Spectrophotometric analysis, thermal analysis and gravimetric determination of some metal ions with oxime and Schiff's base derivatives of N-furoylphenylhydroxylamine

The oxime and Schiff's base of N-furoylphenylhydroxylamine form complexes with Co²⁺, Cu²⁺, Zn²⁺ and Fe³⁺. These complexes were studied by means of the UV — Vis. spectra of nujol mulls, electron spin resonance (ESR) spectra and magnetic susceptibility to determine their stereochemistry. The complexes were characterized via elemental analyses, molar conductivities and thermogravimetric analyses. Organic reagents were used for the gravimetric determination of Co²⁺, Cu²⁺ and Fe³⁺ through the precipitation of their complexes. The compounds were also used for separation of a binary mixture of Cu²⁺ and Cu²⁺. Interferences were studied.     

Studies on heterocyclic enamines: New syntheses of 4H-pyranes,pyranopyrazoles and pyranopyrimidines

The behaviour of several 2-amino-3-cyano-4H-pyran derivatives toward a variety of nucleophilic reagents is reported.     

Three-phase plasma arc atomic-emission spectrometric analysis of environmental samples using an ultrasonic nebulizer

Combination of an ultrasonic nebulizer and plasma excitation sources for spectrochemical analysis offers desirable features of low detection limits, high sample throughput, wide dynamic range of operation, acceptable precision and accuracy, and simultaneous quantitative analytical capabilities. Moreover, the ultrasonic nebulizer does not require sample preconcentration. Recently we have developed a three-phase plasma arc (TPPA) for atomic emission spectrochemical analysis. In the present work, to increase the analytical utility of the three-phase plasma system, an ultrasonic nebulizer was used for sample introduction. The effects of the argon gas flow rate, current, excitation temperature have been studied. The analytical calibration curves are obtained for Ca, Cr, Fe, Mg and Mn, and detection limits have been calculated. The present technique is used to determine the concentration of the elements Ca, Cr, Fe, Mg and Mn in airborne samples.     

Useful dual Diels-Alder behavior of 2-azetidinone-tethered aryl imines as azadienophiles or azadienes: a beta-lactam-based stereocontrolled access to optically pure highly functionalized indolizidine systems

Imines derived from 4-oxoazetidine-2-carbaldehydes have been found to be versatile Diels-Alder reagents in that they exhibit two reactivity patterns. 2-Azetidinone-tethered imines undergo diastereoselective reaction with Danishefsky's diene in the presence of different Lewis acids. The effect of the amount of catalyst on the conversion rate as well as on the product ratio has been studied. Under standard reaction conditions, indium(III) chloride and zinc(II) iodide provided the best yields, and indium(III) triflate the highest diastereoselectivity in the Lewis acid promoted aza-Diels-Alder cycloaddition. Treatment of the aforementioned imines with cyclopentadiene, 2,3-dimethyl-1,3-butadiene or 3,4-dihydro-2 H-pyran led to cycloadducts arising from inverse electron-demand condensation involving the beta-lactam-tethered aryl imine as the heterodiene component. In addition, the first methodology for preparing indolizidines from beta-lactams has been developed. This process involves amide bond cleavage of the beta-lactam ring in the aza-Diels-Alder cycloadducts with concomitant cyclization. Full chirality transfer occurs when the reaction is performed with an enantiomerically pure substrate.     

Carbon‐based Nanosensors for Salicylate Determination in Pharmaceutical Preparations

