Hydralazine-selective PVC membrane electrode based on hydralazinium tetraphenylborate

A hydralazine ion-selective PVC membrane electrode based on hydralazinium tetraphenylborate has been prepared with dioctyl phthalate as plasticizer. The electrode showed linear response with a slope factor of 57.5 mV/concentration decade at 20 degrees over the concentration range from 4 x 10(-4) to 10(-1)M hydralazine. The effects, on the electrode performance, of membrane composition, pH of the test solution and the time of soaking were studied. The electrode exhibited good selectivity for hydralazine with respect to a large number of inorganic cations and organic substances of biological importance. The standard-addition method and potentiometric titrations were used to determine hydralazine concentrations in pure solutions and in a pharmaceutical preparation, with satisfactory results.     

Chromate oxidation of alpha-nitro alcohols to alpha-nitro ketones: significant improvements to a classic method

A series of eight alkyl and aryl alpha-nitro ketones were prepared by the potassium dichromate oxidation of the corresponding nitro alcohols. Short reaction times allowed for the easy isolation of pure nitro ketones that are devoid of starting materials and/or other oxidation side products.     

Rotenoid and isoflavone metabolites from an antioxidant seed extract of Dalbergia lanceolaria subsp. paniculata (roxb.) thoth

Abstract

A new rotenoid named 12-O-methylrotenolol along with five known rotenoid and isoflavone metabolites were isolated from the seeds of Dalbergia lanceolaria subsp. paniculata, collected from Egypt. The structures of these compounds were identified by physical and spectroscopic data measurements ([α]_D, UV, 1D- and 2D-NMR and MS). The methanol extract of the seeds exhibited strong antioxidant activity with IC₅₀ value 0.7?µg/µl against DPPH radical, in respect to quercetin as antioxidant reference (IC₅₀ 1.5?μM), while the tested compounds from this extract showed weak activities with IC₅₀ values ranged from 19.6 to 33.0?µM.     

Spectrophotometric determination of aluminum and copper ions using spadns

Aluminum and copper ions are selectively estimated spectrophotometrically. These ions form colored complexes with spadns which have a maximum absorbance at 580 nm. The complexes formed with both cations are stable and pH dependant; aluminum is favorably complexed at pH 5, while copper is complexed at pH 7.The percentage recoveries were found to be 99.69 ± 0.75 and 99.32 ± 0.6 with a minimum detection limit of 0.08 and 0.23 g ml^–1 for aluminum and copper ions respectively. There is insignificant interference from the 10-fold concentrations of other metal ions under the proposed reaction conditions.     

Spectral properties and temperature-dependence of semiconductivity of various doped bismuth trioxide polycrystals

Several samples of Nb₂O₅-doped Bi₂O₃ and Y₂O₃-doped Bi₂O₃ were carefully prepared and sintered at 700° for 3 hours. Extensive measurements were carried out on these samples, including X-ray diffraction spectra, infrared absorption spectra and the temperature-dependence of the DC-electrical conductivity in the solid state. The results obtained were discussed, correlated and interpreted. Finally, the optimum compositions were established and recommended for doped-Bi₂O₃ in the electronics industry.

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Zusammenfassung Einige Proben von mit Nb₂O₅ und Y₂O₃ gedopten Bi₂O₃ wurden hergestellt und bei 700 °C 3 Stunden gesintert. Von den Proben wurden Röntgendiffraktogramme und IR-Absorptionsspektren aufgenommen und die Temperaturabhängigkeit der elektrischen Gleichstromleitfähigkeit im festen Zustand gemessen. Die erhaltenen Ergebnisse werden diskutiert, zueinander in Beziehung gesetzt und interpretiert. Optimale Zusammensetzungen werden ermittelt und für gedoptes Bi₂O₃ in der Elektronikindustrie empfohlen.

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Bi₂O₃, Nb₂O₅ Y₂O₃, 3 700°. , . . , .

     

Charge-transfer complexes as polymerization inhibitors. I. Amine–chloranil complexes as inhibitors for the radical polymerization of methyl methacrylate

Charge-transfer complexes of N,N-dimethylaniline (DMA) and triethylamine (TEA) with chloranil have been investigated as inhibitors for the sensitized polymerization of methyl methacrylate (MMA) in bulk and in solution. Complete inhibition is achieved by the complexes of both amines followed by retardation only in case of DMA. The higher inhibiting efficiency of the TEA complexes is attributed to their greater stability. The polymers formed in the presence of chloranil alone or its complexes with both amines are quinonoid and contain no combined nitrogen. The results support the idea that inhibition reaction involve electron transfer from the growing chains to the quinone, with formation of molecular complexes of polymeric cations and semiquinone anions. The latter are the actual inhibiting species, so that the efficiency of inhibiting depends on their concentration, which is determined by the stability of the molecular complexes formed. The inhibition reactions should accordingly be considered as oxidation–reduction processes in which the growing chains are the electron donors. The suggested mechanism affords an explanation for the great differences in the inhibiting power of a particular quinone for the polymerization of different monomers.     

Reductive Elimination of Phenylsulfonyl Groups in the 3‐Position of Benzo[a]heptalene‐2,4‐diols

3‐(Phenylsulfonyl)benzo[a]heptalene‐2,4‐diols 1 can be desulfonylated with an excess of LiAlH₄/MeLi?LiBr in boiling THF in good yields (Scheme 6). When the reaction is run with LiAlH₄/MeLi, mainly the 3,3′‐disulfides 6 of the corresponding 2,4‐dihydroxybenzo[a]heptalene‐3‐thiols are formed after workup (Scheme 7). However, the best yields of desulfonylated products are obtained when the 2,4‐dimethoxy‐substituted benzo[a]heptalenes 2 are reduced with an excess of LiAlH₄/TiCl₄ at ?78→20° in THF (Scheme 10). Attempts to substitute the PhSO₂ group of 2 with freshly prepared MeONa in boiling THF led to a highly selective ether cleavage of the 4‐MeO group, rather than to desulfonylation (Scheme 13).     

First synthesis of selenadiazolo[3,4‐i] Benzazepine derivatives

5‐Methyl‐4‐nitro‐2,1,3‐benzoselenadiazole ( 1 ) was converted into (E)‐5‐(2‐dimethylamino)vinylbenzo‐[c](1,2,5)selenadiazole‐4‐amine ( 4 ) by initial treatment with dimethylformamide dimethyl acetal (DMFDMA) ( 2 ) followed by selective reduction using ammonium bromide in methanol. Compound 4 afforded the selenadiazolo[3,4‐i][1]benzazepine derivatives ( 7, 10, 13, 15 ) upon treatment with malononitrile ( 5 ), ethyl cyanoacetate ( 8 ) and cyanoacetamide ( 11 ) respectively.