1B95-41, for methyl acetate, and mPW1B95-44 for ethyl acetate, whereas in reactions with Cl, were obtained with the CCSD(T)//B3LYP method for the methyl acetate and the CCSD(T)//MP2 method for ethyl acetate. The rate constant for the reaction with chlorine are about ten times larger than those for reactions with OH radicals. Reactions with OH and Cl occur in a single step, without stabilization of the intermediary and without significant tunneling effect. The rate constant obtained by the structure-reactivity relationship (SAR) overestimates the reactivity of the hydrogens of the CH3 groups at the carboxylate portion, in both acetates, and at the ethoxide portion of ethyl acetate. This method fails to describe the participation of each group in the reaction with Cl, predicting that the reaction on the CH3 portion of the alkoxide becomes predominant over the reaction on the CH2 group of ethyl acetate, relative to our calculations where the reaction with the CH2 group is predominant. Another flaw by providing the same reactivity for both the CH3 in methyl acetate, is in disagreement with our calculations which indicate that the reaction occurs predominantly in the CH3 group at the alkoxide portion of the molecule.

Made available in DSpace on 2014-10-09T12:50:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:43Z (GMT). No. of bitstreams: 1 10459.pdf: 5417083 bytes, checksum: ed654658e2629338a19dc7ae0a312583 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:50:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:58:43Z (GMT). No. of bitstreams: 1 10459.pdf: 5417083 bytes, checksum: ed654658e2629338a19dc7ae0a312583 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Filmes foram preparados com êxito dissolvendo e misturando quitosana com celulose de sisal no sistema de solvente NaOH/tiouréia. Nenhum solvente residual foi encontrado nos filmes preparados, conforme mostrado por análise elementar (S) e absorção atômica (Na). Os filmes foram caracterizados por técnicas como espectroscopia na região do infravermelho com transformada Fourier, difração de raios-X e análise térmica (TG, DSC e DMTA). A compatibilidade de ambos biopolímeros foi avaliada por microscopia eletrônica de varredura, em cujas imagens o filme de biocompósito mostrou uma organização intermediária entre a rede de fibra de celulose e a homogeneidade do filme de quitosana. Interações com água foram estudadas por medida de ângulos de contatos de uma gota d\'água com a superfície do filme, isoterma de absorção de umidade e relaxometria de RMN T2. A análise de ângulo de contato mostrou uma deformação que pode ocorrer na superfície devido a alta afinidade destes materiais com a gota d\'água. O sistema de solvente NaOH/tiouréia levou a despolimerização de ambos biopolímeros, mas sem provocar perda da capacidade de formação de filme dos mesmos. Resultados de índice de cristalinidade sugeriram que as interações entre quitosana e o solvente foram mais intensas do que as interações entre celulose e o solvente. Os resultados de relaxometria de RMN T2 do biocompósitos mostrou que as características da quitosana prevaleceram sobre as da celulose no que se refere as interações com água. Acetatos de celulose de sisal com diferentes graus de substituição foram preparados em meio homogêneo (DMAc/LiCl como sistema de solvente) e caracterizados por RMN 1H (determinação do grau de substituição), cromatografia de exclusão por tamanho (determinação da massa molar média) e análise térmica (TG e DSC). Filmes deste acetato de celulose de sisal com diferentes graus de substituição, com e sem reforço de celulose de sisal, foram preparados com êxito a partir de soluções de DMAc/LiCl. Nenhum solvente residual foi encontrado nos filmes preparados, conforme evidenciado por análise elementar (Na) e absorção atômica (Li). Na caracterização dos filmes, foram utilizadas técnicas de análise térmica (DSC, TG e DMTA) e ensaio de tração que mostraram que os filmes de acetatos de celulose mais substituídos apresentam decomposição térmica em temperaturas mais elevada e são menos resistentes a tração que os filmes de acetatos de celulose menos substituídos. A partir da análise de isoterma de absorção de umidade, foi possível constatar que os filmes de acetatos de celulose mais substituídos são consideravelmente menos higroscópicos que os filmes de acetatos de celulose menos substituídos. As imagens de microscopia eletrônica de varredura mostraram que os filmes de acetato com diferentes graus de substituição apresentam morfologia distinta. Tanto a associação de celulose de sisal com quitosana quanto com acetato de celulose, obtido de celulose de sisal, mostrou melhoras nas propriedades dos filmes, gerando um interesse em novas pesquisas e aplicações destes materiais. / Films were successfully prepared by dissolving and mixing chitosan and sisal cellulose in NaOH/thiourea solvent system. No residual solvent was found in the prepared films, as shown by elemental analysis (S) and atomic absorption (NA). They were characterized by conventional techniques such as Fourier Transformed Infrared spectroscopy, X-ray diffractometry and thermal analysis (DSC, TG, DMTA). The compatibility of both biopolymers was evaluated by scanning electron microscopic, in which the biocomposite film showed an organization