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

Currently, opioids are extensively used in clinical practices in order to treat pain in patients. However, prolonged administration of opioids are not feasible due to the development of side effects especially tolerance, constipation, addiction and dependence. Our drug design is mainly aimed to reduce opioid induce side effects such as development of tolerance. The first strategy examined involves design and synthesis of peptide based single molecules that have a mu agonist and delta agonist pharmacophore in combination with a COX2 inhibitory pharmacophore. A new molecule, 3-17 having good delta agonist activity, partial COX2 inhibitory activity and weak mu agonist activity was produced. Moreover, Investigation of the bioactivities of the synthesized ligands including 3-17 in terms of their ligand receptor interactions were probed using NMR conformational analysis along with docking analysis to the respective homology modeled mu and delta opioid receptors as well as the COX2 enzyme. As a further continuation of this work, instead of peptide based mu agonist and delta agonist type pharmacophore, the highly mu selective fentanyl pharmacophore was used in combination with a pyrazole based and a pyrazolone based COX pharmacophore. Based on the SAR study and docking analysis of synthesized ligands to the homology modeled mu opioid receptor, an ideal tolerant position without significant loss of mu opioid agonist activity for fentanyl were found. The second strategy involves design and synthesis of a peptide based single molecule that has a mu agonist and a delta antagonist pharmacophore in combination with a NK1 antagonist pharmacophore. A novel molecule (4-2) containing delta antagonist activity, weak mu agonist activity and NK1 antagonist activity was identified. Its homology modeled mu opioid receptor bound conformation was compared with that of reference ligands. Docking analysis of modified 4-2 to the homology modeled mu opioid receptor revealed that it can be further modified to obtain better mu agonist activity. 4-2 showed antinociception for 45 min period of time after injection in tail flick assay. In addition to studies that were directed to avoid tolerance development due to opioid administration, peptide based potential analgesics such as biphalin was modified by introducing more peptidomimetic character in order to enhance its blood brain barrier permeability and proteolytic stability. The novel molecule (6-7) was produced in this study and its antinociception lasted for 30 min period of time after injection in the tail flick assay.

No description available.

No description available.

abstract: In a typical living cell, millions to billions of proteins—nanomachines that fluctuate and cycle among many conformational states—convert available free energy into mechanochemical work. A fundamental goal of biophysics is to ascertain how 3D protein structures encode specific functions, such as catalyzing chemical reactions or transporting nutrients into a cell. Protein dynamics span femtosecond timescales (i.e., covalent bond oscillations) to large conformational transition timescales in, and beyond, the millisecond regime (e.g., glucose transport across a phospholipid bilayer). Actual transition events are fast but rare, occurring orders of magnitude faster than typical metastable equilibrium waiting times. Equilibrium molecular dynamics (EqMD) can capture atomistic detail and solute-solvent interactions, but even microseconds of sampling attainable nowadays still falls orders of magnitude short of transition timescales, especially for large systems, rendering observations of such "rare events" difficult or effectively impossible. Advanced path-sampling methods exploit reduced physical models or biasing to produce plausible transitions while balancing accuracy and efficiency, but quantifying their accuracy relative to other numerical and experimental data has been challenging. Indeed, new horizons in elucidating protein function necessitate that present methodologies be revised to more seamlessly and quantitatively integrate a spectrum of methods, both numerical and experimental. In this dissertation, experimental and computational methods are put into perspective using the enzyme adenylate kinase (AdK) as an illustrative example. We introduce Path Similarity Analysis (PSA)—an integrative computational framework developed to quantify transition path similarity. PSA not only reliably distinguished AdK transitions by the originating method, but also traced pathway differences between two methods back to charge-charge interactions (neglected by the stereochemical model, but not the all-atom force field) in several conserved salt bridges. Cryo-electron microscopy maps of the transporter Bor1p are directly incorporated into EqMD simulations using MD flexible fitting to produce viable structural models and infer a plausible transport mechanism. Conforming to the theme of integration, a short compendium of an exploratory project—developing a hybrid atomistic-continuum method—is presented, including initial results and a novel fluctuating hydrodynamics model and corresponding numerical code. / Dissertation/Thesis / Doctoral Dissertation Physics 2017

