Synthesis of glycerol carbonate from glycerol and urea with gold-based catalysts

The reaction of glycerol with urea to form glycerol carbonate is mostly reported in the patent literature and to date there have been very few fundamental studies of the reaction mechanism. Furthermore, most previous studies have involved homogeneous catalysts whereas the identification of heterogeneous catalysts for this reaction would be highly beneficial. This is a very attractive reaction that utilises two inexpensive and readily available raw materials in a chemical cycle that overall, results in the chemical fixation of CO(2). This reaction also provides a route to up-grade waste glycerol produced in large quantities during the production of biodiesel. Previous reports are largely based on the utilisation of high concentrations of metal sulfates or oxides, which suffer from low intrinsic activity and selectivity. We have identified heterogeneous catalysts based on gallium, zinc, and gold supported on a range of oxides and the zeolite ZSM-5, which facilitate this reaction. The addition of each component to ZSM-5 leads to an increase in the reaction yield towards glycerol carbonate, but supported gold catalysts display the highest activity. For gold-based catalysts, MgO is the support of choice. Catalysts have been characterised by XRD, TEM, STEM and XPS, and the reaction has been studied with time-on-line analysis of products via a combination of FT-IR spectroscopy, HPLC, (13)C NMR and GC-MS analysis to evaluate the reaction pathway. Our proposed mechanism suggests that glycerol carbonate forms via the cyclization of a 2,3-dihydroxypropyl carbamate and that a subsequent reaction of glycerol carbonate with urea yields the carbamate of glycerol carbonate. Stability and reactivity studies indicate that consecutive reactions of glycerol carbonate can limit the selectivity achieved and reaction conditions can be selected to avoid this. The effect of the catalyst in the proposed mechanism is discussed.     

Determination of organic acid impurities in lactic acid obtained by fermentation of sugarcane juice

Lactic acid produced by fermentation process mostly contains a number of aliphatic carboxylic acids as impurities. In this work, carboxylic acid impurities in lactic acid samples from a number of sources were determined at ppm levels. A simple HPLC method was developed that utilized a new generation polar embedded reverse phase, 20mM phosphate buffer at pH 2.20 (±0.05) and UV detection at 210 nm. The method enabled quantitative analysis of the above acids in lactic acid matrix. The experimental conditions for column temperature, mobile phase pH and flow rate were optimized. A detailed validation of the method was performed for linearity, precision, accuracy, selectivity, limit of detection (LOD), limit of quantitation (LOQ), ruggedness and repeatability and reproducibility (R&R).     

Eco‐friendly HClO4–SiO2 catalyzed synthesis of mono‐ and bis‐diaryl‐2h‐1,4 benzothiazines

Mono‐ and bis‐diaryl‐2H‐1,4‐benzothiazines were obtained in quantitative yields through silica‐supported perchloric acid catalyzed reaction cascade of double condensation and 1,4 addition of diaroylacetylenes with 2‐aminothiophenol at room temperature. The structures were confirmed by spectroscopic analyses and X‐ray crystallographic studies. J. Heterocyclic Chem., (2011)     

Interaction energy‐based drug–receptor interaction study of metal–bicyclam complexes

Bicyclams inhibit HIV replication by binding to the CXCR4 chemokine receptor, which is the main coreceptor for gp120 used by X4, T‐tropic strains of HIV for membrane fusion and cell entry. Bicyclam AMD3100 mainly interacts with the aspartic acid residues namely Asp171 and Asp262, which are located at the extracellular ends in the CXCR4 coreceptor. Incorporation of some metal ions by the macrocyclic rings of bicyclam enhances its binding affinity to the CXCR4 receptor and enhances their anti‐HIV activity because the acetate can make a strong coordination bond to the metal and one weaker hydrogen bond to nitrogen in the cyclam ring. The interaction energy (E_int) between 150 metal–bicyclam complexes and aspartic acid has been evaluated. The metal–bicyclam complexes are obtained by the incorporation of six metal ions namely Fe³⁺, Co³⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Pd²⁺ in 25 well‐known bicyclams including AMD3100. In most of the cases, Fe and Co–bicyclam complexes interact best with aspartic acid. The anti‐HIV activity of metal–bicyclam complexes can be predicted on the basis of interaction energy before the synthesis of the metal–bicyclam complex. On the basis of interaction energy, the anti‐HIV activity of bicyclam complexes can be predicted in advance to their synthesis. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Study and fabrication of europium picrate triethylene glycol complex