interposed between the cellulose fiber mesh and chitosan films homogeneity. Water interactions were studied by measuring contact angles, humidity absorption isotherms and NMR T2 relaxometry. Contact angle analysis pointed out the deformation that can occur at the surface due to the high affinity of these materials with the drop of water. The solvent system, NaOH/thiourea, led to depolymerization of both biopolymers, without causing loss of film forming capacities. Results about crystalline-properties index suggested that the interactions between chitosan and solvent were more intense than the interactions between cellulose and solvent. The behavior of the T2 NMR relaxometry of biocomposites showed more evident interaction between chitosan and water compared to cellulose-water interaction. Sisal cellulose acetates with different degrees of substitution (DS) were prepared in homogeneous environment (DMAc/LiCl as solvent) and characterized by NMR 1H (determining the degree of substitution), size exclusion chromatography (determination of molar mass average) and thermal analysis (TG and DSC). Sisal cellulose acetate films of varying degrees of substitution (DS), were successfully prepared using DMAc/LiCl as solvent system, with and without sisal cellulose strengthening. No residual solvent was found in the prepared films, as verified by elemental analysis (Na) and atomic absorption (Li). The characterization of the films were carried out by thermal analysis techniques (DSC, TG and DMTA) and traction test which showed that the cellulose acetate films with bigger DS present thermal decomposition at higher temperatures and are less resistant to traction than cellulose acetate films with smaller DS. From humidity absorption analysis, it was found that the cellulose acetate films with higher DS are considerably less hygroscopic than cellulose acetate films with lower DS. From scanning electron microscopic analysis it was possible to evaluate that acetate films with different DS have distinct morphology. Sisal cellulose association with both chitosan and cellulose acetate obtained from sisal cellulose, showed improvements in the properties of films, generating an interest in new research and applications of these materials.

Les boranes vinyliques,les acides boroniques vinyliques et les boronates vinyliques sont des organoboranes où la différence d'électronégativité entre le carbone et le bore est très faible[C (2. 55)-B (2. 04)] et la liaison entre ces deux atomes est donc peu polaire. Les propriétés caractéristiques du bore permettent de réaliser une grande variété de réactions dans différentes conditions. Beaucoup de groupes de recherche ont exploré les applications synthétiques des organoboranes en synthèse organique. Par exemple les boranes vinyliques peuvent être transformés en les alcènes correspondants par protonolyse,ils peuvent être facilement oxydés avec H2O2 en présence de base(addition d'un groupe hydroxyle sur la double liaison) pour donner des produits cis-anti Markovnikov. Ils peuvent aussi subir des réactions d'addition pour donner des alcools allyliques ou des cycloadditions [4+2] pour former deux nouvelles liaisons carbone- carbone via des réactions de Diels-Alder. Les acides vinylboroniques peuvent être transformés en halogénures vinyliques via une halogénolyse,réagir via une réaction de cyclisation radicalaire utilisant la méthode catalytique de Corey en présence d'un initiateur de réaction radicalaire pour obtenir des diols 1,3- ou 1,4. Ils peuvent participer à des réactions de couplage au palladium de type Suzuki pour former de nouvelles liaisons carbone-carbone. Ils peuvent réagir avec des anhydrides pour donner différentes cétones insaturatées via des catalyses au palladium ou au rhodium . Les acides vinylboroniques ont aussi été utilisés pour la formation de nouvelles liaisons carbone-azote , carbone-oxygène , carbone-fluor via des réactions catalysées au palladium ou au cuivre. Les boronates vinyliques ont été employés pour former de nouvelles liaisons carbone-carbone via des couplages de Suzuki- Miyaura. Ils sont employés dans la réaction multicomposant de Petasis pour donner des hétérocycles azotés fonctionnalisés. Ils participent aux réactions de métathèse croisée pour donner des boronates vinyliques hautement fonctionnalisés , ils réagissent facilement avec des carbènes générés à partir de diazos pour donner des cyclopropanes et ceci à travers des catalyses au palladium et au rhodium. Les boronates vinyliques, en réaction avec des oxides de nitrile subissent des réactions de cycloaddition 1,3-dipolaire pour donner des isoxazoles . Les boronates vinyliques ont aussi été utilisés comme nucléophiles en réaction d'allylation avec catalyse au cuivre ou au palladium. Les transformations précédentes des organoboranes fournissent des précurseurs importants pour la synthèse totale de molécules bioactives complexes qui ont été utilisées dans les domaines de la médecine, de l'agrochimie, des composés pharmaceutiques et de la chimie fine. Les organoboranes peuvent être synthétisés facilement et ceci les rend particulièrement précieux comme intermédiaires clés en synthèse organique. / Vinylboranes, vinylboronic acids and vinylboronates are organoboranes where the electro negativity difference between carbon and boron bond is very low [C (2. 