Solvent effect on tautomeric equilibria and dipole moments of some alpha substituted benzoylacetanilides

Based on dipole moment measurements, a study was made of the keto-enol equilibria of five alpha substituted benzoylacetanilide derivatives in two non-polar and one polar solvents at 30°C. The enol mole fractions of the compounds investigated were determined by analysis of their ultraviolet spectra. The same type of study was extended to salicylanilide for its resemblance to the enol tautomer of these compounds. A deduction of the most probable configurations of the keto and enol forms was tentatively made through a comparison between the dipole moments of some suggested configurations for these forms of benzoylacetanilide and those measured in benzene for the alpha methyl benzoylacetanilide and salicylanilide, respectively. These inferred configurations were used to calculate the dipole moments of both tautomers of the other compounds, and consequently, the dipole moment values of their tautomeric mixtures in dioxane and chloroform. A comparison between the dipole moment values of their tautomeric mixtures in dioxane and chloroform. A comparison between the dipole moment values calculated in this way and those measured indicated a solute-solvent interaction with dioxane, which chloroform behaved as a non-interacting solvent.     

Organocatalytic asymmetric multi-component [C+NC+CC] synthesis of highly functionalized pyrrolidine derivatives

The highly chemo- and enantioselective organocatalytic [C+NC+CC] coupling process between aldehydes, dialkyl 2-aminomalonates and α,β-unsaturated aldehydes is presented. The reaction gives access to highly functionalized pyrrolidine derivatives in good yields with >10:1 dr and 90-98% ee.     

Determination of ethambutol in pharmaceutical preparations by atomic absorption spectrometry,spectrophotometry and potentiometry

Simple methods are described for the determination of ethambutol in pharmaceutical preparations. They are based on the reaction of the drug with copper phosphate suspension in a borate buffer of pH 9.2, whereby a blue 11 water-soluble copper-ethambutol complex is quantitatively formed. Four portions of the reaction solution are used for (i) measurement of copper by atomic-absorption spectrometry at 324.7 nm; (ii) potentiometric titration with EDTA with use of a solid-state copper ion-selective electrode; (iii) visual titration with EDTA (copper-PAN indicator); and (iv) spectrophotometric measurement of the copper-ethambutol complex at 640 nm. The results obtained are in good agreement and are better than those of the British Pharmacopoeia (BP) method.     

137Cs,trace and toxic elements distribution in Austrian mushrooms

Various mushroom species have been analyzed for their elemental composition (i.e., Al, B, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, P, Sr and Zn) by means of ICP-AES. The accuracy of the measurements was confirmed by analyzing a series of the same samples by short time activation analysis. The data were evaluated statistically including the values of¹³⁷Cs. The results denote that the distribution of these elements and their correlation of these elements and their correlation coefficients are highly distinctive for each mushroom species. K, Na and P were found to correlate negatively with¹³⁷Cs in most species. Suillus grevillei and Cantharellus cibarius show high Be values (0.27 and 0.30 g g^–1, respectively), while Pb was high in Suillus grevillei (16.3 g g^–1) and Amanita rubescens (9.3 g g^–1). Higher levels of Cd were found in Rozites caperata and Russula vesca with a mean of 9.2 and 16.1 g g^–1, respectively. Cluster analysis was applied to classify these samples according to their botanical species using their elemental composition. The concentrations of Al, Cr, Mn, Na and¹³⁷Cs have no influence on the classification of these samples.     

Applications involving oxidation with KBrO3: Potentiometric determination of some inorganic white and yellow pigments

Rapid potentiometric methods were given for determination of some sulfide and chromate pigments in pure as well as adulterated samples. The methods are based on oxidation of S^2? or Cr³⁺ with known excess of KBrOs³ to the corresponding (S ↓) or Cr^6?. Oxidation of trivalent chromium proceeds only toward completion in presence of a catalyst such as Co²⁺. Sulfide oxidation needs gradual liberation of H₂S—which can be achieved by dropwise additions of the acid—together with the presence of excessive amount of water, in order to obtain accurate results excess oxidant was subsequently reduced with SO₂ to produce Br^? that can be titrated against Hg(I). The potential breaks are quite sharp for accurate determination of the equivalent points.     

