Polarographic behaviour of salicylaldehyde-2-pyridylhydrazone and its copper(II) complex

The polarographic behaviour of salicylaldehyde-2-pyridylhydrazone (SAPH) has been studied in aqueous buffer solution containing 40% ethanol using DC and DP polarographic methods. In the pH range 1.8–7.5 the observed single irreversible reduction wave is assigned to the splitting of the N-N bond and reduction of C=N centre. In alkaline medium, a second wave appears at a more negative potential due to the reduction of the salicylaldehyde which is formed by hydrolytic decomposition of the SAPH molecule. The effect of pH on the limiting current andE _1/2 as well as the reduction mechanism are discussed and compared with similar compounds. The kinetic parameters of the electrode reaction have been calculated.The analytical properties of the copper(II)-SAPH system is described. The complex gave rise to a single irreversible well-defined wave (E _1/2=–0.58 V at pH=5.2). The reaction process is diffusion controlled. A method is suggested for the determination of Cu(II) in presence of different metal ions as the difference in theirE _1/2 values is sufficient for the purpose.This work is taken partly from the M. Sc. Thesis of Jamal S. Shalabi     

Strategy of analysis for the estimation of the bioavailability of zinc in foodstuffs

After the application of simulated digestive fluids (gastric and intestinale fluid) as extraction solutions, AAS and differential pulse anodic-stripping voltammetry (DPASV) were used as analytical methods in combination with ion-exchange procedures for the determination of zinc species and total zinc contents. The ion exchange procedure and the shifting of electrochemical potentials as well as changes of the calibration slope after standard addition in the polarographic analysis allowed discriminating statements with regard to a possible resorption of zinc. On the basis of these methods, a strategy is presented for in vitro investigations of the bioavailability of zinc in foodstuffs.     

Synthesis of 5-Substituted 1,3-Dimethylpyrazolo[4,3-<Emphasis Type="Italic">e</Emphasis>][1,2,4]triazines

Summary.  A novel method for the synthesis of a new series of 5-substituted 1,3-dimethyl pyrazolo[4,3-e][1,2,4]triazines is described. The new synthetic strategy is based on the classical Bischler 1,2,4-benzotriazine synthesis. This approach involves the preparation of 5-hydrazinopyrazole from 5-chloro-1,3-dimethyl-4-nitropyrazole followed by acylation and nitro group reduction to form the corresponding 4-amino-3-(acylhydrazino)pyrazoles. Intramolecular oxidative cyclization of the latter derivatives, using polyphosphoric acid, produced the respective target pyrazolotriazines.     

Synthesis of 5-Substituted 1,3-Dimethylpyrazolo[4,3-e][1,2,4]triazines

A novel method for the synthesis of a new series of 5-substituted 1,3-dimethyl pyrazolo[4,3-e][1,2,4]triazines is described. The new synthetic strategy is based on the classical Bischler 1,2,4-benzotriazine synthesis. This approach involves the preparation of 5-hydrazinopyrazole from 5-chloro-1,3-dimethyl-4-nitropyrazole followed by acylation and nitro group reduction to form the corresponding 4-amino-3-(acylhydrazino)pyrazoles. Intramolecular oxidative cyclization of the latter derivatives, using polyphosphoric acid, produced the respective target pyrazolotriazines.     

Spectrophotometric determination of ruthenium after extraction of perruthenate with benzyltributylammonium chloride

A simple and convenient extractive spectrophotometric method for the determination of ruthenium has been developed. It is based on the oxidation of the different ruthenium (II, III or IV) species to perruthenate with potassium periodate at pH 7.8. The perruthenate is then extracted with benzyltributylammonium chloride in chloroform followed by direct spectrophotometric measurements at 342 and 380 nm. The optimum concentration range was found to be 0.1–5 mg l^–1, the standard deviation ±2.1%. The method has been successfully applied to the determination of ruthenium in organoruthenium compounds.     

An alternative synthesis of 2-(N-arylhydrazono)-1-benzothiophen-3-ones

In the presence of triethylamine, 2-mercaptobenzoic acid readily adds onto acylhydrazonoyl chlorides (1a-c) (precursors of the reactive nitrile imine 1,3-dipolar species) to afford good yields of the corresponding 2-[(2-oxo-1-arylhydrazonopropan-1-yl)mercapto]benzoic acids (2a-c). The latter acyclic adducts, in THF in the presence of 1,1'-carbonyldiimidazole, undergo intramolecular cyclization involving the activated carboxy and the enol functionality to deliver the respective 2-(N-arylhydrazono)-3-oxobenzothiophenes (3a-c). In the solid state, the latter compounds adopt the (Z)-geometry around the C=N double bond as evidenced by single crystal X-ray structure determination for 3b.     

Utility of N‐[4‐(N‐Substituted Sulfamoyl)Phenyl] Cyanothioformamides in the Synthesis of Heterocyclic Compounds

The novel cyanothioformamides 2a‐d were prepared by treatment of isothiocyanatosulfonamides 1a‐d with potassium cyanide at room temperature. Cyclocondensation of compounds 2b,c with phenyl isocyanate as electrophile furnished the corresponding imidazolidines 3a,b . The reactivity of compound 3a towards some nitrogen nucleophiles was investigated. Thus, the thiosemicarbazone 4 and imidazo[4,5‐b]quinoxaline 6 were synthesized by condensation of compound 3a with thiosemicarbazide and o‐phenylenediamine, respectively. Treatment of 3a with hydrochloric acid afforded compound 7 . Our investigation was extended to include the reactivity of cyanothioformamide 2 towards o‐aminophenol, anthranilic acid, and o‐phenylenediamine and yielded the corresponding heterocycles 9 , 11 and 13 derivatives, respectively. Structures of the synthesized compounds were established by their elemental analysis and spectral data.     

On the Synthesis of Some 2-Arylhydrazono-3-oxothieno[2,3-<Emphasis Type="Italic">b</Emphasis>]pyridines by Reaction of Nitrilimines with 2-Mercaptonicotinic Acid

Summary. 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.     

Adsorptive stripping voltammetric analysis of 2,4,6-tri(2′pyridyl)-1,3,5-triazine at a mercury electrode

The redox behaviour of adsorbed species of 2,4,6-tri(2-pyridyl)-1,3-5-triazine (TPTZ) at the surface of a mercury electrode was examined using cycling voltammetry. Based on the adsorption and accumulation of TPTZ at the charged mercury surface cathodic adsorptive stripping voltammetry (CSV) is applied for the trace determination of TPTZ using a differential pulse (DP) technique. Experimental and operational parameters for the quantitative analysis of TPTZ are optimized and the detection limit was found to be 3×10^–9 mol/l. The effect of some interferences, e.g. organic compounds, cations and anions, are investigated.     

Study of ion beam induced mixing in Sn/Si system using electrical resistivity measurements

The ion-beam mixing of Sn thin film evaporated on silicon has been investigated by continuously measuring the electrical resistivity of the sample during irradiation by Kr ions. The resistivity results exhibit a tendency toward a saturation process and allow the determination of the critical dose corresponding to the total mixing condition. The variation of the volume fraction of intermixed atoms as a function of the ion dose has been deduced and compared with a semiempirical formula to explain the observed mixing kinetics. A linear dependence of the volume fraction of the intermixed atoms on the fluence is observed, which is a signature of recoil type mixing.