Chemistry Journal of Moldova. General, Industrial and Ecological Chemistry

9-19

Authors: Olga Morarescu

This review presents a synthetic transformations of ent-kaurane diterpenes, covering various aspects of the chemical and microbiologically transformations of native ent-kaur-16-en-19-oic acid, namely, its reactions via COOH groups, double bonds and rearrangements of the carbon skeleton, what we offer a wide range of natural and synthetic derivatives potentially biologically actives and convenient synthon for their synthesis.

25-32

Authors: Larisa Postolachi, Vasile Rusu, Tudor Lupascu, Alexei Maftuleac

The following factors which can improve the process of coagulation were studied: (i) the influence of stirring speed during coagulation and (ii) the influence of the concentration of the coagulant solution added in the process of coagulation. The coagulation process was studied on raw water of the Prut River. Application of the recommended procedure contribute to the reduction of the coagulant dose, the contact time, the aluminum concentration in water and the expenses for water treatment.

42-45

Authors: Ecaterina Covaci

The present work was undertaken to study the effect of the treatment temperature on the potassium bitartrate stability and composition of young wines. The thermodynamic parameters, namely ∆G°, ∆H°, ∆S° were calculated to predict the nature of potassium hydrogen tartrate (KHT) precipitation. According to the achieved results, the exothermal nature and thermodynamical feasibility of KHT precipitation in young wines were established. Based on thermodynamics, negative ∆G°, ∆H° values and positive ∆S° value give a spontaneous KHT process at lower temperatures.

52-56

Authors: Ana Lazarescu, Elena Melnic, Sergiu Shova, Victor Kravtsov, Constantin Turta

A lanthanum(III) cyanoacetate complex {[La2(CNCH2COO)6 (H2O)4]∙H2O}n (1) was synthesized and characterized by X-ray single-crystal analysis. The complex 1 exhibits one-dimensional coordination polymer structure. Cyanoacetate ligands coordinated in the bidentate bridging and tridentate-chelating bridging modes. The cyano-group of ligand is not coordinated to the lanthanide ion.

64-70

Authors: Natalia Sucman, Vsevolod Pogrebnoi, Mykola Obushak, Elena Melnic, Victor Kravtsov, Fliur Macaev

Described synthesis of 5-bromo substituted oxindoles linkages in spirocyclic butenolides exhibit relatively dependence of the structure-reactivity relationships of N-substituted isatines, dimethyl acetylenedicarboxylate and triphenylphoshine. The study of the stereochemistry of the atom C(2) of the spiro compounds was also unambiguously confirmed by single crystal X-ray analysis.

76-83

Authors: Tatiana Goreacioc

The surface chemistry of the commercial active carbon AG-5 has been modified by oxidation with concentrated nitric acid. The structural changes caused by oxidative treatment were estimated on the basis of nitrogen adsorption-desorption isotherms and thermal analysis. Boehm titration method and infrared spectral analysis have been used in order to evaluate surface chemistry characteristics of active carbon samples.

89-94

Authors: Mikhail Gorbachev, Natalia Gorinchoy, Ion Arsene

The preferred mechanism of the reaction of dihydroxyfumaric acid and its dimethyl ether with the free stable radical 1,1-diphenyl-2-picrylhydrazyl (DPPH*) was revealed by means of Density Functional Theory (DFT) calculations. The proposed mechanism has an ionic character and includes the formation of charge-transfer complexes as the main stage. It is also shown that the lower antioxidant activity of dimethyl ether of dihydroxyfumaric acid is caused by both its lower acidity (as compared with its precursor acid) and formation of more stable intermediates during its reaction with DPPH*. Our results allow one to rationalize the available experimental data.

104-112

Authors: Alexandru Gonta

After modification of enotannins, flavonols monomer units could be obtained with polyfunctional properties. Moreover, polyphenols are known to generate H2O2 and other ROS under alkaline conditions. ROS generation and catalytic influence of ferrous ions enhance the chemiluminescence light. Therefore in this work, Tox/Tris-Edta/Fe2+ ions have been used for screening luminescent properties of oxidized tannins.