Thiourea derivative‐based carbon paste electrode (TUD1‐CPE) was constructed as a potentiometric sensor for the determination of salicylate anion in pharmaceutical formulations, Aspocid® and Aspirin®. The optimized CPE contained 45.5 % graphite, 0.5 % reduced graphene oxide (rGO), 46.0 % nitrophenyl octyl ether (NPOE) plasticizer, 5.0 % TUD1 ionophore, and 3.0 % tridodecylmethyl ammonium chloride as additive. The incorporation of NPOE of high dielectric constant, and rGO in electrode caused better performance of the sensor; Nernstian response of 59.0 mV decade^?1 in the concentration range of 10^?1–10^?5 mole L^?1, a detection limit of 1×10^?5 mole L^?1 in a very short response time of 6 seconds. The prepared sensor showed high selectivity against similar anions (i. e. , benzoate, I^?, SCN^?). Selectivity was confirmed by calculating the formation constant (K_β) using sandwich membrane method, where K_β for TUD1‐salicylate is 10^0.43. Theoretical calculations at DFT‐B3LY/6‐31G** level of theory were performed to find interaction mechanism, Energies of HOMO and LUMO orbitals, non‐linear optical (NLO) properties (the electronic dipole moment (μ), first‐order hyperpolarizability (β), the hyper‐Rayleigh scattering (β_HRS) and the depolarization ratio (DR)), and other global properties; these calculations showed lower values of β and DR, higher value of β_HRS, and the shortest lengths of the four N?H bonds between TUD1 and salicylate which confirm their strong complexation and salicylate‐selectivity. Also, all the studied anion‐TUD1 exhibited relatively high NLO properties, and these results were considered as a preliminary study for investigating new types of NLO bearing materials. The sensors were applied successfully for the determination of salicylate anion in Aspocid® and Aspirin®.     

Aqueous polymerization of methyl methacrylate catalyzed by copper metal and some of its compounds

The aqueous polymerization of methyl methacrylate (MMA) with sodium bisulfite as initiator was carried out in a nitrogen atmosphere with and without inorganic substances like copper metal, cupric and cuprous oxides, and cupric sulfide. It was also done in the presence of organocopper compounds like copper phthalocyanine and copper biphthalocyanine. The catalytic effect of these compounds was studied. Mildly heated cupric sulfide proved to have a small catalytic effect on the polymerization process that may be attributed to the retarding effect of the released elementary sulfur. The catalytic effect of the different copper compounds and the copper metal equivalent contained in them was studied. The polymerization process revealed that cuprous and cupric oxides possess the highest catalytic influence. An attempt was made to investigate the role of the different anions on the polymerization process. It was found that an increase on the concentration of the copper compounds leads to a corresponding increase in the catalytic effect. It was also observed that the behavior of insoluble copper catalysts is different from that of the soluble. The effect of these catalysts on the average molecular weight of the poly(methyl methacrylate) (PMMA) produced was also examined.     

Electronic structure of the peptide linkage. I. Equilibrium geometry and electronic properties of formhydroxamic acid

The equilibrium geometry of formhydroxamic acid has been calculated within the framework of the INDO –MO formalism. Various structural factors are analyzed and discussed in terms of the calculated force constants and charge distribution. The possibility of internal rotation around the C? N bond of formhydroxamic acid has been examined. The potential energy surface for the amide-imide tautomerism is explored by calculating the geometries and characterizing saddle points on that surface. The cyclic and open dimers of formhydroxamic acid are examined and the hydrogenbond energy and length are calculated.     

The use of Omega Chrome Fast Blue 2G in the microdetermination of some metals

Summary Omega Chrome Fast Blue 2G has been found to be a suitable indicator for the detection of the equivalence point of calcium, magnesium and manganese in the presence of cadmium, nickel, and aluminium, when they are masked by the addition of cyanide or triethanolamine. It is also a suitable indicator for the back titration of aluminium using calcium or magnesium as a back titrant.This dye has also been found to be a suitable reagent for the colorimetric determination of calcium, magnesium, manganese and thorium.     

Synthesis of 1-phenyi-1H-tetrazolo[4,5-d]tetrazole and 5-aryl-1-(4-bromophenyl)-1,2,4-triazolo[4,3-d]tetrazoles

l-Phenyl-lH-tetrazol-5-yIhydrazine (2) was reacted with nitrous acid to yield 1-phenyl-lH-tetrazolo[4,5-d]tetrazole (3). l-Arylidene-2-(l-phenyl-lH-tetrazol-5-yl)hydrazines (4) were generally reactive towards electrophilic reagents. When treated with bromine in acetic acid, 4 yielded mixtures of 1-arylidene-2-[1-(4-bromophenyl)-lH-tetrazol-5-yl]hydrazines (5a-d) and 2-[1-(4-bromophenyl)-lH-tetrazol-5-yl]hydrazidic bromides (6a-d). Solvolysis of 6a-d in aqueous acetone yielded 5-aryl-1-(4-bromophenyl)-1,2,4-triazolo[4,3-d]tetrazoles (7a-d). The structures of the synthesized compounds were confirmed on the basis of elemental analysis, IR and ¹H NMR data.