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Uma perspectiva computacional sobre catálise enzimática; A computational perspective on enzymatic catalysis

ARANTES, Guilherme M.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
36.72%
Enzymes are extremely efficient catalysts. Here, part of the mechanisms proposed to explain this catalytic power will be compared to quantitative experimental results and computer simulations. Influence of the enzymatic environment over species along the reaction coordinate will be analysed. Concepts of transition state stabilisation and reactant destabilisation will be confronted. Divided site model and near-attack conformation hypotheses will also be discussed. Molecular interactions such as covalent catalysis, general acid-base catalysis, electrostatics, entropic effects, steric hindrance, quantum and dynamical effects will also be analysed as sources of catalysis. Reaction mechanisms, in particular that catalysed by protein tyrosine phosphatases, illustrate the concepts.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Silica functionalized sulfonic acid catalyzed one-pot synthesis of 4,5,8a-triarylhex-ahydropyrimido[4,5-d]pyrimidine-2,7(1H,3 H)-diones under liquid phase catalysis

Gupta,Princy; Kumar,Vineet; Paul,Satya
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 Português
Relevância na Pesquisa
36.64%
SiO2-SO3H catalyzed one-pot synthesis of 4,5,8a-triarylhexahydropyrimido[4,5-d]pyrimidine-2,7(1H,3 H)-diones (4a-k) is reported under liquid phase catalysis. The catalyst is easily prepared, highly stable, very simple to handle and recycled for five times without loss of significant activity.

Dual bifunctional catalysis and the α-effect in the reaction of hydroxylamine with phenylacetate

Mazera,Deise J.; Pliego Jr.,Josefredo R.; Almerindo,Gizelle I.; Gesser,José C.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2011 Português
Relevância na Pesquisa
36.72%
The reaction of hydroxylamine with phenyl acetate was theoretically investigated to shed light on the role of catalysis and the origin of the α-effect in this system. Calculations at the B3LYP/6-311+G(2df,2p)//HF/6-31G(d) level and the solvent effect included at the PCM/HF/6-31G(d) level predict that the direct attack of hydroxylamine to the carbonyl centre has a high ΔG‡ barrier, close to 50 kcal mol-1. A second hydroxylamine molecule can catalyse the process through bifunctional catalysis using both the NH2 and OH groups simultaneously. This dual bifunctional catalysis decreases the ΔG‡ to 19 kcal mol-1 and is able to explain the experimentally observed kinetics and product ratio.

Ionic Liquids and Catalysis

Souza,Michèle O. de
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2014 Português
Relevância na Pesquisa
36.64%
This paper explores the growing number of publications concerning the use of ionic liquids (ILs) in the period from 1994 to 2013. Catalysis can be identified as the area responsible for the surge of interest in ILs. The same is true for the Brazilian scientific community. The contributions of the group of Prof Roberto Fernando de Souza and those obtained through numerous collaborations are described in this context. The literature survey shows that in the studied period the significant increase in ILs publications occurs at different times depending on their applied area (catalysis, energy, materials, analytical chemistry, biomass, etc.).