Quinoline derivatives: potential antiparasitic and antiviral agents

The crystal structures of closely related quinoline compounds substituted at the 2‐position by a vinyl group, either including a Cl atom [2‐(1‐chloro‐2‐methylprop‐1‐enyl)‐8‐nitroquinoline, C₁₃H₁₁ClN₂O₂, (I)] or not [2‐(2‐methylprop‐1‐enyl)‐8‐nitroquinoline, C₁₃H₁₂N₂O₂, (II)], show an important deviation of the vinyl group from coplanarity with the quinoline ring system if the Cl atom is present. The nitro group is perpendicular [in (II)] or nearly so [in (I)] to the quinoline ring system. In (II), all non‐H atoms except the nitro O atoms are located on a crystallographic mirror plane.     

Effect of the modifier ion on the properties of MgFe<Subscript>2</Subscript>O<Subscript>4</Subscript> and ZnFe<Subscript>2</Subscript>O<Subscript>4</Subscript> pigments

Magnesium and zinc ferrites have been prepared by the polymeric precursor method. The organic material decomposition was studied by thermogravimetry (TG) and differential thermal analysis (DTA). The variation of crystalline phases and particle morphology with calcination temperature were investigated using X-ray diffraction (XRD) and scanning electronic microscopy (SEM), respectively. The colors of the ferrites were evaluated using colorimetry. Magnesium ferrite crystallizes above 800°C, presenting a yellow- orange color with a reflectance peak at the 600–650 nm range, while zinc ferrite crystallizes at 600°C, with a reflectance peak between 650–700 nm, corresponding to the red-brick color.     

Temperature‐dependent conformational analysis of cyclononane: An ab initio study

Quantum chemical methods were used for the theoretical determination of the conformational population for the relevant conformers of cyclononane, i.e., TBC, TCB, TCC, and M4 (or C1), which have been previously investigated experimentally through detailed examination of the nuclear magnetic resonance (NMR) spectrum. Our best Gibbs free energy result, evaluated with MP4(SDTQ)/6‐31G(d,p)//MP2/6‐31G(d,p) energy differences and MP2/6‐31G(d,p) thermal corrections, lead to a temperature‐dependent population in excellent agreement with the experimental results based on the analysis of the low temperature ¹³C NMR spectrum. The nice agreement with experiment is achieved using MP2 harmonic frequencies for the evaluation of vibration partition functions within the standard statistic thermodynamics formalism. Theoretical temperature‐dependent infrared (IR) and ¹³C NMR spectra were simulated and compared with experimental data, which confirmed the ab initio conformational population reported here. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Perspectives on bioenergy and biotechnology in Brazil

Brazil is one of the world’s largest producers of alcohol from biomass at low cost and is responsible for more than 1 million direct jobs. In 1973, the Brazilian Program of Alcohol (Proalcool) stimulated the creation of a bioethanol industry that has led to large economic, social, and scientific improvements. In the year 1984, 94.5% of Brazil’s cars used bioethanol as fuel. In 2003/2004, 350.3 million of sugarcane produced 24.2 million t of sugar and 14.4 billion L of ethanol for an average 4.3 million cars using ethanol. Since its inception, cumulative investment in Proalcool totals US$11 billion, and Brazil has saved US$27 billion in oil imports. The ethanol production industry from sugarcane generates 152 times more jobs than would have been the case if the same amount of fuel was produced from petroleum, and the use of ethanol as a fuel is advantageous for environmental reasons. In 2003, one of the biggest Brazilian ethanol industries started consuming 50% of the residual sugarcane bagasse to produce electrical energy (60 MW), a new alternative use of bioenergy for the Brazilian market. Other technologies for commercial uses of bagasse are in development, such as in the production of natural fibers, sweeteners (glucose and xylitol), single-cell proteins, lactic acid, microbial enzymes, and many other products based on fermentations (submerged and semisolid). Furthermore, studies aimed at the increase in the biosynthesis of sucrose and, consequently, ethanol productivity are being conducted to understand the genetics of sugarcane. Although, at present, there remain technical obstacles to the economic use of some ethanol industry residues, several research projects have been carried out and useful data generated. Efficient utilization of ethanol industry residues has created new opportunities for new value-added products, especially in Brazil, where they are produced in high quantities.     

Kinetics and mechanism of the benzenethiolysis of 2,4-dinitrophenyl and 2,4,6-trinitrophenyl methyl carbonates and S-(2,4-dinitrophenyl) and S-(2,4,6-trinitrophenyl) ethyl thiolcarbonates