铜及其配合物在生物体系中的作用

自人类有历史记载以来，铜及其配合物即用作药物。铜是人体必需的金属元素。人体的正常代谢过程需要它们，但无法体内合成，因此，需要每天从饮食摄取和吸收。生物药学家和研究者以极大的努力彻底地了解铜及其配合物在生物体系中的作用，希望获得更多地信息以利于人类疾病的预防和治疗。本综述评述了铜在组织中的分配和代谢、铜依赖酶、在病态时铜的非正常代谢、铜配合物的药疗活性和抑制氧自由基的产生。     

Large-scale channel characterization at 28 GHz on a university campus in the United Arab Emirates

Telecommunication Systems - Millimeter wave (mm-wave) communication is one of the key enabling technologies for meeting the requirements of the fifth generation (5G) wireless communication systems....     

Supported Organometallic Complexes. XXXVI [1] Diaminediphosphineruthenium(II) Interphase Catalysts for the Hydrogenation of α, β‐Unsaturated Ketones

The T—silyl functionalized diamine‐bis(ether‐phosphine)ruthenium(II) complexes 1a(T ° ) — 1g(T ° ) (Scheme 1) were sol‐gel processed in the presence of different amounts of the co‐condensation agents CH₃Si(OMe)₃ (Me—T ° ) and (MeO)₂SiMe—(CH₂)₆—MeSi(OMe)₂ (D ° —C₆—D ° ) to produce a library of the interphase catalysts X1a — X1c , X2a — X2g , and X3a — X3g . Due to the remarkable electronic and steric effects of the co‐ligands on the catalytic activity of such complexes, a series of aliphatic and aromatic diamines was selected. The new polymers were investigated by multinuclear CP/MAS solid‐state NMR spectroscopy as well as by EXAFS, EDX, SEM, and BET methods. Selected interphase catalysts show high activities and selectivities in the hydrogenation of trans‐4‐phenyl‐3‐butene‐2‐one.     

Synthesis,characterization and redox properties of a new vic-dioxime and its transition metal complexes

A novel vic-dioxime, 1,2 dihydroxyimino-1-p-tolyl-3-aza-6-morpholine heptane (LH₂) was prepared by reacting anti-p-tolylchloroglyoxime with 4-(3-aminopropyl)morpholine in absolute THF. Mononuclear complexes with a metal–ligand ratio of 1:2 were prepared using Co^II, Cu^II and Ni^II salts. The ligand and its complexes were characterized by elemental analyses, FT-IR, u.v.–vis., ¹H- and ¹³C-n.m.r. spectra, magnetic susceptibility measurements, thermogravimetric analyses (t.g.a.), and by cyclic voltammetry.     

A novel spectrophotometric method for batch and flow injection determination of cyanide in electroplating wastewater

A sensitive and highly selective spectrophotometric method is described for the determination of cyanide. It is based on a reaction of cyanide with aquacyanocobyrinic acid heptamethyl ester (ACCbs) reagent (orange color) at pH 9.5 to give dicyanocobester (DCCbs) (violet color). The increase of the absorption bands of the reaction product at 368 and 580 nm and the decrease of the reagent band at 353 nm are linearly proportional to the cyanide concentration. The method is used in static mode for determining cyanide over the concentration range 0.04-1.20 μg ml⁻¹ with a detection limit of 0.02 μg ml⁻¹ and for hydrodynamic analysis of 0.4-5.2 μg ml⁻¹ cyanide. Application for batch and flow injection monitoring of cyanide in electroplating wastewater samples gives results agree within ± 1.2% with those obtained by the standard potentiometry using the cyanide ion selective electrode. The method is practically free from interferences by PO₄³⁻, NO₃⁻, NO₂⁻, SO₄²⁻, F⁻, Cl⁻, Br⁻, I⁻, S²⁻ and SCN⁻ ions and gives results with average recoveries of 97.6-99.2%. Advantages offered by using ACCbs as a chromogen for cyanide assay are: (i) high selectivity and sensitivity of the coordination site of the reagent towards cyanide ion; (ii) fast reaction, since legation takes place at the axial position of the reagent; (iii) good solubility and stability of the reagent in aqueous solutions over a wide pH range; (iv) high stability of the reagent (ACCbs) and the colored complex product (DCCbs) and (v) possible absorbance measurements at three different wavelengths.