55)-B (2. 04)] and the bond between them is less polar. The characteristic features of borane allow performing wide range of reactions under different conditions. Several research groups explored the synthetic applications of organoboranes in organic synthesis. For example vinylboranes can be transformed to their corresponding alkenes via protonolysis,can be easily oxidized by hydrogen peroxide in presence of base(addition of hydroxy group at double bond)to result cis-,anti Markovnikov products also participate in addition reactions to give allylic alcohols,they undergo[4+2]cyclo adition reactions to form two new carbon- carbon bonds via Diels- Alder reaction. Vinylboronic acids can be transformed to vinylhalides via halogenolysis,react via boron-tethered radical cyclisation using Corey’s catalytic tributyl-stannane method in presence of radical initiator to afford 1,3- or 1,4-diols,participates in palladium catalyzed Suzuki cross coupling reactions to give characteristic carbon-carbon bond,react with anhydrides to result various unsaturated ketones via palladium and rhodium catalysis,vinylboronic acids were also used for the synthesis of new carbon-nitrogen,carbon- oxygen, carbon-fluoine bonds via palladium and copper catalysis. Vinylboronates were used to synthesize new carbon-carbon bonds via Suzuki- Miyaura cross coupling reaction under palladium catalysis, participates in Petasis multicomponent reaction to give functionalized nitrogen based heterocycles, they undergo olefin cross-metathesis to afford highly functionalized vinylboronate deivaives, readily react with carbene generated from diazo compounds to afford cyclopropane derivatives under palladium and rhodium catalysis. Vinylboronates on treatment with arylnitrile oxides undergo 1,3-dipolar cyclo addition reaction to give isoxazole derivatives, vinylboronates were also used as nucleophiles in allylation with copper and palladium catalysisThe above transformations of organoboranes provide important precursors for building complex bioactive molecules which were developed as medicine, agrochemicals, pharmaceuticals and fine chemicals. Organoboranes can be easily synthesized and this easy access for preparation made them useful key intermediates for organic synthesis. Vinylboranes can be synthesized via hydroboration of alkynes with alkylboranes,vinylboronic acids can be synthesized via hydroboration of alkynes with alkoxyboranes followed by hydrolysis where as vinylboronates were synthesized from organometallic reagents by transmetallation with trimethyl orthoborate,also prepared from hydroboration of alkynes with alkoxyboranes. Grafting a substitution in the allylic position of vinyl boronates confers to these units a high degree of versatility to their use in organic synthesis. -substitue.

No description available.

Many bacteria accumulate carbon stores as poly-3-hydroxybutyrate (PHB) when growth is limited but carbon availability is not. This stored carbon can then be utilized during conditions of limited carbon availability. The net PHB accumulation in the cell is dependent on the balance between PHB synthesis and degradation. Sinorhizobium meliloti accumulates PHB in the free-living stage but not in the symbiotic stage. The physiological role of the PHB cycle in S. meliloti is unknown. As a first step to understand the genetics of PHB degradation, transposon-generated mutants that were not able to use PHB degradation intermediates, such as 3-hydroxybutyrate and acetoacetate, as a sole carbon source, were isolated. Genetic mapping revealed that there were at least three chromosomal loci involved in acetoacetate metabolism. Identification of these three loci determined that in S. meliloti: (1) acetoacetyl-CoA synthetase (AcsA), encoded by acsA2 gene, rather than the enzyme acetoacetate:succinyl-CoA transferase, is the enzyme that catalyzes activation of acetoacetate to acetoacetyl-CoA; (2) PHB synthase, encoded by phbC, is required for acetoacetate utilization; (3) a putative transporter protein encoding gene, aau-3, may also be involved in acetoacetate metabolism. acsA2 and aau-3 were 78% linked in co-transduction, while phbC was mapped to somewhere else on the chromosome. Biochemical analysis revealed that acsA2::Tn5 mutants lacked AcsA activity but not acetoacetate:succinyl-CoA transferase activity, while phbC::Tn5 maintained similar level of AcsA activity as wild type in vitro. PHB was absent in the phbC mutant. / One transposon-generated mutant, age-1, showed enhanced growth rate on acetoacetate medium. Genetic mapping and transductional analysis indicated that the location of the mutation in age-1 is tightly linked to acsA2. Fine mapping with PCR and DNA sequence techniques showed that Tn5 in age-1 was located at 132 by upstream of the putative translation start site of acsA2. Gene expression analysis indicated that age-1 insertion results in elevated transcription of acsA2. Thus enhanced growth rate on acetoacetate was due to the increased gene expression. acsA2 transcription was induced by acetoacetate and 3-hydroxybutyrate, and repressed by glucose and acetate. / All mutants formed root nodules that fixed nitrogen with varying decrease of impairment. Acetoacetate metabolism and the PHB degradation are not essential for symbiosis.

