Base catalyzed Mitsunobu reactions as a tool for the synthesis of aryl sec-alkyl ethers

A facile and versatile method for the synthesis of aryl sec-alkyl ethers from phenols with alcohols in the presence of base via a Mitsunobu reaction is described.     

A rapid spectrophotometric method for the determination of carbon monoxide in ambient air

A sensitive spectrophotometric method for the determination of carbon monoxide is described, based on the reduction of palladium(II) by carbon monoxide. The resulting elemental palladium is reacted with iodate in acidic medium in the presence of chloride, to produce an ICl(-)(n) species that is readily extracted as an ion-pair with Pyronine-G into benzene. Measurement of the absorbance of the extract at 535 nm permits the determination of carbon monoxide down to 1 mul/l. in air. The effect of interfering gases is discussed. The method is suitable for determination of carbon monoxide in motor vehicle exhaust gases and ambient air.     

Facile one-pot solvothermal-assisted synthesis of uniform sphere-like Nb2O5 nanostructures for photocatalytic applications

Research on Chemical Intermediates - Preparation of semiconductor nanomaterials with controlled morphology and uniform porous surface is of great interest for enhanced photocatalytic applications....     

Inhibitive action of <Emphasis Type="Italic">Clematis gouriana</Emphasis> extract on the corrosion of mild steel in acidic medium

The inhibitive action of Clematis gouriana (CG) on mild steel (MS) corrosion in 1.0 M HCl solution was studied. Inhibition efficiency of CG was carried out by using various weight loss methods, potentiodynamic polarisation, and electrochemical impedance spectroscopy. Inhibition efficiencies of up to 95.70% for CG can be obtained. Adsorption of CG on the MS surface was found to obey the Langmuir adsorption isotherm. Free energy of adsorption calculated from the temperature studies revealed the possibility of both chemisorptions and physisorption. The adsorbed film on the MS surface containing the CG inhibitor was also characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope and energy-dispersive spectrum. The possible active ingredient responsible for the anticorrosion effect is identified as aporphine alkaloid which is isolated and screened for the anticorrosion effect using electrochemical studies. The possible mode of corrosion inhibition of aporphine alkaloid is also derived using FTIR studies.     

Improved method of sampling and determination of traces of hydrogen sulphide

A sensitive spectrophotometric method for the determination of traces of hydrogen sulphide in environmental samples, after fixation as zinc sulphide, is reported. The method is based on the reaction between iodate and sulphide in the presence of excess of chloride ions. The resulting iodine chloride complex is ion-paired with Pyronine G and the product is extracted into benzene. The colour system obeys Beer's law over the range of 0.05–0.6 g of hydrogen sulphide. The coefficient of variation is 6.3% for 10 determinations of 0.3 g of hydrogen sulphide. The suitability of the method for monitoring hydrogen sulphide in atmospheric air in the vicinity of possible sources such as a sewage treatment plant and in wastewater has been evaluated.     

Facile synthesis of 3-aryl-1-((4-aryl-1,2,3-selenadiazol-5-yl)sulfanyl)isoquinolines

A new series of 1,2,3-selenadiazoles containing an aryl or a 3-arylisoquinoline sulfanyl moiety at carbons 4 and 5, respectively, was prepared by cyclization of the respective semicarbazones in the presence of selenium(II) oxide and tetrahydrofuran at 70–75°C. Semicarbazones required for the reaction were obtained from 2-((3-arylisoquinolin-1-yl)sulfanyl)-1-phenylethanones, I, by a reaction with semicarbazide hydrochloride in ethanol/water mixture and potassium acetate base.     

Al-MCM-48分子筛对苯酚与乙酸异丙酯异丙基化反应的催化性能(英文)

Al-MCM-48 molecular sieves (Si/Al molar ratios = 25, 50, 75, and 100) were synthesized hydrothermally using cetyltrimethyl-ammonium bromide as the structure directing template. The orderly arrangement of mesopores was evident from the low angle X-ray diffraction patterns and transmission electron microscopy images. The catalytic performance of the materials was evaluated in the vapor phase isopropylation of phenol with isopropyl acetate. Phenol conversion decreased with the increase in the Si/Al ratio of the catalysts. The major reaction product was 4-isopropyl phenol with 78% selectivity. The delocalization of phenolic oxygen electron pair over the aromatic ring promoted para-selective alkylation. Such delocalization could be aided by the hydrophilic surface of the molecular sieves. Although an ester was used as the alkylating agent, phenyl isopropyl ether was not formed in the reaction.     

Concise synthesis of chiral pyrazolo[4,3-f] [1,4]oxazepines and pyrazolo[4,3-f] [1,4]thiazepines bearing pyrazole unit

An efficient synthesis of pyrazolo [1,4]-oxazepines and [1,4]-thiazepines bearing a variety of alkyl and aryl groups with a chiral center has been developed. The synthesis started with readily available 5-chloro-pyrazole-4-carbaldehyde and chiral amino alcohols. The key step involves intramolecular imine formation. These classes of compounds are potentially useful as templates for drug discovery.     

Ultrasonic Velocities and Isentropic Compressibilities of Electrolytes in 2-Methoxyethanol from 15 to 35°C

The ultrasonic velocities of lithium tetrafluoroborate (LiBF₄), sodium tetrafluoroborate (NaBF₄), tetraphenylphosphonium chloride (Ph₄PCl), tetraphenylphosphonium bromide (Ph₄PBr), and tetraphenylarsonium chloride (Ph₄AsCl) in 2-methoxyethanol (ME) have been measured at 15, 25, and 35°C. Apparent molar isentropic compressibilities κ_φ of these electrolytes were derived from these data supplemented with their densities. Infinite dilution partial molar compressibilities κ_φ ^o were obtained by extrapolation from the plot of κ_φ vs. the square root of the molarity. The κ_φ ^o values of the electrolytes were split into approximate limiting ionic compressibilities κ_φ± ^o on the basis of the assumption that κ_φ ^o (BF^? ₄) = 0. The results have been interpreted in terms of specific constitutional and structural factors of the solvent molecules and of solute ions.