Several studies have long been carried out for inorganic compounds involving a net of SiO chemical bonds. This is due to fact of these chemical bonds be present in high number of many inorganic materials. The formation process of these compounds involving SiO bonds is well-known as sol-gel technology, which give rises to the molecular systems containg the silanol functional group as one of most important intermediate species of the process. Due to major industrial importance of process, a systematic theoretical studied based on DFT/B3LYP/6-311+G(d,p) methodology was performed to evaluate the conformational and vibrational variation of tetraethoxysilane (TEOS) and its complete and incomplete hydrolysis products. First of all, a conformational analysis was done considering several conformers of silicic acid, Si(OH)4, which was obtained using the following point group symmetry: D2d, S4, C2v e Cs. These structures were investigated by using different rotations for the formation of the potential energy curves, where the most stable geometry was later optimized. These results indicate the S4 conformer as the global minimum structure for complete hydrolysis product,Si(OH)4. At a later time, frequency calculations were performed to investigated the harmonic vibrational spectra of the most stable conformers within the D2d, S4, C2v e Cs symmetry point groups. The obtained results pointed out that the perfil of vibration spectra, between 700-1000 cm-1, shows different characteristics along the decrease of the point group symmetry, which is indicated by the formation of the two active frequency models in C2v and Cs structures. In a second part of this study, a conformational study was carried out to obtain the geometries of the incomplete hydrolysis products of TEOS, Si(OC2H5)4-n(OH)n, withn=1-3. Geometry optimization and vibrational calculations were performed for these structures. The main results are compared with the silicic acid and indicate a hypsocromic shift of vibrational mode Þas SiO as the etoxi group (.OC2H5) is substituted by smaller hydroxil groups (.OH). / Uma ampla serie de trabalhos contendo redes de ligacoes SiO tem sido desenvolvidos nos ultimos anos, pelo fato destas ligacoes estarem presentes em diversos materiais inorganicos. O processo de formacao destas redes SiO e conhecido como tecnologia sol-gel, o qual apresenta moleculas contendo o grupo funcional silanol como uma das mais importantes especies intermediarias formadas.Devido a importancia industrial desse processo, neste trabalho foi abordado um estudo teorico e computacional sistematico sobre a variacao conformacional e vibracional do tetraetoxisilano(TEOS) e seus produtos de hidrolise completa e incompleta, para isso o metodo teorico DFT/B3LYP/6-311+G(d,p) foi usado.Em um primeiro momento, neste estudo, os diversos conformeros do acido silicico, Si(OH)4, foram obtidos considerando os grupos de simetria D2d, S4, C2v e Cs. Essas estruturas foram investigadas utilizando diferentes criterios de rotacao para a geracao das curvas de energia potencial, que posteriormente, tiveram suas geometrias otimizadas. Os resultados obtidos na analise das curvas de energia potencial bem como os calculos de otimizacao de geometria permitiram-nos identificar a estrutura de grupo pontual S4 como sendo o conformero mais estavel em energia para o produto de hidrolise completa do Si(OH)4. Posteriormente, um estudo vibracional foi realizado para os conformeros mais estaveis de cada grupo de simetria D2d, S4, C2v e Cs. Os resultados obtidos mostraram que a aparencia dos espectros de infravermelho, no intervalo entre 700-1000 cm-1, apresentou caracteristicas diferentes no sentido do decrescimo de simetria dos grupos pontuais, provocados pelo desdobramento de alguns modos ativos no infravermelho nos grupos pontuais C2v e Cs. Em um segundo momento,um estudo conformacional foi realizado para se obter as geometrias dos produtos de hidrolise incompleta do TEOS,Si(OC2H5)4-n(OH)n, com n=1-3.Essas geometrias foram otimizadas e, em seguidauma analise espectroscopica foi elaborada para os sistemas molecularesmais estaveis.Os resultados obtidos sao comparados com o acido silicio e mostraram um deslocamento batocromico da frequencia do modo vibracional Þas SiOa medida que grupos etoxi (.OC2H5) vao sendo substituidos por grupos menos volumosos, o hidroxil (.OH).

