The binary system PbO - BiVO4

Phase equilibria established in the PbO - BiVO₄ system over the whole component concentration range up to 1000°C have been investigated. A phase diagram has been constructed using DTA and XRD.      

Ionic liquid promoted Diels-Alder Reaction between anthrone and maleimides

Ionic liquids (IL) are gaining importance as green solvents. Imidazolium ionic liquid [bmim]⁺[Cl]⁻, an environmentally benign solvent, was found to promote the Diels-Alder reaction between anthrone and maleimides at room temperature with excellent yields. The ionic liquid played a dual role as solvent and catalyst.      

Scolecite as an efficient heterogeneous catalyst for the synthesis of 2,4,5-triarylimidazoles

Natural scolecite has been found as an effective catalyst for the one-pot synthesis of 2,4,5-triarylimidazole derivatives via a three component reaction using benzil or benzoin, aldehydes and ammonium acetate. This method provides several advantages such as being environmentally benign, reusable, possessing high yields with increased variations of the substituents in the product and preparative simplicity.      

Simultaneous displacement of a nitro group during coupling of diazotized <Emphasis Type="Italic">o</Emphasis>-nitroaniline with phenols

During the diazo-coupling reaction, nucleophilic displacement of a nitro group was also observed. This was the main reaction (1→7) when the starting amine bore either a chlorine or methoxy group at the para position (1b–c). The newly prepared compounds (7) might serve as convenient building blocks in synthesis of some heterocycles.      

Copper (II) chloride / tetrabutylammonium bromide catalyzed oxidation of 2,6-diisopropylnaphthalene and 4,4′-diisopropylbiphenyl

The oxidation processes of 2,6-diisopropylnaphthalene and 4,4′-diisopropylbiphenyl with oxygen in the presence of a catalyst, composed of copper(II) chloride and tetrabutylammonium bromide, were investigated. It was found that, in essence, only one isopropyl group undergoes oxidation, and obtained mixtures contained mainly peroxide, alcohol, ketone and only small amounts of hydroperoxide.      

N-hexylpyridinium bis(trifluoromethylsulfonyl)imide and Lewis acids — catalytic systems for Diels-Alder reaction

A comparative study of the Diels-Alder reactions between cyclopentadiene (1) and dienophiles (2 a–c) in N-hexylpyridinium bis(trifluoromethylsulfonyl)imide in a temperature range of 20–45°C is reported. The reaction rate constants and activation energies were calculated. Moreover, the catalytic systems based on N-hexylpyridinium bis(trifluoromethylsulfonyl)imide and Lewis acids were tested as a reaction media to perform the Diels-Alder reaction. Yb, Y, Mg, Zn triflates and chlorides (0.005 to 0.1 mmol) were used as catalysts. The recycling of catalytic system consisted of YCl3 and ionic liquid was performed.      

High Stokes shift long-wavelength energy gap regulated fluorescence in the series of nitro/dimethylamino-substituted ortho-analogs of POPOP

A series of novel nitro-substituted ortho-analogs of POPOP was synthesized. Like the most of the other known compounds of this class, the synthesized molecules demonstrate high Stokes shift fluorescence emission owing to the planarization of their molecules at electronic excitation. Significant fluorescence quenching in polar solvents was described as the “energy gap law” action rather than the specific effect of the dialkylamino group excited state twisting.      

Metathesis transformations of unsaturated derivatives of β-diketones

Selected β-diketones bearing unsaturated derivatives have been demonstrated to undergo homo-metathesis and cross-metathesis with selected olefins in the presence of Grubbs catalysts. The reactions led to respective homo- and cross-metathesis products mainly with good yields and selectivities.      

Removal of Pb and Cd from aqueous media and fish liver using novel polyurethane foam functionalized with pyrazolone as a new metal ion collector

In the present paper, an off-line preconcentration procedure for the determination of cadmium and lead by flame atomic absorption spectrometry (FAAS) is proposed. Polyurethane foam (PUF) functionalized with o-aminophenol (o-AP) followed by Pyrazolone (Pyr) packed in a minicolumn was used as a sorbent material. The metals were retained on the modified PUF, from which it could be eluted and effectively preconcentrated. The detection limits were 0.072 and 0.016 μg L⁻¹ for Pb and Cd respectively. Enrichment factors were 250 and 319 for lead and cadmium respectively. The procedure has been applied successfully to metal determination in water samples, fish liver and reference material.      

ZrOCl<Subscript>2</Subscript> · 8H<Subscript>2</Subscript>O: An efficient catalyst for rapid one-pot synthesis of 3-carboxycoumarins under ultrasound irradiation in water

In this report, a rapid, efficient and environmental friendly synthesis of 3-carboxycoumarins under ultrasound irradiation in water media is described. The Knoevenagel condensation of Meldrum’s acid with substituted benzaldehydes in the presence of zirconium oxide chloride (ZrOCl₂·8H₂O) and ultrasonic irradiation in water gave the corresponding 3-carboxycoumarins in good to excellent yields.      