Dans le cadre du projet DISPATMO (étude de prévision des risques de pollution liés à la dispersion atmosphérique de produits chimiques), des études de risques liés aux incendies et explosions dus aux produits chimiques ont été menées. L’objectif de cette thèse était de réaliser une étude cinétique et mécanistique approfondie afin de déterminer la dégradation en phase gazeuse de l'un des principaux constituants du solvant Tiflex, acétate de 1-méthoxy-2-propyle (MPA), par les radicaux OH et les atomes de Cl. En outre, les constantes de vitesse de réaction de OH et Cl avec une série d' acétates d’alcoxyle largement utilisés dans l'industrie du revêtement et la peinture, l'acétate de méthoxy-2-butyle (2MBA), l'acétate de méthoxy-3-butyle (3MBA), l'acétate de méthoxy-éthyle (MEA), l'acétate d'éthoxy-éthyle (EEE) et l’acétate de n-pentyle (n-PA), ont été déterminées. Les expériences ont été conduites en utilisant la technique de photolyse laser pulsée couplée à la fluorescence induite par laser, un réacteur à écoulement à basse pression couplé à un spectromètre de masse et une chambre de simulation atmosphérique couplé à GC-FID, FTIR et GC-MS en utilisant les méthodes absolue et relative. Les données cinétiques ont été utilisées pour déterminer les expressions Arrhenius pour évaluer le devenir environnemental des composés étudiés tels que leur durée de vie et le potentiel de formation d'ozone. D'autre part, le mécanisme réactionnel a été étudié et les principaux produits de dégradation et leurs rendements ont été déterminés en présence de NO. Les spectres d’absorption UV-Vis de MPA, 2MBA et 3MBA ont également été déterminés afin d'évaluer le potentiel de photolyse de ces composés dans l’atmosphère. Les paramètres cinétiques et mécanistiques ainsi que les durées de vie troposphérique déterminés sont utilisés comme données d'entrée dans les modèles de simulation atmosphériques photochimiques et dans les modèles de dispersion atmosphérique de produits chimiques pour évaluer leur impact atmosphérique. / In the context of DISPATMO project (forecast study of pollution risks related to the atmospheric dispersal of chemicals), risk studies linked to the fires and the explosions due to chemical storage were conducted. The purpose of this thesis was to perform a thorough kinetic and mechanistic study to determine the gas phase degradation of one of the main component of Tiflex solvent, the 1-methoxy 2-propyl acetate (MPA). Furthermore, the rate coefficients of OH and Cl with a series of alkoxy acetates widely used in painting and coating industries, 2-methoxy-butyl acetate (2MBA), 3-methoxybutyl acetate (3MBA), methoxy ethyl acetate (MEA), ethoxy ethyl acetate (EEA) and n-pentyl acetate (n-PA), were determined. The experiments were performed employing the pulsed laser photolysislaser induced fluorescence technique, a low pressure flow tube reactor coupled with a quadrupole mass spectrometer and an atmospheric simulation chamber coupled with a GC-FID, a FTIR and a GC-MS using complementary absolute and relative rate methods. The kinetic data were used to derive the Arrhenius expressions as well as to evaluate the environmental fate of the studied compounds such as their lifetimes and the Photochemical Ozone Creation Potential. Besides, the reaction mechanism was investigated, while the major degradation products and their yields were determined in presence of NO. In addition, the UV-Vis absorption cross sections of MPA, 2MBA and 3MBA were measured in order to evaluate their potential photolysis in the atmosphere. The investigation of the chemical processes and the tropospheric lifetimes of the compounds are used as input data in photochemical atmospheric simulation models and in chemical agent atmospheric dispersion models to evaluate their atmospheric impact.