The reactions of 2,4-dinitrophenyl and 2,4,6-trinitrophenyl methyl carbonates (DNPC and TNPC, respectively) and S-(2,4-dinitrophenyl) and S-(2,4,6-trinitrophenyl) ethyl thiolcarbonates (DNPTC and TNPTC, respectively) with a series of benzenethiolate anions were subjected to a kinetic investigation in water, at 25.0 degrees C, and an ionic strength of 0.2 M (KCl). These reactions obey pseudo-first-order kinetics, under excess of benzenethiolate, and are first order in the latter reactant. However, comparable reactant concentrations were used in the reactions of 4-nitrobenzenethiolate anion with TNPC and TNPTC, which showed second-order kinetics. The nucleophilic rate constants are pH independent, except those for the reactions of TNPC with 4-methoxy- and pentafluorobenzenethiolates, and TNPTC with benzenethiolate and 4-chloro- and 3-chlorobenzenethiolates, which show acid dependence. The Br?nsted-type plots for the nucleophilic rate constants are linear with slopes beta = 0.9, 1.0, 0.9, and 0.9 for the reactions of DNPC, TNPC, DNPTC, and TNPTC, respectively. No break in the Br?nsted plot was found for the reactions of DNPC and DNPTC at pK(a) ca. 4.1 and 3.4, respectively, consistent with concerted mechanisms. TNPC is more reactive toward benzenethiolate anions than DNPC, and TNPTC more than DNPTC due to the better leaving groups involved. Comparison of the kinetic results obtained in this work with those for the concerted phenolysis of the same substrates shows that benzenethiolate anions are better nucleophiles toward carbonates than isobasic phenoxide anions. This is explained by Pearson's "hard and soft acids and bases" principle.     

Worst case uncertainty estimates for routine instrumental analysis

A methodology for the worst case measurement uncertainty estimation for analytical methods which include an instrumental quantification step, adequate for routine determinations, is presented. Although the methodology presented should be based on a careful evaluation of the analytical method, the resulting daily calculations are very simple. The methodology is based on the estimation of the maximum value for the different sources of uncertainty and requires the definition of limiting values for certain analytical parameters. The simplification of the instrumental quantification uncertainty estimation involves the use of the standard deviation obtained from control charts relating to the concentrations estimated from the calibration curves for control standards at the highest calibration level. Three levels of simplification are suggested, as alternatives to the detailed approach, which can be selected according to the proximity of the sample results to decision limits. These approaches were applied to the determination of pesticide residues in apples (CEN, EN 12393), for which the most simplified approach showed a relative expanded uncertainty of 37.2% for a confidence level of approximately 95%.     

Thermoanalytical characterization of potentially schistosomicide polymeric derivatives

Oxamniquine (OXA) is a schistosomicide agent that causes some adverse effects in central nervous system. Intending to improve OXA therapeutic properties, a polymeric prodrug was designed. Currently, there is an increasing interest of thermal analytical techniques in the pharmaceutical area, so differential thermal analysis (DTA) and thermogravimetry (TG) were carried out to evaluate the thermal behavior of OXA, polymethacrylic acid (PMA), [poly(methacrylic-co-oxamniquine methacrylate)acid] (PMOXA) and physical mixture (OXA+PMA). The thermoanalytical profile of the physical mixture showed characteristic events of the thermal decomposition of OXA and PMA. Distinctly, PMOXA DTA curve did not show an endothermic peak at 148.5°C indicating that the drug was incorporated into the polymeric system. These results were corroborated by the IR spectroscopy and X-ray diffraction data. This revised version was published online in August 2006 with corrections to the Cover Date.     

Alkylation of phenol with alcohols on an aluminium orthophosphate-alumina system as catalyst

The results obtained in the alkylation of phenol in gas phase with different alcohols on an aluminium orthophosphate-alumina system of Kearby type are presented. We conclude that an O-alkylation coexists with a C-alkylation and that the alkylating ability of the alcohols decreases for higher and more branched hydrocarbon chains. Influences of temperature and space time are also discussed.

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Palladium catalysts deposited on silicon nitride in the deep oxidation of methane

The physicochemical and catalytic properties of palladium catalysts were studied in the deep oxidation of methane. The catalysts were deposited on silicon nitride from aqueous (Pd/Si₃N₄-a) and toluene (Pd/Si₃N₄-t) solutions of palladium acetate. The use of aqueous and organic solutions of palladium acetate, all other preparation conditions being equal, resulted in the formation of palladium systems with different catalytic properties. The sample from Pd/Si₃N₄-t was characterized by high activity and stability. The systems studied had different structures and adsorption properties of palladium nanoparticles, which influenced the form of reagent adsorption, catalytic properties, and mechanism of surface reactions. The suggestion was made that the solvent played a key role in the formation of the active surface of Pd-containing catalytic systems.     

Pore size distribution analysis of selected hexagonal mesoporous silicas by grand canonical Monte Carlo simulations

We combine here a regularization procedure with individual adsorption isotherms obtained from grand canonical Monte Carlo simulations in order to obtain reliable pore size distributions. The methodology is applied to two hexagonal high-ordered silica materials: SBA-15 and PHTS, synthesized in our laboratory. Feasible pore size distributions are calculated through an adaptable procedure of deconvolution over the adsorption integral equation, with two necessary inputs: the experimental adsorption data and individual adsorption isotherms, assuming the validity of the independent pore model. The application of the deconvolution procedure implies an adequate grid size evaluation (i.e., numbers of pores and relative pressures to be considered for the inversion, or kernel size), the fulfillment of the discret Picard condition, and the appropriate choice of the regularization parameter (L-curve criteria). Assuming cylindrical geometry for both porous materials, the same set of individual adsorption isotherms generated from molecular simulations can be used to construct the kernel to obtain the PSD of SBA-15 and PHTS. The PSD robustness is measured imposing random errors over the experimental data. Excellent agreement is found between the calculated and the experimental global adsorption isotherms for both materials. Molecular simulations provide new insights into the studied systems, pointing out the need of high-resolution isotherms to describe the presence of complementary microporosity in these materials.