On the Synthesis of Some 2-Arylhydrazono-3-oxothieno[2,3-b]pyridines by Reaction of Nitrilimines with 2-Mercaptonicotinic Acid

Nitrilimines prepared from N-arylhydrazono chlorides reacted with 2-mercaptonicotinic acid yielding the corresponding addition products, 2-[(2-oxo-1-arylhydrazonopropan-1-yl)mercapto] nicotinic acids, which were treated with 1,1-carbonyldiimidazole in THF affording by cyclocondensation the corresponding hitherto unknown 2-arylhydrazono-3-oxothieno[2,3-b]pyridines.     

Simultaneous determination of dextropropoxyphene napsylate, caffeine, aspirin and salicylic acid in pharmaceutical preparations by reversed-phase HPLC

The official compendial method for the determination of dextropropoxyphene napsylate, caffeine, aspirin and salicylic acid involves a lengthy extraction by gas chromatography and spectrophotometry. The analytical scheme reported here provides a fast, sensitive, and stability-indicating reversed-phase HPLC assay for all these components concurrently. The total elution time is 10 min. The accuracy of the method has been tested on commercial products. The method can easily detect low levels of salicylic acid.     

An ESR study of the photolysis of dicyclopentadienyltitanium dichloride

ESR spectroscopy has been used to monitor the radicals which are formed when dicyclopentadienyltitanium dichloride is photolysed in solution alone or in the presence of various reagents (oxygen, ethers, pyridine, phosphines, 2-methyl-2-nitropropane, nitrosodurene, biacetyl, and 3,6-di-t-butyl-1,2-benzoquinone). The direct observation of the spectrum of the cyclopentadienyl radical, and the unambiguous resolution of the hyperfine coupling by two chlorine atoms in the spin adduct which the titanium fragment forms with 2-methyl-2-nitropropane suggests that, at least in tetrahydrofuran, the principal reaction is, as commonly accepted:

However, under some conditions (e.g. in ether solvent, or in the presence of pyridine, particularly at low temperatures), the spectra of two different titanium(III) radicals, with resolvable hyperfine structure, can be observed, and this simple model needs to be extended.     

Hydrodynamic model for a dynamical jammed-to-flowing transition in gravity driven granular media

Granular material on an inclined plane will flow like a fluid if the angle theta the plane makes with the horizontal is large enough. We study chute flow down a plane using a hydrodynamic model previously used to describe granular Couette flow. Our model predicts a jammed-to-flowing transition as theta is increased even though it does not include solid friction, which might seem necessary to stabilize a state without flow. The transition is driven by coupling between mean and fluctuating velocity. In agreement with experiments and simulations, it predicts flow for layers with a thickness H larger than a critical value H(stop)(theta) and absence of flow for H相似文献   

Vapor-liquid and liquid-liquid equilibrium properties of ethane + methanol system at ambient temperature

The liquid-liquid and vapor-liquid equilibrium data for the binary system of ethane + methanol were measured at ambient temperature over a wide range of pressures using a designed PVT apparatus. The experimental liquid-liquid and vapor-liquid equilibrium data were compared with the modeling results obtained using the Peng Robinson and Soave-Redlich-Kwong equations of state.     

Reverse Homogeneous Liquid–Liquid Extraction as a Miniaturized Method for Extraction of Aflatoxins from Pistachio and Wheat and LC Post-column Derivatization-Fluorescence Detection

A rapid and simple quantitative method for the simultaneous determination of the four aflatoxins (AFs) B1, B2, G1 and G2 was developed using reverse homogeneous liquid–liquid extraction (RHLEE) and HPLC post-column derivatization-fluorescence (HPLC-FL) detection. The method based on the rapid extraction of AFs from a methanolic sample into chloroform after addition of water containing KBr, with a method we called reverse homogeneous liquid–liquid extraction. Recoveries were in the range of 88–125% and the limits of detection were between 0.001–0.042 ng g^?1 for different AFs. Wheat and pistachio were chosen for the analysis of real samples and the method was also successfully applied to a FAPAS^® TEST MATERIAL (T04151).