Capes / Este trabalho teve por objetivos a síntese dos isômeros cis e trans do acetal 2-fenil-5-hidróxi-1,3-dioxano (FHD), e o estudo dos equilíbrios conformacionais por cálculos teóricos. A metodologia experimental consistiu na produção dos acetais através da reação de acetalisação do glicerol com benzaldeído em meio ácido. A separação dos isômeros do FHD promoveu-se por cromatografia de camada fina e em coluna. No estudo teórico as conformações iniciais tiveram suas geometrias otimizadas e comparadas as posições otimizadas com as estruturas semelhantes do 4-fenilcicloexanol (FCO). As superfícies de energias potenciais (PES) foram construídas pelos giros de 10 em 10º dos diedros C7-C8-C2-O1 referente ao anel aromático e ao diedro C4-C5-O13-H25 da hidroxila. A influência de diferentes substituintes nos equilíbrios conformacionais foi determinada através da inserção dos seguintes grupos na posição meta do anel aromático: NO2, CHO, CF3, Cl, F, CH3, OCH3, OH, NH2 e N(CH3)2. Também foram realizados os estudos de NBO e a determinação das cargas atômicas pelos métodos Mulliken, NBO e APT. Nos cálculos teóricos foi utilizado o método B3LYP na função de base 6-311G++(d,p). Os resultados experimentais indicaram que com o eluente hexano/acetona na proporção 1:1 foi possível isolar os isômeros cis e trans do FHD. Quanto ao estudo teórico, a otimização das conformações mostrou a presença das ligações de hidrogênio intramoleculares (LHI) O-H...O entre o hidrogênio da hidroxila e os oxigênios do dioxano, e a existência das inéditas LHI C-H...O entre os hidrogênios orto do anel aromático e os oxigênios do dioxano. A otimização das geometrias e as PES indicaram uma maior estabilização da conformação eqeq em relação ao axax do isômero trans de 1,04 kcal.mol-1, devido a maior força das LHI C-H...O com o fenil na equatorial. No isômero cis a conformação eqax apresentou ser mais estável do que a axeq em 4,29 kcal.mol-1 motivada pela maior força das LHI C-H...O e O-H...O. A influência dos substituintes no isômero trans foi muito significativa a ponto de atingir-se uma redução na proporção da conformação diaxial de 15% para 1% com o substituinte NO2 e um aumento para 44% com o grupo N(CH3)2. Por fim as análises de NBO e a determinação das cargas atômicas mostraram a baixa densidade eletrônica dos hidrogênios orto que favorecem a formação das LHI C-H...O / This work aimed to the synthesis cis and trans isomers of the 2-phenyl-5-hydroxy-1,3-dioxane (PHD) acetal and the study of conformational equilibria by theoretical calculations. Acetals were prepared by acetalization reaction of glycerol with benzaldehyde under acidic conditions. The isomers separations were promoted by thin layer and column chromatography. In the theoretical study the initial conformations were optimized and theirs geometries were compared with the optimized structures of similar 4-phenylcyclohexanol (PCO). The potential energy surfaces (PES) were made by turn dihedral angle C7-C8-C2-O1 and C4-C5-O13-H25 by 10 in 10 degrees to 360o. The influence of substituent on conformational equilibrium were determined by inserting the groups NO2, CHO, CF3, Cl, F, CH3, OCH3, OH, NH2 and N(CH3)2 at the meta position of the aromatic ring. Studies were also performed with NBO and by atomic charges determination using Mulliken, NBO, and APT methods. Theoretical calculations were made using B3LYP method and 6-311++G(d, p) basis function. Experimental results indicated that was possible isolate the cis and trans isomers of PHD with hexane/acetone 1:1. As for the theoretical study, the optimization of the conformations showed the presence of intramolecular hydrogen bonds (IHB) OH...O between the hydroxyl hydrogen and oxygen of dioxane. It was observed the existence of unpublished IHB CH...O between the ortho hydrogen of aromatic ring and dioxane oxygen. The optimization of geometries and PES indicated a more stable conformation eqeq than axax in relation to the trans isomer of 1.04 kcal.mol-1. This is due the greater strength of IHB CH...O with the phenyl group in equatorial position. In the cis isomer the conformation eqax it was more stable than axeq by 4.29 kcal.mol-1 because of greater strength of IHB CH...O and OH...O. The influence of the substituent in the trans isomer werevery significant to reduces diaxial conformer of 15% to 1% with the NO2 group and increases to 44% with N(CH3)2 group. Finally the NBO analysis and the determination of atomic charges showed low electron density of the ortho hydrogen indicating IHB CH...O.

