Chemistry Journal of Moldova. General, Industrial and Ecological Chemistry

24-29

Authors: Ludmila Kiriyak, Tatiana Cazac, M. Revenco and I. Povar

The polarographic catalytic current in acid solutions of Mo(VI), 2,3-dihydroxybenzaldehyde (2,3-DHBA) and chlorate ions has been investigated. The scheme of reactions taking place in the solutions and on the electrode has been elaborated. The increase of the catalytic current is explained by the formation of the active intermediate complex [Mo(V)⋅2,3-DHBA (ClO3 -)]. The rate constant of formation for the active intermediate complex K = 2.5 ⋅ 106 mol-1 ⋅ dm3 ⋅ s-1, the activation energy of reaction Ea=14.0 kcal⋅mol-1 and the activation entropy ΔSa ≠= -28.3 e.u. have also been determined.

37-40

Authors: T. Lupaşcu, M. Ciobanu, V. Boţan, A. Nistor

The intact activated carbon CAN-8, obtained from nutshells by activation with water vapors, in the presence of oxygen and at relatively low temperatures, possesses catalytic activity, caused by the presence of alkaline functional groups on its surface, as well as by the formation, in these experimental conditions, of the OH• radical, which has a high oxidation potential. After 25 cycles of the process of methylene blue oxidation, the data of chromatographic analyses indicate the presence of three organic components in the solution.

47-53

Authors: V. Dragancea, R. Sturza, M. Boujtita

A screen-printed carbon electrode modifi ed with tyrosinase (SPCE-Tyr/Paa/Glut) has been developed for the determination of phenol concentration in real samples. The resulting SPCE-Tyr/Paa/Glut was prepared in a one-step procedure, and was then optimized as an amperometric biosensor operating at 0 mV versus Ag/AgCl for phenol determination in fl ow injection mode. Phenol detection was realized by electrochemical reduction of quinone produced by tyrosinase activity. The possibility of using the developed biosensor to determine phenol concentrations in various smoked products (bacon, ham, chicken and salmon) was also evaluated. Gas chromatography (GC) method was used for result validation obtained in fl ow injection mode using amperometric biosensor. The result showed good correlation with those obtained by fl ow injection analysis (FIA).

59-67

Authors: N. Secara, Gh. Duca, L. Vlad, F. Macaev

The paper describes the syntheses of new derivatives of dihydroxyfumaric acid and investigations of their antioxidant activities using the DPPH method.

73-82

Authors: Vasile Gutsanu, Constantin Turta, George Filoti

In this review there are described the results of studying of iron ions state in the ion-exchange resins (KU- 2, AN-31, AV-17, Varian – AD, EDE-10P), obtained by Mossbauer spectroscopy. The iron ions have been sorbet on ion exchangers, from aqueous solutions at different temperatures and air conditions. The iron state in polymer phase depends of nature of electron donor groups - amine or carboxylic. To explain the form and temperature dependence of Mossbauer spectra of polymer phase containing iron it was proposed the presence of different compounds like β-FeOOH, α-Fe2O3, and jarosite mineral type compounds: (R4N,H3O)[Fe3(OH)6(SO4)2] or coordination modes: {RCOO-Fe(L4)-OOCR}1+, {R-CO2=Fe(X2)=O2C-R}n, {R-COO-Fe(X4)-OOC-R}n, and {(-NCH2CH2N-)= Fe(X2) =(-NCH2CH2N-)}, where X= H2O, OH-, SO4 2-., n= from 3- to 1+. In special conditions the ultrafi ne superparamagnetic particles of Fe2O3 have been obtained.

90-100

Authors: Zinaida Ribkovskaia, Serghei Pogrebnoi, Alic Barba, Fliur Macaev

The synthesis and characterization of [(5-mercapto-1,3,4-oxadiazol-2-yl)aryl]-3,5-diaryl-4,5-dihydro-1Hpyrazole- 1-carbothioamides - derivatives of pyrazolines and 5-[4(3)-isothiocyanatophenyl]-2-thio-1,3,4-oxadiazoles were realized. The synthesized compounds, are crystalline substances, stable in storage and when exposed to air and light.