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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.
| Identifer | oai:union.ndltd.org:IBICT/oai:repositorio.ufrn.br:123456789/19597 |
| Date | 08 August 2014 |
| Creators | Silva, S?rgio Ruschi Bergamachi |
| Contributors | 03306745790, http://lattes.cnpq.br/6586639715910129, Vieira, Davi Serradella, 27800669890, http://lattes.cnpq.br/4185159774625471, Maciel, Maria Aparecida Medeiros, 37320165449, http://lattes.cnpq.br/5360188002708095, Santos, Zilvam Melo dos, 01211514412, http://lattes.cnpq.br/4514068026830748, Firme, Caio Lima |
| Publisher | Universidade Federal do Rio Grande do Norte, PROGRAMA DE P?S-GRADUA??O EM QU?MICA, UFRN, Brasil |
| Source Sets | IBICT Brazilian ETDs |
| Language | Portuguese |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, info:eu-repo/semantics/masterThesis |
| Source | reponame:Repositório Institucional da UFRN, instname:Universidade Federal do Rio Grande do Norte, instacron:UFRN |
| Rights | info:eu-repo/semantics/openAccess |
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