N-BROMOBIS(P-TOLUENESULFONYL)AMINE AS A NOVEL AND MILD REAGENT FOR CONVERSION OF OXIMES TO CARBONYL COMPOUND

N-Bromobis(p-toluenesulfonyl)amine (NBBTA) is a novel and efficient reagent for the conversion of oximes to their corresponding carbonyl compounds in good yields under mild conditions.     

p-Toluenesulfonyl Chloride (p-TsCl)-Catalyzed Trimethylsilylation of Hydroxyl Groups Using Hexamethyldisilazane and Their Regeneration Under Mild Conditions: The First Example for Catalytic Application of p-Toluenesulfonyl Chloride

The first catalytic application of p-toluenesulfonyl chloride (p-TsCl) for the efficient and selective trimethylsilylation of various types of hydroxyl groups with hexamethyldisilazane (HMDS) in dichloromethane and desilylation of these compounds in water is reported. The reactions were carried out at room temperature and were found to proceed in good to excellent yields.     

Investigation of nanostructural,thermal and magnetic properties of yttrium iron garnet synthesized by mechanochemical method

This paper focuses on the magnetic, structural and thermal properties of mechanically alloyed Y₂O₃/α-Fe₂O₃ mixed powders and investigates the effects of the mechanical milling and heat treatment on the synthesis of yttrium iron garnet from the primary materials. The morphological and structural studies were carried out by scanning electron microscope and X-ray diffraction, respectively. The thermal activities were measured by differential thermal analysis. The magnetic properties were studied by vibrating sample magnetometer. The results showed that high-energy milling does not lead to the garnet formation and even does not decrease the temperature of the garnet formation. Furthermore, the orthoferrite phase can be achieved slightly during the milling process (up to 96 h) and completely by the heat treatment at lower temperatures (850 °C).     

Efficient Trimethylsilylation of Alcohols and Phenols with HMDS in the Presence of a Catalytic Amount of 1,3‐Dibromo‐5,5‐Dimethylhydantoin (DBDMH) as a Safe and Cheap Industrial Chemical

1,3‐Dibromo‐5,5‐dimethylhydantoin (DBDMH) is found to be an effective catalyst for trimethylsilylation various alcohols and phenols with hexamethyldisilazane (HMDS) in dichloromethane at room temperature.     

Bioactivity-guided isolation of new antiproliferative compounds from Juniperus foetidissima Willd.

Based on a literature survey on cytotoxic medicinal plants, Juniper species were identified as interesting source of antitumor compounds. Using bioassay-guided fractionation against Caov-4 cancer cells on acetone extract of leaves and branchlets of Juniperus foetidissima led to the isolation of a new 3H-benzofuaran-2-one: 4-methyl-3-methoxy-3H-benzofuaran-2-one (1), a new sesquiterpene: 4,9(α)-dihydroxy-nardosin-6-en (2) and an already known labdane-type diterpene: 15-hydroxy-8(17),13(E)-labdadiene-19-carboxilic acid (3). Compounds 1–3 exhibited cytotoxic effects, with moderate cytotoxicity against the EJ-138 bladder and CAOV-4 ovary cancer cell lines.     

Potentiometric study of binary complexes of methyl 2-pyridyl ketone oxime, phenyl 2-pyridyl ketone oxime and diacetyl monooxime with some transition and heavy metal ions in aqueous solution

The complexation reaction between some oximes including methyl-2-pyridylketone oxime (MPKO), phenyl-2-pyridylketone oxime (PPKO) and diacetyl monooxime (DMO) with some transition and heavy metal ions Co2+, Ni2+, Zn2+, Pb2+, Fe2+, Fe3+, Cr3+ and La3+ has been studied potentiometrically in aqueous solution at 25+/-0.1 degrees C and ionic strength (mu) of 0.1M supported by KCl. The overall stability constants logbeta's of respective species were obtained by computer refinement of pH-volume data using BEST program. The best model among the several proposed models was selected according to the lowest sigma(fit) value. The main species in binary systems are ML, ML2, MLH, MLH2, ML2H, ML2H2, MOHL, M(OH)2L, M(OH)L2 and M(OH)2L2 (L = MPKO or PPKO or DMO).     

