Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-01-14T18:51:53Z No. of bitstreams: 1 SergioRuschiBergamachiSilva_DISSERT.pdf: 4405606 bytes, checksum: 784604c435bd6eb5424d9dbf6448597d (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-01-15T19:10:11Z (GMT) No. of bitstreams: 1 SergioRuschiBergamachiSilva_DISSERT.pdf: 4405606 bytes, checksum: 784604c435bd6eb5424d9dbf6448597d (MD5) / Made available in DSpace on 2016-01-15T19:10:11Z (GMT). No. of bitstreams: 1 SergioRuschiBergamachiSilva_DISSERT.pdf: 4405606 bytes, checksum: 784604c435bd6eb5424d9dbf6448597d (MD5) Previous issue date: 2014-08-08 / No presente trabalho objetivou-se inicialmente, o estudo te?rico da estabilidade de intermedi?rios tetra?dricos formados a partir de rea??es de adi??o ? carbonila utilizando a teoria perturbativa M?ller-Plesset de segunda (MP2) e terceira ordem (MP3). Correla??es lineares entre a diferen?a de energia eletr?nica de rea??es com ?ndices de Wiberg e comprimentos de liga??es C-O foram obtidas, tendo sido observado que a estabilidade dos adutos formados depende diretamente da densidade eletr?nica envolvida entre esses ?tomos. O entendimento dos par?metros eletr?nicos dessas estruturas possui grande import?ncia devido ao grande uso de rea??es qu?micas que em seu curso formam este tipo intermedi?rio tetra?drico. Empregando a metodologia ONIOM (B3LYP:AMBER), avaliou-se a estereosseletividade de uma rea??o enzim?tica entre a enzima CAL B com um ?ster de cadeia longa. Neste estudo, foram obtidas as energias eletr?nicas do estado inicial e do intermedi?rio da etapa lenta da rea??o da transesterifica??o a partir das duas poss?veis faces proquirais Re e Si. O objetivo foi estudar a enantiosseletividade da CAL B e racionaliz?-la a partir da teoria qu?ntica de ?tomos em mol?culas (QTAIM). Um estudo te?rico utilizando compostos inorg?nicos foi realizado com o m?todo ab initio CBS-QB3 objetivando encontrar uma rela??o entre termodin?mica e equil?brio envolvendo ?cidos e bases. Os resultados observados mostraram uma excelente rela??o entre a varia??o da energia livre de Gibbs, ?G, de dissocia??o de ?cidos com o ?G da rea??o de hidr?lise da base conjugada correspondente. Observou-se, ainda, uma rela??o entre o ?G da rea??o de hidr?lise de ?cidos conjugados e seus correspondentes raios at?micos mostrando que a estabilidade desempenha um papel importante nas rea??es de hidr?lise. A import?ncia da solvata??o no comportamento ?cido/base quando comparado a ?Gs te?ricos e experimentais, tamb?m foi avaliada. / The present work aimed first, the theoretical study of tetrahedral intermediate stability formed from carbonyl addition reactions using the second (MP2) and third (MP3) order M?ller?Plesset perturbation theory. Linear correlations between electronic energy difference of reactions with Wiberg Indexes and C-O bond lengths were obtained, and was observed that the stability of adducts formed depends directly of electronic density involved between these atoms. The knowing of electronic parameters of these structures has an important hole due to the large use on reactions that in his course forms this tetrahedral intermediate. Employing the ONIOM (B3LYP:AMBER) methodology, was evaluated the stereoselectivity of a enzymatic reaction between CAL B enzyme and a long chain ester. In this study, were obtained the electronic energies of ground state and intermediate state of transesterification rate-determing step from two possible proquirals faces Re and Si. The objective was study the enantioselectivity of CAL B and rationalizes it using quantum theory of atoms in molecules (QTAIM). A theoretical study employing inorganic compounds was performed using ab initio CBS-QB3 method aiming to find a link between thermodynamic and equilibrium involving acids and bases. The results observed showed an excellent relationship between difference in Gibbs free energy, ?G of acid dissociation reaction and ?G of hydrolysis reaction of the corresponding conjugate base. It was also observed, a relationship between ?G of hydrolysis reaction of conjugate acids and their corresponding atomic radius showing that stability plays an important role in hydrolysis reactions. The importance of solvation in acid/base behavior when compared to theoretical and experimental ?G?s also was evaluated.