Capes / Este trabalho teve por objetivos a síntese dos isômeros cis e trans do acetal 2-fenil-5-hidróxi-1,3-dioxano (FHD), e o estudo dos equilíbrios conformacionais por cálculos teóricos. A metodologia experimental consistiu na produção dos acetais através da reação de acetalisação do glicerol com benzaldeído em meio ácido. A separação dos isômeros do FHD promoveu-se por cromatografia de camada fina e em coluna. No estudo teórico as conformações iniciais tiveram suas geometrias otimizadas e comparadas as posições otimizadas com as estruturas semelhantes do 4-fenilcicloexanol (FCO). As superfícies de energias potenciais (PES) foram construídas pelos giros de 10 em 10º dos diedros C7-C8-C2-O1 referente ao anel aromático e ao diedro C4-C5-O13-H25 da hidroxila. A influência de diferentes substituintes nos equilíbrios conformacionais foi determinada através da inserção dos seguintes grupos na posição meta do anel aromático: NO2, CHO, CF3, Cl, F, CH3, OCH3, OH, NH2 e N(CH3)2. Também foram realizados os estudos de NBO e a determinação das cargas atômicas pelos métodos Mulliken, NBO e APT. Nos cálculos teóricos foi utilizado o método B3LYP na função de base 6-311G++(d,p). Os resultados experimentais indicaram que com o eluente hexano/acetona na proporção 1:1 foi possível isolar os isômeros cis e trans do FHD. Quanto ao estudo teórico, a otimização das conformações mostrou a presença das ligações de hidrogênio intramoleculares (LHI) O-H...O entre o hidrogênio da hidroxila e os oxigênios do dioxano, e a existência das inéditas LHI C-H...O entre os hidrogênios orto do anel aromático e os oxigênios do dioxano. A otimização das geometrias e as PES indicaram uma maior estabilização da conformação eqeq em relação ao axax do isômero trans de 1,04 kcal.mol-1, devido a maior força das LHI C-H...O com o fenil na equatorial. No isômero cis a conformação eqax apresentou ser mais estável do que a axeq em 4,29 kcal.mol-1 motivada pela maior força das LHI C-H...O e O-H...O. A influência dos substituintes no isômero trans foi muito significativa a ponto de atingir-se uma redução na proporção da conformação diaxial de 15% para 1% com o substituinte NO2 e um aumento para 44% com o grupo N(CH3)2. Por fim as análises de NBO e a determinação das cargas atômicas mostraram a baixa densidade eletrônica dos hidrogênios orto que favorecem a formação das LHI C-H...O / This work aimed to the synthesis cis and trans isomers of the 2-phenyl-5-hydroxy-1,3-dioxane (PHD) acetal and the study of conformational equilibria by theoretical calculations. Acetals were prepared by acetalization reaction of glycerol with benzaldehyde under acidic conditions. The isomers separations were promoted by thin layer and column chromatography. In the theoretical study the initial conformations were optimized and theirs geometries were compared with the optimized structures of similar 4-phenylcyclohexanol (PCO). The potential energy surfaces (PES) were made by turn dihedral angle C7-C8-C2-O1 and C4-C5-O13-H25 by 10 in 10 degrees to 360o. The influence of substituent on conformational equilibrium were determined by inserting the groups NO2, CHO, CF3, Cl, F, CH3, OCH3, OH, NH2 and N(CH3)2 at the meta position of the aromatic ring. Studies were also performed with NBO and by atomic charges determination using Mulliken, NBO, and APT methods. Theoretical calculations were made using B3LYP method and 6-311++G(d, p) basis function. Experimental results indicated that was possible isolate the cis and trans isomers of PHD with hexane/acetone 1:1. As for the theoretical study, the optimization of the conformations showed the presence of intramolecular hydrogen bonds (IHB) OH...O between the hydroxyl hydrogen and oxygen of dioxane. It was observed the existence of unpublished IHB CH...O between the ortho hydrogen of aromatic ring and dioxane oxygen. The optimization of geometries and PES indicated a more stable conformation eqeq than axax in relation to the trans isomer of 1.04 kcal.mol-1. This is due the greater strength of IHB CH...O with the phenyl group in equatorial position. In the cis isomer the conformation eqax it was more stable than axeq by 4.29 kcal.mol-1 because of greater strength of IHB CH...O and OH...O. The influence of the substituent in the trans isomer werevery significant to reduces diaxial conformer of 15% to 1% with the NO2 group and increases to 44% with N(CH3)2 group. Finally the NBO analysis and the determination of atomic charges showed low electron density of the ortho hydrogen indicating IHB CH...O.