Preload effect on nonlinear dynamic behavior of a rigid rotor supported by noncircular gas-lubricated journal bearing systems

This paper presents the effect of preload, as one of the design parameters, on nonlinear dynamic behavior of a rigid rotor supported by gas-lubricated noncircular journal bearings. A finite element method has been employed to solve the Reynolds equation in static and dynamical states and the dynamical equations are solved using the Runge–Kutta method. To analyze the behavior of the rotor center in horizontal and vertical directions under different operating conditions, dynamic trajectory, power spectra, Poincare maps, and bifurcation diagrams are used. Results of this study reveal how the complex dynamic behavior of two types of noncircular bearing systems comprising periodic, KT-periodic, and quasi-periodic responses of the rotor center varies with changes in preload value.     

Determination of Cu,Fe, Pb and Zn by Flame‐AAS after Preconcentration Using Sodium Dodecyl Sulfate Coated Alumina Modified with Complexing Agent

A sensitive and simple method for the simultaneous preconcentration of trace transition and heavy metal ions is reported. The method is based on the adsorption of Cu, Fe, Pb and Zn on N,N′‐Diacetyl‐4‐bromo‐2,6‐di(aminomethyl)anisole (DABDAMA) loaded on sodium dodecyl sulfate (SDS) coated alumina. The metal content on the complexes are eluted using 6 mL of 2 mol l⁻¹ nitric acid. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the retentions of the analytes were also examined. The recoveries of analytes were generally higher than 95% with a low RSD. The method has been successfully applied for these metals content evaluation in samples including soil, blood and vegetable samples.     

1,2‐Bis(N‐fluoro‐p‐toluene­sulfon­amido)­ethane chloroform solvate

The title compound, N,N′‐difluoro‐N,N′‐ethylenedi‐p‐tolu­enesulfonamide, C₁₆H₁₈F₂N₂O₄S₂·CHCl₃, is a novel stable compound of the N—F class of reagents containing two R₂N—F functionalities. The compound, as the chloro­form solvate, is the first such bis(N—F) compound to be structurally characterized. It adopts a solid‐state structure in which the two aromatic rings are antiperiplanar and a combination of weak C—H?F and C—H?O hydrogen bonds [distances and angles range from 3.265 (4) to 3.439 (4) Å and 150 to 170°, respectively] and π‐stacking between the rings of different mol­ecules (separations of 3.717 and 3.926 Å) results in a solid‐state structure containing well defined channels in which CHCl₃ solvent mol­ecules are located. The N—F distances are 1.428 (3) and 1.433 (3) Å.     

A distinct intermediate of RNase A is induced by sodium dodecyl sulfate at its pK(a)

The chemical denaturation of RNase A was found to be mediated by sodium dodecyl sulfate (SDS) at various pH. The characterization of the unfolding pathway was investigated by spectrophotometry and differential scanning calorimetry (DSC), and was analyzed by multivariate curve resolution (MCR) as a chemometric method. The spectrophotometric titration curve of RNase A upon interaction with SDS indicated a distinct complex intermediate in glycine buffer at pH 3.3. This was accompanied with the catalytic activation of the enzyme and was concurrent with maximum population of the intermediate, determined by MCR. This was confirmed by the DSC profile of RNase A in the presence of SDS, indicated by two transitions in thermal unfolding. The kinetic data on the unfolding process of RNase A upon addition of SDS showed a two-phase pathway under the same conditions. The intermediate appeared at low pH especially at the pK_a of SDS (pH 3.3). These results provide strong evidence of the influence of low pH (around the pK_a of SDS) on the existence of an intermediate upon interaction of RNase A with SDS.