A mononuclear of [Eu(NO3)(Pic)(H2O)2(EO3)](Pic)·(0.73)H2O complex, where EO3=trietraethylene glycol and Pic=picrate anion, shows a red emission when used as an active layer in a single layer of ITO/EO3-Eu-Pic/Al configuration. The crystal structure of the complex consists of [Eu(NO3)(Pic)(H2O)2(EO3)]+ cation and [Pic]- anion. The Eu(III) ion is coordinated to the 10 oxygen atoms from one EO3 ligand, one Pic anion, one nitrate anion, and two water molecules. The complex is crystallized in triclinic with space group P-1. The hybrids in thin films I and II were prepared in the respective order solution concentrations of 15 and 20 mg/mL the emissive center. Comparing the photoluminescence (PL) and electroluminescence (EL) spectra, we can find that all emissions come from the characteristic transitions of the Eu(III) ion. The EL spectra of both thin films showed the occurrence of the most intense red-light emission around at 612 nm. Comparison of organic light-emitting device (OLED) current intensity characteristics as a function of voltage (I-V) show that the thin film I is better than those found for the thin film II. The thickness of the emitting layer is an important factor to control the current-voltage curve. The sharp and intense emission of the complex at low voltage indicates that the complex is a suitable and promising candidate for red-emitting materials.     

The Binomial-Discrete Poisson-Lindley Model:Modeling and Applications to Count Regression

On the basis of a well-established binomial structure and the so-called Poisson-Lindley distribution,a new two-parameter discrete distribution is introduced.Its...     

Electrochemical Studies on Effects of Psychostimulants,Opioids and Alcohol Intake Towards Level of Hydrogen Peroxide in the Brain Striatum

Hydrogen peroxide (H₂O₂) was the main types of many peroxides produced in living mammalian cells that consumed oxygen. In the brain, the main source of H₂O₂ was the superoxide dismutase (SOD)‐catalyzed reaction in mitochondria. However, the level of H₂O₂ would be elevated through administration of control drugs and alcohol by dopamine metabolism of monoamine oxidase. In this study, a H₂O₂ microsensor was used to investigate the level of H₂O₂ in the brain striatum after administration of methamphetamine (MAP), morphine (MrP) or ethanol (Eth). The placement of microsensor in the brain was done at coordinates A/P 1.1 from bregma, M/L+2.6 and D/V‐1.5. A working potential of +0.05 V vs. Ag/AgCl was applied. The H₂O₂ concentration was measured direct from the current generated by its catalytic reaction at the electro active surface of the electrode. A significant increase of H₂O₂ level was observed after 7 successive injections of the controlled drugs or alcohol. The initial measurement of H₂O₂ is essential as excess dosage of H₂O₂ during treatment will contribute to the formation of neurotoxin oxygenated radicals. The H₂O₂ was the precursor of O_2? and OH radicals. Thus, this study provided a mean to monitor H₂O₂ level in the brain.     

Spectroscopic study of sulforhodamine 640-doped sol-gel silica

The sol-gel process is a technique which provides a low-temperature route for the preparation of organic dye-doped porous silica glass. Extended UV transmission was observed for HCl-catalysed sol-gel silica. Properties of a solute may differ greatly between a free solution and that solution confined in pores of a sol-gel glass. Absorption and fluorescence properties of sulforhodamine 640-doped silica samples prepared by sol-gel process were investigated. In the TEOS-derived gel, the emission of the dye does not shift during aging but exhibits a large change during drying. The emission maximum of sulforhodamine 640 blue shifts was discussed as a function of increasing rigidity of the surrounding matrix.     

YCu3Al2, an example of an AB5 structure type

Yttrium tricopper dialuminium, YCu₃Al₂, is isostructural with hexagonal CaCu₅, in which each Cu atom at the 3g(½,0,½) position in space group P6/mmm (No. 191) is partially replaced by an Al atom. The hydrogen‐uptake properties are usually enhanced in other AB₅ structures by aluminium substitution. YCu₅ does not show any hydrogen absorption, and the goal of the present work is to investigate whether aluminium substitution could expand the metal‐atom lattice enough to provide better interstitial positions for hydrogen storage. However, no enthalpy change was observed up to 773 K under 3 MPa static H₂ pressure by differential thermal analysis (DTA) for the title compound. The compound does not show any significant hydrogen absorption/desorption in the pressure‐composition isotherms (P–C–T diagrams) in the temperature range 298–673 K under 3.3 MPa H₂ pressure.