Um dos maiores desafios atuais na biologia estrutural é como lidar com flexibilidade de proteínas. Além do desafio experimental, uma limitação teórica é a falta de uma linguagem matemática conveniente para representação do espaço conformacional de proteínas. As representações mais populares apresentam diversas limitações, que se refletem nas dificuldades associadas à análise de ensembles conformacionais. Nesse contexto, a aplicação de geometria diferencial (GD) e teoria da informação (TI) foi pouco explorada. Neste trabalho investigamos o uso de descritores de GD e TI como uma representação matemática do espaço conformacional de proteínas aplicada à análise de ensembles conformacionais. O cálculo dos descritores de GD consiste em representar o backbone de proteínas como curvas espaciais e caracterizá-las utilizando os seus valores de curvatura, &kappa;, e torção, &tau; . Baseado nesses valores, definimos medidas de flexibilidade, de distância entre conformações e aplicamos uma estratégia de clustering para identificação de estados conformacionais. Para permitir a aplicação de TI, desenvolvemos um sistema de codificação desses descritores para expressar cada conformação por uma sequência de símbolos finitos. A partir dessas sequências, definimos uma medida da informação associada a um resíduo, Rres, e a uma conformação, Rconf. Para investigar sua eficácia, aplicamos os métodos propostos aos ensembles conformacionais de três sistemas testes: 1) Ubiquitina, 2) E1-DBD do HPV18 e 3) as etapas de formação do complexo c-Myb-KIX. A análise da representação por geometria diferencial se mostrou igualmente eficaz ou superior aos métodos comumente utilizados em todos os sistemas analisados. O método é especialmente útil para monitoramento de estabilidade de hélices e para análise de proteínas e regiões muito flexíveis, pois evita a necessidade de sobreposição estrutural. Os valores de Rconf se apresentaram úteis para análise de processos de enovelamento e resíduos próximos a regiões funcionais tendem a apresentar maiores valores Rres. No entanto, o papel desses resíduos é incerto e mais estudos são necessários para determinar se há e qual é seu real significado. Apesar disso, as medidas de informação se mostraram úteis para comparação de estados conformacionais e permitem levantar hipóteses testáveis em laboratório. Por fim, a representação por GD é computacionalmente conveniente, intuitiva, evita todas as limitações dos métodos popularmente utilizados e se mostrou eficaz para análise de ensembles conformacionais. / One of the major challenges of modern structural biology is how to deal with protein flexibility. Besides the experimental difficulties, a relatively overlooked theoretical challenge is the lack of a proper mathematical language to represent proteín conformational space. The most popular representations have severe limitations, which reflects on the difficulties associated with conformational ensemble analyses. However, differential geometry (GD) and information theory (TI) can help to overcome such difficulties and were not well explored in this context. Here we investigate the usage of DG and TI as a mathematical representation of protein conformational space applied to the analyses of conformational ensembles. The DG descriptors calculation consists of representing protein backbone as a spatial curve and describes it by its curvature, &kappa;, and torsion, &tau; . Based on those values, the distance between conformation and flexibility measurements were defined and a clustering algorithm was applied to identify conformational states. For the application of TI, a coding system for DG descriptors was developed to express each conformation as a sequence of finite symbols. Based on those sequences, information measurements associated to a residue, Rres, and to a conformation, Rconf , were defined. To investigate its efficacy, the proposed method was applied to conformation ensembles of three test systems: 1) Ubiquitin, 2) E1-DBD of HPV18 and 3) the steps of c-Myb-KIX binding. The DG analyses show equally good or superior performance when compared with popular methods on all tested system. In addition, the methods are especially useful to monitoring helix stability and analyses of very flexible proteins (or regions), since avoids the necessity of superposing structures. The values of Rconf are useful to compare different steps of a folding process and residues near regions involved in binding events tend to present higher values of Rres. However, those residues importance is uncertain and further studies are necessary to determinate if and how those can contribute to protein function. Nevertheless, the information measurements were informative on the comparison of compare conformational states and allow to formulate a testable hypothesis. On the other hand, the GD representation is computationally convenient, intuitive and avoid most of the limitations of the popular method applied to conformational ensemble analyses.

