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São Miguel do Guamá, Brazil

Coral N.,University of Sao Paulo | Rodrigues E.,Institute Ciencias Exatas e Naturais | Rumjanek V.,Federal Rural University of Rio de Janeiro | Zamian J.R.,University of Sao Paulo | And 2 more authors.
Magnetic Resonance in Chemistry | Year: 2013

Production of alternative fuels, such as biodiesel, from transesterification of vegetable oil driven by heterogeneous catalysts is a promising alternative to fossil diesel. However, achieving a successful substitution for a new renewable fuel depends on several quality parameters. 1H NMR spectroscopy was used to determine the amount of methyl esters, free glycerin and acid number in the transesterification of soybean oil with methanol in the presence of hydrotalcite-type catalyst to produce biodiesel. Reaction parameters, such as temperature and time, were used to evaluate soybean oil methyl esters rate conversion. Temperatures of 100 to 180 °C and times of 20 to 240 min were tested on a 1: 12 molar ratio soybean oil/methanol reaction. At 180 °C/240 min conditions, a rate of 94.5 wt% of methyl esters was obtained, where free glycerin and free fatty acids were not detected. Copyright © 2012 John Wiley & Sons, Ltd. Source

Scalercio S.R.R.A.,Institute Ciencias da Saude | Pereira G.A.N.,Institute Ciencias Exatas e Naturais | Correa I.D.M.,Institute Ciencias da Saude | Oliveira D.J.,Centro Universitario Do Para | And 3 more authors.
Journal of Computational and Theoretical Nanoscience | Year: 2011

A theoretical study about the chloroquine was executed using DFT method (B3LYP/6-31G*) to clarify anti-malarial influence of 4-amine-quinoline (AQ) tautomerism. Stability and reactivity were determined by geometric and energetic parameters in gas phase for AQ as simplified model of chloroquine (CQ) and compared with water and chloroform solvents using PCM methods. The results have shown that AQ is more stable than 4-imine-quinoline (IQ) on the gas phase and these relative energy differences of the tautomers were increased by solvent effect influence. Copyright © 2011 American Scientific Publishers. Source

Figueiredo A.F.,Institute Ciencias Exatas e Naturais | Ferreira J.E.V.,Institute Ciencias Exatas e Naturais | Barbosa J.P.,Institute Ciencias Exatas e Naturais | Da Cruz MacEdo W.J.,Institute Ciencias Exatas e Naturais | And 4 more authors.
Journal of Computational and Theoretical Nanoscience | Year: 2011

This work employed computational chemistry to study dispiro-1,2,4- trioxolanes with antimalarial activities against K-1 strains of Plasmodium falciparum. Molecules were optimized with B3LYP/6-31G* method. Maps of molecular electrostatic potential helped to identify features related to their activities. Molecular docking was performed to study the complex formed. A predictive model was generated by PLS method, with three latent variables explaining 99.8% of the total variance, Q 2 = 0.87, R 2 = 0.85, obtained for 16/4 molecules in the training/external validation set. The descriptors selected for the model were the binding free energy, logarithm of octanol-water partition coefficient (logP ) and molecular volume. As an application, we tested our PLS model to predict the pIC 50 of 20 dispiro-1,2,4-trioxolanes whose biological tests were not performed with them yet. Three compounds showed higher antimalarial activity than artemether and artesunate. Copyright © 2011 American Scientific Publishers. Source

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