Density functional theory study of the photosensitization mechanisms of indigo

The triplet excited state properties and photosensitization mechanisms of indigo were investigated based on density functional theory calculations. The solvent effects on the photosensitization mechanisms of indigo have also been considered. The thermodynamic feasibility of the possible ¹O₂ and O₂·⁻-photogeneration pathways by triplet excited state indigo in different solvents was explored, in order to gain some deeper insights into the photosensitization characters of the dye.      

A hydroxyaminophosphane derived from 2-imidazolidone and its unusual structure in solution

A novel hydroxyamino phosphane was synthesised through the reaction of 2-imidazolidinone with ClPPh2 and subsequently reaction of the resulting bisphosphino derivative with the Grignard reagent BrMgC₅H₁₁. The interaction of the pentyl substituent with one of the two phosphino groups and the structure in solution is shown by multinuclear NMR-spectroscopy..      

Quick bioanalytical method of quantification and validation of sulbactam in plasma using high performance liquid chromatography

A quick method of quantitative determination of sulbactam in human plasma, using liquid chromatography-UV spectroscopy, has been developed and validated. After derivatization with imidazole, plasma samples were treated by direct deproteinization with acetonitrile as an extraction solvent. After ultracentrifugation, sulbactam extract was directly injected onto the LC column. Chromatographic separation was performed on TSK Gel Super ODS (50 mm × 4.6 mm i.d., 2 μm) using methanol and phosphate buffer with tetrabutylammonium hydroxide solution as a mobile phase. Gradient elution was employed. The method was fully validated according to the United States Food and Drug Administration requirements (linearity, precision, trueness, quantification limit, detection limit, recovery, specificity and stability). The calibration curves were linear within the concentration range of 0.05–4.0 μg mL⁻¹. Good method/system precision and accuracy of the method were demonstrated.      

ZnO-beta zeolite mediated simple and efficient method for the one-pot synthesis of quinoxaline derivatives at room temperature

A rapid and an efficient one-pot method for the synthesis of quinoxalines catalysed by ZnO-beta zeolite at room temperature is described. This environmentally benign method provides several advantages over methods that are currently employed such as a simple work-up, mild reaction conditions, good to excellent yields, and a process to recover and reuse the catalyst for several cycles with consistent activity.      

Ionic liquid mediated recyclable sulphonimide based organocatalysis for aldol reaction

Sulphonimide based organocatalyst was used to catalyze the aldol reaction in ionic liquid media. On the basis of yield and selectivity the ionic liquid mediated system was found superior in comparison with organic solvents. The added advantages of this ionic liquid mediated organocatalysis are easy recovery of product and the recyclability of the organocatalyst.      

Adsorption of triton X-100 on silica gel: effects of temperature and alcohols

Adsorption of Triton X-100 (TX-100) on silica gel has been studied as a function of temperature (308–328 K) and composition for mixtures of water with ethanol or t-butanol. The adsorption capacity of silica gel for TX-100 decreases with increase in alcohol content. Adsorption isotherms of TX-100 on silica gel are four-region and were analyzed using the ARIAN (adsorption isotherm regional analysis) model. Data in regions 2, 3 and 4 were fitted to the Temkin, bilayer and reverse desorption isotherms, respectively. The results show that adsorption of TX-100 on silica gel in water and alcohol-water binary mixtures occurs mainly through formation of monolayer surface aggregates or low bilayer coverage.      

Dispersive liquid-liquid microextraction and liquid chromatographic determination of pentachlorophenol in water

A simple and sensitive dispersive liquid-liquid microextraction method for extraction and preconcentration of pentachlorophenol (PCP) in water samples is presented. After adjusting the sample pH to 3, extraction was performed in the presence of 1% W/V sodium chloride by injecting 1 mL acetone as disperser solvent containing 15 μL tetrachloroethylene as extraction solvent. The proposed DLLME method was followed by HPLC-DAD for determination of PCP. It has good linearity (0.994) with wide linear dynamic range (0.1–1000 μg L⁻¹) and low detection limit (0.03 μg L⁻¹), which makes it suitable for determination of PCP in water samples.      

Efficient and solvent-free synthesis of 1-amidoalkyl-2-naphthols using <Emphasis Type="Italic">N,N,N’,N’</Emphasis>-tetrabromobenzene-1,3-disulfonamide

N,N,N,’N’-Tetrabromobenzene-1,3-disulfonamide [TBBDA] is found to be a reusable catalyst for efficient synthesis of various amidoalkyl naphthols from β-naphthol, aromatic aldehydes and urea in good to high yields under solvent-free conditions.      

Hollow fibre liquid phase microextraction of parabens

A hollow fibre liquid phase microextraction for gas chromatographic determination of some p-hydroxybenzoic acid esters has been developed. Chlorobenzene containing tetradecane as internal standard was used for the extraction. Optimized extraction was carried out at room temperature for 40 min in the presence of 0.4 g mL⁻¹ NaCl in the sample solution. Calibration was linear up to 30 mg L⁻¹. Correlation coefficients were 0.996–0.998. Enrichment factors were 21, 95 and 154, and detection limits were 0.20, 0.03 and 0.01 μg mL⁻¹ for methylparaben, ethylparaben and propylparaben, respectively. Reproducibility was acceptable with relative standard deviations up to 11.7%. The technique was tested for water and urine analysis.