Several studies have long been carried out for inorganic compounds involving a net of SiO chemical bonds. This is due to fact of these chemical bonds be present in high number of many inorganic materials. The formation process of these compounds involving SiO bonds is well-known as sol-gel technology, which give rises to the molecular systems containg the silanol functional group as one of most important intermediate species of the process. Due to major industrial importance of process, a systematic theoretical studied based on DFT/B3LYP/6-311+G(d,p) methodology was performed to evaluate the conformational and vibrational variation of tetraethoxysilane (TEOS) and its complete and incomplete hydrolysis products. First of all, a conformational analysis was done considering several conformers of silicic acid, Si(OH)4, which was obtained using the following point group symmetry: D2d, S4, C2v e Cs. These structures were investigated by using different rotations for the formation of the potential energy curves, where the most stable geometry was later optimized. These results indicate the S4 conformer as the global minimum structure for complete hydrolysis product,Si(OH)4. At a later time, frequency calculations were performed to investigated the harmonic vibrational spectra of the most stable conformers within the D2d, S4, C2v e Cs symmetry point groups. The obtained results pointed out that the perfil of vibration spectra, between 700-1000 cm-1, shows different characteristics along the decrease of the point group symmetry, which is indicated by the formation of the two active frequency models in C2v and Cs structures. In a second part of this study, a conformational study was carried out to obtain the geometries of the incomplete hydrolysis products of TEOS, Si(OC2H5)4-n(OH)n, withn=1-3. Geometry optimization and vibrational calculations were performed for these structures. The main results are compared with the silicic acid and indicate a hypsocromic shift of vibrational mode Þas SiO as the etoxi group (.OC2H5) is substituted by smaller hydroxil groups (.OH). / Uma ampla serie de trabalhos contendo redes de ligacoes SiO tem sido desenvolvidos nos ultimos anos, pelo fato destas ligacoes estarem presentes em diversos materiais inorganicos. O processo de formacao destas redes SiO e conhecido como tecnologia sol-gel, o qual apresenta moleculas contendo o grupo funcional silanol como uma das mais importantes especies intermediarias formadas.Devido a importancia industrial desse processo, neste trabalho foi abordado um estudo teorico e computacional sistematico sobre a variacao conformacional e vibracional do tetraetoxisilano(TEOS) e seus produtos de hidrolise completa e incompleta, para isso o metodo teorico DFT/B3LYP/6-311+G(d,p) foi usado.Em um primeiro momento, neste estudo, os diversos conformeros do acido silicico, Si(OH)4, foram obtidos considerando os grupos de simetria D2d, S4, C2v e Cs. Essas estruturas foram investigadas utilizando diferentes criterios de rotacao para a geracao das curvas de energia potencial, que posteriormente, tiveram suas geometrias otimizadas. Os resultados obtidos na analise das curvas de energia potencial bem como os calculos de otimizacao de geometria permitiram-nos identificar a estrutura de grupo pontual S4 como sendo o conformero mais estavel em energia para o produto de hidrolise completa do Si(OH)4. Posteriormente, um estudo vibracional foi realizado para os conformeros mais estaveis de cada grupo de simetria D2d, S4, C2v e Cs. Os resultados obtidos mostraram que a aparencia dos espectros de infravermelho, no intervalo entre 700-1000 cm-1, apresentou caracteristicas diferentes no sentido do decrescimo de simetria dos grupos pontuais, provocados pelo desdobramento de alguns modos ativos no infravermelho nos grupos pontuais C2v e Cs. Em um segundo momento,um estudo conformacional foi realizado para se obter as geometrias dos produtos de hidrolise incompleta do TEOS,Si(OC2H5)4-n(OH)n, com n=1-3.Essas geometrias foram otimizadas e, em seguidauma analise espectroscopica foi elaborada para os sistemas molecularesmais estaveis.Os resultados obtidos sao comparados com o acido silicio e mostraram um deslocamento batocromico da frequencia do modo vibracional Þas SiOa medida que grupos etoxi (.OC2H5) vao sendo substituidos por grupos menos volumosos, o hidroxil (.OH).