Zvjezdana Lazarević

Synthesis and absorption spectral properties of substituted phenylfurylbenzothiazoles and their vinylogues

SummaryA number of substituted 2-(5-aryl-2-furyl)benzothiazoles and their vinylogues were synthesized from corresponding 5-arylfurfurals by convenient methods. The yields of products and their UV/Vis spectroscopic properties are substituent-dependent.ZusammenfassungEinige substituerte 2-(5-Aryl-2-furyl)benzthiazole und ihre Vinyloge wurden aus entsprechenden 5-Aryl-furfuralen synthetisiert. Die Ausbeuten an Produkten sowie ihre absorption-spektroskopischen Eigenschaften sind vom Substituenten abhängig.

Simultaneous determination of zinc and nickel with 2-(2-pyridylmethyleneamino)phenol by first-derivative spectrophotometry

A first-derivative spectrophotometric method using a zero-crossing technique of measurement is described for the simultaneous determination of zinc and nickel in mixtures. The procedure is based on the reaction of zinc and nickel with 2-(2-pyridylmethyleneamino)phenol in buffered 10% v/v methanol–water solutions at pH 8. The determination of nickel and zinc in mixtures in the concentration ranges 0.3–3.0 and 1.0–6.0 µg ml–1, respectively, shows good linearity of the calibration graphs. The proposed method was applied to the determination of nickel and zinc in a real bronze sample. The main interferences present in copper alloy were also examined.

Simultaneous First-Derivative Spectrophotometric Determination of Nickel and Manganese Complexes with 2-(2-Pyridylmethyleneamino)phenol

Abstract A method is proposed for the simultaneous determination of nickel and manganese by first-derivative spectrophotometry based on their reactions with 2-(2-pyridylmethyleneamino)phenol (PMAP) Schiff base. The method allows the determination of Ni and Mn in the concentration range 0.3–3.0 μg ml−1 in mixtures with their ten-fold concentration ratio. The method has been applied for Ni and Mn determination in bronzes. To optimize the experimental conditions for spectrophotometric determination of Mn with PMAP stability constants at different pH values have been determined. A critical evaluation of the proposed method was performed by statistical analysis of the experimental data.

Absorption and Fluorescence Characteristics of Some 2-Aryl-and 2-Heteroaryl-benzothiazoles in Different Solvents and at Various pH Values

Abstract The parameters characterizing the absorption and fluorescence of seven 2-substituted benzothiazoles in different solvents and at various acid/base concentrations were studied. It was found that both the kind of substituent and the solvent polarity influenced the changes of the spectral properties of the examined molecules. 2-Aryl substituted benzothiazoles exhibit larger Stokes shifts than 2-heteroaryl derivatives. The linear relationship between solvent polarity and pH values against Stokes shift and fluorescence sensitivity, respectively, was observed. The mostly fluorescent compound was 2-(2-benzofuryl)benzothiazole.

Direct determination of zirconium and chromium by first-derivative spectrophotometry.

The solution properties of zirconium complex with the Schiffs base 2-(2-pyridylmethyl-eneamino)phenol have been studied by zero-order absorption spectrophotometry. The influence of pH, stability of the complexes with time and stability constants were investigated. The use of first-derivative spectrometry eliminates the interference of chromium and enables the simultaneous determination of zirconium and chromium without previous separation. The relative overall standard errors, of five independent simultaneous determinations of zirconium and chromium at the 1.0 mug/ml concentration level, were 2 and 4%, respectively. The proposed method has been successfully applied to the analysis of some real samples of zirconium/chromium bronzes.

Effect of Zeolites in AOPs for Dye Wastewater Treatment

Abstract Advanced oxidation processes (AOPs) for the treatment of model wastewater containing organic dye were investigated. C.I. Reactive Red 45 (RR45) was chosen as a representative of the azo type of dyes that cover more than half of the dyes available commercially, as well as a representative of the monochlorotriazine group of reactive dyes, consumption of which is continuously growing worldwide. The aim of the present paper is comparative evaluation of the efficiency and feasibility of applying high voltage pulsed electrical discharge (Corona), as well as Fenton and Peroxone processes to the destructive treatment of RR45. The effect of HY, NaY and Naβ zeolite on decolorization and degradation in those processes is discussed.

β-Tricarbonyl compounds. I. 2,4-Disubstituted 1,3-cyclopentanediones

SummaryStable enolic isomers of 2-aroyl-4-aracyl-1,3-cyclopentanediones such as3 and4 were prepared by condensation of aryl methyl ketones and diethyl maleate using an excess of sodium ethoxide (Aryl=C6H5, 4-C6H4CH3, 4-C6H4Br and 4-C6H4Cl).ZusammenfassungStabile Enol-Isomere von 2-Aroyl-4-aracyl-1,3-cyclopentandionen wie3 und4 wurden durch Kondensation von Arylmethylketonen und Diethylmaleat mit einem Überschuß von Natriumethoxid dargestellt (Aryl=C6H5, 4-C6H4CH3, 4-C6H4Br und 4-C6H4Cl).

Spectroscopic study of tautomerism in 2-benzoyl-4-phenacyl-1,3-cyclopentanedione

Abstract The tautomerism in 2-benzoyl-4-phenacyl-1,3-cyclopentanedione has been studied through an investigation of the solvent and pH dependence of the equilibrium using UV spectrophotometry. The first derivative spectrophotometric technique has been applied for the determination of the ratio of monoenol form in tautomeric mixtures. The results showed that in DMF solution 2-benzoyl-4-phenacyl-1,3-cyclopentane-dione exist only in non-hydrogen-bonded monoenol form while in less polar solvents the predominance of helated dienol form was established.